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Multiplicity of steady states of reaction-regeneration systems with a highly coking catalyst

  • A. G. Nagiev
Article

Abstract

A mathematical model of heat-transfer regimes is proposed for reactor-regenerator systems with powdered catalysts. The model takes into account feedbacks between the thermal and chemical processes. Thermal closeness and a temperature feedback parameter are the two parameters introduced in the model. Catalytic cracking is considered, and the existence of one, two, or three steady-state solutions is demonstrated, which, depending on process parameters, define eight types of topological structure. Process stability and control are discussed.

Keywords

Phase Trajectory Coke Formation Spend Catalyst Heterogeneous Catalytic Process Coke Yield 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notation

A

heat removal parameter

C

degree of coking of the regenerated catalyst,g/g

C0

degree of coking of the spent catalyst, g/g

c

specific heat, kJ/(kg K)

D

parameter accounting for heat loss through the apparatus surface, kJ/kg

d

coking capacity of the feedstock

E

activation energy, kJ/(mol K)

F

mass flux, kg/h

f

dimensionless mass flux

Gcat

weight of catalyst in the fluidized bed, kg

gcat

dimensionless catalyst weight

ΔH

enthalpy of the main reaction

Q

nominal heat abstraction, kJ/h

q

heat of combustion, kJ/kg

R

universal gas constant, J/(mol K)

T

reactivation temperature, K

T0

reaction temperature, K

t

time, h

t*

catalyst residence time in the reactivator, h

u1

dimensionless heat-balance parameter of the reactor

U2

heat-balance parameter of the reactor; K

u2

dimensionless heat-balance parameter of the reactor

W(C, T)

rate of coke combustion, h-1

w(ε, θ)

normalized rate of coke combustion

Z(C, T)

specific coke yield in the main reaction, kg/kg

z(ε, θ)

normalized specific coke yield

α1, α2

mass-balance parameters of the system

β12

heat-balance parameters of the system

γ1, γ2

characteristic parameters of the system

δ

catalyst adsorption capacity, kg/kg

ε

dimensionless degree of coking of the catalyst

θ

dimensionless reactivation temperature

θ0

dimensionless reaction temperature

θcr

dimensionless maximum reactivation temperature

ρ

density, kg/m3

τ

dimensionless time

ψ

degree of conversion of the feedstock

ω

thermal stability region of the system

Indexes

ads

adsorbed hydrocarbons

air

air

feed

feedstock

env

environment

cat

catalyst

*

nominal valu

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References

  1. 1.
    Tanatarov, M.A., Levinter, M.E., and Akhmetshina, M.I., Kinetic Equations for Coking on a Cracking Catalyst, inNeftepererabotka i neftekhimiya (Petroleum Refining and Petrochemistry), Ufa: BashNII, 1968, p. 37.Google Scholar
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Copyright information

© MAIK “Nauka/Interperiodica” 2000

Authors and Affiliations

  • A. G. Nagiev
    • 1
  1. 1.Azerbaijan Industrial InstituteAzerbaijan

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