Application of slurry filtration technology in RFCCU

The application of automatic slurry filtration system in 2.5 MT / a RFCC unit of PetroChina Sichuan Petrochemical Co., Ltd. is introduced. The results show that the system can operate continuously and automatically, the treatment capacity of catalytic oil slurry reaches 19.4 T / h, and the solid content (ash content) of oil slurry changes from 2.070 T / h before filtration μ G / g decreased to 120 μ At the same time, the take out price of oil slurry is increased. The annual profit of the unit can be increased by 32.5 million yuan, and the economic benefit is very significant.

Hydrocracking is one of the most important heavy oil light process. The amount of slurry discharged from FCC units in general refineries accounts for about 5% of the feedstock, and the annual output of FCC slurry in China is more than 5 Mt. Catalytic slurry generally contains 2 000 μ The solid content in the slurry should be reduced when the catalyst particles above g / G are used as fuel oil, coking raw materials, carbon black and needle coke, aromatics extraction to produce rubber additives and other further processing and utilization, or the development of high value-added products.

Due to the unfavorable factors such as high density, high viscosity, high freezing point and solid catalyst particles, the effect of purification and separation of catalytic oil slurry in many petrochemical enterprises is not ideal. For a long time, petrochemical enterprises and scientific research institutions at home and abroad have paid close attention to the technology of purification and separation of catalytic slurry. PetroChina Sichuan Petrochemical Co., Ltd. (hereinafter referred to as Sichuan Petrochemical) has adopted a heavy oil catalytic cracking slurry automatic filtration system, which has been applied in a 2.5 MT / a heavy oil catalytic cracking unit. Since the slurry filter was put into operation in May 2014, it has been in good condition and has treated 27 KT of slurry in total, with remarkable economic benefits.

The principle of the process of the slurry filtration system

The core component of slurry filtration system is porous metal powder sintered filter element.

When the hot oil slurry passes through the filter element, the oil slurry liquid can pass through the filter element, the clean oil slurry (filtrate) enters the downstream device, and the solid catalyst particles are trapped on the inner surface of the filter element. The filtered solid catalyst cake is backwashed with dry gas and discharged to the cake receiving tank.

In the process of slag removal, the solid on the inner surface of the filter element can be quickly stripped by the rapid pressure release and the reverse flow of the filter solution, and all the media in the filter can flow out of the filter through the slag removal valve. After being put into operation, the whole process of slurry filtration is controlled by PLC program, such as preheating, pre membrane and filtration, backwashing, slag removal and shutdown. The control system controlled by PLC program can realize automatic and manual operation. However, as the slurry filtration system is controlled by 32 program-controlled valves, it is generally operated by automatic control without manual intervention.

Industrial application of slurry filter

The slurry filtration system and catalytic cracking unit are constructed simultaneously and the process of purging, pressure test and oil transportation is completed. Strict tests shall be conducted for each control valve, flowmeter, level gauge, pressure gauge and related control procedures, and put into use after the start-up and operation of catalytic unit is stable. The oil filter has the following characteristics: (1) the low temperature viscosity of the slurry is large, so in order to ensure the flow resistance of the slurry is small, the catalyst particles must be effectively separated from the slurry, and it must be filtered at a higher temperature (2) High temperature slurry is easy to self ignite, and the requirement of filter tightness is high (3) The program control valve and operation procedure must be debugged.

The operation of slurry filtration system is very convenient. In the automatic mode, the system can automatically complete all filling, pre film, filtration, backwash, slag removal and other operations. PLC operating system is operated independently in the central control room, and DCS screen is provided for monitoring.

During the shutdown of slurry filtration system, the system does not need any manual switching. The operator can directly carry out the PLC “backwash stop” program, and the system will automatically complete the replacement, backwash, slag removal and other operation procedures. The slurry filtration system is an independent system, and its start and shutdown will not affect the normal operation of the heavy oil catalytic cracking unit.

The designed capacity of the slurry filtration system is 19.4 T / h, with a large capacity and a floor area of only about 10 m2. The filtered slurry is cooled to 70-90 ℃ before being sent out of the unit. Because the differential pressure of the slurry filter is only about 0.02 MPa, the pressure drop is very small and the operating pressure is high, so there is no need to increase the pump pressure and reduce the investment cost.

When the slurry filtration system reaches the following conditions, it will lead to interlock shutdown: the return time of the programmable valve exceeds 15 s, the pressure difference of any one of the three filters exceeds 0.35 MPa, the feed flow reaches 28 T / h overload, and the inlet valves of fine filter a and fine filter B are closed at the same time. During shutdown, the slurry will bypass the filter system, at this time, the bypass valve of slurry filter is opened, and the valve of slurry in and out of filter is closed. Under the fault condition, the automatic interlock shutdown of the slurry filtration system has no effect on the operation of the catalytic cracking unit.

• the slurry filtration system uses porous metal powder sintered filter material as the filtration component, which can realize continuous operation and automatically complete the filling, pre membrane, filtration, backwashing, slag discharge and other processes, with the treatment capacity of 19.40 T / h.
• the results of industrial operation and data filtration of the slurry filtration system showed that the average ash content of the slurry dropped from 2 070 μ G / g to 120 μ The ash removal rate of slurry reaches 94.2%.
• the filtered oil slurry is widely used, and the economic benefit can be increased by 32.5 million yuan per year according to the increase of 200 yuan / T.
• after the oil slurry filtration system is put into operation, there is no need to increase the delivery pump, only the circulating oil slurry pump can meet the operation and delivery needs of the oil slurry filter, with little power and material consumption.
• the slurry filtration system can be used for purging, pressure test, oil transportation and other operations simultaneously with the RFCCU. At the same time, as an independent system, the start-up and shutdown of the RFCCU have no impact on the normal operation of the RFCCU.