Asia's Largest Lignite Based Power Plant's Success Story: Efficient Removal of SO_2 Through A Manmade Forest Canopy

摘要

One of the crucial issues that confronted world leaders in the recently concluded Copenhagen summit was that of achieving sufficient power generation for developing countries without exacerbating the problem of global warming. Developing countries, like India, are poised on the path of massive infra-structural project development still requiring power from conventional sources. Power generation at the point of origin of a particular natural resource such as lignite will still continue for some decades to come. The district of Tamil Nadu in South India is rich in lignite. Hence, it is quite natural that the Ministry of Coals, Government of India, should generate power from this rich natural resource at Neyveli Lignite Corporation (N.L.C.). In fact, N.L.C. is indeed Asia's largest lignite based power plant. The generation of power however comes with a price - this involves the release of large quantities of SO_2, which should be removed effectively. The dry deposition of sulphur dioxide over forested canopies is a subject of intense new research. Ours is a first study over coastal Tamil Nadu in the Indian subcontinent. In this case study, it is shown through fluid mechanical models, how SO_2 pollution emanating from stacks is removed effectively by a hand planted, manmade, forest canopy. This power plant is situated in a hot humid tropical belt, giving one the meteorological advantage of a suitable micro-climate for the proliferation of lush green vegetation in a short span of time. N.L.C.'s astonishing success story really rests on the fact that the founding fathers planted 17 million trees within the complex which acts as an efficient sink for SO_2 capture. Deposition velocity of SO_2 is determined for a particular month, April, where the effects of wet scavenging are nonexistent. Particular emphasis is placed on various resistances including stomatal, mesophyllic, upper canopy, and buoyant convection resistances which are simulated using actual data from N.L.C., during April. Canopy resistance values are determined to be 158.87 and 124.45 s·m~(-1) at 8:30 a.m. and at 2:30 p.m. respectively. The respective deposition velocities at those times are calculated to be 0.55 and 0.73 cm·s~(-1).