Modernization of the digital control system for the beer pasteurization process

The article is devoted to solving the problems of automation of the pasteurizer in LLC «Baltika Brewing Company» - «Voronezh Brewery» to improve the quality of control. The control system structure was developed based on the SIEMENS S7-400 controller, input/output modules SM321, SM331, SM322, SM332 and IEI PPC-5190A touch panel. The equipment includes local automation tools: SENSYCON PT100 temperature sensors; Endress+Hauser Cerabar S PMC631, Aplysens 0…10 bar pressure sensors; Endress+Hauser electromagnetic flow meters; HAFFMANS-PENTAIR oxygen meter; Enress+Hauser CLD134-PLC148AB2 conductivity meter; SPIRAX SARCO valves. The DANFOSS 131B2132 FC-302 frequency converter was adjusted to control the pump to enable working with small beer flows. Algorithmic and software support for the SIEMENS S7-400 control controller (Step7 environment) and the IEI PPC-5190A touch panel (WinCC environment) has been developed. To control the pasteurization process, it is proposed to implement a scheme for combined beer temperature control (steam flow rate) with disturbance compensation based on the heating steam pressure in the pipeline. To synthesize the algorithm for digital combined control, discrete dynamic models of the control channel (“heating steam flow rate – beer temperature at the pasteurization section outlet”) and the disturbance channel (“steam pressure in the coolant supply pipeline – beer temperature at the pasteurization section outlet”) were identified. The channel models were identified based on the experimental data obtained on the pasteurizer using the least squares method (LSM). A numerical optimization method (coordinate descent method) was used to calculate the settings of the digital PID controller and compensator for the control and disturbance channels. Model experiments were conducted, which showed that the use of this algorithm significantly reduces the fluctuation of beer temperature during pasteurization. To synthesize the algorithm, the author's programs for identifying discrete dynamic models of object channels and optimizing the settings of digital regulators and compensators were used. The process control system was put into operation.