CN108218682B - Method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue - Google Patents
Method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue Download PDFInfo
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- CN108218682B CN108218682B CN201711330258.8A CN201711330258A CN108218682B CN 108218682 B CN108218682 B CN 108218682B CN 201711330258 A CN201711330258 A CN 201711330258A CN 108218682 B CN108218682 B CN 108218682B
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Abstract
The invention discloses a method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue, which comprises the following steps: mixing the mixed waste residue with concentrated sulfuric acid, and carrying out a curing reaction after uniformly stirring; after the two phases are solidified, the two phases enter a reactor for solid-solid roasting conversion to obtain a calcium sulfate and oxalic acid mixed crystal; and then water and the mixed crystal product are mixed for size mixing, mixed for leaching, and filtered to obtain an oxalic acid solution. The invention has high oxalic acid conversion efficiency and low sulfuric acid consumption, and overcomes the defects of large residual acid, long process flow, high recovery cost and the like in the traditional process.
Description
Technical Field
The invention relates to a hydrometallurgy technology, in particular to a method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residues.
Background
In the metallurgical industry, oxalic acid or soluble oxalate precipitates are often used for removing impurity ions such as calcium, magnesium, barium and the like, so that insoluble oxalate precipitate waste residues are formed. For example, in the high-temperature roasting process of the mixed rare earth concentrate concentrated sulfuric acid, the roasted rare earth ore is subjected to water leaching, magnesium oxide neutralization and ammonium bicarbonate precipitation to obtain ammonium sulfate wastewater containing magnesium, calcium and rare earth and a mixed rare earth carbonate product. In order to prevent crystallization of calcium sulfate during concentration of magnesium ammonium sulfate, calcium impurities in the solution need to be removed by precipitation with soluble oxalate in advance. But the cost of the oxalic acid is high, and the obtained calcium oxalate, magnesium oxalate and trace rare earth oxalate mixed waste residue has extremely low utilization value, so that a large burden is brought to enterprises.
In order to solve the problems, a sulfuric acid solution with the initial concentration of 35% is mixed with calcium oxalate waste residue and heated, the products are oxalic acid and calcium sulfate dihydrate, and an oxalic acid solution can be obtained by filtration. The method utilizes the reaction mechanism of strong acid in the preparation of the strong acid, but has the problems that the conversion rate of calcium oxalate is low when the dosage of sulfuric acid is low; when the amount of the sulfuric acid is high, although the conversion rate of the calcium oxalate is high, the residual concentration of the sulfuric acid is up to 20 percent; if the acidity of the initial sulfuric acid solution is continuously increased, the generated calcium sulfate cannot be dispersed around the calcium oxalate solid in time, and the viscous substance not only causes the reduction of the conversion rate, but also is difficult to realize industrialization. Therefore, the adoption of the solid-liquid conversion method cannot simultaneously give consideration to high calcium oxalate conversion rate and low sulfuric acid consumption.
And (3) converting relatively less calcium oxalate waste residues by using absolutely excessive sulfuric acid, filtering after the reaction is finished, and supplementing sulfuric acid to continuously react with the calcium oxalate waste residues after the filtrate is cooled and crystallized to obtain oxalic acid. The method adopts a circulating mode, can fully utilize the residual sulfuric acid, and can improve the conversion rate of calcium oxalate. The method has the problems of large volume of sulfuric acid solution, long process flow and energy consumption loss caused by circulating heating reaction-cooling crystallization.
Disclosure of Invention
The technical problem solved by the invention is to provide a method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue, which has high oxalic acid conversion efficiency and low sulfuric acid consumption and overcomes the defects of large residual acid, long process flow, high recovery cost and the like in the traditional process.
The technical scheme is as follows:
a method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue comprises the following steps:
mixing the mixed waste residue with concentrated sulfuric acid, and carrying out a curing reaction after uniformly stirring;
after the two phases are solidified, the two phases enter a reactor for solid-solid roasting conversion to obtain a calcium sulfate and oxalic acid mixed crystal;
and then water and the mixed crystal product are mixed for size mixing, mixed for leaching, and filtered to obtain an oxalic acid solution.
Further: the mixed waste residue comprises calcium oxalate and oxalate containing magnesium, strontium, barium, copper, iron, lead, zinc, manganese or rare earth elements.
Further: mixing the mixed waste residue formed by calcium oxalate and insoluble oxalate with concentrated sulfuric acid with the mass percentage concentration of more than or equal to 80% according to the stoichiometric ratio of 1: 1-1: 1.3 of a chemical reaction, uniformly stirring, and carrying out a curing reaction at the reaction temperature of 60-100 ℃ for 3-15 min.
Further: and after the two phases are solidified, feeding the two phases into a reactor, and carrying out solid-solid roasting and conversion for 20-60 min at the temperature of 100-150 ℃ to obtain a calcium sulfate and oxalic acid mixed crystal.
Further: under the condition of 50-90 ℃, water and the mixed crystal product are mixed into slurry according to the solid-liquid weight ratio of 1: 1-1: 4, mixed and leached, and filtered to obtain an oxalic acid solution.
Compared with the prior art, the invention has the technical effects that:
the invention mixes and solidifies the concentrated sulfuric acid and the calcium oxalate waste residue, carries out high-temperature solid-solid conversion, mixes the thermolysis ore (the calcium sulfate dihydrate and the oxalic acid mixed crystal) generated by the reaction with water, extracts the oxalic acid, and can greatly improve the conversion rate of the calcium oxalate under the condition of effectively controlling the dosage of the sulfuric acid.
The method mixes concentrated sulfuric acid and calcium oxalate waste residues and then continuously converts the mixed waste residues step by step, and firstly performs solid-liquid two-phase quantitative curing reaction, so that most of sulfuric acid reacts with calcium oxalate, the concentration of sulfuric acid in a solid phase is reduced, and the decomposition effect of the oxidizing property of the concentrated sulfuric acid on the oxalic acid is reduced. The obtained solid phase mixture is subjected to high-temperature solid-solid conversion in the reactor, so that the technical problems that the temperature of a liquid-solid reaction system cannot be increased and the conversion efficiency is low are solved, the one-time conversion rate of calcium oxalate is increased, and the continuous operation of the process is realized. The method has high oxalic acid conversion efficiency and low sulfuric acid consumption, and overcomes the defects of large residual acid, long process flow, high recovery cost and the like in the traditional process.
Drawings
FIG. 1 is a flow chart of the method for solid-solid conversion and recovery of oxalic acid from calcium oxalate waste residue in the invention.
Detailed Description
The technical solution of the present invention will be described in detail with reference to exemplary embodiments. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art.
As shown in FIG. 1, it is a flow chart of the method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue in the present invention.
The method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue specifically comprises the following steps:
step 1: mixing the calcium oxalate waste residue with concentrated sulfuric acid, and carrying out a curing reaction after uniformly stirring;
the main component of the calcium oxalate waste residue is calcium oxalate, and the calcium oxalate waste residue also comprises oxalate containing magnesium, strontium, barium, copper, iron, lead, zinc, manganese or rare earth elements.
Mixing the mixed waste residue formed by calcium oxalate and insoluble oxalate with concentrated sulfuric acid with the mass percentage concentration of more than or equal to 80% according to the stoichiometric ratio of 1: 1-1: 1.3 of a chemical reaction, uniformly stirring, and carrying out a curing reaction at the reaction temperature of 60-100 ℃ for 3-15 min.
Step 2: after the two phases are solidified, the two phases enter a reactor for solid-solid roasting conversion to obtain a calcium sulfate and oxalic acid mixed crystal;
and after the two phases are solidified, feeding the two phases into a reactor, and carrying out solid-solid roasting and conversion for 20-60 min at the temperature of 100-150 ℃ to obtain a calcium sulfate and oxalic acid mixed crystal.
And step 3: and then water and the mixed crystal product are mixed for size mixing, mixed for leaching, and filtered to obtain an oxalic acid solution.
Under the condition of 50-90 ℃, water and the mixed crystal product are subjected to size mixing, mixed leaching and filtering according to the solid-liquid weight ratio of water to calcium oxalate (dry weight) of 1: 1-1: 4 to obtain an oxalic acid solution.
Example 1
100g of calcium oxalate mixed waste residue containing rare earth and magnesium, 28.6 percent of waste residue water and 0.16 percent of REO are mixed with 59.9g of concentrated sulfuric acid with the mass percentage concentration of 80 percent, the mixture is stirred uniformly and then undergoes a curing reaction, the reaction temperature is 60-90 ℃, the reaction time is 10min, and the conversion rate of the calcium oxalate is 62 percent. And after the two phases are solidified, the two phases enter a reactor, and are subjected to solid-solid roasting conversion for 40min at the temperature of 150 ℃ to obtain a calcium sulfate and oxalic acid mixed crystal product. And then under the condition of 90 ℃, mixing water and the mixed crystal product according to the solid-liquid weight ratio of 1:2 of water to calcium oxalate (dry weight), leaching by mixing, and filtering to obtain an oxalic acid solution, wherein the total conversion rate of the calcium oxalate reaches 95.7%, and the concentration of sulfuric acid in the solution is 1.5%.
Example 2
500g of calcium oxalate mixed waste residue containing rare earth, manganese and barium, 30.9 percent of waste residue water, 84.7 percent of calcium oxalate and 97.6 percent of total oxalate are mixed with 318.1g of concentrated sulfuric acid with the mass percentage concentration of 92.5 percent, the mixture is uniformly stirred and then undergoes a curing reaction, the reaction temperature is 60-100 ℃, the natural heat release is carried out, the time is 3min, and the conversion rate of the calcium oxalate is 65 percent. And after the two phases are solidified, the two phases enter a reactor, and are subjected to solid-solid roasting conversion for 60min at the temperature of 100 ℃ to obtain a calcium sulfate and oxalic acid mixed crystal product. And then under the condition of 50 ℃, mixing water and the mixed crystal product according to the solid-liquid weight ratio of water to calcium oxalate (dry weight) of 1:4, leaching by mixing, and filtering to obtain an oxalic acid solution, wherein the total conversion rate of the calcium oxalate reaches 98.4%, and the concentration of sulfuric acid in the solution is 5%.
Example 3
900g of calcium oxalate mixed waste residue containing rare earth and magnesium, 28.6 percent of waste residue water and 0.16 percent of REO are mixed with 515.73g of concentrated sulfuric acid with the mass percentage concentration of 92 percent, the mixture is uniformly stirred and then undergoes a curing reaction, the reaction temperature is 60-90 ℃, the reaction time is 10min, and the conversion rate of the calcium oxalate is 62 percent. And after the two phases are solidified, the two phases enter a reactor, and are subjected to solid-solid roasting conversion for 20min at the temperature of 150 ℃ to obtain a calcium sulfate and oxalic acid mixed crystal product. And then under the condition of 60 ℃, mixing water and the mixed crystal product according to the solid-liquid weight ratio of 1:3 of water to calcium oxalate (dry weight), leaching by mixing, and filtering to obtain an oxalic acid solution, wherein the total conversion rate of the calcium oxalate reaches 96.2%, and the concentration of sulfuric acid in the solution is 3%.
Example 4
500g of calcium oxalate mixed waste residue containing rare earth and magnesium, 28.6 percent of waste residue water and 0.16 percent of REO are mixed with 268.97g of concentrated sulfuric acid with the mass percentage concentration of 98 percent, the mixture is stirred uniformly and then undergoes a curing reaction, the reaction temperature is 60-90 ℃, the reaction time is 10min, and the conversion rate of the calcium oxalate is 62 percent. And after the two phases are solidified, the two phases enter a reactor, and are subjected to solid-solid roasting conversion for 30min at the temperature of 120 ℃ to obtain a calcium sulfate and oxalic acid mixed crystal product. And then under the condition of 70 ℃, mixing water and the mixed crystal product according to the solid-liquid weight ratio of 1:3 of water to calcium oxalate (dry weight), leaching by mixing, and filtering to obtain an oxalic acid solution, wherein the total conversion rate of the calcium oxalate reaches 97%, and the concentration of sulfuric acid in the solution is 3%.
The terminology used herein is for the purpose of description and illustration, rather than of limitation. As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.
Claims (3)
1. A method for recovering oxalic acid by solid-solid conversion of calcium oxalate waste residue comprises the following steps:
mixing the mixed waste residue with concentrated sulfuric acid, wherein the mixed waste residue comprises calcium oxalate and oxalate containing magnesium, strontium, barium, copper, iron, lead, zinc, manganese or rare earth elements; mixing the mixed waste residue formed by calcium oxalate and insoluble oxalate with concentrated sulfuric acid with the mass percentage concentration of more than or equal to 80% according to the stoichiometric ratio of 1: 1-1: 1.3 of a chemical reaction, uniformly stirring, and then carrying out a curing reaction at the reaction temperature of 60-100 ℃ for 3-15 min;
after the two phases are solidified, the two phases enter a reactor for solid-solid roasting conversion to obtain a calcium sulfate and oxalic acid mixed crystal;
and then water and the mixed crystal product are mixed for size mixing, mixed for leaching, and filtered to obtain an oxalic acid solution.
2. The method for recovering oxalic acid from calcium oxalate waste residue through solid-solid conversion according to claim 1, wherein: and after the two phases are solidified, feeding the two phases into a reactor, and carrying out solid-solid roasting and conversion for 20-60 min at the temperature of 100-150 ℃ to obtain a calcium sulfate and oxalic acid mixed crystal.
3. The method for recovering oxalic acid from calcium oxalate waste residue through solid-solid conversion according to claim 1, wherein: under the condition of 50-90 ℃, water and the mixed crystal product are mixed into slurry according to the solid-liquid weight ratio of 1: 1-1: 4, mixed and leached, and filtered to obtain an oxalic acid solution.
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| CN101012165A (en) * | 2007-02-09 | 2007-08-08 | 李安民 | Process of preparing oxalic acid by calcium sulfate cycle method |
| CN103086440A (en) * | 2011-11-02 | 2013-05-08 | 深圳市环境友好金属材料工程技术研究开发中心 | Method for processing cobalt oxalate waste |
| CN104232947A (en) * | 2014-09-18 | 2014-12-24 | 龙南县中利再生资源开发有限公司 | Method for extracting and recovering rare earth elements from waste phosphor |
| CN104761444A (en) * | 2015-03-18 | 2015-07-08 | 南京格洛特环境工程股份有限公司 | Process of recycling oxalic acid from rare earth wet-method smelting oxalic acid precipitation waste water |
| WO2016128621A1 (en) * | 2015-02-12 | 2016-08-18 | Outotec (Finland) Oy | Method and arrangement of recovering rare earth elements from ion adsorption clays |
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Patent Citations (6)
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| CN1044499A (en) * | 1989-12-23 | 1990-08-08 | 江西省科学院 | Recycle oxalic acid extracts the technology of rare earth |
| CN101012165A (en) * | 2007-02-09 | 2007-08-08 | 李安民 | Process of preparing oxalic acid by calcium sulfate cycle method |
| CN103086440A (en) * | 2011-11-02 | 2013-05-08 | 深圳市环境友好金属材料工程技术研究开发中心 | Method for processing cobalt oxalate waste |
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| WO2016128621A1 (en) * | 2015-02-12 | 2016-08-18 | Outotec (Finland) Oy | Method and arrangement of recovering rare earth elements from ion adsorption clays |
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