| As China promotes the green and low-carbon transformation of its energy system,the importance of fuel ethanol as biomass energy is becoming increasingly evident.Using sugarcane molasses as raw material to produce fuel ethanol is a model of comprehensive utilization of biomass resources,but the single treatment method of molasses alcohol wastewater discharged from the production process is difficult to meet the discharge standard.In this paper,the COD of molasses alcohol wastewater evaporation gas condensate water reflected by the industry is too high,because of the limitation of detection technology,the cause is difficult to verify the problem,solve the problem of wastewater detection technology,and put forward the treatment process scheme of molasses alcohol wastewater containing low boiling matter.A headspace solid phase microextraction（HS-SPME）method was selected for the analysis of volatile organic compounds in molasses alcohol wastewater due to the complex substrate.The standard addition method was used to quantitatively correct the content of low boiling point components.The parameters of SPME extraction mode,extraction head,sample volume,extraction temperature,sample ionic strength and extraction time were optimized.The method has good reproducibility and precision.The volatile organic compounds（VOCs）in molasses alcohol wastewater were qualitatively analyzed by GC/MS and standard material comparison,and 37 compounds were identified.The contents of ethanol and ethyl acetate in molasses alcohol wastewater determined by standard addition method were 2.853×10-3g/m L and2.616×10-6g/m L,respectively.The limits of detection（LOD）and limits of quantification（LOQ）were 0.295×10-6g/m L and 0.0835×10-6g/m L,respectively.The limits of quantification（LOQ）were 9.83×10-6g/m L and 0.278×10-6g/m L.The spiked recoveries of ethanol and ethyl acetate were 96.11%-105.4%and 83.82%-102.6%respectively.Ethanol is the most important organic matter with low boiling point in molasses alcohol wastewater,which is the main reason for the high COD of steam condensation water in the concentration process.A four-effect evaporation model of molasses alcohol wastewater was established by Aspen Plus to simulate the ethanol content measured by HS-SPME method in feedstock.The error of simulation results was within acceptable range.In view of the high COD caused by the presence of ethanol in the vaporized water,two post-treatment schemes of concentrated vaporized water treatment and four-effect flow distillation were proposed,and the two schemes were simulated by Aspen Plus to optimize the operating parameters of each equipment.Scheme 1:steam condensed water centralized treatment process.The COD of water purification is 395.8mg/L,the reboiler load is 8.77MW,and 89.5 tons of ethanol can be recovered every year.Scheme 2,steam condensed water four-effect distillation process,the COD of water purification is365.2mg/L,the reboiler load of the I-effect retreatment tower is 3.26MW,and 91.5 tons of ethanol can be recovered every year.Depreciation of the device is calculated in 10 years,the treatment cost of scheme 1 and scheme 2 is 16.2 yuan/ton and 7.4 yuan/ton respectively.Comprehensive multiple costs,scheme 2 has more advantages in energy consumption,total cost scheme 2 has more advantages. |
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