&lt;I&gt;In situ&lt;/I&gt; gasification of coal using steam with chemical looping: a technique for isolating CO&lt;SUB&gt;2&lt;/SUB&gt; from burning a solid fuel

Chemical Engineering Journal

Gayán

et al. 2012

In this work the CLC process for solid fuels using ilmenite as oxygen carrier was evaluated in a continuous CLC unit. In this process, gasification of solid fuel happens in the fuel reactor which is fluidized by a gasifying agent, i.e, H 2 O. This process has been referred as in-situ Gasification CLC, iG-CLC. The feasibility of using fuels ranging from lignite to anthracite and the effect of the coal rank on the process performance was evaluated. The carbon capture efficiency followed the trend of the coal rank, as it was higher for lignite, then for the bituminous coals and it was lower for anthracite. Special attention was put on the combustion of the volatile matter of the different fuels. In all cases oxygen demands lower than 10% were found; for anthracite the oxygen demand values were 3.5% because of the lower volatile content of this fuel. A temperature increase was proven to be advantageous to reach high carbon capture and combustion efficiencies for all the fuels tested. Also, the feasibility of using H 2 O:CO 2 mixtures as gasification agent with each type of fuel was also assessed and it was seen that in case of bituminous coals and lignite some of H 2 O can be replaced by CO 2 .

Section: Resultsmentioning

confidence: 99%

“…The gasification process has been identified as the controlling step in this process [24][25][26][27].…”

Section: Solid Fuelmentioning

confidence: 99%

Relevance of the coal rank on the performance of the in situ gasification chemical-looping combustion

Cuadrat

Chemical Engineering Journal

Gayán

et al. 2012

“…Lower reactivity was found for no-supported particles prepared from pure Fe 2 O 3 powder [109,241]. Usually, most of gasification products were burnt, being the char gasification the rate-limiting step in the coal conversion [241].…”

Section: Cu-based Oxygen-carriersmentioning

confidence: 99%

“…Fe 2 O 3 /MgAl 2 O 3 materials showed good performance in a batch fluidized bed [239], whereas Fe 2 O 3 supported on Fe 3 O 4 particles showed loss of reactivity after 20 redox cycles [240]. Lower reactivity was found for no-supported particles prepared from pure Fe 2 O 3 powder [109,241]. Usually, most of gasification products were burnt, being the char gasification the rate-limiting step in the coal conversion [241].…”

Section: Cu-based Oxygen-carriersmentioning

confidence: 99%

Progress in Chemical-Looping Combustion and Reforming technologies

Adánez

Progress in Energy and Combustion Science

Garcı́a-Labiano

et al. 2012

1,922

1,614

This work is a comprehensive review of the Chemical-Looping Combustion (CLC) and Chemical-Looping Reforming (CLR) processes reporting the main advances in these technologies up to 2010. These processes are based on the transfer of the oxygen from air to the fuel by means of a solid oxygen-carrier avoiding direct contact between fuel and air for different final purposes. CLC has arisen during last years as a very promising combustion technology for power plants and industrial applications with inherent CO 2 capture which avoids the energetic penalty present in other competing technologies.CLR uses the chemical looping cycles for H 2 production with additional advantages if CO 2 capture is also considered.The review compiles the main milestones reached during last years in the development of these technologies regarding the use of gaseous or solid fuels, the oxygen-carrier development, the continuous operation experience, and modelling at several scales. Up to 2010, more than 700 different materials based on Ni, Cu, Fe, Mn, Co, as well as other mixed oxides and low cost materials, have been compiled. Especial emphasis has been done in those oxygen-carriers tested under continuous operation in Chemical-Looping 2 prototypes. The total time of operational experience (≈ 3500 h) in different CLC units in the size range 0.3-120 kW th , has allowed to demonstrate the technology and to gain in maturity. To help in the design, optimization, and scale-up of the CLC process, modelling work is also reviewed. Different levels of modelling have been accomplished, including fundamentals of the gas-solid reactions in the oxygen-carriers, modelling of the air-and fuel-reactors, and integration of the CLC systems in the power plant. Considering the great advances reached up to date in a very short period of time, it can be said that CLC and CLR are very promising technologies within the framework of the CO 2 capture options.

“…The second possibility for the use of coal in a CLC is the direct combustion in the CLC process [22,23]. The reactor scheme of the direct CLC process with solid fuels is shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Behavior of ilmenite as oxygen carrier in chemical-looping combustion

Cuadrat

Fuel Processing Technology

Adánez

et al. 2012

217

147

For a future scenery where will exist limitation for CO 2 emissions, Chemical-Looping Combustion (CLC) has been identified as a promising technology to reduce the cost related to CO 2 capture from power plants. In CLC a solid oxygen-carrier transfers oxygen from the air to the fuel in a cyclic manner, avoiding direct contact between them. CO 2 is inherently obtained in a separate stream. For this process the oxygen-carrier circulates between two interconnected fluidized-bed reactors. To adapt CLC for solid fuels the oxygen-carrier reacts with the gas proceeding from the solid fuel gasification, which is carried out right in the fuelreactor. Ilmenite, a natural mineral composed of FeTiO 3 , is a low cost and promising material for its use on a large scale in CLC.The aim of this study is to analyze the behavior of ilmenite as oxygen-carrier in CLC.Particular attention was put on the variation of chemical and physical characteristics of ilmenite particles during consecutive redox cycles in a batch fluidized-bed reactor using CH 4 , H 2 and CO as reducing gases. Reaction with H 2 was faster than with CO, and near full H 2 2 conversion was obtained in the fluidized-bed. Lower reactivity was found for CH 4 . Ilmenite increased its reactivity with the number of cycles, especially for CH 4 . The structural changes of ilmenite, as well as the variations in its behavior with a high number of cycles were also evaluated with a 100 cycle test using a CO+H 2 syngas mixture. Tests with different H 2 :CO ratios were also made in order to see the reciprocal influence of both reducing gases and it turned out that the reaction rate is the sum of the individual reaction rates of H 2 and CO. The oxidation reaction of ilmenite was also investigated. An activation process for the oxidation reaction was observed and two steps for the reaction development were differenced. The oxidation reaction was fast and complete oxidation could be reached after every cycle. Low attrition values were found and no defluidization was observed during fluidized-bed operation. During activation process, the porosity of particles increased from low porosity values up to values of 27.5%. The appearance of an external shell in the particle was observed, which is Fe enriched. The segregation of Fe from TiO 2 causes that the oxygen transport capacity, R OC , decreases from the initial R OC = 4.0% to 2.1% after 100 redox cycles.