CZ2012604A3 - Glass-melting furnace for continuous melting by controlled glass-melt convection - Google Patents

Abstract

A glass melting furnace is described wherein energy sources are arranged in the melting space in at least one row in the longitudinal axis of the melting space, or parallel to the longitudinal axis, between the base wall (2) and the transverse wall (7) in the glass ( 6) optionally, a transverse row (9) of energy sources in the melting portion of the glass (6) to cause a circular flow of molten glass (6) across the melting portion. Energy sources can be arranged in one or both side walls (4). Energy sources are arranged at regular intervals. Energy sources are heating electrodes (10) and / or industrial glass burners (11). The melting portion is preferably terminated by a transverse row (9) of the heating electrodes (10) installed in the bottom (1).

Description

Glass melting furnace for continuous glass melting by controlled glass convection

Technical field

The present invention relates to a glass melting furnace for the continuous melting of glass by controlled glass convection in which molten glass is treated, comprising undissolved particles, in particular glass sand, located in a horizontally oriented and separate through-flow melting space by energy sources acting on the glass in the glass. melting space. The melting chamber comprises a bottom, a foundation wall and a rear flow wall, and between them. opposite side walls, vaults, and enamelled transverse dam wall.

BACKGROUND OF THE INVENTION

Continuous glass melting is a method of preparing traditional mass-scale melting material directly associated with the processing of the resulting raw material in many ways. Its foundations date back to the 19th century, when the emerging glass technology was inspired by another melting process, the production of steel. In accordance with this process, the first continuous glass equipment called glass pans was created as covered horizontal spaces lined with refractory materials into which a glass batch was placed at the entrance, most often a mixture of crystalline raw materials 2ď with variable proportion of glass cullet. melt. The devices were heated by means of burners placed above the surface of the melt with the heating medium gas or oil. It was therefore a compact, top-fired single-space device, which was later divided by flow or constriction into the melting part where the glass-forming homogenization processes were carried out and completed, and to the 2 ° working part, where the melt was mainly thermally homogenized for processing. The melt flow through these devices was essentially horizontal, but due to naturally occurring temperature differences by feeding the cold charge to the melt level, the type and location of the heating and the different levels of heat loss through the interface, the natural circulation flow always stabilized in the melting and working space. with the flow-through flow produced a relatively complicated image 3 '(flow in the furnace space).

Later, other types of glass melting chambers have been developed, mainly heated electrically, and characterized by a substantially vertical melt flow through the melting chamber and with a similar composite melt flow. However, spaces with predominantly vertical flow are not covered by this application.

The problem of melting unusable circulating melt volumes allowed to refine the tests of the so-called transition characteristics of melting spaces [1-3]. In these tests, an indicator was introduced at the inlet of the melter, the indication pattern of which did not change during the melting process and which was identifiable at the outlet of the melter. The most common indicator was γ appropriate radioactive isotopes. Monitoring the character of the dependence of the indicator in the resulting glass over time provided information on the nature of the flow in the melter. It also helped to identify the space in which the melt only circulated. The measured proportion of such spaces, called dead space ratio, was often 0.5 in conventional melting plants, and in some plants it was even larger. So it was clear that the flow pattern plays for

the efficiency of the melting process is important. A little later, Cooper [4] defined, based on flow type and melting process kinetics, a quantity that is the ratio between the rate constant of the controlling melting process and the mass flow rate that provides the degree of termination of the process at a given location or space trajectory. The thesis emphasizes the importance of flow character for melting processes.

The search for an efficient method of melting glass required very detailed knowledge of the conditions under which the melting process takes place in industrial space. Such knowledge was only provided by mathematical modeling of the melting process in operated glass tanks. The application of mathematical models provided detailed temperature and velocity fields of the melt in the melting spaces and enabled the modeling of the melting processes directly when the mixture flows through a specific melting space [5-24]. The results confirmed the conclusions obtained by previous experience and measurements. A relatively complicated type of flow consisting of combinations of longitudinally and transversely rotating regions and a flow was established in the melting rooms, which was strongly influenced by the melt circulation. The dissolution process took place under relatively unfavorable temperature conditions [20], the fining process being essentially

2.5 limited to a small region of the melt temperature maximum [19-24] and the melting compartments indicated a high proportion of dead space [12]. An important problem of the melting processes was the course of the so-called critical paths, ie the melt paths through the melting space, at which the respective homogenization process in terms of time closest to the exit from the space will be completed. There were often short-circuit paths passing through a space with low residence times, moreover, under 30 not very favorable temperature conditions, which substantially limited the melting capacity of the space and increased the specific energy consumption per melting process. Efforts have been made to eliminate such short-circuit path by influencing the flow [25]. The complex natural flow in the melting aggregates was very difficult to influence in the right direction, since the optimum flow pattern in the melting compartments was not investigated in detail. However, Cooper [26] has previously described some of the consequences of a given type of flow for homogenizing the melt (eg accelerating process homogenization and transverse flow temperatures) based on a simple mathematical model of glass melt flow in a simple model space. These results indicate the need to influence the flow in the melting chamber based on a detailed knowledge of the relationship between the individual types of flow and their effect on the respective homogenization process. Recent global challenges to energy, material and environmentally less demanding technologies - including glass technology - have triggered additional activities involving both changes in the necessary melt residence times in the melting space and changes in the overall 10 melting process arrangements [27]. However, the changes require the application of new principles to the melting process, including changes in the spatial arrangement of the process, eg in the form of so-called segmental melters in which the sub-processes take place separately, alternative heating characteristics, etc. distance from commonly modeled existing industrial facilities to simple model spaces operating under precisely defined conditions, on which the principles can be sufficiently identified, to find their general patterns allowing later safe and plikaci. Such a process also includes efforts to overcome the disadvantages of naturally established flow in glass melting furnaces.

2. Summary of the Invention

These disadvantages are overcome or substantially reduced in a glass melting furnace for continuous glass melting by controlled glass convection in the melting chamber of the present invention. SUMMARY OF THE INVENTION The invention provides that energy sources 25 are arranged in at least one row along the longitudinal axis of the melting space or parallel to the longitudinal axis of the melting space between the loading wall and the transverse dam wall in the glass or the transverse row of sources. energy in the molten glass portion to induce a spiral flow of glass with a circular motion across the melting portion.

The main advantage of the invention is that the melting part, by its arrangement of energy sources, allows to generate a spiral flow which significantly reduces dead spaces in the melting space where the process does not take place and where the glass is unnecessarily consuming energy. Thus, a uniform temperature distribution in the glass is created in the melting chamber. The flow of the glass has an excellent homogenizing function and thus the process of dissolving hard-melting particles, especially glass sand or corundum particles, is shortened. The defined arrangement of the energy sources ensures effective achievement of the desired spiral glass flow. The melting chamber exhibits lower heat losses and a high melting capacity, which allows for a possible reduction of the melting part and, as a result, construction savings.

Preferably, the energy sources are arranged in one or both side walls of the melting chamber. When the energy sources are arranged in one side wall of the melting portion, one helical flow occurs across the entire melting portion, which is suitable for narrow melting portions. When the energy sources are arranged in both side walls, two essentially symmetrical spiral flows are formed separated by the longitudinal axis of the melting portion, which is suitable for melter rooms with difficult operator access to the bottom in case of displacement or replacement of heating electrodes. In larger glass furnaces, ie with a larger melting space and width, it is possible to use bottom heating electrodes in two or more rows in the longitudinal direction of the melting space. In this case, spiral flows occur between each side wall and the row of heating electrodes and between the individual row of electrodes.

It is also preferred that the energy sources are arranged at regular intervals from each other. Regular spacing ensures uniform heating of the melt and thus a favorable even flow of glass.

Energy sources are heating electrodes and / or industrial glass burners. The heating electrodes are the most advantageous for the spiral flow because of the direct supply of energy to the glass and the easy regulation of the heating electrodes. The heating electrodes may be

M may be arranged vertically or obliquely in the bottom, or may act on the enamel from above as vertical. Plate electrodes installed in the side walls seem to be suitable. There may be other sources of heating energy, such as microwaves or plasma torches.

It is also preferred that the melting portion terminates in a transverse row of heating electrodes installed in the bottom. This transverse row of heating electrodes creates a transverse thermal barrier, which is an alternative to the transverse dam wall, and moreover allows for better regulation of the heat output depending on the melting capacity of the glass furnace.

For very small melting rooms for special glass, other sources can be used as energy sources, eg microwaves, plasma burners or resistive sources in the side walls, or indirect sources of heating energy in the side walls, super-channel loops.

• 4

The main advantage of the present invention is the noticeable reduction in the space in the melting portion, i.e., Vol.

dead areas, ie places where the melting process does not take place or only with very low to zero efficiency and the glass is unproductively heated in these places and so the heat losses increase. An important advantage of the present invention is the possibility of adjusting the ratio of the transverse temperature gradient to the longitudinal temperature gradient that is formed by a suitable

AND the arrangement of the energy sources, and which creates favorable conditions for the spiral flow of the glass through the melting chamber. This also ensures a uniform temperature distribution in the melting chamber and an optimum homogenizing ability of the glass flow. Thus, there is a significant reduction in heat loss and a significant increase in the melting capacity of the glass furnace, which eventually allows a proposal to reduce the melting portion and thereby save costs on the construction of the glass melting furnace. It is preferred that the ratio of the transverse temperature gradient to the longitudinal temperature gradient be in the range of 1 to 30, which represents the real widest limits. Optimally, this ratio is used in the range of 5 to 20. If the ratio is less than 1, then to the spiral AND the flow of glass does not occur. If this ratio were higher, a spiral flow would also be advantageous, but the efficiency of adjusting this ratio does not outweigh the technical difficulties in implementation. The preferred spiral flow of glass passes through a space whose use for dissolving particles, especially glass sand, amounts to 0.6 to 0.8 of the total space, X defined by the height of the glass, the length between the transverse dam wall in the glass or the transverse row of energy sources and the facing base wall and the width between the opposing side walls. The spiral flow of the present invention provides the highest previously known defined utilization of the melting space. The utilization of the melting space is the amount utilized X parts of the melting chamber unused. BRIEF DESCRIPTION OF THE DRAWINGS 1a and 1b, taken from W. Trier, Advances in Glass Technology, Plenum Press, 1962, p. 619, where X Fig. 1 shows a longitudinal axial section of a constant temperature glass furnace, without circulation and Fig. 1b shows a longitudinal axial section through a glass furnace in the presence of temperature gradients and thus with circulation. κ The invention is described in detail in the following description of the invention, which is generally illustrated in the accompanying schematic drawings, of which FIG. 2 is a perspective view of a simplified basic model of a melting chamber with full inlet and outlet, FIG. 3 is an axonometric view of a simplified melting chamber with a simplified critical

Figure 4 is a graph of the maximum utilization of the model melting space, the dissolution time of the glass sand particles, and the length of the model channel of the melting space.

X

Exemplary embodiments 1 to 4 schematically illustrate in Fig. 5 ^ 24 a vertical longitudinal axial section of a proposed glass pan module with a melting portion of a typical shape and arrangement of heat sources, electrodes, in Figs. 24 combinations of vertical heating electrodes with side wall burners.

More specifically, an exemplary embodiment 1 for melting flat glass is shown in Figs. 5-and 13, schematically shown in Fig. 5, a melting portion of a typical shape and arrangement of vertical electrodes, with a lower inlet and a lower outlet; Fig. 5 for melting flat glass, with the upper inlet and lower outlet of the molten glass, Fig. 7, the resulting velocity distribution shown by the sections of the melt trajectories embedded in the

Fig. 20s, in longitudinal axial section through the melting chamber of Fig. 6, Fig. 8 are projections of the critical trajectory and other critical trajectories of the nearest trajectories for dissolving the sand grains into the longitudinal axial vertical section through the melting chamber of Fig. 6; velocity distribution in longitudinal axial section through the melting chamber, shown by the melt trajectory sections traveled in 30s of the melting chamber of Figure 6, for the optimum case, Figure 10 shows projections of the critical trajectory and other slowest trajectories for melting sand grains into the longitudinal axial vertical section FIG. 6, for optimum case, FIG. 11 shows a melting chamber for melting flat glass with a lower inlet and a lower outlet, FIG. 12 shows the resulting velocity distribution in longitudinal axial section through the melting chamber of FIG. for optimal 13 shows the projections of critical and other slowest trajectories for dissolving the grains of sand into a longitudinal axial vertical section through the space of FIG. 11, for the optimum case.

An exemplary embodiment 2 for the manufacture of spectacle moldings is shown in FIG. 14 ** 16, where the resulting velocity distribution in longitudinal axial section through the melting space shown in sections of melt trajectories traveled in 30s is schematically shown in FIG. the critical trajectory and other slowest trajectories for dissolving the grain of sand into the longitudinal axial vertical section through the space, for the reference case, FIG. 15 the resulting velocity distribution in the longitudinal axial section through the melting space shown velocity distribution in longitudinal axial section through melting space shown by IQ section of melt trajectories traveled in 30 s, Fig. 17 projections of critical and other slowest trajectories for melting sand grains into longitudinal axial vertical section through space, for optimum ROUND case.

An exemplary embodiment 3 for the production of glass enamel is shown in Fig. 18a H 22, where the melting chamber of Fig. 18a is schematically shown in longitudinal section, Fig. 18b in cross section below the enamel level, Fig. 19 resulting speed distribution in longitudinal axial section. sections of the enamel trajectories traveled in 30sec by the melting space, for the reference case,

Fig. 20 shows projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal axial vertical section through space, for the reference case, Fig. 21 the resulting velocity distribution in longitudinal axial section through the melting space shown by enamel trajectory sections traveled for 30s for the first optimized case; Fig. 22 shows the projections of critical and other slowest trajectories for dissolving the grains of sand into a longitudinal axial vertical section through the space, for the first optimized case;

An exemplary embodiment 4 for the production of utility glass is shown schematically in Fig. 239,24, in which the melting chamber is schematically shown in longitudinal axial section, and in Fig. 23 with the burners in the side walls, for reference case and

Fig. 24 with the heating of the vertical electrodes and side burners, for an optimum case.

DETAILED DESCRIPTION OF THE INVENTION

W. Trier, Advances in Glass Technology, Plenum Press, 1962, p. 619 shows a typical longitudinal axial sectional view of the horizontal glass melting furnace without constant temperature circulation in the attached FIG. glass furnace in the presence of temperature gradients, including circulation.

The naturally occurring type of glass flow evident from FIG. 1b has had a significant effect, in particular in the melting portions of glass furnaces, on the melting process and hence on the efficiency of the entire melting apparatus in terms of its performance and energy consumption per melting process. For the melting process, the resulting type had some advantages, in particular the fact that the massive return of the molten glass from the temperature peak to the trunk layer in the initial part of the furnace, as shown by the left circulation circuit in FIG. reaction of raw materials. A second advantage of the natural flow was the often present glass return from the flow to the melting temperature region, as shown in Figure 1b, at the bottom of the right circulation circuit. The return flow returned to the melting process of inhomogeneity, especially the bubbles that were due to the imperfect flow of the melting process. A disadvantage of the established type of flow was the resulting continuous flow of glass from the charge layer to the bottom of the melting furnace, where it moved forward at the lowest temperatures up to the maximum temperature range, where it was only circulated to bring it to high temperatures. 2Q. The consequence of this flow was slow homogenization of the glass (dissolution of particles and chemical inhomogeneities) and the practical absence of a fining process (bubble output) in a substantial part of the active furnace space at the bottom of the furnace. While the dissolution processes could be completed after the molten glass was brought from the bottom to the surface, the process of removing primary bubbles in the high temperature region at the surface was practically only beginning. Thus, both processes took place in the post-glass reaction region essentially in series, with the dissolution being carried out at the bottom of the furnace for most of the time required at low temperatures. The sequence of processes (instead of their intensive parallel run) and the large proportion of unfavorable conditions during the dissolution process were reflected in the high heat losses of the melting process and in the small specific melting performance of the aggregates, which required relatively robust 20Q equipment at higher planned outputs. In addition, it has been shown that the established circulation flow at low specific power of the melting compartments creates significant volumes of long-term circulating glass in the compartments, in which the melting process is essentially not performed (dead compartments - overprocessing compartments). This glass is therefore maintained at the melting temperature without its own effect and causes unnecessary heat loss.

In the recent past, the authors of this application have begun to look in detail at the effect of flow patterns on the two most important melting processes, ie dissolving unreacted glass batch particles, which in most cases represent glass sand and bubble removal (fining), mostly the slowest melting process. 35]. They defined the specific energy consumption and specific melting capacity of a given melting space as the quality criteria of the past 5 melting process. They chose a flow-through cuboid-shaped horizontal space with inlet and outlet as the model melter space with all or part of the front walls. Its diagram is shown in Figure 2, the shape of the melting chamber was simple to achieve the most general results, the dimensions of the equipment were small in accordance with the effort to miniaturize the next melting chamber - 10 lm length, glass melt width and height 0.5 m. with the ability to apply the results to other dimensions of the real device. The mathematical model of the melting space with the possibility of wide variability of conditions was chosen as a means of investigation.

/

Figure 2 is a schematic diagram of a simplified model melting chamber with full inlet and outlet. The appropriate flow pattern was adjusted using 15 > linear temperature gradients embedded on the glass level, the bottom and walls of the space were isolated. Because the dissolution process and the bubble removal process are carried out on different principles, the investigation was performed separately for each process, with a compromise between optimal conditions being chosen in applications, or a separate segment of the equipment would be designed for each process.

^ 0 In order to understand the results of the monitoring, the theoretical basis of the investigation should be given for this application concerning the dissolution of glass sand particles, which is usually a major part of most industrial glasses and is the glass raw material that is most difficult to dissolve in glass melt. .

✓

For a process without energy recycling, the criteria of the specific energy consumption and the volumetric power of the melting chamber ŽS are described by the following equations including the process duration (its kinetics) and the influence of the flow pattern separately. The influence of the flow pattern is expressed by a newly introduced variable called the use of melting space, uq [31, 33-35]:

(1)

3Ů v

- ^At D ·>

(2) where H ^Q M is the specific energy consumption [Jkg ^-1 ]; H'm is the theoretical heat required for chemical reactions, phase and modification conversions, and heating of the incoming mixture and the resulting glass to the melting temperature [Jkg ^-1 ]; is the total heat flow through the interfaces into the environment [Js ¹ ]; U is the mean dissolution time of all glass sand particles under different time-applicable temperature regimes of 5 s [s]; p is the specific gravity of glass [kg / m ³ ]; V is the volume of the melting chamber [m ³ ];

V is the volume flow of glass through the space assuming the completion of the melting process [m ³ s -1] and the utilization of the melting space for dissolution. Here, uq expresses the relationship between the mean time for the process itself, and the theoretical residence time of the molten glass in the melting medium, the so-called geometric residence time, which is equal to the ratio of volume and volume flow V

W by space r _G = Ž:

^at d = -, at _D e (Q; l) (3)

L

It can be seen from equations (1-2) that the specific energy consumption is inversely proportional and the volumetric power is proportional to the utilization of the melting space.

The term for the use of melting space in the case of dissolving sand grains is composed of two parts of dead space, where np, includes closed circulation and regions of almost static glass (eg corners). This value has been previously determined, for example, by the method of transient characteristics as mentioned above, then indicates the area where all the grains of sand are already dissolved, but the respective glass is still heated in space (overprocessing). The use of the melting space for the dissolution of sand is then given by:

at _D = (\ - \\ m _G - _D m \ m = ^T _c c ^T - · m _D ^T -J = ^D (4) + ^{τ α τ} wherein r is the average residence time chamber in fluid flowing glass, and the median dissolution of sand grains under isothermal or near isothermal conditions then satisfies: ř _/ = = r _D = r _Dcnl , where the _engraving time required for dissolving all sand grains at a given or average temperature ar _{/) (} . ", is the residence time of the glass to the fastest The calculation of the utilization of the melting space then works with the values of sand grain dissolution times and the results of modeling the dissolution process in the model melting space under time-temperature regimes on the enamel trajectories (thus negligible buoyancy force acting on sand particles).

In particular, when investigating the effect of flow patterns on power and specific energy consumption, the sand grain dissolution time is constant, or the temperature dissolution time temperature is constant, the effect of the very slow glass convection there is not considered. The dissolution time values of the glass sand particles are determined experimentally. In order to compare individual cases, a reference state is established. When the reference state is reached, the last - critical - particle is dissolved at the exit of the melting chamber. Technologically, such a state corresponds to the state of a “no reserve” process and the real performance would actually be lower. The resulting specific modeling value is the space utilization value ud, which at a constant dissolution kinetics 10 is directly proportional to the space performance (equation 2) and inversely proportional to the specific energy consumption (equation 1). For information, the value of _D for a melting chamber of the melting chamber type assuming a piston flow is 1, and for an isothermal melting chamber with a parabolic glass velocity distribution equal to 0.445. However, a higher value is only achievable with an ideal liquid, the isothermal flow of the glass being difficult to implement in high temperature melting spaces, H where a multi-stage horizontal temperature difference already causes effective circulation flow and a reduction in uq.

Detailed modeling of the influence of elementary and mixed types of flow was performed on the given model melting space, where pure longitudinal circulation flow in both clockwise and anticlockwise directions was considered as the basic flow types (circulation 2 (5 running in vertical planes parallel to main-working flow direction). ) and transverse flow, where the circulation takes place in planes perpendicular to the main-working direction of the flow, and the mixed flows included flow types whose intensity ratio was adjusted by the ratios between the inserted horizontal temperature gradients. dead space, where the utilization of the melting space was only 0.1 to 0.2, while the net cross-flow provided a recovery value of 0.4 to 0.5 due to the disappearance of part of the dead space. however, it was achieved with a mixed flow type where the rapid forward flow component at the enamel level was hampered by a small temperature gradient with a higher temperature at the exit of the space and where a relatively intense transverse flow was produced by a transverse temperature gradient. A temperature gradient of 5 to 10. This optimal type of flow was characterized by spiral enamel trajectories, as shown in Figure 3, and a very low dead space value iiiq as well as a partially reduced dead space value wd (see equation (4)).

Further research has shown how this optimal type of flow and its setting conditions change as the independent variables change, such as the ratio of transverse to longitudinal flow, total circulation flow rate, glass sand particle dissolution time, and melting space length. The effect of the glass properties and the height of the glass layer 5 can then be included in the influence of the overall flow rate. The width of the space, while maintaining temperature gradients, will not substantially affect the utilization. For each pair of dissolution time of the glass sand particles in a given glass and the length of the melting chamber while maintaining the glass layer height, the maximum value of the melting chamber utilization for the dissolving process can then be found. These maximum values ranged above 0.5 over a wide range of sand dissolution times and 10 melting channel lengths; in most cases even between 0.6 to

0.8, which were noticeably better than can even be achieved in the isothermal melting chamber. The dependence of these maximum utilization values on both mentioned quantities in the model melting space is shown in Figure 4. Figure 4 shows the dependence of the maximum utilization value of the melting space on the melting time of glass sand for different lengths of the melting space. It is apparent from the depicted dependencies that the maximum utilization rates of the melting chamber increase with both the dissolution time of the sand and the length of the melting chamber. At the same time, laws have been found governing the temperature gradient values that need to be set to achieve optimal utilization of the melting space.

The results obtained show that it is possible to find and define the optimum type of spiral flow in terms of dissolving glass sand particles and define the optimum conditions for achieving it. There were also defined patterns of changes in optimum utilization and optimal conditions for changes in input parameters. Thus, the prerequisites for transferring the results to real melting spaces were obtained.

2 $ Example 1 / \ (Fig. 5 to 13)

However, in order to apply the results, it is necessary to define a specific melting space, specific energy sources, their distribution and heat output to enable the desired type of spiral flow to be set, which is the object of the present invention.

Achieving the goal is to design a special glass melting space for dissolving glass batch components, especially glass sand, ie to design the shape and suitable dimensions of the melting space, its typical material composition, the way of heating and distribution of heat sources in the melting space, heat so that the melting process takes place at a known average temperature and to achieve a spiral flow type that ensures high utilization of the melting space for the glass melting process. To achieve this state, the prescribed process of mathematical modeling of the melting space is used together with the calculation of its utilization.

In carrying out the process according to the invention, molten glass containing undissolved glass sand particles and located in a horizontal flow-through melting space, an energy source, typically by heating electrodes or industrial glass burners, is treated so that a temperature distribution is created in the molten glass type of flow in the direction of glass flow through the space, thereby achieving high utilization of the given melting space for the dissolution process, thus also high space performance and low specific energy losses.

A cuboid appears to be a special space, the length of which is generally greater than its width and the level of the glass level in the melting space of the glass furnace. The melting chamber is horizontally oriented, flowable and separated and comprises a bottom 1, a foundation wall 2 and an opposing rear flow wall 3 and opposed side walls 4, a vault 5 and a transverse dam wall 7 immersed in the glass 6 in the melting chamber. in at least one row along the longitudinal axis of the melting chamber or parallel to this longitudinal axis, between the loading wall 2 and the transverse dam wall 7 in the glass 6 or the transverse row 9 of energy sources in the glass melting part 6 to induce spiral flow of glass 6 with a circular moving across the melting portion. The energy sources are preferably heating electrodes 10 or industrial burners 11.

The mixture of molten glass 6 with inhomogeneities enters the melting chamber through the upper inlet or the lower inlet 12, which may be tapered or occupy the entire width of the melting chamber and may have different heights. However, too narrow an inlet 12 and an outlet 13 affect the set flow pattern in the space and it is therefore recommended that the inlet 12 or the outlet 13 do not occupy less than about 20% of the front loading wall 2 or the rear flow wall 3. The melting space is lined with a refractory lining used in glass melting furnaces. According to modeling results, electrical heating by means of electrodes 10, which are generally molybdenum, has proved to be the best heating. However, heating by gas or oil burners 11 can also be used, especially in combination with electric heating. A schematic diagram of a typical electrically heated melting chamber is shown in Figure 5.

The melting process takes place in a range of temperatures suitable and common for melting industrial glass, the specific temperature depends on the type of glass, but for conventional glass the average melting temperatures of 1300 to 1500 ° C are to be expected. Continuous flow is ensured by the inflow of glass mixture with solid and gaseous inhomogeneities from the previous space, where the incoming mixture of glass raw materials is heated and melted and taken to another space where homogenization is completed, bubbles are removed, or temperature is stabilized and finished vitreous glass. The performance of the melting chamber can be adjusted in addition to adjusting the appropriate type of spiral flow object of the present invention by particle size distribution (sand grains), by adjusting the composition of the resulting glass and by the average temperature in the dissolving chamber. In the melting chamber of the glass furnace, the same amount of glass 6 is maintained by inlet and outlet.

The typical shape and arrangement of the heat sources, electrodes 10, in the proposed dissolution module 10 is shown in Figure 5.

The object of the present invention is to achieve a certain type of spiral flow in the flow space by arranging heat sources, or by dimensioning the glass furnace insulation so that a transverse circulation flow occurs in the melting space under both factors simulating the optimal type of spiral flow with embedded temperature gradients. This transverse circulation flow has a partially suppressed longitudinal longitudinal component of the glass melt movement at the surface in order to reduce the differences between the residence times of the glass 6 on different trajectories. This can be achieved, for example, by a longitudinal row of electrodes 10 positioned generally from the bottom 1 of the glass furnace so as to form a longitudinal thermal barrier either along the longitudinal axis of the melting chamber where the electrodes 10 will also be located. from the side walls 4 of the melting chamber, where a longitudinal row of electrodes 10 would also be located. More than one longitudinal row of electrodes W can be accommodated in melting spaces designed for high power, but this arrangement seems less advantageous for slowing the horizontal velocity component. level. In order to better achieve the desired type of spiral flow, it is advisable, but not necessary, to place additional sources in the space, for example, a transverse row 9 of electrodes 10, which better ensures retardation of the fast forward component at the surface or prevents longitudinal circulation of glass. Similarly, the burners 11 must be arranged above the surface of the glass furnace, either by placing the burners in the furnace crown 5 or in the side walls 4 and orienting them so as to form a temperature 30 barrier in the melting chamber along the longitudinal axis of the glass furnace. When using the burners 11 as heat sources, it is possible to simultaneously use electrodes 10, predominantly in the longitudinal axis of the melting chamber or at one of the walls which will support the formation of a longitudinal temperature barrier. The distribution of energy into heat sources or the necessary insulation of the melting chamber or its parts, ensuring the optimum character of the spiral flow, must be set by targeted mathematical modeling of the melting chamber. For modeling it is necessary to determine experimentally the dependence of the glass melting time on temperature in the expected melting temperature range. The same temperature dependence can be used for glasses of similar composition and the same grain size of the glass sand. The melting capacity and the specific energy consumption of the melting chamber 10 operating in the critical mode, i.e. without reserve, are determined by modeling, i.e. the last dissolving particles are dissolved just at the outlet 13 of the melting chamber. The energy distribution on the sources is gradually adjusted so that the calculated value of the utilization of the melting space reaches the maximum achievable value or is the highest value in a technically achievable arrangement. During modeling, corrections can also be made in the arrangement of heat sources, but always in order to create the desired type of spiral flow. Required space utilization values should be at least about 0.4, but rather above 0.5.

It is, of course, very useful to estimate how the spiral flow and the corresponding use of the melting chamber will behave at the extreme setting values, i.e. at very low or very high transverse and longitudinal flow intensities ratios with potential return at glass level 6, low or very high. high intensities of glass circulation 6, with very slow or very fast dissolution or with short or very long melting spaces.

A very low transverse flow ratio when there is a longitudinal flow will always result in a decrease in utilization and will approach zero at increasing longitudinal flow intensities. Conversely, at a very high ratio of transverse to longitudinal flow intensities, the value of utilization will approximate and then remain around 0.5.

In the region of the ratio between the flow intensities of the glass 6, which is expressed by the transverse to longitudinal temperature gradient of 5 to 20, the utilization will reach a maximum value of 0.6 to 0.8. Here, the technologically advantageous area is characterized by the maximum value of space utilization. In another region of the ratio of flow intensities, it does not make sense to operate at virtually any total flow intensities, dissolution rates or melting chamber lengths.

The maximum utilization of the melting space in this ratio range is 0.445 at zero circulating flow rate, where the glass 6 flows through the isothermal 3EL rectangular melting space, and gradually increases to a total circulating flow rate of 0.6 to 0.8 at commonly achievable values. circulating intensities, and reach values of 0.5 to 0.6 at high circulating intensities, which, however, are not achieved under normal conditions. Maximum utilization values in the area of optimal ratio between transverse and longitudinal flow intensities are little dependent on dissolution rate and

5, and X within a wide range between 0.6 and 0.8. The very short melting chamber channels show low utilization rates because they do not suffice to develop a spiral flow pattern, the values decrease to 0.4 at a melting chamber length of 0.5 m, and will approach 0.4 for even shorter spaces. For very long melting chamber channels, the utilization value will be kept relatively high, around 0.6 and above, but the necessary optimum ratio between transverse and longitudinal flow intensities will increase disproportionately. The specific objective is to transfer the character of the temperature field created in the model melting space by means of temperature gradients to the proposed specific melting space, which differs from the model melting space mainly by exhibiting temperature losses through interfaces and heated by specific sources such as electrodes 10 or burners 11 in such an assembly. and distributing the supplied energy such that a temperature field is created within the space that produces the desired spiral type of glass flow 6, characterized by high utilization of the melting space and corresponding flow pattern in the model device. This object is achieved by designing a first arrangement of the melting chamber, based on the knowledge of the original model x • X device by mathematical modeling of the temperature and velocity field of the glass melt and the course of the dissolution of sand grains on the trajectories of the glass produced by the inserted energy into the ordered heat sources and losses in the proposed variant. The performance of this arrangement is adjusted after the first calculation so that at a predefined and maintained average temperature in the melting chamber, the last glass sand grain melts just at the outlet 13 of the melting chamber, i.e. to operate without the melting margin. This state is called critical. Calculations are obtained dissolution time of the sand grains thereon disadvantageous critical path TDcrii, space (grain dissolved just at the outlet from the space and the given trajectory determined maximum melting power based on the critical state) and the relevant geometrical time V _R ^T G ^ ~ _rr, ... ₅ delays V, sand dissolution times on the other trajectories to be monitored _(d is 10 a X more) also their mean value of glass sand particles dissolution time, and from the distribution of times glass residence time on monitored trajectories its mean residence time τ in space at critical setting. Using the equation (4), the corresponding use of the space ud is then obtained, and the specific energy consumption for heat losses is calculated from the power and energy data. io The first arrangement may be, but does not necessarily have to be, reference and simulates an arrangement corresponding to a conventionally heated device that exhibits low space utilization value. The results of the calculations at the expected advantageous type of flow with high utilization of the melting space (hereinafter the space) are then compared with the reference and from their comparison

other modified variants come out. As already mentioned, it is not always necessary to calculate the reference setting, and when searching for the optimum spiral flow, the following calculations can be based only on the obtained space utilization values, where good values start at around 0.4. The aim is then to get as high a value as possible for the utilization of the melting space Ø between about 0.6 to 0.8.

The second arrangement is also based on the results of modeling on the melting chamber with pre-set temperature boundary conditions, however, the location and dimensioning of selected heat sources or the dimensioning of the interface insulation are already set to better achieve the described advantageous type of spiral flow. In the first variant, the use of the melting space in this variant, the capacity of the space and the specific energy consumption are calculated according to the 1V procedure already mentioned, and optionally compared with the reference values of the first arrangement. According to the results, the arrangement of sources, eventually insulation and distribution of supplied energy will be adjusted in the direction in which the utilization is expected to increase. The direction of the adjustment is determined by means of the already acquired general laws governing the use of the melting space. In the second variant, a second set of recovery, specific energy consumption and power is obtained. Where appropriate, the design of improved variants shall continue until the maximum achievable value of space utilization is achieved.

Thus, the process for designing a high utilization melting chamber is broken down into the following steps:

1. Determination of temperature dependence of sand grain dissolution time in laboratory and determination of temperature dependence of average dissolution rate on temperature.

2. Design of basic dimensions and method of heating of the new melting space using common design knowledge and results from the original model space on the basis of performance requirements and observing the necessary melting conditions (average temperature).

3. Calculation of the utilization of the melting space in the reference arrangement corresponding to the conditions in a classically operated plant. This step is not inevitable.

4. Calculation of utilization in the melting chamber with proposed parameters corresponding to the expected desired type of spiral flow.

5. Repeated adjustments of conditions and calculations leading to the arrangement and conditions at which the highest utilization of the melting chamber and its corresponding melting capacity and specific losses are achieved in terms of theory and practice.

Special melting room for melting of glass sand grains in flat glass of the tloat type operating at an average temperature of 1400 ° C and with the required output of at least 20t / 24h. Due to the high specific powers obtained in the previous model space with set temperatures, a relatively small 5-cuboid melting space with a length of 2m, a width of 1m and a glass level of 6 0.5m was designed. A detailed diagram of this space is shown in Figure 6. The walls of the melting chamber are composed of layers of refractory material, the vault 5 being low, slightly arched. Input 12 is positioned across the width of the melting free of either one at the bottom, or at the level of the glass 6, and occupies 20% of the front foundation wall 1U second output 13 is then formed by flow of molten glass near the surface 6 across the width of the melting space ^/ area whose ^x it also represents 20% of the rear flow wall. The melting chamber is heated by a longitudinal row of 6 molybdenum electrodes 10 positioned from the bottom 1 along the axis of the melting chamber. The electrodes 10 are connected in a manner wherein the row of electrodes is divided into three pairs, each pair comprising one transformer. This makes it possible to divide the power of the electrodes into three 15 zones and thus set the desired power and therefore temperature gradient. The method makes it possible to regulate the energy supply to the molten glass in the individual parts of the furnace and thus to adjust the nature and intensity of the natural flow in the melting chamber.

Figure 6 is a detailed diagram of the proposed space for melting flat glass with the upper inlet 12. In the first phase of modeling, the energy distribution at 20 electrodes 10 was set to simulate the type of flow common in conventional glass furnaces (reference setting). The inlet 12 to the melting chamber was at the molten glass level 6. By concentrating the energy on electrodes Nos. 5 and 6, a transverse thermal barrier was created which induces the usual longitudinal circulation flow. The distribution of energy on electrodes in% is given in Table 1.

2.5 Table 1

Energy distribution on the electrodes 10 according to their numbering in Figure 6 at the reference heating setting and with the upper input 12.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 0 0 118.6

The flow pattern was controlled to match the pattern known from conventional 3Q glass melting furnaces.

In Figure 7, the resulting velocity distribution in longitudinal axial section through the melting space is shown by sections of glass trajectories traveled in 30 s, representing the reference case.

Critical and other disadvantageous dissolution paths have also been obtained, the projections of which in longitudinal axial vertical section through the melting space are shown in Figure 8, which illustrates a reference case.

The resulting velocity distribution and trajectory shapes correspond to the results obtained on conventional devices, so the reference case is qualitatively set correctly.

For the dissolution of sand, experimental data were obtained by repeated laboratory melting of the glasses and by counting the undissolved grains of sand in the resulting glass samples obtained in time sequence at temperatures of 1300 to 1500 ° C and at intervals of 50 ° C. For an average sand grain dissolution rate of an initial maximum grain diameter of 0.5 mm, 1R I was obtained by an empirical equation [36]: v _Diss = 1 ₍ 56x10 'exp (0.0153T) [ms'], where T is the temperature in K.

This equation was applied to the dissolution process taking place in the melting chamber with temperatures and flow set to the reference case and later to other cases.

The following values were obtained by modeling of the final variant describing the classical setting, complying with the average temperature of 1400 ° C and processing:

Average temperature: 1400 ° C.

Dimensions of the melting chamber 2x1x0,5 m - length, width, height.

Input 12: Upper.

Electric heating output E: 118.6 kW.

Critical Power V: 6.79x10)? mV = 13.65 t / 24h = 6.82 t / (24hm ² ).

Average residence time of enamel in space A 13 888 s.

Average time of sand grain dissolution * 0: 2451 s.

Geometric residence time ^τ ΰ = V: 14724 s.

Dead space fraction by enamel circulation mg: 0.050.

Dead space fraction after sand grain dissolution mo: 0.825.

Share of utilization of melting space wq: 0 _f 166.

. Em

Specific loss ^V P: 751 kJ / kg.

The measured reference power of the melting module 6.82 t / (24hm ² ) is high compared to that of conventional glass furnaces, but it should be noted that in this case the set average temperature of 1400 ° C is relatively high; the highest possible power

Critical - when there is no melting reserve in the space and that the performance is only related to the completion of the dissolution of the sand grains. With a 50% margin, the specific power is only 3.41 t / (24hm) and this value is already realistic. The same situation applies to specific losses, which at 50% reserve would be 1502 kJ / kg, which is also a realistic value given the high average melting temperature of 1400 ° C.

The detected dead space portion mr, for a given type of flow, is much lower than expected and is measured, for example, by measuring the furnace transition characteristics. However, checking the furnace residence time distribution curve in the furnace did not reveal irregularities on this curve, which could reveal the recycling of some continuous trajectories due to numerical errors in the IQ calculation (then increasing the ř value and decreasing the calculated ma value). j is the fact that the transverse temperature barrier was only adjusted by the power on the axially positioned electrodes W. This has already produced a certain amount of transverse flow and, as a result, reduced the mr value. Using a conventional transverse temperature barrier would make the use of the melting space even lower.

4.5. Next, the energy was adjusted on the individual electrodes 10 to achieve the desired type of spiral flow.

*

At the final setting, see Table 2, substantial changes in the glass flow pattern and the typical spiral nature of the critical and close glass trajectories are shown, as shown in Figures 9 and 10. Figure 9 shows the resulting velocity distribution over the longitudinal axial section through the melting space shown and is the optimum case. Figure 10 shows the projections of critical and other slowest trajectories for dissolving sand grains into longitudinal axial vertical section through space and represents an optimal case.

Table 2

The energy distribution on the electrodes 10 according to their numbering in Figure 6 at the optimal variant of the heating setting and at the upper input 12.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 33.5 39.4 46.6

The final variant with the power distribution shown in Table 2 gave the optimum result:

Average temperature: 1400 ° C.

Dimensions of melting chamber 2x1x0,5 m- length, width, height.

Š Input 12: Upper.

Electric heating output E: 119.5 kW.

An average transverse temperature gradient of 45 K / m, an average longitudinal gradient of 8K / m, an average transverse to longitudinal gradient of 5.6.

Critical power P: 2.63x10 ⁴ m ³ s ^- l = 52.86 t / 24h = 26.43 t / (24hm ² ).

The average residence time of the glass in the space ϋ 3760 s.

Average time of sand grain dissolution: 2498 s.

IN

Geometric residence time ^r G = V: 3807 s.

The proportion of dead space through the circulation of enamel we. 0.012.

Dead space share after melting grains of sand mp: 0.336.

15. Share of utilization of melting space uy. 0,656.

Specific losses kp _; 196 kJ / kg.

This result already shows a substantial improvement due to the setting of a more efficient type of flow in the melting chamber. Utilization of the melting space up increased by 3.95x compared to the reference case, the melting capacity of the space increased by 3.87x and the specific losses decreased by 3.83x. Considering 50% of the melting reserve, the space output would be 26.43 t / 24h and the specific dissolution capacity would be 13.22 t / (24hm ² ). The conditions for the required performance of the melting chamber were met.

When operating an optimized glass flow device, the problem arises in the occasional leakage of the unsold batch from the level of the previous space through the upper inlet into the dissolution chamber. This problem was solved by placing the inlet 12 in the area at the bottom 20 of the dissolution chamber, as shown in Figure 11. Figure 11 shows a detailed diagram of the proposed lower glass inlet flat glass melting chamber.

In this case, it will be demonstrated to achieve optimum flow settings using two variants, the first and the last variant - optimal. The first setup was based on the results obtained on the original model device with the set temperature field [33-34]. In the first ►

In the variant, virtually the same power was set on all electrodes 10 as shown in Table 3.

Table 3

The energy distribution on the electrodes 10 according to their numbering in Figure 11 at the first heating setting variant and at the upper input 12.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 40.6 40.6 41.8

$ The results of the calculation of the first variant are as follows:

Average temperature: 1400 ° C.

Dimensions of melting chamber 2xlx0 ₍ 5 m - length, width, height.

Input] _2: Lower.

Electric heating output £: 122.9 kW.

Average transverse temperature gradient 40 K / m, average longitudinal gradient 8K / m, average transverse to longitudinal gradient 5.

Critical power É: 2.49x10 ' ⁴ mV ¹ = 50.11 t / 24h = 25.05 t / (24hm ² )

Average residence time of glass in the space: 3988 s.

Average time of sand grain dissolution: 2531 s.

IN

J25 Geometric residence time ^T G: 4011 s.

Dead space fraction of enamel circulation 0,006.

The proportion of dead space after melting grains of sand mo '. 0.365.

Utilization rate of melting space uq: 0.631.

Specific losses bp 212 kJ / kg.

2Q The flow pattern with the change of the location of the inlet 12 has not changed. Modeling continued until the optimum case was reached.

The optimum case is illustrated by Table 4 and Figures 12 and 13. Figure 12 shows the resulting velocity distribution in longitudinal axial section through the melting space shown by sections of the glass trajectories traveled in 30 s as an optimal case. Figure 13 shows $ 2. projections of critical and other slowest trajectories for dissolving sand grains into longitudinal axial vertical section through space, an optimal case.

The energy flow setting in the optimal case is in Jabula 4.

Table 4

Energy distribution on the electrodes 10 according to their numbering in Figure 6 at the optimum heating setting and at the inlet 12 at the bottom 1.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 34.8 41.0 48.4

The results of the last - optimal - variant calculation are as follows:

Average temperature: 1400 ° C.

Dimensions of melting chamber 2x1x0 ^ m - length, width, height.

Entry 12: Lower.

Electric heating output E: 124.2 kW.

Average transverse temperature gradient 45 K / m, average longitudinal gradient 7K / m, average transverse to longitudinal gradient 6.4.

Critical power 5 2.54x10 ⁴ mV = 51.05 t / 24h = 25.53 t / (24hm ² ).

Average residence time of glass in space t; 3915 s.

Average time of sand grain dissolution: 2545 s.

IN

Geometric residence time ^r G = Ø: 3943 s.

Dead space fraction by glass circulation m _c : 0.007.

The proportion of dead space after melting grains of sand mo. 0.350.

Share of utilization of melting space ud '. 0,646.

Vp specific losses _; 210 kJ / kg.

Comparison of the first and the optimal variant shows that the first assumed variant already differs little from the optimal variant. Thus, the results are less sensitive to small changes if there is a well-founded idea of what is to be achieved.

For comparison, values from the reference case were used with the inlet located at the surface. According to the calculation, space utilization increased 3.89x, melting power increased 3.74x and specific Τξ, losses decreased 3.58x. Power at 50% melting reserve would reach 25.53 t / 24h and specific power 12.76 t / (24hm ² ). The values are only slightly worse than in the case of a level inflow, the performance of the space exceeds the required 20t / 24h and the last arrangement can be used with both inputs.

Example 2 (Figs. 14-17) v

0.5n as in the example

Special space for melting grains of glass sand in glass for the production of spectacle moldings operating at an average temperature of 1300 ° C and with the required output of at least 8t / 24h.

5 (The same special area of length prostorm, width Im and height of layer 1 is available for melting, the inlet 12 to the melting chamber is located at the bottom 1 (see Figure 11), the heating is again electric, but the heat sources allow dissolution of only 1300 ° C. Due to the similar composition of the glass and the same raw materials used, the same temperature dependence of the temperature of the sand grains was used as in Example 10. The reference case was also solved, although it was assumed that lowering the average temperature would not on the utilization of melting space [34], the resulting reference variant yielded the following distribution of electrical power on the electrodes 10.

Table 5

Energy distribution on the electrodes 10 according to their numbering in Figure 6 at the reference heating setting.

Electrodes 1 + 2 3 + 4 5 + 6 Power [kW] 0 0 106.5

The resulting type of flow and the course of critical and similar trajectories did not differ substantially from the flow at 1400 ° C at the reference setting, as shown in Figures 14 and 15. s as a reference case. Figure 15 shows projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal axial vertical section through space as a reference case.

The results of the solution of this reference case are as follows:

Average temperature: 1300 ° C.

Dimensions of the melting chamber 2x1x0,5 m - length, width, height.

Entry 12: Lower.

Electric heating output E: 106.3 kW.

Critical power Ø: 3,78x10 ⁶ mV = 0,76 / 24h = 0,38 t / (24hm ² )

Average residence time of glass in space τ: 63206 s.

/

Average time of sand grain dissolution: 10131 s.

IN

Geometric residence time ^r G = 1 ': 264355 s.

Dead space ratio by glass circulation mc: 0.761.

Dead space share after melting grains of sand mp 0.840.

Share of utilization of melting space ud. 0,038.

Specific losses: 12080 kJ / kg.

The case is very disadvantageous, the lower entrance to space plays a big negative role. There has already been a large proportion of mc dead space, losses are extremely large, critical trajectories and others are moving close to the bottom 1 at low temperatures, and the power is then very low. The IQ case cannot serve as a reference because of its extreme disadvantage, but it shows the extraordinary effect of an inappropriate type of flow on the efficiency of the dissolution process.

In a further procedure, the powers on the electrodes 10 have been adjusted to create the desired type of optimum flow in the melting chamber. The power distribution is shown in Table 6, while the velocity distribution and critical trajectory along with similar ones are shown in Figures 16 and 17.

Table 6

Energy distribution on the electrodes 10 according to their numbering in Figure 6 at optimal heating settings.

Electrodes 1 + 2 3 + 4 5 + 6 Performance [kW] 29.4 34.7 41.0

Figure 16 shows the resulting velocity distribution in a longitudinal axial section through the melting space shown by sections of glass enamel trajectories traveled in 30 s, which is the optimal case. Figure 17 shows projections of critical and other slowest trajectories for dissolving sand grains into longitudinal axial vertical section through space, representing an optimal case.

The results of the optimal variant solution are as follows:

Average temperature: 1300 ° C.

Dimensions of melting chamber 2x1x0,5 m - length, width, height.

Entry 12: Lower.

Electric heating output E: 105.2 kW.

An average transverse temperature gradient of 50 K / m, an average longitudinal gradient of 7K / m, an average transverse to longitudinal gradient of 7.1. Critical power Ě; 5,59x10 ' ⁵ mV = 11,23 t / 24h = 5,62 t / (24hm ² ) Average residence time of the glass in the space ΰ 17025 s. Average dissolution time of sand grains D: 10599 s. V Geometric residence time of the glass ^T G = Ø: 17895 s. Dead space fraction by glass circulation mp: 0.049 sec. Dead space fraction after sand grain dissolution mo: 0.378. Share of melting space utilization uq. 0.592. 71 = ^Stg ió Μ Specific losses: 809 kJ / kg. The resulting values meet the assumption of power, which at the assumed 25% melting reserve reached 8.42 t / 24h for the entire plant, ie 4.21 t / (24hm ² ). The specific losses in kJ / kg are again very low as expected. EXAMPLE 3 (Figures 18 to 22) It is necessary to design a special room for melting the glass sand in white enamel, which will achieve a power of at least 300 t / 24 h at an achievable average melting temperature of 1425 ° C. The required energy was to be supplied as needed by both gas burners and electrodes 10, but only the electrodes 10 proved to be sufficient to cover the losses. , with a total volume of 146 m ³ . A diagram of the space with the proposed heating of the electrodes 10 in both reference and optimized cases and with the inlet 12 at the bottom of the inlet face is shown in Figure 18a (vertical section along the longitudinal axis) and 18b (horizontal section below the surface). In more detail, Figs. 18a, 18b show a schematic of a proposed melting chamber with heating of the electrodes 10 and the location of the electrodes 10 in sections XZ (a) and XY (b). Table 7 shows the energy distribution of the electrodes 10 according to their numbering in the figure over their sources in the reference arrangement even in the first optimized case. & Table 7 The energy distribution on the electrodes according to their numbering in Figure 18 at the reference and first optimized variant of the heating setting.

Electrodes 1 -2 3-4 5-6 7-8 9 - 10 11-12 13 - 14 15 - 16 20-21 22-23 23-24 25 - 26 Performance Ref. 0 0 0 0 0 0 0 0 117.7 117.7 117.7 117.7 Oot. 14.8 19.7 24.6 39.4 49.2 49.2 49.2 49.2 49.2 49.2 49.2 49.2

The resulting velocity distribution in the longitudinal axial section through the melting space shown by the 30-second melt trajectory sections in the reference case is shown in Figure 19 and the projections of critical and other slowest trajectories for dissolving sand grains into both longitudinal and axial vertical cross-sectional spaces are also shown in Figure 20.

Figure 19 shows the resulting velocity distribution in longitudinal axial section through the melting space shown by sections of enamel trajectories traveled in 30 s as a reference case.

Figure 20 shows the projections of critical and other slowest trajectories for dissolving sand grains into a longitudinal axial vertical section through space as a reference case.

tQ The results of the reference case are as follows:

Average temperature: 1425 ° C.

Entry 12: Lower.

Dimensions of melting chamber 6,57x2x1,0 m - length, width, height.

Heating power: 471.0 kW.

Critical power ý: 2,20x10 ' ⁴ m ³ s'' = 44,1 t / 24h = 3,35 t / (24hm ³ ) i

Average residence time of glass in space 1: 36 450 s.

Average time of sand grain dissolution: 2433 s.

IN

Geometric residence time ^r G = V: 59 875 s.

Dead space fraction by enamel circulation mc,: 0.391.

Dead space fraction after sand grain dissolution mg: 0,933.

The utilization rate of the melting space ue> 0.041

Specific Loss = 924 _: kJ / kg.

The resulting values characterize well the classic glass melting furnace. The relatively high specific power is again given by the fact that it is a critical (maximum possible) power 25 of the space and the process involves only dissolving the sand grains.

In the next procedure, based on past calculations on the model melting space and the experience gained, a new distribution of the energy supplied to the electrodes 10 has been proposed, which is shown in Table 7 for the optimum case. The resultant distribution of velocities in the longitudinal axial section through the melting space shown by sections of the enamel trajectories traveled in 30 s in the first optimized case is shown in Figure 21 and the projections of critical and other slowest trajectories for dissolving sand grains into the longitudinal vertical vertical section through space. also in the first optimized case are shown in Figure 22.

The results of the first optimized case are as follows:

$ Average temperature: 1425 ° C.

Entry 12: Lower.

Dimensions of melting chamber 6,57x2x1,0 m - length, width, height.

Heating power: 492.3 kW.

Average transverse temperature gradient 55 K / m, average longitudinal gradient 10 K / m, average 10 transverse to longitudinal gradient 5.5.

Critical power Ř: 2,97x10 ' ³ mV = 597 t / 24h - 45,4 t / (24hm ³ ).

Average residence time of glass in the space: 3994 s.

Average time of sand grain dissolution: 1795 s.

IN

Geometric residence time ^τ ΰ: 4419 s.

Dead space fraction by glass circulation mc / · 0.096.

Dead space fraction after dissolution of sand grains m _D : 0.551.

Utilization rate of melting space uo: 0.406

Specific ^L = 71.2 _: kJ / kg.

The resulting values provide an unexpectedly high dissolution performance of the melting chamber. This is due to an increase in the utilization of the melting space by one order compared to the reference case. Lower values of the average dissolution time of the sand grains show that the dissolution in the optimized case took place under more favorable temperature conditions. The high performance of the equipment results in very low specific losses. If we add about 16% melting reserve, the space would provide a dissolution capacity of 500 t / 24h. However, a utilization value of 0.41 shows that the space flow can still be optimized.

In subsequent steps, the melting power distribution on the electrodes 10 has been altered to extend the residence time of the glass that corresponds to the critical trajectory. Two other cases with optimized energy distribution to individual electrode pairs were calculated. The second variant achieved a significant improvement in utilization, the third variant differed very little from the previous one by 3Θ, thus the utilization approached the optimal value. The third variant was thus considered za finite. The distribution in the third optimized variant is in Table 8.

Table 8

The energy distribution on the electrodes 10 according to their numbering in Figure 18 at the third optimized variant of the heating setting.

Electrodes 1 -2 3-4 5-6 7-8 9 - 10 11-12 13 - 14 15 - 16 20-21 22-23 23-24 25-26 Performance Γ> n r. * · * ’· * / j Ref. 0 0 0 0 0 0 0 0 25 25 25 25 From T. 10.0 9 9 8 8 7 7 6 9 9 9 9

The resulting velocity distribution in the longitudinal axial section through the melting chamber and the projections of critical and other slowest trajectories for dissolving sand grains into the longitudinal axial vertical section through the space are very similar to the first optimized case.

The results of the third optimized case are as follows:

1 (5 Average temperature: 1425 ° C).

Entry 12: Lower.

Dimensions of melting chamber 6,57x2x1,0 m - length, width, height.

Heating power: 507 kW.

An average transverse temperature gradient of 55 K / m, an average longitudinal gradient of 8 K / m, an average ratio of 15 transverse to the longitudinal gradient of 6.9.

Critical power Ě; 4,39x1O ' ³ m ³ s'' = 881 b / 24h = 67 b / (24hm ³ )

Average residence time of enamel in space *; with.

Average time of sand grain dissolution: 1782 s.

IN

Geometric residence time: 2994 s.

Dead space fraction by enamel circulation mg: 0.164.

Dead space fraction after sand grain dissolution mg: 0,288.

Share of use of melting space up: 0.595

Specific losses: kJ / kg.

The resulting values show extremely high performance and very low specific losses. Thus, the proposed space with optimized spiral flow has a very high ability to dissolve glass sand even after considering a considerable melting margin. The case shows that the dissolution of glass sand in a given space under given conditions cannot very likely become an event limiting the intensity of the entire melting process.

Example 4 (Figures 23 to 24)

There is a melting chamber, heating with three pairs of transverse burners 11 for melting soda-lime glass and pressing to produce domestic glass products. The device has a length of 6 m and a width of 2 m in the diameter of the melting part. The height of the glass level 6 is 0.6 m. The average melting temperature is about 1400 ° C. A diagram of half of the original apparatus is shown in Figure 21. Figure 21 shows the original glass melting furnace in longitudinal axial section. In the original configuration, the heating energy was distributed to the individual burners 11 according to Table 9. The numbering in the table follows from left to right according to the W figure.

^of \

Table 9

The energy distribution over the three pairs of burners 11 according to Figure 23 from left to right at the original burner setting 11 and the reference case is as follows:

Output of the first pair of burners 11: 637 kW.

¹ \

Output of the second pair of burners 11: 700 kW.

Output of the third pair of burners 11: 750 kW.

Total burner output: 2087 kW.

Electrode input: 0 kW.

2.The results of the reference case are as follows:

Average temperature: 1400 ° C.

Input 12: With surface charge.

Dimensions: length 7,2 m in total, length of melting section 5,2 m, width 1,65 m, enamel depth 6 is

0,6 m.

Critical power É: 6.47x10 ⁵ mV = 2.52 t / (m ³ 24h) = 13 t / 24h.

IN

Geometric residence time = Ø: 79598 s.

Share of utilization of melting space 0 _f 059.

- ^Exg

Specific energy consumption ' ^l ' P: 13866 kJ / kg.

The resulting values show a small utilization of space, which corresponds to a low melting capacity of 30 devices. In the present arrangement of the burners 11, however, it was not possible to substantially influence the flow pattern in the desired direction. Therefore, the heating system has been reconstructed by placing 14 vertical electrodes 10 from the bottom 1 in the longitudinal axis of the melting chamber.

Thus, the necessary longitudinal temperature barrier in the glass melt and the desired type of spiral glass flow have been created. Dissolution of sand grains was considered a critical process. The resulting melting process arrangement is shown in Figure 24 and the energy distribution to the burners 11 and electrodes in Table 10. With the new setting, the transverse spiral flow required was achieved in the electrode region 10, 5.

Figure 24 shows the arrangement of the burners 11 in the melting chamber in an optimized case.

Table 10

Energy distribution to the burners according to their numbering in Figure 22 in an optimized setting of 10 burners and electrodes.

Electrode input: 1400 kW (electrodes 1-2 -> 308 kW; electrodes 3-4 -> 266kW; electrodes 5-6 A210kW; electrodes 7-8 -> 168kW; electrodes 9-10 -> 112kW; electrodes 11-12 - > 70 kW; electrodes 13-14 -> 70kW; electrodes 15-18 -> 98kW)

Burner output: 16.8 kW

The results of the optimized layout are as follows:

Average temperature: 1425 ° C

Input 12: With surface charge.

Dimensions of the melting chamber: length 7.2 m in total, length of the melting section 5.2 m, width 1.65 m, 20 °. enamel depth 0.6 m.

Heating output: 1400 kW on electrodes 10, 16.8 kW on TL burners

An average transverse temperature gradient of 55 K / m, an average longitudinal gradient of 12 K / m, an average transverse to longitudinal gradient of 4.6.

Critical power V: 1 ₍ 81 χ 10 ' ⁴ mV = 7.05 t / (m ³ 24h) = 36.3 t / 24h

IN

2 ^ 3, Geometric residence time ^r G = V: 28453 s.

Utilization rate of melting space ud '· 0 ₍ 239.

- ^Ετ °

Specific energy consumption * Vp: 3335 kJ / kg.

The melting power of 30t / 24h can be achieved at the given setting in Figure 24 and Table 10 at about 17% reserve. This reserve is not too high, but in steady operation, 3Q is sufficient. Although the specific melting capacity of 3.02 t / (24hm ² ) is 2.8 times higher than the reference setting, it is relatively low compared to the previously mentioned cases. The problem is in the existence of a layer of trunk on the surface that does not allow the desired spiral flow to develop fully. However, the furnace operates in both cases uneconomically in terms of energy consumption; in the optimized case, the burners 11 can be eliminated and the furnace operated as an all-electric furnace.

In the majority of cases mentioned in the examples, extremely high dissolution rates of the designed space were achieved. However, the results cannot be automatically applied to the entire melting process. It is a realization of only one melting process, the dissolution of sand grains, in a situation where the melting space has no reserve. The performance of such a special melting chamber can then be further reduced, but not substantially [31], considering also the refining process ld. Most significantly, however, the performance of the melting chamber can be reduced if the batch is also converted into glass in the same chamber, as is evident from the results in Example 4. Indeed, once the melting performance limitations have been removed by optimized glass flow, it becomes a control event. of the entire melting process, precisely the batch conversion and the entire dissolution capacity of the space will not be utilized unless the batch conversion rate is increased. Nevertheless, specific melting capacities higher or significantly higher than 10 t / m ³ 24h can be expected. Major efforts should then be made to increase the conversion capacity of the batch to glass.

Reference numbers Bottom Foundation wall Rear flow wall Side walls Vault Enamel Transverse dam wall Transverse row 9 Power sources Heating electrodes Industrial burners Inlet outlet

3.

Literature

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36.

International Conference of Glass Experts, Brig, March 26-29 (Switzerland). Nemec, L., Jebava, M .: Eur. J. Glass Sci. Technol. A, 47 (3), 68-77 (2006). Nemec, L., Jebava, M., Cincibusova, P .: Ceramics-Silicates, 50 (3), 140-152 (2006).

Nemec, L., Cincibus, P .: Ceramics-Silicates, 52 (4), 240-249 (2008).

Nemec, L., Cincibus, P .: Ceramics-Silicates, 53 (3), 145-155 (2009). Polak, M., Nemec, L .: Ceramics-Silicates, 54 (3), 212-218 (2010).

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Polak, M., Nemec, L .: Journal of Non-Crystalline Solids 358 (2012). Cincibus, P., Nemec, L .: Accepted in: Eur. J. Glass Sci. Technol. A, 53 (2012).

Polák, M .: Unpublished Results.

Claims (5)

5, 1. A glass melting furnace for the continuous melting of glass by controlled glass convection, in which molten glass is treated, comprising undissolved particles, in particular glass sand, located in a horizontally oriented flow and separate melting space by means of energy sources; the melting chamber comprises a bottom (1), a foundation wall (2) and a rear flow wall (3), and opposed side walls (4), a vault (5), and a transverse dam wall (8) submerged in the glass (6); characterized in that energy sources are arranged in the melting chamber in at least one row in the longitudinal axis of the melting chamber or parallel to this longitudinal axis, between the loading wall (2) and the transverse dam wall (7) in the glass (6) or a transverse row (9) of energy sources in the glass melting portion (6) to induce a spiral flow of glass (6) with circular motion across the melting portion. Glass melting furnace according to claim 1, characterized in that the energy sources are arranged in one or both side walls (4). Glass melting furnace according to claim 1 or 2, characterized in that the energy sources are arranged at regular intervals from one another. Glass melting furnace according to claims 1 to 3, characterized in that the energy sources are heating electrodes (10) and / or industrial glass burners (11). / \ Glass melting furnace according to one of the preceding claims 1 to 4, characterized in that the melting portion is terminated by a transverse row (9) of heating electrodes (10) installed in the bottom (1).