STEAM % CANE & BODY HEATING SURFACE CALCULATION

 

Steam%Cane and Individual Body Heating Surface Calculation in Sugar Industry

 

1.Calculation of steam%cane and evaporator set individual bodies heating surface have placed one of the major calculation in equipment design drawing of sugar process industry.

2. In the steam%cane calculation involve so many factors like type of multiple effect evaporators, types of juice heaters, types of pans,  bleeding arrangement for juice heating and massecuite boiling  ect.

3. Concentration of sugarcane juice in sugar industry is done in multiple effect evaporators either in Quadruple, Quintuple or DEVC + Quad. These evaporator systems are based on Reileaux principle selected on the basis.

4. In maximum sugar industries Quintuple effect evaporator has been installed keeping in mind to get lower steam consumption in boiling house using extensive vapour bleeding.

5. In this article proved formulas for steam%cane  calculation  and also gave formulas to find required heating surface of the individual  evaporator bodies. And also provided one powerful online calculator for above calculations.

Formulas involving in this calculation:

1. First step in this calculation find the pressure drop across the evaporator set and also find individual bodies pressures, temperatures and Latent heat for given exhaust pressure and lost body vacuum of the evaporator set. It has explained in my another article please go through the below link

Principles and Pressure Drop Calculation across the Multiple Effect Evaporator Bodies

2. Vapour required for juice heating = [ Q x Cp x ΔT ] / λ

Q=Quantity of juice flow in Ton/hr

Cp =Specific heat of juice Kcal/kg/^oC

ΔT =Temp difference of inlet and outlet of the juice

λ =Latent Heat  of the vapour in kal/kg 

(Note: If the DCH( direct contact heater) will use for juice heating than vapour required quantity for juice heating to be add into the quantity of juice for further calculation. Latent heat value to be take as per heating vapour.)

3. Vapour required for massecuite boiling = K x M x [ (Brix of massecuite – Brix of feed material) / Brix of massecuite]

K = 1.5 for Batch Pan and 1.2 for Continuous Pan.

M = Quantity of massecuite in Ton/hr.

Note:

a) It is better to add moment water percentage to above required vapour.

b) For better understanding and analysis propose to be calculate specific steam consumption of the individual massecuites like A,B & C m/c. The units of  specific steam consumption is Ton of vapour per Ton of massecuite.  ( i.e Specific steam consumption = Vapour required for massecuite boiling per tonofmssecuite)

4. Vapour consumption for miscellaneous like pan washing, seed melting, molasses reconditioning, sulphur melting and super heated wash water system.

Generally these were considering as on percentage of crushing rate. Generally consider the values as follow as

a) For Pan washing take 0.2 to 0.25 % cane

b) For Seed melting take 0.4 to 0.6 % cane.

c) For molasses reconditioning take 0.4 to 0.6 % cane

d) For Super heated wash water (SHWW) system take 0.2 to 0.25% cane

e) For Sulphur melting purpose take 0.2 to 0.4 % cane. Now a days for sulphur melting follows like E- boiler or wapcon system ect. to avoid 7ata steam.

5. Total Evaporation Rate = [ (Brix of Syrup) – (Brix of C.Jc) / (Brix of syrup) ] x Final clear juice quantity.

a) Here Brix of clear juice = Brix of mixed juice x [ (Mixed juice Quantity  / Final clear juice quantity) ]

b) C.Jc % Cane = Final quantity of clear juice x 100 / Crushing rate

c) Final clear juice quantity = Juice quaintly after the juice heating – Mud quantity in mixed juice ( Final clear juice quantity will change in the case of heating the juice in DCH otherwise it will same to quantity of mixed juice).

Vapour Production = Evaporation Rate x Clear Juice Quantity in Ton/hr than calculate “ X “ Value ( X =Quantity of Vapour goes to the condenser  of evaporator in Ton/hr)

( Note: ” X ” should be have positive value.

X =  Positive valve than given bleeding arrangement is ok

X =  Negative value than given bleeding arrangement should not possible so to be change the bleeding arrangement (i.e Require vapour is more than vapour produced from Evaporators)

6. Total Exhaust required for Process in Ton/hr = X +  Vapour require for Juice heating + Vapour required for massecuite boiling +  Vapour required for miscellaneou

7. Steam% Cane = Total Exhaust required for Process x 100 / Crushing Rate in TCH

For better understanding and analysis purpose we can calculate individual steam consumption as follow as

a) Steam%cane for total Juice Heating = Total Vapour required for juice heating x 100 / Crushing Rate in TCH.

b) Steam%Cane for massecuite Boiling = Total Vapour required for massecuite boiling x 100 / Crushing Rate in TCH.

c) Steam % Cane for Evaporators = Total Quantity of Vapour goes to the evaporator condenser in Ton/hr x 100 / Crushing Rate in TCH.

Steam%Cane for Miscellaneous= Total Vapour required for Miscellaneous x 100 / Crushing Rate in TCH

Total Steam%cane = Steam%cane for total Juice Heating + Steam%Cane for massecuite Boiling   + Steam % Cane for Evaporators + Steam % Cane for Miscellaneous.

It is also helpful to cross checking of calculation.

8. Heating surface requirement for individual bodies as per general method.

Heating surface requirement = vapour production from the body in kg/hr / Evaporation rate of the body.

Evaporation rates can be calculate by the existing bleeding vapour arrangement.

Evaporation Rate = Vapour production in that body in Ton/hr x 100/ Total vapour production in all set of evaporator bodies.

But in calculation of heating surface will be taking general evaporation rates of evaporator bodies.

	Quadruple Effect  in Kg/m2/hr		Quintuple Effect in  Kg/m2/hr
	Max	Min	Max	Min
1st effect	35	30	35	30
2nd effect	30	25	30	25
3rd effect	25	20	25	20
4th effect	25	20	20	15
5th effect			15	10

 

As Per Hugot given Evaporation Rate of The Several Vessels of a multiple effect working under the condition of temperature drop from 120^oC to 55^oC

	Triple Effect		Quadruple Effect		Quintuple Effect
	Kg/m2/hr	Lb/Ft2/hr	Kg/m2/hr	Lb/Ft2/hr	Kg/m2/hr	Lb/Ft2/hr
1st effect	53	11	37	7.6	28	5.7
2nd effect	48	9.8	35	7.2	26	5.3
3rd effect	43	8.8	32	6.6	25	5.1
4th effect			28	5.7	25	5.1
5th effect					17	3.5

9. Heating surface requirement for evaporator bodies as per E.Hugot formula.

Heating surface requirement= vapour production/ ΔT * coefficient of heat transfer.

Outlet Brix of the body = [ (Juice Inlet Quantity  x Brix of inlet juice) / ( Juice inlet Quantity – Vapour Production in that particular body) ]

Average Brix of the body = [ Outlet Brix + Inlet Brix ] / 2

Boiling Point elevation =  Boiling point elevation found from HANDBOOK OF CANE SUGAR ENGINEERING by E.Hugot Page No. 501 table no.  32.3

(Note: In this table considered the parameter liquid column height  in the body, Brix of the body and temperature of the liquid in that body.

a) For liquid column height generally take 1/3^rd height of the tube in Robert type body and 20% height of the tube in semi kestner body.

b) For Brix of the body to be take average brix.)

Effective boiling point of the body = Temperature of the body +  Boiling Point elevation.

ΔT = Temperature of inlet vapour of the body – Effective boiling point of the body

Coefficient of heat transfer calculated from the Dessin formula as follow as.

Dessin proposed a formula permitting the evaporation coefficient to be calculated for any vessel of a multiple effect:

C  = 0.001 (100 – B) (T – 54)

C = specific evaporation coefficient for the evaporator, in kg of vapour/ m²/^oC/hr

B = Brix of the juice leaving the vessel

T = temperature of the heating steam in the calendria, in °C (°F).

(Note: To get better result from the above formula to be take in the place of coefficient 0.001 as follow as

For 1^st effect = 0.001,

2^nd effect = 0.0009,

3^rd effect= 0.0009,

4^th effect = 0.0008,

5^th effect = 0.0008).