MIL-HDBK-1003/6
Table 19
Effectiveness of Water Treatment
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*
*
*
Average Analysis of Effluent
*
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* Hardness
*
*
Alkalinity
CO2
Dissolved
*
*(as CaCO3)
*
(as CaCO3) Grains per
Solids
Silica
*
* Grins per
Grains per Square Foot Grains per Grains per *
*
*Square Foot Square Foot
Square Foot Square Foot*
(mg/L)
* (mg/L)
*
*
Treatment
(mg/L)
in steam
(mg/L)
(mg/L)
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* Cold lime
* 0 to 0.87 (2)
3.5 (8) *
328 (75)
Med - high
Reduced
* ion exchange *
*
*
*
*
* Hot lime soda * 7.43 (17) to 15.3 (35) - Med - high
1.3 (3) *
Reduced
*
*
*
10.9 (25)
21.9 (50)
*
*
*
* Hot lime ion * 0 to 0.87 (2) 8.7 (20) -
*
Low
Reduced
* exchange
*
*
10.9 (25)
* Sodium ion
* 0 to 0.87 (2)
Unchanged Low - high Unchanged Unchanged*
* exchange
*
*
* Sodium +
* 0 to 0.87 (2) 4.4 (10) -
Unchanged*
Low
Reduced
*
13.1 (30)
* exchange
*
*
* Sodium zeolite* 0 to 0.87 (2) 6.6 (15) -
Unchanged Unchanged*
Low
* + chloride
*
*
15.3 (35)
* anion
*
*
* exchange
*
*
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Note:
mg/L = ppm
Concentration of Dissolved Solids. Concentration of dissolved
7.3.3
solids in boiler water are given in Table 17. The percent of boiler blowdown
is governed by the allowable concentration ratio (CR) or the number of times a
dissolved solid may be concentrated over the amount of dissolved solids in the
feedwater. The allowable concentration ratios are determined by a chemical
analysis of the boiler feedwater and by the type of makeup water treatment.
Refer to Kemmer, 1979 for further information.
A boiler operated on exceptionally high quality feedwater or
subject to minimal make-up may be able to operate successfully with very
little blowdown. The required blowdown may be accomplished with a short
bottom blow. Border line cases may reduce blowdown to acceptable intermittent
operation by proper external treatment of make-up water. An economic analysis
can determine if the added cost of heat recovery equipment is justified.
Intermittent Blowdown of Steam Drum. The boiler water is
7.3.4
periodically discharged through an open blowoff valve for short times when the
dissolved solids concentrations reach a maximum (or often before); this
operation often results in high-low cycles of dissolved solids concentrations
and excessive heat loss. This is more costly than continuous blowdown.
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