CN107473552B - Comprehensive utilization method of heat energy of sludge pyrolysis system of multi-hearth furnace - Google Patents
Comprehensive utilization method of heat energy of sludge pyrolysis system of multi-hearth furnace Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/10—Treatment of sludge; Devices therefor by pyrolysis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D50/00—Combinations of methods or devices for separating particles from gases or vapours
- B01D50/40—Combinations of devices covered by groups B01D45/00 and B01D47/00
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/84—Biological processes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
- F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material
- F23J15/04—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material using washing fluids
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/12—Heat utilisation in combustion or incineration of waste
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/40—Valorisation of by-products of wastewater, sewage or sludge processing
Abstract
The invention provides a comprehensive utilization method of heat energy of a multi-hearth furnace sludge pyrolysis system, which comprises the following steps: the tail gas of the pyrolysis process is fully mixed and combusted with secondary air fed by an air blower in a secondary furnace, and finally high-temperature flue gas containing a small amount of dust pollutants and trace acid gas components is generated to enter a waste heat steam boiler, and then medium-pressure superheated steam is generated and fed into a mud cake conveying pump set at the front end of the pyrolysis process and a main induced draft fan at the tail end of the pyrolysis process to directly drive a steam turbine in the mud cake conveying pump set and the main induced draft fan at the tail end of the process. The invention adopts the waste heat steam boiler to recover and utilize the heat energy of the tail gas and the high-temperature flue gas of the pyrolysis process, and the produced superheated medium-pressure steam is applied to a steam turbine driving medium of a high-power electric appliance, a heat source medium of a sludge supplementary drying device, a heat preservation/heating medium of a raw material sludge storage bin and liquid distribution/washing inlet water (hot water) of a gas washing tower in a step-by-step manner, thereby improving the comprehensive utilization efficiency of the heat energy of the flue gas.
Description
Technical Field
The invention relates to the technical field of wastewater treatment, in particular to a comprehensive utilization method of heat energy of a sludge pyrolysis system of a multi-hearth furnace.
Background
The core equipment types of the sludge heat reduction technology comprise: multi-hearth furnaces, fluidized bed furnaces, grate furnaces, rotary furnaces, and the like, mainly including the two. The fluidized bed furnace, the grate furnace and the converter can only adopt an incineration operation mode so far (the research on the pyrolysis operation mode of the fluidized bed furnace is still in the technical development stage), while the multi-hearth furnace can adopt the incineration operation mode and the pyrolysis operation mode, and the pyrolysis operation mode is gradually developed into a mainstream sludge heat reduction process.
However, because of the complex nature and composition of wastewater and sludge in China, low overall heat value, various types of pollutants, large fluctuation range of pollutant concentration and poor dehydration performance of conventional sludge, the sludge heat treatment project introduced in a whole disc or designed by carrying out a mature process in the whole disc abroad generally runs unsmoothly and has frequent faults. The insufficient cognition degree of the three core sludge indexes of the sludge dry solid matter (DS), the volatile dry solid matter (VS) and the low calorific value of the raw sludge is one of the main reasons for the overhigh energy consumption of almost all the built multi-hearth furnace sludge pyrolysis device systems. In addition, although the property characteristics of domestic sludge are considered in some projects, the problems of water balance and heat energy balance in the sludge heat treatment process cannot be sufficiently considered in the design, so that the project energy consumption is overlarge and the due technical competitiveness is lost.
Disclosure of Invention
The object of the present invention is to solve at least one of the technical drawbacks mentioned.
Therefore, the invention aims to provide a comprehensive utilization method of heat energy of a multi-hearth furnace sludge pyrolysis system, which can comprehensively utilize the heat energy of pyrolysis process tail gas and high-temperature flue gas and furthest realize the aim of energy conservation.
In order to achieve the aim, the invention provides a comprehensive utilization method of heat energy of a sludge pyrolysis system of a multi-hearth furnace, which comprises the following steps:
conveying raw sludge into a multifunctional sludge storage bin of a multi-hearth furnace sludge pyrolysis system through a filter pressing process of a wastewater treatment plant, uniformly mixing the raw sludge with high water content by a forced spiral stirring mechanism arranged in the multifunctional sludge storage bin, forcibly conveying the raw sludge to a subsequent sludge cake conveying pump set, and feeding the raw sludge into a sludge supplementary drying device through the sludge cake conveying pump set;
step two, introducing exhausted steam exhausted by a steam turbine in a sludge cake conveying pump set and a steam turbine of a tail end total induced draft fan of a pyrolysis process into a drier jacket and a hollow blade of the sludge supplementary drying device, further reducing the pressure of the superheated exhausted steam in a steam passage of the sludge supplementary drying device and providing heat energy to evaporate partial moisture of raw sludge in a main cavity of the sludge supplementary drying device, and conveying the formed saturated steam containing odor to a special scrubbing tower for treatment by a special pipeline and the induced draft fan;
discharging the dried sludge evaporated by the sludge supplementary drying device from the sludge supplementary drying device, and immediately feeding the dried sludge into a multi-hearth furnace or a body furnace by a forced spiral feeding unit at the rear end for pyrolysis treatment;
step four, the dried sludge entering the multi-hearth furnace or the body furnace automatically completes the heat treatment process from top to bottom in the furnace, solid residues generated after pyrolysis of the dried sludge are discharged from the bottom of the multi-hearth furnace or the body furnace, and pyrolysis process tail gas of the multi-hearth furnace or the body furnace is discharged from a furnace top exhaust pipeline and then enters a secondary furnace;
step five, mixing the pyrolysis process tail gas with secondary air sent by an air blower in a secondary furnace, fully combusting, maintaining a certain furnace temperature requirement value in the secondary furnace, completely burning all combustible components in the hot process tail gas, and finally generating high-temperature flue gas containing a small amount of dust pollutants and trace acid gas components;
step six, high-temperature flue gas discharged by the secondary furnace enters a waste heat steam boiler, then medium-pressure superheated steam is generated and sent to a mud cake conveying pump set at the front end of the pyrolysis process and a main induced draft fan at the tail end of the pyrolysis process, and the high-temperature flue gas is used for directly driving a steam turbine in the mud cake conveying pump set and a steam turbine in the main induced draft fan at the tail end of the process;
step seven, the flue gas discharged by the waste heat steam boiler sequentially enters a multi-hearth furnace flue gas scrubbing tower and a biological deodorization tower to be condensed, dehydrated, dedusted and deodorized; the rich waste water discharged from the multi-hearth furnace flue gas scrubbing tower and the biological deodorization tower enters a water collecting trap and then is discharged into a total water inlet of a waste water treatment plant, and then enters a conventional waste water treatment process for treatment;
and step eight, the flue gas discharged by the biological deodorization tower passes through a cyclone demister before entering a main induced draft fan at the tail end, liquid drops in the flue gas are removed, and finally the flue gas is discharged into the air by the main induced draft fan.
Furthermore, the water inlet of the special scrubber tower adopts heat source process steam condensate water and supplementary cold water discharged from the multifunctional sludge storage bin, the odorous steam is condensed by adopting a direct spraying method, and is discharged to a water collecting well in a wastewater form after an odorous compound is absorbed by an added chemical agent, and then the odorous steam is discharged to a total water inlet of a wastewater treatment plant for conventional wastewater treatment.
Furthermore, the heat energy required by the heat treatment process in the multi-hearth furnace or the body furnace is completely provided by the reaction process and the heat exchange process in the furnace, auxiliary fuel is not required to be added, and only process air which is subjected to metering control is added in the process.
Furthermore, a heating jacket is arranged in the multifunctional sludge storage bin, water-containing exhaust steam sent from a dryer jacket of the sludge supplementary drying device is introduced into the heating jacket, the water-containing exhaust steam is condensed in the heating jacket and releases latent heat, and condensed water generated by the heating jacket enters a water collecting trap and then is discharged into a total water inlet of a wastewater treatment plant for conventional wastewater treatment.
Furthermore, the mud cake conveying pump set adopts a motor and steam turbine dual-drive mode, the motor is adopted for driving only under the working condition of opening the multi-hearth furnace, when the multi-hearth furnace sludge pyrolysis system enters the normal operation working condition, the multi-hearth furnace sludge pyrolysis system is automatically switched into the steam turbine for driving, the steam turbine is driven by medium-pressure superheated steam, and the medium-pressure superheated steam is supplied by a waste heat boiler device arranged at the rear end of the secondary furnace.
Furthermore, after a steam turbine in the sludge cake conveying pump group applies work, the pressure value of the exhausted superheated steam is 0.15-0.40 MPa, the temperature is 110-136 ℃, and when the exhausted superheated steam is used as a heat source medium of a sludge supplementary drying device, raw sludge with the content of sludge dry solid substances of 30% can be dried to the level of the content of sludge dry solid substances of 45%.
Furthermore, the evaporation load of the waste heat steam boiler is designed to be 1.8-3.2 tons of superheated steam/ton, the pressure of the superheated steam is 1.2-2.0 MPa, and the temperature is 210-260 ℃.
Furthermore, all or part of the central shaft cooling waste hot air discharged by the multi-hearth furnace or the body furnace is recycled into the cooling section of the multi-hearth furnace, the central shaft cooling waste hot air exchanges heat with high-temperature sludge ash and then rises to the pyrolysis section to participate in an anoxic combustion process, and the burnt sludge pyrolysis process tail gas enters the secondary furnace.
Further, the sludge ash after the combustion of the multi-hearth furnace or the main body furnace is sent to a disposal site for treatment.
Further, before the raw sludge enters the multi-hearth furnace sludge pyrolysis system, the following three pretreatment modes are carried out:
a. when the volatile dry solid content level of the raw sludge is kept unchanged, the sludge dry solid content of the raw sludge is increased to be more than or equal to 30 percent, and at least one or more of the following pretreatment modes are adopted, including: solar drying technology, drying pool technology and natural air drying technology;
b. keeping the content level of sludge dry solid matter of the raw sludge unchanged, increasing the content of volatile dry solid matter of the raw sludge to be more than or equal to 78 percent, and adopting the following pretreatment steps: before the sludge filtering process of a wastewater treatment plant, industrial or agricultural wastes with high organic matter content are added into liquid raw sludge, so that the filterability of the sludge is improved, and the volatile dry solid content level of the sludge is improved;
c. meanwhile, the content levels of sludge dry solid substances and volatile dry solid substances of the raw material sludge are improved, so that the content of the sludge dry solid substances of the raw material sludge is improved to be more than or equal to 25%, the content of the volatile dry solid substances is improved to be more than or equal to 67%, and the pretreatment comprises the following steps: industrial or agricultural wastes with high organic matter content are added into the liquid raw material sludge, and the sludge is dewatered by adopting a high-efficiency filter pressing machine.
The invention has the following beneficial effects:
1. through detailed measurement and calculation and pilot test verification, the comprehensive utilization method of the heat energy of the multi-hearth furnace sludge pyrolysis system can achieve the aim of energy conservation to the greatest extent, and simultaneously ensures that waste water sludge is treated and utilized in a reduction, stabilization, harmless and recycling manner.
2. All the environmental protection measures of the invention aim to prevent the gas phase pollution of the surrounding environment caused by the scattered emission of the sludge odor and protect the health and safety of operators, a biological deodorization tower and a gas washing tower are added at the tail end of a pyrolysis process tail gas and flue gas purification treatment system, and the treated pyrolysis process tail gas is combined with the flue gas after the temperature is reduced and part of steam condensate water is removed, so that the operation load of a preceding stage environmental protection facility is reduced to the maximum extent, and the power consumption level of the whole system is reduced; and meanwhile, the air inlet flow speed of the subsequent cyclone demisting device is improved, so that the dehydration efficiency of the cyclone demisting device is improved, and the chimney plume type visual pollution degree of the final flue gas is weakened.
3. The process fluid which can be respectively treated or treated adopts the design principle and concept of 'divide-and-conquer' so as to obviously reduce the energy consumption level of the whole technical system.
4. The invention adopts the waste heat steam boiler to recover and utilize the heat energy of the tail gas and the high-temperature flue gas of the pyrolysis process, and the produced superheated medium-pressure steam is applied to a steam turbine driving medium of a high-power electric appliance, a heat source medium of a sludge supplementary drying device, a heat preservation/heating medium of a raw material sludge storage bin and liquid distribution/washing inlet water (hot water) of a gas washing tower in a step-by-step manner, thereby improving the comprehensive utilization efficiency of the heat energy of the flue gas.
5. The invention recycles part or all of the waste hot air discharged by cooling the shaft in the multi-hearth furnace to the pyrolysis treatment process, improves the heat energy utilization efficiency of the multi-hearth furnace, and reduces the consumption of auxiliary fuel which may need to be supplemented.
6. The invention uses the steam condensate water discharged by the jacket in the multifunctional sludge storage bin as raw water and/or circulating water for gas washing for preparing chemical agents of two sets of gas washing devices (namely a special gas washing tower and a multi-hearth furnace flue gas washing tower), and can accelerate the dissolution speed of the agents and improve the gas washing efficiency.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a general process flow diagram of the comprehensive utilization method of heat energy of a sludge pyrolysis system of a multi-hearth furnace of the invention;
FIG. 2 is an optimized process flow diagram of the comprehensive utilization method of heat energy of the sludge pyrolysis system with multiple chambers.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The invention provides a comprehensive utilization method of heat energy of a sludge pyrolysis system of a multi-hearth furnace, which is shown by referring to the attached figures 1-2 and comprises the following steps:
step one, raw sludge is conveyed into a multifunctional sludge storage bin with functions of buffering, mixing, homogenizing and the like of a multi-hearth sludge pyrolysis system through a filter pressing process of a wastewater treatment plant, the multifunctional sludge storage bin is provided with a jacket heat preservation and heating facility, the raw sludge with high water content is uniformly mixed by a forced spiral stirring mechanism arranged in the multifunctional sludge storage bin and is forcedly conveyed to a subsequent sludge cake conveying pump set, and the raw sludge is fed into a sludge supplementary drying device through the sludge cake conveying pump set; the multifunctional sludge storage bin is internally provided with a heating jacket, the heating jacket is filled with water-containing spent steam sent from a dryer jacket of the sludge supplementary drying device, the water-containing spent steam is condensed in the heating jacket and releases latent heat, condensed water generated by the heating jacket enters a water collecting trap and then is discharged into a total water inlet of a wastewater treatment plant for conventional wastewater treatment, and when the designed treatment capacity of raw sludge is 100 tons/day, the temperature of the raw sludge entering a subsequent sludge cake conveying pump set can be maintained at more than 25 ℃ (winter) and 45 ℃ (summer), so that the normal operation of the pump set is ensured, and the purpose of energy conservation (reduction of the initial operation temperature value of the sludge drying unit) is achieved.
A mud cake conveying pump set (represented by a plunger mud cake pump and a sludge screw pump) is additionally provided with a forced feeding screw mechanism, the drive of the forced feeding screw mechanism adopts a motor-steam turbine dual-drive device, the motor drive is adopted only under the blow-in working condition of the multi-hearth furnace, and the steam turbine drive is automatically switched after the whole technical system enters the normal operation working condition, so that the electric energy can be obviously saved. The steam turbine is driven by medium-pressure superheated steam supplied from a waste heat boiler device provided at the rear end of the secondary furnace (afterburner).
And step two, introducing exhausted steam (still superheated steam, the pressure and the temperature of which are greatly reduced) exhausted by a steam turbine in a sludge cake conveying pump set and a steam turbine of a main induced draft fan at the tail end of a pyrolysis process into a drier jacket and a hollow blade of a sludge supplementary drying device (a typical drier type is a hollow blade type or a hollow disc type), further reducing the pressure of the superheated exhausted steam in a steam passage of the sludge supplementary drying device and providing heat energy, evaporating partial water of raw sludge in a main chamber of the sludge supplementary drying device, and conveying the formed saturated steam containing odor to a special gas washing tower for treatment by a special pipeline and the induced draft fan.
The water inlet of the special scrubber adopts heat source process steam condensate water (the temperature is about 35-55 ℃) discharged by a multifunctional sludge storage bin and supplementary cold water (20 ℃), the odorous steam is condensed by adopting a direct spraying method, and is discharged to a water collecting trap in a wastewater form after an odorous compound is absorbed by an added chemical agent, and then the odorous steam is discharged to a total water inlet of a wastewater treatment plant for conventional wastewater treatment.
And step three, discharging sludge (sludge dry solid matter, namely DS content reaches a design required value) dried due to partial water evaporation from the sludge supplementary drying device, and immediately feeding the sludge into a multi-hearth furnace or a body furnace for pyrolysis treatment by a forced screw feeder at the rear end.
And step four, the dried sludge entering the multi-hearth furnace or the main body furnace automatically completes a series of heat treatment processes such as drying, pyrolysis, cooling and the like from top to bottom in the furnace, the heat energy required by the heat treatment process is completely provided by the reaction process and the heat exchange process in the furnace, auxiliary fuel is not required to be added, and only process air subjected to metering control is added in the process. Solid residues (ash residues containing a certain amount of residual carbon organic matter components) generated after pyrolysis of dried sludge are discharged from the bottom of the multi-hearth furnace or the body furnace, and pyrolysis process tail gas (mainly comprising water vapor, carbon dioxide, nitrogen and the like, and the temperature is about 300-450 ℃) of the multi-hearth furnace or the body furnace is discharged from a furnace top exhaust pipeline and then enters a secondary furnace. And the sludge ash after the combustion of the multi-hearth furnace or the main body furnace is sent to a disposal place for treatment.
Step five, mixing the pyrolysis process tail gas in a secondary furnace with secondary air sent by an air blower to be fully combusted, wherein under an ideal working condition, the multi-hearth furnace is in a self-heating balance state, the residence time of the process tail gas in the secondary furnace exceeds 2 seconds and is in a complete turbulence state, the secondary furnace can maintain a certain furnace temperature required value (such as 850 ℃) to completely burn all combustible components in the hot process tail gas, and finally high-temperature flue gas (the temperature of the high-temperature flue gas leaving the secondary furnace is about 750 ℃) containing a small amount of dust pollutants and trace acid gas components is generated; it should be noted that these data are not intended to limit the scope of the present invention.
Step six, high-temperature flue gas discharged by the secondary furnace enters a waste heat steam boiler, then medium-pressure superheated steam is generated and sent to a mud cake conveying pump set at the front end of the pyrolysis process and a main induced draft fan at the tail end of the pyrolysis process, and the high-temperature flue gas is used for directly driving a steam turbine in the mud cake conveying pump set and a steam turbine in the main induced draft fan at the tail end of the process; the temperature of the flue gas discharged from the boiler was about 150 ℃.
Step seven, the flue gas discharged by the waste heat steam boiler sequentially enters a multi-hearth furnace flue gas scrubbing tower and a biological deodorization tower to be condensed, dehydrated, dedusted and deodorized; the rich waste water discharged from the multi-hearth furnace flue gas scrubbing tower and the biological deodorization tower enters a water collecting trap and then is discharged into a total water inlet of a waste water treatment plant, and then enters a conventional waste water treatment process for treatment;
step eight, the temperature of the smoke discharged by the biological deodorization tower is about 35 ℃, the smoke contains a large amount of liquid drop components, the total flow is obviously increased (the environment-friendly air collection airflow flow of a sludge conveying device system is added), the smoke passes through a cyclone demister before entering a total induced draft fan at the tail end, more than 99% of liquid drops (fog) in the smoke are removed, and therefore an impeller and an air pipe of the induced draft fan can be protected, and the visual pollution of 'plume' at an outlet of a chimney can be greatly reduced.
And finally, the air is discharged into the air by a main induced draft fan.
The invention adopts the design of heat supply medium fluid, which is the most important 'heat carrying fluid' design for realizing the aim of comprehensive utilization of heat energy. The fluid is in an initial form of medium-pressure superheated steam generated by a waste heat steam boiler, the first-stage heat energy utilization is two steam turbine devices (which are respectively used for driving a raw material sludge conveying pump set and a main induced draft fan), the superheated steam pressure and the temperature after acting are both remarkably reduced, but the spent steam at the moment is still designed as superheated steam fluid; the second-stage heat energy utilization is an indirect heating heat source for the sludge supplementary drying device, and the heat energy is converted into partial saturated steam (the saturated steam containing condensed water, the pressure is 0.1MPa, and the temperature is 80-100 ℃) after the partial saturated steam exchanges heat with raw sludge and releases latent heat after condensation; and the third stage of heat energy utilization is to convey the saturated vapor containing water discharged from the sludge replenishing and drying device to the heating jacket facility in the multifunctional sludge storage bin to exchange heat with the raw sludge, ensure the conveyability of the raw sludge in winter and evaporate a small amount of sludge water, and finally discharge the heat condensate water with the temperature of about 35-50 ℃ for the liquid preparation of the special gas washing tower.
The temperature of the raw sludge is gradually increased, the temperature of the process flue gas is gradually decreased, the power consumption of two mechanical devices (and a multi-hearth furnace and a secondary furnace) with the highest power consumption in the system is reduced to zero through steam/hot water heat-carrying fluid, and simultaneously the DS content of the sludge entering the multi-hearth furnace is ensured to reach the level of the self-heating balance design requirement value, so that the consumption of auxiliary fuel of the multi-hearth furnace and the secondary furnace is reduced to zero.
Through the design scheme and the technical measures, the total energy consumption of the multi-hearth furnace sludge pyrolysis system for the wastewater sludge is reduced to the minimum degree, and the market competitiveness level of the technical process is improved.
In addition, before the raw sludge enters the multi-hearth furnace sludge pyrolysis system, the following three pretreatment modes are carried out:
a. when the volatile dry solid content level of the raw sludge is kept unchanged, the sludge dry solid content of the raw sludge is increased to be more than or equal to 30 percent, and at least one or more of the following pretreatment modes are adopted, including: solar drying technology, drying pool technology and natural air drying technology;
b. the method keeps the content level of the sludge dry solid of the raw sludge unchanged (15-20%, as long as the filter type of a wastewater treatment plant is not changed and an inorganic filter aid or a sludge modifying agent is not excessively added, the value cannot be greatly changed), improves the content of the volatile dry solid of the raw sludge to be more than or equal to 78%, and adopts the following pretreatment steps: before the sludge filtering process of a wastewater treatment plant, industrial or agricultural wastes with high organic matter content, such as brewing residues/wine residues, rice hulls, sawdust, industrial oil/fat-containing sludge, livestock and poultry farm sludge and the like, are added into liquid raw material sludge, so that the filterability of the sludge is improved, and the volatile dry solid content level of the sludge is improved;
c. meanwhile, the content levels of sludge dry solid substances and volatile dry solid substances of the raw material sludge are improved, so that the content of the sludge dry solid substances of the raw material sludge is improved to be more than or equal to 25%, the content of the volatile dry solid substances is improved to be more than or equal to 67%, and the pretreatment comprises the following steps: industrial or agricultural wastes with high organic matter content, such as wine brewing residues/wine lees, rice hulls, sawdust, industrial oil/fat-containing sludge, livestock farm sludge and the like, are added into the liquid raw material sludge, and the sludge is dewatered by adopting a high-efficiency filter pressing machine.
Through measurement and test verification, for typical domestic wastewater sludge (the content of volatile dry solids VS is 45-60% of DS, and the average value of the heat value is about 2800 kcal/kgDS), the self-heating balance working condition state of a multi-hearth furnace and a post-combustion chamber can be realized only when the content of the sludge dry solids DS is more than or equal to 45%.
On the premise of self-heating balance working condition states of a multi-hearth furnace and a post-combustion chamber, the method has the following design values:
(1) the evaporation load of the waste heat steam boiler is designed to be 1.8-3.2 tons of superheated steam/ton DS, the pressure (gauge pressure) of the superheated steam is designed to be 1.2-2.0 MPa, and the temperature is 210-260 ℃.
(2) The maximum working value of the superheated steam reaches 90-110 KWh/ton DS, the requirement that high-power electromechanical equipment with unit load installed capacity of 90-110 KW/ton DS is provided with a corresponding steam turbine can be met, electric energy of an equipment system can be remarkably saved, and operation cost is reduced.
(3) After the superheated steam pushes a steam turbine to do work, the design value of the pressure (gauge pressure) of the exhausted superheated exhausted steam is 0.15-0.40 MPa, the temperature is 110-136 ℃, and when the superheated exhausted steam is used as a heat source medium of a sludge supplementary drying device, raw sludge with the DS content of 30% can be dried to the level of the DS content of 45%, so that a multi-hearth furnace and a secondary furnace can realize a self-heating balance working condition state, the consumption of auxiliary fuel is remarkably saved, and even the consumption of the auxiliary fuel is reduced to zero.
(4) The exhausted steam discharged by the sludge supplementary drying device is saturated steam containing a large amount of condensed water, the designed value of the pressure (gauge pressure) is 0.10MPa, the temperature is 80-100 ℃, the saturated exhausted steam containing water is conveyed to a heating jacket facility of the multifunctional sludge storage bin to be further condensed and release heat, the sludge transportability is improved, and a small amount of sludge moisture is evaporated.
(5) The steam condensate water discharged from the heating jacket facility of the multifunctional sludge storage bin has the temperature of about 30-50 ℃ and is used as raw water and/or circulating water for gas washing for preparing chemical agents of two sets of gas washing devices (namely a special gas washing tower and a multi-hearth furnace flue gas washing tower). Can accelerate the dissolution speed of the medicament and improve the gas washing efficiency.
(6) All environment-friendly air collecting airflow flow of the sludge conveying system (used for preventing sludge odor from diffusing and discharging to cause gas phase pollution to the surrounding environment and protecting the health and safety of operators) is merged with the flue gas after cooling and removing part of steam condensate water (realized in a special scrubber) at the tail end (a biological deodorization tower) of a process tail gas and flue gas purification treatment system, so that the operation load of a preceding stage environment-friendly facility is reduced to the maximum extent, and the power consumption level of the whole system is reduced; and meanwhile, the air inlet flow speed of the subsequent cyclone demisting device is improved, so that the dehydration efficiency of the cyclone demisting device is improved, and the chimney plume type visual pollution degree of the final flue gas is weakened.
(7) The central shaft cooling waste hot air (the temperature is about 180-220 ℃) discharged by pyrolyzing the sludge of the multi-hearth furnace is wholly or partially recycled to the cooling section of the multi-hearth furnace, and the waste hot air is subjected to heat exchange with high-temperature ash and then rises to the pyrolysis section to participate in the anoxic combustion process, so that the heat energy utilization efficiency in the multi-hearth furnace can be remarkably improved, and the using amount of auxiliary fuel which may need to be added is further reduced.
(10) Saturated steam which is discharged by the sludge supplementary drying device and contains obvious odor (high concentration of odor compounds) is dried and evaporated, and is conveyed to a special gas washing tower by a separately-arranged pipe valve system for washing and deodorizing treatment, and is not combined with the process tail gas and/or the process flue gas of the multi-hearth furnace, so that the treatment load of the flue gas moisture can be reduced, and the total energy consumption level of the device system can be reduced.
When the waste water sludge with the DS content of 15-20% and the VS content of 45-60% is directly used as the raw material, although the multi-hearth furnace cannot reach the self-heating balance working condition state, the method can ensure that the post-combustion chamber automatically maintains the furnace temperature requirement of 850 ℃ by realizing the 'carbon-containing ash thorough burning process' (adopting the measures of adding excessive process air in a directional manner and supplementing a small amount of auxiliary fuel) in two hearths at the bottom of the multi-hearth furnace, and generates sufficient superheated steam to realize the comprehensive heat energy utilization target shown in figure 2. At the moment, the DS content of the sludge discharged by the sludge supplementary drying machine (namely the sludge charged into the multi-hearth furnace) is within the range of 21.5-25%, and the consumption of the auxiliary fuel is within the range of 850-1550 kcal/kgDS/hour.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the appended claims and their full range of equivalents.
Claims (5)
1. A comprehensive utilization method of heat energy of a multi-hearth sludge pyrolysis system is characterized by comprising the following steps:
conveying raw sludge into a multifunctional sludge storage bin of a multi-hearth furnace sludge pyrolysis system through a filter pressing process of a wastewater treatment plant, uniformly mixing the raw sludge with high water content by a forced spiral stirring mechanism arranged in the multifunctional sludge storage bin, forcibly conveying the raw sludge to a subsequent sludge cake conveying pump set, and feeding the raw sludge into a sludge supplementary drying device through the sludge cake conveying pump set;
step two, introducing exhausted steam exhausted by a steam turbine in a sludge cake conveying pump set and a steam turbine of a main induced draft fan at the tail end of the process into a drier jacket and a hollow blade of the sludge supplementary drying device, further reducing the pressure of the superheated exhausted steam in a steam passage of the sludge supplementary drying device and providing heat energy to evaporate partial moisture of raw sludge in a main cavity of the sludge supplementary drying device, and conveying the formed saturated steam containing odor to a special scrubbing tower for treatment by a special pipeline and the induced draft fan;
discharging the dried sludge evaporated by the sludge supplementary drying device from the sludge supplementary drying device, and immediately feeding the dried sludge into a multi-hearth furnace or a body furnace by a forced spiral feeding unit at the rear end for pyrolysis treatment;
step four, the dried sludge entering the multi-hearth furnace or the body furnace automatically completes the heat treatment process from top to bottom in the furnace, solid residues generated after pyrolysis of the dried sludge are discharged from the bottom of the multi-hearth furnace or the body furnace, and pyrolysis process tail gas of the multi-hearth furnace or the body furnace is discharged from a furnace top exhaust pipeline and then enters a secondary furnace;
step five, the tail gas of the pyrolysis process is fully mixed and combusted with secondary air sent by an air blower in a secondary furnace, the secondary furnace can maintain a certain furnace temperature required value, all combustible components in the tail gas of the pyrolysis process are completely burnt, and finally high-temperature flue gas containing a small amount of dust pollutants and trace acid gas components is generated;
step six, high-temperature flue gas discharged by the secondary furnace enters a waste heat steam boiler, then medium-pressure superheated steam is generated and sent to a mud cake conveying pump set at the front end of the pyrolysis process and a main induced draft fan at the tail end of the process, and the high-temperature flue gas is used for directly driving a steam turbine in the mud cake conveying pump set and a steam turbine in the main induced draft fan at the tail end of the process;
step seven, the flue gas discharged by the waste heat steam boiler sequentially enters a multi-hearth furnace flue gas scrubbing tower and a biological deodorization tower to be condensed, dehydrated, dedusted and deodorized; the rich waste water discharged from the multi-hearth furnace flue gas scrubbing tower and the biological deodorization tower enters a water collecting trap and then is discharged into a total water inlet of a waste water treatment plant, and then enters a conventional waste water treatment process for treatment;
step eight, the flue gas discharged by the biological deodorization tower passes through a cyclone demister before entering a main induced draft fan at the tail end of the process, liquid drops in the flue gas are removed, and finally the flue gas is discharged into the air by the main induced draft fan;
the water inlet of the special scrubber tower adopts heat source process steam condensate water and supplementary cold water discharged by a multifunctional sludge storage bin, and the steam condensate water containing odor is condensed by adopting a direct spraying method, is discharged to a water collecting well in a wastewater form after an added chemical agent absorbs odor compounds, and is discharged to a total water inlet of a wastewater treatment plant for conventional wastewater treatment;
the heat energy required by the heat treatment process in the multi-hearth furnace or the main furnace is completely provided by the reaction process and the heat exchange process in the furnace, auxiliary fuel is not required to be added, and only process air which is subjected to metering control is added in the process;
a heating jacket is arranged in the multifunctional sludge storage bin, water-containing exhaust steam sent from a dryer jacket of the sludge supplementary drying device is introduced into the heating jacket, the water-containing exhaust steam is condensed in the heating jacket and releases latent heat, and condensed water generated by the heating jacket enters a water collecting trap and then is discharged into a total water inlet of a wastewater treatment plant for conventional wastewater treatment;
the mud cake conveying pump set adopts a motor and steam turbine dual-drive mode, the mud cake conveying pump set is driven by the motor only under the working condition of opening the multi-hearth furnace, when the multi-hearth furnace sludge pyrolysis system enters the normal operation working condition, the mud cake conveying pump set is automatically switched into the steam turbine for driving, the steam turbine is driven by medium-pressure superheated steam, and the medium-pressure superheated steam is supplied by a waste heat boiler device arranged at the rear end of the secondary furnace;
all or part of the central shaft cooling waste hot air discharged by the multi-hearth furnace or the main body furnace is recycled into the cooling section of the multi-hearth furnace, the central shaft cooling waste hot air exchanges heat with high-temperature sludge ash and then rises to the pyrolysis section to participate in the anoxic combustion process, and the burnt sludge pyrolysis process tail gas enters the secondary furnace.
2. The comprehensive utilization method of heat energy of the sludge pyrolysis system with the multiple hearths as claimed in claim 1, is characterized in that: after a steam turbine in the sludge cake conveying pump set works, the pressure value of the exhausted superheated steam discharged is 0.15-0.40 MPa, the temperature is 110-136 ℃, and when the exhausted superheated steam is used as a heat source medium of a sludge supplementary drying device, raw sludge with the content of sludge dry solid substances of 30% can be dried to the level that the content of the sludge solid substances is 45%.
3. The comprehensive utilization method of heat energy of the sludge pyrolysis system with the multiple hearths as claimed in claim 1, is characterized in that: the evaporation load of the waste heat steam boiler is designed to be 1.8-3.2 tons of superheated steam/ton, the pressure of the superheated steam is 1.2-2.0 MPa, and the temperature is 210-260 ℃.
4. The comprehensive utilization method of heat energy of the sludge pyrolysis system with the multiple hearths as claimed in claim 1, is characterized in that: and the sludge ash after the combustion of the multi-hearth furnace or the main body furnace is sent to a disposal place for treatment.
5. The comprehensive utilization method of heat energy of the sludge pyrolysis system with the multiple hearths as claimed in claim 1, is characterized in that: before raw sludge enters a multi-hearth furnace sludge pyrolysis system, any one of the following three pretreatment modes is carried out:
a. when the volatile dry solid content level of the raw sludge is kept unchanged, the sludge dry solid content of the raw sludge is increased to be more than or equal to 30 percent, and one or more of the following pretreatment modes are adopted, including: solar drying technology, drying pool technology and natural air drying technology;
b. keeping the content level of sludge dry solid matter of the raw sludge unchanged, increasing the content of volatile dry solid matter of the raw sludge to be more than or equal to 78 percent, and adopting a pretreatment mode as follows: before the sludge filtering process of a wastewater treatment plant, industrial or agricultural wastes with high organic matter content are added into liquid raw sludge, so that the filterability of the sludge is improved, and the volatile dry solid content level of the sludge is improved;
c. meanwhile, the content levels of sludge dry solid substances and volatile dry solid substances of the raw material sludge are improved, so that the content of the sludge dry solid substances of the raw material sludge is improved to be more than or equal to 25%, the content of the volatile dry solid substances is improved to be more than or equal to 67%, and the pretreatment mode is as follows: industrial or agricultural wastes with high organic matter content are added into the liquid raw material sludge, and the sludge is dewatered by adopting a high-efficiency filter pressing machine.
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| CN101776379A (en) * | 2009-01-13 | 2010-07-14 | 王绍良 | Fume hollow blade drier |
| CN202621544U (en) * | 2012-05-07 | 2012-12-26 | 浙江利保环境工程有限公司 | Solid waste treatment device secondarily utilizing heat recuperation and mainly utilizing pyrolysis |
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| CN101776379A (en) * | 2009-01-13 | 2010-07-14 | 王绍良 | Fume hollow blade drier |
| CN202621544U (en) * | 2012-05-07 | 2012-12-26 | 浙江利保环境工程有限公司 | Solid waste treatment device secondarily utilizing heat recuperation and mainly utilizing pyrolysis |
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