A method for preparing multifunctional water-soluble fertilizer from sludge incineration fly ash phosphorus resources and multifunctional water-soluble fertilizer

Abstract

The present application relates to a kind of sludge incineration fly ash phosphorus resource preparation multifunctional water-soluble fertilizer method, multifunctional water-soluble fertilizer;With biological sludge incineration fly ash as core raw material, by weak acid directional solvus-potassium sulfate synergistic cooperation-alkaline complex liquid selective chelation heavy three-stage type core process, realize the efficient solvus of phosphorus, heavy metal and arsenic are removed in depth and multifunctional nutrient in situ coupling.The process of the present application is normal temperature and pressure, mild and efficient, fly ash and alkaline complex liquid are zero-cost raw materials, only a small amount of sulfuric acid, potassium sulfate adjuvant, with high phosphorus solvus rate (≥80%), heavy metal and arsenic removal rate (≥99%) and low production cost, solve the biological sludge incineration fly ash phosphorus-heavy metal-arsenic associated separation difficult, agricultural and building material path double limited industry pain points, realize solid waste resource, phosphorus resource high value and the coordinated development of green agriculture, overall technology reaches international leading level, some core innovation is unique in the world.

Description

Technical Field

[0001] This invention relates to sludge treatment, specifically to a method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration, and the multifunctional water-soluble fertilizer. Background Technology

[0002] Phosphorus is an indispensable core nutrient element for agricultural production and a key basic raw material in the chemical and materials industries, possessing strategic attributes that are non-renewable and irreplaceable. Currently, global reserves of high-quality phosphate rock resources are declining at an accelerated pace, and the difficulty and cost of mining are continuously rising, exacerbating the contradiction between phosphorus resource supply and demand. Developing unconventional phosphorus sources has become a core path to ensure food security and promote sustainable industrial development.

[0003] Biological sludge incineration fly ash, a general solid waste generated after the reduction and incineration of sludge from urban wastewater treatment plants, contains approximately 15% phosphorus pentoxide (P2O5) on a dry basis, making it a secondary phosphorus resource with significant development potential. Its resource utilization can not only alleviate the shortage of phosphorus resources but also achieve the reduction and harmless treatment of solid waste, aligning with the national development strategy of circular economy and green low-carbon development, and possessing significant dual value in terms of resources and the environment. Summary of the Invention

[0004] This invention proposes a method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration, and the multifunctional water-soluble fertilizer.

[0005] The technical solution of the present invention: A method for preparing multifunctional water-soluble fertilizer from phosphorus resources in sludge incineration fly ash, the method comprising: using dry-based biological sludge incineration fly ash as raw material; 1) mixing dry-based biological sludge incineration fly ash with process water to prepare fly ash slurry; 2) slowly adding concentrated sulfuric acid to the fly ash slurry to adjust the pH to 3.0-4.0, causing reaction I (efficiently dissolving phosphorus in fly ash, while releasing heavy metals, arsenic, and other impurities); after reaction I is completed, adding potassium sulfate to cause reaction II (using sulfate competitive coordination to inhibit secondary phosphorus precipitation and replenish phosphorus). Potassium nutrient); After reaction II is completed, add an alkaline composite solution containing protein and amino acids to produce reaction III (utilizing the alkaline environment to achieve alkaline precipitation of heavy metals and arsenic, while through the selective chelation of protein and amino acids in the composite solution, heavy metals and arsenic are converted into inert slag state and efficiently separated from phosphorus); After reaction III is completed, a solid-liquid mixture is obtained; 3) Separate the solid-liquid mixture to obtain a solid phase and a liquid phase, the liquid phase being the mother liquor of the multifunctional water-soluble fertilizer; 4) Blend the mother liquor of the multifunctional water-soluble fertilizer to obtain a multifunctional water-soluble fertilizer.

[0006] By slowly adding concentrated sulfuric acid to fly ash slurry and adjusting the pH to 3.0-4.0, a mild, weakly acidic environment is created. This environment can precisely disrupt the bonding bonds and lattice structure of stable phosphorus in fly ash, achieving efficient phosphorus dissolution. At the same time, it promotes the simultaneous release of impurities such as heavy metals and arsenic. Unlike traditional strong acid / strong alkali leaching processes, this method significantly reduces reagent consumption and equipment corrosion risks, and improves phosphorus dissolution efficiency and selectivity.

[0007] The selection of sulfuric acid and potassium sulfate: Utilizing the ionic strength effect of potassium sulfate to compete with sulfate for coordination, it blocks the secondary precipitation of dissolved phosphorus with calcium, iron, and aluminum ions, ensuring efficient retention of phosphorus in the liquid phase and improving phosphorus dissolution rate; it also supplements the essential potassium nutrient for agriculture, making the final product contain both phosphorus and potassium as core nutrients, broadening the application scenarios of fertilizer and achieving the integration of "phosphorus enhancement + potassium supplementation"; the sulfur components introduced by sulfuric acid and potassium sulfate form a stable sulfate ion form in the system, which is non-toxic, does not interfere with the chelation reaction, and its content meets the national fertilizer standards, requiring no additional treatment.

[0008] Further refining the above technical solution, the core indicators of the multifunctional water-soluble fertilizer mother liquor are as follows: phosphorus pentoxide content is 23.0-25.0 g / L, potassium oxide content is 14.1-16.1 g / L, total nitrogen is 2300-2500 mg / L, chelated calcium is 2300-2500 mg / L, pH is H9.0-9.5, sulfate is 28.1-30.1 g / L, and heavy metals and arsenic were not detected; the proportion of organic nitrogen in the total nitrogen is ≥90%.

[0009] Further refining the above technical solution, the alkaline composite liquid containing protein and amino acids is a biological solid resource raw material. The biological solid resource raw material is an extract obtained through the thermal alkaline reaction of activated sludge; see: An extract for controlling plant diseases and pests (202010865786.9). Its applications are further broadened here.

[0010] Further refining the above technical solution, the key indicators of the biological solid resource raw materials are: pH 11.5-12.0, total nitrogen 4000 mg / L, chemical oxygen demand 40000 mg / L, chelated calcium 4000 mg / L and rich in biostimulants; the proportion of organic nitrogen in the total nitrogen is ≥90%.

[0011] Further refining the above technical solution, the mass-to-volume ratio of the dry-based biological sludge incineration fly ash to the process water is 1 kg: 2.0 L; the amount of concentrated sulfuric acid used is 60-80 g / kg fly ash; the amount of potassium sulfate used is 140 g / kg fly ash; and the amount of alkaline composite solution used is 3.0 L / kg fly ash.

[0012] The multifunctional water-soluble fertilizer was prepared using the above-mentioned method for the resource utilization of phosphorus from sludge incineration fly ash.

[0013] The advantages of this invention are its reasonable design and ingenious concept, and it has the following beneficial effects: 1. Breaking through the traditional approach of "single impurity removal," this method achieves the synergistic separation of phosphorus, heavy metals, and arsenic: It utilizes a weakly acidic environment to achieve efficient dissolution of phosphorus, simultaneously releasing heavy metals and arsenic; through the alkaline precipitation and selective chelation of the alkaline composite solution, heavy metals and arsenic are converted into inert slag, while retaining phosphorus and potassium nutrients, thus solving the industry's core pain point of "difficult separation of phosphorus from associated heavy metals / arsenic"; the sulfur component is introduced by sulfuric acid and potassium sulfate, with compliant content and non-toxicity, without affecting the separation process and product safety.

[0014] 2. By coupling fly ash phosphorus leaching with potassium sulfate supplementation and compound liquid organic nutrients (nitrogen, calcium, and biostimulants), multifunctional water-soluble fertilizers can be prepared in situ without the need for subsequent complex nutrient blending. This achieves the integration of "phosphorus recovery + nutrient value-added + fertilizer preparation", which greatly improves resource utilization efficiency and product added value.

[0015] 3. The entire process requires no high temperature or high pressure, and no consumption of strong corrosive reagents. The alkaline composite liquid is a resource-based product of organic waste as raw material (cost ≈ 0), and fly ash is solid waste (cost ≈ 0). Only a small amount of sulfuric acid and potassium sulfate additives are needed. The process is simple, green and environmentally friendly, and suitable for large-scale industrial promotion. Detailed Implementation

[0016] Using dry-based biological sludge incineration fly ash as raw material; Fly ash slurry dispersion (10 min): Add 2.0 L of process water to the reactor, add 1.0 kg of dry-based biological sludge incineration fly ash, turn on the stirring device, and continue stirring until the dry-based biological sludge incineration fly ash is completely dispersed and free of lumps, forming a uniformly flowing fly ash slurry.

[0017] Weak acid-directed phosphorus dissolution (15-20 min): Slowly add 60-80g of concentrated sulfuric acid to the fly ash slurry, stirring continuously throughout the process, monitoring the pH value of the system in real time, and precisely adjusting the pH to 3.0-4.0 to achieve efficient phosphorus dissolution and simultaneous release of heavy metals and arsenic.

[0018] Potassium sulfate enhances phosphorus stabilization (10 min): Add 140 g of potassium sulfate to the dissolution system and stir. Stir until completely dissolved. Utilize the ionic strength effect and coordination with sulfate ions to inhibit secondary precipitation of phosphorus and ensure the stability of phosphorus in the liquid phase.

[0019] Synergistic reaction of alkaline composite solution (20-30 min): Add 3.0 L of alkaline composite solution containing protein and amino acids at one time, stir and react. Use the alkalinity of the alkaline composite solution containing protein and amino acids to adjust the pH of the system to 9.0~9.5, and simultaneously complete the alkaline precipitation and chelation solidification of heavy metals and arsenic, so as to achieve precise separation from phosphorus.

[0020] Solid-liquid separation and product collection: A special plate and frame filter press was used for solid-liquid separation, yielding two types of products: Liquid phase: Multifunctional water-soluble fertilizer mother liquor ≈ 5.0L, rich in P2O5, K2O, and organic nitrogen. Equal nutrients; Solid phase: Heavy metal stabilized sludge cake ≈ 1.21 kg, which poses no environmental risk after harmless treatment.

[0021] Phosphorus dissolution rate ≥80% (≈120g P2O5 retained in mother liquor), heavy metal removal rate ≥95%, arsenic removal rate ≥95%, and all exogenous nutrients are retained in the product.

[0022] The multifunctional water-soluble fertilizer mother liquor is prepared to obtain the multifunctional water-soluble fertilizer.

[0023] The above embodiments are only for illustrating the technical concept and features of the invention, and are intended to enable those skilled in the art to understand the content of the invention and implement it accordingly. They should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be covered within the scope of protection of the invention.

Claims

1. A method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration, the method comprising: It uses dry-based biological sludge incineration fly ash as raw material; its characteristic is that... 1) Mix dry-based biological sludge incineration fly ash with process water to prepare fly ash slurry; 2) Slowly add concentrated sulfuric acid to the fly ash slurry to adjust the pH to 3.0-4.0, and reaction I occurs; after reaction I is completed, add potassium sulfate, and reaction II occurs; after reaction II is completed, add an alkaline composite solution containing protein and amino acids, and reaction III occurs; after reaction III is completed, a solid-liquid mixture is obtained. 3) Separate the solid-liquid mixture to obtain a solid phase and a liquid phase, wherein the liquid phase is the mother liquor of the multifunctional water-soluble fertilizer; 4) The multifunctional water-soluble fertilizer mother liquor is prepared by blending to produce multifunctional water-soluble fertilizer.

2. The method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration according to claim 1, characterized in that, The core indicators of the multifunctional water-soluble fertilizer mother liquor are as follows: phosphorus pentoxide content is 23.0-25.0 g / L, potassium oxide content is 14.1-16.1 g / L, total nitrogen is 2300-2500 mg / L, chelated calcium is 2300-2500 mg / L, pH is H9.0-9.5, sulfate is 28.1-30.1 g / L, and heavy metals and arsenic were not detected; the proportion of organic nitrogen in the total nitrogen is ≥90%.

3. The method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration according to claim 2, characterized in that, The alkaline composite liquid containing proteins and amino acids is a biological solid resource raw material.

4. The method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration according to claim 3, characterized in that, Key indicators of the bio-solid resource raw materials are: pH 11.5-12.0, total nitrogen 4000 mg / L, chemical oxygen demand 40000 mg / L, chelated calcium 4000 mg / L and rich in biostimulants; organic nitrogen accounts for ≥90% of the total nitrogen.

5. The method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration according to claim 4, characterized in that, The mass-to-volume ratio of dry-based biological sludge incineration fly ash to process water is 1 kg: 2.0 L; the amount of concentrated sulfuric acid used is 60-80 g / kg fly ash; the amount of potassium sulfate used is 140 g / kg fly ash; and the amount of alkaline compound solution used is 3.0 L / kg fly ash.

6. A multifunctional water-soluble fertilizer is prepared by means of any one of claims 1-5, which describes a method for preparing multifunctional water-soluble fertilizer from fly ash phosphorus resources of sludge incineration.