Ammonia absorption process

Existing single-contact acid plants can also be converted to doublecontact plants (63). In such cases, however, using add-on scrubber systems is an alternative, and several such systems have been used commercially. The Cominco ammonia absorption process has been used for many years (22, 64). The Lurgi Sulfacid process (65) and Wellman-Lord process (66) have had more recent and limited use. The Mitsu-bishi-JECCO process has also been applied to acid plant tail gases (27, 67, 68), but the gypsum by-product would be essentially a waste in the United States. 

Bogart, M., Ammonia Absorption Refrigeration in Industrial Process, Gulf Publishing Co., Houston, Texas (1981). 

All gas absorption processes are surface area dependent. Hence water fog may be an effective means of dealing with emissions of soluble gases, e.g. ammonia or hydrogen fluoride. 

GL 28] [R 2] [P 30] Ammonia absorption in dilute acidic solution containing Cresol Purple indicator was rapid, as expected [7]. By appropriate choice of processing parameters, neutralization was achieved close to the gas/liquid contacting zone or distributed over the full contact length. This is evidence for having controls by both solution and gas-phase transport. 

A liquid absorption process for the removal of SO2 involves the absorption of the S02 into a solution of ammonia and water with resultant formation of ammonium sulfide. The liquid is then sent to an oxidizing unit to form ammonium sulfate, which can be sold as a by-product or reacted with milk of line to regenerate the ammonia and produce gypsum.28... 

Figure 8.27. An ammonia absorption refrigeration process for a load of 50 tons at 30°F. The conditions were established by Hougen, Watson, and Ragatz (Thermodynamics, Wiley, New York, 1959, pp. 835-842).

The most widely used is ammonia absorption in water. A flowsketch of the process is in Figure 8.27. Liquid ammonia at a high pressure is obtained overhead in a stripper, and then is expanded through a valve and becomes the low temperature vapor-liquid mixture that functions as the refrigerant. The low pressure vapor is absorbed in weak liquor from the bottom of the stripper. Energy input to the refrigeration system is primarily that of the steam to the stripper reboiler and a minor amount of power to the pump and the cooling water circulation. 

Purification of Synthesis Gas. This involves the removal of carbon oxides to prevent poisoning of the NIT3 catalyst. An absorption process is used to remove the bulk of the C02, followed by methanation of the residual carbon oxides in the methanator, Modern ammonia plants use a variety of C02-removal processes with effective absorbent solutions. The principal absorbent solutions currently in use are hot carbonates and cthanolamincs. Other solutions used include methanol, acetone, liquid nitrogen, glycols, and other organic solvents. 

The single-pressure ammonia oxidation/absorption process is selected based upon theoperating criteria used in thesingle-pressure process developed by C l Girdler. 

Reactive absorption is very old as a processing technique and has been used for production purposes in a number of classical bulk-chemical technologies, such as nitric or sulfuric acid. The Raschig process for the production of hydroxylamine, an important intermediate in classical caprolactam technologies (Stamicarbon, Inventa), is also an example of a multistep reactive absorption process. Here, water, ammonia, and carbon dioxide react together in an absorption column to give a solution of ammonium carbonate, which subsequently forms an alkaline... 

The BYAS (Bypass Ammonia Synthesis) process can be used for economical expansion of existing ammonia synthesis plants. This process introduces additional natural gas at an intermediate stage in the process. The additional nitrogen in the air, which also has to be introduced, is removed by PSA (pressure swing absorption). The process was developed and offered by Humphreys and Glasgow in the UK1. 

In the chemical absorption process, the C02 reacts with chemical solvents to form a weakly-bonded intermediate compound that is then broken down by the application of heat. The heat regenerates the original solvent and produces a CO2 stream. Typical solvents are amine- or carbonate-based. Examples are MEA, diethanolamine (DEA), ammonia and hot potassium carbonate. These processes can be used at low C02 partial pressures, but the feed gas must be free of S02, 02, hydrocarbons and particulates. Hydrocarbons and particulates cause operating problems in the absorber199. 

Vapor-Liquid Equilibria for the Ammonia, Hydrogen, Nitrogen, Argon, Methane System (Fig. 4). Because of the great importance of absorption processes in synthesis loop engineering (see Section 4.5.6), these binary and multicomponent systems have been experimentally and theoretically reinvestigated several times. The updates are based mainly on thermodynamic relationships in combination with equations of state. 

M. Bogart, Ammonia Absorption Refrigeration in Imkistrial Processes, Gulf, Houston, 1981. 

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