Study On Sepatation And Correlation Theory Of Dimethylbenzene And Butylacetate From Spent Solvent By Batch Distillation

The industrial spent solvent had some features, such as toxic, flammable, explosive, corrosive, reactive or volatile and so on. They were seen as the first class hazard waste material, they also had great harm to environmental and humanity's heathy. On the other hand, most of them had higher economic value, the price had rose from 4000yuan/ton to 14000yuan /ton with demands for dimethylbenzene upward trend year after year in all the countries , but it didn't satisfy the denmand. At present,The waste solvents oil was dealed with burning, diluted, vacuum distillation and solvent reacovery equipment.These methods had some defects, for instance it gave rise to a lot of organic solvents dissipation which had economic value, it caused serious water and atmosphere contamination, and it also consumed much energy or had highly reacovery cost. Therefore, from views of saving resorce, reducing the ecological and environmental pollution of waste solvents and realizing complex resource of waste solvents, Which exploiting new batch distillation polytechnic, equipment and theoretical studies which used to saving energy and diminishing displacement for dealing with the waste solvent had important environmental and economic benefit.The article reseach result was not only solve the contamination of the waste solvents oil which is from auto industry and the proccessing of producting pesticide and oil paint, but also separated the mixtures of organic from petrochemical works, pharmacy and electronic equipment .The studying had impornt signification.The preliminary treatment of spent solvent was researched, and obtained uncolor and transparent mixture solvent oil which applied with all total reflux technical to remove the other materials of the waste solvent oil. The spent solvent could be separated into dimethylbenzene and butylacetate with a new, energy saving and high efficiency batch distillation equipment. The dimethylbenzene and butylacetate products were obtained, simultaneously the azeotropic agent could be cycled using. A new and energy saving batch distillation column which all- condenser on top of column had the fuction such as condensation, reservoir, lamination and reflux was devised. The influence fators of batch distillation were studied, and the technical conditions of homogeneous batch distillation and heterogeneous azeotropic batch distillation were explored and optimized. The simulation calculation of the new batch distillation was finished.The accurated Vapor-liquid equilibrium facility was utilized to determine a series of vapor- liquid equilibrium datum from duality mixtures. It showed that the distance of the curve between gas and liquid was little and the different of volatizition was very little from the three groups datum of the Vapor-liquid equilibrium between butyl acetate/p-xylene, butyl acetate/ethyl benzene, and ethyl benzene/p-xylene. There was no azeotropic point in the vapor- liquid equilibrium curves, so the three object departments was not azeotropic. All the experimental data have been tested by the method proposed and the results showed that the experimental data conform to the demand of thermodynamic consistency.The variable reflux and the constant reflux ratios were employed to undertake the homogeneous batch distillation experiment for pretreated spent solvent, respectively, and the influences of the reflux ratio, separation time and distillation temperature on dimethylbenzene and butylacetate separation were investigated. The results showed as follows: (1) the variable reflux ratio could identify dimethylbenzene and butylacetate separation temperature range, and access to a certain purity of dimethylbenzene andbutylacetate, but the separation process is operated complicatedly, control difficult, low yields, and difficult to achieve large-scale production; (2) at different reflux ratios, the distillate of the distillation column was complicated in the initial stage of batch distillation, in addition to dimethylbenzene andbutylacetate , also contained a relatively quantitative of heavy components.The principal constituent was dimethylbenzene in distillate and caldron liquorat at advanced stage; (3) at reflux ratio R = 3,4,5,7, respectively, the comparisons of experimental results could be seen that the high reflux ratio is favorable in dimethylbenzene and butylacetate recovery, and this is different with continuous distillation; (4) the separation time was150min around, the temperature range of the butylacetate distilled was about 105-125℃and dimethylbenzene about 125-135℃, Using homogeneous batch distillation method to separate dimethylbenzene and butylacetate from the waste solvents which had been pretreatment; (5) the average yield of dimethylbenzene was 70% and butylacetate 80% by homogeneous batch distillation; (6) there were a high separation temperature, longer separation time and the energy of separation process too much for homogeneous batch distillation process.Because dimethylbenzene, butylacetate and water could synthesize low boiling point azeotropes, to realize separation of dimethylbenzene and butylacetate from spent solvent through hetegeneous azeotropic batch distillation, which water was used as azeotropic agent. The hetegeneous azeotropic batch distillation experimemt was done for pretreated spent solvent and the operating paramemters effect of temperature, time, oil and water ratio on separation efficiency were explored. The results showed as follows: (1) when water used as an entrainer for hetegeneous azeotropic batch distillation, the temperature was lower than 100℃and the process reduced energy consumption. (2) the recovery rates and puritys of dimethylbenzene and butylacetate would be significantly improved in contrast to conventional batch distillation. The recovery rate of dimethylbenzene was above 85%, and butylacetate nearly achieve around 99%. Meanwhile, the dimethylbenzenecan of 98% over could be acquired. (3) the time of hetegeneous azeotropic batch distillation was shorter than that of homogeneous batch distillation; (4) The ration of oil : water had little effect on the recovery of dimethylbenzene and butylacetate, but batch distillation temperature and energy in distillation process increased with the water increasing; (5) the water - n-butyl acetateazeotrope, the water– dimethylbenzene azeotrope , as well as the mixture of a small of the weight components were distilled off, at initial stage of distillation. (6) The dimethylbenzene and butylacetate could be constituted of low-boiling point azeotropic system, and these two kinds of goal product nearly could be carried over.The distillate of batch distillation was basically no losses, and thus, the volatile compared to homogeneous batch distillation was reduced. There was non-toxic, convenient to be acquired and recycled in contrast to conventional distillation which water was used as extrainer; (7) the purity of dimethylbenzene was above 99% by hetegeneous azeotropic distillation and the second refining.The simple effective mathematical model was established based on the material balance, vapor - liquid equilibrium equation and the quantity of heat perseverance calculation, and meanwhile, it also considered that the relative volatility was regarded as variables or constants. The model overcame the shortcomings that it do not forecast the outcome of the accuracy of the previous assumption which the relative volatility was of the constant, and it could predict more accurately the distillate concentration changes of multi-component batch distillation and hetegeneous azeotropic distillation top. Through the comprarison of batch distillation simulation and the experimental results, the results showed that the experimental datum and simulation was fit to good agreement after 40 min.The Aspen Plus simulation software was adopted to simulate continuously industrial process that separated dimethylbenzene and n-butyl acetateazeotrope from spent solvent. Considering of dimethylbenzene and butyl acetate's recovery and purity, the appropriate operating parameters of column design and performance were obtained, and laied foundation of industrial process.The spent solvent was treated by batch distillation, it is not only recoved important value industrial solvents and realized of comprehensive utilization, whlie reduced energy consumption process, but also reduced environmental pollution of industrial hazardous waste substance--spent solvents, which assumed a higher social and environmental benefits. By the benefit analysis, it should be known that annual savings of processing costs was 2,678,830,000yuan if 2,400 tons of each year, and annual savings of processing costs was more than 214,000,000,000 yuan if 20,000 tons each year. The technology had notable economic benefits and it was pertain to provising environmental protection technology, and owned wide industry prospects.