RU2469428C2 - Processing method of uranium metal chips, and device for its implementation - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: processing method of uranium metal chips involves preparation and combustion of chips. Chips with thickness of 0.3÷3 mm are used for combustion. Combustion process is performed with the air supplied in the direction of chips movement in two stages: drying and heating is performed at the first stage at material bed temperature of 100÷300°C, and ignition and combustion is performed at the second stage at the temperature of 300÷900°C during 5÷30 min. Device used for implementation of the above method includes combustion plant that is made in the form of horizontal rotating tubular electric furnace containing a housing lined with refractory materials, pipe with internal coils and blades, can be rotated about its axis and separated into working zones with independent heating supplies to perform subsequent stages of chips combustion, device for air supply to the pipe in the direction of chips movement, loading and unloading assemblies for chips combustion products and removal of gases, assemblies of unloading, loading, heating, pipe rotation, unloading of chips combustion products and removal of gases.

EFFECT: group of inventions allows improving the quality of oxide combustion product of uranium metal chips as per particle size and content of active uranium.

10 cl, 3 dwg, 1 tbl

Description

The invention relates to the field of processing solid radioactive waste and recycled products, in particular to methods and devices for burning recycled metallic uranium.

During machining of ingots and products in uranium production, uranium metal chips are formed, which, after burning, can be used as a starting material to produce high purity uranium tetrafluoride.

A known method of burning solid radioactive waste, including preliminary grinding of radioactive waste and layer-by-layer pouring them with a powdered exothermic mixture, which consists of magnesium powder 50 ÷ 80 wt. %, potassium nitrate 1 ÷ 5 wt. %, industrial oil 1 ÷ 2 wt. %, powder aluminum-magnesium alloy - the rest. (RF patent No. 2086023, 6 G21F 9/32, publ. 07.27.1997)

The known method does not provide a high quality product for burning metal chips of uranium due to contamination with a large amount of impurities present in the powder exothermic mixture. The increased content of impurities in the combustion product leads to the need for additional costs for cleaning it from impurities, which ultimately leads to an increase in the cost of processing the oxide product of burning metal chips of uranium into uranium tetrafluoride.

A known method of burning solid radioactive waste, including the sprinkling of radioactive materials with exothermic material and burning. As exothermic material, waste from the production of fuel elements and fuel assemblies in the form of chips and sawdust of zirconium alloy obtained after cutting tubes to the size of the shells of fuel elements, the manufacture of lower gratings, spacer grids and channels guiding for fuel assemblies, and sprinkling with zirconium chips and sawdust are used radioactive waste is carried out in small portions immediately before loading them for burning. The ratio of zirconium chips and sawdust to solid radioactive waste in weight units is 0.1: (80 ÷ 100). (RF patent No. 2228552 C2, 7 G21F 9/32, publ. 05.10.2004)

The known method does not provide high quality product for the combustion of uranium metal shavings due to contamination with impurities present in the exothermic material (zirconium shavings and sawdust). The increased content of impurities in the combustion product requires additional cleaning costs, which ultimately leads to an increase in the cost of processing the oxide product of burning metal chips of uranium into uranium tetrafluoride.

Closest to the claimed method is a method of processing uranium-containing waste, described in RU 2236477 (publ. 09/20/2004, bull. No. 26), including the preparation and burning of chips before using the waste as raw material for the manufacture of metal uranium.

The known method does not allow to obtain the product of combustion of the required standard in chemical and fractional composition due to the presence of a large number of impurities in combustible uranium materials, products and waste from the production of metal uranium. Therefore, additional costs are required to refine the resulting oxide product of combustion to the required standard in chemical and fractional compositions, which leads to an increase in the cost of processing the oxide product of combustion into high quality uranium tetrafluoride.

A device for the oxidation of metal waste containing a combustion chamber placed in the chamber obliquely grateless fireless grate, a feed unit to the grate of oxidized material, an oxidizer feed system, an unloading unit of solid combustion products from the chamber, a unit for removing gaseous combustion products, is provided with a fixed on the camera body with a groove, the grate is placed in the groove with the possibility of reciprocating movement along the groove and is connected to a mechanical source their vibrations, a cavity is formed between the bottom of the gutter and the grate, which is connected to the oxidizer supply system, the grates are made with cavities that are connected in the end zones to the gas supply and exhaust manifolds for cooling the grate, and the upper walls of the grate are provided with heat-removing ribs, while the angle of inclination of the working surface of each grate to the horizontal is from 5 to 15 degrees. (RF patent for utility model No. 38381 U1, 7 F23В 1/38, publ. 24.11.2003.)

The known device for the oxidation of metal waste does not provide a high quality product for the combustion of uranium metal shavings due to the fact that the combustion process proceeds intensively in one zone, in which it is difficult to regulate the optimal process temperature. This leads to sintering of the product and incomplete burning of the uranium chips, as a result of which there is a lot of active (with metal particles) and large agglomerated fractions in the resulting oxide product. Further development of the product to the required condition requires additional costs, which requires an increased cost of processing the product of the combustion of metal chips (uranium oxide) into uranium tetrafluoride. The known device also has a relatively complex structure and high cost, which leads to an additional increase in the cost of the obtained uranium tetrafluoride.

A known installation for burning waste containing a vertical shaft furnace with nozzles for supplying liquid fuel, a mechanism for continuous supply of waste, a hopper, rotary grate, placed at different levels and equipped with nozzles for feeding the oxidizing agent to the furnace, a tube-in-pipe heat exchanger and a separator, soot outlet nozzles of which are in communication with the ash outlet nozzle from the furnace. The installation is equipped with a pulsator of the oxidizer supply and a shell-and-tube exchanger, lavsan filter and an absorption column located in the direction of the gases after the heat exchanger and the separator, the outlet pipes of which are interconnected with the soot outlet pipe from the separator, while the rotary grate in the form of pipe rings communicated with the oxidizer supply pulsator, oxidizer supply nozzles are placed along the entire length of the rings with a direction from the center to the periphery tangentially and upward, the nozzles liquid fuel feeds are installed at an angle above each grate to meet the movement of gases and oxidizer, and the separator is equipped with metal-woven filters, oxidizer supply nozzles are installed at an angle of 30-45 degrees to the axis of the ring, fuel supply nozzles are installed at an angle of 30-45 degrees to the vertical axis of the chamber and equipped with electric incendiary devices, the outlet pipe of gases from the absorption column is in communication with the fan, and the loading hopper is equipped with a pusher in the form of a pneumatic cylinder. (A.S. USSR No. 1191685 A, F23G 5/18, publ. 15.11.1985)

The known waste incinerator does not provide a high quality product for the combustion of uranium metal chips due to the fact that the combustion process proceeds intensively in one zone, in which it is difficult to regulate the optimal process temperature. This leads to sintering of the product and incomplete burning of the uranium chips, as a result of which there is a lot of active (with metal particles) and large agglomerated fractions in the resulting oxide product. In addition, additional costs are required to refine the product to the required condition, which leads to an increase in the cost of processing the product of burning metal chips (uranium oxide) into uranium tetrafluoride. The well-known waste incinerator is also characterized by a relatively complex construction and high cost, which leads to an additional increase in the cost of processing the product of the combustion of uranium metal shavings into uranium tetrafluoride.

Known rotary drum furnace for burning solid waste, containing a furnace body lined with refractory materials, a loading device, a burner, a two-section discharge chamber, an ash and gas section, a gas duct, emergency lights for ash removal, a rotation mechanism of the furnace and a gas afterburner. (M.N. Bernadiner, A.P. Shurygin. Fire processing and neutralization of industrial waste. M., "Chemistry" 1990, p. 37-39.)

The known rotary drum for burning solid waste does not provide a high quality product for burning uranium metal shavings due to the fact that the combustion process proceeds intensively in one zone, in which it is difficult to control the optimal process temperature. This leads to sintering of the product and incomplete burning of the uranium chips, as a result of which there is a lot of active (with metal particles) and large agglomerated fractions in the resulting oxide product. In addition, additional costs are required to refine the product to the required condition, which leads to an increase in the cost of processing the product of burning metal chips (uranium oxide) into uranium tetrafluoride.

In patent RU 2236477 (publ. September 20, 2004, bull. No. 26) describes processing equipment, including a combustion unit.

For the reasons described above in the description of the closest method, the known device does not allow to obtain high-quality metal uranium in the processing of chips without additional refinement.

The objective of the claimed invention is to improve the quality of the oxide product of burning metal chips of uranium by size and active uranium content, to reduce the cost of processing the oxide product of burning metal chips of uranium by reducing the amount of impurities, to obtain uranium oxide-oxide of predominantly small fractions.

The technical result is achieved by the fact that in the method of processing uranium metal chips, including the preparation and burning of chips, chips using a thickness of 0.3 ÷ 3 mm are used for burning, the combustion process is carried out with successive movement of chips from one working zone to another with air flow in the direction of movement and carried out in several stages, including drying and heating at a temperature in the material layer of 100 ÷ 300 ° C, and then ignition and combustion at a temperature of 300 ÷ 900 ° C for 5 ÷ 30 min.

After the burning stage of the chips, a stage of afterburning of the combustion products in the smoldering layer at a temperature of 200 ÷ 700 ° C for 20 ÷ 60 minutes can be additionally carried out.

Chips can be crushed before incineration.

To achieve a technical result, a device is proposed that includes a combustion unit, which is made in the form of a horizontal tubular electric furnace, comprising a housing lined with refractory materials, a pipe with internal coils and vanes, rotatable around its axis, divided into working zones with autonomous heating sources for the implementation of successive stages of the combustion process, means for supplying air to the pipe in the direction of movement of the chips, loading units, unloading products of burning chips and gas removal.

Preferably, the pipe with internal turns and blades of the combustion unit can be cast from a heat-resistant alloy.

The pipe of the combustion unit may have two working zones, while between the turns of the second working zone, blades are made with a height equal to the height of the turns, and are located on the turns through 180 degrees.

The pipe of the incinerator may have three working zones, while between the turns of the second and third working zones blades are made with a height equal to the height of the turns and are located on the turns through 180 degrees.

Preferably, the device for burning chips further comprises an afterburner for the products of combustion of chips, connected in series with the combustion unit in one unit.

The afterburner of the combustion products of the shavings may include a housing, a screw with turns and blades, means for supplying air, a heating source, loading and unloading units for the product and gas removal.

Between the turns of the auger of the afterburner of the products of combustion of the chips, blades can be made with a height equal to the height of the turns, and are located on the turns of the screw through 240 degrees.

When analyzing patent and scientific and technical sources, no technical solutions have been identified that have the entire set of essential features of the claimed technical solutions.

Comparison of the claimed technical solutions not only with the closest analogues, but also with other technical solutions in this technical field showed that it is known to grind industrial waste before incineration (M.N. Bernadiner, A.P. Shurygin. Fire processing and disposal of industrial waste . M., "Chemistry" 1990).

Known horizontal rotary rotary kilns for burning solid waste containing mechanisms for loading, unloading, heating and drum. (M.N. Bernadiner, A.P. Shurygin. Fire processing and disposal of industrial waste. M., "Chemistry" 1990, p. 37-41).

However, in the claimed technical solutions, only the entire combination of known and new significant features allows us to solve the problem - to significantly reduce the cost of processing the oxide product of the burning of uranium metal chips into uranium tetrafluoride and to improve the quality of the product itself.

The use of the claimed method of processing uranium metal chips for the operation of burning chips with a thickness of 0.3 ÷ 3 mm and the combustion process with air supply in the direction of movement of the chips several stages, including drying and heating at a temperature in the material layer of 100 ÷ 300 ° C, and then ignition and combustion at a temperature of 300 ÷ 900 ° C for 5 ÷ 30 min, can significantly improve the quality of the oxide product of the combustion of uranium metal chips, mainly to small fractions of uranium oxide, which are easily and completely conve tiruyutsya to obtain high quality uranium tetrafluoride and uranium hexafluoride in more corresponding standards. The absence of large agglomerated fractions (the fraction fraction +0.4 mm is less than 5%), as well as the heterogeneity of the chemical composition of different uranium oxides of variable composition, the minimum amount of active uranium (less than 1.0 wt.%) In the oxide product of burning metal uranium chips by the present method ) leads to the fact that no additional costs are required to refine the oxide product of burning uranium metal shavings to the required condition (for example, using leaching, extraction refining), which ultimately leads to a significant reduction in the cost of processing the oxide product of the burning of uranium metal shavings into high quality uranium tetrafluoride in comparison with known methods.

Carrying out an additional third stage in the process of burning chips: afterburning of combustion products in the smoldering layer at a temperature of 200 ÷ 700 ° C for 20 ÷ 60 minutes, as well as the use of crushed chips, it is possible to further increase the productivity of the device for burning chips while ensuring the quality of the uranium oxide product by the size and content of active uranium, and also allows to reduce the cost of processing the oxide product of burning metal chips of uranium into high-quality uranium tetrafluoride by cf knowledge of known methods.

The claimed design of a device for burning metal chips allows for the translational-rotational movement of chips through working zones, in which sequential processing of uranium chips under the claimed conditions is carried out under the claimed conditions, which ensure the achievement of a technical result.

No blades are provided in the first working area of the pipe of the incinerator due to the fact that intensive mixing is not required at the stage of drying, removing moisture and heating the chips. In addition, this avoids premature ignition of chips containing residual water, which catalyzes the process of rapid combustion with intense dust formation.

The use according to the claimed technical solution of the combustion installation, in which the pipe has three working zones with the execution between the turns of the second and third working zones of the blades with a height equal to the height of the turns, and located on the turns through 180 degrees, or containing the afterburner of the combustion products of the chip the installation of combustion in the claimed conditions, makes it possible to carry out additional afterburning of the combustion products, which, under the conditions claimed by the method, allows to create optimal conditions for metal burning uranium chips and significantly increase the productivity of the device and the quality of the oxide product of combustion to the required condition, mainly to fine fractions of uranium oxide, which are easily and fully converted to produce high-quality uranium tetrafluoride and then to uranium hexafluoride in accordance with the requirements of the standards. The absence of large agglomerated fractions in the oxide product of burning metal uranium chips by the present method (fraction fraction +0.4 mm is less than 5%), as well as the heterogeneity of the chemical composition of different uranium oxides of variable composition, the minimum amount of active uranium (less than 1.0 wt.% ) leads to the fact that no additional costs are required to refine the oxide product of the burning of uranium metal chips to the required condition (for example, using leaching, extraction and refining), which ultimately leads to a significant reduction in the cost of processing the oxide product of the burning of uranium metal shavings into high quality uranium tetrafluoride in comparison with known devices.

The invention is illustrated by drawings, which depict:

figure 1 presents the inventive device for burning metal chips of uranium, which carries out the process of burning chips in two stages;

figure 2 presents the inventive device for burning metal chips of uranium, which carries out the process of burning chips in three stages without an afterburner;

figure 3 presents the inventive device for burning metal chips of uranium, which carries out the process of burning chips in three stages with an afterburner.

The proposed method is carried out in the following sequence. Prepared uranium chips with a thickness of 0.3 ÷ 3 mm are loaded into the combustion unit, where they are first dried and heated. Then the dried and heated chips are burned with vigorous stirring and air supply in the direction of movement of the chips, which contributes to its complete combustion.

To verify the claimed technical solution, the following work was carried out. Uranium metal shavings formed during the machining of uranium ingots were burned.

Example 1

Used uranium metal shavings of different thicknesses: 0.2; 0.3; 1.6; 3.0; 3.1 mm both not crushed, and previously crushed. The chips were loaded into a processing device (FIG. 1). In the direction of movement of the chips, air was supplied. The process of burning chips was carried out in two stages. At the first stage, the chips were dried and heated in the first working zone of the pipe 2 of the combustion unit at different temperatures: 98, 100, 150, 300, 305 ° С. In the second stage, ignition and combustion of the chips in the second zone of the pipe 2 of the combustion unit at different temperatures: 295, 300, 600, 900, 905 ° C for different times: 4; 5; 17.5; thirty; 31 minutes The duration of the combustion of the chips was regulated by the rotation speed of the pipe 2 of the combustion unit. The finished oxide product was discharged into a container.

Example 2

Uranium shavings of different thicknesses: 0.3; 1.6 and 3.0 mm, both non-crushed and pre-crushed, were loaded into a processing device (FIG. 2). In the direction of movement of the chips, air was supplied. The process of burning chips was carried out in three stages. At the first stage, the chips were dried and heated in the first working zone of the pipe 2 of the combustion unit at different temperatures: 100, 150, and 300 ° С. In the second stage, ignition and combustion of chips in the second zone of the pipe 2 of the combustion unit were carried out at different temperatures: 300, 600 and 900 ° C for different times of 5, 17.5 and 30 minutes. In the third stage, the combustion products were burned in the smoldering layer in the third zone of the pipe 2 of the combustion unit at different temperatures: 195; 200; 450; 700 and 705 ° C for different times: 19; twenty; 40; 60 and 61 minutes The duration of the combustion of the chips was regulated by the rotation speed of the pipe 2 of the combustion unit. The finished oxide product was discharged into a container.

Example 3

Uranium shavings of different thicknesses: 0.3; 1.6 and 3.0 mm, both uncrushed and pre-crushed, were loaded into a processing device (FIG. 3). In the direction of movement of the chips, air was supplied. The chip combustion process was carried out in three stages: at the first stage, the chips were dried and heated in the first working zone of the pipe 2 of the combustion unit I at different temperatures: 100, 150, and 300 ° С. At the second stage, ignition and combustion of the chips were carried out in the second part of the pipe 2 of the combustion unit I at different temperatures: 300, 600, 900 ° C for different times: 5; 17.5 and 30 minutes In the third stage, the combustion products of the chips were burned in the smoldering layer in the afterburner II at different temperatures: 200; 450; 700 ° C for different times: 20; 40 and 60 minutes The burning time was regulated by the rotation speed of the pipe 2 of the combustion unit I and the screw 7 of the afterburner II. The finished oxide product was discharged into a container.

Example 4

To obtain comparative data, chips were burned according to the closest analogue. Combustible materials containing uranium, metal uranium production wastes and uranium metal shavings were used as feedstock for combustion. These raw materials were burned in a vertical combustion plant in a single stage. The finished oxide product was discharged into a container.

Uranium tetrafluoride was obtained from the methods obtained according to Examples 1-4 of oxide products.

Example 5

The inventive device for burning metal chips of uranium (figure 1) consists of a combustion unit, which is made in the form of a horizontal rotating tubular electric furnace containing a housing 1 with a lining, a pipe 2 with internal turns 3, a loading unit (not shown), means for supplying air in the direction of movement of the chips (not shown), a tube rotation unit (not shown), a combustion product discharge unit (not shown) and a gas removal unit (not shown). The pipe 2 of the combustion plant has two working zones I and II for the first and second stages of the chip combustion process with separate heat sources 4, between the turns 3 of the pipe 2 of its second working zone II, blades 5 are made with a height equal to the height of the turns 3 and are located on the turns 3 through 180 degrees. The pipe 2 with internal coils 3 and blades 5 is cast from a heat-resistant alloy.

The device operates as follows. They include heating sources 4 combustion plants. Upon reaching the set temperatures in the working zones I and II of the pipe 2 (FIG. 1), the combustion unit includes a tube rotation unit 2. The crushed chips 0.3–3 mm thick are loaded into the loading unit of the combustion unit. In the pipe 2 serves air in the direction of movement of the chips. From the loading unit, the chip due to rotation of the pipe 2 enters its first working zone I, where it is dried and heated at a temperature in the material layer of 100 ÷ 300 ° C, then the chip due to rotation of the pipe 2 enters the second working zone II of the pipe 2, where it lights up and burns at a temperature of 300 ÷ 900 ° C. The process of active combustion of the chip proceeds, while the burning chip with the help of blades 5 is intensively mixed, the outer cortical layer of the chip is destroyed and air is accessed to the new internal chip layers, which contributes to the complete burning of the uranium metal chip in the smoldering layer of the product and bring it to the required condition . The finished oxide product is discharged through the unloading unit of the combustion products of the chips, and the gases are removed for disposal. At the end of the operation of the device, the heat sources 4 and the rotation of the pipe 2 of the combustion unit are turned off.

Example 6

A device for burning uranium metal shavings (Fig. 2) consists of a combustion unit, which is made in the form of a horizontal rotating tubular electric furnace containing a body 1 with a lining, a pipe 2 with internal coils 3, a loading unit (not shown), a pipe rotation unit (not shown), means for supplying air (not shown), a unit for unloading combustion products (not shown), and a gas removal unit (not shown). The pipe 2 of the combustion plant has three working zones (I, II and III in figure 2) for the implementation of the three stages of the process of burning chips with separate heat sources, between the turns 3 of the pipe 2 of the second II and third III of its working zones, blades 5 are made with a height equal to the height of the turns 3, and are located on the turns 3 through 180 degrees. The pipe 2 with internal coils 3 and blades 5 is cast from a heat-resistant alloy.

The device operates as follows. They include heating sources 4 combustion plants. Upon reaching the set temperatures in the working areas of the pipe 2 of the combustion unit, the rotational unit of the pipe 2 is turned on. The crushed chips 0.3–3 mm thick are loaded into the loading unit of the combustion unit. In the pipe 2 serves air in the direction of movement of the chips. From the loading unit, the chip due to rotation of the pipe 2 enters its first working zone I, where it is dried and heated at a temperature in the material layer of 100 ÷ 300 ° C, then the chip due to rotation of the pipe 2 enters the second working zone II of the pipe 2, where it lights up and burns at a temperature of 300 ÷ 900 ° C. The process of active combustion of the chip proceeds, while the combustion product with the help of the blades 5 is intensively mixed, the outer cortical layer of the chip is destroyed and air is accessed to the new internal layers of the chip. Further, the combustion product due to the rotation of the pipe 2 enters its third working zone III, where it is burned in the smoldering layer at a temperature of 200-700 ° C. This contributes to the complete burning of metal chips of uranium and bringing the combustion product to the required condition. The finished oxide product is discharged through the unloading unit of the combustion products of the chips, and the gases are removed for disposal. At the end of the operation of the device, the heat sources 4 and the rotation of the pipe 2 of the combustion installation are turned off.

Example 7

A device for burning uranium metal shavings (Fig. 3) consists of a combustion unit, made similarly to the installation described in Example 5, and an afterburner 6 of chip combustion products, connected in series with the combustion unit in one unit, while the combustion unit and afterburner 6 are equipped with means air supply (not shown), and the pipe 2 of the combustion unit contains a unit for reloading the combustion products of the chips into the afterburner 6 (not shown).

The afterburner 6 comprises a housing 7, a screw 8 with turns 9 and blades 10, a loading unit (not shown), a rotating unit for screw 8 (not shown), a product unloading unit (not shown), and a gas removal unit (not shown). The blades 10 of the screw 8 are made with a height equal to the height of the turn, and are located on the turns through 240 degrees.

The device operates as follows. They include heating sources 4 of the combustion unit and afterburner 6 (not shown). Upon reaching the set temperatures in the working zones I and II of the pipe 2 and in the afterburner 6, the rotation units of the pipe 2 and the screw 8 are turned on. The crushed chips 0.3–3 mm thick are loaded into the loading unit of the combustion unit. In the pipe 2 serves air in the direction of movement of the chips. Due to the rotation of the pipe 2, the shavings from the loading unit enter the first working zone I, where drying and heating are carried out at a temperature of 100 ÷ 300 ° C, then the chips with the help of turns 3 enter the second working zone II of the pipe 2, where it lights up and burns at a temperature of 300 ÷ 900 ° C. The process of active combustion of the chips proceeds, while the burning chips with the help of the blades 5 are intensively mixed, the outer cortical layer of the chips is destroyed and air is accessed to the new internal layers of the chips. From the second working zone II of the pipe 2, the resulting combustion products of the chips enter the afterburner 6, into the housing 7. In the afterburner 6 at a temperature of 200 ÷ 700 ° C, this product is moved by turns 9 of the screw 8 at a given speed. At the same time, it is intensively mixed by the blades 10, which contributes to the complete burning of metal uranium chips in the smoldering layer of the product and bringing it to the required condition. The finished oxide product is discharged from the afterburner 6, and the gases are removed for disposal. At the end of the operation of the device, the sources of heating and rotation of the pipe 2 and the screw 8 of the afterburner 6 are turned off.

In the course of the work, the chemical and fractional compositions of the oxide combustion products and the grade of uranium tetrafluoride obtained after processing the oxide product were determined by standard methods. The test results are shown in the table.

Analysis of the data in the table shows that the inventive method allows to obtain the oxide product of the combustion of metal chips of uranium of higher quality in chemical and fractional compositions. So, this product contains significantly less impurities (active uranium concentration less than 1%) and large fractions (mass fraction of the fraction +0.4 mm less than 5%). From this product, by standard processing, grade A uranium tetrafluoride is obtained, unlike grade B tetrafluoride, obtained from an oxide combustion product obtained by the closest method. Application of the third stage of chip burning: afterburning of combustion products in the smoldering layer allows to achieve even higher productivity of the combustion process and to improve the quality of the finished product in chemical and fractional compositions. In addition, the claimed technical solutions are characterized by a lower cost of processing the obtained oxide product into uranium tetrafluoride (84.2 ÷ 86.3% according to the claimed technical solutions instead of 100% according to the closest analogues).

The optimal parameters of the process of burning metal chips of uranium are the following (experiments No. 2-4, 7-9, 12-14, 17-19, 22-24, 27-29, 32, 33):

- chip thickness 0.3 ÷ 3 mm;

- pre-crushing chips;

- step-by-step management of the process of burning chips:

- at the first stage at a temperature of 100 ÷ 300 ° C;

- in the second stage at a temperature of 300 ÷ 900 ° C for 5 ÷ 30 min;

- in the third stage at a temperature of 200 ÷ 700 ° C for 20 ÷ 60 min;

- air is fed into the device in the direction of movement of the chips.

Reducing the parameters of the process of burning metal chips of uranium:

- chip thickness less than 0.3 mm;

- the temperature of the first stage is less than 100 ° C;

- the temperature of the second stage is less than 300 ° C;

- the duration of the second stage is less than 5 minutes;

- the temperature of the third stage is less than 200 ° C;

- the duration of the third stage is less than 20 minutes

leads to a sharp deterioration in the quality of the oxide product of combustion in chemical and fractional compositions, as well as to a decrease in the productivity of the combustion process, loss of chips during crushing, and fine oxide-oxide with gases.

The increase in the parameters of the process of burning metal chips of uranium:

- chip thickness more than 3 mm;

- the temperature of the first stage is more than 300 ° C;

- the temperature of the second stage is more than 900 ° C;

- the duration of the second stage is more than 30 minutes;

- the temperature of the third stage is more than 700 ° C;

- the duration of the third stage is more than 60 minutes

leads to a deterioration in the quality of the oxide combustion product in fractional composition, as well as to an increase in the cost of burning uranium metal chips and to a reduction in the maintenance-free life of the equipment.

The inventive method and device for the processing of uranium metal chips tested in the production conditions of OAO CMP with a positive result. The experimental batch of uranium metal shavings was processed by the claimed method and on the claimed devices. A batch of uranium tetrafluoride meeting the requirements of TU 95. 1713-2005 grade A, which was sent to the customer, was obtained from the obtained oxide product of combustion by standard technology.

Claims (10)

1. A method of processing uranium metal chips, including the preparation and burning of chips, characterized in that they use chips with a thickness of 0.3 ÷ 3 mm for combustion, the combustion process is carried out with the successive movement of chips from one working area to another with air supply in the direction of movement of the chips and carried out in several stages, including drying and heating at a temperature in the material layer of 100 ÷ 300 ° C, and then ignition and combustion at a temperature of 300 ÷ 900 ° C for 5 ÷ 30 min. 2. The method according to claim 1, characterized in that after burning the chips, they additionally conduct the afterburning of the combustion products in the smoldering layer at a temperature of 200 ÷ 700 ° C for 20 ÷ 60 minutes 3. The method according to claim 1, characterized in that the chips before burning are crushed. 4. A device for implementing the method, comprising a combustion installation, characterized in that the combustion installation is made in the form of a horizontal tubular electric furnace containing a housing lined with refractory materials, a pipe with internal coils and vanes, made to rotate around its axis and divided into working zones with autonomous heat sources for the implementation of successive stages of the process of burning chips, means for supplying air to the pipe in the direction of movement of the chips, loading units, unloading of combustion products of chips and removal of gases. 5. The device according to claim 4, characterized in that the pipe with internal coils and blades of the combustion unit is cast from a heat-resistant alloy. 6. The device according to claim 5, characterized in that the pipe of the combustion installation has two working zones, while between the turns of the second working zone, blades are made with a height equal to the height of the turns, and are located on the turns through 180 °. 7. The device according to claim 4, characterized in that the pipe of the combustion unit has three working zones for implementing the chip combustion process, while between the turns of the second and third working zones blades are made with a height equal to the height of the turns and are located on the turns through 180 °. 8. The device according to claim 6, characterized in that it further comprises an afterburner of the products of combustion of the chips, connected in series with the combustion unit in one unit. 9. The device according to claim 8, characterized in that the afterburner of the products of combustion of the chips contains a housing, a screw with turns and blades, means for supplying air, a heating source, loading units, product unloading and gas removal. 10. The device according to claim 9, characterized in that between the turns of the auger of the afterburner of the products of combustion of the chips, blades are made with a height equal to the height of the turns, and are located on the turns of the screw through 240 °.

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