Particulate plugging

In a hot gas expander, the major problems associated with catalyst fines are centered on erosion of components and particulate plugging. Either problem can cause machine vibration and sometimes power train emergency shutdown. Because many failures have resulted from these factors, machinery manufacturers recommend that the maximum permissible solids concentration upstream of an expander not exceed 200 ppm. It is further stipulated that 97% of the particles be smaller than 10 p. Allowing concentrations of 160 ppm with 95% of the particle less than 10 p is considered reasonable. 

Low temperature units are particularly susceptible to fouling in high sulfur applications. Plus, some low temperature catalysts are susceptible to particulate plugging. 

Well production may also start to decrease due to heavier petroleum deposits (tars, waxes, etc.) or other particulates plugging the rock pores, strata collapse, etc., in the area coming to the well. Reservoir engineers evaluate the production concerns and usually recommend a workover to revitalize or stimulate the well by various means based on the well characteristics and the problem encountered. 

Module type Channel Packing spacing(cm) density (m Energy " ) costs Particulate plugging Ease of cleaning... 

Mesh beds of knitted wire mesh, plastic, or glass fibers are used for the removal of Hquid particulates and mist. They will also remove soHd particles, but win plug rapidly unless irrigated or flushed with a particle-dissolving solvent. 

Using 2eohte catalysts, the NO reduction takes place inside a molecular sieve ceramic body rather than on the surface of a metallic catalyst (see Molecularsieves). This difference is reported to reduce the effect of particulates, soot, SO2/SO2 conversions, heavy metals, etc, which poison, plug, and mask metal catalysts. ZeoHtes have been in use in Europe since the mid-1980s and there are approximately 100 installations on stream. Process applications range from use of natural gas to coal as fuel. Typically, nitrogen oxide levels are reduced 80 to 90% (37). 

Solid particulates are captured as readily as hquids in fiber beds but can rapidly plug the bed if they are insoluble. Fiber beds have frequently been used for mixtures of liqmds and soluble sohds and with soluble solids in condensing situations. Sufficient solvent (usually water) is atomized into the gas stream entering the collector to irrigate the fiber elements and dissolve the collected particulate. Such nber beds have been used to collect fine fumes such as ammonium nitrate and ammonium chloride smokes, and oil mists from compressed air. 

Particulates deposition possibly causing plugging of the bed or plates... 

Prefiltering of gas stream possibly required to remove any particulate capable of plugging the adsorbent bed... 

Many compounds can cause problems in pollutant-control equipment. Particulate matter, liquids, or solids in the waste stream can plug the adsorber beds, heat-recovery beds in regenerative thermal incinerator systems and biofilters. Conventional filtration systems are used to remove particulate matter before or after the process. 

Cyclones are designed for continuous operation and must be protected from plugging. In intermittent applications, the operating practices must include specific steps to purge the entire system of particulates prior to shutdown. 

May plug if large particulates are present or precipitates form from reactions Fumes require very slow rates. 

May incorporate device for continually wetting column High loadings of particulates may plug unit with packing... 

There are a number of methods that have been proposed to help prevent the loss of circulation fluid [1214]. Some of these methods use fibrous, flaky, or granular material to plug the pores as the particulate material settles out of the slurry. Examples are oat hulls [855], rice products [294,295], waste olive pulp [519], nut cork [654,1532], pulp residue waste [750], petroleum coke [1840], and shredded cellophane [296]. 

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