Method of carbonisation of viscose fibrous materials in process of obtaining carbon fibres

FIELD: chemistry.

SUBSTANCE: invention relates to chemical technology, in particular to processes of carbonisation of fibrous viscose materials, and can be used in production of graphitised fibrous materials, used as filling agents of composite materials; electrodes; flexible electric heaters; filters of aggressive media; in products for sport and medical purposes, etc. The material is preliminarily subjected to relaxation processing. The obtained material, which contains a pyrolysis catalyst, is continuously transported through zones of carbonisation heating. Carbonisation is carried out to 320-360°C in not less than three zones of heating, heat- and gas-isolated one from another by transporting material with inclination from bottom to top, with increase of heating temperature from 160-200°C in the first zone by 40-60°C in each next zone of heating, in comparison with the previous one. Volatile products are simultaneously removed from the said zones into the evacuation zone, heat- and gas-isolated from the external environment and located above the heating zones and connected with them via a perforated wall. Temperature in the evacuation zone of volatile substances is set by 5-15°C higher than temperatures of the respective heating zones, temperature of the output branch piece being 5-15°C above the maximum temperature of carbonisation.

EFFECT: invention ensures increase of the process efficiency and improvement of quality of the obtained carbon fibrous materials.

2 dwg, 1 tbl, 5 ex

 

The alleged invention relates to the chemical industry, in particular, to processes for thermal treatment of carbonaceous fibrous products in the form of threads, wire harnesses, ribbon, tissue and the like From viscose fibers to become carbonized fibrous materials used as semi-finished products to obtain graphite fibrous materials used as fillers of composite materials for various purposes; electrodes electrical industries; flexible heaters; filters aggressive gases, liquids and melts at normal and high temperatures; high temperature insulation thermal equipment; sports products and medical devices etc.

The known method for the production of carbon fibrous materials from viscose fibers, which includes the impregnation of viscose material with an aqueous solution of chemical compounds, catalytic pyrolysis process, continuous or intermittent heat treatment at carbonization temperatures of 1200°C and subsequent gravity up to 3000°C in inert atmosphere. [1]

The disadvantages of the known method of producing carbon fibers occur in low-intensity process of thermochemical transformation of viscose fibers in the carbon fiber, the heating during carbonization to a high temperature is low speed, in carrying out the carbonization under such conditions that evolved pyrolysis products at all stages of heating the fibers interact with carbonitriles material, the temperature of which differs from the temperature of volatile products. The result is significantly deteriorate the properties and reduced productivity of the process for the production of carbon fibrous materials.

The known method for the production of carbon fibrous materials from viscose fibres, previously subjected to a relaxation treatment and containing the catalyst pyrolysis by carbonization in several stages, the initial stage of which is carried out at a temperature from 250°C to 350°C with a temperature increase of 10°C/min to 60°C/min, the intermediate stage from 350°C to 500°C with a lower heating rate of 2°C/min to 10°C/min and final phase at temperatures from 500°C to 750°C with a newly enhanced rate of 5°C/min to 40°C/min with subsequent high temperature processing (by gravity) to (1000-1200)°C. [2]

This method is used as a prototype, as the closest to the proposed technical solution on substantive grounds.

The method according to the prototype of the inherent shortcomings of the above-described analog: volatile products released at all stages of carbonization interact with carbonitriles material for all p is ateenyi process, moreover, low-temperature volatile in contact with the material in the high temperature zone, high temperature volatile interact with the material in the low temperature zone. As a result of such interaction, as in the first and in the second case, there is a reduction properties of the obtained material. In addition, at the stages of carbonization intervals of the heating temperature of the material is very large: in the first stage, up to 250-350°C, and the second is from 350°C to 500°C, the third - from 500°C to 750°C. When heated in such a wide temperature range, especially at the first stage occurs at the same time a large number of parallel and consecutive reactions of pyrolysis and condensation with the release of a large amount of volatile and heat.

Carrying out carbonization under such conditions adversely affect the formation of the properties of the resulting carbonized and graphitized carbon fiber. The achievement of acceptable strength characteristics of the finished carbon fiber may only reducing the heating rate of the source material during carbonization, as recommended in the prototype. This significantly lengthens the process.

In addition, the carbonation in conditions of unlimited interaction of volatile pyrolysis products with carbonitriles material reduces the intensity of the formation properties of the latter, which forced p is igodit to increase the temperature of carbonization up to 750°C. After the graphitization thus obtained carbonized material can be obtained graphitized carbon fiber with acceptable strength properties. However, the increase of treatment temperature in the carbonization significantly complicates the process of carbonization and its instrumentation, increases the duration of the process.

The task which created the alleged invention is to eliminate drawbacks of the methods for analog and prototype, the increase in the intensity of the process and the quality of the obtained carbon fibrous materials. The aim is achieved in that the carbonisation of viscose fiber materials in the process of producing carbon fibers by heat treatment in continuous transport through the heating zone camera carbonization viscose fiber materials, subjected to preliminary relaxation process and containing on the surface and in the porous catalyst system pyrolysis, with variable speed multistage-increasing heating and subsequent graphitisation, in accordance with the proposed technical solution, the carbonation to a temperature of 320-360°C hold in heat and insulated from one another in not less than three heating zones, removing the volatile products of pyrolysis directly from their education in the heat gazoizmeritelnuyu from the outside the evacuation zone, located above the heating zones and soamsawali with heating zones through the perforated wall, and from the evacuation zone volatile products are removed by natural convection through a heated outlet volatile, transported carbonenergy material through the heating zone at a slant from the bottom to the top, increasing the heating temperature in the direction of transportation, since the temperature of 160-200°C. in the first heating zone, at 40-60°C in each subsequent heating area compared with the previous, the temperature in the evacuation zone volatile set at 5-15°C above the temperatures of the respective heating zones, and the temperature of the outlet of 5-15°C above the maximum temperature of carbonization.

The figure 1 shows the setup for the carbonization of viscose fiber materials (patent application No. 2012129694 from 13/07/2012 year) in the process of producing carbon fibers according to the intended method longitudinal section, figure 2 - section a-a of figure 1. The apparatus consists of a furnace with multiple heating zones 1, separated from each other by insulating spacers 2. In strip 2 can be placed cooling medium to reduce the temperature of roaming over them material that increases the efficiency of heat exchange between carbonitrile material and environment. The top wall 3 of the heating zones executed perf is ture, through holes 4 which are removed from the reaction zone of the heat evolved volatile products of pyrolysis. The reaction zone 1 is divided by a flexible partition walls 5, gasosaurus heating zones from one another. Over heating zones 1 posted by evacuation zone volatile products 6 and above the zone of maximum temperature carbonization integrated socket remove volatile products. The heating zone and the evacuation zone volatile are installed at an angle to the horizontal plane. Submission carbonizing material 7 is carried out from the bottom through bolt 8 and is transported upward through the heating zone to the outlet with shutter 9. Heating heating zones produce electric heating elements 10.

The physico-chemical nature of the processes taking place during carbonization of viscose fibers, is that the composition and pressure of the gaseous pyrolysis products affect the rate of thermal decomposition of solids. This effect is especially enhanced when these gaseous products of pyrolysis (i.e. volatile products) participate in reactions or interact with the formed product of carbon fiber). In addition, pressure and composition of the gaseous volatile over pirolizom substance lead to changes in the heat transfer between the environment and the body [3, 4], and the interaction of g is sobrannyh pyrolysis products with carbonitriles fiber has a negative impact on the strength of the resulting fiber.

The challenge in developing this technical solution has been reduced to reduce the effect of self-heating carbonizing fiber, which occurs as a result of heat by flow of exothermic reactions of pyrolysis, the normalization process of removal of volatile products, minimizing the duration of their interaction with carbonitriles fiber. The solution to this problem when carrying out the carbonization of the proposed method made it possible, firstly, on the basis of experimental work to reduce the maximum temperature of carbonization to (320-360°C., thus obtaining carbonized fiber, allowing gravity to high temperatures to obtain carbon fibers of high strength. This contributes to the technological method, when the carbonization temperatures of (320-360)°With hold, conveying carbontheme material through the heating zone from the bottom up, by increasing the heating temperature in the direction of transportation starting with temperature (160-200°C (40-60)°With each subsequent stage - heating area in comparison with the previous one. Thus, the whole complex carbonization reactions are split into separate temperature stage, not so very different from each other according to the temperatures, which are sequentially flow characteristic for the data of the temperatures of the reaction, and released the product of the pyrolysis are not mixed with each other and do not interact with the material, in other temperature stages zones. This is important in the implementation of this principle carbonation. Heating zone insulated from each other to eliminate as conductive flow of heat from one zone to another, and convective heat transfer due to infiltration of volatile products from one heating zone to another. The flow of volatile products between heating zones has a more negative influence on the process of carbonization than caused by convective heat transfer, due to the interaction with carbonitriles material at temperatures different from the temperature of the emission of volatile. Therefore, the heating zone should be gazizullovna from one another.

Heating the viscose fibers to a temperature (160-200°C. in the first heating zone was determined experimentally. Not such a high level of heating is performed for two reasons: first, carrying out the carbonization of the proposed method reduces the temperature at which appreciable pyrolysis fiber; secondly, carbonenergy material must be thermally prepared for the main pyrolysis, which runs in the second and third heating zones.

The increase in the heating temperature in each subsequent zone (40-60)°With established empirically. The aim of the conducted experiments was to reduce the number of parallel running Rea is implemented in a separate heating zone, that reduce the release of volatile products, prevents the imposition of reactions and eliminates the occurrence of thermocatalytic pyrolysis in General. Temperature of 40°C is the minimum temperature, increasing the heat which contributes to the development of high-temperature reactions. When increasing the heating temperature in the following area of more than 60°C, there is a large number of simultaneously occurring reactions, and the effect of separation of pyrolysis on the serial reaction decreases.

Removal of volatile pyrolysis products directly occurs in the heat - insulated from the external environment the evacuation zone above the heating zone of carbonization chamber connected with the heating zones through the perforated wall, and removing the volatile components from the evacuation zone by natural convection is conducted through a heated outlet volatile. Such actions are aimed at the implementation of the principle of selectivity and normalization of removal from the reaction zone of the volatile products of pyrolysis, reduction in the duration of their interaction with carbonitriles material, increasing the efficiency of the heat sink and thermal stabilization conditions for the reactions of pyrolysis in each of the heating zones. Under selective removing means removing the volatile components from the local place in which they stood out from the reactive ox is mounted systems not being mixed with volatile released in other places of the reaction zone. It is provided "filtering" flying through the perforation holes in the wall separating the heating zone from the evacuation zone. This directional movement is volatile under the action of temperature difference and pressure in the heating zone of carbonization and in the evacuation zone, i.e. the conditions for convective transfer of gaseous volatile products from the heating zone in the evacuation zone, and then out through the heated outlet. This additionally contributes to slope areas, which increases the vertical component of the movement of volatile products and eliminates the possibility of formation of stagnant gas areas in the evacuation zone, in which are collected volatile and increases their condensation, calipatria condensate.

The following hallmark, amplifying the effects from the implementation of this technical proposal - setting temperature in the zone of evacuation of volatiles on (5-15°C above the temperature of the respective heating zones and the temperature of the outlet pipe volatile (5-15°C above the maximum temperature. These actions provide for the creation of discontinuities in density in some places gas environment. When the local temperature increase of the gas density decreases and more heated the AZ is moved upward under the action of arhimedova forces in the gravity field of a continuous gas environment, and its place is a more chilled gas. This determines the vertical movement of the volatile in the evacuation zone, which is accelerated by increasing the temperature of the heating zones as they rise one above the other. The increase in the temperature of the outlet pipe volatile compared with the maximum heating temperature in the carbonization increases speed flying in the evacuation zone.

Temperature range (5-15)°C, which increase the temperature in the area of evacuation flying directly above the corresponding heating zone, defined as experimentally. Setting the heating temperature in this area for more than 15°C, is impractical because it leads to the increase of temperature in the heating zone and the change in her mode of carbonization.

The temperature increase is less than 5°C, greatly reduces the effect of convectively when removing volatile products.

An example of a specific implementation.

Textile tape twill weave 2/2 thickness of 1.1 mm of viscose filament linear density of 192 Tex subjected to relaxation treatment and containing on the surface and in the porous catalyst system pyrolysis, is stitched to the textile tape-feeding of heat-resistant fibers, for example, glass or basalt fibers. The carbonization is carried out in the above installation. When o open the gates 8 and 9 installation stretch the tape is drawn through the heating zone 1 and fill in transporting mechanism at the output carbonizing material from the installation of carbonization.

Shut o valves 8 and 9 on the inlet and outlet installation, include the heaters of the heating zones, evacuation zone and the outlet of removing volatile: the first area of the tape is heated to 200°C, the second to 260°C, in the third - to 320°C, respectively, the temperature in the zone of evacuation of volatile over the first heating zone set at 215°C, over the second area is 275°C, over a third zone and the temperature of the outlet pipe is set to 335°C.

Heat evacuation zone volatile perform using the top set of heaters (figure 1), which can be set at different distances from the reaction zone 1.

Include a supply of inert gas through the respective fittings in sealing closures. Upon reaching a predetermined temperature include transporting mechanism with the transportation rate of 20 m/h, at which the duration of the process of carbonization is 11 minutes. Transportation carbonitriles viscose ribbon is conducted from the bottom up. Volatile products of pyrolysis are of the heating zones in the evacuation zone through the perforated wall of the evacuation zone are output through acrobat. On the release of volatile products can digitise in the flame of a suitable burner or ignition. The products of combustion of the volatiles are removed by exhaust ventilation. The obtained carbonized tape has good flexibility, wrinkle resistant and has a tensile strength of 85 kgf/5 cm width. The resulting tape is subjected to the graphitization in an inert atmosphere at a temperature of 2350°C. the Carbon filaments of graphite tapes have a tensile strength of 1800 kgf/thread.

For comparison viscose tape was carbonizable by a known method prototype.

In addition, viscose tape was carbonizable on the proposed method for modes 2, 3, 4.

The table shows the modes carbonization and properties of the resulting carbonized and graphitized tapes.

According to the data presented in the table shows, the use of this technical proposal allows 3-6 times to increase the productivity of the carbonization process and increase the strength of carbonized and graphitized carbon fiber products.

Table 1
- Mode of carbonization and properties of carbonized and graphitized carbon fabrics
Experience No. p.p Mode settings carbonizationTensile strength at break carbonized material, GS/threadthe graphitization temperature, °CTensile strength at break of graphite material, GS/thread
The temperature of the heating zonesThe temperature of the outlet pipe, °C
Temperature plots evacuation zone, °C
1st2nd3rd4th5th
The proposed method of carbonization
1--335250023501700
2 330280023501570
3-365240023501640
437032002350 1900
The known method of carbonization Protocol
5200350500750--150023501200

References.

1 Patent RU 2258773 D01F 9/16 published 20.08.2005, bull. No. 23. A method of obtaining a carbon fiber material [Similar]

2 Patent RU 2257429 D01F 9/16 published 27.07.2005, bull. No. 21. A method of obtaining a fabric of carbon fibers by continuous tissue carbonization of cellulose fibers. [Prototype]

3 Andreeva I.N., Palkow S. p. the Mechanism of the initial stage of thermal decomposition of cellulose fibers. - GIR.: New chemical fibres for technical applications Ed. by V.S. Smirnov, CA Perepelkina and LI L. Friedman, Izd-vo "Chemistry", 1973, p.55-60

4 Boldyrev V.V. Methods of investigating the kinetics of thermal decomposition of solids. Tomsk, Publishing house of Tomsk University, 1958.

The method of carbonization of viscose fiber materials in the process of producing carbon fibers by heat treatment in continuous transportation through the area is agrevo carbonization viscose fiber materials, subjected to preliminary relaxation process and containing on the surface and in the porous catalyst system pyrolysis, speed-increasing heat, characterized in that the carbonization is conducted to a temperature of 320-360°C in heat and insulated from one another not less than three heating zones, transporting material is tilted upwards and increasing the heating temperature from 160-200°C. in the first zone, at 40-60°C in each subsequent and simultaneously removing from the specified zones volatile products in heat and insulated from the external environment the evacuation zone, located above the heating zones and built with them through the perforated wall, while setting the temperature of 5-15°C above the temperature of the corresponding heating zone, followed by natural convection flying through the outlet at a temperature of 5-15°C above the maximum temperature of carbonization.



 

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16 cl, 1 dwg

FIELD: metallurgy.

SUBSTANCE: invention can be used as fillers of composite materials of structure, heat protecting, anti-electro-static purpose and also at production of carbon fibrous adsorbents, catalyst carriers, materials for protection from electro-magnetic radiation, nano structured composite, fullerenes, nano tubes etc. The procedure consists in impregnation of a source unidirectional braid with solution of fire retardant. Braid is made of hydrated cellulose fibres with fine crystal non-tensioned structure with diametre of filament from 8.5 to 15 mcm at its linear density 0.07-0.17 tex. Further, the procedure consists in drying, non-oxidation stabilising carbonisation and graphitisation. As a fire retardant there is used water solution containing 150-200 g/l of ammonia chloride and 10-30 g/l of urea or water solution containing 250-300 g/l of ammonia sulphate and 20-40 g/l of urea. Drying is carried out by electric heating at 120-140°C during 30-60 min. Before carbonisation braid is treated in oxygen containing atmosphere at 140-180°C during 30-90 min. Multi-zone carbonisation is performed in current of inert medium at rate 2.5-4.5 m3/hour during 40-80 min for 5-10 min in each zone with shrinkage of source hydrated cellulose fibre at 10-30 % and at temperature from 170-230°C to 690-710°C. During carbonisation products of pyrolysis in a zone of their highest release are withdrawn due to a low excessive pressure of neutral gas of 120-150 mm of water column at continuous oxidation in spots of combustion. Graphitisation is carried out at 1000-2400°C in medium of nitrogen or argon with contents of oxygen not over 0.001% at rate of drawing 15-50 m/hour.

EFFECT: reduced duration of process, considerable reduction of humidity of produced carbon fibre, multi-zone carbonisation with guaranteed maintenance of uniform temperature of each zone, reduced release of amorphous carbon as product of resin decomposition and prevention of its settling on surface of produced carbon fibre.

7 cl, 2 ex

FIELD: electricity.

SUBSTANCE: invention can be used for creation of fillers of composite materials, gas-distributing layers in fuel elements, components of lubricants, hydrogen storage batteries, filter materials, carbon electrodes of lithium batteries, glue composites, carriers of catalysts, adsorbents, anti-oxidants during production of cosmetics, cold emission sources of electrons, modifying agents to special-purpose concrete, as well as for coatings screening microwave and RF radiation. Method involves pyrolysis of gaseous carbon-containing compounds on surface of metallised dust catalyst in flow reactor having the possibility of gas medium mixing. Aerosil particles containing clusters of the following metals on the surface as catalyst: nickel, cobalt or iron. Catalysts are obtained prior to the beginning of pyrolysis by reactivation of catalyst sprayed in reactor in current of hydrogen-containing gas at simultaneous mixing of gaseous medium. It is expedient to mix gaseous medium in reactor in fluidised bed mode with ultrasonic material dispersion. Outer diameter of obtained nanotubes is 5 to 35 nm; inner diameter is 4 to 12 nm; packed density is 0.3-0.4 g/cm3; total content of impurities is less than 1.2-1.5%; length is 0.5 to 3 mcm.

EFFECT: invention allows synthesising thinner nanotubes with high cleanliness, which have smaller spread in values as to diameters.

2 cl, 3 ex

FIELD: production of charcoal-fibrous adsorbents.

SUBSTANCE: the invention is dealt with the field of production of charcoal-fibrous adsorbents, in particular, with devices of charcoal-fibrous materials activation. The installation contains a vertical furnace for activation of a carbon fabric and a conjugated with it steam generator, which are connected to the power source and a control unit. And at the furnace output there is a reception device. At that the furnace contains a through heated muffle, through which the treated charcoal-fibrous fabric is continuously passing. At that the muffle is located inside the detachable heat-insulating furnace body, on the inner side of which there are heating elements. Besides at the furnace outlet there is a movable container with water, in which the lower end of the through muffle is dipped. The invention offers an installation for production of activated charcoal-fibrous material, which ensures a continuous process of treatment of the charcoal-fibrous material with an overheated steam and formation of the activated fabric with high mechanical properties and a cellular structure, simple in assembly and reliable in operation.

EFFECT: the invention ensures production of the activated fabric with high mechanical properties and a cellular structure, simple in assembly and reliable in operation.

8 cl, 4 dwg

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