Description of Operating Process
Tavda Hydrolysis Plant
November 1997.
1.
History and background.
The Tavda Hydrolysis
Plant is located in the town of Tavda, on the western side of the Siberian
Lowlands, in Sverdlovsk Oblast, about 300 km northeast of the oblast capital
Yekaterinburg, and about 1700 km east of Moscow.
The Tavda Hydrolysis
Plant was established in 1943, with an initial production capacity of 5 million
litres of ethanol per year. In 1955,
the production capacity was increased to 8 million litres per year.
In 1970, the plant was reconstructed, to give a design production capacity
of 13.5 million litres per year.
Currently, the plant
produces approximately 36,000 litres of ethanol per day, and operates 345
days per year, for an overall output of approximately 12.4 million litres
per year. About 70% of the ethanol
production is derived from wood-cellulose hydrolysate, together with 20% derived
from wheat-starch hydrolysate and 10% from beet molasses. (All three feedstocks are combined in a single
fermentation process.)
2.
Feedstock processing. (See
attached flowdiagram.)
2.1 Wood.
The
plant uses about 450m³ (180 tonnes) of wood per day, usually made up of a
mix of about 70% coniferous wood, and about 30% non-coniferous (mainly birch)
wood.
Wood
is brought in as logs, by rail, from up to 300 km away, for chipping on site.
Woodchips and sawdust are also brought in by truck from mills up to
100 km away. In the past, the plant also received woodchips and sawdust by conveyor
belt from a neighboring lumber mill, but it has now ceased operating.
A mixture of about 80% woodchips and 20% sawdust are processed in
a "downward-percolation dilute-acid hydrolysis process", (somewhat
similar to the German "Scholler Process," the U.S. "Madison
Process" and the "New Zealand Forest Research Institute Process".)
The
plant has 18 hydrolysis reactors which operate batchwise, in parallel. Only 7 are actually in use at any time.
The
reactors each have a total capacity of 40m³, and a working capacity of about
37m³. The reactors are made of carbon
steel, with an interior layer of cement and a lining of acid-resistant tiles,
and are mounted on weighing scales.
The
hydrolysis process is commenced by filling a reactor with 4.5 to 5 tonnes
of woodchips and sawdust. (The wood
weights are calculated on an absolutely-dry basis). This represents 11 - 12 m³ of wood in its original solid state.
The wood loading, (from a conveyor belt passing over the tops of the
reactors), takes 25 minutes.
About
11.5m³ of water containing about 55 litres of concentrated sulphuric acid
are added into the reactor over a period of 20 minutes. This gives an acid concentration of 0.75 w/v.
The
reactor is then sealed, and heated with high-pressure steam at 250°C, over
a period of 40 minutes. During this time there are two purges of about 5 minutes
each, to vent air and other gases to the atmosphere via a vent chamber. First, when the reactor pressure reaches 3
atmospheres, it is vented back to 1 atmosphere, and then the vent is reclosed,
and steaming recommenced. Next, when
the pressure reaches 5 atmospheres, the vent is reopened, to drop the pressure
down to 2 atmospheres. Then, the vent
is reclosed, and the steaming is recommenced, to take the pressure up to 6
atmospheres.
At this
point, the vertical percolation is commenced. Over the next 20 minutes, as the pressure is raised to 7 atmospheres,
13m³ of water containing 40 litres of concentrated sulphuric acid (0.5% of
acid) are added to the top of the reactor while a corresponding amount of
liquid is withdrawn from the bottom of the reactor.
Then,
while the pressure is raised to 9 atmospheres, over another 20-minute period,
12m³ of water
containing 35 litres of concentrated sulphuric acid (0.46% of acid) are added
to the top of the reactor, and a corresponding amount of liquid is withdrawn
from the bottom.
In the next 20-minute period, in which the pressure is raised to
12 atmospheres, 10m³ of water containing 30 litres of concentrated sulphuric
acid (0.48% of acid) are added to the top and the same volume of liquid is
withdrawn from the bottom of the reactor.
This
acid-addition and liquid-withdrawal process is repeated with the same volumes
over the next 20-minute period, while the pressure is raised to 12.5 atmospheres.
Then,
with the pressure held at 12.5 atmospheres, 10m³ of water containing 20 litres
of concentrated acid (0.32%) are added over the ensuing 20-minute period.
After
a total of 100 minutes, the percolating is discontinued, and the reactor is
rinsed with 5m³ of water, over a 10-minute period, while holding the pressure
at 12.5 atmospheres. The water and
steam are then shut off, and the liquid is drained over a period of 30 minutes,
reducing the load in the reactor from 24 tonnes to 9 tonnes, and reducing
the pressure to 7 atmospheres.
Then,
a quick-acting valve on the base of the reactor is opened, to cause the remaining
solids to be blown into a cyclone tank over a period of 5 minutes, while the
liquid flashes as vapor, to the atmosphere. The solids dry down to about 8 tonnes, which is about 65% lignin
at 60 - 80% moisture. It is discharged
into three trucks, to be taken to a specially prepared dumpsite about 10 km
away.
The
reactor operating conditions may be varied, depending on the mix of coniferous
and non-coniferous wood. For example,
if there is more than 30% non-coniferous wood, the maximum pressure in the
reactor may be 12 atmospheres or less.
Previously
the lignin residue was dried to about 40% moisture, and burnt in a boiler.
This involved sending the residue through a pipeline of about 700 - 800 metres
in length. In the 1980's it was concluded
that this procedure of drying and burning was uneconomical, so the dumping
was commenced. At that time, there
were no "ecological penalties" or charges for such dumping. Now, however, there is a charge paid to the
oblast (county), equivalent to $24
per dry tonne of residue. With an
annual output of approximately 60,000 dry tonnes of residue and a total annual
charge of about $1.4 million, the disposal economics are being reassessed. (It is reported that it would cost about $500,000
to refurbish and reinstate the original, vertical, oil-fired, hot-air dryer
system, which was susceptible to catching fire. So other uses of lignin are being sought. For any commercial purposes, the lignin would
probably have to be dried to 5 - 10% moisture.)
A problem
of accumulation of tarry caramel deposits occurs in the bottom of the reactor
and in the piping from it. This necessitates
special cleaning every 300 usage cycles. The tarry caramel scale is removed from the bottom of the reactor
by scraping by hand, while the copper pipes have to be dismantled and cleaned
by hand and with a water hose at 5 atmospheres pressure.
The
acidic liquid drawn off from the reactor is piped to two flash-tanks which
operate in series, to serve as evaporators.
The liquid contains pentoses from the hydrolysis of the wood hemicellulose,
some furfural and dissolved, partially-hydrolysed cellulose.
(When grain is being processed, the grain-starch hydrolysate also joins
the liquid flow to the flash tanks, as described in section 2.2.)
The
two flashtank-evaporators are each 16m³ in capacity and operate in series. With the drop in pressure from the reactor into the flashtanks,
about 10% of the liquid volume flashes off as steam, together with most of
the furfural. (No attempt is made
to recover the furfural, as the concentration is low, and the recovery costs
are reported to be very high. Some
other hydrolysis plants do, however, recover furfural for various uses, including
the production of rocket fuel). The
degree of removal of furfural in the flash tanks is of importance, as it can
inhibit the subsequent fermentation.
The
concentrated liquid from the second flash tank is pumped to a 1000m³ inverter tank, where it is held for 4.5
hours at 105°C, to complete the hydrolysis of the cellulose to glucose and
other hexoses, including galactose, raffinose, and mannose. The hydrolysate emerges from the inverter at
about pH 1.6, and is sent to the neutralization tanks.
There
are 7 neutralization tanks, 5 having capacities of 34m³ and two having capacities
of 100m³ All are fitted with vertically mounted agitators. (Normally, two of the 34m³ tanks are kept on
standby.) The tanks are operated in
various combinations to suit the rate of hydrolysate flow, which is normally
about 130m³ per hour. The hydrolysate
enters the first neutralization tank, where it is mixed with milk of lime
(a suspension of calcium hydroxide in water), to raise the pH to 3.2. It is then transferred to a holding tank, where
it is agitated, before going to a second neutralization tank. There, it is
mixed with ammonium hydroxide, to raise the pH to 3.8 - 4.0. Ammonium phosphate
and a mixture of ammonium and potassium salts are added, to provide nutrients
for the subsequent fermentation. The
liquid is then transferred to one of five shallow precipitator tanks which
are of 285m³ capacity, and have a liquid surface area of 113m³. (They resemble sewage-plant clarifier tanks,
having a very slow moving sludge agitator, and an overflow channel around
the top circumference).
The
solids from the bottom of the precipitator are composed to about 70% calcium
sulphate, with the remainder being mostly tars, lignin and some sand. They are drawn off at a concentration of 400
- 600 grams per litre, to go to a 20m³ precipitate-holding tank, from which they are fed to a vacuum
belt filter. The liquid drawn off
from the filter, which represents about 30% of the original volume, is recycled
to the precipitator, while the solids are loaded onto trucks, to be sent to
the lignin-waste dumpsite.
The
supernatant liquid which is drawn off from the top of the precipitator at
80 - 100°C, goes into a 40m³ holding tank, from where it is pumped through
a 4-stage vacuum cooler, to be cooled down to 32 - 34°C.
(Much of the furfural remaining in the hydrolysate is drawn off into
the water jet used to pull the vacuum). The
cooled hydrolysate, now referred to as "wort", then goes into a
holding tank of 160m³ capacity. A
small amount of mostly organic sludge is discarded from the cone-bottom of
the holding tank, while the main flow of wort goes to a 30m³ "yeast-activator" tank. Here, the wort is mixed with centrifuged yeast
recycled from the continuous fermentation system. The wort is dosed with ammonium phosphate. A stream of 3.5m³ per hour of diluted molasses may also be
added to the activator tank (as described in section 2.3), to give a mixture
of about 2.7 - 3.0% fermentable sugars.
There is provision for aeration of the activator, but it has not been
considered necessary to use it in recent years.
2.2 Grain.
Local wheat, containing 48 - 52% starch, is processed by acid hydrolysis,
in batches, in either of two of the 18 reaction vessels, which are otherwise
used for cellulose hydrolysis.
The wheat is dumped from the delivery trucks onto the floor of the
storage building. There, it is sampled and then checked in the laboratory
for moisture content, trash and starch content.
(These parameters are taken into account in calculating the wheat purchase
price.)
The wheat is lifted by clamshell bucket to feed directly into a hammermill.
The feedrate is regulated by adjusting the degree of opening of the
clamshell, and the grain drops through a chicken-wire screen with holes of
about 2 cm in diameter, to remove any large pieces of trash.
The hammermill is also fitted with a magnet, to remove any tramp iron.
The hammermill has a grinding capacity of 4 tonnes of wheat per hour,
using a 6mm-diameter round-hole screen. The
meal is then blown up to a cyclone to feed into a mash-mix tank.
The meal has a wide range of particle sizes, together with some whole
grains and some large pieces of chaff. The
only other screen available for the hammermill has 3mm holes, and produces
a meal which is too finely ground. No
sieve analysis is performed on the meal.
There is a roller mill which serves as a standby for milling. It is mounted on top of a mash-mix tank, to
feed meal directly into the tank.
The mashing water comes from the cellulose-hydrolysis building.
It is heated to about 90°C and pumped backwards through the mash line
to the mash-mix tank in the grain-mashing building, to flush out any mash
solids left in the line. (In summer, the water is replaced with waste
liquid from fodder-yeast production. It
is heated to 80°C before pumping to the grain-mashing building.)
Three tonnes of wheat meal are added to one of two 20m³ mash-mix tanks containing 15m³ of water
at about 80°C. The addition of the meal lowers
the temperature to about 75°C, and the mixture, which is agitated mechanically
by a top-mounted, vertical agitator, is held at that temperature for about
one hour, to gelatinize the starch.
The mixture is then pumped into acid-hydrolysis reactor 9 or 10,
to which 95 litres of concentrated sulphuric acid are added, to give an acid
concentration of 0.8%. (The mash transfer
takes 10 - 15 minutes.) The reactor
is then sealed, and heated by the injection of high-pressure steam, to a pressure
of 4 atmospheres. The vent is then opened, to purge air, and to mix the contents,
(as the reactor has no agitation). When the pressure has dropped to about
1.5 atmospheres, the vent valve is closed again, and steaming is recommenced,
to take the pressure up to 7.5 atmospheres.
At this point, after about 60 - 70 minutes in the reactor, the steaming
is stopped, and the hydrolyzed grain mash is discharged into the pipe which
conveys cellulose hydrolysate from the other reactors to the flashtank evaporators.
Usually 4 grain batches are cooked in an 8-hour shift. The starch hydrolysate contains about 8 - 10%
of sugars.
The alcohol production from wheat reportedly averages about 250 litres
per tonne.
2.3 Molasses.
Beet molasses is obtained from sugar mills in the vicinity of Kazan,
in Tartarstan, about 900 km to the west of Tavda. The molasses has a total dry matter of 73% - 80%, and contains 43 - 51%
sugars. (The term Brix is not used
in the plant to refer to molasses concentrations.)
The molasses is diluted with water to 15% total dry matter, and acidified
with sulphuric acid to a pH range of 4 - 5. Then 3 - 5m³ of the diluted molasses
are pumped into the yeast activator, to mix with each 120m³ of hydrolysate coming from the cellulose
and grain processing units.
3.
Fermentation.
The mixture of cellulose
hydrolysate, wheat-starch hydrolysate and diluted molasses, which is referred
to as "wort", is pumped together with recycled yeast, at a rate
of about 120m³ per hour, from the activator tank, into the first of a pair
of continuous fermentation vessels which are operated in series. There are 5 primary fermenters, each of 170m³
capacity, and one secondary fermenter of 110m³ capacity. None of the vessels
has any agitation or aeration. The
number of primary vessels in use at any time is adjusted to match the feed
flow rate, to give a total fermentation time in the primary and secondary
vessel of 6 - 8 hours.
The wort is fed
in at the top of the primary fermenter, and continuously pumped from the bottom,
into the top of the secondary fermenter. The temperature in the fermenters is controlled at a maximum of
34 - 35°C, by adjusting the temperature of the feed from the 4-stage vacuum
cooler. The fermenters do not have
any other means of temperature control.
The yeast used in
the fermentation is a strain of the fission yeast Schizosaccharomyces, which
is propagated from slants in the laboratory, and through a series of propagation
vessels in the plant.
Carbon dioxide is drawn off from the fermenters, and is piped to
a processing unit for scrubbing and compression to a liquid product.
Fermented wort,
known as “beer” (or “brew”) (or "brazhka"), is drawn off continuously
from the bottom of the single secondary fermenter, and is pumped to a battery
of 10 Russian Laval vertical centrifuges, which separate the beer from the
yeast, which is sent back to the activator tank. (Normally, only 5 or 6 centrifuges are in use at any time.)
The centrifuged
beer contains about 1.3% alcohol, if it is derived solely from cellulose hydrolysate,
or about 1.6% alcohol, if grain and molasses have also been used. The beer is pumped to a holding tank of 70m³ capacity, from where it is pumped to the
distillation unit.
4.
Distillation.
The objective of
the distillation is to produce a fairly high
quality alcohol for industrial uses.
4.1 Equipment.
The distillation equipment, (as shown in the attached flowdiagram)
consists of:-
(a) Four beer-stripping
columns. All are 2 metres in diameter,
with 2cm-thick cast-iron shells and 19 titanium-alloy trays. Three of the columns have perforated trays,
similar to a Nutter design), while the fourth has bubble-cap trays. Only 2 of the columns are in operation at any
time. Each column has its own beer-preheater/condenser, and all share a common,
vertical, second condenser of 15m² and a final horizontal vent condenser of
7m².
(b) An "epuration"
(aldehyde) column, of 2.2 metres in diameter, fabricated entirely of stainless
steel, with 40 bubble-cap trays. It has a 150m² primary condenser, and a 7m² vent condenser.
It is heated via a 38m² external reboiler.
(c) A "spirits"
(rectification) column of 2.2 metres in diameter, fabricated entirely of stainless
steel, with 72 bubble-cap trays. It has a 150m² primary condenser, and a 57m² vent condenser.
(d) A "methanol"
(demethylizing) column of 2.14 metres in diameter, fabricated entirely of
copper, with 70 bubble-cap trays. It has four horizontal condensers and two vertical
condensers, arranged in series. It
is fitted with an external 38m² reboiler, for indirect heating.
(e) A heads-and-esters
concentration column (no longer in use.)
It is 60 centimetres in diameter, has 30 bubble-cap trays, and is fabricated
entirely of stainless steel.
(f) An old methanol
column (dating from the 1950's), which is being refurbished and reinstalled,
to replace the existing methanol column.
It is approximately 2.5 metres in diameter, and has a total of 72 trays.
The lower 44 trays and their shell are fabricated of stainless steel, while
the upper 28 trays and their shell are fabricated of copper. Note: The objective in replacing the existing
methanol column is to be able to increase the distillation and rectification
capacity from the present level of 36,000 - 40,000 litres per day, to 60,000
litres per day. (The existing methanol
column was originally designed to operate at 30,000 litres per day, and is
reported to be the main bottleneck in the system at present.)
4.2 Mode of Operation.
4.2.1 Beer distillation.
There are 4 beer-distillation columns, but normally only 2 are in operation
(in parallel), at any time. They all
share in common their second and third condensers, so their outputs are mingled
together. Each of the 3 beer columns which have perforated trays, has a feed
capacity of 90m³ per hour, while the column with bubble caps has a feed capacity
of 50m³ per hour. The combined feed
rate to the two columns in operation varies, but averages about 120m³ per hour.
Beer containing about 1.6% alcohol is first preheated by the overhead
vapors in the dephlegmator-preheater, and is then introduced into the 19-tray
column on tray 18. Live steam is introduced
at the base of the column, and distills the alcohol out of the descending
stream of beer. The alcohol vapors
rise up into the overhead dephlegmator and condensers.
All of the condensate from the dephlegmator is refluxed to the top
of the column, while all of the condensate from the other two condensers,
at 10 - 15% alcohol, goes down into a 75cm-diameter horizontal collector pipe. From there it is raised by a steam-lift system,
to feed the epuration column.
The beer distillation columns can operate for up to 3 months between
cleanings, when operating solely on cellulose feedstock, but the cleaning
has to be more frequent when molasses is used.
4.2.2. Rectification.
The 10 - 15% alcohol feed enters the 40-tray epuration (aldehyde) column on tray 30. The column is heated indirectly through a reboiler at the base. (No dilution water is added to the column.) The ethanol portion of the feed tends to go down the column, while the more volatile aldehydes and esters rise into the overhead condensers. A heads purge, amounting to about 0.5% of the alcohol feed volume, is drawn off from the condenser reflux loop, to be sold as low-grade industrial alcohol.
The alcohol descending to the bottom of the epuration column is pumped to the 72-tray spirits (rectification) column, entering on tray 15. The column is heated by live steam at the base. There are fusel-draw valves on each tray, from No. 10 to No. 19. A fusel draw is taken from several of the valves, to give an average alcohol concentration of about 35 - 40°C. It goes to a decanter, and the decanted oil is sent to the drain, while the alcohol-water portion, at 12 - 16% alcohol, is returned to the beer tank. The temperature is monitored at tray 22, and near the top of the column. A 4% solution of caustic soda is introduced into the column at tray 26, at a rate which is varied with the acidity of the product. The alcohol product is drawn off from tray 68, while an aldehyde heads purge is taken from the reflux loop at a rate of about 0.5% of the feed, to be sold as low-grade industrial alcohol ("methanol, esters and aldehydes fraction").
The alcohol flow from the spirits column at <96.2% is fed to the 70-tray methanol column, entering on tray 40. The methanol column is heated indirectly, via a reboiler on the base. The methanol portion of the feed tends to fractionate upwards, to be drawn off at a rate of 0.5% of the feed volume. (It normally contains 70 - 90% methanol, and may be used for subsequent denaturation of products.) The final product is drawn off from the base of the methanol column and is passed through a cooler and a filter. If denatured alcohol is being produced, the product is diluted with steam condensate to 93.5 - 94%, before going through a metering system. If "extra" quality industrial is being produced, there is no dilution.
4.3 Product specifications.
The
two types of final product are required to meet the following state specifications:
-
A. "Extra" rectified industrial
alcohol.
1. Appearance: Transparent, colorless liquid,
without extraneous matter.
2. Odor: Odor characteristic of rectified ethanol,
without extraneous odors.
3. Ethanol content by volume: Greater than 96.2%.
4. Purity test. (Absence of color change
on heating with sulphuric acid.) Passes the test.
5. Permanganate time: >15 minutes.
6. Aldehyde content in mg per litre
of absolute alcohol.
<4 (ppm)
7. Fusel content in mg per litre: <4 (ppm)
8. Acid content (as acetic acid) in mg per
litre: <10 (ppm)
9. Ester content in mg per litre: <25 (ppm)
10. Methanol content in volume percent:
<0.03% (300 ppm)
11. Furfural test: Not detected.
12. Solid residue on evaporation, in mg per
litre: <1 (ppm)
13. Alkali content by weight, as sodium hydroxide:
Not detected.
14. Electrical resistance, in ohm.cm: >1.3x106
B. Denatured industrial alcohol. ("Multi-component industrial liquid mixture")
without extraneous matter.
2. Density at 20°C, in grams per cm³: 0.829-0.816
3. Refractive index:
1.3630-1.3655
4. Permanganate time: >
15 minutes
5. Aldehyde content in mg per litre: <4 (ppm)
6. Content of propyl, butyl and amyl alcohols,
in mg per litre:
<4 (ppm)
7. Acid content (as acetic acid), in mg per litre: <10 (ppm)
8. Ester content in mg per litre: <25 (ppm)
9. Methanol content as volume percent: <0.2% (2000 ppm)
10. Furfural test: Not detected.
11. Solid residue on evaporation, in mg per litre: <4 (ppm)
12. Arsenic content: in mg per litre: <0.2 (ppm)
13. Copper content: in mg per litre: <5 (ppm)
14. Mercury content: in mg per litre: <0 5 (ppm)
15. Lead content: in mg per litre: <0.03 (ppm)
16. Cadmium content: in mg per litre: <0.03 (ppm)
17. Zinc content: in mg per litre: <10 (ppm)
18. Benzene content: Not detected.
Note:
The state regulations on denatured alcohol appear to be a little vague. The product should be denatured to a maximum level
of 0.2% methanol. There is, however,
no clearly stated minimum, but if the methanol concentration is less than
0.05%, the product will be subject to excise tax.
In practice, it is assumed that the required minimum level of methanol
is 0.1%, and the product is denatured to about 0.12% methanol, using the heads
fraction from the methanol column.
4.4 Energy usage.
The
beer columns are reported to use 140 kg of steam per 1000 litres of
beer distilled. On the basis of an
alcohol content of 1.6%, this represents 8.75 kg of steam per litre of alcohol
distilled.
The
epuration (aldehyde) column is reported to use 2.3 kg of steam per
litre of alcohol.
The
spirits (rectification) column is reported to use 1.8 kg of steam per
litre of alcohol.
The
methanol (demethylizing) column is reported to use 1.4 kg of steam
per litre of alcohol.
Thus,
the total steam usage for distillation and rectification amounts to
14.25 kg per litre of alcohol.
Converted
to U.S. terms, for purposes of making a direct comparison with the steam usage
in U.S. plants, this amounts to 118.75 lbs of steam per U.S. gallon of
alcohol distilled to 192 proof. The
beer distillation consumes 72.9 lbs. of steam per U.S. gallon of alcohol,
while the three-column rectification system utilizes 45.85 lbs. of steam
per U.S. gallon. (This does not
include any reprocessing of heads fractions.)
Steam
usage is reported to represent 35 - 40% of the overall production costs.
4.5 Product cost structure.
Tavda's
overall production cost for cellulose-hydrolysis spirit is reported to be
in the range of 6000 to 9000 roubles per litre (which, at an exchange rate
of 6000 roubles per US$, is equivalent to US $3.78 to $5.67 per U.S. gallon.
The
breakdown of production costs, on a percentage basis, for the month of October
1997 was:-
1. Raw materials
35.5%
2. Auxiliary materials
(chemicals etc.) 6.0%
3. Fuel
35.1%
4. Labor
1.5%
5. Equipment maintenance
5.4%
6. Direct overheads
2.3%
7. "Other expenses"
3.6%
8. General overheads 10.4%
9. "Non-production
costs"
0.2%
TOTAL 100%
4.6 Products, markets and prices.
About 10% of the alcohol output is sold as undenatured "extra
rectified industrial alcohol" at a minimum concentration of 96.2% alcohol
by volume, while the remaining 90% of output is sold as "denatured industrial
alcohol" at 93.5 - 94.0% alcohol by volume.
The "extra" grade product sells at a price of 30,000 roubles
per litre inclusive of excise and value-added taxes, from which the producer
receives a net 12,000 roubles per litre (approximately US$2 ).
The denatured industrial alcohol sells at a price of 11,500 roubles
per litre, and is exempt from excise taxes. It is only denatured with about 0.12% methanol, (which is less than
usually naturally present in tequila, grappa and some other beverages) and
does not contain any colorant, Bitrex or other, similar taste or odor modifier,
so it is suitable for a wide range of uses.
Currently, beverage-grade neutral spirit sells for a net price of
3000 - 4000 roubles per litre, but its production and sale is limited by government
quotas.
5.
Stillage utilization.
The stillage from
the beer distillation contains 0.85 to 1.1% of pentose sugars, mainly xylose
and arabinose, from the hydrolysis of the hemicellulose in the wood.
The stillage is
used as a feedstock for the production of a torula fodder yeast, using a strain
of Candida scotti. The product is
sold both in powder and pellet form, for use as a protein supplement in animal
feeds.
6.
Utilities, etc.
6.1 Steam and electricity.
There
are 4 boilers, each capable of producing 75 tonnes of steam per hour, at a
pressure of 40 atmospheres, fired by coal or fuel oil.
Only two boilers are in operation at any time, and two are on standby.
The high-pressure steam is passed through a 6.2-megawatt electricity
cogeneration turbine, to give low-pressure steam for most process applications,
at 5 atmospheres.
A major
use of energy is the district-heating system. The plant supplies hot water for heating the homes of about 60%
of the town's population of 40,800. This
means that the steam demand is much greater in winter than in summer, with
a consequent change in electricity cogeneration. Thus, the plant produces only 20% of its electricity
requirements in summer, and about 90% in winter. The remainder of the electricity requirement
comes from the public supply grid.
6.2 Water.
Process
water is taken from the nearby Tavda River, and is filtered and treated. Cooling water is also taken from the Tavda
River, but it is unfiltered, and is discharged back into the river after use. Thus, there is no need for cooling towers.
6.3 Lime Kilning.
The
plant operates a lime kiln, to burn calcium carbonate limestone, by coke firing.
(The resultant calcium oxide is used for neutralizing the cellulose
hydrolyzate.) Currently, the lime throughput is 16 tonnes per day, but the unit
has a maximum capacity of 35 tonnes per day.
6.4 Waste treatment.
Apart
from the lignin and other solid wastes which are taken to a special dumpsite,
the plant has a large liquid effluent treatment system, to handle a flow of
about 800 m³ per hour, much of which comes from the fodder- yeast production
unit.
The
waste-treatment system has 18 precipitation tanks, each of 18 metres in diameter,
a 25,000 m³ aerated tank, and two lagoons, each of 100 metres square.
The
B.O.D. of the effluent entering the system is reported as 1,500 mg per litre,
while at the discharge, it is about 500 mg per litre.
The plant is required to bring the B.O.D. at the discharge down to
about 60 - 100 mg per litre, and ozonation is currently being considered. It is recommended that the possibility
of using floating aerators be investigated, as an alternative system for lowering
the B.O.D.
The
waste-treatment operating costs are currently about 1 billion roubles per
month, excluding labor. This is equivalent
to US$2 million per year.
7.
Employment.
The plant currently
employs a total of 1341 persons. The
distribution is:-
A. Administration Departments
|
Department |
Managerial |
Non- Managerial |
Total |
|
|
1. |
Director General |
1 |
- |
1 |
|
2. |
Chief Engineer |
1 |
- |
1 |
|
3. |
Deputy Director General |
1 |
- |
1 |
|
4. |
Deputy Director General, Economics |
1 |
- |
1 |
|
5. |
Chief Technologist |
1 |
- |
1 |
|
6. |
Legal Department |
1 |
1 |
2 |
|
7. |
Capital Construction |
1 |
1 |
2 |
|
8. |
Chief Mechanical Engineer's Department |
1 |
3 |
4 |
|
9. |
Chief Energy Engineer's Department |
2 |
2 |
4 |
|
10. |
Planning and Economics |
1 |
3 |
4 |
|
11. |
Safety Department |
1 |
2 |
3 |
|
12. |
Personnel Department |
1 |
3 |
4 |
|
13. |
Facilities and Community Department |
2 |
3 |
5 |
|
14. |
Supplies |
2 |
4 |
6 |
|
15. |
Marketing |
2 |
4 |
6 |
|
16. |
Production Department |
1 |
3 |
4 |
|
17. |
Environmental Protection |
1 |
2 |
3 |
|
18. |
Design Department |
1 |
4 |
5 |
|
19. |
Accounting |
3 |
11 |
14 |
|
20. |
Computerization |
1 |
2 |
3 |
|
Total |
26 |
48 |
74 |
|
B. Plant and General Services.
|
Department |
Managerial |
Non- Managerial |
Total |
|
|
1. |
Administration |
12 |
4 |
16 |
|
2. |
Laboratory |
8 |
14 |
22 |
|
3. |
Hydrolysis |
10 |
129 |
139 |
|
4. |
Yeast |
8 |
71 |
79 |
|
5. |
Carbon Dioxide |
1 |
15 |
16 |
|
6. |
Raw Materials |
9 |
117 |
126 |
|
7. |
Heating and Power |
19 |
168 |
187 |
|
8. |
Truck Transportation |
10 |
133 |
143 |
|
9. |
Rail Transportation |
7 |
56 |
63 |
|
10. |
Mechanical Maintenance |
3 |
65 |
68 |
|
11. |
Electrical Maintenance |
2 |
33 |
35 |
|
12. |
Control and Instrumentation |
4 |
35 |
39 |
|
13. |
Lime Kilning |
1 |
17 |
18 |
|
14. |
OI3 (?) |
11 |
1 |
12 |
|
15. |
Stores |
- |
13 |
13 |
|
16. |
Salt, Minerals |
1 |
27 |
28 |
|
17. |
Purification Works |
5 |
56 |
61 |
|
18. |
Repairs and Construction |
1 |
39 |
40 |
|
Total |
102 |
1003 |
1105 |
|
C. Employee and Community Services.
|
Department |
Managerial |
Non- Managerial |
Total |
|
|
1. |
Communal and Housing |
10 |
63 |
73 |
|
2. |
Nursery |
18 |
29 |
47 |
|
3. |
Sports Facilities and Medical Centre |
18 |
4 |
22 |
|
4. |
Club |
3 |
5 |
8 |
|
5. |
Hostel and Hotel |
2 |
10 |
12 |
|
Total |
51 |
111 |
162 |
|
Overall Totals: Managerial Non-Managerial Total
179
1,162
1,341
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