PGSRET 2018

Abstract

There are coal reserves of about 185 Billion Tons in Pakistan at various sites such as Lakhra, Thar, Badin, Jhimpir, Makerwal, Ziarat, Dighari, Harnai, Hangu, Cherat, Kotli etc. The estimated coal only at Thar site is about 175 billion tons spread over an area of 9000 square kilometer with coal bed thickness of about 12-21 meters that should be sufficient for 150 years of our required power supply. The only difficulty is that it is dirty lignite type with about 1.5% nitrogen and Sulphur, with larger moisture content and low calorific value ~5774 Btu/lb. Considering one factor at a time e.g. nitrogen content in the coal implies that on combustion it would produce appreciable nitrogen oxides (NOx). International donner agencies or foreign investors are not interested in Pakistani coal reserves based power plants due to environmental concerns leading to smog, acid rains, ozone problem etc. Environmental Protection Agencies (EPAs) have implemented emission limits on NOx from new or old power plants that ranges from 200 to 1000 mg/Nm3 internationally, while in Pakistan it is a bit lenient i.e. upto 1200 mg/Nm3. Even with this soft upper value, clean technologies are still required to be incorporated in prospective future coal fired power plants to comply these limits. Considering the global environmental scenario, it is eminent that future limits will be more stringent and may approach to two-digits values only. One of the emerging post-combustion NOx control technology is 'Selective Non-Catalytic Reduction (SNCR)' that can be implemented in coal fired power plants is becoming popular due to its simplicity in application, catalyst free characteristic, retrofit in nature, flexibility to use with other techniques as well as lower capital and operating cost involved. This talk would explain the technical features of this emerging technique that may be applied with or without other control technologies and may be considered to be used in existing and future coal fired power plants that would use locally available coal reserves in Pakistan.

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