Sludge resource recovery method based on hydrothermal treatment of digested sludge

Abstract

The invention discloses a sludge resource recovery method based on hydrothermal treatment of digested sludge. The method comprises the following steps: performing dehydration treatment on sludge so as to obtain dehydrated sludge with the solid content of 15-20%; mixing the dehydrated sludge and a press filtrate in which nitrogen and phosphorus are removed in a slurrying and tempering reactor, preheating, slurrying and tempering; pumping the sludge subjected to slurrying and tempering into an anaerobic digestion system so as to produce biogas; introducing the sludge subjected to anaerobic digestion into a pyrohydrolysis reactor for performing hydrothermal treatment, relieving pressure and cooling after pyrohydrolysis so as to obtain a mixed solution, and performing plate-frame pressure filtration dehydration so as to form high-dryness biogas residues; regulating the pH value of the press filtrate to 9-11, adding a magnesium salt to produce struvite so as to realize phosphorus recovery; regulating the pH value to 11-13, and performing ammonia stripping, thereby realizing nitrogen recovery; and refluxing the press filtrate in which nitrogen and phosphorus are removed back to the slurrying and tempering reactor, mixing with the dehydrated sludge, and performing cycle treatment. The method disclosed by the invention has the advantages that the sludge degradation rate and methane yield are effectively improved, and nitrogen and phosphorus resources are recovered.

Description

technical field [0001] The invention relates to the technical field of solid waste recycling, in particular to a sludge resource recovery method based on hydrothermal treatment of digested sludge. Background technique [0002] With the development of urbanization and sewage treatment in our country, a large amount of surplus sludge is produced and needs to be safely treated and disposed of. As of March 2016, my country has built more than 3,910 urban sewage treatment plants, with a sewage treatment capacity of 167 million cubic meters per day, and an annual output of 30 million to 40 million tons of municipal sludge (with a moisture content of 80%). However, due to my country's lagging sludge treatment and disposal technology, imperfect management and laws and regulations, there has always been the status quo of "heavy water and light sludge". 80% of sludge is dumped and disposed of irregularly. Promote sludge treatment and disposal. [0003] According to research, about 60...

AI Technical Summary

Problems solved by technology

However, the existing thermal hydrolysis pretreatment + high-solids sludge anaerobic digestion process also has the following problems: (1) part of the energy and volume of the thermal hydrolysis system is wasted in hydrolyzing easily degradable organic matter, (2) sludge Thermal hydrolysis can be used to dehydrate directly without adding chemicals, but the dehydration performance of biogas residues will be relatively poor after thermal hydrolysis sludge is digested. (3) The stability and quality of anaerobic digested sludge will be improved with the development (4) A large amount of nitrogen and phosphorus resources in sludge have not been effectively recovered

This method mainly adopts the post-thermal hydrolysis process, which greatly improves the energy utilization efficiency, but does not consider the dehydration of biogas residues and the recovery of nitrogen and phosphorus resources, does not make full use of the hydrothermal effect of thermal hydrolysis, and contains high ammonia nitrogen. Backflow of decomposed sludge may be an inhibitory effect on the digestive system

[0006] At present, research on thermal hydrolysis technology at home and abroad mainly focuses on sludge pretreatment. The role of conventional thermal hydrolysis pretreatment is mainly to solve the rate-limiting step of slow hydrolysis of sludge organic matter, improve sludge fluidity and subsequent dehydration performance, However, the current engineering application shows that the dehydration performance of the sludge after hydrothermal pretreatment is greatly improved, but the dehydration performance of the biogas residue after anaerobic digestion decreases again, resulting in unsatisfactory dehydration dosage and moisture content.

Thermal hydrolysis technology was first used to improve sludge dewatering performance, but there are only a few reports on subsequent thermal hydrolysis, and the advantages of thermal hydrolysis to enhance sludge dehydration and release nitrogen and phosphorus have not been fully utilized.

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