Pulverised Fuel Measurement with Split Control: Project Summary

Abstract:

<p>The objectives from this project are: <bl> <li>To investigate the performance of pulverised fuel meters to measure the relative mass flow rate in two parallel pneumatic conveyors.</li> <li>To demonstrate, on a small-scale, control of the distribution (split) of pulverised coal between two parallel pneumatic conveyors, fed from a source via a bifurcator, using pulverised fuel meters to measure the mass flow rate The meters providing signals used to actuate a flow control device.</li> </bl></p> <p>To improve the combustion efficiency of pulverised fuel (p.f.) fired furnaces in electrical power generation, it is desirable to measure, optimise and then, ideally, control the p.f. flow velocity and the solids distribution (split) between pneumatic conveyors leading to burners in the furnace.</p> <p>On leaving the pulverising mill, the solids-air mixture is split into several different pipes each feeding an individual burner. One mill can feed as many as eight burners. Usually the fuel and air are metered before the mill where the ratio can be accurately set. Differences in routing of the lines injecting p.f. into the furnaces, and phase maldistribution at the splitting points, results in an uneven feed to the burners. Consequently, the combustion stoichiometry at the burners is disturbed. This leads to increased fuel costs, higher levels of carbon in the ash and excessive specific emissions in the flue gas. If the mass flow rate of the fuel can be measured, and the flow splitter controlled, then, in principle, the air-fuel ratio can be accurately set and the combustion stoichiometry optimised.</p> <p>This experimental project has confirmed that the use of mass pf flowmeters combined with mechanical actuators can be used to control the solids split between two conveyors fed from a bifurcator. It is appreciated that this project was restricted to using 40mm diameter pipes and conditions in 375mm diameter pneumatic conveyors found on large boilers can be expected to be more challenging. However, as a first attempt, the exercise can be judged to have been very successful. Refinements to the flow test rig are planned so that the operation is aligned with industry practice.</p> This summary provides information on: <bl> <li>Objectives</li> <li>Summary</li> <li>Cost</li> <li>Duration</li> <li>Contractor</li> <li>Collaborators</li> <li>Test Section</li> <li>ABB PF Meter</li> <li>Control System</li> <li>Conclusions</li> <li>Future Work</li> <li>Acknowledgements</li> </bl>

Author(s):

DTI