This paper considers the problem of scheduling the work cycles of multiple Sequential Batch Reactors. The paper proposes a decision model based on the Flow-Shop Scheduling Problem. Three tank sizes and tasks with variable number of phases were assumed. The application of the model for task scheduling has been tested using an optimisation algorithm. Task scheduling problems belong to NP-hard problems and are often solved by non-deterministic algorithms. The solution of the presented problem was realised by using the differential evolution algorithm for three different objective functions. Assuming both the criterion of minimising the maximum execution time (makespan) and the criterion of even operating time of the Sequential Batch Reactors.