Analysis of heat recovery of oil-free air compressor

Analysis of heat recovery of oil-free air compressor

1.The working principle of oil-free air compressor cooling

The air enters the first-stage low-pressure rotor pressurization and intercooler cooling through the filter, and then enters the second-stage high-pressure rotor pressurization and aftercooler cooling through the pipeline system, so that the high-oil compressed air is reduced to acceptable degree. The external cooling water enters the aftercooler, intercooler and oil cooler to cool high-temperature compressed air and high-temperature oil. The oil cools the low-pressure rotor and the high-pressure rotor through the pipeline system, and the high-temperature oil enters the oil cooler for cooling, and then circulates inside. For air compressor air compressed by the second-stage high-pressure rotor, it can generally reach a temperature of 180℃～190℃. After cooling, the compressed air temperature is generally controlled at 40℃～45℃ and enters the dryer for drying. The input of the air compressor About 90% of the power (mostly shaft power) is taken away as heat through the cooler and consumed in the environment.

　　2, current situation analysis

　　2.1 Current status analysis of air compressor system

　　 2 ZR200 recovery hot water situation.

　　ZR200 heat recovery analysis:

　　The recovery efficiency is 85%, and the loading rate is 90%. The heat that the two ZR200 air compressors can run for 20 hours at full load is:

　　6120kWH (400×85%×90%×20=6120kWH.).

　　2.2 Analysis of current situation of heating system

　　①Winter. Heating application + bath water = comprehensive application

　　A. Heating application

　　 The return water temperature of the heating pipeline in winter is about 50 degrees, the inlet water temperature is about 65 degrees, the air compressor can recover the temperature: up to 90 degrees, and the air compressor allows the cooling water inlet temperature to be up to 35 degrees. The air compressor heat energy recovery and heating, the outlet water temperature is higher than 65 degrees (up to 90 degrees), the return water temperature is lower than 35 degrees, 90% loading, 85% recovery. The daily circulation volume of heat recovery water = 174.86 tons. 400*0.85*0.9*3.6/4.2/(65-35)*20=174.86 tons.

　　 Available heating heat per hour=174.86*1.17/24*(65-50)=153.44kW.

　　 (Winter heating requires an outlet water temperature of 65 degrees and a return water temperature of 50 degrees.) The available heating area is: 153.44/0.12=1278. (According to the HVAC regulations, the heating area is 120W/calculated).

　　 The daily calories used for heating are:

　　3068.8kWH. (153.44*20=3068.8kWH)

　　3068.8kWH is equivalent to 11047MJ

　　 The calorific value of 180 tons of steam: 2520 MJ/ton

　　 The equivalent of saving steam per day is 5.5 tons. (Calculation of using 80% of steam thermal efficiency)

　　 Steam is 250 yuan/ton, and it can save 1375 yuan per day.

　　 130 days heating calculation, a winter heating can save 178750 yuan.

　　B. Bathing application

　　 The temperature of tap water in winter is about 0 degrees, and it needs to be heated to 50 degrees for workers to bathe.

　　 After heating, the hot water recovery temperature of the air compressor is about 50-55 degrees, which can heat the bath water to 45 degrees.

　　 2 ZR200 air compressors can recover heat per hour: 306kWH (400*0.85*0.9=306)

　　 Heating consumption per hour: 153.44kWH

　　The amount of heat that can be used to heat bath water per hour: 152kWH.

　　 Bath water can be heated from 0 degrees to 45 degrees per day: 2.9 tons/hour.

　　 can produce heated bath water all day: 58 tons/day (2.9*20)

　　 Heating bath water in winter can save steam: 5.5 tons.

　　A comprehensive heating application in winter can save steam: 11 tons per day.

　　A comprehensive heating application in winter can save steam: 357,500 yuan. (130 days calculation)

　　 Winter heat is used for heating and bathing applications. After the bath water tank is heated, all the heat is used for heating applications.

　　②Other seasons bath water = comprehensive application

　　 bath application

　　 The temperature of tap water is about 15 degrees, and it needs to be heated to 50 degrees for workers to bathe.

　　 2 ZR200 air compressors can recover heat per hour: 306kWH (400*0.85*0.9=306)

　　The amount of hot water from 15 degrees to 50 degrees is 7.5 tons/hour.

　　 can produce heated bath water all day: 150 tons/day (7.5*20)

　　 The heating system will be turned off during the rest of the season to meet the application of the bathing system.

　　 For the rest of the season (200 days calculation), if all the heat is used, steam can be saved: 2200 tons. (200*11) Steam saving: 550,000 yuan.

　　③Calculation of annual savings:

　　 2 sets of ZR200 heat energy are fully utilized, and the annual steam can be saved: 907,500 yuan.

　　④ The cooling supplement water can be greatly reduced in summer. According to the reduction of 30 tons of supplement per day, 1.5 yuan per ton, 150 days can save: 30×150×1.5=6750 yuan.

　　⑤ Total cost savings:

　　 Air compressor heat application + cooling water reduction = 913,000 yuan.

　　3, transformation plan

　　 The main content of the renovation: the air compressor provides a high-quality heat source, the outlet water temperature can reach the required temperature through renovation and control, and the internal cooling water system, circulating pump system and heat exchange system of the air compressor are modified.

　　After the air compressor is modified, the heat energy is output through the thermal energy output module C. When the external heat is not used, the spare cooling water (water from the original cold water tower) is used for heat dissipation to ensure the normal operation of the air compressor. The air outlet temperature of the air compressor is cooled by an additional aftercooler A to ensure that the air outlet temperature meets the inlet requirements of the dryer. When the air compressor is turned on, the corresponding electric valve DF is opened to extract heat. When the air compressor is closed, the corresponding DF is closed but 10% of the opening is left to ensure that the residual heat of the air compressor is dissipated. Bath heat exchange application, the bath water tank and the bath plate heat exchanger F1 heat exchange, the outlet temperature is controlled by J1, when the temperature in the water tank reaches the requirement, the water pump group G1 stops running. For bathing application, 15 minutes before bathing, the return water electronic valve H2 opens, and the constant pressure water pump G3 runs to preheat the water in the pipeline. The return water electronic valve H2 will be closed after a 15-minute delay. The bath is in progress, and the constant-pressure water pump G3 is closed after the bath. When the water level in the bath water tank drops to a certain percentage, the electronic water replenishment valve H1 opens, and water can also be refilled manually. The soft water tank is heated, and the water in the soft water tank flows back to the soft water tank after reaching the F2 heat exchanger by the original water pump. When the water temperature of the soft water tank reaches a certain temperature, the temperature control electronic valve H2 is closed. When heating in winter, close the valve of the soft water tank, open the G2 pump, and send the heated return water to the heat exchanger F1 for heating. The temperature is controlled by the temperature control valve J2, and then back to the heating return line.

　　 Air compressor is a kind of power equipment commonly used in the market. It can provide a high-grade heat source for boiler inlet water preheating, domestic hot water, air-conditioning heating, etc., only with appropriate modification. While ensuring the maximum heat recovery efficiency, it also controls the oil temperature of the equipment within a normal and reasonable range, ensuring the normal operation of the equipment, and will not have any negative impact on the air compressor.