Study Of Ortho-xylene Oxidation And The Parameter Control Of Crude Phthalic Anhydride Separation Technology

Jinzhou Petrochemical Corporation introduced the 40,000 tons/yearphthalic anhydride apparatus from LURGI Corporation in Germany, whose designedproductivity capacity can reach up to 100g/Nm~3 and whose reactor is 7 meter indiameter, with 16,300 3.7-meter-long tube and a 3.4-meter catalyst filling height andthe catalyst being HYHL－III type from WACKER company. Since this equipmentwas completed and put into production in September, 2000, there have appearedseveral problems, for example, the reaction heating points are unstable andchangeable, and the datum mark is not rightly positioned in switching the condenserto control the cold and hot oil, thus bringing greater harm to the quality and the yieldof phthalic anhydride.This article, with the production technology of this set of equipment in JinzhouPetrochemical Corporation as background, by means of setting up math model and onthe basis of complete understanding of various technique process, equipment controland operational conditions, makes an analysis on the reaction between ortho-xyleneand air with phthalic anhydride as the product dynamically and draws a conclusiontheoretically about the hot spot distribution and puts forward a production controlprogram of the reactor according to the production practice. In the meantime, thisarticle makes a theoretical calculation about the material constituent property of thegas from the reactor outlet, sets up reaction products distribution model, gets an ideaof the distribution of phthalic anhydride oxidation products and the dew-points of allmaterials under different production capacities, poses a series of requirements overthe gas temperatures from the ends of gas cooler, pre-condenser and switchingcondenser, thus providing better theoretical basis for the optimization of the apparatuscontrol parameter, for the technological training of the production operational workersand for the production direction of the technique management staff, and guaranteeingthe normal working order of the equipment and increasing the product yield.The establishment of math model helped find the best control scheme, enhancedthe operational staff's ability in maintaining stable operation, reduced and avoided the unplanned shutdown, and decreased unnecessary energy waste and equipment losses. The reliability of the math model was tested by one year's production practice and achieved great success. In 2006, the average yield of this apparatus was 108%, the production of phthalic anhydride 45,000 tons, the yield increase 1.5% and the annual economic profit RMB3,200,000.