Control of mercury emissions by enhanced oxidation with hydrogen peroxide and absorption: Design and set up of a lab scale experiment.

摘要

Industries are open systems interacting with social, economic, government and environmental considerations. Different strategies are being developed to respond to various requirements that results due to those interactions. Innovative and optimized air pollution control technologies (APCT) are necessary to reduce the environmental effects of air pollution from industries and meet new and more stringent local, regional and global needs of today. Mercury has been classified by the 1990 Clean Air Act Amendments as a type of hazardous air pollutant and since that period of time, it has been mandated to the United States Environmental Protection Agency (U.S.EPA) to control mercury emissions. On December 2011, U.S.EPA announced the new Mercury and Air Toxics Standards (MATS) for power plants, where limits for new and existing coal-fired power plants are established, together with the requirements for performance testing, in which the method that has been used and validated by the present study (ASTM D6784) is required for quantifying mercury concentration. Power Plants industries release to the environment 75 tons of mercury per year in United States, of which 50 tons are annually released to the atmosphere.;A lab scale experiment for testing the removal and oxidation efficiency of mercury from coal-fired power plants has been designed and implemented; in order to validate previous kinetic modeling study where hydrogen peroxide (H2O2) is used as an oxidizing agent to enhance oxidation of elemental mercury from coal-fired utility boilers and then remove oxidized species by using absorption column. Six critical experimental parameters (temperature, air flow rate at the reactor and permeation chamber, H2O2 and mercury concentration, and sampling time) were found critical for this study. Hg concentration present at the flue gas, before oxidation, was experimentally quantified using a modified Ontario Hydro Method (ASTM Method D6784-02) and the inductively coupled plasma mass spectrometry (ICP-MS X-Series). Results allowed determining the optimum preservation time for analyzing the samples (18 hours) and standardize procedures for preparing stock and rinse solutions, as well as the calibration standards.;A proposed methodology has been designed based on Six Sigma and Total Quality Management (TQM), in order to establish a structured problem-solving methodology based on five phases Define, Measure, Analyze, Improve and Control (DMAIC) that will characterize the mercury oxidation and removal efficiency, evaluate the statistical distribution involved, accuracy and precision of the results, and the best possible arrangement between the critical experimental parameters using Taguchi method.