A stainless steel (stainless acid resistant steel) tubular Baijiu cooler is currently used in the production of Baijiu in the liquor making workshop of a distillery, and a large amount of cold water is required to meet the needs of cooling liquor production. After the cold water flows through the cooler, it will be discharged when the temperature rises, and the cold water will only be used once. In addition, the hardness of the water supply used for production is high. The water quality is worse and the calcium and magnesium ion concentration is higher due to evaporation and contact with the atmosphere during the cooling process, which will cause serious scaling, corrosion and corrosion on the process equipment (sh è b è i), making the heat exchange process difficult to proceed smoothly, increasing the use of cooling water. With the increase of the market, the production water consumption and wastewater discharge of the distillery are increasing year by year, and the original production cooling water is not recycled reasonably, wasting water resources. Therefore, reasonable recycling of production cooling water can save a lot of water resources every year. This is a positive response to the national energy conservation and emission reduction policy and will be put into effective measures.
Closed circulating water cooling system is configured for water cooling of production equipment. A cooling water system that uses water as the cooling medium and circulates. The cooling system uses water to cool and remove the heat emitted by the process medium or heat exchange equipment. After the cold water flows through the production equipment (often called heat exchange equipment, such as heat exchanger, condenser (category: heat exchange equipment), reactor) that needs to be cooled, the temperature rises. When the heated cold water flows through the cooling equipment, the water temperature drops back. The cold water can be pumped back to the production equipment for recycling. The consumption of cold water is greatly reduced, often saving more than 95%. Cooling water accounts for about 70% of industrial water consumption. Therefore, the circulating cooling water system plays a role in saving a large amount of industrial water. The purpose of circulating cooling water is to effectively save water resources and reduce heat pollution.
2. Control requirements for cooling circulating water system in liquor workshop
According to the long-term research and production data, it is finally concluded that the requirements for the control of the cooling circulating water system of the Maotai flavor Baijiu making workshop are: the ambient wet bulb temperature is 28 ℃, the cooling water demand of one production room is 25m3/h, the total water demand of four buildings is 100m3/h, the water temperature before cooling is 55 ℃, and the water temperature after cooling is 32 ℃.
3. Feasibility analysis
(1) Water saving efficiency analysis
According to the data obtained from the investigation, the cooling water required by the system is 100m3/h, and the cooling temperature difference is 23 ℃. The consumption of evaporation water is about 0.16%/℃ of circulating water, that is, evaporation water consumption=100m3/h * 0.16%/℃ * 23 ℃=3.68m3/h. In order to reduce pipeline scaling (belonging to chemical residues) and inhibit microbial production, the controlled sewage discharge and make-up water volume are 5% of the circulating flow, that is, the sewage discharge volume=100m3/h * 5%=5m3/h. At the beginning of each cellar period, the whole water tank and the cooling tower should be flushed once. The water tank and cooling tower should be emptied. According to the maximum amount (the water tank is full before emptying), the water tank stores 60m3 of water, 0.5m3 for flushing, 2m3 for cooling tower, and 0.5m3 for flushing. Therefore, the shared water is 63m3. The flushing water consumption is calculated as 63/(20 * 16)=0.2m3/h based on the production time of 20 days and 16 hours per day.
Conclusion: Compared with non circulating water, sewage discharge and clean water consumption decreased by 94.8% and 91.12% respectively after using circulating water supply.
(2) Power efficiency analysis
According to the distance, elevation difference and flow between the pump station and the high-level pool, it is estimated that the power consumption for clean water is about 2 (kW/h)/m3, and that for sewage treatment (ch ǔ  l ǐ) Since the power consumption in the downstream can be ignored, that is, the power consumption of non circulating water supply is about 2 (kW/h)/m3. Electric energy consumption=booster pump 30kW+fan 11kW * 2+apron pump 1.5kW * 2+filter 2kW+control loop 1kW=58kW, circulating water volume 100m3/h, frequency conversion control is adopted for the system, and the average electric energy consumption is 0.464 based on the energy saving coefficient of 0.8
（kW/h）/m3。
Conclusion: Compared with the data, the electric energy consumption is reduced by 25.4% after using the circulating water, and the energy-saving effect is obvious.
(3) Technical feasibility
According to the circulating water volume and temperature difference, calculate the heat dissipation load, and select the HBY type cross flow cooling tower with good heat dissipation capacity, which can meet the requirements. The antifreeze problem of the spray water system of the closed cooling tower is usually that an electric heater is added in the water pan, which is generally started when the spray water is lower than 5 ℃ and stopped when the temperature is higher than 8 ℃. The temperature probe transmits the signal to the control cabinet to automatically control the start and stop of the electric heater. The power of the electric heater is determined according to the circulating water volume and the ambient temperature. According to the requirements of circulating water volume and pressure, the corresponding pumps are also conventional products, which are easy to meet.
4. System scheme (f) ā Ng à n) Design
(1) Scheme design of circulating cooling water
The cooling tower can be divided into open cooling tower and closed cooling tower according to whether the cooling circulating water is in direct contact with the atmosphere for cooling. The closed cooling tower is to place the tubular heat exchanger in the tower and ensure the cooling effect through the heat exchange of circulating air, spray water and circulating water. The air in the open cooling tower is in full contact with the water. The dust in the atmosphere continuously mixes with the water, causing bacteria and algae to breed; The pipe network is blocked due to salt dirt formed by evaporation, splash, leakage and concentration of cooling water; In addition, only ordinary filtering devices are installed in the system, which cannot completely remove these impurities, leading to the increase of water conductivity and corrosion of the pipeline; When the cooling water passes through the equipment to be cooled, the temperature rises, and the solubility of calcium and magnesium ions in the water changes, which will form scale. It reduces the heat exchange efficiency and affects the normal operation of the system. Therefore, the open cooling circulating water has problems such as scale, dirt, corrosion, bacteria and algae, pipe network corrosion and control of concentration multiple.
Closed cooling tower (also known as evaporative air cooler or closed cooling tower) is to place the tubular heat exchanger in the tower and ensure the cooling effect through the heat exchange of circulating air, spray water and circulating water. Because it is a closed cycle, it can ensure that the water quality is not polluted, which can protect the efficient operation of the main equipment and improve the service life. The closed cooling tower is divided into cross flow cooling tower and counter flow cooling tower according to the flow direction of the wind. The wind of the cross flow cooling tower enters from both sides and exits from above. The wind intersects with the spray water from below. The wind of the counter flow cooling tower enters from below and exits from above in the opposite direction to the spray water. Compared with the counter flow cooling tower, the cross flow cooling tower has the advantages of small fan power, small bulk water pump power, low noise, small floating water, daily maintenance during operation, modular assembly, and convenient expansion.
(2) Design of return water pipeline of power house
The liquor workshop consists of four production plants, each of which has four shifts. Eight shifts take one bus and use DN110 PPR environmental protection water supply pipes. A DN160 PPR environmental protection water supply pipe is gathered at the outlet of the cooling tower. All water pipes use PPR environmental protection water supply pipes, which fully comply with GB/M318,742.1, GB/M318,742.2, GB/M318,742.3 and GB/M317,219 health standards and relevant health and safety evaluation regulations of the Ministry of Health. PP-R product has heat resistance, pressure resistance, thermal insulation and energy conservation, long service life and economy (j ī Ng j ì) will gradually replace other existing types of water pipes and become the leading product.
The circulating water overflow pipe of each cooling tank is a DN32 PPR pipe, and a DN32 union ball valve is installed at the overflow outlet. Two overflow pipes of each shift collect water into the DN63 return pipe through DN63 to DN32 reducing joints; The overflow cooling water of the two distant shifts is collected into the DN110 return water pipe through the DN110 to DN63 special-shaped joint or reducer joint; The backwater of the last four shifts is collected into the DN160 header pipe and flows back to the water tank (components: high water tank, storage tank and low water tank) through the DN160 tee, DN160 to DN110, DN110 to DN63 reducer, and then passes through the basket filter to remove the slag before entering the water tank to ensure the return water quality. The antifreeze problem of the spray water system of the closed cooling tower is usually that an electric heater is added in the water pan, which is generally started when the spray water is lower than 5 ℃ and stopped when the temperature is higher than 8 ℃. The temperature probe transmits the signal to the control cabinet to automatically control the start and stop of the electric heater. The power of the electric heater is determined according to the circulating water volume and the ambient temperature. Among them, A12-03, A12-04 and A12-05 are located higher than the water tank, so they can borrow the pressure of water to return naturally, while A12-06 is located at the same level as the water tank, so the water should not return, so a circulating water pump is added to the main pipe.
(3) Full automatic control design of the system
The system adopts Siemens 200 PLC for data processing and control, realizing full automatic, unattended and keyless operation. There are many forms of such cooling equipment for closed cooling towers. The common feature is that water is sprayed outside the interwall heat exchanger and forced ventilation is adopted. Heat is transferred from the cooled fluid inside the interwall heat exchanger to the spray water outside the wall through the wall surface, and then transferred to the air through forced convection of spray water and air. The heat transfer of spray water to air is mainly composed of the latent heat of spray water evaporation and the sensible heat exchange of spray water and air.
       a.  Constant pressure water supply control: carry out PID control on the water supply pressure, control the frequency converter to adjust the speed of the booster pump, so that the pressure is stabilized at the set value.
       b.  Constant temperature water supply control: PID control of cooling temperature, control the frequency converter to adjust the speed of the draught fan, so that the temperature is lower than the set value.
       c.  Automatic start stop control: workers do not need to operate any buttons, just open/close the inlet valve of the ice tank, the system can be started/stopped, and idle shutdown can be achieved to save energy. When the production is stopped and the water inlet valve of the cooling cylinder is closed, there is no water flow in the pipeline, the pressure increases, and the system automatically enters the dormant state after the frequency converter has been working at low frequency for a long time, and all equipment stops running. When the water valve is opened, start the booster pump immediately when the water supply pressure is detected to be low, and quickly recover the water supply pressure.
       d.  Automatic water tank level control: control the make-up valve to keep the water level of the water tank within a certain range. When the water level of the water tank is lower than the set value, open the make-up valve. When the water level of the water tank is higher than the set value, close the make-up valve.
       e.  Automatic coarse filtration of water tank: 3mm filter screen and flushing and slag sweeping device are set in the water tank, which operate regularly to ensure that large impurities do not enter the water tank.
       f.  Pipeline fine filtration: install a 100 micron filter on the main water supply pipe to filter impurities larger than 100 microns and wash regularly.
       h.  Touch screen interface: display system topology diagram, display operation status of each device, display operation data, manually operate each device, set operation parameters, etc.
5. System operation benefit analysis
(1) Cooling effect: according to the operation data of 7 rounds of liquor, the water temperature of the system after cooling meets the design requirements, which is lower than 32 ℃.
(2) Constant pressure water supply: the outlet pressure of the booster pump is stable at 0.51MPa, and the water pressure at the farthest end is higher than 0.25MPa, which achieves the purpose of constant pressure water supply.
(3) Water condition: 1363m3 of water is added to the system in 7 rounds, including leakage caused by manually opening the original overflow port of the ice tank, water consumption for flushing slag, washing tools, etc. 12289m3 of water will be shared in this round in the production rooms 1, 2, 7 and 8 of the same workshop without circulating water.
(4) Power consumption: the power consumption of the circulating system in this round is 5731 (kW/h).
(5) Calculation of system cost saved in this round: based on electricity cost: unit price 0.71 yuan/(kW? H), water resource cost: unit price 0.05 yuan/m3, the water consumption of production room without system is 12289m3 according to statistics.
Water saving amount of the system: 12289-1363=10926m3;
System power saving: 10926m3 × 0.7（kW/h）/m3-5731（kW/h）=1917.2（kW/h）
System cost saving: 1917.2 (kW/h) 3 × 0.71 yuan/(kW? H)+10,926 m3 × 0.05 yuan/m3=1907.51 yuan.
(6) Calculation of energy conservation: the coal conversion coefficient of electricity is 0.36kg standard coal/(kW/h), and the coal conversion coefficient of water is 0.2429kg standard coal/cubic meter of fresh water.
Energy saved by the system: 10926m3 × 0.249kg standard coal/m3 fresh water+1917.2 (kW/h) × 0.36kg standard coal/(kW/h)=3410.766kg standard coal=3.412t standard coal
In this project (xi à ng m ù), 3.412 tons of standard coal can be saved in one round for one production room, with remarkable energy-saving effect.
6. Conclusion
Through investigation and demonstration, implementation of scheme design and operation observation, the project has systematically realized the cooling and recycling of production cooling water in the liquor workshop, reduced wastewater discharge, and ensured the supply of cooling water for liquor reception by all use teams. Fully meet the design requirements, and ultimately achieve the purpose of energy conservation and emission reduction.