Roots piston vacuum system for deodorization in oil industry. In the process of deodorizing grease, the vacuum device should be set up to ensure stable operation. Steam ejection vacuum pump is easy to operate, but it is necessary to check and maintain the pressure stability of power steam frequently. The drainage temperature of air pressure condenser affects the working efficiency of steam jet pump. It is necessary to check the drainage temperature of air pressure condenser frequently to ensure the stability of water supply and strictly prevent the interruption of cooling water. Normally, the drainage temperature of the first stage condenser should be controlled in the range of 20-30 C. Conditional enterprises can save energy and improve economic benefits by automatically adjusting power steam consumption through drainage temperature sensor.
The exhaust port of the last stage jet vacuum pump should also be equipped with a pneumatic condenser or an effective check valve to avoid the system vacuum damage caused by the sudden interruption of power steam. Before the vacuum device terminates operation, the stripping direct steam should be shut down first, then the heating steam valve, deodorizer exhaust valve, jet pump power steam valve and air pressure condenser intake valve should be shut down in order to ensure safe operation.
In the 1970s and 1980s, the main vacuum equipment used in this process was steam jet vacuum pump unit. However, with the introduction of national energy saving and emission reduction policies, the steam jet vacuum pump unit with high energy consumption and low efficiency was gradually replaced by Roots liquid ring (sliding valve) vacuum unit. According to the customer’s investigation, Roots liquid ring (sliding valve) vacuum unit saves about 75% of energy consumption.
1. A deodorization method for grease, including evaporator, grease and vacuum tower, is characterized by heating the grease to 110 (+5) Celsius at room temperature and evaporating at constant temperature, then volatilizing the odor gas by steam agitation in a vacuum tower of 0.2-1 kpa, and then filtering it with activated carbon in a melted liquid state. Make the “odor” ingredient controlled below 0.01% to meet the needs of various environments.
Remove before entering deodorization stage. Semi-continuous and continuous deodorization process, oil deoxidization can be carried out continuously in the gas separator. The working pressure of the deodorizer is the same as that of the deodorizer, and the operating temperature is controlled below 70 C.
2. Stripping Deodorization
Stripping deodorization is the core process of oil deodorization. The operation conditions of stripping deodorization directly affect the quality and economic benefits of deodorized oil. Intermittent deodorization equipment can be operated at low temperature for a long time. The loading capacity of each batch of oil does not exceed 60-70% of the total volume of the equipment. The amount of steam used for stripping is 30-50 kg/ton of oil per hour. The deodorization time is determined by the composition of volatile components in oils and fats. The deodorization time is 5-8 hours under the operating temperature of 180 C and pressure of 0.65-1.3 Kpa (stainless steel deodorizer can be operated at high temperature and short time, operating temperature of 230-250 C, pressure of 0.65 KPa and deodorization time of 2.5-4 hours). When the pressure and operating temperature can not meet the above requirements, it can be compensated by prolonging stripping deodorization time according to stripping principle. Semi-continuous deodorization with operating pressure of 0.26-0.78KPa and operating temperature of 240-270 C. The residence time of oil in deodorizer is 10-135 minutes (depending on the type of deodorizer and the type of deodorizer). The amount of direct steam used in stripping is 4.5% in semi-continuous form and 4.0% in continuous form.
All kinds of deodorizers, in stripping deodorization process, must strictly prevent air leakage from accessories below reservoir, external heater, cooler and oil pump. At the beginning and end of the operation of ordinary carbon steel deodorizer, citric acid should be added at 0.01-0.02% of the oil content (to prepare a solution with a concentration of 5%) in order to make the metal ions accidentally mixed in the deodorization process chelated, so as to ensure the quality of oil and grease.
3. Stripping Steam Treatment
In the process of oil deodorization, high quality steam stripping is an important condition to ensure deodorization effect. Normal small capacity steam boilers are usually not equipped with feedwater deoxidizer. Oxygen is unavoidable in the steam. Therefore, the steam for stripping should be deoxidized by boiler feed water in enterprises with conditions. The deaeration of boiler feed water can be carried out by atmospheric thermal deaerator. After the boiler feed water is heated to 100-105 C for deoxidization, it is pumped into the stripping steam generator or boiler. Steam conveyed by boiler or steam generator should be free of furnace water. Before entering the tower, condensate water which may be carried in the steam should be strictly separated by steam-water separator to prevent salt from furnace water or metal ions from gas pipeline from mixing into oil and causing oil oxidation.
4. Cooling filtration
After recovering heat from oil-oil heat exchanger, deodorized oil still has a relatively high temperature, which needs further cooling by water cooler. When oil temperature drops below 40 C, it can contact air for filtration. The purpose of deodorizing oil filtration is to remove impurities such as metal chelates, which is called safe filtration. The safe filtration of deodorized oil is different from that of crude oil. The filter cloth of filter media should be cleaned up in time and replaced frequently. It is strictly forbidden to use the filter cloth for a long period of time without being cleaned up. The filtered product oil should be packaged or added with antioxidants in time to ensure the storage stability of the oil.
5. Heat Recovery
The operation temperature of oil deodorization is higher. Oil and steam condensate, which complete the deodorization process, have higher calorific value. In order to reduce operating costs, this part of heat can be recycled. For example, the heat carried by deodorized product oil can be recovered by oil-oil heat exchanger to feed tower (or tank) cold grease; the condensate water of heat medium steam can be utilized by depressurizing secondary evaporation, or be sent to boiler feed pool.
6. Fatty acid capture
In the process of deodorization of oils and fats, many volatile components proposed by vapors are substances with high utilization value (such as free fatty acids and vitamin E). In order to recover these components, a fatty acid trap can be connected to the exhaust passage to capture them. In deodorization, the trap can be connected behind the first stage steam jet pump, and in front of the first stage steam jet pump when the free fatty acid content is high, so as to ensure the concentration of the captured fatty acid. Fatty acid gas can be recovered by direct spray condensation of cooled fatty acids. The temperature of liquid fatty acid used for spraying is about 60 C.
The advantages of Roots piston vacuum system in modern chemical production are becoming more and more prominent. The application of Roots piston vacuum system in deodorization of oil and grease industry is also vivid and vivid.