Integrated Gasification Combined Cycle Syngas Research Articles

Separation of IGCC syngas by using ZIF-8/dimethylacetamide slurry with high CO2 sorption capacity and sorption speed but low sorption heat

An absorption-adsorption hybrid method for separating the integrated gasification combined cycle (IGCC) syngas using ZIF-8/dimethylacetamide (DMAC) slurry was proposed. The viscosity of ZIF-8/DMAC slurries and its sorption performance of pure CO2 were investigated and one optimized slurry with moderate viscosity and high sorption capacity was proposed. Parallel absorption experiments show that the apparent solubility of CO2 in the slurry was doubled compared with that in pure liquid DMAC or propylene carbonate; it even overcomes that in aqueous monoethanolamine solutions at middle to high pressure range. More importantly, the slurry exhibits higher CO2 capture speed compared with conventional absorbents, while its desorption heat is only ∼16 kJ/mol. The equilibrium separation results on H2/CO2 mixtures using ZIF-8/DMAC slurry show that the selectivity of CO2 over H2 ranged from 22 to 119; it increases with decreasing temperature or pressure, increasing initial gas to slurry ratio or CO2 concentration in feed gas. Only 4 theoretical equilibrium stages are required to achieve a sufficient separation of IGCC syngas. Regeneration test shows that the crystal structure of recovered ZIF-8 remains intact after 6 sorption-desorption cycles. This work provides an efficient method for the separation of IGCC syngas at pressure of 2–5 MPa.

The Effect of CO2 Partial Pressure on CH4 Recovery in CH4-CO2 Swap with Simulated IGCC Syngas

To investigate the influence of CO2 partial pressure on efficiency of CH4-CO2 swap from natural gas hydrates (NGHs), the replacement of CH4 from natural gas hydrate (NGH) is carried out with simulated Integrated Gasification Combined Cycle (IGCC) syngas under different pressures, and the gas chromatography (GC), in-situ Raman, and powder X-ray diffraction (PXRD) are employed to analyze the hydrate compositions and hydrate structures. The results show that with the P-T (pressure and temperature) condition shifting from that above the hydrate equilibrium curve of IGCC syngas to that below the hydrate equilibrium curve of IGCC syngas, the rate of CH4 recovery drastically rises from 32% to 71%. The presence of water can be clearly observed when P-T condition is above the hydrate equilibrium curve of IGCC syngas; however the presence of water only occurs at the interface between gas phase and hydrate phase. No H2 is found to present in the final hydrate phase at the end of process of CH4-CO2 swap with IGCC syngas.

Methane recovery from natural gas hydrate with simulated IGCC syngas

Methane (CH4) recovery from natural gas hydrates (NGHs) by CO2-CH4 replacement is considered as a win-win technology for producing CH4 and sequestrating CO2 synchronously. In this investigation, simulated Integrated Gasification Combined Cycle (IGCC) syngas of CO2/H2 gas mixture is used to replace CH4 from simulated methane hydrate which is formed in pure water at 274.15 K and 4.5 MPa. The changes of concentrations of CH4, CO2 and H2 in gas phase during the replacement process are supervised by Gas Chromatograph (GC), and the gas hydrates are determined through in situ Raman. Meanwhile, the CH4 recovery and the replacement mechanism are qualitatively analyzed. The results indicate that, on one hand, the replacement consists of two steps, CH4 hydrate dissociation at the first and followed by CO2 hydrate formation, on the other hand, the CH4 recovery from CH4-CO2/H2 replacement is more than 71% which is significantly higher than that from CH4-CO2 replacement. Notably, no H2 is found in the hydrate phase in the replacement process, which implying that H2 does not compete with CH4 molecules occupying hydrate cages but plays promotion role in CO2-CH4 replacement.

H2 pressure swing adsorption for high pressure syngas from an integrated gasification combined cycle with a carbon capture process

The integrated gasification combined cycle (IGCC) process, possessing high efficiency and environmental advantages, produces H2-rich syngas at high pressures (30–35bar) after capturing CO2. Since the syngas pressure is very high for conventional PSA processes, development of an efficient PSA process at the pressure conditions is required for H2 production. In this study, the H2 PSA process for IGCC syngas was developed experimentally and theoretically. Breakthrough and PSA experiments using activated carbon or activated carbon/zeolite LiX were performed at 25–35bar by using a five-component hydrogen mixture (H2:CO:N2:CO2:Ar=88:3:6:2:1mol%) as a simulated syngas. The overall PSA performance was evaluated in terms of the purity, recovery and productivity of H2 product. According to the results from using single or layered beds, the two-bed PSA process produced 99.77–99.95% H2 with 73.30–77.64% recovery experimentally. A four-layered bed PSA at 35bar was able to produce 99.97%-purity H2 with 79% recovery, and it contained Ar and N2 impurities. The quality of tail gas from the PSA process could be used for the gas turbine without losing H2 and CO. A rigorous mathematical model that included mass, energy, and momentum balances was employed to elucidate the dynamic behaviors and separation performance of the adsorption bed and PSA process.

An experimental and modeling study of CO2-selective membranes for IGCC syngas purification

In recent years, integrated gasification combined cycle (IGCC) technology has gained significant attention for large-scale power generation with carbon capture. In an IGCC power plant, the syngas is typically directed to the gas turbine (for power generation) after CO2 and H2S removal. This work describes the transport properties of the CO2-selective polymeric facilitated transport membranes for syngas purification at different pressures (2–15bar) and 107°C. These membranes contain amines as CO2-carriers that are dispersed in a crosslinked polyvinylalcohol (PVA) matrix. Furthermore, a two-stage membrane process is proposed for CO2 removal from syngas in an IGCC plant. A process modeling and cost-sensitivity analysis of the proposed two-stage membrane process was performed. The effects of feed pressure, temperature, membrane permeance, and selectivity on the overall increase in the cost of electricity (COE) were analyzed. An increase in the COE of 14–18% was estimated for 90% CO2 removal and >99% H2 recovery using the two-stage membrane process in an IGCC power plant.

Synergic effect of cyclopentane and tetra-n-butyl ammonium bromide on hydrate-based carbon dioxide separation from fuel gas mixture by measurements of gas uptake and X-ray diffraction patterns

The synergic effect of Cyclopentane (CP) and Tetra-n-butyl Ammonium Bromide (TBAB) on the hydrate-based carbon dioxide (CO 2) separation from IGCC (Integrated Gasification Combined Cycle) syngas is investigated by measuring the gas uptake and the power X-ray diffraction (PXRD) patterns in this work. The CP with CP/TBAB solution ratio of 5 vol% added into the 0.29 mol% TBAB solution can remarkably increase the gas uptake at 4.0 MPa and 274.65 K. The PXRD patterns of the semi-clathrate (sc) hydrate and structure II (sII) hydrate are obtained for the CP/TBAB/gas/H 2O system. The synergic effect of the CP and the TBAB includes two aspects: On one hand, the CP molecules housed in the hollow centers of the large cavities together with TBAB cations (TBA +) make the sc hydrate more stable. On the other hand, the TBA + displaced out of the large cavities by the CP molecules make the ionization reaction of TBAB in the solution going toward the reverse direction. Thus, the more TBAB molecules exist in the solution and form the more sc hydrate, resulting in the considerable increase of the gas uptake.

Molecular dynamics simulation of CO2 separation from integrated gasification combined cycle syngas via the hydrate formation

Molecular dynamics (MD) simulation is used to study the microscopic mechanism of CO2 separation from integrated gasification combined cycle(IGCC) syngas (CO2/H2) via the hydrate formation. The stable structures and microscopic properties of CO2 hydrate, H2 hydrate, and CO2/H2 hydrate from one stage separation for IGCC syngas are investigated systematically. The binding energy for loading the hydrate structure with the guest molecules, ΔEn, was analyzed. It was shown that the binding between CO2 and water is more stable than that between H2 and water. That is, CO2 can more easily form the hydrate. Therefore, CO2 in the CO2/H2 gas mixture more easily transfers into the hydrate phase. Based on this, CO2 can be separated from the IGCC syngas. The binding energy for loading the single cavity with the guest molecules, ΔEGH, was analyzed. It was found that the gas mixture can form structure Ⅰ(SⅠ) hydrate, in which CO2 molecules preferably occupy the big cavity and then occupy the small cavity, and H2 molecules only occupy the small cavity. The simulation was carried out at pressure of 85 MPa and temperature of 2737 K for the stable structure of the CO2/H2 hydrate in one stage separation for IGCC syngas. From the ΔEn and ΔEGH of the systems with H2 single and double occupancy in the small cavity, it is concluded that the configurations with the single occupancy is most stable. The stable structure of the hydrate in one stage separation is attained by MD. It provides a theoretical evidence of CO2 separation for formation hydrate in IGCC syngas.

A sulfur-tolerant Pd/CeO 2 catalyst for methanol synthesis from syngas

The catalytic activity of ceria-supported Pd for selective hydrogenation of CO is well preserved in the presence of 30 ppm H 2S due to the parallel oxidation of sulfur by CeO 2 under standard methanol synthesis conditions. The bifunctional nature of this catalyst opens a route for the conversion of sulfur-contaminated gas streams such as the integrated gasification combined cycle syngas or biogas into liquid fuels if desulfurization by conventional means is not practical.