Study on the Stability of Sorbents Removing H 2 S from Hot Coal Gas (original) (raw)
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Separation Science and Technology, 1997
Hot-gas desulfurization for the integrated gasification combined cycle (IGCC) process has been investigated to effectively remove hydrogen sulfide with various metal oxide sorbents at high temperatures and pressures. Metal oxide sorbents such as zinc titanate oxide, zinc ferrite oxide, copper oxide, manganese oxide.and calcium oxide were found to be promising sorbents in comparison with other removal methods such as membrane separation and reactive membrane separation. The removal reaction of H,S from coal gas mixtures with zinc titanate oxide sorbents was conducted in a batch reactor. The main objectives of this research are to formulate promising metal oxide sorbents for removal of hydrogen sulfide from coal gas mixtures, to compare reactivity of a formulated sorbent with a sorbent supplied by the Research Triangle Institute at high temperatures and pressures, and to determine effects of concentrations of moisture contained in coal gas mixtures on equilibrium absorption of H,S into metal oxide sorbents. Promising durable metal oxide sorbents with high-sulfur-absorbing capacity were formulated by mixing active metal oxide powders with inert metal oxide powders and calcining these powder mixtures.
Retention of Arsenic and Selenium during Hot Gas Desulfurization Using Metal Oxide Sorbents
Energy & Fuels, 2004
The present work explores the possibility of capturing toxic elements other than sulphur in coal gasification flue gases using metal oxide mixtures. Arsenic and selenium compounds were the elements selected for study because they are toxic species which are present in coal gasification flue gases in different amounts, depending on temperature. Among the regenerable sorbents already developed for hot gas cleaning systems in Integrated Gasification Combined Cycles, metal oxide mixtures based on iron, titanium or zinc oxides (zinc ferrites and zinc titanates) were tested for arsenic and selenium retention. These sorbents have previously proved to possess good characteristics for H 2 S(g) retention. The study was carried out in a laboratory scale reactor, using the sorbent in a fixed bed, at 550ºC. Good retention capacities (56 mg g-1) were obtained in these conditions for selenium in a metal oxide mixture containing zinc titanate. A metal oxide mixture containing zinc ferrite proved to be an appropriate sorbent for both elements, retention capacities being 21 mg g-1 for arsenic and 55 mg g-1 for selenium. The results obtained indicate that arsenic and selenium compounds can be retained together with sulphur compounds in these sorbents and be desorbed in the sorbent regeneration processes.
Sulfidation of a Novel Iron Sorbent Supported on Lignite Chars during Hot Coal Gas Desulfurization
Physics Procedia, 2012
The sulfidation behavior of novel iron oxide sorbents supported using activated-chars during desulfurization of hot coal gases has been studied. The sulfidation of the char-supported sorbents was investigated using a fixed-bed quartz reactor in the temperature range of 673K to 873K. The product gases were analyzed using a GC equipped with a TCD and a FPD detector. The sorbent samples before and after sulfidation were examined using SEM and XRD.
Stability of Zinc Oxide High-Temperature Desulfurization Sorbents for Reduction
Energy & Fuels, 1994
Zinc oxide was examined as a high-temperature desulfurization sorbent. At high temperature ( h a . 600 "C), the zinc oxide sorbent is reduced to metallic zinc with reductive gas in a coal derived gas, and then the metallic zinc evaporates. This reduction and vaporization was not completely prevented by the additions of ZrO2, TiOz, and A1203 to the zinc oxide. Thereduction and vaporization tendencies of zinc oxide were studied by the temperature-programmed reduction (TPR) method using thermobalance, under different conditions which simulated practical desulfurization of hot coal-derived gases. From these results, the stability of zinc oxide for reduction followed by vaporization could be expressed by an experimental equation using concentrations of H2, CO, H20, and C02 in coal-derived gases and temperature as functions. From the measurements of TPR profiles and reactivities of the zinc oxide sorbents containing the additives, it is suggested that stabilization of zinc oxide by additives without a decrease of the reactivity of zinc oxide is a very difficult problem.
Performance of Mn and Cu Mixed Oxides as Regenerable Sorbents for Hot Coal Gas Desulfurization
Energy & Fuels, 2000
Mixed oxides, prepared by calcination at 950°C for 6 h of powder mixtures of manganese and copper oxides, have been studied as regenerable sorbents for hot coal gas desulfurization. For the stabilization of copper in the oxidation states 2+ or 1+ under strong reducing conditions of coal gas, different concentrations of component oxides have been used enhancing the formation of different mixed oxides. Copper was not stabilized by manganese oxides, but its presence in the fresh sorbent was completely necessary because it increases the sorbent reactivity and keeps the H 2 S concentration in the outlet gas from a reactor below 50 ppmv. Thermogravimetric experiments and performance tests in a fixed bed reactor have allowed the optimization of the operating conditions for a sorbent MC (1:0.1) showing a good performance in multicycle tests without apparent decay.
Advanced Hot-Gas Desulfurization Sorbents
1996
The objective of this project is to develop advanced hot-gas desulfurization sorbents for relatively low temperature application that show stable and high sulfidation reactivity at 343 to 538 {degrees}C. A number of zinc-based formulations will be prepared and screened for testing in a fixed-bed reactor at high pressure (1 to 20 atm) and high temperatures using simulated coal-derived fuel gases. One of the superior formulations will be tested for long- term durability and chemical reactivity in the reactor. To prevent sulfation, catalyst additives will be investigated, which would promote a lower regeneration temperature.
Mixed-oxide sorbents for high-temperature removal of hydrogen sulfide
Industrial & Engineering Chemistry Process Design and Development, 1986
O?-Al,O,) were investigated as regenerable sorbents for the removal of H,S at high temperatures. A special technique was used to prepare the sorbents in highly porous form. The sorbents were subjected to successive sulfiation-regeneration cycles in a packed-bed microreactor. Sulfidation was carried out at 538-650 OC with H,S-H,O-H,-N, mixtures, regeneration with 02-N2-H20 mixtures. Fresh, sulfided, and regenerated sorbents were characterized by XRD, SEM-EDS, and BET surface area analysis. Solid conversion and the prebreakthrough exit concentration of H,S are discussed in terms of physical structure and thermodynamic properties of the sorbents. The performance of the sorbents CuO-Fe,O,, Cu0-A1,03, and CuO-Fe,O,-AI2O3 is discussed in terms of changes in the oxidation state of copper during sulfidation.
Energy & Fuels, 1998
The reactivity and performance of different zinc-titanium-based sorbent extrudates for desulfurization of coal gas at high temperature in successive sulfidation-regeneration cycles were studied in both a thermobalance and a fixed-bed reactor. The study showed that the sulfidation and the regeneration of these sorbents as cylindrical extrudates was mostly a diffusioncontrolled process. In order to change the degree of dispersion of the active phase and porosity of the sorbent extrudates, some of them were prepared by coprecipitation and others by using graphite as a high-temperature pore-modifier additive. The study showed that the high degree of dispersion of the active phase achieved in the first stages of the coprecipitation process is practically destroyed during sorbent calcination at high temperature. Additionally, coprecipitation enhanced thermal sintering during preparation and the porosity of these fresh sorbents was low. Consequently, the reactivity in thermobalance tests was also low and performance in the reactor was very poor. On the contrary, graphite increased substantially the porosity of the fresh sorbent extrudates and, because it is eliminated at high temperature, this effect prevailed during calcination and successive sulfidation-regeneration cycles. Consequently, graphite notably improved the performance of zinc titanate extrudates as hot temperature sorbents which under the operation conditions used was clearly evidenced by an increase of the sorbent efficiency.
Hydrogen sulfide removal from hot coal gas by various mesoporous silica supported Mn2O3 sorbents
Applied Surface Science, 2014
A series of 50 wt% Mn 2 O 3 sorbents was prepared using various mesoporous silica, MCM-41, HMS, and KIT-1 as support. The influence of textural parameters of mesoporous silica, especially type of channel on the desulfurization performance of Mn 2 O 3 sorbents was investigated at 600-850 • C using hot coal gas containing 0.33 vol.% H 2 S. The fresh and used sorbents were characterized by means of N 2-adsorption, x-ray diffraction (XRD), high resolution transmission microscopy (HRTEM) and H 2 temperature-programmed reduction (H 2-TPR) techniques. The results confirmed that the manganese oxide was dispersed highly in regular pore channel of the mesoporous supports due to high surface area. Compared with the Mn 2 O 3 /diatomite, all mesoporous silica supported Mn 2 O 3 sorbents exhibited high breakthrough sulfur capacity and a sharp deactivation rate after the breakthrough point. Compared to Mn 2 O 3 /MCM-41 and Mn 2 O 3 /HMS sorbent, the Mn 2 O 3 /KIT-1 showed better desulfurization performance because of the 3D wormhole-like channel. The high sulfur capacity of the Mn 2 O 3 /KIT-1 sorbent was maintained during the eight consecutive desulfurization-regeneration cycles. The Mn 2 O 3 /KIT-1 still presented high desulfurization activity when hot coal gas contained low steam (<5%).