The following are the standard operating procedures and key control points for scraper film evaporators:
1、 Equipment preparation stage
1. Mechanical integrity inspection
It is necessary to confirm that the gap between the scraper and the heating wall (0.5-2mm) is uniform, the heating jacket has no leakage, and the vacuum system connection has good sealing (which can be tested for leakage with soapy water). For new equipment, it is also necessary to check whether the radial swing of the rotor meets the design requirements.
2. System cleaning and drying
After using alkaline cleaning agents to remove oil stains, it is necessary to thoroughly dry the inner wall with compressed air to prevent residual moisture from affecting material film formation.
2、 Start up phase
1. Auxiliary system linkage
First, turn on the circulating cooling water pump, then start the vacuum pump to establish negative pressure (thermal sensitive materials need to maintain a vacuum degree of 1-10 kPa). The heating medium (steam/thermal oil) needs to be slowly heated to avoid wall overheating and coking.
2. Feed control strategy
The initial feed rate is 30% -50% of the rated value, and the flow rate is controlled by regulating the valve. High viscosity materials need to be preheated to near evaporation temperature (such as traditional Chinese medicine extract, it is recommended to preheat to 60-70 ℃).
3、 Key points of operation monitoring
1. Film quality assessment
Observe the uniformity of the liquid film on the heating wall. If there is a broken film, adjust the scraper speed (100-500r/min) or check if the distributor is blocked. The secondary steam outlet should be free of droplet entrainment.
2. Dynamic adjustment of process parameters
Adjust the feed rate and heating temperature in real-time based on the concentration detection results of the concentrated solution. It is recommended to control the steam pressure at around 0.15MPa.
4、 Shutdown specifications
1. Sequential shutdown program
First, close the heating medium valve, wait for the material to be completely discharged, then stop the scraper motor, and finally break the vacuum. Rinse residual materials with hot water at 60 ℃.
2. Emergency shutdown conditions
Immediately cut off the power supply in case of abnormal vibration, sudden drop in vacuum degree, or overheating of the heating wall surface (>150 ℃).
Note: During the operation, it is necessary to regularly check the flow rate of mechanical seal cooling water and the oil level of the reducer to ensure that the equipment is in a lubricated state.