JP5897821B2 - Steam utilization system in sludge incineration plant. - Google Patents

Description

  The present invention relates to a steam utilization system in a sludge incineration plant for recovering the retained energy of the steam generated in the sludge incineration plant without waste.

  Currently, most of the sewage sludge generated in large quantities from sewage treatment plants is incinerated in an incinerator. Since the incineration temperature of the incinerator is set to about 850 ° C. for the purpose of suppressing the generation of nitrous oxide having a large global warming potential, high-temperature exhaust gas of about 850 ° C. is discharged from the incinerator. In order to recover the thermal energy possessed by the high-temperature exhaust gas, a heat recovery system using a waste heat boiler as shown in Patent Document 1 has been conventionally employed.

  FIG. 1 is a diagram showing a more specific example of a heat recovery system using a waste heat boiler. Hot exhaust gas discharged from a fluid incinerator is first heated with a fluid air preheater and then discarded. It is led to a heat boiler to generate steam. In FIG. 1, a part of the generated steam is led to the white smoke prevention device to heat the white smoke prevention air, and the remaining portion drives the exhaust gas induction blower, and is condensed by the condenser and circulated to the waste heat boiler. To do. On the other hand, the exhaust gas that has passed through the waste heat boiler is sent to a dust collector such as a ceramic filter to remove dust, and after removing SOx etc. in the flue gas treatment tower, it is released from the chimney together with white smoke prevention air. Is done.

  In the heat recovery system shown in FIG. 1, the heat energy of the generated steam is used for heating white smoke prevention air, and the pressure energy is used for driving the exhaust gas induction blower. However, most of these methods use pressure energy, which is a part of the energy of steam, and most of the energy (heat energy and pressure energy) of steam is returned to water by the condenser. In many cases, it was thrown out of the system as hot wastewater.

JP 2000-213725 A

  As mentioned above, the energy of the steam generated in the boiler connected to the sludge incinerator has not been fully utilized in the past, and most of it is thrown out of the system and must be used effectively in the system. There were few. Accordingly, an object of the present invention is to provide a steam utilization system in a sludge incineration plant that solves such conventional problems and can sufficiently recover the thermal energy of steam and effectively use it in the system. .

The steam utilization system in the sludge incineration plant of the present invention made in order to solve the above-mentioned problem is a boiler that uses air heated by heat exchange with high-temperature exhaust gas discharged from a sludge incinerator as a main heat source , Steam turbine that is driven by steam generated in the boiler to extract power, steam compressor that is driven by steam that has passed through this steam turbine to generate compressed air, and heat exchange that further recovers exhaust heat from the steam that has passed through this steam compressor It is characterized by having a vessel.

  The heat exchanger is preferably a white smoke prevention air preheater or a sludge heating heat exchanger, and the heat exchanger is a condensate in addition to the white smoke prevention air preheater or the sludge heating heat exchanger. It is preferable that a vessel is provided.

  The steam compressor preferably includes a steam motor driven by steam and a compressor driven by the steam motor to compress air. Furthermore, it is preferable that the boiler uses white smoke prevention air heated by high-temperature exhaust gas discharged from the sludge incinerator as a heating fluid.

According to the steam utilization system in the sludge incineration plant of the present invention, the energy held by the steam generated in the boiler whose main heat source is air heated by heat exchange with the high-temperature exhaust gas discharged from the sludge incinerator is high pressure. In this stage, it can be recovered as power by the steam turbine, in the intermediate pressure stage as compressed air by the steam compressor, and in the low pressure stage as heat energy by a heat exchanger that recovers exhaust heat. For this reason, the energy of the steam can be thoroughly recovered from both the pressure and temperature sides, and can be effectively used in the system.

  If a white smoke prevention air preheater or a sludge heating heat exchanger is used as a heat exchanger for recovering exhaust heat as in claim 2, the recovered heat can be effectively used in the system of the sludge incineration plant. In addition to the white smoke prevention air preheater or the sludge heating heat exchanger as in claim 3, if the condenser is provided, the steam can be completely condensed and returned to the boiler. According to another aspect of the present invention, when a steam compressor including a steam motor driven by steam and a compressor driven by the steam motor to compress air is used, compressed air is obtained using the pressure of the steam as a power source. Can do. Further, if white smoke prevention air heated by high-temperature exhaust gas discharged from a sludge incinerator is used as a boiler heating fluid as in claim 5, the boiler is not likely to be blocked by dust in the exhaust gas. The boiler can be inspected while continuing the sludge incineration.

It is explanatory drawing of the conventional heat recovery system which uses a waste-heat boiler. It is explanatory drawing which shows embodiment of this invention. It is a conceptual sectional view of a steam compressor.

Hereinafter, preferred embodiments of the present invention will be described.
In FIG. 2, 1 is a sludge incinerator installed in a sewage treatment plant, for example, a fluidized incinerator. As described above, the exhaust gas having a high temperature of about 850 ° C. is discharged from the sludge incinerator 1. 3, heat exchange is performed with the air for preventing white smoke, and the air for preventing white smoke is heated to 400 ° C., for example. In this way, when the sludge incinerator 1 is a fluidized incinerator, the fluidized air preheater 2 is disposed in front of the white smoke preventer 3, and the fluidized air heated to a high temperature can be blown into the furnace. preferable.

  The exhaust gas that has passed through the white smoke suppressor 3 is discharged from the chimney 6 after the dust is removed by a dust collector 4 such as a ceramic filter or a bag filter, and the SOx is removed by the flue gas treatment tower 5 as in the prior art. Is done. Such an exhaust gas treatment system itself is not significantly different from the conventional one.

The white smoke prevention air heated to about 400 ° C. by the white smoke prevention device 3 is sent to the boiler 7. The boiler 7 uses white smoke prevention air as a main heat source, and generates high-temperature and high-pressure steam at, for example, 200 ° C. and 1.5 MPa. The air for preventing white smoke at about 1700C passing through the boiler 7 is sent to the chimney 6 to heat the exhaust gas cooled in the flue gas treatment tower 5 to prevent the generation of white smoke. Thus, if the air for preventing white smoke is used as the heating fluid for the boiler 7, unlike the conventional waste heat boiler, the boiler 7 is not likely to be blocked by dust in the exhaust gas. Further, since the boiler 7 is installed separately from the main line for exhaust gas treatment, there is an advantage that the operation of inspecting the boiler 7 can be performed while the sludge incineration is continued by operating the dampers 18, 19, and 20.

  The high-temperature and high-pressure steam generated in the boiler 7 is first sent to the steam turbine 8 and converted into power. Generally, this power is used for power generation, but it can also be used as auxiliary power for a blower for obtaining aeration air used in a sewage treatment plant, for example. In this way, the pressure of the high-temperature and high-pressure steam generated in the boiler 7 is converted into power. This is the first use of steam energy. The steam turbine 8 used in the present invention is a back pressure turbine, and the steam that has passed through the steam turbine 8 is, for example, 160 ° C. and 0.5 MPa medium pressure steam. Moreover, in this embodiment, it is the system which does not generate electric power with the steam which generate | occur | produced in the boiler 7, but converts into compressed air with the motive power of the steam turbine 8, and a steam compressor. For this reason, the boiler 7 has the effect of significantly reducing the installation burden, such as boiler specifications and inspections, as compared with a boiler that converts power into a boiler under the jurisdiction of the Ministry of Health, Labor and Welfare.

  This medium pressure steam is then sent to the steam compressor 9. The steam compressor 9 is a device that pressurizes air or steam using steam as a driving source. In this embodiment, as shown in FIG. 3, the steam motor 10 driven by steam and the air compressed by the steam motor 10 are compressed. And a compressor 11 (a turbo compressor 11 in FIG. 2). The steam motor 10 and the compressor 11 are provided with screw-type rotary blades, and the supplied steam drives the drive shaft 12 while advancing while expanding inside the steam motor 10, and the turbo compressor 11 is driven by this drive shaft. 12 rotates a screw-type rotary blade to compress air. In this way, the pressure of the medium pressure steam is taken out as compressed air from the steam compressor 9, and for example, an air source for various instrumentation equipment in a sludge incineration plant, an air source for backwashing a dust collector, an air source for transporting incineration ash, etc. Can be used as This is the second use of steam energy. In addition, the steam compressor 9 of such a structure can use what is marketed as a steam drive air compressor.

  The steam that has passed through the steam compressor 9 becomes, for example, low-pressure steam at 110 ° C. and 0.05 MPa. In the present invention, exhaust heat is further recovered from the heat energy of the low-pressure steam by a heat exchanger. This is the third use of steam energy. As the heat exchanger for exhaust heat recovery, various devices can be used. In FIG. 2, the white smoke prevention air preheater 13 and the sludge heating heat exchanger 14 are used. The white smoke prevention air preheater 13 is a heat exchanger that preheats the air supplied to the white smoke prevention device 3. The sludge heating heat exchanger 14 is a device for heating the sewage sludge charged into the sludge incinerator 1 and reducing the water content during dehydration by the dehydrator. These devices are used in sludge incineration plants and are suitable for effectively using the thermal energy of low-pressure steam.

  Thus, if the air supplied to the white smoke prevention device 3 is preheated by the white smoke prevention air preheater 13, the amount of heat required to heat the white smoke prevention air in the white smoke prevention device 3 is reduced. More energy can be recovered by the boiler 7. Moreover, if the moisture content of the sludge thrown into the sludge incinerator 1 is reduced by heating and dewatering the sewage sludge by the heat exchanger 14 for sludge heating, a larger amount of energy can be taken out from the sludge incinerator 1. It becomes possible.

  The low-pressure steam is cooled while passing through these heat exchange devices 13 and 14, condensed and returned to the boiler 7. However, since the amount of steam varies depending on the operating condition of the sludge incinerator 1 and the amount of sludge treatment, the amount of steam can be changed only by condensate by effective use of the white smoke prevention air preheater 13 and the heat exchanger 14 for sludge heating. In some cases, it is difficult to ensure condensate. Therefore, as an actual facility, in addition to the white smoke prevention air preheater 13 and the sludge heating heat exchanger 14 as shown in FIG. 2, a condenser is used so that condensate can be completely performed even when the amount of steam fluctuates. 15 is preferably provided. In FIG. 2, the condenser 15 is arranged in parallel with these heat exchangers, but can also be arranged in series. The condensate is returned to the boiler 7 by the feed water pump 16. The temperature is, for example, less than 100 ° C., and the pressure is not more than atmospheric pressure.

  As described above, according to the present invention, it is possible to thoroughly recover the energy of steam from both the pressure and temperature sides. For example, when the present invention is applied to a sludge incineration plant with a sewage sludge treatment scale of 250 t / day, approximately 80 kW is produced by assisting blower power by the steam turbine 8, and approximately 150 kW is produced by producing compressed air using the steam compressor 9. By preheating the air with the smoke-preventing air preheater 12, energy of about 800 kW can be recovered. Therefore, there is an advantage that energy recovery of 1000 kW or more is possible as a whole.

DESCRIPTION OF SYMBOLS 1 Sludge incinerator 2 Flowing air preheater 3 White smoke prevention device 4 Dust collector 5 Smoke treatment tower 6 Chimney 7 Boiler 8 Steam turbine 9 Steam compressor 10 Steam motor 11 Turbo compressor 12 Shaft 13 White smoke prevention air preheater 14 For sludge heating Heat exchanger 15 Condenser 16 Drain tank 17 Water supply pump 18 Damper 19 Damper 20 Damper

Claims (5)

A boiler that uses air heated by heat exchange with high-temperature exhaust gas discharged from a sludge incinerator as a main heat source, a steam turbine that is driven by the steam generated in the boiler to extract power, and steam that has passed through the steam turbine A steam utilization system in a sludge incineration plant, comprising: a steam compressor driven by a steam generator to generate compressed air; and a heat exchanger for recovering exhaust heat from the steam that has passed through the steam compressor.   The steam utilization system in a sludge incineration plant according to claim 1, wherein the heat exchanger is a white smoke prevention air preheater or a heat exchanger for sludge heating.   The steam utilization system in a sludge incineration plant according to claim 2, wherein the heat exchanger includes a condenser in addition to a white smoke prevention air preheater or a sludge heating heat exchanger.   The steam utilization system in a sludge incineration plant according to claim 1, wherein the steam compressor comprises a steam motor driven by steam and a compressor driven by the steam motor to compress air.   The steam utilization system in a sludge incineration plant according to claim 1, wherein the boiler uses white smoke prevention air heated by high-temperature exhaust gas discharged from a sludge incinerator as a heating fluid.

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