关于Shell的陶瓷过滤器？ scgp - hpht fly ash filter reliability improvement experience and journey the purpose of this presentation is to provide an short overview of the experiences with the installed pall fly ash filters, analyze filter operations, and provide recommendations for improved filter operation, service and preventive maintenance to increase the filter availability and reliability, based on last three years experiences. 1. upset of venturi ejectors • problem first recognized january 10, 2007 • design improvement / modifications were communicated to all clients on january 19, 2007 and used for all further projects. • the optimized / modified design solved the problem 2. blowback valve failure • there are several reasons for the blowback valves failures, like incorrect electrical wiring, broken or unattached cable contaminated control air. particles plug the fine holes of the solenoid valve and stop the blowback valve from operating internal corrosion of blowback valves from the blowback gas (syngas). lack of insulation and electrical heat tracing led to condensation and h2s corrosion. no preventive maintenance for the blowback valves 3. filter feed (fly ash) outside specifications • the characteristics of the fly ash in the filter feed have periodically been outside specification, in particular the dust characteristics, like the consistency and particle size distribution. there are indications that below factors may have played a role: a. feed coal quality outside specification (used “fouling” coal) unusual operating conditions or damage inside gasifier, resulting in foreign particles entering the filter and abrasive destruction of ceramic candle insufficient reaction in the gasifier which produces a different fly ash, e.g. residual carbon b. elevated moisture (h2o content in the syngas), leading to partial condensation and/or a more sticky dust cake out of specification dust characteristics lead to dust cakes that are more difficulty or even impossibly to remove from the surface of the candles by blowback. this results in a lack of or incomplete cleaning of the candles and the formation of dust bridges. dust bridges between the candles have a high probability of leading to candle breakage. 4. other operational actions possible leading to damage to the filter • important prerequisites for optimum blowback operation were not met a. unstable blowback gas pressure, due to simultaneous demand from as many as three consumers. the insufficient pressure results in reduced cleaning effectiveness b. out of specification blowback gas quality. oil contamination (up to 200 ppm) of the blowback gas lead to internal contamination of the candles by oil, which plugged the pores and reduced the cleaning effectiveness。 • incorrect operator actions can cause candle breakage, like pall expects a ceramic candle life without extra cleaning outside the filter of: pall at minimum two years or 16,000 operating hours on an average three years or 24,000 operating hours and can be externally cleaned a minimum of 2 times. this expectation is based on the historical experience operating fly ash filters and is conditional on: 1. all operating conditions being within specification 2. all pall operating and maintenance recommendations are followed most of the pall corporation's clients operate in such way, that a complete set of candles is replaced by a new set and the used set of candles cleaned for reinstallation after the next operating period. the mechanical strength of the candles have not shown any signs of degradation. a. process leakage leading to fire and damage to blowback valves. not working valves lead to no blowback cleaning, dust bridges formation and finally candles breakage. b. pressure equalization between filter and sluice vessels, following sluicing at too high differential pressure. the pressure equalization into the filter damaged nearby cluster of ceramic candles. the following actions will increase both the availability and reliability of the filter: (1) correct installation of the ceramic filter candles and filter internals, like modular tube sheet, venturies, lock plates (2) follow suitable startup and shutdown procedure, ensuring that no syngas below its dew point (recommended 200°c) is allowed to enter the filter vessel (3) keeping of specified process / operation parameter (4) control and monitoring of filtration process a. control and monitoring of the filter differential pressure (p) b. operation with the correct and optimized interval time c. control and monitoring blowback valves (5) preventive maintenance a. annual (every 12 months) inspection of filter internals b. annual (every 12 months) inspection of blowback valves c. stocking of spare and wear parts (6) use of safety fuses (called also safety filters) (1) three scheduled service visits per year to customer site, each lasting 3 to 5 working days a. inspection of the filter unit, mainly the filter internals and blowback valves b. evaluation of the current operating parameters and filter operation optimization c. operator training d. candle replacement supervision e. candle cleaning supervision (2) one customer initiated/requested service visit per year to customer site, lasting 3 to 5 working days (3) laboratory-technical examinations of: a. used filter candles (removed during annual filter inspection) b. cleaned filter candles c. dust samples (4) evaluation of current operation data providing: a. optimization recommendations for filter operation b. replacement recommendations for filter candles the analysis of filter operations, observed problems, and the experiences of the past three years clearly show that： 1. the filters works well, if operated according to pall recommendations and within all specified operating conditions 2. preventive maintenance is one of the main pre-condition for a high filter availability and reliability 3. there are significant levels of improvement of the filter operation and reliability based on: a. operation within filter specifications b. operation and maintenance according to the pall instructions outlined in the instruction manual c. co-operation and information exchange between the end-user and pall查看更多
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