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INVENTION
Russian Federation Patent RU2070307

PLASMA shaft furnace waste treatment

PLASMA shaft furnace waste treatment

Name of the inventor: Litvinov VK .; Knyazev IA .; Morozov AP .; Knyazev OA
The name of the patentee: Alexander Morozov Prokopevich
Address for correspondence:
Starting date of the patent: 1990.10.20

Use: waste management of low and intermediate level of activity and the conversion of solid and liquid waste in a chemically stable, firm and product to be disposed of, and and recycling of valuable components. The inventive plasma processing after waste 34 in the shaft 2 of a slag melt (P) 35 is collected in a homogenisation chamber 6 and 36 is heated by a plasma torch plasma reactor 13 and the electromagnetic device 20 from the source 23. The source 24 is then turned on and P 35 through port 16 27 is fed into a centrifugal casting machine with simultaneous supply through the pipe 31 from the ash postcombustion chamber 9 and the filter 11 to form an ingot (C) 37. Further, the container 19 is placed in the die 38 C, and in the cavity 39 through the slurry pipe 32 is fed from the cooling system 10 in a mixture of cement mortar 33. The furnace unit can increase the level of radiation safety due to the controlled output for the melt temperature and composition, and obtaining a textured hollow castings with recycling them in the secondary radioactive waste.

DESCRIPTION OF THE INVENTION

The invention relates to nuclear energy and technology, in particular to devices for the processing of radioactive waste of medium and low level of activity and can be used to convert solid and liquid waste in a chemically stable, firm and product to be disposed of, and for the recycling of valuable components.

Known shaft plasma furnace for radioactive waste disposal, which contains the vertically and successively established waste loading unit, a mine with a drying zone, pyrolysis, combustion and assembly of slag formation, located in the zone of combustion oxidant inlet device and a plasma generator, and also for the output device and slag collection communicating slag with a node [1]

This furnace slag collection and derivation is carried out with a spray granulation containers therefore deteriorate the strength characteristics of the castings and increases the ability of leaching of radionuclides that lowers radiation safety. The furnace conditions are not realized for the controlled withdrawal and cooling the molten slag-metal mixture, and the conditions of filling containers do not provide optimal uniformity and crystallization texture castings because unstable temperature and pouring speed of the melt composition. In this furnace ash is collected at the outlet gases from the shaft, is again supplied to the furnace through a waste loading unit, which reduces the radiation safety, since in this zone there radionuclide sorbed onto solid particles of soot, ash, salts and other compounds having a low temperature evaporation and easily gasifiable, therefore increases the load on the gas cleaning system. Gathering unit in superheated slag slag containers leads to the destruction of their walls and the ingress of contaminated melt to radiation device for slag collection and output, which significantly reduces the radiation safety of the kiln.

The aim of the present invention is to improve the radiation safety waste melt through a regulated output for temperature and composition, and obtaining a textured hollow castings with recycling them in the secondary radioactive waste.

To achieve this goal in the famous plasma shaft furnace for the processing of radioactive waste of low and intermediate level, containing a download site, a mine with a sloping hearth furnace connected with the shaft afterburning gas chamber with a cooling system and filter, the oxidizer supply device, plasma generators, horizontal homogenizing chamber slag with a plasma reactor, the slag heating device, a formation of castings and apparatus slag removal in a sealed chamber and a discharge mechanism is provided connected to the camera slag removal and cooling system afterburning gas chamber feeder cement mortar cast formation device is designed as a horizontally positioned with rotatably mounted in the chamber slag removal of the mold from the runner connected to the afterburner gases filter and through a pipe with a homogenization chamber, homogenizing chamber is provided with hearth inclined towards the hearth of the shaft, and a slag heating device is in the form of inductors, placed on the outer surfaces of the nozzle, pods shaft and homogenising chamber.

Brief Description of the drawing, which shows a perspective view of the shaft furnace for the plasma treatment of radioactive waste in section.

PLASMA shaft furnace waste treatment

The furnace includes a vertically mounted and sequentially loading unit 1 and the shaft 2 with a sloping hearth 3. The shaft 2 is provided with an oxidant supply device 4 and the plasma generators 5, and communicates with the horizontal chamber homogenization slag 6 and 7 in the upper part through the branch pipe 8 with the gas afterburner 9, 10 connected through the cooling filter 11. homogenization chamber 6 has a top portion 12 of plasma reactor 13 and is formed with a sloping hearth 14 towards the hearth of the shaft 3 slag removal system 2. The apparatus 15 includes inlet 16 that connects the homogenization chamber 6 sealed chamber 17, wherein the discharge mechanism 18 mounted to the containers 19. The slag heating device 20 is in the form of flat inductors 21 disposed on the outer surfaces of the inclined shaft of the hearth 3 of the hearth 2 and 14 homogenization chamber 6, and the inductor ring 22 disposed around the nozzle 16. inductors 21 and 22 sequentially or simultaneously connected to two power supplies 23 and 24, respectively, of bringing energy to heat and melt conveying. For cooling inductors 21 and 22 and connected to a source of water 25. The homogenizing chamber 6 is connected through a pipe 16 with sprue formation casting apparatus 26, 27 installed in the sealed chamber 17. The device 27 formation of castings made in the form of horizontally disposed rotatable in the slag removal apparatus 15 mold 28 mounted on the support rollers 29, driven in rotation by a motor 30. The end of the die 28 is mounted gate 26 connected via pipe 31 with gas afterburner 9 and the filter 11.

Slurry feed apparatus 33 is connected to the cooling chamber 10 and a post-combustion gas 9, for supplying a mixture of slag cement mortar, is communicated via outlet 32, mounted over the containers 19 located on the discharge mechanism 18 with the hermetically sealed chamber 17 slag removal device 15. By numeral 34 shows the waste disposed in the shaft 2. The reference numeral 35 depicts the slag and the molten metal on the surface of pods 3 and 14. By reference numeral 36 shows a plasma torch generated plasma reactor 13. By numeral 37 depicts a bar 28 formed in the die unit 27. By the formation of castings numeral 38 shows a shaped ingot, fixed in the container 19. by reference numeral 39 shows a cavity in the ingot 38, which is fed through the pipe 32 a mixture of mud water from the cooling system 10 and the cement solution from the feeder 33.

The plasma shaft furnace for the processing of radioactive waste is as follows. After 1 loading unit in the shaft 2 is continuously or intermittently loaded solid radioactive waste elements 34. In the water cooled plasma generator 5, the plasma reactor 13, the die 28, inductors 21 and 22, cooling water is supplied from the power supply 25. With exhauster (not shown in the drawing ) mounted behind the filter 11 in the shaft 2 through the nozzle 8 in the upper part 7, a vacuum of 200 Pa. By means of the device 4 for supplying the oxidizer 5 via the plasma generator is supplied oxidant. Plasma generator 5 generates high-known methods streams entering the shaft 2. Solid waste 34 passing through the shaft 2 successively subjected to drying, pyrolysis, gasification, burning the combustible components and melting ash and incombustible components to form a melt 35, which drains into the homogenization chamber 6 and going on podah 3 and formed in the shaft 14. The gaseous products 2 through a pipe 8 installed in the upper part 7 of the shaft 2, enter the afterburning chamber 9 of known design, such as once-through or vertical cyclone, where post-combustion is carried out and the thermal decomposition of combustible components and chemically corrosive substances with a partial separation of the large ash. Next, the gases are fed into the cooling system 10, for example in scrubbing shelltube or heat exchanger, where the temperature is lowered to 200-300 o C. The gases are then cleaned in the filter 11, for example, a sintered fine filter, with complete separation of ash and aerosols, and drops in atmosphere. In the plasma reactor 13 of known construction, for example, with pryamostruyny mixing chamber installed at the upper portion 12 of the homogenization chamber 6, and liquid oxidizer fed combustible waste, and then afterburned plasma arc from a DC source (not shown). Liquid waste combustibles are converted into a plasma reactor 13 with a predetermined excess air ratio and fed to the homogenization chamber 6, 35 heating the molten bath 36. The plasma torch furnace start time and the accumulation of the melt on the hearths 35 and 14 of pipe 3 is closed the temporary stopper 16, and a pressurized chamber 17 a vacuum of 200 Pa. Next, from the power source 23 to the inductors 21 and 22 are supplied with alternating current, for example, from the engine generator, and held an additional induction heating and melting of the melt 35 in the temporary plug from the nozzle 16. The source 24 is supplied to the inductors 21 and 22 conveying the alternating current frequency ( 200-500 Hz), and output held the melt 35 through the port 16 to the gate 26. in the heating unit 20, performed for example in the form of electromagnetic trough, molten slag or metal 35 is exposed to the running magnetic field and travels in a free flow with overcoming the forces flow resistance and gravity. The free surface of the melt 35 is heated plasma torch 36. By adjusting the frequency and amplitude of the magnetic field induction running, you can change the depth of penetration of the electromagnetic forces in the melt 35 and thus selectively transporting melts with different conductivity. By adjusting the inclination of the hearth 14 may separate from maloprovodyaschih metal melts, such as slag. To compensate for heat losses through the liner while cooling inductors 21 and 22 uses the induction heating of the melt 35 from the source 23. This dual-frequency heating can be used for applying one or two winding inductor of the inductor 21, and a frequency selection of a compromise that provides the necessary heating and conveying effect. Electromagnetic forces generated by running magnetic field, provide transport of the melt 35 from an oblique hearth 14 through the outlet 16 into the gate 26 and may compensate for static pressure of the melt 35 in the homogenization chamber 6, and to prevent leakage of the melt 35 through the open port 16, located below the level of the melt 35 . This allows you to adjust the composition and flow rate of the melt 35 supplied to the device formation castings 27 and sealing the drain hole nozzle 16 with periodic release of melt 35, by reversing the movement of the traveling magnetic field. The melt 35 at an inclined hearth 14 is exposed to electromagnetic forces and accelerate the separation of slag and metal, which allows you to clean the metal of radionuclides to the implementation of subsequent recycling. Sealing downcomer pipe 16 may be carried out by crystallisation melt 35 in the pipe 16 by the heating source 23 is turned off, followed by melting the resulting tube. The lining of the hearth 14 and the inclined pipe 16 is made of refractory material with low or zero conductivity. Using the laws of magnetohydrodynamics, the melt 35 through the sprue 26 is supplied to a mold 28 formation casting apparatus 27 installed in the sealed chamber 17. In this metal mold 28 is rotated on the support rollers 29 by a motor 30. The melt 35 by centrifugal force is distributed evenly the inner surface of the die 28. Pouring the melt 35 and may be carried out in horizontal, vertical or at some angle located metal mold 28, and on its inner surface applied pre shortbread coating thickness of 2 mm or set the container 19 (not shown). The casting 37 may be formed of slag or metal from the slag-metal layered structure. Simultaneously with the feeding of the melt 35 through the gate 26 to a mold 28 is carried a constant or intermittent supply of the ash through the pipe 31, by mechanical or pneumatic transport of the afterburning chamber 9 and a filter 11. The ashes under action of centrifugal forces on the metal mold 28 is separated and immobilized in a cast structure 37 with minimal gasification radionuclides. The rotational speed of the die 28 is determined by the composition and temperature of the melt 35. When using a vertical mold 28 may be formed gluhodonnoy casting 37. After reaching the desired thickness of the casting layer 37 stops the supply of the melt 35. The rotation of the die 28 stops after solidification 37 at 300-600 o C. solidification rate depends on the temperature of the melt 35 and the thickness of the casting 37. casting 37 After curing is carried out its removal from the mold 28 by the ejector (not shown) such as a hydraulic pusher for unloading mechanism 18, for example a conveyor, where using known devices, for example, the crane clamps, electromagnets or manipulators, castings 38 are installed in the containers 19 and transported by the mechanism of discharge 18 by pipe 32 so that the slurry mixture that occurs when the cooling gas in the system 10 with the cement of the mortar unit 33 is supplied to a centrifugal casting cavity 38. The final step is the sealing of the container lid 19 (not shown) by known methods, for example by welding.

We perform a comparative study to determine the radiation safety in the processing of radioactive waste in the furnace of the prototype and the proposed plasma furnace. In both cases the processing of exposed solid waste 34 into a timber a mixture with a humidity of 20% and an ash content of 5% a and steel scrap in an amount of 30% as a material simulating radionuclides used inactive salt of cesium chloride, with a solution which is saturated with waste briquettes 34 simulating low activity level. Performance of both solid waste furnace is 60 kg / h. Total electric power delivered to the plasma generator 5, the plasma reactor 13 is 70 kW. Consumption of liquid combustible waste is in the form of diesel oil 2 g / s. As the oxidizing agent used with a total air flow rate of 15 g / s. The total run time of 200 hours each furnace. In the prototype furnace slag-metal melt is formed in the vacuum suction casting method. Number 200 kg casting produced in both cases equal to 26. In the proposed kiln slurry feed apparatus 33 used turbulent mixer type Sa-43b, with a capacity of 65 l / h of solution. The binder used in the cement Portland cement 600 secluded himself in a water solution of a slurry of gas cooling system 10 and water decontamination solutions arising from the operation of the furnace to the ratio of aggregate, which is used as a molding sand of the exhaust device 27, the formation of castings, about 1 3 and the ratio of solid phase cement of 1: 0.7. Inductor 21 traveling magnetic field was carried out in the form of expanded stator with three-phase current power supply. Winding 21 and inductor 22 has a tubular water-cooled, the number of pole pairs 60, the number of successive windings in Phase 120, the single-layer type compounds triangle wave. Same electric power supplied to the inductors 21, 22 from power sources 23, 24 and in the prototype two inductors, and is 30 kW. As a source of the converter machine 23 used with HPV series heating current frequency 2400 Hz, and as a source of the inverter transformer 24 with current carrier frequency of 300 Hz. 35 melt casting speed regulated amplitude and frequency of the electromagnetic traveling field. At 14, the homogenization chamber 6 and the port 16 are lined shamotografitovymi blocks. The device formation casting chill 27 28 carried a steel detachable water-jet cooling. 35 The melt temperature at the exit of the gate 26 was varied in the range of 1300-1500 o C. The inner diameter of the die 28, 0.3 m; 1 m; rotation speed of 250 rev / min. In the cooling system 10 and the heat exchanger used shelltube gravity sludge separator. Sintered metal filter 11 provides a cleaning factor of 10 June. The ash from the post combustion chamber 9 and the filter 11 comprises a particle diameter of 0.01-5 mm.

Radiation safety was assessed by the dynamics simulator removal of radionuclides in the gaseous products, the waste from the furnace, and the simulator and on the removal of the slag removal device 15. In the prototype ash from the secondary combustion chamber 9 and the filter 11, and a slurry cooling system 10 is fed into the mold during the formation of castings vacuum suction, as proposed in the furnace via pipe 31, respectively in the formation casting apparatus 27 through pipe 32 and into the cavity 39 of the casting 38. Additionally assessed degree of leaching of the slag, the mechanical strength limit of casting, the waste volume reduction rate, depth of recycling metals contained in the waste. The results of the comparative studies are shown in Table.

As seen from the table of parameters modeling the recycling process, the application of the proposed plasma shaft furnace can increase the level of radiation safety over the prior art by reducing the removal of radionuclides from the waste gases in the modes:

1) without entering the secondary waste by 7% through better sealing of the furnace and eliminate uncontrolled air leaks through the slag removal device;

2) after the input and sludge ash by 27% by eliminating the gasification of volatile radionuclides from the secondary waste.

Maximizing Radiation Safety is achieved by reducing the removal of radionuclides in the slag removal device by 40% due to the organization of the regulated output electromagnetic forces melt and holding fast crystallization casting using centrifugal casting device formation. An additional factor increasing radiation safety of recycling is to reduce the leaching slag rate 4 times due to fast crystallization and impregnation of volatile ash and cast reinforced matrix. Increases the mechanical strength limit of casting 2.5 times due to a dense structure and the metal reinforcement. Increases the volume of waste reduction ratio of 2.4 times, by arranging compact casting it with the introduction of secondary radioactive waste. This increased furnace depth recycling metals from waste in two times, and due to refining selektirovaniya electromagnetic forces.

Supply device furnace slurry feed chamber connected to the slag removal system and cooling gas afterburning chamber increases radiation safety by utilizing volatile secondary radioactive waste collected in a water slurry into gas cooling system, and cementing them by immobilisation and centrifugal casting cavity. Using hollow slag-metal casting as a container for the disposal of cemented secondary volatile radioactive waste allows for a closed technological cycle with an integrated waste treatment, which increases the radiation safety.

Performing device formation casting a horizontally disposed rotatable in the chamber slag removal of the mold from the runner connected to the afterburner gases filter and through a pipe with a homogenization chamber, allows to increase the radiation protection at processing waste by efficient immobilization of secondary radioactive waste in the form of volatile ash a structure formed by a high speed centrifugal slag-metal castings. The use of centrifugal casting effect improves the crystallization ability of the melt, reduces the temperature of crystallization of molten material, contributes to the creation of small and dense structure of castings, improves radiation and chemical properties metalloshlakovogo casting. Reaching effects of organized stratification improves the physical and mechanical properties of castings to produce a unique set of properties and macroheterogeneous composite structure that enhance radiation safety during transportation and disposal of radioactive waste recycled. When a centrifugal forming castings from a melt with dispersed radiation-inactive metal particles of active slag inclusions of slag having a lower density of the metal density, float under the influence of centrifugal force and thus formed radiation-contaminated slag casting with a metal inactive cast casing, which increases the radiation protection on subsequent containerization, transportation and disposal. When processing waste with alkaline radionuclides (e.g., cesium 137) reliable fixation is achieved in the slag basicity is less than 1, however, the casting of such toxins are highly fragile due to thermal stress so realized in the furnace centrifugal casting increases the mechanical strength and chemical resistance of castings for reinforcing the metal. Input from the secondary ash postcombustion chamber and filter in the high speed crystallizing molten slag radionuclides prevents gasification and ensures a secure fit in metalloshlakovom composite.

Perform homogenization chamber hearth inclined towards the hearth of the mine and the implementation of slag heating device in the form of inductors, placed on the outer surfaces of the pipe, decks mines and homogenization chamber enhances radiation safety due to electromagnetic conveying the melt through a nozzle located above the level of the melt, which prevents accidental releases radiation-contaminated materials. The use of electromagnetic inductors can improve radiation safety levels during the O and slag and metal collection due to mechanization and automation of activities related to radiation exposure. With the help of electromagnetic inclined hearth possible fractionation of waste, separation of fissile elements from the perspective of their further utilization at a high degree of recycling of metals. On inclined hearth conducted electromagnetic selektirovanie radioactive components, using the difference in electrical conductivity, temperature control and the composition of the melt output from the pipe. Reversal of the electromagnetic field on a sloping hearth made hydraulic pipe sealing hole during furnace operation. Sealing drain pipe and realized when disconnecting the inductor around the nozzle and melt crystallization in it to form a temporary plug, with subsequent melting of the organization of the melt output.

CLAIM

The plasma shaft furnace for the processing of radioactive waste of low and medium activity levels, comprising loading unit, a mine with a sloping hearth furnace connected with the shaft afterburning gas chamber with a cooling system and filter, the oxidizer supply device, plasma generators, horizontal camera slag homogenization Plasma reactor unit slag heating device formation castings and slag removal device in the form of a sealed chamber and a discharge mechanism, characterized in that, in order to improve the radiation safety, it is provided with a feeder grout connected to cam slag removal and cooling system afterburning gas chamber castings formation device is configured a horizontally disposed rotatable in the chamber bottom ash kokkilya a sprue connected to the afterburner gases filter and through a pipe with a homogenization chamber, homogenizing chamber is provided with hearth inclined towards the hearth of the shaft, and a slag heating device is in the form of inductors, placed on outer surfaces of the nozzle, and the shaft pods homogenization chamber.

print version
Publication date 19.02.2007gg