RU166734U1 - DEVICE FOR PRODUCING THERMALLY SPLITTED GRAPHITE - Google Patents

Abstract

A device for producing thermally split graphite, which includes serially mounted and connected an oxidized graphite feed unit, a tubular heater splitting unit and a receiving hopper, characterized in that the feed graphite feed unit is made in the form of three parallel screw feeders in a horizontal plane with a common rotation drive , and the splitting unit is made on the basis of three vertically placed tubes-reactors of siliconized carbon fabric, each of which is connected to a source three-phase voltage circuit according to the 0-phase scheme.

Description

The utility model relates to the field of production of thermally split graphite (TEG) and can find application in the production of this material used in ferrous and non-ferrous metallurgy, the production of semiconductor crystals, nuclear, aviation, automotive, shipbuilding and chemical industries, as well as for the protection of surfaces from spills petroleum products.

A device for producing TRG is known (Fialkov A.S., Maley L.S. Some aspects of the manufacturing technology of expanded graphite. In Sat: Electric-carbon and metal-ceramic products for electrical engineering. - M .: Energoatomizdat, 1985, pp. 65-72) [ 1], containing a device for supplying the original graphite material and removing the finished product and a heat treatment chamber with a heater that directly heats the carrier tape with the processed material. The disadvantages of the known device are low productivity (less than 0.2 kg / h), quick equipment failure and heterogeneity of the finished product.

A known installation for the production of penografite (TEG according to the terminology used by us) (RF patent No. 2102315, IPC СО1В 31/04, publ. 01.20.1998) [2], including sequentially installed and connected means for supplying oxidized graphite, a mixer of oxidized graphite with gas -carrier, a heating chamber with heating elements, an intermediate rarefaction chamber and a TRG accumulator.

The above device is closest in technical essence to the claimed device, therefore, is selected as a prototype.

The disadvantages of the device [2] are the horizontal placement of the heating elements (pipes), which requires the use of an oxidized graphite mixer with a carrier gas, as well as an intermediate rarefaction chamber. In the patent specification [2], the number of heating elements is from 1 to 5-7. Under the assumption that the device’s power source is a three-phase system, it is desirable that the number of heaters be equal to or a multiple of 3. Otherwise, a phase shift of the power source with leakage of stray current through the neutral conductor is unavoidable, which is unacceptable when using relatively low-power (especially mobile performance of the device) power generator. The description also proposes a conveyor scheme for supplying oxidized graphite powder to a splitting unit, which, in the presence of strong gas flows inside the device, can lead to blowing of powder from the conveyor belt, its contact with live parts and lowering technical safety. The use of an intermediate rarefaction chamber is associated with the horizontal layout of the heating elements, since without the artificially created vacuum the TEG will not enter the storage ring.

The technical result, the achievement of which is directed by a utility model, is to simplify the design of the known device and reduce the specific energy consumption.

To achieve the specified technical result in a known device for producing TWG, including sequentially installed and connected means for supplying oxidized graphite, a mixer of oxidized graphite with a carrier gas, a heating chamber with heating elements, an intermediate rarefaction chamber and a penografite accumulator (TEG), the feed unit graphite is made in the form of three parallel screw feeders in a horizontal plane with a common rotation drive, and the splitting unit is made on the basis of three vertices silicon-plated carbon-fiber pipe reactor reactors, each of which is connected to a three-phase voltage source according to the 0-phase scheme.

The simplification of the design of the known device consists in the fact that an oxidized graphite mixer with a carrier gas and an intermediate chamber between the splitting unit and the storage device (receiving hopper) are excluded from its structure. Oxidized graphite powder is supplied from screw feeders to tubular heaters in an upward flow of air and the use of a mixer is not required. After splitting the flakes, the TEGs enter the receiving hopper through three pipelines without using a separate rarefaction chamber. The reduction in specific energy consumption compared to the known device is 17-20% and is ensured by the fact that the average temperature along the length of the heater is lower than in the heater of the known device. High quality TRG is provided by a significant temperature gradient and, accordingly, the heating rate. It also provides a slight increase in technical safety compared to the device [2], which is caused by the use of screw feeders of oxidized graphite powder closed from the external environment, in contrast to the conveyor belt used in the prototype. The operational experience of the equipment for thermal splitting of graphite shows that the ingress of particles of conductive powder on the current-carrying elements of the installation can lead to short circuits and create a danger to maintenance personnel.

Distinctive features of the proposed device from the above and closest to it are the execution of the feed unit for the supply of oxidized graphite powder in the form of three parallel screw feeders in a horizontal plane with a common rotation drive, a splitting unit in the form of three vertical tube reactors made of composite material based on siliconized carbon fabric and connected to a three-phase power supply according to the 0-phase scheme.

Due to the presence of these features, the design of the device is greatly simplified. The screw feeder block, in contrast to the conveyor feeder used in the prototype device, is closed from the external environment, which eliminates the possible ingress of graphite powder on the live parts of the device elements. The implementation of the splitting unit in the form of three vertically mounted pipe reactors allows for upward flows of air (carrier gas) from bottom to top along each of the pipes, which does not require the use of an oxidized graphite mixer with a carrier gas and an intermediate rarefaction chamber. TRG flakes rise up due to the sailing effect and enter the receiving hopper when cooled. Silicon carbon fabric based heaters provide effective cleavage of oxidized graphite at a temperature of 1150 ° C in their middle part, in contrast to the traditionally used lanthanum chromite heaters: 1350-1500 ° C. This is due to the semiconductor type of conductivity of the material, which provides a significant alternating temperature gradient (positive from the lower end to the geometric center and negative from the center to the upper end of the reactor pipe) along its height. The temperature gradient is also enhanced by the use of water-cooled copper current leads fixed to the end sections of each of the reactor tubes. Copper was chosen as the material of the current leads, both due to the high thermal conductivity and due to the fact that it does not form carbides upon contact with heated carbon-containing materials.

Thermal decomposition of graphite is a purely physical process, for the successful implementation of which the heating rate is more important than the average temperature. According to the calculation and experimental estimates, the heating rate for actually used carrier gas consumption reaches 2500 ° C / s in the heaters of the proposed device. Reducing the specific energy consumption is achieved both by reducing the average temperature along the length of each of the pipe reactors, and by using the scheme of their mutual connection. Three identical reactor tubes connected according to the 0-phase scheme create conditions for coordination with a three-phase generator (minimum phase shift, which is especially important when using low-power autonomous diesel generators if it is necessary to manufacture the device in a mobile version). The scheme used does not exclude the possibility of smoothly regulating the temperature of each of the three pipe reactors separately, which is provided by thyristor voltage regulators installed on the phase buses of step-down transformers of the power supply.

The proposed device is illustrated by the circuit diagram of FIG. one.

The control panel 1 includes controls and control devices of the operating mode of the device. The remote control is equipped with three thermocouples that send a signal to the temperature controllers. The splitting unit 2 contains three reactor tubes 3, vertically mounted in a block of refractory bricks, surrounded by a water-cooled metal casing (not shown in the diagram). Copper water-cooled current leads 4 are used to supply electric supply voltage to the end sections of the pipe reactors 3. The ballast tank 7 arriving in the upward air flow into the cavity of the heaters 3 of the turbine engine in three pipelines 5 settles in a receiving hopper 6. To ensure water cooling of the device’s pipe reactors with water (antifreeze for the operation of the device in a mobile version in winter conditions), from which through the valve 8 through the pump 9 the cooling fluid is circulated. The three-phase power supply unit 10 contains three step-down furnace transformers and three groups of thyristors with fuses and RC filters. In the lower part of the splitting unit 2 is placed a centrifugal fan 11 for supplying air. Continuous supply of the initial oxidized graphite is carried out by a block 12 of three parallel screw feeders, driven into rotation through a reducer 13 by an electric motor 14. The oxidized graphite powder is periodically added by the operator to the feed hopper 15. Three ball valves 16 are used to smoothly control the air flow.

The experimentally measured wall temperature distribution of an individual heater without supplying a carrier gas and with its maximum flow rate is shown in FIG. 2. The heater provides high values of the temperature gradient, which also means a high rate of heating of oxidized graphite at a relatively low average temperature and, therefore, power consumption.

The device operates as follows.

After the pump 9 is turned on and the device is circulated with cooling water, an electric voltage is applied to the reactor tubes 3 until a signal is received from each of the thermocouples, confirming the achievement of a temperature of 1150 ° C. Then open the ball valves 16 and turn on the centrifugal fan 11. Approximately 2 kg of oxidized graphite powder is poured into the feed hopper 15 and the rotary drive of the screw feeder unit 12 is turned on. As the TRG of the hopper 6 is filled (controlled through transparent windows with illumination), periodic addition of powder is carried out oxidized graphite into the hopper 15. After the hopper 6 is completely filled, its contents are unloaded into the packaging container without turning off the device and the process continues. Turning off the device at the end of the process is carried out in the reverse order. Due to the inevitable evolution of acid residues from oxidized graphite, the device must be equipped with an autonomous exhaust ventilation system including a scrubber to neutralize them.

Claims (1)

A device for producing thermally split graphite, which includes serially mounted and connected an oxidized graphite feed unit, a tubular heater splitting unit and a receiving hopper, characterized in that the feed graphite feed unit is made in the form of three parallel screw feeders in a horizontal plane with a common rotation drive and the cleavage unit is made on the basis of three vertically placed silica carbon fiber reactor tubes, each of which is connected to a source three-phase voltage circuit according to the 0-phase scheme.

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