Division BAT 73 In order to prevent and/or reduce NOX emissions to air while limiting CO emissions to air from IGCC plants, BAT is to use one or a combination of the techniques given below.
United Kingdom
| Technique | Description | Applicability | |
|---|---|---|---|
| a. | Combustion optimisation | See description in Section 8.3 | Generally applicable |
| b. | Water/steam addition | See description in Section 8.3. Some intermediate-pressure steam from the steam turbine is reused for this purpose | Only applicable to the gas turbine part of the IGCC plant. The applicability may be limited due to water availability |
| c. | Dry low-NOX burners (DLN) | See description in Section 8.3 | Only applicable to the gas turbine part of the IGCC plant. Generally applicable to new IGCC plants. Applicable on a case-by-case basis for existing IGCC plants, depending on the availability of a retrofit package. Not applicable for syngas with a hydrogen content of > 15 % |
| d. | Syngas dilution with waste nitrogen from the air supply unit (ASU) | The ASU separates the oxygen from the nitrogen in the air, in order to supply high-quality oxygen to the gasifier. The waste nitrogen from the ASU is reused to reduce the combustion temperature in the gas turbine, by being premixed with the syngas before combustion | Only applicable when an ASU is used for the gasification process |
| e. | Selective catalytic reduction (SCR) | See description in Section 8.3 | Not applicable to IGCC plants operated < 500 h/yr. Retrofitting existing IGCC plants may be constrained by the availability of sufficient space. There may be technical and economic restrictions for retrofitting existing IGCC plants operated between 500 h/yr and 1 500 h/yr |
Table 43
BAT-associated emission levels (BAT-AELs) for NOX emissions to air from IGCC plants
| IGCC plant total rated thermal input(MWth) | BAT-AELs (mg/Nm3) | |||
|---|---|---|---|---|
| Yearly average | Daily average or average over the sampling period | |||
| New plant | Existing plant | New plant | Existing plant | |
| ≥ 100 | 10–25 | 12–45 | 1–35 | 1–60 |
As an indication, the yearly average CO emission levels for existing plants operated ≥ 1 500 h/yr and for new plants will generally be < 5–30 mg/Nm3.