JP4396843B2 - Multi-stage fluidized bed combustion method - Google Patents

Description

In the present invention, a residue with high added value can be obtained by properly combusting a solid woody organic unused resource having a large inorganic content (containing SiO ₂ ≈15%) such as straw. It is related with the baking method to produce | generate.

[Problems of rice bran production (annual generation amount)]
The amount of rice bran generated as a by-product of rice, which is the main food crop, is enormous since it corresponds to about 20% of the raw material rice processed by rice milling.
In recent years, the amount of straw generated every year has increased as food production and consumption increased, and now the amount of waste generated in the world has reached about 100 million per year, and it is also about every year in Japan. Two million tons of straw are generated.

[Situation of reuse of potatoes]
As for how to use rice bran, many researches and developments have been carried out on a global scale for many years, and in each country that actually produces rice, the usage rooted in that region has been taken. We cannot find anything that is low and fully recycled.
Among them, the reuse method, which has been popularized in Southeast Asian rice-producing countries, has achieved certain results. In this method, the reciprocating engine is operated using low-pressure steam (approximately 5 to 7 kg / cm ² ) generated in a boiler that uses the combustion heat as a power source. Because of the advantage that it is possible to operate rice mills that provide rice bran using this power source and to be self-sufficient in energy, this method has been introduced in many rice mills in these regions.

However, this system is very low in fuel efficiency and has a low output, so it is required to increase the size and efficiency. In addition, in the recent rice mill production system of rice producing countries, a new electrification system is required. The actual situation is changing.
[Disposal issue]
The increase in size and electrification of rice mills in recent years has directly led to serious pollution problems related to the disposal of rice bran, which occurs in large quantities every year in many rice-producing countries. In order to deal with such an increasing amount of potato waste pollution, some large rice mills around urban areas in Thailand are incinerating a huge amount of potato waste that is mixed with municipal waste.

In Japan, the amount of rice crackers generated is about 2 million tons per year as described above, and with the recent modernization of post-harvest rice cereals, the generation is concentrated in the region and almost throughout the year. A certain amount tends to be discharged.
Currently, when the processing situation of rice bran generated in rice production areas is seen nationwide, about 80% is processed as agricultural materials, and the rest is disposed as agricultural waste.
There are two types of processing of rice crackers: utilization as agricultural materials and incineration. As examples of utilization as agricultural materials, compost materials, barn bedding, underdrain materials, soil improvement materials, etc. are all low-value-added materials, and it is difficult to say that they are effectively used.

[Status of energy conversion in Tsurugagara]
In order to expand reuse as an energy source, it is expected to promote energy conversion technology with higher added value by conducting research and development projects on energy conversion technology.
This technology has been researched and developed mainly in the world's advanced countries for the last half century. This research and development extends from the physical properties of straw to the process of thermochemical energy conversion. 1) to 3), and some of them are put into practical use.

1) Carbonization (decomposition of volatile matter) charcoal production method When charcoal is heated to about 300-400 ° C and burned, it is carbonized to generate combustible gas and tar as volatile matter. The carbon content of the produced charcoal is about 30 to 40%, and uses other than fuel include horticultural floor soil, anti-oxidant for iron making, and heat insulating material (those that retain the original shape of straw and do not contain moisture). It is used for
2) Dry distillation system The carbon dioxide is continuously carbonized and dry distilled in a dry distillation furnace maintained at a dry distillation temperature (400 to 500 ° C.) to recover the dry distillation gas, gas liquid, tar and fixed carbon. Both are used as heat sources, but the dry gas has a low calorific value of 750-1300 Kcal / Nm ³ .

3) Steam turbine power generation system This is one of the methods to improve the energy conversion efficiency by directly burning firewood, and its target is a system for cogeneration including commercial power generation, but it has been difficult to develop until now. It has been said.
[Physical properties of firewood and difficulty of complete combustion]
The reason why it is difficult to effectively use rice bran as a renewable energy resource is attributed to physical properties that inhibit the thermochemical conversion action inherent to rice bran as shown in the following 1) to 4).

1) Since the decomposition combustion reaction rate due to heating of the volatile component (about 60%) is faster than the surface combustion reaction rate of the carbon component, it is difficult to accurately adjust the operating temperature range of the furnace atmosphere. For this reason, the ambient temperature becomes locally high, and silica in the ash generated on the surface of the soot reacts with a small amount of basic components and water of crystallization, sintering and premature melting occur, and the clinker ingot is formed. As a result, continuous combustion is hindered. In addition, the hardly volatile gas content is tarized and is likely to cause condensation.
2) Ash content is about 20% (containing SiO ₂ ≈15%), which is the highest value among biomass. During the combustion reaction of soot, a large amount of ash generated as the surface combustion progresses condenses due to local overheating, obstructing the diffusion of O ₂ and CO, resulting in combustion unevenness, and stable continuous combustion becomes impossible.

3) Sugagara contains 12 to 17% by weight of fixed carbon. Under high temperature of 500 ° C. or higher in the atmospheric temperature condition of the combustion apparatus, fixed carbon obtains O ₂ supply and performs surface combustion, but its combustion rate is regulated by the atmospheric temperature condition. That is, if the ambient temperature is raised, the combustion time can be shortened, and if it is lowered, the combustion time takes longer. This phenomenon is an important parameter for setting the atmospheric temperature conditions and the average residence time necessary and sufficient for complete combustion of the soot in the furnace.
4) High hardness. It is harder than mild steel because the surface layer of sawdust having a hardness of 5.5 to 6.5 on the scale with MOH is coated with fine-structured silica. This is in the fields of solid fuel, transportation, storage, etc. Cause wear problems of the equipment.

The present invention overcomes the incomplete combustion of soot, which is a problem when directly utilizing the above-described unused soot as a renewable energy resource, and has an inorganic content (SiO ₂ ≈15 Set the organic unused resources of solid wood with a lot of content) to a temperature below the fusing point, to suppress the generation of flying dust particles (carryover) and to burn properly properly Thus, an object of the present invention is to provide a firing method for producing a residue with high added value.

That is, the said subject is achieved by the means of the following summary.
Primary combustion zone and secondary combustion configured to continuously burn completely while setting the soot inside the furnace temperature of 400 to 800 ° C. below the fusion point and adjusting the furnace atmosphere to an oxidizing atmosphere On the bottom floor of the secondary combustion zone located in the lower part of the primary combustion zone, the charcoal that is continuously charged into the primary combustion zone of the firing furnace comprising the zone and carbonized by heating and burning in the primary combustion zone. Fluidized air blown from the bottom floor of the secondary combustion zone in order to superimpose soot on the surface of the multistage fluidized bed that has already been laminated, The cross-flow contact reaction between the air generated in the stack and the soot particles is increased by laminating the air from the multistage air port installed on the side wall of the furnace facing the furnace front edge wall of the firing furnace. The stirrer is stirred and the fluidized bed thus formed A multi-stage fluidized bed that stays in the bed for about the same time as the time required to completely burn all the soot particles in the soot-fired bed, and ashes, and thus has a low crystallinity and solubility. A multistage fluidized bed combustion method of soot obtained by obtaining soot ash mainly composed of a porous body of highly active silica.

  According to the present invention, in addition to a cogeneration system including power generation obtained by optimizing firewood baking technology, an active silica porous body having a fine structure, soluble and reactive, and low crystallinity can be produced. It can be effectively recovered as a raw material resource.

The present invention will be described below. First, combustion characteristics of soot and basic design of the firing method will be described.
[Combustion characteristics of rice cake]
Sugagara has the following characteristics as fuels 1) to 3).
1) Oxidation is significant at a treatment temperature of 200 ° C. or higher, and the critical volatilization rate is remarkable between 220 and 360 ° C. In this operating temperature range, generation of volatile components due to thermal decomposition of organic components (cellulose, lignin, etc.) and their significant gas phase combustion occur, and the temperature rises rapidly.
2) From 360 to 500 ° C., the critical volatilization rate increases with a small amount. In this working temperature range, it is considered that thermal combustion residue or surface combustion of tar or fixed carbon which is difficult to be pyrolyzed occurs.

3) Unlike the quartz and silica stones, the porous active silica having a fine structure occupying the ash content undergoes crystal transformation by polymorphic transformation in the working temperature range of 950 to 1000 ° C. and crystallizes into cristobalite silica.
In addition, rice bran contains moisture in addition to these three components.
[Basic design of combustion method]
In the following 1) to 4), a combustion furnace designed to develop a firing method using a microstructure control technique optimal for the combustion characteristics of soot is described.
1) The entire combustion process was divided into carbonization (decomposition combustion of volatile matter) and ashing (surface combustion of fixed carbon), and the combustion furnace for firing was designed.

2) The furnace shape is applied to the firing method with a multi-stage fluidized bed that strengthens the turbulence in the bed by blowing air from the three side walls of the furnace and forms a fluidized state by countercurrent reaction with the soot particles. The main body is a vertical square lined with a refractory material, and the furnace width is shorter than the furnace length. An air port was provided in the bottom floor of the furnace, and a groove was provided along the central axis of the furnace to give an inclination. The interior of the furnace has a simple structure with no moving parts and is designed to be durable and easy to maintain.
3) Ventilation in the furnace system is an equilibrium ventilation method that uses both indentation and induction methods to effectively adjust heat transfer and heat exchange in the carbonization process (primary combustion zone) and ashing process (secondary combustion zone). It was adopted. A multistage air port was installed in the secondary combustion zone, and the aeration pressure in the furnace system could be operated at -2 to -5 mmAq using the adjustment mechanism of the ventilation quantity in the furnace system. Multi-stage fluidized bed combustion is performed with this ventilation design and furnace shape to suppress the scattering of dust containing silica, and it is possible to prevent the heat transfer surface from wearing out and becoming deposited on the surface of the flue as a scale. .

4) As for the furnace type of the ashing process, the temperature condition of surface combustion of fixed carbon is set to 600 to 900 ° C. below the fusion point in the working temperature range in the furnace, and an accurate model for firing soot is developed. Therefore, the functions having the characteristics shown in the following a) and b) were provided.
a) In-furnace air blow-in system allows fluidization air ports arranged on the slope of the bottom of the furnace to be air blown in order to enable the practical use of a combustion method that is optimal for firing in the furnace shape, and multistage flow in the bed The plurality of air ports forming the gas were arranged on the furnace side wall surface opposite to the furnace front edge wall surface. In addition, air ports were also provided in the complementary combustion zone.
Slag is retained in a plurality of fluidized beds formed by using the countercurrent effect caused by friction and collision between the dust particles generated by the air blown toward the center of the furnace from the multistage air port group on the side wall surface of the three sides. A multi-stage fluidized bed combustion method with a counter-current function to increase the reaction rate of the combustion air in the inside became possible. Multi-stage fluidized bed combustion, which is caused by countercurrent reaction between the air blown from the air inlets on the furnace bottom surface and the furnace side wall, and soot particles, removes and separates the ash generated on the surface of soot particles and stratifies the combustion. Because of the progress, the air diffused quickly, the temperature distribution became uniform, and it was possible to prevent sintering of the particles caused by local overheating.

b) Inclined slope toward the ash pit on the bottom floor of the furnace so that it is easy to move by preventing ash clogging and clinker formation in large quantities in the groove along the central axis of the furnace as surface combustion progresses I put on.
As described above, the basic design of the combustion method for burning soot is made by the forced-air combustion method using a stalker that burns according to the amount of air blown, which is a normal combustion method, or a fluid medium. There are fluidized-bed combustion methods that fluidize using methane, but all of them have defects that make it difficult to use and process soot as a fuel. In order to optimize, the multi-stage fluidized bed combustion method furnace that realizes the following two functions a) and b) was adopted.

B) The multi-stage fluidized bed combustion method with the countercurrent effect added enables the formation of multiple fluidized beds without using a fluidized medium and grids between stages. The formed multistage fluidized bed can sufficiently counter flow reaction between the soot particles and the air, so that the stirring and mixing effect is promoted, and both the soot particles and the air can be easily preheated and cooled, and the whole is fused. Since the low temperature reaction below the point can be performed uniformly, if the residence time of the soot particles is adjusted until the combustion of the fixed carbon is completed, it is possible to recover and secure thermal energy with high thermo economic efficiency.
B) Since precise adjustment and homogenization are easy with respect to the temperature of multistage fluidized bed combustion in the soot combustion chamber, an operating temperature that matches the roasting conditions of silica in soot is set and the combustion reaction is complete , The soot ash produced does not contain unburned matter and clinker particles, has a stable quality, and has a homogenized microstructured active silica porous body as a main component. This formed silica has the same or better microstructure than the silica in ash that is burned by using a low temperature reaction combustion method for the same soot and taking a long residence time to complete combustion. It has physical properties with high reactivity.

Below, the outline of the combustion method for optimizing baking in this invention and the outline of a combustion apparatus are demonstrated.
[Outline of combustion method to optimize firing]
In the present invention, the soot is introduced into the primary combustion zone at the upper part of the main combustion furnace, the primary combustion air is sent and decomposed and burned, and then the carbonized soot particles are dispersed as much as possible on the bed.
The soot supplied to the furnace in the oxidizing atmosphere is immediately heated by the primary combustion air and decomposes and burns.

Slag particles (charcoal) charred by cracking and burning fallen and deposit on the surface of the relatively dense layer of the burnt layer in the secondary combustion zone at the bottom of the main combustion furnace, fixing the main component occupying the unburned part Carbon is a multi-stage fluidized bed combustion functioning with a certain amount of fluidized air blown from the air port group on the bottom surface of the furnace and a set amount of multi-stage air blown from the multi-stage air port group arranged in the central direction on the furnace side wall. Surface combustion is performed by the method, and complete combustion is performed over a set reaction temperature range and reaction time precisely until ashing.
The calcined ash moves along the slope of the bottom floor of the furnace to the ash pit at the discharge end without ash clogging that prevents stable continuous combustion.
The incomplete combustion gas generated by the combustion in the secondary combustion zone is sucked and moved to the complementary combustion zone using the ejector effect of the induction fan in order to secure thermal energy together with the complete combustion gas, and the air placed on the furnace side wall Combustion air is blown from the mouth to complete combustion and recover thermal energy.

[Outline of combustion equipment for optimizing firing]
Next, the outline of the combustion apparatus for carrying out the present invention will be described.
A combustion apparatus for carrying out the present invention is composed of a main combustion furnace and a supplementary device that recovers and secures thermal energy by completely combusting the generated gas generated in the main combustion furnace, and the main combustion furnace and the supplementary device communicate with each other. Configured.
The soot introduced through the inlet provided on the side wall of the front edge of the main combustion furnace is volatilized soot in the two combustion areas (primary and secondary combustion areas) of the main combustion furnace constituting the combustion process. Decomposition combustion and surface combustion of fixed carbon proceed, and by adjusting the set temperature range below the fusing point necessary for firing by complete combustion of soot and the necessary residence time, low calorific value of soot is 3000 Kcal Almost all of / kg can be secured as heat energy.

The ash obtained by multi-stage fluid roasting is mainly composed of an active silica porous body having a fine structure, has a uniform quality, a low crystallinity, and does not contain clinker grains.
Next, the outline of an example of the structure of the combustion apparatus for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an overall structure of an example of a combustion apparatus for carrying out the present invention, and FIG. 2 is a diagram showing a cross section taken along the line AA of FIG. The main combustion apparatus main body 1 has a vertical square shape suitable for forming a multistage fluidized bed, and includes a vertical supply apparatus 2 and an air port 5 from two side walls facing the side wall of the furnace front edge toward the center of the furnace. A cooling thermal energy recovery device 3 such as a boiler is mounted on the top of the furnace. Except for these device parts, the side walls and bottom floor of the furnace body are all lined with refractory bricks. In addition, the bottom of the furnace floor is when the ash produced in large quantities mainly in the center during the firing process is pushed by the air from the air port 5 that is blown into the furnace and heads toward the ash pit 4 installed at the bottom of the complementary combustion zone. In order to prevent ash clogging, the surface of the furnace bottom floor 9 is provided with a groove along the slope and the furnace center axis. In the figure, 6 is a pushing fan, 7 is a heavy oil burner for temperature-ignition ignition, and 8 is an ash discharge conveyor.

Below, the combustion method and combustion apparatus for optimizing baking in this invention are demonstrated in detail.
[Detailed description of combustion method to optimize firing]
The combustion method of the present invention will be described in detail in the following 1) to 3).
1) Primary combustion area (decomposition combustion area)
The soot collected in the silo and sent to the soot supply device 2 through the conduit is continuously controlled in the primary combustion zone (free board; space above the fluidized bed in the combustion chamber) of the main combustion device body 1 by automatic control. It is inserted. Soot is mixed with the air blown from the indenter fan 6 and the combustible gas discharged from the lower soot layer, and is dispersed on the soot layer as much as possible so as not to create a local high temperature region after ignition. To charge.
In addition to the soot supply device 2, the side wall of the primary combustion zone is provided with an attachment port for the temperature rising ignition heavy oil burner 7 at the time of the initial operation of the furnace and an air port 5 for adjusting the air supply amount.

In the furnace atmosphere in which the temperature in the primary combustion zone after furnace charging is 300 ° C. or higher, soot powder is dried and its components are reduced by the heat supplied from the furnace even if the temperature of the soot particles is low. Thermal decomposition of the organic volatile matter occupying 60% occurs, and the generated decomposition product gas burns and carbonizes.
In the decomposition combustion process, since the combustion reaction rate (temperature increase rate) of combustible volatile matter generated by thermal decomposition of organic matters such as cellulose and lignin is fast, the ambient temperature rapidly rises.
Three control functions shown in a) to c) below to suppress clinkeration of ash and condensation of tar due to local overheating as a harmful side reaction that occurs due to the high combustion reaction rate of volatile matter. Was provided.

a) In order to recover a large amount of sensible heat held by the cracked combustion gas, a boiler 3 (convection heat transfer device) and a heat transfer heat transfer tube for adjusting the temperature were arranged at the top of the main combustion apparatus main body 1 .
b) The primary combustion zone is also the furnace space (freeboard) above the multi-stage fluidized bed in the secondary combustion zone, and the fine soot particles popping out of the fluidized bed are mixed and burned with the soot particles that are decomposed and burned. A system that suppresses the generation of soot particles (carryover).
c) In order to minimize the fluctuations in the set temperature of the furnace atmosphere (maximum 900 ° C), the incomplete combustion gas generated in the multistage fluidized bed combustion uses the parallel flow ejector effect by the balanced ventilation method together with the complete combustion gas. At the same time, it is attracted to the complementary combustion zone, and after complete combustion, the generated heat energy is secured.

2) Secondary combustion zone (surface combustion)
The soot is decomposed and burned in the primary combustion zone of the previous process, carbonized, dispersed on the soot layer in the secondary combustion zone at the bottom of the main combustion device, and deposited in layers.
So far, it has been considered difficult to complete combustion suitable for firing with ordinary combustion methods. Therefore, the amount of unburned residual carbon required for firing conditions for soot is necessary for the development of furnace-type technology for main combustion equipment. It is indispensable to establish a new combustion system capable of controlling the complete combustion of ash and the change in the properties of activated porous silica with fine structure in ash.

As an attempt to develop a firing method for that purpose, the fluidized medium that is indispensable for fluidized bed combustion of soot may be mixed as impurities in the ash to be fired. In addition, we conducted experimental research using a pilot plant with a countercurrent contact function that keeps soot until it completely burns in the fluidized bed, and as a result, a furnace type that enables control technology of soot fine structure. Combustion method has been put to practical use.
In the multistage fluidized bed combustion method using this furnace type, the combustion air blown into the charged soot layer is arranged on both sides of the furnace bottom floor 9 surface of the main combustion apparatus along the furnace center axis. Through the air port 5 and the air ports 5 arranged on the three furnace side walls toward the furnace center axis, it is possible to adjust the air supply amount and set the furnace temperature freely.

The fluidized air blown up from the air port 5 on the surface of the furnace bottom floor 9 and the multistage air blown into the soot layer from the air ports 5 on the three side walls of the furnace function to function soot particles in the layer. Is stirred vigorously and becomes a homogeneous mixture with air while maintaining a state of dynamic suspension, and the multi-stage fluidized bed combustion method formed from this countercurrent reaction effect controls the set operating temperature range and residence time while Stable firing and roasting of the waste can be achieved.
The main parameters required for the development of a multi-stage fluidized bed combustion system that is optimal for the firing of soot are as follows: soot supply amount, furnace pressure, fluidized bed temperature (freeboard, furnace bottom, furnace side wall), blowing air There are speed, amount of air, thickness of smoked layer, distribution of layer density, shape change due to silica temperature, temperature increase rate, etc. A new multi-stage fluidized bed combustion method that does not use a fluidized medium has been put into practical use by systematically grasping the parameters necessary for the combustion conditions for firing that can minimize each carbon content, and performing simulations.

Ashed soot derived from the center part of the soot glazed layer is successively moved downward along the groove part while receiving the cooling effect by the air blown from the air port 5 on the surface of the bottom 9 of the hearth. Then, it falls into the ash pit 4 at the bottom of the complementary combustion zone. The ash deposited in the ash pit 4 is periodically discharged out of the furnace by the ash discharge conveyor 8.
3) Complementary combustion zone Combustible gas generated by both oxidation and reduction in the process of multistage fluidized bed combustion in the furnace system of the primary and secondary combustion zones by the operation of equilibrium ventilation is transferred to the main combustion device together with the complete combustion gas. It reverses by the ejector effect of the ventilation by the attracting fan in the complementary combustion device that communicates.

The incomplete combustion gas that has flowed in is completely burned by the air blown from the multistage air ports 5 arranged on the side wall of the furnace in the complementary combustion zone.
The high-temperature combustion gas generated in the complementary combustion zone is converted into thermal energy by flowing while contacting the heat transfer surface of the boiler 3, super heater, economizer, etc. It is released into the atmosphere through a chimney.

Examples of the present invention are shown below.
Embodiment
The following 1) to 4 show embodiments of the present invention.
1) Firewood steam turbine power generation facility (ensuring thermal energy)
Output 445KWH
Boiler evaporation 5500kg / H
Steam pressure × temperature 15.5kg / cm ² × 325 ℃
Rice bran consumption 1780kg / H

2) Analysis of soot ash C, SiO ₂ and residual calorific value were measured from the collected soot ash sample.
Analysis value of rice husk ash SiO ₂ 93.20%
C 1.84%
Residual calorific value 344 kcal (residual fixed carbon)

3) Data of calorific value Measurement result of calorific value of Kaigagar High calorific value 3932Kcal / kg
Lower heating value 3165Kcal / kg
Moisture content 10.5%
Ash / residue 20.5%

4) The amount of heat that can be converted using the combustion device Q = 3165 Kcal / kg-{(20.5 × 344) / 100}
= 3094 Kcal / kg
Combustion efficiency n = (3094/3165) × 100 = 97.76%

[About the characteristics of the combustion system of the present invention]
1) Combustion comparison experiment when the set temperature of the furnace atmosphere is changed By using the multistage fluidization of the soot burning layer of this combustion mechanism, the countercurrent reaction between soot and fluid is sufficiently imparted. Since the heating and cooling of both fluids can be precisely controlled, the following experiments were conducted to study the fine structure control technology of soot ash obtained from the soot that is fired at different preset temperatures.

From the simulation results, the furnace atmosphere temperature of multistage fluidized bed combustion was set to 650 ° C. and 750 ° C., and two combustion experiments were performed at ± 50 ° C. The results are shown in Table 1.
Test 1 Set temperature: 650 ° C ± 50 ° C
Test 2 Set temperature: 750 ° C ± 50 ° C
Residence time in fuel furnace: 20 minutes The soot ash obtained from tests 1 and 2 showed clear differences in the degree of crystal grain development. All ash microstructures are made of porous active silica (SiO ₂ ), which is more porous than raw straw containing a small amount of residual carbon, and there is no local overheating that occurs during the firing process. Does not contain clinker grains due to

Although these calcined fine ash ash has a difference in the cristobalite formation due to the change in the properties of SiO ₂ due to the temperature difference, the reactivity and solubility are not cristobalite without destroying the microstructure in this temperature range. It is a porous body of silica that is higher than rocks (rocks with much cristobalite) and has low crystallinity.
2) Differences in combustion characteristics from other combustion systems For the purpose of comparing the combustion characteristics of this combustion system with those of other systems, Malaysia has been introduced to Southeast Asian countries so far and is still operating in Malaysia. The composition of soot ash produced from the soot ash-fired power generation facility was analyzed and compared with the analytical value of the composition of soot ash produced from this combustion facility. The results are shown in Table 2.

From Table 2, when comparing the amount of residual carbon (unburned part) in the soot ash produced from both combustion devices, the control technology for complete combustion at the set temperature below the fusion point of this combustion method is It can be seen that it functions extremely precisely compared to the method (Stalker method, Reactor method).
The difference in the form of soot ash affected by the combustion conditions will be discussed below.
The chemical component value of the ash obtained by baking the soot varies mainly depending on the temperature range of combustion, the heating rate, the residence time, and the amount of air, but in the case of complete combustion, SiO ₂ is 90 to 98% A high-purity silica having a low crystallinity containing 1 to 3% of residual carbon is obtained by firing.

In general, in the working temperature range between 300 and 500 ° C. at which the volatile matter of the soot is decomposed and burned, the potassium in the component reacts with silica from the sintering phenomenon generated in the ash due to a rapid rise in the local temperature of combustion, and excessively In the surface combustion zone of carbon above 600 ° C, it gradually aggregates into an ingot, obstructs ventilation, and incorporates unburned carbon to achieve stable complete combustion. It cannot be sustained.
This phenomenon is a drawback that the inherent SiO ₂ skeletal structure of soot is an obstacle to complete combustion and is difficult to use as a fuel. Therefore, no method other than this combustion method has established the technology to control the combustion characteristics of soot, so that combustion failure occurs in the operating temperature range of the furnace and continuous combustion cannot be performed. It must be discharged outside the furnace while leaving a part, and complete combustion is almost impossible.

Unburnt soot ash that is forcibly discharged to maintain continuous combustion has a heterogeneous quality with advanced crystallization mixed with clinker. _Components, SiO 2: _50~80%, residual carbon: 8-35% and vary widely. Generally, soot ash SiO ₂ baked to reduce the amount of residual carbon is often crystallized and clinkered.
For this reason, it is not possible to burn soot ash that is valuable in connection with its utilization technology, together with the problem of securing thermal energy, using a method other than the present combustion method.
Incidentally, the amount of residual carbon contained in the ash discharged from the power generation facility by the combined combustion of municipal waste and straw that has recently moved in Thailand is more than 7%, which is not the result of this combustion method. Soot ash produced by this combustion method and soot ash emitted by other combustion methods can be clearly distinguished from the clinkerization and the progress of crystallization due to the presence or absence of fine structure of soot. .

[Use of soot ash containing porous activated silica produced by this combustion method]
Porous activated silica having a fine structure contained in soot ash fired by this combustion method has a higher SiO ₂ purity than cristobalite rock (rock with a lot of cristobalite). The following fields of industrial use are conceivable as a new material for linking the characteristics of porous activated silica contained in straw ash to utilization technology.
・ Microbial carrier (excellent adhesion of microorganisms)
・ Activated sludge additive (Promotes digestion, eliminates bulking, and improves processing capacity.)
・ Gas adsorption capacity (A strong adsorption capacity for ammonia gas, water and protein)
・ Deodorizer ・ Silica fertilizer raw material ・ Agricultural chemical carrier (can be used as a material for agriculture, food processing and environmental purification)
・ Other

As compared with cristobalite rock silica gel and the like that are distributed in industrial applications as described above, the advantages of the organic porous active silica having a fine structure developed can include the following. .
・ The content of SiO ₂ is high.
-Highly soluble and reactive, with low crystallinity.
- basic oxide groups impurities _{(Fe 2 O 3, MgO,} Al 2 O 3, CaO , etc.) a low content of.

FIG. 1 is a view showing the whole of a soot burning apparatus for carrying out the present invention. FIG. 2 is a diagram illustrating a cross-section taken along the line AA in FIG. 1.

Explanation of symbols

In the figure,
1: Main combustion device body 2: Slag supply device 3: Thermal energy recovery device 4: Ash pit 5: Air port
6: Pushing fan 7: Heavy oil burner for temperature rising ignition 8: Ash discharge conveyor 9: Furnace bottom floor

Claims (1)

Primary combustion zone and secondary combustion configured to continuously burn completely while setting the soot inside the furnace temperature of 400 to 800 ° C. below the fusion point and adjusting the furnace atmosphere to an oxidizing atmosphere On the bottom floor of the secondary combustion zone located in the lower part of the primary combustion zone, the charcoal that is continuously charged into the primary combustion zone of the firing furnace comprising the zone and carbonized by heating and burning in the primary combustion zone. Fluidized air blown from the bottom floor of the secondary combustion zone in order to superimpose soot on the surface of the multistage fluidized bed that has already been laminated, The cross-flow contact reaction between the air generated in the stack and the soot particles is increased by laminating the air from the multistage air port installed on the side wall of the furnace facing the furnace front edge wall of the firing furnace. The stirrer is stirred and the fluidized bed thus formed A multi-stage fluidized bed that stays in the bed for about the same time as the time required to completely burn all the soot particles in the soot-fired bed, and ashes, and thus has a low crystallinity and solubility. A multistage fluidized bed combustion method of soot obtained by obtaining soot ash mainly composed of a porous body of highly active silica.

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