CN111646878A - Method for recovering byproduct chloromethane in maltol production - Google Patents
Method for recovering byproduct chloromethane in maltol production Download PDFInfo
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- CN111646878A CN111646878A CN202010439454.4A CN202010439454A CN111646878A CN 111646878 A CN111646878 A CN 111646878A CN 202010439454 A CN202010439454 A CN 202010439454A CN 111646878 A CN111646878 A CN 111646878A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/383—Separation; Purification; Stabilisation; Use of additives by distillation
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Abstract
The invention relates to a method for recovering a byproduct methyl chloride in maltol production, wherein after chlorination reaction in the maltol production is finished, chlorination liquid is subjected to hydrolysis reaction to generate methyl and ethyl maltol, and the byproduct contains water, hydrogen chloride, methanol and other organic matter impurity methyl chloride gas.
Description
Technical Field
The invention relates to the field of food additive production, and particularly relates to a method for recovering a byproduct methyl chloride in maltol production.
Background
Methyl chloride (CH 3Cl), a colorless and flammable toxic gas, is also called methyl chloride, a colorless and easily liquefied gas, and is stored in a steel cylinder for pressurization and liquefaction. Belongs to organic halide. Slightly soluble in water, and easily soluble in chloroform, diethyl ether, ethanol, and acetone. Flammable, explosive, moderate hazard (poison hazard index 43). Reacting methanol and hydrochloric acid with water at high temperature (above 400 ℃) and under strong light, and heating or generating phosgene when meeting flame. Methyl chloride can result from the substitution reaction of methane with chlorine and can be further halogenated. Slightly soluble in water and easily soluble in ether, benzene, etc. No corrosion; it is flammable and can form explosive mixture with air, and the explosion limit is 8.1% -17.2% (volume). Methyl chloride produces methanol when hydrolyzed above 60 ℃.
In the production of maltol, furfural reacts with ethyl magnesium chloride to obtain ethyl furfuryl alcohol (alpha-furylalcohol), then the ethyl furfuryl alcohol is oxidized by chlorine gas in methanol aqueous solution at-7 ℃ or below, then the ethyl maltol is hydrolyzed by heating to 98 ℃ to obtain ethyl maltol, and a large amount of methyl chloride gas is generated in the chlorination and hydrolysis processes, wherein various impurities (hydrogen chloride, water and methanol) are mixed. The impurity removal process of the chloromethane in the prior art is simple, so that the purity of the obtained finished chloromethane is not enough, and the energy consumption is large due to the adoption of steam for distillation.
Disclosure of Invention
The invention content is as follows:
the invention aims to provide a method for removing and purifying chloromethane gas generated by chlorination hydrolysis reaction in the production process of maltol, so as to reduce the content of impurities in liquid chloromethane and achieve the purpose of removing and purifying impurities.
The purpose of the invention is realized by the following technical scheme:
a method for recovering a byproduct methyl chloride in maltol production is characterized by comprising the following steps:
1) sending a byproduct methyl chloride feed gas in maltol production into a primary alkali washing tower, removing part of hydrogen chloride acidic gas by using liquid alkali washing, and controlling the pH of a primary alkali washing solution to be more than or equal to 8;
2) the methyl chloride gas after the primary alkali washing sequentially enters a primary water washing tower and a secondary water washing tower for water washing to remove the methanol in the methyl chloride gas;
3) the washed chloromethane gas sequentially enters a second-stage alkaline washing tower and a third-stage alkaline washing tower, the PH of a second-stage alkaline washing solution is controlled to be more than or equal to 9, the PH of a third-stage alkaline washing solution is controlled to be more than or equal to 10, acid gas in the feed gas is further removed, and the PH value of the washing solution passing through the third-stage alkaline washing tower is ensured to be alkaline or neutral;
4) condensing the alkali-washed methyl chloride gas in a dewatering condenser to remove water carried in the methyl chloride gas, and controlling the water content in the methyl chloride gas to be lower than 0.2%;
5) compressing the dewatered methyl chloride gas to 0.5-0.6 MPa by a compressor, then rectifying the gas in a rectifying tower, controlling the temperature at the bottom of the tower to be 38-42 ℃ and the temperature at the top of the tower to be 18-22 ℃, feeding the rectified methyl chloride gas into a condenser at the top of the rectifying tower through an outlet at the top of the rectifying tower, cooling the methyl chloride gas in the condenser at the top of the tower by using condensation circulating water provided by an evaporation condenser to obtain methyl chloride liquid, returning a part of the methyl chloride liquid into the rectifying tower for re-rectification, feeding the other part of the methyl chloride liquid and the un-liquefied methyl chloride gas into the evaporation condenser for re-cooling to obtain the methyl chloride liquid.
The further technical scheme is that pure water is used for washing substances such as methanol and the like dissolved in water in raw material gas, and the washed water is transported to a production line through a pump for reuse.
The further technical scheme is that the methyl chloride gas after alkaline washing enters a water removal condenser, the water removal condenser is used for condensing through liquid ammonia, the condensing temperature is controlled to be 0-5 ℃, water entrained in the methyl chloride gas is removed, and the water content in the methyl chloride gas is lower than 0.2%.
The further technical scheme is that the dewatered methyl chloride gas is compressed to 0.6MPa and 20 ℃ by a compressor, the bottom temperature of the tower is controlled to be 38-42 ℃ and the top temperature of the tower is controlled to be 18-22 ℃, the rectified methyl chloride gas enters a tower top condenser through an outlet at the top of a rectifying tower, the methyl chloride gas in the tower top condenser is cooled to 0-10 ℃ by utilizing condensation circulating water provided by an evaporation condenser to obtain methyl chloride liquid, one part of the methyl chloride liquid is returned to the rectifying tower for rectification again, and the other part of the methyl chloride liquid enters the evaporation condenser for cooling again to obtain the methyl chloride.
The further technical proposal is that the evaporative condenser uses desalted water with the temperature of 0-5 ℃ after being processed in a public engineering workshop as cooling water.
The invention has the advantages that:
1. in order to reduce the hydrogen chloride acid gas component in the feed gas chloromethane, the invention adopts three times of alkaline washing, thereby greatly removing the acid gas of the feed gas and improving the purity of the chloromethane finished product;
2. compared with the prior art, the dehydration condenser is adopted, a molecular sieve fixed bed is not needed for removing water (calcium chloride), the cost of the calcium chloride is reduced, and the quality indexes of the obtained methyl chloride finished product reach high grade;
3. the adopted water washing process is used for other production lines again after water washing, so that the water is recycled and saved.
4. The operation flow is simple, the operation is convenient, and the consumption of steam is reduced.
5. The dual-purpose structure of the evaporation condenser is adopted, firstly, the evaporation condenser is used for condensing the tower top condenser, and secondly, the evaporation condenser is used for condensing the tower top condenser again, so that the condensing effect of the methyl chloride is ensured, and the yield of the methyl chloride finished product is improved.
Description of the drawings:
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
As shown in FIG. 1, the invention provides a method for recovering methyl chloride as a byproduct in maltol production, which comprises the following steps:
1) in the production process of maltol, generating a byproduct methyl chloride feed gas (comprising 95 percent, 2 percent, 1 percent and 2 percent of methyl chloride, hydrogen chloride, methanol and water respectively) at the pressure of 2KPa and the temperature of 20 ℃, entering a primary alkali washing tower, carrying out alkali washing by using 10 percent of sodium hydroxide to remove part of hydrogen chloride acid gas and the like in the methyl chloride feed gas, and requiring the pH value of the primary alkali washing tower to be more than or equal to 8;
2) pumping the methyl chloride gas subjected to primary alkali washing by a roots machine (the outlet pressure of the roots machine is controlled to be about 0-30 KPa), and washing in a primary washing tower and a secondary washing tower (the outlet water flow of the primary washing tower is controlled to be 600L/h, the water replenishing flow of the secondary washing tower is controlled to be 600L/h, the general pressure is about 15KPa, and the temperature is about 20 ℃), so as to remove methanol;
3) introducing the washed chloromethane gas into a gas holder, exhausting gas through a roots machine (the pressure at the outlet of the roots machine is controlled to be about 0-30 KPa), introducing the gas into a second-level alkaline tower and a third-level alkaline tower for alkaline washing (15% sodium hydroxide solution is adopted, the PH of the second-level alkaline tower is controlled to be more than or equal to 9, and the PH of the third-level alkaline tower is controlled to be more than or equal to 10), further removing acid gas in the feed gas, and ensuring that the PH value of the washing solution of the third-level alkaline tower is alkaline or neutral in the;
4) condensing the alkali-washed gas (at 20 ℃ and 15 KPa) in a water removal condenser, controlling the temperature of a chloromethane gas outlet at 5 ℃, removing water carried in the raw material gas, and controlling the content of chloromethane water to be lower than 0.2%;
5) the dehydrated methyl chloride gas (the pressure is about 15KPa and the temperature is about 5 ℃) is compressed by a compressor, then (the first-stage pressure is about 0.1MPa and the second-stage pressure is about 0.6 MPa) enters a rectifying tower to be rectified (the tower bottom temperature is 40 ℃ and the tower top temperature is 20 ℃), the rectified methyl chloride (the pressure is about 0.6MPa and the temperature is about 20 ℃) enters a tower top condenser through an outlet at the top of the rectifying tower, cold circulating water provided by an evaporation condenser is used for cooling to the temperature of 5 ℃ to obtain partial methyl chloride liquid, and then the partial methyl chloride liquid flows back to the rectifying tower to be rectified again; and (4) feeding the partially condensed methyl chloride liquid and the condensed methyl chloride gas into an evaporative condenser for cooling again (desalted water treated in a public engineering workshop is used as cooling water for evaporation cooling), so as to obtain the methyl chloride liquid.
Claims (5)
1. A method for recovering a byproduct methyl chloride in maltol production is characterized by comprising the following steps:
1) sending a byproduct methyl chloride feed gas in maltol production into a primary alkali washing tower, removing part of hydrogen chloride acidic gas by using liquid alkali washing, and controlling the pH of a primary alkali washing solution to be more than or equal to 8;
2) the methyl chloride gas after the primary alkali washing sequentially enters a primary water washing tower and a secondary water washing tower for water washing to remove the methanol in the methyl chloride gas;
3) the washed chloromethane gas sequentially enters a second-stage alkaline washing tower and a third-stage alkaline washing tower, the PH of a second-stage alkaline washing solution is controlled to be more than or equal to 9, the PH of a third-stage alkaline washing solution is controlled to be more than or equal to 10, acid gas in the feed gas is further removed, and the PH value of the washing solution passing through the third-stage alkaline washing tower is ensured to be alkaline or neutral;
4) condensing the alkali-washed methyl chloride gas in a dewatering condenser to remove water carried in the methyl chloride gas, and controlling the water content in the methyl chloride gas to be lower than 0.2%;
5) compressing the dewatered methyl chloride gas to 0.5-0.6 MPa by a compressor, then rectifying the gas in a rectifying tower, controlling the temperature at the bottom of the tower to be 38-42 ℃ and the temperature at the top of the tower to be 18-22 ℃, feeding the rectified methyl chloride gas into a condenser at the top of the rectifying tower through an outlet at the top of the rectifying tower, cooling the methyl chloride gas in the condenser at the top of the tower by using condensation circulating water provided by an evaporation condenser to obtain methyl chloride liquid, returning a part of the methyl chloride liquid into the rectifying tower for re-rectification, feeding the other part of the methyl chloride liquid and the un-liquefied methyl chloride gas into the evaporation condenser for re-cooling to obtain the methyl chloride liquid.
2. The method according to claim 1, wherein the recovery of methyl chloride as a by-product in the production of maltol comprises: the pure water is used for washing substances such as methanol and the like dissolved in water in the raw material gas, and the washed water is transported to a production line by a pump for reuse.
3. The method according to claim 1, wherein the recovery of methyl chloride as a by-product in the production of maltol comprises: and (3) allowing the methyl chloride gas after alkali washing to enter a water removal condenser, condensing the water removal condenser through liquid ammonia, controlling the condensation temperature to be 0-5 ℃, and removing water entrained in the methyl chloride gas, wherein the water content in the methyl chloride gas is lower than 0.2%.
4. The method according to claim 1, wherein the recovery of methyl chloride as a by-product in the production of maltol comprises: compressing the dewatered methyl chloride gas to 0.6MPa and 20 ℃ by a compressor, then rectifying the gas in a rectifying tower, controlling the temperature at the bottom of the tower to be 38-42 ℃ and the temperature at the top of the tower to be 18-22 ℃, feeding the rectified methyl chloride gas into a top condenser through an outlet at the top of the rectifying tower, cooling the methyl chloride gas in the top condenser to the temperature of 0-10 ℃ by using condensation circulating water provided by an evaporation condenser to obtain methyl chloride liquid, returning a part of the methyl chloride liquid to the rectifying tower for rectifying again, and feeding the other part of the methyl chloride liquid into the evaporation condenser for cooling again to obtain the methyl chloride.
5. The method according to claim 4, wherein the recovery of methyl chloride as a by-product in the production of maltol comprises: the evaporative condenser uses demineralized water at a temperature of 0-5 ℃ after treatment in a utility workshop as cooling water.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010439454.4A CN111646878A (en) | 2020-05-22 | 2020-05-22 | Method for recovering byproduct chloromethane in maltol production |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010439454.4A CN111646878A (en) | 2020-05-22 | 2020-05-22 | Method for recovering byproduct chloromethane in maltol production |
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| CN111646878A true CN111646878A (en) | 2020-09-11 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202010439454.4A Withdrawn CN111646878A (en) | 2020-05-22 | 2020-05-22 | Method for recovering byproduct chloromethane in maltol production |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112194646A (en) * | 2020-09-16 | 2021-01-08 | 广东省肇庆香料厂有限公司 | Method for recovering chloroethane in chlorination hydrolysis process in ethyl maltol production process |
| CN112573995A (en) * | 2020-12-11 | 2021-03-30 | 安徽金禾实业股份有限公司 | Method for recovering byproduct chloromethane in maltol production process |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101875596A (en) * | 2009-04-28 | 2010-11-03 | 苏州佳辉化工有限公司 | Process for reclaiming chloromethane |
| CN103044185A (en) * | 2012-12-24 | 2013-04-17 | 龙海市贝特利生物科技有限公司 | Method for recovering chloromethane from chloromethane-containing waste gas in maltol production |
| CN109438172A (en) * | 2018-12-10 | 2019-03-08 | 安徽金禾实业股份有限公司 | The recovery method of methyl chloride gas in a kind of production of maltol |
| CN110041164A (en) * | 2019-05-08 | 2019-07-23 | 江西金龙化工有限公司 | A method of recycling chloromethanes |
-
2020
- 2020-05-22 CN CN202010439454.4A patent/CN111646878A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101875596A (en) * | 2009-04-28 | 2010-11-03 | 苏州佳辉化工有限公司 | Process for reclaiming chloromethane |
| CN103044185A (en) * | 2012-12-24 | 2013-04-17 | 龙海市贝特利生物科技有限公司 | Method for recovering chloromethane from chloromethane-containing waste gas in maltol production |
| CN109438172A (en) * | 2018-12-10 | 2019-03-08 | 安徽金禾实业股份有限公司 | The recovery method of methyl chloride gas in a kind of production of maltol |
| CN110041164A (en) * | 2019-05-08 | 2019-07-23 | 江西金龙化工有限公司 | A method of recycling chloromethanes |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112194646A (en) * | 2020-09-16 | 2021-01-08 | 广东省肇庆香料厂有限公司 | Method for recovering chloroethane in chlorination hydrolysis process in ethyl maltol production process |
| CN112573995A (en) * | 2020-12-11 | 2021-03-30 | 安徽金禾实业股份有限公司 | Method for recovering byproduct chloromethane in maltol production process |
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Application publication date: 20200911 |
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