Blockages occurring in Cement Plant Cyclones and/or Cyclone under flow pipes can be dangerous and difficult to detect. These typically occur as follows:-
Under normal conditions the cyclone under flow pipe is never full of material. Abnormal changes in the process can sometimes result in blockages in this underflow. Hence gamma type blockage detectors are traditionally installed to the cyclone underflow.
Unfortunately interrupting the kiln feed, after detecting such a blockage, does not always solve the problem. Due to the inertia of the process, the material to the cyclone under flow is not immediately interrupted. In-flight material continues to be delivered to the already blocked cyclone under flow pipe – which may result in this material backing up into the cyclone itself!
Such blockages are normally very difficult and dangerous to clear. Since the material has a poor thermal conductivity, it takes a long time to cool sufficiently to allow the pipe work to be opened. Opening it too soon can cause extremely hot process to flush out of the poke-hole, often threatening the lives of those attempting to clear the condition. Waiting for it to cool down means lost productivity.
Should the kiln be restarted after clearing the cyclone underflow, and the choke had in fact already formed a bridge in the lower portion of the cyclone, it will result in the choke situation being considerably aggravated by the collection of further material into the already blocked cyclone.
The situation can rapidly deteriorate into a major production disruption, not to mention the dangers associated with the difficulty of removing the, now large volumes, of very hot process material. The initial blockage problem has now been significantly compounded.
Typically this will result in extremely long plant down time in order to allow the material in the cyclone to cool sufficiently to be cleared safely.
The Traditional Solution
By installing a non-invasive, gamma type, blockage detector to the cyclone under flow, it is possible to detect whenever this underflow pipe/chokes with material. This provides a reliable detection system which is non-contacting and non-intrusive to the process.
Such a gauge provides a relay output which may be used to alarm/trip the kiln so as to allow appropriate action to be taken to clear the blockage.
Unfortunately such an instrument only warns once there is a blockage in the underflow. The problem of a bridge in the cyclone is not addressed at all.
The Complete Solution
By making use of our proprietary Cyclone Blockage Detection System®, it is possible to avoid the problems of blockages in the cyclones.
The Cyclone Blockage Detection System® allows one to monitor the mass of material in the Cyclone (normally flowing down the Cyclone walls).
Under normal operational conditions the material in the cyclone will be within certain defined limits. By monitoring the output from the Cyclone Blockage Detection System® it has been proven that it is possible to avoid the blockage in the first instance!
Should the output from the Cyclone Blockage Detection System® change beyond the normal operating values, an alarm may be generated for appropriate action by the operator. Kiln operators have been able to avert a pending blockage/choke condition using this information. This effectively provides an early warning of an impending choke!
The system provides both a continuous analogue (4-20 mA) output and a programmable alarm (relay) output. Field Bus output is also available.
Should the early warning provided from the Cyclone Blockage Detection System® be ignored, resulting in a choke in the Cyclone under-flow, the (traditional) underflow choke detector will indicate an alarm as before.
Clearing the cyclone under-flow pipe, will remove the cyclone underflow alarm, but only if no resultant bridging exists will the Cyclone Blockage Detection System®indicate it is safe to restart the process. Should the Cyclone Blockage Detection System® indicate a blockage or bridge in the cyclone also, this too would need to be cleared prior to restarting the process, thereby avoiding a compounding of the problem.
The Cyclone Blockage Detection System® provides:-
- Early warning of an impending blockage.
- Indication of the full extent on any blockage which occurred.