Recycling of organic wastes is an extremely important and challenging environmental task. One of the promising trends in this field is the creation of multi-mode (combustion, pyrolysis and gasification) plants for processing organic wastes with production of such useful products as thermal energy and energy carriers (biocoal, bio-oil, pyrolysis resins, synthesis gas, etc.) and fertilizers. When creating such plants, the main problems include instability of the properties of a source material, its high water and ash content. This drives the developers to use non-standard equipment and atypical control algorithms, the creating of which requires a lot of experimental work to be done. At the same time, conducting field experiments is an expensive, difficult and long process that highlights the need for extensive use of mathematical and computer modeling. In this paper, mathematical models of elements of the gas-air path of the organic waste processing plant are obtained. The characteristics of the gas-air path of the plant as of an object of regulation for pressure in the lower and vacuum in the upper part of the combustion chamber are determined. The gas-air flow consists of the flue and the air ducts and serves to remove flue gases from the combustion chamber and supply air needed to maintain fuel combustion. When developing new automation systems, modeling allows assessing the applied solutions accurately, simplifying and reducing the cost of their development, solving the problems of system stability, optimizing transient processes, etc. The nonlinearity of the obtained mathematical models on the "the pressure at the inlet to the n-th section air-gas flow path — the pressure at the outlet of the n-th section of the air-gas flow path" channels, the nonstationarity of objects of control and dependence of their dynamic characteristics on operating mode of the plant are determined. Due to developed models, the two-way relationship of the gas and air paths has been revealed. When modeling, the gas-air flow of the plant is divided into several sections for which the mathematical models are obtained. They are required to synthesize controllers of flue gases vacuum in the upper part and the air pressure in the lower part of the combustion chamber.
A research team from ICT SB RAS is actively developing a system to control a pilot plant for processing organic waste automatically. The pilot plant can produce thermal energy and energy carriers (solid products, e.g. bio-coal, liquid products, e.g. bio-oil, and gaseous products, i.e. synthesis gas), for example, from biomass with different chemical composition and physical properties. The equipment can process "complex" types of waste characterized mainly by high moisture and high ash content. During tests of the pilot plant, the complexity of stabilizing the parameters of technological processes and ensuring the stability and reliability of operation of the equipment of the complex as a whole were identified. This is especially important when implementing high-temperature modes of biomass processing. In order to primarily solve these most important tasks, an automatic control system of the plant is being created. When a system for automatic control of technological parameters of the gas-air path of the pilot-industrial plant is developed, a mathematical model that describes the dynamic characteristics of the gas and air paths under various throughput rates of the plant was used. When determining mathematical models, a two-way relationship between the gas path and air path was identified (interchannel connections). When technologically complex real objects of control are being automated, in the inaccuracy of a priori information about the object, when the system operates in various uncertain external and internal situations, disturbing influences, a robust control method should be used. PID controllers were selected as corrective devices for stabilizing the technological parameters that characterize the operation mode of the gas-air path of the plant including pressure in the lower part and rarefaction in the upper part of the combustion chamber. The most appropriate method for determining the PID controller settings has been elected. Synthesis and simulation of the operation of the controllers of the pressure in the lower part and rarefaction in the upper part of the combustion chamber are performed. Basing on the results of mathematical modeling, the efficiency of the controllers of the pressure in the lower part and the rarefaction in the upper part of the combustion chamber for various loads of the plant has been shown, and their stability reserves by amplitude and phase are determined. The results of mathematical modeling of the stabilization contours of the technological parameters of the gas-air path of the plant are presented for two cases: without inter-channel connections and without the account of these connections. A simulation of the joint operation of the control circuits of the gas-air path of the plant is performed. Compensators for adjacent (interchannel) connections of the gas and air paths of the plant have been developed. The advantage of the proposed automation schemes is shown.
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