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CN-121990533-A - Method for rapidly recovering phosphorus from municipal sludge

CN121990533ACN 121990533 ACN121990533 ACN 121990533ACN-121990533-A

Abstract

The invention discloses a method for rapidly recovering phosphorus from municipal sludge, which comprises the following steps of adding sludge to be treated and an iron salt catalyst into a hydrothermal reaction vessel for iron catalytic hydrothermal oxidation to obtain a hydrothermal oxidation liquid-phase product of the sludge, adding a sodium hydroxide solution into the obtained hydrothermal oxidation liquid-phase product of the sludge to rapidly adjust the pH value, removing phosphorus from the liquid-phase product and entering into precipitation to obtain a phosphorus-rich precipitate, and drying the obtained phosphorus-rich precipitate to obtain a final phosphorus-containing product. The invention can realize iron catalytic hydrothermal oxidation of sludge in a lower temperature range, promote phosphorus in the sludge to migrate and convert to liquid phase, greatly reduce organic impurities in the product by quickly regulating pH and precipitating process, and has short time required by the whole process flow.

Inventors

  • WANG RUOCHEN
  • YANG YANG
  • DAI HONGLIANG
  • WANG XINGANG

Assignees

  • 江苏科技大学

Dates

Publication Date
20260508
Application Date
20260127

Claims (10)

  1. 1. A method for rapidly recovering phosphorus from municipal sludge, comprising the steps of: Step 1, adding sludge to be treated and an iron salt catalyst into a hydrothermal reaction vessel together for iron-catalyzed hydrothermal oxidation to obtain a hydrothermal oxidation liquid-phase product of the sludge; step 2, adding sodium hydroxide solution into the obtained sludge hydro-thermal oxidation liquid-phase product to quickly adjust the pH value, so that phosphorus is removed from the liquid-phase product and enters into precipitation to obtain phosphorus-rich precipitate; And 3, drying the obtained phosphorus-rich precipitate to obtain a final phosphorus-containing product.
  2. 2. The method for rapidly recovering phosphorus from municipal sludge according to claim 1, wherein in the step 1, the ferric salt catalyst is ferric chloride or ferric sulfate, and the adding proportion is 2.0% -3.0%.
  3. 3. The method for rapidly recovering phosphorus from municipal sludge according to claim 1, wherein the oxidant added in the process of performing iron-catalyzed hydrothermal oxidation in the step 1 is sodium persulfate solution with a concentration ranging from 0.10 to 0.20 mol/L.
  4. 4. A method for rapid recovery of phosphorus from municipal sludge according to any of claims 1-3, wherein in step 1, the liquid-to-solid ratio of the sludge in terms of dry basis, hydrothermal oxidation is in the range of 15:1 to 20:1.
  5. 5. The method for rapidly recovering phosphorus from municipal sludge according to claim 1, wherein in the step 1, the initial pH of the hydrothermal oxidation is 1-3, the reaction temperature is 60-90 ℃ and the reaction time is 60-120 min.
  6. 6. The method for rapidly recovering phosphorus from municipal sludge according to claim 1, wherein in the step 1, the content of phosphorus in the hydrothermal oxidation liquid phase product of the sludge ranges from 500 to 850mg/L, the content of nitrogen ranges from 45 to 100 mg/L, the content of COD ranges from 650 to 1300 mg/L, and the pH ranges from 1.0 to 2.0.
  7. 7. The method for rapidly recovering phosphorus from municipal sludge according to claim 1, wherein in the step 2, the rapid adjustment of the pH value is specifically performed within a pH value adjustment time range of 5-10 min.
  8. 8. The method for rapidly recovering phosphorus from municipal sludge according to claim 1 or 7, wherein the result of rapid pH adjustment in the step 2 is 9 to 10.
  9. 9. The method for rapidly recovering phosphorus from municipal sludge according to claim 1 or 7, wherein in the step 2, the time period from the rapid adjustment of the pH value to the end of the phosphorus-rich precipitate is 15-20 min.
  10. 10. The method for rapidly recovering phosphorus from municipal sludge according to claim 1, wherein in the step 3, the drying temperature is 60 ℃ and the drying time is 30-60 min.

Description

Method for rapidly recovering phosphorus from municipal sludge Technical Field The invention relates to the technical field of sludge treatment, in particular to a method for rapidly recovering phosphorus from municipal sludge. Background Phosphate ores, a non-renewable and highly concentrated resource, circulate on earth mainly in the form of sediment circulation. The human development and use of phosphorus resources in a large scale can quickly exhaust phosphorus resources existing in the form of phosphorite in the nature, and the search for alternative renewable sources is urgent, which is related to the safety and stability of industrial and agricultural supply chains. At present, the eutrophication phenomenon of natural water body occurs and the municipal sewage treatment requirement is greatly increased. As a core of water treatment, municipal sludge is the most important phosphorus sink and is a very potential source of phosphorus. It is worth noting that although the phosphorus content of municipal sludge is very high compared with water, compared with phosphorus products or phosphorus raw materials which are required to be used in industry and agriculture, the phosphorus content of municipal sludge is low, the volume is huge, and the sludge phosphorus needs to be further enriched and converted into a regenerated phosphorus product with smaller volume so as to be convenient for further use. If sludge phosphorus is extracted by acid leaching or traditional heat treatment, the problems of insufficient phosphorus release and high energy consumption often exist, and if phosphorus is obtained from supernatant liquid of anaerobic fermentation, the fermentation time is long, so that the inventory turnover period of sludge is long. Hydrothermal oxidation has the advantage of promoting decomposition of organic matter and rapid dissolution of phosphate in aqueous systems, but conventional hydrothermal oxidation generally requires higher temperatures and pressures, and therefore requires high temperature and pressure equipment to be fitted, increasing engineering complexity and cost. Therefore, the development of the product which can realize high-efficiency phosphorus release at lower temperature and normal pressure and can rapidly recover high-phosphorus content is of great significance. Disclosure of Invention Aiming at the defects in the prior art, the invention provides a method for rapidly recovering phosphorus from municipal sludge, which aims to solve the technical problems of low phosphorus content and large volume in municipal sludge, low economic benefit in direct recovery, high phosphorus recovery cost and long service time in the prior art. The invention provides a method for rapidly recovering phosphorus from municipal sludge, which comprises the following steps: Step 1, adding sludge to be treated and an iron salt catalyst into a hydrothermal reaction vessel together for iron-catalyzed hydrothermal oxidation to obtain a hydrothermal oxidation liquid-phase product of the sludge; step 2, adding sodium hydroxide solution into the obtained sludge hydro-thermal oxidation liquid-phase product to quickly adjust the pH value, so that phosphorus is removed from the liquid-phase product and enters into precipitation to obtain phosphorus-rich precipitate; And 3, drying the obtained phosphorus-rich precipitate to obtain a final phosphorus-containing product. Further, in the step 1, the ferric salt catalyst is ferric chloride or ferric sulfate, and the adding proportion range is 2.0% -3.0%. Further, in the step 1, the oxidant added in the iron catalytic hydrothermal oxidation process is sodium persulfate solution, and the concentration range is 0.10-0.20 mol/L. In step 1, the liquid-solid ratio of the sludge in terms of dry basis and hydrothermal oxidation is 15:1-20:1. In step 1, the initial pH range of the hydrothermal oxidation is 1-3, the reaction temperature range is 60-90 ℃, and the reaction time range is 60-120 min. Further, in the step 1, the content of phosphorus in the hydrothermal oxidation liquid phase product of the sludge ranges from 500 to 850mg/L, the content of nitrogen ranges from 45 to 100 mg/L, the content of COD ranges from 650 to 1300 mg/L, and the pH ranges from 1.0 to 2.0. Further, in the step 2, the fast adjustment of the pH value is specifically that the adjustment time range of the pH value is 5-10 min. Further, in the step 2, the result range of the rapid adjustment of the pH value is 9-10. Further, in the step 2, starting from the rapid adjustment of the pH value until the phosphorus-rich precipitate is finished, the time range of the process is 15-20 min. Further, in the step3, the drying temperature is 60 ℃ and the drying time range is 30-60 min. The invention has the beneficial effects that: The invention can realize iron-catalyzed hydrothermal oxidation of sludge at a lower temperature of 60-90 ℃ and promote the migration and conversion of phosphorus in the sludge to liquid p