Separation equipment electrostatic precipitator

The process gases enter a forced-circulation-type waste heat boiler at 800-1000 °C. Several changes have been made to the mechanical rapping equipment and cooling pipe bundles of the boiler to improve the performance and maintenance access. The gases exit the waste heat boilers at a temperature of 300-350 °C and pass through the hot cyclone separators and electrostatic precipitators into the mercury removal towers. Two electrostatic precipitators are installed simultaneously in both lines to ensure continuous processing. 

To reduce catalyst losses even further, additional separation equipment external to the regenerator can be installed. Such equipment includes third-stage cyclones, electrostatic precipitators, and more recentiy the Shell multitube separator, which is Hcensed by the Shell Oil Co., UOP, and the M. W. Kellogg Co. The Shell separator removes an additional 70—80% of the catalyst fines leaving the first two cyclones. Such a third-stage separator essentially removes from the due gas stream all particles greater than 10 p.m (36). 

Elutriation is important in most industrial fluidized beds and is generally thought of as a disadvantage. In addition to the small particles which may be present in the initial particle size distribution, fines may be created in the course of operation by the attrition of bed particles. Elutriated particles usually need to be collected and recovered either because they represent the loss of product particles of a given size, because they must be separated from the exhaust gas for environmental reasons, or because of safety concerns there is a considerable risk of a dust explosion with very fine particles and perhaps especially so with many food particulates. Therefore the fluidized bed plant will require ancillary gas cleaning equipment such as a cyclone, filter or electrostatic precipitator to separate the fines from the gas. The loss of a particular size fraction from the bed may change fluidized bed behaviour and it then becomes important to return the fines to the bed continuously. 

A review of Table 8 and Fig. 3-2 indicates that large-diameter particles can be removed with low-energy devices such as settling chambers, cyclones, and spray chambers. Submicron particles must be removed with high-energy units such as bag filters, electrostatic precipitators, and venturi scrubbers. Intermediate particles can be removed with impingement separators or low-energy wet collectors. Obviously, other equipment performance characteristics as noted in Table 8 will also have their influence on the final equipment... 

Cost data for blenders and mixers, kneaders, centrifugal separators, crystallizers, crushing and grinding equipment, dust collectors, electrostatic precipitators, and screens are presented in Figs. 14-66 through 14-88. 

Many types of particulate collection devices are available commercially (see Table 53.2). Each operates on a different principle for accomplishing removal of particulates from the gas stream. Four basic types are common in drying systems (1) the drying vessel itself (in the case of vessel dryers), (2) cyclones, (3) bag filters, and (4) wet scrubbers. Electrostatic precipitators (ESPs) are not used widely in drying installations in spite of their low-pressure drop and high collection performance. The initial cost of purchase and construction is high. For this reason, the emphasis in Section 53.3 will be on the three most widely used devices, e.g., cyclones, fabric filters, and wet scrubbers. For a concise discussion of various types of solid-gas separation equipment and guidelines for selection of dust collectors,... 

Absorption is a process that relies on a solvent s chemical affinity with a solute to dissolve preferably one species into another. It is widely proposed for CO2 separation where a solvent, generally, monoethanolamine (MEA) or a solid absorbent like lithium zirconate is used to dissolve CO2, but not the other components of a flue gas stream. C02-rich solution is typically pumped to a regeneration column, where CO2 is stripped out from the solution and the solvent recycled for a new batch of flue gas. The absorption equipment should be placed after the flue gas desulfurization-step and before the stack. Optimal conditions for absorption are low temperature and high pressure, making this the best location for absorption to occur. In addition, most solvents are easily degraded by compounds such as fly ash, other particulates, 80, (SO2, SO3) and (NO, NO2), so the absorption step must take place after electrostatic precipitation and desulfurization. In a typical absorption process, the C02-lean flue gas is either emitted to the atmosphere or possibly used in other applications e.g. chemical production). 

The main types of air cleaning equipment are mechanical separators, filtration devices, wet collectors, electrostatic precipitators, gas adsorbers, and combustion incinerators. 

Aside from meeting ambient air quality targets, various types of separation equipment, including knock-out drmns, bag filters, electrofilters/electrostatic precipitators (ESP s), scrubbers and cyclones are also used to captme solid particles for ... 

Obviously, if pressure drops on the order of 6 to 8 kPa are acceptable from a process point of view, an 8 or 13-unit multicyclone (or some number in between) could prove to be a viable option for the task at hand. If not, other types of separation equipment may have to be considered such as a baghouse, an electrostatic precipitator, or a wet scrubber. Nevertheless, even if the pressure drop across the cyclones were acceptable, one would still need to consider the long-term wear implications associated with operating the cyclones at velocities in the range of 35 to 40 m/s. If the solids being processed are not especially abrasive and/or if they are sufficiently flne in size, it may be possible to operate at these velocities. If not, erosion-protective liners may need to be installed. Some bare-metal multicyclone systems have been observed to operate for many years at velocities of 70 to 85 m/s while processing several tons per day of rather abrasive sand-like particles that were under about 25 fim in size. 

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