Emission regulation often necessitates the need for flue gas treatment of acid gases within the utility and industrial sectors. In the US today, a number of important regulations including Utility MATS, Industrial Boiler MACT, Portland Cement MACT, regional haze rules, new source review (NSR), and site permits are direct drivers for the need to reduce acid gases such as HCl, SO2, SO3, and HF. Additionally, other rules, such as the coal combustion residue rule and water rules such as the 316(b) rule for cooling tower intakes and the effluent limit guidelines (ELG) can also be significant and may also lead to the need for flue gas treatment as a part of an entire system.
Whether you call it the utility Hazardous Air Pollutants (HAPS) rule, the utility MACT (Maximum Achievable Control Technology) rule or the Mercury Air Toxics Standards (MATS) rule, this rule developed for the power sector presents new challenges for coal fired utilities.
Fortunately, Dry Sorbent Injection (DSI) technology with Sorbacal® products has been proven to be capable of capturing enough HCl to achieve these new standards with all but the highest chloride fuels. This is a relatively easy to install, low capital cost compliance solution for many coal fired utilities.
One example of MATS compliance within a utility is shown in the graph. In this case standard hydrate was not able to achieve the HCl emission limit outlined in MATS, while using Sorbacal® SP the limit could be achieved. In addition, at every level, the amount of reagent required when using Sorbacal® SP is much lower than with standard hydrated lime.
Sorbacal® DSI technology can also be utilized to capture SO3 and maximize native carbon mercury capture or to enhance capture with activated carbon (AC) injection systems.
Industrial Boiler MACT
The recently promulgated industrial boiler MACT (Maximum Achievable Control Technology) rule presents significant challenges for smaller coal or biomass fired boilers being used in industrial applications. The high capital costs associated with traditional acid gases control systems can put continued operations in jeopardy.
One example of testing at an industrial boiler to achieve MACT limits for HCl is shown below. In this case, Sorbacal® SP is shown to achieve the HCl emission limit outlined in IB MACT with half the amount of reagent when compared to standard hydrated lime.
Fortunately, Dry Sorbent Injection (DSI) technology with Sorbacal®products has been demonstrated to capture HCl on a wide variety of industrial boiler applications in order to meet the emission limits set forth in this rule. This is a relatively low capital cost compliance solution that can mean the difference between shutdown and being able to continue operations.
In addition, Sorbacal® DSI technology can be utilized to capture SO3 and maximize native carbon mercury capture or to enhance capture with activated carbon (AC) injection systems.
With the Environmental Protection Agency (EPA) renewing its emphasis on Regional Haze rule making, a wide variety of utilities and industrial facilities combusting coal and/or biomass are being required to meet strict new emission limitations to improve visibility.
In many cases controlling SO3, whether inherent in the existing process or compounded by NOx control technology retrofits, can address this concern. Over the last 10 years, Dry Sorbent Injection (DSI) technology with Sorbacal® products has been proven to be highly effective for SO3 capture and has become the preferred solution for utility applications. This technology is in use at literally dozens of coal fired plants today.
Portland Cement MACT
After years of legal wrangling, the Portland Cement MACT (Maximum Achievable Control Technology) rule has been finalized. This rule establishes a number of new emission limits, including HCl, for Portland Cement kiln operations. While the specific kiln type, fuels, raw materials and methods of operation come into play, many cement kiln operators will need to actively control chlorides.
One example of testing at a U.S. cement plant is shown on the graph. In this case, the limit in the PC MACT for HCl can be achieved using hydrated lime, but the amount of Sorbacal® SP to achieve the same emission limit is significantly reduced.
For many kiln configurations, Dry Sorbent Injection (DSI) technology with Sorbacal® products has been proven to be a viable technology to meet the HCl limits associated with this rule with relatively low capital costs. Additional benefits related to SO2 capture have also been demonstrated.
Cross State Air Pollution Impacts
While the status of a final rule centered on cross state impacts related to SO2 emissions from coal fired power plants is still uncertain, further limitations are being placed on these facilities as a result of consent decrees, local permit limitations or regional haze concerns. The capital cost of traditional hardware intensive FGD systems for SO2 control can be difficult to justify for older smaller coal fired units.
Advancements in calcium hydroxide DSI reagents, specifically Sorbacal®, have resulted in products that are capable of achieving between 60-80% capture of utility SO2 with relatively low capital cost injection systems. The ultimate effectiveness will be a function of a wide variety of variables, including particulate collection devices and injection system configuration.
Coal Combustion Residue (CCR) Rules
With the development of rules for management of CCR materials in 2014, the impacts of retrofitting emission control technology must be considered. This is especially true with Dry Sorbent Injection (DSI) technology. Both sodium and calcium based DSI reagents will impact the resulting CCR materials.
Whether bound for disposal or a reuse market, the impacts on the CCR metals leachability and solubility must be considered. In general, CCR materials impacted by the use of sodium DSI reagents leach higher levels of metals and result in dramatically higher potential for dissolved solids than the raw CCR or CCR impacted by calcium DSI reagents.
These impacts can be modeled and estimated for a given DSI application.
if interested in evaluating these important potential impacts on your CCR material.
Effluent Limitation Guidelines (ELG) Rules
The development of the ELG and the proposed 316(b) rules related to process water intake requirements result in utilities being highly motivated to minimize process water intake by recirculating to the maximum extent possible. For many fuel types, the amount of recirculation is limited by chloride build up in the process water. While treatment options are available, they are generally quite expensive.
An alternative approach being employed by some utilities is to remove chlorides from the wet scrubber chemistry by using Dry Sorbent Injection (DSI) with Sorbacal® to capture chlorides and remove the reaction product, calcium chloride, with the dry fly ash collection. This results in minimizing the chlorides ultimately in the process water, thereby allowing for higher recirculation of process waters without expensive treatment alternatives. The resulting chloride reaction products can then be more economically handled in the solid state.
to discuss the possibility of performing a full scale field trial using Sorbacal® DSI technology to remove chlorides prior to your wet scrubber system.