JP5995685B2 - Waste heat recovery equipment - Google Patents

Description

  The present invention relates to a waste heat recovery facility, and more particularly, to a waste heat recovery facility incorporated in a waste treatment furnace equipped with a waste heat boiler.

  In order to treat organic sludge generated in the sewage treatment facility, an incineration facility and a melting facility for sludge are installed in the sewage treatment plant. For example, a fluidized bed incinerator or a coke bed melting furnace.

  In order to operate such incineration equipment and melting equipment, not only fossil fuels such as heavy oil and coke are required, but electric power is required to operate the equipment, and a certain maintenance cost is required.

  Waste treatment facilities such as large-scale waste incineration facilities have built-in power generation facilities that generate electricity from the steam generated in the waste heat boiler. The power required to operate the facilities is covered by self-generated power and surplus power is provided. Selling electricity to electric power companies.

  However, a small-scale waste incineration facility with a small amount of processing cannot earn much power generation, so that installation of the power generation facility is often forgotten from the viewpoint of economy and the like.

  Under such a background, it is considered that combustible components contained in organic sludge generated in a sewage treatment facility are incinerated or melted together with waste in a waste treatment furnace.

  According to such a waste treatment furnace, even when the amount of waste treated is not so large, by burning sludge as a heat source, steam can be generated to a certain extent with a waste heat boiler, and power generation equipment Can be installed. And it becomes possible to reduce an electric power cost and a fuel cost by utilizing the generated electric power in order to operate the installation containing a waste processing furnace.

In addition, the nitrogen (N) content in sewage sludge is very high, about five times that of general waste, so a large amount of nitrous oxide (N ₂ O) is generated during incineration of sludge at the sewage sludge incineration facility. Have an impact on global warming. In the sewage sludge incineration facility, in order to suppress the generation amount of nitrous oxide (N ₂ O), improvement is made by burning high temperature sludge from about 800 ° C to 850 ° C or more. There was a problem that the amount increased. Therefore, if sludge is co-fired with general waste in a garbage incinerator, high-temperature combustion is possible without using fossil fuel, and generation of nitrous oxide (N ₂ O) can be suppressed.

  By the way, in order to efficiently burn sewage sludge containing organic components as a heat source, it is necessary to dry the sludge in advance to reduce the water content. Therefore, in Patent Document 1 and Patent Document 2, the dewatered cake of sewage sludge is dried by a dryer and incinerated by an incinerator, and steam generated in the incinerator is supplied to the dryer to dry the dehydrated cake. A method for incinerating sewage sludge has been proposed.

  Patent Document 3 discloses a configuration in which the latent heat of exhaust steam from a back pressure turbine is used as a heat source for drying sludge.

JP 2004-278950 A JP 09-273704 A Japanese Patent Laid-Open No. 10-30809

  However, in the method for incinerating sewage sludge as described in Patent Document 1, it is necessary to use a part of the steam generated in the waste heat boiler installed in the incinerator for heating and drying the dehydrated cake. There was a problem that the amount of power generated by steam generated in the heat boiler was reduced.

  Moreover, in the method using the latent heat when the steam changes to condensate as described in Patent Document 3, it is difficult to sufficiently dry the sludge because the temperature is low. Moreover, when recovering the retained heat of the chimney exhaust gas and drying the sludge, for example, when exchanging heat between the exhaust gas at 200 ° C. and air at room temperature, the tube wall temperature does not decrease from the temperature at which low temperature corrosion occurs, It is necessary to adopt a circulation system that circulates a part of the air, and the heat exchanger becomes large, which is difficult to realize from the viewpoint of an increase in equipment cost and a restriction on installation space.

  In view of the above-described problems, an object of the present invention is a waste heat recovery facility capable of drying sludge by effectively utilizing waste heat of a waste treatment furnace without causing a reduction in power generation amount or low-temperature corrosion. Is to provide

  In order to achieve the above-mentioned object, the first characteristic configuration of the waste heat recovery facility according to the present invention is the waste heat incorporated in the waste treatment furnace equipped with the waste heat boiler as described in claim 1 of the claims. It is a recovery facility, and is installed in the flue and heat exchange is performed by the heat exchanger in which the pressurized feed water of the deaerator supplied to the waste heat boiler is branched and supplied as a heated medium. And a sludge dryer that dries the sludge with the medium to be heated.

  Usually, the retained heat of the exhaust gas flowing down to the flue through the waste heat boiler can be efficiently recovered by the heat exchanger.For example, the exhaust gas that has been sufficiently reduced in temperature by the heat exchanger can be bugged as it is without installing a temperature reduction tower. The filter can be made to flow down. As a result, it is not necessary to use steam generated by a waste heat boiler as in the prior art in order to dry sludge, and power generation efficiency is not reduced by steam.

  Since pressurized feed water, which is boiler feed water, is used as the heated medium for recovering waste heat, the heat transfer rate can be improved as compared with the case where gas is used as the heated medium, and the sludge can be dried more efficiently. It will be able to let you.

  In the second feature configuration, as described in claim 2, in addition to the first feature configuration described above, the heat exchanger is installed in a downstream flue of an economizer and supplied to the economizer The pressurization water supply of a vessel is branched and supplied as a to-be-heated medium.

  An economizer and a heat exchanger are arranged in this order along the flue, and pressurized water degassed by the deaerator is supplied to the economizer and the heat exchanger, respectively. For example, pressurized feed water heated by an economizer is supplied to a waste heat boiler, pressurized feed water heated by a heat exchanger is sent to a sludge dryer, and exhaust gas reduced in temperature after passing through the heat exchanger It is supplied to the exhaust gas treatment facility at the latter stage. Normally, exhaust gas that has passed through the economizer is sent to a dust collector such as a bag filter through a temperature reducing tower. However, according to the above configuration, the temperature is sufficiently reduced by a heat exchanger, so it is necessary to provide a temperature reducing tower. In addition, waste heat can be recovered efficiently. As a result, it is not necessary to use steam generated by a waste heat boiler as in the prior art in order to dry sludge, and power generation efficiency is not reduced by steam.

  In addition to the first or second feature configuration described above, the third feature configuration is the heat feature so that the exhaust gas discharged from the heat exchanger does not fall below a predetermined temperature. A control mechanism for adjusting the amount of water supplied to the exchanger is provided.

  Since the properties of the waste treated in the waste treatment furnace vary variously, the amount of exhaust gas flowing into the heat exchanger also varies. Even if the combustion state of the waste is greatly reduced and the amount of exhaust gas is reduced, the amount of water supplied to the heat exchanger is adjusted by the control mechanism so that the exhaust gas discharged from the heat exchanger does not fall below a predetermined temperature. The occurrence of low temperature corrosion can be prevented in advance.

  In addition, waste treatment furnaces equipped with an economizer with a large heat transfer area to eliminate the temperature-decreasing tower in front of the dust collector and adopting a so-called low-temperature eco that efficiently recovers waste heat has a large combustion state of waste. If the amount of exhaust gas decreases and the amount of exhaust gas decreases, the economizer absorbs heat more than necessary and the outlet temperature decreases, which may cause low-temperature corrosion. However, according to the above-described configuration, even if a normal economizer that is not so-called low-temperature ecology is used, not only a temperature-decreasing tower is unnecessary, but also the amount of water supplied to the heat exchanger is adjusted by the control mechanism. Can be prevented in advance.

  In the fourth feature configuration, in addition to any one of the first to third feature configurations described above, the sludge dried by the sludge dryer is treated as the waste. It is in the point provided with the sludge supply mechanism which supplies a furnace as waste.

  Since the sludge dried by the sludge dryer is supplied as waste to the waste treatment furnace via the sludge supply mechanism, the amount of heat retained by the sludge can be used effectively for power generation, and at least that power can be used to operate the equipment. Therefore, the operation cost can be reduced.

  In the fifth feature configuration, in addition to any one of the first to fourth feature configurations described above, the sludge vapor generated in the sludge dryer is supplied to the waste treatment furnace. It is in the point provided with the gas supply mechanism which supplies as stirring gas of a secondary combustion part.

  Since sludge vapor contains various odor components, a filter device that removes odor gas components is required to open the atmosphere. However, according to the above-mentioned configuration, since the sludge vapor generated in the sludge dryer is supplied as the stirring gas of the secondary combustion part of the waste treatment furnace, the odor component is thermally decomposed in the secondary combustion part. Moreover, since it is supplied to the secondary combustion section as high-temperature steam, secondary combustion can be promoted without causing a decrease in the secondary combustion temperature.

  In the sixth feature configuration, in addition to any one of the first to fifth feature configurations described above, the heated medium discharged from the sludge dryer is a deaerator. It is in the point provided with the supply path which supplies as a heat source.

  The boiler feedwater is circulated and supplied to the waste heat boiler after being deaerated by the deaerator. Conventionally, a part of the steam generated in the waste heat boiler and accumulated in the steam reservoir has been supplied to the deaerator as a heat source for deaeration. Pressurized water is supplied from the sludge dryer to the deaerator through the supply path, and is used as a heat source for deaeration. The power generation efficiency can be further increased.

  In addition to the sixth feature configuration described above, the seventh feature configuration is the same as the sixth feature configuration described above, and a steam reservoir that accumulates steam generated in the waste heat boiler, and is stored in the steam reservoir. A steam supply path for supplying a part of the steam as a heat source for the deaerator and a control mechanism for adjusting the amount of steam supplied to the deaerator are provided.

  If the pressurized water supplied from the sludge dryer to the deaerator is lowered to a temperature at which it becomes insufficient as a heat source for deaeration or the flow rate is lowered, there is a possibility that the deaeration may not be performed sufficiently. According to the above configuration, a part of the steam generated in the waste heat boiler and accumulated in the steam reservoir is supplied to the deaerator through the steam supply path as a heat source for deaeration, and the shortage of the heat source Can be supplemented. At this time, the supply amount of the steam to the deaerator can be adjusted by the control mechanism in accordance with the degree of shortage of the deaeration heat source supplied to the deaerator.

  As described above, according to the present invention, there is provided a waste heat recovery facility capable of drying sludge by effectively utilizing waste heat of a waste treatment furnace without causing a decrease in power generation amount or low temperature corrosion. I was able to do that.

Explanatory diagram of a waste treatment furnace incorporating waste heat recovery equipment according to the present invention Flow chart of control procedure executed by control device of heat exchanger Explanatory drawing of the operation mode of the waste heat recovery equipment by this invention Explanatory drawing of the model for calculating the mechanical size of the heat exchanger according to the present invention Explanatory drawing of the waste treatment furnace of another aspect in which the waste heat recovery equipment according to the invention is incorporated

Hereinafter, a waste heat recovery facility according to the present invention will be described with reference to the drawings.
FIG. 1 shows a stoker-type incinerator 1 which is an example of a waste treatment furnace constructed within a site of a sewage treatment plant. Waste such as municipal waste thrown into the hopper 2 is charged into the furnace by the pusher mechanism 3 below the hopper 2 and is primarily burned while being stirred and pressed by the stalker mechanism 4, and the combustion gas is in the upper space. Complete combustion is performed at a temperature of about 950 ° C. in the secondary combustion section 5.

  The primary combustion air is supplied from the primary combustion air supply mechanism 6 provided below the stalker mechanism 4 so that the waste is primarily burned on the stoker, and the vaporized combustible gas and the air that has not contributed to the primary combustion are secondary combustion. Secondary combustion is performed in part 5. Installed on the side wall of the secondary combustion section 5 is a gas supply mechanism 7 composed of a gas injection nozzle group for supplying a stirring gas for stirring the unburned gas and air completely in the secondary combustion section. Has been.

  A waste heat boiler 8 and a superheater 9 are installed above the secondary combustion unit 5, and steam generated by the waste heat boiler 8 and superheated by the superheater 9 is supplied to the power generation equipment 20 via the steam reservoir 27. Is done. The exhaust gas that has passed through the waste heat boiler is exhausted from the chimney 15 through the economizer 10, the heat exchanger 11, the bag filter 12, and the like disposed along the flue.

  The power generation facility 20 includes a steam turbine 21 to which superheated steam from a steam reservoir 27 is supplied, a generator 22 that is rotationally driven by the steam turbine 21, a condenser 23, a condensate tank 24, a deaerator 25, and the like. ing. The exhaust steam from the steam turbine 21 is condensed by the condenser 23, and the boiler feed water deaerated by the deaerator 25 is recirculated and supplied to the waste heat boiler 8 after remaining in the economizer 10.

  A waste heat recovery facility 30 according to the present invention includes the above-described heat exchanger 11 and a sludge dryer 31. The heat exchanger 11 is installed in a flue on the downstream side of the economizer 10, and pressurized supply water of the deaerator 25 supplied to the economizer 10 is branched and supplied as a medium to be heated.

  Boiler feed water heated by the economizer 10 is supplied to the waste heat boiler 8, and pressurized water heated by the heat exchanger 11 is sent to the sludge dryer 31. Then, the exhaust gas whose temperature has been reduced after passing through the heat exchanger 11 is supplied to the exhaust gas treatment facility at the subsequent stage.

  Normally, the exhaust gas that has passed through the economizer 10 is sent to a dust collector such as a bag filter through a temperature reducing tower. However, according to this configuration, the temperature is sufficiently reduced by the heat exchanger 11, so that the temperature reducing tower or the like is separately provided. Therefore, the waste heat can be efficiently recovered.

  As a result, it is not necessary to use the steam generated in the waste heat boiler 8 in the conventional manner to dry the sludge, and the power generation efficiency is not reduced by the steam.

  A water supply valve mechanism 32a is provided in the inlet path of the pressurized water supply to the heat exchanger 11, and a water discharge valve mechanism 32b is provided in the outlet path. The control device 33 controls the opening degree of these valve mechanisms 32 (32a, 32b). (33a, 33b) are provided.

  The control device 33 (33a, 33b) measures the temperature of the exhaust gas that has passed through the heat exchanger 11 with a temperature sensor, adjusts the opening degree of the water supply valve mechanism 32a based on the measured temperature, and outputs the heat exchanger 11 at the outlet. The pressure of the pressurized water is measured with a pressure sensor, and the opening degree of the water discharge valve mechanism 32b is adjusted based on the measured value.

  As shown in FIG. 2, when the temperature of the exhaust gas that has passed through the heat exchanger 11 falls below a predetermined lower limit temperature set to avoid low-temperature corrosion, for example, 160 ° C. (S1, S33). Y) The water supply valve mechanism 32a is closed or throttled to avoid a decrease in exhaust gas temperature (S2), and when the exhaust gas temperature is higher than the predetermined lower limit temperature (S1, N), the water supply The opening degree of the valve mechanism 32a is adjusted to maintain the exhaust gas temperature at a predetermined temperature or higher (S3).

  Furthermore, if the pressure of the pressurized water at the outlet of the heat exchanger 11 is within a predetermined pressure range, for example, 3 MPa to 4 MPa (S4, Y), the control device 33b (33) opens the outlet valve mechanism 32b. Is maintained (S5), and if it deviates from the predetermined pressure range (S4, N), the opening degree of the water discharge valve mechanism 32b is adjusted by PID control so as to be maintained within the predetermined range (S6). When the pressure rises above the pressure, the heat exchanger is prevented from blowing out, and the pressurized water is prevented from evaporating in the heat exchanger.

  In step S3, for example, PID control can be performed in which the opening target value of the feed water valve mechanism 32a is calculated based on the deviation between the current exhaust gas outlet temperature and the exhaust gas outlet target temperature, and the target value is controlled. For example, the above-described lower limit temperature for avoiding low-frequency corrosion can be set as the exhaust gas outlet target temperature.

  In step S6, for example, PID control is performed to calculate the opening target value of the water discharge valve mechanism based on the deviation between the current pressure of the pressurized water and the target pressure set in the predetermined pressure range, and to control to the target value. be able to. Note that the same PID control may be performed in step S5.

  That is, the control device 33 (33a) and the valve mechanism 32 (32a) constitute a control mechanism that adjusts the amount of water supplied to the heat exchanger 11 so that the exhaust gas discharged from the heat exchanger 11 does not fall below a predetermined temperature. Has been. For convenience of explanation, the control device 33 is described as being composed of two blocks 33a and 33b. However, the control device 33 may be composed of independent separate bodies, or may be configured integrally. In addition, each may be configured to control the controlled object independently.

  The sludge dryer 31 is a device for drying dehydrated sludge using pressurized water, which is a medium to be heated that has been heat-exchanged by the heat exchanger 11, as a heat source. The inner cylindrical body 34b is a drive mechanism with respect to the outer cylindrical body 34a. It is composed of a coaxial double cylindrical body (kiln) 34 that is rotatably supported via (not shown). The dewatered sludge is surplus sludge generated in a sewage treatment facility and is sludge dehydrated by a dehydrator such as a filter press.

  The dewatered sludge supplied from one end side of the cylindrical body (kiln) 34 to the inner cylindrical body 34b via the feeder 37 is stirred and conveyed by the stirring blade provided on the inner wall as the inner cylindrical body 34b rotates. While being heated and dried, it is discharged from the other end. The pressurized water heated by the heat exchanger 11 is supplied from the other end side to the space partitioned by the outer cylindrical body 34a and the inner cylindrical body 34b so as to face the sludge conveyance direction, and the inner cylindrical body 34b. After the sludge is indirectly heated through the wall surface, it is discharged from one end side.

  Since pressurized water is used as a heated medium for recovering waste heat, the heat transfer rate can be improved as compared with the case where a gas such as steam or air is used as the heated medium, and sludge can be dried more efficiently. You can also do it.

  The heated medium discharged from the sludge dryer 31 is sent to the deaerator 25 through the supply line 26 as a heat source for deaeration.

  The sludge dried by the sludge dryer 31 is supplied to the lower part of the hopper 2 of the waste treatment furnace through a sludge supply mechanism 35 constituted by a screw type transport mechanism or the like, and is put into the furnace by the pusher 3 and incinerated. It is processed.

  The sludge dryer 31 is provided with a control device 33 (33c) for controlling the amount of sludge charged into the sludge dryer 31. The control device 33 (33c) receives the measurement value of the sludge humidity at the outlet of the sludge dryer 31, the throttle amount of the valve mechanism 32a, or the flow rate of pressurized water so that the sludge humidity falls within a predetermined target humidity range. The feed amount of the feeder 37 that feeds the sludge into the sludge dryer 31 is controlled.

  As shown in FIG. 2, the control device 33 determines whether or not the sludge humidity at the outlet of the sludge dryer 31 is maintained within a predetermined target humidity range (S7). (S8, Y), the correction amount determined according to the flow rate of the pressurized water at that time or the throttle amount of the valve mechanism 32a is calculated, and the amount of sludge input by the feeder 37 is decreased (S9), and the deviation deviates downward. If this occurs (insufficient drying) (S8, N), a correction amount determined according to the flow rate of the pressurized water at that time or the throttle amount of the valve mechanism 32a is calculated, and the amount of sludge input by the feeder 37 is increased (S10). .

  When deviating downward (insufficient drying), the rotational speed of the inner cylindrical body 34b is reduced to promote drying, and when deviating upward (insulating insufficiently), the inner cylindrical body 34b rotates. Control may be performed so as to increase the speed and quickly discharge.

  The sludge vapor generated inside the inner cylindrical body 34 b of the sludge dryer 31 is sent to the gas supply mechanism 7 provided on the side wall of the secondary combustion unit 5 through the steam duct 36. Since the high-temperature steam is supplied to the secondary combustion unit 5 as the stirring gas, the unburned gas and air are well stirred and the complete combustion is achieved without causing a decrease in the secondary combustion temperature. At this time, since the odor component contained in the sludge vapor is also thermally decomposed in the secondary combustion unit 5, it is not necessary to provide a separate filter mechanism for removing the odor.

  In order to supply the sludge vapor to the gas supply mechanism 7 at a predetermined pressure, the steam duct 36 may be provided with a blower mechanism or a pressure adjusting mechanism such as an accumulator.

  As described above, the waste heat recovery facility 30 performs the sludge drying process in the sludge dryer 31 using the pressurized water, which is the heating medium heat-exchanged in the heat exchanger 11, as a heat source, and further in the deaerator 25. It is comprised so that a deaeration process may be performed.

  However, the pressurized water supplied from the mud dryer 31 to the deaerator 25 via the supply pipeline 26 may be insufficient as a heat source for deaeration. For example, when the temperature of the pressurized water supplied from the sludge dryer 31 to the deaerator 25 via the supply line 26 is lower than the temperature necessary for deaeration, or the temperature of the pressurized water is a temperature necessary for deaeration. However, when the flow rate is small, the deaerator 25 cannot sufficiently deaerate.

  Therefore, a steam supply path 28 for supplying a part of the steam superheated by the superheater 9 to the deaerator 25 is provided, and control for adjusting the amount of steam supplied to the deaerator 25 via the steam supply path 28 is provided. A valve mechanism 32c as a mechanism and a control device 33 (33d) are provided.

  As described above, the steam generated by the waste heat boiler 8 and superheated by the superheater 9 is supplied to the steam turbine 21 via the high-pressure steam reservoir 27. Further, a part of the superheated steam is accumulated from the high pressure steam reservoir 27 to the low pressure steam reservoir 29, and the low pressure superheated steam is used for various heat sources. The low pressure steam reservoir 29 is also supplied with a portion of the steam whose pressure has been reduced somewhat by applying pressure energy to the steam turbine 21.

  The control device 33 (33d) measures the internal pressure of the deaerator 25, and adjusts the opening degree of the valve mechanism 32c when the target pressure necessary for deaeration is not reached, and causes the deaerator 25 to overheat at a low pressure. Supply steam.

  When the amount of heat consumed in the sludge dryer 31 is small, such as when the amount of sludge input to the sludge dryer 31 is small, the amount of heat flowing into the deaerator 25 inevitably increases. In this case, although the pressure of the deaerator 25 becomes high, the steam consumption for deaerator heating is reduced by adjusting the opening degree of the valve mechanism 32c to a necessary opening degree by the PID calculation, and the steam turbine is correspondingly increased. Since the amount of power generation increases, the energy recovered by the heat exchanger 11 can be used as energy for drying sludge and power generation.

  In the description using FIG. 1, the control device 33 is configured by four blocks indicated by reference numerals 33 a, 33 b, 33 c, and 33 d, but each block may be configured by one control device or individually. May be configured, or two blocks indicated by reference numerals 33a and 33b are integrated into one control apparatus, and two blocks indicated by reference numerals 33c and 33d are integrated into one control apparatus. May be.

  In addition, when each block is configured by an individual control device, the control information may be transmitted and received with a signal line connecting the control devices. For example, the control mechanism 33d can obtain the flow rate of the pressurized water by receiving the throttle amount of the valve mechanism 32a from another control device.

Hereinafter, the operation mode of the waste treatment furnace and the waste heat recovery facility will be described with reference to FIG.
The 4 MPa, 400 ° C. superheated steam obtained by the waste heat boiler 8 and the superheater 9 installed in the secondary combustion section 5 that burns in the range of about 800 ° C. to 1000 ° C. is supplied to the steam turbine 21 via the steam reservoir 27. And the generator 22 is driven.

  The exhaust steam from the steam turbine 21 is condensed through the condenser 23 and collected in the condensate tank 24, and then condensate of about 60 ° C. is supplied from the condensate tank 24 to the deaerator 25. Water is supplied to the economizer 10 and the heat exchanger 11 as boiler feed water that has been degassed and heated to 143 ° C.

  Boiler feed water heated to 200 ° C. by the economizer 10 is circulated and supplied to the waste heat boiler 8, and pressurized water heated to a pressure of 3 MPa to 4 MPa and a temperature of 160 ° C. by the heat exchanger 11 is supplied to the sludge dryer 31. The high-temperature pressurized water discharged from the sludge dryer 31 is supplied to the deaerator 25 and used as a heat source for deaeration.

  Organic sludge having a water content of 80% to 90% is charged into the sludge dryer 31 and indirectly heated with pressurized water at 160 ° C., and dried to a water content of 10% to 20% at a high temperature close to 100 ° C. The dried sludge is transported to the incinerator 1 via the sludge supply mechanism 35 and incinerated with other waste. The sludge vapor generated in the sludge dryer 31 is supplied via the gas supply mechanism 7 with the stirring gas of the secondary combustion unit 5 of the incinerator 1.

  The exhaust gas heat-exchanged by the waste heat boiler 8 and the superheater 9 and reduced in temperature by about 350 ° C. is reduced in the range of 210 ° C. to 180 ° C. by the economizer 10 and further 180 ° C.-160 ° C. by the heat exchanger 11. After the temperature is reduced to the range of ° C., the dust is removed by the bag filter 12, and the acid gas component is removed, and then exhausted from the chimney 15.

  FIG. 4 (a) shows an example in which a boiler feed water of 143 ° C. is preheated to 200 ° C. and the exhaust gas is reduced to 210 ° C. by using a general economizer with 350 ° C. exhaust gas. 4 (b) shows an example in which the boiler feed water at 143 ° C. is preheated to about 210 ° C. and the exhaust gas is reduced to 180 ° C. by the exhaust gas at 350 ° C. using a high efficiency low temperature economizer. .

  According to the former, it is necessary to install a temperature reducing tower, for example, a temperature reducing tower that sprays water on the exhaust gas to reduce the temperature between the economizer and the subsequent bag filter. Therefore, it is not necessary to provide a temperature reducing tower, and waste heat can be efficiently recovered.

  In FIG. 4 (c), the heat exchanger of the present invention is arranged after the economizer so that the boiler feed water at 143 ° C. is preheated to about 200 ° C. by the economizer and the exhaust gas is reduced to 210 ° C. by the economizer. Further, an example is shown in which boiler feed water at 143 ° C. is preheated to about 160 ° C. by a heat exchanger with 210 ° C. exhaust gas, and the temperature of the exhaust gas is reduced to 180 ° C.

Heat absorption Q, overall heat transfer coefficient K, heat transfer area A, temperature T, logarithmic mean temperature difference ΔT, specific heat C, flow rate W, exhaust gas heat exchanger inlet temperature Tg1, outlet temperature Tg2, heat medium inlet temperature Assuming Tw2 and outlet temperature Tw1, the following approximate expression is established.
[Formula 1]
Q = KAΔT
[Formula 2]
Q = {WCT (exit)-WCT (entrance)} ∝ (T (exit)-T (entrance))
[Formula 3]
ΔT = {(Tg1-Tw1)-(Tg2-Tw2)} / {ln (Tg1-Tw1) -ln (Tg2-Tw2)}
Here, K and WC are assumed to be substantially constant.

  When the logarithmic temperature difference ΔT in each of FIGS. 4A, 4B, and 4C is obtained, Q is obtained from Equation 2, and Q and ΔT are substituted into Equation 1 to obtain KA. In a), KA = 1.359, in FIG. 4B, KA = 2.218, in FIG. 4C, the front stage has KA = 1.359 and the rear stage has KA = 0.622. These values correspond to the total area of the heat transfer section.

  Based on the heat transfer area of the basic economizer in FIG. 4 (a), the heat transfer area is about 1.63 times larger in the high-efficiency low-temperature economizer in FIG. 4 (b), and FIG. When the heat exchanger of the present invention and the conventional economizer are combined, the heat transfer area is about 1.48 times.

  That is, the exhaust gas temperature can be reduced equally with a smaller heat transfer area than the high-efficiency low-temperature economizer of FIG.

Below, based on FIG. 5, another embodiment of the waste-treatment furnace provided with the waste heat recovery equipment 30 by this invention is described.
In addition, the structure different from the waste treatment furnace mainly shown in FIG. 1 will be described in detail, and the same structure will be denoted by the same reference numeral and the description will be simplified.

  The waste treatment furnace shown in FIG. 5 is similar to the waste treatment furnace shown in FIG. 1 in the incinerator 1, the waste heat boiler 8, the power generation equipment 20, the waste heat recovery equipment 30 (the heat exchanger 11 and the sludge dryer 31). ) Etc. However, the configuration of the equipment arranged in the flue from the incinerator 1 to the chimney 15 is different from the waste treatment furnace shown in FIG.

  In the flue, an economizer 10, a temperature reducing tower 16, a bag filter 12, a reheater 17, a catalytic reaction tower 18, and a heat exchanger 11 are arranged from the upstream side, and the heat-exchanged exhaust gas is exhausted from the chimney 15. . That is, the heat exchanger 11 constituting the waste heat recovery facility 30 is arranged between the catalytic reaction tower 18 and the chimney 15.

  The exhaust gas whose temperature has been reduced to 180 to 210 ° C. by the economizer 10 is reduced to 160 to 180 ° C. by the temperature reducing tower 16, dust is removed by the heat-resistant bag filter 12, and steam generated in the waste heat boiler 8 is used as a heat source. After being reheated to 180 to 210 ° C. by the reheater 17, nitrogen oxides and dioxins are decomposed by the catalytic reaction tower 18.

  The retained heat of the exhaust gas at 180 to 210 ° C. discharged from the catalytic reaction tower 18 is recovered by the heat exchanger 11 according to the present invention. In other words, the waste heat recovery facility is installed in the flue downstream of the economizer 10, and heat exchange is performed with the heat exchanger 11 in which the pressurized water supply of the deaerator 25 supplied to the economizer 10 is branched and supplied as a heated medium. And a sludge dryer that dries the sludge with the heated medium heat-exchanged in the vessel 11.

  In the above-described embodiments, the configuration in which the economizer 10 is provided in the flue downstream of the waste heat boiler 8 has been described, but heat exchange is performed in the flue downstream of the waste heat boiler 8 without providing the economizer 10. The structure provided only with the container 11 may be sufficient.

  In the above-described embodiment, the example in which the waste heat recovery facility is incorporated in the stoker-type incinerator has been described. However, the waste treatment furnace in which the waste heat recovery facility is incorporated is not limited to the stoker-type incinerator, and is a fluidized bed. It may be an incinerator of another type such as a type incinerator or a melting furnace such as a coke bed type melting furnace or a surface melting furnace.

  The embodiment described above is a specific example of the present invention, and the scope of the present invention is not limited by the description, and the specific configuration of each part of the waste heat recovery facility exhibits the effects of the present invention. Needless to say, the design can be changed as appropriate within the range.

1: Incinerator (waste treatment furnace)
5: Secondary combustion section 7: Gas supply mechanism 8: Waste heat boiler 10: Economizer 11: Heat exchanger 25: Deaerator 26: Supply pipeline (supply path)
30: Waste heat recovery equipment 31: Sludge dryer 32: Valve mechanism (control mechanism)
33: Control device (control mechanism)
35: Sludge supply mechanism

Claims (7)

A waste heat recovery facility incorporated in a waste treatment furnace equipped with a waste heat boiler,
A heat exchanger that is installed in a flue and is branched and supplied with pressurized feed water of a deaerator supplied to the waste heat boiler as a heated medium;
A sludge dryer for drying the sludge by the heated medium heat-exchanged by the heat exchanger;
Waste heat recovery equipment equipped with.   The waste heat recovery facility according to claim 1, wherein the heat exchanger is installed in a flue downstream of an economizer, and pressurized feed water of a deaerator supplied to the economizer is branched and supplied as a medium to be heated.   The waste heat recovery facility according to claim 1 or 2, further comprising a control mechanism that adjusts the amount of water supplied to the heat exchanger so that the exhaust gas discharged from the heat exchanger does not fall below a predetermined temperature.   The waste heat recovery facility according to any one of claims 1 to 3, further comprising a sludge supply mechanism that supplies the sludge dried by the sludge dryer as waste to the waste treatment furnace.   The waste heat recovery equipment according to any one of claims 1 to 4, further comprising a gas supply mechanism that supplies the sludge vapor generated in the sludge dryer as a stirring gas for a secondary combustion section of the waste treatment furnace.   The waste heat recovery facility according to any one of claims 1 to 5, further comprising a supply path for supplying a heated medium discharged from the sludge dryer as a heat source of a deaerator.   A steam reservoir for accumulating the steam generated in the waste heat boiler; a steam supply path for supplying a part of the steam accumulated in the steam reservoir as a heat source for the deaerator; and a steam supply to the deaerator The waste heat recovery facility according to claim 6, further comprising a control mechanism for adjusting a supply amount.

Images