CN109809994B - Method for recovering n-propyl acetate-n-propanol solvent from waste liquid in printing industry - Google Patents
Method for recovering n-propyl acetate-n-propanol solvent from waste liquid in printing industry Download PDFInfo
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- CN109809994B CN109809994B CN201811432697.4A CN201811432697A CN109809994B CN 109809994 B CN109809994 B CN 109809994B CN 201811432697 A CN201811432697 A CN 201811432697A CN 109809994 B CN109809994 B CN 109809994B
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Abstract
The invention provides a method for recovering an n-propyl acetate-n-propanol solvent from waste liquid in the printing industry, belonging to the field of solvent recovery. The invention comprises the following steps: washing the waste liquid collected by an adsorption and desorption device in the printing industry by using an alkaline solution to remove acetic acid in the waste liquid; distilling to remove salt dissolved in the waste liquid; rectifying by two rectifying towers, and separating to obtain n-propyl acetate-n-propanol solvent; the top of the rectifying tower 1 of the two rectifying towers adopts a reflux tank with a phase splitting function to reflux the oil phase and extract the water phase, and the top of the rectifying tower 2 obtains the n-propyl acetate-n-propanol solvent. The recovery process has simple operation flow, can recycle the n-propyl acetate-n-propanol in the waste liquid, improves the economic benefit and reduces the pollution and damage to the environment.
Description
Technical Field
The invention belongs to the field of solvent recovery, and particularly relates to a process for recovering an n-propyl acetate-n-propanol solvent from waste liquid in the printing industry.
Background
The printing industry uses a large number of organic solvents as diluents for printing inks, such as n-propyl acetate and n-propanol solvents. During the use of n-propyl acetate and n-propanol solvents, in order to improve the printing quality, some printing enterprises usually add a small amount of solvents such as propylene glycol methyl ether or propylene glycol ethyl ether. The organic solvents are completely volatilized in the drying process to become organic waste gas; in addition, there is also a significant amount of organic solvent evaporation during the open ink mixing process. The emission of the volatile organic compounds is harmful to human health and atmospheric pollution on one hand, and also causes huge waste of organic solvents on the other hand, thereby seriously affecting the economic benefit of enterprises.
At present, printing enterprises can recover and collect volatile organic compounds through adsorption and desorption devices such as zeolite rotating wheels. However, the desorbed high-temperature environment causes the ester solvent to undergo hydrolysis reaction, such as the hydrolysis of n-propyl acetate to generate n-propanol and acetic acid; during the process of collecting the waste liquid, impurities such as moisture may also enter the waste liquid, such as moisture in the air. The resulting hydrolysis reaction and the increase in the water content of the waste stream result in complex thermodynamic properties of the waste stream system: substances such as water and n-propyl acetate may form a minimum azeotrope; acetic acid and n-propyl acetate can form a minimum azeotrope, and the azeotropic temperature is close to the boiling point of n-propyl acetate, making it difficult to remove acetic acid efficiently. Due to the harsh requirements of the ink on the acetic acid and water content, the collected waste liquid cannot be directly reused.
The common disposal method for printing enterprises is to dispose the collected waste liquid or send the concentrated volatile organic compounds to the RTO incinerator. This makes the waste liquid treatment without economic benefit, and can not exert its due value, causing huge waste. If the n-propyl acetate and the n-propanol solvent in the waste liquid can be recovered, the water and acetic acid content in the recovered solvent can be controlled, and the recovered solvent can be used indiscriminately; if the content of propylene glycol methyl ether or propylene glycol ethyl ether can be controlled, the recovered solvent can be transported to other enterprises needing the n-propyl acetate and the n-propyl alcohol solvent, such as enterprises adopting the same type of ink.
Disclosure of Invention
The invention aims to provide a process for recovering an n-propyl acetate-n-propanol solvent from waste liquid in the printing industry and an operation method for separating and recovering the high-purity n-propyl acetate-n-propanol solvent by using the process. The separation operation process is simple, can improve the recovery rate of the n-propyl acetate-n-propanol solvent, and can reduce the environmental pollution while improving the economic benefit of enterprises.
The object of the invention can be achieved by the following measures:
a method for recovering an n-propyl acetate-n-propanol solvent from waste liquid in the printing industry comprises the following steps: washing waste liquid collected by an adsorption and desorption device in the printing industry by using alkaline solution to remove acetic acid; distilling to remove salt dissolved in the waste liquid; rectifying by two rectifying towers, and separating to obtain n-propyl acetate-n-propanol solvent; the top of the rectifying tower 1 of the two rectifying towers adopts a reflux tank with a phase splitting function to reflux the oil phase and extract the water phase, and the top of the rectifying tower 2 obtains the n-propyl acetate-n-propanol solvent.
The raw material liquid used by the invention is a waste solvent generated in the printing industry process. Because the conditions of the solvents in the ink preparation and use process or the adsorption and desorption process are different, the content of the same solvent in each batch is different. The waste liquid collected in the process of the printing industry mainly contains n-propyl acetate, n-propanol, acetic acid, water, propylene glycol monomethyl ether and/or propylene glycol diethyl ether. Further, the printing industry process collection waste contains: 70 to 99 percent of n-propyl acetate, 0.1 to 30 percent of n-propanol, 0.1 to 5 percent of acetic acid, 0.1 to 5 percent of water, 0 to 5 percent of propylene glycol methyl ether and 0 to 5 percent of propylene glycol ethyl ether.
Washing the collected waste liquid with alkali liquor, wherein the adopted equipment can be conventional equipment in the industry, such as a stirring kettle, a mixing tank, an extraction tower and the like. The alkaline solution is one or more of sodium carbonate solution, sodium bicarbonate solution and sodium hydroxide solution. Preferably selecting a stirring kettle, respectively conveying the waste liquid and the alkali liquor to the stirring kettle, operating at 20-40 ℃, stirring for 0.1-5 hours, standing for 0.1-5 hours, separating phases, taking out the upper phase liquid, and conveying to a distillation device. The lower phase liquid is replaced or supplemented according to the degree of acid removal of the upper phase.
The distillation equipment adopts the conventional equipment in the industry. The pressure of the distillation treatment is 0.01-101kPa, the temperature is 30-140 ℃, impurities (such as salt) dissolved in the collection process and salt dissolved in the acid removal process are removed in a distillation mode, so that the impurities are prevented from being separated out in the rectifying tower after entering the rectifying tower, and the internal parts or pipelines of the rectifying tower are blocked.
The number of theoretical plates of the rectifying tower 1 is 5-50, preferably 10-30, and the feeding position is the middle part of the tower; a split-phase reflux tank is adopted at the tower top and is attached with a jacket, cooling water is introduced into the tower top, and the temperature of the split-phase reflux tank is kept at 25-40 ℃; the upper phase (oil phase) of the phase-splitting reflux tank is refluxed to the top of the rectifying tower 1, and the lower phase (water phase) is extracted. And (3) conveying the tower bottom material liquid of the rectifying tower 1 to a rectifying tower 2 for further rectifying treatment.
The number of theoretical plates of the rectifying tower 2 is 5-50, preferably 10-30, and the feeding position is the middle lower part; the reflux ratio of the rectifying tower 2 is 0.3-4.0: 1; the purity of the n-propyl acetate-n-propanol mixed solvent obtained from the tower top reaches up to 99.9 percent, and the recovery rate reaches up to 98 percent; the heavy component products of propylene glycol methyl ether and/or propylene glycol ethyl ether are obtained at the bottom of the tower.
The rectifying tower can be a conventional rectifying tower in the industry, such as a packed tower, a plate tower, a supergravity rectifying tower and the like.
Drawings
FIG. 1 is a process flow diagram of the present invention.
In the process, the waste liquid collected by an adsorption and desorption device in the printing industry is washed by alkaline solution, and then acetic acid is removed; removing dissolved salts from the waste liquid by distillation treatment; rectifying by using two rectifying towers, and separating to obtain a high-purity n-propyl acetate-n-propanol solvent; the top of the rectifying tower 1 of the two rectifying towers adopts a reflux tank with a phase splitting function to reflux the oil phase and extract the water phase, and the top of the rectifying tower 2 obtains the high-purity n-propyl acetate-n-propanol solvent.
Detailed Description
The detailed flow structure and operation method of the present patent will be described in detail below with reference to the accompanying drawings.
In a specific embodiment, the method comprises 3 main parts of acid removal process, distillation impurity removal and rectification recovery. Washing the waste liquid with alkaline solution (one or more of sodium carbonate, sodium bicarbonate and sodium hydroxide) to remove acetic acid; removing the dissolved salt in the waste liquid by a distillation treatment mode; rectifying by two rectifying towers, and separating to obtain the high-purity n-propyl acetate-n-propanol solvent: because water and n-propyl acetate form the lowest azeotrope, the lowest azeotrope is easy to extract from the top of the rectifying tower 1, phase separation is carried out in a reflux tank after cooling to form a water phase and an oil phase, the water phase is mainly water, the oil phase is mainly n-propyl acetate, and the oil phase is refluxed from the top of the rectifying tower 1; the kettle materials extracted from the tower kettle of the rectifying tower 1 mainly comprise n-propyl acetate-n-propanol solvent and a small amount of propylene glycol methyl ether and/or propylene glycol ethyl ether solvent; according to the requirements on propylene glycol methyl ether and/or propylene glycol ethyl ether, whether the propylene glycol methyl ether and/or propylene glycol ethyl ether needs to enter the rectifying tower 2 is judged, the propylene glycol methyl ether and/or propylene glycol ethyl ether is taken as a heavy component and is extracted from the bottom of the rectifying tower 2, and an n-propyl acetate-n-propanol solvent is extracted from the top of the rectifying tower 2.
The process of this patent is further described below with reference to examples.
Example 1
There was a batch of collected waste liquor consisting of 90.5% n-propyl acetate, 3.3% water, 3.8% n-propanol, 0.5% acetic acid, 1.9% propylene glycol methyl ether. And conveying the waste liquid to a stirring kettle, adding a saturated sodium carbonate solution, stirring at 30 ℃ for 1 hour, and standing for 1 hour for layering. The oil phase is the upper layer and the water phase is the lower layer. Acetic acid was removed from the oil phase and the water content was reduced from 3.3% to 2.1%. And (3) conveying the oil phase into a distillation tank, distilling at the pressure of 5 kPa and the temperature of 80 ℃, collecting distillate, and introducing collected condensate into a rectifying tower 1, wherein the collected condensate comprises 92% of n-propyl acetate, 2.1% of water, 3.9% of n-propanol and 2% of propylene glycol monomethyl ether. The number of theoretical plates of the rectifying tower 1 is 20, the materials are fed from 12 plates, the operating pressure of the whole tower is normal pressure, the temperature of a phase separator at the top of the tower is 25 ℃, the water phase in the phase separator is extracted, and the oil phase reflows from the top of the rectifying tower 1. And (3) conveying the kettle material extracted from the kettle of the rectifying tower 1 to the rectifying tower 2. The number of theoretical plates of the rectifying tower 2 is 20, the materials are fed from 14 plates, the operating pressure of the whole tower is normal pressure, the reflux ratio is 2.5, and a mixed solvent of n-propyl acetate and n-propanol is extracted from the top of the tower, wherein the content of the n-propyl acetate is 96.08 percent, the content of the n-propanol is 3.85 percent, the total content is 99.93 percent, and the recovery rate is 97 percent.
Example 2
There was a batch of collected waste liquor consisting of 94% n-propyl acetate, 2% water, 1% n-propanol, 0.6% acetic acid, 2.4% propylene glycol ether. And (3) conveying the waste liquid to a stirring kettle, adding a saturated sodium bicarbonate solution, stirring at 35 ℃ for 2 hours, and standing for 0.5 hour for layering. The oil phase is the upper layer and the water phase is the lower layer. Acetic acid in the oil phase was removed. Conveying the oil phase into a distillation tank, distilling under the pressure of 2 kPa at 100 ℃, collecting distillate, and introducing collected condensate into a rectifying tower 1, wherein the collected condensate comprises 94.8% of n-propyl acetate, 1.8% of water, 1% of n-propanol and 2.4% of propylene glycol monomethyl ether. The number of theoretical plates of the rectifying tower 1 is 25, the materials are fed from 15 plates, the operating pressure of the whole tower is normal pressure, the temperature of a phase separator at the top of the tower is 25 ℃, the water phase in the phase separator is extracted, and the oil phase reflows from the top of the rectifying tower 1. And (3) conveying the kettle material extracted from the kettle of the rectifying tower 1 to the rectifying tower 2. The number of theoretical plates of the rectifying tower 2 is 20, the materials are fed from 13 plates, the operating pressure of the whole tower is normal pressure, the reflux ratio is 2.5, and a mixed solvent of n-propyl acetate and n-propanol is extracted from the top of the tower, wherein the content of the n-propyl acetate is 99.06 percent, the content of the n-propanol is 0.82 percent, the total content is 99.88 percent, and the recovery rate is 98 percent.
Example 3
There was a batch of collected waste liquor consisting of 88.4% n-propyl acetate, 3% water, 8% n-propanol, 0.4% acetic acid, 0.2% propylene glycol methyl ether. And (3) conveying the waste liquid to a stirring kettle, adding a saturated sodium bicarbonate solution, stirring at 35 ℃ for 2 hours, and standing for 0.5 hour for layering. The oil phase is the upper layer and the water phase is the lower layer. Acetic acid in the oil phase was removed. Conveying the oil phase into a distillation tank, distilling under the pressure of 2 kPa at 100 ℃, collecting distillate, and introducing collected condensate into a rectifying tower 1, wherein the condensate consists of 89.6% of n-propyl acetate, 2% of water, 8.1% of n-propanol and 0.2% of propylene glycol monomethyl ether. The number of theoretical plates of the rectifying tower 1 is 30, the materials are fed from 18 plates, the operating pressure of the whole tower is normal pressure, the temperature of a phase separator at the top of the tower is 28 ℃, a water phase in the phase separator is extracted, and an oil phase reflows from the top of the rectifying tower 1. And (3) conveying the kettle material extracted from the kettle of the rectifying tower 1 to the rectifying tower 2. The number of theoretical plates of the rectifying tower 2 is 20, 12 plates are fed, the operating pressure of the whole tower is normal pressure, the reflux ratio is 1.5, and a mixed solvent of n-propyl acetate and n-propanol is extracted from the top of the tower, wherein the content of the n-propyl acetate is 91.74%, the content of the n-propanol is 8.04%, the total content is 99.78%, and the recovery rate is 95%.
It should be understood that after reading the above description of the present invention, various changes or modifications can be made by those skilled in the art to the relevant conditions of the present invention, and these equivalents also fall within the scope of the appended claims of the present application.
Claims (6)
1. A method for recovering n-propyl acetate-n-propanol solvent from waste liquid in printing industry is characterized in that the acetic acid in the waste liquid is removed by washing the waste liquid collected by an adsorption and desorption device in the printing industry with alkaline solution; distilling to remove salt dissolved in the waste liquid; rectifying by two rectifying towers, and separating to obtain n-propyl acetate-n-propanol solvent; the top of the rectifying tower 1 adopts a reflux tank with a phase splitting function to reflux the oil phase and extract the water phase; the tower top of the rectifying tower 2 obtains an n-propyl acetate-n-propanol solvent;
the printing industry waste liquid through adsorbing desorption device collection contain: 70 to 99 percent of n-propyl acetate, 0.1 to 30 percent of n-propanol, 0.1 to 5 percent of acetic acid, 0.1 to 5 percent of water, 0 to 5 percent of propylene glycol methyl ether and 0 to 5 percent of propylene glycol ethyl ether;
the number of theoretical plates of the rectifying tower 1 is 5-50, the feeding position is the middle part of the rectifying tower, the number of theoretical plates of the rectifying tower 2 is 5-50, and the feeding position is the middle lower part;
the reflux ratio of the rectifying tower 2 is 0.3-2.5: 1.
2. The method according to claim 1, wherein the alkaline solution is one or more of a sodium carbonate solution, a sodium bicarbonate solution, and a sodium hydroxide solution.
3. The method according to claim 1, wherein the pressure of the distillation treatment is 0.01 to 101kPa and the temperature is 30 to 140 ℃.
4. The method according to claim 1, wherein the phase separation reflux drum of the rectification column 1 is provided with a jacket and cooling water is introduced therein to maintain the temperature of the phase separation reflux drum at 25-40 ℃.
5. The method as claimed in claim 4, wherein the upper phase in the phase separation reflux tank is an oil phase, the lower phase is a water phase, the oil phase is refluxed to the top of the rectifying tower 1, and the water phase is extracted.
6. The method according to claim 1, wherein the purity of the obtained n-propyl acetate-n-propanol mixed solvent is up to more than 99.9%, and the recovery rate is up to 98%.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4210566A (en) * | 1978-12-26 | 1980-07-01 | American Can Company | Jet ink compositions |
| CN101466803A (en) * | 2006-06-12 | 2009-06-24 | 东洋油墨制造株式会社 | Printing ink composition of solvent recovery/reuse type, diluent solvent, and method of reusing recovered solvent |
| JP2010037286A (en) * | 2008-08-06 | 2010-02-18 | Ueno Fine Chem Ind Ltd | Method for producing n-propyl acetate |
| CN104557529A (en) * | 2014-12-26 | 2015-04-29 | 江苏九天高科技股份有限公司 | Refining method and device for n-propyl acetate esterification synthesis |
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2018
- 2018-11-28 CN CN201811432697.4A patent/CN109809994B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4210566A (en) * | 1978-12-26 | 1980-07-01 | American Can Company | Jet ink compositions |
| CN101466803A (en) * | 2006-06-12 | 2009-06-24 | 东洋油墨制造株式会社 | Printing ink composition of solvent recovery/reuse type, diluent solvent, and method of reusing recovered solvent |
| JP2010037286A (en) * | 2008-08-06 | 2010-02-18 | Ueno Fine Chem Ind Ltd | Method for producing n-propyl acetate |
| CN104557529A (en) * | 2014-12-26 | 2015-04-29 | 江苏九天高科技股份有限公司 | Refining method and device for n-propyl acetate esterification synthesis |
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