Advanced Stainless Steel Membranes：FCC Slurry Oil Filtration

Composite Stainless Steel Membrane Filter | A Petrochemical Enterprise in China – 228,000 t/y Heavy Oil Catalytic Slurry Oil Filtration Project

Project Overview

Basic Unit Information

A domestic petrochemical enterprise is equipped with a 3.3 Mt/y heavy oil fluid catalytic cracking (FCC) unit, producing 228,000 tons of catalytic slurry oil (CSO) annually. The feed CSO has a solids content of 3,000–8,000 ppm, with impurities mainly consisting of catalyst fines and coke residue. These solid particles severely erode pipelines and clog tower internals, restricting the downstream upgrading of CSO into high‑value products such as needle coke and low‑sulphur marine fuel oil.

The original plant started up in November 2017 with a complete two‑stage European‑imported filtration system:

l  Pre‑filtration: Belgian Trislot wedge‑wire filter elements (15 μm)

l  Fine filtration: German GKN sintered metal powder filter elements (0.5 μm)

l  Design capacity: 27 t/h, peak load: 35 t/h

Critical Long‑term Operational Issues with Imported Equipment

Due to the processing of domestic low‑quality heavy crude oil, the entire imported system experienced frequent failures after commissioning and could not achieve stable long‑term operation:

l  Consistently high transmembrane pressure difference (TMP): Pre‑filter TMP approached 200 kPa, fine filter peak TMP reached 250 kPa, leading to significant energy consumption overruns.

l  Frequent filter element breakage and leakage: Cartridge housings suffered pressure damage, filtrate solids content exceeded limits, and product quality failed to meet specifications.

l  Extremely high shutdown and maintenance frequency: Multiple full‑line overhauls were required in 2018–2019, with complete filter element replacements every six months.

l  Prohibitive overall operation and maintenance costs: Imported elements were expensive with long overseas delivery lead times, annual maintenance expenditure was enormous, and the equipment failure rate remained persistently high.

Domestic Alternative Technology Solution

Leveraging the State Key Laboratory of Materials‑Oriented Chemical Engineering and the National Engineering Research Center for Special Separation Membrane Technology at Nanjing Tech University, Nanjing GaoQ independently developed a composite microporous stainless steel membrane filter element, overcoming the industry‑wide technical bottleneck of simultaneously achieving filtration precision, low flow resistance, and high dirt‑holding capacity.

In August 2019, more than 1,000 imported fine‑filter elements on site were fully replaced with GaoQ’s self‑developed stainless steel membrane elements. During subsequent operation, the original pre‑filter elements all fractured and failed, leaving the entire filtration load to be borne solely by the domestic stainless steel membranes – fully verifying their exceptional impact resistance and high‑load tolerance. The project directly eliminated the entire pre‑filtration stage, simplifying the conventional two‑stage process into a single‑stage filtration system, significantly reducing footprint and capital investment.

Core Structural Advantages of the Product

l  Composite asymmetric stainless steel membrane structure: high‑strength macroporous metal support substrate, surface‑coated with an ultra‑thin (50–500 μm) microporous separation layer, with customizable pore sizes from 0.1 to 5 μm. The membrane surface is smooth and dense, resisting coke deposition and pore clogging, and exhibits excellent flux recovery after backwashing.

l  Material options: 316L, 310L, Hastelloy, Monel, Inconel, Invar, and Other special alloys.

l  Process adaptability: Resistant to high temperature, high pressure, and severe temperature/pressure fluctuations, suitable for low‑quality CSO with widely varying solids content.

l  Process simplification: Eliminates the wedge‑wire pre‑filtration unit; single‑stage filtration reduces civil construction and equipment procurement costs.

l  Energy‑saving operation: Reuses the existing pressure from the fractionator bottom pump, requiring no additional booster equipment.

l  High resource utilization: CSO feed recovery rate can reach up to 98%.

Long‑term Operation Performance Data

l  Initial stage after retrofitting (commissioned in 2019):
TMP: 30–50 kPa; Filtrate solids content: 30–60 ppm; Backwash interval: 12–18 h

l  Continuous stable operation for over 6 years (current status):
TMP: 75–100 kPa; Filtrate solids content stable at 30–60 ppm; Backwash interval: 6–8 h

The filter elements have remained online throughout without any large‑scale batch replacement, setting a domestic record for the longest continuous operation of a catalytic slurry oil filtration unit – far exceeding the 1‑ to 2‑year service life of imported elements.

Retrofit Benefits

l  Drastic reduction in O&M costs: Eliminates the need for frequent shutdown overhauls and full‑batch element replacements, saving over RMB 10 million per year in operating costs.

l  More than doubled service life: Imported elements lasted only 1–2 years; GaoQ stainless steel membrane elements have been running stably for over 6 years and are still capable of continued online service.

l  High‑value utilization of CSO: Filtrate solids content is stably controlled below 60 ppm, allowing the qualified oil to be directly used for producing high‑value chemical materials such as needle coke, low‑sulphur marine fuel oil, mesophase pitch, and carbon black.

l  Reduced initial capital expenditure: By completely removing the pre‑filtration equipment, associated piping, and civil works, the project significantly lowers the initial equipment procurement and infrastructure investment.

Enterprise Technical Service Capability

Nanjing GaoQ Functional Materials Co., Ltd. is a National High‑Tech Enterprise and a Nanjing “Specialized and Sophisticated” SME. It holds more than 50 authorized invention patents both domestically and internationally. Its R&D team comprises university professors and PhDs, with core technologies originating from the National 863 Program, the EU Framework Program, and the National Natural Science Foundation of China.

One‑stop Full‑chain Services

Membrane material customisation → Complete filtration system process design → Equipment fabrication → On‑site installation and commissioning → Long‑term technical support for operation and maintenance

Wide Application Fields

Beyond catalytic slurry oil solid‑liquid separation, the stainless steel membrane filtration technology is applicable to: industrial liquid‑solid separation, high‑temperature flue gas dedusting, oil‑water separation, and process gas demisting. The supporting membrane materials can also be used in aeration, noise reduction, functional coating substrates, and other scenarios.