JP6214885B2 - Waste heat recovery system and waste heat recovery method - Google Patents

Description

  The present invention recovers the thermal energy of the heated air obtained when the exhaust gas from the incinerator is treated with the exhaust gas through the exhaust gas heat exchanger and the flue gas treatment tower and the thermal energy of the flue gas from the flue gas treatment tower. The present invention relates to an exhaust heat recovery system and an exhaust heat recovery method having an exhaust heat energy recovery conversion device that converts energy into energy.

  The exhaust gas from an incinerator such as a sewage sludge incinerator is a high-temperature exhaust gas of about 800 to 850 ° C. For this reason, as shown in Patent Document 1, it has been proposed that this high-temperature exhaust gas is guided to a waste heat boiler to generate water vapor, and a generator is rotated by a steam turbine to perform exhaust heat power generation. However, there is a demand for a system with a higher energy recovery rate because the amount of power generation corresponding to the amount of capital investment cannot be obtained.

For this reason, in general incineration plants, high-temperature exhaust gas discharged from incinerators is passed through a white smoke prevention air preheater and other heat exchangers to collect part of the exhaust heat, and dust is collected in the dust collector. Usually, only exhaust gas treatment is performed in which the components are separated and removed, and further washed with water through a flue gas treatment tower to remove components such as HCl and SO _X in the exhaust gas.

  When the incinerator is a fluidized incinerator, the fluidized air preheater may be installed before the white smoke preventing air preheater. In addition, when the dust collector is a ceramic filter, high temperature dust collection of about 400 ° C. is possible, but when it is a bag filter, the dust is collected after the temperature is lowered to 200 ° C. or less in the cooling tower. .

  In such a normal exhaust gas treatment system, exhaust gas at 200 to 400 ° C. is cooled to about 30 ° C. in the flue gas treatment tower, while smoke washed waste water is discharged at 50 to 75 ° C. Although the smoke washing wastewater is relatively low in temperature, the specific heat of water is large, so the amount of heat is large and exceeds 50% of the amount of heat of the exhaust gas. This energy is almost wasted other than being used for a conventional hot water pool or the like, and its effective use is expected. However, since the temperature range is a low level of 50 to 75 ° C., effective use has been considered difficult.

JP-A-2005-323131 JP 2010-174845 A JP-A-51-108145

  For this reason, in Patent Document 2, waste heat generation using exhaust gas from an incinerator that can effectively recover energy as electric power by effectively using the retained heat of the smoke washing wastewater of the flue gas treatment tower that has been exhausted in the past. A method is described.

  In the exhaust heat power generation method described in Patent Document 2, the retained heat of the smoke-washed waste water that is discarded is recovered. However, in order to condense and discharge the water vapor in the exhaust gas, the input exhaust gas needs to be lower than the dew point temperature by the smoke-washed water circulated in the smoke treatment tower. In this case, since the temperature of the circulating smoke cleaning water rises due to the retained heat of the exhaust gas and it becomes impossible to maintain the temperature below the dew point, it is necessary to supply cooling water to the smoke cleaning water from the outside. Energy loss due to wastewater temperature drop cannot be ignored.

  Further, according to the knowledge of the present inventor, the latent heat of water vapor contained in the exhaust gas has extremely high thermal energy compared to the sensible heat of the exhaust gas. Specifically, the latent heat of water vapor contained in the exhaust gas is 600 kcal / kg, whereas the sensible heat of water vapor in the exhaust gas is 0.4 kcal / kg · K, and the sensible heat of dry gas other than water vapor is 0.25 kcal. / Kg · K. Therefore, if the thermal energy of the latent heat of the water vapor can be recovered, the heat retained in the smoke washing wastewater of the smoke treatment tower can be used more effectively.

  The present invention has been made in view of the above, and an object of the present invention is to recover not only sensible heat energy in exhaust gas but also latent heat energy in water vapor contained in the exhaust gas. An object of the present invention is to provide an exhaust heat recovery system and an exhaust heat recovery method that can further increase the energy recovery rate in the processing tower.

  In order to solve the above-mentioned problems and achieve the object, an exhaust heat recovery system according to the present invention includes an exhaust gas heat exchanger for exchanging heat of exhaust gas from an incinerator and an exhaust gas treatment tower for processing exhaust gas. The exhaust air that collects the thermal energy of the heated air obtained when the exhaust gas is treated through the exhaust gas heat exchanger and the flue gas treatment tower and the smoke washing water in the flue gas treatment tower and converts it into other energy The heat of the smoke-washing water flowing through the smoke-washing circuit on the smoke-washing circuit that has a thermal energy recovery conversion device and the smoke treatment tower circulates the smoke-washed water collected in the lower part of the tower to wash the exhaust gas. A smoke washing heat exchanger for supplying the recovered heat energy to the exhaust heat energy recovery and conversion device is provided, and the input exhaust gas is sprinkled with the smoke washing cooling water cooled by the smoke washing heat exchanger Waste heat recovery system washed with water The flue gas treatment tower is configured to be able to input treated water that cools the exhaust gas that has been washed with sprinkling of the smoke washing cooling water, and the treated water after cooling the exhaust gas is washed. It has a supply destination selection means that selects at least one of mixing with smoke and discharging to the outside, and keeps the temperature of the smoke cleaning water above the operating temperature of the exhaust heat energy recovery converter and below the temperature based on the saturated absolute humidity in the exhaust gas As described above, the apparatus includes control means for controlling the supply destination selection means.

  The exhaust heat recovery system according to the present invention is characterized in that, in the above invention, the exhaust heat energy recovery conversion device forms a heat cycle using a medium having a boiling point lower than that of water.

  In the exhaust heat recovery system according to the present invention, in the above invention, the exhaust heat energy recovery conversion device includes a steam turbine disposed on a thermal cycle, and outputs electric power via a generator connected to the steam turbine. Or the rotational power of the steam turbine is output.

  Further, in the exhaust heat recovery system according to the present invention, in the above invention, the condensed post-treatment water used for the condenser cooling water used in the condenser arranged on the thermal cycle is supplied to the upper part of the flue gas treatment tower. It is used as treated water for cooling.

  The exhaust heat recovery method according to the present invention includes an exhaust gas heat exchanger for exchanging heat of exhaust gas from the incinerator, and an exhaust gas treatment tower for processing the exhaust gas, the exhaust gas heat exchanger and the exhaust gas In an exhaust heat recovery system having an exhaust heat energy recovery conversion device that recovers thermal energy of heated air obtained when treating exhaust gas through a treatment tower and smoke washing water in the exhaust treatment tower and converts it into other energy In the smoke cleaning circuit that circulates the smoke cleaning water accumulated in the lower part of the flue gas treatment tower and cleans the exhaust gas with water, recover the thermal energy of the smoke cleaning water flowing through the smoke cleaning circuit and collect the recovered thermal energy. A waste heat recovery method for supplying exhaust gas to a waste heat energy recovery conversion device and washing the exhaust gas with a sprinkle of smoke wash cooling water cooled by the recovery of heat energy. By watering Input the treated water that cools the exhaust gas that has been washed with water, and the temperature of the smoke cleaning water is higher than the operating temperature of the exhaust heat energy recovery converter for the treated water after cooling the exhaust gas, based on the saturated absolute humidity in the exhaust gas It is characterized by selectively controlling at least one of mixing with smoke-washing water and discharging to the outside so that the temperature is maintained below the temperature.

  The exhaust heat recovery method according to the present invention is characterized in that, in the above invention, the exhaust heat energy recovery conversion device forms a thermal cycle using a medium having a boiling point lower than that of water.

  In the exhaust heat recovery method according to the present invention, in the above invention, the exhaust heat energy recovery conversion device includes a steam turbine disposed on a thermal cycle, and outputs electric power via a generator connected to the steam turbine. Or the rotational power of the steam turbine is output.

  Further, in the exhaust heat recovery method according to the present invention, in the above invention, the post-condensation treated water for the condensing cooling water used in the condenser disposed on the thermal cycle is supplied to the upper part of the flue gas treatment tower. It is used as treated water for cooling.

  According to the present invention, not only sensible heat energy in exhaust gas but also latent heat heat energy in water vapor contained in exhaust gas can be recovered, and the energy recovery rate in the flue gas treatment tower can be further increased. .

FIG. 1 is a block diagram showing a schematic configuration of a sludge incineration system including an exhaust heat recovery system according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing the configuration of the flue gas treatment tower and its surroundings according to the first embodiment of the present invention. FIG. 3 is a block diagram showing a schematic configuration of a sludge incineration system including an exhaust heat recovery system according to the second embodiment of the present invention. FIG. 4 is a block diagram showing a configuration of Modification 1 of the exhaust heat recovery system. FIG. 5 is a block diagram showing a configuration of Modification 2 of the exhaust heat recovery system. FIG. 6 is a block diagram showing a configuration of Modification 3 of the exhaust heat recovery system.

  Embodiments of the present invention will be described below with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals. Further, the present invention is not limited to the embodiments described below.

(First embodiment)
First, a sludge incineration system including an exhaust heat recovery system according to a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a schematic configuration of a sludge incineration system including an exhaust heat recovery system according to the first embodiment.

  As shown in FIG. 1, this sludge incineration system includes an incinerator 1, a fluid air preheater 2, a white smoke prevention air preheater 3, a dust collector 4, a flue gas treatment tower 5, a chimney 6, a control unit 7, and a temperature sensor 8. And an exhaust heat energy recovery conversion device 10.

  The incinerator 1 is a fluidized incinerator for incinerating sewage sludge, and outputs high-temperature exhaust gas of about 800 to 850 ° C. The incinerator 1 is not limited to a fluidized incinerator, and may be another incineration type gasification furnace such as a circulating incinerator, and the incinerator is not limited to sewage sludge.

  The fluidized air preheater 2 receives the exhaust gas from the incinerator 1, raises the air temperature to, for example, 650 ° C. fluidized air A 1, and supplies it to the bottom of the incinerator 1. The white smoke prevention air preheater 3 is an example of a heat exchanger for exhaust gas. The white smoke prevention air preheater 3 is arranged at the rear stage of the fluidized air preheater 2 and uses the thermal energy of the exhaust gas output from the fluidized air preheater 2 to White smoke prevention air A2, which is heated air for preventing the water vapor in the discharged exhaust gas from being seen as white smoke, is generated. The temperature of the white smoke prevention air A2 is about 400 ° C. The temperature of the exhaust gas that has passed through the white smoke prevention air preheater 3 is lowered to about 200 to 400 ° C.

  The hot water generator 22 is a heat exchanger, collects a part of the thermal energy from the white smoke prevention air A2, and supplies it to the exhaust heat energy recovery conversion device 10. The hot water generator 22 supplies the heated air whose temperature has decreased to the chimney 6 through the blower B. A control valve V1 is connected in parallel to the hot water generator 22. And the amount of heat recovery from the white smoke prevention air A2 by the hot water generator 22 can be adjusted by adjusting the control valve V1. Further, the heated air in which a part of the heated air sent from the blower B and the new atmosphere are mixed is resupplied to the white smoke prevention air preheater 3.

  The dust collector 4 is disposed downstream of the white smoke prevention air preheater 3 and removes dust in the exhaust gas input from the white smoke prevention air preheater 3. The dust collector 4 is a ceramic dust collector with excellent heat resistance, and can collect the impurities of the exhaust gas that has passed through the white smoke prevention air preheater 3 as it is. The temperature drop of the exhaust gas in the dust collector 4 is small, and the temperature of the exhaust gas G1 after passing through the dust collector 4 is 200 to 400 ° C. The dust collector 4 may use a bag filter. In this case, it is necessary to arrange a cooling tower in front of the bag filter to lower the temperature to the heat resistance temperature of the bag filter.

Flue gas treatment tower 5 introduces exhaust gas G1 from the bottom of the column, contained into contact with water sprinkled from the top of the water spray nozzles 5a and HCl in the flue gas G1, a component such as SO _X in Araikemuri water W It is a device to remove. This smoke-washing water W is water containing heat to be recovered that was used to wash exhaust gas with water, collected in the lower part of the tower, and sent to the spray nozzle 5a by the smoke-washing circulation path R and the circulation pump P1. And recycled. Further, a smoke washing heat exchanger 21 is provided at the subsequent stage of the pump P1. The smoke-washing heat exchanger 21 recovers heat from the smoke-washing water W discharged from the inside of the smoke treatment tower 5, and is sent to the water spray nozzle 5a as smoke-washing cooling water W1. The heat energy recovered by the smoke washing heat exchanger 21 is supplied to the exhaust heat energy recovery conversion device 10 side. In addition, in order to suppress the increase in the concentration of the smoke washing water W, a part of the smoke washing cooling water W1 is branched from the smoke washing circulation path R between the smoke washing heat exchanger 21 and the water spray nozzle 5a to obtain a smoke washing drain W3. Discard.

  Here, in the above-described flue gas treatment tower 5, since the exhaust gas G1 and the smoke-washing cooling water W1 are in contact, most of the heat energy of the exhaust gas G1 at 200 to 400 ° C. moves to the smoke-washing water W side. Note that the temperature of the smoke wash water W is measured by the temperature sensor 8. The smoke washing water W having the thermal energy recovered from the exhaust gas G1 is recovered by the smoke cleaning heat exchanger 21, and the recovered thermal energy is supplied to the exhaust heat energy recovery conversion device 10 side. Although details will be described later, in the first embodiment, by controlling the temperature of the smoke-washed water W, not only the sensible heat energy of the exhaust gas G1, but also the heat of latent heat of water vapor contained in the exhaust gas G1. It also recovers energy.

  A chimney 6 is disposed in the upper part of the flue gas treatment tower 5, and the exhaust gas G <b> 2 cleaned in the flue gas treatment tower 5 is subjected to white smoke prevention treatment in the chimney 6 and then released from the chimney 6 to the atmosphere. The The treated water W <b> 4 is supplied to the upper stage of the flue gas treatment tower 5 and upstream of the chimney 6. The treated water W4 is sufficiently washed with the exhaust gas G2 to wash the exhaust gas G2. The amount of discarded low-temperature waste water W5 that has been washed with water is controlled by a control valve 9 serving as a supply destination selection unit whose amount of opening is adjusted by the control of the control unit 7. That is, when the opening degree of the control valve 9 is 0, that is, in the closed state, all of the low temperature waste water W5 is mixed with the smoke-washed water W. When the opening degree of the control valve 9 is such that it can pass through all of the low temperature waste water W5, all of the low temperature waste water W5 is discarded. And when the opening degree of the control valve 9 is between them, that is, when the opening degree is not 0 and the low temperature waste water W5 is not completely allowed to pass through, a part of the low temperature waste water W5 is in the smoke treatment tower 5. While being mixed with the smoke-washing water W, the remainder is discarded or discharged to the outside and reused.

  The exhaust heat energy recovery conversion device 10 has a function of recovering the thermal energy of the white smoke prevention air A2 that is heated air and the smoke cleaning water W of the exhaust gas treatment tower 5 and converting it into other energy, and the evaporator 11 , Superheater 12, steam turbine 13, condenser 14, generator 15, and circulation pump P4. Then, the evaporator 11, the superheater 12, the steam turbine 13, the condenser 14, and the circulation pump P4 are used to generate a low-boiling point medium such as chlorofluorocarbon having a lower boiling point than water, alternative chlorofluorocarbon, ammonia, or a mixed fluid of ammonia and water. A thermal cycle S such as a Rankine cycle or a carina cycle circulated as the working medium L is formed. CFCs and CFC substitutes are preferable because they have a low boiling point and are easy to handle. Ammonia is a colorless and transparent low-boiling medium originally existing in nature, and its evaporation temperature is −33.3 ° C. and 4.0 MPa at 79.6 ° C. in the atmosphere, and has good thermophysical properties. The global warming potential is zero and the ozone depletion potential is zero.

  The evaporator 11 receives the heat energy recovered by the smoke washing heat exchanger 21 via the high-temperature circulating water L2 circulated by the circulation pump P2, and evaporates the working medium L. The high-temperature circulating water L2 sent from the evaporator 11 side is heated by the smoke washing heat exchanger 21 and sent to the evaporator 11 side.

  The superheater 12 receives the thermal energy recovered by the hot water generator 22 via the hot water L1 circulated by the circulation pump P3, and superheats the working medium L. The hot water L1 sent from the superheater 12 side is heated by the hot water generator 22 and sent to the superheater 12.

  The steam turbine 13 is rotated by the steam superheated by the superheater 12. The generator 15 connected to the rotating shaft of the steam turbine 13 generates power by rotating the steam turbine 13 and outputs electric power. Note that the rotating shaft of the steam turbine 13 may be directly or indirectly connected to a rotating device such as a fan and output as rotating power of the steam turbine 13. Further, the rotational shaft of the steam turbine 13 may be directly or indirectly connected to the rotational shaft of a rotational drive device such as an electric motor to assist the rotational drive of the rotational drive device.

  The condenser 14 condenses the steam output from the steam turbine 13 with the cooling water W6 supplied from the pump P5, and supplies the condensed working medium L to the evaporator 11 with the circulation pump P4. In addition, the cooling water W6 input into the condenser 14 is about 20 degreeC, for example, and this cooling water W6 heats up with condensation heat. The evaporator 11 may function as a preheater, and the superheater 12 may function as an evaporator.

  The control unit 7 is a control unit configured to be capable of controlling each of the above-described facilities, and configured to control each facility by supplying a control signal to each facility based on various input signals. ing.

(Temperature control of smoke washing water in the flue gas treatment tower)
Next, temperature control for the smoke-washed water W in the smoke treatment tower 5 will be described. FIG. 2 is a schematic diagram showing the smoke treatment tower 5 in FIG. 1 and its peripheral part.

  As shown in FIG. 2, the control unit 7 measures the temperature of the smoke-washed water W by the temperature sensor 8 and supplies the measured value of this temperature to the control unit 7. Note that the temperature of the smoke-washed water W discharged from the smoke-treating tower 5 may be measured instead of the smoke-washed water W accumulated in the lower part of the smoke-treating tower 5. And the control part 7 controls the amount of drainage of the low temperature waste_water | drain W5 by controlling the control valve 9 according to the temperature of the smoke-washing water W. FIG.

  Specifically, the control unit 7 controls when the temperature of the smoke-washed water W is higher than, for example, 78 to 79 ° C., which is a temperature based on the saturation absolute humidity in the exhaust gas G1, that is, a temperature at which the water vapor is saturated in the exhaust gas G1. The valve 9 is controlled so as to reduce the opening degree. Thereby, the amount of the waste water is decreased, the amount of the low temperature waste water W5 mixed with the smoke washing water W is increased, and the temperature of the smoke washing water W is lowered. Then, the control unit 7 lowers the temperature of the smoke-washed water W to, for example, about 70 ° C., which is the lower limit of the operable temperature of the exhaust heat energy recovery conversion device 10 at the subsequent stage.

  On the other hand, the control unit 7 controls the opening degree of the control valve 9 to be opened when the temperature of the smoke-washed water W becomes less than the lower limit of the operable temperature of the exhaust heat energy recovery conversion device 10 at the subsequent stage. Thereby, the amount of waste water to the outside of the low temperature waste water W5 is increased, the low temperature waste water W5 mixed with the smoke wash water W is reduced, and the temperature of the smoke wash water W is improved. And the control part 7 raises the temperature of the smoke-washed water W to the operable temperature of the waste heat energy recovery conversion apparatus 10 of the back | latter stage, for example, about 70 degreeC.

Here, the exhaust gas G1 sewage sludge is incinerated in, HCl, a mixture gas of incineration gas and water vapor containing components such as SO _X. According to the knowledge of the present inventor, these incineration gas and water vapor are mixed at about 67:33 to 56:44. Therefore, the present inventor sets the temperature of the smoke-washed water W to a temperature that is equal to or higher than the operable temperature in the exhaust heat energy recovery conversion device 10 at the subsequent stage and is lower than the temperature based on the saturation absolute humidity of the exhaust gas G1, that is, lower than the temperature at which water vapor is saturated. Thus, it was recalled that in addition to the sensible heat energy contained in the exhaust gas G1, heat energy as latent heat of water vapor (moisture) contained in the exhaust gas G1 can be recovered.

More specifically, for example, the absolute humidity (weight absolute humidity) in the exhaust gas G1 from sewage sludge is about 0.5 kgH ₂ O / kg-DA. The weight absolute humidity is the ratio of the weight of water vapor to the weight of dry air contained in the humid air. In this case, for example, when the sewage sludge is incinerated into the exhaust gas G1, the temperature based on the saturation absolute humidity, that is, the temperature at which the water vapor in the exhaust gas G1 is saturated is about 78 ° C.

  Therefore, the inventor collects the latent heat when the water vapor in the exhaust gas G1 changes from the gas phase to the liquid phase as thermal energy if the temperature of the smoke-washed water W is lower than the temperature at which the water vapor in the exhaust gas G1 is saturated. I recalled what I could do. Specifically, if the temperature based on the saturation absolute humidity of the exhaust gas G1 is about 78 ° C. and the lower limit temperature of the smoke-washed water W at which the exhaust heat energy recovery conversion device 10 operates is 70 ° C., from 78 ° C. When the temperature is lowered to 70 ° C., the saturated water vapor amount is reduced by a temperature drop of about 8 ° C. Thereby, a part of the water vapor (gas phase) in the exhaust gas G1 changes to water (liquid phase) while releasing the heat energy of latent heat. After this latent heat has moved to the smoke-washing water W, it is supplied to the exhaust heat energy recovery conversion device 10 via the smoke-washing heat exchanger 21 and output as electric power.

  According to the study of the present inventor, the lower the temperature of the smoke cleaning water W, the more heat energy of latent heat in the exhaust gas G1 can be recovered. On the other hand, if the temperature of the smoke cleaning water W is too low, the exhaust heat energy recovery conversion device 10 Becomes inoperable. Therefore, the temperature of the smoke-washed water W needs to be lower than the temperature at which water vapor is saturated based on the saturation absolute humidity of the exhaust gas G1 and higher than the temperature at which the exhaust heat energy recovery conversion device 10 can operate. And in order to collect | recover the latent heat in waste gas G1 to the maximum, the constant control which makes the temperature of the smoke-washed water W the temperature which can operate | move the exhaust heat energy recovery conversion apparatus 10 is desirable. That is, in the first embodiment, the temperature control of the smoke-washed water W is controlled to be 70 ° C. or higher and lower than 78 ° C., for example, and in order to recover the latent heat in the exhaust gas G1 to the maximum, 70 It is preferable that the temperature is controlled constant at around 0 ° C.

  According to the first embodiment of the present invention described above, the thermal energy possessed by the exhaust gas G1 is heated by the smoke washing heat exchanger 21 disposed on the smoke washing circulation path R via the smoke washing water W. Since the energy is recovered and supplied to the exhaust heat energy recovery conversion device 10 side, and the exhaust gas G1 is cooled using the smoke cleaning water W1 cooled by the smoke cleaning heat exchanger 21, Patent Document 3 discloses Compared to the conventional flue gas treatment tower as described, the thermal energy recovery rate can be improved. Moreover, in this 1st Embodiment, since the smoke-washing heat exchanger 21 serves as both the collection | recovery of thermal energy, and cooling of the smoke-washing water W, the loss of the thermal energy accompanying supply of the low temperature waste_water | drain W5 mentioned above is carried out. In addition, the heat energy recovery rate can be further improved. Furthermore, according to the first embodiment, the temperature of the smoke-washed water W is controlled to be equal to or higher than the operable temperature of the exhaust heat energy recovery conversion device 10 and lower than the temperature based on the saturation absolute humidity in the exhaust gas G1, While recovering the sensible heat energy contained in the exhaust gas G1, it is also possible to recover the latent heat of the water vapor contained in the exhaust gas G1, which is more energy efficient.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing a schematic configuration of a sludge incineration system including an exhaust heat recovery system according to the second embodiment of the present invention. As shown in FIG. 3, this sludge incineration system includes an incinerator 1, a fluidized air preheater 2, a white smoke prevention air preheater 3, a dust collector 4, a flue gas treatment tower 5, a chimney 6, and a waste heat energy recovery conversion device. 10

  The incinerator 1 is a fluidized incinerator for incinerating sewage sludge, and outputs high-temperature exhaust gas of about 800 to 850 ° C. The incinerator 1 is not limited to a fluidized incinerator, and may be another incineration type gasification furnace such as a circulating incinerator. Moreover, the object of incineration is not limited to sewage sludge.

  Exhaust gas from the incinerator 1 is input to the fluidized air preheater 2, and the atmosphere is heated to, for example, 650 ° C. fluidized air A1 and supplied to the bottom of the incinerator 1. The white smoke prevention air preheater 3 is an example of a heat exchanger for exhaust gas. The white smoke prevention air preheater 3 is arranged at the rear stage of the fluidized air preheater 2 and uses the thermal energy of the exhaust gas output from the fluidized air preheater 2 to White smoke prevention air A2, which is heated air for preventing the water vapor in the discharged exhaust gas from being seen as white smoke, is generated. The white smoke prevention air A2 is about 400 ° C. The temperature of the exhaust gas that has passed through the white smoke prevention air preheater 3 is lowered to about 200 to 400 ° C.

  The hot water generator 22 is a heat exchanger that collects part of the thermal energy from the white smoke prevention air A2 and supplies it to the exhaust heat energy recovery conversion device 10 and also uses the blower B as heated air whose temperature has decreased. The heated air mixed with a part of the heated air sent from the blower B and the new atmosphere is re-supplied to the white smoke prevention air preheater 3. Further, by adjusting the control valve V1 connected in parallel to the hot water generator 22, the amount of heat recovered from the white smoke prevention air A2 by the hot water generator 22 can be adjusted.

  The dust collector 4 is disposed downstream of the white smoke prevention air preheater 3 and removes dust in the exhaust gas input from the white smoke prevention air preheater 3. The dust collector 4 is a ceramic dust collector having excellent heat resistance, and can collect the exhaust gas that has passed through the white smoke prevention air preheater 3 as it is. The dust collector 4 may use a bag filter. In this case, it is necessary to arrange a cooling tower in front of the bag filter to lower the temperature to the heat resistance temperature of the bag filter. The temperature drop of the exhaust gas in the dust collector 4 is small, and the exhaust gas G1 is 200 to 400 ° C.

The flue gas treatment tower 5 introduces the exhaust gas G1 from the lower part of the tower, contacts the water sprinkled from the upper watering nozzle 5a, and removes components such as HCl and SO _X in the exhaust gas G1 as the smoke washing water W. It is. The smoke washing water W is collected in the lower part of the tower, and is sent to the watering nozzle 5a by the smoke washing circulation path R and the circulation pump P1 for circulation. Further, a smoke washing heat exchanger 21 is provided at the subsequent stage of the pump P1, heat is recovered from the smoke washing water W in the smoke treatment tower 5, and is sent to the water spray nozzle 5a as the smoke washing cooling water W1. The thermal energy recovered by the smoke washing heat exchanger 21 is supplied to the exhaust heat energy recovery conversion device 10 side. Further, in order to suppress an increase in the concentration of the smoke washing water W, the smoke washing circulation path R is branched between the smoke washing heat exchanger 21 and the water spray nozzle 5a, and a part of the smoke washing cooling water W1 is used as the smoke washing drain W3. Discard.

  Here, in the above-described flue gas treatment tower 5, since the exhaust gas G1 and the smoke-washing cooling water W1 are in contact, most of the heat energy of the exhaust gas G1 at 200 to 400 ° C. moves to the smoke-washing water W side. The smoke washing water W having the thermal energy recovered from the exhaust gas G1 is recovered by the smoke cleaning heat exchanger 21, and the recovered thermal energy is supplied to the exhaust heat energy recovery conversion device 10 side.

  A chimney 6 is disposed in the upper part of the flue gas treatment tower 5, and the exhaust gas G <b> 2 cleaned in the flue gas treatment tower 5 is subjected to white smoke prevention treatment in the chimney 6 and then released from the chimney 6 to the atmosphere. The The treated water W4 is supplied to the upper stage of the flue gas processing tower 5 and in front of the chimney 6, and the treated water W4 and the exhaust gas G2 are sufficiently brought into contact with each other so that sufficient water washing is performed. ing. This drained water is discarded as low temperature drainage W5.

  The exhaust heat energy recovery conversion device 10 has a function of recovering the thermal energy of the white smoke prevention air A2 that is heated air and the smoke cleaning water W of the exhaust gas treatment tower 5 and converting it into other energy, and the evaporator 11 , A superheater 12, a steam turbine 13, a condenser 14, a generator 15, and a circulation pump P4, and a low-boiling point medium such as chlorofluorocarbon having a lower boiling point than water, alternative chlorofluorocarbon, ammonia, or a mixed fluid of ammonia and water A thermal cycle S such as a Rankine cycle or a carina cycle is formed by circulating as a working medium L. CFCs and CFC substitutes are preferable because they have a low boiling point and are easy to handle. Ammonia is a colorless and transparent low-boiling medium originally existing in nature, and its evaporation temperature is −33.3 ° C., 4.0 MPa, 79.6 ° C. under air, and has good thermal properties. Moreover, it has a global warming potential of zero and an ozone depletion potential of zero, which is preferable since it has little environmental impact.

  The evaporator 11 receives the heat energy recovered by the smoke washing heat exchanger 21 via the high-temperature circulating water L2 circulated by the circulation pump P2, and evaporates the working medium L. The high-temperature circulating water L2 sent from the evaporator 11 side is heated by the smoke washing heat exchanger 21 and sent to the evaporator 11 side.

  The superheater 12 receives the thermal energy recovered by the hot water generator 22 via the hot water L1 circulated by the circulation pump P3, and superheats the working medium L. The hot water L1 sent from the superheater 12 side is heated by the hot water generator 22 and sent to the superheater 12.

  The steam turbine 13 is rotated by the steam superheated by the superheater 12 and outputs electric power via a generator 15 connected to the rotating shaft of the steam turbine 13. Note that the rotating shaft of the steam turbine 13 may be directly or indirectly connected to a rotating device such as a fan and output as rotating power of the steam turbine 13. Further, the rotational shaft of the steam turbine 13 may be directly or indirectly connected to the rotational shaft of a rotational drive device such as an electric motor to assist the rotational drive of the rotational drive device.

  The condenser 14 condenses the steam output from the steam turbine 13 with the cooling water W6 supplied from the pump P5, and supplies the condensed working medium L to the evaporator 11 with the circulation pump P4. In addition, the cooling water W6 input into the condenser 14 is about 20 degreeC, for example, and this cooling water W6 heats up with condensation heat. The evaporator 11 may function as a preheater, and the superheater 12 may function as an evaporator.

  In the second embodiment, the heat energy stored in the exhaust gas G1 is recovered through the smoke wash water W by the smoke wash heat exchanger 21 disposed on the smoke wash circulation path R to exhaust heat. Since the exhaust gas G1 is cooled by using the smoke-washing cooling water W1 cooled by the smoke-washing heat exchanger 21 while being supplied to the energy recovery conversion device 10 side, the conventional technology as described in Patent Document 3 is used. Loss of thermal energy can be eliminated as compared with the flue gas treatment tower by technology, and the recovery rate of thermal energy can be improved. Further, since the smoke washing heat exchanger 21 serves for both the recovery of thermal energy and the cooling of the washing water W, there is no loss of thermal energy due to the supply of the low temperature waste water W5, and the thermal energy recovery rate is further improved. be able to. Furthermore, since the amount of discharged smoke washing waste water W3 is very small, the recovery rate of thermal energy can be improved also from this point. In the second embodiment, the amount of smoke washed waste water W3 released is only the amount corresponding to the amount of water solidified by the water vapor in the exhaust gas G1. And it has the advantage that the recovery rate of the thermal energy by the smoke washing heat exchanger 21 can be enlarged by increasing the flow volume of the smoke washing water W and the smoke washing cooling water W1.

  In the second embodiment described above, the wall surface of the flue gas treatment tower 5 is insulative, and the temperature at which the water vapor in the exhaust gas G1 becomes saturated water vapor (dew point temperature) is about 80 from the moisture content of the sludge. ° C. Therefore, the exhaust gas G1 needs to be less than about 80 ° C. Therefore, in this 2nd Embodiment, the smoke-washing cooling water W1 and the smoke-washing water W are made to become less than 80 degreeC. And the thermal energy corresponding to the temperature difference between this smoke-washing cooling water W1 and smoke-washing water W is collect | recovered.

(Modification 1)
In the first and second embodiments described above, the treated water W4 supplied to the flue gas treatment tower 5 and the water W7 heated by the condenser 14 of the exhaust heat energy recovery conversion device 10 are separated from each other. Although W7 was discarded, in the first modification, water W7 is supplied as treated water W4 as shown in FIG. Thereby, since the cold energy of the water W7 can be used, the energy efficiency of the whole exhaust heat recovery system can be improved. The water W7 may be radiated through a separately provided cooling tower or the like and circulated and used as the cooling water W6.

(Modification 2)
In the second modification, as shown in FIG. 5, a heat pump 30 for forcibly cooling the treated water W4 to the treated water W24 is provided. The heat pump 30 is connected to both ends of an on-off valve 31 provided between the circulation pump P1 and the smoke washing heat exchanger 21, and when the on-off valve 31 is in a closed state, the smoke washing circulating water W2 is supplied to the heat pump. 30, the energy corresponding to the forced cooling is returned as the smoke-washing circulating water W <b> 22 heated up and supplied to the smoke-washing heat exchanger 21. The smoke wash circulating water W2 is input to the smoke wash heat exchanger 21 as smoke wash circulating water W22. In this case, the thermal energy supplied to the exhaust heat energy recovery conversion device 10 side can be increased by the temperature difference between the smoke wash circulating water W22 and the smoke wash cooling water W1. The on-off valve 31 can be adjusted in opening.

  Moreover, since the temperature of the treated water W24 is lowered, the temperature of the exhaust gas is further lowered, and the amount of water vapor in the exhaust gas is increased. Therefore, the amount of water vapor in the exhaust gas is reduced, which is necessary for the white smoke prevention treatment. The amount of energy of the heated air can be greatly reduced. As a result, conversely, in correspondence with this reduction, the heat energy in the white smoke prevention air A2 can be greatly supplied to the exhaust heat energy recovery conversion device 10.

(Modification 3)
In the first and second embodiments and the first and second modifications described above, the superheater 12 receives the thermal energy recovered by the hot water generator 22 via the hot water L1 circulated by the circulation pump P3, and operates. The medium L is heated, and the evaporator 11 receives the heat energy recovered by the smoke washing heat exchanger 21 via the high-temperature circulating water L2 circulated by the circulation pump P2, and evaporates the working medium L. . In the third modification, as shown in FIG. 6, the exhaust heat energy recovery conversion device 10 ′ deletes the circulation pump P 3, the hot water L 1, and the superheater 12, and directly flows the working medium L into the hot water generator 22. The hot water generator 22 functions as a superheater, the circulation pump P2, the high-temperature circulating water L2, and the evaporator 11 are deleted, and the working medium L is directly introduced into the smoke washing heat exchanger 21 for washing. The smoke heat exchanger 21 functions as an evaporator. Thereby, the heat exchange efficiency can be increased. In addition, any one may be sufficient as the structure which makes the hot water generator 22 function as a superheater, and functions the smoke-washing heat exchanger 21 as an evaporator. Further, the smoke washing heat exchanger 21 may function as a preheater, and the hot water generator 22 may function as an evaporator.

  Note that the first and second embodiments described above and the components of the first to third modifications can be appropriately combined.

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible. For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as necessary.

  For example, in the above-described first embodiment, the example of incineration of sewage sludge has been described. However, in the case of incineration other than sewage sludge, the ratio of the dry gas and water vapor contained in the above-described exhaust gas G1 changes. . Further, the operable temperature of the exhaust heat energy recovery conversion device 10 is also a temperature that varies from device to device. Therefore, it is desirable to change the temperature at which the smoke-washed water W should be controlled according to the exhaust heat energy recovery conversion device 10 to be used and the material to be incinerated.

DESCRIPTION OF SYMBOLS 1 Incinerator 2 Flowing air preheater 3 White smoke prevention air preheater 4 Dust collector 5 Flue gas processing tower 5a Sprinkling nozzle 6 Chimney 7 Control part 8 Temperature sensor 9 Control valve 10, 10 'Waste heat energy recovery converter 11 Evaporator 12 Superheater 13 Steam turbine 14 Condenser 15 Generator 21 Smoke washing heat exchanger 22 Hot water generator 30 Heat pump 31 On-off valve G1, G2 Exhaust gas A1 Fluid air A2 White smoke prevention air S Thermal cycle L Working medium L1 Hot water L2 Hot circulating water R Smoke wash circuit W Smoke wash water W1 Smoke wash cooling water W2, W22 Smoke wash circulation water W3 Smoke wash drain W4, W24 Treated water W5 Low temperature drain W6 Cooling water W7 Water V1 Control valve B Blower P1-P4 Circulation pump P5 Pump

Claims (12)

An exhaust gas heat exchanger for exchanging heat of the exhaust gas from the incinerator and a flue gas treatment tower for treating the exhaust gas, and exhaust gas treatment via the exhaust gas heat exchanger and the flue gas treatment tower A heat exhaust energy recovery conversion device that recovers the thermal energy of the heated air and smoke cleaning water in the flue gas processing tower and converts it into other energy,
The flue gas treatment tower collects thermal energy of the smoke washing water flowing through the smoke washing circulation path on the smoke washing circulation path for washing the exhaust gas by circulating the smoke washing water accumulated in the lower part of the tower. A smoke washing heat exchanger for supplying the recovered thermal energy to the exhaust heat energy recovery conversion device is provided, and the input exhaust gas is sprinkled with smoke washing cooling water cooled by the smoke washing heat exchanger. An exhaust heat recovery system that is washed with water,
The flue gas treatment tower is configured to be able to input treated water that cools the exhaust gas that has been washed with water by spraying the smoke washing cooling water, and the treated water after cooling the exhaust gas is in contact with the exhaust gas. Supply destination selection means for selecting at least one of mixing with the smoke-washed water flowing through the smoke-cleaning circuit after the heat-exchange with the smoke-washing heat exchanger, or discharging to the outside ,
The treated water mixed with the smoke-washed water when the temperature of the smoke-washed water measured by the temperature sensor for measuring the temperature of the smoke-washed water is higher than the temperature based on the saturated absolute humidity in the exhaust gas. When the temperature of the smoke cleaning water measured by the temperature sensor is less than the operable temperature of the exhaust heat energy recovery conversion device by increasing the amount and decreasing the temperature of the smoke cleaning water, By reducing the amount of the treated water mixed with the smoke cleaning water and increasing the temperature of the smoke cleaning water, the temperature of the smoke cleaning water is higher than the operable temperature of the exhaust heat energy recovery conversion device in the exhaust gas. Controlling the supply destination selection means so as to be maintained below the temperature based on the saturation absolute humidity, the control means for collecting the latent heat of the exhaust gas in the smoke-washed water is provided. Yield system.   2. The control unit according to claim 1, wherein the control unit discharges a part of the smoke-washed water flowing through the smoke-wash circuit so that a discharge amount corresponds to an amount of water solidified by the water vapor in the exhaust gas. Waste heat recovery system.   The exhaust heat recovery system according to claim 1, further comprising a heat pump that cools the treated water before being put into the smoke exhausting treatment tower.   The exhaust heat recovery system according to any one of claims 1 to 3, wherein the exhaust heat energy recovery conversion device forms a heat cycle using a medium having a boiling point lower than that of water.   The exhaust heat energy recovery conversion device arranges a steam turbine on the thermal cycle, outputs electric power via a generator connected to the steam turbine, or outputs rotational power of the steam turbine. The exhaust heat recovery system according to claim 4.   The post-condensation treated water for condensing cooling water used in a condenser disposed on the thermal cycle is used as cooling treated water supplied to the upper part of the flue gas treatment tower. Or the waste heat recovery system of 5. An exhaust gas heat exchanger for exchanging heat of the exhaust gas from the incinerator and a flue gas treatment tower for treating the exhaust gas, and exhaust gas treatment via the exhaust gas heat exchanger and the flue gas treatment tower In the exhaust heat recovery system having an exhaust heat energy recovery conversion device that recovers the thermal energy of the heated air and smoke cleaning water in the exhaust gas processing tower and converts it into other energy, On the smoke cleaning circuit that circulates the accumulated smoke cleaning water and cleans the exhaust gas, the thermal energy of the smoke cleaning water flowing through the smoke cleaning circuit is recovered, and the recovered thermal energy is used as the exhaust heat energy. A waste heat recovery method for supplying water to the recovery conversion device and washing the exhaust gas with water sprayed with smoke-washing cooling water cooled by recovery of thermal energy,
The treated water for cooling the exhaust gas washed with water by the sprinkling of the smoke washing cooling water is input to the flue gas treatment tower, and the temperature of the smoke washing water is measured with respect to the treated water after the exhaust gas is cooled. When the temperature of the smoke-washed water measured by the temperature sensor is higher than the temperature based on the saturation absolute humidity in the exhaust gas, the amount of the treated water mixed with the smoke-washed water is increased, and the smoke washed water The treated water mixed with the smoke-washed water when the temperature of the smoke-washed water measured by the temperature sensor is lower than the operable temperature of the exhaust heat energy recovery conversion device by lowering the temperature of the water the amount to reduce the maintenance the by raising the temperature of the wash smoke water below the temperature based on the saturated absolute humidity in the exhaust gas operable temperature above the wash smoke water the exhaust heat energy recovery converter So as to selectively control at least one of mixing with the smoke-washing water flowing through the smoke-washing circulation path after contact with the exhaust gas and before recovering the thermal energy, or discharging the smoke energy to the outside. Thus, the exhaust heat recovery method is characterized in that the smoke washing water recovers the latent heat of the exhaust gas.   The exhaust heat recovery method according to claim 7, wherein a part of the smoke washed water flowing through the smoke washing circulation path is discharged to the outside so that a discharge amount corresponds to an amount of water solidified by water vapor in the exhaust gas.   The exhaust heat recovery method according to claim 7 or claim 8, wherein the treated water before being introduced into the flue gas treatment tower is cooled by a heat pump.   The exhaust heat recovery method according to any one of claims 7 to 9, wherein the exhaust heat energy recovery conversion device forms a heat cycle using a medium having a boiling point lower than that of water.   The exhaust heat energy recovery conversion device arranges a steam turbine on the thermal cycle, outputs electric power via a generator connected to the steam turbine, or outputs rotational power of the steam turbine. The exhaust heat recovery method according to claim 10.   The post-condensation treatment water for condensing cooling water used in a condenser disposed on the thermal cycle is used as cooling treatment water supplied to the upper part of the flue gas treatment tower. Or the exhaust heat recovery method of 11.

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