Scrubbing spray tower

By far the greatest number of instaUations is for the removal or recoveiy of mostly small concentrations of acidic and other components from air, hydrocarbons, and hydrogen. Hundreds of such plants are in operation, many of them of great size. They mostly employ either packed or tray towers. Power requirements for such equipment are small. When the presence of solid impurities could clog the equipment or when the pressure drop must be low, spray towers are used in spite of their much larger size for a given capacity and scrubbing efficiency. 

Wet scrubbers rely on a liquid spray to remove dust particles from a gas stream. They are primarily used to remove gaseous emissions, with particulate control a secondary function. The major types are venturi scrubbers, jet (fume) scrubbers, and spray towers or chambers. Venturi scrubbers consume large quantities of scrubbing liquid (such as water) and electric power and incur high pressure drops. Jet or fume scrubbers rely on the kinetic energy of the liquid stream. The typical removal efficiency of a jet or fume scrubber (for particles 10 g. or less) is lower than that of a venturi scrubber. Spray towers can handle larger gas flows with minimal pressure drop and are therefore often used as precoolers. Because wet scrubbers may contribute to corrosion, removal of water from the effluent gas of the scrubbers may be necessary. 

Wet scrubbers have found widespread use in cleaning contaminated gas streams because of their ability to effeetively remove both particulate and gaseous pollutants. Specifically, wet scrubbing describes the technique of bringing a contaminated gas stream into intimate contact with a liquid. The types most widely used for particulate control are spray towers, packed-bed units, ionizing wet scrubbers, and venturi scrubbers. 

Total enclosure Wet scrubbing Absorption tower Fluidized bed scrubber Impingement scrubber Irrigated target scrubber Pressure spray scrubber Rotary scrubber ... 

The air coming from the tower will be carrying dust particles that must be scrubbed, thus generating a wastewater stream. The spray towers are periodically shut down and cleaned. The tower walls are scraped and thoroughly washed down. The final step is mandatory because the manufacturers must be careful to avoid contamination to the subsequent formulation. 

The scrubbing liquid is controlled to a neutral pH with reagent addition to drive SO2 absorption. Caustic soda (NaOH) is typically used as the alkaline reagent. However, other alkalis, such as soda ash, magnesium hydroxide, and lime have also been utilized with excellent results in terms of performance and reliability. For FCCU applications, however, where a 5-7 year continuous operation is required, the use of lime as a reagent is not recommended. Multiple levels of spray nozzles provide sufficient stages of gas/liquid contact to remove both particulate and SO2. An illustration of the spray tower and the spray nozzles is provided in Figure 16.6. 

For scrubbing of sulfur dioxide and a large portion of catalyst fines, a countercurrent spray tower with a multiple stage nozzle system is typically applied. The WESP is applied after the scrubber section to remove the residual particulate matter with a... 

Figure 1. Flow schematic of a spray-tower adsorber. The scrubbing solution is contacted with hot flue gas, collected in the bottom, and continuously recycled and contacted. Suspended solids and pH of liquid in the recycle loop of Plant D spray towers ranged from 5.2 to 8.7%, and from 5.2 to 6.80%, respectively.

Satriana (2) provides a summary of the development of flue gas treatment technology. The first commercial application of flue gas scrubbing for sulfur dioxide control was at the Battersea-A Power Station [228 MW(e)] in London, England, in 1933. The process used a packed spray tower with a tail-end alkaline wash to remove 90 percent of the sulfur dioxide and particulates. Alkaline water from the Thames River provided most of the alkali for absorption. The scrubber effluent was discharged back into the Thames River after oxidation and settling. A similar process was also operated at the Battersea-B Power Station [245 MW(e)] beginning in 1949. The Battersea-B system operated successfully until 1969, when desulfurization efforts were suspended due to adverse effects on Thames River water quality. The Battersea-A system continued until 1975, when the station was closed. 

Hydrogen escaping from electrolyzers in a plant that operates properly contains 3—5 % oxygen and 0.5—2 % chlorine. Sometimes this can be further utilized. In this event the gas is first scrubbed in towers with a caustic soda solution to remove the chlorine, then it passes into the catalytic chambers, where, at 500 °C the oxygen is removed on a catalyst consisting of platinum dispersed on a suitable carrier. The hot purified hydrogen is cooled by spraying with water, then dried and delivered to where required. 

Fluorine is recovered at the evaporator station by scrubbing the vapors leaving the flash chamber. The vapors pass through an entrainment separator to remove fine droplets of phosphoric acid and then into a spray tower where they are scrubbed with a weak solution of fluosilicic acid according to the reaction ... 

Figure 2. Flow diagram for adipic acid-enhanced scrubbing in the venturi/spray tower system with two scrubber loops and forced oxidation.

Lime tests with One Scrubber Loop and Without Forced Oxidation. Tests with adipic acid in lime scrubbing also were impressive in enhancing S02 removal, both on the venturi/spray tower and TCA systems. Table 4 shows some typical results of adipic acid-enhanced lime tests from the Shawnee TCA without forced oxidation. The flow diagram for these tests is shown in Figure 3. 

Alkali scrubbing system consisting of alkali dissolving tank (if solid flakes are put in), water supply, pH indicator-controller venturi and packed/spray tower, circulation pumps, demister candle, and fiberglass chimney. 

The light oil (consisting primarily of benzene, toluene, and xylene) may be left in the gas and burned with it or extracted for subsequent distillation. Extraction is accomplished by scrubbing with a wash oil in packed or spray towers. The light oils are then separated from the wash oil by distillation (Figure 16.2). 

Many devices are used for wet gas scrubbing such as spray towers, packed towers, plate scrubbers such as the Peabody scrubber or Venturi scrubber. Scrubbing liquor is circulated through the scrubbing system and becomes acidic due to the absorption of SO3 contained in sinter plant gas. Often the... 

Caiazzo G, Langella G, Miccio F, Scala F (2012) Seawater SO2 Scrubbing in a Spray Tower for Marine Application. Paper presented at the 35th Meeting of the Italian Section of the Combustion Institute, Milano, Italy, 10-12 Oct 2012... 

---