Division 8.4 Techniques to reduce emissions of SOX, HCl and/or HF to air
United Kingdom
| Technique | Description |
|---|---|
| Boiler sorbent injection (in-furnace or in-bed) | The direct injection of a dry sorbent into the combustion chamber, or the addition of magnesium- or calcium-based adsorbents to the bed of a fluidised bed boiler. The surface of the sorbent particles reacts with the SO2 in the flue-gas or in the fluidised bed boiler. It is mostly used in combination with a dust abatement technique. |
| Circulating fluidised bed (CFB) dry scrubber | Flue-gas from the boiler air preheater enters the CFB absorber at the bottom and flows vertically upwards through a Venturi section where a solid sorbent and water are injected separately into the flue-gas stream. It is mostly used in combination with a dust abatement technique. |
| Combined techniques for NOX and SOX reduction | See Section 8.3 |
| Duct sorbent injection (DSI) | The injection and dispersion of a dry powder sorbent in the flue-gas stream. The sorbent (e.g. sodium carbonate, sodium bicarbonate, hydrated lime) reacts with acid gases (e.g. the gaseous sulphur species and HCl) to form a solid which is removed with dust abatement techniques (bag filter or electrostatic precipitator). DSI is mostly used in combination with a bag filter. |
| Flue-gas condenser | See Section 8.2 |
| Fuel choice | The use of a fuel with a low sulphur, chlorine and/or fluorine content |
| Process gas management system | See Section 8.2 |
| Seawater FGD | A specific non-regenerative type of wet scrubbing using the natural alkalinity of the seawater to absorb the acidic compounds in the flue-gas. Generally requires an upstream abatement of dust. |
| Spray dry absorber (SDA) | A suspension/solution of an alkaline reagent is introduced and dispersed in the flue-gas stream. The material reacts with the gaseous sulphur species to form a solid which is removed with dust abatement techniques (bag filter or electrostatic precipitator). SDA is mostly used in combination with a bag filter. |
| Wet flue-gas desulphurisation (wet FGD) | Technique or combination of scrubbing techniques by which sulphur oxides are removed from flue-gases through various processes generally involving an alkaline sorbent for capturing gaseous SO2 and transforming it into solids. In the wet scrubbing process, gaseous compounds are dissolved in a suitable liquid (water or alkaline solution). Simultaneous removal of solid and gaseous compounds may be achieved. Downstream of the wet scrubber, the flue-gases are saturated with water and separation of the droplets is required before discharging the flue-gases. The liquid resulting from the wet scrubbing is sent to a waste water treatment plant and the insoluble matter is collected by sedimentation or filtration. |
| Wet scrubbing | Use of a liquid, typically water or an aqueous solution, to capture the acidic compounds from the flue-gas by absorption. |