ABSTRACT

A case study was conducted to evaluate the SO₂ emission reduction in a power plant in Central Mexico, as a result of the shifting of fuel oil to natural gas. Emissions of criteria pollutants, greenhouse gases, organic and inorganic toxics were estimated based on a 2010 report of hourly fuel oil consumption at the “Francisco Pérez Ríos” power plant in Tula, Mexico. For SO₂, the dispersion of these emissions was assessed with the CALPUFF dispersion model. Emissions reductions of > 99% for SO₂, PM and Pb, as well as reductions >50% for organic and inorganic toxics were observed when simulating the use of natural gas. Maximum annual (993 µg/m³) and monthly average SO₂ concentrations were simulated during the cold-dry period (152–1063 µg/m³), and warm-dry period (239–432 µg/m³). Dispersion model results and those from Mexico City’s air quality forecasting system showed that SO₂ emissions from the power plant affect the north of Mexico City in the cold-dry period. The evaluation of model estimates with 24 hr SO₂ measured concentrations at Tepeji del Rio suggests that the combination of observations and dispersion models are useful in assessing the reduction of SO₂ emissions due to shifting in fuels. Being SO₂ a major precursor of acid rain, high transported sulfate concentrations are of concern and low pH values have been reported in the south of Mexico City, indicating that secondary SO₂ products emitted in the power plant can be transported to Mexico City under specific atmospheric conditions.

Implications: Although the surroundings of a power plant located north of Mexico City receives most of the direct SO₂ impact from fuel oil emissions, the plume is dispersed and advected to the Mexico City metropolitan area, where its secondary products may cause acid rain. The use of cleaner fuels may assure significant SO₂ reductions in the plant emissions and consequent acid rain presence in nearby populated cities and should be compulsory in critical areas to comply with annual emission limits and health standards.

摘要

进行了案例研究，以评估由于燃料油向天然气转移而导致墨西哥中部发电厂的SO ₂排放量减少。根据2010年墨西哥图拉“ FranciscoPérezRíos”电厂每小时燃油消耗量的报告，估算标准污染物，温室气体，有机和无机有毒物质的排放。对于SO ₂，使用CALPUFF扩散模型评估了这些排放的扩散。当模拟天然气的使用时，观察到SO ₂，PM和Pb的排放减少> 99％，有机和无机毒物的排放减少> 50％。每年最高（993 µg / m ³）和每月平均SO ₂在冷干期（152–1063 µg / m ³）和暖干期（239–432 µg / m ³）中模拟浓度。色散模型结果和墨西哥城的空气质量预测系统的结果表明，发电厂的SO ₂排放在冷干期影响墨西哥城北部。对在Tepeji del Rio进行24小时SO ₂测量浓度的模型估计的评估表明，观测模型和扩散模型的组合可用于评估由于燃料转移而减少的SO ₂排放。如此₂作为酸雨的主要前兆，令人担忧的是运输的硫酸盐浓度很高，并且据报道墨西哥城南部的pH值低，这表明发电厂排放的二次SO ₂产品可以在特定的大气条件下运输到墨西哥城。

潜在影响：尽管位于墨西哥城北部的发电厂周围环境受到燃油排放的大部分直接SO ₂影响，但烟气却散布并流向墨西哥城都会区，其次级产品可能会引起酸雨。使用更清洁的燃料可以确保大幅减少工厂排放的SO ₂，并因此在附近人口稠密的城市中减少酸雨的存在，因此在关键地区应强制执行这些措施，以符合年度排放限值和健康标准。