Abstract BatchKit is a knowledge integration environment for process engineering. It provides a broad range of problem representation and solving capabilities, from trivial calculations and simple inferences to complex optimization problems that are addressed by the integration of problem solvers of varying generality such as GAMS (general modelling language and optimization solvers) or SPEEDUP (mass and energy equilibrium and dynamic process simulator for chemical processing plants). BatchKit currently provides prototype conceptual models of plants, processes, production plans and their various specializations. Representation is based on the integration of object-oriented, logic and constraint programming. The integration of logic programming (LP) supports backtracking search formulations and problem analysis (such as problem-specific consistency checks) using resolution-based inference. The integration of constraints as in constraint logic programming (CLP) rounds up the modelling capabilities by introducing the equations and inequalities and establishes the prerequisites of integrating the special-purpose solvers. Human interaction widely relies upon graphic interfaces developed and implemented using the graphic building tools of the KEE system by IntelliCorp. Knowledge maintenance is facilitated by providing multiple external representations for every type of object-graphs, tables and, for more detailed inspection, an assert and query language of the logic programming. Complete history is maintained to support chronological backtracking or checkpoint rollback and knowledge state backup.