Simulation of non-catalytic gas–solid reactions: application of grain model for the reduction of cobalt oxide with methane

Abstract

A mathematical model based on grain model, is presented. The model considers dynamic changes of gas and solid concentrations and temperature in the pellet of the solid reactant. In addition, structural changes of solid reactant (porosity and grain size changes) and diffusion of gaseous reactants through the product layer are considered. Effective diffusion coefficient is assumed to change with porosity in the pellet as a quadratic function in the mass balance equation. Effective heat capacity and conductivity are also modelled as functions of porosity in the heat balance equation. The finite volume method has been selected for solving mass and heat balance equations in the pellet and the computations are done by a program developed in MATLAB. The results of the program show good agreement in comparison with analytical solutions for both isothermal and non-isothermal systems. The model was used to simulate the reduction of cobalt oxide with methane and also the carbon gasification reaction with carbon dioxide. The results show good agreement for experimental conditions where both chemical kinetics and product layer diffusion are significant in the first reaction and the reaction obeys a non-linear chemical kinetics in the second reaction.

Keywords

SIMULATION NON-CATALYTIC GAS-SOLID REACTIONS GRAIN MODEL REDUCTION OF COBALT OXIDE WITH METHANE

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References

WEN

C. Y

: ‘Noncatalytic heterogeneous solid fluid reaction models’, Ind Eng. Chem., 1968, 60, 34–54.

RAMACHANDRAN

P. A.

and DORAISWAMY

L. K.

: ‘Modeling of noncatalytic gas-solid reactions’, AIChE.1, 1982, 28, 881–900.

UHDE

and HOFFMANN

: Noncatalytic gas—solid reactions: modelling of simultaneous reaction and formation of surface with a nonisothermal crackling core model’, Chem. Eng. Sc., 1997, 52, 1045–1054.

ABBA

I. A.

and HASTAOGLU

M. A.

: ‘Modelling of multi gas-solid reactions: effect of inert solids’, Trans IChemE, 1997, 75 Part A, 33–41.

SZEKELY

, EVANS

J. W

and SOHN

H. Y

: ‘Gas—solid reactions’, Chapter 4, New York, Academic Press, 1976.

SZEKELY

and EVANS

J. W.

: ‘Studies in gas-solid reactions: part II. An experimental study of nickel oxide reduction with hydrogen’, Met. Trans., 1971, 2, 1699–1710.

SZEKELY

and UN

C. I.

: ‘The reduction of nickel oxide discs with carbon monoxide’, Met. Trans., 1976, 7B, 493.

EVANS

J. W

, SOHN

and LEON-SUCRE

C. E.

: ‘The kinetics of nickel oxide reduction by hydrogen, measurements in a fluidized bed and in a gravimetric apparatus’, Met. Trans., 1976, 7B, 55–65.

COSTA

E. C.

and SMITH

J. M.

: ‘Kinetics of noncatalytic, nonisothermal, gas-solid reactions: hydrofluorination of uranium dioxide’, AIChE.1, 1971, 171, 947–958.

10.

GIBSON

J. B.

and HARRISON

D. P.

: The reaction between hydrogen sulfide and spherical pellets of zinc oxide’, I & EC, Proc. Des. Dev., 1980, 19, 231.

11.

PAT1SSON

, FRANCOIS

M. G.

and ABLITZER

: ‘A non-isothermal, non-equimolar transient kinetic model for gas-solid reactions’, Chem. Eng. Sc., 1998, 53, 697–708.

12.

LIU

and BHATIA

S. K.

: ‘Solution techniques for transport problems involving steep concentration gradients: application to noncatalytic fluid solid reactions’, Comput. Chem. Eng., 2001, 25, 1159–1168.

13.

WAKAO

and SMITH

J. M.

: ‘Diffusion in catalyst pellets’, Chem. Eng. Sc., 1962, 17, 825–834.

14.

MASON

E. A.

, MALINAUSKAS

A. P.

and EVANS

R. B.

: ‘Flow and diffusion of gases in porous media’, .1. Chem. Phys., 1967, 46, 3199–3216.

15.

R. B.

, STEWART

W E.

and LIGHTFOOT

E. N.

: ‘Transport phenomena’, chapter 16, New York, Wiley, 1960.

16.

RANZ

W. E.

and MARSHALL

W. R.

: ‘Evaporation from drops’, Chem. Eng. Prog, 1952, 48, 141-146, 173–180.

17.

VERSTEEG

H.K.

and MALALASEKERA

: ‘An introduction to computational fluid dynamics, the finite volume method’, chapter 8, London, Adison Wesley Longman, 1995.

18.

KHOSHANDAM

: ‘Reduction of cobalt oxide, chromium oxide, and manganese oxide with methane’, chapter 3, Unpublished PhD Thesis, Amir-Kabir University of Technology (Tehran Polytechnic), Tehran, Iran, 2003.

19.

SOHN

H. Y.

and WADSWORTH

M. E.

: ‘Rate processes of extractive metallurgy’, New York, Plenum, 1979.

20.

HARTMAN

and COUGHLIN

R. W

: ‘Reaction of sulfur dioxide with limestone and the influence of pore structure’, Ind Eng. Chem. Proc. Des. Dev., 1974, 13, 248–253.

21.

HARTMAN

and COUGHLIN

R. W

: ‘Reaction of sulfur dioxide with limestone and the grain model’, AIChE.1, 1976, 22, 490–498.

22.

SZEKELY

, LIN

C. I.

and SOHN

H. Y

: ‘A structural model for gas-solid reactions with a moving boundary V An experimental study of the reduction of porous nickel-oxide pellets with hydrogen’, Chem. Eng. Sc., 1973, 28, 1975–1989.

23.

CHU

W F.

and RAHMEL

: ‘The kinetics of reduction of chromium oxide by hydrogen’, Met. Trans. B., 1979, 10B, 401407.

24.

CANNON

K. J.

and DENBIGH

K. J.

: ‘Studies on gas-solid reactions. I The oxidation of zinc sulfide’, Chem. Eng. Sc., 1957, 6, 145–154.