JP2013108629A - Waste melting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste melting method, by which the amount of use of coal coke in a vertical waste melting furnace can be decreased, consequently an emission amount of carbon dioxide is reduced and an increase in the running cost of the waste melting furnace can be suppressed, combustion heat of a volatile component of a biomass raw material can be effectively used, and a stable operation is achieved.SOLUTION: The waste melting method comprises charging waste into a waste melting furnace 1, pyrolyzing and combusting the waste, and melting a pyrolysis combustion residue. Coal coke and a biomass molded material obtained by press-molding a biomass raw material are charged to the waste melting furnace; a high-temperature fire grate is formed by the coal coke in a lower part of the melting furnace; the coal coke and the biomass molded material are combusted, which is used as a heat source for melting the pyrolysis combustion residue. A molded material obtained by press-molding a biomass raw material containing 80 wt.% or more of SiOin the ash content of the raw material is used for the biomass molded material.

Description

  The present invention relates to a waste melting method for thermally decomposing, burning, and melting waste in a waste melting furnace.

  As a technology for treating waste such as municipal waste and shredder dust, waste melting treatment is known in which waste is pyrolyzed and burned to melt the pyrolysis residue into slag and discharge it.

  This treatment method can recover the heat of combustion by pyrolyzing and gasifying waste, and it should be disposed of in landfills after melting the pyrolysis residue and discharging it as slag. It has the advantage that the volume can be reduced. There are several methods for such melting treatment, and one of them is a method using a shaft furnace type waste gasification melting furnace having a vertical shape.

  This shaft furnace type waste gasification melting furnace, for example, burns coke deposited in the lower part of the furnace, throws the waste on this high temperature coke, pyrolyzes and partially oxidizes it, and gasifies it as residue Is a furnace that performs a process of melting slag into slag (see Patent Document 1).

  In the shaft furnace type waste gasification and melting furnace of Patent Document 1, the functions of a vertical cylindrical furnace body are roughly divided into three regions in the vertical (up and down) direction. That is, a high-temperature combustion zone having a coke bed with coke deposited at the lower part of the furnace is formed, a waste layer is formed on the high-temperature combustion zone, and a large space above the waste layer at the upper part of the furnace body. The free board part is made.

  In such a gasification melting furnace, oxygen-containing gas is blown into the furnace in each of the three regions. A main tuyere is provided in the high-temperature combustion zone at the bottom of the furnace, and oxygen is enriched to obtain a melting heat source that burns the coke of the coke bed deposited and deposited to melt the pyrolysis residue of waste Air is blown. In addition, the waste layer is provided with a sub tuyere, and air is blown in order to gently flow the waste deposited and deposited, and to thermally decompose and partially oxidize the waste. In addition, the free board part is provided with a third stage tuyere to partially burn part of the pyrolysis gas (combustible gas) generated by pyrolyzing waste and maintaining the inside at a predetermined temperature Air is blown.

  As described above, the shaft furnace type waste gasification and melting furnace is a facility capable of performing both pyrolysis gasification treatment and melting treatment in one furnace as the waste falls in the furnace. The input waste is pyrolyzed to produce gas and residue. The coke in the coke floor is combusted by blowing oxygen-enriched air from the main tuyere to form a high-temperature combustion zone, and the pyrolysis residue of the waste is melted and discharged as slag and metal. The coke floor is a gap created between cokes, and it functions as a high-temperature grate that allows oxygen-enriched air from the main tuyere and high-temperature gas generated by coke combustion to flow, and also allows molten slag and metal to flow. ing. The high-temperature gas generated by coke combustion in the high-temperature combustion zone heats the waste in the waste layer formed on the high-temperature combustion zone, and the waste is thermally decomposed by blowing air from the sub tuyere. The gas containing the combustible gas generated by the gas rises in the waste layer, and is discharged to the secondary combustion chamber outside the furnace from the exhaust flue provided in the upper part of the furnace through the free board part. The gas contains a large amount of combustible gas and is combusted in the secondary combustion chamber, and heat is recovered by the boiler to generate steam, which is used for power generation and the like. Exhaust gas treatment, such as removing relatively coarse dust with a cyclone, cooling with a temperature reducing device, removing harmful gas by reaction with a hazardous substance remover, and removing dust with a dust collector And then released from the chimney to the atmosphere.

  In such a waste gasification melting furnace, a coke bed in which coke is deposited at the bottom of the furnace is formed, and the coke burns to become a heat source for melting pyrolysis residues. There is a demand for reducing carbon dioxide emissions by reducing the amount used. It has been proposed to use biomass as an alternative to coal coke, and use mass biomass charcoal such as charcoal and charcoal obtained by heat compression molding of sawdust from building waste (see Patent Document 2), or pressurizing biomass A waste melting method has been proposed in which formed solid biomass such as briquette is put into a waste gasification and melting furnace and carbonized in the furnace to form a carbide layer (see Patent Document 3), thereby reducing the amount of coke used. Yes.

JP 09-060830 A JP-A-2005-249310 JP-A-2005-274122

  In order to reduce carbon dioxide emissions, in order to reduce the amount of coke used in a waste melting furnace, as in Patent Documents 2 and 3, bulk biomass charcoal is used as an alternative to coke, or biomass solids are used in the furnace. Even if it is carbonized and used, there are the following problems. That is, when using a biomass biomass as in Patent Document 2 or when putting a biomass solid as it is into a waste melting furnace and converting it into a carbide in the furnace as in Patent Document 3, the volatile content of the biomass material The heat of combustion is consumed in the process of carbonization, and the heat energy equivalent to the fixed carbon of the biomass raw material is used as a melting heat source as a substitute for coke. For this reason, it is necessary to input a large amount of massive biomass charcoal and biomass solids with respect to the amount of coal coke to be reduced, and these are expensive compared to coal coke, which reduces the amount of coal coke used. For this reason, there is a problem that the cost required for this is increased and the operating cost of the waste melting furnace is increased. Moreover, there is also a problem that the combustion heat of the volatile component of the biomass raw material cannot be used effectively. In addition, carbides obtained by carbonizing massive biomass carbides and biomass solids in a furnace have low strength at high temperatures and are less stable as coal grate than coal coke, and are inferior in gas permeability and liquid permeability. There is a problem that the temperature of the lower part of the melting furnace is lowered and the discharge of the molten slag is poor, and the operation of the waste melting furnace becomes unstable.

  The present invention has been made to solve the above-described problems, and reduces the amount of coal coke used in a waste melting furnace to reduce carbon dioxide emissions, while reducing the operating cost of the waste melting furnace. It is an object of the present invention to provide a waste melting treatment method that can suppress the increase in volume, can effectively use the combustion heat of volatile components of the biomass material, and can perform stable operation.

  In the waste melting method according to the present invention, waste is put into a waste melting furnace, the waste is pyrolyzed and burned, and the pyrolysis combustion residue is melted.

In such a waste melting method, in the present invention, coal coke and a biomass molded product obtained by pressure-molding a biomass raw material are put into a waste melting furnace, and a high-temperature grate is formed in the lower part of the melting furnace with coal coke. Formed and combusted with coal coke and biomass molding to obtain a heat source for melting pyrolysis combustion residue, and obtained by pressure molding a biomass raw material containing 80 wt% or more of SiO _{2 in} its ash as the biomass molding. It is characterized by using a molded product.

Biomass is categorized by FAO (International Food and Agriculture Organization). As biomass, woody biomass such as forest residue, thinned wood, unused trees, lumber, construction waste, rice straw, rice husk, herbaceous biomass, Furthermore, paper-based biomass, agricultural residues, livestock manure, unused biomass resources such as food waste can be listed. In the present invention, a molded product obtained by press-molding a biomass material containing 80% by weight or more of SiO _{2 in} its ash is used as the biomass molded product.

The main components of pyrolysis combustion residue (ash) of municipal waste such as municipal waste are SiO ₂ , Al ₂ O ₃ , CaO, MgO, and Fe ₂ O ₃ , and the melting point of ash is higher than 800 ° C. The main components of the ash content of the biomass raw material are SiO ₂ , CaO, MgO, Fe ₂ O ₃ and further contain K ₂ O. Therefore, as in the present invention, the ash content contains SiO _{2 in an amount} of 80% by weight or more. By using a molded product obtained by pressure-molding the biomass material (hereinafter referred to as biomass molded product), the ash content of the biomass molded product includes CaO, MgO, Fe ₂ O ₃ , high concentration of SiO ₂ and slight K ₂ O is included, and there is a portion where the melting point of ash is lower than 800 ° C. due to the presence of K ₂ O. When a biomass molded product obtained by pressure-molding biomass grains is put into a melting furnace, the biomass particles of the biomass molded product are pyrolyzed if the temperature in the melting furnace is about 800 ° C. while descending the melting furnace. The surface of the ash particles becomes higher than the melting point temperature and melts to form a melt on the surface of the ash particles. This melt melts the carbide particles produced by the thermal decomposition of the biomass particles of the biomass molded product, the biomass particles in the middle of the thermal decomposition, and the ash particles, and binds the respective particles constituting the biomass molded product to form the biomass. Suppressing the collapse of the product, the biomass molded product reaches the lower part of the melting furnace while maintaining the shape of the molded product. The biomass molded product that has reached the bottom of the melting furnace is suppressed from releasing volatiles while descending the melting furnace, and contains volatiles. By using the melting heat source of the combustion residue, it is possible to effectively use the combustion heat of the volatile content of the biomass raw material. In addition, since the biomass molded product reaches the lower part of the furnace in a short time because the release of volatile components while descending in the melting furnace is suppressed and the decrease in the weight per piece is suppressed, it is melted in the lower part of the melting furnace. It is efficiently used as a heat source.

The reason why the biomass molded product is preferably a molded product obtained by pressure-molding a biomass raw material containing 80% by weight or more of SiO _{2 in} its ash is based on the result of the evaluation test described below.

<Evaluation test>
The ash composition after combustion was changed by adding fine particles of limestone (CaCO ₃ ), dolomite (CaCO ₃ .MgCO ₃ ) and iron oxide (Fe ₂ O ₃ ) to rice husk grains (ash composition is shown in Table 1-1). Samples 1-12 were prepared. The sample was burned in a muffle furnace in an air atmosphere maintained at 800 ° C., and ash particles were observed with a microscope to evaluate the occurrence of ash particle fusion.

As shown in Tables 1-2, 1-3, and 1-4, when the biomass molded product has an SiO ₂ content of 80% by weight or more in the ash content of the biomass raw material, there is ash particle fusion, and the particles are Although it is preferable that the biomass molded product is bonded and does not collapse, if it is lower than 80% by weight, ash particle fusion does not occur. That is, when the SiO ₂ content in the ash content of the biomass raw material is lower than 80% by weight, the melting point of the ash content including SiO ₂ , CaO, MgO, Fe ₂ O ₃ and K ₂ O becomes higher than 800 ° C. As the molten metal descends in the melting furnace, no melt is generated on the surface of the ash particles, the particles constituting the biomass molding cannot be combined, and the biomass molding collapses. Since it cannot reach the lower part while maintaining the shape of the molded product, it is not preferable.

  According to the present invention in such a configuration, the coal coke forming the high-temperature grate is naturally a high temperature at which air passage and liquid passage are reliably ensured by the gap formed between the cokes due to the lump shape. It has a function as a grate and a function as a heat source for melting. On the other hand, the biomass molded product only needs to have the minimum strength and shape that can be reached while maintaining the shape to the lower part of the melting furnace, and has a function as a melting heat source that supplements the heat of fusion of coal coke. Therefore, the minimum amount of coal coke required to form a high-temperature grate is sufficient, and the shortage as a heat source for melting can be compensated by the above biomass molding, while ensuring a sufficient heat source for melting with both. Coal coke can be used to form a high-temperature grate layer. As a result, the amount of coke used in the waste melting furnace can be reduced, and the amount of carbon dioxide emissions can be reduced.

  If an attempt is made to form a high-temperature grate only with a biomass molded product, a high-temperature strength and a biomass molded product having a predetermined size or more are required, but the price is high. Moreover, the stability as a high-temperature grate is also inferior to coal coke. On the other hand, according to the present invention, the high-temperature strength is not required for the biomass molded product as long as it serves only as a source of melting heat, that is, as a melting heat source. Therefore, it is not necessary to use expensive biomass carbide, and it is possible to suppress an increase in the operating cost of the waste melting furnace.

  In this way, when a high temperature grate is formed with coal coke, the coal coke and biomass molding are burned by the combustion air from the main tuyere, and the combustion gas rises well through the high temperature grate and is discarded. The material is heated to pyrolyze, burn and melt the pyrolysis combustion residue, and the molten material descends through the high-temperature grate well.

Further, in the present invention, as a biomass molded product, by using a molded product obtained by pressure-molding a biomass raw material containing 80% by weight or more of SiO _{2 in} its ash, while being put into the melting furnace and descending in the melting furnace, By suppressing the collapse of the biomass molded product and maintaining the shape of the molded product down to the lower part of the melting furnace, it is possible to reach the lower part of the melting furnace. It is not necessary to use this molding machine, and a biomass molded product can be molded simply and efficiently using a simple continuous compression molding machine.

In the present invention, the biomass raw material has an ash content of 10 to 30% by weight with respect to the dry weight of the biomass raw material, and contains 80% by weight or more of SiO ₂ in the ash, CaO, MgO, Fe ₂ O ₃ The total content of is preferably 20% by weight or less. Furthermore, it is preferable that 0.3% by weight or more of K ₂ O is contained in the ash.

  By using a biomass raw material having such a composition, the melting point of ash is surely lower than 800 ° C., and the above-mentioned effects are more reliably obtained. It is possible to prevent the product from collapsing and to reach the lower part of the melting furnace while maintaining the shape of the molded product.

  In the present invention, the biomass molded product can be a molded product that is pressure-molded while heating the biomass raw material at room temperature or a temperature lower than the carbonization temperature. In this specification, the carbonization temperature refers to a temperature at which the volatile matter of the biomass raw material starts to volatilize, and is also a temperature at which dry distillation starts.

  Since the biomass molded product that has been pressure-molded while heating the biomass raw material at room temperature or at a temperature lower than the carbonization temperature contains volatile components, this biomass molded product is charged and the lower part of the melting furnace. By combusting at a melting heat source, the combustion heat of the volatile content of the biomass material can be used effectively. In addition, when molding biomass raw materials, there is no need to use a molding machine that requires high-pressure and long-time processing or a batch-type molding machine, and a simple and continuous compression molding machine is used to easily and efficiently form a biomass molded product. be able to.

In the present invention, the biomass raw material may include at least one of rice husk, wheat husk, rice straw and wheat straw. Rice husk and wheat husk have a high ash content, and the SiO ₂ content in the ash is 80% by weight or more. Further, SiO ₂ content in the ash of rice straw and wheat straw is 80 wt% or more.

In the present invention, the biomass molded product preferably has an apparent density of 1.2 g / cm ³ or more, more preferably 1.3 g / cm ³ or more. If the apparent density of the biomass molded product is 1.2 g / cm ³ or more, the particles constituting the biomass molded product are densely pressed, so that the biomass molded product is kept in a high-temperature atmosphere while descending in the melting furnace. Thus, the biomass molded product can reach the lower part of the melting furnace while maintaining the shape of the molded product without being fused and collapsed. The reason for making the apparent density in this way is that when the apparent density of the biomass molded product is smaller than 1.2 g / cm ³ , the pressure of particles constituting the biomass molded product is not sufficient, and the biomass molded product descends in the melting furnace. This is because it is not preferable because it cannot collapse and reach the lower part of the melting furnace while maintaining the shape of the molded product.

Furthermore, in the present invention, the biomass molded product preferably has an apparent density of 1.2 g / cm ³ or more and a weight per piece of 100 g or more. The reason is that if the weight per biomass molded product is less than 100 g, it takes longer time for the biomass molded product to descend in the melting furnace and reach the lower part of the melting furnace, This is because the ratio of the volatile matter released before reaching the temperature increases, so that the biomass molded product cannot sufficiently hold the volatile matter and reach the lower part of the melting furnace, which is not preferable.

  Furthermore, in the present invention, it is preferable that the amount of coal coke introduced into the furnace is at least an amount necessary for forming a high-temperature grate, and the amount of heat necessary as a melting heat source is supplemented by a biomass molded product.

  In the present invention, as described above, when the waste is melted in the waste melting furnace, the coal coke and the biomass molded product are charged, so that a high temperature grate is formed by the coal coke in the furnace. With the combustion gas up-flow and the melt down-flow maintained well, the minimum coal coke required for high-temperature grate formation and biomass molding to supplement this can secure a melting heat source, While reducing the amount of carbon dioxide emitted by reducing the amount of coal coke used, the operating cost of the waste melting furnace can be reduced, and the combustion heat of the volatile content of the biomass feedstock can be used effectively. It is possible to provide a waste melting method that enables stable operation.

It is a figure which shows schematic structure of the one Embodiment apparatus of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 of the accompanying drawings. The present embodiment is characterized in that coal coke and biomass molding are supplied as fuel to the shaft furnace waste gasification melting furnace. Prior to the description of these characteristics, this shaft furnace waste gas A schematic configuration of the chemical melting furnace will be described.

  In the shaft furnace type waste gasification melting furnace of one embodiment of the present invention shown in FIG. 1, waste as a processing object, coal coke as fuel and biomass molding are formed in the upper part of the gasification melting furnace 1. An inlet 2 is provided for introducing limestone as a material and slag component adjusting material into the furnace, and a gas outlet 3 for exhausting the gas inside the furnace to the outside of the furnace is provided on the upper side. It has been. In addition, an outlet 4 for discharging molten slag and molten metal is provided at the bottom of the gasification melting furnace 1.

  In the shaft furnace type waste gasification and melting furnace, the internal space of the gasification and melting furnace 1 is roughly divided into three regions in the vertical direction. This is a region having a middle shaft portion II located at the top and a free board portion III formed at the top. Each of these parts I, II, and III is an area having the following functions. That is, the lower shaft portion I is a region where the deposited coal coke and biomass molded product are burned to form a high temperature combustion zone, and the middle shaft portion II is formed by the accumulation of waste material put on the high temperature combustion zone. The region where the waste in the generated waste layer is thermally decomposed, the free board part III, is a region where the generated combustible gas is partially combusted.

  Disposed above the waste gasification and melting furnace 1 is a supply device (not shown) for supplying waste such as municipal waste, coal coke, biomass molding, and limestone used as a component adjusting material for the generated slag. The waste, coal coke, biomass molded product, and limestone supplied from this supply device are conveyed by a conveyer (not shown) and charged into the furnace through the inlet 2 at the top of the furnace.

  A tuyere for blowing oxygen-containing gas is provided on the furnace wall for each of the lower shaft portion I, the middle shaft portion II, and the freeboard portion III formed in the waste gasification melting furnace. In other words, the lower shaft portion I is provided with a main tuyere 5 for injecting oxygen-enriched air for melting the pyrolysis residue by burning the deposited coal coke and biomass molding to form a high temperature combustion zone. The middle shaft portion II is provided with a sub tuyere 6 that blows air for partially combusting the deposited waste and thermally decomposing and burning the waste while gently flowing the waste. III is provided with a three-stage tuyere 7 for blowing air for partially burning a combustible gas generated by thermal decomposition of waste and maintaining the inside at a predetermined temperature.

  A secondary combustion chamber 10 is connected to the gas discharge port 3 and burns combustible gas generated by pyrolyzing waste. An air blowing port 11 for blowing air for secondary combustion is provided. Further, the secondary combustion chamber 10 is provided with a boiler 12 adjacent to which heat is recovered from the combustion gas obtained by burning the combustible gas in the secondary combustion chamber 10.

On the other hand, the biomass molded product charged into the furnace through the charging port 2 is obtained by pulverizing a biomass material containing 80% by weight or more of SiO _{2 in} its ash, and using a continuous compression molding machine, an extrusion molding machine, etc. It can be obtained by pressure molding while heating the raw material at normal temperature or without heating to a temperature lower than the carbonization temperature. By using such a biomass molded product, it is possible to maintain the molded product shape and reach the lower portion of the melting furnace without collapsing the biomass molded product while it is charged into the melting furnace and descended in the melting furnace. After the biomass molded product is put into the melting furnace, the pyrolysis and combustion of the volatile matter in the furnace is suppressed, and it can reach the lower part of the furnace, and the combustion heat of the biomass raw material has as the melting heat source. It can be used effectively.

  The shape of the biomass molded product is preferably, for example, a columnar shape having a diameter of about 50 mm and a length of about several tens of mm, and a hole having a diameter of several tens of mm penetrating the central axis is suitable. It goes without saying that it is not limited.

The biomass raw material may be at least one of rice husk, wheat husk, rice straw and wheat straw, and may be a mixture thereof. Table 2 shows examples of properties of the biomass molded product formed from rice husk. It can be seen that the volatile content is high and the content of SiO _{2 in} the ash is high.

  In the present embodiment configured as described above, the waste gasification and melting treatment is performed as follows.

  Waste from the supply device, coal coke, biomass molding, and limestone are introduced into the furnace by a predetermined amount through the inlet 2 provided in the upper part of the gasification melting furnace 1, respectively. Oxygen-enriched air or air is blown into the furnace from the mouth 6 and the three-stage tuyere 7, respectively. The waste introduced from the inlet 2 is deposited on the middle shaft part II in the furnace to form a waste layer, and from the high temperature gas and sub tuyere rising from the high temperature combustion zone of the lower shaft part I. It is dried by blown air and then partially burned and pyrolyzed. The combustible gas generated by pyrolysis is combusted by the air blown from the three-stage tuyere at the freeboard section III and maintained at a temperature of 850 ° C. or higher, and is subjected to a treatment for decomposing harmful gas and tar. After that, it is sent to a secondary combustion chamber provided outside the furnace, and the combustion gas is recovered by the boiler. Coal coke descends to the lower shaft part I, and the biomass molded product descends without collapsing, and the volatiles are lowered to the lower shaft part I while being suppressed from being pyrolyzed and combusted along the way. And a high-temperature combustion zone in which the biomass molding is burned is formed, a residue obtained by pyrolyzing the waste in the waste layer of the middle shaft portion II descends, and a high-temperature combustion zone in which the coal coke and the biomass molding are burned The lower shaft portion I is formed, and in the lower shaft portion I, the volatile matter in the biomass molded product, the coal coke and the fixed carbon in the biomass molded product burn, the incombustible material melts, and the molten slag Become a molten metal. The molten slag and molten metal are discharged from the tap 4 and supplied to a water granulating device provided outside the furnace, cooled and solidified, and the cooled and solidified granulated slag and granulated metal are recovered.

  By putting coal coke and biomass molding into the waste gasification and melting furnace, a high-temperature grate is formed in the lower part of the gasification melting furnace 1 with coal coke, and the coal coke and biomass molding are burned and discarded. A heat source for melting thermal decomposition residue (ash) and non-combustible material. The amount of coal coke introduced into the furnace is an amount necessary for forming a high-temperature grate, and the amount of heat necessary as a melting heat source is supplemented by a biomass molded product, and a predetermined amount is respectively charged.

  In such a process of gasification and melting of waste, coal coke as a fuel and a biomass molded product are in a lump from the beginning of charging into the furnace, and in the high temperature combustion zone of the lower shaft portion I. A high-temperature grate is formed by a gap between coal cokes. The upper surface of this high-temperature grate layer is located above the main tuyere 5, and oxygen-enriched air or air from the main tuyere 5 ascends and ventilates the gaps, and coal coke and biomass moldings. Is burned well and sufficient combustion gas reaches the waste layer. On the other hand, incombustible waste and ash in the high-temperature combustion zone are sufficiently melted by the amount of heat generated by the combustion of coal coke and biomass molding, resulting in molten slag and molten metal. The molten slag and the molten metal flow down well through the gap between the high-temperature grate and reach the taphole 4.

  According to such a gasification and melting method for waste, the coke that forms the high-temperature grate is surely ensured to ensure ventilation and liquid passage in the gap formed between the cokes due to its bulk shape. It has a function as a high-temperature grate and a function as a heat source for melting. On the other hand, the biomass molded article only needs to have a strength and a shape that can be reached while maintaining the shape up to the lower shaft portion I, and has a function as a melting heat source that supplements the heat of fusion of coal coke. Therefore, the minimum amount of coal coke required to form a high-temperature grate is sufficient, and the shortage as a heat source for melting can be compensated by the above biomass molding, while ensuring a sufficient heat source for melting with both. Coal coke can be used to form a high-temperature grate layer. As long as the biomass molded product only serves as a source of melting heat, that is, as a melting heat source, high-temperature strength is not required. Therefore, a low-cost biomass molded product can be used, and the operating cost of the waste melting furnace can be reduced.

  In this way, when a high-temperature grate is formed with coal coke, the coal coke of this high-temperature grate and the biomass molding deposited on the high-temperature grate are burned by the combustion air from the main tuyere and the combustion gas becomes high temperature. The grate is lifted and ventilated well, and the waste is heated to thermally decompose, burn and melt, and the molten material descends through the high-temperature grate well.

  As described above, in the high-temperature grate, coal coke as a fuel and a biomass molded product are combusted while maintaining good upflow of combustion gas and downflow of molten slag and molten metal. During the combustion, only the amount of coal coke required for the formation of the high-temperature grate is required, and the amount of heat necessary for gasification and melting of the waste is supplemented with the biomass molding. Furthermore, the combustion heat of the volatile content of the biomass material can be effectively used as a melting heat source.

  Thus, the amount of coal coke used can be suppressed as much as possible. On the other hand, as for the biomass molded product, it is only necessary to maintain the shape and reach the lower shaft portion I, and to obtain a low-cost biomass molded product. But it can be used as fuel. In this way, the amount of coal coke used can be reduced to reduce carbon dioxide emissions, the operating cost of the waste melting furnace can be reduced, and the waste can be melted for stable operation.

  Using the waste melting furnace shown in FIG. 1, a biomass molded product formed from rice husk shown in Table 2 was supplied to examine the reduction effect of coal coke.

  A concern when reducing the amount of coal coke used by using biomass molding is that heat for melting the slag is insufficient at the lower part of the melting furnace, making it difficult to melt and discharge the slag. Therefore, in this example, while increasing the amount of biomass molded product used, the slag output status is confirmed, and the slag temperature (reference value) is secured so that the slag does not become difficult to melt and discharge. Coke consumption was reduced, and the relationship between coal coke reduction rate and biomass molding usage rate was investigated.

In evaluating the reduction effect of coal coke, the biomass molding usage rate R _B (% by weight) and the coal coke reduction rate R _ΔC (% by weight) are defined as follows.
R _B = B / C _O × 100 (1)
R _ΔC = (C _O −C) / C _O × 100 (2)
Here, _CO is the basic unit of coal coke (kg / t-garbage) under the condition of operation using only coal coke,
C is the basic unit of coal coke (kg / t-garbage) when using biomass molding,
B shows biomass basic unit (kg / t-garbage).

Moreover, the biomass heat utilization rate R _H (heat amount%) in which the heat utilization efficiency of the biomass molded product is compared with the heat utilization efficiency of coal coke is defined as follows.
R _H = H _B / H _ΔC × 100 (3)
Here, H _B represents the calorific value basic unit (MJ / t-garbage) of the input biomass molded product, and H _ΔC represents the calorific value basic unit (MJ / t-garbage) corresponding to the reduced coal coke. The calorific value basic unit corresponds to the heat utilization efficiency, and it goes without saying that this calorific value includes the calorific value of volatile matter.

And coal coke reduction ratio R _{[Delta] C} and biomass heat utilization rate R _H, the relationship between the biomass molding utilization R _B shown in Table 3. By using the biomass molded product, it was possible to obtain a coke reduction rate of 38% by weight at the maximum while ensuring that the slag did not become difficult to melt and discharge. Moreover, the heat utilization rate of the biomass molded product was 100 calorie% or more, and it was shown that the biomass molded product replaced a considerable amount of coal coke by the calorific value including volatile matter. This greatly contributes to the amount of heat that contains the volatile content of the biomass molding in the melting heat source of slag melting, and the biomass molding loses less heat than coal coke before reaching the lower shaft part I. It shows that.

  1 Gasification melting furnace

Claims (6)

In a waste melting treatment method in which waste is put into a waste melting furnace, the waste is pyrolyzed and combusted, and the pyrolysis combustion residue is melted, coal coke and biomass formed by pressure-molding biomass raw materials are discarded A high-temperature grate is formed in the lower part of the melting furnace with coal coke, and the coal coke and the biomass molding are burned to obtain a heat source for melting pyrolysis combustion residue. A waste melting method characterized by using a molded product obtained by pressure-molding a biomass material containing 80% by weight or more of SiO ₂ therein.   2. The waste melting method according to claim 1, wherein the biomass molded product is a molded product obtained by pressure-molding a biomass raw material at normal temperature or while being heated to a temperature lower than a carbonization temperature.   The waste material melting treatment method according to claim 1 or 2, wherein the biomass raw material contains at least one of rice husk, wheat husk, rice straw and wheat straw. The method for melting waste according to any one of claims 1 to 3, wherein the biomass molded product has an apparent density of 1.2 g / cm ³ or more.   The method for melting waste according to claim 4, wherein the biomass molded product has a weight of 100 g or more.   The amount of coal coke charged into the furnace is at least an amount necessary for forming a high-temperature grate, and the amount of heat necessary for a melting heat source is supplemented by a biomass molded product. A waste melting method according to one of the above.

Images