A process for refining low-grade calcium formate and preparing high-purity calcium-based compounds based on calcium formate

Abstract

The invention discloses a process method for refining low-grade calcium formate and preparing high-purity calcium-based compounds based on the downstream of calcium formate. The process method is to remove the adsorbed methylal (ML) and methanol (ME) from the crude calcium formate obtained by treating methyl formate waste liquid by drying, recover ML and ME by tail gas condensation, and then separate them in the distillation section; the solid phase is mixed with water in a certain proportion at room temperature, stirred and dissolved, and then filtered; the filtrate is concentrated, crystallized, centrifuged, and then dried to obtain food / feed grade calcium formate; the mother liquor water and the tail gas condensed water in the process can be recycled, and the filter residue can be used to prepare cement. Food / feed grade calcium formate can be heated and decomposed at 500°C to obtain high-purity calcium carbonate, and heated and decomposed at high temperature of 800°C to obtain high-purity calcium oxide, and tail gas carbon monoxide, hydrogen and carbon dioxide are collected and used as synthesis gas or fuel gas. The process method is simple, safe and reliable, does not produce three wastes, has high continuous production efficiency, high product added value, and effectively extends the industrial chain while maximizing the utilization of resources.

Description

Technical Field

[0001] The invention relates to the field of inorganic chemical industry for refining and purifying calcium formate and preparing high-purity calcium carbonate and calcium oxide, and specifically to a process for refining and purifying calcium formate produced by comprehensive utilization of methyl formate (MF) waste liquid in the process of coal-to-ethylene glycol and preparing high-purity calcium carbonate and calcium oxide. Background Art

[0002] In 2022, China's ethylene glycol production capacity will be 21.711 million tons / year, of which coal-based ethylene glycol production capacity will be 7.67 million tons, accounting for 35.33% of the total capacity; oil-based equipment will be 11.32 million tons, accounting for 60.43% of the total capacity; and MTO will account for about 4%. Ethylene glycol has a rich technical route. Coal-based ethylene glycol has the advantages of short process flow, few intermediate links, and low cost. It is currently the most widely used coal-based ethylene glycol route in China. Under the current oil price conditions, the use of coal-based ethylene glycol is relatively more competitive. Coal-based ethylene glycol produces side reactions during esterification and carbonylation, and methyl formate MF waste liquid is produced in the DMO and DMC distillation sections. The composition of MF waste liquid is complex, and the boiling points of each component are similar. It is easy to form azeotropes and difficult to separate. MN aggregation is prone to explosion hazards, which makes concentration and enrichment a safety hazard. At present, the commonly used disposal method in China is incineration after denitration, which leads to a great waste of carbon resources and is not conducive to the realization of dual carbon goals.

[0003] Calcium formate, also known as calcium formate, or CAF for short, is a white crystal or powder, slightly hygroscopic, non-toxic, slightly bitter, insoluble in alcohol, soluble in water, neutral pH, and decomposed by heating at around 400°C. At present, calcium formate in the domestic market is divided into two specifications: food / feed grade and industrial grade. In addition, there is no national or industry quality standard for calcium formate in my country, and its production is carried out in accordance with the quality standards of domestic enterprises. Industrial-grade calcium formate is mainly used in the construction industry and cement early strength agent. Food / feed grade calcium formate is mainly used in animal feed additives to increase and improve animal physique, enhance appetite, reduce diarrhea rate, and improve calcium absorption. The difference between the two is that food / feed grade calcium formate has a pure white crystal appearance, uniform particles, and good fluidity; the calcium formate content is above 99%, and the calcium content is ≥30%; the heavy metal content Pb≤0.002%, AS≤0.0005%.

[0004] Calcium carbonate is basically insoluble in water, but soluble in hydrochloric acid. It is mainly used in plastics, papermaking, coatings, rubber, adhesives, chemical building materials, medicine, food, feed, ink and other fields. Calcium oxide is used in analytical reagents, manufacturing calcium carbide, soda ash, bleaching powder, refractory materials, desiccants, glass manufacturing processes, etc. High-purity calcium carbonate and calcium oxide can be used in high-end fields such as medicine, ink, feed, reagents, etc.

[0005] The crude calcium formate produced by comprehensive utilization of coal-based ethylene glycol methyl formate (MF) waste liquid meets industrial-grade enterprise standards and is used as cement early strength agent in the construction industry. There are many types of early strength agents, with average economic efficiency and low product added value. In order to increase the economy and risk resistance of the overall process and improve the quality of the product, it is urgent to develop a process method that is simple, safe, reliable, economical and environmentally friendly. Summary of the invention

[0006] In order to improve the quality of crude calcium formate produced by comprehensive utilization of methyl formate (MF) waste liquid and develop diversified products, the present invention provides a process for refining low-grade calcium formate in the process and preparing high-purity calcium-based compounds based on downstream products of calcium formate. The method removes the adsorbed methylal (ML) and methanol (ME) from the crude calcium formate (mainly containing calcium formate, adsorbed organic substances methylal (ML) and methanol (ME), etc., and insoluble matter in calcium salt) obtained by treating methyl formate (MF) waste liquid by drying, and recovers the tail gas by condensation and distillation section for separation and purification. The solid phase is mixed with water in a certain proportion at room temperature, stirred and dissolved, and then filtered. The filtrate is concentrated, crystallized, centrifuged, and then dried to obtain food / feed grade calcium formate. The mother liquor water and tail gas condensate water in the process can be recycled, and the filter residue can be used to prepare cement. Food / feed grade calcium formate can be heated and decomposed to obtain high-purity acid calcium, and high-temperature heating and decomposition can obtain high-purity calcium oxide.

[0007] The crude calcium formate is obtained by filtering the waste liquid from coal-based ethylene glycol methyl formate (MF).

[0008] The crude calcium formate is vacuum dried at a vacuum degree of 0.07 MPa, a temperature of 60° C. to 110° C., and a drying time controlled at 2 to 6 hours.

[0009] After being condensed and recovered, the dried tail gas can be directly fed into the distillation section to separate and purify methylal (ML) and methanol (ME).

[0010] The solid-liquid ratio of the calcium formate and water is 1: (6-10).

[0011] After the centrifugal separation, the calcium formate solid is vacuum dried at a vacuum degree of 0.07 MPa and a temperature of 60-110° C. After drying for 2-8 hours, a calcium formate product that meets the food / feed grade enterprise standards can be obtained.

[0012] The mother liquor water and tail gas condensate in the refining process can be recycled for the water washing process.

[0013] The calcium formate is heated and decomposed at 350° C. to 550° C. for 3 to 8 hours to obtain a high-purity calcium carbonate product.

[0014] The calcium formate is heated and decomposed at 600° C. to 900° C. for 3 to 8 hours to obtain a high-purity calcium oxide product.

[0015] The hydrogen, carbon monoxide and carbon dioxide gases generated during the thermal decomposition can be recovered and reused.

[0016] The present invention provides a process for refining low-grade calcium formate and preparing high-purity calcium-based compounds based on the downstream of calcium formate. In the process, low-grade calcium formate is derived from the comprehensive treatment of methyl formate (MF) waste liquid, the raw materials are cheap, and the crude product is generally economical; no other substances are introduced in the refining process; the waste liquid generated in the refining process can be recycled and reused, and there is no discharge of three wastes; the refined food / feed grade calcium formate is widely used and has a huge market; in order to improve the economy and risk resistance of the process, the high-purity calcium carbonate and calcium oxide produced from the refined calcium formate have considerable economy and broad application fields. The process has low energy consumption, simple flow, and good economy, and has great strategic significance for the treatment of three wastes in coal chemical industry, recycling of resources, and the realization of dual carbon goals of atomic economic chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the implementation cases of the present invention or the technical solutions in the prior art, the drawings required in the implementation cases or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Instruction Manual

[0019] Figure 1 A specific process flow chart of a process for refining low-grade calcium formate and preparing a high-purity calcium-based compound based on calcium formate provided in an embodiment of the present invention.

[0020] Figure 2 The present invention provides a process for refining low-grade calcium formate and a process for preparing high-purity calcium-based compounds based on calcium formate, and TG analysis of water-washed refined calcium formate. DETAILED DESCRIPTION

[0021] In order to better illustrate the present invention, the following examples are given. However, the scope of the present invention is not limited to the examples, and the scope of protection required is recorded in the claims.

[0022] The MF waste liquid (methyl formate waste liquid in the coal-to-ethylene glycol process) is reacted with water and calcium inorganic substances (at least one of calcium oxide or calcium hydroxide) at near room temperature and normal pressure, and methyl nitrite (MN) is obtained in the gas phase and recycled to the carbonyl chemical section. After the reactants are filtered, the solid phase is crude calcium formate, and the liquid phase is a saturated aqueous solution of calcium formate containing methylal (ML) and methanol (ME). The crude calcium formate mainly contains calcium formate, adsorbed organic substances such as methylal (ML) and methanol (ME), calcium salt insolubles, and other ionic impurities insolubles.

[0023] Add 450g MF waste liquid (MF content is 70%, MN content is 9%, ME content is 18%, ML content is 3%) to a three-necked flask, put it into a temperature-controlled water bath magnetic stirrer, mix thoroughly and cool down, control the temperature between 0℃~12℃, slowly add 64g water under stirring, and add 195g calcium hydroxide solid in 10 batches after the temperature is constant. Strictly control the temperature after each addition of calcium hydroxide, slow down the addition speed when the temperature is high, and continue to add after the reaction is stable. After the addition is completed, control the speed at 500r / min, control the temperature between 0℃~12℃, and the pressure at about 0.05MPa. Stop stirring after reacting for 4h, let it stand for 2h and filter, put the filter residue crude calcium formate into a vacuum drying oven, the vacuum degree is 0.07MPa, and the temperature is set at 70℃ for 4h to obtain 305g calcium formate solid. The sample number is crude calcium formate. The crude calcium formate is used for subsequent refining experiments. Example 1

[0024] Add 50g of the above-mentioned crude calcium formate after drying to a 500ml beaker, then slowly add 400g of water to the beaker, stir to fully dissolve, let stand for 30min, filter and separate the insoluble matter, concentrate and crystallize the filtrate (the water bath is set at 95℃, after stirring and evaporating for 5h, a large amount of crystal film appears on the surface of the concentrated liquid, and more solids precipitate at the bottom of the concentrated liquid. When the concentrated liquid is one-sixth of the original concentrated liquid, stop heating, and cool naturally to evaporate the remaining liquid), then centrifuge, vacuum dry the solid, the vacuum degree is 0.07MPa, and the temperature is 80℃. After drying for 6h, a calcium formate product that meets the food / feed grade enterprise standards can be obtained. After refining in this experiment, 42.25g of calcium formate was obtained, and the sample was marked as 1#.

[0025] Example 2

[0026] Add 50g of the above-mentioned crude calcium formate after drying to a 500ml beaker, then slowly add 300g of water to the beaker, stir to fully dissolve, let stand for 1h, filter and separate the insoluble matter, and concentrate the filtrate for crystallization (the water bath is set at 98℃, and after stirring and evaporating for 4h, a large amount of crystal film appears on the surface of the concentrated liquid, and more solids precipitate at the bottom of the concentrated liquid. When the concentrated liquid is one-sixth of the original concentrated liquid, stop heating, and cool naturally to evaporate the remaining liquid), and then centrifuge and vacuum dry the solid. The vacuum degree is 0.09MPa, and the temperature is 70℃. After drying for 5h, a calcium formate product that meets the food / feed grade enterprise standards can be obtained. After refining in this experiment, 43g of calcium formate was obtained, and the sample was marked as 2#. Example 3

[0027] Add 50g of the above-mentioned crude calcium formate after drying to a 500ml beaker, then slowly add 500g of water to the beaker, stir to fully dissolve, let stand for 1h, filter and separate the insoluble matter, and concentrate the filtrate for crystallization (the water bath is set at 95℃, and after stirring and evaporating for 5h, a large amount of crystal film appears on the surface of the concentrated liquid, and more solids are precipitated at the bottom of the concentrated liquid. When the concentrated liquid is one-sixth of the original concentrated liquid, stop heating, and cool naturally to evaporate the remaining liquid), and then centrifuge and vacuum dry the solid. The vacuum degree is 0.04MPa, and the temperature is 90℃. After drying for 3h, a calcium formate product that meets the food / feed grade enterprise standards can be obtained. After refining in this experiment, 43.73g of calcium formate was obtained, and the sample was marked as 3#.

[0028] Weigh 20g of the above refined calcium formate sample and put it into a crucible and place it in a tube furnace. After calcining at 800℃ for 5h in air atmosphere, high-purity calcium oxide product can be obtained. 8.53g of high-purity calcium oxide was obtained in this experiment, which is consistent with the theoretical calculated value. Example 4

[0029] According to the HG / T 5614-2019 industry standard, the crude calcium formate and the refined samples were subjected to the determination of calcium formate, and the heavy metals Pb, A S The results show that as shown in Table 1, the calcium formate content of the refined sample is ≥99%, the heavy metal Pb is ≤0.002%, and the As is ≤0.0005%, which meets the quality standards of food grade / feed grade calcium formate.

[0030] Table 1 Detection and analysis of calcium formate product content

[0031] Sample No. Calcium formate content% Pb content% As content% Crude calcium formate 98.00% 0.0011 0.0006 Refined product 1# 99.00% 0.0011 0.0005 Refined product 2# 99.10% 0.0013 0.0005 Refined product 3# 99.10% 0.0012 0.0003 Example 5

[0032] A TG analysis was performed on the purified calcium formate sample obtained in the experimental results. The analysis results are shown in the attached manual. Figure 2 As shown: The thermal decomposition of calcium formate is divided into two stages. The first thermal decomposition stage: room temperature ~ 400 ° C, 550 ° C tends to be stable; the mass loss rate is 25.2%. The second thermal decomposition stage: 600 ° C ~ 800 ° C, tends to be constant after 800 ° C, and the mass loss rate is 34.07%. According to the calculation of the weight loss rate of the chemical decomposition equation and the physical properties of the material, the chemical reaction equation of the first thermal decomposition stage is determined as: ; The chemical reaction equation of the second thermal decomposition stage is: The overall reaction equation is: . Example 6

[0033] Weigh 20 g of the refined calcium formate sample in Example 2, put it into a crucible and place it in a tube furnace. After nitrogen replacement, calcine it at 550° C. for 3 h in a nitrogen atmosphere to obtain a high-purity calcium carbonate product. 15.10 g of high-purity calcium carbonate was obtained in this experiment. Example 7

[0034] Weigh 10 g of the high-purity calcium carbonate sample obtained in Example 6, put it into a crucible and place it in a tube furnace, and calcine it at 850°C for 6 hours under a nitrogen atmosphere to obtain a high-purity calcium oxide product. 4.25 g of high-purity calcium oxide was obtained in this experiment, which is consistent with the theoretical calculated value.

Claims

1. A process for refining low-grade calcium formate and preparing high-purity calcium-based compounds based on calcium formate, characterized in that: The crude calcium formate obtained from treating methyl formate waste liquid is dried to remove adsorbed methylal and methanol, and the tail gas is condensed to recover methylal and methanol and then separated in the distillation section; the solid phase is mixed with water in a certain proportion at room temperature, stirred to dissolve and then the insoluble matter is filtered out, the filtrate is concentrated, crystallized, centrifuged and then dried to obtain food / feed grade calcium formate, the mother liquor water and the tail gas condensate water in the process are recycled, and the filter residue is used to prepare cement; food / feed grade calcium formate is heated and decomposed to obtain high-purity calcium carbonate, and high-temperature heating and decomposition are used to obtain high-purity calcium oxide, and the tail gas carbon monoxide, hydrogen and carbon dioxide are collected and used as synthesis gas or fuel gas.

2. The method according to claim 1, characterized in that The crude calcium formate is obtained by filtering the waste liquid from coal-based ethylene glycol methyl formate (MF).

3. The method according to claim 1, characterized in that The crude calcium formate is vacuum dried at a vacuum degree of 0.07 MPa, a temperature of 60° C. to 110° C., and a drying time controlled at 2 to 6 hours.

4. The method according to claim 1, characterized in that After condensation and recovery, the tail gas directly enters the distillation section to separate and purify methylal and methanol.

5. The method according to claim 1, characterized in that The solid-liquid ratio of the solid phase mixed with water in a certain proportion at room temperature is 1: (6-10).

6. The method according to claim 1, characterized in that The filtrate is dried after centrifugal separation, the vacuum degree of drying is 0.04MPa~0.09MPa, the temperature is 60℃~110℃, and the calcium formate product is obtained after drying for 2~8 hours.

7. The method according to claim 1, characterized in that The mother liquor water and tail gas condensate in the refining process are both recycled to the water washing process.

8. The method according to claim 1, characterized in that The calcium formate is heated and decomposed at 350° C. to 550° C. for 3 to 8 hours to obtain a high-purity calcium carbonate product.

9. The method according to claim 1, characterized in that: The food / feed grade calcium formate is heated and decomposed at 600° C. to 900° C. for 3 to 8 hours to obtain a high-purity calcium oxide product.

10. The method according to claim 1, characterized in that The carbon monoxide, hydrogen and carbon dioxide gases generated during the thermal decomposition are recovered and used as synthesis gas or fuel gas.

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