Process Description
The Biomass Fermentation process converts a cellulosic, biomass-derived feed into a solution of ethanol and water and smaller amounts of byproducts and solids. This solution can be distilled into fuel-quality ethanol. There are three main processing sections:
– Production of cellulase (enzymes) which are used to break down feed cellulose into sugars (saccharification)
– Production of a biological seed for converting sugars to ethanol (seed fermentation)
– Simultaneous saccharification of cellulose and fermentation of sugars to produce ethanol
All three sections use an acid-treated feed derived from ground wood chips as a main reactant/carrier. Cellulase is produced the first section and is used in both of the other sections. Saccharification of cellulose and fermentation of sugars occur simultaneously in the process. Therefore the process is characterized by simultaneous saccharification and co-fermentation (SSCF).
Biomass Feedstock (Hydrolyzate)
The biomass feed (called hydrolyzate) is a water-based slurry produced from hydrolysis of ground wood chips using a dilute sulfuric acid solution. As a result of the acid hydrolysis, the feed contains exposed cellulose and sugars which can be converted to ethanol. The main sugars are glucose, xylose and arabinose. The feed has also been neutralized and detoxified to remove compounds that will inhibit the organisms used in the process.
The feed contains 16.2 weight % insoluble solids. The solids are mainly cellulose and lignin. Total sugar content is 5.6 weight %. Other soluble impurities amount to 1.8 weight % and the balance is water.
The hydrolyzate feed is pumped and split into three streams. About 5% of the total feed, on average, is used for cellulase production; about 10%, on average, is used for fermentation seed production; and the balance is sent to the main fermenter for ethanol production. Holdup tanks are provided for each fermenter to hold the product from each fermenter to buffer the fermenters from each other. In batch operations this provides feed scheduling flexibility.
Cellulase Production Overview
A portion of the hydrolyzate feed is used as an environment to grow enzymes, known as cellulase, which are used to hydrolyze the exposed cellulose in the pre-treated feed to form sugars such as glucose and xylose. To produce the enzymes, hydrolyzate, ammonia, water and air are combined in an agitated aerobic bioreactor vessel called the Cellulase Fermenter. Cellulase seed organisms (Trichoderma reesei) grown from smaller batch fermenters are also added to the Cellulase Fermenter. These organisms will continue to grow in the Cellulase Fermenter and produce the desired collection of enzymes. While growing enzymes, the Cellulase Fermenter operates in batch mode with air blown into the vessel continuously. Heat produced from the bioreactions is removed using cooling water which circulates through the coils in the vessel.
After the cellulase has reached the desired concentration it is transferred from the Cellulase Fermenter to the Cellulase Hold Tank where it can be pumped to the SSCF Seed Fermentation Section and the Fermentation Section.
Note that in an industrial operation, the processing section for cellulase production may consist of several parallel cellulase fermentation vessels which operate in various stages: standby, supplying finished enzymes, and charging and fermenting. For purposes of training, only one vessel is simulated. The Cellulase Hold Tank is sized large enough where additional batches of cellulase can be produced in the Cellulase Fermenter while supplying cellulase to the other sections of the process without disruption.
F-301 Cellulase Fermenter
The Cellulase Fermenter F-301 is designed to produce large quantities of cellulase from a feed stream of cellulase seed containing seed organisms grown in smaller batch reactors. F-301 is charged with:
– Hydrolyzate feed (via FIC-301)
– Recycled water (via FIC-302)
– Ammonia (via FIC-303)
– Cellulase seed (via FIC-304)
Hydrolyzate for all three fermenters is pumped from battery limit by pump P-301. P-301 is a rotary lobe type of pump to handle the solids present in the hydrolyzate. The pump is designed to nominally move 1,580 GPM of hydrolyzate.
Each of the non-hydrolyzate feed flows to F-301 can be controlled in a ratio to the hydrolyzate feed flow during charging of the Cellulase Fermenter. To expedite training, the simulated process runs about 25 times faster than commercial processes, since the fermenters may take on the order of a day or days to conduct charging and reaction.
F-301 is a cylindrical vessel 30 feet in diameter and 60 feet high. The liquid contents are internally stirred with an agitator system that keeps conditions as well-mixed as possible, considering that materials in all three phases (liquid, solid and vapor) participate in the reactions in F-301. A sparger system in the lower part of the fermenter distributes air evenly throughout the vessel.
The cellulase seed stream contains the active organisms which will produce the cellulase (enzymes for converting cellulose to sugars) in F-301. The hydrolyzate and water feeds provide a fertile environment for the growth of the enzymes. As cellulase is produced, it converts some of the hydrolyzate to sugars. Cellulase is aerobically (using oxygen) grown from these sugars. Ammonia is provided for pH control as well as for providing nitrogen as a nutrient for growing the cellulase.
Both the saccharification reaction and the cellulase growth reaction produce heat which must be removed. F-301 normally operates at 84 deg F. Operation at significantly higher temperatures results in destruction of the seed organisms while lower temperatures result in slow reaction rates. F-301 is outfitted with internal cooling coils that allow the heat to be carried away by cooling water. The agitator system also imparts heat to the contents of F-301 through the shear forces of the impellers.
Air is fed to F-301 at a rate of 22,271 SCFM. A small portion of the oxygen in the air is used to produce cellulase. Carbon dioxide (CO2) is produced and is carried away along with some water that evaporates by the air stream passing through F-301. The air, CO2 and water vapor are routed from the top of F-301 to an atmospheric vent.
In batch mode, the cellulase concentration will reach about 2.1 weight % in about an hour under proper conditions of feed ratios, air flow, temperature and agitation. The reactor may also be operated in continuous mode where feeds are added while product cellulase is simultaneously being drawn off to the Cellulase Hold Tank, T-301. In this case, the cellulase concentration will only reach about 1.5 weight %.
In commercial operations the fermenters are normally operated in batch mode since there are parallel fermentation trains operating in a staggered schedule so that a near-continuous product of highest possible ethanol concentration is produced. The simulator allows operation of a single train in either batch or continuous mode. The final ethanol concentration from a single train will naturally be lower when running in continuous mode, but a higher continuous production rate will result.
A cleaning system is provided for F-301 to wash away toxic organisms that would inhibit cellulase growth. A specially designed spray system ensures all internal parts of F-301 are thoroughly washed. The cleaning solution is routed to the Cellulase Hold Tank T-301 and/or a disposal system as needed.
K-301 Air Blower
Air for the production of cellulase is compressed from ambient conditions by Air Blower K-301. The increase in air pressure causes the discharge temperature to be too high for direct introduction to F-301. The air is cooled using cooling water in heat exchanger E-301 prior to introduction to F-301. In case of low flow operation to F-301, an automatic vent to atmosphere will open to ensure enough air flow through K-301 so it is not damaged by surge.
T-301 Cellulase Hold Tank
The Cellulase Hold Tank T-301 is used to store the cellulase product from the Cellulase Fermenter F-301 for feed to SSCF Seed Fermenter F-311 and the SSCF Fermenter F-321. The Cellulase Hold Tank allows the flexibility to clean F-301 and ready it for additional cellulase production while feeding the other two fermenters.
Cellulase product is pumped from the Cellulase Fermenter F-301 by the Cellulase Transfer Pump P-302 to the Cellulase Hold Tank T-301. P-302 is a rotary lobe type of pump so it can handle the solids present in F-301 that come from the hydrolyzate feed. The cellulase from P-302 can also be routed to the disposal system in case of cleaning F-301 or if the cellulase batch needs to be dumped because of a quality problem.
T-301 is sized identically to F-301. T-301 also has an agitator system that keeps the solids of the cellulase product suspended. The cellulase product in T-301 is pumped to the two other fermenters by Cellulase Pump P-303 which is also a rotary lobe type pump. T-301 is vented to atmosphere.
P-302 and P-303 are sized to nominally pump 166 GPM of liquid.
T-301 is cleaned using cleaning solution from F-301 after it has been cleaned. The contents of T-301 are then routed to fermenters F-311 and F-321 to clean the lines. F-311 and F-321 have wash and disposal capabilities like F-301.
SSCF Seed Fermentation Overview
This section produces a biological seed for the fermentation of sugars to produce ethanol. The seed is produced by growing an inoculum (Zymomonas mobilis) in the SSCF Seed Fermenter. The inoculum requires sugars and other nutrients to grow.
Hydrolyzate is fed to the agitated SSCF Seed Fermenter vessel along with corn steep liquor, inoculum and cellulase from the Cellulase Fermenter. The corn steep liquor is a nutrient for growing the inoculum. The SSCF Seed Fermenter normally operates in batch mode. Heat produced from anaerobic fermentation of the inoculum and from saccharification of cellulose is removed by cooling coils in the vessel.
The produced mixture is called the SSCF Seed and after reaching the desired concentration it is transferred to the SSCF Seed Hold Tank and then charged to the Fermentation Section to produce ethanol. The SSCF Seed Hold Tank is sized large enough to provide sufficient flow of the SSCF Seed to the Fermentation Section while another batch of SSCF Seed is prepared. In an industrial operation, several parallel trains of fermentation vessels would be in operation. For training purposes, only one vessel is simulated.
F-311 SSCF Seed Fermenter
Hydrolyzate destined for the SSCF Seed Fermenter F-311 is pumped from P-301 and cooled in heat exchanger E-311 using cooling water. Corn steep liquor, inoculum and cellulase from the Cellulase Hold Tank T-301 are also fed to F-311. Cellulase is added to convert the cellulose in the hydrolyzate feed to sugars so that the inoculum seed will grow.
The SSCF Seed Fermenter F-311 is designed to produce large quantities of SSCF Seed from a feed stream of inoculum containing seed organisms grown in smaller batch reactors. F-311 is charged with:
– Hydrolyzate feed (via FIC-311)
– Inoculum (via FIC-312)
– Corn Steep Liquor (via FIC-313)
– Cellulase (via FIC-314)
Each of the non-hydrolyzate feed flows to F-311 can be controlled in a ratio to the hydrolyzate feed flow during charging of the SSCF Seed Fermenter. To expedite training, the simulated process runs about 25 times faster than commercial processes, since the fermenters may take on the order of a day or days to conduct charging and reaction.
F-311 is a cylindrical vessel 30 feet9 meters in diameter and 45 feet high. The liquid contents are internally stirred with an agitator system that keeps conditions as well-mixed as possible in F-311. F-311 is vented to an exhaust gas scrubber for odor control before being discharged to the atmosphere.
The growth of Zymomonas mobilis occurs anaerobically (without oxygen) in F-311 and generates heat along with the saccharification of the hydrolyzate. F-311 normally operates at 88 deg F. Operation at significantly higher temperatures results in destruction of the inoculum while lower temperatures result in slow growth rates. F-311 is outfitted with internal cooling coils that allow the heat to be carried away by cooling water. The agitator system also imparts heat to the contents of F-311 through the shear forces of the impellers.
In batch mode, the SSCF seed concentration will reach about 0.44 weight % in about an hour under proper conditions of feed ratios, temperature and agitation. The reactor may also be operated in continuous mode where feeds are added while product cellulase is simultaneously being drawn off to the SSCF Seed Hold Tank, T-311. In this case, the SSCF seed concentration will only reach about 0.32 weight %.
A cleaning system is provided for F-311 to wash away toxic organisms that would inhibit seed growth. A specially designed spray system ensures all internal parts of F-311 are thoroughly washed. The cleaning solution is routed to the SSCF Seed Hold Tank T-311 and/or a disposal system as needed.
T-311 SSCF Seed Hold Tank
The SSCF Seed Hold Tank T-311 is used to store the SSCF seed product from the SSCF Seed Fermenter F-311 for feed to the SSCF Fermenter F-321. The SSCF Seed Hold Tank allows the flexibility to clean F-311 and ready it for additional SSCF seed production while feeding F-321
SSCF Seed product is pumped from the SSCF Seed Fermenter F-311 by the SSCF Seed Transfer Pump P-311 to the SSCF Seed Hold Tank T-311. P-311 is a rotary lobe type of pump so it can handle the solids present in F-311 that come from the hydrolyzate feed. The SSCF Seed from P-311 can also be routed to the disposal system in case of cleaning F-311 or if the SSCF seed batch needs to be dumped because of a quality problem.
T-311 is sized identically to F-311. T-311 also has an agitator system that keeps the solids of the SSCF seed product suspended. T-311 is vented to an exhaust gas scrubber for odor control before being discharged to the atmosphere.
The SSCF seed product in T-311 is pumped to the SSCF Fermenter F-321 by SSCF Seed Pump P-312 which is also a rotary lobe type pump.
P-311 and P-312 are sized to nominally pump 160 GPM of liquid.
T-311 is cleaned using cleaning solution from F-311 after it has been cleaned. The contents of T-311 are then routed to SSCF Fermenter to clean the line. F-321 has wash and disposal capabilities like F-311.
SSCF Fermentation Overview
The SSCF Fermentation section simultaneously converts cellulose to sugars (mainly glucose and xylose) and ferments these sugars to ethanol. The resulting mixture has an ethanol content high enough to be concentrated to fuel grade ethanol using distillation.
The bulk of the hydrolyzate feed is first cooled in heat exchanger E-321 using cooling water and fed to the SSCF Fermenter which is a large cylindrical tank. Cellulase from the Cellulase Hold Tank is charged to the SSCF Fermenter along with SSCF Seed from the SSCF Hold Tank. Ammonia and corn steep liquor are added as nutrients for the bacteria for cellulose conversion (saccharification) and for ethanol fermentation.
The SSCF Fermenter operates anaerobically and normally in batch mode. Any gases produced from fermentation are routed to a scrubber for odor control and ethanol recovery prior to venting to atmosphere. As enzymatic saccharification and fermentation simultaneously proceed, heat is given off from the mixture in the SSCF Fermenter. To keep the temperature at an optimal value, the mixture (called beer) is circulated through the SSCF Fermenter Cooler and returned to the SSCF Fermenter.
After most of the sugars have been converted to ethanol, the beer is transferred to the Beer Storage Tank and is then sent to the Beer Column for distillation of the ethanol from the water.
F-321 SSCF Fermenter
Hydrolyzate destined for the SSCF Fermenter F-321 is pumped from P-301 and cooled in heat exchanger E-321 using cooling water. Corn steep liquor, SSCF seed from the SSCF Seed Hold Tank T-311, cellulase from the Cellulase Hold Tank T-301, and ammonia are also fed to F-321. Cellulase is added to convert the cellulose in the hydrolyzate feed to sugars. SSCF seed is the active agent that converts the sugars to ethanol.
F-321 is charged with:
– Hydrolyzate feed (via FIC-321)
– Cellulase (via FIC-322)
– SSCF seed (via FIC-323)
– Corn Steep Liquor (via FIC-324)
– Ammonia (gas) (via FIC-325)
Each of the non-hydrolyzate feed flows to F-321 can be controlled in a ratio to the hydrolyzate feed flow during charging of the SSCF Fermenter. To expedite training, the simulated process runs about 25 times faster than commercial processes, since the fermenters may take on the order of a day or days to conduct charging and reaction. For commercial SSCF Fermenters, the hold time of the batch is on the order of several days to a week.
F-321 is a cylindrical tank 72 feet in diameter and 36 feet high. The liquid contents are internally stirred with an agitator system that keeps conditions as well-mixed as possible in F-321. F-321 is vented to an exhaust gas scrubber for odor control and ethanol recovery before being discharged to the atmosphere.
The saccharification and fermentation reactions generate heat which must be removed. The agitator system also imparts heat to the contents of F-321 through the shear forces of the impellers. F-321 normally operates at 93 deg F. Operation at significantly higher temperatures results in destruction of the seed resulting in lower yields while lower temperatures result in low production rates.
F-321 is externally cooled with chilled water using a pumparound system. To ensure sufficient circulation two SSCF Circulation & Transfer Pumps (P-321A/B) are normally operating. The SSCF Fermenter Cooler E-322 uses chilled water. The normal circulation flow through E-322 is 1,125 GPM. The outlet temperature of the beer from E-322 is normally 65 deg F. The circulation flow through E-322 should be reduced if the temperature of F-321 (as indicated on the suction of the circulation pumps) becomes too low.
In batch mode, the ethanol concentration will reach about 5.40 weight % in about two to three hours on the simulator under proper conditions of feed ratios, temperature and agitation. The fermenter may also be operated in continuous mode where feeds are added while product beer is simultaneously being drawn off to the Beer Storage Tank, T-321. In this case, the ethanol concentration will only reach about 3.24 weight %.
A cleaning system is provided for F-321 to wash away toxic organisms that would saccharification and/or ethanol production. A specially designed spray system ensures all internal parts of F-321 are thoroughly washed. The cleaning solution is routed to the Beer Storage Tank T-321 and/or a disposal system as needed.
T-321 Beer Storage Tank
The Beer Storage Tank T-321 is used to store the beer product from the SSCF Fermenter F-321 for feed to the Beer Column (off plot) where it will be distilled and the ethanol will be concentrated into a fuel grade product. The SSCF Seed Hold Tank allows the flexibility to clean F-321 and ready it for additional beer production while feeding the Beer Column.
Beer (SSCF Fermenter product) is pumped from the SSCF Fermenter F-321 by the SSCF Circulation & Transfer Pumps P-321A/B to the Beer Storage Tank T-321. P-321A/B are rotary lobe types of pumps so they can handle the solids present in F-321 that come from the hydrolyzate feed. The beer from P-321A/B can also be routed to the disposal system in case of cleaning F-321 or if the SSCF batch needs to be dumped because of a quality problem.
T-321 is a round vessel that is 40 feet in diameter and 40 feet high. T-311 also has an agitator system that keeps the solids of the beer product suspended. F-321 is vented to an exhaust gas scrubber for odor control before being discharged to the atmosphere.
The beer product in T-321 is pumped to the Beer Column by Beer Pump P-322 which is also a rotary lobe type pump. T-301 is vented to atmosphere.
P-321A/B are sized to nominally pump 1,378 GPM of liquid each. P-322 is sized to nominally pump 1,630 GPM of liquid.
T-321 is cleaned using cleaning solution from F-321 after it has been cleaned. The contents of T-321 are then routed to Beer Colum (off plot) to clean the line.
Instrumentation
The motor for P-301 is operated by switch HS-301. The hydrolyzate flow rate to F-301 is controlled by controller FIC-301. The water, ammonia and cellulase feed flows are controlled by controllers FIC-302, FIC-303 and FIC-304, respectively. Each of these controllers can be operated in cascade/ratio control to the flow rate of FIC-301 by placing them into cascade mode.
Note that a selector switch, HS-301R, is present on page 2 of the group and trend displays. When this switch is in the AUTO position, the ratio of FIC-302, FIC-303 and FIC-304 will be automatically set when these controllers are not in cascade mode to provide bumpless transfer when switched into cascade mode. If HS-301R is in the MAN position, the operator must adjust the ratio manually from detail display of the controller before placing the controller into cascade mode, or leave the controllers in automatic mode and adjust the setpoints manually.
The flow rate of cleaning solution to F-301 is controlled by FIC-300. When cleaning F-301, the solution should initially be routed to the disposal facilities using HIC-302. Once F-301 is clean, the solution from F-301 can be pumped to T-301 via FIC-307 for cleaning the downstream equipment and lines.
The level of F-301 is indicated on LI-301. The operator must manually adjust inflows and outflows of F-301 to avoid overfilling it or to avoid operation of P-302 with a low liquid level in F-301. Overfilling F-301 will result in liquid carryover to the atmospheric vent line and should be avoided. Operation of P-302 with a low liquid supply level can result in damage to the pump.
The motor of the agitator for F-301 is operated by switch HS-304. It should not be operated whenever there is not a measurable liquid level in F-301.
The temperature of F-301 is controlled by controller TIC-303 which adjusts the flow of cooling water through the coils within F-301.
The concentration of the cellulase enzymes in F-301 is indicated on AI-301.
The motor of Air Blower K-301 is operated by switch HS-306. The outlet temperature of Air Cooler E-301 is controlled by TIC-308 which adjusts the cooling water flow through E-301.
The flow rate of air to F-301 is controlled by FIC-305. The air flow through K-301 is kept from going below a minimum flow of 18,000 SCFMXXX SM3/H by controller FIC-306.
The motor of Cellulase Transfer Pump P-302 is operated by switch HS-302. The cellulase transfer flow rate to T-301 is controlled by FIC-307. The manual control valve from P-302 to the disposal facilities is controlled by HIC-302. The flow in this line is not metered.
Cellulase Hold Tank
The level of T-301 is indicated on LI-302. The operator must manually adjust inflows and outflows of T-301 to avoid overfilling it or to avoid operation of P-303 with a low liquid level in T-301. Overfilling T-301 will result in liquid carryover to the atmospheric vent line and should be avoided. Operation of P-303 with a low liquid supply level can result in damage to the pump.
The temperature of T-301 is indicated on TI-304. Unexpected increase of this temperature likely indicates reaction(s) are occurring in T-301 (e.g. saccharification) or there are excessive shear forces on the agitator.
The motor of the agitator for T-301 is operated by switch HS-305. It should not be operated whenever there is not a measurable liquid level in T-301.
The motor of Cellulase Pump P-303 is operated by switch HS-303. The flow rate through the pump is set by flow controllers FIC-314 at SSCF Seed Fermenter F-311 and FIC-322 at SSCF Fermenter F-321.
The concentration of the cellulase enzymes in the discharge line of P-303 is indicated on AI-302.
SSCF Seed Fermentation
The hydrolyzate flow rate to F-311 is controlled by controller FIC-311. The inoculum, corn steep liquor and cellulase feed flows are controlled by controllers FIC-312, FIC-313 and FIC-314, respectively. Each of these controllers can be operated in cascade/ratio control to the flow rate of FIC-311 by placing them into cascade mode.
Note that a selector switch, HS-311R, is present on page 6 of the group and trend displays. When this switch is in the AUTO position, the ratio of FIC-312, FIC-313 and FIC-314 will be automatically set when these controllers are not in cascade mode to provide bumpless transfer when switched into cascade mode. If HS-311R is in the MAN position, the operator must adjust the ratio manually from detail display of the controller before placing the controller into cascade mode, or leave the controllers in automatic mode and adjust the setpoints manually.
The temperature of the hydrolyzate feed to the SSCF Seed Fermenter is controlled by TIC-312 which adjusts the cooling water flow through Feed Cooler E-311.
The flow rate of cleaning solution to F-311 is controlled by FIC-310. When cleaning F-311, the solution should initially be routed to the disposal facilities using HIC-311. Once F-311 is clean, the solution from F-311 can be pumped to T-311 via FIC-315 for cleaning the downstream equipment and lines.
The level of F-311 is indicated on LI-311. The operator must manually adjust inflows and outflows of F-311 to avoid overfilling it or to avoid operation of P-311 with a low liquid level in F-311. Overfilling F-311 will result in liquid carryover to the exhaust gas scrubber and should be avoided. Operation of P-311 with a low liquid supply level can result in damage to the pump.
The motor of the agitator for F-311 is operated by switch HS-313. It should not be operated whenever there is not a measurable liquid level in F-311.
The temperature of F-311 is controlled by controller TIC-313 which adjusts the flow of cooling water through the coils within F-311.
The concentration of the SSCF seed in F-311 is indicated on AI-311.
The motor of SSCF Seed Transfer Pump P-311 is operated by switch HS-311. The cellulase transfer flow rate to T-311 is controlled by FIC-315. The manual control valve from P-311 to the disposal facilities is controlled by HIC-311. The flow in this line is not metered.
SSCF Seed Hold Tank
The level of T-311 is indicated on LI-312. The operator must manually adjust inflows and outflows of T-311 to avoid overfilling it or to avoid operation of P-312 with a low liquid level in T-311. Overfilling T-311 will result in liquid carryover to the exhaust gas scrubber and should be avoided. Operation of P-312 with a low liquid supply level can result in damage to the pump.
The temperature of T-311 is indicated on TI-314. Unexpected increase of this temperature likely indicates reaction(s) are occurring in T-311 (e.g. saccharification) or there are excessive shear forces on the agitator.
The motor of the agitator for T-311 is operated by switch HS-314. It should not be operated whenever there is not a measurable liquid level in T-311.
The motor of SSCF Seed Pump P-312 is operated by switch HS-312. The flow rate through the pump is set by flow controller FIC-323 at SSCF Fermenter F-321.
The concentration of the SSCF Seed in the discharge line of P-312 is indicated on AI-312.
SSCF Fermentation
The hydrolyzate flow rate to F-321 is controlled by controller FIC-331. The cellulase, SSCF seed, corn steep liquor and ammonia feed flows are controlled by controllers FIC-322, FIC-323, FIC-324 and FIC-325, respectively. Each of these controllers can be operated in cascade/ratio control to the flow rate of FIC-321 by placing them into cascade mode.
Note that a selector switch, HS-321R, is present on page 9 of the group and trend displays. When this switch is in the AUTO position, the ratio of FIC-322, FIC-323, FIC-324 and FIC-325 will be automatically set when these controllers are not in cascade mode to provide bumpless transfer when switched into cascade mode. If HS-321R is in the MAN position, the operator must adjust the ratio manually from detail display of the controller before placing the controller into cascade mode, or leave the controllers in automatic mode and adjust the setpoints manually.
The temperature of the hydrolyzate feed to the SSCF Fermenter is controlled by TIC-321 which adjusts the cooling water flow through Feed Cooler E-321.
The flow rate of cleaning solution to F-321 is controlled by FIC-320. When cleaning F-321, the solution should initially be routed to the disposal facilities using HIC-321. Once F-321 is clean, the solution from F-321 can be pumped to T-321 via FIC-327 for cleaning the downstream equipment and lines.
The level of F-321 is indicated on LI-321. The operator must manually adjust inflows and outflows of F-321 to avoid overfilling it or to avoid operation of P-321A/B with a low liquid level in F-321. Overfilling F-321 will result in liquid carryover to the exhaust gas scrubber and should be avoided. Operation of P-321A/B with a low liquid supply level can result in damage to the pump.
The motor of the agitator system for F-321 is operated by switch HS-323. It should not be operated whenever there is not a measurable liquid level in F-321.
The temperature of F-321 is indicated by TI-322 on the line to the suction of pumps P-321A/B. The circulating beer return temperature is controlled by TIC-323 which adjusts the flow of chilled cooling water through the heat exchanger E-322. If the temperature of F-321 becomes too low or too high, adjust the circulating beer flow rate through E-322 using FIC-326.
The concentration of the ethanol in F-321 is indicated on AI-321.
The motor of SSCF Circulation & Transfer Pumps P-321A/B are operated by switches HS-321A/B. The beer transfer flow rate to T-321 is controlled by FIC-327. The manual control valve from P-321A/B to the disposal facilities is controlled by HIC-321. The flow in this line is not metered.
Beer Storage Tank
The level of T-321 is indicated on LI-322. The operator must manually adjust inflows and outflows of T-321 to avoid overfilling it or to avoid operation of P-322 with a low liquid level in T-321. Overfilling T-321 will result in liquid carryover to the exhaust gas scrubber and should be avoided. Operation of P-322 with a low liquid supply level can result in damage to the pump.
The temperature of T-321 is indicated on TI-324. Unexpected increase of this temperature likely indicates reaction(s) are occurring in T-321 (e.g. saccharification and/or ethanol production) or there are excessive shear forces on the agitator.
The motor of the agitator for T-321 is operated by switch HS-334. It should not be operated whenever there is not a measurable liquid level in T-321.
The motor of Beer Pump P-322 is operated by switch HS-322. The flow rate through the pump is set by flow controller FIC-328.
The concentration of the ethanol in the discharge line of P-322 is indicated on AI-322.
Interlocks
There are no interlocks in the Biomass Fermentation process. The operator must take care to monitor all instruments to ensure safe operation. Alarms will alert the operator to potentially unsafe operating conditions.