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AUDUBON SUGAR INSTITUTE
CANE-TO-SYRUP PILOT PLANT
OPERATING MANUAL
Unit Operations Laboratory Edition – Fall 2015
Shivkumar Bale
Abstract Background, Operations Concepts, Startup and Shutdown and Experimental Protocols
2
Table of Contents Title Page ....................................................................................................................................................... 1
Operating Manual ......................................................................................................................................... 3
Overview of Cane Sugar Production ......................................................................................................... 3
General .................................................................................................................................................. 3
Sugarcane Production ........................................................................................................................... 3
Sugarcane Processing ............................................................................................................................ 4
Biofuels Pilot Plant at the Audubon Sugar Institute ............................................................................... 10
Milling ................................................................................................................................................. 11
Clarification ......................................................................................................................................... 13
Evaporation ......................................................................................................................................... 15
Minimum Safety Regulations .............................................................................................................. 17
Protocols ................................................................................................................................................. 20
Process Protocols ................................................................................................................................ 20
Analytical Protocols............................................................................................................................. 22
Simulating Counter-Current Extraction on a Sample Mill ....................................................................... 24
Startup and Shutdown Procedures ..................................................................................................... 24
Operating Procedures ......................................................................................................................... 24
Literature Cited ........................................................................................................................................... 27
Appendices .................................................................................................................................................. 28
Appendix A .............................................................................................................................................. 28
Appendix B .............................................................................................................................................. 29
3
Operating Manual
Overview of Cane Sugar Production
General
Sugar is one of the dominant products in the agricultural sector and its global production has increased
linearly from 100 million tons in 1988 to more than 165 million tons in 2008/09 [1]. Sugar is also known
as sucrose, which belongs to the family of saccharides. Saccharides are naturally occurring
carbohydrates with the general chemical formula CnH2nOn. Glucose is the simplest saccharide, a
monosaccharide with the formula C6H12O6. Sucrose is a disaccharide, C12H22O11, made up of two glucose
molecules. Plants produce saccharides through photosynthesis – the process of combining carbon
dioxide and water to generate saccharides and oxygen, with sunlight as the energy source.
2 2 6 12 6 2
Glucose
6 6 6SunlightCO H O C H O O (1)
2 2 212 22 11
Sucrose
12 11 12SunlightCO H O OC H O (2)
Sugar is produced from plants like sugarcane and sugar beet. Sugarcane accounts for approximately 70%
of the global sugar production, whereas remaining 30% is produced from sugar beets [2].
This manual focuses on sugar production from sugarcane. Much of the general information and process
description in the remainder of this section is a condensation of material from United States
Environmental Protection Agency documentation on sugarcane processing [3].
Sugarcane Production
Sugarcane is a tropical grass, which rather looks like a bamboo cane, where the sucrose is stored in its
stem. Sugarcane prefers strong sunlight and abundant water for its satisfactory growth. Sugarcane is a
group of Saccharum species and its species include S. officinarum, S. spontaneum, S. barberi and S.
sinense. The cane can grow up to 5 meters tall depending upon the species, whereas it can reach its
maturity between about 10 and 22 months depending upon the local climatic conditions [4]. The local
conditions also dictate the cane yields, which ranges from 50 to 120 x 103 kg/hectare/year [5, 6]. The
sugar content of a mature cane depends upon the species, the season and the location; however,
typically it is 10% by weight. There are two methods to harvest sugarcane: hand cutting and mechanical
harvesting. If the land is flat, the mechanical harvesting has been used for several years; however hand
cutting is the most common method. The sugarcane is different from most crops because they can
regrow after harvesting, if the roots are kept undisturbed. This cycle of regrowing the plant and cropping
it, is known as ratooning, and the plant lasts many cycles until it is worn out. The number of cycles
depends upon the vigor of the cane and the growing location.
4
The refined (white) sugar is produced from sugarcane in two stages. In the first stage, the raw sugar,
which is also known as cane sugar, is produced from sugarcane in a cane sugar mill. The process flow
diagram for cane sugar production is shown in Figure 1. In the second stage, the cane sugar is refined to
white sugar in a sugar refinery. In U.S., the sugarcane is produced, harvested and processed through the
first stage in four states: Florida, Texas, Louisiana and Hawaii. The second stage is carried out in eight
states: Florida, Texas, Louisiana, Hawaii, New York, California, Maryland and Georgia [3].
In cane sugar production, the other products are bagasse, molasses and filter cake. Bagasse is
the fibrous residue of sugarcane after milling process and it is a very high value by-product. It can be
used in numerous ways, however in the cane sugar industry it is used as an energy generation source by
burning it in boilers. Molasses is the runoff syrup after the final step of crystallization, from which no
additional sugar can be extracted.
There are two forms of molasses: edible and non-edible (blackstrap). The edible molasses is
used as blends with maple syrup, inverted sugars, or corn syrup, whereas the non-edible molasses is
mainly used as an animal feed additive, however it is also used to produce ethanol, compressed yeast,
citric acid and rum. The filter cake (filter mud) is the filtration residue of the mud, which is obtained
from the clarification process. The filter cake is used as an animal feed supplement, fertilizer and source
of sugarcane wax [3].
Sugarcane Processing
After harvesting, the cane is transported to the mill. In the mill, the cane is unloaded, cleaned and
prepared for the extraction of the juice. The preparation requires the cane to be cut into small pieces,
shredded and crushed. Thus, the preparation step involves knives, a shredder and a crusher. This step is
carried out to break the hard structure of the cane and make the juice readily available for the
extraction. After preparation, the cane is passed through a multiple sets of three roller mills for the
extraction of juice. This step is known as milling or grinding. The process flow diagram for milling is
shown in Figure 2. As per requirement, the four, five and six roller mills are also available for milling.
Conveyors are used to transport the cane from one mill to other and, to enhance the extraction, water
or thin juice is sprayed on the cane before it enters the next mill. This technique is known as imbibition.
In imbibition, fresh water is sprayed on the cane before it enters the last mill, and then it is transferred
from one mill to other until it reaches the second mill. Whereas, the cane travels from the first mill to
the last mill. The crushed cane exiting the last mill is known as bagasse. The juice from the first two mills
is filtered to remove large particles of bagasse, and then it is clarified [3].
In the clarification process, the juice is treated with lime and heat. The lime neutralizes the organic
acids, and the temperature of the juice is raised to 95oC. Thus, a heavy precipitate is formed, which
settles down in the clarifier. The limed juice is separated from the precipitate, which is also known as
mud, by gravity or centrifuge. The mud is filtered and the filter cake is rinsed. The clarified juice is
preheated and then transferred to the evaporation station.
5
Figure 1. PDF for cane sugar production. The dotted rectangle represents the Audubon Sugar Institute pilot plant process.
6
Figure 2. PDF for the milling portion of the process.
7
The evaporation station consists of a series of evaporators and the employed method is known as
multiple-effect evaporation. The process flow diagram for multiple-effect evaporation system is shown
in Figure 3. In multiple-effect evaporation, the steam from a boiler is used to heat the first evaporator,
and the steam generated from the first evaporator is used to heat the second evaporator and so on. The
temperature decreases from first to last evaporator due to the heat loss. Hence, to reduce the boiling
temperature in subsequent evaporators, the pressure is decreased. The raw sugar syrup exiting the
evaporation station has 65% solids and 35% water. From evaporation station, the syrup is transferred to
the vacuum pans for crystallization [3].
The process flow diagram for crystallization is shown in Figure 4. The purpose of vacuum pans is to
produce sugar crystals from the syrup. In the vacuum pan, the syrup is boiled until it reaches the
supersaturation stage. At this stage, the crystallization is initiated by ‘seeding’ the solution. The seeding
is carried out by adding isopropyl alcohol, ground sugar, or sugar crystals from the process to the syrup.
After seeding, the mixture of liquor and sugar crystals, which is also known as massecuite, is further
evaporated in the vacuum pan until the final massecuite is formed. The massecuite from the vacuum
pan (called “strike”) is transferred to crystallizer to maximize the sugar crystal extraction from the syrup.
The massecuite (massecuite A) from the crystallizer is centrifuged to separate the crystals from the
mother liquor (molasses A). The crystals are rinsed and the wash water is centrifuged from the crystals
[3].
The liquor (molasses A) from the first centrifugal is reboiled in the vacuum pans to form massecuite B.
The massecuite B is discharged to the crystallizer and centrifuged to separate raw sugar from the liquor
(molasses B). The liquor separated from massecuite B is reboiled to form a low-grade massecuite C. The
massecuite C is crystallized and centrifuged to separate a low-grade cane sugar, which is used for
“seeding” the solution or mixed with the syrup. The liquor (blackstrap molasses) separated from
massecuite C is a heavy, viscous material, which is used as a supplement for cattle feed. The cane sugar
from massecuite A and B are dried and cooled. After cooling, the raw cane sugar is transferred to the
packing bins and stored [3].
8
Figure 3. PFD for the triple effect evaporator system.
9
Figure 4. PFD for crystallization.
Commented [HJT1]: This figure needs to be modified to show pots and pans in every box and stream names outside the boxes. There’s some inconsistency with this at this point.
10
Biofuels Pilot Plant at the Audubon Sugar Institute At the Audubon Sugar Institute (ASI), a biofuels pilot plant has been constructed and commissioned as
part of the Sustainable Bioproducts Initiative (SUBI) [7]. This pilot plant produces raw sugar syrup from
sugarcane, part of an overall cane sugar production process. The process flow diagram of the pilot plant
at ASI that was shown as Figure 1 can be seen in the photo of the pilot plant shown in Figure 5 below.
To produce raw sugar syrup, the sugarcane is processed through the milling, clarification and
evaporation stages of cane sugar production. The syrup from the pilot plant is distributed to ASI’s
research and manufacturing partners to make biofuels and bioproducts. The pilot plant is designed to
process one ton of feedstock per hour and to produce 300 pounds per hour of syrup.
Description of the operations of the Audubon Sugar Institute pilot plant will divided into the following
process unit operations: 1) milling, 2) clarification, and 3) evaporation.
Figure 5. Photograph of the pilot plant at Audubon Sugar Institute.
11
Milling
Objective
The objective of the milling operation is to extract the juice from the sugarcane.
Basic Theory
The basic theory of the milling process is to squeeze the juice from the sugarcane by applying pressure.
Therefore, the cane is passed through multiple sets of three, four or five roller mills. Water or thin juice
is added to the bagasse after each mill to dilute the contained juice and enhance the extraction. This
technique is known as imbibition.
Principle of Operation
In ASI, the milling process consists of four mills in series and each mill has four rollers. The process flow
diagram for milling process in ASI is shown in the earlier Figure 2, and it is similar to a countercurrent
solid-liquid extraction (leaching). Pretreated cane enters the first mill and bagasse exits the last mill.
Fresh water is added to the bagasse entering the last mill, and the juice from the last mill is added to the
bagasse entering the preceding mill, until it reaches the second mill. The dry milling is carried out in the
first mill, and the juice from the first and the second mill is pretreated and sent for clarification process.
Pretreatment
In ASI, the pretreatment for the milling process involves two sets of revolving knives, a shredder and a
magnet. The revolving knives cut the cane into small pieces and the shredder tear the cane into shreds.
The knives and the shredder help break the hard structure of the cane and make the juice readily
available for extraction. The magnet is used to separate broken or loose pieces of metal from the
shredded cane.
Critical Variables
Sucrose content in the juice is the critical variable indicating the efficiency of extraction in a mill. The
efficiency of milling is expressed as sucrose in juice percent sucrose in cane. The sucrose content in the
juice of a mill varies with the pressure in the mill and the extent of imbibition.
Startup and Shutdown procedures
Start the master switch on the motor control center (MCC). The MCC has both manual and
automatic provisions to start the motors in the pilot plant. In order to start a motor
automatically, a digital input signal is provided by the control panel to the MCC panel. The
control panel consists of programmable logic controllers (PLCs).
Open the seal water valves for all the pumps and maintain the seal water flow.
Start the computers in the control room and click on the ASI icon. Ask lab coordinator for the
password to access the computers. The control cabinet is also located in the control room.
[Equipment and process color representation: 1. Grey indicates the equipment is on and
working. 2. Green indicates the process reached the stable state. 3. Blue indicates the process is
in transition state. 4. Red indicates alarms.]
12
The milling operation is divided into two stages: 1) preparation, and 2) milling. Photographs of
the equipment used in these operations are shown in Figures 6 and 7, respectively. During
startup, start milling first and then preparation, whereas during shutdown, stop preparation first
and then milling.
Preparation is further divided into three sections: 1st Run/Stop magnet, discharge gate and
rolling equipment, 2nd Run/Stop conveyors, and 3rd Enable/Disable feed deck. During startup,
start in the order of 1st, 2nd, and 3rd, because 3rd section depends on 2nd section, and 2nd section
depends on 1st section. During shutdown, stop 1st section and then everything stops.
Similarly, the milling stage is further divided into three sections: 1st Run/Stop mills, 2nd Run/Stop
intermediate carriers, and 3rd Enable/Disable pumps. The order of startup and shutdown is
similar to the preparation stage.
There are three emergency stops: two automatic and one manual. Two automatic emergency
stops can be accessed through the computers in the control room, and one each for preparation
and milling stage. Click once on the emergency stop icon to stop and then click once again to
relieve it. The manual emergency stop is located on the panel in one of the corners of the milling
stage.
Figure 6. Photograph of the preparation stage in the milling operation at the Audubon Sugar Institute.
13
Figure 7. Photograph of the milling stage in the milling operation at the Audubon Sugar Institute.
Process Control
Two types of controller are used in the milling operation: PID controller and on-off controller. PID
controller is used to control the weight at the feed deck and the flow rate of the imbibition water. On-
off controller is used to control the juice level in the juice tank from each mill, the level of bagasse
entering the first mill, and the steam valve’s open/close time for rotary screen cleaning. VFD, stands for
variable-frequency drive, with soft starters is used to control the motor speed and torque of the pumps
by varying motor input frequency and voltage. Rotation sensor is used to indicate the condition of the
pump (running or stopped).
Clarification
Objective
The objective of the clarification operation is to remove both soluble and insoluble impurities from the
raw juice. A photograph of the clarification section of the Audubon Sugar Institute pilot plant can be
seen in Figure 8.
Basic Theory
The basic theory of the clarification process is to use lime and heat as the clarifying agents. The raw juice
from the milling process is acidic and turbid. Lime neutralizes the organic acids and forms insoluble lime
salts. The juice is heated to boiling or slightly above, which helps to coagulate albumin and varying
proportions of fats, waxes, and gums. The flocculent precipitate thus formed traps finely suspended
materials of the juice. The heavy precipitate, also known as mud, is separated from the clarified juice by
sedimentation.
14
Figure 8. Photograph of the clarification operation at the Audubon Sugar Institute.
Principle of Operation
In ASI, hot liming process is used to clarify the raw juice. As per the hot liming process, the juice is
heated to 96oC and then the milk of lime is added, to precipitate the certain colloids of the juice due to
heat and pH. The advantages of this process are faster settling rate, less mud volume, better turbidity
level, and better color at 420 nm. A polymer flocculent is also added to the limed juice. The main
purpose of a flocculent is to increase the clarity of the clarified juice, but it also improves flocculation,
increases settling rate, reduces mud volume, and decreases sucrose in cake. The treated juice is sent to
the settling tank, also known as clarifier, where the mud is separated from the clarified juice by gravity.
Pretreatment
According to the pretreatment to the clarification process, the raw juice from the mills is passed through
a rotary screen, which is a high quality filter for solid-liquid separation, to remove additional fiber from
the juice. This pretreatment improves clarifier capacity, increases clarity of the juice, and gives a denser
mud.
Critical Variables
Increase in sucrose content between raw juice and clarified juice, is the critical variable indicating the
efficiency of the clarification process, whereas the pH is the critical variable dictating the efficiency.
Startup and Shutdown Procedures
Switch on the main power supply for clarification-evaporation skid.
Switch on the MCC for the skid.
Open the drain valve by two turns to drain the condensate.
15
Open the main steam valve and close the drain valve.
Open the seal water valves for all the pumps and maintain the seal water flow to 2 GPH.
Start the laptop in the control room and click on the PAC Display Runtime Professional icon.
Choose Clarification tab in the pop-up window. The control cabinet is located within the MCC for
the skid.
Equipment and process color representation: 1. Green indicates the equipment is on and
working. 2. Red indicates the equipment is off.
Start the main steam system on the control panel, and then start the mixed juice mixer.
Wait until the level in the mixed juice tank reaches 50%, then start the clarifier/heater system
on the control panel.
In order to shutdown, wait until the mixed juice tank is empty and then stop the
clarifier/heater system on the control panel. In case of emergency shutdown, simply stop the
clarifier/heater system and the main steam system on the control panel.
Equipment being controlled has both manual and automatic provisions. While under control,
equipment is in automatic mode; but if one needs to override an action, the equipment should
be in manual mode and then the necessary changes should be made.
Process Control
PID controllers are used in the clarification operation. It is used to control the level of the mixed juice in
the mixed juice tank, the main steam pressure, the exit temperature of the mixed juice through the
mixed juice preheater, and the pH of the clarifier.
Evaporation
Objective
The objective of the evaporation operation is to concentrate the juice by evaporating water.
Basic Theory
The basic theory of the evaporation process is to concentrate a non-volatile solute from a solvent -
mostly water - by difference in their boiling point. An evaporator consists of a heat exchanger to boil the
solution and a separator to separate vapor from the boiling liquid. The energy consumption of the
evaporation process is significant; therefore a multiple-effect evaporation system is typically employed
to reduce the energy cost. In multiple-effect evaporation, the vapor generated in the first effect is used
as the heat source for the second effect.
Principle of Operation
In the biofuels pilot plant, a triple-effect evaporator with forward feed is employed in the evaporation
process. The process flow diagram for this triple-effect evaporation system is shown in Figure 3 and a
photograph of this section of the pilot plant can be seen in Figure 9. In a forward feed design, the
preheated clarified juice enters the first effect and the syrup is withdrawn from the third (and last)
effect. The juice and the steam flow parallel to each other from one effect to another. Each effect
consists of a plate-type heat exchanger and a vapor separator. Since the vapor from each prior effect is
used to heat the next effect, the pressure is reduced in each subsequent effect to operate at lower
boiling temperature. Indeed, the last effect is operated under vacuum.
16
Figure 9. Photograph of the evaporation stage at the Audubon Sugar Institute.
Pretreatment
The clarified juice is heated before entering the triple-effect evaporator to increase the efficiency of the
evaporation process and minimizes the thermal shock to the components. In the ASI biofuels pilot plant,
preheating is carried out in a plate-type heat exchanger.
Critical Variables
The total mass of water evaporated is the critical variable indicating the efficiency of the evaporation
process. The efficiency of an evaporator is expressed as the total mass of water evaporated with respect
to the total mass of steam supplied. The liquid level in vapor separators is the critical variable in
dictating the efficiency of the evaporation process, because the separator needs air space in the
chamber to be effective.
Startup and Shutdown Procedures
To access the evaporation window through the clarification window on the control panel, just
click the ‘To Evaporator’ tab on the clarification window.
[Equipment and process color representation: 1. Green indicates the equipment is on and
working. 2. Red indicates the equipment is off.]
When the level in the clarified juice tank reaches 50%, start the evaporator system on the
control panel.
17
In order to shutdown, wait until the third evaporator is empty, and then stop the evaporator
system on the control panel. Meanwhile don’t leave the pre-heater, first and second evaporator
empty, pass water through them by opening water valve on the clarified juice tank. In case of
emergency shutdown, simply stop the evaporator system and main steam system on the control
panel.
Equipment being controlled has both manual and automatic provisions. While under control,
equipment is in automatic mode; but if one needs to override an action, the equipment should
be in manual mode and then the necessary changes should be made.
Process Control
PID controllers are used in the evaporation operation. It is used to control the main steam pressure, the
exit temperature of the clarified juice through the clarified juice preheater, the flow rate of the pre-
heated clarified juice, the level of the juice in the first vapor separator, the level of the juice in the
second vapor separator, the flow rate of the juice through the third vapor separator (before the Brix is
achieved), the level of the juice in the third vapor separator (after the Brix is achieved), the pressure in
the third vapor separator, and the level of the condensate in the vacuum condensate tank.
Minimum Safety Regulations
Authorization
Each student must read and understand the minimum safety regulations section of this
document, and sign and submit the statement of understanding and compliance form (see
Appendix B) to the pilot plant coordinator before working in the facility.
Each student must receive instructions on using the assigned equipment prior to
beginning any work. They must also fill out Job Safety Analysis Form in order to be
trained on the specific hazards of their equipment before to be allowed to work. Job
Safety Analysis Form can be accessed by following the link:
http://www.uolab.lsu.edu/documents/JSA_Form.pdf
Only certified forklift operator is allowed to use forklift for feeding sugarcane.
Intent
The intent of minimum safety regulations is to protect students from the potential hazards of working in
a pilot plant and promote safe practices.
Access
The schedule for students to access the pilot plant would be prepared by the pilot plant coordinator
before the start of a semester. On the scheduled date, the pilot plant facility would be available from 8
am to 4pm and the work should be finished within the time frame. Students must always work in
groups, and not allowed to work in the pilot plant during evenings, holidays, or weekends without
permission and supervision.
18
Services and Equipment Usage
Any equipment must be operated only after receiving proper instructions from the coordinator.
Proper use of valves is very important in operating a pilot plant. There are different types of
valves and one must receive instructions to open, close or adjust a valve before using it.
Student’s work may involve use of services such as: cold and hot water, industrial steam,
electricity, vacuum and compressed air. Students must avoid spraying water on electrical outlet
and check carefully for shredded cord or loose connections. If noticed, contact the pilot plant
coordinator immediately. Steam lines are under high pressure and they are common dangers in
a pilot plant. Students must not operate steam lines and the coordinator would be available to
perform steam line operations.
Personnel Protection Equipment
Safety Glasses and Helmets: Students must always wear safety glasses and helmets in a pilot
plant. Full face shield should be worn if the procedure dictates during chemical transfer and
handling operations.
Footwear: The wet floors of the pilot plant can be extremely slippery. Non-skid shoes are highly
recommended. Sandals and open-toed shoes are prohibited.
Clothing: Students must wear long pants in the pilot plant and no loose clothing. Shorts or skirts
are prohibited. A lab coat should be worn if procedure dictates (e.g., during chemical transfer).
Insulated Gloves: Students must wear rubberized insulated gloves while working with steam or
chemicals.
Others: Students must wear their hair in such a manner that it does not interfere with the work.
Jewelry, watches and rings should not be worn in the pilot plant.
Chemical Handling/Storage
The instructions about chemical handling/storage must be obtained from the appropriate Material
Safety Data Sheet (MSDS), container label, or the coordinator.
General Safety Procedures
Smoking, eating, drinking, or chewing gum is not allowed in the pilot plant.
If you notice someone not following the safety procedures, contact the pilot plant coordinator
immediately.
In case of an accident involving injury: a) one or more persons should attend the needs of the
injured person; b) another person, in case of a serious accident, should call the ambulance – dial
911 and immediately notify the injury to the pilot plant coordinator.
First aid kit (location ?)
Fire extinguisher (location ?)
Safety shower and eye wash station (location ?)
Commented [HJT2]: Need locations for each of these items, perhaps even a photograph.
19
Each group of students is responsible for the clean-up of their assigned equipment throughout
the cycle, in order to prevent the slip/trip/fall hazard. Sample containers must be
cleaned/properly disposed at the end of the cycle. Avoid spraying water on the electrical outlet,
and completely disconnect the equipment from the electricity before cleaning it.
Do not insert hands, fingers or any utensils in any equipment while it is operating or even
plugged it.
Think before you act, to prevent an accident for happening.
Miscellaneous Information
Contact information of the pilot plant coordinator.
Commented [HJT3]: We need to add this information.
20
Protocols
Process Protocols
Protocol P1 – Estimation of the absolute (1st Mill) juice flow rate
Switch off the juice pump #1, and check if the valves R1 and C1 are closed.
Get a stopwatch and note the level in the juice tank # 1. At the very same moment, start timing.
Wait until the level in the juice tank # 1 is increased by 5% and then stop timing.
Note down the time in the stopwatch and calculate 5% of the volume of the juice tank # 1.
The absolute (1st Mill) juice flow rate is 5% of the volume of the tank divided by the time needed
to raise the level of the tank by 5%.
The above procedure should be repeated several times, in order to get a set of flow rate
measurements. The variation between several measurements taken in succession will give an
indication of the accuracy of the results.
Instead of using 5% of the volume of the tank to calculate the flow rate, one can use any percent
of the volume of tank as per convenience.
During flow rate calculations, make sure the juice tank # 1 doesn’t overflow, and after
calculations, switch back on the juice pump # 1.
Protocol P2 – Estimation of bagasse flow rate
Locate the end of the final bagasse conveyor, and get a stopwatch and a drum.
Place the drum under the end of the final bagasse conveyor and at the very same moment, start
timing.
Fill the drum for a fixed amount of time and then stop timing. Don’t let the drum overflow
during calculations.
Note down the time in the stopwatch and weigh the drum.
The bagasse flow rate is the weight of the drum divided by the time in the stopwatch.
The above procedure should be repeated several times, in order to get a set of flow rate
measurements. The variation between several measurements taken in succession will give an
indication of the accuracy of the results.
Protocol P3 – Estimation of the process characterization parameters of the pH system
Click the TRENDS tab on the control panel.
Check if the pH is stable, and then increase the speed of the M.O.L. tank pump by 5%
Monitor the change in the pH of the system.
Once the pH is stable, decrease the speed of the M.O.L. tank pump by 5% and monitor the pH
until it is again stable.
Then, extract the data and calculate the first-order-plus-dead-time (FOPDT) model process
characterization parameters of the pH system by using Loop-Pro or other appropriate software.
Protocol P4 – Estimation of clarifier flow rate
Note the level in the clarified juice tank and the flow rate of the pre-heated clarified juice.
If the level in the clarified juice tank is constant, then the clarifier flow rate is equal to the flow
rate of the pre-heated clarified juice.
21
If the level in the clarified juice tank is increasing, then note down the level, get a stopwatch and
at the very same moment, start timing.
Wait until the level in the clarified juice tank is increased by 5% and then stop timing.
Note down the time in the stopwatch and calculate 5% of the volume of the clarified juice tank.
Then divide the 5% of the volume of the tank by the time needed to raise the level of the tank
by 5%, in order to calculate the differential flow rate.
The clarifier flow rate is the flow rate of the pre-heated clarified juice plus the differential flow
rate.
If the level in the clarified juice tank is decreasing, the procedure is similar to that of increasing
level, but the clarifier flow rate is the flow rate of the pre-heated clarified juice minus the
differential flow rate.
The above procedure should be repeated several times, in order to get a set of flow rate
measurements. The variation between several measurements taken in succession will give an
indication of the accuracy of the results.
Protocol P5 – Examination of strainers deposits
Protective gear should be worn while operating the strainers, since clarified juice is at high
temperature.
Pay close attention to the four valves V1, V2, V3 and V4 around two strainers S1 and S2.
Two out of the four valves would be closed because only one strainer is used at a time. Open the
closed valves and now, the juice is flowing through both the strainers.
Close the valves around the strainer, which needs to be examined. Close valve V1 and V2 for
strainer S1, whereas close valve V3 and V4 for strainer S2.
Slowly loosen the lid in order to bleed the pressure. Open the lid and then remove the strainer
basket.
Collect the deposits from the strainer basket for further examination, photography.
Put the strainer basket back in to the strainer and close the lid. Make sure the lid is closed
tightly.
Again open all the four valves around the two strainers, so the juice can flow through both the
strainers.
Keep the two valves open, around the strainer just examined and close the other two valves.
Protocol P6 – Estimation of the mixed juice flow rate
Switch off the mixed juice pump, and check if the valves M1 and M2 are closed.
Get a stopwatch and note the level in the mixed juice tank. At the very same moment, start
timing.
Wait until the level in the mixed juice tank is increased by 5% and then stop timing.
Note down the time in the stopwatch and calculate 5% of the volume of the mixed juice tank.
The mixed juice flow rate is 5% of the volume of the tank divided by the time needed to raise
the level of the tank by 5%.
22
The above procedure should be repeated several times, in order to get a set of flow rate
measurements. The variation between several measurements taken in succession will give an
indication of the accuracy of the results.
During flow rate calculations, make sure the mixed juice tank doesn’t overflow, and after
calculations, open valve M1 and switch back on the mixed juice pump.
Protocol P7 – Estimation of the combined mud plus condensate flow rate
Locate the exit of mud + condensate flow to the dumpster, and get a stopwatch and a bucket of
known volume.
Place the bucket under the exit of the mud + condensate flow and at the very same moment,
start timing.
Wait until the bucket is full and then stop timing.
Note down the time in the stopwatch.
The mud + condensate flow rate is the volume of the bucket divided by the time required to fill
it.
The above procedure should be repeated several times, in order to get a set of flow rate
measurements. The variation between several measurements taken in succession will give an
indication of the accuracy of the results.
Protocol P8 – Estimation of syrup flow rate
Get a stopwatch and note the level in the syrup tank. At the very same moment, start timing.
Wait until the level in the syrup tank is increased by 5% and then stop timing.
Note down the time in the stopwatch and calculate 5% of the volume of the syrup tank.
The syrup flow rate is 5% of the volume of the tank divided by the time needed to raise the level
of the tank by 5%.
The above procedure should be repeated several times, in order to get a set of flow rate
measurements. The variation between several measurements taken in succession will give an
indication of the accuracy of the results.
During flow rate calculations, if the syrup is being drained, close the drain valve or if the syrup
tank is full, drain some of the syrup by opening the drain valve.
Analytical Protocols
Protocol A1 – Measurement of % Brix
Brix concentrations are measured using a lightweight and compact refractometer.
Apply two to three drops of sample onto the prism, press the start key, and the % Brix is
displayed in seconds.
After the measurement, clean the prism and apply two to three drops of distilled water onto the
prism, press start key, and the displayed % Brix should be 0 before the next measurement.
Calibration – clean off the prism, add water, and press the zero key.
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Protocol A2 – Measurement of Turbidity
Collect a sample in a clean container. Fill the sample cell to the line. Take care to handle the
sample cell and cap it.
Hold the sample cell by the cap, and wipe to remove water spots and finger prints.
Place the sample cell in the instrument cell compartment, and close the cell cover.
Read and record the results.
Protocol A3 – Measurment of % Pol (Reference)
Pol is estimated by using saccharimeter.
The clarifying agent Octopol is added to the sample
The sample is then allowed to stand briefly before filtering it through a funnel with a filter paper
into a beaker.
When sufficient filtrate has been collected to rinse and fill the tube, the funnel with filter paper
can be removed.
Rinse the tube twice with the filtrate.
Fill the tube with the filtrate and make sure no air bubbles are entrapped in the sample.
Place the tube in a saccharimeter and note down the reading.
Measure the temperature of the sample before emptying the tube.
Before measuring the Pol for another sample, rinse the tube twice with that sample.
After measurements, wash the tube with distilled water and fill it with water.
Calculation of % Pol juice
The Pol is calculated by using Schmitz’s table. For example, assume that the Brix % of the juice is
10.59 and the saccharimeter reading is 35.85. Then from table, % Pol juice is 8.96. In order to
use Schmitz’s table, the Brix measurement of the solution and the saccharimeter reading must
be obtained at the same temperature. If the temperatures differ, then it will be necessary to
adjust the refractometer Brix for the temperature difference. The adjustment to be made is
obtained from Table ??. For example, assume the saccharimeter reading is 35.85 was made at
27 oC, then
If Brix % juice (at 20 oC) = 10.59, then the adjustment for 27 oC = -0.42 and adjusted Brix reading
is therefore = 10.17. From Schmitz’s table, the % Pol juice using a Brix reading of 10.17 and
saccharimeter reading of 35.85 = 8.97.
Protocol A4 – Submission of samples to ASI Lab for analysis.
We need a procedure / form(s) for this.
Commented [HJT4]: We need to get the table or find the reference or something, here.
Commented [HJT5]: Need a procedure and form(s).
24
Simulating Counter-Current Extraction on a Sample Mill During the period of mill outage, the counter-current extraction will be simulated on a sample mill.
Startup and Shutdown Procedures
Start the master switch on the front side of the sample mill.
Sample mill has an inlet for feed. Feed is supplied to the mill through a feeding tray and feed
could be a batch of sugarcane or a mixture of bagasse and juice. Feed inlet is located on the
front side of the sample mill.
Sample mill has two outlets, one for bagasse and the other one for juice. Bagasse outlet is
located on the back side of the mill, whereas the juice outlet is located on the left side of the
mill.
There is an emergency shutdown push-off switch on the front side of the mill.
Operating Procedures
In order to simulate the counter-current extraction on a sample mill, one must follow the following
procedure, as exemplified in the Figure 10 schematic:
The actual milling process of the ASI pilot plant has four mills. The first mill performs the dry
milling whereas the other three mills perform the counter current extraction.
Therefore, a batch of feed will be processed through the sample mill four times.
1st Cycle
A bucket (B) of shredded sugarcane is introduced in the sample mill through the feeding tray.
The bagasse is collected in the same bucket (B) and the juice is collected in the bucket (0).
2nd Cycle
Bagasse in the bucket (B) is mixed with the juice in the bucket (2) from previous batch (A) and
then the mixture is introduced in the sample mill. The bagasse is collected in the same bucket
(B) and the juice is collected in the bucket (1).
3rd Cycle
Bagasse in the bucket (B) is mixed with the juice in the bucket (3) from previous batch and then
the mixture is introduced in the sample mill. The bagasse is collected in the same bucket (B) and
the juice is collected in the bucket (2).
4th Cycle
Bagasse in the bucket (B) is mixed with the water in the bucket (W) and then the mixture is
introduced in the sample mill. The bagasse is collected in the same bucket (B) and the juice is
collected in the bucket (3).
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In order to achieve steady state, several batches of the feed would be processed through the same four
cycles. During the first batch, in the 2nd and 3rd cycle, water is mixed with the bagasse instead of juice. In
order to monitor the steady state, on-site Brix analysis should be carried out on the juice in every bucket
in each cycle. Please refer the section on Protocol for Determination of % Brix for details on Brix
analysis. If the Brix of the juice from 2nd, 3rd and 4th cycle becomes constant for successive batches, then
steady state is reached. For calculation purposes, data from steady state must be used. The maximum
capacity of the buckets would be about 50 lbs. and every bucket in each cycle should be weighed. The
juice from the bucket 0 and 1 would go for further processing and therefore should be stored in mixed
juice tank. The juice samples from the bucket 0 and 1 of the steady state run should be collected for Pol
analysis. The bagasse leaving the 4th cycle should be dumped outside as per plant coordinator’s
instruction. The bagasse samples entering the 1st cycle and leaving the 4th cycle of the steady state run
should also be collected for Pol analysis.
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Figure 10. Simulation flow of the milling process in the Audubon Sugar Institute pilot plant using a sample mill.
1st Cycle - A 2nd Cycle - A 3rd Cycle -
A
4th Cycle - A
1st Cycle -
B
2nd Cycle - B 3rd Cycle - B 4th Cycle - B
4th Cycle -
C
3rd Cycle - C 2nd Cycle - C 1st Cycle - C
Water
Water
0 - A 1 - A 2 - A 3 - A
0 - B 1 - B 2 - B 3 - B
0 - C 1 - C 2 - C 3 - C
Water Water Water
27
Literature Cited
[1] J. Villadsen, "The sugar industry – the cradle of modern bio-industry," Biotechnology Journal,
vol. 4, pp. 620-631, 2009.
[2] (2013, May 22). Learn How Sugar Is Made. Available: http://www.sucrose.com/learn.html
[3] "AP 42 - Compilation of Air Pollution Emission Factors - Sugarcane Processing," vol. I, 5th ed:
Office of Air Quality Planning and Standards, Office of Air and Radiation, U.S. Environmental
Protection Agency, 1997.
[4] O. D. Cheesman, Environmental impacts of sugar production: the cultivation and processing of
sugarcane and sugar beet. Wallingford: CABI Publishing, 2004.
[5] A. P. Ruschel, "Report of the work group on sugarcane," Plant and Soil, vol. 67, pp. 395-397,
1982.
[6] P. P. Dua, "Sustainable Energy Supply in Asia - Chapter 18: Sustainable Energy Systems for Rural
Areas," in Proceedings of the International Conference, Asia Energy Vision 2020, New Delhi,
India, 1996, p. 639.
[7] R. Bogren. (2013, May 29). AgCenter biofuels pilot plant commissioned in La. Available:
http://www.lsuagcenter.com/en/crops_livestock/crops/Bioenergy/biofuels_bioprocessing/
subi/plant/AgCenter-biofuels-pilot-plant-commissioned-in-La-.htm
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Appendices
Appendix A P&ID of the pilot plant.
(See the attachment to this document.)
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Appendix B
STATEMENT OF UNDERSTANDING AND COMPLIANCE
Please sign and return this page to the Pilot Plant Coordinator before working in the facility.
I have read, understand and will comply with the Minimum Safety Regulations.
___________________________________________
Print Name
___________________________________________
Signature
___________________________________________
Date
