The injection of hydrated lime, sodium bicarbonate (SBC) into the flue gas for the removal of SO2 and SO3, is a proven solution and a preferred technology world-wide. India is experiencing stricter emission norms and injection of these dry sorbents become eminent in the current scenario, where space and capital cost is a challenge to many power industries.
A dry sorbent injection or so called DSI system enables plants to remain in business when the capital investment of a wet/dry flue gas desulphurization (FGD) system is too high for the smaller captive power plants and also where space is an issue. Injection of these sorbents (alkali) can also offer other benefits to the plant like lower operating costs, less corrosion and reduced activated carbon usage for mercury removal in high SO3 environments.
DSI for SO3 removal is mostly by hydrated lime as a high-efficiency sorbent and at a low cost. The hydrated lime can be injected into several locations throughout the flue gas route, depending on the preferred operation. Performance can vary based on mixing, location of injection, and whether the station has an ESP (Electrostatic Precipitator) or Bag filters after the boiler. Nowadays, the trend is to inject lime directly in Boiler combustion area giving good spread across which directly reduces the emissions. DSI is an easily retrofitted, low capital cost system that is capable of relatively high (>85 to 90%) SO2 removal. Dry sorbent feeding is an effective and flexible technology and, if designed well, system plugging does not occur. Poorly designed systems give distribution and choking issues, which affects performance and the ability to benefit from all the advantages that it provides.
DSI’s flexibility in process allows most coal-fired boilers (CFBC, AFBC Boilers) in running, to achieve compliance with the new air emission limits in a cost-effective manner. It can be applied as an independent SOx removal device, or as an aid under performing FGDs in Thermal Power Plants.
- DSI for SO3 removal is mostly by hydrated lime as a high-efficiency sorbent at a low cost
- Easy to install, Compact design, ensuring flexibility in layout
- Can save Capital cost in Place of FGD
- Low maintenance due to less Rotating parts
- Precise metering of Lime depending upon SOX emissions
- Dust free operation
- Less spillage resulting in good yield recovery