METHOD TO CONTROL DRYING PROCESS Russian patent published in 2013 - IPC F26B25/22 F26B21/04 A23B9/02 

FIELD: heating.

SUBSTANCE: method to control grain drying process provides for preliminary heating of moist grain, its drying and cooling; supply of a mixture of drying agent after grain drying and cooling into a cyclone for cleaning from suspended solid matter it contains; cooling and drying of the mixture in a cold receiver of a steam ejector refrigerating machine; heating of one part of the mixture in a condenser of the steam ejector refrigerating machine and the heater with subsequent supply first to a dryer, and then into the cyclone to create a closed circuit, cooling of the grain with another part of the mixture; production of the working steam in a steam generator with electric heating elements and a safety valve and its supply under pressure of 0.8…1.0 MPa into the ejector nozzle, creating at the same time lower pressure of 0.0009…0.001 MPa and temperature of 4…7°C in an evaporator of the steam ejector refrigerating machine with recirculation of coolant in the cold receiver; supply of coolant vapours and working steam downstream the ejector with pressure of 0.2…0.3 into the condenser for heating of the drying agent; supply of one part of condensate generated in the condenser, into the evaporator to make-up water loss and removal of its other part together with the condensate generated in process of drying agent cooling in the cold receiver, first into the condensate collector, and then into the steam generator with formation of a closed cycle; measurement of grain consumption prior to drying, moisture and temperature of grain before and after drying, temperature of cooled grain, temperature and flow rate of a drying agent in zones of drying and cooling, the underpressure value in the evaporator and flow rate of the ejected steam of the coolant from the evaporator, temperature of coolant in the evaporator, level of condensate in the evaporator; using measured values of flow rate and moisture content of the drying agent mixture after drying and cooling of grain, they determine amount of water vapours in the spent drying agent, according to which the coefficient of ejection of the steam ejector refrigerating machine is established by action at the ratio of flow rates of working steam supplied into the ejector nozzle, and ejected from the evaporator, by variation of the working steam flow; the current value of ratio of heat transfer from the coolant to the drying agent via the cooling surface of the cold receiver is determined; besides, if the temperature of the drying agent supplied to the cooling of grain deviates from the specified interval to the side of increase, the coefficient of heat transfer is increased by increasing the ejection ratio by action at increase of the working steam flow rate at the inlet to the ejector's nozzle, and in case of deviation of temperature of the drying agent supplied to grain cooling from the specified range of values to the side of decrease, the heat transfer ratio is reduced by reduction of the ejection coefficient by action at reduction of working steam flow rate at the inlet to the ejector's nozzle. On the basis of temperature of the drying agent downstream the condenser the steam flow to the heater is established, as well as the flow rate of the drying agent into the drying zone with correction by temperature and moisture of grain after drying; by temperature of the drying agent downstream the cold receiver, the flow rate of the drying agent is established into the cooling zone.

EFFECT: method makes it possible to narrow a range of drying agent parameters from specified values, and accordingly to stabilise mode of drying in the area of the specified process properties of grain; to reduce field of allowance for final moisture, reducing its spread, to increase efficiency of a dryer and to reduce specific power inputs, due to rational use of drying agent potential in a recirculation circuit specified by accuracy of its parameters control.

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