There are essentially four requirements to be met for the good design of a calandria batch pan
The strike level, that is the maximum level of massecuite above the top tube plate, must be as small as possible to prevent excessive hydrostatic head and hence boiling point elevation
The circulation ratio, that is the ratio of total tube cross sectional area to downtake cross sectional area, should be such that adequate circulation is achieved.
The graining volume ratio, or the ratio of the volume of massecuite contained in the calandria and in the pan bottom to the total volume of the pan at strike, should be as small as possible to limit the number of cuttings required to achieve the grain size desired.
The heating surface to volume ratio should suit the massecuite being boiled.
In order to prevent excessive boiling point elevation the strike level should be between 1300mm and 1400mm above the top tube plate.
The reccommended circulation ratio is 2.5 ie between 2.0 and 3.0
Graining Volume Ratio
The graining volume should not exceed 40% of the strike volume.
Heating Surface to Volume Ratio
The heating surface to volume ratio depends on the type of massecuite being boiled and on the heating steam pressure. The graph below gives an indication of the heating surface to volume ratio for various massecuites and steam pressures.
Batch Pan Specification
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