Simulated Coal-derived Gas Research Articles

Desulfurization Behavior of Cerium–Iron Mixed Metal Oxide Sorbent in Hot Coal Gas

Ce–Fe mixed metal oxide sorbent C2F3B850 was prepared by using cerium oxide and red mud (an iron oxide waste from a steel company). The ability of C2F3B850 (CeO2/red mud = 0.85) was evaluated over a fixed-bed reactor in a simulated coal-derived gas. It was found that the main active components of sorbent C2F3B850 were cerium and iron oxides, the addition of red mud in CeO2-based sorbent could decrease sulfurization temperature, and 500 °C is the best temperature for sulfurization in the range of 500–700 °C. After eight successive sulfurization–regeneration cycles over C2F3B850, the regenerated sorbent still performed well with no apparent deterioration. The average breakthrough sulfur capacity corresponding to H2S concentrations below 50 ppmv is 9.97 (g S/100 g sorbent). Sorbent C2F3B850 during successive sulfurization–regeneration cycles was characterized by means of X-ray photoelectron spectroscopy, X-ray diffraction, and nitrogen adsorption–desorption techniques. The results reveal that the C2F3B850 so...

Desulfurization behavior of zinc oxide based sorbent modified by the combination of Al2O3 and K2CO3

In order to reduce the unfavorable effect of carbon oxide on desulfurization efficiency for zinc oxide based sorbent and decrease the concentration of carbonyl sulfide in effluent gas during desulfurization process, the modification of zinc oxide based sorbent is necessary in the preparation of zinc oxide based desulfurization sorbent. In this paper, the modified ZnO based desulfurization sorbents were obtained by mixing of active zinc oxide with different additives, which include graphite, Al2O3 and K2CO3, then shaping at ambient temperature, drying at 120°C and calcinating at 550°C. The desulfurization performances for the prepared ZnO based desulfurization sorbents were tested in a quartz upflow fixed-bed reactor under the condition of 300°C, 2000h−1 and simulated coal-derived gas. The phases of sorbents before and after desulfurization were characterized by X-ray diffractometer, and their pore structures were measured by N2 adsorption–desorption method. The experimental results show that COS was present in effluent gas for ZnO based sorbent while removing H2S from simulated coal-derived gas at experimental condition. ZnO based desulfurization sorbent modified by the combination of K2CO3 and Al2O3 achieves obvious improvements in the desulfurization performance, and H2S and COS concentrations in exit gas are below 0.1 mgS/m3 before breakthrough point as well as the accumulated breakthrough sulfur capacity reaches 14wt.%. Adding Al2O3 can improve the pore structure of ZnO based desulfurization sorbent, which benefits H2S to diffuse in the pore of sorbent and improves desulfurization performance. Loading K2CO3 can increase the basicity of ZnO based desulfurization sorbent, which raises the COS catalytic hydrolysis rate on sorbent and decreases concentration of COS present in exit gas.

Preparation of Sorbents Loaded on Activated Carbon to Remove H2S from Hot Coal Gas by Supercritical Water Impregnation

A series of sorbents were prepared by depositing the oxide particles of Cu, Mn, and Zn onto the activated carbon (AC) using the supercritical water impregnation (SCWI) method. The morphology and structure, amounts of loading metals, pore volume, and surface area of sorbents were characterized by X-ray diffraction (XRD), inductively coupled plasma−atomic emission spectrometry (ICP−AES), and nitrogen sorption measurements. The sulfidation tests of sorbents were performed using a fixed-bed reactor under ambient pressure and simulated coal-derived gas. The results show that the metal-active component, preparation temperature, and impregnation time during SCWI are the main influencing factors of the desulfurization activity of the sorbent. These factors behave mainly by changing the micropore volume and surface area of sorbents and the dispersion of metal oxide particles on the support. The optimal SCWI conditions for preparing Mn-based sorbents are 0.46 mol/L precursor solution concentration, 380 °C preparing...

Catalytic decomposition of ammonia in simulated coal-derived gas over supported nickel catalysts

As a hot gas clean-up technology for integrated coal gasification combined-cycle (IGCC) power plants, the catalytic decomposition of ammonia using simulated coal-derived gas was studied. Based on the selective catalytic oxidation of ammonia to nitrogen and water, the characteristics of five kinds of supported nickel catalysts were investigated. Ammonia decomposition experiments were carried out at 0.9 MPa, and the surface properties of the catalysts were investigated through surface area measurement, the temperature programmed desorption of ammonia (NH 3-TPD), carbon analysis, XRD analysis, and transmission electron microscope (TEM) observation. The results showed that a nickel catalyst supported on ZSM-5 zeolite has the highest activity and selectivity for ammonia decomposition to nitrogen without carbon deposition from 250–400 °C among the tested catalysts.

Reduction Behavior of Iron Oxide Sorbent and Its Effect on Sulfidation

The study of reduction of metal oxide sorbents for desulfurization at high temperatures has been attractive for many years. To investigate the reduction behaviors of iron oxide sorbent prepared from red mud and different additives and to evaluate the effects of reduction on the subsequent sulfidation kinetics, temperature-programmed reduction (TPR) tests and isothermal experiments were carried out using a thermogravimetric technique in a gaseous mixture consisting of30% H 2 in nitrogen and a simulated coal-derived gas, respectively. It was found that the sorbents prepared from different clay additives had different reduction behaviors, and the compensation effect existed in the reduction of iron oxide sorbents. In a strong reducing atmosphere, such as a coal-derived gas from a Texaco gasifier, iron oxide was converted to lower oxidation states and the degree of reduction differed as the temperature changed. There was no evidence of reduction bellow 400 °C, whereas iron oxide was reduced quite rapidly and even to a very deep reduction state of metallic iron at 600 °C. The low oxidation states of iron, such as those in Fe 3 O 4 and FeO, are active for sulfidation.

Effect of Simulated Coal-Derived Gas Composition on H2S Poisoning Behavior Evaluated Using a Disaggregation Scheme

poisoning is an important issue for solid oxide fuel cells (SOFCs) operated with syngas. The effect of simulated coal-derived gas composition on poisoning behavior was evaluated using a disaggregation scheme where the influence of content was determined separately using a typical anode-supported SOFC operated with a mixture gas, while the effect of other compositions (CO, , and ) was investigated with simulated coal-derived gas having constant and CO flow rates balanced by a mixture gas (83% and 17% ). The results indicated that the extent of poisoning was not pertinent to content when the cell was tested galvanostatically with a current density of at using a mixture gas containing 10 ppm , and the poisoning impact can be completely removed by switching to sulfur-free gas. The CO, , and high water vapor content aggravated the poisoning effect, and the performance was almost irrecoverable when the cell was tested with a 35% mixture gas containing 12.5 ppm . However, the introduction of 10% and an increase in content from 3 to 10% in the mixture gas can promote the performance recoverability to a larger extent.

Ni-based amorphous alloy membranes for hydrogen separation at 400 °C

Amorphous alloy membranes composed primarily of Ni and early transition metals (ETMs) are an inexpensive alternative to Pd-based alloy membranes, and these materials are therefore of particular interest for the large-scale production of hydrogen from carbon-based fuels. Catalytic membrane reactors can produce hydrogen directly from coal-derived synthesis gas at 400 °C, by combining a commercial water–gas-shift (WGS) catalyst with a hydrogen-selective membrane. In order to explore the suitability of Ni-based amorphous alloys for this application, the thermal stability and hydrogen permeation characteristics of Ni–ETM amorphous alloy membranes has been examined. A fundamental limitation of these materials is that hydrogen permeability is inversely proportional to the thermal stability of the alloy. Alloy design is therefore a compromise between hydrogen production rate and durability. Amorphous Ni 60Nb 40− X Zr X membranes have been tested at 400 °C in pure hydrogen, and in simulated coal-derived gas streams with high steam, CO and CO 2 levels, without severe degradation or corrosion-induced failure. Ni–Nb–Zr amorphous alloys are therefore prospective materials for use in a catalytic membrane reactor for coal-derived syngas.

Catalytic decomposition of ammonia in simulated coal-derived gas

Alumina-supported Ni and/or Ru catalysts were prepared and their ability to decompose ammonia in simulated coal-derived gas fuel from 250 to 900 °C using a conventional fixed-bed flow reactor at atmospheric and high pressure (0.9 MPa) was tested. The surface properties of the catalysts were investigated using BET, CO chemisorption, XRD, and TPD after NH 3 adsorption. Supported Ni catalyst promoted NH 3 decomposition to N 2 above 700 °C with and without oxygen addition in the fuel. Supported Ni catalyst had the potential to decompose NH 3 to N 2 from 400 to 550 °C with the addition of a small amount of oxygen in the fuel, while the addition of Ru significantly reduced the potential. Ni selectively promotes NH 3 oxidation to N 2 at low temperature, while Ru selectively promotes H 2 oxidation to H 2 O .

High-temperature hydrogen sulfide removal from coal-derived gas by iron ore

Six kinds of hematite and two kinds of magnetite were examined as solid sorbents of H 2 S for high-temperature desulfurization. The hematite samples were more reactive than the magnetite samples, and reactivity of the sample of iron ore depended on the specifiic ore. The hematite ores were confirmed to be effective sorbents of H 2 S in H 2 O-poor and/or H 2 -rich gas. The reactivities of the samples of the hematite were decreased by the partial reduction to Fe 3 O 4 with the simulated coal-derived gas (in the absence of H 2 S). Impurities and thermal history of an iron ore seemed to affect its reactivity