LDX Solutions

DUSTEXTM CIRCULATING DRY SCRUBBER (CDS)

DUSTEX^TM CIRCULATING DRY SCRUBBER (CDS)

The Dustex^TM Circulating Dry Scrubber (CDS) system is designed for multi-pollutant removal efficiency, addressing SOx, NOx, HCl, HF, Hg, Pb, Dioxins, and Furans.

CDS Basics
The Dustex^TM CDS system is available for a range of sizes. Single units can be installed at plants up to 300+ MW. For plants larger than 300 MW, multiple reactor vessels can be utilized. The technology brings high levels of fine water droplets, hydrated lime, and flue gas together within a circulatory fluidized bed reactor to create ideal reaction conditions.

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Independent injection of lime products and water lower flue gas temperature and enhance removal. The fluid bed material is comprised of solids including: Ca (OH)₂, fly ash from the combustion process, and solid reaction products. Due to the reduced flue gas temperature and the high solids content in the system, mercury (Hg) and other pollutants are also removed in the process.

A CDS uses an entrained fluidized bed reactor for contacting the reagent, usually hydrated lime, with sulfur dioxide and particulate laden flue gas. The intensive gas solid mixing that occurs in the reactor promotes the reaction of sulfur oxides in the flue gas with the dry lime particles. The mixture of reaction products (calcium/sulfate), unreacted lime, and fly ash is carried to a downstream particulate collector (baghouse) that is separated from the gas stream. Most of the waste product is mixed with fresh calcium hydroxide for use in the reactor and reinjected into the reactor with only a small portion of the dry waste product being removed for disposal. Water spray is introduced into the fluidized bed separately to enhance (for maximum SO₂ capture with minimum lime utilization) the surface moisture content of the lime.

The Process
In the Dustex^TM CDS process hydrated lime is injected directly into the reactor. Flue gas enters the CDS reactor at the bottom, flows vertically upward through a venturi section and enters an upper cylindrical vessel. The height of the vessel is designed to accommodate the mass of bed-material required to achieve the desired residence time. The process is easy to maintain and operate because it does not require high maintenance mechanical equipment such as abrasion resistant slurry pumps, atomized H₂O or sludge dewatering devices, in contrast to spray dryers or wet scrubbers. The process can achieve >99% SO₂ removal efficiency.

Benefits

• 99% SO₂ Removal Efficiency
• Flexible
  • Multi-Pollutant Removal
    • SO₂, SO₃, HCl, HF, Pb, Dioxins, Furans
    • Hg Removal
    • NOx removal
  • Fuel Switching
  • Works in High Moisture Applications

• Low Capital Cost
  • Modular fabrication
  • Simplicity of design with small footprint
  • No slurry systems
  • Exotic Alloys not required
• Lower Maintenance compared to other technologies
  • No Slurry handling issues
  • Very few moving parts
• Operational Advantages
  • Adsorption of heavy metals
  • High recycle rate allows for low reagent consumption
  • Lower power consumption than alternative systems
  • No waste water stream