RU158206U1 - DEVICE FOR CONDITIONING OF COMBUSTIBLE ORGANIC RADIOACTIVE WASTE - Google Patents

Abstract

A device for conditioning combustible organic radioactive waste containing a thermal decomposition chamber (KTR) with a loading door at the top for loading solid organic radioactive waste, a pipe for supplying air to the upper zone of the thermal decomposition chamber for burning pyrolysis gases, a pipe for supplying air to the lower zone of the thermal chamber decomposition for burning carbon in the coke ash residue, a cooled pipe-heat exchanger connected to the upper part of the KTP for exhaust gas removal with a filter for exhaust gas cleaning, and the grate and ash pan located in the lower part of the thermal decomposition chamber, characterized in that the device is additionally supplied with a liquid organic RW supply unit containing a storage measuring tank, a hose connecting it to the bottom of the ash pan through a nozzle with a shut-off valve, a jet chipper in the form of a horseshoe-shaped plate welded from the inside of the ash pan bottom.

Description

The utility model relates to the field of conditioning solid and liquid combustible radioactive waste (wood, paper, rags, rubber gloves, plastic film, mineral oils, organic solvents, etc.) generated during research and production work in organizations , in order to reduce their volume for subsequent export to the disposal site or long-term storage.

Known devices for conditioning radioactive waste due to the thermal decomposition of waste in an oxygen-free atmosphere (pyrolysis). Thermal decomposition (pyrolysis) of waste in an oxygen-free atmosphere allows you to transfer the bulk of the organic substances contained in the waste into a gaseous state, thereby concentrating the bulk of the radioactive components in the solid coke residue. The afterburning of the coke residue makes it possible to concentrate more than 80% of the initial radioactive waste in the ash and reduces the amount of ash to be disposed of.

A device for conditioning solid organic radioactive waste is described in the patent of the Russian Federation No. 2335700 [1]. The device is based on the thermal decomposition of radioactive waste without access to air (pyrolysis).

The device contains: a box for storing solid waste, which is under vacuum, a loading device (where the waste is moved), a thermal decomposition chamber (KTR), heated externally by flue gases generated from burning external fuel in the burner. The waste is heated in a chamber at a temperature of 650-700 ° C without oxygen, while pyrolysis occurs, which results in approximately 60-70% of gaseous combustible gases and 30-40% of a coke-ash residue. The gaseous pyrolysis products then enter the furnace, where they are burned together with the fuel from the burner. Further, in the subsequent nodes, low-temperature oxidation of the residues of organic compounds occurs. In the heat exchanger, the temperature of the gases is reduced to a level of 150-120 ° C, and in the dust cleaning system, the flue gases are first cleaned of dust in a “dry” cyclone. Then they are washed with liquid in a “wet” scrubber. The cleaned flue gases enter the flue through which they are emitted into the atmosphere. The captured dust is unloaded from the cyclone of the system as it accumulates in a sealed container through a box under vacuum.

The coke ash residue formed as a result of pyrolysis as it accumulates in the chamber is discharged through the discharge device onto the grate, under which atmospheric air enters to burn these residues due to the exhaust fan draft. The inorganic part of the coke ash residue (ash) remaining after combustion is removed from under the grate by a special transport device through a special box under vacuum. Ash is discharged into a sealed container. Its disposal is carried out by special technology.

The device has the following disadvantages:

1. A rather complex design of the device, due to the fact that the thermal decomposition chamber is heated, is produced by the flue gases generated in the furnace when external fuel is burned in the burner. The temperature is not adjustable. Pyrolysis is carried out at a temperature of 650-700 ° C.

2. This design does not provide for a separate exhaust gas outlet of the burner and gases generated during pyrolysis in KTP. This leads to the formation of a large amount of radioactive soot arising from the mixing of gaseous products of thermal decomposition with the products of combustion of the burner.

3. The high temperature of pyrolysis and burning of coke oven residue, due to the heating system of the thermal decomposition chamber, increases the likelihood of entrainment of volatile radionuclides, in particular, cesium radionuclides.

4. A complex cleaning system, in particular, associated with the need to rinse off-gases in a wet scrubber leads to the formation of secondary (liquid) waste products.

5. The device is intended for conditioning only solid radioactive waste.

Closest to the claimed device in terms of essential features is a device for conditioning solid organic radioactive waste described in the patent of the Russian Federation No. 2479877 [2].

This device is also based on the thermal decomposition of radioactive waste in the first stage without air access, when the bulk of the organic matter contained in the waste is converted to a gaseous state, and the bulk of the radioactive components are concentrated in solid coke residue.

Device - a prototype eliminates many of the disadvantages of a similar device. KTP heating is carried out electrically, therefore: the causes of the appearance of flue gases generated from the burning of external fuel are eliminated; it is possible to adjust and maintain a certain temperature and carry out pyrolysis at a lower temperature, which prevents significant entrainment of radionuclides.

KTP is conditionally divided into two zones: the lower one is pyrolyzed at T = 400 ° C, the upper one is the pyrolysis gas burning in an air stream at a higher temperature, and the whole process takes place in one chamber.

The device contains the following nodes: a thermal decomposition chamber (CTE), in the lower zone of which, without oxygen access, the thermal decomposition of the original organic radioactive waste occurs, and in the upper zone, the pyrolysis gases are burnt in the air stream; loading hatch; grate; an ashpit; a pipe for supplying air to the lower zone of the KTP; a pipe for supplying air to the upper zone of the KTP; pipe heat exchanger for exhaust gases from KTP; coarse flue gas filter; fine filter of flue gases (from Petryanov’s fabric).

The material decomposed into the block, to be conditioned, previously impregnated with a solution of cesium sulfate in sulfuric acid, is fed into a vertically mounted thermal decomposition chamber through a loading hatch. Water cooling of the manhole cover is turned on, the required air flow through the pipe in the upper zone of the KTP is set, and then the heating of the upper zone of the KTP is turned on. Upon reaching a temperature of 800 ° C in it, the lower zone of the KTP is heated to a temperature of 400 ° C. Due to thermal decomposition in an oxygen-free medium, the impregnated material pressed into the block is pyrolyzed to form a coke residue (heating of the upper and lower zones of the KTP is carried out using two tubular electric furnaces). At the end of the pyrolysis process, the heating of the upper KTP zone is turned off, and the air supply to it ceases. Air is supplied to the lower zone of the KTP, where the coke ash residue is burned at t = 400 ° C. The resulting ash residue falls into the ash pan, from which it is extracted after the end of the process and transferred to the collection container for temporary storage.

The pyrolysis gases generated during pyrolysis enter the upper chamber of the KTP, in which they are burned and converted into exhaust flue gases, which, passing through the air heat exchanger, cool down and enter the coarse filter, then the fine filter for purification of soot and radioactive aerosols. Thus, the cleaning unit of the device provides the cleaning of flue gases from solid particles and from volatile radionuclides.

The coarse and fine filters that have exhausted their service life are air-conditioned using the same installation.

The disadvantage of this device is that it is not intended for the conditioning of liquid radioactive waste that is generated during industrial and research work (mineral oils, organic solvents, liquid organic scintillators, etc.),

The objective of the claimed device is to expand its functionality, namely, the conditioning of both solid and liquid combustible radioactive waste, without re-equipment of the device.

The technical effect is to create a universal in operation and more economical device.

The problem is achieved in that in the known device for conditioning combustible organic radioactive waste containing a thermal decomposition chamber (CTE) with a loading door for loading solid organic radioactive waste, a pipe for supplying air to the upper zone of the thermal decomposition chamber for burning pyrolysis gases, a pipe for air supply to the lower zone of the thermal decomposition chamber for burning carbon in the coke residue, connected to the upper part of the KTP, a cooled pipe for removal of exhaust gases with a filter for purification of exhaust gases, and the grate and ash pan located in the lower part of the thermal decomposition chamber, it is new that the unit for supplying liquid organic RW consisting of a storage measuring tank, a hose connecting it to the bottom of the ash pan through nipple with shut-off valve, fender baffle in the form of a horseshoe-shaped plate welded from the inside of the bottom of the ash pan.

In FIG. 1 shows a diagram of a device.

The device comprises: a thermal decomposition chamber - 1; loading hatch with a cover - 2; pipes for supplying air to the upper and lower zones of the thermal decomposition chamber - 3; a pipe for venting exhaust gases - 4; the filter for purification of exhaust gases - 5; a tank with running water for cooling the pipe for exhaust gases - 6; grate - 7; ashpit - 8; chipper - 9; nipple with shut-off valve - 10; connecting hose - 11; cumulative measured capacity - 12;

Accumulative measured capacity - 12 is connected to the ash pan - 8 with a hose - 11, which is connected to the bottom of the ash pan - 8 through a shut-off valve - 10 with a fitting. A chipper - 9 in the form of a horseshoe-shaped plate is welded to the inside of the bottom of the ash pan - 8.

The principle of operation of the device. When conditioning solid combustible radioactive waste, a vertically mounted thermal decomposition chamber - 1 through the loading hatch - 2 is supplied with impregnated material pressed into the block, which is to be conditioned and falls onto the grate - 7. The cover of the loading hatch is closed using a clamping device. The water cooling of the lid is turned on, the required air flow through the pipe - 3 is set in the upper zone of the KTP. After that, the heating of the upper zone of the KTP is turned on. Upon reaching a temperature of 800 ° C in it, the lower KTP zone is heated to a temperature of 400 ° C without air access, and pyrolysis occurs (heating of the upper and lower KTP zones is performed using two tubular electric furnaces).

At the end of the pyrolysis process, the heating of the upper KTP zone is turned off, the air supply to it is stopped, and air is supplied with the same flow rate through the pipe-3 to the lower KTP zone, where the coke ash residue is burned at t = 400 ° C. The resulting ash residue goes to ash pan - 8, from which it is extracted after the end of the process and transferred to the collection container for temporary storage.

Pyrolysis gases generated during pyrolysis enter the upper chamber of the KTP, in which they burn and turn into flue gases, which, passing through the pipe-4, located in a tank with running water-6 (heat exchanger), cool and enter the filter from Petryanov’s fabric FPP-15 -1.5 - 5 and further through the local suction device with a fine filter into the special ventilation system of the building (structure).

For conditioning of liquid radioactive waste, a node for supplying liquid organic radioactive waste has been developed - positions 9-12 in FIG. 1, which is connected to the installation without requiring retooling.

The procedure for conditioning liquid organic waste. After the unit reaches the temperature regime of pyrolysis-burning with the valve open, 10 portion of LRW with the help of the excess pressure created by the inert gas from the cylinder is transferred through the hose - 11 through the chipper - 9 to the ash pan - 8. After which the valve - 10 closes and pyrolysis of LRW with simultaneous burning of pyrolysis gases, and then afterburning of the remaining carbon. The chipper - 9 serves to prevent the liquid from jetting when transferring it from the measuring tank to the ash pan. The pyrolysis procedure - burning is the same as in the case of SRW.

The pyrolysis gas is burned in the upper part of the KTP during the pyrolysis. Carbon combustion in the coke ash residue at the end of the pyrolysis process occurs on the grate in the case of SRW or in the ash pan in the case of LRW.

In the table. 1 shows the results of the distribution of activity, weight and volume as a percentage of the initial, in various nodes of the laboratory installation of the pyrolysis-burning of combustible organic waste during conditioning of typical solid and liquid wastes.

From the table. 1 it can be seen that even after the coarse filter, the C3-137 leakage is a fraction of a percent of the initial activity, while other less volatile radionuclides are less than 0.01%. Taking into account the fact that the output fine filter from Petryanov’s fabric, according to published data, increases the degree of purification of ventilation exhausts by at least 3 orders of magnitude, they can be emitted through the central system of special ventilation into the atmosphere without violating applicable radiation safety standards.

The inventive method has passed an experimental test in the Decontamination Workshop of UEAU FSBI PNPI. As a result of the verification, the possibility of burning solid RW, as well as liquid RW without re-equipping the device, was confirmed.

Concrete implementation example

A package of a dirty oiled jacket weighing 1 kg was pyrolyzed, and the coke-ash residue was burned according to the SRW incineration scheme. The result was 4.39 g (0.4%) of ash residue. No leakage of smoke and aerosols by the color of the outer surface of the FPP-15-1.5 filter was found.

The burning of liquid organic waste.

0.6 kg of ID-20 mineral oil was transferred from the measuring tank with compressed air to the ash pan and its pyrolysis was performed according to the pyrolysis scheme - burning of LRW. After that, another 0.6 kg of ID-20 oil was transferred to the ash pan, it was pyrolyzed and the coke ash residue was burned. The weight of the ash residue was 0.1% of the weight of the original oil. Smoke leakage and contamination of the outer surface of the filter were not observed.

The calculation results showed that even this pilot plant is capable of processing solid and liquid radioactive organic waste generated during the year in the VVR-M reactor complex, the Department of Molecular Radiation Biology, the Accelerator Department, the Decontamination Workshop, and other departments of the institute (application for long-term removal storage of organic radioactive waste in the federal state unitary enterprise RosRAO in the North-West Federal District Federal State Unitary Enterprise in 2014: 650 kg of solid radioactive waste, 200 kg of liquid radioactive waste).

The device can also be used to destroy small batches of harmful chemical organic substances, medical, biological products, etc. with an expired shelf life.

Bibliography

1. RF patent №2335700, IPC P23C 5/08

2. RF patent №2479877, IPC С21Р 9/32 - prototype

Claims (1)

A device for conditioning combustible organic radioactive waste containing a thermal decomposition chamber (KTR) with a loading door at the top for loading solid organic radioactive waste, a pipe for supplying air to the upper zone of the thermal decomposition chamber for burning pyrolysis gases, a pipe for supplying air to the lower zone of the thermal chamber decomposition for burning carbon in the coke ash residue, a cooled pipe-heat exchanger connected to the upper part of the KTP for exhaust gas removal with a filter for exhaust gas cleaning, and the grate and ash pan located in the lower part of the thermal decomposition chamber, characterized in that the device is additionally supplied with a liquid organic RW supply unit containing a storage measuring tank, a hose connecting it to the bottom of the ash pan through a nozzle with a shut-off valve, a jet chipper in the form of a horseshoe-shaped plate welded from the inside of the ash pan bottom.

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