JP4449704B2 - Combustion method and apparatus - Google Patents

Description

  The present invention relates to a combustion method and apparatus, and more particularly, to a combustion method and apparatus that effectively burns water-containing waste and flame-retardant fuel.

  In recent years, raw garbage, sludge including sewage sludge, etc. have been increasing, and its treatment has become a social problem. Examples of main treatment methods for treating garbage, sewage sludge, and the like include incineration using a combustion furnace. However, sewage sludge contains about 70 to 80% of water, and raw garbage contains about 60% of water, and thus has a high water content. When an attempt is made to incinerate hydrous waste in an incinerator, the temperature in the furnace tends to decrease, and thus hydrous waste cannot be incinerated as it is.

  FIG. 4 shows an example of a conventional sewage sludge incineration processing equipment, wherein 1 is an incinerator, 2 is an air preheater, 3 is a cooling tower, 4 is a bag filter, and 5 is a smoke exhausting device.

  In the incineration treatment facility shown in FIG. 4, sewage sludge a is supplied to the incinerator 1 and auxiliary fuel b such as city gas or kerosene or heavy oil is supplied. When the exhaust gas from the incinerator 1 passes through the air preheater 2, heat is exchanged with the combustion air, and the preheated combustion air is introduced into the incinerator 1. The On the other hand, the exhaust gas that has passed through the air preheater 2 is cooled by water sprayed in the cooling tower 3, and then the incinerated ash is separated and removed by the bag filter 4, and then sprayed in the smoke treatment device 5. The ash that could not be separated and removed by the bag filter 4 is removed by water, and is released into the atmosphere as a clean gas.

  FIG. 5 shows another example of the conventional incineration processing equipment. In the figure, the parts denoted by the same reference numerals as those in FIG. 4 represent the same thing, and the sewage sludge a is dried and incinerated. A dryer 6 to be supplied to the furnace 1 is additionally provided.

  In the incineration treatment facility shown in FIG. 5, the sewage sludge a containing about 70 to 80 [%] of moisture is dried by the dryer 6 and the contained moisture is reduced to about 30 to 50 [%]. The dried sludge is supplied to the incinerator 1, and the dried sludge is self-combusted in the incinerator 1. When the exhaust gas passes through the air preheater 2, it exchanges heat with the combustion air and is preheated combustion air. Is introduced into the incinerator 1, while a part of the exhaust gas discharged from the incinerator 1 is led to the dryer 6, and the waste heat is used for drying the sewage sludge a. . Further, the exhaust gas that has passed through the air preheater 2 is cooled by water sprayed in the cooling tower 3 in the same manner as in the example shown in FIG. 4, and then the incineration ash is separated and removed by the bag filter 4. After that, the ash that could not be separated and removed by the bag filter 4 is removed by the water sprayed in the smoke treatment device 5 and is released into the atmosphere as clean gas.

In addition, there exists patent document 1 as what shows the general technical level which incinerates a sewage sludge, for example.
JP 2002-130641 A

  However, in the conventional incineration processing equipment as shown in FIG. 4, in order to incinerate the sewage sludge a containing about 70 to 80% of moisture in the incinerator 1, city gas, kerosene, heavy oil, etc. A large amount of the auxiliary fuel b is required, and there is a problem that the operating cost is greatly increased.

  Moreover, in the conventional incineration processing equipment as shown in FIG. 5, the sewage sludge containing about 70 to 80 [%] of moisture is first dried by the dryer 6, and the contained moisture is about 30 to 50 [%]. Since the dried sludge reduced to a certain extent is burned by the incinerator 1, city gas by the incinerator 1 of FIG. 4 or auxiliary fuel b such as kerosene or heavy oil can be made unnecessary, but an extra dryer 6 is used. It is necessary to install it in this, and the installation space for it is also required. In addition, since the dried sludge dried by the dryer 6 cannot be pumped by a pump, the belt 6 must be transported from the dryer 6 to the incinerator 1 by using a belt conveyor or the like. Dispersion of odor was unavoidable, and this was a big problem for practical use.

  Moreover, in the apparatus of FIG. 4 and FIG. 5 and Patent Document 1, combustion air heat-exchanged with exhaust gas is supplied to the incinerator, but the combustion air obtained by heat exchange is based on the temperature of the exhaust gas. Since the temperature is low, simply supplying the combustion air to the incinerator 1 cannot significantly increase the in-furnace temperature. For this reason, in the apparatus of FIG. 4 and FIG. 5 and Patent Document 1, in order to significantly increase the temperature in the furnace, auxiliary combustion with the auxiliary gas b such as city gas or kerosene or heavy oil is required. It was.

  Thus, in order to maintain the in-furnace temperature high in the conventional incinerator, there is no method other than increasing the input amount of auxiliary fuel, and therefore, when hydrated waste such as sewage sludge is burned. Had the problem of increasing the operating cost due to an increase in consumption of auxiliary fuel.

  The present invention has been made in view of such a situation, and the in-furnace temperature of the combustion furnace can be significantly increased by utilizing the waste heat of the exhaust gas from the combustion furnace, and thus the in-furnace temperature of the combustion furnace is maintained. It is an object of the present invention to provide a combustion method and apparatus capable of reducing or eliminating the auxiliary fuel for the purpose, and recovering the waste heat of the exhaust gas so that it can be used effectively.

  The present invention is characterized in that the combustion furnace is heated from the outside by guiding a part of the exhaust gas at the outlet of the combustion furnace that forms a fluidized bed and burns fuel along the outer periphery of the combustion furnace. This relates to the combustion method.

  In the combustion method, as the fuel, at least one of raw waste, food waste, factory effluent sludge, sewage sludge, and hydrated waste including urine sludge including livestock excreta can be used.

  In the combustion method, at least one of heating fuel made of solid fuel, easily combustible biomass, and waste plastic can be used as the fuel.

  In the combustion method, the fuel includes at least one of hydrated waste including raw garbage, food waste, factory effluent sludge, sewage sludge, and livestock excreta, and urine sludge; solid fuel; Combustible biomass and at least one heating fuel made of waste plastic can be used simultaneously.

  Moreover, in the said combustion method, it is preferable to supply the said water-containing waste from the upper part with respect to a combustion furnace.

  Further, in the combustion method, it is preferable to preheat the flowing air that is led to the combustion furnace by the exhaust gas derived from the combustion furnace.

  In the combustion method, it is preferable to recover and use thermal energy from the exhaust gas after preheating the air for flow.

  On the other hand, in the present invention, an outer flow path including a spiral flow path is formed on the outer periphery of a combustion furnace that forms a fluidized bed and burns fuel, and a part of exhaust gas from the combustion furnace is supplied to the spiral flow path. The present invention relates to a combustion apparatus characterized in that an exhaust gas supply pipe is provided.

  The combustion apparatus preferably includes an air preheater that preheats the flowing air that exchanges heat with the exhaust gas from the combustion furnace and guides it to the combustion furnace.

  The combustion apparatus preferably includes a thermal energy recovery apparatus that recovers waste heat by exchanging heat with exhaust gas downstream of the air preheater.

  According to the above means, the following operation can be obtained.

  In the combustion method and apparatus of the present invention, first, a fluidized bed is formed by supplying a starting fuel and fluidizing air to a combustion furnace and combusting to bubbling the fluidized medium. At this time, a part of the exhaust gas from the combustion furnace is supplied to the spiral flow path provided on the outer periphery of the combustion furnace by the exhaust gas supply pipe to heat the combustion furnace from the outside, and further, heat exchange with the exhaust gas from the combustion furnace The obtained fluidizing air is supplied to the combustion furnace to form a fluidized bed.

  When the in-furnace temperature of the combustion furnace reaches a predetermined temperature due to the combustion of the starting fuel, the human waste system including raw garbage, food waste, factory effluent sludge, sewage sludge, and livestock excrement from the upper part of the combustion furnace At least one of the hydrated waste made of sludge is supplied and co-fired with the starting fuel. The water-containing waste supplied from above into the combustion furnace is heated while falling in the combustion furnace, and the water is evaporated to dry and burn.

  At this time, the combustion furnace is supplied with flowing air heated by the air preheater and is fluidized and burned, and the combustion furnace is heated from the outside by the high-temperature exhaust gas supplied to the spiral flow path. The furnace temperature inside the furnace will be maintained at a high temperature, so that the hydrated waste is effectively dried and burned. Furthermore, by maintaining the furnace temperature high, even if the flow rate of the starting fuel supplied to the combustion furnace is reduced, the combustion of the hydrated waste will continue and the hydrated waste will self-combust. Then, the supply of the starting fuel can be stopped. Thus, the hydrated waste is efficiently incinerated by self-combustion using the hydrated waste itself as fuel.

  Further, as described above, in the state where the hydrated waste is burning by itself, when the exhaust gas temperature at the outlet of the air preheater is kept high, the waste heat of the exhaust gas is recovered as steam or hot water by the thermal energy recovery device. However, when the obtained steam and hot water can be used for heating and other purposes, and the exhaust gas temperature at the outlet of the air preheater is higher, steam is generated by a boiler and the steam for power generation is generated with this steam. It can also be driven to output power. Therefore, according to the said operation | movement, the effect | action which incinerates a water-containing waste and the effect | action which collect | recovers thermal energy can be achieved simultaneously.

  On the other hand, when the hydrated waste is supplied to the combustion furnace and the heating fuel is supplied to the combustion furnace to perform co-firing, the temperature in the furnace can be further increased to raise the temperature of the exhaust gas, and thus can be recovered from the exhaust gas. The amount of waste heat increases. Therefore, the heat energy such as steam temperature (or steam amount) and hot water temperature (or hot water amount) that can be taken out by the thermal energy recovery device can be greatly increased, and the amount of power generated by steam power generation can also be increased. The combustion furnace can be actively used as a heat energy generator.

  At this time, by using a solid fuel (for example, coal, garbage solid fuel RDF, etc.), easily combustible biomass (for example, waste wood chip), waste plastic, etc., which is relatively inexpensive and easily available, as the heating fuel, Large heat energy can be extracted at low cost.

  According to the combustion method and apparatus of claims 1 to 10 of the present invention, since the furnace temperature of the combustion furnace can be maintained high, raw garbage, food waste, factory effluent sludge, sewage sludge, and livestock When hydrated waste containing excreta and urine sludge is supplied to the combustion furnace as fuel, the hydrated waste is effectively heated and dried and effectively incinerated by self-combustion using the hydrated waste itself as fuel. .

  In addition, in the state where the hydrated waste is self-combusted, when the exhaust gas temperature at the air preheater outlet is kept high, the waste heat of the exhaust gas from the combustion furnace is recovered as steam or hot water by a thermal energy recovery device, Since it can also be used for steam power generation, it has the effect of achieving incineration of hydrous waste and recovery of thermal energy at the same time.

  On the other hand, if hydrated waste and fuel for heating are simultaneously supplied to the combustion furnace and co-fired, the temperature in the furnace and the temperature of the exhaust gas will be significantly increased, and the thermal energy recovered by the thermal energy recovery device will be greatly increased. There is an effect that the furnace can be actively used as a heat energy generating device. Furthermore, at this time, solid fuel, easily combustible biomass, waste plastics, etc., which are relatively inexpensive and easily available, can be used as the heating fuel, so that large heat energy can be taken out at low cost.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is an example of a form which is a first reference example of the present invention. A combustion furnace 7 is provided with a fluidized bed 8 which is supplied with fuel and fluidizing air at the bottom and is mixed and combusted while bubbling with a fluidizing medium. A high temperature free board 9 is formed in the upper part of the combustion furnace 7. At this time, the starting fluid 10 such as city gas, kerosene, and heavy oil generally used for heating the conventional fluidized bed is supplied to the fluidized bed 8 below the combustion furnace 7.

  On the other hand, the upper part of the combustion furnace 7 is supplied with water-containing waste 11 composed of raw garbage, food waste, factory effluent sludge, sewage sludge, and urine sludge including livestock excreta. At this time, one of the hydrated wastes 11 may be supplied, or a plurality of them may be supplied simultaneously.

  An exhaust gas pipe 12 for extracting the exhaust gas after combustion is connected to the upper part of the combustion furnace 7, and the exhaust gas derived from the exhaust gas pipe 12 is led to the air preheater 13 to heat the flowing air. The fluidizing air heated by the air preheater 13 is guided to the combustion furnace 7 to form the fluidized bed 8.

  An outer wall 14 surrounding the combustion furnace 7 is provided outside the combustion furnace 7 to form a double structure, and an outer flow path 15 is formed between the combustion furnace 7 and the outer wall 14. Then, an exhaust gas supply pipe 16 is branched from the exhaust gas pipe 12 at the outlet of the combustion furnace 7, and the exhaust gas supply pipe 16 is connected to the lower end of the outer flow path 15, whereby a part of the exhaust gas in the exhaust gas pipe 12 is provided. Is introduced into the outer flow path 15 outside the combustion furnace 7 from below.

  Further, in the configuration of FIG. 1, the exhaust gas after the air for heating is heated by the air preheater 13 is led to the thermal energy recovery device 17 including the heat exchanger 17 a by the exhaust gas pipe 12 to exchange heat with water. By doing so, steam or hot water is generated. At this time, if the exhaust gas temperature at the outlet of the air preheater 13 is high, a steam can be generated by providing a boiler as the thermal energy recovery device 17, and the power generation turbine can be driven by this steam to output electric power. Further, the exhaust gas after the water is heated by the thermal energy recovery device 17 is guided to the scrubber 18 by the exhaust gas pipe 12, and water is sprayed on the exhaust gas to treat ammonia and tar as well as desulfurization, denitration, and ash treatment. In addition, the vapor in the exhaust gas is condensed and released into the atmosphere as a clean gas.

  Further, the heated exhaust gas after being introduced into the outer flow path 15 on the outer periphery of the combustion furnace 7 and heating the combustion furnace 7 from the outside is taken out by the exhaust gas pipe 19 after being heated and exhausted at the inlet of the scrubber 18. The gas is joined to the pipe 12 and treated with the scrubber 18 together with the exhaust gas. At this time, when the exhaust gas after heating has a temperature at which the heat energy recovery device 17 can recover heat, the exhaust gas after heating is joined to the inlet portion of the heat energy recovery device 17 as indicated by a broken line. The heat energy may be recovered by.

  FIG. 2 is another example of the second embodiment of the present invention, and the heating fuel 20 is supplied to the lower part of the combustion furnace 7 of FIG. As the heating fuel 20, it is possible to use a solid fuel (for example, coal, garbage solid fuel RDF, etc.) that is inexpensive and easily available, an easily combustible biomass (for example, waste wood chip), waste plastic, or the like. One of these heating fuels 20 may be supplied or a plurality of them may be supplied simultaneously. At this time, the starting fuel 10 may be supplied only when the temperature rises.

  Further, the exhaust gas pipe 12 between the air preheater 13 and the thermal energy recovery device 17 is provided with a thermal energy recovery device 21 configured to generate high-temperature and high-pressure steam by a boiler 21a. The steam turbine 22 is driven by the steam generated by the recovery device 21 and electric power is generated by the generator 23. Therefore, in the apparatus of FIG. 2, the combustion furnace 7 is actively used as a heat energy generating apparatus.

  FIG. 3 is a cut side view of a combustion furnace showing an example of the embodiment of the present invention. In the reference example shown in FIG. 1 and FIG. 2, it is desirable that the outer flow path 15 can effectively heat the combustion furnace 7 from the outside by the exhaust gas flowing inside. For this reason, in the form of FIG. An outer flow path composed of a spiral flow path 24 is formed on the outer periphery of the gas flow path, and exhaust gas is introduced into the spiral flow path 24. According to such a shape of the spiral flow path 24, the flow rate of the exhaust gas flowing in the spiral flow path 24 is increased, and the heat transfer is improved, whereby the combustion furnace 7 is effectively heated.

  Next, the operation of the illustrated example will be described.

  In order to start the combustion furnace 7 in the combustion apparatus of FIG. 1, first, the fluidized bed 8 is formed by supplying the starting fuel 10 and the flowing air to the combustion furnace 7 and burning them to bubbling the flowing medium. At this time, a part of the exhaust gas from the combustion furnace 7 is supplied to the outer flow path 15 provided on the outer periphery of the combustion furnace 7 through the exhaust gas supply pipe 16 to heat the combustion furnace 7 from the outside, and from the combustion furnace 7 The fluidized bed 8 is formed by supplying the fluidizing air heat-exchanged with the exhaust gas and the air preheater 13 to the combustion furnace 7.

  When the in-furnace temperature of the combustion furnace 7 rises due to the combustion of the starting fuel 10 and the furnace temperature reaches a predetermined temperature, raw garbage, food waste, factory effluent sludge, sewage from the upper part of the combustion furnace 7 At least one of the hydrated waste material 11 including the sludge and livestock excrement and the urine sludge is supplied and co-fired together with the starting fuel 10. The hydrated waste 11 supplied from above into the combustion furnace 7 is heated while falling on the free board 9 of the combustion furnace 7, and burns as the moisture evaporates and is dried.

  At this time, the fluidizing air heated by the air preheater 13 is supplied to the combustion furnace 7 to form the fluidized bed 8, and high-temperature exhaust gas is supplied to the outer flow path 15 of the combustion furnace 7, so that the combustion furnace 7 Since it is heated from the outside, the furnace temperature of the combustion furnace 7 is maintained at a high temperature.

  Although depending on the scale of the combustion furnace 7 and the type of the hydrated waste 11, the hydrated waste 11 cannot be combusted because the calorific value due to the combustion of the hydrated waste 11 is small particularly in the case of the small-sized combustion furnace 7. In this case, it is necessary to continue the supply of the starting fuel 10. At this time, the flow air heated by the air preheater 13 is supplied to the combustion furnace 7 as described above, and combustion is performed. Since the furnace 7 is heated from the outside by the high-temperature exhaust gas flowing in the outer flow path 15 and the furnace temperature is kept high, the heating / drying of the water-containing waste 11 is promoted and burns, so that the activation The fuel 10 can be supplied at a minimum amount.

  On the other hand, particularly in the large-sized combustion furnace 7, the amount of heat generated by the combustion of the hydrated waste 11 increases, so that the furnace temperature is maintained high. For this reason, the flow rate of the starting fuel 10 supplied to the combustion furnace 7 Since the self-combustion state in which the combustion of the hydrated waste material 11 continues even if the amount is reduced, the supply of the starting fuel 10 can be stopped in this state. As a result, the water-containing waste 11 is efficiently incinerated by self-combustion using the water-containing waste itself as fuel.

  Furthermore, when the exhaust gas temperature at the outlet of the air preheater 13 is kept high in the state where the hydrated waste 11 is self-combusting as described above, the waste heat of this exhaust gas is converted into thermal energy of the heat exchanger 17a or the like. It collect | recovers as a vapor | steam or warm water with the collection | recovery apparatus 17, and the obtained vapor | steam and warm water can be utilized for purposes, such as heating. At this time, when the exhaust gas temperature at the outlet of the air preheater 13 is higher, steam can be generated by the boiler, and the power generation turbine can be driven by this steam to output electric power. Therefore, according to this method, the action of incinerating the hydrated waste 11 and the action of recovering thermal energy can be achieved simultaneously.

  On the other hand, in the combustion apparatus shown in FIG. 2, the hydrated waste 11 is supplied to the combustion furnace 7, and the heating fuel 20 is supplied to the combustion furnace 7 to perform co-firing. When the hydrated waste 11 and the heating fuel 20 are supplied to the combustion furnace 7 for combustion as described above, the temperature in the furnace can be significantly increased, and thus the temperature of the exhaust gas is raised and the amount of waste heat that can be recovered from the exhaust gas. Will increase.

  For this reason, since the recovered heat energy such as the steam temperature (or steam amount), hot water temperature (or hot water amount) obtained by the thermal energy recovery device 21 can be significantly increased, and the amount of power generated by steam power generation can be increased, The combustion furnace 7 can be actively used as a heat energy generator.

  At this time, as the heating fuel 20, a relatively inexpensive and easily available solid fuel (for example, coal, garbage solid fuel RDF, etc.), easily combustible biomass (for example, discarded wood chip), waste plastic, etc. are used. Large heat energy can be taken out at a low operating cost.

  In addition, when the furnace temperature of the combustion furnace 7 is low, there is a problem that a fuel with a large amount of fixed carbon such as coal is difficult to burn. However, as described above, the fluidized air heated by the air preheater 13 is burned. The temperature inside the furnace is kept high by supplying a part of the high-temperature exhaust gas to the outer flow path 15 and heating the combustion furnace from the outside while leading to the furnace 7, so that the fixed carbon content is high and the moisture content is high. High peat, lignite, lignite and the like, which are generally referred to as lower coal, can be easily and efficiently burned, and thus the lower coal can also be effectively used as the heating fuel 20.

  And, according to the embodiment of the present invention shown in FIG. 3, the outer flow path composed of the spiral flow path 24 is formed on the outer periphery of the combustion furnace 7 and the exhaust gas is introduced into the spiral flow path 24. The flow rate of the exhaust gas flowing in the passage 24 is increased, and the heat transfer is improved, whereby the combustion furnace 7 is heated more effectively.

  As described above, since the furnace temperature of the combustion furnace 7 can be maintained high, the water-containing waste composed of raw waste, food waste, factory effluent sludge, sewage sludge, and urine sludge including livestock waste By supplying the material 11 to the combustion furnace 7, the water-containing waste 11 itself can be effectively heated and dried as a fuel to be burned and incinerated, and further, the heat energy is recovered in a state where the water-containing waste 11 is self-combusted. Or by supplying a heating fuel 20 such as solid fuel, easily combustible biomass, waste plastic or the like to the combustion furnace 7 and recovering thermal energy, thereby incinerating the hydrous waste 11 and recovering thermal energy at the same time. It can be carried out.

  Note that the combustion method and apparatus of the present invention are not limited to the illustrated examples described above, but can be applied to various combustion furnaces that are required to increase the furnace temperature of the combustion furnace. Of course, various changes can be made without departing from the scope of the invention.

1 is an overall schematic configuration diagram of a combustion apparatus as an example of a form that is a first reference example of the present invention. It is a whole schematic block diagram of the combustion apparatus as another example of the form which is the 2nd reference example of this invention of this invention. It is a cut side view of a combustion furnace showing an example of the form of the present invention. It is a whole schematic block diagram which shows an example of the conventional incineration processing equipment. It is a whole schematic block diagram which shows the other example of the conventional incineration processing equipment.

7 Combustion furnace 8 Fluidized bed 11 Hydrous waste (fuel)
12 exhaust gas pipe 13 air preheater 15 outer flow path 16 exhaust gas supply pipe 17 thermal energy recovery device 17a heat exchanger 20 heating fuel (fuel)
21 Thermal energy recovery device 21a Boiler 22 Steam turbine 23 Generator 24 Spiral flow path

Claims (10)

  A combustion method characterized by heating the combustion furnace from the outside by guiding a part of the exhaust gas at the outlet of the combustion furnace that forms a fluidized bed and burns fuel along the outer periphery of the combustion furnace.   The combustion method according to claim 1, wherein the fuel is at least one of water-containing waste composed of raw waste, food waste, factory effluent sludge, sewage sludge, and human waste sludge including livestock waste.   The combustion method according to claim 1, wherein the fuel is at least one of a heating fuel made of solid fuel, easily combustible biomass, and waste plastic.   The fuel is at least one of water waste including food waste, food waste, factory effluent sludge, sewage sludge, and livestock waste, and sewage sludge, solid fuel, easily combustible biomass, and waste plastic. The combustion method according to claim 1, wherein at least one of the heating fuels is simultaneously supplied.   The combustion method according to claim 1, wherein the hydrated waste is supplied to the combustion furnace from above.   The combustion method according to any one of claims 1 to 5, wherein the fluidizing air led to the combustion furnace is preheated by the exhaust gas derived from the combustion furnace.   The combustion method according to claim 6, wherein thermal energy is recovered and used from the exhaust gas after the air preheating for flow.   An outer flow path consisting of a spiral flow path is formed on the outer periphery of a combustion furnace that forms a fluidized bed and burns fuel, and an exhaust gas supply pipe that supplies part of the exhaust gas from the combustion furnace to the spiral flow path is provided. A combustion apparatus characterized by that.   The combustion apparatus according to claim 8, further comprising an air preheater that preheats the flowing air that is exchanged with the exhaust gas from the combustion furnace and led to the combustion furnace.   The combustion apparatus according to claim 9, further comprising a thermal energy recovery device that recovers waste heat by exchanging heat with exhaust gas downstream of the air preheater.

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