Slurry Oil Filtration

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Why filter the FCC slurry oil?

Fluid catalytic cracking (FCC) is an important technology for producing gasoline and diesel fuels from heavy oil, and is currently one of the most important and widely used technologies in the refining industry. However, catalytic cracking produces a byproduct called slurry. Catalytic slurry has unique properties and is a mixture of high-molecular-weight hydrocarbons primarily composed of carbon and hydrogen, containing saturated hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes. It is a colloidal dispersion system with a high molecular weight and no long side chains. It is generally not used as a feedstock, but as a fuel oil. Catalytic slurry is rich in polycyclic aromatic hydrocarbons (PAHs), which can be used as raw materials for producing bunker fuels, carbon black, carbon fibers, and have wide applications in petroleum processing and petrochemical industries. However, catalytic slurry contains about 3000-7000 ppm catalyst particles, which limit its potential as a high-value product. If the operation fluctuates, the catalyst content can even increase to 12000-15000 ppm. These solid impurities make erosion of pipelines, equipment, and other problems more severe, and can even clog furnace nozzles, affecting the quality of fuel oil. By removing solid impurities from the slurry, its quality can be improved, thus increasing its utilization value. Therefore, it is necessary to first remove solid particles from the slurry. There are various methods for removing solid particles, such as sedimentation, coagulation, centrifugation, etc., but these methods have low removal efficiency. Thus, filtration is the best method for removing solid particles from the slurry.

Slurry Oil Filtration

Slurry oil filtration consists of pre-filtration and fine-filtration, with sintered porous metal powder filter cores being the core and key components in fine-filtration. When the slurry with heat flows through the filter element, the liquid portion of the slurry can pass through the filter core and the clean slurry can go directly to a downstream device. Solid catalyst particles will be intercepted and remain on the surface of the filter core, and then be washed into the filter cake receiving device through a dry gas backwashing method. In order to quickly separate the solid residues on the filter core surface when discharging waste residue, the pressure needs to be quickly released, and the filtrate needs to flow back in the opposite direction so that the media in the filtration equipment can be discharged through a slag discharge valve. After use, the slurry oil filtration process is fully controlled by a PLC program, including preheating, pre-coating, filtration, backwashing, and slag discharge. There are automatic and manual controls in the PLC program, and since there are a relatively large number of program controlled valves in the slurry filtration system, it is usually operated automatically without manual intervention.

The typical process can be summarized as follows: FCC slurry oil first enters filter A, and the catalyst particle content in the filtrate is reduced to 50-100 ppm. When the filter differential pressure or filtration time reaches the set value, the slurry feed switches to filter B, filter A enters the regeneration process, and the filter residue is washed away by backwashing medium and discharged into a receiving tank. The entire process is controlled by an on-site PLC.

MstnLand's slurry oil filtration system uses automatic backwashing, multi-stage filtration, and high-precision sintered metal powder filter cores to meet the requirements of high filtration accuracy and continuous operation of the equipment system. The filtration system consists of two or more filtration vessels (e.g. 2x100%, 3x50%), a backwashing receiver vessel, and a gas accumulator vessel, including all necessary pumps, controls, valves, instruments, and pipes. High-quality sintered metal powder filter cores are used and installed in the vessels, so that solids are retained on the inner surface of the filter core, while clean filtrate flows out through the solid "cake" and the filter core at the top of the vessel. Solids are periodically removed from the vessel by a gas-assisted backwashing program. During this process, the inlet and outlet valves close, and the gas pressure is built up at the liquid level on the clean side of the filter. Opening the bottom valve quickly causes solids to precipitate from inside the element and be carried out of the vessel. These filters are then put back online to repeat the cycle.

Application of Slurry Oil Filtration

In the petroleum refining industry, catalytic cracking units and slurry filtration systems are constructed together, and blowdown, pressure testing, and oil transportation steps are implemented, with strict measurement of values from control valves, pressure gauges, flow meters, liquid level gauges and other procedures. The slurry filtration system is generally used after the catalytic cracking unit has been operating stably. The slurry filtration system has certain characteristics - the slurry has high viscosity at low temperatures. In order to make the slurry flow smoothly and reduce resistance, it is necessary to separate the catalyst particles from the slurry, and this operation requires a relatively high temperature environment. High temperature slurry is prone to self-ignition and requires the filter to be highly air-tight. In addition, process control valves and operation programs need to be adjusted. Through analysis of the operating conditions, it is relatively simple and convenient to operate the slurry filtration system, which can carry out pre-coating, filtration, backwashing and slag discharge under the automation control of the PLC operating system, which is an independent work unit that can be monitored. If the slurry filtration system needs to stop working, it does not need to be switched manually. It only needs to initiate the PLC "backwash shutdown" program. The filtration system can automatically perform replacement, backwashing, and slag discharge operations. As the slurry filtration system is independent, even if there is work such as start-up and shut-down, it will not have an adverse effect on the operation of the catalytic cracking unit.

In the fluid catalytic cracking unit, the slurry oil filtration system is only a small part, occupying a relatively small area, with not much cost investment, but it has higher processing load than catalytic cracking. During operation, there is great flexibility and can be operated automatically without manual intervention, reducing labor costs. Taking a 2.5 Mt catalytic cracking unit slurry filtration system as the research object, it was found in practice that the consumption of materials and power after input use was not high, and even if there are start-up and shut-down operations, it will not have an adverse effect on the operation of the catalytic cracking unit.

Statistics show that a 2.5 Mt catalytic cracking unit can produce 162. kt of product slurry per year, and the price of slurry filtered by the slurry filter can increase by USD 29 per ton, resulting in an annual increase of USD 4,628,500 in revenue. This reduces the cleaning cost caused by catalyst deposition during heavy oil transportation and storage processes, such as pipeline blockages, and has significant economic benefits.

Standards of MSTNLAND Slurry Oil Filter System

MstnLand's slurry oil filtration system is a skid-mounted design with a compact structure, low installation space requirements and low installation workload. System without mechanical pump equipment, less failure, less maintenance workload. Suitable for raw materials and particles with various viscosity, particle removal rate &gt; 99.5%. Low replacement rate of filter element, stable backwash cycle, reliable filtration performance. It uses a unique sintered metal powder filter element, has a unique surface filtration technology, with high filtration accuracy, large pressure difference resistance, with efficient online backwashing technology, not easy to clog. Long cycle stable operation, can ensure continuous operation of a cycle (≥4 years) without stopping, sustainable to ensure the discharge of dust content < 50ppm/wt. The equipment system is equipped with advanced PLC or DCS control system, which can achieve continuous and stable operation without manual attendance. Efficient gas assisted on-line backwash and osmotic backwash, backwash effect is good, can maintain a stable base pressure drop. The amount of blowback is small, there is no large flow reflux pump, the operation cost is low, and the price competitiveness and cost efficiency ratio are high in the same equipment in the industry.

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