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DE-102021103303-B4 - Tubular filter element and method for cleaning it

DE102021103303B4DE 102021103303 B4DE102021103303 B4DE 102021103303B4DE-102021103303-B4

Abstract

Tubular filter element (1) comprising a) a clean-gas-side cylindrical internal volume with at least one clean-gas-side outlet, b) a lateral surface surrounding the internal volume designed as filter surfaces (9), c) Cleaning agent (7, 8, 10) for the outer surface, wherein the cleaning agent has a tubular cleaning lance (7) fixedly arranged coaxially in the cylindrical inner volume with several outlet openings (15) distributed axially over the axial extent of the filter surfaces into the inner volume, d) Closure devices (11) which have at least one outlet on the clean gas side and e) at least one cleaning valve (10) for a purge gas inlet in the tubular cleaning lance, characterized in that f) the closure means (11) shall comprise at least one hydraulic or pneumatic flow valve (17) without moving parts.

Inventors

  • Hans Leibold
  • Robert Mai

Assignees

  • Karlsruher Institut für Technologie (Körperschaft des öffentlichen Rechts)

Dates

Publication Date
20260513
Application Date
20210212
Priority Date
20200213

Claims (13)

  1. Tubular filter element (1) comprising a) a clean gas-side cylindrical inner volume with at least one clean gas-side outlet, b) a shell surface surrounding the inner volume designed as filter surfaces (9), c) cleaning means (7, 8, 10) for the shell surface, wherein the cleaning means has a tubular cleaning lance (7) fixedly arranged coaxially in the cylindrical inner volume with several outlet openings (15) distributed axially over the axial extent of the filter surfaces into the inner volume, d) sealing means (11) having at least one clean gas-side outlet, and e) at least one cleaning valve (10) for a purge gas inlet in the tubular cleaning lance, characterized in that f) the sealing means (11) comprise at least one hydraulic or pneumatic flow valve (17) without moving parts.
  2. Tubular filter element according to Claim 1 , characterized in that the closure means comprise at least one non-return valve (12).
  3. Tubular filter element according to Claim 1 or 2 , characterized in that the at least one hydraulic or pneumatic flow valve (17) consists of porous materials such as foams, metal fibers, fabrics or other fibrous materials, granular ceramics or sintered metals with a continuous pore system with cross-sections of a few hundred µm.
  4. Tubular filter element according to one of the preceding claims, characterized in that the at least one hydraulic or pneumatic flow valve (17) has a lower permeability than the at least one filter surface.
  5. Tubular filter element according to one of the preceding claims, characterized in that the closing means (11) has a response threshold to a closing position which is at a pressure gradient between 30 and 250 Pa or a flow velocity of 2.5 cm/sec.
  6. Tubular filter element according to one of the preceding claims, characterized in that the closing means comprise a mechanically, electromechanically or pneumatically controllable closing valve (18, 20, 21).
  7. Tubular filter element according to Claim 6 , characterized in that the mechanically, electromechanically or pneumatically controllable shut-off valve (18, 20, 21) is functionally coupled with the at least one cleaning valve (10) for a purge gas supply.
  8. Tubular filter element according to one of the preceding claims, characterized in that the outlet openings from the tubular cleaning lance (7) are distributed axially and radially on it and directed into the inner volume.
  9. Tubular filter element according to one of the preceding claims, characterized in that the filter surfaces (9) consist of Si 3 N 4 , ZrO 2 , SiC, Al 2 O 3 , spinel or sintered metals.
  10. Method for cleaning a tubular filter element (1) exposed to a flow of raw gas with cleaning agents (11) according to one of the preceding claims by backflushing the filter element with a purge gas flow or pulse (16) from the clean gas side, characterized in that the purge gas flow or pulse is introduced through an opening of a cleaning valve (10) into a tubular cleaning lance (7) arranged coaxially in the cylindrical inner volume and is directed through the inner volume and the filter surfaces (9) via several outlet openings (15) of the cleaning lance arranged axially over the axial extent of the filter surfaces, and the closing means (11) for the at least one clean gas-side outlet (19) are closed from the inner volume.
  11. Procedure according to Claim 10 , characterized in that the purge gas flow or pulse (16) is carried out under overpressure.
  12. Procedure according to Claim 10 or 11 , characterized in that the purge gas stream or pulse (16) consists of a gas mixture or dried/superheated water vapor.
  13. Procedure according to one of the Claims 10 until 12 , characterized in that the purge gas flow or pulse has a temperature equal to the system temperature.

Description

The present invention relates to a tubular filter element according to the first claim and to a method for cleaning the tubular filter element exposed to a flow of raw gas according to claim 10. The aforementioned tubular filter elements are known in particular in the form of cartridge filters or filter candles, in which the outer surface is formed by rigid, i.e., stiff and non-flexible filter surfaces, and preferably one end is open. The diameter-to-length ratio (L/D ratio) is typically greater than 25. They serve for dust separation, especially at high gas temperatures, for example, in combustion processes (hot gas filtration, preferably above 500°C), and have diameters exceeding 100 mm with lengths up to 6 m. It is understood, however, that the method according to the invention is in principle applicable to all tubular or hollow cylindrical filter elements. For particle filtration at high temperatures, ceramic filter elements are used almost exclusively, with the exception of special metallic materials. These tubular filter elements are typically exposed to a raw gas flow (i.e., a dust-laden gas) on the raw gas side. The raw gas penetrates the filter surfaces and enters the clean gas-side interior of the tubular filter elements, where it is discharged axially, preferably through only one open end of the filter element. Particle fractions from the raw gas typically separate onto the filter surfaces, leading to a gradual clogging of the filter elements with a so-called filter cake—a layer of compacted, often adhering, particle fractions—as the filtration time increases. In the filtration of dust-laden gases, i.e., free-flowing and/or extremely fine dusts or particles, the particles already separated on the filter surfaces on the raw gas side are usually detached by cleaning through periodically recurring counter-currents or counter-current pulses and sediment into a dust collection chamber; however, some are also resuspended in the gas, i.e., finely dispersed again in the raw gas chamber of the filter system. From the DE 199 17 165 A1 For example, a method for cleaning filter cartridges exposed to a raw gas flow from the outside is described, with each cartridge having a safety filter located downstream of it in the clean gas chamber. This cleaning is achieved by backflushing the filter cartridge from the clean gas side. The purge gas flow required for backflushing, originating in the clean gas chamber behind the filter cartridge, is guided through the safety filter into or through the filter cartridge, while the safety filter is shut off from the exhaust air side. This shut-off is accomplished by a fluid-dynamic, pneumatic switch without moving parts. The flow path of this switch is alternately opened by the lower process pressure from the clean gas chamber and closed by the higher backflushing pressure. As the L/D ratio increases, the amount of gas that can effectively be introduced through the inlet cross-section decreases, so that the purge gas flow rate relative to the filter area steadily declines. However, the effectiveness of cleaning decreases not only with the lateral extent of the filter surfaces, but also with an increasing length-to-diameter ratio of the tubular filter elements. This results in unevenly distributed cleaning gas flows and impulses across the filter surface areas, leading to locally insufficient cleaning of the dust adhering to the filter surfaces. In conventional systems, the cleaning intensity is further limited by the speed of sound, which acts as the upper limit for the flow through the filter channels. Since the overpressure in filter cartridges, necessary for cleaning, is derived from the kinetic energy of the gas, it remains limited. Operational performance deteriorates further if the filters exhibit high resistance, for example, due to ingress of fine dust, high dust concentrations, or high filtration velocities. Clogged filters, especially those with a higher L/D ratio, often cannot be adequately cleared by blowing if the dust is highly adhesive. In the DE 36 20 489 A1 A method and device for cleaning bag- and tube-shaped filter elements is proposed, in which a back pressure is briefly built up on the clean gas side of each filter element by injecting a cleaning gas via a blow lance, which removes the raw gas-side deposits on the filter element by means of a counter-flow. Further relevant prior art is the DE 10 2016 212 676 A1 . Based on this, one object of the invention is to design the aforementioned method and the tubular filter element in such a way that reliable cleaning is ensured even with larger L/D ratios. The task is accomplished with a tubular filter element having the features of the first claim. as well as by a method for cleaning the tubular filter element having the features of claim 10. The dependent claims relating thereto describe advantageous embodiments. The basis for solving this problem is a conventional tubular filter element comprising a clean-ga