One: system start-up process
The operating procedures should be strictly followed to prepare before driving.
1. First, carefully check whether there is water in the heating chamber, to avoid the violent overall vibration of the evaporator caused by excessive heat or water hammer when steam is introduced;
2. Check whether the pumps, meters, steam and condensate pipes, and feed pipes are in good condition.
3. When driving, according to the different materials, evaporation equipment and attached automatic control devices, according to the pre-set procedure, open the feeding valve and steam valve through the control room according to the specified opening degree and the specified order, and check in turn The liquid level of each effect separation tank is displayed.
4. When the liquid level reaches the specified value, turn on the relevant delivery pump; set the set value of the relevant instrument and set it to the automatic state at the same time;
5. Vacuum the devices that need to be evacuated; monitor the temperature of each effect and check the evaporation; observe the product concentration through the relevant instruments, and then increase the opening of the relevant steam valve to increase the steam flow;
6. When the steam flow rate reaches the desired value, adjust the feed flow rate to control the concentration of the concentrated solution. Generally speaking, reducing the feed flow rate will increase the product concentration, while increasing the feed flow rate will reduce the concentration.
7. Common faults and handling during driving; many faults often occur due to abnormal operation during driving. The most common is the unstable steam supply. This may be caused by cold piping or air in the condensing piping. Pay attention to check the valve, pump seal and outlet. This problem will not occur when the normal operating temperature is reached;
It may also be caused by air leaking into the two-effect and three-effect evaporators. When the process steam pressure of the first-effect separator tank rises above a certain value, this leakage will disappear by itself.
Two: Operational operation
1. The equipment must be carefully operated and strictly controlled during operation. Pay attention to monitoring the operation of each part of the evaporator and the specified indicators. Under normal circumstances, the operator should check and adjust the operation of the evaporator at the specified time interval, and provide operating instructions truthfully.
2. When the device is in a stable operation state, do not change the performance parameters easily, otherwise the device will be in an unbalanced state, and it will take a certain time to adjust to smooth it out, which will cause production loss or even worse effects.
3. Controlling the liquid level of the evaporation device is the key, the purpose is to make the device run smoothly, and the flow rate from one effect to another becomes more reasonable and constant. Effective control of the liquid level can also avoid the “cavitation” phenomenon of the pump. Most pumps deliver boiling liquid, so the danger of “cavitation” should not occur. Only by controlling the liquid level can the service life of the pump be guaranteed.
4. Check the readings of the control room instruments and on-site instruments according to the prescribed time. If it exceeds the regulations, find the cause quickly.
5. If the evaporating liquid is a corrosive solution, check the sight glass to prevent corrosion. Once the sight glass is severely corroded, it will cause danger when the liquid level sensor fails.
Three: parking process
Parking is divided into complete parking, short-term parking and emergency parking. When the evaporator device will not start for a long time or needs to be emptied due to maintenance, it should be completely shut down. When small maintenance of the device only needs to be stopped for a short time, the device should be placed in a standby state. If a major accident occurs, an emergency stop should be taken. For accidental parking, it is very foreseeable that it may happen, and the following points should generally be followed:
1. When an accident occurs, first cut off the steam in the fastest way (or close the pneumatic valve in the control room, or close the manual shut-off valve on site) to avoid the temperature of the material and liquid from continuing to rise.
2. Consider whether it is safe to stop the supply of material and liquid. If it is safe, use the fastest way to stop the feed.
3. Then consider what happens when the vacuum is broken. The steam judges that no adverse situation will occur, and the switch near the final effect vacuum should be opened to break the vacuum state and stop the evaporation operation.
4. Be careful to handle the hot liquid to avoid casualties.