CN111018309B - Efficient sludge energy treatment method based on hydrothermal pretreatment - Google Patents
Efficient sludge energy treatment method based on hydrothermal pretreatment 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
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
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- 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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- 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
- C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
- C02F11/122—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using filter presses
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
- C10J2300/0913—Carbonaceous raw material
- C10J2300/0946—Waste, e.g. MSW, tires, glass, tar sand, peat, paper, lignite, oil shale
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
- C10J2300/00—Details of gasification processes
- C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
- C10J2300/0953—Gasifying agents
- C10J2300/0973—Water
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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
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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 relates to a high-efficiency sludge energy treatment method based on hydrothermal pretreatment, which comprises the following steps: step one, carrying out hydrothermal pretreatment on sludge generated by a sewage treatment plant with a solid content of 5-20%; step two, the filter residue obtained by dehydration enters a pyrolysis gasification system for conversion, and the sludge is pyrolyzed and gasified by using vapor generated by sludge hydrothermal and moisture existing in the dehydrated sludge as gasification agents; the pyrolysis retention time is 60min, and the carrier gas used is N2; pyrolyzing and gasifying to obtain hydrogen-rich gas, pyrolysis oil and biochar; and step three, collecting and conveying the filtrate after the dehydration treatment for anaerobic digestion treatment to obtain the biogas. The invention has the advantages that the sludge is liquefied or partially carbonized through hydrothermal pretreatment, so that the high-efficiency separation of solid phase and liquid phase in the sludge is realized, and the high-efficiency resource treatment method for preparing hydrogen-rich gas fuel and catalyst through catalytic gasification of the solid phase is realized.
Description
Technical Field
The invention relates to the technical field of solid waste recycling, in particular to a high-efficiency sludge recycling treatment method based on hydrothermal pretreatment.
Background
Along with the continuous improvement of the industrialization and urbanization level of China, the discharge amount of town sewage is increased year by year, and in addition, the treatment intensity of the sewage of China is increased, and the discharge standard of the sewage becomes stricter. By 12 months end in 2017, the treatment capacity of national urban sewage plants reaches 1.82 billion cubic meters per day, sludge is the largest byproduct generated in the sewage treatment process, and the national sludge yield reaches 808.40 million tons (dry basis). Because the sludge contains a large amount of organic matters, pathogenic bacteria, heavy metals, inorganic matters and the like, how to effectively and safely treat the sludge becomes a research hotspot of domestic and foreign scholars. The traditional sludge treatment mainly comprises anaerobic digestion, landfill, incineration, aerobic composting, sludge drying and the like. In recent years, the thermochemical treatment technology has great advantages in stabilizing, reducing and recycling sludge. The thermochemical treatment is a process of converting organic matters in the sludge into energy products in different forms and different phase states by utilizing high temperature, and mainly comprises an incineration technology, a hydrothermal technology, a pyrolysis technology and a gasification technology.
The sludge pyrolysis technology is a potential sludge treatment and disposal technology, can control the sludge pollution environment and simultaneously recover energy, and becomes one of the most popular sludge reduction and resource treatment technologies in the world at present. Pyrolysis can reduce the volume of sludge; pathogenic bacteria are destroyed, and sludge stabilization is realized; the produced pyrolysis gas and pyrolysis oil can be used as fuel. The pyrolysis oil is one of important products for sludge pyrolysis, and has the characteristics of high calorific value, high viscosity and poor stability. Many scholars try to improve the quality of pyrolysis oil by adding a catalyst or to convert pyrolysis oil and pyrolysis char into synthesis gas that can be directly utilized by means of gasification. Currently, scholars at home and abroad commonly use O2Water vapor, CO2As a gasifying agent, the pyrolysis oil is converted into synthesis gas. When CO is used2As a gasifying agent, the scholars find that the sludge can fix CO in the pyrolysis gasification process2And C emission is reduced. When water vapor is used as the gasifying agent, the H in the gasified product can be improved2The yield of (2). Due to the sludge contentA large amount of water exists, and a large number of scholars consider utilizing the water carried by the scholars in the sludge to evaporate in the pyrolysis process to generate vapor sludge for the pyrolysis gasification process. It was found that when the water content of the sludge reached 43.38%, the gasification effect of the sludge was the best and the hydrogen yield was the highest. With the further increase of the water content of the sludge, the gasification effect of the sludge is reduced due to the fact that a large amount of heat is consumed by evaporation of the water in the sludge. Therefore, the pyrolysis technology is combined with the gasification technology to be used as a novel sludge thermochemical treatment process unit.
The hydrothermal technology is used as a sludge dewatering technology, and the sludge can be converted into free water through hydrothermal treatment, so that the dewatering performance of the sludge is greatly improved. In addition, in the hydrothermal treatment process, solid organic matters in the sludge are dissolved and hydrolyzed along with the continuous increase of the hydrothermal temperature, so that the hydrolytic liquefaction of the sludge is realized. And then when the temperature exceeds 180 ℃, the small molecular organic matters in the sludge undergo reactions such as dehydration, decarboxylation, polycondensation, aromatization and the like, so that the carbonization of the sludge is realized. Carrying out hydrothermal modification on sludge: firstly, the dehydration performance of the sludge is obviously improved; secondly, liquefaction and partial carbonization of the sludge are beneficial to improving the gasification efficiency of the subsequent pyrolysis and gasification of the sludge and reducing the generation of pyrolysis oil. The hydrothermal pretreatment of the sludge lays a foundation for the efficient resource utilization of the subsequent sludge. The change of the dehydration performance and the argillaceous quality of the sludge by the hydrothermal pretreatment is beneficial to separating out the hydrothermal carbon rich in organic matters in the sludge for pyrolysis gasification treatment, and the separated filtrate can be subjected to efficient anaerobic digestion treatment. The existing sludge recycling treatment processes are anaerobic, aerobic, pyrolysis, land utilization and the like, and are different from the technical route of the invention.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art and provides a high-efficiency resource treatment method of sludge based on hydrothermal pretreatment, which is a high-efficiency resource treatment method for liquefying or partially carbonizing the sludge by performing hydrothermal pretreatment on the sludge to realize high-efficiency separation of a solid phase and a liquid phase in the sludge and preparing hydrogen-rich gas fuel and a catalyst by performing catalytic gasification on the solid phase.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a high-efficiency sludge energy treatment method based on hydrothermal pretreatment comprises the following steps:
step one, carrying out hydrothermal pretreatment on sludge generated by a sewage treatment plant with a solid content of 5-20%:
the working condition I is as follows: for sludge generated by a sewage treatment plant with a solid content of 5-10%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping for 5-30 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, and adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge to serve as a framework, wherein when the temperature of the hydrothermal pretreatment is 120-179 ℃, the addition amount of the iron-containing conditioner is 1% -5% of the dry weight of the hydrothermal sludge, and the addition amount of the biochar is 60% -90% of the dry weight of the hydrothermal sludge; when the temperature of the hydrothermal pretreatment is 180-300 ℃, the addition amount of the iron-containing conditioner is 0.2-1% of the dry weight of the sludge after hydrothermal treatment. The adding amount of the biochar is 5-10% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the dewatered sludge is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
working conditions are as follows: for sludge generated by a sewage treatment plant with a solid content of 10-15%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping the sludge for 30-60 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, and adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge to serve as a framework, wherein when the hydrothermal temperature is 120-179 ℃, the addition amount of the iron-containing conditioner is 5% -10% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 60% -90% of the dry weight of the sludge after hydrothermal treatment; when the temperature of the hydrothermal pretreatment is 180-300 ℃, the addition amount of the iron-containing conditioner is 1% -2% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 10% -20% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the sludge after dehydration is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
working conditions are as follows: for sludge generated by a sewage treatment plant with a solid content of 15-20%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping the sludge for 60-90 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, and adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge to serve as a framework, wherein when the hydrothermal temperature is 120-179 ℃, the addition amount of the iron-containing conditioner is 10% -15% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 60% -90% of the dry weight of the sludge after hydrothermal treatment; when the temperature of the hydrothermal pretreatment is 180-300 ℃, the addition amount of the iron-containing conditioner is 2-5% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 20-30% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the sludge after dehydration is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
step two, the filter residue with the water content lower than 60 percent obtained in the step one is sent into a pyrolysis gasification system for conversion, and the sludge is subjected to pyrolysis gasification treatment by using vapor generated by sludge hydrothermal and moisture in the dehydrated sludge as gasification agents; when the addition amount of the biochar in the first step is 60-90% of the dry weight of the sludge, the reaction condition of pyrolysis gasification is 700-800 ℃; when the addition amount of the biochar in the first step is 5-30% of the dry weight of the sludge, the reaction condition of pyrolysis gasification is 800-900 ℃; the pyrolysis residence time is 60min, and the carrier gas used is N2(ii) a Pyrolyzing and gasifying to obtain hydrogen-rich gas, pyrolysis oil and biochar;
and step three, collecting and conveying the filtrate subjected to dehydration treatment in the step one for anaerobic digestion treatment to obtain the biogas.
In order to optimize the technical scheme, the adopted measures further comprise:
in the first step, the iron-containing conditioner is FeSO4Or Fe2(SO4)3。
In the first step, the sludge is placed in a hydrothermal high-pressure reaction kettle by adopting sequencing batch feeding or semi-continuous feeding.
In the second step, the filter residue enters the pyrolysis gasification system in a sequencing batch feeding or semi-continuous feeding mode.
The sludge is one or a mixture of a plurality of primary sludge, excess sludge, concentrated sludge, dehydrated sludge and digested sludge.
Compared with the prior art, the efficient sludge energy treatment method based on hydrothermal pretreatment has the following advantages:
(1) the invention adopts a process of hydrothermal pretreatment and pyrolysis gasification, and is a novel sludge treatment process route. After the sludge is subjected to hydrothermal pretreatment, microbial cells in the sludge are hydrolyzed and destroyed, and bound water in the sludge is converted into interstitial water and free water, so that the sludge dewatering performance is remarkably improved, the water content after dewatering is not higher than 60%, and the energy consumption of the sludge is 10-70% of that of the conventional sludge dewatering heat drying treatment; and the secondary pollution and harm generated by the hydrothermal treatment are lower. Performing pyrolysis gasification treatment on the dehydrated sludge, and converting pyrolysis oil generated by sludge pyrolysis into hydrogen-rich synthetic gas by using water vapor generated by sludge hydrothermal and moisture in the dehydrated sludge as gasifying agents; the problem that pyrolysis oil is difficult to utilize in the traditional pyrolysis process is solved, green energy rich in hydrogen is formed, and carbon emission is reduced.
(2) The process route of 'hydrothermal pretreatment + pyrolysis gasification' is a high-efficiency and energy-saving process route optimized by a large number of experiments. Compared with the defects of rough regulation and control of process parameters of the existing hydrothermal and pyrolysis gasification processes, the process provides corresponding process parameters for different sludge qualities. The sludge solid content of the sewage treatment plant is fully covered, and the purposes of reducing energy consumption and medicament cost are achieved. The energy consumption of the method is 60-80% of that of the traditional rough mode. The energy input of the whole process is 560-960 kcal/kg of wet basis, and the energy generated by an energy output unit (anaerobic digestion, pyrolysis and gasification) is 2500-3000 kcal/kg of wet basis. After the sludge is treated by the process, the net energy output (1540-2400 kcal/kg) can be realized; the invention makes full use of biomass energy in the sludge and realizes the maximum energy production (as shown in figure 2).
(3) The reaction temperature in the hydrothermal modification link is high, the sludge is firstly hygienized, and the subsequent anaerobic treatment of the filtrate and the pyrolysis gasification of the residue fully realize the recycling and harmless treatment.
(4) In order to improve the gasification efficiency of the sludge and improve the catalytic performance of solid products, the composite conditioner is added in the sludge dehydration stage. Compared with the methods of dipping, ball milling and the like, the method adopts a wet mixing mode to fully mix the substances with the catalytic action and the sludge particles, thereby more effectively improving the gasification efficiency of the sludge and improving the hydrogen content in the synthesis gas. The yield of hydrogen in the hydrogen-rich gas generated by pyrolysis and gasification of the dewatered sludge is improved by 10-50%. On the premise of the same hydrogen-rich gas yield, the energy consumption of pyrolysis gasification in the process is reduced by 20-40% compared with that of the traditional process. The ferric salt, the biochar and the sludge remained in the sludge interact in the pyrolysis gasification process, so that the void ratio and the specific surface area of the pyrolysis gasification solid product can be effectively improved, the iron content on the surface of the biochar catalyst is increased, and the prepared biochar catalyst has higher catalytic performance; the process comprehensively realizes the resource utilization of organic matters and inorganic matters in the sludge.
Drawings
FIG. 1 is a process flow diagram of the present invention;
figure 2 is an energy balance diagram of the process of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
As shown in figures 1 and 2 of the drawings,
a high-efficiency sludge energy treatment method based on hydrothermal pretreatment comprises the following steps:
step one, placing sludge generated by a sewage treatment plant with a solid content of 5-20% into a hydrothermal high-pressure reaction kettle by adopting sequencing batch feeding or semi-continuous feeding for hydrothermal pretreatment: aiming at different sludge properties, the sludge is subdivided into three different working conditions, and the aim is to achieve the purposes of high efficiency and energy saving while the solid content of the dewatered sludge is not higher than 60%.
The working condition I is as follows: for sludge generated by a sewage treatment plant with a solid content of 5-10%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping for 5-30 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, and adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge to serve as a framework, wherein when the temperature of the hydrothermal pretreatment is 120-179 ℃, the iron-containing conditioner (FeSO)4Or Fe2(SO4)3) The adding amount of the biological carbon is 1% -5% of the dry weight of the sludge after hydrothermal treatment, and the adding amount of the biological carbon is 60% -90% of the dry weight of the sludge after hydrothermal treatment; when the temperature of the hydrothermal pretreatment is 180-300 ℃, an iron-containing conditioner (FeSO)4Or Fe2(SO4)3) The addition amount of the sludge is 0.2-1% of the dry weight of the sludge after hydrothermal treatment. The adding amount of the biochar is 5-10% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the dewatered sludge is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
working conditions are as follows: for sludge generated by a sewage treatment plant with a solid content of 10-15%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping the sludge for 30-60 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge as a framework, wherein the iron-containing conditioner (FeSO) is used when the hydrothermal temperature is 120-179 DEG C4Or Fe2(SO4)3) The adding amount of the biochar is 5% -10% of the dry weight of the sludge after hydrothermal treatment, and the adding amount of the biochar is 60% -90% of the dry weight of the sludge after hydrothermal treatment; when the temperature of the hydrothermal pretreatment is 180-300 ℃, an iron-containing conditioner (FeSO)4Or Fe2(SO4)3) The addition amount of the sludge is 1 percent of the dry weight of the sludge after hydrothermal treatment-2%, wherein the addition amount of the biochar is 10% -20% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the sludge after dehydration is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
working conditions are as follows: for sludge generated by a sewage treatment plant with a solid content of 15-20%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping the sludge for 60-90 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge as a framework, wherein the iron-containing conditioner (FeSO) is used when the hydrothermal temperature is 120-179 DEG C4Or Fe2(SO4)3) The adding amount of the biological carbon is 10% -15% of the dry weight of the sludge after hydrothermal treatment, and the adding amount of the biological carbon is 60% -90% of the dry weight of the sludge after hydrothermal treatment; when the temperature of the hydrothermal pretreatment is 180-300 ℃, an iron-containing conditioner (FeSO)4Or Fe2(SO4)3) The addition amount of the biochar is 2% -5% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 20% -30% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the dewatered sludge is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through the heat exchanger, and then the sludge in the storage barrel is preheated.
The physicochemical characteristics of the sludge after hydrothermal pretreatment are as follows: the solid content of the obtained sludge is reduced by 20-40%, and the carbonization rate is 0-70%. Under the condition of high temperature and high pressure, the thermal motion of the particles is aggravated, the mutual collision frequency among the particles is increased, so that the agglomeration among the particles is promoted, meanwhile, cell bodies in the sludge are broken due to the heated volume expansion, proteins, minerals and cell membrane fragments inside the cells are released, the cell structure is destroyed, and the combined water in the sludge is converted into interstitial water and free water, so that the dehydration performance of the sludge is remarkably improved. And main organic matters such as polysaccharide, protein and the like in the sludge are hydrolyzed and converted into micromolecular organic matters such as monosaccharide, amino acid and the like, and dehydration, decarboxylation and polycondensation are further carried out along with the change of hydrothermal conditions to realize partial carbonization. Water (W)After the thermal pretreatment is finished, an iron-containing conditioner (FeSO) is added into the sludge in the process of dehydrating the sludge4Or Fe2(SO4)3) As a flocculant, flocculation of sludge is promoted. And the biochar is used as a framework, so that the compressibility of the sludge can be improved. The method is characterized in that hot water process parameters and the addition amount of a conditioner are adjusted according to different sludge properties, the aim of high efficiency and energy saving is achieved while the solid content of dewatered sludge is not higher than 60%, and the energy consumption is 80-260 kcal/kg and is 10-70% of that of conventional sludge dewatering and drying treatment.
Step two, filter residues with the water content lower than 60 percent obtained in the step one by dehydration enter a pyrolysis gasification system for conversion in a sequencing batch feeding or semi-continuous feeding mode, and the sludge is subjected to pyrolysis gasification treatment by using vapor generated by sludge hydrothermal and moisture in the dehydrated sludge as gasification agents; when the addition amount of the biochar in the first step is 60-90% of the dry weight of the sludge, the reaction condition of pyrolysis gasification is 700-800 ℃; when the addition amount of the biochar in the first step is 5-30% of the dry weight of the sludge, the reaction condition of pyrolysis gasification is 800-900 ℃; the pyrolysis residence time is 60min, and the carrier gas used is N2(ii) a And pyrolyzing and gasifying to obtain hydrogen-rich gas, pyrolysis oil and biochar.
Wherein, the yield of the pyrolysis oil can be reduced to below 10 percent, and the yield of pyrolysis gas (hydrogen-rich gas) reaches above 40 percent. Compared with the traditional sludge pyrolysis gasification, the conditioner added in the step one has stronger catalytic performance, so that the yield of hydrogen in the hydrogen-rich gas generated by the pyrolysis gasification of the dewatered sludge is increased by 10-50%, and the energy consumption of the pyrolysis gasification in the process is reduced by 20-40% compared with that of the traditional process on the premise of the same yield of the hydrogen-rich gas.
And step three, collecting and conveying the filtrate subjected to dehydration treatment in the step one for anaerobic digestion treatment to obtain the biogas.
The sludge is one or a mixture of a plurality of primary sludge, excess sludge, concentrated sludge, dehydrated sludge and digested sludge.
The invention pretreats the sludge by a hydrothermal technology, so that organic matters in the sludge are dissolved and hydrolyzed to be converted into micromolecular organic matters, and further polycondensation is carried out to realize partial carbonization. Finally, the soluble micromolecular organic matter is enriched in a liquid phase, the residual solid organic matter and the hydrothermal carbon are enriched in a solid phase, and solid-liquid separation is realized through plate-and-frame filter pressing and other modes. The method is different from the traditional treatment mode that the sludge is subjected to dehydration and heat drying treatment and then subjected to pyrolysis energy regeneration.
The pyrolysis gasification of the dewatered sludge and the preparation of the catalyst are carried out simultaneously. The iron-containing conditioner and the biochar conditioner remained in the mud cake are uniformly distributed in the interior of the sludge particles, so that the content of elements such as Fe, C and the like in the sludge is increased, and the functions of the sludge are realized from two aspects:
in the aspect of preparing hydrogen-rich gas fuel, the ferric salt can effectively improve the reaction rate of sludge gasification, and the biochar can supplement a C source and improve CO and CH4And the like. The high-activity biochar can promote the breakage of carbon-hydrogen bonds and carbon-carbon bonds on the surface of sludge particles, promote macromolecular organic matters to convert micromolecular gas, promote the formation of gaps in particles and improve the specific surface area of the sludge particles. Meanwhile, the biochar can catalyze the pyrolysis of the pyrolysis oil, promote the gasification reaction and the steam reforming of the steam, and improve the yield of the synthesis gas, particularly the hydrogen.
In the aspect of influencing the performance of the catalyst, a solid product generated by pyrolysis and gasification of the dewatered sludge has higher porosity and specific surface area, and supports inorganic oxides such as ferric oxide with high activity, so that the catalytic performance of the catalyst is obviously improved, and the catalyst is suitable for catalytic reforming of pyrolysis oil.
Example 1
The solid content of dewatered sludge of a certain sewage treatment plant is measured to be 10%, 80kg of sludge in a sludge storage tank is placed into a liner of a hydrothermal reaction kettle with the effective volume of 100L, the set temperature is 180 ℃, the pressure is 1MPa, the sludge is maintained for 30min after reaching the set temperature, water vapor is recycled and used for preheating the sludge in the sludge storage tank, the solid content of the sludge is reduced to 6% after the sludge is subjected to hydrothermal treatment, and the sludge is subjected to hydrothermal treatmentAdding solid FeSO into mud4The adding amount is 2 percent of the weight of the dry basis of the sludge, and the materials are uniformly mixed and stirred for 10 min; and then adding 0.15g/g (DS) of biochar generated by subsequent pyrolysis and gasification, carrying out plate-and-frame filter pressing and dehydration to obtain mud cakes with the water content of 45%, feeding filtrate into an anaerobic digestion system to produce methane and collect biogas, and feeding the generated wet mud cakes into a sequencing batch fixed bed pyrolysis and gasification system to be converted, wherein the pyrolysis temperature is 800 ℃ and the pyrolysis time is 60 min. The yields of final pyrolysis gas, pyrolysis oil and biochar were 50%, 12% and 38%, respectively, with a volume ratio of hydrogen in the pyrolysis gas of 43.56%. The specific surface area of the prepared sludge-based biochar catalyst is 110m2The content of the supported Fe is 1.5 percent per gram.
Example 2
Measuring the solid content of dewatered sludge of a certain sewage treatment plant to be 20%, feeding the sludge into a hydrothermal reactor with the temperature of 200 ℃ and the pressure of 1.6MPa in a semi-continuous mode through a high-pressure pump, maintaining for 60min after the sludge reaches a set temperature, recovering water vapor and preheating sludge in a sludge storage tank, measuring the solid content of the sludge after hydrothermal modification to be reduced to 15%, and adding solid FeSO into the sludge after hydrothermal treatment4The adding amount is 5 percent of the dry weight of the sludge, and the materials are uniformly mixed and stirred for 10 min; then adding 0.27g/g (DS) of biochar generated by subsequent pyrolysis and gasification, carrying out plate-and-frame filter pressing and dehydration to obtain mud cakes with the water content of 30%, carrying out multistage reduced pressure cooling on reaction materials, then feeding the reaction materials into a dehydration system, feeding dehydrated filtrate into an anaerobic system for subsequent biogas recovery, feeding the dehydrated mud cakes into a sequencing batch fixed bed pyrolysis and gasification reactor, wherein the pyrolysis temperature is 800 ℃, and the pyrolysis time is 60 min. The yields of final pyrolysis gas, pyrolysis oil and biochar were 70%, 4.2% and 25.8%, respectively, with a hydrogen volume ratio of 40.45% in the pyrolysis gas. The specific surface area of the prepared sludge-based biochar catalyst is 132m2The content of the supported Fe is 10 percent per gram.
Example 3
Measuring the solid content of dewatered sludge of a certain sewage treatment plant to be 7%, feeding the sludge into a hydrothermal reactor with the temperature of 250 ℃ and the pressure of 4.0MPa in a semi-continuous mode through a screw pump, maintaining for 30min after the sludge reaches a set temperature, recovering water vapor and preheating sludge in a sludge storage tank, and measuring the sludge after hydrothermal modificationThe solid content of the sludge is reduced to 20 percent, and solid Fe is added into the sludge after the hydrothermal treatment2(SO4)3The adding amount is 0.5 percent of the weight of the dry basis of the sludge, and the components are uniformly mixed and stirred for 10 min; then adding 0.50g/g (DS) of biochar generated by subsequent pyrolysis and gasification, carrying out plate-and-frame filter pressing and dehydration to obtain mud cakes with the water content of 20%, feeding dehydrated filtrate into an anaerobic system for subsequent biogas recovery, feeding the dehydrated mud cakes into a semi-continuous fixed bed pyrolysis and gasification reactor, wherein the pyrolysis temperature is 850 ℃ and the pyrolysis time is 60 min. The yields of final pyrolysis gas, pyrolysis oil and biochar were 65%, 6.5% and 28.5%, respectively, with a hydrogen volume ratio of 41% in the pyrolysis gas. The specific surface area of the prepared sludge-based biochar catalyst is 101m2The content of the supported Fe is 4 percent per gram.
While the preferred embodiments of the present invention have been illustrated, various changes and modifications may be made by one skilled in the art without departing from the scope of the invention.
Claims (5)
1. A high-efficiency sludge energy treatment method based on hydrothermal pretreatment is characterized by comprising the following steps: the method comprises the following steps:
step one, carrying out hydrothermal pretreatment on sludge generated by a sewage treatment plant with a solid content of 5-20%:
the working condition I is as follows: for sludge produced by a sewage treatment plant with a solid content of 5% -10%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping for 5-30 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, and adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge to serve as a framework, wherein when the temperature of the hydrothermal pretreatment is 120-179 ℃, the addition amount of the iron-containing conditioner is 1% -5% of the dry weight of the hydrothermal sludge, and the addition amount of the biochar is 60% -90% of the dry weight of the hydrothermal sludge; when the temperature of the hydrothermal pretreatment is 180-300 ℃, the addition amount of the iron-containing conditioner is 0.2-1% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 5-10% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the sludge after dehydration is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
working conditions are as follows: for sludge generated by a sewage treatment plant with a solid content of 10% -15%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping the sludge for 30-60 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, and adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge to serve as a framework, wherein when the hydrothermal temperature is 120-179 ℃, the addition amount of the iron-containing conditioner is 5% -10% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 60% -90% of the dry weight of the sludge after hydrothermal treatment; when the temperature of the hydrothermal pretreatment is 180-300 ℃, the addition amount of the iron-containing conditioner is 1% -2% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 10% -20% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the sludge after dehydration is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
working conditions are as follows: for sludge generated by a sewage treatment plant with a solid content of 15% -20%:
placing the sludge in a hydrothermal high-pressure reaction kettle, and keeping the sludge for 60-90 min under the conditions of high temperature and high pressure; the reaction conditions of the hydrothermal pretreatment are as follows: the temperature is 120-300 ℃, and the pressure is 0.2-8.6 MPa; dewatering the sludge after the hydrothermal pretreatment, and adding an iron-containing conditioner and biochar generated in the second pyrolysis gasification process into the sludge to serve as a framework, wherein when the hydrothermal temperature is 120-179 ℃, the addition amount of the iron-containing conditioner is 10% -15% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 60% -90% of the dry weight of the sludge after hydrothermal treatment; when the temperature of the hydrothermal pretreatment is 180-300 ℃, the addition amount of the iron-containing conditioner is 2-5% of the dry weight of the sludge after hydrothermal treatment, and the addition amount of the biochar is 20-30% of the dry weight of the sludge after hydrothermal treatment, so that the solid content of the sludge after dehydration is not higher than 60%; high-temperature steam generated after the sludge is subjected to hydrothermal treatment is used for recycling heat through a heat exchanger and then preheating sludge in the storage barrel;
step two, the filter residue with the water content lower than 60 percent obtained in the step one is sent into a pyrolysis gasification system for conversion, and the sludge is subjected to pyrolysis gasification treatment by using vapor generated by sludge hydrothermal and moisture in the dehydrated sludge as gasification agents; when the addition amount of the biochar in the first step is 60-90% of the dry weight of the sludge, the reaction condition of pyrolysis gasification is 700-800 ℃; when the addition amount of the biochar in the first step is 5-30% of the dry weight of the sludge, the reaction condition of pyrolysis gasification is 800-900 ℃; the pyrolysis retention time is 60min, and the carrier gas used is N2; pyrolyzing and gasifying to obtain hydrogen-rich gas, pyrolysis oil and biochar;
and step three, collecting and conveying the filtrate subjected to dehydration treatment in the step one for anaerobic digestion treatment to obtain the biogas.
2. The efficient sludge energy treatment method based on the hydrothermal pretreatment as claimed in claim 1, which is characterized in that: in the first step, the iron-containing conditioner is FeSO4 or Fe2(SO4) 3.
3. The efficient sludge energy treatment method based on the hydrothermal pretreatment as claimed in claim 1, which is characterized in that: in the first step, the sludge is placed in a hydrothermal high-pressure reaction kettle by adopting sequencing batch feeding or semi-continuous feeding.
4. The efficient sludge energy treatment method based on the hydrothermal pretreatment as claimed in claim 1, which is characterized in that: and in the second step, the filter residue enters the pyrolysis gasification system in a sequencing batch feeding or semi-continuous feeding mode.
5. The efficient sludge energy treatment method based on the hydrothermal pretreatment as claimed in claim 1, wherein the sludge is one or a mixture of primary sludge, excess sludge, concentrated sludge, dewatered sludge and digested sludge.
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| CN112774628B (en) * | 2021-01-07 | 2022-12-02 | 昆明理工大学 | Method for preparing biochar by self-boosting carbonization of traditional Chinese medicine residues activated by phosphoric acid |
| CN112811783B (en) * | 2021-01-14 | 2022-04-12 | 华中科技大学 | Sludge conditioning and dewatering method for activating molecular oxygen by sludge-based iron-rich biochar |
| CN113025367B (en) * | 2021-03-01 | 2022-05-27 | 浙江工业大学 | Method for efficiently recycling tank bottom oil sludge |
| CN113480124B (en) * | 2021-07-29 | 2022-10-14 | 华中科技大学 | Method for recovering phosphorus in steam activated sludge pyrolytic carbon |
| CN114733527B (en) * | 2022-04-08 | 2023-05-12 | 同济大学 | Preparation method of Ca-Ni ash-based catalyst and hydrogen-rich synthetic gas |
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