How can you design a cost-effective mercury control system?

1 Mercury speciation

The first factor to consider is the form of mercury in the flue gas, also known as mercury speciation. Mercury can exist as elemental mercury (Hg0), oxidized mercury (Hg2+), or particulate-bound mercury (HgP). The speciation affects the capture efficiency of different mercury control technologies, as well as the fate of mercury in the downstream processes. For example, Hg0 is the most difficult to remove, as it is highly volatile and does not react with most sorbents or catalysts. Hg2+ is more soluble and reactive, and can be removed by wet scrubbers or selective catalytic reduction (SCR) systems. HgP is associated with fly ash particles, and can be captured by particulate matter (PM) control devices, such as electrostatic precipitators (ESPs) or fabric filters (FFs).

4 Site-specific factors

The fourth factor to consider is the site-specific factors that can affect the feasibility and suitability of the mercury control system. These include the flue gas composition, temperature, pressure, and flow rate, the availability and quality of the sorbents, oxidants, catalysts, and other materials, the space and layout of the plant, the compatibility and integration with the existing processes and equipment, the reliability and availability of the system, and the local environmental and social conditions.

5 Optimization and evaluation

The fifth factor to consider is the optimization and evaluation of the mercury control system. This involves using mathematical models, simulation tools, or pilot tests to optimize the design parameters, such as the injection rate, location, and distribution of the sorbents or oxidants, the catalyst type, size, and configuration, the flue gas temperature and residence time, and the performance indicators, such as the mercury removal efficiency, the pressure drop, and the energy consumption. The optimization and evaluation also involve monitoring and measuring the mercury emissions, the flue gas characteristics, and the system performance, using appropriate sampling and analytical methods, such as continuous emission monitors (CEMs), Ontario Hydro method, or cold vapor atomic fluorescence spectroscopy (CVAFS).

6 Best practices and recommendations

The sixth factor to consider is the best practices and recommendations for designing a cost-effective mercury control system. These include conducting a comprehensive and systematic analysis of the mercury speciation, the mercury control technologies, the cost-benefit analysis, the site-specific factors, and the optimization and evaluation, using reliable and updated data and information, consulting with experts and stakeholders, and following the relevant guidelines and standards. Additionally, these include adopting a flexible and adaptive approach, that can accommodate the changes in the mercury emission regulations, the market conditions, the technological innovations, and the plant operations.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?