Development of a spray dryer’s mathematical model for control tasks

Abstract

The sustainable development paradigm includes the most efficient material and energy resources using in production processes. One of the ways to achieve this goal is creating the effective automated control systems. At the same time, such systems effective functioning is impossible without adequate mathematical models for control objects. Thus, the actual task of this study is to create the control object – a spray dryer -model-, which could be used in the control system. It was established that one of the main devices in the sodium tripolyphosphate production is a spray dryer in which the aqueous salts suspension is dried by flue gases. The obtained powdery product which is fed into the calcination furnace. The work investigated convective drying, where the material is in direct contact with the drying agent – furnace gas. To drying process control by the drying agent temperature. The existing works analysis showed that the mathematical model developing process of a spray dryer requires in-depth research into the physical nature of processes which taking object's operation’s various factors into account. The object presentation can be carried out with different approaches taking into account various important production factors, but at the same time it should be as close as possible to the nature of process. The development of the spray drying process model is carried out for regulation the moisture at the finished product. The beginning of the research is the structural and parametric diagram creation of a spray dryer taking into account all input and output values which allow to determine the control disturbance channels. A material balance based on the moisture and loose matter amount and a gas environment heat balance is compiled. The transfer functions component calculation is carried out using the Kramer method. The presented results of the research make it possible to build and analyse the spray dryer mathematical model taking into account the requirements for the substance moisture content be dried and the control process analysis by the drying agent temperature changing. The transient characteristics of the spray dryer by the disturbance and control channels, which are calculated and presented in the research make it possible to compare the control object behaviour with and without taking heat loss into the environment the assumptions into account.