Water Scrubbing

Gas leaves electrostatic precipitators at 600 K. It still contains 0.1 to 1 g of dust and unwanted vapors per Nm of gas. These are now removed by intimately contacting the gas with water sprays. This contact  

Venturi, radial flow, packed bed and Dynawave , Fig. 4.5 (Enviro-chem, 2005) scrubbers are used. 

The downcomer often enters through the roof of the settler. Multiple sprays at one level, rather than a single spray at two levels, are also used. 

Scrubber data type of scrubber radial flow, 2 sets radial flow 

Gas data gas source dry precipitator exit gas precipitator exit gas 

Acid plant builder Korea Zinc Engineering Outokumpu-Lurgi 

Acid production (tonnes H2SO4 per day) 1150 (two roasters, two gas cleaning plants, one acid plant) 2200 (nominal) 

Gas source Zinc sulfide roaster Noranda smelting furnace, air dUution and water quenching 

Precipitator details Each precipitator Each (H ipitator 

Height X length x width (m) 7.5x10.45x4.8 19.2x20.1 X 8.5 

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Incineration water scrubbing (nonrecirculating type) Depressure and purge to vapor recovery... 

Environmental impacts. Discharges to atmosphere (particulates and other toxic or noxious emissions), surface waters (scrubbing water), and land (furnace residues) may require extensive treatment to assure protection of the environment. 

A flue gas is to be desulfurized using water scrubbing in a stagewise column. It is desired to remove 95% of SO2 from the flue gas containing 100 ppm SO2. The flowrate of the gas is 0.03 kg mol/s (approximately 2 MMscfd). The water entering the absorber is free of SO2. The equilibrium data for transferring SO2 from the gas to the water may be described by ... 

Water is mainly used as noncontact cooling water, scrubbing water, and in the transportation of gypsum as slurry to the wastewater treatment facility. The water in the heat exchangers is used to... 

Carbon Removal, in which residual carbon and ash are removed from the syngas in a two-stage water scrubbing unit... 

High temperature The high-temperature off-gases from combustion-based sources of inerts typically must be quenched before use. Water scrubbing, in addition to reducing the temperature, can remove soot and sulfur compounds (which could react with moisture to form corrosive acids) present in the off-gas. The humidity of the resultant gas stream may make it unsuitable for inerting applications where moisture cannot De tolerated. 

The mechanically retained impurities in water gas are removed by scrubbing the gas with water, that is to say, by passing it up a tower, down which water is falling. Not only does this water scrubbing remove the mechanically retained impurities, but it also, by reducing the temperature of the gas, causes the condensation and removal of the minute quantity of iron carbonyl contained in the gas. 

The whole of the sulphur compounds in the blue s are converted into sulphuretted hydrogen and are mpletely absorbed by the high pressure water scrub-... 

Water-scrubbing devices are often used to control emission to the air. Most of these devices generate wastewater streams that are potentially contaminated with pesticide ingredients. Although the quantity of water in the system is high - about 20 gallons per 1000 cfm - water consumption is kept low by a recycle-sludge removal system. 

Nitric acid is produced by the oxidation of NH3 in air at pressures up to 10 atm over a R catalyst to produce NO, followed by further air oxidation and hydration to produce Eff 03. This is a two-step process with water scrubbing to remove HNO3 fiom N2 and excess air. Since over 90% of the NH3 fed into the process is converted into HNO3, we can describe this process quahtatively as the overall single reaction... 

It is apparent from these equations that significant quantities of sulfur dioxide are generated. For selenium, the reaction shown for oxidation of elemental selenium reverses itself at the lower temperatures employed for water scrubbing, thus regenerating sulfuric acid. The tellurium dioxide remains in the sulfated slimes. 

Under running water, scrub it inside and out with a toothbrush (if possible other than the one used for brushing teeth). 

On the other hand, the exhaust gases from BOP converters contain relatively large amounts of red c -Fe203 dust this, however, can be trapped by electrostatic precipitation or water scrubbing and recycled, and the exit gases can be scrubbed with water to reduce air pollution. 

Compressed air and o-xylene or naphthalene vapor are mixed in an approximately 20 1 ratio and oxidized at 400°C. The product phthalic anhydride is recovered by condensation and purified by vacuum distillation. Maleic anhydride, a byproduct in both oxidations may be recovered from the waste gases in the form of maleic acid after water scrubbing. 

Oxides of nitrogen, NO, can also form. These are generally at low levels and too low an oxidation state to consider water scrubbing. A basic reagent picks up the N02, but not the lower oxidation states the principal oxide is usually NO, not N02. Generally, control of NO, is achieved by control of the combustion process to minimize NO ie, avoidance of high temperatures in combination with high oxidant concentrations, and if abatement is required, various approaches specific to NO have been employed. Examples are NH3 injection and catalytic abatement (43). 

The use of a nonsilicone mold release (such as a vegetable oil spray) in an aluminum mold may help. The mold release must be removed with a solvent such as isopropanol and water scrubbing. 

The hydrogen from the cells can be used to make NH3 and other chemicals. It can also be used as a boiler fuel. This requires cooling to remove water scrubbing to remove traces of chlorine, caustic, and salt and then compressing sufficiently to satisfy the feed requirements of the burner. Of increasing importance is the burning of the hydrogen with the dilute chlo-... 

About 70% of the dust-in-offgas is removed in the waste heat boiler and about 30% in electrostatic precipitators. The small remainder ( 1%) is removed by water scrubbing, next section. 

Table 7.1. Compositions of furnace offgases and catalyst bed feed gases. Sulfur burning gases don t change. Metallurgical and waste acid decomposition furnace offgases lose S03 and H20(g). The SO3 is removed during water scrubbing. The H20(g) is removed during condensation and dehydration. ...

In the process, 99.8 percent ethylene, 99.5 percent oxygen, and recycle gas are directed to a vertical reactor and are contacted with the catalyst solution under slight pressure. The water evaporated during the reaction absorbs the exothermic heat evolved, and make-up water is fed as necessary to maintain the catalytic solution concentration. The reacted gases are water-scrubbed and the resulting acetaldehyde solution is fed to a distillation column. The tail gas from the scrubber is recycled to the reactor. Inerts are eliminated from the recycle gas in a bleed stream which flows to an auxiliary reactor for additional ethylene conversion. 

LoTOx A process for removing NOx from FCC off-gases. Injection of ozone oxidizes the NOx to N205, which is easily removed by water scrubbing. Developed by BOC. 

Ammonia (mp —77 C, bp. ois —33J C. 4 " 0.6650y recovered during the water scrubbing of raw coke oven gases accounts for only a very small firaction in comparison with ammonia manufactured from its elements. 

Dehydration is carried out at atmospheric pressure and between 250 and 300 on alomina. Conversion is virtually total A num of by iFoducts are retained by water scrubbing. The catalyst is easily regenerated by the combustion of carbon d sits. 

In these studies, thermodynamic equilibrium conditions were assumed. Constant pH monitoring was used as an estimator of the equilibration times involved, since a stable pH is an overall indicator of the Internal chemical stability of pH dependent processes. In order to allow the assumptions of atmospheric O2 and CO2 partial pressures, water scrubbed compressed air was pumped into the reaction vessels under constant temperature and constant vigorous mixing conditions. The air was introduced by fritted glass bubblers which had been teflon coated while air flowed through them in order to minimize the glass-solution interface. 

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