A tubular fixed-bed reactor filled with solid sorben consisting of zeolite pellets is considered for removing carbon dioxide from biogas to produce biomethane. To generate biomethane continuously, three batch reactors are operated in coordinated cycles. The control system has a two-level structure: a high-level coordination algorithm determines the transition from one process step to the next for each reactor and calculates references for the low-level controllers of each reactor; the low-level controllers adjust process variables, such as inlet gas flow rate, inlet or outlet gas pressure, and sorbent temperature, according to the references.

In this work, we first model the batch process by conservation equations of mass, energy and momentum. Concurrent adsorption of methane is also taken into account. The model parameters are identified by a two-step procedure, using experimental measurements from two plants: one laboratory-scale (located in Piacenza) and one pilot-scale (located in Camposampiero). Using the identified model, a control system is designed to coordinate three batch reactors.