Pre-combustion Decarbonisation Research Articles

Green hydrogen production from decarbonized biomass gasification: An integrated techno-economic and environmental analysis

Biomass gasification represents an effective and promising conversion technology to different energy carriers/chemicals. Biomass gasification with CO2 capture will give an energy conversion system with negative CO2 emissions. This work assesses the techno-economic and environmental implications of decarbonized green hydrogen generation using the biomass gasification. Several pre-combustion decarbonization technologies were evaluated: chemical and physical scrubbing (absorption), membrane, hybrid membrane - chemical scrubbing. All evaluated biomass gasification concepts have 300 MW hydrogen output (corresponding to 100,000 Nm3/h hydrogen with purity above 99.95% vol.) with 90% carbon capture rate. Different system engineering tools were employed for the integrated assessment. As an important novelty outcome of this work, the green hydrogen production from decarbonized biomass gasification has promising potential to deliver high energy conversion efficiency (in the range of 57–59%), lower energy and cost penalties for decarbonization (about 2.2–3.5 net points), negative carbon emissions (considering that the primary fuel - biomass - is of renewable source). Among various assessed decarbonization technologies, the membrane system shows better techno-economic performances than the gas-liquid absorption (e.g., reduced CAPEX and OPEX by 7% and 7–9% respectively, inferior hydrogen production cost by about 7% etc.).

Techno-economic assessment of blast furnace gas pre-combustion decarbonisation integrated with the power generation

Aiming at the iron and steel industry decarbonisation with blast furnace gas (BFG) utilisation, a techno-economic feasibility of the pre-combustion carbon capture with methyl diethanolamine (MDEA) is evaluated herein. The effectiveness of water gas shift (WGS) implementation on the capture performance is also investigated. The integration of a power plant with decarbonised fuel from the capture unit is taken into account from both technical and economic perspectives. Aspen Plus® is used to develop the process. The results obtained from the techno-economic analysis showed that the WGS implementation increases the capture efficiency from 46.5% to 83.8%, with increased CO2 capture cost from € 39.8/tCO2 to €44.3/tCO2. The sensitivity analysis on the effect of 1) different BFG composition and 2) different carbon capture rate (CCR) on the capture unit integrated with WGS performance is performed. The obtained results revealed that BFG with a lower calorific value is less practical from a techno-economic point of view as it increases the specific primary energy consumption for CO2 capture avoidance (SPECCA) from 3.3MJLHV/kgCO2 to 3.8MJLHV/kgCO2. Moreover, the lower CCR increases the thermal energy of the H2-rich gas from the capture unit from 266.8 MW to 269.6 MW. The techno-economic advantages of the based case do not results beneficial for na environment point of view since at lower CCR the specific CO2 emissions increase from 51 kgCO2/GJLHV to 70 kgCO2/GJLHV. The fully integrated power plant to the capture unit reveals that the 37.52% (without WGS) and 24.27% (with WGS) efficiencies are achievable through the combined cycle integration. For the combined cycle, the integration of WGS reactor will reduce the CO2 specific emission to 675.1 kgCO2/MWh in comparison to 1391.5 kgCO2/MWh for the case with no WGS.

Performance analysis of a novel low CO2-emission solar hybrid combined cycle power system

This paper is a proposal and analysis of a novel low-CO2 emission solar hybrid combined cycle power system, which is based on solar-driven methane reforming. Nearly full methane conversion is achieved at a mild temperature (∼550 °C) using a methane reforming reactor integrated with a hydrogen separation membrane, enabling the solar thermal energy collected at middle temperature to be applied as the reaction heat in methane reforming, thereby converting the solar heat to chemical energy of the produced syngas. The membrane reactor also offers the advantage of continuously withdrawing hydrogen from the reaction zone, which is then burned at high temperature for power generation in the proposed advanced combined cycle system. The CO2-enriched gas concentrated at the end of the reaction zone is processed through pre-combustion decarbonization. It is shown that system thermal efficiency of 51.6% can be obtained, which is 2.2%-points higher than that of a referenced gas-steam combined cycle system with post-combustion decarbonization (CC-Post) at an equal CO2 removal ratio and no solar assistance. Fossil fuel saving ratio of 31.2% is achieved with a solar thermal share of 28.2%. Exergy analysis indicates that the main contributors for efficiency improvements are the reduced exergy destructions in the combustion and CO2 separation processes. The hybrid system has an exergy efficiency of 58% with 91% CO2 capture, which is 10%-points higher than that of a comparable CC-Post system. A preliminary economic analysis predicts that levelized electricity cost and payback period for the system are found to be 0.062 $/kWh and 10 years, respectively, and cost of CO2 avoided is 81 $/(ton CO2), which is 42.5% lower than that for a CC-Post system. The proposed system hybridization approach simultaneously achieves the dual-purpose of high-efficiency solar heat conversion and low-energy penalty CO2 capture.

Pre-combustion CO2 capture

This paper, which is part of a special issue of the International Journal of Greenhouse Gas Control, gives an overview of the latest achievements in the pre-combustion decarbonisation route for the production of electricity with CO2 capture. Pre-combustion technologies applied to two different fuels are considered, natural gas and coal, since they cover most of electricity production from fossil fuels worldwide. The work first discusses in detail the different sections in which a power plant with pre-combustion CO2 capture can be divided. For each section, the available technologies with corresponding advantages and disadvantages are presented. Next, the plant lay-outs for natural gas and coal proposed in literature, including heat & mass balances and the economic assessment, are discussed. In general, research activity in pre-combustion decarbonisation for power production focused more on coal than on natural gas-based plant since in the latter case the plant complexity and costs are not competitive with post-combustion CO2 capture, which is a technology on the verge of commercialization. Finally the paper briefly discusses pre-combustion CO2 capture in industry especially those projects where CO2 is captured and stored or used for EOR.

Performance comparison of two low-CO 2 emission solar/methanol hybrid combined cycle power systems

Abstract Two novel hybrid combined cycle power systems that use solar heat and methanol, and integrate CO2 capture, are proposed and analyzed, one based on solar-driven methanol decomposition and the other on solar-driven methanol reforming. The high methanol conversion rates at relatively low temperatures offer the advantage of using the solar heat at only 200–300 °C to drive the syngas production by endothermic methanol conversions and its conversion to chemical energy. Pre-combustion decarbonization is employed to produce CO2-free fuel from the fully converted syngas, which is then burned to produce heat at the high temperature for power generation in the proposed advanced combined cycle systems. To improve efficiency, the systems’ configurations were based on the principle of cascade use of multiple heat sources of different temperatures. The thermodynamic performance of the hybrid power systems at its design point is simulated and evaluated. The results show that the hybrid systems can attain an exergy efficiency of about 55%, and specific CO2 emissions as low as 34 g/kW h. Compared to a gas/steam combined cycle with flue gas CO2 capture, the proposed solar-assisted system CO2 emissions are 36.8% lower, and a fossil fuel saving ratio of ∼30% is achievable with a solar thermal share of ∼20%. The system integration predicts high efficiency conversion of solar heat and low-energy-penalty CO2 capture, with the additional advantage that solar heat is at relatively low temperature where its collection is cheaper and simpler. The systems’ components are robust and in common use, and the proposed hybridization approach can be also used with similar benefits by replacing the solar heat input with other low heat sources, and the system integration achieves the dual-purpose of clean use of fossil fuel and high-efficiency conversion of solar heat at the same time.

Novel Catalytic Membrane Micro-reactors for CO2 Capture Via pre-combustion Decarbonization Route

Novel Catalytic Membrane Micro-reactors for CO2 Capture Via pre-combustion Decarbonization Route

Low-CO2 Emission Solar/methanol Hybrid Power System

This paper proposes and analyzes a novel gas/steam combined cycle power system integrated with low/mid temperature solar heat thermo-chemical conversion and CO2 capture. The power system uses methanol as the input fuel. Methanol reformation is highly endothermic and can achieve over 90% conversion into H2-rich syngas at temperatures around 250°C. The high conversion rate at relatively low temperature enables the following configuration arrangement, (1) solar heat collected at 200-300°C can be used to heat the endothermic methanol reformation and is thereby converted into syngas chemical energy; (2) the produced syngas is enriched with H2 and CO2 (24.4% CO2 and 74.7% H2 by volume), thus is ready for pre-combustion decarbonization. The processed CO2- lean syngas is used to fuel a gas/steam combined cycle. In form of the fuel chemical exergy, the collected low level (low temperature) solar heat is released as high temperature thermal energy for power generation, achieving a highefficiency heat-power conversion in the advanced combined cycle system. The hybrid system is simulated with Aspen Plus code and analyzed. The results show that with 91% CO2 captured, the system attains a net exergy efficiency of ∼55%. Fossil fuel saving ratio of 30.5% is achievable with a solar thermal share of 21.5%.

Testing of hydrotalcite based sorbents for CO2 and H2S capture for use in sorption enhanced water gas shift

The sorption enhanced water-gas shift technology is attractive for pre-combustion decarbonisation of power production based on IGCC, but only when the SEWGS technology can be applied for sour syngas. To this extend, it was recently demonstrated that 2000 ppm of H2S did not influence the CO2 sorption behaviour of a potassium promoted hydrotalcite material at a relatively low pressure of 5 bar. This paper highlights ongoing sorbent testing at pressure swing operation between 30 bar adsorption and 2 bar regeneration, crucial for the successful development of the technology. The sorbent has good catalytic activity for the water-gas shift reaction during SEWGS conditions. At 30 bar pressure and 400 °C feed temperature, a CO, CO2 and H2S free H2-product is obtained when feeding a syngas containing 200 ppm H2S. This implies that mixing in a separate WGS catalyst is not needed, which significantly simplifies the technology. Moreover, multi-cyclic testing at 30 bar and 400 °C for 110 cycles shows good sorbent stability in the presence of 200 ppm H2S. Deliberately induced slips of CO2 and H2S stabilize within a limited number of cycles. By simply reducing the adsorption period, the mass-transfer zones for both CO2 and H2S are readily pushed back into the column, again producing a product free of CO2 and H2S. These observations suggest that reversibility of sorption processes on the material that have been tested is fully appropriate for the further development of the long-term operation of sour-SEWGS technology.

2-dimensional membrane separator modelling: Mass transfer by convection and diffusion

Hydrogen selective membranes may present a technologically and economically efficient method for the separation of H2 from CO2 in pre-combustion decarbonisation of power production from fossil fuels. Accurate scale-up and performance prediction of membranes strongly depends on adequate representation of the prevailing resistances to mass transfer, especially for present-day high flux membranes. In a series of experiments, H2/N2 separation is measured as a function of feed flow and retentate pressure for a supported palladium membrane enclosed by annular channels for feed/retentante and sweep/permeate flow. Comparison of model predictions with measured data reveals that mass transfer resistances in the gas phase are significantly reduced by a radial velocity component in cases of high transmembrane flux, which can only be adequately described by a 2D model. For accurate interpretation of experiments, scale-up, and design of modules with high flux membranes, 2D modelling is required. © 2010 Elsevier Ltd. All rights reserved

Correlation between structural rearrangement of hydrotalcite-type materials and CO2 sorption processes under pre-combustion decarbonisation conditions

Alkali-promoted hydrotalcite-based materials have showed CO2 sorption capacity up to 1.6 mmol⋅g−1 when CO2 separation is carried out at relatively high temperature (300–500 °C) and high partial pressure of steam and CO2, conditions that are prevalent in pre-combustion CO2 capture conditions. In addition to CO2 breakthrough experiments in situ XRD experiments have allowed identifying magnesium carbonate crystalline phase formation during CO2 sorption. The alkali promoted hydrotalcite-based material (Mg/Al ratio 2.9) has revealed that high CO2 capacities can potentially be achieved by using the extra storage capacity offered by the presence of excess magnesium oxide that can be converted into magnesium carbonate. The use of this extra capacity in Pressure Swing Adsorption process is further discussed.

Comparison of carbon capture IGCC with pre-combustion decarbonisation and with chemical-looping combustion

Carbon capture from conventional power cycles is accompanied by a significant loss of efficiency. One process concept with a potential for better performance is chemical-looping combustion (CLC). CLC uses a metal oxide to oxidize the fuel, and the reduced metal is then re-oxidized in a second reactor with air. The combustion products CO 2 and water remain unmixed with nitrogen, thereby avoiding the need for energy intensive air separation. In this paper, the performance of various configurations of CLC used in integrated gasification combined cycle power plants (CLC-IGCC) are analyzed and compared to a conventional IGCC design with pre-combustion carbon capture by physical absorption. The analysis is based on process simulation using Aspen Plus and GateCycle. Key design parameters are varied, and the results are interpreted using exergy analysis. The CLC-IGCC offers the advantages of higher plant efficiency and more complete carbon capture. The efficiency is very sensitive to changes in the gas turbine inlet temperature for both the CLC and the conventional IGCC designs. The development of oxygen carrier particles with a high thermal stability is therefore crucial for capitalizing on the potential efficiency advantage of CLC.

On the potential of nickel catalysts for steam reforming in membrane reactors

Hydrogen membrane reactors have been identified as a promising option for hydrogen production for power generation from natural gas with pre-combustion decarbonisation. While Pd or Pd-alloy membranes already provide good hydrogen permeances the most suitable catalyst design for steam reforming in membrane reactors (SRMR) is yet to be identified. This contribution aims to provide insight in the suitability of nickel based catalysts in SRMR. The use of nickel (Ni) catalysts would benefit the cost-effectiveness of membrane reactors and therefore its feasibility. For this, the activity of nickel catalysts in SRMR was assessed with kinetics reported in literature. A 1D model was composed in order to compare the hydrogen production rates derived from the kinetics with the rate of hydrogen withdrawal by permeation. Catalyst stability was studied by exposing the catalysts to reformate gas with two different H/C ratios to mimic the hydrogen lean reformate gas in the membrane reactor. For both the activity (modeling) and stability study the Ni-based catalysts were compared to relevant catalyst compositions based on rhodium (Rh). Using the high pressure kinetics reported for Al 2O 3 supported Rh and MgAl 2O 4 and Al 2O 3 supported Ni catalyst it showed that Ni and Rh catalysts may very well provide similar hydrogen production rates. Interestingly, the stability of Ni-based catalysts proved to be superior to precious metal based catalysts under exposure to simulated reformate feed gas with low H/C molar ratio. A commercial (pre-)reforming Ni-based catalyst was selected for further testing in an experimental membrane reactor for steam reforming at high pressure. During the test period 98% conversion at 873 K could be achieved. The conversion was adjusted to approximately 90% and stable conversion was obtained during the test period of another 3 weeks. Nonetheless, carbon quantification tests of the Ni catalyst indicated that a small amount of carbon had deposited onto the catalyst. The activity of the Ni catalyst for carbon formation is expected to eventually cause performance loss due to plugging or fouling. Ongoing research efforts are devoted towards the preparation of cost-effective nickel based catalysts with suppressed carbon formation activity.

Carbon Capture by Sorption-Enhanced Water−Gas Shift Reaction Process using Hydrotalcite-Based Material

A novel route for precombustion decarbonization is the sorption-enhanced water−gas shift (SEWGS) process. In this process carbon dioxide is removed from a synthesis gas at elevated temperature by adsorption. Simultaneously, carbon monoxide is converted to carbon dioxide by the water−gas shift reaction. The periodic adsorption and desorption of carbon dioxide is induced by a pressure swing cycle, and the cyclic capacity can be amplified by purging with steam. From previous studies is it known that for SEWGS applications, hydrotalcite-based materials are particularly attractive as sorbent, and commercial high-temperature shift catalysts can be used for the conversion of carbon monoxide. Tablets of a potassium promoted hydrotalcite-based material are characterized in both breakthrough and cyclic experiments in a 2 m tall fixed-bed reactor. When exposed to a mixture of carbon dioxide, steam, and nitrogen at 400 °C, the material shows a breakthrough capacity of 1.4 mmol/g. The sharp adsorption front is accompa...

Carbon capture and storage (CCS) options for co-production of electricity and synthetic fuels from indigenous coal in an Indian context

India has the second largest population in the world and is ranked number six in terms of CO 2 emissions generated from fossil fuels. A large portion of its power plants is old and inefficient, and it is expected that India in the coming 10–15 years will need to upgrade and extend its power sector significantly. This may give rise to new initiatives that bring the harnessing of indigenous coal in a green manner into question. This article takes into consideration opportunities of emerging polygeneration schemes intended (mainly) for the electric power sector with inclusion of additional yields like synthetic fuels, chemicals and heat. Reference is made to European-based initiatives pertaining to the capture and storage of carbon dioxide (CCS) — especially a Sino-European project COACH 1 1 Cooperation Action within CCS China-EU, EC/FP6 Contract #038966, co-ordinated by Institut Français du Petrole (IFP), France. that is operated under the auspices of the European Commission and the Chinese Ministry of Science and Technology (MOST). Some main principles of COACH have been transferred from the EU-based DYNAMIS 2 2 Towards Hydrogen and Electricity Production with Carbon Dioxide Capture and Storage, EC/FP6 Contract #019672, co-ordinated by SINTEF Energy Research, Norway. project, although in a different setting. Both projects emphasise technologies and options that can be realised by 2012 (and beyond) for co-production of hydrogen and electricity via pre-combustion decarbonisation from fossil fuels with safe geological storage of the CO 2. It is believed that the European Commission – in due course – will make provisions for similar arrangements with India. A main challenge of CCS – in any context – is the techno-economic aspect of fuel penalty and cost. In addition to the higher investment cost, an energy potential corresponding to 20–30% additional fuel is inherently sacrificed in order to isolate and compress the CO 2 stream before it can be injected into a permanent sink. For this reason CCS is entirely policy driven rather than motivated by profit. Although CCS is far more costly and requiring substantially more primary energy, it is likely to assume that India will be forced to either implement CCS or to retire parts of its generating capacity. This suggests that India may become attractive for industrialised countries to make “green” investments in its power sector provided however, that CCS will become eligible for joint mitigation actions beyond the Kyoto treaty that expires by 2012. The energy supply situation of India is seen as a matter of growing concern. In contrast to Europe where the issue of greenhouse gas emissions is high on the political agenda, India seemingly is more focused on cost, energy supply and local pollution. Coal is still the prevalent fuel in the Indian power sector, and is likely to be so in the foreseeable future. This suggests that time is due for India to embark on pre-normative research and technology initiatives in order to pave the ground for a cleaner energy policy in an Indian context. One step in this direction is to gain knowledge on prevalent carbon capture techniques — in theory and via major CCS projects and storage sites.

Pre-combustion decarbonisation in IGCC: Gas turbine operating window at variable carbon capture ratios

This paper presents the results of gas turbine simulations that were conducted to compare state-of-the-art and re-designed gas turbines operated on syngas, in Integrated Gasification Combined Cycles (IGCC) with pre-combustion CO 2 capture. The effects of the desired carbon capture ratio on efficiency and power output were evaluated, for retrofit applications both with and without capacity building. The results indicate that re-designed gas turbines for syngas applications can achieve higher efficiencies than natural gas turbines that were modified for syngas applications.

Staged water-gas shift configuration: Key to efficiency penalty reduction during pre-combustion decarbonisation in IGCC

Abstract This paper presents the results of system assessments that were conducted to compare conventional and advanced water-gas shift reaction section in Integrated Gasification Combined Cycles (IGCC) with pre-combustion CO 2 capture. The advanced shift reaction section comprises four staged reactors with distributed feeds of syngas and quench water in between the reactors. This configuration reduces the steam requirement of the shift reaction up to 70% in comparison with conventional configurations, at carbon capture ratios of approximately 85%. The specific lost work per amount of CO 2 was used to determine the optimum carbon capture ratio for each case.

Performance of Water–Gas Shift Catalysts under Sorption-Enhanced Water–Gas Shift Conditions

Abstract The second pre-combustion decarbonisation technology Sorption Enhanced Water-Gas Shift (SEWGS) combines the WGS reaction with simultaneous CO 2 capture by using a mixture of WGS catalyst and CO 2 sorbent. Accordingly, the WGS catalyst is exposed to all conditions encountered in the cyclic SEWGS process, such as exposure to steam in the regeneration step. This paper shows that commercial precious metal, FeCr, and CoMo WGS catalysts are robust towards periodic exposure to these atypical conditions. Catalyst behavior is reported to periodic exposure to these atypical conditions at a temperature of 400 ∘ C, pressures up to 5 bara and H 2 S contents from 1 ppm to 2,000 ppm. Although additional experiments need to be performed at increased pressure, it appears that all catalysts can potentially be used in the SEWGS process.

Reduction in the cost of pre-combustion CO2 capture through advancements in sorption-enhanced water-gas-shift

Abstract Sorption-enhanced water-gas-shift (SEWGS) is a pre-combustion decarbonisation technology combining adsorption of CO2 with the water-gas-shift reaction. This process maximises the production of hydrogen from syngas whilst simultaneously capturing and separating CO2. Simulations have been completed to evaluate the use of SEWGS for power generation from natural gas with carbon capture. The modelling results show that using the SEWGS process could significantly reduce the cost of capturing CO2 versus a reference design that uses amine absorption. Work has also been completed to show that using a counter-current steam-rinse step may be an improvement over a co-current CO2-rinse cycle proposed previously.

Performance of sorption-enhanced water-gas shift as a pre-combustion CO2 capture technology

Abstract The sorption-enhanced water-gas shift (SEWGS) process is a promising technology for pre-combustion decarbonisation. It is well suited for decarbonising syngas produced from natural-gas and coal based fuels in combined-cycle power production schemes. Higher capture rates could be obtained by SEWGS at lower efficiency penalties and at lower costs than by absorption. In the SEWGS process, multiple reactor vessels are packed with mixtures of CO 2 sorption pellets and water-gas shift catalyst pellets. The technology is developed using potassium promoted hydrotalcite-based materials as the CO 2 sorbent. In a first series of experiments, the performance of this material is investigated under typical SEWGS process conditions. The sorbent was loaded in 2 m and 6 m tall fixed-bed reactor vessels. Breakthrough capacities of 1.3–1.4 mmol/g are reported. After breakthrough the sorbent continues to take up CO 2 , albeit at a much lower rate. Total sorption capacities exceeding 8 mmol/g are observed. This capacity is attributed to the formation of MgCO 3 in the bulk of the sorbent material and requires moderate to high partial pressures of CO 2 and steam. The stability of the sorbent material during cyclic operation was demonstrated for more than 4,000 adsorption and desorption cycles. A stable and low slip of CO 2 was established, corresponding to a carbon capture ratio of well above 90%. After investigation of the relevant sorbent characteristics, the reactor was loaded with sorbent and catalyst material in order to provide a proof-of-principle of the SEWGS technology and establish the performance and stability of sorbent and catalyst material. When the reactor was fed with a gas mixture that simulated a syngas typically produced by auto-thermal reforming of natural gas, it was demonstrated that carbon monoxide conversion can be enhanced from 55% in absence of a sorbent to 100% in the presence of a sorbent. Neither the change of gas composition nor the mixing of sorbent with catalyst did significantly impact CO 2 breakthrough capacity. In a cyclic duration test, the carbon capture rate and carbon monoxide conversion were confirmed to be above 98% without excessive steam demand, and reasonably stable for at least 500 cycles. The experimental data will be used for modelling, cycle optimization, and scale-up to a pilot unit.

Towards cleaner technologies: emissions reduction, energy and waste minimisation, industrial implementation

This editorial introduces and provides an overview of a Special Issue dedicated to the jubilee 10th Conference of Process Integration, Modelling and Optimization for Energy Saving and Pollution Reduction—PRES’07. It contains thirteen selected papers covering various fields of cleaner technologies and environment policy problems. The technologies address recent developments in CO2 capture in Combined Cycle power plants, CO2 reduction in pulp and paper mills, process efficiency increases combined with energy savings at a mill, distillation separation enhancements and emissions control at gas plants, pre-combustion decarbonisation for polygenertion from fossil fuels, minimisation of CO2 emissions in steam and power plants, a study of co-pyrolysis of biomass and plastic wastes, waste-to-energy system design (with a focus on incineration and gasification technologies), optimal design of wastewater treatment systems, and integrated production of sugar and biofuels from sugar beet. Among these topics, The Special Issue includes demonstration of the technologies in the form of Advanced Case studies.