阅读说明：本技术 从污泥焚烧灰中回收及纯化磷的方法和装置 (Method and device for recovering and purifying phosphorus from sludge incineration ash ) 是由 张作泰 方乐 颜枫 于 2019-05-06 设计创作，主要内容包括：本发明涉及环保与资源回收技术领域,尤其涉及一种从污泥焚烧灰中回收及纯化磷的方法和装置。该方法包括以下步骤：酸提,酸洗所述污泥焚烧灰,过滤得到酸提液；电化学纯化,以所述酸提液为阳极液,含硝酸根的盐溶液为阴极液,惰性电极为阳极和阴极,在所述阳极液与所述阴极液之间设置阳离子交换膜,进行电化学反应,电化学反应后的所述阳极液为已纯化磷酸根的溶液。该方法可实现污泥焚烧灰中磷元素的高效回收及高度纯化,可操作性强,具有良好的工业化应用前景。(The invention relates to the technical field of environmental protection and resource recovery, in particular to a method and a device for recovering and purifying phosphorus from sludge incineration ash. The method comprises the following steps: acid extraction, namely pickling the sludge incineration ash, and filtering to obtain acid extract; and (2) performing electrochemical purification, namely taking the acid extract as anolyte, a nitrate-containing salt solution as catholyte, taking inert electrodes as an anode and a cathode, arranging a cation exchange membrane between the anolyte and the catholyte, and performing electrochemical reaction, wherein the anolyte after the electrochemical reaction is a solution of purified phosphate radical. The method can realize the high-efficiency recovery and high purification of the phosphorus element in the sludge incineration ash, has strong operability and has good industrial application prospect.)

1. A method for recovering and purifying phosphorus from sludge incineration ash, characterized in that the method comprises the following steps:

acid extraction: pickling the sludge incineration ash, and filtering to obtain an acid extract;

electrochemical purification: and (2) taking the acid extract as anolyte, taking a nitrate-containing salt solution as catholyte, using inert electrodes as an anode and a cathode, arranging a cation exchange membrane between the anolyte and the catholyte, and carrying out electrochemical reaction, wherein the anolyte after the electrochemical reaction is a solution of purified phosphate radical.

2. The method according to claim 1, wherein in the acid extraction step, the acid agent used in acid washing is a sulfuric acid solution, a nitric acid solution, a phosphoric acid solution or a hydrochloric acid solution with a concentration of 0.2-1moL/L, the solid-to-liquid ratio of the sludge incineration ash to the acid agent is 1:5-1:20g/mL, the acid washing time is 4-24 hours, and insoluble solids are filtered out after acid washing to obtain the acid extract, wherein the acid extract contains phosphate ions and metal ions.

3. The method according to claim 2, wherein the metal ions in the acid extract comprise one or more of calcium ions, magnesium ions, aluminum ions, iron ions, copper ions, zinc ions, manganese ions, lead ions, nickel ions and cadmium ions.

4. The method according to any one of claims 1 to 3, wherein in the step of electrochemical purification, the electrochemical reaction is carried out with a constant current of 15 to 300mA for an electrochemical reaction time of 72 to 168 hours, the inert electrode is a platinum sheet electrode, a gold electrode or a graphite electrode, and the electrode area is 1 to 100cm²。

5. The method of claim 4, wherein the inert electrode is a platinum sheet electrode and the nitrate-containing salt solution is 0.01moL/L sodium nitrate solution.

6. The method according to any one of claims 2 to 3, characterized in that it further comprises, after said step of electrochemical purification, a step of cyclic enrichment: and using the purified phosphate solution as the acid agent in the acid extraction step, and recycling the acid agent for acid-washing the sludge incineration ash until the concentration of phosphoric acid in the purified phosphate solution is greater than or equal to 450 g/L.

7. A method according to any one of claims 1 to 3, wherein in the step of electrochemical purification, the catholyte produces a hydroxide precipitate of one or more of calcium, magnesium or aluminium ions.

8. An apparatus for recovering and purifying phosphorus from sludge incineration ash, the apparatus comprising:

the anode reaction tank is filled with anolyte, and an anode is inserted into the anode reaction tank;

the cathode reaction tank is filled with cathode liquid, and a cathode is inserted into the cathode reaction tank;

cation exchange membrane: the cation exchange membrane is arranged between the anode reaction tank and the cathode reaction tank to separate the anode reaction tank from the cathode reaction tank;

a clapboard: the separator is respectively transversely arranged in the anode reaction tank and the cathode reaction tank, and the anode and the cathode are fixed on the separator;

the apparatus is used in the method for recovering and purifying phosphorus from sludge incineration ash according to any one of claims 1 to 7.

9. The device according to claim 8, wherein the partition is a plastic partition or a ceramic partition, the partition comprises a plurality of transverse strips and a plurality of longitudinal strips, and the transverse strips and the longitudinal strips are intersected to form a plurality of squares; the device also comprises a potentiostat.

10. The apparatus of claim 8 or 9, wherein the anode reaction cell and the cathode reaction cell are detachable reaction cells, and the cation exchange membrane is detachably arranged between the anode reaction cell and the cathode reaction cell.

Technical Field

The invention relates to the technical field of environmental protection and resource recovery, in particular to a method and a device for recovering and purifying phosphorus from sludge incineration ash.

Background

With the acceleration of modern construction and urbanization process, China needs to treat a large amount of wastewater every year with the generation of large amount of wastewaterAnd (4) measuring the municipal sludge. The main treatment means of the municipal sludge is incineration, the sludge incineration technology can effectively meet the requirement of sludge reduction, the pressure on a landfill area is greatly reduced, and the sludge volume is reduced by about 80%. Sludge incineration ash formed after sludge incineration is a main phosphorus-containing waste, but the sludge incineration ash contains about 10% of P₂O₅In addition, it contains a large amount of metal compounds, and these metal compounds present in a large amount make the sludge incineration ash not directly usable as a raw material for a phosphorus-forming resource.

In order to recover phosphorus from sludge incineration ash, the prior art is mainly carried out by using a pyrogenic process and a wet process. Among them, the reaction conditions of the pyrogenic process are harsh, the energy consumption is large, and only the removal of volatile metals can be realized, but the non-volatile harmful metals (such As, Ni, etc.) cannot be removed. The wet method is more widely used, and mainly extracts phosphorus in the sludge incineration ash through an acid agent. However, the disadvantage is that the pickling solution still contains a large amount of metal ions, and the purity of phosphorus is low, which may prevent the recovery and further use of phosphorus. Nowadays, a large number of methods for recovering phosphorus from sludge incineration ash are limited to laboratory use due to complex equipment, high raw material cost and low usability, so that the industrial popularization and application of the methods are limited, and improvement is needed.

Disclosure of Invention

The invention aims to provide a method and a device for recovering and purifying phosphorus from sludge incineration ash, which aim to solve the problems that the existing method for recovering phosphorus from sludge incineration ash has harsh reaction conditions, low phosphorus purity, complicated equipment for recovering phosphorus and the like and hinders industrial application of the process.

In a first aspect, the present invention provides a method for recovering purified phosphorus from sludge incineration ash, comprising the steps of:

acid extraction: pickling the sludge incineration ash, and filtering to obtain an acid extract;

electrochemical purification: and (2) taking the acid extract as anolyte, taking a nitrate-containing salt solution as catholyte, using inert electrodes as an anode and a cathode, arranging a cation exchange membrane between the anolyte and the catholyte, and carrying out electrochemical reaction, wherein the anolyte after the electrochemical reaction is a solution of purified phosphate radical.

Further, in the acid extraction step, the acid agent used in acid washing is a sulfuric acid solution, a nitric acid solution, a phosphoric acid solution or a hydrochloric acid solution with the concentration of 0.2-1moL/L, the solid-to-liquid ratio of the sludge incineration ash to the acid agent is 1:5-1:20g/mL, the acid washing time is 4-24 hours, insoluble solids are filtered out after acid washing to obtain the acid extraction liquid, and the acid extraction liquid contains phosphate ions and metal ions.

Further, the metal ions in the acid extraction solution include one or more of calcium ions, magnesium ions, aluminum ions, iron ions, copper ions, zinc ions, manganese ions, lead ions, nickel ions and cadmium ions.

Further, in the step of electrochemical purification, the electrochemical reaction is carried out by applying a constant current of 15-300mA for 72-168h, the inert electrode is a platinum sheet electrode, a gold electrode or a graphite electrode, and the area of the electrode is 1-100cm²。

It is understood that the constant current of 15-300mA in the step of electrochemical purification includes any point value within the numerical range of the current, for example, the constant current applied by the electrochemical reaction is 15mA, 20mA, 25mA, 30mA, 50mA, 75mA, 80mA, 100mA, 150mA, 200mA, 250mA, or 300 mA. The electrochemical reaction time of 72-168h includes any point in the time range, for example, the electrochemical reaction time is 72h, 76h, 80h, 96h, 100h, 120h, 144h, 150h or 168 h.

Preferably, the inert electrode is a platinum sheet electrode and the nitrate-containing salt solution is 0.01moL/L of sodium nitrate solution.

Further, in the step of electrochemical purification, the catholyte generates hydroxide precipitates with one or more ions of calcium ions, magnesium ions or aluminum ions.

Further, the method further comprises, after the step of electrochemical purification, a step of cyclic enrichment: and taking the purified phosphate solution as the acid agent in the acid extraction step, and recycling the acid agent for pickling the sludge incineration ash until the concentration of phosphorus in the purified phosphate solution is more than or equal to 450 g/L.

In a second aspect, the present invention provides an apparatus for recovering and purifying phosphorus from sludge incineration ash, the apparatus comprising:

the anode reaction tank is filled with anolyte, and an anode is inserted into the anode reaction tank;

the cathode reaction tank is filled with cathode liquid, and a cathode is inserted into the cathode reaction tank;

cation exchange membrane: the cation exchange membrane is arranged between the anode reaction tank and the cathode reaction tank to separate the anode reaction tank from the cathode reaction tank;

a clapboard: the separator is respectively transversely arranged in the anode reaction tank and the cathode reaction tank, and the anode and the cathode are fixed on the separator;

the device is used for the method for recovering and purifying the phosphorus from the sludge incineration ash.

Furthermore, the partition board is a plastic partition board or a ceramic partition board, the partition board comprises a plurality of transverse strip-shaped boards and a plurality of longitudinal strip-shaped boards, and the transverse strip-shaped boards and the longitudinal strip-shaped boards are intersected to form a plurality of grids; the device also comprises a potentiostat.

Further, the anode reaction tank and the cathode reaction tank are detachable reaction tanks, and the cation exchange membrane is detachably arranged between the anode reaction tank and the cathode reaction tank.

Further, in the acid extraction step, the acid agent used in acid washing is a sulfuric acid solution, a nitric acid solution, a phosphoric acid solution or a hydrochloric acid solution with the concentration of 0.2-1moL/L, the solid-to-liquid ratio of the sludge incineration ash to the acid agent is 1:5-1:20g/mL, the acid washing time is 4-24 hours, insoluble solids are filtered out after acid washing to obtain the acid extraction liquid, and the acid extraction liquid contains phosphate ions and metal ions.

Further, the metal ions in the acid extraction solution include one or more of calcium ions, magnesium ions, aluminum ions, iron ions, copper ions, zinc ions, manganese ions, lead ions, nickel ions and cadmium ions.

Further, in the step of electrochemical purification, the electrochemical reaction is carried out by applying a constant current of 15-300mA for 72-168 h.

It is understood that the constant current of 15-300mA in the step of electrochemical purification includes any point value within the numerical range of the current, for example, the constant current applied by the electrochemical reaction is 15mA, 20mA, 25mA, 30mA, 50mA, 75mA, 80mA, 100mA, 150mA, 200mA, 250mA, or 300 mA. The electrochemical reaction time of 72-168h includes any point in the time range, for example, the electrochemical reaction time is 72h, 76h, 80h, 96h, 100h, 120h, 144h, 150h or 168 h.

Further, in the electrochemical purification step, the inert electrode is a platinum sheet electrode, a gold electrode or a graphite electrode, and the area of the electrode is 1-100cm²。

Preferably, the inert electrode is a platinum sheet electrode and the nitrate-containing salt solution is 0.01moL/L of sodium nitrate solution.

Further, in the step of electrochemical purification, the catholyte generates hydroxide precipitates containing one or more of metal ions such as calcium ions, magnesium ions and aluminum ions.

Further, the method further comprises, after the step of electrochemical purification, a step of cyclic enrichment: and using the purified phosphate solution as the acid agent in the acid extraction step, and recycling the acid agent for acid-washing the sludge incineration ash until the concentration of phosphoric acid in the purified phosphate solution is greater than or equal to 450 g/L.

Firstly, the high purification of phosphorus element in sludge incineration ash is realized. According to the method, firstly, phosphate ions in the sludge incineration ash are extracted along with metal ions through acid extraction, then the metal ions are electrophoresed from an anode to a cathode under the driving force of current through electrolysis, and the phosphate ions are still remained in anolyte due to the obstruction of a cation exchange membrane, so that the separation between the phosphate ions and the metal ions is realized, the purification of the phosphate in the acid extraction solution is further realized, and the separation and purification purposes are achieved.

Secondly, the method has strong operability and good industrial application prospect. Firstly, the method has few steps and simple and convenient operation, can realize the high-efficiency recovery of the phosphorus element through two steps of acid extraction and electrolysis, and has stronger feasibility. Secondly, the method has short period for purifying the phosphorus element, and the solution of the purified phosphate radical can be obtained within 3 to 7 days. Compared with the processes which have longer period and need 14 days to obtain the purified solution, the period is obviously shortened.

And thirdly, the high-concentration enrichment of phosphorus element can be conveniently realized, so that the obtained solution of purified phosphate radical can be more easily applied to practical production. After the electrochemical reaction is carried out, because a large amount of hydrogen ions are generated on one side of the anode, the anode liquor has higher acidity, can be used for pickling new sludge incineration ash again, further carries out electrochemical reaction again to purify phosphate radical, and ensures that the solution of the finally purified phosphate radical contains phosphorus with higher concentration and has less residual metal and other impurities through cyclic reciprocation, thus being applicable to the industries of phosphoric acid and phosphate fertilizer.

The device provided by the invention is not complex, is not easy to cause cation membrane blockage, and further improves the feasibility of industrial application.

Drawings

FIG. 1 is a schematic view showing the structure of an apparatus for recovering purified phosphorus from sludge incineration ash according to an embodiment.

Fig. 2 is a schematic structural diagram of a plastic partition plate in the device of the first embodiment.

FIG. 3 is a graph showing the tendency of the metal ions to decrease during 4 hours of the electrochemical reaction in the second example.

FIG. 4 is an analysis of metal ion remaining during an electrochemical reaction according to the hexagonal method of the embodiment.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "comprises" and "comprising," and any variations thereof, of embodiments of the present invention are intended to cover non-exclusive inclusions, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.