Absorption process, glycol

At low vapor rates, valve trays will weep. Bubble cap trays cannot weep (unless they are damaged). For this reason, it is generally assumed that bubble cap trays have nearly an infinite turndown ratio. This is true in absorption processes (e.g., glycol dehydration), in which it is more important to contact the vapor with liquid than the liquid with vapor. However, this is not true of distillation processes (e.g., stabilization), in which it is more important to contact the liquid with the vapor. 

Contactor pressures have little effect on the glycol absorption process as k>ng as the pressures remain below. 3,000 psig. At a constant temperature liic water content of the inlet gas decreases with increasing pressure, thus less water must be removed if the gas is dehydrated at a higher pre.s-sure. In addition, a smaller contactor can be used at high pressure as the actual velocity of the gas is lower, which decreases the required diameicr of the contactor. 

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. 

In the physical absorption process, the CO2 is absorbed in a solvent according to Henry s Law and then regenerated using heat, pressure reduction or both heat and pressure reduction. Typical solvents are Selexol (dimethylether of polyethylene glycol) and Rectisol (cold methanol) which are applied at high pressure. At lower pressures, the chemical absorption processes are more economical. The Selexol physical solvent process is frequently specified for coal gasification applications199. 

SD alcohol 27-A SD alcohol 27-B SD alcohol 30 SD alcohol 37 SD alcohol 38-B SD alcohol 39-B SD alcohol 40 SD alcohol 40-A SD alcohol 40-B SD alcohol 40-C solvent, furniture polishes Petroleum distillates, hydrotreated light solvent, furniture/floor polishes C13-14 isoparaffin solvent, gas absorption Diethylene glycol dibutyl ether Ethylene glycol dimethyl ether PEG-4 dimethyl ether solvent, gas absorption processes Petroleum distillates, hydrotreated light paraffinic... 

If the gas is to be compressed andiransported by sub-sea pipe line, then it may be necessary to remove carbon dioxide. If only a few per cent is present it is cheaper to transport the unwanted gas and remove it on-shore than to remove it off-shore. If, as with one North Sea field, the amount is 20 per cent, then removal off-shore is undertaken. The absorption process uses monoethanolamine and is basically the same as that on an ammonia plant. Absorption can also be used to remove water, and the re-usable absorbent which is cycled between absorption tower and regenerator is triethylene glycol. Water removal limits corrosion damage and prevents the formation of solid hydrocarbon hydrates which can plug gas lines. 

Dehydration can be performed by a number of methods cooling, absorption and adsorption. Water removal by cooling is simply a condensation process at lower temperatures the gas can hold less water vapour. This method of dehydration is often used when gas has to be cooled to recover heavy hydrocarbons. Inhibitors such as glycol may have to be injected upstream of the chillers to prevent hydrate formation. 

Certain chemicals (sorbents) have the ability to absorb moisture from a gas they may be either solid or liquid. Performance of a chemical dehumidifi cation device depends on the sorbent used. The sorbent must t>e able to attract and remove the sorbate, such as water, from the gas stream, Stirbems absorb water on the surface of the material by adsorption or by chemically combining with water (absorption). If the unit is regenerative, the process is reversible, allowing water to be removed. This is achieved by a sorbent such as silica gel, alumina gel, activated alumina, lithium chloride salt, lithium chloride solution, glycol solution, or molecular sieves. In the case of nonregenerative equipment, hygroscopic salts such as calcium chloride, urea, or sodium chloride are used. 

Important processes commercially used are the Selexol, the Sulfinol, and the Rectisol processes. In these processes, no chemical reaction occurs between the acid gas and the solvent. The solvent, or absorbent, is a liquid that selectively absorbs the acid gases and leaves out the hydrocarbons. In the Selexol process for example, the solvent is dimethyl ether of polyethylene glycol. Raw natural gas passes countercurrently to the descending solvent. When the solvent becomes saturated with the acid gases, the pressure is reduced, and hydrogen sulfide and carbon dioxide are desorbed. The solvent is then recycled to the absorption tower. Figure 1-1 shows the Selexol process. ... 

Figure 1-4. Flow diagram of the Dehydrate process (1) absorption column, (2) glycol sill, (3) vacuum drum.

Silica fillers also react with the rubber causing an increase in viscosity and dry and unmanageable processing behaviour. Filler activators need to be added to silica-reinforced compounds to overcome these problems. The usual filler activators used are diethylene glycol, polyethylene glycol and amines such as triethanolamine. Some of these activators not only overcome the problems of processing and accelerator absorption, but depending on the cure system used, will also act as vulcanisation activators. 

Townsend A process for removing hydrogen sulfide from natural gas by absorption in triethylene glycol containing sulfur dioxide. Part of the sulfur produced is burnt to sulfur dioxide in order to provide this solution. The hydrogen sulfide and sulfur dioxide react in the presence of water to generate elemental sulfur. Invented in 1959 by F. M. Townsend. 

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