Scrubber technologies

Condensation scrubbing is a relatively recent development in wet scrubber technology. Most conventional scrubbers rely on the mechanisms of impaction and diffusion to achieve contact between the PM and liquid droplets. In a condensation scrubber, the PM act as condensation nuclei for the formation of droplets. Generally, condensation scrubbing depends on first establishing saturation conditions in the gas stream. Once saturation is achieved, steam is injected into the gas stream. The steam creates a condition of supersaturation and leads to condensation of water on the fine PM in the gas stream. The large condensed droplets are then removed by one of several conventional devices, such as a high efficiency mist eliminator. 

Scrubbers are the most commonly used technique for separating particulates from gas streams. The field of scrubber technology is very mature, with literally hundreds of thousands of scrubbers in operation worldwide, scrrne in operation for more than 50 years. 

Condensation scrubbing is a relatively recent development in wet scrubber technology. Most conventional scrubbers... 

SCGP. See gasification, Shell coal SCO. See oxidation, selective catalytic SCOT process, 471 scrubber technology, 330-331 SCT. See reactor, short contact time selective catalytic reduction (SCR), 464 Selectra PROX I, 345, 352 Selexol, 212-213, 283-285, 471, 472,... 

In addition to lime and limestone, a number of other absorbents have been used to improve the efficiency of sulfur removal or to recover the sulfur in a marketable form while regenerating the absorbent. Next-generation scrubbers are therefore under development to improve the efficiency and reduce the quantity of unmarketable waste products.Several of the scrubber technologies that use other absorbents are listed here ... 

By most measures, the Acid Rain Program has been a model for successful emission trading systems. Allowances in Phase I sold for approximately 100 per ton of SOj, well under half of what had been forecast (about 250/ton.). Since 1994, allowances have cost 65 to 210 per ton as scrubber technology has become cheaper, and it has become less expensive to switch to low-sulfur coal. Sulfur dioxide emissions declined faster than anticipated and the market has now reached a value of 2 billion/year. Twenty-seven units added scrubbers accounting for 45% of the reductions in 1995-96. Seven large units accounted for two-thirds of this amount. Many units also switched fuels - almost all from high to lower sulfur coal. ... 

The aluminum process involves fluoride emissions originated from the electrolyte and SO2 from the anode. In the early days the fumes from the cell were not treated, but both for environmental and economical reasons the dry scrubber technology was developed to remove fluorides. 

McGraw-Hill, 1991, EPRI Official Few Utilities Willing to Try New SO2 Scrubber Technologies, Utility Environment Report, Dec. 13, p. 7. 

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