We produce stainless steel Johnson screen filter element (wedge wire screen filter) for FCC filtration system.
Catalytic cracking is one of the most important processes for lightening heavy oil.
Generally, the amount of slurried oil slurry outside the catalytic cracking unit of an oil refinery plant accounts for about 5% of the amount of raw materials.
The catalytic slurry generally contains more than 2 000 μg / g of catalyst particles, whether it is used as fuel oil for ex-factory or coking raw materials, raw materials for carbon black and needle coke production, or aromatics extraction to produce rubber additives, etc. Further processing and utilization or development of high value-added products need to reduce the solid content in the oil slurry.
Due to the disadvantages of high density, high viscosity, high freezing point, and solid catalyst particles of the catalytic slurry, a professional slurry filter is required for filtration.
(Heavy oil catalytic cracking unit, consisting of a reaction regeneration unit, a thermal unit, a flue gas desulfurization unit, a fractionation unit, an absorption stabilization unit, and a product refining unit)
With hydrogenated heavy oil as raw material, it mainly produces dry gas, liquefied gas, gasoline, diesel and oil slurry.
Process Principle Of Slurry Filtration System
The core element of the slurry filtration system is a Johnson screen filter element (wedge wire filter element).
When the hot oil slurry passes through the wedge wire screen filter, the oil slurry liquid can pass through the filter element, and the clean oil slurry (filter liquid) enters the downstream device.
The solid catalyst particles are trapped on the inner surface of the Johnson vee wire filter. The filtered solid catalyst cake is backwashed with dry gas and discharged to the cake receiving tank.
During the slag discharge process, the rapid pressure release and the reverse flow of the filtrate can quickly strip the solids on the inner surface of the wedge wire screen filter element, and make all the media inside the filter flow out of the filter through the slag discharge valve.
The entire slurry filtration process is controlled by programmable logic controller (PLC) programs such as preheating, pre-membrane and filtration, backwashing, slag discharge, and shutdown. The control system controlled by the PLC program can realize both automatic and manual operation modes.
Process flow of slurry filtration system
Slurry filtration system consists of 1 pre-filter, 2 fine filters, filter cake receiving tank, 1 dry gas pressure tank and supporting instrument valves.
- After the slurry of the catalytic device is cooled, the temperature is reduced to 280 to 300 ° After passing through the pre-filter, the slurry is divided into two paths and enters fine filter A and fine filter B respectively.
(The built-in metal filter element of the precision filter is a wire wrapped screen filter element)
- Backwash dry gas enters from the top of pre-filter, fine filter A, fine filter B, and discharges the filter cake from the bottom of the filter to the cake receiver.
- The filter cake in the filter cake receiving tank is sent to the catalytic cracking raw material oil tank with the dry gas pressure for catalytic refining oil for recycling.
- The gas phase of the pre-filter, fine filter A, fine filter B and filter cake receiving tank is vented to the flare line through a vent valve.
Industrial applications of Johnson screen slurry filters
The slurry filtration system is constructed synchronously with the catalytic cracking unit and completes the processes of purge, pressure test and oil transportation. Each control valve, flow meter, level gauge, pressure gauge and related control procedures need to be strictly tested. The catalytic device was put into operation after it started smoothly.
The wedge wire screen slurry filter has the following characteristics:
- The viscosity of the oil slurry is large at low temperature. In order to ensure that the oil slurry has low flow resistance and to be effectively separated from the catalyst particles, it must be filtered at a higher temperature.
- High temperature oil slurry is easy to ignite spontaneously, and the requirements for filter tightness are high.
- Programmable valves and operating procedures must be commissioned.
- The slurry filtration system uses v wire screen filter element material as the filter component, which can realize continuous operation and automatically complete the processes of filling, pre-membrane, filtration, back washing, and slag discharge.
- The industrial operation and data filtering effect of the slurry filtration system, the ash content of the externally slurried slurry dropped from an average of 2 070 μg / g to 120 μg / g, and the removal rate of the slurry ash reached 94.2%.
- Filtered slurry can be monetized.
- After the slurry filtration system is put into use, there is no need to increase the delivery pump. Only the circulating slurry pump can meet the operation and transportation requirements of the slurry filter, and the power and material consumption are very small.