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CN-120097599-B - Multi-effect sludge anaerobic digestion strengthening method and system based on sodium disilicate and thermal hydrolysis

CN120097599BCN 120097599 BCN120097599 BCN 120097599BCN-120097599-B

Abstract

The invention discloses a sludge anaerobic digestion strengthening method and system based on sodium disilicate and thermal hydrolysis, and belongs to the technical field of sludge recycling and energy recovery. By innovatively introducing sodium disilicate as a chemical conditioner and combining the thermal hydrolysis pretreatment of specific temperature and pressure parameters, the multiple synergistic effects of efficient cracking of sludge cell structures, improvement of organic matter dissolution rate and heavy metal passivation are realized. Compared with the prior art, the method improves the methane yield by 50-70%, improves the volatile solid degradation rate by 30-45%, shortens the digestion period by 30-50%, and obviously reduces the toxic influence of inhibitory substances (such as sulfide and ammonia nitrogen) and heavy metals. The method has high efficiency, environmental protection and economy, and provides a breakthrough solution for sludge energy.

Inventors

  • CHEN HONGBO
  • Niu Zizhi

Assignees

  • 湘潭大学

Dates

Publication Date
20260512
Application Date
20250407

Claims (10)

  1. 1. The sludge reinforced methanogenesis method based on sodium disilicate and thermal hydrolysis is characterized by comprising the following steps of: a) Adding sodium disilicate with the particle size of 50-200 meshes into the sludge, wherein the adding amount is 0.5-3% of the dry weight of the sludge, stirring and mixing uniformly by 50-200 rpm, and carrying out microwave radiation on the sludge for 2-10 minutes by 200-500W before adding the sodium disilicate; b) Carrying out thermal hydrolysis pretreatment on the mixed sludge, wherein the temperature is controlled to be 120-180 ℃, the pressure is controlled to be 0.5-1.5 MPa, and the treatment time is controlled to be 10-60 minutes; c) Introducing the pretreated sludge into an anaerobic digestion unit, reacting for 10-25 days at 35-55 ℃, collecting methane gas, and filling modified zeolite or biochar with the pore diameter of 2-5 nm into the anaerobic digestion unit.
  2. 2. The method according to claim 1, wherein the sodium disilicate addition in step a) is positively correlated with the sludge organic matter content, specifically, sodium disilicate addition is 0.2 x sludge VS/sludge ts+0.1, wherein sludge VS/sludge TS is 0.4-0.8.
  3. 3. The method according to claim 1, wherein the rate of temperature rise in the thermal hydrolysis pretreatment in step b) is 3-8 ℃ per minute, and the temperature and pressure are controlled such that P=0.007×T+0.1, wherein T is 120-180 ℃ and P is 0.5-1.5 MPa.
  4. 4. The method of claim 1, wherein the methanogenic bacteria enriching agent is added to the anaerobic digestion unit in step c), and the enriching agent comprises Methanosarcina, methanothrix bacteria and the adding volume is 1% -5% of the sludge volume.
  5. 5. The method according to claim 1, wherein the pH of the sludge after the stirring and mixing in step a) is adjusted to 9.0-10.5 and the pH is reduced to 7.5-8.5 by carbon dioxide stripping after the thermal hydrolysis pretreatment.
  6. 6. A sludge reinforced methane production system based on sodium disilicate and thermal hydrolysis is used for realizing the method of any one of claims 1-5, and is characterized by comprising a sludge mixing unit (1) provided with a screw feeder for quantitatively adding sodium disilicate, a variable-frequency speed-regulating stirring device and a pH on-line monitor, a thermal hydrolysis reaction unit (2) which adopts a multistage gradient heating jacket type reaction tank and integrates a pressure feedback control system, and an anaerobic digestion unit (3) which is internally provided with a gas-liquid separator and a methane purification module and is connected with a methane storage device.
  7. 7. The system according to claim 6, wherein the circulating medium in the jacket of the thermal hydrolysis reaction unit (2) is supercritical carbon dioxide for enhancing heat transfer and organic matter dissolution.
  8. 8. The system according to claim 6, wherein a microwave pre-radiation module is arranged between the sludge mixing unit (1) and the thermal hydrolysis reaction unit (2), the radiation power is 200-500W, and the radiation time is 2-10 minutes.
  9. 9. The system according to claim 6, characterized in that the anaerobic digestion unit (3) is configured with a heavy metal adsorption bed filled with modified zeolite or biochar for adsorption passivation of heavy metal ions.
  10. 10. The system of claim 6, wherein the system is adapted for refractory industrial sludge having a solids content of 5% -20% and a total Cu, zn, pb >500 mg/kg.

Description

Multi-effect sludge anaerobic digestion strengthening method and system based on sodium disilicate and thermal hydrolysis Technical Field The invention relates to the technical field of sludge treatment, in particular to an energy treatment method for high-solid and high-toxicity sludge, which improves anaerobic digestion efficiency and reduces environmental risk through chemical-physical cooperative pretreatment. Background Along with the acceleration of the urban process and the expansion of industrial scale, the sludge yield is increased year by year. Anaerobic digestion is used as a mainstream sludge recycling technology, and organic matters can be converted into methane through microbial metabolism, so that the dual aims of energy recovery and pollution reduction are achieved. However, the organic matter in the sludge is mainly wrapped in a dense structure composed of microbial cell walls and Extracellular Polymers (EPS). In the conventional anaerobic digestion process, the rate of the hydrolysis stage is extremely slow, and the hydrolysis stage becomes a speed limiting step. Studies have shown that only 30% -40% of the Volatile Solids (VS) of the untreated sludge are degraded, with methane yields generally below 200mL/gVS. Although high temperature digestion (55 ℃) can partially increase the reaction rate, the energy consumption increases by more than 50% and has limited effect on cell disruption. How to release the biodegradable organic matters in the sludge efficiently becomes a core challenge for improving the anaerobic digestion efficiency. In order to break the sludge structure, pretreatment technologies such as thermal hydrolysis, ultrasonic and ozone oxidation are developed in the industry. The thermal hydrolysis is widely applied because of relatively simple operation, but the short plates of the technology are increasingly developed, namely the problems of energy consumption and secondary pollution are that the typical thermal hydrolysis needs to maintain high temperature above 160 ℃ and pressure above 1.0MPa, and the energy consumption for treating each ton of sludge is as high as 150-250kWh. Meanwhile, maillard reaction can be caused by high temperature, and degradation-resistant substances such as melanoidin and the like (accounting for 5% -15% of the total organic matter) are generated, so that the subsequent digestion process is inhibited. And secondly, under the high-temperature and high-pressure environment, the activity of originally stable heavy metal (such as Cu, zn and Cr) ions in the sludge is obviously enhanced, the leaching rate can be improved by 40-60%, and the activity of methanogens is seriously inhibited. For example, when the Cu 2+ concentration exceeds 50mg/L, the methane yield can be reduced by 30% -50%. Chemical conditioning methods (such as alkali treatment and Fenton oxidation) improve the dissolution rate of organic matters by destroying the EPS structure, but introduce new problems of pH fluctuation and salt accumulation. The adjustment of strong base (NaOH) or strong acid (H2 SO 4) tends to cause pH imbalance in the digestive system, requiring additional buffer. And the Fenton method of adding Fe 2+/H2O2 can generate a large amount of iron mud, thereby increasing the solid waste disposal burden. Secondly, the economy is not enough. Taking municipal sludge as an example, if NaOH is adopted for pretreatment (the dosage is 4% -6% of dry weight), the cost of the medicament accounts for 35% -45% of the total treatment cost, and the large-scale popularization is difficult. In recent years, researchers have tried to enhance effects by physical-chemical combination pretreatment, but have not yet broken through the key technical bottlenecks. First, the synergistic effect is insufficient. Patent CN115611492a proposes a method for treating sludge based on sodium sulfite assisted thermal hydrolysis, which promotes the dissolution of organic matters and reduces the thermal hydrolysis temperature, but sulfite is a recognized carcinogen, and secondary pollution and toxicity to microorganisms may be generated in the treatment process, and additional treatment is required. Secondly, the equipment is complicated. The patent CN108483831A adopts microwave ultrasonic wave to cooperate with a microbial fuel cell technology to treat the residual sludge, the SCOD removal rate is more than 82.3%, the VS degradation rate is increased to 33.1%, but the equipment investment cost is increased by more than 2 times, and the composite operation is excessive. Sodium disilicate (Na 2Si2O5) has been widely used in the detergent and ceramic industries as an environment-friendly silicate, but its value in the sludge treatment field has not been fully exploited. The prior studies focused on the conditioning effect of diatomaceous earth or sodium monosilicate (Na 2SiO3), one being diatomaceous earth conditioning. Patent CN108083614B shows that the dewatering performance of sludge can be improved by a co