Sugar Definition Sucrose is common table sugar obtained from sugar cane and sugar beets. The chemical Formula C12H22O11 which does not reduce Tollens or Feling’s reagents is determined by the stereochemistry of the D-Glucoside and D-Fructroside linkage to form sucrose. The results of X-Ray studies and the Synthesis of +sucrose lead to the conclusion that (+) Sucrose is a beta D-Fructoside and an alpha D-Glucoside. The Chemical Form of the Sucrose

In Simple Form of sucrose

Physical properties of Sucrose

1) Pure Sucrose Crystal are Transparent and colorless 2) Heat Conductivity of crystallized Sucrose Only Crystal of sucrose 00.00139 cal/cm-sec°c

3) The Dipole moment is found to be 3.1x10­18 dyne/cm² 4) The Dielectric constants of sucrose Crystal is different directions values and between 3.5 and

3.85 was found.

5) Piezoelectric effect of sucrose was observed, the sucrose is Dia-magnetic, and the specific magnetic susceptibility is being 0.57.

6) The density of crystalline Sucrose at 1.5°c is 1.5879gm/ml, were found powdered crystalline

sucrose.

7) Linear thermal expansion

8) Melting point of sucrose is 185-186°c

9) Specific Volume of Crystallized Sucrose is 0.63ml/gm @ 15°c under Normal pressure.

10) Molecular weight of sucrose is 342.296

11) Normal Entropy of sucrose is 86.1kcal/mole 12) Enthalpy of formation is 530.8 kcal/mole

13) Work of formation amount to -317.6kcal/mole at 25°c and 760mm pressure of Hg.

14) Enthalpy of combustion is -1351.3kcal/mole

Chemical Properties of Sucrose:

1) Sucrose is a carbohydrate of the formula C12H22O11 2) It is a disaccharide, consisting of monosaccharide components.

3) Refined sugar contains about 99.99% of sucrose.

4) Purest sucrose is obtained by redissolving sugar in water precipitating with absolute Ethyl

Alcohol.

5) Sucrose is very soluble in water and faintly hygroscopic.

6) Small quantities of salt decrease the solubility of sucrose, while higher quantities of salt increase it.

7) When sucrose solutions are treated with metal hydroxides under suitable conditions, colloidal

turbidities, syrup gels or flake precipitates are obtained.

8) In the presence of hydrogen ions a hydrolytic, decomposition of sucrose takes place.

9) When the sucrose solutions are heated in presence of OH-Ions, decomposition takes place.

10) In a solution of sucrose with lime of Ph 12, the sugar loss in one hour boiling under normal

pressure was found to be about 0.5%. Cane Preparation Equipment The following table gives recommendations on cane preparation equipment Installed Specific powers and tip speeds.

Cane Preparation Equipment Installed Power

Description

Specific Power [kW/tfh]

Tip Speed [m/s]

Tip Clearance [mm]

Leveller knives 6 50 1000 First knives 15 60 150 Second knives (heavy duty) 30 60 50 Shredder 60 100 Total 111 Southern African industry average 84

Installed Specific Power for Milling Table of required installed power for a milling tandem

Number of Mills Specific Power per Mill [kW/tfh]

Four mills 22

Five mills 20

Six mills 18

Diffuser + two mills 25

Mill Capacity Calculations There are a large number of formulae for the calculation of the capacity of a milling tandem

Hugot gives the following formula:

A = 0.8 c·n·√N· (1-0.06·n·D) ·L·D2/f

Where

c is a factor dependent on the cane preparation equipment,

c= 1.3 if the tandem is preceded by a shredder

n is the mill speed in rev/min N is the number of rollers in the tandem L is the length of the roll in meters D is the mean diameter of the rollers in meters f is the fiber percent cane

Example: Capacity of the plant---------------------5000 TCD Cane crushing per hour--------------5000/22 =227.27 TCH Imbibitions percentage of cane-----------35±2% Bagasse percentage on cane--------------29±1% Hugot gives the following formula:

A = 0.8 c·n·√N· (1-0.06·n·D) ·L·D2/f (Or) Mill setting calculation (based on Fiber Index loaded Method) Fiber loaded in various mill the following formula FL=1000x AxF/60x3.14xDxNxl (Kg/m2) Where, A=Total Cane crushing per hour F=Fiber percentage of cane (i.e-14%) D=Pitch Circle Diameter of the Top Roller N=Speed of the Roller (rpm) L=Length of the Roller A, Fiber % of Bagasse Approximately percentage of fiber in bagasse foe each mill first mill=34% Second mill=39% Third mill=45% Fourth mill=50%

Formula for fiber Index is given =Fiber % of bagassex1.75x10 kg/m³

Discharge roller setting Dr=Fiber Load/Fiber Index (mm) Feed Roller setting Fr=mill ratio x Discharge work opening Trash plate setting

Tp=1.75 x feed roller work opening

Mill Sizing Nomogram The nomogram below from is a quick guide to sizing a milling tandem

Geometry of Mills

Ratio of feed opening to discharge opening in the working position mill ratio = 2

Tooth Profile

Mill Operating Parameters

Top roll mean diameter MDT = 45 in

Discharge roll mean diameter MDD = 45 in

Feed roll mean diameter MDF = 45 in

Tooth Pitch TP = 2 in

Tooth Flat Tfl = 6 mm

Tooth Angle Tang = 45°

Tooth Depth Tdepth = (TP - Tfl) / (2 · tan(Tang / 2))

Roll Length lroll = 7 ft

Speed of top roll n = 3 rpm

Cane throughput

tch = 250 ton/hr

f%c = 15%

fiber % cane fibre throughput

fibrethput = tch · f%c fibrethput = 567 kg/min

Average peripheral velocity of top/feed rolls

vTF = n / 2 · (MDT + MDF) / 2 vTF = 10.77 m/min

Average peripheral velocity of top/discharge rolls

vTD = n / 2 · (MDT + MDD) / 2 vTD = 10.77 m/min

fibre fill in the discharge opening

ffD = 850 kg/m3

fibre fill in the feed opening

ffF = ffD / mill ratio

described volume in the discharge opening

volEscrD = fibrethput / ffD volEscrD = 0.667 m3/min

Feed Work Opening

woF = volEscrF/ (vTF · lroll) woF = 58 mm

Top - Feed roll Centers (Working)

TF = MDT / 2 + MDF / 2 + woF TF = 1201 mm

Top - Discharge roll Centers (Working)

TD = MDT / 2 + MDD / 2 + woD TD = 1172 mm

Vertical distance between top and side roll centers at rest

Vrest = 33.25 in

mill lift

l = 15 mm

Horizontal distance between top roll and feed roll centers

HF = √(TF2 - (Vrest + l)2) HF = 839 mm

Horizontal distance between top roll and discharge roll centers

HD = √(TD2 - (Vrest + l)2) HD = 797 mm

set feed opening (Tip to Bottom)

soF = √(HF2 + Vrest2) - MDT / 2 + MDF / 2 soF = 47 mm

set discharge opening (Tip to Bottom)

soD = √(HD2 + Vrest2) - MDT / 2 + MDD / 2 soD = 18 mm

Trash Plate Settings Hugot notes that the ideal shape of a trash plate is the logarithmic spiral, and points out that the Simplest approximation to this is an arc whose center is offset from the centre point (in the Working position) of the top roll along a horizontal line towards the discharge roll. The amount Of the offset is given below.

The work opening on the vertical plane through the centre of the top roll is 1.75 times the feed work opening.

Recommended fibre fill [kg/m3] for a milling train

Mill No

7 Mill Tandem 6 Mill Tandem 5 Mill Tandem

1

500.0 500.0 500.0

2

583.3 600.0 625.0

3

666.7 700.0 750.0

4 750.0 800.0 875.0

5

833.3 900.0 1000.0

Offset Distance from center of top roll to center of radius for trash plate surface

Ow = (MDT / 2 + woF) / 25 Ow = 25.2 mm

Radius of Trash Plate in working position

Rw = MDT / 2 +1.75 · woF Rw = 673.1 mm

Length of vertical line from centre point of top roll (in set position) to top surface of Trash Plate

Rs = MDT / 2 +1.75 · woF – l Rs = 658.1 mm

6

916.7 1000.0

7

1000.0

Mill Bearings

Bearing Pressures The maximum pressure that a bearing can withstand is mainly a function of the bearing material. The bronzes that are common in sugar mills have a recommended maximum bearing pressures of up to 100 MPa for phosphor bronze and 50 MPa for tin-bronzes. Standard sugar mill practice limits the bearing pressure to about 10 MPa.

Materials for Plain Bearings The two essential elements in a plain bearing are the bearing or bearing

material itself, and the shaft or moving member. The bearing or bearing material is located in a housing or structure, and may or may not be integral with it.

Separating these two elements is the lubricant, introduced, generally in the case of sugar mills, by external pressure feeding.

The material of the shaft or journal is established from considerations of strength and rigidity, and will invariably be steel. Because the conditions under which bearings must operate in service may vary over a wide range, it is necessary that bearing materials be used which have certain desirable properties. Amongst these we must include such factors as

mechanical strength; softness and low melting point; low modulus of elasticity; corrosion resistance; high thermal conductivity; and of course, Economic considerations.

Since these factors cannot all be obtained to a desirable degree in a single material, it is necessary in practice to make a compromise. The most common bearing materials consist of

a. white metals, b. copper base alloys, and c. Aluminum-base alloys.

White Metal White metals is a term used to include the tin and lead-base metals, broadly referred to as Babbitt (after Isaac Babbitt, 1839), and since such metals are highly competitive, they are recommended for most applications where the loading is not severe. Babbitt bearings are manufactured with the white metal lined onto steel, cast iron and copper base alloys. Since white metal suffers a reduction in fatigue strength with increase in temperature, and this reduction is a function of thickness, it is usual to limit the thickness to between about 0.100-0.175 mm and thicknesses of only 0.025-0.050 mm are used with copper lead over the back-up material. White metal is not commonly used as a sugar mill bearing material

Copper-base Alloys Copper-base alloys including lead-bronze, gun-metal and phosphor-bronze are widely used as bearing materials.

Lead-bronze is the cheapest, and is used for general service bearings. It has a low tendency to seizure, in common with the white metal bearings, and has greater fatigue strength to withstand higher temperatures. Lead bronze bushes are frequently used in the form of single, solid units, i.e. as bushes without the supporting shell surrounding the bearing material, as is required of the Babbitt or white metal bearing materials. Gun-metal provides a relatively cheap and easy to machine material, having well bearing properties and capable of withstanding Somewhat higher loads than the lead-bronze alloys. This alloy also has good resistance to corrosion in sea water.

Phosphor-bronze is used for heavily loaded bearings, where high frictional stresses are likely to occur. Because of the high hardness of this material, it demands the use of a hardened steel journal.

Typical Sugar Mill Bearings Rein in Cane Sugar Engineering states that typically sugar mill bearings are tin bronzes with the following composition Cu

84%

Sn 10%

Pb 3%

Zn 3%

Lubrication Sugar mill shafts do not turn sufficiently fast for a hydrodynamic film of lubricant to be formed between the journal and the bearing. Consequently hydrostatic lubrication is required. This is achieved by supplying lubricant to the bearing under pressure. Under these conditions, attention must be given to the adequate supply of lubricant at all times, and in particular to the location of oil Supply holes and grooves. Bitumen based lubricants are often used in sugar mill bearings.

Bearing Loads and Sizes Specific roll loads are in the range of 2 to 3 MN per square metre of projected roll area. This together with the allowable bearing pressure mentioned above indicates that the total bearing area should be about 20% to 30% of the projected roll area. It is usual practice to allow the top roll of a sugar mill to float in the vertical direction to:

keep a nearly constant pressure on the mat of bagasse in the mill allow some throughput variation without sacrificing extraction protect the mill from damage from tramp iron

Typically hydraulic rams together with a gas accumulator provide the downward force on the bearing caps to resist the upward force of the bagasse on the mill roll. The gas accumulator acts as an air spring. The hydraulic oil in the system is not compressible, but the gas in the accumulator is and it is this gas that has the give that allows the roll to float. The gas in the accumulator is precharged with a particular gas pressure. The higher the precharge pressure the softer the spring rate. A low precharge pressure will make the system very stiff and may not allow sufficient float to let tramp iron through the mill, which may cause damage. A high precharge pressure will make the system very soft and the top roll bearing may continually rise up to its maximum lift. This means the mill headstock may be subjected to very high forces, not anticipated in design. The correct precharge pressure which ensures that the top roll floats about its design position is important to ensure good extraction and to protect the mill from damage.

Sugar Mill Lubricants

Castrol SMR Grades Castrol SMR lubricants are especially formulated for sugar mill roll bearings and gearboxes. They are viscous black oils fortified with load bearing additives and incorporate emulsifiers to resist the harmful effects of the inevitable contamination with sugar juices encountered in use. They also find use in other heavily loaded open gears and pinions. These grades are now lead free.

Description SMR MEDIUM

SMR HEAVY CLEAR ASMR MEDIUM* ASMR HEAVY*

Bagasse Calorific Value Gross calorific value, also known as the higher calorific value (HCV) of bagasse is calculated from the following formula:

HCV= [19 605 - 196, 05(moisture % sample) - 196, 05(ash % sample) - 31, 14(brix % sample)] kJ.kg-1

The net calorific value, also known as the lower calorific value (LCV), assumes that the water formed by combustion and also the water of constitution of the fuel remains in vapor form. In industrial practice it is not practicable to reduce the temperature of the combustion products below dew point to condense the moisture present and recover its latent heat, thus the latent heat of the vapor is not available for heating purposes and must be subtracted from the HCV. By ASTM standards the HCV is calculated at atmospheric pressure and at 20°C. LCV of bagasse is calculated by the formula:

Density @

20°C 0,949 0,914 0,952 0,995

Viscosity @

40°C (mm2/s) 1205 1925 1 228 11450

Viscosity @ 100°C (mm2/s) 50,5 126,0 50,5 167,0

VIE 84 160 83 74

Color Black Red/Green Black Black

Pour Point (°C) 0 6 0 +12

Flash Point CCC (°C) 250 212 254 256

Bitumen Yes Nil Yes Yes

Compounding Yes Yes Yes Yes

EP Additives Yes Yes Yes

LCV= [18 309 - 207, 6 (moisture % sample) - 196, 05 (ash % sample) - 31, 14 (brix % sample)] kJ.kg-1

Do online calculations of HCV and LCV. Select the parameter to be used as the graphs X-axis by clicking the appropriate radio button.

Example: Capacity of the plant---------------------5000 TCD Cane crushing per hour--------------5000/22 =227.27 TCH Imbibitions percentage of cane-----------35±2% Bagasse percentage on cane--------------29±1% Mixed Juice Percentage on cane-------------------105±2%

As per our capacity of the mill:

Imbibitions percentage of cane-----------79.54 tons (227.27 TCH) Bagasse percentage on cane--------------68.181 tons (227.27 TCH) Mixed Juice Percentage on cane-------------------238.6 Tons (227.27 TCH) Mill Balance calculation: Mill Input=Mill Out put Cane + Imbibitions water=Bagasse + Mixed Juice 227.27+79.54=238.6+68.181

306.81≈306.781

Pipe sizing Use these pages to calculate pipe sizes and pressure drops due to friction in the

pipes, for the following products:

The pressure drop is calculated from the following formula

hf = 4·f·le / d · v2/ 2·g

where

hf = head loss due to friction f = friction factor calculated from the formula below le = equivalent pipe length taking into account valves and fittings d = bore of pipe v = average flow velocity g = acceleration due to gravity 9.81m/s2

f = 0.001375 · (1 + (20000· k / d + 106 / Re)1/3)

Where

k = relative roughness of the bore of the pipe Re = Reynolds Number = ρ·v·d / μ ρ = density µ = dynamic viscosity

To be select the imbibitions water pump & motor Specific Speed of Pumps Pumps (and fans) can be characterized by various dimensionless parameters.

Specific Speed, Ns Flow parameter, φ Pressure parameter, ψ Power parameter, Π Diameter parameter Δ

The most important of these is the specific speed

Pump Selection These dimensionless parameters can be used calculate how similar pumps operate

under differing conditions (the similarity laws). These similarity laws (detailed

below) can be used to select a pump given a duty point.

Specific Speed The specific speed,Nsis given by;

Ns = Q0.5·n/ (g·H)0.75

Specific speed can also be calculated as follows where φ

and ψ are defined below

Ns = φ0.5/ψ0.75

The specific speed of a pump is associated with the impeller shape

Low Specific Speed Ns=0.05

Medium Specific Speed Ns=0.10

High Specific Speed Ns=0.20

Flow Parameter The flow parameter, φ

is given by;

φ = Q/n/D3

Pressure Parameter The pressure parameter, ψ is given by;

ψ = g·H/n2/D2

Power Parameter The power parameter, Π is given by;

Π = φ·ψ·η

Diameter Parameter The diameter parameter, Δ is given by;

Δ = ψ0.25/φ0.5

Pipe Specifications Each sugar factory needs a pipe specification so that when a pipe is being repaired

or a section of plant is being added those implementing the change know exactly

which type of pipe, fittings, flanges, gaskets and valves to use.

The following are the main types of pipe that will be needed with recommended

pressure, temperature, corrosion allowance and material parameters

Sl.no Product Pressure Temperature Corrosion Allowance Material

01 Non food grade Full vacuum to 10 bar g 100°C 2 mm Carbon Steel

02 Food grade Full vacuum to 10 bar g 100°C 0.5 mm Stainless

steel

03 Low pressure steam

Full vacuum to 3 bar g 200°C 2 mm Carbon Steel

04 Condensates Full vacuum to 10 bar g 130°C 3 mm Carbon Steel

05 High pressure steam 31 bar g 400°C 1.6 mm Carbon Steel

06 Vacuum Full vacuum 100°C 0.5 mm Stainless steel

Pipe Stress Analysis

Why? The reasons one does a pipe stress analysis on a piping system are as follows

to comply with legislation to ensure the piping is well supported and does not sag or deflect in an unsightly way under its

own weight to ensure that the deflections are well controlled when thermal and other loads are applied to ensure that the loads and moments imposed on machinery and vessels by the thermal

growth of the attached piping are not excessive to ensure that the stresses in the pipe work in both the cold and hot conditions are below the

allowable

How? The model is constructed from piping general arrangement drawings, piping

isometric drawings and piping and valve specifications. Once the system is

accurately modeled, taking care to set the boundary conditions, comprehensive

stress analysis calculations are done, modifications to the model are made to ensure compliance with the above requirements. The modifications may include one or more of the following tools

Restraints A device which prevents, resists or limits the free thermal movement of the pipe.

Restraints can be either directional, rotational or a combination of both.

Anchors A rigid restraint which provides substantially full fixity, i.e. encastre or built-in,

Ideally allowing neither movement nor bending moments to pass through them.

True anchors are usually difficult to achieve. A seemingly solid gusseted bracket

Welded to a house column does not qualify as an anchor if the column does not

Have the strength to resist the loads applied to it.

Expansion Loops A purpose designed device which absorbs thermal growth; usually used in

Combination with restraints and cold pulls.

Neutral Planes of Movement This refers to the planes on the 3 axes of a turbo machine or pump from where expansion of the machine starts eg the fixed end of a turbine casing. This information is normally provided by the equipment manufacturer. If not available from this source, the fixed points of the machine must be determined by inspection and an estimation of the turbine growths calculated.

A pipe restraint positioned in line with a neutral plane prevents differential Expansion forces between the pipe and the machine.

Cold Pull or Cold Spring This is used to pre-load the piping system in the cold condition in the opposite direction to the expansion, so that the effects of expansion are reduced. Cold pull is usually 50% of the expansion of the pipe run under consideration. Cold pull has no effect on the code stress, but can be used to reduce the nozzle loads on machinery or vessels.

Spring Hangers Used to support a piping system that is subjected to vertical thermal movements.

Commercially available single coil spring units are suitable for most applications.

Supplier's catalogues adequately cover the selection of these springs. According to Hooke's law, the spring's supporting capacity will vary in direct proportion to the amount of displacement the spring undergoes due to thermal movement. This variation between cold and hot should be between 25 and 50% of the hot loaded condition.

Solid Vertical Support In places where vertical thermal movement does not create undesirable effects, or where vertical movement is intentionally prevented or directed, solid supports in the form of rollers, rods or slippers are used. It is important that free horizontal movement of the pipe is not impeded unless horizontal restraint is desired.

Slipppers and rollers must be well designed and lubricated.

Fluid Flow Velocities Guidelines for the acceptable ranges of flow velocity for various fluids found in a sugar factory

Goodall

Description Velocity[m/s]

Water for space heating 2 4

Water for boiler feed 3 6

Saturated steam 30 50

Superheated steam 50 100

Hugot

Description Velocity[m/s]

Superheated steam 40 76 Saturated steam 24 37 Exhaust (wet/oily) 31 46 Bled vapor 37 49 Vapor under vacuum 46 76 Suction

Water 1 1.25

Juice 1 1.2 Syrup 0.5 1 Molasses 0.25 0.5 Massecuites 0.1 0.2 Delivery

Water 1.25 2.5 Juice 1.2 2 Syrup 0.75 1.25 Molasses 0.5 0.75 Massecuites 0.15 0.3

Lyle

Description Velocity[m/s]

Water 1.22 2.44 Superheated steam 46 61 Dry Saturated steam 31 40 Wet exhaust steam 21 31 Moderate vacuum water vapor 46 61 High vacuum water vapor 61 107

Babcock & Wilcox

Description Velocity[m/s]

High pressure steam 41 61

Low pressure steam 61 76

Water general 2.54 3.81

From a source on the internet Maximal velocity in pipes Water m/s ft/s Tap water (low noise) 0.5 - 0.7 1.6 -8.2

Tap water 1.0 - 2.5 3.3 - 8.2

Cooling water 1.5 - 2.5 4.9 - 8.2

Boiler feed water. Suction 0.5 - 1.0 1.6 - 3.3

Boiler feed water. Discharge 1.5 - 2.5 4.9 - 8.2

Condensate 1.0 - 2.0 3.3 - 6.5

Heating circulation 1.0 - 3.0 3.3 - 9.8

Steam m/s ft/s Saturated Steam. high pressure 25 - 40 82 - 131 Saturated Steam. in special cases - 60 - 197

Saturated Steam. medium and low pressure 30-40 99 - 131

Saturated Steam. at peak load - 50 - 164 Steam / Water emulsion - 25 - 82

Oil m/s ft/s

Suction lines for pumps - 0.5 -1.6

Suction lines for pump (low pressure) 0.1 - 0.2 0.3 - 0.65

Discharge line for booster pump 1.0 - 2.0 3.3 - 6.5

Discharge line for burner pump - 1.0 - 3.3

Air m/s

ft/s

Combustion air ducts 12 - 20 40 - 66

Air inlet to boiler room 1 - 3 3.3 - 9.8

Warm air for house heating 0.8 - 1.0 2.6 - 3.3 Vacuum cleaning pipe 8 - 15 26 - 49

Compressed air pipe 20 - 30 66 - 98

Ventilation ducts (hospitals) 1.8 - 4 5.9 - 13

Ventilation ducts (office buildings) 2.0 - 4.5 6.5 - 15 Exhaust gas

m/s ft/s

Ducts at minimum load - 4.0 - 13

Stack at minimum load - 5.0 - 16

Boiler with one-step burner (on - off) 5.0 - 8.0 16 - 26

Boiler with two-step burner (high - low) 10 - 15 31 - 49

Boiler with modulating burner (3:1) 15 - 25 49 - 82

To keep the surface free from soot the velocity should always exceed

3.0 - 4.0 9.8 - 13

It is recommended that the maximum inlet velocities applied to control valves should be as shown in the tables below Gate Valve Size

Liquid Steam or Gas

mm m/s ft/s m/s ft/s 15 - 25 9 30 120 400

40 - 50 7.5 25 90 300

65 - 100

6

20

75

250

150 - 200 6 20 70 225

250 – 400

4.5 15 55 175

Angle Valves Liquid Steam or Gas

Size mm m/s ft/s m/s ft/s 15 - 25 13.5 45 135 450

40 - 50 12 40 105 350

65 - 100 10.5 35 90 300

150 - 200 9 30 85 275

250 - 400 7.5 25 70 225

Cavitations in Centrifugal Pumps There may be, on the low-pressure side of the runner, regions in which the pressure falls to values considerably below atmospheric. In a liquid, however, the pressure cannot fall below the vapor pressure at the temperature concerned. If at any point the vapor pressure is reached, the liquid boils and small bubbles of Vapor form in large numbers. These bubbles are carried along by the flow, and on reaching a point where the pressure is higher they suddenly collapse as the vapor condenses to liquid again. A cavity results and the surrounding liquid rushes in to fill it. The liquid moving from all directions collides at the centre of the cavity, thus giving rise to very high local pressures (up to 1 GPa). Any solid surface in the vicinity is also subjected to these intense pressures, because, even if the cavities are not actually at the solid surface, the pressures are propagated from the cavities by pressure waves similar to those encountered in water hammer.

This alternate formation and collapse of vapor bubbles may be repeated with a frequency of many thousand times a second. The intense pressures, even though acting for only a very brief time over a tiny area, can cause severe damage to the surface. The material ultimately fails by fatigue, aided perhaps by corrosion, and so the surface becomes badly scored and pitted. Parts of the surface may even be torn completely away. Associated with cavitating flow there may be considerable vibration and noise; when cavitations occurs in a turbine or pump it may sound as though gravel were passing through the machine. Not only is cavitation destructive: the larger pockets of vapor may so disturb the flow that the efficiency of a machine is impaired. Everything possible should therefore be done to eliminate cavitation in fluid machinery, that is, to ensure that at every point the pressure of the liquid is above the vapour pressure. When the liquid has air in solution this is released as the pressure falls and so air cavitation also occurs.

Although air cavitation is less damaging than vapour cavitation to surfaces, it has a similar effect on the efficiency of the machine.Since cavitation begins when the pressure reaches too low a value, it is likely to occur at points where the velocity or the elevation is high, and particularly at those where high velocity and high elevation are combined.Cavitation is likely to occur on the inlet side of a pump particularly if the pump is situated at a level well above the surface of the liquid in the supply reservoir. For the sake of good efficiency and the prevention of damage to the impeller, cavitation should be avoided.

Applying the energy equation between the surface of liquid in the supply reservoir and the entry to the impeller (where the pressure is a minimum) we have, for steady conditions

p0 /ρg + z1 - hf = pmin /ρg + v12 /2g

where

v1 is the fluid velocity at the point where the static pressure has its least value pmin is the minimum static pressure

z1 the elevation of the surface of the liquid in the reservoir above this point where the static pressure has its least value

p0 the absolute pressure at that surface

p0 = pgauge + patm

ρis the density of the fluid at its operating temperature

hf is the head loss due to friction in the suction line, care must be taken to include the effect of all devices such as strainers and valves in the suction line.

Re-arranging the above equation gives

pmin /ρg = p0 /ρg - hf - v12 /2g + z1

For cavitation not to occur

pmin > pv

where

pv is the vapour pressure of the liquid. These equations can be rearranged to give the criterion for no cavitation in the pump suction line.

p0 /ρg - pv /ρg - hf - v12 /2g + z1 > 0

A parameter called Nett Positive Suction Head (NPSH) is defined as

NSPHa = p0 /ρg - pv /ρg - hf + z1

The NPSH available at the inlet flange of the pump can be calculated from the

above equation. The pump curves in the pump catalog generally give the NPSH

required at each volume flow the pump is required to do. For good pump operation

NPSHavailable > NPSHrequired

Mixed Juice Percentage on cane-------------------238.6 Tons (227.27 TCH)

So selection of the pipe materials as per the reference of the table above

Sl.no Product Pressure Temperature Corrosion Allowance

Material

01 Food grade Full vacuum to 10 bar g

100°C 0.5 mm Stainless steel

So, we can select the pipe line material is Stainless steel.

We can consider the following points to select the pipe size:

Density is a physical characteristic, and is a measure of mass per unit of volume of a Material or substance. It is a measurement of the amount of matter in a given volume of Something. The higher an object's density, the higher its mass per unit of volume. The average density of an object equals its total mass divided by its

total volume. A denser object (such as iron) will have less volume than an equal mass of some less dense substance (such as water). Water is the reference with its highest density at 3.98 °C (ρ = 1 g/cm3) and the correct

SI unit of ρ = 1000 kg/m3.

1 m3 = 1,000,000 cm3.

Density Examples: Solid - water - noble gas

Copper has a density of 8950 kg/m3 = 8.95 kg/dm3 = 8.95 g/cm3.

Water has a density of 1000 kg/m3 = 1000 g/L = 1.000 kg/dm3 = 1.000 kg/L = 1.000 g/cm3 = 1.000 g/mL.

Helium has a density of 0.1785 kg/m3 = 0.1785 g/L = 0.0001785 kg/dm3 = 0.0001785 kg/L = 0.0001785 g/cm3 = 0.0001785 g/mL.

Density of Sugar Factory Products The tables below give the approximate range of densities for selected cane factory

products. This data is taken from multiple sources including Hugot and Tromp

Sugar Cane lb/ft3 kg/m3

Whole stick cane, tangled and tamped down as in a cane transport vehicle 12.5 200.2

Whole stick cane, neatly bundled 25 400.5

Billeted cane 22 352.4

Whole stick tangled cane but loosely tipped into cane carrier 10 160.2

Knifed cane 18 288.3

Shredded cane 20 320.4

Bagasse exiting the final mill 7.5 120.1

Bagasse stacked to 2 metre height (moisture = 44%) 11 176.2

Sucrose crystal 99.0 1586.2

Amorphous sucrose 94.1 1507.7

Bulk white sugar 54.9 880

Bagged white sugar 43.7 700

Raw sugar (96° Pol) in a pile 56.2 900

Bagged raw sugar 42.4 680

The International Standard Atmosphere For the design of pans, evaporators, barometric condensers and in NPSH

calculations for pumps it is necessary to know the atmospheric pressure. While

many cane sugar factories are close to the sea, there are those that are at higher

altitudes where atmospheric pressure is below the well known 101325 Pa for sea

level there are tables of atmospheric pressure variation with altitude; the table

below is the International Standard Atmosphere adapted from Thermodynamic and

Transport Properties of Fluids arranged by GFC Rogers and YR Mayhew, 3rd edition

International Standard Atmosphere

Z [m]

p [Pa]

T [K]

ρ [kg/m3]

-2500 135210 304.4 1.5473 -2000 127780 301.2 1.4782 -1500 120700 297.9 1.4114 -1000 113930 294.7 1.3470 -500 107480 291.4 1.2849 0 101325 288.15 1.2250 500 95460 284.9 1.1673 1000 89880 281.7 1.1117 1500 84560 278.4 1.0582 2000 79500 275.2 1.0066 2500 74690 271.9 0.9570

3000 70120 268.7 0.9093 3500 65780 265.4 0.8634 4000 61660 262.2 0.8194 4500 57750 258.9 0.7770 5000 54050 255.7 0.7365 5500 50540 252.4 0.6975 6000 47220 249.2 0.6602 6500 44080 245.9 0.6243 7000 41110 242.7 0.5901 7500 38300 239.5 0.5573 8000 35650 236.2 0.5258 8500 33150 233.0 0.4958 9000 30800 229.7 0.4671 9500 28580 226.5 0.4397 10000 26500 223.3 0.4136 10500 24540 220.0 0.3886 11000 22700 216.8 0.3648

Tables are not convenient for computer calculations: regression formulae have

been prepared from the above data for temperature and density; pressure can

then be calculated from the universal gas law.

T = 288.15 - 0.006492255 · Z

ρ = 1.225 · e(-0.09543718·(Z/1000) - 0.001321598·(Z/1000)2)

p = ρ·R0/M·T

where

T is temperature in Kelvin ρ is density in kg/m3 p is pressure in pascals Z is altitude (above mean sea level) in meters R0 is the universal gas constant = 8134.4 J/kg/K M is the molar mass of air = 28.9647 kg/kmol

Water Pipe Sizing

Water Properties

Temperature

°C

Pressure

bar abs

Mass Flow ton/h

Max Flow Velocity

m/s

Pipe System

Type

Description

Numbers/Length

Short Radius 90º Bends

Long Radius 90º Bends

Short Radius 45º Bends

Tees - Line Flow

Tees - Branch Flow

180º Return Bends

Gate Valves (Fully Open)

Globe Valves (Fully Open)

Angle Valves (Fully Open)

Butterfly Valves (Fully Open)

Ball Valves (Fully Open)

Plug Valves (Fully Open)

Swing Check Valves

Wafer Check Valves

The above are consider to be select the pipe size:

Example: Mixed Juice

Temperature

45 °C

Pressure

5 bar abs

Mass Flow

238.6 ton/h

Max Flow Velocity

1.2 m/s

Type

Description

Numbers/Length

Pipe length

60mtrs

Short Radius 90º Bends

5

Long Radius 90º Bends

2

Short Radius 45º Bends

2

Tees - Line Flow

0

Tees - Branch Flow

0

180º Return Bends

0

Gate Valves (Fully Open)

4

Globe Valves (Fully Open)

0

Angle Valves (Fully Open)

0

Butterfly Valves (Fully Open)

0

Ball Valves (Fully Open) 0

Plug Valves (Fully Open) 0

Swing Check Valves 0

Wafer Check Valves 0

Water Pipe Sizing – Results

Water Temperature 45.0°C Mass Flow 238.0 ton/h Density 990.4 kg/m3 Viscosity 0.6 mPa.s Volume Flow 240.3 m3/h Flow Velocity 0.9 m/s Frictional Head Loss 0.4 m Pipe Size DN300 Short Radius 90° Bends 5 Long Radius 90° Bends 2 Short Radius 45° Bends 2 Tees - Line Flow 0 Tees - Branch Flow 0 180° Return Bends 0 Gate Valve (Fully Open) 4 Angle Valve (Fully Open) 0 Butterfly Valve (Fully Open) 0 Ball Valve (Fully Open) 0 Plug Valve (Fully Open) 0 Swing Check 0 Wafer Check 0

Steam Pipe Sizing

Steam Properties

Temperature

°C

Pressure

bar abs

Mass Flow

ton/h

Max Flow Velocity

m/s

Pipe System

Type Description

Numbers/Length

Short Radius 90º Bends

Long Radius 90º Bends

Short Radius 45º Bends

Tees - Line Flow

Tees - Branch Flow

180º Return Bends

Gate Valves (Fully Open)

Globe Valves (Fully Open)

Angle Valves (Fully Open)

Butterfly Valves (Fully Open)

Ball Valves (Fully Open)

Plug Valves (Fully Open)

Swing Check Valves

Wafer Check Valves

Example Evaporator Steam Inlet Pressure—3kg/cm² Temperature----120°c Flow rate---35 t/hr

Saturated steam velocity----50

Steam Properties

Temperature

120 °C

Pressure

3 bar abs

Mass Flow

35 ton/h

Max Flow Velocity

50 m/s

Pipe System

Type

Description

Numbers/Length

Pipe length

60mtrs

Short Radius 90º Bends

Long Radius 90º Bends

5

Short Radius 45º Bends

3

Tees - Line Flow

0

Tees - Branch Flow

0

180º Return Bends

0

Gate Valves (Fully Open)

2

Globe Valves (Fully Open)

0

Angle Valves (Fully Open)

0

Butterfly Valves (Fully Open)

0

Ball Valves (Fully Open) 0

Plug Valves (Fully Open) 0

Swing Check Valves 0

Wafer Check Valves 0

Steam Pipe Sizing – Results

Steam Temperature 120.0°C Steam Pressure 3.0 bar abs Mass Flow 35.0 ton/h Specific Volume 0.6 m3/kg Viscosity 12.9 µPa.s Volume Flow 5.7 m3/s Flow Velocity 49.6 m/s Frictional Pressure Loss 12.6 kPa Pipe Size DN400 Short Radius 90° Bends 0 Long Radius 90° Bends 5 Short Radius 45° Bends 3 Tees - Line Flow 0 Tees - Branch Flow 0 180° Return Bends 0 Gate Valve (Fully Open) 2 Angle Valve (Fully Open) 0 Butterfly Valve (Fully Open) 0 Ball Valve (Fully Open) 0 Plug Valve (Fully Open) 0 Swing Check 0

Pump selection The following data can required the pump selection Pump duty

Volume flow= ______________m3/h

Head = m

Density = kg/m3

Line Frequency=50Hz/60Hz

Example:

Mixed Juice: 238 tons/hr

Volume Flow: 238tons/hr (or) m³/h

Head= 30 m (approx)

Density=320.4 kg/m³

Line Frequency=50 Hz

Selection

Speed [rpm] Pump Size Imp Dia

[mm] Max Eff [%]

Op Power [kW]

Installed Power [kW]

2955 No Selection 173 75.8 8.2 11

1478 150-315 315 72.0 8.7 11

985 No Selection 459 65.3 9.5 11

739 No Selection 604 58.5 10.6 15

Mixed Juice: 238 tons/hr

Volume Flow: 238tons/hr (or) m³/h

Head= 30 m (approx)

Density=320.4 kg/m³

Line Frequency=60 Hz

Selection

Speed [rpm] Pump Size Imp Dia

[mm] Max Eff [%]

Op Power [kW]

Installed Power [kW]

3546 No Selection 150 76.0 8.2 11

1773 125-315 267 73.8 8.4 11

1182 No Selection 387 68.8 9.1 11

887 No Selection 507 63.0 9.9 15

Liquid - Liquid Heater Rapid Design

Usually imbibitions water is hot condensate from the process house, often

contaminated with sugar and not suitable for boiler feed water. This hot

condensate is too hot for imbibitions duty, for two reasons;

hot imbibitions releases waxes from the canes causing the mills to slip during the winter months hot imbibitions can cause clouds of mist in the mill house

which reduces visibility (a safety hazard)

This hot condensate must be cooled before it can be used as imbibitions. The

obvious product to cool it against is the mixed juice from the mills. Hence a liquid

liquid heater

Cane throughput TCH

Fibercon %

Brix%Cane %

Imbibition%Fibre in Cane %

Moisture%Bagasse %

Brix%Bagasse %

Imbibition Temperature (into heater) °C

Imbibition Temperature (out of heater) °C

Juice Temperature (into heater) °C

Mixed Juice Purity %

Tube Length m

OHTC kW/m2K

Example:

Cane throughput 227TCH

Fibercon 15%

Brix%Cane 15%

Imbibition%Fibre in Cane 300%

Moisture%Bagasse 50%

Brix%Bagasse 2%

Imbibition Temperature (into heater) 95°C

Imbibition Temperature (out of heater) 70°C

Juice Temperature (into heater) 35°C

Mixed Juice Purity 85%

Tube Length 3.8m

OHTC 0.4kW/m2K

Basic Data

Juice Flow 258.2t/h

Imbibition Flow 102.2t/h

Juice Inlet Temp 35.0°C

Juice Outlet Temp 44.9°C

Imbibition Inlet Temp 95.0°C

Imbibition Outlet Temp 70.0°C

LMTD 42.1°C

Tube Length 3.8m

Heat Flux 2978.5kW

Heating Surface 176.9m2

Design Options The following table gives a number of options that should provide an acceptable

design of liquid liquid heater

Tube Dia Tubes per Pass Passes Flow Velocity

35 37 13 2.3

42 31 13 1.9

42 37 11 1.6

54 19 16 1.8

76 7 29 2.5

Vacuum Equipment

Purpose of the Vacuum Equipment The vacuum equipment's function is to remove the incondensable gases that find

their way into the vapour stream.

The incondensable gases come from the following sources:

leakage of air into the vessels; inherently in the juice; air in the heating steam air in the cooling water

Quantity of Air to be Removed A number of authors have expressed an opinion on the the amount of

incondensable gas to be removed from the condensers. Sadly, and as is typical

there is little agreement among them. the quantities of air to be removed as

follows.

leakage of air [kg/h] = 0.345·V, where V is the volume of the vessel [m3] air in the juice [kg/h] = 0.1·mj, where mj is the flow of juice [t/h] air in the cooling water = 0.035·mw, where mw is the flow of cooling water [t/h] air in the heating steam is not counted

Juice Clarifiers

Introduction A clarifier is used to separate out the solids suspended in the cane juice. These

solids originate from sand adhering to the cane stalks as well as from material

inherent in the cane stalk. The separation takes place by allowing the solid

particles to settle out onto a tray. The solids are swept from the tray into a mud

compartment, from which it is pumped to filters for desweetening and dewatering.

In the past multitray clarifiers, such as the Dorr, Graver, Bach and RapiDorr were

popular, but the SRI clarifier is almost standard for all new installations. The SRI

clarifier is a single tray clarifier (also known, oddly, as a tray less clarifier),

characterized by short juice retention times (usually 40 minutes or less).

The benefits of the single tray short retention clarifier are:

Short retention time, hence less sucrose destruction, and color formation Higher throughput capacity Lower capital cost Lower maintenance cost Easy to liquidate and hence regular cleaning is possible

Flocculent usage and operability appear to be no different from multitray clarifiers

Design The main design parameters are up flow velocity and the residence time

Up flow Velocity The up flow velocity is calculated as half the initial settling rate of the mud in the

juice. The initial settling rate is the slope of the steeply downward sloping part of

the settling curve below. In the case of a Greenfield project where the settling

characteristics of the mud are unknown, the up flow velocity can be assumed in

the range 65 to 80 mm/min (Most SRI clarifiers in South Africa operate with an

Up flow velocity below 72mm/min).

Residence Time The residence time is usually on the range of 40 to 45 minutes.

Sizing Given the volumetric juice flow and the above two parameters; the cross sectional

area (hence diameter) and the operating depth of the clarifier can be calculated

Specification for Vacuum Pan, Evaporators And Juice Heater Tubes Less Than Three Meters Long

Scope This specification covers the material selection, dimensional tolerances, heat

treatment, surface condition, inspection and testing, marking, and packing for

tubes that will be installed in vacuum pans, evaporators and juice heaters in which

the tubes are less than three meters long.

Quantities and Sizes Number of tubes required: Length of tube required: Nominal outside diameter of tubes Wall thickness of tubes

Material The tubes shall be of TP304L stainless steel, with a longitudinal welded seam

Code of Manufacture The tubes shall be manufactured, inspected and tested in accordance with ASTM

A269 Standard Specification for Seamless and Welded Austenitic Stainless Steel

Tubing for General Service

Dimensional Tolerances The dimensional tolerances shall be in accordance with ASTM A269

Heat Treatment The heat treatment shall be in accordance with ASTM A269

Surface Condition The external and internal weld bead shall be made flush. The tubes shall be

supplied free of mill scale. This can be achieved either by pickling or bright

annealing. The tube ends shall be cut square and deburred.

Inspection and Testing The tubes shall be inspected and tested in accordance with ASTM A269. The

inspection and testing will be done using an independent inspection authority, at

the client's cost.

Marking Each shall be marked in accordance with ASTM A269 and in addition shall bear the

following marks Sugartech Specification

Packing The tubes shall be packed in bundles with wooden frames to protect the tube

ends. The bundles shall be strapped and shrink-wrapped in plastic. A means of

lifting the bundle, in a way that will not damage the tubes, shall be provided.

Specification for Vacuum Pan, Evaporators And Juice Heater Tubes More Than Three Meters Long

Scope This specification covers the material selection, dimensional tolerances, heat

treatment, surface condition, inspection and testing, marking, and packing for

tubes that will be installed in vacuum pans, evaporators and juice heaters in which

the tubes are more than three meters long.

Quantities and Sizes

Number of tubes required: Length of tube required: Nominal outside diameter of tubes Wall thickness of tubes

Material The tubes shall be of TP439 stainless steel, with a longitudinal welded seam

Code of Manufacture The tubes shall be manufactured, inspected and tested in accordance with ASTM

A268 Standard Specification for Seamless and Welded Ferritic and Martensitic

Stainless Steel Tubing for General Service

Dimensional Tolerances The dimensional tolerances shall be in accordance with ASTM A268

Heat Treatment The heat treatment shall be in accordance with ASTM A268

Surface Condition The external and internal weld bead shall be made flush. The tubes shall be

supplied free of mill scale. This can be achieved either by pickling or bright

annealing. The tube ends shall be cut square and deburred.

Inspection and Testing The tubes shall be inspected and tested in accordance with ASTM A268. The

inspection and testing will be done using an independent inspection authority, at

the client's cost.

Marking Each shall be marked in accordance with ASTM A268 and in addition shall bear the

following marks Sugartech Specification

Packing The tubes shall be packed in bundles with wooden frames to protect the tube

ends. The bundles shall be strapped and shrink-wrapped in plastic. A means of

lifting the bundle, in a way that will not damage the tubes, shall be provided.

Sugar Factory Tubes for Heating, Evaporating and Crystallizing Some desirable characteristics of tubes for juice heaters, evaporators and pans are

easy to expand into the tube plate corrosion resistant similar co-efficient of thermal expansion to the shell of the vessel have a good heat conductivity have a smooth and bright inside surface: a very low surface roughness favors a higher flow of

the juices have a long life have a good cost : benefit ratio

The choice material is between:

mild steel copper (or brass)

austenitic stainless steel (types AISI 304 and / or 316) special alloys (with higher chromium / nickel contents) ferritic stainless steel

In practice the choice is between mild steel, 304 stainless steel or 439 stainless

steel. 304 for shorter tubes and 439 for longer tubes. Carbon steel is not

recommended because in the long run (a period of say 20 years) carbon steel

tubes work out more expensive.

Carbon Steel If it is decided that carbon steel tubes are to be used the recommended

specification is BS3605 Gr 320

304 Stainless This grade of stainless steel can be used where the tube length is less than three

meters. The coefficient of thermal expansion for 304 is 1.8×10-2 mm/m/°C which

is substantial more than that of carbon steel. When the vessel is hot the thermal

stresses in the tubes will be high. Tubes of 304 stainless steel should always be

annealed after welding.

439 Stainless Steel ASTM TP439 is a titanium stabilized ferritic grade of stainless steel (17-19% Cr)

which is recommended for long evaporator or pan tubes (in excess of 5m long)

Advantages of grade 439

fully ferritic metallurgical structure (ensured by the titanium stabilization) very good weld ability and ductility; inter-crystalline corrosion resistance; pitting corrosion resistance; Full immunity to stress corrosion. Coefficient of thermal expansion (in the range 0°C - 100°C) is 1.02×10-2 mm/m/°C

Stress corrosion cracking This type of corrosion occurs when

A susceptible material is subject to mechanical stress in a corrosive environment

In an evaporator, pan or juice heater under the above conditions the result will be

cracks leading to breakage in the area near the tube plate.

The danger of stress corrosion cracking exists in virtually all evaporators. The risk

will be higher if tubes over 7 meters in length (some designs of continuous pans,

Falling-film evaporators and Kestner evaporators). Ferritic stainless steels are

immune to stress corrosion cracking

Heat transfer Thermal conductivity of ferritic stainless material is 40% higher than that of

austenitic grades (like 304, 304L, 316 or 316L) i.e.: 26 vs. 15 watt/metre/°C.

Recommended Wall Thickness For evaporators and heaters, with tube length less than five meters a wall

thickness of 1.2 mm is acceptable, for tubes longer than five meters a wall-

thickness of 1.50 mm is quite sufficient (even on longer lengths up to 11 m) Tubes

with 2.0 mm would be harder to swage into the holes and would require a 600°C

Pre-heating of tube ends.

Wall-thickness 1.6 or 1.75 mm are recommended for those tubes located near

Steam-entrance and subject to some vibration during the process.

For vacuum pans with 100 mm diameter tubes the recommended wall thickness is

1.5 or 1.6mm.Allow 0.6 mm clearance between tube and plate.

Tube Hole Tolerances and Clearances The following definitions will help explain the calculation of hole clearances

Tolerance

Is the amount by which the actual size of the hole or tube varies from the nominal size. This variation depends on the manufacturing process and on

random errors.

Clearance

Is the difference in size between the hole and the tube. Because there is a maximum and a minimum tube outside diameter and a maximum and a minimum hole diameter there will be a range of clearances.

Tolerances The tube OD tolerances depend on the tube manufacturer and his equipment and

process. In the same way the tube sheet hole tolerances are a function of the hole

making process. The best we can do is specify tolerances the manufacturer can

achieve at a reasonable cost.

Clearances The designer of a vessel can control the clearance between tube OD and tube

sheet hole diameter. But as noted above this will be a range.

The minimum clearance should be such that the tube material once expanded

into the tube undergoes plastic deformation; that is, the strain has exceeded the

yield point. In most stainless steels there is no definite yield point, rather a 0.2%

proof strain is regarded as the yield criterion. The criterion set for minimum

clearance is thus 0.3% strain for no good reason other than it is greater than

0.2%.The maximum clearance shall be such that the tube material is not strained

more than 2.0%. See graph below (from Thum and Micleots)

It must be noted that both the minimum and maximum clearance criteria are

Somewhat arbitrary, but they have proved themselves in practice in a number of

Different types of vessels.

Practical Application

Kestner evaporator tube For this example we will consider a 2 in nominal diameter tube. The tube OD

Tolerance is given by the manufacturer as +/- 0.23 mm.

Tube nominal diameter

Dtnom = 50.8 mm

Tube OD tolerance

told = 0.23 mm

Minimum tube diameter

Dtmin = Dtnom - told

Dtmin = 50.57 mm

Maximum tube diameter

Dtmax = Dtnom + told Dtmax = 51.03 mm

In order to get plastic deformation of the tube as it is expanded it must be

strained more than 0.2%, say 0.3%

Diametral strain

ε = 0.30%

Diametral dilation

Δd = ε Dtnom Δd = 0.152 mm

Nominal hole diameter

Dhnom = Dtmax + Δd Dhnom = 51.18 mm

The hole is going to be drilled and an ISO tolerance of H12 is achievable i.e. the

tube hole diameter is 51.18H12. The H12 tolerance is +0.000 +0.300

Tube hole tolerance

tolh = 0.300 mm

Minimum hole size

Dhmin = Dhnom + 0.000 mm Dhmin = 51.18 mm

Maximum hole size

Dhmax = Dhnom + tolh Dhmax = 51.48 mm

Check We will now check that the calculated clearances meet our criteria set above

Minimum clearance

Clmin = Dhmin - Dtmax Clmin = 0.15 mm

Minimum diametral strain

εmin = Clmin / Dtnom εmin = 0.3% - Okay

Maximum clearance

Clmax = Dhmax - Dtmin Clmax = 0.91 mm

Maximum diametral strain

εmax = Clmax / Dtnom εmax = 1.796% - Okay

Continuous vacuum pan tube In this example we will consider a 4 in nominal diameter tube. The tube OD

Tolerance is given by the manufacturer as +/- 0.38 mm.

Tube nominal diameter

Dtnom = 101.6 mm

Tube OD tolerance

told = 0.38 mm

Minimum tube diameter

Dtmin = Dtnom - told Dtmin = 101.22 mm

Maximum tube diameter

Dtmax = Dtnom + told

Dtmax = 101.98 mm

In order to get plastic deformation of the tube as it is expanded it must be

Strained more than 0.2%, say 0.3%

Diametral strain

ε = 0.30%

Diametral dilation

Δd = ε Dtnom Δd = 0.305 mm

Nominal hole diameter

Dhnom = Dtmax + Δd Dhnom = 102.28 mm

The hole is going to be drilled and an ISO tolerance of H12 is achievable ie the

Tube hole diameter is 102.28H12. The H12 tolerance is +0.000 +0.350

Tube hole tolerance

tolh = 0.350 mm

Minimum hole size

Dhmin = Dhnom + 0.000 mm Dhmin = 102.28 mm

Maximum hole size

Dhmax = Dhnom + tolh Dhmax = 102.63 mm

Check We will now check that the calculated clearances meet our criteria set above

Minimum clearance

Clmin = Dhmin - Dtmax Clmin = 0.30 mm

Minimum diametral strain

εmin = Clmin / Dtnom εmin = 0.3% - Okay

Maximum clearance

Clmax = Dhmax - Dtmin Clmax = 1.41 mm

Maximum diametral strain

εmax = Clmax / Dtnom εmax = 1.393% - Okay

Tube Installation Points to note when expanding tubes into tube plates

1. Ends of expanded tubes must never be welded to tube plates. 2. When expanding tubes into plates it is essential to start at the top of the vessel surplus of 5 mm

(3/16") must be kept. One must ensure that tube ends remain exposed above the tube plates. 3. Five-roller expander with safety clutch should preferably be used instead of usual three-finger

expander. 4. Provide a crash stop in order to avoid swelling of the tubes just inside the plate-level. 5. When replacing tubes in plates, make sure that the surface of the bottom plate is quite clean

and smooth. If necessary it must be repaired adequately. 6. It is necessary to protect tubes near the steam entrance. Baffles should be built in. This will

avoid thermal shock and mechanical stresses which might be especially high at this particular part of the vessel.

Sugar Factory Tubes Sheet Ligaments The ligament on a tube sheet is the material between two tube holes. In a perfect

World the all the ligaments on a tube sheet will be exactly the same size. However

Due to the variation in hole size due to tolerance and also due to mistakes in hole

Centre positioning there may be ligaments which are smaller than the theoretically

Calculated ligament. Now if it is found that on a particular tube sheet one or more

Of the ligaments is smaller than the others are we to reject the tube sheet and all

The work done on it? If the tube sheet is rejected, the manufacturing Programme

Will be delayed, and costs incurred.

The Tubular Exchanger Manufacturers Association (TEMA) has guidelines on

Minimum allowable ligaments on tube sheets. Unfortunately their

Recommendations only go up to 2 inch OD tubes, and so some extrapolation for 4

Inch tubes are required.

tube dia [inch]

tube pitch [inch]

maximum hole diameter [inch]

nominal ligament [inch]

minimum permissible ligament [inch]

dt p p/dt p-dt dh p-dh

0.250 0.313 1.250 0.063 0.259 0.054 0.025

0.250 0.375 1.500 0.125 0.259 0.116 0.060

0.375 0.500 1.330 0.125 0.384 0.116 0.060

0.375 0.531 1.420 0.156 0.384 0.147 0.075

0.500 0.625 1.250 0.125 0.510 0.115 0.060

0.500 0.656 1.310 0.156 0.510 0.146 0.075

0.500 0.688 1.380 0.188 0.510 0.178 0.090

0.625 0.781 1.250 0.156 0.635 0.146 0.075

0.625 0.813 1.300 0.188 0.635 0.178 0.090

0.625 0.875 1.400 0.250 0.635 0.240 0.120

0.750 0.938 1.250 0.188 0.760 0.178 0.090

0.750 1.000 1.330 0.250 0.760 0.240 0.120

0.750 1.063 1.420 0.313 0.760 0.303 0.150

0.750 1.125 1.500 0.375 0.760 0.365 0.185

0.875 1.094 1.25 0.219 0.885 0.209 0.105

0.875 1.125 1.290 0.250 0.885 0.240 0.120

0.875 1.188 1.360 0.313 0.885 0.303 0.150

0.875 1.250 1.430 0.375 0.885 0.365 0.185

1.000 1.250 1.250 0.250 1.012 0.238 0.120

1.000 1.313 1.310 0.313 1.012 0.301 0.150

1.000 1.375 1.380 0.375 1.012 0.363 0.185

1.250 1.563 1.250 0.313 1.264 0.299 0.150

1.500 1.875 1.250 0.375 1.518 0.357 0.180

2.000 2.500 1.250 0.500 2.022 0.478 0.250

Standard Ligaments 96% of ligaments shall be greater than

ligstd = p - dh - (0.0032 t / dt in + 0.030 in)

Where t = tube sheet thickness

Minimum Permissible Ligament No ligament shall be less than

ligmin = -0.0010465 + 0.510467 · (p-dh)

The factors in the above formula come from a linear regression of the data in the

Table above.

Example 1 In this example we consider a 2 in kestner evaporator type tube

Tube plate thickness

t = 25 mm

Tube outside diameter

dt = 2 in dt = 50.8 mm

Maximum tube hole dia

dmax = 51.48 mm

Tube hole pitch

p = 70 mm

Drill drift tolerance

toldd = 0.0016 in · t / dt toldd = 0.02 in

Standard ligament

lstd = p - dmax - (2 · toldd + 0.030 in) lstd = 17.72 mm

Minimum ligament

lmin = 0.0010465 mm + 0.5067383 · (p - dmax) lmin = 9.38 mm

Example 2 In this example we consider a 4 in continuous vacuum pan type tube

Tube plate thickness

t = 25 mm

Tube outside diameter

dt = 4 in dt = 101.6 mm

Maximum tube hole dia

dmax = 102.63 mm

Tube hole pitch

p = 120 mm

Drill drift tolerance

toldd = 0.0016 in · t / dt toldd = 0.01 in

Standard ligament

lstd = p - dmax - (2 · toldd + 0.030 in) lstd = 16.59 mm

Minimum ligament

lmin = 0.0010465 mm + 0.5067383 · (p - dmax) lmin = 8.78 mm

Desuperheating of Steam A desuperheater is a device that cools superheated steam to a temperature close

to its saturation temperature, usually by spraying atomized droplets of water into

The flow of superheated steam. Superheated steam is steam that is at a

Temperature above its saturation temperature.

Desuperheating of steam is an almost universal feature of a sugar factory. This is

for two reasons

Steam turbines are generally designed to leave some superheat in their exhaust to prevent erosion of turbine blades by water droplets

Juice and syrup should be boiled at less than about 125°C to reduce color formation and sucrose destruction

There are numerous methods of desuperhing steam each with their own

advantages and disadvantages: a good discussion on the various approaches to

Desuperheating is given by Sprirax Sarco

Theory A heat and mass balance over the desupeheater yield two equations

ms2hs2 = ms1hs1 + mwhw

ms2 = ms1 + mw

Combining these yields

mw = ms1 · (hs1 - hs2) / (hs2 - hw)

Symbols

m --mass flow rates [kg/s] h -- enthalpy [kJ/kg] Subscripts w

--cooling water s1

--steam upstream of the desuperheater s2

--steam downstream of the desuperheater

Sucrose Losses in a Cane Sugar Factory The data below are the industry average figures from South African factories as

published in SASTA Procedings. The figures given in the table and graph below are

as a percentage of the sucrose entering the factory in cane.

The losses in 1993 and 1994 were high as a result of the drought at that time. It is

quite clear that the losses in bagasse and filter cake are almost constant, while the

loss in molasses varies a lot, the undetermined loss is fairly stable from year to

year

Sucrose losses as a percentage of sucrose entering the factory Bagasse Filter Cake Molasses Undetermined Total 1988

2.37 0.27 9.64 1.96 14.24

1989

2.40 0.27 9.26 1.85 13.78

1990

2.33 0.26 8.76 1.98 13.33

1991

2.25 0.29 9.02 1.92 13.48

1992

2.05 0.27 8.86 1.76 12.94

1993

2.19 0.25 11.31 2.23 15.98

1994

2.25 0.25 12.07 2.29 16.86

1995

2.13 0.22 10.97 2.01 15.33

1996

2.31 0.22 11.37 2.15 16.05

1997

2.28 0.25 9.84 1.81 14.18

1998

2.26 0.24 9.40 2.00 13.90

1999

2.27 0.25 9.29 2.10 13.91

2000

2.07 0.19 9.25 1.99 13.50

2001

2.25 0.18 9.45 1.92 13.80

2002

2.04 0.18 8.62 1.87 12.71

2003

2.21 0.15 8.96 1.67 12.99

2004 2.13 0.17 9.48 1.95 13.73

2005 2.02 0.14 9.65 1.96 13.77

Average

2.21 0.23 9.73 1.97 14.14

Sulphitation Part I Sulphitation processes are subject to almost as many modifications as simple

Defecation. The variations may include the following:

1. modifications of the sequence of addition of lime and SO2 (liming first, sulphiting first, simultaneous addition of lime and gas, fractional procedures);

2. temperature modifications (sulphiting cold or hot, stepwise heating); and

3. Addition of reagents (batch, continuous, with either manual or automatic control). Obviously these variables permit a large series of combinations, and only the most commonly used are outlined here.

Cold Sulphitation The cold raw juice is pumped through a tower or box with a counter-current of SO2

to absorb as much gas as possible (acidity 3.0-4.0 ml 0.1 N alkali for 10 ml of

juice; pH 4.0 or below). Liming to slight acidity (pH about 6.5) is followed by

heating, settling, and decanting as in the defecation process. Evaporation to a thin

syrup follows, and the syrup is settled for 6-24 h before vacuum pan boiling. One

boiling, yielding a near-white sugar that is heavily washed in the centrifugal, is

frequently followed by a second boiling to a raw sugar. The "boil-back" molasses is

allowed to settle for several weeks before it is placed on the market. The success

of the process is largely dependent on the quality and price of this molasses.

Sulfitation can also be carried out by injecting SO2 (industrial liquid SO2 in

cylinders) into the cold raw juice to a level of about 400 ppm SO2. This is for the

production of raw sugar and A molasses. The A molasses is inverted to yield a

sucrose-invert ratio of about 1:1, giving a total sugar of 65% at 80 Brix, with an

SO2 level of 30-40 ppm.

Sulphitation after Liming This process is termed alkaline sulphitation as opposed to acid sulphitation

previously described. It uses about 8 gal (30 liters) of 26 Brix milk of lime per 100

gal (378 liter) of juice giving a large excess of lime. Sulphitation is then carried out

to about pH 7.5 producing a heavy precipitate that may be removed with settling

and decantation. Heavier liming (10-12 gal, 38 - 45 liter), will result in a

precipitate that permit filter-pressing. After evaporation the syrup is cooled and

sulphited to slight acidity (pH 6.5). Treating diffusion juice with lime and then

sulphitation decreases the color of syrup, raw sugar, and refined sugar by 25%

46% and 35% respectively the filterability is improved and molasses purity is

lower, giving better sugar recovery

Hot Sulphitation Hot sulphitation serves to reduce the solubility of calcium-sulphite, which is more

soluble at low temperatures, the minimum solubility is at about 75°C (167 °F).

The juice is first heated to this temperature then sulphited and limed boiled, and

settled. Harloff's process is a hot treatment procedure in which the juice is heated

to 75 °C and the lime and SO2 are added simultaneously in such a way as to

maintain the reaction acid to phenolphthalein and alkaline to litmus (pH about 7.4-

7.8), except toward the end, when a quantity of lime is added to attain a strongly

alkaline reaction (pH 10+), after which the sulphitation is completed to neutrality

to litmus (pH about 7.2). As in all other similar processes, the juice is finally

brought to boiling temperatures in juice heaters and settled.

Continuous Sulphitation Continuous sulphitation means the continuous addition of SO2 and lime to the

constantly flowing stream of juice. Marches shows many different procedures with

diagrams indicating construction details, methods of lime and gas addition, baffles

to ensure proper circulation and other details. Many of the continuous liming

processes may have different fractional procedures, but are not in general

practice.

Sulphitation of Syrup Sulphiting the syrup leaving the evaporators gives a sugar of higher and more

regular quality than juice sulphitation alone. The syrup density is lower than in

ordinary defecation processes, 55 Brix against 65 Brix or higher Sulphited syrup is

usually maintained at a distinct acid reaction, pH 6.1 - 6.5.

Control of Temperatures and Reactions

Good circulation and thorough mixing both of the lime and of SO2 are very

important a bent circulation baffle devised by Thompson gives the best results in

cylindrical sulphitators Avoidance of high alkalinities at high temperatures or for

extended periods is recommended for the same reasons as in defecation control:

such high alkalinities result in decomposition of reducing sugars and in color

formation. Poor mixing of lime and juice may produce local over-liming.

Temperatures above 75 °C are detrimental and some prefer not to exceed 70 °C

until the final pH adjustment is made, to give a clarified juice to the evaporators of

pH 6.9-7.0.

Sulphitators Generally the mixed cold juice is sprayed into tall vertical cylindrical tanks, 4ft (1.2

m) or more in diameter and possibly 15 ft (4.5 m) high, fitted for the upper two-

thirds with a series of hardwood grids made of 2 x 4 ft (0.6 x 1.2 m) timbers set

on edge. The juice enters the top of the tower in a spray and falls through the

wooden grillwork, where it encounters the rising current of SO2. Either the flow of

gas through the system is induced by an air ejector or the SO2 is under pressure.

The sulphitated juices are drawn from the conical bottom of the tower at a pH of

3.8-4.0, limed in a separate liming tank to pH 6.5-6.8, then heated to boiling and

settled.

Continuous sulphitation can be carried out in cylindrical sulphitators holding a fixed

volume of juice. Heated juice (75 °C) flows through the tank continuously, while

the milk of lime is added constantly to the entering juice and a continuous

pressurized flow of SO2 into the liquid near the bottom of the tank supplies the

needed circulation. The supply of gas is kept constant, and the lime addition is

regulated by a controller. In actual practice, the juice is pre-limed before entering

the sulphiting tank, generally to neutrality, then is maintained near the neutral

point by the sulphitation-lime addition.

Zozulya et al. describe a new sulphitator which comprises a vertical tank with a

feed-line at right angles to the top of the side wall. The juice is fed into the feed-

line through a perforated disc and comes into contact with SO2 gas metered

through a valve at right angles to the liquid stream. An internal cyclone at the top

of the tank acts as exhaust gas-liquid separator and as supplementary mixer for

the incoming gas and the juice. Performance data of this new design show results

superior to the conventional spray type with better gas utilization and

Decolourisation.

Sulphitation with Bentonite A process employing colloidal bentonite combined with sulphitation was developed

in Argentina for the production of direct-consumption white sugars, especially with

juices of deteriorated or frozen cane. Bentonite is clay, and the material selected

is sold in Argentina under the trade name Clarigel. The advantages claimed are

lower sulphur and lime consumption, much greater removal of organic non-sugars,

better boiling properties of syrups and molasses because of reduced viscosities,

and less scaling of evaporators.

Sulphur Stoves or Burners The production of SO2 occurs when sulphur is burned in a current of air. Older-

type stoves operate intermittently; modem burners provide for the addition of

sulphur without interruption of the burning.

In any type of sulphur burner the air supplied to the furnace should be dry,

because moisture in the air will cause the formation of sulphuric acid, obviously

detrimental to piping, and soon, and can be especially serious if it reaches the

juice. The drying agent is generally quicklime spread on trays, and it should be

replaced before it becomes saturated with water, about every 8 h.

Rotary sulphur burners use induced draft. Mechanical feed ensures continuous

operation. Best results are obtained with sulphur of high purity (99.6-99.9%). The

sulphur melts by its own heat of combustion in the rotating cylinder, presenting a

large surface for combustion as the sulphur drips through the air. Air is drawn in at

an adjustable neck ring and anti-sublimation sleeve at the connection between the

rotating drum and combustion chamber, a cast-iron or brick lined compartment

with baffles, where the oxidation of the sulphur and mixing with the diluting air are

completed. A uniform gas (5-16% SO2) free of sulphuric acid is delivered to the

sulphitators.

There are new methods of SO2 generation. The Swedish Celleco SBM-250 sulphur

burner

has a burning capacity of 5 t/d but has a turn-down ratio of 20:1, or 250 kg/d. It is normally operated at 2.0-3.0 psig, but can also function effectively at 42 psig. A typical flow scheme for a modern SO2 generation plant is given

Liquid Sulphur Dioxide Where transportation costs will permit, liquid SO2 offers many advantages.

MeGinnis diagrams a system for the introduction of liquid SO2.

The method is comparatively trouble free and adapts itself readily to automatic pH

control. A large reduction in sulphur consumption results; freedom from sulfuric

acid, precise control of SO2 addition, and elimination of sulfur-burning equipment

are other advantages.

Hydrogen Peroxide Hydrogen peroxide has also been tried in sugar refining. and reduced white sugar

color by 46% and ash by 20%.

Sulphitation Part II

Current Technology The carbonated liquor after the first filtration still contains an appreciable amount

of calcium in solution which has to be removed. This is done. By treating the

filtrate with sulphur dioxide to form calcium sulphite precipitate. The latter is then

separated from the liquor during a second filtration to produce a final clear liquor.

Sulphitation is not an essential part of a carbonization refinery, another Process

such as ion-exchange can also be used to remove excess calcium.

Equipment Because sulphitation is only a minor operation in a carbonization refinery, geared

mainly to reducing excessive alkalinity to the neutral point, the amount used is

relatively small and the apparatus sometimes a bit crude. Especially the sulphur

burner. The equipment in use in our refineries to perform liquor sulphitation

consists of:

1. the sulphur burner for production of SO2 gas 2. a tower for contacting liquor and SO2

Or a venturi system of contacting, such as the Quarez sulphitator.

Design Considerations Sulphur burner, Production of SO2 gas:

The combustion of sulphur is required to produce sulphur dioxide, because the

reaction takes place in the gaseous state between sulphur vapour and oxygen,

according to the formula:

S + O2 → SO2 + 293 kJ

The reaction is exothermic and the combustion gas has an SO2content of 6 to

16%. A simple type of sulphur burner is normally used being of the stationary type

and quite suitable for the light sulphitation of liquor required. Ideally the design

and operation of sulphur burners require that some important points be

Recognized, in particular:

1. Keep to a minimum the formation of SO3 which will react with moisture in the air to produce sulphuric acid. The cooling of SO2 gas to below 200°C is essential, the production of SO3 then being negligible (5). The, drying of the air of combustion is also required to prevent the formation of H2SO4.

2. Prevent the sublimation of sulphur, which can cause blockages and impair SO2 production by controlling the furnace temperature to less than 300°C.

3. The air flow should be kept constant and controlled. 4. A regulated supply of sulphur should be provided, if possible.

The points mentioned above are not easy to control in the type of furnace in use,

but then the operation is not critical enough to warrant a more complex approach.

The Sulphur Tower As the name implies this is a tower containing splash trays, stacked on top of one

another and designed to create a continuous passage for the liquor from the top to

the bottom, while the SO2 gas travels up the tower. The liquor is broken into

droplets in falling from one splash tray to the next. The gas is drawn up the tower

by suction from a fan and the exhaust fumes are dispersed into the atmosphere.

Reaction takes place as the SO2 conies into contact with the liquor. The sulphited

liquor, with calcium sulphite precipitate in suspension, exits the tower at the base

into a small seal tank, since the tower is under slight vacuum.

The Quarez The Quarez sulphitation system consists of a holding tank, a circulating pump, a

venturi and sulphur furnace to produce SO2 the level in the tank is kept constant

by means of an overflow. Liquor in the holding tank is circulated by the pump and

a certain amount is forced through an injector creating a vacuum, which causes

the SO2 gas to be sucked in and mixed. The rest of the liquor by-passes the

injector by means of an adjustable valve, the setting of which controls the amount

of gassing and the final pH of the liquor.

This system is in operation in Pongola and the data available on the installation is

given here:

Refined sugar throughput 22 Tons/hr

Tons Brix in Raw Melt 25 Tons/hr

Volume of liquor to Sulphitation

20

m³/hr

Number of circulations 15 /hr

Capacity of circulating pump 300 m³/hr

PRACTICAL CONSIDERATIONS

Operating control Sulphitation is carried out to a pH of 7.0 and even at 6.9 – 6.8; but a lower pH

than this will result in inversion of sucrose and must be avoided. It is therefore of

paramount importance to reliably control the final pH set point. This is generally

done by varying the proportion of SO2 gas to liquor by measuring liquor pH.

Filtration Filtration of the sulphited liquor should take place at or near 85°C to take

advantage of the decreasing solubility of calcium sulphite at high temperatures as

well as lower viscosity. A heat exchanger of the shell and tube type is normally

used for this purpose. The amount of calcium sulphite precipitate is much less than

the carbonate precipitate and less filtering surface is required.

Disposal of Sweet Water The cake from the primary and secondary filters is sent to sludge filters for

sweetening-off. The sweet water should be returned to process that is C and B

sugar melting, B and C, pan movement water, etc and preferably not back to the

raw sugar refinery melter, on account of color and ash increase in refinery melt.

Distillery Yields

Background Just as in a sugar factory there are a number of measures of operational efficiency

in a distillery. In the sugar industry ratios like extraction, boiling house recovery,

and overall recovery are well defined and universally understood. Sadly in the

alcohol industry things are a little more disorderly. To help bring a little order the

following is offered

Theory There are four commonly used measures of yield

Fermentation yield Fermentation efficiency Alcohol recovery Overall Conversion Efficiency

Fermentation yield Fermentation yield is measured in liters of absolute alcohol in beer per ton of

sugars in molasses, and is calculated by the formula below

Yf = Vb · ab / (Mm · fsm)

where

Yf = fermentation yield Vb = volume of beer [liter]

ab = alcohol content of beer (v/v) Mm = mass of molasses [tonne] fsm = fermentable sugars content of molasses (m/m)

Fermentation efficiency Fermentation efficiency is an expression of how much alcohol was actually

produced in beer relative to the amount that could be theoretically produced, and

is given by

Ef = Yf · 0.794 / 0.5111 × (100/1000)

The factor 0.794 corresponds to the specific gravity of absolute alcohol and the

factor 0.5111 is best explained as follows: If one kilogram of sugar was completely

fermented (using theoretical 100% efficient yeast); 511.1 grams of alcohol and

1000 - 511.1 = 488.9 grams of carbon dioxide would result.

Alcohol recovery Alcohol recovery is a measure of how much alcohol was finally produced relative to

the amount that was in the beer. It shows the amount of losses in the evaporation

and distillation sections combined. Alcohol recovery is calculated as follows

Ede = (aaVp + ssVf) / aaVb · 100

where

Ede = Alcohol recovery (or distillation and evaporation efficiency) aaVp = volume of potable alcohol as liters absolute alcohol ssVf = volume of feints as liters absolute alcohol aaVb = volume of beer as liters absolute alcohol

Overall Conversion Efficiency Overall conversion efficiency is a measure of how much alcohol is finally produced

relative to the amount that could be theoretically produced, and is given by

Eo = Ef · Ede · 100

Values of Yield The following table gives values of yield that one would expect in a well run

Distillery

Parameter Value

Alcohol Recovery 98.5%

Fermentation Yield 573

Fermentation Efficiency 89%

Overall Conversion Efficiency 87%

Alcohol from Cane Molasses This article sets out a way of calculating how much alcohol you can make from

the molasses your sugar factory produces.

How much molasses? The fist step is to calculate how much molasses you will produce. In the Southern

African Industry it is usual to express the amount of molasses made per tonne of

cane crushed at a standard molasses brix of 85°

The South African Industry average figures for the past five years are shown

Below

Molasses at a standard 85°Bx

Year

Molasses% Cane

2000/01

3.70

2001/02

3.93

2002/03

4.03

2003/04

3.73

2004/05

4.16

So the amount of molasses produced is

M = C · M85 · 0.85 / Bm

where

M = tonnes molasses produced C = tonnes cane crushed M85 = Molasses at 85° brix as a percentage on cane crushed Bm = Actual brix of molasses produced

Fermentable sugars The next step is to calculate the amount of fermentable sugars (FS) in the

molasses. The fermentable sugars in molasses are sucrose, glucose and fructose;

there are other sugars present in molasses, they are either unfermentable or are

in small enough quantities that they can be ignored.

There are a number of ways of measuring fermentable sugars in molasses; the

most accurate is High Performance Liquid Chromatography (HPLC).

The Lane and Eynon method also described in the SASTA Lab Manual is a two step

process, which measures reducing sugars by titration. Reducing sugars are those

sugars which reduce Fehlings reagents. Glucose and fructose reduce Fehlings

reagents, sucrose does not, so the sucrose is inverted using hydrochloric acid and

the reduction titration is repeated and the total reducing sugars can be calculated.

The problems with this method are

there are other substances in the molasses which are also reducing agents, but are not fermentable sugars, so this method overestimates the amount of fermentable sugars, and

the titration is complex and requires a degree of skill to ensure repeatability, that may not always be present in a sugar factory laboratory.

South African Industry data on molasses quality are given as a guideline

South African Industry Average Molasses Quality

Year Refractometer brix Sucrose/refractometer brix Purity Fructose% Glucose% FS%brix in

molasses 2000/01

84.26% 37.21% 7.55% 5.41% 52.59%

2001/02

84.44% 37.03% 7.58% 5.47% 52.48%

2002/03

85.09% 37.24% 7.14% 5.13% 51.66%

2003/04

84.79% 37.92% 7.08% 5.22% 52.43%

2004/05

83.97% 36.94% 7.93% 5.20% 52.58%

So, it is clear that about 52.5% of the brix in molasses are fermentable sugars. To

calculate the tonnes of fermentable sugars in molasses we use the following

Formula

FS = M · Bm · FS%B

where

FS = tonnes fermentable sugars in molasses M = tonnes molasses produced Bm = Actual brix of molasses produced FS%B = fermentable sugars as a percentage on brix in molasses

Alcohol Yield

The amount of alcohol produced is given by

A = FS · Yf · Ede

where

A = liters of alcohol produced Yf = Fermentation yield Ede = Alcohol recovery (or distillation and evaporation efficiency)

Design a limed juice flash tank

Mixed Juice Flow [tonne/h]

Tank Diameter [mm]

Flash Pipe [DN]

Juice Inlet [DN]

Juice Outlet [DN] Drain [DN]

A B C D E

50 1457 350 150 200 80

60 1625 400 150 200 80

70 1756 400 150 200 80

80 1878 450 150 250 100

100 2097 500 200 250 100

125 2344 550 200 250 100

150 2569 600 200 300 100

175 2774 650 250 300 100

200 2966 700 250 350 150

225 3146 750 250 350 150

250 3146 800 300 350 150

275 3478 800 300 400 150

300 3633 850 300 400 150

325 3700 900 300 450 150

350 3926 950 300 450 150

375 4063 950 350 450 150

400 4194 1000 350 450 150

Juice Heaters Because high pressure steam is very valuable, exhaust steam is often used

for juice heating or, if possible, preferably bled vapour from the evaporators. It is

thus necessary to have a heat exchanger between vapour and juice; this is

provided by the juice heaters. The juice heater (below) consists of an assembly of

tubes; the juice circulates through the tubes, and the vapour outside them.

Suitable headers force the juice to pass a certain number of times from bottom to

top and from top to bottom of the heater by restricting the juice each time to a

few of the tubes.

Vertical Juice Heater (Coil)

The basic calculation of the juice heater is to calculate the amount of heat

transferred using the overall heat transfer co-efficient (OHTC), the log mean

temperature difference

(LMTD) and the heating surface area.

Q = h· A· ΔTlog

Where