A brief discussion on energy-saving technologies in alcohol production

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I. Innovation in efficient and energy-saving fermentation process technologies 　　　Our company has adjusted the crushing process, controlling the diameter of the crushed particles to be between 1.5 mm and 1.8 mm. The water-to-material ratio used in mixing is 1:2.5–2.8, and the mixing temperature is maintained at 70°C–75°C. Such high water temperatures and powder slurry concentrations are chosen in order to reduce steam consumption during the cooking process and to enable a fermentation process using a concentrated slurry. However, high water temperatures can cause the powder slurry to clump together. To resolve this contradiction, heat-resistant α-amylase is added at a dosage of 0.8ц/g to 1.2ц/g of starch; this causes the starch in the raw material to absorb water and swell, or part of the sugar solution to be rapidly hydrolyzed into dextrins, oligosaccharides, etc., under the action of the heat-resistant α-amylase. This approach not only prevents the slurry from clumping together but also helps to reduce the cooking pressure and temperature. 　　In high-concentration alcohol fermentation mixtures, less energy is required to separate the components. During alcohol production, the alcohol content of the fermented broth increases from 8.5% to 10%-11%, allowing for a savings of 350 kg of steam and 23 kWh of electricity per ton of alcohol produced; as a result, the fermentation efficiency improves significantly. Reduce waste liquid discharge and lower wastewater treatment costs. Per ton of alcohol, 1.0–1.3 tons of process water can be saved, and waste lees emissions can be reduced by 1.3–1.7 tons. Electricity consumption for the separation of alcohol waste liquids is also reduced, resulting in a savings of 20 yuan in water costs (Tables 1 and 2). 　　　II. Recycling of cooling water systems and innovation in water-saving technologies The alcohol production industry is a major water consumer, with cooling water accounting for the largest portion of this water usage. 　　Reprinted from Huaxia Wine News · China Wine Industry News Network. Water is not only an important raw material in alcohol production, but also a crucial substance for regulating the production process conditions and assisting in the manufacturing process. Considering the varying requirements of various process equipment in our company’s alcohol production for cooling water temperature, the hierarchical use of cooling water is adopted, and the addition of algicides and corrosion and scale inhibitors in the circulation tank can increase the circulation rate of the cooling water. 　　　A circulating cooling water system and a constant-pressure water supply system were installed to allow the water to be cooled and then reused; the cooling water loses heat through contact heat transfer and evaporation heat transfer. The cooler water with a lower temperature in the tank is sent to the heat exchanger for condensation via a constant-pressure water supply system. The water, after having its temperature raised in the cooler, flows back through the cooling tower, where it is cooled through convective contact between water and air, before being reused. During the circulating cooling process, a small amount of water is continuously lost due to evaporation, wind, and leaks from drainage systems; therefore, the circulating cooling water system requires a small amount of water to be replenished, which has resulted in significant water savings. 　　　The water-saving effect after the renovation is significant, at least 4,500 m3/day, resulting in over 1.48 million tons of water saved annually. 　　　The amount of groundwater extracted has been reduced by about 65%, which plays an important role in protecting water resources. 　　　Using the waste liquid from the distillation tower to scrub the fermentation tanks not only saves water but also serves a sterilizing purpose, reducing steam consumption. 　　　The cooling water from the first distillation cooler is cooled, and the spent liquid is separated for use in crushing and mixing; this reduces both water and steam consumption as well as the burden on wastewater treatment. 　　　III. Preheating of the distillation feed liquid Our company replaced the original preheater, with a surface area of 110 m2, with one that has a surface area of 150 m2. As a result of these technical improvements, the preheating efficiency increased, and the original preheating temperature rose from 60°C to 80°C. This reduction led to a 5%-7% decrease in the amount of steam required for feeding into the distillation column, allowing for a savings of 0.27 tons of steam per ton of alcohol produced. 　　　IV. Waste Heat Recovery Process The alcohol-containing mash is discharged from the bottom of the tower after distillation in a crude tower. At 110°C, the alcohol waste liquid enters the first-stage vacuum tank for waste heat recovery; after gas-liquid separation, it goes into the second-stage vacuum tank. Following another gas-liquid separation, the temperature of the alcohol waste liquid drops from 110°C to 80°C, after which it is sent to the wastewater treatment facility. 　　　At 110°C, the alcohol waste liquid enters the primary and secondary vacuum tanks; after gas-liquid separation, the remaining heat steam goes into the primary and secondary vacuum pumps. These pumps use negative pressure to extract the residual heat steam from the vacuum tanks, which is then utilized in the crude distillation tower. This approach allows for a savings of 0.5 tons of steam per ton of alcohol produced (see the process flow diagram for heat recovery). 　　　V. Renovation and upgrading of the alcohol distillation control system Alcohol distillation is the final step in alcohol production. For a long time, due to limitations in production conditions and a low level of automation, the output and quality of products have been constrained, especially in cases where the entire distillation process takes place within a distillation tower. Therefore, strict requirements are placed on process parameters such as temperature, pressure, and flow rate, and it is difficult to achieve ideal results using conventional manual operations. 　　　Therefore, our company’s upgrade and renovation of the original control system focus on the main functions of the automated control system. 　　　1. Process parameter monitoring: Regularly monitor parameters such as temperature, pressure, and flow rate during distillation. 　　　2. Timely control is implemented to automatically adjust important process parameters such as the top temperature and bottom temperature of the crude tower, the top temperature and middle temperature as well as the bottom temperature of the refined tower, the drum pressure, the steam supply to the crude tower, the steam supply to the refined tower, and the temperature of the condenser. 　　　3. Out-of-limit alarm: Upper and lower limit parameters can be set for both check points and control points; an alarm will be generated whenever the value is above the upper limit or below the lower limit. 　　　4. Record the entire process, including various inspection points, control points, alarm handling, and personnel operations. 　　　5. It can be switched between manual and automatic mode. 　　　Technical features: Parameters are not lost upon power loss, and it has strong anti-interference capabilities ； The system features a high degree of automation and excellent control precision ； The system has low costs and good practicality. 　　　After adopting this system, significant economic and social benefits have been achieved. According to Huaxia Wine News, with the postal distribution code 23-189, it can be subscribed to through local post offices. Alcohol production and quality have also improved markedly, with the product qualification rate increasing by 5–10 percentage points (Tables 3 and 4). 　　　VI. Innovation and advancement in energy conservation 　　　1. Using alcohol distillate filtrate and distillation cooling water for mixing materials helps save water and steam, reduces the burden on wastewater treatment, and enables the recycling of resources. 　　　2. Fermentation with concentrated mash increased the alcohol content of the mature mash, led to significantly improved fermentation results, reduced energy consumption, decreased wastewater discharge, and lowered the costs associated with wastewater treatment. 　　　3. By reusing circulating water, it reduces the consumption of water per ton of alcohol produced, thereby decreasing the amount of groundwater extracted, and plays an important role in protecting water resources. 　　　4. Reduce energy consumption by increasing the preheating temperature and reusing steam from waste heat recovery. 　　　5. After the upgrade of the automated control system, various process parameters are adjusted and controlled to improve production volume and quality.