Selective absorption of H₂S from larger quantities of CO₂ by absorption and reaction in fine sprays

Abstract

Highly selective transfer of hydrogen sulfide (HzS) from much larger quantities of carbon dioxide (COZ) has been accomplished by absorption and reaction into fine sprays of buffered carbonate solution. Selectivity after the intensely agitated atomization zone is dramatically improved once the droplets have formed and stagnate internally. HZS transfer in this latter zone is virtually independent of the presence of COz, even at C02:HzS ratios of 1cO; COZ transfer, however, is adversely affected by the presence of H2S. The gas film resistance for mass transfer is effectively eliminated with the 50 p m mean droplet diameter. The data indicate approximately constant hydrodynamics throughout the formed droplet zone and allow.good theoretical prediction of enhancement factors for this complex system. Thus the design of more efficient equipment is possible if the gas-liquid contacting method is tailored to take advantage of differences in the transfer and reaction rate properties of gases to be separated. E. BENDALL, R. C. AIKEN, and F. MANDAS Department of Chemical EngineeringUniversity of Utah Salt Lake City, UT 84112The need for a selective separation of HzS from COz occurs as it is often too expensive and not necessary to remove large quantities of COz along with the pollutant HzS. Often no process is capable of removing the H2S to specifications without uneconomical removal of the majority of the COz, thus requiring a large purification plant and large capital investment. Situations in which HZS and larger quantities of COz appear include low to medium BTU gas wells or natural COz sources, and in fossil fuel plants operating under partial oxidative environments.There have been few experimental or theoretical studies of mass transfer into a dispersed medium with subsequent intraphase reaction. Applications include topics in liquid-liquid extraction and gas purification where single components are transferred or multiple competitively or synergistically interacting components are transferred. Description of the fluid dynamics for such systems is complicated by the existence of three different regimes always present: atomization, droplet flight, and coalescence. Many atomization techniques exist and none are welldescribed for sprays. Atomization greatly affects the droplet flight regime as it determines the droplet size distribution, dynamics and interaction. Continuous phase backmixing and internal dispersed-phase mixing further can complicate the theoretical description of the fluid dynamics.This article contains a summary of an experimental study on selective removal of HzS from much larger quantities of COz using a conventional liquid solution but sprayed into a chamber as a fine mist. The primary variable between runs was the amount of liquid reagent in solution. Gas and liquid samples were taken throughout the reactor. CONCLUSIONS AND SIGNIFICANCEThere is a significant increase in selective and extensive transport of H2S over COz if the scrubbing liquid is finely divided. This advantage is particularly great outs...

SIMULTANEOUS ABSORPTION OF H2S AND CO2 INTO A SOLUTION OF SODIUM CARBONATE

“…The simultaneous absorption of HzS and COz into carbonate solutions, at high COz to HzS ratios, has previously been studied by several researchers (Srinivasan and Aiken, 1988;Bendall et al, 1983;Yih and Sun, 1987;Gioia et al, 1968 andGarner et al, 1958). The process has been studied with experiments, theoretical…”

“…• The gas-side resistance to mass transport is dominant for H 2S and the liquid-side resistance is dominant for CO 2 (Srinivasan and Aiken, 1988;Bendall et al, 1983;Yih andSun, 1987 andGarner et aI., 1958). The reaction with H 2S in the liquid is much faster than the CO 2 reaction (Gioia et al, 1968).…”

H2S Reactive Absorption from Off‐Gas in a Spray Column: Insights from Experiments and Modeling

“…Bendall et al 7 studied the selective reactive absorption of H 2 S from CO 2 in fine sprays of buffered carbonate solution. They reported that the gas film resistance to mass transfer is negligible when the average droplet diameter exceeds 50 μm.…”

Insights in the development of a new method to treat H2S and CO2 from sour gas by alkali

“…Nevertheless, in spite of its regenerable characteristics, the main product is still H 2 S and CO 2 which are passed to another facility to be treated again which main product is elemental sulfur, making the treatment process costly and time consuming. Another process used to eliminate H 2 S and CO 2 is their absorption in sodium hydroxide solutions, but the problem is that the sodium hydroxide is not regenerable; in consequence, it is limited to the removal of small quantities of acid gases [3][4][5][6][7][8]. The objective of this work is to explore the technical viability of an alkaline system to absorb such acid gases to produce, in situ, valuable products other than elemental sulfur.…”