You can increase or decrease the amount or concentration of a species by a constant value using a zero-order rate rule. For example, suppose species c increases by a constant rate k.
reaction: none rate equation: none rate rule: dc/dt = k species : c = 10 mole(initial amount) parameters: k = 1 mole/second
The analytical solution is c = kt + co, where co is the initial amount or concentration of the species c.
Enter the rule described above as c = k. Set the RuleType property to rate, enter the values for c and k, and then simulate.
Alternatively, you could model a constant increase in a species using Mass Action reaction null -> C.