This column is based on “Ethanolamines from Ethylene Oxide and Ammonia – Cost Analysis,” a report published by Intratec. It can be found at the following URL: www.intratec.us/analysis/monoethanolamine-production-cost.
Ethanolamines are a family of compounds that are used as feedstocks for emulsifiers, detergents, corrosion inhibitors and chemical intermediates, as well as used for scrubbing carbon dioxide from exhaust gas. The family includes monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA). As the names suggest, they can be thought as derivatives of ammonia in which the radical ∙CH2–CH2–OH replaces one, two or three, respectively, of the hydrogen atoms in the base ammonia molecule.
Ethanolamines combine interesting chemical properties exhibited by both alcohols and amines. Under acidic conditions, they may either form acids, due to the presence of a basic amine group, or esters, because of the hydroxyl group. MEA and DEA always yield salts if they are in the presence of organic acids.
The following paragraphs describe a process for ethanolamines production from ethylene oxide and ammonia. The process comprises three major sections: (1) reaction, (2) ammonia recovery, and (3) purification (Figure 1).
Reaction. Ammonia is mixed with water to form an aqueous ammonia solution (45–55 wt.% ammonia). Ammonia is supplied in excess to the reactor, so ethylene oxide is fully consumed in the reaction. Water also plays an important role in accelerating the reaction. The reactions achieve yields in the range of 98–99%. The balance is lost in minor side reactions that generate some heavy byproducts, which need to be separated in the purification section. The final product composition depends exclusively on the molar excess of ammonia fed to the reactor. The reactor output comprises MEA, DEA and TEA, as well as unreacted ammonia dissolved in water and the heavy byproducts.
Ammonia recovery. The reaction product is fed to an ammonia stripping column for separating the excess ammonia present in the mixture. Ammonia and water vapors are recycled to the reaction, while the liquid bottom product is routed to a two-stage evaporator and then to a dehydration column, where residual ammonia and water are separated from ethanolamines and also recycled to the reaction area. Ethanolamines are withdrawn as the bottom product of the dehydration column and transferred to the purification section.
Purification. The ammonia-free ethanolamines are further separated in three purification columns. Small amounts of MEA and DEA may also be recycled to the reactor to balance the desired output of each ethanolamine — MEA: DEA: TEA ratios of 1/3: 1/3: 1/3. A small stream of heavy byproduct waste is separated in the TEA purification step.
Ethanolamines production is almost exclusively based on the reaction of ammonia with ethylene oxide, in such a way that different ethanolamines manufacturing routes are related to different sources of these raw materials. Pathways for ethanolamines production are presented in Figure 2.
The total operating cost (raw materials, utilities, fixed costs and depreciation costs) estimated to produce ethanolamines was about $1,000 per ton of ethanolamines (MEA: DEA: TEA, in a ratio of 1/3: 1/3: 1/3) in the third quarter of 2015. The analysis was based on a plant constructed in the U.S., with the capacity to produce 120,000 metric ton per year of ethanolamines.
Edited by Scott Jenkins
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