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Coal-fired boilers such as vertical water-tube boilers, vertical fire-tube boilers, and horizontal internal combustion boilers.
Parameter | Water supply | Boiler water | ||
Adding medicine to the pot | External chemical treatment | Adding medicine to the pot | External chemical treatment | |
Suspended solids, mg/L | ≤20 | ≤5 | ||
Total hardness, mmol/L | ≤1.75② | ≤0.02 | ||
Total alkalinity, [H+] mmol/L (mgoN/L) | 8～20 | ≤20 | ||
pH (25℃) | >7 | >7 | 10-12 | 10-12 |
Dissolved solids ①, mg/L | <5000③ | <5000③ | ||
Relative alkalinity (free NaOH/dissolved solids) | <0.2④ | <0.2④ | ||
① If it is difficult to determine the dissolved solids, the method of determining chloride ions (Cl-) can be used to indirectly control it. However, the ratio between dissolved solids and chloride ions (Cl-) must be determined by test according to the specific situation, and this ratio should be retested and corrected regularly.
② When the hardness index exceeds this limit, the boiler user unit may appropriately relax the limit after obtaining approval from the superior competent department and the local labor department.
③ The dissolved solids of Lancashire boilers can be <10000mg/L.
④ When the relative alkalinity is ≥0.2, measures should be taken to prevent caustic embrittlement.
Hot water boilers
project | hot water temperature | |||
For temperatures ≤95℃, in-pot chemical addition treatment is employed. | >95℃, external chemical treatment is used. | |||
Water supply | Circulating water | Water supply | Circulating water | |
Suspended solids, mg/L | ≤20 | ≤5 | ||
Total hardness, mmol/L | ≤3 | ≤0.35 | ||
pH (25℃) | >7 | 10-12 | >7 | 8.5～10 |
Dissolved oxygen, mg/L | ≤0.1 | ≤0.1 | ||
① If external chemical treatment is used, the water quality index of hot water temperature > 95℃ should be met.
Oil-fired and gas-fired boilers such as water-tube boilers and water-fire tube combined boilers.
project | Water supply | Boiler water | |||||
Work pressure, MPa | 0.98① | >0.98 | >1.57 | ≤0.98 | >0.98 | >1.57 | |
Suspended solids, mg/L | ≤5 | ≤5 | ≤5 | ||||
Total hardness, mmol/L | ≤0.02 | ≤0.02 | ≤0.02 | ||||
Total alkalinity [H+] mmol/L (mgoN/L) | No superheater | ≤20 | ≤18 | ≤14 | |||
Overheater | ≤14 | ≤12 | |||||
pH (25℃) | >7 | >7 | >7 | 10-12 | 10-12 | 10-12 | |
Oil content, mg/L | ≤2 | ≤2 | ≤2 | ||||
Dissolved oxygen, mg/L | ≤0.1② | ≤0.1② | ≤0.05② | ||||
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≤0.02
≤0.02
≤0.02
Total alkalinity [H+] mmol/L (mgON/L)
No superheater
≤20
≤18
≤14
With superheater
≤14
≤12
pH (25℃)
＞7
＞7
＞7
10～12
10～12
10～12
Oil content, mg/L
≤2
≤2
≤2
Dissolved oxygen, mg/L
≤0.1②
≤0.1②
≤0.05②
