The ionic liquid (IL) [hmim][Tf 2 N] was used as a physical solvent in an Aspen Plus simulation, employing the Peng−Robinson Equation of State (PR-EOS) with Boston−Mathias (BM) α-function and standard mixing rules, to develop a conceptual process for CO 2 capture from a shifted (undergone the water−gas shift reaction) warm fuel gas stream produced from Pittsburgh #8 coal for a 400 MWe IGCC power plant. The physical properties of the IL, including density, viscosity, surface tension, vapor pressure, and heat capacity were obtained from literature and modeled as a function of temperature. Also, available experimental solubility values for CO 2 , H 2 , H 2 S, CO, and CH 4 in this IL were compiled, and their binary interaction parameters (δ ij and l ij ) were optimized and correlated as functions of temperature. The Span−Wager EOS was also employed to generate CO 2 solubilities in [hmim][Tf 2 N] at high pressures (up to 10 MPa) and temperatures (up to 510 K). The conceptual process developed consists of four adiabatic absorbers (2.4 m inner diameter (ID), 30 m high) arranged in parallel and packed with Plastic Pall Rings of 0.025 m for CO 2 capture; 3 flash drums arranged in series for solvent (IL) regeneration with the pressureswing option; and a pressure-intercooling system for separating and pumping CO 2 up to 153 bar to the sequestration sites. The compositions of all process streams, CO 2 capture efficiency, and net power were calculated using the Aspen Plus simulator. The results showed that, based on the composition of the inlet gas stream to the absorbers, 95.12 mol % of CO 2 was captured and sent to sequestration sites; 98.37 mol % of H 2 was separated and sent to turbines; and the solvent exhibited a minimum loss of 1.23 mol %. These results indicate that the [hmim][Tf 2 N] IL could be used as a physical solvent for CO 2 capture from warm shifted fuel gas streams with high efficiency.

This paper presents an extensive review of the kinetics, hydrodynamics, mass transfer, heat transfer and mathematical as well as computational fluid dynamics (CFD) modeling of Low-Temperature Tropsch Synthesis (LTFT) synthesis in Slurry Bubble Column Reactors (SBCRs), with the aim of identifying potential research and development areas in this particular field. The kinetic expressions developed for F-T synthesis over iron and cobalt catalysts along with the water gas shift (WGS) reactions are summarized and compared. The experimental data and empirical correlations to predict the hydrodynamics (gas holdup, Sauter mean bubble diameter, and bubble rise velocity), mass transfer coefficients and heat transfer coefficients are presented. The effects of various operating variables, including pressure, temperature, gas velocity, catalyst concentration, reactor geometry, and reactor internals on the hydrodynamic and transport parameters as well as the performance of SBCRs are discussed. Additionally, modeling efforts of SBCRs, using axial dispersion models (ADM), multiple cell recirculation models (MCCM) and computational fluid dynamics (CFD), are addressed. This review revealed the following:(1) Numerous F-T and WGS kinetic rate expressions are available for cobalt and iron catalysts and one must be careful in selecting the appropriate expressions for LTFT. Iron catalyst suffers from severe attrition and subsequent deactivation in SBCRs and accordingly building a costly catalyst manufacturing facility onsite is required to maintain a steady operation of the F-T reactor;(2) Experimental data on the hydrodynamic and transport parameters at high pressures and temperatures, typical to those of actual F-T synthesis, remain scanty when compared with the plethora of studies conducted using air-water systems in small reactors at ambient conditions; (3) Several empirical correlations for predicting the hydrodynamic and mass as well heat transfer parameters are available and one should select those which consider the reactor diameter, gas mixtures and the potential foamability of the F-T liquids; (4) The effect of cooling internals configuration and sparger design on the hydrodynamic and transport parameters, local turbulence, mixing and catalyst attrition are yet to be seriously addressed; (5) The impact of operating variables on the hydrodynamic and transport parameters as well as the overall performance of the SBCRs should be investigated using actual F-T fluid-solid systems under typical pressures and temperatures using a large-scale reactor ( > 0.15 m ID) in the presence of gas spargers and cooling internals; (6) Significant efforts are still required in order to advance CFD modeling of SBCRs, particularly those pertaining to the relevant closure models, such as drag, lift and turbulence. Also, cooling internals configuration and the design as well as orientation of gas spargers should be accounted for in the CFD modeling; and (7) Proper validations of the CFD formulations using actual systems for F-T SBCR are needed.

The main objective of this study is to predict the performance of an industrial‐scale (ID = 5.8 m) slurry bubble column reactor (SBCR) operating with iron‐based catalyst for Fischer–Tropsch (FT) synthesis, with emphasis on catalyst deactivation. To achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass‐transfer parameters (gas holdup, εG, Sauter‐mean diameter of gas bubbles, d32, and volumetric liquid‐side mass‐transfer coefficients, kLa), and FT as well as water gas shift reaction kinetics, was developed. The hydrodynamic and mass‐transfer parameters for He/N2 gaseous mixtures, as surrogates for H2/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot‐scale (0.29 m) SBCR under different pressures (4–31 bar), temperatures (380–500 K), superficial gas velocities (0.1–0.3 m/s), and iron‐based catalyst concentrations (0–45 wt %). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length‐to‐diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H2 and CO conversions and the C5+ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars to minimize deactivation of the iron‐based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt % to maximize C5+ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H2 and CO conversions were 49.4% and 69.3%, respectively, and the C5+ products yield was 435.6 ton/day. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3838–3857, 2015

Three ionic liquids {butyl-trimethyl-ammonium bis(trifluoromethylsulfonyl)imide [N 1114 ][BTA], 1-methyl-1propyl-piperidinium bis(trifluoromethylsulfonyl)imide [PMPip][BTA], and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMIM][Tf]} and two heat-transfer oils [dibenzyltoluene (DBT) and polydimethylsiloxane (trade name X-BF)] were evaluated for use in the three-phase methanation and the biogas purification processes. The density, viscosity, and surface tension of these liquids were measured and modeled as a function of the temperature. The solubilities of H 2 , CO, CO 2 , and CH 4 in these five liquids were also obtained under different pressures and temperatures. Additionally, the criteria required for each of the two processes considered were identified: the three-phase methanation process requires a thermally stable liquid with a low vapor pressure and a high H 2 , CO 2 and CO solubility, while the biogas purification process requires a highly selective CO 2 solubility liquid at ambient temperature. From the evaluation of both the experimental data and the process requirements, the most suitable liquid for each of the aforementioned processes was identified. For the three-phase methanation process, the two ionic liquids [N 1114 ][BTA] and [PMPip][BTA] and the two heat-transfer oils DBT and X-BF met the minimum requirements, while [EMIM][Tf] showed promising potential for the biogas purification process.

A multiphase-Eulerian, three-dimensional (3-D), computational fluid dynamics (CFD) model was built to investigate the local hydrodynamics of a pilot-scale (0.29 m ID, 3 m height) Slurry Bubble Column Reactor (SBCR). The model was first validated against the gas holdup radial profiles in an air-water-glass beads system obtained in a 0.254 m ID and 2.5 m height column under ambient conditions at various superficial gas velocities by Yu and Kim (Bubble characteristics in the radial direction of three-phase fluidized beds. AIChE Journal 34, 2069–2072, 1988). The model was next validated against the gas holdup radial profile data for N2-Drakeol-glass beads system obtained in a 0.44 m ID and 2.44 m height reactor, including internals, operating under ambient conditions at various superficial gas velocities by Chen et al. (Fluid dynamic parameters in bubble columns with internals. Chemical Engineering Science 54, 2187–2197, 1999). The model was also validated against experimental data obtained in our lab for N2-Fischer Tropsch (F-T) reactor wax-Fe catalyst system obtained in a pilot-scale, Slurry Bubble column Reactor, SBCR (0.29 m ID, 3 m height) under pressures and temperatures up to 25.9 bar and 490 K, respectively. These three validations led to the selection of the turbulence and interphase drag coefficient models, and the optimization of the solution method, mesh size and structure and the step size. Moreover, the inclusion of RNG k-ε turbulence model coupled with the Wen-Yu (Mechanics of Fluidization. Chemical Engineering Progress Symposium Series 62, 100–111, 1966) / Schiller-Naumann (A drag coefficient correlation. Zeitung Ver. Deutsch. Ing 77, 318–320, 1935) drag correlations, and the mass transfer coefficients were found to provide the most accurate predictions of the experimental data. The CFD model was then used to investigate local gas holdup, liquid recirculation, local turbulence intensities, bubble diameters, and solids distribution throughout our pilot-scale SBCR, operating under typical F-T process conditions. The model predictions showed strong liquid recirculation and backmixing near the walls of the reactor, and the solid-phase velocity vectors closely followed those of the liquid-phase. A relatively high liquid turbulence intensities were observed in the vicinity of the sparger upon startup, however, after reaching a steady state, the liquid turbulence intensities became more evenly distributed throughout the reactor. The liquid turbulence intensities were slightly higher near the center of the reactor, and closely resembled the velocity vectors. Also, the Sauter mean bubble diameters increased, whereas the solids distribution decreased with reactor height above the gas distributor.

Two ionic liquids (ILs), TEGO IL K5 and TEGO IL P51P, were used as physical solvents to develop a conceptual process for CO 2 capture from a shifted warm fuel gas stream produced from Pittsburgh no. 8 coal for a 400 MWe power plant. The physical properties of the two ILs and the solubilities of CO 2 , H 2 , N 2 , and H 2 S in the TEGO IL K5 solvent, as well as those of CO 2 and H 2 in the TEGO IL P51P solvent, were measured in our laboratories at pressures up to 30 bar and temperatures from 300 to 500 K. The Peng−Robinson equation-of-state (P-R EOS) with Boston−Mathias (BM) α function and standard mixing rules was used in the development of the process, and the solubility data were used to obtain the binary interaction parameters (δ ij and l ij ) between the shifted gas constituents and the two ILs. The binary interaction parameters were then correlated as functions of temperature. The conceptual process consists of four identical adiabatic packed-bed absorbers (4.5 m i.d., 27 m height, packed with 0.0254 m plastic Pall Rings) arranged in parallel for CO 2 capture, three flash drums arranged in series for solvent regeneration,and two pressure/intercooling systems for separating and pumping CO 2 to sequestration sites. The compositions of all process streams, CO 2 capture efficiency, and net power were calculated using Aspen Plus for the two solvents. The results showed that TEGO IL K5 and TEGO IL P51P were able to capture 91.28% and 90.59% of CO 2 in the fuel gas stream, respectively.

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This work describes the preparation of a set of nine new novel hydrophobic PEG-substituted solvents. These solvents include linear, T-shaped, and disubstituted conformations of the PEG grafted with PDMS molecule. The effect of changing both the molecular conformation and length of PEG side arm on the physical properties and CO2 absorption capacity was studied. These solvents are intended for separation of CO2 and H2 in precombustion CO2 capture and are intended to replace the current-state-of-the-art glycol-based solvents and operate at a higher temperature. The properties of the disubstituted solvents are exceptionally well suited for precombustion CO2 capture applications because of their hydrophobicity, high CO2 solubility, low evaporation rate, and lack of foaming.