Ammonia stripping process

Fisher, B. C., Blackstock, T. Hauke, D. 1997. Fly ash beneficiation using an ammonia stripping process. Proceedings 12th International Symposium on Coal Combustion By-Product (CCB) Management and Use, Vol. 2, Paper 65, pp. 1-8. 

Application To produce urea from ammonia and carbon dioxide using ammonia-stripping process. 

Describe the nitrification, denitrification, and ammonia stripping processes. 

Figure 3.10 A schematic of the Snamprogetti ammonia stripping process. Source [9],...

Ammonia stripping process is based on Reaction 6.3, in which the pH of treated waste water is increased to at least 10, thus forming more dissolved ammonia gas. In a stripping tower, the ammonia can be separated. Lime (CaO) is used to increase the pH and has to be removed periodically from the stripping surface. The lime scaling is often a headache to this process. However, the most basic concern is that the process simply transfers the pollution problem from one medium to another (i.e., water to air in this case) [24,26,27]. 

Two types of compounds, crystalline and amorphous, can be precipitated from tantalum or niobium solutions by an initial ammonia solution containing ammonium ions, with an interface at about pH = 10. Such solutions are used for the stripping of tantalum or niobium from TBP extracts. In the case of pure fluorotantalic or fluoroniobic acids that result from the stripping process with water, the interface occurs at a lower pH level. 

Ammonia stripping also removes cyanide, phenols, and other VOCs typically found in cokemaking wastewater. Phenols may also be removed by conversion into nonodorous compounds or into crude phenol or sodium phenolate by either biological means (phenol concentration <25 mg/L) or by physical processes.21 However, the Koppers dephenolization process is considered to be quite effective as it lowers the phenol content by 80 to 90% in ammonia still wastes. In this process a stream stripping process followed by mixing in a solution of caustic soda results in renewal of pure phenol with the flue gas.8... 

Instead of stripping with carbon dioxide, ammonia can be used (Snam Progetti process). The stripping processes are energetically somewhat more favorable than the recycling processes with high pressure decomposers. 

Theoretically, the rate of ammonia stripping should be proportional to the difference in the partial pressures of ammonia between the liquid and the gaseous phases. Because a decrease of every 10°C in the process water would result in about a 40% decrease in the... 

R. Smith, Ammonia Stripping, In Process Design in Water Quality Engineering (E. Thackston and W. Eckenfelder, eds.), E. Jenkins Publ. Co., Austin, TX, 1972. 

The basic equipment for an ammonia-stripping system includes chemical feed, a stripping tower, a pump and liquid spray system, a forced-air draft, and a recarbonation system. This process requires raising the pH of the wastewater to about 11, the formation of droplets in the stripping tower, and providing air-water... 

Steam stripping is used to remove dilute concentrations of ammonia, hydrogen sulfide, and other volatile components from pharmaceutical waste stream. Steam stripping can typically achieve contaminant removal of 99% or better and is effective for the removal of organics having boiling points of less than 150 C. The steam stripping process is carried out in a distillation column, which may be either a packed or tray tower. Steam enters at the bottom ofthe column while waste water is countercurrently supplied fi"om the top of the distillation column. The product stream, rich in volatile components, may further be treated to recover these components. 

Toyo Engineering Corp. (TOYO) Urea Ammonia (NH3) and carbon dioxide (CO ) Process produces urea from NH and CO using CO stripping process 100-1- NA... 

Wnek, W. J., and R. H. Snow, Design of Cross-Flow Cooling Towers and Ammonia Stripping Towers, Ind. Eng. Chem. Process Des. Develop., 11, 343 (1972). 

The key process unit is an FW Evaporative Scrubbing System (ESS). The raw process condensate from the urea unit is first steam stripped to reduce ammonia content. The stripped process condensate is mixed with a circulating stream of urea solution and enters the distribution system of the ESS, which also acts as a cooling tower. The air from the finishing process (prilling or granulation) is introduced into the bottom of the ESS. Particles entrained in the air are dissolved in the urea... 

The production cycle starts with the extraction of sodium chloride. About 20% of the world s salt consumption goes into soda ash production [24]. The next step after rock salt mining is the production and purification of brine yielding a concentrated aqueous sodium chloride solution [8,25-27]. A parallel step is the production of carbon dioxide gas by calcination of limestone. The brine is treated with ammonia and carbon dioxide under precipitation of the less-soluble sodium hydrogen-carbonate. Ammonia is recovered by mixing the mother liquor with calcium hydroxide and stripping off the ammonia with steam. Thermal decomposition of sodium hydrogencarbonate yields synthetic soda ash [8,20,22,23,28-38]. The output of soda ash produced by the ammonia-soda process amounts to about two-thirds of the world production [22,23]. 

For fuel cell systems operating on reformates, high levels of aimnonia and CO2 may be present in the fuel stream. Ammonia is known to be detrimental to PEM fuel cell catalysts. It is desirable to reduce the concentration of aimnonia in the fuel stream to below 2 ppm. However, ion filters, if used alone, will be quickly saturated due to the high concentration of ammonia in the water. A water "contact cooler" has been used to transfer the ammonia into a reservoir of water, which needs to be dumped or cleaned. To achieve water neutral operation, Bonville et al with International Fuel Cells Corporation (Japan) [63] patented a method to remove the ammonia in the contaminated stack water via a steam stripping process, which removes ammonia around 400 ppm (and CO2 as well) from contaminated water to about 30 ppm. An ammonia-laden steam is discharged to the environment. A demineralization bed is then used to further reduce ammonia concentration in the water to an acceptable low level. 

Many industries generate liquid streams that contain from 0.01 to 2 wt% ammonia nitrogen that have an adverse effect when discharged into lakes or streams. While ion exchange and biological processes can be employed to remove ammonia nitrogen jfrom aqueous solutions, ammonia stripping is the simplest method and easiest to control [8]. In an aqueous solution dissolved ammonia reacts as follows ... 

Rich solution from the bottom of the wash tower is preheated by heat exchange with stripped water then fed to the top of the free ammonia stripper, which operates with direct steam injection at the bottom. Stripped water flnm this column is cooled and recycled to the top of the wash column. Excess stripped water, which stiU contains fixed ammonia, is processed in the fixed ammonia stripper before disposal. Caustic soda (or lime) is used to... 

Caustic Soda. Diaphragm cell caustic is commercially purified by the DH process or the ammonia extraction method offered by PPG and OxyTech (see Fig. 38), essentially involving Hquid—Hquid extraction to reduce the salt and sodium chlorate content (86). Thus 50% caustic comes in contact with ammonia in a countercurrent fashion at 60°C and up to 2500 kPa (25 atm) pressure, the Hquid NH absorbing salt, chlorate, carbonate, water, and some caustic. The overflow from the reactor is stripped of NH, which is then concentrated and returned to the extraction process. The product, about 62% NaOH and devoid of impurities, is stripped free of NH, which is concentrated and recirculated. MetaUic impurities can be reduced to low concentrations by electrolysis employing porous cathodes. The caustic is then freed of Fe, Ni, Pb, and Cu ions, which are deposited on the cathode. 

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