A disposal method for upgrading organic sludge by low-temperature drying and pyrolysis

Abstract

The application discloses a kind of organic sludge low-temperature drying-pyrolysis upgrading disposal method, it is related to organic solid waste resource processing technical field.The method includes: after organic sludge is mechanically dewatered, with biomass conditioner and mineral additive are mixed, remove free water by low-temperature closed drying system;Subsequently, drying sludge is sent into anoxic pyrolysis reactor, and segmented pyrolysis carbonization is carried out, and pyrolysis gas, pyrolysis oil and pyrolysis carbon are obtained;Wherein pyrolysis gas is recycled after purification for drying and pyrolysis system heating, and pyrolysis carbon is modified and used as alternative fuel or soil improvement material.The application is coupled by low-temperature cascade drying and pyrolysis, improves sludge reduction, stabilizes and resource level, reduces dioxin and malodorous gas generation risk, with the advantages of low energy consumption, high thermal efficiency, less secondary pollution and high product added value.

Description

Technical Field

[0001] This invention relates to the field of organic solid waste resource utilization technology, and in particular to a method for the low-temperature drying-pyrolysis upgrading of organic sludge. Background Technology

[0002] With the acceleration of urbanization and the continuous expansion of industrial wastewater treatment scale in my country, sludge production is showing a rapid growth trend. Sludge mainly comes from municipal sewage treatment plants and industrial wastewater treatment systems in printing and dyeing, papermaking, pharmaceuticals, food processing, and chemicals. It is essentially a complex organic solid waste with high water content, high organic matter, and high ash content. Under normal circumstances, municipal dewatered sludge still has a water content as high as 75-85 wt% and an organic matter content of 35-65 wt%. It also contains pathogens, parasite eggs, heavy metals, and recalcitrant organic pollutants. If not properly disposed of, it can easily cause secondary pollution of soil, water bodies, and the atmosphere.

[0003] Currently, the mainstream methods for sludge disposal include sanitary landfill, land application, composting, incineration, and utilization in building materials. Among them:

[0004] (1) Sanitary landfills occupy a large area, and the organic matter in the sludge is prone to produce greenhouse gases such as methane and hydrogen sulfide under anaerobic conditions. At the same time, leachate is prone to causing groundwater pollution.

[0005] (2) Although composting and land application can achieve partial resource utilization, the heavy metals, antibiotics and pathogenic microorganisms in sludge will limit its agricultural application.

[0006] (3) Although traditional high-temperature incineration has a high volume reduction efficiency, it requires a large amount of auxiliary fuel due to the high water content of sludge, resulting in high operating costs. In addition, NOx, SO2 and dioxin pollutants are easily generated during high-temperature combustion.

[0007] In recent years, pyrolysis technology has received widespread attention due to its advantages of volume reduction, stabilization, and resource recovery. Sludge pyrolysis is a resource recovery technology that converts the organic components in sludge into pyrolysis gas, pyrolysis oil, and pyrolysis char under anoxic or anaerobic conditions through thermal cracking. Compared with direct incineration, the pyrolysis process has a lower oxygen content, which can inhibit dioxin formation to some extent, and can recover combustible gas and char materials, improving energy utilization efficiency.

[0008] Existing technologies include some research on the coupling of sludge pyrolysis and drying. For example:

[0009] The patent document "CN101708938A 'High and Low Temperature Coupled Pyrolysis Method for Sludge or Organic Waste'" discloses a high and low temperature coupled pyrolysis process that realizes the resource utilization of sludge through low temperature pyrolysis, medium temperature carbonization and high temperature gasification. It can obtain products such as biochar and combustible gas, but its process flow is long, the system is complex, and the requirements for graded control of pyrolysis temperature are high.

[0010] The patent document "CN102211844A Deep Dewatering, Drying and Low Temperature Pyrolysis Treatment Sludge Device" proposes a synergistic system for deep dewatering, low temperature drying and pyrolysis of sludge. It realizes the utilization of thermal energy by combining a sludge dryer and a low temperature pyrolysis furnace. However, this technology is more inclined to equipment system integration and has less to do with improving the calorific value of sludge, controlling tar and optimizing the quality of pyrolysis char.

[0011] Furthermore, some existing sludge pyrolysis technologies employ high-temperature direct pyrolysis or gasification to increase gas yield. However, high-temperature conditions easily lead to equipment coking, the generation of large amounts of pyrolysis tar, and corrosion of the pyrolysis system. Simultaneously, high-temperature operation significantly increases system energy consumption, hindering large-scale industrial application. Some studies indicate that high-nitrogen organic sludge is also prone to coking and secondary condensation reactions during high-temperature heat treatment, affecting the quality of pyrolysis oil and system stability.

[0012] On the other hand, existing sludge pyrolysis processes generally suffer from the following problems:

[0013] 1. High sludge moisture content and high energy consumption in front-end drying: Traditional hot air drying usually requires a high-temperature heat source of over 120°C, which has low thermal efficiency and high operating costs;

[0014] 2. Low calorific value of pyrolysis char: Due to the high ash content and low fixed carbon ratio of sludge, the obtained pyrolysis char is difficult to use directly as a high-quality alternative fuel;

[0015] 3. High tar production: During pyrolysis, large organic molecules are prone to condensation reactions, leading to tar deposition and blockage of pipes and heat exchange equipment;

[0016] 4. Insufficient heat energy recovery and utilization rate: Some pyrolysis gas is not effectively recycled, resulting in low overall energy utilization efficiency of the system;

[0017] 5. Limited effect of heavy metal stabilization: some heavy metals in pyrolytic char still exist in active form, which limits their subsequent resource utilization.

[0018] 6. Insufficient process synergy: Existing drying and pyrolysis processes mostly operate independently, lacking cascade utilization of heat and system coupling optimization.

[0019] Therefore, there is an urgent need to develop an integrated low-temperature drying-pyrolysis treatment method for organic sludge that can achieve low-energy drying, low-temperature stable pyrolysis, calorific value enhancement, and heat energy recycling, thereby realizing the synergistic improvement of sludge reduction, harmlessness, and resource utilization, and meeting the current development needs of green, low-carbon, and resource recycling. Summary of the Invention

[0020] Based on the problems raised in the background technology mentioned above, this invention proposes a method for the treatment of organic sludge by low-temperature drying-pyrolysis and upgrading.

[0021] The technical solution is as follows:

[0022] A method for treating organic sludge by low-temperature drying and pyrolysis upgrading includes the following steps:

[0023] (1) Sludge pretreatment steps:

[0024] The organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 58-72 wt%. 100 parts of the dewatered sludge, 8-18 parts of the wood biomass conditioner, 4-10 parts of the alkaline mineral additive, and 1-4 parts of the iron catalyst were mixed in a twin-shaft paddle mixer for 15-40 minutes to obtain homogeneous pyrolysis precursor material.

[0025] (2) Low-temperature drying step:

[0026] The pyrolysis precursor material is fed into a closed-loop low-temperature drying device, and 2-5 parts of drying and dehumidification synergist are added. Low-temperature circulating drying is carried out under slight negative pressure conditions. The drying temperature is controlled at 75-105℃, the drying time is 45-120min, the drying wind speed is 1.0-2.5m / s, and the system negative pressure is -80 to -300Pa, so that the moisture content of the material is reduced to 12-28wt%, and low-temperature dried material is obtained.

[0027] (3) Low-temperature pyrolysis step:

[0028] The low-temperature dried material is continuously fed into an oxygen-deficient pyrolysis reactor and pyrolysis reaction is carried out under nitrogen or circulating pyrolysis gas protection conditions. The oxygen content is controlled to be ≤3 vol%, the pyrolysis temperature is 380-520℃, the heating rate is 5-15℃ / min, and the pyrolysis residence time is 30-80min, to obtain pyrolysis gas, pyrolysis oil and pyrolysis char.

[0029] (4) Gas-liquid separation step:

[0030] The mixed gas generated by pyrolysis is sequentially processed by a cyclone dust collector, a tube condenser and an oil-water separator, with the condensation temperature controlled at 10-35℃ to obtain pyrolysis oil and non-condensable combustible gas; the non-condensable combustible gas is purified by an alkaline scrubbing tower and then reused for heating in the low-temperature drying and low-temperature pyrolysis steps.

[0031] (5) Upgrading steps for pyrolytic carbon:

[0032] The pyrolytic char is activated under a steam or carbon dioxide atmosphere at an activation temperature of 650–850℃ for 20–60 min, with an activation gas flow rate of 0.8–2.5 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 15–24 MJ / kg and a specific surface area of ​​180–650 m². 2 / g.

[0033] Optionally, the organic sludge is one or more of municipal sludge, food processing sludge, papermaking sludge, printing and dyeing sludge, and pharmaceutical sludge; the organic matter content in the organic sludge is 35-65 wt%, and the ash content is 15-45 wt%.

[0034] Optionally, the wood biomass conditioner is one or more of sawdust, bamboo powder, straw powder, rice husk powder, coconut shell powder or fruit shell powder; the particle size of the wood biomass conditioner is 0.2-2.5 mm and the moisture content is ≤12 wt%.

[0035] Optionally, the alkaline mineral additive is one or more of calcium oxide, calcium hydroxide, dolomite powder, kaolin, and bentonite.

[0036] Optionally, the iron-based catalyst is one or more of Fe2O3, Fe3O4, FeCl3, red mud, or iron-carbon composite catalyst.

[0037] Optionally, the preparation method of the drying and dehumidifying synergist is as follows:

[0038] By weight, 23-45 parts of acetic acid distillation residue (main component: acetic acid, containing carboxyl functional groups, produced by a company in Zhejiang) and 115-225 parts of ethylamine industrial wastewater (mass concentration 3%-7%, main component: ethylamine, containing primary amine functional groups, produced by a company in Zhejiang) are mixed evenly. 0.09-0.45 parts of zinc chloride are added as a low-temperature amidation catalyst, and the mixture is stirred and reacted at a constant temperature of 35-55℃ for 85-125 minutes. After the reaction, the wastewater discharged from dialysis purification is collected and purified by distillation. The material is then concentrated under negative pressure and air-dried at low temperature to obtain a drying and dehumidifying synergist.

[0039] Optionally, the low-temperature drying step employs a heat pump circulating drying system, with a heat pump condensing temperature of 45–65°C, an evaporating temperature of 5–20°C, and a circulating air volume of 8000–20000 m³ / h. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0040] Optionally, the anoxic pyrolysis reactor is a rotary kiln pyrolysis furnace, a screw propeller pyrolysis furnace, a fixed bed pyrolysis furnace, or a fluidized bed pyrolysis furnace; wherein the material filling rate in the pyrolysis reactor is 35-70 vol.

[0041] Optionally, the gas-liquid separation step employs a two-stage condensation method; the first-stage condensation temperature is 60–90°C, used to separate heavy tar; the second-stage condensation temperature is 10–35°C, used to separate light pyrolysis oil.

[0042] Optionally, the total integral of H2, CH4, and CO in the non-condensable combustible gas is 45–78 vol%, and the lower heating value is 10–18 MJ / Nm³. 3 The non-condensable combustible gas provides 35-80% of the total heat load of the low-temperature drying step after re-ignition.

[0043] Reaction mechanism:

[0044] This invention addresses the industry challenges of high water content, easily degradable organic matter, dense pore aggregation, and poor quality of pyrolysis products in organic sludge. It constructs an integrated closed-loop treatment system encompassing composite conditioning and modification, enhanced low-temperature drying, anoxic controlled pyrolysis, gas-liquid resource separation, and pyrolysis carbon activation and upgrading. This system achieves high-value resource utilization of organic sludge through volume reduction, harmlessness, energy conversion, and recycling. After mechanical dewatering pretreatment, the organic sludge undergoes compound modification with lignocellulosic biomass conditioners, alkaline mineral additives, and iron-based catalysts. This effectively breaks down the dense, agglomerated structure of the sludge, eliminates the hydrophilic stability of the sludge colloids, reconstructs the pore channels, replaces internal bound water, and pre-regulates the acid-base environment and pyrolysis catalytic activity sites, laying a material foundation for subsequent efficient drying and upgrading pyrolysis.

[0045] The introduction of a self-prepared drying and dehumidification synergist during the low-temperature drying stage is the core key to improving sludge drying efficiency and solving the problem of drying highly viscous sludge. The carboxyl functional groups carried by the acetic acid distillation residue in the synergist possess strong hydrophilicity, demulsification, and interface modification capabilities. These groups can replace bound water on the surface of sludge particles and adsorbed water in pores, disrupting the hydrogen bonds between water molecules and sludge colloids, weakening the solid-water binding force, and significantly reducing the difficulty of water removal. The primary amine functional groups contained in ethylamine industrial wastewater can undergo interfacial cross-linking modification with sludge organic matter, optimizing the material's pore structure, clearing water vapor diffusion channels, and avoiding material caking and pore blockage during the drying process. Under the low-temperature catalytic action of zinc chloride, the carboxyl groups and primary amine groups undergo a mild amidation reaction to generate active components with interface activation, hydrophobic and breathable properties, further improving the material's water vapor conduction efficiency and achieving low-temperature, low-energy, and high-efficiency deep drying.

[0046] The homogeneous material, after enhanced drying, enters an oxygen-deficient low-temperature pyrolysis system. Under the synergistic effect of a low-oxygen inert atmosphere and an iron-based catalyst, the organic matter undergoes directional pyrolysis, controlling the breakage of large organic molecular chains and selectively releasing pyrolysis oil and combustible non-condensable gases. Simultaneously, it enriches fixed carbon components, avoiding calorific value loss due to excessive pyrolysis. The mixed gas produced by pyrolysis undergoes staged condensation, dust removal, and oil-water separation to achieve precise separation of gaseous, liquid, and solid products. The purified combustible gas is then recycled back to the drying and pyrolysis processes in a closed loop, constructing a self-circulating thermal energy system. Finally, through steam and carbon dioxide coupled activation modification, the pore structure of the pyrolysis carbon is reshaped, surface active sites are enriched, and the specific surface area and calorific value of the pyrolysis carbon are significantly increased, achieving high-value utilization of all components of the organic sludge.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] 1. Significantly reduce system energy consumption: This invention adopts a low-temperature closed-loop drying process, which can reduce heat loss compared with traditional high-temperature steam drying, and achieve partial energy self-circulation through pyrolysis gas re-ignition.

[0049] 2. Improve the quality of pyrolysis char: Biomass conditioner improves the pore structure of sludge and the fixed carbon content, thereby increasing the calorific value of pyrolysis char and making it usable as an alternative fuel.

[0050] 3. Reduce tar formation: Iron-based catalysts promote the cracking of large organic molecules, reduce tar deposition, and increase the proportion of combustible gas.

[0051] 4. Reduce pollutant emissions: Low-temperature anaerobic pyrolysis can effectively inhibit the formation of dioxins, while mineral additives have a fixing effect on HCl and SO2.

[0052] 5. Improve the stability of heavy metals: Heavy metals in pyrolytic char are transformed from an exchangeable state to a stable residue state, reducing the risk of leaching. Detailed Implementation

[0053] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments.

[0054] Example 1

[0055] (1) Sludge pretreatment steps

[0056] Organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 58 wt%. The organic sludge was municipal sludge with an organic matter content of 35 wt% and an ash content of 15 wt%. 100 kg of dewatered sludge, 8 kg of wood biomass conditioner, 4 kg of alkaline mineral additive, and 1 kg of iron-based catalyst were mixed in a twin-shaft paddle mixer for 15 min to obtain homogeneous pyrolysis precursor material. The wood biomass conditioner was sawdust with a particle size of 0.2 mm and a moisture content ≤12 wt%. The alkaline mineral additive was calcium oxide. The iron-based catalyst was Fe2O3.

[0057] (2) Low-temperature drying step

[0058] The pyrolysis precursor material was fed into a closed-loop low-temperature drying device, and 2 kg of drying and dehumidification synergist was added. Low-temperature circulating drying was carried out under slight negative pressure conditions. The drying temperature was controlled at 75℃, the drying time at 45 min, the drying air velocity at 1.0 m / s, and the system negative pressure at -80 Pa, reducing the material moisture content to 12 wt% to obtain the low-temperature dried material. This step employed a heat pump circulating drying system with a heat pump condensing temperature of 45℃, an evaporation temperature of 5℃, and a circulating air volume of 8000 m³ / s. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0059] The preparation method of the drying and dehumidification synergist is as follows: 23 kg of acetic acid distillation residue and 115 kg of ethylamine industrial wastewater (mass concentration 3%) are mixed evenly, and 0.09 kg of zinc chloride is added as a low-temperature amidation catalyst. The mixture is stirred and reacted at a constant temperature of 35℃ for 85 min. After the reaction is completed, the wastewater discharged from the dialysis purification is collected and purified by distillation. The material is then concentrated under negative pressure and air-dried at low temperature to obtain the drying and dehumidification synergist.

[0060] (3) Low-temperature pyrolysis step

[0061] The low-temperature dried material is continuously fed into an anoxic pyrolysis reactor, which is a fixed-bed pyrolysis furnace with a material filling rate of 35 vol%. The pyrolysis reaction is carried out under nitrogen protection, with the oxygen content controlled at ≤3 vol%. The pyrolysis temperature is 380℃, the heating rate is 5℃ / min, and the pyrolysis residence time is 30 min, yielding pyrolysis gas, pyrolysis oil, and pyrolysis char.

[0062] (4) Gas-liquid separation step

[0063] The mixed gas produced by pyrolysis is sequentially processed through a cyclone dust collector, a tube condenser, and an oil-water separator, employing a two-stage condensation method. The first-stage condensation temperature is 60℃, used to separate heavy tar; the second-stage condensation temperature is 10℃, used to separate light pyrolysis oil. The overall condensation temperature is controlled at 10℃, yielding pyrolysis oil and non-condensable combustible gas. The total integral of H2, CH4, and CO in the non-condensable combustible gas is 45 vol%, and the lower heating value is 10 MJ / Nm³. 3 Non-condensable combustible gases, after being purified by an alkaline scrubbing tower, are reused for heating in the low-temperature drying and low-temperature pyrolysis processes, providing up to 35% of the total heat load of the low-temperature drying process.

[0064] (5) Upgrading steps of pyrolytic carbon

[0065] The pyrolytic char was activated under a carbon dioxide atmosphere at a temperature of 650℃ for 20 minutes, with an activation gas flow rate of 0.8 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 15 MJ / kg and a specific surface area of ​​180 m². 2 / g.

[0066] Example 2

[0067] (1) Sludge pretreatment steps

[0068] Organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 65 wt%. The organic sludge was food processing sludge with an organic matter content of 45 wt% and an ash content of 30 wt%. 100 kg of dewatered sludge, 13 kg of wood biomass conditioner, 7 kg of alkaline mineral additive, and 2.5 kg of iron-based catalyst were mixed in a twin-shaft paddle mixer for 28 min to obtain homogeneous pyrolysis precursor material. The wood biomass conditioner was a 1:1 mixture of sawdust and rice husk powder with a particle size of 1.2 mm and a moisture content ≤12 wt%. The alkaline mineral additive was a 1:1 mixture of calcium oxide and kaolin. The iron-based catalyst was Fe3O4.

[0069] (2) Low-temperature drying step

[0070] The pyrolysis precursor material was fed into a closed-loop low-temperature drying device, and 3.5 kg of drying and dehumidification synergist was added. Low-temperature circulating drying was carried out under slight negative pressure conditions. The drying temperature was controlled at 90℃, the drying time at 80 min, the drying air velocity at 1.8 m / s, and the system negative pressure at -190 Pa, reducing the material moisture content to 20 wt% to obtain the low-temperature dried material. This step employed a heat pump circulating drying system with a heat pump condensing temperature of 55℃, an evaporation temperature of 12℃, and a circulating air volume of 14000 m³ / h. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0071] The preparation method of the drying and dehumidification synergist is as follows: 34 kg of acetic acid distillation residue and 170 kg of ethylamine industrial wastewater (mass concentration 5%) are mixed evenly, and 0.27 kg of zinc chloride is added as a low-temperature amidation catalyst. The mixture is stirred and reacted at a constant temperature of 45℃ for 105 min. After the reaction is completed, the wastewater discharged from the dialysis purification is collected and purified by distillation. The material is then concentrated under negative pressure and air-dried at low temperature to obtain the drying and dehumidification synergist.

[0072] (3) Low-temperature pyrolysis step

[0073] The low-temperature dried material is continuously fed into an anoxic pyrolysis reactor, which is a spiral propeller pyrolysis furnace with a material filling rate of 50 vol%. The pyrolysis reaction is carried out under nitrogen protection, with the oxygen content controlled at ≤3 vol%. The pyrolysis temperature is 450℃, the heating rate is 10℃ / min, and the pyrolysis residence time is 55 min, yielding pyrolysis gas, pyrolysis oil, and pyrolysis char.

[0074] (4) Gas-liquid separation step

[0075] The mixed gas produced by pyrolysis is sequentially processed through a cyclone dust collector, a tube condenser, and an oil-water separator, employing a two-stage condensation method. The first-stage condensation temperature is 75℃, used to separate heavy tar; the second-stage condensation temperature is 22℃, used to separate light pyrolysis oil. The overall condensation temperature is controlled at 22℃, yielding pyrolysis oil and non-condensable combustible gas. The total integral of H2, CH4, and CO in the non-condensable combustible gas is 62 vol%, and the lower heating value is 14 MJ / Nm³. 3 Non-condensable combustible gases, after being purified by an alkaline scrubbing tower, are reused for heating in the low-temperature drying and low-temperature pyrolysis processes, providing up to 55% of the total heat load of the low-temperature drying process.

[0076] (5) Upgrading steps of pyrolytic carbon

[0077] The pyrolytic char was activated under a steam atmosphere at a temperature of 750℃ for 40 minutes, with an activation gas flow rate of 1.6 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 20 MJ / kg and a specific surface area of ​​420 m². 2 / g.

[0078] Example 3

[0079] (1) Sludge pretreatment steps

[0080] Organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 69 wt%. The organic sludge was a 1:1 mixture of dyeing and printing sludge and pharmaceutical sludge, with an organic matter content of 55 wt% and an ash content of 38 wt%. 100 kg of dewatered sludge, 16 kg of wood biomass conditioner, 9 kg of alkaline mineral additive, and 3.2 kg of iron-based catalyst were mixed in a twin-shaft paddle mixer for 35 min to obtain homogeneous pyrolysis precursor material. The wood biomass conditioner was a 1:1 mixture of bamboo powder and straw powder with a particle size of 2.0 mm and a moisture content ≤12 wt%. The alkaline mineral additive was a 1:1 mixture of dolomite powder and bentonite. The iron-based catalyst was FeCl3.

[0081] (2) Low-temperature drying step

[0082] The pyrolysis precursor material was fed into a closed-loop low-temperature drying device, and 4.2 kg of drying and dehumidification synergist was added. Low-temperature circulating drying was carried out under slight negative pressure conditions. The drying temperature was controlled at 98℃, the drying time at 100 min, the drying air velocity at 2.2 m / s, and the system negative pressure at -240 Pa, reducing the material moisture content to 25 wt% to obtain the low-temperature dried material. This step employed a heat pump circulating drying system with a heat pump condensing temperature of 60℃, an evaporation temperature of 16℃, and a circulating air volume of 18000 m³ / h. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0083] The preparation method of the drying and dehumidification synergist is as follows: 40 kg of acetic acid distillation residue is mixed evenly with 200 kg of ethylamine industrial wastewater (mass concentration 6%), and 0.36 kg of zinc chloride is added as a low-temperature amidation catalyst. The mixture is stirred and reacted at a constant temperature of 50℃ for 115 min. After the reaction is completed, the wastewater discharged from the dialysis purification is collected and purified by distillation. The material is then concentrated under negative pressure and air-dried at low temperature to obtain the drying and dehumidification synergist.

[0084] (3) Low-temperature pyrolysis step

[0085] The low-temperature dried material is continuously fed into an anoxic pyrolysis reactor, which is a fluidized bed pyrolysis furnace with a material filling rate of 62 vol%. The pyrolysis reaction is carried out under the protection of circulating pyrolysis gas, with the oxygen content controlled at ≤3 vol%. The pyrolysis temperature is 490℃, the heating rate is 12℃ / min, and the pyrolysis residence time is 65 min, yielding pyrolysis gas, pyrolysis oil, and pyrolysis char.

[0086] (4) Gas-liquid separation step

[0087] The mixed gas produced by pyrolysis is sequentially processed through a cyclone dust collector, a tube condenser, and an oil-water separator, employing a two-stage condensation method. The first-stage condensation temperature is 82℃, used to separate heavy tar; the second-stage condensation temperature is 28℃, used to separate light pyrolysis oil. The overall condensation temperature is controlled at 28℃, yielding pyrolysis oil and non-condensable combustible gas. The total integral of H2, CH4, and CO in the non-condensable combustible gas is 70 vol%, and the lower heating value is 16 MJ / Nm³. 3 Non-condensable combustible gases, after being purified by an alkaline scrubbing tower, are reused for heating in the low-temperature drying and low-temperature pyrolysis processes, providing 68% of the total heat load of the low-temperature drying process.

[0088] (5) Upgrading steps of pyrolytic carbon

[0089] The pyrolytic char was activated under a steam atmosphere at a temperature of 800℃ for 50 minutes, with an activation gas flow rate of 2.0 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 22 MJ / kg and a specific surface area of ​​530 m². 2 / g.

[0090] Example 4

[0091] (1) Sludge pretreatment steps

[0092] Organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 72 wt%. The organic sludge was a mixture of municipal sludge, food processing sludge, papermaking sludge, printing and dyeing sludge, and pharmaceutical sludge, with an organic matter content of 65 wt% and an ash content of 45 wt%. 100 kg of dewatered sludge, 18 kg of wood biomass conditioner, 10 kg of alkaline mineral additives, and 4 kg of iron-based catalyst were mixed in a twin-shaft paddle mixer for 40 min to obtain homogeneous pyrolysis precursor material. The wood biomass conditioner was a compound of coconut shell powder and fruit shell powder with a particle size of 2.5 mm and a moisture content ≤12 wt%. The alkaline mineral additives were a compound of calcium oxide, calcium hydroxide, and dolomite powder. The iron-based catalyst was an iron-carbon composite catalyst.

[0093] (2) Low-temperature drying step

[0094] The pyrolysis precursor material was fed into a closed-loop low-temperature drying device, and 5 kg of drying and dehumidification synergist was added. Low-temperature circulating drying was carried out under slight negative pressure conditions. The drying temperature was controlled at 105℃, the drying time at 120 min, the drying air velocity at 2.5 m / s, and the system negative pressure at -300 Pa, reducing the material moisture content to 28 wt% to obtain the low-temperature dried material. This step employed a heat pump circulating drying system with a heat pump condensing temperature of 65℃, an evaporation temperature of 20℃, and a circulating air volume of 20,000 m³ / h. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0095] The preparation method of the drying and dehumidification synergist is as follows: 45 kg of acetic acid distillation residue and 225 kg of ethylamine industrial wastewater (mass concentration 7%) are mixed evenly, and 0.45 kg of zinc chloride is added as a low-temperature amidation catalyst. The mixture is stirred and reacted at a constant temperature of 55℃ for 125 min. After the reaction is completed, the wastewater generated by dialysis purification is collected and purified by distillation. The material is then concentrated under negative pressure and air-dried at low temperature to obtain the drying and dehumidification synergist.

[0096] (3) Low-temperature pyrolysis step

[0097] The low-temperature dried material is continuously fed into an anoxic pyrolysis reactor, which is a rotary kiln pyrolysis furnace with a material filling rate of 70 vol%. The pyrolysis reaction is carried out under the protection of circulating pyrolysis gas, with the oxygen content controlled at ≤3 vol%. The pyrolysis temperature is 520℃, the heating rate is 15℃ / min, and the pyrolysis residence time is 80 min, yielding pyrolysis gas, pyrolysis oil, and pyrolysis char.

[0098] (4) Gas-liquid separation step

[0099] The mixed gas produced by pyrolysis is sequentially processed through a cyclone dust collector, a tube condenser, and an oil-water separator, employing a two-stage condensation method. The first-stage condensation temperature is 90℃, used to separate heavy tar; the second-stage condensation temperature is 35℃, used to separate light pyrolysis oil. The overall condensation temperature is controlled at 35℃, yielding pyrolysis oil and non-condensable combustible gas. The total integral of H2, CH4, and CO in the non-condensable combustible gas is 78 vol%, and the lower heating value is 18 MJ / Nm³. 3 Non-condensable combustible gases, after being purified by an alkaline scrubbing tower, are reused for heating in the low-temperature drying and low-temperature pyrolysis processes, providing up to 80% of the total heat load of the low-temperature drying process.

[0100] (5) Upgrading steps of pyrolytic carbon

[0101] The pyrolytic char was activated under a carbon dioxide atmosphere at a temperature of 850°C for 60 minutes, with an activation gas flow rate of 2.5 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 24 MJ / kg and a specific surface area of ​​650 m². 2 / g.

[0102] Comparative Example 1

[0103] (1) Sludge pretreatment steps

[0104] Organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 58 wt%. The organic sludge was municipal sludge with an organic matter content of 35 wt% and an ash content of 15 wt%. 100 kg of dewatered sludge, 8 kg of wood biomass conditioner, 4 kg of alkaline mineral additive, and 1 kg of iron-based catalyst were mixed in a twin-shaft paddle mixer for 15 min to obtain homogeneous pyrolysis precursor material. The wood biomass conditioner was sawdust with a particle size of 0.2 mm and a moisture content ≤12 wt%. The alkaline mineral additive was calcium oxide. The iron-based catalyst was Fe2O3.

[0105] (2) Low-temperature drying step

[0106] The pyrolysis precursor material is fed into a closed-loop low-temperature drying device and subjected to low-temperature circulating drying under slight negative pressure. The drying temperature is controlled at 75°C, the drying time is 45 minutes, the drying air velocity is 1.0 m / s, and the system negative pressure is -80 Pa, reducing the material moisture content to 12 wt% to obtain low-temperature dried material. This step uses a heat pump circulating drying system with a heat pump condensing temperature of 45°C, an evaporation temperature of 5°C, and a circulating air volume of 8000 m³ / s. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0107] (3) Low-temperature pyrolysis step

[0108] The low-temperature dried material is continuously fed into an anoxic pyrolysis reactor, which is a fixed-bed pyrolysis furnace with a material filling rate of 35 vol%. The pyrolysis reaction is carried out under nitrogen protection, with the oxygen content controlled at ≤3 vol%. The pyrolysis temperature is 380℃, the heating rate is 5℃ / min, and the pyrolysis residence time is 30 min, yielding pyrolysis gas, pyrolysis oil, and pyrolysis char.

[0109] (4) Gas-liquid separation step

[0110] The mixed gas produced by pyrolysis is sequentially processed through a cyclone dust collector, a tube condenser, and an oil-water separator, employing a two-stage condensation method. The first-stage condensation temperature is 60℃, used to separate heavy tar; the second-stage condensation temperature is 10℃, used to separate light pyrolysis oil. The overall condensation temperature is controlled at 10℃, yielding pyrolysis oil and non-condensable combustible gas. The total integral of H2, CH4, and CO in the non-condensable combustible gas is 45 vol%, and the lower heating value is 10 MJ / Nm³. 3 Non-condensable combustible gases, after being purified by an alkaline scrubbing tower, are reused for heating in the low-temperature drying and low-temperature pyrolysis processes, providing up to 35% of the total heat load of the low-temperature drying process.

[0111] (5) Upgrading steps of pyrolytic carbon

[0112] The pyrolytic char was activated under a carbon dioxide atmosphere at a temperature of 650℃ for 20 minutes, with an activation gas flow rate of 0.8 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 15 MJ / kg and a specific surface area of ​​180 m². 2 / g.

[0113] Comparative Example 2

[0114] (1) Sludge pretreatment steps

[0115] Organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 58 wt%. The organic sludge was municipal sludge with an organic matter content of 35 wt% and an ash content of 15 wt%. 100 kg of dewatered sludge, 8 kg of wood biomass conditioner, 4 kg of alkaline mineral additive, and 1 kg of iron-based catalyst were mixed in a twin-shaft paddle mixer for 15 min to obtain homogeneous pyrolysis precursor material. The wood biomass conditioner was sawdust with a particle size of 0.2 mm and a moisture content ≤12 wt%. The alkaline mineral additive was calcium oxide. The iron-based catalyst was Fe2O3.

[0116] (2) Low-temperature drying step

[0117] The pyrolysis precursor material was fed into a closed-loop low-temperature drying device, and 2 kg of drying and dehumidification synergist was added. Low-temperature circulating drying was carried out under slight negative pressure conditions. The drying temperature was controlled at 75℃, the drying time at 45 min, the drying air velocity at 1.0 m / s, and the system negative pressure at -80 Pa, reducing the material moisture content to 12 wt% to obtain the low-temperature dried material. This step employed a heat pump circulating drying system with a heat pump condensing temperature of 45℃, an evaporation temperature of 5℃, and a circulating air volume of 8000 m³ / s. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0118] The preparation method of the drying and dehumidification synergist is as follows: 0.09 kg of zinc chloride is added to 23 kg of acetic acid distillation residue as a low-temperature amidation catalyst, and the mixture is stirred and reacted at a constant temperature of 35°C for 85 min. After the reaction, the wastewater generated by dialysis purification is collected and purified by distillation. The material is then concentrated under negative pressure and air-dried at low temperature to obtain the drying and dehumidification synergist.

[0119] (3) Low-temperature pyrolysis step

[0120] The low-temperature dried material is continuously fed into an anoxic pyrolysis reactor, which is a fixed-bed pyrolysis furnace with a material filling rate of 35 vol%. The pyrolysis reaction is carried out under nitrogen protection, with the oxygen content controlled at ≤3 vol%. The pyrolysis temperature is 380℃, the heating rate is 5℃ / min, and the pyrolysis residence time is 30 min, yielding pyrolysis gas, pyrolysis oil, and pyrolysis char.

[0121] (4) Gas-liquid separation step

[0122] The mixed gas produced by pyrolysis is sequentially processed through a cyclone dust collector, a tube condenser, and an oil-water separator, employing a two-stage condensation method. The first-stage condensation temperature is 60℃, used to separate heavy tar; the second-stage condensation temperature is 10℃, used to separate light pyrolysis oil. The overall condensation temperature is controlled at 10℃, yielding pyrolysis oil and non-condensable combustible gas. The total integral of H2, CH4, and CO in the non-condensable combustible gas is 45 vol%, and the lower heating value is 10 MJ / Nm³. 3 Non-condensable combustible gases, after being purified by an alkaline scrubbing tower, are reused for heating in the low-temperature drying and low-temperature pyrolysis processes, providing up to 35% of the total heat load of the low-temperature drying process.

[0123] (5) Upgrading steps of pyrolytic carbon

[0124] The pyrolytic char was activated under a carbon dioxide atmosphere at a temperature of 650℃ for 20 minutes, with an activation gas flow rate of 0.8 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 15 MJ / kg and a specific surface area of ​​180 m². 2 / g.

[0125] Comparative Example 3

[0126] (1) Sludge pretreatment steps

[0127] Organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 58 wt%. The organic sludge was municipal sludge with an organic matter content of 35 wt% and an ash content of 15 wt%. 100 kg of dewatered sludge, 8 kg of wood biomass conditioner, 4 kg of alkaline mineral additive, and 1 kg of iron-based catalyst were mixed in a twin-shaft paddle mixer for 15 min to obtain homogeneous pyrolysis precursor material. The wood biomass conditioner was sawdust with a particle size of 0.2 mm and a moisture content ≤12 wt%. The alkaline mineral additive was calcium oxide. The iron-based catalyst was Fe2O3.

[0128] (2) Low-temperature drying step

[0129] The pyrolysis precursor material was fed into a closed-loop low-temperature drying device, and 2 kg of drying and dehumidification synergist was added. Low-temperature circulating drying was carried out under slight negative pressure conditions. The drying temperature was controlled at 75℃, the drying time at 45 min, the drying air velocity at 1.0 m / s, and the system negative pressure at -80 Pa, reducing the material moisture content to 12 wt% to obtain the low-temperature dried material. This step employed a heat pump circulating drying system with a heat pump condensing temperature of 45℃, an evaporation temperature of 5℃, and a circulating air volume of 8000 m³ / s. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

[0130] The preparation method of the drying and dehumidification synergist is as follows: 0.09 kg of zinc chloride is added to 115 kg of ethylamine industrial wastewater (mass concentration 3%) as a low-temperature amidation catalyst, and the mixture is stirred and reacted at a constant temperature of 35℃ for 85 min. After the reaction is completed, the wastewater discharged from the dialysis purification is collected in a unified manner, and after distillation purification, the material is concentrated under negative pressure and air-dried at low temperature to obtain the drying and dehumidification synergist.

[0131] (3) Low-temperature pyrolysis step

[0132] The low-temperature dried material is continuously fed into an anoxic pyrolysis reactor, which is a fixed-bed pyrolysis furnace with a material filling rate of 35 vol%. The pyrolysis reaction is carried out under nitrogen protection, with the oxygen content controlled at ≤3 vol%. The pyrolysis temperature is 380℃, the heating rate is 5℃ / min, and the pyrolysis residence time is 30 min, yielding pyrolysis gas, pyrolysis oil, and pyrolysis char.

[0133] (4) Gas-liquid separation step

[0134] The mixed gas produced by pyrolysis is sequentially processed through a cyclone dust collector, a tube condenser, and an oil-water separator, employing a two-stage condensation method. The first-stage condensation temperature is 60℃, used to separate heavy tar; the second-stage condensation temperature is 10℃, used to separate light pyrolysis oil. The overall condensation temperature is controlled at 10℃, yielding pyrolysis oil and non-condensable combustible gas. The total integral of H2, CH4, and CO in the non-condensable combustible gas is 45 vol%, and the lower heating value is 10 MJ / Nm³. 3 Non-condensable combustible gases, after being purified by an alkaline scrubbing tower, are reused for heating in the low-temperature drying and low-temperature pyrolysis processes, providing up to 35% of the total heat load of the low-temperature drying process.

[0135] (5) Upgrading steps of pyrolytic carbon

[0136] The pyrolytic char was activated under a carbon dioxide atmosphere at a temperature of 650℃ for 20 minutes, with an activation gas flow rate of 0.8 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 15 MJ / kg and a specific surface area of ​​180 m². 2 / g.

[0137] Test method:

[0138] 1. Moisture content test

[0139] The determination of dry matter and moisture content in solid waste was carried out in accordance with HJ 613-2011.

[0140] Test steps:

[0141] (1) Take approximately 50g of sample;

[0142] (2) Dry in a forced-air drying oven at 105℃ until constant weight;

[0143] (3) Calculate the weight loss rate.

[0144] Calculation formula:

[0145] Moisture content (%) = (Mass before drying - Mass after drying) / Mass before drying × 100%

[0146] 2. Calorific value test of pyrolytic carbon

[0147] The determination of calorific value of coal was carried out in accordance with GB / T 213-2008.

[0148] Test equipment:

[0149] Oxygen bomb calorimeter.

[0150] Test conditions:

[0151] Ambient temperature: 25℃;

[0152] Oxygen pressure: 2.8 MPa;

[0153] Sample particle size: ≤0.2mm.

[0154] The test results are the average of three parallel experiments.

[0155] 3. Pyrolysis gas composition test

[0156] The analysis was performed using gas chromatography (GC-TCD / FID).

[0157] Test conditions:

[0158] Column: TDX-01;

[0159] Carrier gas: High-purity argon;

[0160] Column temperature: 80℃;

[0161] Detected components: H2, CO, CH4, CO2.

[0162] Calculate the lower heating value based on the component concentration.

[0163] 4. Tar content test

[0164] The "condensation trap-solvent extraction method" was adopted.

[0165] Test steps:

[0166] (1) The pyrolysis gas passes through a two-stage condenser;

[0167] (2) The condensate was extracted with dichloromethane;

[0168] (3) Weigh the product after removing the solvent by rotary evaporation.

[0169] Tar yield calculation:

[0170] Tar yield (wt%) = Tar mass / Dry sludge mass × 100%

[0171] Table 1 Test Results

[0172] Moisture content after drying (wt%) Calorific value of pyrolytic char (MJ / kg) Fixed carbon content (wt%) Tar yield (wt%) <![CDATA[Low heating value of pyrolysis gas MJ / Nm 3 > Example 1 11.6 17.4 63.4 8.1 12.4 Example 2 10.2 18.6 65.0 7.8 12.9 Example 3 9.5 19.5 66.6 7.4 13.3 Example 4 8.8 20.8 68.3 7.2 13.8 Comparative Example 1 14.6 14.8 57.8 9.0 10.2 Comparative Example 2 12.4 16.0 60.5 8.6 11.0 Comparative Example 3 12.0 16.3 61.1 8.5 11.4

[0173] Based on the characteristics of process operation and the performance law of products, it is clear that the drying and dehumidification synergist independently developed in this invention plays a decisive role in improving the quality and efficiency of the entire process. The multi-component functional groups have clear division of labor and synergistic complementarity, which thoroughly optimizes the drying effect of organic sludge and the quality of pyrolysis products. Compared with traditional treatment processes without synergistic modification, it has significant technical advantages.

[0174] Among them, the carboxyl functional groups in the acetic acid distillation residue are the core hydrophilic demulsifying components, which can precisely disrupt the stable binding system between sludge colloids and water molecules, weaken the adsorption force of solid and water, and fundamentally solve the problems of difficult water removal and high drying limit of organic sludge, effectively improving the depth of low-temperature drying and dewatering efficiency. The primary amine functional groups carried by the ethylamine component mainly play a structural modification role, which can modify the interface of sludge organic matter, improve the permeability of material pores, prevent the drawbacks of surface crusting and internal water vapor retention during low-temperature drying, and ensure the continuous and stable progress of the drying process. With the help of the zinc chloride catalytic system, the cross-linking reaction between carboxyl and primary amine groups can be promoted to generate stable interfacial active modified substances, further enhancing the dehumidification efficiency and material modification effect, and maximizing the advantages of low-temperature drying.

[0175] Based on the modification of synergists, combined with a composite conditioning system and catalytic pyrolysis process, the sludge pyrolysis reaction environment can be significantly optimized, improving the organic matter conversion efficiency and product calorific value, thus achieving deep sludge reduction and high-value utilization. The overall process relies on the synergistic effect of multiple components of the synergist to overcome the technical bottlenecks of low efficiency, high energy consumption, and poor product quality in traditional low-temperature drying of organic sludge. The process exhibits good stability and outstanding quality improvement effects, possessing extremely high value for industrial promotion and application.

[0176] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for treating organic sludge by low-temperature drying-pyrolysis and upgrading, characterized in that, Includes the following steps: (1) Sludge pretreatment steps: The organic sludge was mechanically dewatered to obtain dewatered sludge with a moisture content of 58-72 wt%. 100 parts of the dewatered sludge, 8-18 parts of the wood biomass conditioner, 4-10 parts of the alkaline mineral additive, and 1-4 parts of the iron catalyst were mixed in a twin-shaft paddle mixer for 15-40 minutes to obtain homogeneous pyrolysis precursor material. (2) Low-temperature drying step: The pyrolysis precursor material is fed into a closed-loop low-temperature drying device, and 2-5 parts of drying and dehumidification synergist are added. Low-temperature circulating drying is carried out under slight negative pressure conditions. The drying temperature is controlled at 75-105℃, the drying time is 45-120min, the drying wind speed is 1.0-2.5m / s, and the system negative pressure is -80 to -300Pa, so that the moisture content of the material is reduced to 12-28wt%, and low-temperature dried material is obtained. (3) Low-temperature pyrolysis step: The low-temperature dried material is continuously fed into an oxygen-deficient pyrolysis reactor and pyrolysis reaction is carried out under nitrogen or circulating pyrolysis gas protection conditions. The oxygen content is controlled to be ≤3 vol%, the pyrolysis temperature is 380-520℃, the heating rate is 5-15℃ / min, and the pyrolysis residence time is 30-80min, to obtain pyrolysis gas, pyrolysis oil and pyrolysis char. (4) Gas-liquid separation step: The mixed gas generated by pyrolysis is sequentially processed by a cyclone dust collector, a tube condenser and an oil-water separator, with the condensation temperature controlled at 10-35℃ to obtain pyrolysis oil and non-condensable combustible gas; the non-condensable combustible gas is purified by an alkaline scrubbing tower and then reused for heating in the low-temperature drying and low-temperature pyrolysis steps. (5) Upgrading steps for pyrolytic carbon: The pyrolytic char is activated under a steam or carbon dioxide atmosphere at an activation temperature of 650–850℃ for 20–60 min, with an activation gas flow rate of 0.8–2.5 L / min·kg char, to obtain upgraded pyrolytic char. The upgraded pyrolytic char has a higher heating value of 15–24 MJ / kg and a specific surface area of ​​180–650 m². 2 / g.

2. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The organic sludge is one or more of municipal sludge, food processing sludge, papermaking sludge, printing and dyeing sludge, and pharmaceutical sludge; the organic matter content in the organic sludge is 35-65 wt%, and the ash content is 15-45 wt%.

3. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The wood biomass conditioner is one or more of sawdust, bamboo powder, straw powder, rice husk powder, coconut shell powder, or fruit shell powder; the particle size of the wood biomass conditioner is 0.2-2.5 mm, and the moisture content is ≤12 wt%.

4. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The alkaline mineral additive is one or more of calcium oxide, calcium hydroxide, dolomite powder, kaolin, and bentonite.

5. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The iron-based catalyst is one or more of Fe2O3, Fe3O4, FeCl3, red mud, or iron-carbon composite catalyst.

6. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The preparation method of the drying and dehumidifying synergist is as follows: By weight, 23-45 parts of acetic acid distillation residue and 115-225 parts of ethylamine industrial wastewater are mixed evenly. The mass concentration of ethylamine industrial wastewater is 3%-7%. 0.09-0.45 parts of zinc chloride are added as a low-temperature amidation catalyst. The mixture is stirred and reacted at a constant temperature of 35-55℃ for 85-125 minutes. After the reaction, the wastewater generated by dialysis purification is collected and purified by distillation. The material is then concentrated under negative pressure and air-dried at low temperature to obtain a drying and dehumidification synergist.

7. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The low-temperature drying step employs a heat pump circulating drying system, with a heat pump condensing temperature of 45–65°C, an evaporating temperature of 5–20°C, and a circulating air volume of 8000–20000 m³ / h. 3 / h; the dried exhaust gas is condensed and dehumidified and then recycled, while the exhaust gas condensate is returned to the wastewater treatment system.

8. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The anoxic pyrolysis reactor is a rotary kiln pyrolysis furnace, a spiral propeller pyrolysis furnace, a fixed bed pyrolysis furnace, or a fluidized bed pyrolysis furnace; wherein the material filling rate in the pyrolysis reactor is 35-70 vol.

9. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The gas-liquid separation step employs a two-stage condensation method; the first-stage condensation temperature is 60–90°C, used to separate heavy tar; the second-stage condensation temperature is 10–35°C, used to separate light pyrolysis oil.

10. The method for treating organic sludge by low-temperature drying-pyrolysis and upgrading according to claim 1, characterized in that: The total integral of H2, CH4, and CO in the non-condensable combustible gas is 45–78 vol%, and the lower heating value is 10–18 MJ / Nm³. 3 The non-condensable combustible gas provides 35-80% of the total heat load of the low-temperature drying step after re-ignition.