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HyPulse LSI filter system Mott Corporation has installed the two largest HyPulse LSI filter systems in two major refineries forremoving FCC catalyst fines from slurry oil. The first system has operated successfully for overthree years and is a testament to the unique features and operating characteristics of thisadvanced filtration system design. Its proven performance led to the purchase of a second systemby the same customer. Each installation is a triple vessel system designed to provide continuousoperation at capacities in excess of 10,000 BPD. The systems are totally automatic, and continueto provide a high degree of reliable high efficiency particle separation.

Mott process systems division

Mott Corporation of Farmington, Connecticut has been manufacturing porous metal products for over 40 years. Mott’s Process Systems Division makes porous metal filter elements in variousalloys and installs them in the HyPulse® line of filters. Mott has an installed base of hundreds of HyPulse filters in successful liquid/solid and gas/solid applications. In the mid 1980s, as the petroleum refining industry began to express serious interest in removing catalyst particles from FCC slurry oil, Mott began testing the use of porous metal filters for this application. The slurry oil process requires the filter to withstand rigorous service conditions and the benefits of an all-metal filter are obvious. Mott demonstrated how successful the HyPulse LSI filter could be in this application through both laboratory tests and on-site pilot scale evaluations. Mott’s installed systems demonstrate the calability of HyPulse LSI filters to handle high flow rates and solids capacities. Several refineries became aware of the benefits of an efficient catalyst removal system. A key goal for removing the catalyst particulate was, and remains to be, upgrading of product fuel oils or upgrading to provide feedstock for production of carbon black or other products. Removing the catalyst fines also reduced the wear of downstream components due to the abrasive nature of the particles. More recently, there has been added emphasis on removing the catalyst fines to prevent settling and sludge formation in slurry oil storage tanks in addition to concerns over the hazardous waste classification of catalyst-containing tank sediments. Since 1990, Mott has delivered HyPulse LSI Filters and Systems to nine refinery sites located in the US, Europe, and China. Systems operate reliably over multiple cycles with consistent cycle lengths and long filter element lifetime. Operating systems continue to utilize filter elements originally provided with the system.

Inner diagram of Mott HyPulse LSI Filter

HyPulse LSI Filter Description: Mott’s HyPulse LSI filters are backwashable metal filters that contain tubular porous metal elements installed in a tubesheet at the bottom of a vessel. During operation, the feed slurry containing suspended solids is introduced to the filter below the tubesheet and flows through the inside of the filter elements. Solids collect on inside surface of the elements as filtrate passes through the elements to the outside surface.

The accumulation of solids on the inside surface of the filter elements is followed by backflushing to remove the solids as highly concentrated slurry. This process is as simple as flushing a slurrythrough a pipe. The benefits of this configuration and operation are many: Elements can be packed closer together in a smaller housing. Solids are retained on the inside surface of the filter elements under hydraulic control as slurries are in pipes. There is no interference with adjacent elements on cake formation. Solids retained in the elements are immobile and fluids can be exchanged for maximum product recovery and backwash effectiveness. Higher pressure drops can be accommodated which result in longer filter cycles and higher filter throughput efficiency. Scale-up from pilot testing or smaller filters is readily determined. High flow rates and solids loadings can be accommodated without complex hydraulic calculations affecting solids deposition and fluid flow patterns. Simple outside-in backwash eliminates the strain and stress on adjacent elements during the backwash, resulting in a stronger, more reliable mechanical installation.

Materials of Construction: Mott’s standard filter elements are constructed entirely of 316L stainless steel. Other alloys are available for severe process conditions. For refinery FCC slurry oil, carbon steel is typically used as the filter vessel material for operating temperatures up to 600°F.

Mott Precision Filter Media: There are many types of backwashable filters in the commercial marketplace in a variety of mechanical configurations. What truly distinguishes one from the other is the filter media used in the filter.

Media selection: It is the key parameter for achieving the desired separation and for ensuring long operating life.Mott precision porous metal filter media has controlled porosity and pore size that maximizes efficiency. For backwash filters to be successful over time, the media must provide the particleretention efficiency required and backwash clean cycle after cycle.

Image of Pressure Drop Profile for Multiple Filter Cycles
Mott media, with its tightly controlled pore size, offers exceptional particle removal efficiency with minimal particle penetration into the media. The tightly controlled pore size and backwash operation of HyPulse LSI filters enable long operating periods between cleanings. Keeping the solids on the surface results in efficient backwashing and long filter element life. Several HyPulseLSI filters in slurry oil service have been operating with their original elements, contributing to low operating costs.

Filter Mechanical Construction: The HyPulse LSI filter assembly is constructed for ease of service and operation. The filter vesselis cylindrical with standard ASME heads. A tubesheet is welded into the bottom of the vessel where the elements are installed with a 2 inch NPT thread. A high temperature thread sealer is used to seal the elements in the tubesheet. A stainless steel spider assembly is installed on top of the elements to maintain spacing. The flanged cover is sealed with Flexitallic gaskets.The filter elements are 2 inch diameter, 80 inches long, each with an active surface area of 3.27 ft2.

The installation end has a 2 inch NPT threaded adapter to screw into the tubesheet. An installation tool is provided to screw in the elements. Filtrate outlet nozzles are positioned both high and low on the vessel to allow for complete filtrate withdrawal and maximum product recovery. Additional nozzles are provided for auxiliary services and instrumentation. This simple arrangement has proven to be an extremely reliable configuration that allows modification of operating parameters to maximize the process benefit of the filter installation. The versatility of the design allows for customization of process operation for maximum economic benefit.


Mott has designed and installed slurry oil filtration systems with 24, 36, 42, and 66 inch HyPulseLSI filters. The 36 and 42-inch systems are single vessel installations operating on a continuous basis with an interruptible flow. The 24 and 66-inch systems are triplex filter system operating on a continuous basis. One filter operates online, one is on standby, and one is a spare used during maintenance periods. These filters operate on a simple cycle of filtration and backwash with an occasional flush with Light Cycle Oil. They have operated reliably and effectively since 1993.

RECENT ADVANCEMENTS: When a major refinery approached Mott with a requirement for a high flow, high efficiency filter for FCC slurry oil, the scalability of the Mott HyPulse LSI filter provided the obvious choice. The highflow requirement was satisfied by selecting a filter of sufficient size to contain the required number of filter elements. The high efficiency particle removal requirement was met with the proven Mott precision porous stainless steel media. Pilot filter testing confirmed all operating parameters. The required filter was 66 inches in diameter and is capable of processing in excess of 10,000 BPD slurry. The requirement for a continuously operating process was satisfied by a Mott triplex filtration system, which included a backwash receiver. The normal operating mode has one filter on line, one on standby, and one as a spare. Given the reliability of Mott filters, extended cycle times were obtained by running two filters simultaneously, but staggered in cycle time, with the third filter being on standby for utilization when one of the online filters requires backwashing. All three filters are employed in the filtration cycle to make maximum utilization of the available surface area. For maximum operating efficiency, product oil is purged from the filter housing and is replaced with LCO for backwashing. This is completed without loss of solids during the fluid exchange, one ofthe features of the HyPulse LSI design. This filter installation represents a major enhancement of HyPulse filter technology in both thescale of design and operating efficiency. The system operation takes advantage of every design feature of the HyPulse LSI filter, resulting in maximum economic benefit to the refinery. As noted earlier, Mott’s customer realized the benefits of the HyPulse LSI design and promptly selected an identical system for a second refinery. A review of the system’s process conditions, filtration requirements, design specifications, and operating results is summarized below:


Process Fluid: FCC Slurry Oil
Gravity, API: -1.0
Process Rate: more than 10,000 BPD
Slurry Solids Concentration: 1,000 ppm
Product Solids Concentration: Not to exceed 50 ppm
Operating Temperature: 450-550 F
Operating Pressure: 50-130 psi
Minimum Cycle Time
(interval between Backwashes):
2 hours
Filter Backflush Liquid: Light Cycle Oil
Operation: Continuous with maximum interchangeability between the filter vessels. Backwash solids to a receiver tank with LCO.
Filter System Design Specifications

A Mott HyPulse LSI filter system consisting of three 66-inch LSI filters and one 96-inch backwash receiver was selected to meet the specified requirements. Each filter is capable of handling the full process flow and meeting the requirements of 2-hour intervals between backwashes. Mott’s precision filter media delivers the required product quality. The scope of supply was a complete filter system, including all interconnecting piping, valves, controls and instrumentation. System design specifications are as follows:

Filters: Three (3) HyPulse LSI Filters, Model 846680-421-2-0.5
Vessel Diameter: 66 inches
Design Conditions: 300 psi at 600 F
Maximum Available Pressure Drop: 100 psid
Operating Cycle Pressure Drop: 30-60 psid program adjustable
Filter Elements: 2-inch diameter by 80 inches long, 316L stainless steel
Control Valves: Actuated Eccentric Plug
Instrumentation: Rosemont Smart Transmitters for pressure, level, and temperature
Flow Measurement: Orifice meters
Process Control: PLC communication to the refinery DCS


Filtrate Quality: The filter system has consistently delivered product solids concentration well below the required maximum.

Filter Cycle Time: With low viscosity resulting from high slurry temperatures, and high cycle pressure drop of 60 psid, filter cycles between backwashes exceeded 4 hours with one filter online at full flow rates, and more than 16 hours with two filters online.

Process Efficiency: With long cycle times, the efficiency of recovered product as a percentage of feed slurry exceeds 99.8%. For every 1000 barrels of filtered product slurry, only 2 barrels are lost to the backwash. Cycle time is affected by the oil viscosity, operating filtration flux rate, and rate of solids to the filter. Since the filter loads to a certain solids level under prescribed conditions, the filtration cycle can change with these variables.

Filter Pressure Drop: Clean pressure drop (i.e. pressure drop seen after a backwash) has been very stable at under 3 psi, indicating that the filter media is being cleaned effectively by the backwash. The dirty filter pressure drop is program adjustable up to the design limit of 100 psid. The typical cycle pressure drop is set for 60 psid for routine operation to reduce wear and tear on the equipment. The unique HyPulse LSI design provides for high pressure drop capability that significantly extendsthe filter cycle time. The precision pore size filter media is designed to work at these pressures without plugging due to particle penetration. In actual operation, inadvertent pressure drop excursions as much as 40% above desired operating limits have had no affect on the filter, the media, or subsequent filter cycle performance.

CONCLUSIONS The Mott HyPulse LSI has performed from startup beyond the requirements and expectations of the customer. The mechanics of the system have functioned very well with few corrections required. This latest installation is one of a series of successful HyPulse LSI applications that continue to demonstrate state of the art filtration with Mott filters.

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