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pro- A new approach to an established product mines co mize th mine (N Id Cost-efficient production et en p co of ethanolamines ap u ca tr in te as PETER FÄSSLER Sulzer Chemtech has over 30 years of experience in is SULZER CHEMTECH the field of ethanolamine technology. Its expertise AUREO CELEGHIN includes the provision of comprehensive engineering F CELEGHIN services for the modernization of existing plants, p as well as the manufacturing of key components for Th plants such as distillation column internals (Fig. 1). m Sulzer Chemtech and Celeghin Consultants et et Corporation of Houston, TX, USA, teamed up to m create an innovative new ethanolamine techno- d logy solution that optimizes product quality and m process flexibility while lowering energy con- et sumption during production. This complete U solution reduces the investment and operating p costs related to the production of ethanolamines. of of ca C ti fi p d th va m of et T h ra of M

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t Ethanolamines are flamma- minimizing the volume of TEA operate economically even at am- ble, corrosive, colorless, vis- produced (Fig. 4). monia to ethylene oxide ratios of t p cous liquids that are produced by 6:1 or above. Furthermore, the the reaction between ammonia Lower costs presence of water as a catalyst in

(NH3) and ethylene oxide (EO). The volume of water used in the synthesis of ethanolamine en- Identified many years ago, ethanolamine production can sures a rational and economical re- n ethanolamines are a key ingredi- vary: if the water content remains actor setup. The use of water pro- ent in a number of important low during the process, it is neces- vides the greatest control over the product formulations such as sary for the reaction to be conduct- temperature rise in the reactor sys- cosmetics and personal hygiene ed under high pressure—resulting tem and allows a reduction in the s applications, agricultural prod- in high investment costs. These re- volume of the reactor. The average ucts, wood-preservation chemi- actions consume a low level of en- reaction temperature can be low- cals, soaps and detergents, gas ergy. In order to lower investment ered and adjusted to minimize sec- treatments. They can also be used costs, a high water content may be ondary side reactions that could in the production of non-ionic de- used under low pressure, but the compromise the quality of the tergents, emulsifiers, and soaps, related energy consumption will resulting ethanolamine. as well as in emulsion paints, pol- consequently be higher. The new ishes, and cleansers. ethanolamine technology solution Ammonia recovery offered by Sulzer Chemtech com- The key to saving energy in the Flexible ethanolamine bines the advantages of the high- production of ethanolamine lies in production technology pressure ammonia route with the the design and operating pressure There are 3 types of ethanolamines: benefits of the low-pressure of the main ammonia absorber. monoethanolamines (MEA), di- process. The process allows the The ammonia stripper is integrat- ethanolamines (DEA), and tri- use of a relatively low-pressure ed directly with the absorber by ethanolamines (TEA). The for- reaction and incorporates very feeding the stripper overhead va- mation of MEA, DEA, or TEA advanced heat integration, which pors into the bottom of the ammo- depends on whether an ammonia saves costs across the board. nia stripper. In other words, there molecule reacts with 1, 2, or 3 The Sulzer Chemtech water recov- is a direct connection between the ethylene oxide molecules (Fig. 2). ery system, which uses the energy two columns. In addition, the Unlike conventional ethanolamine integration concept, thermally ties overhead vapors from the main production technology, which is the water evaporator to the ammo- water distillation columns are often limited in terms of the ratio nia stripper column and mini- used as a heat source for the am- of ammonia to ethanolamine that mizes the size of the drying col- monia stripper reboiler. can be handled, the flexible Sulzer umn. It thus enables the plant to The pressure at the top of the main Chemtech solution offers the op- tion of altering the amounts of the final product generated. The com- 1 Jilin ethanolamine position of the resulting mixture is production plant determined by the ratio between in China. the raw materials, which can be varied in accordance with require- ments. The higher the proportion of ammonia, the more mono- ethanolamine is formed (Fig. 3). The Sulzer Chemtech process can handle ammonia to ethanolamine ratios up to or exceeding 6:1 and offers the customer a high level of MEA or DEA distribution while

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2 Mono-, di-, and water evaporation column is lim- ture, thus reducing the possible on H2N triethanolamines are ited by the maximum permissible degradation of the product and re produced by reacting OH temperature at the bottom of the minimizing the corrosion of equip- bu ethylene oxide with ammonia. NH column. Hence, the boundary op- ment. qu HO OH erating conditions of the ammonia The high ammonia concentration of NH3 OH absorber, ammonia stripper, and allowed by the Sulzer Chemtech si main water evaporation column process further reduces the size of av N HO are basically fixed. The only de- the ammonia stripper and ammo- w gree of flexibility in the design is nia scrubber and eliminates the p OH in the selection of the column op- need for an additional auxiliary re- in erating conditions, column inter- boiler heated by an external heat- th nals, and the heat exchanger. ing source. These features signifi- co Sulzer Chemtech has added ther- cantly reduce investment costs. mal and energy integration to the A ammonia absorber, the ammonia A clear advantage P stripper, and the water distillation Ethanolamines are sensitive to te column. As a direct consequence heat and therefore tend to degrade gr of this thermal and process heat in- and must be separated with great of tegration, the energy required by care. The higher the temperature be the improved process is compara- (respectively the pressure), the st ble to the high-pressure route more colored the ethanolamines an (Fig. 5). become. Color is, however, the to The increase in the ammonia con- most important characteristic de- p centration in the ammonia ab- termining their quality and value; ti sorber is a direct result of the the more colorless the substances be process heat integration and has a are, the higher their market value. th significant impact on overall ener- The use of high-efficiency pack- th

3 The ratio of MEA, DEA, and TEA produced can gy consumption. The higher the ings from Sulzer Chemtech and tu be varied by altering the ratio of the reactants. operating pressure in the ammo- the rational design of the distilla- T nia absorber, the higher the ammo- tion train minimizes the packing re Ethanolamine (EA) product distribution (reaction 1) 60 nia concentration. The higher the volume and enables the column to re ammonia content, the less water be operated at a lower tempera- ly MEA DEA has to be handled in the system. ture, with narrow residence time h

% TEA Since the water must be recycled distribution and minimum per- C back into the system by means of manent holdup. The separation of 10 evaporation, each percentage ethanolamines at these carefully 36 NH3/EO ratio point increase in the ammonia con- maintained conditions improves P e centration leads to an approximate the product color and reduces ~ energy saving of between 1.5 and the corrosion at the bottom of the w 2%—which represents a signifi- column. 4 The second reaction is required to produce a higher level of DEA. cant reduction in absolute terms. The ammonia concentration can Accelerated production without Ethanolamine (EA) product distribution (reaction 2) ethanolamine recycling 80 also be set to allow for the efficient and economical recovery of the The ethanolamines produced are MEA DEA residual ammonia from the reac- often recycled back into the main TEA tion loop. This recovery occurs at reactor system in order to adjust Amine % a pressure that is sufficiently low the desired MEA:DEA:TEA ratio. 20 to ensure that the ammonia strip- If the reaction is performed in the 15 MEA/EO ratio ping takes place at a low tempera- primary reactor, the recycling not

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5 Sulzer Chemtech le only consumes more energy and Ethanolamine technology: overview provides a complete d requires a higher residence time Demi-water Ammonia absorption Water purge and flexible solution p- but can also lower the product NH3 MEA for ethanolamine quality through the development production. EO DEA Reaction 1 Ammonia Concen- Distillation n of color and an increase in corro- stripping tration TEA h sion. The Sulzer Chemtech concept Residue/TEA of avoids the difficulties associated EO Reaction 2 o- with recycling and eliminates re- he peated process steps, thus reduc- e- ing the overall residence time in t- the plant and lowering energy i- consumption. amine production makes effective designs. Any adjustments that are use of the product stress concept required, e.g. relating to product Avoiding product stress to ensure the best handling of the capacity and product distribution, Product stress is defined as the hot product at the bottom of the can be implemented relatively to tendency of the product to de- column. quickly and with a high degree of de grade and carbonize at the bottom reliability. at of the column. Product stress can Purification In addition, the accumulation of re be minimized through the rational The synthesis and purification of unwanted byproducts or feed im- he study of the temperature profile ethanolamines is a relatively com- purity products trapped in the es and the configuration at the bot- plex process as the final product process loops can be detected and he tom of the column, resulting in less quality is determined by the pres- eliminated through purging at e- product degradation. Side reac- ence of minor impurity streams specific locations. e; tions, such as color precursors, can in the feed, as well as by internal Since such complex design ap- es be suppressed to a certain extent recycle streams, thermal process proaches are very time consuming, e. through the smooth execution of integration, and the reaction of they are only justified for selected k- the process at the lowest tempera- individual components including process steps in ethanolamine pro- d tures possible. side reactions. duction—an area in which Sulzer a- The level of product stress is di- Chemtech has extensive experi- ng rectly related to the hot product Integrated approach ence, supported by a diversified to residence time and is exponential- A fully integrated approach range of market applications. a- ly related to the temperature of the throughout the plant is a prerequi- me hot product (see box). The Sulzer site for a successful design. Sulzer r- Chemtech process for ethanol- Chemtech and Celeghin have of therefore adopted a single block ly for the entire process simulation. es Product stress This module has been systemati- es ~ A×(residence time)T cally improved not only by inte- he where: grating the accumulated know- Residence time = the time in how but also by relying on real minutes during which the plant operating data and perfor- Contact ut average bottom product mance characteristics. This type of Sulzer Chemtech AG molecule stays in the bottom comprehensive simulation tool is Peter Fässler re of the column. sophisticated enough to provide a Sulzer-Allee 48 in T = the absolute temperature satisfactory description of plant 8404 Winterthur st of the hot stream at the details and serves as a powerful Switzerland o. bottom of the column. tool for the analysis of possible Phone +41 52 262 37 29 he A = a proportionality factor. process improvements, for heat Fax +41 52 262 00 64 ot integration, and for new plant [email protected]

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