Study On Extraction Of Phenol From Coal Chemical Wastewater And Process Simulation

China's growing demand for natural gas,and coal clean gas is an effective way to ease the pressure of China's natural gas demand.Due to the high methane production and low investment,more than 90%of coal-based clean gas projects use fixed bed gasification.But the fixed bed gasification produced a large number of high concentrations of phenol wastewater,in addition to the unit phenol,polyphenols accounted for about 1/3 to 1/2 of total phenol.But at the same time,phenol has high added value as a basic chemical raw materials.However,the valuable recovery efficiency of phenols is not high in the industry.In this paper,how to efficiently recover phenolic compounds is studied by means of experiment and process simulation.After thoroughly analyzing the solvents such as esters,ketones,ethers and others,it is preferred that the sec-butyl acetate is used as the phenol removal agent.The effects of extraction conditions such as extraction temperature,solvent ratio and pH value on the reaction of phenol and polyphenols were studied.Then,two kinds of ternary compounds,"sec-butyl acetate-phenol-water" and "sec-butyl hydroquinone-hydroquinone-water",were measured by liquid-liquid equilibrium kettle combined with gas chromatography.at 25 ?,40 ?,50 ?.And also measured the "sec-butyl acetate-phenol-hydroquinone-water" quaternary system at 40 ?.After the binary interaction parameters were fitted by the activity coefficient equation,the extraction tower,solvent recovery tower and solvent stripping tower were simulated use binary interaction parameters,and the parameters of each tower were obtained.At this point,the extraction process conditions parameters and extraction process tower set parameters are got,after a small continuous extraction device test and verification,to achieve the best extraction and phenol remo-val effect.The experimental results are:(1)After the experiment,the optimum extraction conditions were obtained at pH=8,compared with R = 1:4-1:5 and the temperature T = 40-45 ?;(2)Through the liquid-liquid phase equilibrium experiment,two kinds of ternary systems,"sec-butyl acetate-phenol-water" and "sec-butyl acetate-hydroquinone-water",were obtained at 25?,40? and 50?,and the quaternary system "sec-butyl acetate-phenol-hydroquinone-water" were obtained at 40?.And the resulting data were thermodynamically verified.The results show that the correlation coefficient R2 values are greater than 0.99,indicating that the measured liquid-liquid equilibrium data is valid.The NRTL and UNIQUAC thermodynamic activity coefficient equation were used to correlate the obtained phase equilibrium data.The binary interaction parameters of each equation were obtained by regression.After the error analysis of the experimental value and the simulated value,the results showed the root mean square deviation(RMSD)were about 0.2%,indicating that NRTL and UNIQUAC activity coefficient model fit very well.(3)The Aspen flow simulation software was used to simulate the extraction tower,solvent recovery tower and solvent stripping tower using UNIQUAC and NRTL thermodynamic activity coefficient equation.Set the feed flow rate of 100t/h,the temperature is 40?,the pressure is 0.1 MPa.The extraction tower uses UNIQUAC equation,to determine the extraction sequence n = 6,extraction compared to R = 1:4.The solvent recovery tower and solvent stripping tower use NRTL to determine the solvent recovery tower theoretical plate number N = 10,the feed position for the fifth tray;solvent stripper theoretical plate number N = 5,the feed position is the first tray.The total phenol concentration decreased from 13000mg/L to 400mg/L,and the concentration of phenol decreased from 8750mg/L to 50mg/L after the parameters were determined,and the extractant recycling rate reached 99%or more.(4)The experimental results were verified by continuous experiment with small test device.When the extraction stage of extraction column was n = 6,solvent ratio =1:4,the total phenol removal rate was over 90%,the phenol removal rate was up to 96%.In conclusion,the process parameters of the extractant and the parameters of the industrial tower are optimized.The experimental results can provide the basic data for the industrial design and contribute to the reduction of environmental pollution.