L. Cañadas

Influence of plate spacing and ash resistivity on the efficiency of electrostatic precipitators

Abstract This paper contributes to the knowledge of the behaviour of electrostatic precipitators in pulverized-coal power plants. The information was obtained through real tests carried out on different types of coal with real flue gases in a pilot precipitator installed at a pulverized-coal power plant. In particular, the influence of different plate spacings, the characteristics of the ash generated by each type of coal and the mass load of ash in the gas flow are considered. The tests carried out lead to conclusions with respect to the most advantageous arrangement of the plates for each case. Conclusions with respect to other variables that affect the efficiency, such as gas velocity, can also be drawn.

Theoretical modelling of electrostatic precipitators performance (PRELEC code)

Abstract This paper presents a model designed to characterize the performance of plate-type electrostatic precipitators (ESP). PRELEC is a rigorously Deutschian model, completely theoretically derived, that avoids the use of empirical estimations in its calculations. In the present version, those estimations related with non-ideal effects are not considered. PRELEC calculates electric fields, based on the applied voltage wave, including the effects of ionic and particulate space charge. It is able to simulate two possible types of ESP energization: full-wave rectified current and pulse generation. It also allows the transient evolution of electrical conditions inside the ESP during the rapping intervals to be analysed, taking into account the dust build-up influence. The model predictions show good agreement with experimental measurements taken at two ESPs of Spanish Power Plants under several operational conditions, including different dust characteristics, very high resistivity ashes, operation before and after the installation of a flue gas conditioning plant, and the use of rectified current and pulse energization. PRELEC predictions are also compared with those obtained from Version 3 of EPA/SRI model.

OPTICOM: Advanced automatic monitoring system of local combustion conditions for improving boiler performance in PC power plants ☆

Abstract Improving combustion in pulverised coal power stations offers the greatest potential for economic savings. However, optimisation of these facilities is normally limited by an inability to adequately monitor operational conditions. This paper presents the OPTICOM technology, a novel monitoring approach for characterising local combustion conditions, that will contribute to avoid the mentioned limitation concerning monitoring of operational conditions. OPTICOM technology allows one to obtain temperature and gas concentration (O2, CO, NOx, SO2) profiles that exist within the most critical regions of the furnace. These measurements provide a local evaluation of the combustion process, which allows the operator to consider the unit as a set of small virtual units, each consisting of a single burner, that can therefore be individually optimised. Adequate adjustment of each of these ‘smaller facilities’ brings about overall optimisation of the boiler.

Characterization and conditioning by cementation and compaction of ashes coming from simulated radwastes

Abstract The statement and the results of a systematic programme of characterization and evaluation of conditioning by cementation and supercompaction of ashes coming from different simulated radwastes are presented. The main programme objectives are to define the influence of the most important operating parameters of conditioning methods on the mechanical properties of the conditioned products and to obtain the guidelines for the optimization of their final storage, evaluating the achievable volume reduction and its relation with mechanical strength. The study is based on the physical and chemical characterization of the ashes and the determination of their behaviour with respect to two conditioning methods: cementation and high pressure compaction, to determine the strength development, the mechanical stability, and the volume reduction achieved. The ashes are obtained by incineration of low activity simulated radwastes, which represent different real wastes with high volume to activity ratio. The conditioning by cementation is tested over a series of cementitious pastes made with two cement types, changing in ash and water content. Products are controlled by measuring volume, setting time, expansion, and strength. High pressure compaction tests are made at laboratory scale, measuring the ash volume reduction as a function of compacting pressure.