Pulverized coal plasma gasification

Abstract

A number of experiments on the plasma-vapor gasification of brown coals of three types have been carried out using an experimental plant with an electric-arc reactor of the combined type. On the basis of the material and heat balances, process parameters have been obtained: the degree of carbon gasification (ζc), the level of sulfur conversion into the gas phase (ζs), the synthesis gas concentration (CO+Hz) in the gaseous products, and the specific power consumption for the gasification process. The degree of gasification was 90.5-95.0%, the concentration of the synthesis gas amounted to 84.7–85.7%, and the level of sulfur conversion into the gas phase was 94.3–96.7%. Numerical study of the process of plasma gasification of coals was carried out using a mathematical model of motion, heating, and gasification of polydisperse coal particles in an electric-arc reactor of the combined type with an internal heat source (arc). The initial conditions for a conjugate system of nonlinear differential equations of the gas dynamics and kinetics of a pulverized coal stream interacting with the electric arc and oxidizer (water vapor) agree with the initial conditions of the experiments. The computation results satisfactorily correlate with the experimental data. The mathematical model can be used for the determination of reagent residence time and geometrical dimensions of the plasma reactor for the gasification of coals.

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Abbreviations

c i :

volume concentration of components (kmol m−3)

x :

longitudinal coordinate (m)

f i :

source members, determined by variation of the ith component due to chemical reactions in unit volume in unit time (kmol m−3s−1)

υ :

velocity (m s−1)

M s :

ash mass in one particle (kg)

C D :

particle drag coefficient

π:

3.14

r s :

particle radius (m)

d :

particle diameter (m)

ρ :

density (kg m−3)

C p :

heat capacity of components (J molt− K−1)

Q j :

thermal effect of reaction (J kmol−1)

Ej :

activation energy of reaction

N l :

volume concentration of particles of thelth fraction (m−3)

T :

temperature (K)

ε:

emissivity factor of coal particles

σ:

5.67 × 10−8, blackbody emissivity coefficient (W m−2 K−4)

P :

pressure (Pa)

S :

reactor cross section (m2)

D :

reactor diameter (m)

V :

reactor volume (m3)

L R :

reactor length (m)

F W :

friction force on the wall (N)

f g :

friction coefficient

τ:

residence time (s)

Nu:

Nusselt number

Re:

Reynolds number

Pr:

Prandtl number

λ:

thermal conductivity of gas (J m s−1 K−1)

R :

8.3 × 103, universal gas constant (J kmol K−1)

µ i :

molecular mass of component (kg kmol−1)

η :

dynamic viscosity coefficient of gas (kg m−1 s−1)

ξ :

thermal efficiency of plasma reactor

qarc :

specific heat flow from arc (W m−3)

P 1 :

heat supplied in vapor at T = 405 K (W)

P 2 :

heat loss to wall (W)

P 3 :

heat loss in the gas and slag separator chamber (W)

P 4 :

heat loss in the synthesis gas oxidation chamber (W)

P 5 :

heat loss in the slag catcher (W)

P 6 :

heat carried away in the off-gas (W)

ΔP:

heat input of arc (W)

P arc :

electric power of arc (W)

Qsp :

specific power consumption (kw Hr kg−1)

d w :

specific heat flow to wall (W m−2)

ξ c :

degree of carbon gasification (%)

ξ s :

level of sulfur conversion into gas phase (%)

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Correspondence to R. A. Kalinenko.

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Kalinenko, R.A., Kuznetsov, A.P., Levitsky, A.A. et al. Pulverized coal plasma gasification. Plasma Chem Plasma Process 13, 141–167 (1993). https://doi.org/10.1007/BF01447176

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Key words

  • Plasma gasification
  • lower-grade coals
  • electric-arc reactor
  • mathematical model of plasma gasification of coals