Petroleum coke gasification: A review

Effect of High Calcium and High Iron Coal on Ash Fusion Characteristics of Petroleum Coke during Cogasification

Entrained flow gasification provides a more efficient utilization method for high-sulfur petroleum coke. The operation temperature of the entrained flow gasifier must be above the ash fusion temperature (AFT) of petroleum coke due to the liquid slag discharge. In this work, petroleum coke was blended with high-calcium coal and high-iron coal, respectively, under a reducing atmosphere, and the variations in AFTs were recorded by an ash fusion temperature analyzer. The influence of mineral transformations on the ash fusion characteristics of blended ash was analyzed by X-ray diffraction and FactSage. The results showed that both high calcium coal and high iron coal could efficiently reduce the AFTs of petroleum coke. When the ratio of high calcium coal and high iron coal reached 60 wt %, the corresponding flow temperature (FT) of mixed ash decreased to 1225 and 1312 °C, respectively. With the content of high calcium coal increasing, coulsonite (FeV2O4), vanadium trioxide (V2O3) and nickel (Ni) with high-melting points tended to decrease, causing the decrease of AFT for mixed ash. As high iron coal was added, Ni and V2O3 continuously kept decreasing. In particular, the percentage of FeV2O4 first increased and thereafter decreased with high iron coal above 40 wt %.

Investigation of Petroleum Coke Gasification with CO2/H2O Mixtures and S/N Removal Mechanism via ReaxFF MD Simulation

The removal of environmentally harmful S/N is crucial for utilization of high-S petroleum coke (petcoke) as fuels. Gasification of petcoke enables enhanced desulfurization and denitrification efficiency. Herein, petcoke gasification with the mixture of two effective gasifiers (CO₂ and H₂O) was simulated via reactive force field molecular dynamics (ReaxFF MD). The synergistic effect of the mixed agents on gas production was revealed by altering the CO₂/H₂O ratio. It was determined that the rise in H₂O content could boost gas yield and accelerate desulfurization. Gas productivity reached 65.6% when the CO₂/H₂O ratio was 3:7. During the gasification, pyrolysis occurred first to facilitate the decomposition of petcoke particles and S/N removal. Desulfurization with the CO₂/H₂O gas mixture could be expressed as thiophene-S → S → COS → CHOS, thiophene-S → S → HS → H₂S. The N-containing components experienced complicated mutual reactions before being transferred into CON, H₂N, HCN, and NO. Simulating the gasification process on a molecular level is helpful in capturing the detailed S/N conversion path and reaction mechanism.

High-Purity Graphitic Carbon for Energy Storage: Sustainable Electrochemical Conversion from Petroleum Coke

The petroleum coke (PC) has been widely used as raw materials for the preparation of electrodes in aluminium electrolysis and lithium-ion batteries (LIB), during which massive CO₂ gases are produced. To meet global CO₂ reduction, an environmentally friendly route for utilizing PC is highly required. Here, a simple, scalable, catalyst-free process that can directly convert high-sulfur PC into graphitic nanomaterials under cathodic polarization in molten CaCl₂ -LiCl at mild temperatures is proposed. The energy consumption of the proposed process is calculated to be 3 627.08 kWh t^-1 , half that of the traditional graphitization process (≈7,825.21 kWh t^-1 graphite). When applied as a negative electrode for LIBs, the as-converted graphite materials deliver a competitive specific capacity of ≈360 mAh g^-1 (0.2 C) compared with commercial graphite. This approach has great potential to scale up for sustainably converting low-value PC into high-quality graphite for energy storage.

Predicting Pyrolysis of a Wide Variety of Petroleum Coke Using an Independent Parallel Reaction Model and a Backpropagation Neural Network

In this work, the pyrolysis behavior and gaseous products of petroleum coke were investigated by nonisothermal thermogravimetric analysis (TGA) and thermogravimetry-mass spectrometry (TG-MS). Then, the pyrolysis kinetics of six kinds of petroleum coke (Fushun (FS), Fuyu (FY), Wuhan (WH), Zhenhai (ZH), Qilu (QL), and Shijiazhuang (SJZ)) were determined by an independent parallel reaction (IPR) model, and the kinetic parameters (activation energy and preexponential factor) were obtained. In addition, an efficient backpropagation neural network (BPNN) was developed to predict the thermal data of six kinds of petroleum coke. The BPNN-predicted thermal data were used to calculate the kinetic parameters based on the IPR model, and the results were compared with the ones calculated using experimental data. The results showed that the pyrolysis process of six kinds of petroleum coke was divided into three stages, of which stage II (250-900 °C) had the significant mass loss, corresponding to the devolatilization of petroleum coke. MS fragmented ion intensity analysis indicated that the main pyrolysis products were methane CH _x (m/z = 13, 14, 15, and 16), aliphatic hydrocarbon C₃H₅, H₂, CO, CO₂, and H₂O. The thermal data predicted by the IPR, BPNN, and BPNN-IPR (BPNN combined with IPR) models were in good agreement with the experimental data. Most importantly, it was concluded that the BPNN-predicted data can be further applied to calculate the kinetic parameters using the IPR kinetic model.

Combined Bio-Hydrogen, Heat, and Power Production Based on Residual Biomass Gasification: Energy, Exergy, and Renewability Assessment of an Alternative Process Configuration

Bio-hydrogen from residual biomass may involve energy-intensive pre-treatments for drying and size management, as in the case of wet agro-industrial residues. This work assesses the performance of an alternative process layout for bio-hydrogen production from citrus peel gasification, with the aim of cogenerating heat and power along with hydrogen, using minimal external energy sources. The process consists of an air-steam fluidized bed reactor, a hydrogen separation unit, a hydrogen compression unit, and a combined heat and power unit fed by the off-gas of the separation unit. Process simulations were carried out to perform sensitivity analyses to understand the variation in bio-hydrogen production’s thermodynamic and environmental performance when the steam to biomass ratios (S/B) vary from 0 to 1.25 at 850 °C. In addition, energy and exergy efficiencies and the integrated renewability (IR) of bio-hydrogen production are evaluated. As main results, the analysis showed that the highest hydrogen yield is 40.1 kgH2 per mass of dry biomass at S/B = 1.25. Under these conditions, the exergy efficiency of the polygeneration system is 33%, the IR is 0.99, and the carbon footprint is −1.9 kgCO2-eq/kgH2. Negative carbon emissions and high values of the IR are observed due to the substitution of non-renewable resources operated by the cogenerated streams. The proposed system demonstrated for the first time the potential of bio-hydrogen production from citrus peel and the effects of steam flow variation on thermodynamic performance. Furthermore, the authors demonstrated how bio-hydrogen could be produced with minimal external energy input while cogenerating net heat and power by exploiting the off-gas in a cogeneration unit.

Co-pyrolysis of petroleum coke and banana leaves biomass: Kinetics, reaction mechanism, and thermodynamic analysis

Insights into thermal degradation behaviour, kinetics, reaction mechanism, possible synergism, and thermodynamic analysis of co-pyrolysis of carbonaceous materials are crucial for efficient design of co-pyrolysis reactor systems. Present study deals with comprehensive kinetics and thermodynamic investigation of co-pyrolysis of petroleum coke (PC) and banana leaves biomass (BLB) for realizing the co-pyrolysis potential. Thermogravimetric non-isothermal studies have been performed at 10, 20, and 30 ^°C/min heating rates. Synergistic effect between PC and BLB was determined by Devolatilization index (D_i) and mass loss method. Kinetic parameters were estimated using seven model-free methods. Standard activation energy for PC + BLB blend from FWO, KAS, Starink, and Vyazovkin methods was ≈165 kJ/mol and that from Friedman and Vyazovkin advanced isoconversional methods was ≈171 kJ/mol. The frequency factor calculated for the blend from Kissinger method was found to be in the range of 10⁶-10¹⁶s^-1. Devolatilization index (D_i) showed synergistic effect of blending. The data pertaining to co-pyrolysis was found to fit well with R2 (second order) and D3 (three dimensional) from Z(α) master plot. Thermodynamic parameters, viz. ΔH ≈ 163 kJ/mol and ΔG ≈ 151 kJ/mol were calculated to determine the feasibility and reactivity of the co-pyrolysis process. The results are expected to be useful in the design of petcoke and banana leaves biomass co-pyrolysis systems.

Robust Assessment of Controllable Operating Parameters of Entrained Flow Cogasification of Petcoke with Coal: Considering Some Uncertainties

This paper is focused on the effects of some controllable operating parameters on the robustness of the coke/coal entrained flow cogasification process considering some uncertainties in it. In the present work, the operating variables were categorized into controllable parameters (CPs) (oxygen and steam concentrations, OC and SC) and hard-to-control parameters (temperature and coal/coke blending ratio) according to the actual modes during the cogasification process. Then, some robust response surface methodology (RSM) models, that is, mean RSM model and variance RSM model, for some important performance indexes [H₂, CO, and (H₂ + CO) production] with the CPs as independent variables, were found using combined array methodology. Then, the effects of OC and SC not only on the mean but also on the variance of each performance index were systematically investigated. Finally, the cogasification process was robustly optimized using the mean square criterion and desirability function. The result shows that the average production of H₂ and that of (H₂+ CO) increases with increasing OC but decreases with increasing SC. Additionally, higher OC suppresses the fluctuations in H₂ and (H₂ + CO) production, while higher SC enlarges the fluctuations in H₂ production. Assuming that the variance of temperature in a gasifier is 20 °C and the variance of the coal/coke blending ratio is 5%, the multiobjective robust optimization solutions of OC and SC are 1.56 and 50%, respectively, and a satisfactory performance for high syngas production with low fluctuation can be gained.

A Modified Model for Kinetic Analysis of Petroleum Coke

In this study, a nonisothermal kinetics analysis of petcoke was performed at heating rates of 10, 15, and 20°C/min using thermal gravimetric analysis (TGA). The behaviour of petcoke at different gasification stages (dewatering, volatilization, char burning, and burnout) was studied. The effect of heating rate on the activation energy of petcoke gasification was also investigated. The activation energy of petcoke was estimated using different kinetic models that include volume reaction model (VRM), shrinking core model (SCM), random pore model (RPM), Coats and Redfern model (CRM), and normal distribution function (NDF). The NDF model was modified in this study. It was found that the experimental data were best fitted with the modified normal distribution function (MNDF) and SCM. The results also showed that activation energy decreases as heating rate increases, leading to reduction in gasification completion time.

Removal of H2S pollutant from gasifier syngas by a multistage dual-flow sieve plate column wet scrubber

The objective of this study was to observe the performance of a lab-scale three-stage dual-flow sieve plate column scrubber for hydrogen sulfide (H₂S) gas removal from a gas stream, in which the H₂S concentration was similar to that of gasifier syngas. The tap water was used as scrubbing liquid. The gas and liquid were operated at flow rates in the range of 16.59 × 10^-4-27.65 × 10^-4 Nm³/s and 20.649 × 10^-6-48.183 × 10^-6 m³/s, respectively. The effects of gas and liquid flow rates on the percentage removal of H₂S were studied at 50-300 ppm inlet concentrations of H₂S. The increase in liquid flow rate, gas flow rate and inlet H₂S concentration increased the percentage removal of H₂S. The maximum of 78.88% removal of H₂S was observed at 27.65 × 10^-4 Nm³/s gas flow rate and 48.183 × 10^-6 m³/s liquid flow rate for 300 ppm inlet concentration of H₂S. A model has also been developed to predict the H₂S gas removal by using the results from the experiments and adding the parameters that affect the scrubber's performance. The deviations between experimental and predicted H₂S percentage removal values were observed as less than 16%.

Enhanced Dispersion and Stability of Petroleum Coke Water Slurries via Triblock Copolymer and Xanthan Gum: Rheological and Adsorption Studies

The rheology of petroleum coke (petcoke) water slurries was investigated with a variety of nonionic and anionic dispersants including poly(ethylene oxide) (PEO)-b-poly(propylene oxide) (PPO)-b-PEO triblock copolymers (trade name: Pluronic, BASF), poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), poly(ethylene oxide) (PEO), poly(carboxylate acid) (PCA), sodium lignosulfonate (SLS), and poly(acrylic acid) (PAA). Each effective dispersant system shared very similar rheological behavior to the others when examined at the same volume fraction from its maximum petcoke loading. Triblock copolymer, Pluronic F127 (F127), was found to be the best dispersant by comparing the maximum petcoke loading for each dispersant. The yield stress was measured as a function of petcoke loading and dispersant concentration for F127, and a minimum dispersant concentration was observed. An adsorption isotherm and atomic force microscopy (AFM) images reveal that this effective dispersion of petcoke particles by F127 is due to the formation of a uniform monolayer of brushes where hydrophobic PPO domains of F127 adhere to the petcoke surface, while hydrophilic PEO tails fill the gap between petcoke particles. F127 was then compared to other Pluronics with various PEO and PPO chain lengths, and the effects of surface and dispersant hydrophilicity were examined. Finally, xanthan gum (XG) was tested as a stabilizer in combination with F127 for potential industrial application, and F127 appears to break the XG aggregates into smaller aggregates through competitive adsorption, leading to an excellent degree of dispersion but the reduced stability of petcoke slurries.