A FRIENDLY TOOL TO ASSIST PLANT OPERATORS AND DESIGN ENGINEERS TO CONTROL FLY ASH EMISSIONS: ORCHIDEE

Either in the Operation Control Room, the Handling/Logistics Department, the Maintenance Department…or even in the Environmental Section, the operating personnel can contribute to control the dust emission of a power plant unit. To satisfy current regulations, the efficiency of the electrostatic precipitator must always be mantained greater than 99.5%. These high performances require continuous control of the impact of possible malfunctions on the emission level, by adjusting the process conditions from the coal yard to the stack, including the electrostatic-precipitator itself. To evaluate quickly the impact of coal characteristics, combustion parameters and electrical malfunctions on dust emission the operator can use a user -friendly software based on physical modelling of the dust collection process: ORCHIDEE. Without using experimental databases or manufacturer' s empirical data, the operator becomes able to get a better real time understanding of the problems, and to react efficiently. Version 2 of ORCHIDEE software offers additional functions, based on the non-linear coupling of different effects (ash layer chatacteristics, particles resistivity, current and voltage rapping processes, etc.) By proper introduction of all input data, ORCHIDEE 2 makes possible: to evaluate the impact of combustion parameters on du st emission (excessive airleakages, flue gas temperature at precipitator inlet). to test blending hypotheses of various types of coal to avoid back-corona. to evaluate the impact of rapping sequences or SO3 injection on dust emission. to simulate electrical malfunctions: field or section out of service, wire and plate fouling, electrode misalignment, etc. to evaluate the impact of back -corona on precipitator efficiency and voltage-current characteristics. Validated with industrial precipitators data, ORCHIDEE is a very helpful tool to assist operation and maintenance of electrostatic filters. It is unique for its high scientific content and its user-friendly interface, and it has already shown to fulfil the expectations of industrial users.