Welsh Journals

CONTROL OF AIR POLLUTION AT PEMBROKE POWER STATION R.T. Jarman and C.M. de Turville Summary The ground level concentrations of smoke and sulphur dioxide have been monitored at 10 sites in the vicinity of Pembroke Power Station before, during and after the commissioning of the power station. The seasonal mean sulphur dioxide concentrations show little change in recent years. Specially devised statistical tests to examine the effect of the power station on the local air quality show that this is too small to be detected from the other sulphur dioxide present. INTRODUCTION In the late 1950's the demand for electricity was growing rapidly, and the Central. Electricity Generating Board (CEGB) decided to build large, 2000 MW fossil-fuelled .stations to meet future requirements. Each power station was to consist of four 500 MW sets, in contrast with the previous practice based largely on the operation of substantially small units. The aim of the new policy was to achieve substantial savings in capital, fuel and manpower and limit the number of new units and sites required. The large projected increase in the output of these new stations made it imperative to maintain the control of the ground level concentration of chimney effluents. Whereas previous practice had been to use two or more stacks, it was decided to minimise ground level concentrations of pollutants by using a single tall multi-flue chimney (Clarke et aI, 1966). To sustain a high efflux velocity, each 500 MW set was provided with an individual flue, and the four chimney flues mounted within a single wind shield. The underlying theoretical idea behind this policy, already confirmed by direct observation, was that under particular meteorological conditions the ground level concentration of any pollutant varied as Q/H2 where Q is the rate of emission of that pollutant, and H the effective height of emission, defined as the sum of the chimney height and plume rise. As the quantity of sulphur dioxide emitted would be greater in large power stations the stack height and plume rise were increased accordingly. In this way Q/H2 was maintained at previous levels and the power station contribution to the ground level concentration of sulphur dioxide was to remain at a low level! PEMBROKE POWER STATION These principles were applied to the design of Pembroke Power Station, which is a 2000 MW oil-fired power station consisting of four 500 MW sets. The choice of this site, close to a National Park, was determined by the relative proximity of important load centres in South Wales, easy access to residual oil supplies from the Milford Haven refineries, and the availability of ample cooling water in the adjacent estuary. At full load, the power station consumes about 400 tons of fuel oil per hour, with a maximum sulphur content of