JP5591269B2 - Heat treatment equipment and method - Google Patents

Description

  The present invention relates to a heat treatment facility and method for economically recovering the amount of heat of a dry exhaust gas generated in an indirect heat dryer and using it as a heat source for the dryer, after drying an object to be treated containing moisture and organic matter. It can be applied to facilities that incinerate by heat treatment or collect flammable gases and carbides.

  In recent years, various processes have been developed for pyrolyzing biomass, coal, oil shale, oil sand and the like to produce combustible gas and carbide. And if these substances are pre-dried before being supplied to the thermal decomposition step, the heat treatment can be carried out more economically.

  Here, as a dryer for pre-drying, a heating medium such as steam is used as a heating source, an indirect heating type dryer that dries the object to be processed without directly contacting the object to be processed with the heat medium, and burns fuel. In addition, there are known a direct heating type dryer in which the generated hot air is brought into direct contact with an object to be processed, and a dryer in which indirect heating and direct heating are used in combination.

JP 2005-279331 A

  Conventionally, the dry exhaust gas used in these dryers is discharged after removing dust and harmful substances, and the amount of heat of the dry exhaust gas (mainly latent heat of steam) has not been effectively recovered. In addition, although the method (patent document 1) which heat-recovers from dry exhaust gas and obtains warm water and uses this warm water as a heating source to dry by indirect heating under reduced pressure is known, in this method, the temperature of the heating source is low. Economic drying was difficult.

  In view of this, the present inventor proposed in Japanese Patent Application No. 2010-238228 an aspect in which the amount of heat of the dry exhaust gas generated in the dryer can be economically recovered and effectively used as a heat source for the dryer. Sex has been confirmed.

  When heat is recovered from the dried exhaust gas to obtain warm water, and steam is obtained by the evaporator using the warm water as a heating source, the temperature of the warm water is usually 100 ° C. or lower, so the evaporator is operated under negative pressure and is lower than the warm water It must be evaporated at temperature. When this steam is used as a heat source for drying, since the temperature is 100 ° C. or lower, efficient drying cannot be performed. Therefore, it is necessary to increase the temperature by compressing the steam.

  However, even when trying to increase the pressure from a negative pressure with a mechanical booster, due to the leakage of air due to the structure of the booster, it was not suitable as a steam to be used as a heat source for the dryer. For example, 5% leakage air reduces the heat of exchange by about 30%.

  The present invention has been made in view of the above circumstances, and its main problem is to provide a heat treatment facility and method for economically recovering the amount of heat of the dry exhaust gas generated in the dryer and using it as a heat source for the dryer. There is to do.

  Another problem is to produce steam that is suitable as a heat source for a dryer even when the steam generated by heat recovery has a negative pressure.

The heat treatment facility according to claim 1 is an indirect heating type dryer using steam as a heat source for drying a material to be treated containing moisture and organic matter, and a heat treatment facility for heating the material to be treated dried by the dryer. In heat treatment equipment including
First steam generating means for recovering the retained heat of the dry exhaust gas generated by the indirect heating dryer and generating first steam;
Second steam generating means for generating second steam using at least one of combustible gas or combustion exhaust gas generated in the heat treatment facility as a heat source;
First boosting means for boosting the first steam using the second steam generated by the second steam generating means as a drive source;
Mechanical compression means for mechanically compressing the steam boosted by the first first pressure boosting means;
Mechanical compressed steam supply means for supplying the compressed steam by the mechanical compression means as a heating source for drying an object to be processed by the indirect heating dryer.
It is the heat processing characterized by this.

  The indirect heating dryer in the present invention includes an indirect heating dryer using a heat medium such as steam as a heating source, and a direct heating drying using hot air generated by burning fossil fuel as a heating source. There are dryers and dryers that use both indirect heating and direct heating, but excluding direct heating dryers that use hot air generated by burning fossil fuel as a heating source.

  Examples of the indirect heating type dryer in the present invention include a disc type dryer (inclined disc dryer), a steam tube dryer, and a fluidized dryer with an indirect heating tube.

  The heat treatment in the present invention may be a treatment for heating a dried object to be processed, and includes combustion such as thermal decomposition such as carbonization and gasification, and incineration.

  The general configuration of the present invention is shown in FIG. 3 (not limited to the embodiment shown in FIG. 3), so that it can be easily understood.

(Function and effect)
The higher the steam temperature (pressure), the more economical the dryer can be made. On the other hand, running costs are required to obtain high temperature (high pressure) steam. There is therefore an optimum steam temperature (pressure). ADVANTAGE OF THE INVENTION According to this invention, even if the vapor | steam produced | generated by heat recovery is a negative pressure, a vapor | steam suitable as a heat source of a dryer can be manufactured.

  In the heat treatment facility according to claim 2, the first steam generating means is a vacuum evaporator, the first pressure raising means is an ejector, and the second steam generated by the second steam generating means is generated. 2. The heat treatment equipment according to claim 1, wherein the first steam generated by the first steam generating means is sucked and boosted as driving steam, and the inside of the vacuum evaporator is reduced to an atmospheric pressure or less by the suction. It is.

  When the first vapor generating means is a vacuum evaporator and the first pressure increasing means is an ejector, the inside of the vacuum evaporator is reduced to atmospheric pressure or less by the suction force of the ejector, thereby generating steam in the evaporator. Further, the generated steam can be surely boosted by the ejector.

  The invention according to claim 3 is the heat treatment according to claim 1 or 2, wherein the condensate of the steam in the indirect heating dryer is returned to at least one of the first steam generating means and the second steam generating means as a steam source. Equipment.

  Since it returns as a steam source, the amount of steam can be increased.

According to a fourth aspect of the present invention, there is provided an indirect heating type dryer using steam as a heat source for drying an object to be processed containing moisture and organic matter, and a heat treatment facility for heating the object to be processed dried by the dryer. In the heat treatment method using
A first steam generation step of recovering the retained heat of the dry exhaust gas generated in the indirect heating dryer to generate the first steam;
A second steam generating step for generating a second steam using at least one of a combustible gas or combustion exhaust gas generated in the heat treatment facility as a heat source;
A first boosting step of boosting the first steam using the second steam generated in the second steam generation step as a drive source;
A mechanical compression step of mechanically compressing the steam that has been boosted in the previous first pressurization step;
A mechanical compressed steam supply step of supplying the compressed steam from the mechanical compression step as a heating source for drying an object to be processed by the indirect heating dryer.
It is the heat processing method characterized by the above-mentioned.

    There exists an effect substantially the same as Claim 1.

  As described above, according to the present invention, it is possible to provide heat treatment equipment that economically recovers the amount of heat of dry exhaust gas generated in a dryer and uses it as a heat source of the dryer.

  In addition, according to the present invention, after drying an object to be processed containing moisture and organic matter, when the object to be processed is heated with a heating facility, an effective drying heat source is obtained by economically recovering heat from the dried exhaust gas. I was able to do that.

  For example, when the processing amount is 100 t / day of sewage sludge, the treatment unit price of sewage sludge is reduced by 1,700 yen / t according to the present invention, compared with the conventional carbonization equipment with hot air drying equipment by combustion of fuel. The amount of CO2 emission is reduced to 2,600 t / year.

  Furthermore, according to the present invention, it is possible to produce steam suitable as a heat source for a dryer even if the steam generated by heat recovery is negative pressure.

1 is a partially broken perspective view of a steam tube dryer according to an embodiment of an indirect heating dryer of the present invention. It is the schematic which shows the drying and carbonization equipment of the sewage sludge concerning this Embodiment. It is an outline explanatory view of the present invention.

  An embodiment of a heat treatment facility according to the present invention will be described below with reference to the drawings. First, prior to the description of the present embodiment, an example of a steam tube dryer (STD) that is an indirect heating dryer applied to the embodiment of the present invention will be described with reference to FIG. explain.

  This steam tube dryer 3 shown in FIG. 1 has a plurality of heating pipes 31 arranged between both end plates in parallel with the axis in a rotary cylinder 30 that is rotatable around the axis. Heating steam as a heat medium is supplied to the heating pipes 31 through the attached heat medium inlet pipes 51 and is distributed to the respective heating pipes 31, and then drains of the heating steam K through the heat medium outlet pipes 52. Will be discharged.

  The steam tube dryer 3 is provided with a charging device (not shown) having a screw or the like for charging the workpiece into the rotary cylinder 30. For example, an organic substance containing moisture, which is an object to be processed, which has been thrown into the rotary cylinder 30 from the insertion port 53 of the charging device, is brought into contact with the heating tube 31 heated by the heating steam K and dried. It becomes like this. At the same time, since the rotating cylinder 30 is installed with a downward slope, it is moved smoothly in the direction of the discharge port 54 so that the workpiece is continuously discharged from the other end side of the rotating cylinder 30. Yes.

  As shown in FIG. 1, the rotating cylinder 30 is installed on a base 36, and the tire 34 is mounted by two sets of support rollers 35 that are spaced apart from each other in parallel with the axis of the rotating cylinder 30. It is supported through. The width between the two sets of support rollers 35 and the inclination angle in the longitudinal direction thereof are selected in accordance with the downward gradient and the diameter of the rotating cylinder 30.

  On the other hand, in order to rotate the rotating cylinder 30, a driven gear 40 is provided around the rotating cylinder 30, and the drive gear 43 meshes with the driven gear 40, and the rotational force of the prime mover 41 is transmitted via the speed reducer 42. Thus, it rotates around the axis of the rotating cylinder 30. Further, a carrier gas is introduced into the inside of the rotary cylinder 30 from a carrier gas inlet 61, and these carrier gases are accompanied by vapors in which water contained in the organic substance as the object to be processed is evaporated, from the carrier gas outlet 62. Discharged.

  In addition, the whole structure of the said steam tube dryer 3 is an example, and this invention is not limited by the said structure.

FIG. 2 is a schematic view showing a sewage sludge drying / carbonizing facility according to the present embodiment.
In addition, the pressure described in a present Example is an absolute pressure reference | standard.

As shown in FIG. 2, a paddle type or multi-shaft type mixer 2 is disposed on the charging side of the steam tube dryer 3, and in this mixer 2, for example, moisture 75 to 85 from the sludge supply pump 1. % Of the sewage sludge and the dried product returned through the return conveyor 8 to make the water content about 30%. The mixed product is dried in the steam tube dryer 3 as a dry product S having a water content of about 10%.
The dry exhaust gas G discharged from the steam tube dryer 3 is sent to the dry exhaust gas wet scrubber 9, and the heat recovered by the dry exhaust gas wet scrubber 9 is heat-exchanged in the evaporator heater 10, A heating source for the evaporator 11 is used.

  In the evaporator 11 (which constitutes the first steam generating means together with the dry exhaust gas wet scrubber 9 and the evaporator heater 10), the first steam is generated, and this first steam is generated by the ejector 12 as the first pressure increasing means. Boost the pressure. The evaporator 11 is preferably a vacuum evaporator. The pressure in the evaporator 11 becomes atmospheric pressure or less due to the suction force generated when the ejector 12 is driven. The steam boosted by the ejector 12 is further compressed by the compressor 13 as the second boosting means, and the compressed steam is fed into the steam tube dryer 3 via the path 22 and used as heating steam for heating. Some are used or discarded as traces. The drain heated by the steam tube dryer 3 is sent to at least one of the evaporator 11 and the boiler 19 through the path 23.

  In this example, the first exhaust gas wet scrubber 9, the evaporator heater 10, and the evaporator 11 constitute the first steam generating means. However, the dry exhaust gas wet scrubber 9 and the heat pump can constitute the first steam generating means. .

  On the other hand, the dry product S in the steam tube dryer 3 is discharged on the dry product transfer conveyor 4 on the lower side of the discharge side, and is then sieved by the sieve 5, and the small particle dry product S1 is returned to the return hopper 7. To be collected. In addition to being sent to the dried product hopper 14, the large-sized dried product S <b> 2 is partly crushed in the crusher 6 and then collected in the return hopper 7.

  A small particle dried product S1 is cut out from the return hopper 7, placed on the return conveyor 8, sent to the mixer 2, mixed with sewage sludge, and then returned to the steam tube dryer 3. .

  On the other hand, from the lower part of the dry product hopper 14, the large dry product S 2 can be put on the dry product transfer conveyor 15 and charged into the carbonization furnace 16 as a heating facility. Carbonized.

  The carbonization furnace 16 is supplied with hot air generated by burning fuel in the hot air generator 17 for carbonization furnace. The combustible gas N is discharged from the carbonization furnace 16 and sent to the afterburner 18 as a fuel element, and the combustible gas N is combusted together with air and fuel. Further, the steam generated in the boiler 19 is sent to the ejector 12 as the first pressurizing means, and the steam generated in the evaporator 11 is boosted using the steam generated in the steam boiler 19 as a drive source. The exhaust gas from the steam boiler 19 is processed by the exhaust gas processor 21 via the heat exchanger 20 and discharged to the outside. The heat exchanger 20 is configured to heat the exhaust gas from the dry exhaust gas wet scrubber 9 and send it to the steam tube dryer 3.

  Next, specific steps in the heat treatment facility will be described.

  For example, sewage sludge with a water content of 75% to 85% is supplied to the sludge supply pump 1, and this sewage sludge is sent to the mixer 2 and mixed with the dried product S <b> 1 to obtain a workpiece S <b> 0 having a water content of about 30%. . The object to be processed S0 containing moisture and organic matter is supplied to a steam tube dryer 3 which is an indirect heating dryer, and the moisture of the mixed product S0 is dried to about 10%, for example, to obtain a dried product S.

  At this time, the dry exhaust gas G having a dew point of desirably 80 ° C. to 100 ° C. (about 85 ° C. is optimum) is discharged from the steam tube dryer 3. The dry exhaust gas G is composed of, for example, a plurality of stages. It is sent to a dry exhaust gas wet scrubber 9 to be cooled and dehumidified. The higher the gas temperature at the lowermost outlet of the dry exhaust gas wet scrubber 9, the higher the pressure steam can be recovered economically in the evaporator 11. However, when the gas temperature is high, the dry exhaust gas wet scrubber 9 recovers the gas. The amount of heat decreases. At this time, it is preferable to operate so that the gas temperature at the lowermost outlet of the dry exhaust gas wet scrubber 9 is 60 ° C to 80 ° C.

  The carrier gas used in the steam tube dryer 3 is discharged from the steam tube dryer 3 as a dry exhaust gas G. The dry exhaust gas G is processed by the dry exhaust gas wet scrubber 9 and the heat of the dry exhaust gas G is added to the scrubber circulating water. To recover heat. And although there is no restriction | limiting in particular in the final stage exit temperature of this dry exhaust gas wet scrubber 9, About 30-40 degreeC is suitable. The carrier gas discharged from the wet scrubber 9 is supplied to the afterburner 9 through a blowing means such as a circulation blower, and the others are heated and then recycled.

  The heat recovered at the lowest stage of the dry exhaust gas wet scrubber 9 heats the liquid in the evaporator 11 in the evaporator heater 10 to generate steam. In the evaporator 11, the internal pressure is reduced to an atmospheric pressure or less as the ejector 12 is driven. The vapor pressure generated in the evaporator 11 is about 0.015 to 0.05 MPa, and is equal to or lower than the saturated vapor pressure of the gas temperature at the lowermost outlet of the dry exhaust gas wet scrubber 9. At this pressure, the drying efficiency is low, and it is inevitable to increase the size of the dryer that uses this steam as a heating source. Therefore, the low-pressure steam generated in the evaporator 11 is sent to the ejector 12 to increase the pressure.

  On the other hand, the dried product S dried by the steam tube dryer 3 is sent to the sieve 5 by the transfer conveyor 4 and sieved into large particles and small particles. Part of the sieved large particles is crushed by the crusher 6 and then sent to the return hopper 7. Further, the sieved small particles are sent directly to the return hopper 7. The dried product S1 cut out by the return hopper 7 is sent to the mixer 2 by the return conveyor 8 and then mixed with sewage sludge (object to be treated).

  Separately, the remainder of the sieving large particles is sent to the dry product hopper 14 and cut out, and then sent to, for example, an external heat kiln type carbonization furnace 16 by the dry product transfer conveyor 15. It is pyrolyzed at 250 ° C. to 600 ° C. to become carbide and combustible gas N. At this time, since the thermal decomposition is an endothermic reaction, it is indirectly heated by hot air generated by burning fuel in the hot air generator 17 for carbonization furnace. And the carbide | carbonized_material discharged | emitted from the carbonization furnace 16 is cooled with the cooler which is not shown in figure, Then, it is carried out, On the other hand, combustible gas N is combusted with the afterburner 18. FIG.

  Next, the exhaust gas generated by burning the combustible gas N as the combustion material in the afterburner 18 is supplied to the boiler 19 through a supply path such as a duct. The boiler 19 generates steam of 1.6 MPa or more if desired by the boiler 19 with 0.8 Mpa or more. At this time, exhaust gas discharged from the boiler 19 conveys the exhaust gas of the dry exhaust gas wet scrubber 9 through the path 24 and heats it with the heat exchanger 20, and the exhaust gas of the dry exhaust gas wet scrubber 9 is discharged into the steam tube. The dryer 3 is used as a carrier gas. Thereafter, the exhaust gas from the boiler 19 is processed by the exhaust gas processor 21 and then released to the atmosphere.

  On the other hand, the pressure of the low-pressure first steam generated in the evaporator 11 is further increased. That is, the high-pressure second steam generated in the boiler 19 is sent to the ejector 12 via the path 25, and the low-pressure first steam generated in the evaporator 11 is generated using the high-pressure second steam as a drive source. Aspirate and pressurize.

  After the pressurized steam is compressed by the mechanical compressor 13, finally, the pressurized steam of 0.2 MPa to 0.8 MPa is preferably supplied to the steam tube dryer 3, and the mixed product S0 is supplied by the steam tube dryer 3. Is dried to obtain a dried product S.

  The following can be considered as a modification of each step in the present embodiment.

  First, in the above embodiment, heat is recovered from the dry exhaust gas G to obtain steam. As a method for recovering heat from the dry exhaust gas G at this time, in this embodiment, the dry exhaust gas G is converted into the dry exhaust gas wet scrubber 9. The method of transferring the heat of the dry exhaust gas G to the scrubber circulating water and recovering the heat as the circulating water is used, but a method of directly recovering the heat from the dry exhaust gas G with a heat exchanger or the like may be used.

  Furthermore, as a method of obtaining steam from the recovered heat of the dry exhaust gas G, a method of generating 0.015-0.05 MPa of steam in the water evaporator 11 using the recovered heat as a heat source was used in the present embodiment. A method of supplying recovered heat to a steam generation type heat pump to obtain steam of about 0.1 to 0.25 MPa may be used. However, obtaining steam of 0.2 MPa or more with a heat pump is not economical because the coefficient of performance (COP) decreases.

  Since the upper limit value of the temperature of heat recovered from the dry exhaust gas is substantially equal to the dew point of the dry exhaust gas G, the vapor pressure generated in the evaporator 11 is equal to or lower than the saturated water vapor pressure of the dew point temperature of the dry exhaust gas G, but a higher pressure. The higher the dew point of the dry exhaust gas G, the better. However, when the dew point of the dry exhaust gas G is increased, the temperature of the product becomes almost equal to the dew point of the dry exhaust gas G by constant rate drying in the indirect heating type dryer. The drying capacity of the machine is reduced. Accordingly, there is an optimum dew point of the dry exhaust gas G. Here, the dew point of the dry exhaust gas G is preferably 80 ° C. to 100 ° C., although it depends on the amount of water evaporated by the indirect heating dryer.

  The pressurized steam is compressed by the compressor 13 to increase the pressure. At this time, the type of the compressor 13 is not particularly limited, but a screw compressor that does not require countermeasures against mist is suitable. In this case, the compression ratio (ratio between the discharge pressure and the suction pressure) in the compressor 13 is economical in the range of 2 to 10. Roots blowers and multistage blowers can also be used.

  The heat treatment of the dried product S is not limited to the carbonization treatment, and for example, a gasification treatment, an incineration treatment, or the like can be employed.

  The boiler 19 is a known waste heat boiler, and generates high-pressure steam from the combustion exhaust gas N generated from the afterburner. The fuel used as the combustion material for the afterburner is not particularly limited, and any of a pyrolysis product combustible gas N, carbide, and other fuels may be used. Note that as the combustion exhaust gas N supplied to the boiler 19, exhaust gas obtained by burning the fuel may be used directly, or exhaust gas burned by a gas turbine, a gas engine, or the like may be used.

  By the way, when a process for discharging high-temperature exhaust gas such as incineration of a product to be dried is performed, the discharged high-temperature exhaust gas can be directly supplied to the waste heat boiler.

  The compressor is driven by high-pressure steam generated in the boiler 19 to further pressurize the compressed steam. As a method for increasing the pressure, a steam turbine driven compressor may be used, but as shown in the embodiment, the ejector 12 system is inexpensive and economical.

  The evaporator 11 may adopt a so-called multiple effect can system in which a plurality of evaporators 11 are installed in series.

  The present invention can be applied to drying of woody biomass, organic waste, etc., as well as drying of resins, foods, organic substances and the like.

3 Steam tube dryer (indirect heating dryer)
9 Dry exhaust gas wet scrubber 10 Evaporator heater 11 Evaporator 12 Ejector 13 Compressor 16 Carbonization furnace (heat treatment equipment)
18 Afterburner 19 Boiler

Claims (4)

In a heat treatment facility including an indirect heating type dryer using steam as a heat source for drying a treatment object containing moisture and organic matter, and a heat treatment facility for heating the treatment object dried by the dryer,
First steam generating means for recovering the retained heat of the dry exhaust gas generated by the indirect heating dryer and generating first steam;
Second steam generating means for generating second steam using at least one of combustible gas or combustion exhaust gas generated in the heat treatment facility as a heat source;
First boosting means for boosting the first steam using the second steam generated by the second steam generating means as a drive source;
Mechanical compression means for mechanically compressing the steam boosted by the first first pressure boosting means;
Mechanical compressed steam supply means for supplying the compressed steam by the mechanical compression means as a heating source for drying an object to be processed by the indirect heating dryer.
Heat treatment equipment characterized by that.   The first steam generating means is a vacuum evaporator, the first boosting means is an ejector, and the second steam generated by the second steam generating means is used as driving steam, and the first steam generating means is used. The heat treatment equipment according to claim 1, wherein the first steam generated by the suction is sucked to increase the pressure, and the vacuum evaporator internal pressure is reduced to atmospheric pressure or less by the suction.   The heat treatment equipment according to claim 1 or 2, wherein the condensate of the steam in the indirect heating dryer is returned to at least one of the first steam generating means and the second steam generating means as a steam source. In a heat treatment method using an indirect heating type dryer using steam as a heat source for drying a treatment object containing moisture and organic matter, and a heat treatment facility for heating the treatment object dried by the dryer,
A first steam generation step of recovering the retained heat of the dry exhaust gas generated in the indirect heating dryer to generate the first steam;
A second steam generating step for generating a second steam using at least one of a combustible gas or combustion exhaust gas generated in the heat treatment facility as a heat source;
A first boosting step of boosting the first steam using the second steam generated in the second steam generation step as a drive source;
A mechanical compression step of mechanically compressing the steam that has been boosted in the previous first pressurization step;
A mechanical compressed steam supply step of supplying the compressed steam from the mechanical compression step as a heating source for drying an object to be processed by the indirect heating dryer.
The heat processing method characterized by the above-mentioned.

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