Solids entrainment

Bubble-Tube Systems The commonly used bubble-tube system sharply reduces restrictions on the location of the measuring element. In order to ehminate or reduce variations in pressure drop due to the gas flow rate, a constant differential regulator is commonly employed to maintain a constant gas flow rate. Since the flow of gas through the bubble tube prevents entiy of the process liquid into the measuring system, this technique is particularly usefiil with corrosive or viscous liquids, liquids subjec t to freezing, and hquids containing entrained solids. 

Abra.sion. If there are entrained solids in the hquid, it is desirable to have a flushed single inside type with a face combination of veiy hard material. 

Entrained Solids Bubble Columns with the Solid Fluidized... 

Property Trickle bed Flooded Stirred tank Entrained solids Fluidized bed... 

Interfacial area 20-50% of geometrical Like trickle bed reactor 100-1,500 mVm 100-400 mVm Less than for entrained solids... 

Abrasion. When evaluating the possibility of installing a seal in a liquid that has entrained solids, several factors must be considered. Is the seal constructed in such a way that the dynamic motion of the seal will be restricted by fouling of the seal parts The seal arrangement that is usually preferred when abrasives are present is a flushed single inside type with a face combination of very hard material. Flowever, factors such as toxicity or corrosiveness of the material may dictate that other arrangements be used. 

Ultrafiltration membranes are commercially fabricated in sheet, capillary and tubular forms. The liquid to be filtered is forced into the assemblage and dilute permeate passes perpendicularly through the membrane while concentrate passes out the end of the media. This technology is useful for the recovery and recycle of suspended solids and macromolecules. Excellent results have been achieved in textile finishing applications and other situations where neither entrained solids that could clog the filter nor dissolved ions that would pass through are present. Membrane life can be affected by temperature, pH, and fouling. 

They are not recommended for dirty or fouling services, because of plugging of the pilot valve and small-bore pressure-sensing lines. If the pilot valve or pilot cormections become fouled, the valve will automatically open. In special cases where fouling is a function of entrained solids, this limitation may be countered by the use of a nonflowing pilot valve and a pilot line filter. With a nonflowing pilot valve, there is no normal flow in the pilot system and therefore solids entrainment is reduced. 

By-product HCl from the heavy organic-chemicals industry (p, 798) now accounts for over 90% of the HCl produced in the USA, Where such petrochemical industries are less extensive this source of HCl becomes correspondingly smaller. The crude HCl so produced may be contaminated with unreacted CI2, organics, chloro-organics or entrained solids (catalyst supports, etc,), all of which must be removed. 

Nature of gas corrosion, entrained solid particles, entrained fibers, and entrained moisture. 

Other acid gases such as hydrogen chloride and oxides of nitrogen produce similar corrosion problems. The corrosion effects produced by acid condensate are amplified by the motion of the gas stream (typically 20-53 m/s) and erosion effects due to entrained solids and impingement at bends, damper plates, reheaters, etc. 

Erosion resistance The mechanical properties of paints prevent their use in conditions where impingement or erosion by entrained solids is expected. 

In most processes of coal conversion the corrosive action of the gaseous environment may be aggravated to some degree by the erosive action of the entrained solids, the ashes or partly-burned fuel termed char. 

For other environments, such as in sea-water or in chemical plants, exposure conditions that most nearly duplicate those of the related service and are at the same time reproducible, are used. Impingement by water or water carrying entrained solids, thermal effects and physical abuse are among the factors to be considered. 

The use of steam washing equipment. Apart from the removal of entrained solids and water, steam washers are quite effective at removing vaporous silica carryover (typically 60-70% removal). 

A fluidized-bed reactor consists of three main sections (Figure 23.1) (1) the fluidizing gas entry or distributor section at the bottom, essentially a perforated metal plate that allows entry of the gas through a number of holes (2) the fluidized-bed itself, which, unless the operation is adiabatic, includes heat transfer surface to control T (3) the freeboard section above the bed, essentially empty space to allow disengagement of entrained solid particles from the rising exit gas stream this section may be provided internally (at the top) or externally with cyclones to aid in the gas-solid separation. A reactor model, as discussed here, is concerned primarily with the bed itself, in order to determine, for example, the required holdup of solid particles for a specified rate of production. The solid may be a catalyst or a reactant, but we assume the former for the purpose of the development. 

Entrained solids bubble columns with the solid fluidized by bubble action. The three-phase mixture flows through the vessel and is separated downstream. Used in preference to fluidized beds when catalyst particles are... 

Instead of filtration or centrifuging as a means of separating the crystallized wax from oil, an electrical precipitation method has been proposed, similar to that employed in desalting of crude or removal of entrained solids from gases. 

The dry product is primarily collected in cyclone collectors (a few bag houses still remain), sieved, and finally packaged in moisture barrier containers. The exit air from the dryer often has to be treated to meet local pollution control laws. While many of the older dryers use gas incineration, as energy costs have increased these incineration systems have become quite costly to operate. New dryer installations use scrubbing systems (e.g., aqueous/chemical sprays) to remove entrained solids and gaseous volatile flavors. 

Equilibrium relations in leaching usually are simpler than in liquid-liquid equilibria, or perhaps only appear so because few measurements have been published. The solution phase normally contains no entrained solids so its composition appears on the hypotenuse of a triangular diagram like that of Example 14.8. Data for the raffinate phase may be measured as the holdup of solution by the solid, K lb solution/lb dry (oil-free) solid, as a function of the concentration of the solution, y lb oil/lb solution. The correspond-... 

The paper provides an overall cooling system model called Unimod. The model is applied to present and future cooling system requirements, and eliminates plant trials of treatment chemicals. At a midwest refinery petrochemical plant, oil leaks, the use of four alternating water sources, and entrained solids were causing heat transfer losses and unscheduled shutdowns. In less than an hour, the model identified the best of the available water sources and blends, and recommended a treatment program for use before each water change. This enabled the refinery to increase heat transfer by 20%, eliminate unscheduled shutdowns, and with treatment, use the plant wastewater safely for all cooling water makeup. 

The fluidized bed reactor is a vertical steel vessel to which TDF is fed through a side port. A fluidized bed of TDF is maintained with hot air. The abrasive action of the fluidized particles erode the char from the TDF, reducing the tire material to small pieces. As the TDF decomposes, ash and char are swept out of the reactor with the fluidizing air. The biggest disadvantages of a fluidized bed system are the need to remove entrained solids from the vapors, and the need to maintain the hot, fluidizing gas. 

Example. Bitumen is recovered in the form of a froth when a separation-flotation process is applied to surface mined oil sand. Once de aerated, this bituminous froth is a W/O emulsion from which the water must be removed prior to upgrading and refining. At process temperature (80 °C) the emulsion viscosity is similar to that of the bitumen, but the density, due to entrained solids, is higher. Taking t) = 500 mPa-s and f> = 1.04 g/mL, the rate of creaming of 20 pm diameter water droplets under gravitational force will be very slow ... 

Cell recovery is mainly concerned with what is known as clear mash, i.e. sugar solutions without any entrained solids suchas as those in a whole-grain mash. The use of cell recovery on mash can be accomplished by clarifying the mash prior to fermentation or else incorporating a wet-milling front end and taking the saccharified starch as substrate. However the production of a clear mash directly from cereal mash is presently not feasible. This is due to excessive losses of carbohydrate in the cake or non-fermentable extract ranging from 10 to 20 per... 

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