Badania emisji zanieczyszczeń z kotła CWF 235 MWeStudy of emissions from the 235 MWe CFB boiler

Przedstawiono analizę danych dotyczących emisji zanieczyszczeń gazowych SO2 i NOx oraz pyłu lotnego z kotłów CWF (Cyrkulacyjna Warstwa Fluidalna) 235 MWe, uzyskanych w wyniku badań przeprowadzonych w Elektrowni Turów na kotłach CWF 670t/h nr 1 i nr 2. Analizując wyniki pomiarów, określono wpływ obciążenia kotła, temperatury warstwy fluidalnej, stosunku molowego Ca/S oraz współczynnika nadmiaru powietrza na wielkość emisji wymienionych zanieczyszczeń. Potwierdzono zależność wzrostu sprawności odsiarczania gazów spalinowych wraz ze zwiększaniem ilości sorbentu podawanego do komory paleniskowej, przedstawiono także wpływ obciążenia kotła na wartość koncentracji dwutlenku siarki w spalinach. Potwierdzono również tendencję wzrostu wielkości emisji tlenków azotu w miarę podwyższania temperatury panującej wewnątrz komory spalania oraz wzrostu stężenia NOx w gazach wylotowych wraz z wartością współczynnika nadmiaru podawanego powietrza. Analiza koncentracji popiołu lotnego w spalinach przeprowadzona została z kolei pod kątem wpływu obciążenia kotła.

To run in this article data of SO2, NOx and fly ash emissions from the 235 MWe CFB (Circulating Fluidized Bed) boilers have been worked out on the basis of the research in Turow Power Station on the 670 t/h CFB boilers no. 1 and no. 2. On the basis of the analysis of measurement results it has been described, among other things, the effect of boiler load, fluidized bed temperature, Ca/S molar ratio and air excess ratio on the scale of emissions. Application in the power industry and heat engineering fuel combustion by fluidized bed technique offers the possible broad range of fuel recycling, among other things low-calorie fuel, high-ash fuel and high-humidity fuel. It offers to reduce pollutant emissions such as SO2 and NOx, too. Quick development of fluidized combustion technique gives many interesting constructions of fluidized bed boilers. One of them is fuel combustion in the circulating fluidized bed. Owing to uncomplicated furnace gas desulphurization technique, which is realized simultaneously with the combustion process and relatively low investment and utilization cost, fluidized combustion technology in a circulating bed is very attractive. Besides, desulphurization efficiency 80÷95% is possible at 2÷4 Ca/S molar ratio, depending on sulphur content in the fuel. Owing to low temperature of the combustion process and air staging without use additional installation the level 200÷300 mg/Nm3 of NOx emission is obtained. To present in this article study of SO2, NOx and fly ash emissions have been realized in Turow Power Station on the 235 MWe CFB boilers. So far, the boilers have been brown coal-fired. During research, the feed fuel has had 9600÷11300 kJ/kg calorific value and the contents of coal, sulphur, fly ash ranged from 26.5 to 30.5%, 0.28 to 0.64%, 9.7 to 16.5%, respectively. The applied sorbent has been powdered calcium carbonate CaCO3 had. During measurements, the feed sorbent has been 97% CaCO3. Since the boilers are chiefly operated at 100% load, the special emphasis has had placed on study of pollutant emissions during 100% boilers load. The analysis of measurement result shows that the desulphurization efficiency has increased by 5% when the Ca/S mole ratio increased from 2.58 to 3.13, at 100% boiler load. The SO2 concentration in the flue gas has increased when the boiler load increased. The measurement results of NOX emissions show that the NOX concentration in the exhaust gas has increased when the bed temperature increased from 874 to 886°C, at 100% boiler load. The NOX concentration in the flue gas has increased when the air excess ratio increased. However, the measurement results of fly ash emissions show that the fly ash concentration in the exhaust gas has increased insignificantly when the boiler load increased from 50 to 100%.