GORE Mercury Control Systems

The GORE Mercury Control System (GMCS) is a unique fixed sorbent system for capturing elemental and oxidized gas phase mercury from industrial flue gas. The system is based on discrete stackable modules that are installed downstream of a particulate collection system. The modules are designed with a unique open channel structure which provides extremely low pressure drop, avoiding the need for an additional booster fan.

At the heart of the technology is an innovative, fluoropolymer-based material developed by scientists at Gore: Sorbent Polymer Catalyst (SPC) composite material. The sorbent in this material efficiently captures both elemental and oxidized mercury from the flue gas stream. As such, it is insensitive to fuel or process changes that affect mercury speciation. Mercury is securely bound within the SPC via chemisorption. Unlike many activated carbon sorbents, the presence of SO₃ does not inhibit mercury capture by the SPC, making it a very effective solution for high sulfur coals or units with SO₃ gas conditioning. Since there are no injected sorbents, there is absolutely no concern over fly ash contamination or creating additional particulate matter that needs to be collected. Chemicals for oxidation are also not needed thus eliminating halogen-induced corrosion concerns or wastewater treatment complications.

Coal-fired power plants are subject to increasingly strict emissions regulations. In the United States, the Mercury and Air Toxics Standard (MATS) requires plants to achieve very low outlet emissions. In an increasingly competitive power market, The GORE Mercury Control System provides a simple, cost-effective solution.

Operation of the GMCS is exceedingly simple. Since the modules contain no moving parts, there is no need for any adjustments to maintain performance as unit operations change. The modules are resistant to fouling or plugging, in part due to the smooth, non-stick nature of the SPC, and in part due to the continual acid wash created by the conversion of SO₂ to liquid sulfuric acid. A simple water rinse system is typically installed above and below the modules, similar to a mist eliminator wash, but only operated once or twice per day to help rinse acid and dust off the module surfaces. Other than this small amount of water usage, there are no other consumables, power, or maintenance requirements to operate the system. The system has a very low operating cost, since module replacement is very infrequent. The SPC can retain 5% of its weight in mercury without a drop in removal efficiency, equating to 1 to 2 tons of mercury holding capacity for a 1000 MW plant. As a result, the projected module lifetime for most power plants based on mercury capacity of the modules is often greater than 10 years.

GORE Mercury Control Systems are currently in operation in five absorbers in the coal-fired power industry. Several more are currently under construction for start-up in early 2016, at which point the installed operating capacity will exceed 2100 MW.

Including full-scale and slip stream pilot experience, GMCS Modules have successfully operated on flue gas from power plants burning all types of coal: high and low sulfur bituminous, PRB, and lignite.

• On-site field tested in operating cement plants
• High efficiency maintained over extended operation periods
• Full scale system implementation already under consideration

Numerous field tests have been performed over the past several years, and our fleet of pilot test units are continuosly deployed at a number of commercial cement operations. The GORE Mercury Control System is a leading candidate to enable the cement industry to effectively and simply meet their mercury emissions compliancy targets.

Eliminates Activated Carbon Injection Drawbacks

There is no impact on the final product – the finished cement remains essentially mercury-free and carbon-free. By continually removing mercury from the process, it does not continually concentrate in the CKD. This eliminates the need for Dust Shuttling or Dust Wasting and their associated process changes. The kiln dust can be completely recycled back into the process to maximize clinker yield as is standard for the industry. There is also no need to worry about the logistics and safety of transporting and storing large amounts of powdered sorbents.

Sewage sludge, municipal solid waste, and hazardous waste incinerators around the world are under continual pressure to reduce emissions of various pollutants.  Many countries have or are proposing new regulations limiting mercury emissions.  Activated carbon injection and fixed carbon beds are two commonly accepted technologies to control mercury.  The GORE Mercury and SO₂ Control System offers a significantly lower capital cost alternative to fixed beds and eliminates the need for activated carbon injection, preserving ash properties and minimizing operating costs. 

The modules are simple and cost-effective to operate, with no moving parts, no chemicals to manage and a long lifetime. Modules can be stacked to achieve the desired level of mercury removal requirements. Based on a novel Sorbent Polymer Composite (SPC) material developed by Gore, it provides both high efficiency and a high capacity for removing elemental and oxidized mercury from flue gas streams. In addition, it also reduces SO2 concentrations. Due to the unique chemistry employed, the SPC material is insensitive to process or material changes that impact mercury speciation and to common sorbent "poisons" such as SO3 and VOCs. This allows it to continually reduce mercury and SO2 concentrations in a gas stream for long periods of time before needing replacement. 

The SPC can function in a wide range of operating conditions, including the most challenging high humidity (wet) acid gas streams, making it ideal for location above the mist eliminators in a wet FGD (flue gas desulfurization) system. When installed in the outlet of a wet scrubber, the GMCS serves as a barrier to mercury re-emissions. This allows a plant to avoid the use of scrubber re-emissions additives, and focus the scrubber operation on avoiding other unwanted problems like selenate formation. SO₂ in the flue gas is converted to sulfuric acid which is expelled out of the hydrophobic SPC material. This provides increased SO₂ compliance margin and may eliminate the need for a scrubber upgrade. Some operators may take advantage of this SO₂ removal and choose to detune their scrubber (i.e., turn off a spray header) thus saving on power costs.

When the modules have reached end of life, the SPC material can be removed from the metal frames for disposal while the frames (which are constructed of corrosion-resistant alloy) can be reused. Options for SPC disposal include landfill in an approved hazardous waste landfill or sending to a retort facility for mercury removal and disposal in a non-hazardous landfill. The quantity of SPC material that needs to be disposed of at the module end-of-life is typically several orders of magnitude smaller than the quantity of injected sorbents that would be used to control mercury with a sorbent injection system for the same period of time. As a result, the disposal costs are typically much lower than the disposal costs associated with an activated carbon system.

Installation of GMCS inside a wet scrubber results in no additional footprint requirements on-site, which is particularly important for sites with space constraints. A typical new installation inside of a wet scrubber can be completed during a 3–4 week outage. Module stacks are supported on beams and the modules fill the cross-sectional area of the scrubber above the mist eliminators. If there is insufficient vertical space in an existing scrubber design, the mist eliminators can be replaced with a compact design and installed in a lower position in the scrubber to make space for the modules. Gore will team with utilities and their preferred engineering partners to insure a successful design and resulting installation.

For plants that do not have wet FGD’s installed, this technology can be applied after a dry scrubber, or even as a stand-alone solution for mercury and SO₂. Depending on the temperature of the flue gas, an evaporative cooler may be installed upstream of the Gore modules to cool the gas stream to below 180°F (82°C) for maximum effectiveness. For plants that do not have any acid gas scrubbing systems and need to reduce SO₂ emissions, the GMCS can be configured as a very attractive alternative to a new wet or dry scrubber. GORE Mercury Control Systems have been tested and installed in numerous industrial non-power applications including incinerators, cement and metals plants. The robust nature of the modules makes them suitable in a wide range of applications.