Glycol Dehydration Example

Sat w/water at 1,000 psig, 100°F Dehydrate to 7 Ib/MMscf Use triethylene glycol No stripping gas, 

Determine glycol circulation rate and estimate reboiler duty. 

Calculate duties for gas/glycol exchanger and glycol/glycol exchangers. 

Determine Glycol Circulation Rate and Reboiler Duty 

Use a 750 MBtu/hr reboiler to allow for startup heat loads. Calculate Duties of Heat Exchangers 

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In this example we selected a final outlet temperature of 100°F, This would be sufficiently low if the gas were only going to be compressed and dehydrated. For our case, we must also treat the gas for H2S and COt removal (Chapter 7). If we chose an amine unit, which we will in all likelihood, the heat of the reaction could heat the gas more than 10° to 20 T. making the next step, glycol dehydration, difficult (Chapter 8). In such a case, it may be better to cool the gas initially to a lower temperature so that it is still below 110°F at the glycol dehydrator. Often this is not possible, since cooling water is not available and ambient air conditions are in the 95°F to 1()0°F range. If this is so, it may be necessary to use an aerial cooler to cool the gas before treating, and another one to cool it before dehydration. 

Solvent loss elsewhere] upstream units, for example for glycol dehydration glycol dumped with hydrocarbons separated in upstream flash drum/loss in downstream solvent stripper. 

Function is to strip species from the liquid to produce a quality bottoms product for example, a solvent ready to be recycled as in glycol dehydration, amine absorption, extractive distillation or water that has been stripped of contaminants as in Sour Water strippers deodorize edible oils. Used to regenerate solvent for absorption or extractive or azeotropic distillation. Other equipment that is used for stripping include distillation. Section 4.2, gas-liquid separators. Section 5.1 and gas-liquid-liquid separation in flash drum. Section 5.4. The general characteristics of gas-liquid contacting are described in Section 1.6.1. Other operations that use this type of contactor include gas absorption. Section 4.8 reactors. Sections 6.13-6.16 and 6.19 and direct contact heat exchange Sections 3.7-3.9. 

The reaction of diketosulfides with 1,2-dicarbonyl compounds other than glyoxal is often not efficient for the direct preparation of thiophenes. For example, the reaction of diketothiophene 24 and benzil or biacetyl reportedly gave only glycols as products. The elimination of water from the P-hydroxy ketones was not as efficient as in the case of the glyoxal series. Fortunately, the mixture of diastereomers of compounds 25 and 26 could be converted to their corresponding thiophenes by an additional dehydration step with thionyl chloride and pyridine. 

The partial reduction of benzofuroxans, discussed in Section 4.05.5.2.4, represents an effective route to numerous benzofurazans. The conversion may be achieved either directly by deoxygention, for example, with sodium azide in ethylene glycol or acetic acid <75Ci(M)243> or using phosphites, or in two stages via the dioxime with subsequent dehydration as described above. 

Polymers usually are prepared by two different types of polymerization reactions — addition and condensation. In addition polymerization all of the atoms of the monomer molecules become part of the polymer in condensation polymerization some of the atoms of the monomer are split off in the reaction as water, alcohol, ammonia, or carbon dioxide, and so on. Some polymers can be formed either by addition or condensation reactions. An example is polyethylene glycol, which, in principle, can form either by dehydration of 1,2-ethanediol (ethylene glycol), which is condensation, or by addition polymerization of oxacyclopropane (ethylene oxide) 1... 

Erlenmeyer was first to consider ends as hypothetical primary intermediates in a paper published in 1880 on the dehydration of glycols.1 Ketones are inert towards electrophilic reagents, in contrast to their highly reactive end tautomers. However, the equilibrium concentrations of simple ends are generally quite low. That of 2-propenol, for example, amounts to only a few parts per billion in aqueous solutions of acetone. Nevertheless, many important reactions of ketones proceed via the more reactive ends, and enolization is then generally rate-determining. Such a mechanism was put forth in 1905 by Lapworth,2 who showed that the bromination rate of acetone in aqueous acid was independent of bromine concentration and concluded that the reaction is initiated by acid-catalyzed enolization, followed by fast trapping of the end by bromine (Scheme 1). This was the first time that a mechanistic hypothesis was put forth on the basis of an observed rate law. More recent work... 

The reaction chemistry of simple organic molecules in supercritical (SC) water can be described by heterolytic (ionic) mechanisms when the ion product 1 of the SC water exceeds 10" and by homolytic (free radical) mechanisms when <<10 1 . For example, in SC water with Kw>10-11 ethanol undergoes rapid dehydration to ethylene in the presence of dilute Arrhenius acids, such as 0.01M sulfuric acid and 1.0M acetic acid. Similarly, 1,3 dioxolane undergoes very rapid and selective hydration in SC water, producing ethylene glycol and formaldehyde without catalysts. In SC methanol the decomposition of 1,3 dioxolane yields 2 methoxyethanol, il lustrating the role of the solvent medium in the heterolytic reaction mechanism. Under conditions where K klO"11 the dehydration of ethanol to ethylene is not catalyzed by Arrhenius acids. Instead, the decomposition products include a variety of hydrocarbons and carbon oxides. 

Paradoxically, it is reactions which follow the Br0nsted law too well which now require explanation. The best example is the dehydration of methylene glycol, which gives a linear plot of logi 0 k against pK of catalyst for a range in pK of 16 units [41]. The reaction is subject to both acid and base catalysis, and can be considered as proceeding by the mechanisms... 

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