| Acrylic Acid (AA) is a key raw material in chemical manufacturing industry and has a very extensive application range. Based on LanZhou Pretochemical Co. of CNPC 80,000 ton/yr acrylic acid project, two-step oxidation of propylene production of acrylic acid production process operating conditions were optimized through catalyst performance test.LanZhou Pretochemical Corp of CNPC acrylic acid item adopted two–step-oxidation propylene technics. The catalyst of the plant is provided by NKC corporation of Japane while the reactor comes from MAN-DWE corporation of German. The production capability is 80,000 ton/yr.Two-steps-propylene-oxidation method is an important way to produce acrylic acid. Propylene and oxygen in the air was used as the reactant and passed the catalyst bed with steam. Propylene was oxidated to acrolein in the first reactor. Then in the second reactor acrolein was continuously oxidated to acrylic acid. The catalyst was filled in reaction tube, and the reaction heat was moved by flowing heat transfer salt(HTS) which was circulated in the shell of the reactor and finally used for producing steam by heat exchange. Gaseous phase airylic acid from the reactor outlet was absorbed by water and turn into acrylic acid solution in the absorption tower, which was further purified through distillation by removing water and get pure acrylic acid.The operational parameter was optimized by testing the property of the NKC catalyst. The optimum parameters of oxidation reaction are as follows: the temperature in the first reactor is 320±10℃; the mole ratio of propylene:oxygen:water:nitrogen is 1/1.7/1/2.4, the space velocity of propylene is 95hr-1; the temperature in the second reactor is 260±10℃; the space velocity of acrolein is 96.5hr-1; the ratio of propylene to oxygen is 1/0.5. Under the optimum condition, the conversion of propylene in the forst reactor and the conversion of acrolein in the second reactor is over 98%and 99.85% respectively.According to the above results, the parameter was designed as follows: in the first reactor, feeding flow rate of propylene is 8t/h, the compressed air 54t/h, the steam flow rate 830kg/h, the circulate gas flow rate 18t/h, the temperature 320℃, in the second reactor, the compensatory air flow rate is 13.5t/h, the temperature 260℃. The main operating condition of absorption and distillation process is as follows: the content of acrylic acid at bottom of the absorption tower is 60%, the temperature at the top is 60℃, 19t/hr acrylic acid solution is feeded into the distillation tower and the flow from the acetic acid tower to the Azeotropic distillation tower is 50t/h; the top press of the distillation tower is 15.5kPa(A); the temperature at the bottom of this tower is 82℃; reflux ratio is 9; the flow to the Acetic acid tower is 61t/h; the temperature at the bottom of the tower is 90℃, the top press is 5.6kPa(A); the flow to the rectification tower is 14t/h; the press of the top is 2.9kPa(A); the temperature of the top is 53℃; the reflux ratio is 1.3 . |
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