Syngas Pressure Research Articles

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.

Hydroformylation of 1-Octene Mediated by the Cobalt Complex [CoH(dchpf)(CO)2

Hydroformylation of 1-octene with the heterodinuclear (Fe, Co) complex [CoH(dchpf)(CO)2] (1) was investigated (dchpf = 1,1′-bis(dicyclohexylphosphino)ferrocene). In agreement with this cobalt complex possessing a preformed hydride as well as carbonyl ligands, the pre-activated catalyst does not require any induction process or activation treatment to become reactive in hydroformylation. The catalyst activity and (chemo-)selectivity proved to be strongly dependent on the applied reaction conditions. Higher syngas pressures suppress alkene isomerization and favor the hydroformylation reaction. The overall regio-selectivity remains very similar within the investigated reaction space, with the C1-selectivity varying between 48 and 69 %. An increase of the reaction temperature at 40 bars results in a progressive decrease of the C1-selectivity and an increase in the C2- and C3-selectivity due to a higher isomerization activity at elevated temperatures. Furthermore, at high temperatures (170 °C) and low syngas pressures (10–20 bar) the main oxygenated products are the alcohols, resulting from reduction of the aldehydes. However, when using a combination of higher syngas pressures and intermediate temperatures, the reaction could be optimized towards the formation of aldehydes. At 140 °C and 40 bars syngas pressure quite selective hydroformylation of 1-octene could be achieved, yielding 57 % aldehydes and only 1.3 % over-reduction to the corresponding alcohol.

Sensitivity test of low rank Indonesian coal utilization using steady state and dynamic simulations of entrained-type gasifier

Gasification is a process in which a solid fuel is transformed into a gas, which acts as a useful energy source. Coal gasification provides a wide range of products such as chemical, power, liquid, and gaseous fuels. A simulation study was undertaken to calculate the composition, mass flow rate, temperature, pressure of syngas, ash slag layer thickness, heat dissipation from the reactor, and carbon conversion of the coal under steady state conditions. The effect of changes in the input parameters such as the changes in the O2 and H2O to coal ratios, operating temperature, and most importantly the change in the fuel, was considered. Besides steady state simulations, dynamic simulations were also conducted to predict the starting and shutdown conditions of the gasifier. The g-proms process modeling software was utilized to conduct the simulations based on mathematical equations, which are capable of calculating time dependent derivatives. In order to obtain the actual physical and chemical properties of coal and its ash, as well as the reaction kinetics of coal, some experiments were performed. Proximate analysis, elemental analysis, and coal pyrolysis, combustion and gasification kinetics were conducted using thermogravimetry (TGA), elemental analysis method (EA), and a pressurized wire mesh heating reactor (PWMR), respectively. Ash viscosity and ash mineral composition were determined using rheometer and X-ray fluorescence (XRF), respectively. The results of these experiments were fitted into the model and served as input for the calculations. Berau and Kideco are low rank Indonesian coals with different characteristics. The results showed major problems associated with slag tapping in the case of Kideco coal. On the other hand, Berau coal performed without any issues.

Process design for CO2 absorption from syngas using physical solvent DMEPEG

Pre-combustion IGCC is one of the leading technologies having potential for effective control of greenhouse gas emission. Process design for CO2 Capture from power plant is becoming increasingly important in the past decades in view of the need for optimization of Capital Cost and Utility consumption. In this article, a configuration of the process design for CO2 absorption using physical solvent DMEPEG is proposed, which is described using the process flow diagram (PFD) and the Flowsheet. CO2 absorption performance of DMEPEG solvent is assessed based on a rate based mass transfer model using ProTreat® simulation software. The rate based mass transfer simulation by ProTreat software adds to the reliability of the simulation result (as evident by its acceptance within industry). The trade-off between H2 recovery (by syngas recycle) and CO2 re-absorption is described which reveals that more than 55% H2 recovery may significantly increase the load on the system (in terms of syngas processing and CO2 re-absorption).Objective of this research is to develop a detailed process model for CO2 absorption by DMEPEG solvent (to enable detailed techno-economic assessment by bottom up approach). In the second section of this article, the process of CO2 capture by physical solvent DMEPEG is explained. In the fourth section, the boundary conditions such as the inlet pressure, temperature and composition of syngas and solvent feed are defined. In the fourth and fifth section, the design and performance of the packed tower is described and the utility consumption is estimated. Moreover, the outlet condition of the solvent is described and its saturation (by CO2) is estimated. In the fourth section, the strategy of solvent heating to recycle the syngas to CO2 absorber (for H2 recovery) is described. Importance of CO2 absorption in solvent (at high concentration) for minimization of equipment size and utility consumption for CO2 capture is explained.Using RSR packing (6.4m Dia., 16m Ht. (9+6+1)) results in 90.7% CO2 absorption and 89% saturation of CO2 dissolved in DMEPEG solvent. Out of 3.34 kmol/s H2 fed to the CO2 Absorber (as part of syngas), 1.464% (equivalent 5.9 MW power generation by Gas Turbine in open cycle) is co-absorbed (along with CO2) in DMEPEG solvent. Out of this co-absorbed H2, 55.7% is recovered which is equivalent to 3.267 MW Power Generation.In terms of hydraulic design, the CO2 Absorber using RSR packing operating at 72.5% flood condition results in packing pressure drop of 87.5Pa/m (1.4kPa). Packed section diameter and height is suggested for various random packing materials (tower internal) to achieve almost comparable gas absorption performance.

Using exergy to analyse the sustainability of fermentative ethanol and acetate production from syngas via anaerobic bacteria (Clostridium ljungdahlii)

In this study, exergetic performance assessment of ethanol and acetate fermentation in a batch bioreactor using Clostridium ljungdahlii under various syngas pressures in the range of 0.8–1.8atm was carried out. The exergetic parameters of the bioreactor were determined using both conventional exergy and eco-exergy concepts in order to select the most sustainable and productive operational conditions. In general, a significant difference was found between the exergetic values of the process using the conventional exergy and eco-exergy approaches. Overall, the eco-exergy concept showed to be a more appropriate approach for analysing and optimizing energy conversion systems including living organisms due to the incorporation of the work of the genetic information embodied in the genomes of microorganisms. The lowest overall normalized exergy destruction was found to be 49.96kJ/kJ Ac+EtOH and 40.54kJ/kJ Ac+EtOH at initial pressure of 1.8atm using the conventional exergy and eco-exergy concepts, respectively. Accordingly, this condition would be recommended to be applied in pilot- or industrial-scale bioreactors. Finally, the employed approach herein could be used to shed light on on-going attempts to improve the performance of the bioreactors for biofuel production considering the sustainability and productivity perspectives.

Hydrate-based hydrogen purification from simulated syngas with synergic additives

Hydrated-based separation process has recently raised as a novel technology for hydrogen (H2) purification from mixture gases containing carbon dioxide (CO2). However, the practical application requires suitable hydrate formation condition, hydrate formation rate, gas selectivity, gas storage capacity and so on. This work presents the effect of synergic additives on the hydrate-based syngas purification process based on the thermodynamic, kinetic, purification characteristic studies as well as microcosmic structure analysis. The synergic additives comprise traditional hydrate promoter (tetra-n-butyl ammonium bromide, TBAB) and gas solvent (dimethyl sulfoxide, DMSO). 40.2 mol% CO2/H2 binary mixtures were selected as the simulated syngas. The results show that the synergic additives (TBAB-DMSO) can reduce the equilibrium hydrate formation pressure of the simulated syngas by 80%. Compared to single TBAB for the hydrate-based purification process, the synergic additives could improve the gas consumption rate of the unit system, gas storage capability and gas selectivity by about 32%, 105% and 51% respectively, and decrease the loss ratio of H2 by 1.45%. The Raman analysis reveals that the simulated syngas forms semiclathrate framework with TBAB-DMSO. DMSO only performs as a gas solvent during the gas dissolution and diffusion process, and not participates in the hydrate framework formation.

Optimization using response surface methodology and kinetic study of Fischer–Tropsch synthesis using SiO2 supported bimetallic Co–Ni catalyst

Catalyst using bimetallic Ni–Co on SiO2 as support was prepared, characterized and tested for Fischer–Tropsch synthesis. RSM (Response surface methodology) and the CCD (Central composite design) were employed in determining the optimal condition for light olefin production. The process parameters of syngas ratio, operational pressure, and reaction temperature were chosen as independent variables in CCD. The quadratic model was developed for process optimization and statistical experimental designs. It is found that the syngas ratio, operational pressure, and reaction temperature are significant to CO conversion and light olefin (C2–C4) selectivity. The combination of temperature and pressure is found to be significant to CO conversion, while the combination of syngas ratio and pressure is found to be only significant to alkene selectivity. The optimal conditions with setting maximum CO conversion and alkene selectivity are the following: syngas ratio 2, total pressure 36 bar, reaction temperature 302 °C. At optimal condition, the predicted CO conversion and alkene selectivity reach 20% and 29%, respectively. Thirty different models derived from 10 different mechanisms according to LHHW (Langmuir–Hinshelwood–Hougen–Watson) type rate expressions were tested against experimental data. The CO insertion mechanism is found to yield the best fit with activation energy being 98.5 kJ/mol. The literature comparison of activation energy and light alkene selectivity among different supports were made.

First rhodium-catalyzed hydroformylation of cyclopentadiene

This paper describes the first rhodium-catalyzed hydroformylation of cyclopentadiene (Cpd) using a homogeneous catalyst system consisting of [Rh(OAc)2]2 and the chelate ligand BISBI. At a reaction temperature of 100°C and a syngas pressure of 30bar the cyclopentane carbaldehyde is formed in 68% yield while 20% of the respective dialdehyde species are obtained within 3hours. An important side reaction in Cpd hydroformylation reaction can be the dimerization of Cpd to its dimer dicyclopentadiene (Dcpd). This unwanted side reaction could be overcome by the use of tertiary alkyl amines as additives. Furthermore, the possibility to steer the reaction via the influence of the bite angle of diphosphine ligands was found.

Modeling and simulation of H2S effect in high-temperature water–gas shift reaction using coal-derived syngas

In this study, a model including hydrogen sulfide (H2S) effect on high-temperature water–gas shift reaction (WGSR) performance was built using coal-derived syngas as feedstock. Based on this model, it was found that the H2S coverage rate increases with the decrease in reaction temperature, leading to more significant carbon monoxide (CO) conversion reduction at low reaction temperature. It was also found that the H2S effect can be ignored when the reaction temperature is in the range at which reverse WGSR occurs. In such a temperature range, CO conversion for both with and without the H2S effect approaches equilibrium result. Through parametric studies using this model, it was found that CO conversion depends significantly on the residence time which can be adjusted by varying the flow rate, steam to carbon molar ratio, inlet pressure of syngas and reactor size. For syngas with fixed CO/H2 molar ratio, CO conversion was found to decrease with the increase in carbon dioxide (CO2) content.

Rhodium-Catalyzed Hydroformylation of 1,3-Butadiene to Adipic Aldehyde: Revealing Selectivity and Rate-Determining Steps

The reaction mechanism of Rh-catalyzed hydroformylation of 1,3-butadiene with triptycene-derived bisphosphite ligands L was studied by in situ NMR and IR experiments, kinetic measurements, and deuterioformylation. Under CO pressure the η3-crotyl complex (κ2-L)Rh(η3-crotyl)(CO) is a stable intermediate that slowly liberates 3-pentenal when hydrogen is added. It also represents the most stable intermediate under real hydroformylation conditions and exists in high concentrations during the catalysis. The rate law of the reaction is found to be second-order in syngas pressure and independent of the butadiene concentration. This agrees with the total barrier between the η3-crotyl complex and one of the transition states of hydrogen addition or reductive elimination being rate determining. The olefin insertion step is found to be partly reversible depending on the pressure, which means that n/iso regioselectivity is not controlled by this step alone.

From alkenes to alcohols by cobalt-catalyzed hydroformylation–reduction

The cobalt-catalyzed hydroformylation of alkenes in the presence of a range of novel cyclic phosphine ligands was investigated. The effect of various parameters such as solvents, additives, cobalt/phosphine ratio, CO/H2 (1:2), and nature of the alkenes was examined. The results revealed that both terminal and internal alkenes are hydroformylated in high yields to give mainly linear products at moderate temperature and syn gas pressure. The linearity ranges from 43 to 85%, with Lim-10 giving the highest proportion of linear product.

Thermal–mechanical–numerical analysis of stress distribution in the vicinity of underground coal gasification (UCG) panels

During underground coal gasification (UCG), whereby coal is converted to syngas in situ, a panel (cavity) is formed in the coal seam. Unlike other underground mining methods, the coal and country rocks in the vicinity of a UCG panel are subjected to high temperatures which may be in excess of 1000°C. UCG operation imposes significant geomechanical changes to the strata. In order to understand these changes, numerical modeling can provide a comprehensive and qualitative understanding of the UCG process. In this paper, a new approach, namely, Underground Coal Gasification-Pillar Stability Analysis (UCG-PSA) is presented to estimate the protection pillar width in UCG based on the Controlled Retraction Injection Point (CRIP) configuration. The UCG-PSA approach considers development load, side abutment load, front abutment load, thermal stress along with cavity syngas pressure as a lateral pressure to determine the protection pillar width. Furthermore, the role of the crushed zone around a pillar was considered in the estimation of the pillar strength. A new 3D Thermal–Mechanical (TM) model is developed for UCG based on the CRIP configuration to predict stress distribution in the vicinity of the UCG panel and to verify the UCG-PSA approach results using the FLAC3D software. In this model, a panel is subjected to high syngas pressure and high temperature. Moreover, after each step of gasification the modeling of caved material is performed. The results of the TM model compared with the Mechanical (M) model show that the stress distribution increased at the front of the face and pillar edge due to the thermal stress. In addition, the results show that the maximum side abutment stress at a depth of 600m is 63.1MPa and applied at a distance about 3.5m away from the pillar edge while in the M model it is 59.2MPa. The proposed methodology could provide a consistent and simple way for the stability analysis of pillars in UCG sites.

Enrichment and optimization of anaerobic bacterial mixed culture for conversion of syngas to ethanol

The main aim of the present study was to enrich anaerobic mixed bacterial culture capable of producing ethanol from synthesis gas fermentation. Screening of thirteen anaerobic strains together with enrichment protocol helped to develop an efficient mixed culture capable of utilizing syngas for ethanol production. Physiological and operational parameters were optimized for enhanced ethanol production. The optimized value of operational parameters i.e. initial media pH, incubation temperature, initial syngas pressure, and agitation speed were 6.0±0.1, 37°C, 2kgcm−2 and 100rpm respectively. Under these conditions ethanol and acetic acid production by the selected mixed culture were 1.54gL−1 and 0.8gL−1 respectively. Furthermore, up-scaling studies in semi-continuous fermentation mode further enhanced ethanol and acetic acid production up to 2.2gL−1 and 0.9gL−1 respectively. Mixed culture TERI SA1 was efficient for ethanol production by syngas fermentation.

ChemInform Abstract: Regioselective Hydroaminomethylation of Vinylarenes by a Sol—Gel Immobilized Rhodium Catalyst.

In the course of our studies toward the development of new heterogeneous conditions for better controlling regioselectivity in organic reactions, we investigated the application of sol-gel immobilized organometallic catalyst for regioselective hydroaminomethylation of vinylarenes with aniline or nitroarene derivatives in an aqueous microemulsion. By immobilization of 6 mol % [Rh(cod)Cl]2 within a hydrophobic silica sol-gel matrix we were able to perform efficient hydroaminomethylation under mild conditions and isolate 2-arylpropylamines with high regioselectivity. The regioselectivity of the reaction was found to be mainly dependent on the hydrophobicity of the catalyst support. It is also significantly affected by the electronic nature of the substrates, by the reaction temperature, and by syngas pressure. The heterogenized catalyst can be reused for several times.

Sequentially coupled flow-geomechanical modeling of underground coal gasification for a three-dimensional problem

Underground coal gasification (UCG) has been identified as an environmentally friendly technique for gasification of deep un-mineable coal seams in situ. This technology has the potential to be a clean and promising energy provider from coal seams with minimal greenhouse gas emission. The UCG eliminates the presence of coal miners underground hence, it is believed to be a much safer technique compared to the deep coal mining method. The UCG includes drilling injection and production wells into the coal seam, igniting coal, and injecting oxygen-based mix to facilitate coal gasification. Produced syngas is extracted from the production well. Evolution of a cavity created from the gasification process along with high temperature as well as change in pore fluid pressure causes mechanical changes to the coal and surrounding formations. Therefore, simulation of the gasification process alone is not sufficient to represent this complex thermal-hydro-chemical–mechanical process. Instead, a coupled flow and geomechanical modeling can help better represent the process by allowing simultaneous observation of the syngas production, advancement of the gasification chamber, and the cavity growth. Adaptation of such a coupled simulation would aid in optimization of the UCG process while helping controlling and mitigating the environmental risks caused by geomechanical failure and syngas loss to the groundwater. This paper presents results of a sequentially coupled flow-geomechanical simulation of a three-dimensional (3D) UCG example using the numerical methodology devised in this study. The 3D model includes caprock on top, coal seam in the middle, and another layer of rock underneath. Gasification modeling was conducted in the Computer Modelling Group Ltd. (CMG)’s Steam, Thermal, and Advanced processes Reservoir Simulator (STARS). Temperature and fluid pressure of each grid block as well as the cavity geometry, at the timestep level, were passed from the STARS to the geomechanical simulator i.e. the Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D) computer program (from the Itasca Consulting Group Inc.). Key features of the UCG process which were investigated herein include syngas flow rate, cavity growth, temperature and pressure profiles, porosity and permeability changes, and stress and deformation in coal and rock layers. It was observed that the coal matrix deformed towards the cavity, displacement and additional stress happened, and some blocks in the coal and rock layers mechanically failed.

Regioselective Hydroaminomethylation of Vinylarenes by a Sol–Gel Immobilized Rhodium Catalyst

In the course of our studies toward the development of new heterogeneous conditions for better controlling regioselectivity in organic reactions, we investigated the application of sol-gel immobilized organometallic catalyst for regioselective hydroaminomethylation of vinylarenes with aniline or nitroarene derivatives in an aqueous microemulsion. By immobilization of 6 mol % [Rh(cod)Cl]2 within a hydrophobic silica sol-gel matrix we were able to perform efficient hydroaminomethylation under mild conditions and isolate 2-arylpropylamines with high regioselectivity. The regioselectivity of the reaction was found to be mainly dependent on the hydrophobicity of the catalyst support. It is also significantly affected by the electronic nature of the substrates, by the reaction temperature, and by syngas pressure. The heterogenized catalyst can be reused for several times.

Very Low Pressure Rh-Catalyzed Hydroformylation of Styrene with (S,S,S-Bisdiazaphos): Regioselectivity Inversion and Mechanistic Insights

Rates and selectivities of styrene hydroformylation as catalyzed by the rhodium coordination complex of (S,S,S)-bis-diazaphos (BDP) under extremely low pressures of syngas (CO/H2) are reported. At pressures <10 psia, the catalyst system is selective for the linear regioisomer, 3-phenyl-1-propanal, whereas at high pressure, it is highly selective for branched (R)-2-phenylpropanal. Lowered pressures severely degrade the enantioselectivity of the branched product. Qualitative kinetic data reveal large changes in the form of the apparent rate law, suggesting significant changes in catalyst speciation prior to selectivity-determining transformations. Most strikingly, under low-pressure conditions, the qualitative kinetic data imply that the catalyst accumulates as either 4-coordinate (bisphosphine)Rh(CO)(alkyl) (4) or 5-coordinate (bisphosphine)Rh(CO)(alkyl)(styrene) (5) complexes, neither of which have been previously observed as hydroformylation resting states under catalytic conditions. Although styrene is ...

Mixed Alcohol Synthesis over a K Promoted Cu/ZnO/Al2O3Catalyst in Supercritical Hexanes

Mixed alcohol synthesis (MAS) from syngas involves an overall reduction in the number of moles (i.e., volume reduction) and is highly exothermic. As such, the high-pressure, dense-phase solvent conditions of a supercritical reaction medium afford opportunities to enhance the performance of these reactions. In this paper, the effect of supercritical hexanes (a mixture of hexane isomers) on the reaction performance of MAS was studied in a fixed bed reactor. Experiments were carried out over a 0.5 wt % K promoted Cu based mixed metal oxide catalyst in the temperature range of 200 °C–300 °C, a partial pressure of syngas of 4.5 MPa, and the hexanes/syngas molar ratio ranging from 0 to 3. The results of mixed alcohol synthesis under supercritical hexanes phase conditions demonstrated remarkable enhancement in CO conversion and methanol productivity, while the CH4 and CO2 selectivity was notably reduced. In addition, the effect of temperature has also been investigated on conversion, selectivity, and alcohol pro...

Enhanced hydroformylation by carbon dioxide‐expanded media with soluble Rh complexes in nanofiltration membrane reactors

A novel process for continuous hydroformylation in CO2‐expanded liquids (CXLs) is demonstrated using bulky phosphite ligands that are effectively retained in the stirred reactor by a nanofiltration membrane. The reactor is operated at 50°C with a syngas pressure of 0.6 MPa to avoid CO inhibition of reaction rate and selectivity. The nanofiltration pressure is provided by ∼3.2 MPa CO2 that expands the hydroformylation mixture and increases the H2/CO ratio in the CXL phase resulting in enhanced turnover frequency (∼340 h−1), aldehydes selectivity (&gt;90%) and high regioselectivity (n/i ∼8) at nearly steady operation. The use of pressurized CO2 also reduces the viscosity in the CXL phase, thereby improving the mass‐transfer properties. Constant permeate flux is maintained during the 50 h run with Rh leakage being less than 0.5 ppm. This technology concept has potential applications in homogeneous catalytic processes to improve resource utilization and catalyst containment for practical viability. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4287–4296, 2013

Improving high temperature heat capture for power generation in gasification plants

As part of the gasification process, hot syngas is cooled to low temperatures for gas cleaning by generating high pressure steam in a radiant heat exchanger. The steam, in turn, is used to generate electric power. However, the very large temperature difference that exists between the syngas and generated high pressure steam results in significant losses during the heat transfer process. These losses can be reduced, and hence the overall plant efficiency improved, by choosing materials and working fluids that reduce the temperature difference in the syngas heat exchanger. A set of alternatives to high pressure steam is liquid metals or molten salts. These liquids can be kept at a pressure equal to the syngas pressure, reducing the tensile hoop stress in the heat exchanger tubes. Since the strength of steel decreases with temperature, reducing the hoop stress allows tubes (and the liquids inside them) to reach higher temperatures. The liquid metals or molten salt can then be used in a secondary heat transfer loop to transfer heat to a steam generator. This paper describes a cost-effective radiant heat exchanger that can be used to transfer heat from high temperature syngas to these alternative heat transfer fluids, and also quantifies the increase in overall IGCC plant efficiency by doing so. A capital cost assessment shows a small payback time and improved revenue is achieved by using this technology, making this a realistic option for gasification processes.