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Anders Lyngfelt - One of the best experts on this subject based on the ideXlab platform.
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operation of a 100kw chemical looping combustor with mexican petroleum coke and cerrejon coal
Applied Energy, 2014Co-Authors: Pontus Markstrom, Carl Johan Linderholm, Anders LyngfeltAbstract:This study describes the design and operation of a 100kW chemical-looping combustor for solid Fuels. Six experiments of continuous operation, varying between 8 and 32min in length, have been conducted. The Fuels investigated were a Mexican petroleum coke and a bituminous coal from Cerrejon in Colombia. Overall, it was found that operation was stable and loss of char to the air Reactor was small, meaning that the CO2 capture efficiency was high (up to 90% at temperatures close to 950°C in the Fuel Reactor). Gas concentration measurements showed the presence of unconverted CO, H2 and CH4 corresponding to an oxygen demand of around 20%, depending on the Fuel Reactor temperature. In addition, a residence-time analysis was conducted from a batch experiment, enabling an estimation of the mass flow of oxygen carriers through the system using the riser pressure drop in the air Reactor.
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camn0 9mg0 1o3 δ as oxygen carrier in a gas fired 10 kwth chemical looping combustion unit
Industrial & Engineering Chemistry Research, 2013Co-Authors: Malin Kallen, Tobias Mattisson, Magnus Ryden, Cristina Dueso, Anders LyngfeltAbstract:Spray dried particles of the perovskite material CaMn0.9Mg0.1O3-δ have been examined as oxygen carrier for chemical-looping combustion of natural gas. The experiments have been conducted in a continuously operating Reactor with the nominal size 10 kWth. The oxygen carrier particles showed excellent ability to convert Fuel and complete combustion was reached at certain conditions. In general, the CO2 yield increased with increased Fuel Reactor temperature and with increased circulation rate. The oxygen carrier was able to release gaseous oxygen through the so called CLOU-mechanism (Chemical-Looping with Oxygen Uncoupling). When the Fuel Reactor was fluidized by inert gas, there was oxygen release at temperatures above 700°C, reaching a maximum of more than 3% for temperatures above 850°C. Gas phase oxygen was also measured during operation with Fuel, as long as the Fuel conversion was complete. When the Fuel Reactor temperature was above 900°C and a high enough circulation rate was maintained, complete combustion of the Fuel was achieved with an oxygen concentration in the outlet stream from the Fuel Reactor of more than 1%. This suggests that a substantial part of the Fuel is converted by gaseous oxygen released from the particles. The oxygen carrier particles were subject to more than 350 h of fluidization, of which more than 175 h was at high temperature and more than 55 h with addition of Fuel. The particles did not show any tendencies to form hard agglomerations or break down to fines due to attrition during the experiments. Operational problems included high rate of particle elutriation, which was likely an effect of a mismatch between the size and density of the particles, the air flow and the cyclone.
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Fuel Reactor model validation: Assessment of the key parameters affecting the chemical-looping combustion of coal
International Journal of Greenhouse Gas Control, 2013Co-Authors: Alberto Abad, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Juan Adánez, Anders LyngfeltAbstract:The success of a Chemical Looping Combustion (CLC) system for coal combustion is greatly affected by the performance of the Fuel Reactor. When coal is gasified in situ in the Fuel Reactor, several parameters affect the coal conversion, and hence the capture and combustion efficiencies. In this paper, a mathematical model for the Fuel Reactor is validated against experimental results obtained in a 100 kW(th) CLC unit when Reactor temperature, solids circulation flow rate or solids inventory are varied. This is the first time that a mathematical model for Chemical Looping Combustion of coal with in situ gasification (iG-CLC) has been validated against experimental results obtained in a continuously operated unit. The validated model can be used to evaluate the relevance of operating conditions on process efficiency. Model simulations showed that the Reactor temperature, the solids circulation flow rate and the solids inventory were the most relevant operating conditions affecting the oxygen demand. However, high values of the solids circulation flow rate must be prevented because they cause a decrease in the CO2 capture. The high values of CO2 capture efficiency obtained were due to the highly efficient carbon stripper. The validated model is a helpful tool in designing the Fuel Reactor to optimize the CLC process. A CO2 capture efficiency of eta(CC) = 98.5% and a total oxygen demand of Omega(T) = 9.6% is predicted, operating at 1000 C and 1500 kg/MWth in the Fuel Reactor.
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chemical looping combustion of petroleum coke using ilmenite in a 10 kwth unit high temperature operation
Energy & Fuels, 2009Co-Authors: Nicolas Berguerand, Anders LyngfeltAbstract:Chemical-looping combustion with solid Fuel was investigated in a 10 kWth chemical-looping combustor using a petroleum coke as Fuel and ilmenite, an iron titanium oxide, as oxygen-carrier. The Fuel Reactor was fluidized by steam to gasify the coke and the oxygen carrier reacts with the gasification products CO and H2. The temperature in the Fuel Reactor was normally 950°C. Testing involved variation of operational parameters such as particle circulation, fluidizing velocity in the Fuel Reactor and most important, Fuel Reactor temperature. In particular, successful testing was performed at a Fuel Reactor temperature of 1000°C without any operation difficulty and the positive effect of temperature on carbon capture and solid Fuel conversion was verified. The oxygen demand corresponds to the fraction of oxygen lacking to achieve full gas conversion and averaged at 32%, due to presence of CH4, CO, H2 and H2S at the outlet of the Fuel Reactor. During these tests, the CO2/CO ratios usually reached in the Fuel Reactor ranged between 8 and 9 at stable operation. Most of the oxygen demand is associated with the volatiles released from the Fuel and never in contact with oxidized particles. Indeed, investigation based on gas concentration measurements during transitions phases, which correspond to start respectively stop of Fuel addition, indicate that as much as 80% of the total oxygen demand can be associated with the volatiles. The oxygen demand for the actual char oxidation is estimated to be 5-9%, if sulphur is excluded.
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operation in a 10 kwth chemical looping combustor for solid Fuel testing with a mexican petroleum coke
Energy Procedia, 2009Co-Authors: Nicolas Berguerand, Anders LyngfeltAbstract:Abstract Solid Fuel chemical-looping combustion was investigated in a 10 kW th combustor using petroleum coke as Fuel and ilmenite as oxygen carrier. Testing involved operational parameters variations, such as particle circulation, fluidizing velocities, Fuel load and Fuel Reactor temperature. Key parameters indicating the performance include CO 2 capture, solid Fuel and gas conversions from the Fuel Reactor. The CO 2 capture averaged at 75%, the solid Fuel conversion at 65–70% while incomplete gas conversion led to an oxygen demand averaging at 29–30%, due to presence of CH 4 , CO, H 2 and H 2 S. Effect of Fuel Reactor temperature on the solid Fuel conversion was verified.
Juan Adánez - One of the best experts on this subject based on the ideXlab platform.
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Improving the efficiency of Chemical Looping Combustion with coal by using ring-type internals in the Fuel Reactor
Fuel, 2019Co-Authors: Raúl Pérez-vega, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Alberto Abad, José A. Bueno, Juan AdánezAbstract:Abstract Chemical Looping Combustion (CLC) with solid Fuels has been widely developed by using two interconnected fluidized beds, the Fuel Reactor and the air Reactor, with an oxygen carrier continuously circulating between them. Experience gained in this process shows that high CO2 capture values can be reached. However, complete combustion of the Fuel is not achieved, with some H2, CO and CH4 as the main unconverted compounds in the combustion products from the Fuel Reactor. It is believed that the combustion efficiency can be increased by improving the gas-solid contact in the Fuel Reactor. In this work, the solids distribution in the Fuel Reactor was modified by using ring-type internals with the objective of enhancing the gas-solid contact. Two experimental campaigns were carried out in a 50 kWth CLC unit burning a bituminous coal with ilmenite particles in the temperature interval of 900–1000 °C. The first campaign was conducted with the original riser of the Fuel Reactor, which was characterized by a smooth section from bottom to top. For the second campaign, three ring-type internals were implemented in the riser in order to modify the solids distribution in the Fuel Reactor. The presence of the internals had a beneficial effect on the coal combustion. The major benefit was an improved oxidation of volatile matter in the form of CH4 and the full conversion of H2. As a result, the total oxygen demand decreased by 20%, from 12.2% to 9.8%, with the implementation of the internals.
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kinetic analysis of a cu based oxygen carrier relevance of temperature and oxygen partial pressure on reduction and oxidation reactions rates in chemical looping with oxygen uncoupling clou
Chemical Engineering Journal, 2014Co-Authors: Inaki Adanezrubio, Alberto Abad, F Garcialabiano, P Gayan, L F De Diego, Juan AdánezAbstract:Abstract The kinetic of reduction of CuO to Cu 2 O with N 2 + O 2 mixtures and the oxidation of Cu 2 O to CuO with O 2 of a Cu-based oxygen carrier for the CLOU process has been determined in a TGA. For kinetic determination, the O 2 concentrations were varied between 0 and 9 vol.% for reduction, and between 21 and 1.5 vol.% for oxidation reactions; temperature was varied between 1148 and 1273 K for the reduction and between 1123 and 1273 K for the oxidation. The oxygen carrier showed high reactivity both in oxidation and reduction reactions. The nucleation and nuclei growth model with chemical reaction control properly described the evolution of solids conversion with time. The Langmuir–Hinshelwood model was able to describe the effect of oxygen concentration on reduction and oxidation rates. The reaction order was 0.5 for reduction and 1.2 for the oxidation. The kinetic constant activation energies were 270 kJ mol −1 for the reduction and 32 kJ mol −1 for the oxidation. The kinetic model was used to calculate the solids inventory needed in the Fuel Reactor for complete combustion of three different rank coals. It was possible to use a low oxygen carrier inventory in the Fuel Reactor (160 kg/MW th ) to supply the oxygen required to full lignite combustion. However, to reach high CO 2 capture efficiencies (⩾95%), oxygen carrier inventories in Fuel Reactor higher than 600 kg/MW th were needed with the lignite.
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Fuel Reactor modelling in chemical-looping combustion of coal: 2—simulation and optimization
Chemical Engineering Science, 2013Co-Authors: Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Alberto Abad, Juan AdánezAbstract:Abstract Chemical-looping combustion of coal (CLCC) is a promising process to carry out coal combustion with carbon capture. The process should be optimized in order to maximize the carbon capture and the combustion efficiency in the Fuel Reactor, which will depend on the Reactor design and the operational conditions. In this work, a mathematical model of the Fuel Reactor is used to make predictions about the performance of the CLCC process and simulate the behaviour of the system over different operating conditions. The mathematical model considers the fluid dynamic characteristics of the Fuel Reactor, being a high-velocity fluidized bed Reactor. It also considers the chemical processes happening inside the Reactor, and the effect of a carbon separation system on the char conversion in the process. A sensitivity analysis of the effect of the efficiency of the carbon separation system, the solids inventory in the Fuel Reactor, the temperature in the Fuel Reactor, ratio of oxygen carrier to Fuel, oxygen carrier reactivity, coal reactivity and coal particle on the carbon capture and combustion efficiency is carried out. Also the relevance of the water–gas shift reaction (WGS) is evaluated. The most relevant parameters affecting the carbon capture are the Fuel Reactor temperature and the efficiency of the carbon separation system, η CSS . A value for η CSS as high as 98% should be necessary to reach a carbon capture efficiency of 98.6% when the solids inventory was 1000 kg/MW th . Regarding the combustion efficiency, to use highly reactive oxygen carrier materials are desirable. In any case, additional actions or a modified design for the Fuel Reactor should be implemented to reach complete combustion of coal.
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Fuel Reactor modelling in chemical-looping combustion of coal: 1. model formulation
Chemical Engineering Science, 2013Co-Authors: Alberto Abad, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Juan AdánezAbstract:Abstract A fundamental part of the reliability of the chemical-looping combution system when a solid Fuel, such as coal, is fed to the Reactor is based on the behaviour of the Fuel Reactor, which determines the conversion of the solid Fuel. The objective of this work is to develop a model describing the Fuel Reactor in the chemical-looping combustion with coal (CLCC) process. The model is used to simulate the performance of the 1 MWth CLCC rig built in the Technology University of Darmstadt. The Fuel Reactor is a fluidized bed working at high velocity regime, using ilmenite as oxygen carrier. The developed model is based on semi-empirical correlations, and considers the Reactor fluid dynamics, the coal conversion and the reaction of the oxygen carrier with evolved gases from coal. The efficiency of a carbon separation system is also considered in order to analyze this parameter on the Fuel Reactor performance. The main outputs of the model are presented in this work, i.e., (1) the fluid dynamics structure of the Reactor; (2) the axial profiles of gas composition and flows (volatiles, CO, H2, CO2 and H2O); (3) the conversion of the oxygen carrier and char in the Reactor; (4) the char concentration in the Reactor; (5) the gas composition and solids flow in the upper Reactor exit; and (6) the char flow to the air Reactor. From these outputs the oxygen demand of the flue gases and the CO2 capture efficiency are calculated. Simulations on the effect of the efficiency of the carbon separation system are presented. A highly efficient carbon separation system should be used to reach a high carbon capture value. Also incomplete combustion of gases is predicted in the Fuel Reactor, mainly from unconverted volatile matter. The model can be later used to obtain basic design parameters of the Fuel Reactor and optimize its operation.
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Fuel Reactor model validation: Assessment of the key parameters affecting the chemical-looping combustion of coal
International Journal of Greenhouse Gas Control, 2013Co-Authors: Alberto Abad, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Juan Adánez, Anders LyngfeltAbstract:The success of a Chemical Looping Combustion (CLC) system for coal combustion is greatly affected by the performance of the Fuel Reactor. When coal is gasified in situ in the Fuel Reactor, several parameters affect the coal conversion, and hence the capture and combustion efficiencies. In this paper, a mathematical model for the Fuel Reactor is validated against experimental results obtained in a 100 kW(th) CLC unit when Reactor temperature, solids circulation flow rate or solids inventory are varied. This is the first time that a mathematical model for Chemical Looping Combustion of coal with in situ gasification (iG-CLC) has been validated against experimental results obtained in a continuously operated unit. The validated model can be used to evaluate the relevance of operating conditions on process efficiency. Model simulations showed that the Reactor temperature, the solids circulation flow rate and the solids inventory were the most relevant operating conditions affecting the oxygen demand. However, high values of the solids circulation flow rate must be prevented because they cause a decrease in the CO2 capture. The high values of CO2 capture efficiency obtained were due to the highly efficient carbon stripper. The validated model is a helpful tool in designing the Fuel Reactor to optimize the CLC process. A CO2 capture efficiency of eta(CC) = 98.5% and a total oxygen demand of Omega(T) = 9.6% is predicted, operating at 1000 C and 1500 kg/MWth in the Fuel Reactor.
Alberto Abad - One of the best experts on this subject based on the ideXlab platform.
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Improving the efficiency of Chemical Looping Combustion with coal by using ring-type internals in the Fuel Reactor
Fuel, 2019Co-Authors: Raúl Pérez-vega, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Alberto Abad, José A. Bueno, Juan AdánezAbstract:Abstract Chemical Looping Combustion (CLC) with solid Fuels has been widely developed by using two interconnected fluidized beds, the Fuel Reactor and the air Reactor, with an oxygen carrier continuously circulating between them. Experience gained in this process shows that high CO2 capture values can be reached. However, complete combustion of the Fuel is not achieved, with some H2, CO and CH4 as the main unconverted compounds in the combustion products from the Fuel Reactor. It is believed that the combustion efficiency can be increased by improving the gas-solid contact in the Fuel Reactor. In this work, the solids distribution in the Fuel Reactor was modified by using ring-type internals with the objective of enhancing the gas-solid contact. Two experimental campaigns were carried out in a 50 kWth CLC unit burning a bituminous coal with ilmenite particles in the temperature interval of 900–1000 °C. The first campaign was conducted with the original riser of the Fuel Reactor, which was characterized by a smooth section from bottom to top. For the second campaign, three ring-type internals were implemented in the riser in order to modify the solids distribution in the Fuel Reactor. The presence of the internals had a beneficial effect on the coal combustion. The major benefit was an improved oxidation of volatile matter in the form of CH4 and the full conversion of H2. As a result, the total oxygen demand decreased by 20%, from 12.2% to 9.8%, with the implementation of the internals.
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1 Effect of operating conditions in Chemical-Looping Combustion of coal in a 500 Wth unit
2016Co-Authors: Ana Cuadrat, Francisco García-labiano, Pilar Gayán, Alberto Abad, Diego Juan AdánezAbstract:Chemical-Looping Combustion, CLC, is one of the most promising processes to capture CO2 at a low cost. It is based on the transfer of the oxygen from air to the Fuel by using a solid oxygen-carrier that circulates between two interconnected fluidized-bed Reactors: the Fuel- and the air-Reactor. The CO2 capture is inherent to this process, as the air does not get mixed with the Fuel. In this work, the CLC technology with coal was investigated in a continuous 500 Wth rig using ilmenite as oxygen-carrier. The plant was basically composed of two interconnected fluidized-bed Reactors, a riser for solids transport from the air- to the Fuel-Reactor, a solid valve to control the flow rate of solids fed to the Fuel-Reactor and a cyclone. A Colombian bituminous coal is fed by a screw feeder at the bottom of the bed. In the Fuel-Reactor the oxygen-carrier is reduced by the volatile matter and gasification products of coal. Reduced oxygen-carrier particles were led to the air-Reactor where they were re-oxidized and got ready to start a new cycle. This work is focused on the study of the Fuel-Reactor within the process. The behaviour of th
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coal combustion in a 50 kwth chemical looping combustion unit seeking operating conditions to maximize co2 capture and combustion efficiency
International Journal of Greenhouse Gas Control, 2016Co-Authors: Raul Perezvega, Luis F. De Diego, Alberto Abad, F Garcialabiano, P Gaya, Jua AdanezAbstract:Abstract In-situ Gasification Chemical-Looping Combustion (iG-CLC) with coal has been proposed as a low-cost process for the capture of CO2 during the energy generation. Previous experimental works have highlighted that high CO2 capture efficiency, close to 100%, can be achieved. However, a certain amount of unburnt gases (mainly CH4, CO and H2) are present in the CO2 stream. These gases can be treated in an oxygen polishing step placed downstream from the CLC unit where they are burnt with pure oxygen, which defines the so-called oxygen demand for the process. The aim of this work was to optimize the performance of the iG-CLC process with coal in order to minimize oxygen demand while maintaining CO2 capture at high levels. Ilmenite was used as the oxygen carrier to burn a bituminous coal in a 50 kWth CLC unit, which consisted of a Fuel Reactor, an air Reactor and a carbon stripper unit between them. The Fuel Reactor temperature, solids inventory in the Fuel Reactor, solids circulation rate, coal feeding rate and carbon stripper efficiency were varied, and the CO2 capture efficiency and oxygen demand were calculated for each set of operating conditions. The effect of the Fuel Reactor temperature was higher on the CO2 capture than on the oxygen demand, with a temperature close to 1000 °C advisable in order to reach CO2 capture rates higher than 90%. In order to further increase CO2 capture, the efficiency of char separation in the carbon stripper was increased. The solids circulation flow rate and the coal feeding rate -which define the oxygen carrier-to-Fuel ratio-, in addition to the solids inventory in the Fuel Reactor, showed a strong influence on the combustion efficiency. Thus, the total oxygen demand was able to be decreased from 10% to 7% by increasing the oxygen carrier-to-Fuel ratio from 1.1 to 1.5 and the solids inventory from 450 to 720 kg/MWth. However, an increase in the circulation rate showed a detrimental effect on CO2 capture, which could be offset by increasing the carbon stripper efficiency.
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kinetic analysis of a cu based oxygen carrier relevance of temperature and oxygen partial pressure on reduction and oxidation reactions rates in chemical looping with oxygen uncoupling clou
Chemical Engineering Journal, 2014Co-Authors: Inaki Adanezrubio, Alberto Abad, F Garcialabiano, P Gayan, L F De Diego, Juan AdánezAbstract:Abstract The kinetic of reduction of CuO to Cu 2 O with N 2 + O 2 mixtures and the oxidation of Cu 2 O to CuO with O 2 of a Cu-based oxygen carrier for the CLOU process has been determined in a TGA. For kinetic determination, the O 2 concentrations were varied between 0 and 9 vol.% for reduction, and between 21 and 1.5 vol.% for oxidation reactions; temperature was varied between 1148 and 1273 K for the reduction and between 1123 and 1273 K for the oxidation. The oxygen carrier showed high reactivity both in oxidation and reduction reactions. The nucleation and nuclei growth model with chemical reaction control properly described the evolution of solids conversion with time. The Langmuir–Hinshelwood model was able to describe the effect of oxygen concentration on reduction and oxidation rates. The reaction order was 0.5 for reduction and 1.2 for the oxidation. The kinetic constant activation energies were 270 kJ mol −1 for the reduction and 32 kJ mol −1 for the oxidation. The kinetic model was used to calculate the solids inventory needed in the Fuel Reactor for complete combustion of three different rank coals. It was possible to use a low oxygen carrier inventory in the Fuel Reactor (160 kg/MW th ) to supply the oxygen required to full lignite combustion. However, to reach high CO 2 capture efficiencies (⩾95%), oxygen carrier inventories in Fuel Reactor higher than 600 kg/MW th were needed with the lignite.
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Fuel Reactor modelling in chemical-looping combustion of coal: 2—simulation and optimization
Chemical Engineering Science, 2013Co-Authors: Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Alberto Abad, Juan AdánezAbstract:Abstract Chemical-looping combustion of coal (CLCC) is a promising process to carry out coal combustion with carbon capture. The process should be optimized in order to maximize the carbon capture and the combustion efficiency in the Fuel Reactor, which will depend on the Reactor design and the operational conditions. In this work, a mathematical model of the Fuel Reactor is used to make predictions about the performance of the CLCC process and simulate the behaviour of the system over different operating conditions. The mathematical model considers the fluid dynamic characteristics of the Fuel Reactor, being a high-velocity fluidized bed Reactor. It also considers the chemical processes happening inside the Reactor, and the effect of a carbon separation system on the char conversion in the process. A sensitivity analysis of the effect of the efficiency of the carbon separation system, the solids inventory in the Fuel Reactor, the temperature in the Fuel Reactor, ratio of oxygen carrier to Fuel, oxygen carrier reactivity, coal reactivity and coal particle on the carbon capture and combustion efficiency is carried out. Also the relevance of the water–gas shift reaction (WGS) is evaluated. The most relevant parameters affecting the carbon capture are the Fuel Reactor temperature and the efficiency of the carbon separation system, η CSS . A value for η CSS as high as 98% should be necessary to reach a carbon capture efficiency of 98.6% when the solids inventory was 1000 kg/MW th . Regarding the combustion efficiency, to use highly reactive oxygen carrier materials are desirable. In any case, additional actions or a modified design for the Fuel Reactor should be implemented to reach complete combustion of coal.
Hermann Hofbauer - One of the best experts on this subject based on the ideXlab platform.
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Detailed fluid dynamic investigations of a novel Fuel Reactor concept for chemical looping combustion of solid Fuels
Powder Technology, 2016Co-Authors: Stefan Penthor, Michael Stollhof, Tobias Pröll, Hermann HofbauerAbstract:Abstract In the present study, the fluid dynamic characteristics of the Fuel Reactor of a novel Reactor concept for chemical looping combustion of solid Fuels were investigated. In this Reactor concept based on two interconnected circulating fluidized beds, flow obstacles are arranged along the height of the Fuel Reactor to improve gas–solid contact. The experiments have been performed at the scaled cold flow model of a [100]kW pilot plant and were focused on the solids distribution in the Fuel Reactor and on the limitations of the operating range caused by the flow obstacles. The flow obstacles increase the solids fraction in the upper part of the Reactor above the dense zone and cause a more homogenous solids distribution. Both, solids distribution and solids fraction can be influenced by the fluidization rates of the two Reactors. Increasing the fluidization rate of one or both Reactors shifts the solids distribution towards the upper part of the Reactor. Although the global solids distribution of the Fuel Reactor can be influenced by fluidization parameters, the solids distribution between two constrictions cannot be influenced, i.e. particles are always concentrated directly above the constrictions. The new Reactor concept shows operation limits far above standard load. Under such unstable operating conditions, particles start to concentrate in the constriction and the area above the constriction is filled with particles. These effects can be reduced by adapting the design of the constrictions.
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influence of ring type internals on the solids residence time distribution in the Fuel Reactor of a dual circulating fluidized bed system for chemical looping combustion
Chemical Engineering Research & Design, 2014Co-Authors: Diana Carolina Guioperez, Tobias Pröll, Hermann HofbauerAbstract:Abstract The intensification of gas-solids contact in the Fuel Reactor of a chemical looping combustion system is enhanced with the installation of ring-type internals. This can be a key issue for achieving the necessary Fuel conversion rates. Wedged rings, previously designed and tested, were found to increase the particle concentration in the counter current section of the Fuel Reactor and hence, to achieve a more homogeneous particles concentration along this zone. The present work investigates the effect of the mentioned internals on the residence time distribution of particles in the Fuel Reactor of a dual circulating fluidized bed system for chemical looping. The study was carried out in a cold flow model especially designed for the fluid-dynamic analysis of the system equipped with a recently developed residence time measurement device based on the detection of ferromagnetic tracer particles through inductance measurement. Ring internals proved the positive effect on the particles residence time, the residence time distribution is more symmetric and shows lower dispersion, the flow pattern is more plug-flow-like, these effects are intensified with the reduction of the aperture ratio of the rings. On the other hand, the upward particle transport in the counter-current zone of the Fuel Reactor also increases with the installation of the rings, increasing the bypass flow of solids through the Fuel Reactor's return loop (internal circulation). For high internal circulation rates the solids residence time distribution of the Fuel Reactor is dominated by the bypass effect. The findings may be used for focused design improvement of the investigated fluidized bed system.
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design of a chemical looping combustor using a dual circulating fluidized bed dcfb Reactor system
Chemical Engineering & Technology, 2009Co-Authors: Philipp Kolbitsch, Tobias Pröll, Johannes Bolharnordenkampf, Hermann HofbauerAbstract:A dual circulating fluidized bed (DCFB) Reactor system for chemical looping combustion is proposed. The Reactor is designed to operate with a Ni-based oxygen carrier and is Fueled with either natural gas or designed mixtures of CH4, CO, H2, and higher hydrocarbons at 120-kW Fuel power. The main design parameters are determined and the DCFB system, which promises large scale applicability, is introduced. The DCFB Reactor system features effective control of the solid circulation rate via the primary fast fluidized bed (air Reactor) without changing the fluidization regime in the secondary Reactor (Fuel Reactor). Therefore, the secondary Reactor can be optimized on Fuel conversion without affecting the global solid circulation rates. The air Reactor design can focus on the transportation of the solids to the Fuel Reactor. Besides a short introduction of the auxiliary units of the Reactor system, a pressure profile of the pilot rig in hot operation is presented.
Luis F. De Diego - One of the best experts on this subject based on the ideXlab platform.
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Improving the efficiency of Chemical Looping Combustion with coal by using ring-type internals in the Fuel Reactor
Fuel, 2019Co-Authors: Raúl Pérez-vega, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Alberto Abad, José A. Bueno, Juan AdánezAbstract:Abstract Chemical Looping Combustion (CLC) with solid Fuels has been widely developed by using two interconnected fluidized beds, the Fuel Reactor and the air Reactor, with an oxygen carrier continuously circulating between them. Experience gained in this process shows that high CO2 capture values can be reached. However, complete combustion of the Fuel is not achieved, with some H2, CO and CH4 as the main unconverted compounds in the combustion products from the Fuel Reactor. It is believed that the combustion efficiency can be increased by improving the gas-solid contact in the Fuel Reactor. In this work, the solids distribution in the Fuel Reactor was modified by using ring-type internals with the objective of enhancing the gas-solid contact. Two experimental campaigns were carried out in a 50 kWth CLC unit burning a bituminous coal with ilmenite particles in the temperature interval of 900–1000 °C. The first campaign was conducted with the original riser of the Fuel Reactor, which was characterized by a smooth section from bottom to top. For the second campaign, three ring-type internals were implemented in the riser in order to modify the solids distribution in the Fuel Reactor. The presence of the internals had a beneficial effect on the coal combustion. The major benefit was an improved oxidation of volatile matter in the form of CH4 and the full conversion of H2. As a result, the total oxygen demand decreased by 20%, from 12.2% to 9.8%, with the implementation of the internals.
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coal combustion in a 50 kwth chemical looping combustion unit seeking operating conditions to maximize co2 capture and combustion efficiency
International Journal of Greenhouse Gas Control, 2016Co-Authors: Raul Perezvega, Luis F. De Diego, Alberto Abad, F Garcialabiano, P Gaya, Jua AdanezAbstract:Abstract In-situ Gasification Chemical-Looping Combustion (iG-CLC) with coal has been proposed as a low-cost process for the capture of CO2 during the energy generation. Previous experimental works have highlighted that high CO2 capture efficiency, close to 100%, can be achieved. However, a certain amount of unburnt gases (mainly CH4, CO and H2) are present in the CO2 stream. These gases can be treated in an oxygen polishing step placed downstream from the CLC unit where they are burnt with pure oxygen, which defines the so-called oxygen demand for the process. The aim of this work was to optimize the performance of the iG-CLC process with coal in order to minimize oxygen demand while maintaining CO2 capture at high levels. Ilmenite was used as the oxygen carrier to burn a bituminous coal in a 50 kWth CLC unit, which consisted of a Fuel Reactor, an air Reactor and a carbon stripper unit between them. The Fuel Reactor temperature, solids inventory in the Fuel Reactor, solids circulation rate, coal feeding rate and carbon stripper efficiency were varied, and the CO2 capture efficiency and oxygen demand were calculated for each set of operating conditions. The effect of the Fuel Reactor temperature was higher on the CO2 capture than on the oxygen demand, with a temperature close to 1000 °C advisable in order to reach CO2 capture rates higher than 90%. In order to further increase CO2 capture, the efficiency of char separation in the carbon stripper was increased. The solids circulation flow rate and the coal feeding rate -which define the oxygen carrier-to-Fuel ratio-, in addition to the solids inventory in the Fuel Reactor, showed a strong influence on the combustion efficiency. Thus, the total oxygen demand was able to be decreased from 10% to 7% by increasing the oxygen carrier-to-Fuel ratio from 1.1 to 1.5 and the solids inventory from 450 to 720 kg/MWth. However, an increase in the circulation rate showed a detrimental effect on CO2 capture, which could be offset by increasing the carbon stripper efficiency.
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Fuel Reactor modelling in chemical-looping combustion of coal: 2—simulation and optimization
Chemical Engineering Science, 2013Co-Authors: Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Alberto Abad, Juan AdánezAbstract:Abstract Chemical-looping combustion of coal (CLCC) is a promising process to carry out coal combustion with carbon capture. The process should be optimized in order to maximize the carbon capture and the combustion efficiency in the Fuel Reactor, which will depend on the Reactor design and the operational conditions. In this work, a mathematical model of the Fuel Reactor is used to make predictions about the performance of the CLCC process and simulate the behaviour of the system over different operating conditions. The mathematical model considers the fluid dynamic characteristics of the Fuel Reactor, being a high-velocity fluidized bed Reactor. It also considers the chemical processes happening inside the Reactor, and the effect of a carbon separation system on the char conversion in the process. A sensitivity analysis of the effect of the efficiency of the carbon separation system, the solids inventory in the Fuel Reactor, the temperature in the Fuel Reactor, ratio of oxygen carrier to Fuel, oxygen carrier reactivity, coal reactivity and coal particle on the carbon capture and combustion efficiency is carried out. Also the relevance of the water–gas shift reaction (WGS) is evaluated. The most relevant parameters affecting the carbon capture are the Fuel Reactor temperature and the efficiency of the carbon separation system, η CSS . A value for η CSS as high as 98% should be necessary to reach a carbon capture efficiency of 98.6% when the solids inventory was 1000 kg/MW th . Regarding the combustion efficiency, to use highly reactive oxygen carrier materials are desirable. In any case, additional actions or a modified design for the Fuel Reactor should be implemented to reach complete combustion of coal.
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Fuel Reactor modelling in chemical-looping combustion of coal: 1. model formulation
Chemical Engineering Science, 2013Co-Authors: Alberto Abad, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Juan AdánezAbstract:Abstract A fundamental part of the reliability of the chemical-looping combution system when a solid Fuel, such as coal, is fed to the Reactor is based on the behaviour of the Fuel Reactor, which determines the conversion of the solid Fuel. The objective of this work is to develop a model describing the Fuel Reactor in the chemical-looping combustion with coal (CLCC) process. The model is used to simulate the performance of the 1 MWth CLCC rig built in the Technology University of Darmstadt. The Fuel Reactor is a fluidized bed working at high velocity regime, using ilmenite as oxygen carrier. The developed model is based on semi-empirical correlations, and considers the Reactor fluid dynamics, the coal conversion and the reaction of the oxygen carrier with evolved gases from coal. The efficiency of a carbon separation system is also considered in order to analyze this parameter on the Fuel Reactor performance. The main outputs of the model are presented in this work, i.e., (1) the fluid dynamics structure of the Reactor; (2) the axial profiles of gas composition and flows (volatiles, CO, H2, CO2 and H2O); (3) the conversion of the oxygen carrier and char in the Reactor; (4) the char concentration in the Reactor; (5) the gas composition and solids flow in the upper Reactor exit; and (6) the char flow to the air Reactor. From these outputs the oxygen demand of the flue gases and the CO2 capture efficiency are calculated. Simulations on the effect of the efficiency of the carbon separation system are presented. A highly efficient carbon separation system should be used to reach a high carbon capture value. Also incomplete combustion of gases is predicted in the Fuel Reactor, mainly from unconverted volatile matter. The model can be later used to obtain basic design parameters of the Fuel Reactor and optimize its operation.
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Fuel Reactor model validation: Assessment of the key parameters affecting the chemical-looping combustion of coal
International Journal of Greenhouse Gas Control, 2013Co-Authors: Alberto Abad, Francisco García-labiano, Luis F. De Diego, Pilar Gayán, Juan Adánez, Anders LyngfeltAbstract:The success of a Chemical Looping Combustion (CLC) system for coal combustion is greatly affected by the performance of the Fuel Reactor. When coal is gasified in situ in the Fuel Reactor, several parameters affect the coal conversion, and hence the capture and combustion efficiencies. In this paper, a mathematical model for the Fuel Reactor is validated against experimental results obtained in a 100 kW(th) CLC unit when Reactor temperature, solids circulation flow rate or solids inventory are varied. This is the first time that a mathematical model for Chemical Looping Combustion of coal with in situ gasification (iG-CLC) has been validated against experimental results obtained in a continuously operated unit. The validated model can be used to evaluate the relevance of operating conditions on process efficiency. Model simulations showed that the Reactor temperature, the solids circulation flow rate and the solids inventory were the most relevant operating conditions affecting the oxygen demand. However, high values of the solids circulation flow rate must be prevented because they cause a decrease in the CO2 capture. The high values of CO2 capture efficiency obtained were due to the highly efficient carbon stripper. The validated model is a helpful tool in designing the Fuel Reactor to optimize the CLC process. A CO2 capture efficiency of eta(CC) = 98.5% and a total oxygen demand of Omega(T) = 9.6% is predicted, operating at 1000 C and 1500 kg/MWth in the Fuel Reactor.
