1. Converting a Chemical Engineering Problem into Excel VBA Program
Problem Solving
Converting a Chemical Engineering Problem into Excel VBA Program

2. Problem: Batch Reactor
A batch reactor is used to carry out a 1st order reaction: A  B
-r = k * [A]
d[A]/dt = -r
d[B]/dt = r
Initial concentrations: [A]0, [B]0.

3. Program Requirements Calculation mode: User need to input:
Find the final concentrations and yield with given initial conditions, and given reaction time.
User need to input:
[A]0, [B]0, k, t, Δt ( iteration step size for solving the differential equations )
Above values are positive decimal numbers, Δt > 0.
Expected output:
[A]t, [B]t, Y = ([A]0 - [A]t ) / [A]0
Above values are positive decimal numbers.

4. Numerical Method for Solving Differential Equations
Simplest method – Euler method.
Solving dx/dt = f(x).
At time t, we have value xt.
We can calculate the slope at time t as f(xt).
The new value of x at t + Δt:
xt+Δt = xt + f(xt) * Δt
Repeat the above steps from t = 0 to the end.