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This paper has analyzed the functioning conditions for the technological system of secondary condensation (TSSC) in a typical ammonia synthesis unit of the AM-1360 series with the use of a system-control approach. The coordinates of control vectors and external disturbances have been determined. An algorithm has been developed for predicting the coordinates of the control vector for the subsystem of decision support under the conditions of external disturbances for such a complex inertial object with high metal consumption as TSSC. The method of mathematical modeling was used to determine, based on the developed algorithm, the patterns and quantitative dependences of the influence of external disturbances such as the temperature of primary condensation and the flow rate of circulation gas on the efficiency of TSSC heat exchange processes. The regularity of increase in the heat flows and coordinates of control vector with an increase in the temperature of primary condensation has been established. The parametric sensitivity of the coordinates of the control vector under the conditions of change in the temperature of the primary condensation has been determined, which, compared with the circulation gas flow rate, exceeds it by more than six times. The executed software implementation of the algorithm employing the MATLAB programming environment makes it possible, owing to the embedded client part (ORC client), free software access to the current data on the technological process. The functional structure of computer-integrated TSSC technology with the proposed correction subsystem under a supervisory control mode has been designed. Correction solutions involving the additional hardware and software based on the programmable logic controller VIPA and SCADA-system Zenon have been practically implemented. The implementation of the developed system ensures the stabilization of the secondary condensation temperature at the regulatory level of −5 °C, which reduces the consumption of natural gas by almost 1 million nm3 per year.

The object of research is the technological complex of secondary condensation (TCSC) and the control system of a typical ammonia synthesis unit of the AM-1360 series. The analysis of the conditions of its functioning and hardware and technological design was carried out. The coordinates of the control vector are determined. The features of the proposed functional diagram and the necessary algorithmic software for the computer-integrated control technology of the TCSC with a correction subsystem for decision-making under uncertainty are established. The implementation of the proposed solutions is complicated by the use of the information and control complex TDC-300 (USA) with closed-type software installed on the existing ammonia synthesis units. The need for such a control complex to implement a decision-making subsystem under conditions of uncertainty is shown to supplement the existing control system with hardware and software of an «open» type. A computer-integrated TCSC technology based on a three-level hierarchical structure has been created. The implementation of the zero and first levels of such a structure form single software and hardware complex consisting of a programmable logic controller and an automated operator's workplace based on an industrial computer with installed software. A software implementation of decision-making on the correction of the coordinates of the control vector by additional hardware and software based on the VIPA logic controller and the Zenon SCADA system was made. A scheme of network information flows has been implemented, which illustrates the functioning of the decision-making correction subsystem in the general structure of the TCSC computer-integrated control technology. Implementation of the developed system allows, under the existing uncertainties, to reduce the secondary condensation temperature by an average of 3 °C, which ensures an annual reduction in natural gas consumption by 1 million nm3. The proposed approach to the possibility of combining «open» and «closed» type hardware and software can be applied in other industries.