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Supervisory control system for continuous drying

  • US 4,704,805 A
  • Filed: 10/20/1986
  • Issued: 11/10/1987
  • Est. Priority Date: 10/20/1986
  • Status: Expired due to Fees
First Claim
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1. Supervisory control arrangement system for controlling the operation of a dryer for the continuous drying of a moist solid product with a gaseous drying medium such as air for close control of the dried product moisture, which comprises:

  • temperature determining means for determining the wet bulb temperature of the medium in the dryer from the measurements of the prevailing outlet dry bulb temperature and outlet relative humidity of the medium in the dryer,supervisory adjustment means for determining from the measurements of the prevailing inlet dry bulb temperature and outlet dry bulb temperature of the medium in the dryer and from the determined wet bulb temperature a supervisory value corresponding to the energy supply rate of the heating energy supply needed for heating the medium to an optimum inlet dry bulb temperature operating value for drying the product to a predetermined moisture content at a predetermined medium flow rate and a predetermined product feed rate to the dryer, and for producing from the supervisory value in relation to the measurement of the prevailing outlet dry bulb temperature a corresponding supervisory signal, and;

    supervisory control means including energy supply control means for limiting the supervisory signal to a set point value which does not exceed a predetermined maximum supervisory value corresponding to a predetermined maximum energy supply rate for heating the medium to a predetermined maximum inlet dry bulb temperature operating value, and for producing from the set point value limited signal in relation to the measurement of the prevailing inlet dry bulb temperature a corresponding energy control signal for controlling the energy supply for heating the medium to an optimum inlet dry bulb temperature operating value which does not exceed said predetermined maximum operating value, whereby to prevent product scorching.

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