Towers sulfur dioxide, spray

Sulfur Dioxide, Spray Towers Flue gases and offgases from sulfuric acid plants contain less than 0.5 percent SO9 smelter gases like those from ore processing plants may contain 8 percent. The high-concentration streams are suitable for the manufacture of sulfuric acid. The low concentrations usually are regarded as contaminants to be destroyed or recovered as elemental siilfur by, for example, the Claus process. 

Burning Pyrites. The burning of pyrite is considerably more difficult to control than the burning of sulfur, although many of the difficulties have been overcome ia mechanical pyrite burners. The pyrite is burned on multiple trays which are subject to mechanical raking. The theoretical maximum SO2 content is 16.2 wt %, and levels of 10—14 wt % are generally attained. As much as 13 wt % of the sulfur content of the pyrite can be converted to sulfur trioxide ia these burners. In most appHcations, the separation of dust is necessary when sulfur dioxide is made from pyrite. Several methods can be employed for this, but for many purposes the use of water-spray towers is the most satisfactory. The latter method also removes some of the sulfur... 

A variation of the n on regen erabi e absorption is the spray dry process. Time slurry is sprayed through an atomizing nozzle into a tower where it countercurtendy contacts the flue gas. The sulfur dioxide is absorbed and water in the slurry evaporated as calcium sulfite-sulfate collects as a powder at the bottom of the tower. The process requires less capital investment, but is less efficient than regular scmbbing operations. 

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... 

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. 

If the gas emerging from the beds is sprayed with oleum in a tower, the absorbed sulfur dioxide does not form sulfuric acid, oleum with a higher sulfur trioxide content is obtained instead. 

Originally, bubble cap plates had been used for absorption of pollutant gases such as sulfur dioxide. However, the solids in the slurries used as absorbents can more readily plug bubble caps. Typical absorbents used in current processes include, for example, conventional lime slurry lime-limestone slurries mixed sodium sulfite/ lime slurries and magnesium sulfite/bisulfite mixed with lime slurries. Conventional lime slurry towers may consist of a multilevel spray tower combined with a venturi scrubber. Venturi scrubbers will be discussed briefly below. Mixed sodium sulfite/lrme slurries may be contacted in a plate tower. Sieve plates might be used with larger than normal holes to help prevent plugging due to the solids in the slurries. 

As a further stage to ensure the removal of any small particles of dust, flue gas can be directed to a Venturi-type dust collector. At both the Met and the outlet of this type of collector, dust is covered by condensate through adiabatic expansion and collected by sprayed water that is circulated via tanks installed at the inlet and the outlet, respectively. This system is also a useful preparation for the removal of traces of sulfur dioxide by passing the gases through an absorber tower where the sulfur oxides are removed by contact with circulating water that is sprayed into the tower. 

Qince the first large sulfur dioxide control system was installed at the Battersea plant in London, it has taken almost 50 yrs for calcium-based scrubbing technology to become commercially acceptable. In 1926, the 125 MW coal-fired Battersea power plant was equipped with a spray packed tower and final alkaline wash section which removed more than 90% of the sulfur dioxide and particulate (I). Thames River water provided most of the alkali for absorption, and about 20% was made up from lime addition. The process operated in an open-loop manner, returning spent reagent to the Thames. 

Research-Cottrell is also supplying a gas cleaning system using an electrostatic precipitator for dry particulate collection followed by a multi-stage gas liquid contactor for sulfur dioxide removal. The first stage is a cyclonic quencher for gas saturation and moderate sulfur dioxide absorption followed by a spray and packed-tower section where the major sulfur dioxide absorption takes place. Again the reagent is applied countercurrent to the gas flow. 

Sulfur Dioxide 3.6 106-118 4148 - E — — about one-half saturated with spray water in scrubber tower. Alloy C - 0.2 mpy... 

Sulfur Dioxide — 130 54 - - E E in gas stream with spray from cooling tower containing H7SO3. aeration... 

Aerators are often used for iron and manganese removal from deep well waters. Dissolved sulfur gases and some carbon dioxide are also removed, resulting in a slight elevation in pH levels. There are various designs but pressure aerators, aeration towers, and spray ponds, are common. 

From the foregoing reactions, it is seen that nitric oxide is liberated upon formation of sulfuric acid. In order to avoid the loss of this catalyst, the gases that leave the last chamber are led upward through the packed Gay-Lussac tower, against a downward spray of concentrated sulfuric acid. Nitric oxide and nitrogen dioxide are dissolved by virtue of the reformation of nitrosylsulfuric acid ... 

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