How to simulate a counter current fixed Bed Reactor

Hey,

my actual Code ist below

% Iterationsschleife im Zersetzer
for i=2:length(t)
    nNa(i)=nNa(i-1)-r(i-1);
    cNa(i)=nNa(i)/(nHg+nNa(i));
    mNa(i)=nNa(i)*MNa/1000;
    nEtOH(i)=nEtOH(i-1)-r(i-1)-nvEtOH(i-1);
    mEtOH(i)=nEtOH(i)*MEtOH/1000;
    nNaEt(i)=nNaEt(i-1)+r(i-1);
    mNaEt(i)=nNaEt(i)*MNaEt/1000;
    cNaEt(i)=nNaEt(i)/(nEtOH(i)+nNaEt(i));
    wNaEt(i)=mNaEt(i)/(mEtOH(i)+mNaEt(i));
    y(i)=fun_Leitfaehigkeit(cNaEt(i),T(i-1)); %elektr. Leitfähigkeit in 1/Ohm oder S/m
    eta(i)=fun_NatriumethylatViskositaet(wNaEt(i),TK(i-1))/1000; %Viskosität in kg/(m*s)
    rho(i)=fun_EthylatDichte(wNaEt(i),TK(i-1)); % Dichte in kg/m³
    cel(i)=wNaEt(i)/MNaEt*rho(i)/1000; %Elektrolytkonzentration in mol/m³
    D(i)=y(i)*R*TK(i-1)/F^2; %Diffusionskoeffizient in m²/s
    Sc(i)=eta(i-1)/rho(i-1)/D(i-1); %Schmidt-Zahl
    Re(i)=1/(1-Epsilon)*rho(i)*vl/eta(i)*dKat; %Reynolds-Zahl Kurzweil S.289
    Sh(i)=A*Re(i)^B*Sc(i)^C; %Sherwood-Zahl
    j(i)=Sh(i)*F*D(i)/dh; %Stromdichte in A/m²
    I(i)=j(i)*AKat; %Stromstärke in A
    rk(i)=I(i)/F; % Reaktionsgeschwindigkeit in mol/s
    k(i)=k0*exp(-EA/(R*TK(i-1)));
    rr(i)=k(i)*cNa(i)^0.5; %Reaktionsgeschwindigkeit in mol/s
    if rk(i)>rr(i);
        r(i)=rr(i);
    else r(i)=rk(i);
    end
    H2(i)=r(i)*0.5;
    nvEtOH(i)=H2(i)/(1-x);
    HvEtOH(i)=dHvEtOH*nvEtOH(i);
    Gr(i)=Hr-Sr*TK(i-1)/1000+Hsolv;
    cpEt(i)=fun_Waermekapazitaet(cNaEt(i),TK(i-1)); % in J/mol
    dGr(i)=r(1)*Gr(i)+HvEtOH(i); %in kJ/mol
    dTK(i)=abs((dGr(i)*1000-QHgdt)/(cpEt(i)*((nNaEt(i)+nEtOH(i)+nvEtOH(i)))));
    TK(i)=TK(i-1)+dTK(i);
    T(i)=TK(i)-273.15;
end
goal=(nNa(1)-nNa(end))==3527

This Code runs my fixed Bed Reactor as a cocurrent Reactor with variables nEtOH and nNa. I want to write this code as a countercurrent Reactor, nEtOH(1) meets nNa(end) and nEtOH(end) meets nNa(1) and i have absolutly no idea how to do this. A classic logarithmic mean concentration difference is not accurate enough.

I have build this model on the Data from my Reactor. In this example nNa(1) and nEtOH(1) is given, but i also want to let this loop calculate nNa(1) itself, by defining my "goal". Help is higly welcome.

Answer 1

[Mrutyunjaya Hiremath]

Here's how you can modify your code for a countercurrent reactor:

% Update initial conditions for countercurrent reactor
nNa(1) = % Define the initial value for nNa(1) (e.g., nNa_initial_value)

% Iterationsschleife im Zersetzer
for i = 2:length(t)
    % ... (existing code remains the same) ...
    
    % Update boundary conditions for countercurrent reactor
    nNa(end) = % Define the value of nNa at the end (e.g., nNa_end_value)
    nEtOH(end) = % Define the value of nEtOH at the end (e.g., nEtOH_end_value)

    % ... (remaining code remains the same) ...
    
    % Check if the goal is met
    goal = (nNa(1) - nNa(end)) == 3527;
    if goal
        break; % Exit the loop if the goal is met
    end
end

• In the code above, you need to define the initial value for nNa(1) as well as the values for nNa at the end and nEtOH at the end, based on your specific problem and conditions. The loop will continue until the goal is met, i.e., (nNa(1) - nNa(end)) is equal to 3527.
• Keep in mind that modifying the reactor type from cocurrent to countercurrent may require further adjustments to the equations and parameters, depending on the specific characteristics of your system. Make sure to double-check the physical meaning of each parameter and equation to ensure the model accurately represents the countercurrent reactor.

[Kevin]

thank you for your quick response.