Method for recycling biogas slurry and vinasse clear liquid and producing ethanol

Abstract

The invention discloses a method for recycling biogas slurry and a vinasse clear liquid and producing ethanol, and belongs to the technical field of wastewater treatment and ethanol fermentation industries. Calcium oxide is added into the biogas slurry obtained through anaerobic digestion to soften the biogas slurry, the softened biogas slurry is deaminized and then is mixed with the vinasse clearliquid, membrane separation is performed, and obtained filtrate returns to a crushing and mixing section as mixing water. After the biogas slurry is softened, the concentration of calcium ions is reduced to 20 mg/L or below, so the scaling problem of calcium carbonate in subsequent deamination and membrane separation operation is solved, and the device investment and operation cost of membrane separation are reduced; single-stage or multi-stage high-vacuum negative-pressure deamination is adopted, so that the risk of atmospheric secondary pollution is avoided, and the deamination operation cost is greatly reduced; and the biogas slurry and the vinasse clear liquid are mixed and subjected to membrane filtration, so bacteria in the biogas slurry and the vinasse clear liquid are eliminated,smooth ethanol fermentation is guaranteed, the operation pressure is lower than that of a tubular ultrafiltration membrane, and the operation cost is low.

Description

technical field [0001] The invention relates to a method for recycling biogas slurry and distiller's grains to produce ethanol, and belongs to the technical field of wastewater treatment and ethanol fermentation industry. Background technique [0002] Ethanol is an important industrial raw material, widely used in food, medicine, chemical industry and renewable energy and other fields. At present, more than 80% of the world's ethanol is mainly produced by fermentation. In the traditional process of liquid fermentation to produce ethanol, starchy raw materials are crushed, mixed with water, liquefied and saccharified, and then inoculated with yeast to ferment and distilled to obtain ethanol. At present, ethanol production mainly uses starchy crops such as cassava, corn, wheat, etc. as raw materials, and the ethanol fermentation level is generally 10-20% (v / v), and a large amount of distillation waste liquid will be produced after the fermentation liquid is distilled. Accord...

AI Technical Summary

Problems solved by technology

Stripping and deamination usually consumes 100-150kg of steam per ton of wastewater, high energy consumption and high cost

Secondly, whether it is air stripping or steam stripping, caustic soda or lime needs to be added before wastewater deamination to raise the pH of wastewater to above 10.5. The disadvantage of adding caustic soda is that the cost is high, and the concentration of sodium ions in wastewater increases. Low, but the deamination equipment is easy to scale, and needs to be cleaned and descaled with dilute acid from time to time, causing secondary pollution

[0009] In summary, in the disclosed technical solutions involving the reuse of distiller's lees clear liquor and biogas liquor (also known as anaerobic digestion liquor), there are still problems such as high cost of deamination and easy fouling of deamination equipment; secondly, biogas The hardness of the liquid is high, the calcium ion concentration is 400-600mg / L, and the alkalinity is as high as 4000-7000mg / L. During the membrane separation process, calcium carbonate precipitates and scales on the membrane surface, resulting in low membrane filtration flux, which requires additional investment to expand the filtration area of ​​membrane equipment. , increase the operating cost of membrane separation; although the reuse of part of the distiller's grains can reduce the sulfuric acid consumption in the ethanol production process and improve the utilization rate of raw materials, but because the distiller's grains contain microorganisms (miscellaneous bacteria) that are harmful to ethanol fermentation, some of the distiller's grains After the liquid is reused, the risk of bacterial contamination in ethanol fermentation is increased. Once contaminated, the acidity of the fermentation mash will increase and the utilization rate of raw materials will decrease.

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