Combined process

Multiple Options

Adding a dry sorbent injection (DSI) or a furnace sorbent injection (FSI) to an existing FGT operation helps to increase the scope and efficiency of pollutant capture. This is easier and more economical than other options.

Lhoist solution

In principle, DSI can be used in combination with all existing FGT processes, including wet or all dry processes. Such combined processes usually have two main purposes:

Removing a “new” pollutant that cannot be handled by an existing FGT process, such as:

  • Sorbacal® SPS injection for selective HF removal in a waste-to-energy plant, using sodium bicarbonate for SO2 and HCl control.
  • Sorbacal® SP injection for HCl removal downstream from a coal or residue derived fuel fired CFB boiler using limestone for in situ SO2 removal.
  • Sorbacal® SP injection upstream of a wet scrubber in a coal-fired power plant, for selective SO3 and/or HF removal to reduce air preheater fouling, corrosion and “blue plume” (sulfuric acid aerosol emission).
  • Sorbacal® Micro dry injection upstream of filtration, for mercury removal in a coal-fired power plant using wet scrubbing for acid gas removal.

Increasing the removal performance of an existing FGT process, such as:

  • Sorbacal® SPS injection at multiple locations in the process for optimized SO2 removal.
  • Sorbacal® SPS injection in the boiler (FSI) in waste-to-energy plants, for additional SO2 control before the existing FGT installation (DSI/SDA).
  • Sorbacal® SP injection before or after the SDA process for HCl and SO2 removal. This widely used combination is often called 3/4 dry or modified, conditioned dry sorption.
  • Sorbacal® SP injected downstream for increased SO2 removal in a coal-fired CFB boiler using limestone for in situ SO2 removal.


Each combined process is a unique tailor-made solution for the specific needs of the individual customer. Our experts can assist you in selecting the right type of process and sorbent to optimize and upgrade your existing FGT process. Based on this assessment, our Customer Technical Service experts can conduct full-scale plant trials to confirm the performance of the proposed solution.

Pollutants captured

Discover the optimum solution for your process and facility by contacting our experts.