TECHNIQUE OF AUTOMATIC CONTROL OVER PROCESS OF DISPERSION MATERIALS DRYING IN ACTIVE HYDRODYNAMICS DEVICES WITH HEAT MEDIUM RECIRCULATION

摘要

FIELD: heating, drying.;SUBSTANCE: invention relates to drying machinery immediately dealing with techniques of automatic control over the process of dispersion materials drying in active thermodynamics devices with heat medium recirculation; it is to be implemented in such spheres as food and chemical industries as well as other economy branches allied thereto. The proposed technique of automatic control over the process of dispersion materials drying in active thermodynamics devices with heat medium recirculation envisages the dispersion material(s) pre-drying and drying and measurement of the following parameters: feed material flow rate, moisture content and temperature, ready dried material flow rate and moisture content, flow rate, moisture content and temperature of the heat medium supplied and moisture content of the heat medium discharged. Data retrieved by the sensors performing measurement of the feed material flow rate, moisture content and temperature, ready dried material flow rate and moisture content, flow rate, moisture content and temperature of the heat medium supplied and moisture content of the heat medium discharged is transmitted to a microprocessor unit. The latter, using an embedded algorithm, specifies the optimum thermal regime and heat medium delivery regime depending on the content of moisture and heat in the feed material and material to have undergone drying treatment and operates the executive mechanisms of the calorifiers and the blower fans to provide for establishment of the optimum regime (mode) aforesaid with a view of ensuring reliable maintenance of the preset parameters of the material being treated. The above process additionally envisages deployment of sensors registering wattage consumption with the calorifiers and the blower fans with the information thus retrieved transmitted to the microprocessor unit that performs continuous calculation of total power consumption per weight unit of the material being treated. In case of a power consumption increase or decrease registered the microprocessor unit generates a command to accordingly decrease or increase the heat medium temperature and flow rate. Optimum feed material flow rate value is taken to be determined by minimisation of the power consumption cost function. In addition to that the drying process control regime is initially adjusted with tangentially delivered fluxes of heat medium whose temperature and flow rate are modulated based on deviation of the currently actual quantity of moisture being evaporated within the suspension-and-swirl layer dryer zones from the values preset. After that if modulation of temperature and flow rate of the tangentially delivered fluxes of heat medium fails to ensure maintenance of the required value of moisture content in the material to have undergone treatment, temperature and flow rate of the heat medium axial flux are modulated. The innovation consists in one of the rapid dryer sections being pre-dried with the heat medium discharged and in drying with the suspension-and-swirl layer dryer being performed within the discharged heat medium recirculation system. Depending on the moisture content in the discharged heat medium within each of the three sections the discharged heat medium may either be mixed with or give up heat to the atmospheric air delivered in auxiliary calorifiers. The auxiliary valves the heat medium delivery system is equipped with enable direction of the atmospheric air supplied into the auxiliary calorifiers (when the discharged heat medium due to its high moisture content is delivered for heat exchange into the auxiliary calorifiers on a command issued by the microprocessor unit). If the content of moisture in the discharged heat medium is insignificant the microprocessor unit commands to deliver it for mixture with the atmospheric air supplied with the valves directing the atmospheric air supplied to bypass the auxiliary calorifiers which finally results in reduction of resistance in the heat medium delivery system. Additionally control is exercised over entrainment of the material being treated with the help of sensors of feed material flow rate and feed material and ready-dried material moisture content; based on their readings the microprocessor unit calculates the amount of the ready-dried material without allowance for entrainment. The actual amount of the ready-dried material is registered by the ready-dried material flow rate sensor. Based on the data retrieved the microprocessor unit calculates the amount of the ready-dried material entrainment by the discharged heat medium and, depending on the currently applicable requirements to the drying process, generates a command to modulate operation of the blower fans executive mechanisms to provide for the heat medium delivery rate reduction.;EFFECT: improved quality of the material to have undergone treatment; environmental impact minimisation; specific energy consumption decrease; reduction of material entrainment during drying.;1 dwg