Multiple Recycling Of Cellulose Ethanol Fermentation Wastewater In Biorefinery Pretreatment Process

The production of cellulose fuel ethanol from lignocellulosic biomass feedstock will produce a large amount of high COD fermentation wastewater.Wastewater treatment process is complicated and expensive.Different from corn ethanol,cellulosic ethanol factory are generally built in rural areas where are close to raw materials due to the limitation of the raw material collection radius.Rural areas have weak infrastructure.The technical characteristics of high wastewater discharge make it difficult for the cellulosic ethanol industry to expand on a large scale.In order to find a practical way to discharge cellulose ethanol wastewater,this paper attempts to recycle cellulose ethanol fermentation wastewater to the pretreatment stage of biorefinery.Cellulose ethanol fermentation wastewater is used to configure the dilute acid catalyst of pretreatment.Study the feasibility of wastewater recycling.The first part of this paper study the feasibility of directly recycling cellulose ethanol fermentation wastewater to the pretreatment stage of biorefinery.The cellulose ethanol fermentation wastewater is used directly in the pretreatment step of the next round of biorefinery process,and it is recycled repeatedly in this way.After two rounds of recycling,it was found that the production of cellulose ethanol decrease with the increase in the number of direct use of fermentation wastewater,the magnitude of which was that the ethanol production after each reuse was about 5%lower than the previous one.The reason why the decrease in the ethanol production for the direct recycling of fermentation wastewater was found.It was found that the concentration of metal salt ions in the fermentation wastewater was rapidly enriched with the number of direct cycles,resulting in ethanol fermentation efficiency and the gradual decline in production.In the second part of this paper,an improved experiment was conducted on the recycling of ethanol fermentation wastewater.Before each cycle,the fermentation wastewater was evaporated and condensed to remove metal salt ions in the wastewater.Distilled water was used in the next round of pretreatment step.The fermentation results of wastewater reuse showed that the ethanol concentration in the three cycles of wastewater reuse was 76.42 g/L,76.61 g/L,and 75.82 g/L,respectively close to the ethanol concentration of normal biorefinery(77.85 g/L).Wastewater reuse to produce ethanol can proceed normally.For every 1t of wheat straw biorefinery,the amount of fresh water used is reduced from 2.868 t to 0.423 t.The reuse of wastewater reduces the use of fresh water.This solution is extremely effective in solving the problem of rapid enrichment of metal salt ions in the reuse of fermentation wastewater.The biological refining efficiency is effectively guaranteed,but the steam energy consumption is huge.The rationality is based on the uniqueness of lignocellulose biological refining process.After cellulose ethanol rectification,solid-liquid separation will produce a large amount of lignin residue with high calorific value.The heat is enough to provide energy for the evaporation and condensation of fermentation wastewater,and 60%of the lignin residue remains after heat production.In summary,this paper successfully recycles the cellulose ethanol fermentation wastewater in the biorefinery pretreatment process.The ethanol production after each reuse is very close to the normal biorefinery ethanol production.The recycling of cellulose ethanol wastewater effectively reduces the production cost of ethanol and provides a reasonable and effective solution for the treatment of cellulose ethanol wastewater.