JP5939020B2 - Rotary kiln for cement production - Google Patents

Description

  The present invention relates to a rotary kiln for manufacturing cement that uses flammable waste such as waste plastic as an auxiliary fuel for firing cement clinker.

  Combustible waste such as waste plastic generates a sufficient amount of heat by incineration. For this reason, in order to effectively use the amount of heat generated by the combustion, in many cement manufacturing facilities, the above combustible waste is burned by blowing it in an air flow from the front of the kiln into a rotary kiln for cement clinker firing. Technology that reduces the amount of pulverized coal used in the main fuel burner is employed.

  By the way, when this kind of combustible waste is thrown into the rotary kiln, if the combustible waste ejected from the auxiliary burner lands on the cement clinker in the firing zone in the rotary kiln, As a result, the cement clinker around the combustible waste is exposed to a reducing atmosphere. As a result, an increase in free lime and a change in color occur, resulting in a decrease in cement quality.

  For this reason, the combustible waste is blown out at a high speed with air, landed at the position of the raw material beyond the firing zone, and the combustion of the combustible waste is completed before moving to the firing zone together with the raw material. Technology has been proposed, but if the flammable waste is spouted with air at a high speed, for example, the supply pipe will be worn out, the power consumption of the blower will increase, or the heat loss in the system will increase. By doing so, on the contrary, it will cause economic deterioration.

  In order to solve such a problem, the inventors previously disclosed in Patent Document 1 below that the end of the rotary kiln is rotatably supported on the end wall of the front part of the kiln, and combustible disposal toward the rotary kiln. A plurality of combustible waste burners for blowing out objects together with air are installed at intervals, and combustible waste to a rotary kiln in which the amount of protrusion of these combustible waste burners is set to 200 to 500 mm. The input structure was proposed.

  According to the flammable waste input structure having the above-described configuration, a plurality of flammable waste burners are provided at intervals from each other, so that the flammable waste can be reliably and securely placed in a predetermined position in the rotary kiln. It can be divided and landed. For this reason, the above-mentioned problems can be solved and it is not necessary to blow the air at a high speed to fly the combustible waste far away. Therefore, the energy consumption for supplying air to the combustible waste burner is reduced. The effect that reduction can be aimed at is acquired.

  However, in the above-mentioned combustible waste input structure, since it is necessary to install a plurality of combustible waste burners, the structure of the front of the kiln and the facilities such as piping are complicated, and a small amount However, there is a problem that it is impossible to prevent the combustible waste before burning from landing on the cement clinker.

JP 2003-90522 A

  On the other hand, in the rotary kiln using pulverized coal as the main fuel, as the main fuel burner, in order to efficiently diffuse the pulverized coal to be ejected and promote combustion, primary air for injecting the pulverized coal is used. A structure in which the main fuel burner is swung around its axis and ejected is adopted.

  Therefore, the present inventors have diligently analyzed measures that can reduce the landing combustion of combustible waste blown into the kiln body in a rotary kiln using pulverized coal as fuel and swirling primary air. As a result of research, it has been found that the landing combustion can be surely reduced between the swirling direction of the primary air and the position of the auxiliary burner for ejecting combustible waste.

  The present invention has been made on the basis of the above-mentioned knowledge, and without causing the flammable waste to be jetted together with the air at high speed, the landing combustion is surely reduced, and the harmful effects caused by the blowing of the flammable waste. It is an object of the present invention to provide a rotary kiln for manufacturing cement that can avoid the occurrence and can efficiently burn combustible waste and effectively use the amount of heat.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that a cylindrical kiln main body is rotatably provided between the kiln front housing and the kiln bottom housing, and the cross section of the kiln main body is provided in the front kiln housing. In the rotary kiln for cement production, provided with a main fuel burner that blows pulverized coal toward the center and heats the inside to a firing temperature, and an auxiliary burner that blows combustible waste into the kiln body. The burner is supplied so that the primary air swirls in one direction around the axis in the axial direction view of the kiln main body from the front side of the kiln, and the auxiliary burner is outside the main fuel burner. and with respect to the vertical line passing through the axis, the top portion of the main fuel burners (0 °) from 10 ° to 45 ° to said one direction and opposite direction to the axis around And it is characterized in that it is arranged within a range.

According to the first aspect of the present invention, the primary air is supplied to the main fuel burner using pulverized coal as the main fuel so that the primary air swirls in one direction around the axis when viewed in the axial direction from the front side of the kiln main body. In this case, the auxiliary burner for injecting the combustible waste is placed in the one direction around the axis from the top of the main fuel burner with respect to the vertical line passing through the axis and outside the main fuel burner. Is disposed in the range of 10 ° to 45 ° in the reverse direction, the swirling flow of the primary air promotes the floating of the flammable waste. As shown in the analysis results described later, the flammability is Most of the waste can be burned in a floating state, and thus the landing rate on the cement raw material (or clinker) can be reduced.

  As a result, it is possible to avoid the adverse effects such as the deterioration of the quality of the cement clinker due to the above-mentioned landing combustion of the combustible waste, and to increase the amount of air to be blown in or to install a large number of auxiliary burners Therefore, since most of the combustible waste can be burned in a floating state in the kiln body, the combustion efficiency can be improved and the amount of heat can be used effectively.

  At this time, the swirling flow by the primary air of the main fuel burner has a smaller influence (flow velocity) at a portion exceeding the half of the radius of the kiln main body and a position deviated from the flame of the main fuel burner. There is a risk that a part of the flammable waste will be put into the chamber and the flammability will deteriorate.

Therefore, the desired floating effect by the swirling flow of the primary air is obtained with respect to the combustible waste blown into the kiln body, and it is reliably burned by the flame of the main fuel burner, and the thermal efficiency for firing. to increase the returns an upper Symbol auxiliary burner is preferably disposed in the range of from the axis of the kiln body and half the inner radius of the kiln body.

Further, the front end surface of the auxiliary burner, by arranging the rear side of the ejection direction than the front end surface of the main fuel burner, the auxiliary burner, be熔損by 1400 ° C. or more high temperature flame from the main fuel burner Can be prevented.

It is the schematic block diagram which looked at the longitudinal cross-section which shows one Embodiment of the rotary kiln for cement manufacture of this invention. It is the schematic block diagram seen from the cross section of the said embodiment. FIGS. 2A and 2B show a front end portion of the main fuel burner of FIG. 1, wherein FIG. 1A is a longitudinal sectional view and FIG. 1B is a transverse sectional view. It is a graph which shows the analysis result of the relationship between the distance from the main fuel burner end surface with respect to the installation position of the auxiliary burner with respect to the main fuel burner, and the average gas temperature of the cross section of a kiln main body. It is a figure which shows the gas temperature distribution of the cross section of the kiln main body of FIG. It is a graph which shows the analysis result of the relationship between the distance from the main fuel burner end surface with respect to the installation position of the auxiliary burner with respect to the main fuel burner, and the average residual oxygen concentration of the cross section of the kiln main body. It is a graph which shows the analysis result of the relationship between the distance from the main fuel burner end surface with respect to the installation position of the auxiliary burner with respect to the main fuel burner, and the average residual volatile content concentration of the cross section of the kiln main body. It is a graph which shows the analysis result of the change of the landing rate of the combustible waste with respect to the installation position of the auxiliary burner with respect to the main fuel burner. It is a longitudinal cross-section which shows the floating and landing locus | trajectory of the combustible waste in the kiln main body of FIG.

  1 to 3 show an embodiment of a rotary kiln for manufacturing cement according to the present invention. A cylindrical kiln main body 1 is provided at one end by a support roller (not shown) provided on an outer peripheral portion. The kiln main body 2 is rotatably supported between the kiln front housing 2 and the kiln bottom housing (not shown) provided at the other end of the kiln main body 1. A pulverized coal burner (main fuel burner) 3 extending substantially in line with the pulverized coal burner 3 is provided, and a waste plastic burner (auxiliary) for blowing waste plastic (combustible waste) into the kiln body 1 in parallel with the pulverized coal burner 3 (Burner) 4 is provided.

  Here, as shown in FIG. 3, the pulverized coal burner 3 has a multi-cylindrical shape, an ignition burner insertion hole 5 is formed at the center, and an inner primary air flow path 6 is formed on the outer peripheral side thereof. Is formed. A central portion primary air outlet 6 a and an inner primary air outlet 6 b are formed at the tip of the inner primary air flow path 6. In addition, a pulverized coal flow path 7 is formed on the outer peripheral side of the inner primary air flow path 6, and a pulverized coal outlet 7 a is formed at the front end thereof. Further, an outer primary air flow path 8 is formed on the outer peripheral side of the pulverized coal flow path 7, and an outer primary air outlet 8a is bored at a tip portion thereof.

  A large number of inner primary air outlets 6b are arranged closely in the circumferential direction on the inner side of the pulverized coal outlet 7a, and are respectively drilled in directions twisted with respect to the axial direction of the pulverized coal burner 3. Thus, as indicated by a dotted arrow in FIG. 2, the primary air flows in one direction around the axis of the pulverized coal burner 3 in the axial direction view from the rear end wall 2 a side before the kiln (in the figure, counterclockwise). In the direction of rotation). At this time, the swirling direction of the primary air can be changed by changing the direction of the inner primary air outlet 6b.

  Moreover, the center part periphery primary air blower outlet 6a provided inside these inner side primary air blower outlets 6b is a fine small hole drilled along the circumferential direction, and primary air is made into the pulverized coal burner 3 by it. It is formed to blow out in parallel with the axial direction.

  On the other hand, the outer primary air outlet 8a arranged on the outer side across the pulverized coal outlet 7a is a large number of small holes arranged at equal intervals in the circumferential direction inside the outer wall of the pulverized coal burner 3, The primary air is blown out parallel to the axial direction of the pulverized coal burner 30.

  Furthermore, the pulverized coal flow path 7 is supplied with the pulverized coal from the pulverized coal hopper 10 through the line 10a together with the carrier air, and the pulverized coal serving as the main fuel from the pulverized coal outlet 7a is supplied to the pulverized coal burner 3. It can be blown out on the carrier air flow parallel to the axial direction.

  A waste plastic burner 4 for blowing waste plastic into the kiln body 1 is attached to the outer peripheral side of the pulverized coal burner 3. The waste plastic burner 4 is a cylindrical member, and waste plastic previously pulverized to a predetermined size and stored in the hopper 11 is supplied from the line 11a by carrier air.

  As shown in FIG. 2, the waste plastic burner 4 is located outside the pulverized coal burner 3, and when viewed in the axial direction from the rear end wall 2 a side of the furnace front housing 2, the vertical line L passing through the axis line L On the other hand, with the top of the pulverized coal burner 3 being 0 °, the pulverized coal burner 3 is disposed within a range of 55 ° in the clockwise direction opposite to the swirling direction of the primary air (counterclockwise in the figure) around the axis from the top. ing.

Moreover, the waste plastic burner 4 is outside the pulverized coal burner 3 and the dimension L _{1 in} the radial direction of the kiln main body 1 from the axis is within ½ of the inner radius of the kiln main body 1. Is arranged. Further, as shown in FIG. 1, the waste plastic burner 4 is set to have a length L _{2 in} which the front end surface is positioned on the rear end wall 2 a side of the pre-furnace housing 2 with respect to the pulverized coal burner 3.

Next, the grounds for disposing the waste plastic burner 4 within the range of 55 ° in the clockwise direction opposite to the swirling direction of the primary air around the axis from the top of the pulverized coal burner 3 are shown in FIGS. 4 to 7. This will be described based on the analysis results shown.
1 and 2, the waste plastic burner 4 is disposed at the top of the pulverized coal burner 3 (0 °), 10 ° clockwise from the top (10 ° on the right), and the same 30 A position separated by 30 ° (right 30 °), a position separated by 45 ° (right 45 °), a position separated by 55 ° (right 55 °), a position separated by 60 ° (60 ° right), and 90 ° (also Gas in the kiln main body 1 for each of the eight types installed 90 degrees to the right and 45 degrees away from the top that is the same direction as the swirl direction of the primary air in a counterclockwise direction (45 degrees left). The temperature and the landing rate of waste plastic were analyzed.

In this analysis model, the kiln body 1 has an inner diameter of 5.0 m, a length of 80 m, a clinker production amount of 145 t / h, pulverized coal is blown from the pulverized coal burner 3 at a speed of 25 m / s, and the waste plastic burner 4 Assuming that the amount of 11 t / h was blown into the waste plastic at a speed of 27 m / s, the supply amount of pulverized coal and waste plastic was 50% in terms of the calorie ratio. Further, the blowing ratio of the theoretical air amount A ₀ of the air amount and the kiln fuel complete combustion from inside the primary air outlet 6b for forming the swirling flow, and 3.4%, the turning direction after the previous furnace The counterclockwise direction was set when viewed in the axial direction from the end wall 2a side.

  4 and 5 show the distance from the end face of the pulverized coal burner 3 in the kiln main body 1 and the gas temperature in the cross section of the kiln main body 1 at each location for the five types of installation positions of the waste plastic burner 4. The result of analyzing the relationship is shown.

  From FIG. 4, the gas temperature is higher when the waste plastic burner 4 is placed at (right 30 °), (right 45 °) and (right 60 °) than when it is placed at (left 45 °). Therefore, it turns out that combustibility is good. Similarly, from FIG. 5, the temperature distribution in the cross section of the kiln body 1 is around the axis when the waste plastic burner 4 is arranged at (right 30 °), (right 45 °) and (right 60 °). It can be seen that the heat receiving of the heat-resistant member (brick) forming the inner wall of the kiln body 1 becomes uniform and the heat load that affects the service life is reduced.

  Moreover, as seen in FIGS. 6 and 7, the disposition of the waste plaburner 4 at (0 °) to (60 ° to the right) of the kiln main body 1 is arranged at (45 ° to the left). Since the unburned oxygen concentration on the kiln bottom side is low and the residual volatile concentration is low, combustion of volatile components from the waste plastic in the kiln body 1 is further promoted. As a result, the combustibility of the waste plastic can be improved.

  Next, FIG. 8 shows the result of analyzing the landing ratio of the waste plastic for each of the eight installation positions of the waste plastic burner 4 and FIG. 9 shows the five installation positions of the waste plastic burner 4. In addition, a landing rate is a calorie | heat amount rate (%) of an unburned part when waste plastics land on the bottom part of the kiln main body 1. FIG.

  From these figures, when the waste plastic burner 4 is installed in the range of (0 °) to (right 55 °), the landing rate becomes particularly low, thereby improving the utilization efficiency of the waste plastic. Further, it is possible to prevent quality deterioration and damage to refractories caused by exposure of the clinker to a reducing atmosphere. Conversely, it can be seen that the landing rate increases rapidly when the waste plastic burner 4 is installed at an angle larger than (right 55 °).

  In view of the above, in the present invention, the waste plastic burner 4 is placed within a range of 55 ° from the top (0 °) of the pulverized coal burner 3 in the clockwise direction opposite to the swirling direction of the primary air around the axis. It was arranged.

  As described above, according to the rotary kiln for producing cement having the above-described configuration, the primary air is applied to the pulverized coal burner 3 counterclockwise around the axis when viewed from the rear end wall 2a side of the kiln main body before the kiln. When supplied so as to turn in the direction, the waste plastic burner 4 is placed outside the pulverized coal burner 3 and with respect to a vertical line L passing through the axis, the top (0 °) of the pulverized coal burner 3. Is arranged in a clockwise direction around the axis up to 55 ° so that the swirling flow of the primary air promotes the floating of combustible waste, and most of it is in the kiln body 1. Can be burned in a floating state, and thus the landing rate on the cement raw material (or clinker) can be reduced. More preferably, the landing rate can be reduced to 5% or less by disposing within a range of 10 ° to 45 °, particularly within a range of 20 ° to 40 °.

  As a result, it is possible to avoid the occurrence of adverse effects such as deterioration of cement clinker quality caused by landing combustion of flammable waste, and without increasing the amount of air blown or installing a large number of auxiliary burners. Since most of the combustible waste can be burned in the kiln body 1 in a floating state, the combustion efficiency can be improved and the amount of heat can be used effectively.

  In addition, this invention is not limited to the said embodiment, For example, a main burner is supplied so that primary air may turn in one direction around an axis in the axial direction view from the kiln front side of a kiln main body. As long as it is, the configuration may be different from that shown in FIG. 3, and the swirling flow can be similarly applied to the case of the clockwise direction instead of the above-described counterclockwise direction. .

1 Kiln body 2 Housing in front of kiln 3 Pulverized coal burner (Main fuel burner)
4 Waste plastic burner (auxiliary burner)
10, 11 Hopper 6b Inner primary air outlet L Vertical line

Claims (1)

A cylindrical kiln main body is rotatably provided between the kiln front housing and the kiln bottom housing, and pulverized coal is jetted toward the center of the cross section of the kiln main body to the firing front temperature. In a rotary kiln for cement production provided with a main fuel burner to be heated and an auxiliary burner for blowing inflammable waste into the kiln body,
The main fuel burner is supplied so that the primary air turns in one direction around the axis in the axial direction view from the kiln front side of the kiln body,
The auxiliary burner 10 be a person outside of the main fuel burner, and with respect to the vertical line passing through the axis, the top portion of the main fuel burners (0 °) from the said one direction and opposite direction to the axis around A rotary kiln for producing cement, wherein the rotary kiln is disposed within a range of from ° to 45 ° .

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