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Файл:The bases of special methods of biomass processing into prospective materials. Tutorial
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thermoplastic polymer composites (WPC), in which it is (by weight) to
80 % or more. Thermoplastic WPC can be processed by extrusion, injection
molding and other.
It can be assumed that new applications of wood flour, including
those associated with the development of biotechnology and
nanotechnology will emerge in the near future.
Regulatory documents on the wood flour:
– GOST (national standard) 16361-87. Wood flour. Specifications;
– GOST (national standard) 16362-86. Wood flour. Test methods.
3.2. Extraction technologies
3.2.1. General information about woody vegetation
Wood vegetation is a specific kind of wood raw material in which the
cells of the needles (leaves), young shoots and bark structure predominate.
In recent years, the food, perfume and cosmetics industry, household and
agriculture sharply increased the demand for natural supplements. The use
of woody vegetation, rich in biologically active substances may be of great
importance in solving this issue.
Components of woody vegetation are divided into 4 groups:
The first group consists of substances called lipids, which are soluble
in nonpolar organic solvents, but insoluble in water. These include
hydrocarbons, alcohols, aldehydes, fatty acid derivatives, fat-soluble
vitamins, pigments, sterols, resinous substances and essential oils.
Oil products are referred as «secondary exchange» products. Their
functions are not clear, although primarily associated with the protective
action against insect pests and plant diseases. They are usually extracted
from the green wood by means of live steam, although in some cases they
are extracted with organic solvents, and carbon monoxide. The main
components of essential oils of coniferous trees are terpenic hydrocarbons
Monoterpenic hydrocarbons dominate as part of conifer essential
oils, and comprise from 60 to 90 % of their total content. The essential oil
of Siberian pine is the richest in them.
When using woody vegetation, especially in feed-stuff preparation,
vitamins play an important role. There are fat-soluble vitamins K and E
(tocopherol) in the green of the conifers. It is important that the content of
the last in the needles increases sharply in the summer. There is less of
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vitamin K. However, unlike tocopherol its level in winter is higher than in
summer.
The second group is represented by water-soluble components, which
comprise 30 % of the biomass of woody vegetation. Their quantity and
composition vary greatly depending on the ratio of elements in the green,
tree species, season and growing conditions. The importance of evaluation
in the study of processing of raw materials by means of steam distillation is
determined by the passage of a significant part in the bottoms condensate.
Most of the water-soluble substances are carbohydrates, the content of
which is subject to significant changes, including seasonal variations. Their
structure consists of a close relationship of pentose and hexose. There is
relatively large amount of phenolic compounds in free and bound state in
green, most often in the form of glycosides. The components of watersoluble products are many vitamins (C, B1, B2, B6, E, PP, etc.).
Insoluble in water and organic solvents compounds are isolated as the
third group. They are polysaccharides, polymeric phenols (lignin) and
nitrogen-containing components. A special group is composed of mineral
compounds. Allowed and several other classification of woody vegetation
components for specific groups is allowed. One of the most important
factors in the allocation of extractive products is the nature of the extractant.
Their maximum quantity (40 %) of woody vegetation is extracted by polar
solvents, especially ethyl and propyl alcohols. Extraction of non-polar
solvents is less effective. Up to 10 % of these components are extracted
from the vegetative organs of pine and spruce by means of hexane. Not
much more than they extracted with petroleum ether (12 %).
3.2.2. Methods of processing wood greens
Woody green, as a rich source of energy and biologically active
substances, has a direct practical application, and can be efficiently
processed into valuable economic products. In limited quantities it has long
been used to feed livestock, as a therapeutic drug in agriculture to cover
planting and for soil loosening. The standards for the inclusion in the diets
of animals and birds have been developed. Good results were obtained in
the treatment of scurvy, wound healing, and for other therapeutic purposes.
In the industry, though in limited proportion, woody vegetation is
processed to produce a small (getting conifer-vitamin meal, stripping
essential oils) as well as relatively large range of commercial products
(organic solvent extraction followed by fractionation). In the pilot plant the
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extracting is carried out by highly volatile liquids and liquefied gases. The
obtained products, including essential oils and their components are widely
used as ingredients in detergents, fragrances, deodorants, as raw materials
for organic synthesis.
The only relatively voluminous direction of the original wood is
green feed-stuff for farm animals and poultry. It can be consumed
throughout the year, but acquires special value in winter, during an acute
shortage of vitamins and other biologically active compounds. The
supplements containing it help to normalize metabolic processes in the
body. Wood green can play an important role as a feeding resource,
especially during periods of drought and other adverse weather conditions.
In addition to increasing the productivity of animals, its inclusion improves
the quality of the fur.
We know the technological scheme of processing of green wood to
produce essential oils and natural extracts of coniferous plants by
continuous. It is used to extract soluble substances from the wood of pine
green by means of the screw unit of continuous operation. The unit consists
of two columns, the first of which is designed for the distillation of essential
oils, and the second – for the extraction of water-soluble substances. At the
bottom of the first column is the condensation of steam, which is sent for
the distillation of oils and condensate, extracts some of water-soluble
substances. Their further extraction is carried out in the second column by
irrigation of raw material. To increase the yield of the extract the spent
woody green, from the second column, is continuously squeezed in a screw
press. This technology allows obtaining 23.6 kg of natural pine extract from
a ton of raw material.
The technology of extraction with hot water and steam inlet (3 atm.)
for 3 hours yields an aqueous extract containing 1.4–2.5 % of sugar, which
is used for cultivation of fodder yeast protein.
A disk extractor is used for water extracts that allows grinding raw
materials in the environment of the extractant.
Till now only pine oil and Siberian pine oil in limited quantities are
produced by means of distillation with live steam in Russia on an industrial
scale. Their extraction is carried out at the units of periodic and continuous
types. These devices do not provide high yield and quality of pine oil. Most
of the plants of periodic or cyclic operation refers to the western Siberian
type, a small part of them – to the Volga-Vyatka’s one. Their difference lies
in the arrangement of the steam generator. In the Volga-Vyatka’s version, it
is packed with the vat, while in West Siberia – apart from it. There are
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several versions of such systems: single-vat and double-vat, stationary and
mobile. In the latter case, all the equipment of the unit is mounted on a sled
and transported by tractors. Currently the pine-oil system consists of
separate units of full factory readiness, which ensures quick replacement.
Sealing of the vat is achieved by a fixed location of the rubber gasket in
between the vat and the cover. All equipment is mounted on the frame,
placed on two powerful runners with a pitman device for towing. Loading
and unloading of raw materials, as well as mounting of blocks can be
performed using the hoist.
Despite the presence of valuable components and large amounts of
raw materials their extraction from woody vegetation is fulfilled poorly.
The only organic solvent used for this purpose in semi-industrial scale, is
gasoline. So far, this method is used for processing only green wood of pine
and spruce in the enterprises of the European part of the country. The
technology involves the extraction of individual fractions of extractives by
gasoline or gasoline-water emulsion and their further processing.
The simplest version of such technology is the extraction of
pigments, vitamins, wax and pine essential crude oil from wood green by
gasoline at 70 0C. Cooling and 16–20-hour settling provide water separation
and deposition of coniferous wax that remains on the filter. From the
clarified extract gasoline is distilled, and goes to reuse. The remaining
soluble products are neutralized with 40 % sodium hydroxide, which allows
the extraction of essential oil from a mixture after the transformation of
acids into salts. Together with the remnants of gasoline it is distilled with
live steam from the pasta and is divided into mild, moderate and heavy
fractions, which differ significantly in properties and areas of practical
application.
Further development of this technology is to supplement gasoline
extraction by water with the implementation of the combined watergasoline extraction. Along with the lipid components water-soluble
compounds are released then. After the separation the gasoline fraction is
processed in the traditional way, and water-soluble products are
concentrated to 50 % solution of dry matter. The concentrate is used in the
diet of farm animals and birds. Application of this technology allows
significant increasing of the yield of gasoline-soluble fraction. It results
from more complete separation, due to better permeability of the solvent in
the volume of the particles.
A modified version of this technology is that the extractor is fed by
vapor of gasoline, which forms miscella after condensation. After settling
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and removal of the wax the miscella is reprocessed to produce chlorophyllcarotene paste, which can be further refractioned into a number of valuable
products.
To use the beneficial properties of green pine and to neutralize the
negative ones different ways of processing are used. They can be divided
into mechanical and chemical.
Mechanical processing methods include the production of conifer
vitamin meal and getting pine juice.
Chemical methods include processes for essential oils extraction and
technology of green wood extraction processing, which consists in
extracting of biologically active substances from the crushed material with
various solvents, their concentration, processing and use of chemical agents
as a final product or as a raw material for the isolation of various
concentrates or individual compounds with valuable properties.
All existing technological schemes can be divided into continuous
and discontinuous with the use of water as an extractant, the hydrophobic or
hydrophilic solvents
Using units of periodic operation is justified in cases where the
amount of processing of raw materials is low. According to most experts, in
a real forest harvesting the volumes of coniferous wood green is 600–1200
tons per year. An important factor is the simplicity of maintenance and
repair of equipment in forestry and timber industry.
A very effective method for extracting the components of wood
green and bark is using of volatile solvents, freon and especially the
liquefied carbon dioxide. Thanks to the removal of the extractant from the
solution at low temperature extractives are produced almost in the native
form. This allows receiving products, characterized by different properties,
so that it is effectively used in several industries.
When extracting the components of wood green of coniferous species
a most commonly used agent is liquid carbon dioxide. As waste microbial
production, it is available, inexpensive, and low-toxic. In addition, the
connection is fireproof and its use, due to the specific physico-chemical
properties is high-tech. The boiling point of carbon dioxide, depending on
the pressure ranges from –60 to +30 ° C, thus maintaining the desired mode
in a wide range. An exhaustive evaporation of CO2 from the extract under
normal atmospheric conditions should be noted, which means the ease of
isolation of extractives in the native state. There is no difficulty in
regeneration of carbon monoxide, which is carried out by controlling
pressure at different stages of the process. A major advantage of the method
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is the selectivity of biologically active substances, due to the nonspecific
solvation of compounds. Carbon dioxide is inert with respect to the
extracted components, does not support the oxidation and maintains the
quality of products for a long time.
The study of the extraction of wood green by liquefied carbon
dioxide was carried out. It was found that the highest yield of CO2 – extract
for fir tree green is reached when the specific surface area of raw materials
is 1200 m2/kg, 15 % humidity and liquid module 9.5.
However, the drawback of using carbon dioxide for the processing of
wood green is a low degree of extraction of extractives. It was found that
the liquid carbon dioxide did not extract chlorophyll, triterpene acids, the
components of pine wax and polyprenols. In recent studies the use of
carbon dioxide in the complex processing of raw materials was examined.
There is a known method of sequential extraction with carbon dioxide,
water and ethyl alcohol. It allows extracting 5 % and 6.5 %, respectively, at
a total output of extractives 33.1 % and 25.1 % from the green wood and
bark at the first step.
Besides the equipment operating under pressure requires special
attention. Complete installation is relatively difficult because the regulation
of gas pressure is performed at various stages of extraction. The operation
of the installation requires approvals of several organizations. The delivery
of CO2 to the place of raw material processing also presents some
difficulties. Apparently, these circumstances are the reason that carbon
dioxide technology, despite its great advantages, is still rarely implemented
in practice.
3.3. Technologies for production and use of vitamin flour
3.3.1. Production of conifer-vitamin flour
Vitamin flour production is carried out both on mobile and stationary
installations. The mobile unit is mounted on a tractor sledge. Its
productivity is 0.1 t/h of finished flour. Technological scheme of conifervitamin flour production at this facility (fig. 3.3) includes chopping boughs,
separated from the branches by the crusher, high-speed drying in the tumble
dryer and grinding of the dried mass in the grinder. The supply of chopped
boughs from the crusher into the hopper of crude herbs and finished flour in
a cyclone hopper is performed in pneumoconveyor by air flow and the
supply of boughs from the hopper to the foot dryer drum – by the screw, as
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well as unloading the dried herbs from the dryer. From the cyclone hopper,
powder is discharged through the feeder metering. A dryer is 4.6 m in
length and its diameter is 1 m, it rotates on rollers at a speed of 6 r/min.
Fig. 3.3. Technological scheme of conifer-vitamin flour production on
a movable unit SKHBP-0,1:
1 – separator of wood green, 2 – chipper grinder- ДКУ-М; 3 – bunker;
4 – posterior chamber of the dryer SZPB-2, 0, 5 – drum of the dryer, 6 – anterior
chamber of the dryer, 7 – a fan, 8 – unloading hatch; 9 – cyclone hopper,
10 – feeder-weigher, 11 – grinding mill for drying pine needles into the flour;
A – a bough; B – fuel; C – finished products; D – outgassing
Drying of the crushed boughs is performed by flue gas fed from the
furnace dryers. The coolant temperature is 250–300 0 C (400 0 C), the
drying period is about 10 s.; the final moisture content is about 10 %. The
drum must be fully filled with dried mass, the particle mass during in the
drum should not be heated above 60–70 0C and the temperature of the spent
coolant should vary in the range of 75–80 0 C.
Stationary unit is designed for the production of 650 t/y of vitamin
grass flour. The productivity of this unit in wood green processing runs
1000 tons/year or more. A unit includes a wood green chopper, the unit, a
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stitching machine, scales, conveyors, etc. The unit consists of an input
Product
Field of application
Conifer-vitamin flour
Feed additive for livestock and
poultry
Chlorophyll-carotene paste
A component of ointments for
treatment of burns, ulcers, various
skin diseases; lowers blood
pressure
Sodium chlorophyllin
Haematogenous, tonic and healing
agent used in atherosclerosis,
gastro-intestinal and skin diseases,
lowers blood pressure, is a part of
cosmetic products.
conveyor apparatus for combustion of diesel fuel, a rotary dryer drum, a
hammer mill, a cyclone bunker-dry weight and a screw device for feeding
the finished flour to the bags. The temperature of the coolant (a mixture of
combustion products with air) is 350 0 C in summer, 400 0 C in winter. The
drying period of fine particles is a few seconds. The final moisture content
of flour is 10%. Consumption of boughs is up to 3 tons per 1 ton of flour.
According to GOST (national standard) 13797-84 vitamin flour from
wood green is divided into grades according to the content of carotene, mg /
kg: premium flour has at least 90, the first grade – 75 and the second
grade – 60. The content of crude fiber shall be not more than 30, 33 and
35 % respectively.
Flour from the autumn and winter preparation boughs has higher
quality, because the carotene content in the needles during this period is
significantly higher than in summer. In the flour made of fresh boughs
carotene content is higher than that of the waste (after separation of
essential oils).
3.3.2. Fields of application
There are different fields of application of wood flour, presented in
the Table 3.2.
Table 3.2
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Conifer wax
Used in dozens of industries, in
particular to make the best grades
of gloss paper, and furniture polish,
staining leather and in cosmetics
Provitamin concentrate
Biologically active additive for
cosmetics
Essential oil extraction
a) the average fraction
b) the heavy fraction
Component of perfumes and
cosmetic products
The essential oil of steam
distillation
a) fir tree
b) spruce
c) pine
The source for artificial camphor,
is also used for the production of
celluloid and smokeless powders,
components of cosmetic products,
drug for inhalation, for rubbing in
rheumatism, as well as for air
refreshing in hospitals
The extract for baths, etc.
Hygiene, preventive and
therapeutic agent
The natural cell sap
Vitamin supplement for nonalcoholic beverages; also used in
animal industry
3.4. Technologies for production and use of nanocellulose
Nanocellulose is nanoscale filamentary crystals contained in plant
fibers. These are the most common natural nanoparticles in the world.
There are two forms of nanocellulose: nanocrystalline (defect-free single
crystals of filamentous – “whiskers”) and nanofibrillous (filamentous
particles with alternating crystalline and disordered sites).
Cellulose crystals are defect-free on the nanoscale, thus having an
extremely high durability. The surface of these nanoparticles is chemically
active and can be modified to give them desirable properties defining a
wide range of possible applications of nanocellulose.
In free state the individual particles of nanocellulose can only exist in
small concentrations in the liquid medium. With increasing concentration of
particles of nanocellulose bind in three-dimensional grid. The ability to
generate strong nanocellulose grid allows its use as reinforcing filler in the
composite polymer materials. At the same time small additions of
Table end 3.2
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nanocellulose can increase the original strength of the material manifold.
Nanocellulose is considered a promising material for the creation of new
light strong composite materials, biodegradable materials, “smart» materials
with different functional properties.
Since the raw materials for nanocellulose are natural vegetable fibers
that decay in the soil to form humus, nanocellulose creates a special interest
as biodegradable material. The role of nanocellulose is to give the required
strength and barrier properties to biodegradable polymer.
Technology for producing nanocellulose and polymeric composite
materials based on it is intensively developed in the United States, Canada,
Brazil, China, Japan, Israel and European Union countries – Sweden,
Norway, Finland, Germany, France and England. In 2010 an innovative
Swedish company “Inventia” announced about the plan of launching of the
first pilot production of nanocellulose made of wood. Nevertheless,
industrial production of nanocellulose has not yet realized, and
nanocellulose is not present as a freely traded commodity in the market.
Cellulose is traditionally derived from wood. The stages of
production of cellulose from wood are:
– wood Sawing;
– chopping wood chippers, the formation of chips;
– part of the timber is boiled in the cooking pots with a solution of
sulfur dioxide;
– another part of the timber is machined – triturated in the mines.
The product is wood pulp which is consumed in the paper production.
But the morphological and physical structure of natural cellulose in
higher plants is complex and heterogeneous, besides, the cellulose
molecules are closely related to lignin in the cell walls of plants, which
blocks the functional, active groups of cellulose and thus automatically
withdraws the structural properties of cellulose.
An alternative raw material in the production of nanocellulose is
crops and by-products of food production. The fibers of such crops as flax,
hemp, Mexican agave plant and other products from the waste recycling
represent a significant additional source of raw materials for cellulose
production. For obtaining nanocellulose the products related to waste from
the processing of corn, wheat, rice, sorghum, barley, sugar cane, sugar
beets, pineapple, banana and coconut can be used. Now the bulk of
agricultural by-products is incinerated, or used as feedstuffs for livestock or
for biofuel production.
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