Neutralization
Neutralization processing.
A chemical process, which allows the CO2 removal with neutralization reaction per a basic reagent.

Main simplified formula: xOH- + CO2 >>> x[HCO3-]

NB: No action on calcium hardness (calcium is unchanged).

Note:
neutralization to be complete, does not continue until complete disappearance of carbonic acid [CO2, H2O] in the water: decision of neutralizing action is to balance saturation of calcium carbonate [CaCO3] water, or calcocarbonic balance.
If you continue to add reagent, then produce a softening by precipitation of CaCO3 as it, in excess, can remain solubilized and thus is deposited (in terms of concentration reached). At this point, the residual CO2 is said balancing, and is therefore considered more aggressive CO2.

Possible main practices (formulas) :

(click on name of the reagent for more information)

Notes: as regards fltration on limestone neutralization action is relatively slow (relative to injection of reagents), and also decreases the efficiency of progressively reducing the CO2 content; it is therefore necessary to provide substantial filters (possibly see dimensioning programs Neutral and Neutral-F (in french) > link Hydro-Land site).

Doses in mg of product (100% pure) for 1 mg of neutralized aggressive CO2 (mg / mg or g/m3):

Reactive >
lime (Ca[OH]2)
caustic soda (NaOH)
sodium carbonate (Na2CO3)
limestone (CaCO3)
Dose
0.84
0.91
2.41
2.273

Increased alkalinity (TAC), and total hardness (TH), according to the reagent employed (in °F / mg/L as CaCO3, per mg of removed CO2 ):

Reactive >
Ca(OH)2
NaOH
Na2CO3
CaCO3
TAC, °F (mg/L as CaCO3)
0.1136 (1.136)
0.1136 (1.136)
0.2273 (2.273)
0.2273 (2.273)
TH, °F (mg/L as CaCO3)
0.1136 (1.136)
0
0
0.2273 (2.273)

Special case:
Neutralization with sodium bicarbonate ,

NaHCO3 + CO2 + H2O >>> 2 NaHCO3

In this case there is a constancy of free CO2 content: transformation of aggressive CO2 in free CO2, balancing and training NaHCO3, thus increasing the Alkalinity (can go up the balance of CaCO3 saturation).

Dose in mg of product (100% pure) 1 mg of for aggressive CO2 "transformed" (mg / mg or g/m3)

Reactive >
sodium bicarbonate (NaHCO3)
Dose
1.91

Increasing alkalinity (TAC) and TH (° F / mg/L CaCO3, per mg of NaHCO3 injected)

TAC, °F (mg/L CaCO3)
0.119 (1.19)
TH, °F
0


Reagents which act only on calcium hardness (no neutralization of CO2):


Increasing hardness according to the employed reagent (mg of pure anhydrous reagent to be injected for increased 1° F or 10 mg/L as CaCO3):

Reactives >
calcium chloride
calcium sulfate
mg
11.1
13.6

NB :
The doses shown are to100% reagent purity and it is necessary to correct the dose taking into account the purity (100% pure reagent) of commercial product.

CORRECTION OF DOSES BASED ON COMMERCIAL PRODUCT:

Quantity by mass (weight) of the commercial product:

Qm = (100 / p)Dt

Volume amount of commercial product:

Qv = (1 / d x Qm)
or,
Qv = (1 / C x Dt)


So as,


EXAMPLES.
Example 1:
Dt theoretical dose of lime indicated = 30 g as Ca [OH]2 / m³ of water

Weight amount of commercial solid lime (Qm): (100/80 x 30) = 37.5 g / m³ of water,
Amount by volume of lime solution (Qv): (1/1, 65 x 30) = 18.19 liters / m³ water.


Example 2  :
Dt theoretical dose of sodium carbonate Na2CO3 = 40 g/m³ d’eau,

Amount by weight of trade sodium carbonate (Qm) : (100/96x 40 = 41.7 g/m³ d’eau,

Amount by volume of sodium carbonate solution (Qv) : (1/50 x 40) = 0.8 liter / m³ water (800 ml/m3)

Example 3  :
Dt theoretical dose of caustic soda NaOH = 25 g/m³ water,

Amount by weight of trade caustic soda (Qm) : (100/30x25 = 83.3 g/m³ water.

Amount by volume of trade caustic soda  (Qv) : (1 / 1328 x 83.3) = 0.0627 liter / m³ water (or 62.7 ml/m3).
...........................................................or (Qv) : (1 / 398.4 x 25) = 0.0627 L/m³


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