Supercritical technology based system and method for recycling nitrogen and phosphor from city sludge

Abstract

The invention discloses a supercritical technology based system and method for recycling nitrogen and phosphor from city sludge. The system comprises a pretreatment system, a supercritical oxidation system, a nitrogen recycling system, a phosphor recycling system, and a biological processing system. A supercritical oxidation technology is used to maximally recycle nitrogen and phosphor from city sludge; nitrogen and phosphor exist in a liquid phase in forms of ammonia nitrogen and phosphate; ammonia nitrogen in the liquid phase is recovered by an ammonia recycling unit; phosphate in wastewateris recovered by a phosphor recovering system, phosphate is precipitated, and phosphor is recycled. The pH of effluent of the supercritical oxidation system is matched with the ammonia recycling unitand the phosphor recovering system; the heat generated by the supercritical oxidation system is matched with the ammonia recycling unit and the biological processing system; the total using amount ofalkalis and required heat are reduced; wastewater can reach the discharge standards, a wastewater harmless treatment is realized, nitrogen and phosphor are maximally recovered, and good environmentaland economic benefits are generated.

Description

technical field [0001] The invention belongs to the technical field of chemical industry and environmental protection, and relates to a system and method for recovering nitrogen and phosphorus from municipal sludge based on supercritical technology. Background technique [0002] Municipal sludge is a by-product of urban sewage treatment process. With the increase of population and the improvement of urbanization level, the sewage treatment plants are continuously expanded, and every 10,000 tons of sewage treated produces an average of 5.6 tons of wet sludge with a moisture content of 80%. By 2016, my country's sludge production has exceeded 40 million tons. With the aggravation of eutrophication and the improvement of urban sewage discharge standards, various enhanced phosphorus recovery processes have been proposed and applied in large quantities, resulting in the phosphorus in wastewater being fixed into sludge, which also leads to phosphorus-rich pollution. The amount o...

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Problems solved by technology

The landfill method has the risk of occupying a large area of ​​land and polluting groundwater

The incineration method has high energy consumption, high treatment cost, and serious secondary flue gas pollution

There are problems with the biological safety of the land use law, and it is easy to cause biochemical safety hazards where toxic and harmful substances in the sludge are transmitted along the biological chain

The anaerobic digestion method and aerobic composting method of sludge both have complex process systems, occupy a large area, and produce a large amount of organic sludge that still needs to be landfilled

Wet oxidation treatment is not thorough (removal rate 70-90%), the reaction time is slow, and catalysts are introduced at the same time, causing secondary pollution of water bodies

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