1. Biological method, the typical biological enzymatic catalysis process technology is the biological enzymatic catalysis method of Japan Nitto Company. The process: one is bacterial culture to prepare biological enzyme catalyst; the other is AN hydration process, which is carried out under the action of biological enzyme catalyst. The production process has the characteristics of high selectivity, high yield, reaction at normal temperature and normal pressure, few by-products, high product quality, and low investment, Polyacrylamide company, polyacrylamide production technology.
my country's biological enzyme catalysis method has been successful in the fields of strain screening, strain cultivation, fermentation technology, immobilized cell preparation, nitrile hydratase catalytic properties, catalytic reaction technology, product separation and other fields. The catalyst activity has reached the international advanced level. Level (Japan Nitto's enzyme is 2480u/mL, domestic is 2857u/mL), the required equipment and raw materials are all localized. After the hydration reaction is completed in the production process, the AN conversion rate is greater than or equal to 99.9%, the acrylamide yield is close to 100%, and the concentration is 25% to 30%. Acrylamide does not contain harmful impurities such as copper ions and has high purity. It is an ideal raw material for the production of high molecular weight PAM.
1. Process overview
The culture medium of the seed tank is sterilized and then inoculated with the bacteria, and the culture is matured by controlling the temperature, pressure, and ventilation. Under the action of the pressure difference, the bacteria are injected into the fermentation liquid storage tank after the elimination, and the fermentation liquid centrifuge is hit The biologically active enzyme required for the hydration reaction is separated, diluted with water in the mixing tank, and the catalytic reaction kettle is driven by a pump. In the catalytic reactor, first hit the non-ionized water.
Under the control of the operator and the chromatograph, refined acrylonitrile is slowly added and combined with hydration to form acrylamide. After the reaction, the crude acrylamide solution is sent to the reaction solution centrifuge through the reaction solution storage tank to separate and remove the remaining bacteria in the reaction, and then sent to the crude acrylamide storage tank, and then sent to the gas stripping tank by the crude acrylamide transfer pump , By controlling a certain temperature and vacuum degree in the gas stripping kettle, the low boilers in acrylamide are removed. After air stripping, the acrylamide solution reaches the transfer tank, and then the acrylamide transfer pump is used to remove the macromolecular fibrin in the acrylamide solution in the membrane separation system. Because of the limited processing capacity of the membrane separation system, the crude acrylamide that cannot be processed is returned The transfer tank is formed by the pump and the acrylamide transfer tank-a cyclic treatment. The acrylamide solution separated by the membrane enters the carbon column tank for collation treatment and then enters the transfer tank. After the acrylamide transfer pump is pumped into the anion and cation exchange tower to remove the excess ions in the solution, it becomes a refined acrylamide monomer, which is driven into the refined acrylamide storage tank and sent to the polymerization workshop through the refined acrylamide transfer pump.
2. Process flow, mainly including AN raw material preparation, air purification, biological fermentation, catalytic reaction and acrylamide refining process, process flow, (1) AN raw material preparation. The purpose of this process is to remove the polymerization inhibitor (hydroquinone monomethyl ether) added during the storage and transportation of AN raw materials. The AN from the storage tank enters the flash tank after being heated, and flashes in a vacuum state. The gas phase is condensed and cooled and then enters the AN intermediate storage tank. Each process is continuously operated. (2) Air purification. The purpose is to produce oil-free, sterile air for bacterial culture. The compressed air (0.35MPa) is cooled to separate part of the moisture, and the dew point of the air is controlled below 20C. After reheating, it enters the total filter to eliminate the bacteria in the air and send it to the fermentation process. (3) Biological fermentation. Its role is to cultivate bacteria that produce nitrile hydratase. The first step is to send the culture medium to the seed tank, breeding tank, and fermentation tank; the second step is to use steam to strictly disinfect the equipment and culture solution; the third step is to transplant, propagate, and ferment to produce high Enzymatically active fermentation broth. This process is intermittent operation. (4) The catalytic reaction is the conversion of AN and H20 to AM under the action of a biological enzyme catalyst. The fermentation broth is produced by immobilized cell technology to produce a granular biological enzyme catalyst, which is fed into the catalytic reactor in a fixed proportion with water; the refined AN is metered and dropped into the catalytic reactor to control the AN in the solution in the reactor The concentration is between 3% and 4%, while controlling the temperature of the reactor. When AM reaches a predetermined concentration (AN concentration ≤500mg/L), enter the AM intermediate tank. The effective activity of the biological enzyme catalyst is two cycles. After the two cycles, it is separated by filtration and sent to incineration. (5) AM refining is to separate the light component impurities in the AM from the raw materials and the biological cells, organic matter, metal ions and other impurities in the culture medium, catalyst, and equipment. The AM aqueous solution is flashed under vacuum to remove the light component impurities brought in by the AN raw material; enter the activated carbon filter and ultrafiltration membrane to decolor, remove biological cells, organic matter, etc.; and then demetal ions by ion exchange resin, and the output meets AM water solution products required by subsequent processes, Polyacrylamide company, polyacrylamide production technology.
3. AM refining process, acrylamide produced by microbial catalyzed hydration with AN as the raw material must be refined, because the chain extender in the polymerization reaction is sensitive to the reaction of inorganic ions and organic impurities in the AM solution, which will greatly reduce PAM Relative molecular mass. The organic macromolecules in the enzyme cells and curing agent shed during the catalyzed hydration reaction will reduce the processing capacity of the activated carbon-ion exchange resin. The amount of AM monomer refined each time is only about ten times that of the resin, and the resin is frequent The regeneration increases the consumption of acid and alkali, increases the flushing water, reduces the life of the resin, and increases the cost. Shengli Oilfield has developed ultrafiltration membrane-positive bed refining technology, which greatly reduces the cost of using activated carbon-ion exchange resin, and also solves the problem of the impact on the relative molecular weight of PAM. Ultrafiltration membrane-positive bed refining process. The process can be composed of three parts: AM flash evaporation, AM refining, and ultrafiltration membrane refining.
(1) AM flashing.
The crude 28% AM from the hydration section is stored in the AM storage tank, and then pumped to the AM flash distillation tower, where it is flashed under high vacuum conditions to separate and remove the light component impurities and unreacted components in the raw material AN The trace amount of AN, AM is circulated to receive the kettle and pumped to the crude 30% AM storage tank. In order to improve the flashing effect, the flashing tower is equipped with an AM cycle process.
(2) AM refined. The AM solution in the crude 30% AM storage tank is sent to the activated carbon filter, the AM membrane refining device and the cation exchange bed by the pump to remove impurities and metal ions, and then sent to the refined 30% AM storage tank through the cooler, and finally passed through Pump to PAM unit.
(3) Ultrafiltration membrane refining. AM monomer (containing bacteria and other impurities) is filtered and sent to the AM circulation tank. After the AM circulation tank is full, the ultrafiltration circulation pump is turned on, and the material is filtered step by step to remove the large suspension in the monomer. In the cation exchange bed, a large amount of monomer is returned to the AM circulation tank. If the amount of ultrafiltration membrane passing material drops or the material supply is not timely, cleaning operations are required. Use desalinated water or air to press the residual AM monomer in the bag filter to the cation exchange bed, and part of the material is hydraulically transferred to the AM circulation tank, and then the ultrafiltration system is cleaned with desalinated water in the cleaning tank.
(4) Process parameters.
① Main process parameters of AM flash evaporation system.
Vacuum degree of AM flash evaporation system: >0. 05MPa;
Air volume of AM flash system: 3m'/h;
AM flashing system output: 6m'/h.
②Process parameters of ultrafiltration device.
Ultrafiltration operating temperature: <18C;
Refined capacity of ultrafiltration device: 6m'/h;
Operating pressure of ultrafiltration device: <0. 5MPa.
③Sun bed process parameters.
The discharge conductivity of the anode bed: <200μs/cm;
PH value of anode bed discharge: 5.4;
AM concentration of the anode bed discharge: 30%.
④ 30% refined AM storage tank process conditions.
Storage temperature in the tank: 13C in summer, 15C in winter;
Air volume in the storage tank: 0.025m) air/m';
The monomer concentration in the storage tank: 30%.