Simulator Aspen Plus Research Articles

ASPEN PLUS desulfurization simulations for the scrubber of a large-scale marine diesel engine: main scrubbing section's desulfurization share optimization and superiority confirmation for the seawater/seawater cascade-scrubbing solution.

Aiming at perfecting the proposed three-stage cascade-scrubbing desulfurization technology, ASPEN PLUS simulations of seawater/seawater cascade-scrubbing desulfurization for an exhaust gas scrubber designed for a 10-MW large-scale marine diesel engine were performed to fix a reasonable desulfurization share for the main scrubbing section. Accordingly, three typical desulfurization share setups of 80%, 85%, and 90% were compared under various operational conditions by varying the fuel-sulfur content, liquid/gas ratio, and seawater alkalinity. In complying with the desulfurization requirements of emission control areas, 85% was obtained as the optimal desulfurization share among the three setups. Again, under the selected 85% setup, the cascade-scrubbing desulfurization was numerically compared with the conventional once-through open-loop solution, so as to confirm the seawater-saving advantage of the cascade-scrubbing desulfurization technology used for the exhaust gas of large-scale marine diesels. At relatively higher sulfur content above 3.5%, the open-loop solution solely achieved the desulfurization requirements of non-emission control areas by using higher liquid/gas ratio levels of 6.5-8.0L/Nm3, while fully failed to meet the much stricter requirements of emission control areas except the lowest 1.5% fuel-sulfur conditions. On the contrary, the cascade-scrubbing solution could meet the requirements of emission control areas under various fuel-sulfur content conditions and reduced the liquid/gas ratio by about 45%, in comparison to the open-loop solution.

Kinetics study and process simulation of reactive distillation for the synthesis of ε‐caprolactone

AbstractA novel three‐stage catalytic reactive distillation (RD) column integrated chemical reaction and distillation process for the continuous synthesis of ε‐caprolactone (ε‐CL) was proposed to overcome the disadvantages of previous batch processes. Reaction kinetics according to the two‐step indirect oxidation method was studied firstly, which was essential in reactor design and process optimization as well as lacking in the current literature. Kinetics models obtained by data fitting were tested by residual distribution and model statistics. And then, according to the thermodynamic characteristics and reaction kinetics of this process, a steady‐state simulation of RD column was carried out with the process simulator Aspen Plus. The influence of operation parameters was investigated on process performance. Under the optimal operating conditions, the conversion of cyclohexanone was 97%, and the mass fraction of ε‐CL in the bottom products was 62.31%. The simulation showed that RD column worked with excellent results in respect to conversion and product purity because of integrating the processes of chemical reaction and distillation.

Multi-energy Complementary System for Joint Production of Liquid Fuel and Power

By taking the energy complementation as an idea and the steam methane reforming as well as coal partial gasification and Fischer-Tropsch synthesis as the core technological means, this paper establishes a coal and methane to co-produce liquid fuels and power generation system using an ASPEN PLUS simulator, and realizes that the H2/CO can be adjusted by directly changing the charging rate of raw materials with no need for additional equipment. At the same time, the coal char that has not yet been gasified is burned to provide the needed heat for the reaction of steam methane reforming, which can not only solve the demand of high heat of steam methane reforming, but also realize the gradient utilization of energy, thus reducing the loss in energy. In addition, some Fischer-Tropsch steam is used to generate power to further reduce the energy damage of the system. Two key parameters, namely coal input and Fischer-Tropsch recycle ratio, are discussed and their effects on system performances are analysed. At the optimum condition, the energy efficiency of this novel system reaches 52.5%, and the primary energy saving ratio reaches 30.4%.

Evaluation of waste heat recovery technologies for the cement industry

Abstract Cement is the world’s most widely used construction material. In 2019, global production amounted to 4086 MT, of which Colombia contributed 12.59 MT. The main component of cement is Clinker and it appears as an intermediate product in the manufacturing process that is produced in a kiln system at sintering temperatures. Such a process exhibits high environmental impacts due to both elevated emissions of Carbon Dioxide and fuel consumption and it is inherently prone to thermal inefficiencies, as heat losses to the surroundings, because of the large flow rates and high temperatures. In this work, the waste heat obtained from the cooling of a high-temperature gas effluent from the rotary kiln in a Colombian cement plant is analysed for its potential use either to dry wet raw material (limestone) or to generate electricity through an ORC. Material, energy and exergy balances for the steady-state were assisted with simulations in Aspen Plus V.10 software. Exergo-economics analysis followed the traditional approach using the net present value (NPV) of the investment as decision criteria. To achieve a holistic view of the waste heat recovery scenario a sensitivity analysis is carried out varying the outlet temperatures of the hot gases for various working fluids in the ORC. Results showed that the best alternative, NPV = 0.37 MUSD at market conditions of electricity and fuel sale price, delivers a maximum of 3.77 MW of electricity with a thermal efficiency of 15.96% and an exergy efficiency of 37.52% using Cyclo-Pentane as working fluid. None of the dryer units attained a positive NPV and were discarded. However, the highest moisture reduction in the solids stream was 5.67% at T = 120 ∘C. The option of placing a drying unit immediately after an ORC to completely cool down the gases was economically analysed for ORC cases with best NPV, T= 150 ∘C and T = 180 ∘C. But no substantial improvement was found over using the ORC alone. The possibility to improve the simple ORC performance is explored through the inclusion of an internal heat exchanger, such recuperated cycle outperforms its simpler configuration in terms of thermal and economic performance delivering 4.1 MW of net work with an NPV = 0.42 MUSD, a rate of return of 15.58% and a payback time of PB = 6.07 years. This is 8.75% more work with 13.51% better economic performance than the simple ORC.

Evaluation of Biorefining Scenarios for Advanced Fuels Production from Triticale Grain

This study explored the potential of triticale feedstock for biofuel biorefining scenarios that included (i) producing ethanol, (ii) biochemically producing acetone–butanol–ethanol (ABE), and annexing catalytic processes to ethanol production for (iii) butanol and (iv) hydrocarbons (liquefied petroleum gas, gasoline, jet fuel, diesel). Based on simulations in Aspen Plus, the net greenhouse gas reduction (GHG) and minimum fuel energy price (MFEP) were determined. The maximum contracting prices of triticale (MCP) were then determined and benchmarked against historic animal feed prices to ascertain market competition. Thus, producing ethanol had the lowest MFEP of 18.3 US$/GJ and highest GHG reduction of 81%, while ABE had the highest MFEP of 27.3 GJ/kg and lowest GHG reduction of 63%; therefore, catalytically producing butanol was preferable (MFEP = 22 US$/GJ). If a CAPEX rebate of 30% is applied to the ethanol and butanol scenarios, the chances that existing animal feed prices outcompeted the MCPs were 50–98%. For the hydrocarbon fuels, the MFEPs were 60% higher than the fossil equivalent, though the GHG reduction was 75%. If the jet fuel product received a carbon tax rebate, the chances of the animal feed market outcompeting the MCP were only 22%. Thus, the need for incentivizing mechanisms for biofuels was further emphasized.

Design of the CO2 Removal Section for PSA Tail Gas Treatment in a Hydrogen Production Plant

CO2 Capture, Storage and, recently, Utilization (CCSU) is considered effective for achieving the target of 2°C established to reduce the gradual increase in global warming. In the literature, most of research has focused on the removal of carbon dioxide from power plants, particularly those fed by coal, which account for higher amounts of CO2 emissions if compared to those fed by natural gas. CCSU in other non-power sectors is still not fully considered, while its importance in mitigating the environmental impact of industrial activities is equivalent to the one of power plants. In the field of hydrogen production, treatment of gaseous streams to remove carbon dioxide is performed for producing a stream of almost pure H2 starting from syngas and for reducing the carbon dioxide emissions, so that CO2 removal units can be part of different sections of the plant. In this work, a state-of-the-art Steam Methane Reforming (SMR) plant for production of 100 000 Nm3/h of hydrogen has been considered. Hydrogen is produced from syngas by employing the Pressure Swing Adsorption (PSA) technology and the exiting tail gas is fed to the burners of the SMR unit, after removal of carbon dioxide. This work focuses on the design of the units for the treatment of the PSA tail gas by employing an aqueous solution of MethylDiEthanolAmine (MDEA). Simulations have been performed with the commercial process simulator ASPEN Plus®, customized by the GASP group of Politecnico di Milano for best representing both the thermodynamics of the system and the mass transfer with reaction. For the scheme composed of the absorber and the regenerator, several column configurations have been considered and the optimal solution, which minimizes the operating costs of the plant, has been selected.

Process design and evaluation of syngas-to-ethanol conversion plants

Synthesis gas (syngas) is mostly known by its use on ammonia (Harber-Bosch process) and hydrocarbons (Fischer-Tropsch process) production processes. However, a less explored route to produce chemical products, among them alcohols and other oxygenates, from syngas has been gaining attention over the last few years. In this route, an initial feedstock as biomass is firstly gasified to synthesis gas, which is reformed, cleaned, compressed and finally catalytically converted into a mixture of alcohols and oxygenated products. After separation steps, these products attain sufficient purity to be sold. In this work, the thermochemical route, is used aiming ethanol production from syngas. Using the commercial simulator Aspen Plus, were proposed four study cases using 3 different categories of catalysts in 4 different process layouts. All the cases were evaluated regarding their productivity, energy consumption, and aspects of economic importance. The results show the technical viability to produce ethanol from syngas, proving an energy surplus of all processes and a reasonable production of the main product.

A multi-objective optimization of the integrated copper-chlorine cycle for hydrogen production

This paper considers a multi-objective optimization study performed on an integrated copper-chlorine cycle for hydrogen production developed and built at the Ontario Tech. University using genetic algorithm. The system is thermodynamically modeled in the Aspen-plus software considering all components in the cycle. A varied range of steam-to-copper ratios is selected for this study and four different cases are considered based on various steam input temperatures. The objective of this study is to maximize the rate of hydrogen production and overall system exergy efficiency, hence minimizing overall cost of cycle operation. The results of the multi-objective optimization study are presented in the form of the Pareto frontier solutions for identification of the optimal points. A comparison of the optimization results with Aspen-plus simulations is also presented for validation purposes. For all the cases considered, the optimal trade-off point results in steam-to-copper ratios ranging from 15.7 to 16.9. The steam input temperature is found to have a significant influence on the exergy efficiency and overall operating cost. The highest exergy efficiency is reported as 17.8% at a steam input temperature of 300 °C, while the minimum exergy efficiency is obtained to be 6.5% at a steam input temperature of 25 °C.

Multi-Scale Analysis of Integrated C1 (CH4 and CO2) Utilization Catalytic Processes: Impacts of Catalysts Characteristics up to Industrial-Scale Process Flowsheeting, Part II: Techno-Economic Analysis of Integrated C1 Utilization Process Scenarios

In the second part of this paper (Part II), the potentials and characteristics of an industrial-scale Oxidative Coupling of Methane (OCM) process integrated with CO2-hydrogenation, ethane dehydrogenation, and methane reforming processes are highlighted. This novel process concept comprises a direct conversion of methane to ethane and ethylene and further conversion of the resulted carbon dioxide and remaining unreacted methane, respectively, to methanol and syngas. In this context, the selected experimental results of the catalytic CO2-hydrogenation to methanol reported in the first part of this paper (Part I), were utilized to represent its industrial-scale performance. The experimental results of the mini plant-scale operation of an OCM reactor and CO2 removal units along with the experimental and industrial data available for representing the operation and performance of all process-units in the integrated process structures were utilized to perform a comparative techno-economic environmental analysis using Aspen-Plus simulation and an Aspen Economic Process Analyzer. The experimental procedure and the results of testing the sequence of OCM and CO2-hydrogenation reactors are particularly discussed in this context. It was observed that in the sequential operation of these reactors, ethylene will be also hydrogenated to ethane over the investigated catalysts. Therefore, the parallel-operation of these reactors was found to be a promising alternative in such an integrated process. The main assumptions and the conceptual conclusions made in this analysis are reviewed and discussed in this paper in the light of the practical limitations encountered in the experimentations. In the context of a multi-scale analysis, the contributions of the design and operating parameters in the scale of catalyst and reactor as well as in the process-scale represented by analyzing the type and operating conditions of the downstream-units and the process-flowsheets on the economic and environmental performance of the integrated process structures were studied. Moreover, the economic impacts of extra ethylene and methanol produced respectively via the integrated ethane dehydrogenation and CO2-hydrogenation sections were analyzed in detail. The required capital investment was found to be even smaller than the yearly operating cost of the plant. The environmental impacts and sustainability of the integrated OCM process were found to be enhanced by securing a minimum direct CO2-emission and energy-efficient conversion of CO2 and the unreacted CH4, respectively, to methanol and syngas. Besides producing such value-added by-products, efficient operation of downstream process-units was secured by minimizing the energy usage and ethylene losses. Under the considered conditions in this analysis, the specifications of the finally selected integrated OCM process structure, providing the fastest return of investments (less than 8 years), are highlighted.

Techno-economic evaluation of methanol production using by-product gases from iron and steel works

Aiming at achieving large-scale CO2 mitigation in the iron & steel industries via efficient utilization of the by-product gases such as the coke oven gas (COG) and Linz-Donawitz converter gas (LDG) in the iron & steel works, conceptual design of a LDG-to-methanol process (option 1) and two LDG/COG-to-methanol processes (options 2 and 3 without or with H2 purification, respectively) was implemented using the process simulator Aspen Plus. Both the process development and economic analysis for all the three proposed options were conducted to determine the technical performance via indicators such as the energy efficiency and CO2 reduction rate, and the profitability via indicators such as the total capital investment and the net methanol production cost. Meanwhile, six case studies under different recycle ratios (0.5–0.95) were conducted for each proposed option to investigate the effects of recycle ratio on the technical and economic performance. The techno-economic analysis results clearly show that all the three proposed options are highly efficient for CO2 mitigation via methanol production using the by-product gases LDG and COG. More specifically, options 1 and 3 seem to be more energy efficient and eco-friendly than option 2, in terms of energy efficiency and CO2 reduction rate. Whereas, options 2 and 3 seem to be more economically feasible than option 1, considering the net methanol production cost. From the aspects of both technical and economic performance, option 3 is considered as the most competitive process. This work provides candidate process routes for the iron & steel industries to become more sustainable and profitable, especially in the event of a high carbon tax and a low H2 price in the future.

Reuse of manganese sulfate as raw material by recovery from pesticide's wastewater using nanofiltration and electro-electrodialysis: process simulation and analysis from actual data.

Reuse of wastewater, as well as recovery of valuable, toxic or harmful products in industrial discharges, still represents an important issue, not only because it reduces the effect on receiving water bodies, but also because of the economic resources it represents for industry itself. In this research, in situ regeneration of Mn2SO4 is evaluated, for its reuse as the main raw material in the original process of a fungicide plant. The regeneration is evaluated by selective recovery of Mn2+, Zn2+ and SO4 = present in the wastewater produced by the industrial plant, and utilizing nanofiltration, electro-electrodialysis and chemical precipitation as separation alternatives. Each alternative was designed and evaluated technically and economically through simulations in Aspen Plus®, with data and information of the real process supplied by the company. Because zinc concentration is relatively low, its selective recovery was not attractive. The resulting Mn2SO4 solution and treated water quality in conventional alternatives were significantly poor with high costs. In contrast, nanofiltration and electro-electrodialysis alternatives generate water and by-products of higher quality and reuse potential with significantly lower costs. However, their viability depends on the membrane performance. The results were satisfactory, but future experimental studies are required to optimize the alternatives and define the correct pretreatment process.

Simulation of heat-mass transportation characteristics for removal of CO in a liquid nitrogen wash sieve plate column

The liquid nitrogen wash process and sieve plate columns have been popular for removal of deleterious impurities (primarily including carbon monoxide) in chemical raw gas. It is of great guiding significance for precise description of distribution of components in column plates and phase variation rules, and prediction of column plate efficiency for optimization of operating conditions and geometric structure dimensions. A mathematical model of velocity field of gas and liquid in an industrial grade distillation sieve plate column was established and the corresponding CFD model was also presented to study flow characteristics of gas and liquid and the separation efficiency; those simulation results such as CO flow field, concentration variation and single plate separation efficiency were discussed; in addition, comparative analysis was carried out with reference to those classic experimental results. Our ASPEN PLUS simulation is carried out for effective removal of primary impurities (CO, CH4 and Ar), which can be removed to below 1 ppm, 1 ppm and 18 ppm through extraction and distillation of 50 plates, respectively. Thus, the requirements of the process standard may be satisfied. Results indicate that the important advantage of the simulation is that those influence factors may be automatically taken into account. It is investigated our simulation results are realistic and reliable to a certain degree to provide powerful technical support for practical engineering design.

Distribution, transformation and toxicity evaluation of 2,6-Di-tert-butyl-hydroxytotulene in aquatic environment

2,6-Di-tert-butyl-hydroxytotulene (BHT), as a significant synthetic phenolic antioxidant (SPA), has received increasing attention in the environmental field. In the present study, the BHT is confirmed to be mainly distributed in the liquid phase in the environment base on the Aspen PLUS simulation results. The mechanism and kinetics of BHT transformation initiated by OH radicals were conducted in aquatic environment using density functional theory (DFT) method. Briefly, seven initiation reactions and three detailed transformation pathways of BHT were reported. The H atoms in the t-butyl and methyl group were found more favorable to be abstracted. The C1 site of the BHT was susceptible to addition by OH radicals. Rate constants of different initial reactions were calculated and they were inhibited by temperature rise. Meanwhile, the acute and chronic toxicities of BHT and its metabolites were evaluated at three different trophic levels using the ECOSAR program. During the degradation process, the toxicities of these metabolites gradually decreased, but the toxicities of the final product 2,6-di-tert-butyl-2,5-cyclohexadien-1,4-dione (BHT-Q) were significantly increased. These results could help to reveal the transformation mechanism and risk assessment of BHT in aquatic environment, and further design the experimental and industrial applications of SPAs.

Thermodynamic and kinetic evaluation of ionic liquids + tetraglyme mixtures on CO2 capture

The mixture of ionic liquids (ILs) with a low viscous solvent such as tetraglyme (TGM) may be interesting to reach new absorbent formulations with improved performance in CO2 capture technologies. In this work, CO2 absorption by IL/TGM mixtures was analyzed by equilibrium and kinetic gravimetric measurements and packed column simulations in Aspen Plus. Four ILs with remarkable different absorbent properties were employed. The ILs 1-butyl-methylimidazolium tricyanomethanide ([Bmim][TCM]) and 1-butyl-methylimidazolium methylsulfate ([Bmim][MeSO4]) present CO2 physical absorption, with remarkably different viscosity values. On the other hand, the ILs trihexyltetradecylphosphonium 2-cyanopyrrolide ([P66614][CNPyr]) and1-butyl-methylimidazolium acetate ([Bmim][Acetate]) were selected as CO2 chemical absorbents, being the former significantly less viscous. CO2 absorption experiments were carried out in a magnetic suspension microbalance using a wide composition range of IL/TGM mixtures, measured at 303 K and at different pressures, from 1 up to 20 bar. The results were analyzed considering thermodynamics (CO2 solubility in IL/TGM) and kinetics (CO2 diffusivity in IL/TGM) features. ILs with physical absorption presented higher CO2 solubilities and diffusivities when increasing TGM composition. In fact, the neat TGM shows higher CO2 physical absorption capacity and rate than IL/TGM mixtures at any studied opeating conditions. In contrast, ILs with CO2 chemical absorption generally present higher CO2 absorption capacity than TGM/IL mixtures, but a certain amount of TGM improves drastically the CO2 absortion kinetics with a slight decrease of the solubility. The simulation analysis of IL/TGM performance in the absorption column reveals that: i) TGM is better physical absorbent for CO2 capture than IL/TGM mixtures and neat ILs; and ii) it is possible to select finest IL/TGM mixtures which minimize the solvent and energy expenses in CO2 capture by chemical absorption.

Development of computer aided modelling and optimization of microwave pyrolysis of biomass by using aspen plus

Biomass energy is nowadays recognized as a potential source which constitutes the main portion of expected renewable energy supplies in the future. Biomass resources such as municipal solid waste, agricultural residue food processing industry waste, energy crops are a common type of renewable energy source and it help to produce energy, chemicals, and fuels. The useful energy recovered from biomass can be effectively utilized by a bio-energy conversion technique known as pyrolysis. Pyrolysis is considered as a kind of thermo-chemical conversion technique of waste material in the inert atmosphere to harvest biochar, syn-gas and bio fuel. Bio fuel harvest from forestry biomass through the microwave pyrolysis technology has been significantly attracting attention in the renewable energy sector over recent years. This is because of fact that microwave pyrolysis can possibly reduce greenhouse gases and contribute to energy security. A simulation model of pyrolysis process is developed by using a software called advanced system for process engineering it is basically a simulation tool for computer-aided energy modelling. This software is used to optimize and analyse the efficiency of the process involved in pyrolysis and to increase the output product yield such as bio-oil, syn-gas, and biochar with respect to the function of input parameters such as pyrolysis temperature and physio-chemical character of the biomasses. The ASPEN PLUS simulation is carried out using four different variety of biomasses namely Acacia Nilotica, Calophyllum inophyllum seed, rice husk, and Bael shell. The simulation results demonstrate that Calophyllum inophyllum seed is best suited for bio-oil production through microwave pyrolysis as it contains low moisture content and higher cellulose. The obtained bio-oil yield is up to 48% can be found from this non-edible biomass.

Achieving a better understanding of binary azeotropic mixtures distillation through Aspen Plus process simulations

AbstractMass transfer operations are at the heart of every chemical engineering curriculum, as they are the basis of separation procedures extensively used in the chemical industry. Distillation, which involves mass transfer between vapor and liquid phases, is, by far, the most extended separation practice. However, the presence of azeotropes in most of the mixtures with industrial interest complicates the process analysis due to tedious and complex calculations, even in the simplest case of binary mixtures. Moreover, the need for recycle streams makes convergence and variables specification very difficult as compared with the separation of nonazeotropic mixtures. Initial training in process simulators results fundamentally in high‐quality chemical engineering teaching programs. It yields a better understanding of enhanced distillation and entails the use of professional tools highly demanded by employers. This paper reports how the use of the commercial simulator Aspen Plus can help students explore azeotropic distillation by their own, and thus enables looking into aspects which are beyond the scope of problems solved by hand.

Process synthesis and simulation-based optimization of ethylbenzene/styrene separation using double-effect heat integration and self-heat recuperation technology: A techno-economic analysis

Ethylbenzene/styrene separation is a typical example of the most costly processes in the chemical industry due to their close-boiling points of these two species. To reduce the cost of their separation, the concepts of double-effect distillation (DED) and self-heat recuperation technology (SHRT) have been implemented to produce three energy-efficient distillation configurations in either an individual or synergistic manner. To obtain a fair comparison, all the candidate processes were optimized to a minimum in total annual cost (TAC), using a simulation-based optimization framework on a simulator Aspen Plus and an optimizer programmed in MATLAB with a metaheuristic algorithm. For a small treatment capacity (100 kmol/h) and a short payback period (PBP, 3 years), the DED and SHRT configurations were found to reduce the TAC by ~8% compared to the conventional process design. The TAC reduction can be improved to as much as ~28% with a larger capacity (1000 kmol/h). The synergistic DED-SHRT configuration has the lowest energy consumption, but its high capital investment makes it only economically viable for longer PBPs. The best scheme under either short or long PBP appeared to be SHRT. Since the conventional design and SHRT share close technical parameters, the former will benefit more when retrofitted into the latter when minimum process modifications are applied.

Hydrogen Gas Production from Gasification of Oil Palm Empty Fruit Bunch (EFB) in a Fluidized Bed Reactor

Malaysia is one of the largest producers of palm oil and this industry plays an important role in Malaysia economic growth. As this industry grows larger, a significant amount of oil palm waste is generated, creating the problem of overloading biomass waste. Since the oil palm waste has many significant uses such as empty fruit bunches (EFB), the interest in production of hydrogen gas as the renewable energy from EFB also increases. The most common and favorable thermochemical processes to produce the hydrogen gas is gasification process in fluidized bed reactor. Regardless of tremendous experimental studies done on effectiveness of using EFB for production of hydrogen, the process implementation in industry is still discouraging. This is due to lack of proven technology and high capital cost of investment. In this study, a computational modeling was developed for EFB gasification in fluidized bed gasifier using the ASPEN PLUS simulator (v. 8.8) to optimize the gasification temperature, pressure and to study the different of chemical behavior. The results indicated that increase in temperature will increases the production of hydrogen and enhances carbon conversion efficiency. The optimum temperature and pressure was 850 °C and 1.035 bar respectively. The result shows that the char was removed significantly after several gas cleaning process. The final product for purified hydrogen gas is 14.5 kg/hr which is around 21% of hydrogen yield. Based on the result, it indicates that EFB has a potential to be used as a source of energy in a future.

Black liquor-based hydrogen and power co-production: Combination of supercritical water gasification and syngas chemical looping

An integrated system to efficiently harvest energy from the waste produced in the pulp mill industry, namely black liquor (BL), is proposed and investigated. The proposed system mainly comprises the supercritical water gasification (SCWG) of BL and syngas chemical looping (SCL). In addition, to effectively minimize the circulation of heat throughout the system, and therefore optimize the energy efficiency, the process design and integration are conducted by simultaneously adopting the concepts of exergy recovery and process integration. The available technologies for electricity generation and hydrogen production from BL recovery are discussed and compared with the proposed system. In this study, hydrogen is set as the main output, while power is produced by utilizing the heat generated throughout the process. Process simulation is performed using a steady state process simulator Aspen Plus. Energy efficiency is classified into three categories: hydrogen production efficiency, power generation efficiency, and total energy efficiency. Compared to other BL recovery systems, the proposed integrated system combining SCWG and SCL processes seems to be very promising. The integrated system shows very high total energy efficiency and carbon capture of about 80% and 75%, respectively.

Estimation of cold gas efficiency and reactor size of low-temperature gasifier for advanced-integrated coal gasification combined cycle systems

In order to achieve power-generation efficiency higher than those of integrated coal gasification combined cycle plants, advanced integrated coal gasification combined cycle systems have been developed. Here, we developed a triple-bed combined circulating fluidized bed gasifier model using the commercial process simulator Aspen Plus® (version 8.6) and Excel®. The heat balance and reaction kinetics, including the inhibition of steam gasification by H2, were simulated for a combustor temperature of 950 °C using porous alumina particles as heat-carrying particles. The theoretical maximum cold gas efficiency of the triple-bed combined circulating fluidized bed gasifier model was 85.0% for a gasification temperature of 800 °C. However, when the temperature was increased to 900 °C, the efficiency decreased to 80.9%. This indicates that, for triple-bed combined circulating fluidized bed gasifiers, a relatively low gasification temperature is suitable for ensuring higher cold gas efficiency and reducing the amount of circulating heat-carrying particles needed. On the other hand, gasification temperatures lower than 850 °C resulted in significantly higher bubbling fluidized bed gasifier volumes even when an effective Ca-based catalyst was used. The cold gas efficiency can be increased further by 8.6% by converting and recovering the missing hydrogen as H2 gas. Hence, there is a trade-off between the cold gas efficiency, gasifier size, and heat-carrying particle/coal ratio. The optimal gasification temperature for triple-bed combined circulating fluidized bed gasifier is 850 °C.