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Ethanol recovery

Distillation - molecular sieve membrane coupling technique

Case 1:8 000 tons/year distillation - molecular sieve membrane coupling ethanol separation device

Used for synthetic drugs enalaprilat or cleaning drugs used for extraction solvent, in the process of the ethanol mother liquor containing acetic acid, sodium chloride, the byproduct in the process of drug synthesis and branched chain group, such as yellow, mother liquor has a stench, the conductivity of 600 ~ 1000 mu s/cm, water content of about 10 wt. %, ethanol to recycle, the moisture content must be 0.4 wt. % of the following is colorless and transparent. Original owner using ethylene glycol and potassium acetate as extraction agent, respectively on two kinds of mother liquor extraction distillation recycling, need to use 4 height only 20 ~ 25 m column, use the process while also accord with standard of recycled ethanol can be obtained, but there are high energy consumption, operation trival, open parking, when long time parking is easily blocked tower and glycol should be replaced periodically. So in view of the project the rectification - molecular sieve membrane coupling technology, the project will be acid-base neutralization device, distillation desalination plant dehydration and molecular sieve membrane equipment integration, step to complete removal of ethanol in inorganic acid, organic acid and water, and eventually get moisture acuities were 0.4 wt. %, colorless transparent enterprise recycling use standard qualified ethanol.

The process flow




Craft contrast

Comparison of recovery technology of enalapril ethanol mother liquor


Extractive distillation

Distillation-molecular sieve membrane coupling

Steam (t/t raw material)



Circulating water (m3/t raw material)



Low temperature water (m3/t raw material)



Electricity (kwh/t raw material)



Operating cost (yuan/t raw material)



Yield %



Maximum operating pressure (MPa(G))



Required steam pressure (MPa(G))

≥1 (recovery tower) 
≥0.4 (extraction tower)


Rectification tower installation height (m)




4-6 people/class

1~2 people/shift

Operational complexity

Complex, need to coordinate with many people, long parking time, stable equipment takes a long time

Simple, only one person can complete the parking work, the equipment can be stabilized in a short time


Long-term operation will lead to high-boiling impurities in the mother liquor of ethanol, salt mixed with ethylene glycol, ethylene glycol needs to be treated or replaced regularly, the equipment is easy to block the tower after long-term parking, cleaning is cumbersome

Molecular sieve membranes are strictly controlled on the properties of raw materials, requiring high attention and regular inspection by personnel, otherwise the membrane tubes are easily damaged.



Enalapril ethanol mother liquor recovery distillation - molecular sieve membrane coupling device


Acetonitrile recovery

Ceftriaxone sodium is a broad-spectrum and long-acting antibiotic released by Swiss Roche in 1982. It has a large market share with small dosage and side effects, and is the third generation of cephalosporin with broad-spectrum antibacterial activity. In the actual production, acetonitrile was used as the solvent in the preparation of ceftriaxone sodium crude from the raw material 7-aca. After the reaction, acetonitrile mother liquor was separated to obtain certain quality indexes, and then acetonitrile was recycled and used again as the reaction solvent. In the production process, acetonitrile inevitably mixes with water and other impurities to produce acetonitrile waste liquid. Since acetonitrile and water will form azeotrope (the water content of acetonitrile and water azeotrope is about 16 wt.% under normal pressure), it is impossible to directly separate and refine acetonitrile waste liquid into a reusable reaction solvent by conventional distillation method (the water content of solvent acetonitrile is usually ≤0.05wt.%). From this process, the quality of acetonitrile recovery has a decisive influence on the quality of ceftriaxone sodium crude products.

In the traditional process of recovering acetonitrile, there are four main separation and refining processes: variable pressure distillation, azeotropic distillation, salting out and dehydrating agent. These methods all use the two steps of coarse distillation and distillation, and the special distillation method is used for separation treatment, which has the problems of complex treatment method, high equipment cost, low separation efficiency, high energy consumption and low yield of acetonitrile.




1 is preheater, 2 is concentration tower, 3 is neutralization tank, 4 is impurity removal tower, 5 is superheater, 6 is pervaporation separation unit, 7 is percolating condenser, 8 is vacuum pump, 9 is refining tower.

The acetonitrile waste liquid from the synthesis of ceftriaxone sodium was put into the concentration tower and part of the water and recombination were removed by distillation. After concentration, acetonitrile distillate was sent to the neutralization tank to adjust ph. The neutralized acetonitrile distillation solution is sent to the impurity removal tower for further impurity removal. After removing impurities in the impurity removal tower, acetonitrile distillation solution enters the pervaporation membrane separation unit. After separation by pervaporation membrane separation unit, crude acetonitrile was obtained. The water in the solution on the feed-liquid side and a small amount of acetonitrile passed through the pervaporation membrane in the form of steam to obtain the percolation liquid, which was cooled and set and returned to the neutralization tank for recycling. The crude acetonitrile obtained from the pervaporation separation unit is sent to the refining tower for refining, and the finished acetonitrile is obtained. The acetonitrile from the distillation tower is returned to the acetonitrile recovered from the impurity removal tower.




Recovery of isopropanol

A distillation - pervaporation membrane coupling technique

The isopropanol feed liquid from the production process is transported by the feed pump. After heat exchange with the finished membrane product, it enters into the distillation tower and is pressurized continuously. After full reflux and stable operation, isopropyl alcohol steam with water content of ~12wt.% is extracted from the top of the distillation tower. After partial condensation by the separator, it flows into the reflux tank and is transported to the top of the distillation tower by reflux pump. The membrane separation unit is composed of several membrane components in series. The water in the raw material and a small amount of isopropanol permeate through the membrane components from the upstream side of the membrane to the downstream side of the membrane. The final product is obtained at the upstream side of the membrane. On the downstream side of the membrane, the vapor pressure difference between the upstream and downstream components of the membrane is formed by means of vacuum extraction and condensation. The percolating liquid vapor is pumped into the condenser by the vacuum unit, and the condensed percolating liquid is sent to waste water for treatment. The waste liquid in the distillation tower is cooled by the cooler and then sent to the wastewater treatment.







Shenyang sanjiu pharmaceutical co., LTD. 3000 tons/year distillation - molecular sieve membrane coupling isopropanol separation device

B adsorption-pervaporation membrane coupling technique

Zhangjiagang kalen chemical 34400 tons of ethanol, isopropanol dehydration projects: the enterprise adopts the isopropyl acetate and hydrogen as raw material, through the catalyst, acetic acid isopropyl ester hydrogenation reaction of ethanol and isopropyl alcohol, but in ethanol and isopropanol product separation process, due to the presence of a small amount of moisture separation process is complicated, so we must separate the reaction mixture after removing water production to further obtain ethanol and isopropyl alcohol. Sent to the original process will reaction liquid molecular sieve adsorption process isopropyl alcohol dehydrated by anhydrous ethanol mixture, further more refined products, the molecular sieve adsorption process, the molecular sieve adsorption saturation after need to stripping, stripping of 2 ~ 3% ethanol, isopropanol aqueous mixture can't handle, and the water mixture annual production of about 34400 tons, if not effective recycling, the yield of the entire production line, economic benefits and environmental pressure will be serious test. Therefore, the enterprise orders a set of molecular sieve membrane dehydration device of ethanol isopropyl alcohol mixed system from jiangsu jiutian high-tech co., LTD., which has a treatment capacity of 34,400 tons/year. It is used to treat the desorption solution generated by molecular sieve adsorption device.




Molecular sieve adsorption - molecular sieve membrane coupling device for the hydrogenation of isopropyl acetate to ethanol isopropyl alcohol

After adopting this technology, it is calculated that compared with traditional technology, each ton of products can save 1.2 tons of steam and 90m3 of circulating water, and at the same time significantly reduce labor and environmental protection costs, adding 9 million yuan of benefits every year, greatly improving the competitiveness of enterprises in the market.