Method for Online Cleaning of Air Preheaters

Abstract

A method of cleaning air preheaters of the type having a rotor which passes through a stream of flue gas and a stream of intake combustion air is disclosed. A soot blower is operated in step-wise fashion to blow a soot blowing medium through passageways in the rotor. The passageways are arranged in concentric rings and move at a tangential velocity which depends on the speed of the rotor and the location of the passageway relative to the center of the rotor. In the present method the speed of the rotor is adjusted in accordance with the position of the soot blower so that every passageway moves over the soot blower at the same or substantially the same tangential velocity.

1 . A method of cleaning air preheaters of the type comprised of a heat exchange rotor containing adjacent passageways of selected depths from an outer circumference of the rotor through which air and flue gas are directed and which is rotated about an axis and a soot blower capable of being positioned adjacent any selected depth such that a soot blowing medium can be blown from the soot blower into passageways of the selected ring as the rotor is rotated, the method comprised of:
 positioning the soot blower adjacent passageways at a first depth;   rotating the rotor at a first selected speed so that each passageway at the first depth passes over the soot blower;   blowing a soot blowing medium through the passageways at the first depth while the rotor is being rotated at the first selected speed;   positioning the soot blower adjacent passageways at a second depth;   rotating the rotor at a second selected speed so that each passageway at the second depth passes over the soot blower;   blowing a soot blowing medium through the passageways at the second depth while the rotor is being rotated at the second selected speed; and   selecting the first speed and the second speed so that all of the passageways pass over the soot blower at a substantially same tangential velocity.   
     
     
         2 . The method of  claim 1  wherein the rotor contains at least one additional set of passageways at another selected depth and further comprising:
 sequentially positioning the soot blower adjacent the passageways at another selected depth; 
 rotating the rotor at a selected speed for each additional set of passageways so that each passageway of that set passes over the soot blower; 
 blowing a soot blowing medium through the passageways in that additional set while the rotor is being rotated at the selected speed for that set of passageways; and 
 selecting all of the speeds so that all of the passageways pass over the soot blower at a substantially same tangential velocity. 
 
     
     
         3 . The method of  claim 1  wherein the soot blowing medium is air, water or steam. 
     
     
         4 . The method of  claim 1  wherein some, but not all passageways in the rotor are blown with soot blowing medium. 
     
     
         5 . The method of  claim 1  wherein the soot blower first blows soot blowing medium through an innermost depth of passageways. 
     
     
         6 . The method of  claim 1  wherein the soot blower first blows soot blowing medium through an outermost depth of passageways. 
     
     
         7 . The method of  claim 1  wherein passageways at two adjacent depths are blown with a soot blowing medium and the rotor turns at a same rotations per minute while all passageways are being blown.