Working Principle
After passing through the rear cooler, the temperature of NMP hot exhaust gas drops to about 20 C, so it can be used to pre-cool the hot exhaust gas from the coating machine into the recovery device, so as to realize the second cooling of the hot exhaust gas and the last recovery of NMP in the shell side.
Using circulating water to reduce the temperature of heat waste gas, the third stage cooling of heat waste gas is realized and part of NMP is recovered.
The circulating water flow rate is about 8 tons/hour, the inlet temperature of the circulating water is 30 C, and the outlet temperature is not higher than 40 C. If the recovery unit uses air-cooled refrigeration units (without cooling towers), the circulating water in this temperature range needs to be allocated with the return water of the ground temperature water and the rear cooler.
By using the low temperature water of about 10 C made by the recovery device, the fourth stage cooling of the hot exhaust gas can be realized and most of the NMP can be recovered.
The low-temperature water circulation is about 8 tons/hour. The temperature is set by the outlet temperature of the induced draft fan. Generally, the setting value is between 20 and 30 degrees C, depending on the recovery effect.
5. Process flow chart of recovery unit
Process description:
1. The heat exhaust gas in the coating machine is fully exchanged through the heat exchanger, and the fresh air temperature is raised by 30-50 degrees (depending on the coating machine) and then sent back to the coating machine, which saves a lot of energy consumption.
2. After heat exchange, the exhaust gas is cooled in the first stage and sent to the first cooler for condensation and recovery, and then to the second condenser for recovery.
3. After the second recovery, the exhaust gas is filtered through the purifier to realize the third recovery, which is discharged outdoors through the fan.
4. The internal structure of the recycling system adopts new materials and new technology, which greatly improves the recovery rate, service life and reliability of the equipment. The air duct of the equipment is connected by 304 stainless steel flanges to eliminate drip leakage.
Through the above process, the recovery system achieves two purposes. First, it reduces the energy consumption of the coating machine, and second, it achieves a high recovery rate and eliminates the phenomenon of leakage.