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The top of the urea granulation tower is exposed to the air; the main pollutant is urea dust. The emission concentration of this dust must be kept at ≤50 mg/Nm3, in order to meet the requirements of the **Integrated Emission Standards for Air Pollutants (GB16297-1996)**, specifically the standard for particulate matter of ≤120 mg/Nm3. Emissions are to take place at a height of 90 meters. Table 8.2-2: Maximum allowable emission concentrations of pollutants (mg/m3), maximum allowable emission rates, unorganized emissions, monitoring concentration limits (mg/m3), standard sources, height of exhaust stacks (m), emission rates (kg/h). Sulfur dioxide: 960 (for sulfur production); 550 (for other applications). Monitoring concentration limits: 30, 60, 80; 22, 83, 110. Emission rate: 0.40. Standard: GB16297-1996 “Comprehensive Emission Standards for Air Pollutants”. Nitrogen oxides: 1400; 60; 25. Monitoring concentration limit: 0.12. Particulates (urea dust): 120; 75; 132.8. Emission rate: 1.0. Methanol: 190; 15; 5.1. Emission rate: 12. Hydrogen sulfide: 30; 60. Monitoring concentration limit: 1.3. Emission rate: 5.2. 0.32 (factory boundary standard value). Standard: GB14554-93 “Emission Standards for Odorous Pollutants”. Ammonia: 30; 60; 75. Monitoring concentration limits: 20, 75, 117.2. Emission rate: 4.0 (factory boundary standard value). Dust: 50. Standard: GB13223-2003 “Emission Standards for Air Pollutants from Thermal Power Plants”. SO2: 400; NOx: 450. For noise levels, the Class III standards specified in “Noise Standards for Industrial Enterprises” (GB12348-90) apply, namely 65 dB(A) during the day and 55 dB(A) at night. Wastewater Discharge Standards Table 8.2-1 Sequence Number Pollutant Discharge Concentration (mg/L) Discharge Amount (kg/t of NH3) Standard Source 1 Ammonia nitrogen (NH3-N) 40 0.4 GB 13458-2001 2 Chemical oxygen demand (CODcr) 100 1 3 Cyanides (CN-) 0.2 0.002 4 Suspended solids (SS) 60 0.6 5 Oil 5 0.05 6 Volatile phenols 0.1 0.001 7 Sulfides 0.50 0.005 8 Water discharge volume 10 m3/t of NH3 9 Biochemical oxygen demand (BOD5) 150 GB 5084-92 10 Kjeldahl nitrogen 30 11 pH 5.5–8.5 12 Coliform bacteria count 10,000 per/L