scholarly journals Chemical Looping Co-Gasification Characteristics of Cyanobacterial/Coal Blends

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2352
Author(s):  
Tianxu Shen ◽  
Jiang Zhang ◽  
Laihong Shen ◽  
Lei Bai ◽  
Jingchun Yan
Keyword(s):  
Interaction Effect ◽  
Alkali Metals ◽  
Coal Gasification ◽  
Oxygen Carrier ◽  
Molar Ratio ◽  
Chemical Looping ◽  
Coal Pyrolysis ◽  
Pyrolysis Process ◽  
Residual Moisture ◽  
Char Gasification

The frequent outbreak of cyanobacteria bloom results in an urgent need for the resource utilization of cyanobacteria. However, the development of routine thermal treatment (i.e., gasification and pyrolysis) is hindered by the issue of high moisture content. In order to minimize the dewatering requirement, this study investigated the chemical looping co-gasification of the cyanobacteria/coal mixture. The results showed that the residual moisture of cyanobacteria not only could serve as the gasifying agent of coal, but also presented a better gasification effect than the injecting steam. Meanwhile, blending cyanobacteria also improved the performance of coal chemical looping gasification in terms of the syngas quality, gasification rate, and carbon conversion efficiency. Cyanobacteria pyrolysis supplied abundant hydrocarbons and hydrogen-rich gases. The highest syngas yield of 1.26 Nm3/kg was obtained in the mixture fuel of 46 wt.% cyanobacteria and 54 wt.% coal under a 0.3 oxygen carrier-to-fuel ratio. A slight interaction effect was observed in the pyrolysis process, in which the reactivity of coal pyrolysis was enhanced by the oxygenated groups of cyanobacteria volatile. The dominant motive of the interaction effect was the catalytic effect of alkali metals of cyanobacteria ash on the coal gasification. However, the formation of aluminosilicates deactivated alkali metals and further inhibited the char gasification. The intensity of interaction effect was demonstrated to be highly relevant with the (Na + K)/Al molar ratio of ash. The most prominent interaction effect occurred for the sample with 82 wt.% cyanobacteria, but a negative interaction was observed in the sample with 10 wt.% cyanobacteria. Both homogeneous reaction and shrinking core models showed the excellent fitting performance in the char gasification process. However, these two models could not be applied to the initial pyrolysis process because of the intricate mechanisms.

Simulation of a Novel Chemical Looping System for Recovering Elemental Sulfur from Acid Gases Using Ca-Based Oxygen Carriers

2013 ◽  
Vol 724-725 ◽  
pp. 1136-1139
Author(s):  
Jing Chang ◽  
Ming Dong Han ◽  
Hong Jing Tian
Keyword(s):  
Coal Gasification ◽  
Elemental Sulfur ◽  
Circulating Fluidized Bed ◽  
Oxygen Carrier ◽  
Molar Ratio ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Sulfur Vapor ◽  
Bubbling Bed ◽  
Temperature Ranges

In this paper, a novel chemical-looping process is developed for converting sulfur dioxide (SO2) in the flue gas generated from industries to elemental sulfur using Ca-based oxygen carriers. The system is mainly composed of a bubbling bed gasifier, a bubbling bed reactor and a circulating fluidized bed reactor. The high-purity sulfur vapor can be obtained from the reaction between SO2 and calcium sulfide and then be cooled into solid sulfur particles. From the thermodynamic analysis, the reactions between CaS and SO2 is much more easier to reach equilibrium than Claus reaction between H2S and SO2. When the temperature ranges from 500 to 600 °C, the major sulfur vapor is diatomic sulfur vapor while the solid product is mainly CaSO4, representing the regenerating of the oxygen carrier. In the system, the required heat in the coal gasification comes from the strongly exothermic oxidation of oxygen carrier, by circulating the oxygen carrier particles in the system. The effects of reacting temperature, SO2/CaS molar ratio on the yield of sulfur particle and conversion of SO2 to elemental sulfur are all discussed. The favorable temperature of the reactor to generate elemental sulfur should be between 500 and 600 °C.

In Situ Gasification Chemical Looping Combustion of Coal Using the Mixed Oxygen Carrier of Natural Anhydrite Ore and Calcined Limestone

2016 ◽  
Vol 14 (2) ◽  
pp. 637-652 ◽  
Author(s):  
Zheng Min ◽  
Shen Laihong
Keyword(s):  
Coal Gasification ◽  
Oxygen Carrier ◽  
Molar Ratio ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Transfer Capability ◽  
Fuel Reactor ◽  
Optimum Reaction ◽  
The Stability

Abstract The utilization of CaSO4-based oxygen carrier suffers the deactivation problem caused by sulphur loss. To capture the gas sulphides and to improve the stability of CaSO4 oxygen carrier, calcined limestone was introduced into the fuel reactor of Chemical Looping Combustion (CLC). Kinetic behaviors and thermodynamics of the combined process of coal gasification and oxygen carrier reduction using the mixed oxygen carrier CaSO4-CaO under different atmospheres were investigated. The effects of reaction temperature, gasification intermediate, and molar ratio of CaO to CaSO4 on gas sulphide emissions, CO2 generation, and distribution of other gas emissions and characterization of solid products are taken into account. It is found the CaO-based additive evidently suppressed the sulphur emissions, and improved both chemical reaction rate and CO2 generation efficiency. The sulfation products, both CaS and CaSO4, can be used as oxygen carrier later. The optimum reaction parameters are evaluated and obtained in terms of gas sulphide emissions, CO2 capture, other gas releases and maintenance of oxygen transfer capability.

scholarly journals Influence of different biomass ash additive on anthracite pyrolysis process and char gasification reactivity

2020 ◽  
Vol 7 (3) ◽  
pp. 464-475 ◽  
Author(s):  
Xiaoming Li ◽  
Caifeng Yang ◽  
Mengjie Liu ◽  
Jin Bai ◽  
Wen Li
Keyword(s):  
Coal Gasification ◽  
Structural Parameters ◽  
Vertical Direction ◽  
Pyrolysis Process ◽  
Biomass Ash ◽  
Inhibition Effect ◽  
Gasification Reactivity ◽  
Char Gasification ◽  
High K ◽  
The Cost

Abstract Catalytic coal gasification technology shows prominent advantages in enhancing coal gasification reactivity and is restrained by the cost of catalyst. Two typical biomass ash additions, corn stalk ash (CSA, high K–Na and low Si) and poplar sawdust ash (PSA, high K–Ca and high Si), were employed to study the influence of biomass ash on pyrolysis process and char gasification reactivity of the typical anthracite. Microstructure characteristics of the char samples were examined by X-ray diffraction (XRD). Based on isothermal char-CO2 gasification experiments, the influence of biomass ash on reactivity of anthracite char was determined using thermogravimetric analyzer. Furthermore, structural parameters were correlated with different reactivity parameters to illustrate the crucial factor on the gasification reactivity varied with char reaction stages. The results indicate that both CSA and PSA additives hinder the growth of adjacent basic structural units in a vertical direction of the carbon structure, and then slow down the graphitization process of the anthracite during pyrolysis. The inhibition effect is more prominent with the increasing of biomass ash. In addition, the gasification reactivity of anthracite char is significantly promoted, which could be mainly attributed to the abundant active AAEM (especially K and Na) contents of biomass ash and a lower graphitization degree of mixed chars. Higher K and Na contents illustrate that the CSA has more remarkable promotion effect on char gasification reactivity than PSA, in accordance with the inhibition effect on the order degree of anthracite char. The stacking layer number could reasonably act as a rough indicator for evaluating the gasification reactivity of the char samples.

scholarly journals Enhanced performance of chemical looping combustion of methane with Fe2O3/Al2O3/TiO2oxygen carrier

RSC Advances ◽  
2018 ◽  
Vol 8 (70) ◽  
pp. 39902-39912 ◽  
Author(s):  
Hsuan-Chih Wu ◽  
Young Ku
Keyword(s):  
Oxygen Carrier ◽  
Methane Combustion ◽  
Molar Ratio ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Moving Bed

The effect of Fe2O3/CH4molar ratio on fuel and oxygen carrier conversion for methane combustion in the moving bed.

Simulation of Two-Stage Fuel Reactor Chemical Looping Hydrogen Process Using Solid Fuel

2014 ◽  
Vol 908 ◽  
pp. 349-352 ◽  
Author(s):  
Long Fei Wang ◽  
Shu Zhong Wang ◽  
Ming Luo
Keyword(s):  
Carbon Dioxide ◽  
Solid Fuel ◽  
Flue Gas ◽  
Oxygen Carrier ◽  
Molar Ratio ◽  
Chemical Looping ◽  
Two Stage ◽  
Fuel Reactor ◽  
Simulation Results ◽  
Reactor Temperature

Chemical looping hydrogen (CLH) has become a promising technology for hydrogen production with inherent separation of carbon dioxide. Aspen Plus was used to simulate a two-stage fuel reactor CLH process of coal as solid fuel. Simulation results show that the two-stage reactor can fully convert the fuel and generate the maximum Fe0.947O component to react with the steam in steam reactor. The optimum OC/coal molar ratio in the two-stage fuel reactor was 2.8. The CO2 fraction of the flue gas in the fuel reactor reached 99% when the vapor was condensed at the temperature of 950 °C. The fraction of dry-based H2 in the steam reactor was nearly 100% when the steam reactor temperature was 700 °C and the steam/oxygen carrier molar ratio was 0.48.

Multicycle Study on Chemical Looping Combustion with a CaSO4-CaO Mixed Oxygen Carrier

2019 ◽  
Vol 17 (10) ◽  
Author(s):  
Pu Sixu ◽  
Zheng Min ◽  
Liu Yulou ◽  
Zhao Zhitong ◽  
Sarma Pisupati
Keyword(s):  
Environmental Factor ◽  
Carbon Capture ◽  
Oxygen Carrier ◽  
Total Carbon ◽  
Molar Ratio ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Molar Ratios ◽  
Fuel Reactor ◽  
High Concentrations

Abstract Chemical looping combustion (CLC) is a carbon capture technology which enables CO2 capture with low net efficiency penalty. Calcium sulfate (CaSO4) is an optional oxygen carrier for commercial use, but its usage is limited due to sulfur dioxide (SO2) emission. This study approaches this issue by adding CaO species into the CaSO4 oxygen carrier to inhibit the release of SO2 from CaSO4 oxygen carrier. In this study, the cyclical tests of a CaSO4-based oxygen carrier under alternating reducing and oxidizing conditions were performed at 900 °C and 800 °C respectively in a tubular furnace reactor at atmospheric pressure. The effects of reducing gas concentration and molar ratio of CaO/CaSO4 on the performance of CaSO4-CaO oxygen carrier were studied in terms of CO2 yields, Environmental factors of SO2 and COS, molar ratios of gas sulfides to CO2 generated in fuel reactor, and molar ratios of SO2 and COS to total carbon inlet. The use of CaO additive increased the yields of CO2 obviously. The release of COS in the fuel reactor and SO2 in the air reactor decreased, but while the overall release of SO2 in the fuel reactor increased. However, for per mole CO2 generation, less gas sulfides released from the fuel reactor. High concentrations of CO were beneficial for CO2 production and a low SO2 environmental factor, and meanwhile, the molar ratios of SO2 released to inlet CO {{\text{n}}_{{\text{S}}{{\text{O}}_2}}}/{{\text{n}}_{{\text{CO}}}} decreased. However, it led to a drop in CO2 yield and an increase in COS environmental factor. As a whole, the use of CaO additive and higher CO concentration both accelerated the parallel CaSO4 reductions in fuel reactor, especially the selectivity of CaSO4 reduction to CaS.

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