Cyclones blockages

Blockage or plugging of the dipleg due to an obstruction or catalyst bridging resulting from defluidization or sticky catalyst fines will effectively flood the cyclone, rendering the cyclone inoperative. 

Because most of the ash is removed as molten slag, addition of a bottom grate is not necessary.7 However, small TDF is required, because much of the combustion must occur in suspension.7 TDF that is too large to combust completely can get carried over into the boiler or dust collection system, and cause blockage problems.9 Therefore, particle size may inversely determine the amount of TDF that can be used in a cyclone boiler.11 Three cyclone-fired boilers at utilities have burned 1M x 1" TDF in test operation, one at the 2 percent, one at the 5 percent, and one at up to a 10 percent level.3,9,12 One pulp and paper mill plans the use of TDF in a cyclone-fired hog-fuel boiler.13... 

Set point AFB98/3 was canied out with straw 7 (Barley JB6) at 800 C. This test run was not as successful, as the pressure of the reactor started to rise after one hour operation and consequently, the operation bad to be stopped earlier than planned. The removed bed material was fairly clean, as were also the freeboard and the gas outlet pipe. The blockage that caused the increase in reactor pressure was detected in the gas line after the cyclone. 

Cyclone overloading (i.e., where a mnltiunit installation is involved, partial blockage in one of the inlet ducts may be causing uneven distribution of gas flow). 

Powder transport lines can be considered as very lean fluidized beds. These are encountered in many industries for instance, conveying powder-laden gases to cyclone separators. Here, acoustic emission proves to be a sensitive indicator for the presence of powders or liquid droplets, the detection of blockages, and as a semiquantitative indicator of the particulate mass flow. 

In the case of really small cyclones (e.g. 10 mm diameter units), these are sometimes cast into disks and such disks are stacked into columns. Such systems resemble other chemical engineering columns for mass transfer or cartridge systems for filtration. One problem common to all compact multiple hydrocyclone systems is with the operator s inability to see any blockages. He or she must then diagnose any such difficulties from other operating performance such as an increase in pressure drop. Having detected a blockage problem, the only remedy available is to replace the unit or the whole column and clean it off-line. 

Blockages, usually caused by overloading of the sohds outlet orifice, is one of the most common causes of failure in cyclone operation. The cyclone cone rapidly fills up with dust, the pressure drop increases and efficiency falls dramatically. Blockages arise due to mechanical defects in the cyclone body (bumps on the cyclone cone, protruding welds or gasket) or changes in chemical or physical properties of the solids (e.g. condensation of water vapour from the gas onto the surface of particles). 

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