Properties of Lime and its Application of Sugar Process | Equipment and its Capacity of MOL Preparation
LIME:
Lime is the one of the main important reagents in juice clarification such as defecation, sulphitation, carbonation process. The lime is the cheapest and most required clarifying agent.
The consumption of lime in different processes is as follows
-
- In Defecation Process – 0.08 to 0.12% on cane
- In Sulphitation Process – 0.14 to 0.20% on cane
The availability of lime in different forms like quick lime , limestone and hydrated lime
The standards specification for quick lime(Cao) , lime stone(CaCO3) and hydrated lime[Ca(OH)2] are as follows.
| Lime stone | Quick lime | Hydrated lime | |
| Cao | 55 to 56% | 80 -95% | 70-76% |
| Mgo | 0.5-2% | 0.3-2.5% | 0.5-2.0% |
| Co2 | 33-44% | 0.5-1.5% | 0.3-0.7% |
| Sio2 | 0.5-2.0% | 0.2-1.5% | 0.2-0.5% |
| Al203 | 0.2-0.5% | 0.1-0.5% | 0.1-0.2% |
| Fe2o3 | 0.1-1.5% | 0.1-0.5% | 0.1-0.2% |
| H2o | 0.2-1.5% | 0.1-0.4% | 0.1-0.2% |
Milk of Lime Preparation:
CaO is a strong base and very reactive compound. It combines with water-evolving heat & produces calcium hydrate.
CaO + H2 O 
Ca(OH)2 + 15.54 Kcal
(Calcium Oxide) + (Water) (Calcium hydraoxide) + ( Heat)
The atomic weight of the above equation ( Whereas Ca= 40; O= 16; H= 1)
(40 + 16) + (2+16) 74
56 + 18 74
From the above equation, we can understand 56 units of CaO plus 18 units of H2O results in 74 units of Ca(OH)2.
It means the ratio of hydroxide to CaO is 1.32 (74 ÷ 56). This means 1 Kg of CaO and 0.32 Kg of water will produce 1.32 Kg of Ca(OH)2, This is the minimum water required for preparation of calcium hydroxide. So calcium hydroxide contains 75.7% CaO and 24.3% H2O.
The reaction is exothermic and heat is evolved during reaction.
Solubility of Ca(OH)2 in water is very low as one part of Ca(OH)2 dissolves in 790 parts of water, but the solubility of CaO in sugar solution increases with the concentration of sucrose but decreases as temperature rises.
The milk of lime prepared in the factory consists of fine suspension of Ca(OH)2 in water beside the hydroxide in solution.
White suspension is MOL. This slaked lime is sparingly soluble in water. The solubility of lime is 0.12% at room temperature & 0.08% at 65oC .
Lime is hygroscopic in nature and forms Ca(OH)2 If expose to the atmosphere, it losses its activity.
Under moist conditions, lumps of lime exposed to the atmosphere crumble to small pieces and are disintegrated. Prolonged exposure of lime to atmosphere results in the formation of calcium carbonate due to reaction with CO2.
Hence lime should be fresh, properly burnt, and packed to avoid exposure to the atmosphere. A good quality lime immediately swells-up, heat is evolved and breaks if water is poured over the lump of lime. This is a crube method of judging the quality.
The CaO content of different concentrations of milk of lime expressed in terms of Brix or Beaume. Generally, industry people follows Beaume method.
At different brix the content of Cao in MOL is as follow.
Brix Grams Cao/ 1000ml
5.4 26
7.2 36
9.0 46
10.8 56
12.6 65
14.4 75
18 94
21.7 115
27.2 148
At different Beaume the content of CaO in MOL is as follows as.
| Degree Beaume | Density (gm/ml) | Grams CaO/Lt | CaO Percentage by weight |
| 1 | 1.007 | 7.5 | 0.75 |
| 2 | 1.014 | 16.5 | 1.65 |
| 3 | 1.022 | 26 | 2.55 |
| 4 | 1.037 | 36 | 3.50 |
| 5 | 1.045 | 46 | 4.43 |
| 6 | 1.052 | 56 | 5.36 |
| 7 | 1.060 | 65 | 6.18 |
| 8 | 1.067 | 75 | 7.08 |
| 9 | 1.075 | 84 | 7.87 |
| 10 | 1.083 | 94 | 8.74 |
| 11 | 1.091 | 104 | 9.60 |
| 12 | 1.1 | 115 | 10.54 |
Milk of Lime (MOL) Preparation System Capacity Requirement
| S.No | Description | Values | UOM | Remarks |
| Input Data | ||||
| 1 | Crushing rate | 230 | TCH | 5000TCD @ 22hrs basis |
| 2 | CaO requirement | 1.2 | Kg of CaO/TCH | Generally, 0.9 to 1.3 for sulphitation 0.5 to 0.8 for Defication |
| 3 | CaO % in lime | 75 | % | Depends on Lime Quality |
| 4 | Beaume of Milk of Lime (MOL) | 7 | Deg. | 7 to 10 Deg |
| 5 | Holding volume of MOL | 12 | hrs | Min. 8 hrs & Max 12 hrs |
| Result | ||||
| 1 | Lime % cane | 0.16 | % | 1.2 x 1000 / 75%
0.14% to 0.18% |
| 2 | Lime requirement | 368.0 | Kg/hr | 230 x 0.16% |
| 3 | MOL Preparation Unit Capacity | 1200 | Kg/hr | Considered 8 hours of operation per day |
| 4 | CaO in MOL | 65 | gm/lt. | 368 x 24/8
As per the above table by considered Beaume |
| 5 | Milk of lime required | 4246 | Lts / hr | 230 X 1.2 x 1000 /65 |
| 6 | Milk of lime required | 18.46 | Lts /TCH | 4246 /230
As per considered Beaume |
| 7 | MOL tanks holding capacity | 51.0 | M3 | 4246 x 12 /1000 |
| 8 | MOL tanks holding capacity | 260 | HL x 2 nos. | 51 x 10 /2 |
Calculation for the Identifying Shock Lime Connection to Juice Sulphitor
| S.No | Description | Values | UOM | Remarks |
| Input Data | ||||
| 1 | Crushing rate | 230 | TCH | 5000TCD @ 22hrs basis |
| 2 | Sulphited Juice% | 115 | % | Include filter juice |
| 3 | Shock lime time | 9 | Sec | 8 to 12 sec |
| 4 | Juice inlet line dia | 400 | mm | Juice Pipe dia which goes from absorption tower to sulphitor bottom cone feed |
| 5 | Density of juice | 1.06 | gm/ml | |
| Result | ||||
| 1 | Juice flow rate | 249.53 | M3/hr | 230 x 115% /1.06 |
| 2 | Volume of juice for shock lime | 0.62 | M3 | 249.53 x 9 / 3600 |
| 3 | Length of the pipeline | 4.97 | Mtrs | 0.62 /(0.785x400x400/1000000) |
Hence Shock lime connection is to be provided 5 meter of distance from the juice inlet point of the juice sulphitor feed line.
Related Topics:
Juice Defecator and Juice Sulphitor Design Criteria | Online Calculator
Juice Sulphitation Process | Methods of Sugar Cane Juice Sulphitation
Concepts of Juice Defecation Process and its Mechanization
Sulphur Melter | Sulphur Melting process in sugar processing industry
Flocculants Used in Sugar Processing | Flocculant Dosing Calculation
