Hot spot detection and supression system

A method for controlling the peak temperature in a rotary heat exchanger of the type including a stationary housing having a central axis, a matrix of heat exchange material supported to revolve within the housing about said axis, gas inlet and outlet ducts for introducing a flow of hot gas into the matrix to raise the temperature of the matrix and discharging the gas from the matrix, respectively, air inlet and outlet ducts for introducing a flow of cold air into the matrix to reduce the temperature of the matrix and discharging the air from the matrix, respectively, wherein the method comprises the steps during rotary operation, of:

• sensing a matrix variable indicative of the peak temperature in the matrix and identifying the localized portion of the matrix having the peak temperature;
• maintaining a source of temperature suppressant adjacent the revolving matrix,
• generating an excess temperature signal when the peak temperature as sensed exceeds a threshold value;
• and
• in response to the excess temperature signal, automatically discharging the temperature suppressant into the localized portion of the matrix.

A heat exchanger comprising:

• a stationary housing having hot and cold ends;
• a matrix of heat exchange material supported to revolve within the housing about an axis of revolution passing through the hot and cold end;
• gas duct inlet means and gas duct outlet means fluidly connected to the housing, for introducing a flow of hot gas into the matrix at the housing hot end to raise the temperature of the matrix, and discharging the gas from the matrix at the housing cold end, respectively;
• air duct inlet means and air duct outlet means fluidly connected to the housing, for introducing a flow of cold air into the matrix at the housing cold end to reduce the temperature of the matrix, and discharging the air from the matrix at the housing hot end, respectively;
• detection means situated at any of said duct means, for sensing, while the matrix revolves, whether any portion of the matrix has a temperature exceeding a threshold value;
• suppression means situated at any of said duct means, for discharging a cooling fluid into the matrix in a spray pattern while the matrix revolves;
• and
• control means coupled between the detection means and the suppression means, for activating the suppression means when the temperature of any portion of the matrix exceeds said threshold temperature and deactivating the suppression means when no portion of the matrix exceeds said threshold temperature, the control means including means for computing the lapse of time between the moment that a particular portion of the matrix is detected as exceeding the threshold temperature and the moment said particular portion comes within the range of the spray pattern.