Concurrent scrubber

Column Column Column Gas Recycle Tank Column Colunm Column Concurrent Scrubber Tower... 

In a horizontal flow concurrent scrubber, the gas velocity carries scrubbing liquid into the packed bed and the device actually operates as a wetted entrainment separator. Normally, superficial gas velocity is limited to a maximum of 9.6 ft/s due to liquid reentrainment at higher velocities. Packed bed thickness is restricted because the depth of liquid penetration into the tower packing is limited by the allowable gas velocity. 

Mass transfer driving forces are intermediate between vertical concurrent scrubbers and countercurrent scrubbers [1]. If the absorbed solute obeys Henry s Law in the liquid phase, the mass transfer driving force will limit maximum solute removal efficiency to about 90% of that obtained in a countercurrent scrubber for typical chemical fumes—assuming scrubbing water flow is limited. However, if the absorption of solute is followed by a rapid chemical reaction in the liquid phase, so that there is no appreciable vapor pressure of solute above the solution, the mass transfer driving force will be the same as for a countercurrent scrubber. 

Concurrent scrubber—Scrubber in which the gas and liquid flow in the same direction. 

This operation ensures the transfer of the bulk of the perchloryl fluoride from the reaction vessel and associated lines. Concurrently, some anhydrous hydrogen fluoride from the — 40 C. traps will tend to transfer also (vapor pressure of hydrogen fluoride at -40°C. = ca. 50 mm.) but will be absorbed in the sodium fluoride scrubber. 

Scrubber liquid can be recycled to obtain a salt solution of any desired concentration prior to regeneration of ammonia from the solution. The upper limit on solution concentration presumably will be controlled by the vapor pressures of the components, ammonia and sulfur dioxide. At high pH, ammonia vapor predominates at low pH, sulfur dioxide is the dominant vapor. Therefore, optimum recycle of the scrubber liquid will be controlled at low pH and dilute solution concentration concurrent with and relative to equipment (capital) and operating costs. A solution having low pH (e.g., < 6.0) requires stainless steel or protected carbon steel to prevent corrosion. 

The results of the tests showed adipic acid to be very effective in improving SO2 removal efficiency, even when operating at chloride levels as high as 17,000 ppm. A TCA scrubber, which removed 82 percent of the inlet SO2 without the additive, yielded 89 percent S02 removal with 700 ppm adipic acid, 91 percent removal with 1,000 ppm, and 93 percent removal with 2,000 ppm adipic acid. The limestone utilization was concurrently increased from 77 percent without the additive to 91 percent with 1,600 ppm adipic acid. The observed effects thus confirmed the theoretical expectations in all respects. In addition, the tests showed no serious inteference by adipic acid on the performance of the oxidizer, operating at pH 6.1. 

Packed scrubbers generally are arranged in one of four ways, based on the manner in which the liquid is contacted with the gas stream. Concurrent flow scrubbers make up two of these classifications. In both cases the liquid and gas flow in the same direction through the scrubber. 

A concurrently operated vertical flow scrubber removes the restriction of power input with respect to hydraulic flooding of the packed bed. Therefore, this device can operate at higher gas velocities and greater pressure drops than a countercurrendy operated scrubber. With increased power input possible, concurrendy operated packed scrubbers are much more effective for the removal of particles from 1- to 3-micron equivalent diameter than countercurrent units. Table 5-2 shows typical size ranges for common particulate emissions [3]. Tobacco smoke has been included in this list to provide a comparison of size with commonly encountered particulates. 

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