Evaluation of syngas-based chemical looping applications for hydrogen and power co-generation with CCS

This paper evaluates hydrogen and power co-generation based on coal-gasification fitted with an iron-based chemical looping system for carbon capture and storage (CCS). The paper assess in details the whole hydrogen and power co-production chain based on coal gasification. Investigated plant concepts of syngas-based chemical looping generate about 350–450 MW net electricity with a flexible output of 0–200 MW_th hydrogen (based on lower heating value) with an almost total decarbonisation rate of the coal used.     

Hydrogen production from fossil fuels with carbon capture and storage based on chemical looping systems

This paper analyzes innovative processes for producing hydrogen from fossil fuels conversion (natural gas, coal, lignite) based on chemical looping techniques, allowing intrinsic CO₂ capture. This paper evaluates in details the iron-based chemical looping system used for hydrogen production in conjunction with natural gas and syngas produced from coal and lignite gasification. The paper assesses the potential applications of natural gas and syngas chemical looping combustion systems to generate hydrogen. Investigated plant concepts with natural gas and syngas-based chemical looping method produce 500 MW hydrogen (based on lower heating value) covering ancillary power consumption with an almost total decarbonisation rate of the fossil fuels used.The paper presents in details the plant concepts and the methodology used to evaluate the performances using critical design factors like: gasifier feeding system (various fuel transport gases), heat and power integration analysis, potential ways to increase the overall energy efficiency (e.g. steam integration of chemical looping unit into the combined cycle), hydrogen and carbon dioxide quality specifications considering the use of hydrogen in transport (fuel cells) and carbon dioxide storage in geological formation or used for EOR.     

Renewable hydrogen production concepts from bioethanol reforming with carbon capture

This paper is assessing the hydrogen production from bioethanol at industrial scale (100000 Nm³/h hydrogen equivalent to 300 MW thermal) with carbon capture. Three carbon capture designs were investigated, one based on pre-combustion capture using chemical gas–liquid absorption and two based on chemical looping (one based on syngas and one using direct bioethanol looping). The carbon capture options were compared with the similar designs without carbon capture. The designs were simulated to produce mass and energy balances for quantification of key performance indicators. A particular accent is put on assessment of reforming technologies (steam and oxygen-blown autothermal reforming) and chemical looping units, process integration issues of carbon capture step within the plant, modelling and simulation of whole plant, thermal and power integration of various plant sub-systems by pinch analysis. The results for chemical looping designs (either syngas-based or direct bioethanol) show promising energy efficiency coupled with total carbon capture rate.     

Assessment of flexible energy vectors poly-generation based on coal and biomass/solid wastes co-gasification with carbon capture

This paper evaluates biomass and solid wastes co-gasification with coal for energy vectors poly-generation with carbon capture. The evaluated co-gasification cases were evaluated in term of key plant performance indicators for generation of totally or partially decarbonized energy vectors (power, hydrogen, substitute natural gas, liquid fuels by Fischer–Tropsch synthesis). The work streamlines one significant advantage of gasification process, namely the capability to process lower grade fuels on condition of high energy efficiency. Introduction in the evaluated IGCC-based schemes of carbon capture step (based on pre-combustion capture) significantly reduces CO₂ emissions, the carbon capture rate being higher than 90% for decarbonized energy vectors (power and hydrogen) and in the range of 47–60% for partially decarbonized energy vectors (SNG, liquid fuels). Various plant concepts were assessed (e.g. 420–425 MW net power with 0–200 MW_th flexible hydrogen output, 800 MW_th SNG, 700 MW_th liquid fuel, all of them with CCS). The paper evaluates fuel blending for optimizing gasification performance. A detailed techno-economic evaluation for hydrogen and power co-generation with CCS was also presented.     

Economic implications of pre- and post-combustion calcium looping configurations applied to gasification power plants

Gasification is a promising conversion technology to deliver high energy efficiency simultaneously with low energy and cost penalties for carbon capture. This paper is devoted to in-depth economic evaluations of pre- and post-combustion Calcium Looping (CaL) configurations for Integrated Gasification Combined Cycle (IGCC) power plants. The poly-generation capability, e.g. hydrogen and power co-generation, is also discussed. The post-combustion CaL option is a gasification power plant in which the flue gases from the gas turbine are treated for CO₂ capture in a carbonation–calcination cycle. In pre-combustion CaL option, the Sorbent Enhanced Water Gas Shift (SEWGS) feature is used to produce hydrogen which is used for power generation. As benchmark case, a conventional gasification power plant without carbon capture was considered. Net power output of evaluated cases is in the range of 550–600 MW with more than 95% carbon capture rate. The pre-combustion capture configuration was evaluated also in hydrogen and power co-generation scenario. The evaluations are concentrated for estimation of capital costs, specific investment cost, operational & maintenance (O&M) costs, CO₂ removal and avoidance costs, electricity costs, sensitivity analysis of technical and economic assumptions on key economic indicators etc.     

Assessment of calcium-based chemical looping options for gasification power plants

This paper evaluates various calcium-based chemical looping concepts to be applied in Integrated Gasification Combined Cycle (IGCC) plants for decarbonised energy vectors poly-generation (with emphasis on power generation and hydrogen and power co-generation). Two calcium-based chemical looping configurations were analysed. The first concept is based on post-combustion capture using the flue gases resulted from the power block (combined cycle gas turbine). The second concept is based on pre-combustion capture, the calcium-based chemical looping systems being used simultaneous to capture carbon dioxide (by sorbent enhanced water gas shift) and to concentrate the syngas energy in the form of hydrogen-rich gas.     

Evaluation of power generation schemes based on hydrogen-fuelled combined cycle with carbon capture and storage (CCS)

IGCC is a power generation technology in which the solid feedstock is partially oxidized to produce syngas. In a modified IGCC design for carbon capture, there are several technological options which are evaluated in this paper. The first two options involve pre-combustion arrangements in which syngas is processed, either by shift conversion or chemical looping, to maximise the hydrogen level and to concentrate the carbon species as CO₂. After CO₂ capture by gas-liquid absorption or chemical looping, the hydrogen-rich gas is used for power generation. The third capture option is based on post-combustion arrangement using chemical absorption.Investigated coal-based IGCC case studies produce 400-500 MW net power with more than 90% carbon capture rate. Principal focus of the paper is concentrated on evaluation of key performance indicators for investigated carbon capture options, the influence of various gasifiers on carbon capture process, optimisation of energy efficiency by heat and power integration, quality specification of captured CO₂. The capture option with minimal energy penalty is based on chemical looping, followed by pre-combustion and post-combustion.     

Hydrogen and power co-generation based on coal and biomass/solid wastes co-gasification with carbon capture and storage

This paper investigates the potential use of renewable energy sources (various sorts of biomass) and solid wastes (municipal wastes, sewage sludge, meat and bone meal etc.) in a co-gasification process with coal to co-generate hydrogen and electricity with carbon capture and storage (CCS). The paper underlines one of the main advantages of gasification technology, namely the possibility to process lower grade fuels (lower grade coals, renewable energy sources, solid wastes etc.), which are more widely available than the high grade coals normally used in normal power plants, this fact contributing to the improvement of energy security supply. Based on a proposed plant concept that generates 400–500 MW net electricity with a flexible output of 0–200 MW_th hydrogen and a carbon capture rate of at least 90%, the paper develops fuel selection criteria for coal blending with various alternative fuels for optimizing plant performance e.g. oxygen consumption, cold gas efficiency, hydrogen production and overall energy efficiency. The key plant performance indicators were calculated for a number of case studies through process flow simulations (ChemCAD).     

Techno-economic and environmental performances of glycerol reforming for hydrogen and power production with low carbon dioxide emissions

This paper is evaluating from the conceptual design, thermal integration, techno-economic and environmental performances points of view the hydrogen and power generation using glycerol (as a biodiesel by-product) reforming processes at industrial scale with and without carbon capture. The evaluated hydrogen plant concepts produced 100,000 Nm³/h hydrogen (equivalent to 300 MW_th) with negligible net power output for export. The power plant concepts generated about 500 MW net power output. Hydrogen and power co-generation was also assessed. The CO₂ capture concepts used alkanolamine-based gas–liquid absorption. The CO₂ capture rate of the carbon capture unit is at least 90%, the carbon capture rate of the overall reforming process being at least 70%. Similar designs without carbon capture have been developed to quantify the energy and cost penalties for carbon capture. The various glycerol reforming cases were modelled and simulated to produce the mass & energy balances for quantification of key plant performance indicators (e.g. fuel consumption, energy efficiency, ancillary energy consumption, specific CO₂ emissions, capital and operational costs, production costs, cash flow analysis etc.). The evaluations show that glycerol reforming is promising concept for high energy efficiency processes with low CO₂ emissions.     

Design of an integrated process for simultaneous chemical looping hydrogen production and electricity generation with CO2 capture

This study was aimed at proposing a novel integrated process for co-production of hydrogen and electricity through integrating biomass gasification, chemical looping combustion, and electrical power generation cycle with CO₂ capture. Syngas obtained from biomass gasification was used as fuel for chemical looping combustion process. Calcium oxide metal oxide was used as oxygen carrier in the chemical looping system. The effluent stream of the chemical looping system was then transferred through a bottoming power generation cycle with carbon capture capability. The products achieved through the proposed process were highly-pure hydrogen and electricity generated by chemical looping and power generation cycle, respectively. Moreover, LNG cold energy was used as heat sink to improve the electrical power generation efficiency of the process. Sensitivity analysis was also carried out to scrutinize the effects of influential parameters, i.e., carbonator temperature, steam/biomass ratio, gasification temperature, gas turbine inlet stream temperature, and liquefied natural gas (LNG) flow rate on the plant performance. Overall, the optimum heat integration was achieved among the sub-systems of the plant while a high energy efficiency and zero CO₂ emission were also accomplished. The findings of the present study could assist future investigations in analyzing the performance of integrated processes and in investigating optimal operating conditions of such systems.     

Use of lower grade coals in IGCC plants with carbon capture for the co-production of hydrogen and electricity

This paper investigates the potential use of lower grade coals in an IGCC-CCS plant that generates electricity and produces hydrogen simultaneously with carbon dioxide capture and storage. The paper underlines one of the main advantages of gasification technology, namely the possibility to process lower grade coals, which are more widely available than the high-grade coals normally used in European power plants. Based on a proposed plant concept that generates about 400 MW net electricity with a flexible output of 0–50 MW_th hydrogen and a carbon capture rate of at least 90%, the paper develops fuel selection criteria for coal fluxing and blending of various types of coal for optimizing plant performance e.g. oxygen consumption, hydrogen production potential, specific syngas energy production per tonne of oxygen consumed, etc. These performance indicators were calculated for a number of case studies through process flow simulations. The main conclusion is that blending of coal types of higher and lower grade is more beneficial in terms of operation and cost performance than fluxing high-grade coals.     

Techno-economical evaluations of decarbonized hydrogen production based on direct biogas conversion using thermo-chemical looping cycles

Hydrogen production by biogas conversion represent a promising solution for reduction of fossil CO₂ emissions. In this work, a detailed techno-economic analysis was performed for decarbonized hydrogen production based on biogas conversion using calcium and chemical looping cycles. All evaluated concepts generate 100,000 Nm³/h high purity hydrogen. As reference cases, the biogas steam reforming design without decarbonization and with CO₂ capture by gas-liquid chemical absorption were also considered. The results show that iron-based chemical looping design has higher energy efficiency compared with the gas-liquid absorption case by 2.3 net percentage points as well as a superior carbon capture rate (99% vs. 65%). The calcium looping case shows a lower efficiency than chemical scrubbing, with about 2.5 net percentage points, but the carbon capture rate is higher (95% vs. 65%). The hydrogen production cost increases with decarbonization, the calcium looping shows the most favourable situation (37.14 €/MWh) compared to the non-capture steam reforming case (33 €/MWh) and MDEA and iron looping cases (about 42 €/MWh). The calcium looping case has the lowest CO₂ avoidance cost (10 €/t) followed by iron looping (20 €/t) and MDEA (31 €/t) cases.     

Capturing and using CO2 as feedstock with chemical looping and hydrothermal technologies

Chemical looping technology for capturing and hydrothermal processes for conversion of carbon are discussed with focused and critical assessments. The fluidized and stationary reactor systems using solid, including biomass, and gaseous fuels are considered in chemical looping combustion, gasification, and reforming processes. Sustainability is emphasized generally in energy technology and in two chemical looping simulation case studies using coal and natural gas. Conversion of captured carbon to formic acid, methanol, and other chemicals is also discussed in circulating and stationary reactors in hydrothermal processes. This review provides analyses of the major chemical looping technologies for CO₂ capture and hydrothermal processes for carbon conversion so that the appropriate clean energy technology can be selected for a particular process. Combined chemical looping and hydrothermal processes may be feasible and sustainable in carbon capture and conversion and may lead to clean energy technologies using coal, natural gas, and biomass. Copyright © 2014 John Wiley & Sons, Ltd.     

Integration of large-scale hydrogen storages in a low-carbon electricity generation system

This study investigates the overall feasibility of large energy storages with hydrogen as energy carrier onsite with a pre-combustion carbon capture and storage coal gasification plant and assesses the general impacts of such a backup installation on an electricity generation system with high wind power portion. The developed system plant configuration consists of four main units namely the gasification unit, main power unit, backup power unit including hydrogen storage and ancillary power unit. Findings show that integrating a backup storage in solid or gaseous hydrogen storage configuration allows to store excessive energy under high renewable power output or low demand and to make use of the stored energy to compensate low renewable output or high power demand. The study concludes that the developed system configuration reaches much higher load factors and efficiency levels than a plant configuration without backup storage, which simply increases its power unit capacity to meet the electricity demand. Also from an economical point of view, the suggested system configurations are capable to achieve lower electricity generation costs.     

Performance analysis of a double calcium looping‐integrated biomass‐fired power plant: Exploring a carbon reduction opportunity

Integrating biomass energy generation with carbon capture will result in “carbon neutral” to “carbon negative” technology. Countries like India and China possess significant reserves of limestone. Calcium looping (CaL) technology can prove to be a promising option for carbon capture in these countries. The present work aims at improving the performance of CaL‐integrated biomass‐fired power plant (BFPP) by exploring different looping configurations. In this study, (i) standalone BFPP, (ii) conventional CaL (single stage), and (iii) double CaL‐integrated BFPP have been systematically evaluated. A comparative performance evaluation of these three plants in terms of energy, exergy and ecological assessment, has been carried out. A detailed parametric study and unit‐wise exergy analysis of the best configuration among the three are presented to identify the scope for further improvement in efficiency and energy savings.     

Experiments on chemical looping combustion of coal with a NiO based oxygen carrier

A chemical looping combustion process for coal using interconnected fluidized beds with inherent separation of CO₂ is proposed in this paper. The configuration comprises a high velocity fluidized bed as an air reactor, a cyclone, and a spout-fluid bed as a fuel reactor. The high velocity fluidized bed is directly connected to the spout-fluid bed through the cyclone. Gas composition of both fuel reactor and air reactor, carbon content of fly ash in the fuel reactor, carbon conversion efficiency and CO₂ capture efficiency were investigated experimentally. The results showed that coal gasification was the main factor which controlled the contents of CO and CH₄ concentrations in the flue gas of the fuel reactor, carbon conversion efficiency in the process of chemical looping combustion of coal with NiO-based oxygen carrier in the interconnected fluidized beds. Carbon conversion efficiency reached only 92.8% even when the fuel reactor temperature was high up to 970 °C. There was an inherent carbon loss in the process of chemical looping combustion of coal in the interconnected fluidized beds. The inherent carbon loss was due to an easy elutriation of fine char particles from the freeboard of the spout-fluid bed, which was inevitable in this kind of fluidized bed reactor. Further improvement of carbon conversion efficiency could be achieved by means of a circulation of fine particles elutriation into the spout-fluid bed or the high velocity fluidized bed. CO₂ capture efficiency reached to its equilibrium of 80% at the fuel reactor temperature of 960 °C. The inherent loss of CO₂ capture efficiency was due to bypassing of gases from the fuel reactor to the air reactor, and the product of residual char burnt with air in the air reactor. Further experiments should be performed for a relatively long-time period to investigate the effects of ash and sulfur in coal on the reactivity of nickel-based oxygen carrier in the continuous CLC reactor.     

Evaluation of hydrogen production with iron-based chemical looping fed by different biomass

In this study, the iron-based chemical looping process driven by various biomasses for hydrogen production purposes is studied and evaluated thermodynamically through energy and exergy approaches. The overall system consists of some key units (combustor, reducers and oxidizer) a torrefier, a drying chamber, an air separation unit, a heat exchanger, and auxiliary units as well. The biomasses considered are first dried and torrified in the drying chamber and sent to reactors to produce hydrogen. The exergy and energy efficiencies of the iron based chemical looping facility are investigated comparatively for performance evaluation. The maximum exergy destruction and entropy production rates are calculated for the torrefaction process as 123.15 MW and 4926 kW/K respectively. Under the steady–state conditions, a total of 8 kg/s hydrogen is produced via chemical looping process. The highest energy efficiency is obtained in the looping of rice husk with 86% while the highest exergy efficiency is obtained in the looping using sugarcane bagasse with 91%, respectively.     

Techno – Economic assessment of flexible decarbonized hydrogen and power co-production based on natural gas dry reforming

The need for flexible power plants could increase in the future as variable renewable energy (VRE) share will increase in the power grid. These power plants could balance the increasing strain on electricity grids by renewables. The proposed plant in this paper can adapt to these ramps in electricity demand of the power grid by maintaining a constant feed and producing also high purity hydrogen. Dry methane reforming (DMR) is incorporated into a flexible power plant model and the key performance indicators are calculated from a techno-economic perspective. The net output of the plant is 450 MW with the possibility to lower power production and produce hydrogen, maintaining a high CO₂ capture rate (72%). Two cases are compared to the base case to quantify: (i) energy and cost penalties for CO₂ capture and (ii) advantages of flexible power plant operation. The levelized cost of electricity (LCOE) for the base case is 67 Euro/MWh, the addition of a carbon capture unit increases it to 82 Euro/MWh. In the case of flexible operation, both the LCOE and levelized cost of hydrogen (LCOH) are calculated and the two depend on the cost allocation factor. The LCOE ranges from 65 to 85 Euro/MWh while the LCOH from 0.15 to 0.073 Euro/Nm³. The DMR power plant presented in Cases 1 and 2 present little advantages in today's market conditions however, the flexible plant (Case 3) can be viable option in balancing VRE.     

Thermodynamic evaluation of hydrogen production from methane

Exergetic and energetic analysis has been utilized to estimate the effect of process design and conditions on the hydrogen purity and yield, exergetic efficiencies and CO₂ avoided. Methane was chosen as a model compound for evaluating single stage separation. Simple steam reforming was considered as the base – case system. The other chemical processes that were considered were steam reforming with CO₂ capture with and without chemical looping of a reactive carbon dioxide removal agent, and steam gasification with both the Boudouard reaction catalyst and the reactive carbon dioxide removal agent with and without the solids regeneration. The information presented clearly demonstrates the differences in efficiencies between the various chemical looping processes for hydrogen generation. The incremental changes in efficiencies as a function of process parameters such as temperature, steam amount, chemical type and amount were estimated. Energy and exergy losses associated with generation of syngas, separation of hydrogen from CO_x as well as exergetic loss associated with emissions are presented. The optimal conditions for each process by minimizing these losses are presented. The majority of the exergy destruction occurs due to the high irreversibility of chemical reactions. The results of this investigation demonstrate the utility of exergy analysis. The paper provides a procedure for the comparison of various technologies for the production of hydrogen from carbon based materials based on First and Second Law Analysis. In addition, two figures of merit, namely the comparative advantage factor and the sustainable advantage factor have been proposed to compare the various hydrogen production methods using carbonaceous fuels.     

Thermodynamic modeling and assessment of a combined coal gasification and alkaline water electrolysis system for hydrogen production

The performance of a clean energy system that combines the coal gasification and alkaline water electrolyzer concepts to produce hydrogen is evaluated through thermodynamic modeling and simulations. A parametric study is conducted to determine the effect of water ratio in coal slurry, gasifier temperature, effectiveness of carbon dioxide removal, and hydrogen recovery efficiency of the pressure swing adsorption unit on the system hydrogen production. The exergy efficiency and exergy destruction in each system component are also evaluated. The results reveal that the overall energy and exergy efficiencies of this system are ∼58% and ∼55%, respectively. The weight ratio of the hydrogen yielded to the coal fed to this system is ∼0.126. Although this system produces hydrogen from coal, the greenhouse gases emitted from this system are fairly low.