NOVELTY - The control arrangement comprises: a unit (202) for performing an asynchronous chemical reaction rates calculation process of fuel composition and fuel flow rate to accomplish information in an iterative process on a recirculation ratio of the fuel recirculation through anodes; a unit (204) for generating fuel utilization information and carbon formation information in a synchronous process with the system controller process by utilizing the latest available recirculation ratio information provided by an asynchronous process; and a unit (206) for performing an active cyclic system control.    USE - The control arrangement is useful in a fuel cell system for producing electricity.    ADVANTAGE - The control arrangement improves the efficiency and lifetime of the fuel cell system thus rapidly producing electricity in an environmentally friendly manner.    DETAILED DESCRIPTION - The control arrangement comprises: a unit (202) for performing an asynchronous chemical reaction rates calculation process of fuel composition and fuel flow rate to accomplish information in an iterative process on a recirculation ratio of the fuel recirculation through anodes; a unit (204) for generating fuel utilization information and carbon formation information in a synchronous process with the system controller process by utilizing the latest available recirculation ratio information provided by an asynchronous process; and a unit (206) for performing an active cyclic system control and a system monitoring process by utilizing the fuel utilization information and carbon formation information. The asynchronous process processing unit is performed simultaneously with the synchronous process so that the active cyclic system control and system monitoring process are processed below maximum allowed execution interval. Each fuel cell system comprises an anode side, a cathode side and an electrolyte between the anode side and the cathode side. The fuel cell system comprises a unit for recirculating fuel through the anode sides of the fuel cells, and a system controller in a control processor for controlling the operation of the fuel cell system. The arrangement further comprises: units, which are integrated to a same control processor with the system controller; a unit for processing the asynchronous process simultaneously with the synchronous process in which is performed by using the means recalculations of the fuel utilization information and carbon formation information for each control cycle of the synchronous process based on the latest recirculation ratio information retrieved from the asynchronous process to the synchronous process in each control cycle of the synchronous process or seldom; a unit for performing the asynchronous process by utilizing in the iterative process an iterative algorithm for cyclic execution so that a limited amount of operations is executed on single control cycle of the synchronous process; a unit for performing the synchronous and asynchronous processes simultaneously by accomplishing, in the asynchronous process and in some of the control cycles of the synchronous process, information on chemical reactions to intensify time utilization in the synchronous process; and unit for performing the asynchronous process by accomplishing chemical reaction rates as the information on the chemical reactions. An INDEPENDENT CLAIM is included for a control method for a fuel cell system to produce electricity with fuel cells.    DESCRIPTION OF DRAWING(S) - The diagram shows a block diagram of a control arrangement in a fuel cell device.    Fuel heat exchanger (105)    Reformer (107)    System controller (200)    Unit for performing asynchronous chemical reaction rates calculation process (202)    Control processor. (210)