lime dosing

8/4/2019 Lime Dosing

1/16

Softening

cations mg/l eq.wt mg/l as CaCO3 Anions mg/l eq.wt

Ca2+

1073 20 2682.5 CO32-

0 30

Mg2+

574 12.2 2352.5 HCO3-

46 61

Na+

10165 23 22097.8 Cl-

16415 35.5

Fe2+

1.12 27.9225 2.0 SO42-

3750 48

Concentration

H+

1.94984E-08

HCO3-

0.0009

Ka 4.46684E-07

H2CO3 3.92864E-05

Therefore CO2 = H2CO3

Mol wt of CO2 44.0 g

CO2 1.728602696 1000.0 mg

CO2 3.92864249

Mg2+ Fe+

5038.9 27138.7

37.7

3.93 HCO3-

CO2 3.93

Ca carbonate

hardness 37.7

Mg Carbonate

hardness 0

excess lime 20

Amount of lime

(CaOH)2 required 61.63491803

Mg2+ Fe+

5001.2 27101.0

After the Carbonate Hardness is removed

CO2

Ca2+ Na+

2648.7 27099.0

1) Note: Ca & Mg g

2) first step to remove carbonate hardness

association with Ca & Mg.

alkalinity exist in the form of HCO3-& there w

the alkalinty exist as OH-

so either forms carbonic acid or HCo3- depen

precipitate calcicum and Magnesium carbonat

ness forms CaCO3 which precipitaes

MgCO3 which is soluble and does'nt get rem

convert MgCO3 to Mg(OH)2 which

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

Cl- SO42-

Amount of lime required = (CO2 + Ca carbonate hardness + Mg Carbonate hardness + excess Lime)

Na+

H2CO3 = [H+] x [HCO3

-]/[Ka1], mol/l

expressing CO2 in terms of mg/l

CO2 2686.4 27136.7

23157.4 27063.7

Availability of CO2 @ Ph 7.7

Assume all of H2CO3 forms CO2

expressing CO2 in terms of mg/l as CaCO3

mg/l as CaCO3

Ca2+


2/16

3.93

Ca Non

carbonate

hardness 2648.7

Mg NonCarbonate

hardness 2352.5

Amount of Soda

Ash required 5001.2

Mg Non

Carbonate

hardness 2352.5

Lime 2414.093934

Soda Ash 4494.2

After Ca & Mg being removed

Fe+

24182.3

3.93 Cl- SO42-

CO2

Na+

34748.9

12584.5 17355.3

Cl- SO42-

Amount of Soda Ash required = (Ca Non carbonate hardness + Mg Non Carbonate hardness)

1)Calcium Non Carbonate Hardne2)CaCl2 Or CaSO4 reacts with Na2CO3 and for

dose

3)Mg Non Carbonate Hardness could

4)Firstly Mg Non Corbonate is added with

contributes har

5)secondly Lime is added which reacts with

leaves behind Nacl and Na2SO4 which is

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

23119.7 27026.0

mg/l as CaCO3

Amount of Lime required = ( Mg Non Carbonate hardness)

Total Amount of dosage required

mg/l as CaCO3

mg/l as CaCO3


3/16

mg/l as CaCO3 pH 7.71

0.0 pKa 6.35 at 25C

37.7

23119.7

3906.3

26630.8616380354

27063.7

t to be precipitated to remove hardness.

hich is formed by (HCO3-,CO3

2-,OH

--Contributes to Alkalinity) in

3) At pH < 8.3

ould be presence of CO2 4) At pH > 8.3 all of

5) CO32-

is not stableing upon pH 6) Lime Ca(OH)2 is used to

e hardness 7) Lime + calcium Carbonate hard

8) Lime + Mg Carbonate Hardness forms

oved 9) So further addition of lime is required to

precipitaes 10) finally excess lime is added


4/16

Note:

ss could be removed by addition of Soda Ash (Na2CO3)s CaCO3 which precipitaes and NaCl,Na2SO4 which dissolves and

nt contribute to hardness

be removed by addition of both Lime & Soda Ash (Na2CO3)

CaCO3 ,here MgCO3 is formed which is a soluble product and

dness along with this CaCl2 r CaSO4 .

gCO3 and forms Mg(OH)2 & CaCO3 a product that precipitaes .and

a soluble and non-hardness product, but contributes to TDS.


5/16

Softening


Ca2+

942 20 2355.0 CO32-

0 30

Mg2+

530 12.2 2172.1 HCO3-

45 61

Na+

5921 23 12871.7 Cl-

8935 35.5

Fe2+

0.1 27.9225 0.2 SO42-

4580 48

Concentration

H+

1.94984E-08

HCO3-

0.0009

Ka 4.46684E-07

H2CO3 3.92864E-05



CO2 1.728602696 1000.0 mg

CO2 3.92864249

Mg2+ Fe+

4531.1 17403.0

36.9

3.93 HCO3-

CO2 3.93

Ca carbonate

hardness 36.9

Mg Carbonate

hardness 0

excess lime 20Amount of lime

(CaOH)2

required 60.8152459

Mg2+ Fe+

4494.2 17366.12322.0 17365.9

17392.2

Ca2+ Na+

1) Note: Ca & Mg g








forms MgCO3 which is soluble and does'nt get

to convert MgCO3 to Mg(OH)2 whic

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3



-]/[Ka1], mol/l




17402.8

mg/l as CaCO3

CO2

CO2

2358.9

mg/l as CaCO3

mg/l as CaCO3

SO42-

12621.4

Cl-



Ca2+ Na+


6/16

3.93

Ca Non

carbonate

hardness 2322.0Mg Non

Carbonate

hardness 2172.1

Amount of Soda

Ash required 4494.174544

Mg Non

Carbonate

hardness 2172.1

Lime 2232.946393

Soda Ash 4494.174544


Fe+

24182.3

3.93

mg/l as CaCO3


1)Calcium Non Carbonate Hardne

2)CaCl2 Or CaSO4 reacts with Na2CO3 and for

dose



contributes ha



mg/l as CaCO3

mg/l as CaCO3


12584.5 17355.3

mg/l as CaCO3

Cl- SO42-

mg/l as CaCO3


CO2

12584.5 17355.3Cl- SO42-

Na+

24182.1

mg/l as CaCO3


7/16


0.0 pKa 6.35 at 25C

36.9

12584.5

4770.8

17402.9481974954

17392.2



2-,OH


3) At pH < 8.3

uld be presence of CO2 4) At pH > 8.3 all of

5) CO3

2-is not stable

ing upon pH 6) Lime Ca(OH)2 is used to


8) Lime + Mg Carbonate Hardness

removed 9) So further addition of lime is required



8/16

Note:

ss could be removed by addition of Soda Ash (Na2CO3)

s CaCO3 which precipitaes and NaCl,Na2SO4 which dissolves and


e removed by addition of both Lime & Soda Ash (Na2CO3)






9/16

Softening


Ca2+

319 20 797.5 CO32-

0 30

Mg2+

177 12.2 725.4 HCO3-

65 61

Na+

7311 23 15893.5 Cl-

9928 35.5

Fe2+

0 27.9225 0.0 SO42-

3235 48

Concentration

H+

1.94984E-08

HCO3-

0.0013

Ka 4.46684E-07

H2CO3 5.67471E-05



CO2 2.49687056 1000.0 mg

CO2 5.674705819

Mg2+ Fe+

1528.6 17422.1

53.3

5.67 HCO3-

CO2 5.67

Ca carbonate

hardness 53.3

Mg Carbonate

hardness 0

excess lime 20

Amount of lime

(CaOH)2 required 78.94868852

Mg2+ Fe+

1475.3 17368.8

5.67

mg/l as CaCO3



-]/[Ka1], mol/l




CO2

Ca2+ Na+

803.2 17422.1

14036.4 17406.2

Cl- SO42-


1) Note: Ca & Mg g








MgCO3 which is soluble and does'nt get remconvert MgCO3 to Mg(OH)2 which

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3


CO2

Ca2+ Na+

749.9 17368.8

13983.1 17352.9

Cl- SO42-



10/16

Ca Non

carbonate

hardness 749.9

Mg Non

Carbonate

hardness 725.4

Amount of SodaAsh required 1475.3

Mg Non

Carbonate

hardness 725.4

Lime 804.3585246

Soda Ash 1475.3


Fe+

24182.3

3.93

Na+

19594.0



dose


4)Firstly Mg Non Corbonate is added withcontributes har



mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

12584.5 17355.3

Cl- SO42-


mg/l as CaCO3


mg/l as CaCO3

mg/l as CaCO3

CO2


11/16


0.0 pKa 6.35 at 25C

53.3

13983.1

3369.8



2-,OH


3) At pH < 8.3

ould be presence of CO2 4) At pH > 8.3 all of

5) CO32-

is not stable



8) Lime + Mg Carbonate Hardness forms

oved 9) So further addition of lime is required toprecipitaes 10) finally excess lime is added


12/16

Note:




be removed by addition of both Lime & Soda Ash (Na2CO3)

CaCO3 ,here MgCO3 is formed which is a soluble product anddness along with this CaCl2 r CaSO4 .




13/16

Softening


Ca2+

699 20 1747.5 CO32-

0 30

Mg2+

367 12.2 1504.1 HCO3-

66 61

Na+

6204 23 13487.0 Cl-

9325 35.5

Fe2+

0 27.9225 0.0 SO42-

3400 48

Concentration

H+

1.94984E-08

HCO3-

0.00132

Ka 4.46684E-07

H2CO3 5.76201E-05



CO2 2.535283954 1000.0 mg

CO2 5.762008986

Mg2+ Fe+

3257.3 16744.2

54.1

5.67 HCO3-

CO2 5.67

Ca carbonate

hardness 54.1

Mg Carbonate

hardness 0

excess lime 20Amount of lime

(CaOH)2

required 79.76836066

Mg2+ Fe+

3203.2 16690.1


CO2

Ca2+ Na+

1699.1 16690.1

Cl-

SO42-


1) Note: Ca & Mg g








forms MgCO3 which is soluble and does'nt get

to convert MgCO3 to Mg(OH)2 whic

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

CO2

Ca2+ Na+

1753.2 16744.2

13187.9 16729.6



-]/[Ka1], mol/l




mg/l as CaCO3


14/16

5.67

Ca Non

carbonate

hardness 1699.1Mg Non

Carbonate

hardness 1504.1

Amount of Soda

Ash required 3203.2

Mg Non

Carbonate

hardness 1504.1

Lime 1583.866721

Soda Ash 3203.2


Fe+

24182.3

3.93 Cl- SO42-


mg/l as CaCO3


mg/l as CaCO3

mg/l as CaCO3

CO2

Na+

21592.4

12584.5 17355.3

Cl- SO42-




dose



contributes ha



mg/l as CaCO3

mg/l as CaCO3

mg/l as CaCO3

13133.8 16675.5


15/16


0.0 pKa 6.35 at 25C

54.1

13133.8

3541.7



2-,OH


3) At pH < 8.3

uld be presence of CO2 4) At pH > 8.3 all of

5) CO32-

is not stable



8) Lime + Mg Carbonate Hardness

removed 9) So further addition of lime is required



16/16

Note:




e removed by addition of both Lime & Soda Ash (Na2CO3)





lime dosing

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