Wet gas cleaning

It is generally unacceptable to emit sulfur dioxide, thus the scmbber effluent must be treated for sulfur dioxide removal. If the plant aheady possesses faciUties for the production of sulfuric acid, this rather concentrated sulfur dioxide stream can be easily fed into the wet gas cleaning circuit and disposed of in the sulfuric acid plant. The quantity is so small that it does not put any additional burden on the sulfuric acid plant. Because no tellurium is carried over with the selenium dioxide during roasting, it is possible to produce a selenium product which can be purified to commercial grade (99.5-99.7%). 

The gasification process is based on atmospheric pressure gasification with wet gas clean-up. The bagasse is dried to 10 % moisture in a dryer and fed to the gasifier. The gases pass through a gas clean-up system and are fed to the gas turbine to produce electricity. Steam, produced in the turbine flue gas heat recovery boiler, powers a steam turbine and the low pressure steam from the steam turbine is sent to the sugar mill to meet part of the mill s steam requirement. 

The design of a gas-cleaning system must always take into account the operation of the upstream installations since every process will have a specific set of requirements. In some cases, the application of a dry-dnsting removal unit may not be possible and thus requires a special process design of the wet gas-cleaning plant. 

Smelter gas may occasionally contain a significant amount of fluorine—which may cause accelerated corrosion in the wet gas cleaning plant and acid plant. The corrosimi rate is significantly lowered by adding sodium silicate to the packed bed condensation tower circulating solution (Fig. 4.1 Hasselwander, 2009). 

Despite these defects, wet gas-cleaning installations can be applied with success in the chemical, oil refining, and gas industries, and he black and nonferrous metalluigy, power engineering, and other industries. 

FT technology has been proven with syngas from biomass gasification in a demonstration plant in the Netherlands. The plant included a fluidized bed gasifier followed by wet gas cleaning and conditioning, WGS and FT synthesis to produce waxes that were then cracked to obtain a high-quality sulfur-free diesel fuel (Wender, 1996 Huber et al., 2006). 

In general, plants using SO2 gas derived from metallic sulfides, spent acids, or gypsum anhydrite purify the gas stream before drying it by cold, ie, wet, gas purification. Various equipment combinations including humidification towers, reverse jet scmbbers, packed gas cooling towers, impingement tray columns and electrostatic precipitators are used to clean the gas. 

Gas cleaning by filtration, demisting, electrostatic precipitation, wet collection of particulates, cyclonic separation. 

Wet collector A gas-cleaning device that uses a fluid for the removal of a pollutant from an air or gas stream. 

Wet chemical processes A gas-cleaning process that uses certain chemicals to ensure the maximum retention of a given pollutant in the cleaning fluid. 

A small amount of nickel in the FCC feed has a significant influence on the unit operation. In a clean gas oil operation, the hydrogen yield is about 40 standard cubic feet (scf) per barrel of feed (0.07 wi /r ). This is a manageable rate that most units can handle. If the nickel level increases to 1.5 ppm, the hydrogen yield increases up to 100 scf per barrel (0.17 wt%). Note that in a 50,000 barrel/day unit, this corresponds to a mere 16 pounds per day of nickel. Unless the catalyst addition rate is increased or the nickel in the feed is passivated (see Chapter 3), the feed rate or conversion may need to be reduced. The wet gas will become lean and may limit the pumping capacity of the wet gas compressor. 

As gas cleaning options, a choice can be made for either low-temperature "wet" or high-temperature "dry" gas cleaning. The latter type of gas cleaning is advantageous for the overall energy balance but many process elements are not yet fully proven technology. 

Gas clean up methods can be classified into two distinct routes wet low temperature cleaning and dry high temperature cleaning. 

The readers are referred to another source for more detailed information regarding wet flue gas cleaning blowdown characteristics and treatment [2,3]-... 

From an operator s perspective, the scrubbing system required very little attention. Normally, the only attention required is a routine walk-by of the equipment to ensure that everything is in normal operation. Since 1998 the refinery took the RCC out of operation and moved the EDV Wet Scrubbing System over to their SRU and applied it as a tail gas cleaning device. The system is presently operating at very high efficiency as a tail gas unit to rave reviews of the refinery client. 

A little bit of entrainment is not always bad. For example, entraining a clean naphtha mist into the suction of a wet-gas centrifugal compressor is fine. The mist helps keep the rotor parts clean. If the steam from a boiler is to be used to reboil towers, entrainment is of no consequence. 

Gas hydrates formed during a restart after the platform was shut down due to a hurricane. During the shut-in period the gas dehydrator partially filled with water. After production restarted, since the dehydrator was not cleaned properly, it was not dehydrating gas as designed and wet gas entered the export line, causing... 

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