Air Pollution Control and Air Quality Management
What this domain tests
Stack and ambient standards, oxygen correction, control-technology selection, and the arithmetic that separates a passing answer from a failing one.
Standards you must recall
- GB 3095-2012, Grade 2: SO2 60 annual / 150 daily; NO2 40/80; PM10 70/150; PM2.5 35/75 micrograms per cubic metre; CO 4/10 mg per cubic metre; O3 8-hour 160 micrograms per cubic metre; O3 1-hour 200. Grade 1 is stricter.
- HJ 633-2012 AQI: compute the individual IAQI from breakpoint tables, then AQI equals the highest IAQI, which names the primary pollutant.
- GB 16297-1996: maximum allowable concentration, maximum allowable emission rate (keyed to stack height and area class), and fugitive-emission monitoring concentration at the plant boundary.
- Industry standards: GB 13271 boilers, GB 13223 power, GB 4915 cement, GB 18485 municipal waste incineration. Stricter 特别排放限值 apply in designated regions.
Control technologies
- Dust: cyclones for coarse fractions, fabric filters above 99 percent, electrostatic precipitators sensitive to dust resistivity, wet scrubbers for simultaneous gas removal.
- SO2: limestone-gypsum wet FGD above 95 percent, semi-dry circulating fluidised bed, ammonia and seawater processes.
- NOx: low-NOx burners, SNCR in the 850 to 1,100 C window, SCR over V2O5-WO3/TiO2 at 300 to 400 C.
- VOCs: carbon adsorption, condensation, absorption, catalytic combustion, regenerative thermal oxidation, biofiltration.
Worked example
A power boiler measures SO2 at 80 mg per cubic metre with measured O2 of 8 percent; the limit is 100 mg per cubic metre at 6 percent base oxygen, and inlet SO2 was 2,000 mg per cubic metre.
- Corrected concentration = 80 x (21 − 6)/(21 − 8) = 80 x 15/13 = 92.3 mg per cubic metre.
- 92.3 is below 100, so the concentration passes, though the margin is thin and the emission rate limit must be checked separately.
- Removal efficiency = (2,000 − 92.3)/2,000 = 95.4 percent, consistent with wet limestone FGD but not with a semi-dry unit sized for 85 percent.
Traps
- Comparing a raw measured concentration against a standard without oxygen correction.
- Assuming a taller stack fixes a concentration exceedance; height addresses the rate limit, not concentration.
- Checking only concentration when both concentration and emission rate must be met.
- Fugitive limits are measured at the boundary monitoring point, not at the source.
- Quoting Grade 1 ambient values when the site is Grade 2.