ADM1 Aspen simulation

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  • #619
    AvatarANTONIO
    Participant

    Hello
    i would to simulate anaerobic digestion by mean Aspen plus with ADM1 model.
    my goal is to investigate the variations of CH4 and CO2 in effluent gas with the variation of CSTR reactor temperature.

    The simulations run only with the temperature of 55°C that is reported in model, i try to simulate with lower temperature but the system gives always error :

    ** ERROR PRE-EXPONENTIAL FACTOR IN POWER LAW EXPRESSION
    FOR REACTION NUMBER ‘4’ IS LESS THAN
    ZERO. ITS REACTION RATE IS SET TO ZERO.

    Can i resolve this problem?
    i try also to remove the components of reaction numebr 4 but always the error appear..

    thanks in advance

    #620

    The pre-exponential (k) parameter should be a positive number. Perhaps you have it as a negative number? The equation in aspen is usually in the form of -rA = k * concentration_stuff, and you just type in the k, not -k.

    #621
    AvatarANTONIO
    Participant

    Thank you thomas
    i agree with you!
    i also check the equation
    i don’t type a negative number , the value for k is always a positive number.

    The setting of Aspen give me two options for the power law kinetic expression:

    IF T0 is specified KINETIC FACTOR = k(T/T0)^n *exp -(E/R)[1/T-1/T0)]
    IF T0 is not specified KINETIC FACTOR = kT^n *exp -(E/RT)

    for example we have from the model :

    k=1,27 e-06
    n=0
    E=-1,41 e+07 j/kmol
    T0=328,15 K

    the error always appear

    Could we avoid to set the T0 value??

    #635

    I don’t know. You could also try posting your model and see if someone knows what the problem is.

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