Design of packed, adiabatic absorbers: physical absorption of acid gases in methanol

Abstract

An algorithm was developed to calculate concentration and temperature profiles for an adiabatic, packed absorber. Calculations performed with this algorithm compared favorably wlth data obtained on a pilot scale absorber having a diameter of 0.127 m (5 in.) and packed with 6.2s" (0.25 in.) ceramic Intalox saddles. The data were obtained for absorption of acid gases from a stream produced from cylinder gases and by coal gasification; refrigerated methyl alcohol was the solvent used in the absorber. The systems examined considered both single-component transfer and multicomponent absorption. The data obtained in this study are thought to be the only data available in the literature for multicomponent, adiabatic acked column absorption for which reasonable mass and energy tested against experimental data.balance closures were obtained. Several cove L tions for mass transfer coefficient-interfacial area estimation were

Absorber simulation and design using a nonequilibrium stage model

“…A comprehensive study of a process for removing acid gases using methanol was recently reported by Kelly et al (1984) (see also Kelly et al, 1981 andKelly, 1981). These acid gases must be removed from the main products in order to increase the energy content as well as to meet environmental standards.…”

“…Physical solvents are preferred for bulk removal when all of these factors must be taken into consideration; refrigerated methanol has been found to be a possible alternative to MEA and DEA. A comprehensive study of a process for removing acid gases using methanol was recently reported by Kelly et al (1984) (see also Kelly et al, 1981 andKelly, 1981). A large number of experiments were done on the absorber, using both standard gases (mixtures of nitrogen and carbon dioxide from cylinders) and product gas from a coal gasifier.…”

“…In addition to their experimental work demonstrating the viability of the methanol process, Kelly et al (1984) describe an application of the simulation procedure of Feintuch and Treybal (1978) to their experiments. Elsewhere, we have discussed the relationship among the various model- ling procedures for packed columns and showed that our nonequilibrium model offers greater flexibility, reliability and computational efficiency compared to other methods Taylor 1985d and1985e mixture (carbon dioxide and nitrogen) from cylinders, while in the second set of experiments, the inlet gas to the absorber was the product gas from the gasifier that consisted of as much as nine constituents (specified in Table 2 ) in measurable amounts.…”

“…The temperature profiles and terminal stream compositions predicted by the model compare well with experimental measurements on the ammonia/air/water and acid gas/methanol systems. We have used the nonequilibrium model to simulate: (i) the absorption of ammonia from an air-ammonia stream using water as a solvent, (ii) the absorption of acid gases such as carbon dioxide and hydrogen sulfide using refrigerated methanol as a solvent, a process described by Kelly et al (1984) and (iii) a process in which a heavy hydrocarbon oil is used to absorb a mixture of lighter hydrocarbons.Before we discuss these specific applications in more detail, a brief description of the nonequilibrium stage model is presented below. …”

“…We have used the nonequilibrium model to simulate: (i) the absorption of ammonia from an air-ammonia stream using water as a solvent, (ii) the absorption of acid gases such as carbon dioxide and hydrogen sulfide using refrigerated methanol as a solvent, a process described by Kelly et al (1984) and (iii) a process in which a heavy hydrocarbon oil is used to absorb a mixture of lighter hydrocarbons. Several absorption processes operate at very low efficiencies; a range where the stage efficiency models suffer the most.…”