scholarly journals A Numerical Study of the Influence of Process Parameters on the Efficiency of Staged Coal Gasification Using Mixtures of Oxygen and Carbon Dioxide

2021 ◽  
pp. 27-34
Author(s):  
I. G. Donskoy
Keyword(s):  
Carbon Dioxide ◽  
Reaction Temperature ◽  
Numerical Study ◽  
Process Efficiency ◽  
Conversion Degree ◽  
Fuel Conversion ◽  
Influence Of Process Parameters ◽  
Gasification Process ◽  
Coal Fuel ◽  
Coal Particles

The paper considers a staged conversion process of pulverized coal fuel in the MHPS-type gasifier, which uses mixtures of oxygen and carbon dioxide as a gasifying agent instead of air. Similar conversion processes can be applied in the process diagrams with the capture and disposal of carbon dioxide. The research tool is a reduced-order mathematical model of coal particles' conversion in a reacting gas flow. Replacement of nitrogen with carbon dioxide leads to significant changes in the gasification process characteristics: the average reaction temperature decreases, but this decrease is partially compensated by an increase in the concentration of gaseous reactants. Thus, the gasification process efficiency and the fuel conversion degree increase. Calculations make it possible to identify a range of parameters with the highest cold gas efficiency values. The influence of oxygen concentration is estimated, the dependence of the fuel conversion degree on the reaction temperature is analyzed.

scholarly journals How water vapor and carbon dioxide additives affect oxygen gasification of pulverized coal fuel

2021 ◽  
Vol 21 (1) ◽  
pp. 21-28
Keyword(s):  
Carbon Dioxide ◽  
Water Vapor ◽  
Pulverized Coal ◽  
Gas Content ◽  
Thermochemical Conversion ◽  
Gasification Process ◽  
Cold Gas Efficiency ◽  
Coal Fuel ◽  
Pulverized Coal Fuel ◽  
Gas Efficiency

The paper analyzes entrained-flow high-oxygen gasification of pulverized coal (a Shell type process)is considered. Water vapor is commonly added to increase the yield of combustible components. This research uses a mathematical model in a one-dimensional stationary approximation to see how adding carbon dioxide and a mixture of carbon dioxide and water vapor to the oxygen flow will affect the process. The paper presents estimates of thermochemical conversion rate (cold gas efficiency), combustible gas content, and completeness of fuel carbon conversion for all the tested configurations. Calculations show that adding carbon dioxide can reduce the specific oxygen consumption of the gasification process whilst ensuring more complete fuel conversion. Adjustments in the water vapor to carbon dioxide ratio help control the gas composition (albeit in a rather narrow range) and the temperature of the raw produced gas at the reaction zone outlet.

Photocatalytic Reduction of Carbon Dioxide by Water: A Step towards Sustainable Fuels and Chemicals

2012 ◽  
Vol 734 ◽  
pp. 1-62 ◽  
Author(s):  
V. Jeyalakshmi ◽  
R. Mahalakshmy ◽  
K.R. Krishnamurthy ◽  
B. Viswanathan
Keyword(s):  
Carbon Dioxide ◽  
Process Efficiency ◽  
Reaction Pathways ◽  
Structure Property ◽  
Efficient Catalyst ◽  
Influence Of Process Parameters ◽  
Mixed Oxide Catalysts ◽  
Conversion Rates ◽  
Catalyst Life ◽  
Fuels And Chemicals

Photo catalytic reduction of carbon dioxide orartificial photo synthesisto yield hydrogen and hydrocarbons like methane, methanol etc., has emerged as a subject/process of intensive study due to its potential applications towards abatement of atmospheric CO2levels and conversion to fuels and chemicals. This Chapter provides a comprehensive picture of the process that has posed several scientific and technological challenges, like activation of most stable molecules-CO2and water, extremely low conversion rates, complex reaction pathways involving multi electron transfer steps and short catalyst life. All the major aspects/developments on this process like, the salient features and technological aspects, thermodynamic and kinetic characteristics, various types of photo-active catalysts-, like, titania based catalysts and titania with various dopants and modifiers, various metal oxides/sulfides/nitrides/ layered titanates, binary and ternary oxides of Nb, Ta, Ga & In mixed oxide catalysts, metal complexes, and supra molecular catalysts-, sensitization by macro cylic ligands, influence of process parameters, catalyst structure-property-activity correlations, aspects of deactivation of catalysts, reaction mechanistic aspects and sequential surface reaction pathways, recent trends and future directions have been covered. Design and development of efficient catalyst systems and achieving higher yield of desired products (higher selectivity) and extending the catalyst life are the key issues being pursued by the researchers. The process is in nascent stage and further improvements are needed as CO2conversion rates are extremely small, with products formed in terms of 1-10 micro moles/hr. One of the means of improving the process efficiency is to carry out electrochemical reduction of CO2using solar electric power, with an integrated Photo electrochemical cell (PEC). Yet another option is to reduce CO2to methanol with hydrogen produced using solar powered PEC.

scholarly journals Mathematical modelling of a staged pulverized coal gasification using O2/CO2 mixtures

2021 ◽  
Vol 2057 (1) ◽  
pp. 012064
Author(s):  
I G Donskoy
Keyword(s):  
Carbon Dioxide ◽  
Carbon Capture ◽  
Power Plants ◽  
Coal Gasification ◽  
Pulverized Coal ◽  
Process Efficiency ◽  
Transfer Coefficients ◽  
Process Change ◽  
Gasification Process ◽  
Gaseous Reagent

Abstract Conversion of pulverized coal in a two-stage gasifier is studied. When considering carbon capture power plants, mixtures of oxygen with carbon dioxide may be used as a gasification agent. Carbon dioxide is a gasification agent, so characteristics of the gasification process change significantly compared to gasification in oxygen-nitrogen mixtures. The conversion efficiency is determined by the thermophysical factor (change in the heat capacity of the gas mixture and transfer coefficients) and the concentration factor (increase in the concentration of the gaseous reagent). The ratio of primary and secondary fuel consumption determines the leading stage of the process. The influence of process efficiency on oxygen concentration is estimated in the range of 21–30 vol. %.

scholarly journals Bi-functional heterogeneous catalysts for carbon dioxide conversion: enhanced performances at low temperature

RSC Advances ◽  
2018 ◽  
Vol 8 (45) ◽  
pp. 25342-25350 ◽  
Author(s):  
Adrien Comès ◽  
Xavier Collard ◽  
Luca Fusaro ◽  
Luciano Atzori ◽  
M. Giorgia Cutrufello ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Low Temperature ◽  
Reaction Temperature ◽  
Heterogeneous Catalysts ◽  
Cyclic Carbonates ◽  
Carbon Dioxide Conversion

Novel bi-functional catalysts allowing to decrease the reaction temperature for the synthesis of cyclic carbonates below 150 °C were successfully synthesized.

scholarly journals Separating Hydrogen From Coal Gasification Gases With Alumina Membranes

1991 ◽  
Author(s):  
B. Z. Egan ◽  
D. E. Fain ◽  
G. E. Roettger ◽  
D. E. White
Keyword(s):  
Carbon Dioxide ◽  
Coal Gasification ◽  
Process Development ◽  
Porous Alumina ◽  
Mean Value ◽  
Knudsen Flow ◽  
Gasification Process ◽  
Alumina Membranes ◽  
Separation Factors ◽  
Membrane Permeabilities

Synthesis gas produced in coal gasification processes contains hydrogen, along with carbon monoxide, carbon dioxide, hydrogen sulfide, water, nitrogen, and other gases, depending on the particular gasification process. Development of membrane technology to separate the hydrogen from the raw gas at the high operating temperatures and pressures near exit gas conditions would improve the efficiency of the process. Tubular porous alumina membranes with mean pore radii ranging from about 9 to 22 A have been fabricated and characterized. Based on the results of hydrostatic tests, the burst strength of the membranes ranged from 800 to 1600 psig, with a mean value of about 1300 psig. These membranes were evaluated for separating hydrogen and other gases. Tests of membrane permeabilities were made with helium, nitrogen, and carbon dioxide. Measurements were made at room temperature in the pressure range of 15 to 589 psi. In general, the relative gas permeabilities correlated qualitatively with a Knudsen flow mechanism; however, other gas transport mechanisms such as surface adsorption may also be involved. Efforts are under way to fabricate membranes having still smaller pores. At smaller pore sizes, higher separation factors are expected from molecular sieving effects.

scholarly journals Mathematical modeling of a swirling jet in applications to low-emission combustion of low-grade fuels

2021 ◽  
Vol 23 (3) ◽  
pp. 308-317
Author(s):  
Usama J. Mizher ◽  
Peter A. Velmisov
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
Combustion Chamber ◽  
Negative Impact ◽  
Numerical Study ◽  
Combustion Process ◽  
Theoretical Data ◽  
Modern Society ◽  
Low Grade ◽  
Similar Solutions

Abstract. The search for new solutions in the field of energy, preventing negative impact on the environment, is one of the priority tasks for modern society. Natural gas occupies a stable position in the demand of the UES of Russia for fossil fuel. Biogas is a possible alternative fuel from organic waste. Biogas has an increased content of carbon dioxide, which affects the speed of flame propagation, and a lower content of methane, which reduces its heat of combustion. However, the combined combustion of natural gas and biogas, provided that the mixture of fuel and oxidizer is well mixed, can, on the one hand, reduce the maximum adiabatic temperature in the combustion chamber of power boilers at TPPs, and, on the other, increase the stability of biogas combustion. For the combined combustion of natural gas and biogas in operating power boilers, it is necessary to reconstruct the existing burners. For a high-quality reconstruction of burners capable of providing stable and low-toxic combustion of fuel, it is important to have theoretical data on the combustion effect of combustion of combinations of organic fuels on the temperature distribution in the combustion zone and on its maximum value. In this paper, self-similar solutions of the energy equation for axisymmetric motion of a liquid (gas) in a model of a viscous incompressible medium are obtained. Basing on them, a stationary temperature field in swirling jets is constructed. A set of programs based on the ANSYS Fluent software solver has been developed for modeling and researching of thermal and gas-dynamic processes in the combustion chamber. On the basis of the k - ϵ (realizable) turbulence model, the combustion process of a swirling fuel-air mixture is simulated. The results of an analytical and numerical study of the temperature and carbon dioxide distribution in the jet are presented.

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