CH637751A5 - Method for treating waste, in particular radioactive waste - Google Patents

Description

The invention relates to a method for treating waste. The method is particularly suitable for the treatment of radioactive waste, e.g. contain radioactive halogens 40, for example the isotope iodine 131.

In recent years, energy consumption, including that of nuclear power plants, has increased significantly. The greater demand was accompanied by major processing and disposal problems. A major problem is that the number of processing plants has risen sharply and the demand for available space at the officially approved disposal points has increased accordingly. It also looks like the choice of new commercial deposition sites will be subject to closer official supervision and strict regulation in the future.

In particular, it is expected that disposal facilities for low radioactive waste will be inspected and monitored by the authorities. The requirements for granting this 55 approval will likely also become stricter.

One of the main concerns in waste disposal is safety in transporting the treated waste to its final disposal site. To address this problem, it is desirable on the one hand to reduce the volume of the waste to be transported as much as possible, and on the other hand to increase its stability. Accordingly, the invention aims to provide a treatment method which enables a considerable reduction in the volume of the waste materials.

A major problem with the treatment of wastes from nuclear power plants is that the wastes are chemically and physically

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Distinct features from each other considerably, so that several treatment methods must be tailored to a single system. The invention therefore aims to provide a treatment method which is possibly independent of the chemical composition of the waste materials and which is suitable for treating an endless variety of waste materials.

Fluid beds have been used for several years for calcining liquids and for burning combustible waste in industrial plants. Such giant beds are e.g. on page 239 of the book Principles and Practices of Incinération, by Richard C. Corey, publisher Wiley-Interscience, New York, 1969. A fluid bed calcination process was developed in the Idaho National Engineering Laboratory between 1952 and 1959 for radioactive waste. Liquid radioactive waste was calcined in the Waste Calcining Facility (WCF) of the Idaho Chemical Processing Plant in 1963.

A batch bed fluid calculator was built as part of the Midwest Fuel Recovery Plant (MFRP) in Morris, Illinois for General Electric Company. A calcination process with batch operation on a full radioactive basis was used in the WSEP program between 1966 and 1970. However, this process, developed at Oak Ridge National Laboratory for the specific purpose of solidifying highly radioactive liquid wastes, made no use of a fluid bed.

• The combustion of combustible, radioactive waste has been used as a disposal method since 1948, and ever since an experimental plant with incinerator and exhaust gas cleaning device was built in the Mound Laboratory. Previously used facilities were simply adaptations of ordinary waste incinerators to demonstrate that the volume of waste to be disposed of could be reduced significantly. Experimental data collected at the General Electric Atomic Power Equipment Department in San Jose, California in the early 1960s showed that about 99% of the radioactivity of the incinerated waste was left in the ashes. Similar test results were obtained in a Pratt & Whitney incinerator, which in turn showed that 99.1 to 99.9% of the radioactivity remained in the ashes.

For a discussion of the various existing incinerators for the treatment of radioactive waste, reference is made to the specialist book “Incineration Facilities for Treatment of Radioactive Wastes: A Review”, LA-6252, Los Alamos Scientific Laboratory, Los Alamos, New Mexico, 1976.

Fluid beds that were previously used to convert liquid waste streams, including radioactive waste streams, into solid particles consisted of solid products resulting from earlier drying or calcination of a liquid waste stream similar to the waste stream to be treated.

The following difficulties arose. On the one hand, the fluidized bed particles were subjected to growth, which resulted from the fact that new liquid waste was deposited on the surface from which the water ricocheted off and a layer of resulting solids was left behind; on the other hand a decrease in size, which was caused by the self-grinding effect of the colliding particles or by their impact on a surface standing in their way.

■ The two simultaneous processes, the growth and the decrease in size, are very critical from the point of view of perfect operation, since the fluidized bed particles can no longer be properly fluidized if they become too large, which places serious limits on the chances of a successful process. On the other hand, if the fluidized bed particles become too small, they will be blown away from the surface of the fluidized bed since their final velocity approximates the surface velocity of the fluidizing air in the container. Carrying solid particles through a gas stream is commonly referred to as slurry. Accordingly, because of the critical balance between growth and size reduction in such a system, it is necessary to continuously monitor the particle size distribution of the fluidized bed material and to regulate the operating conditions in such a way that the particle sizes are kept under control and to control the growth phenomena in such a way that permissible particle sizes are ensured.

These processes, the growth and the decrease in size, are strongly influenced by the chemical characteristics and the chemical composition of the liquid waste stream to be converted into solid substances. It is e.g. impossible to grow fluid bed particles if the total solids content (in dissolved and undissolved form) in the waste liquid is less than a predetermined value depending on the chemical identity 20 of the latter. The reason for this is that because of the small amount of the solid material capable of forming solid in the waste liquid, the decrease in size (wear) takes place faster than the increase in size (growth).

25 The dependency of such fluidized bed calcination and evaporation processes on the chemical identity of the waste liquid is an important disadvantage and requires very precise process monitoring in order to achieve trouble-free operation. Accordingly, the invention aims to provide a treatment process in which the calcination and the combustion are not so dependent on the chemical characteristics of the waste liquid.

Furthermore, because of the aforementioned particle size control problem, the calcination processes described above cannot handle very dilute waste liquid streams. Accordingly, it is also the purpose of the invention to treat both very dilute waste liquids and completely solid waste materials. It is also intended to be able to use a single fluid bed under different operating conditions (e.g. 40 at different temperatures) for both calcination and combustion.

In a booklet published by the holders of the present patent with the title "RWR-1 Radioactive Waste Réduction", which was available in October 1975 from a trade conference held in Switzerland, a device was proposed in which after the combustion - and an afterburner calcination furnace was required. (The booklet did not contain any of the fluid bed details that are essential to the present invention). Accordingly, the invention aims at avoiding a separate afterburner, taking into account the necessary control of certain process parameters.

The object of the invention is to avoid the disadvantages described above, and to provide a method of the type mentioned at the beginning, in which the volume of the waste is smaller compared to previously known methods and the method of the chemical composition of the liquid waste and the concentration the solid matter in the waste liquid is largely independent. A method for solving this problem is characterized in that a combustion and calcination furnace with a fluid bed is provided, the bed material of which is resistant to oxidation, sintering and attack by chemicals at least up to 1000 ° C; that combustion conditions 65 are created in the furnace; that the waste is fed to the fluidized bed area of the furnace; supplying oxygen-containing gas to the furnace to maintain combustion conditions; that the gas enters the furnace at a

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4th

speed is supplied, which is sufficient to explain the bed material part with reference to the drawing. This shows a schematic chen in the form of flowing particles to keep; that the waste diagram is burned or calcined with successive steps of the description; that a gas flow to the furnace NEN embodiment of the method.

is removed and fed to a dry cyclone, in which a process for processing waste from lower chemical material particles will be separated from the gas stream; that 5 radioactivity is described. It goes without saying that other solid particles can be removed from the dry cyclone and processed into a waste material.

container are fed; that a gas stream from the dryer. In the drawing, a feed device comprises the container cyclone and is fed to a cooling tank; ter 1,3,4 and 6, a combustion and calcination device that a liquid is fed to the cooling tank, with the use of the furnace 9 and an exhaust gas cleaning device the determination to cool the particles contained in the gas stream and 10 containers 10.12 , 13, 14, 15, 16, 17, 18, 19 and 21.

to wet; that liquid particles are removed from the cooling tank If desired, the waste can be pretreated before it is introduced into and fed to at least one scrubbing solution tank. Really large,

will; that a gas stream is taken from the cooling tank and the non-combustible solids, e.g. Tools, pipes, etc.

water is supplied to a venturi scrubber; that the venturi can be separated in one sorting process. If necessary

Scrubber liquid is supplied, with the provision that 15 agile explosive materials can be supplied by conventional

to wet particles remaining in the gas stream and remove a conode.

cause water vapor condensation; that the Venturi feed device shown in the drawing, the Skrabber a gas stream and wet particles and which - leads to the combustion and calcination furnace 9, for this se a wet cyclone; that three different types of waste liquid particles are removed from the wet cyclone and this reduces the aforementioned. These include a scrubbing solution tank at least due to low radioactivity; that contaminated, combustible waste, spent resins and sludges gas stream taken from the wet cyclone and a condenser as well as liquid waste. Of course, this is a supply-in which water vapor is condensed; direction just one example of an infinite variety of to-that a gas stream and condensed liquid particles from the feeders that could be used are taken out of the condenser and fed to a dehumidifier depending on the particular waste being processed; that liquid particles are removed from the dehumidifier and from the fact whether the system is already equipped with a feed and said at least one washer solution tank.

be led; that a gas stream is taken from the dehumidifier when processing combustible waste, it can be supplied as and a warmer to make the temperature of the desirably the sizes of the individual particles

Increase gas flow and reduce the remaining liquid droplet 30, for example by shredding, so that they

vaporize; and that the gas stream can be transported through a filter to the incinerator,

The maximum size of the particles must be smaller than the internal

Gas flow are removed, and then be through a diameter of the process container and is when pneumatic

sorption container, in which feed is used from the gas stream, see through the flow rate

be removed. 35 of the feed gas limited. In addition, the partial

The tank or tanks for the scrubbing solution will be small enough to allow a migration of the particles mainly as a collecting container in which to the bottom of the furnace 9, in front of which the combustion takes place.

a reserve amount of the scrubber solution is kept. The forest has to be practically excluded.

If necessary, the shear solution can be taken from the tank or from the

Tanks are removed in order to supply the cooling tank and the Venturi 40 with the inner diameter of the transport pipe, the upper scrubber with liquid and / or the scrubbing limit of the particle sizes. The preferred, largest solution to be returned to the waste liquid system of the system the particle is in the mentioned commercial type. In this way, radioactive halogens that are less than 5.08 mm (2 ") in length. If a reduction in the partial scrubbing solution tank is advised long enough in the treatment size, this can be done by means of a in the feeding device are held in order to allow their disintegration by means of dioactive elements which are accommodated in non-funnel hopper 6. Preferably, the laundry will be carried out if such a cutting device is provided in the storage solution tank with a means for treating the halogen funnel 6 , the cutting process can be carried out at the same time. take place at the same time as the hopper loading process, with

The method according to the invention has the following advantages. effort and minimal radiation dose. It is desirable

The volume of waste, whether liquid or solid, radioactive or so worth seeing that the storage funnel is large enough to make it non-radioactive, is reduced considerably. There is sufficient supply of shredded

can concentrated chemical waste, filter sludge, for tem waste can be stored in the funnel. The memory-

Resin beads, scraps and other funnels 6 used up by ion exchange should preferably be insulated from the atmosphere,

Similar materials are processed. All liquid and to prevent the risk of radioactive contamination of the environment

combustible solid wastes can bow to anhydrous, granular 55. Include low radioactivity waste materials

Solids are reduced. Protective clothing made of fabric, gloves, scraps, artificial

The process is largely independent of the chemicals, respiratory filters made of paper, wood and others.

see composition of waste material. The combustible waste can therefore be burned and calcined.

the most diverse waste materials in a single plant low-pass furnace 9, e.g. can be processed via a screw conveyor 31 and one. Highly diluted waste flows can also be fed to line 32. Of course, liquids, as well as very solid waste materials can be used for processing as well as other subsidies. The furnace 9 is coming at the device. The same fluid bed, maintained at different pressures less than ambient pressure,

Operating conditions for calcination and incineration and the waste is fed to such a location of the furnace 9,

be applied. No afterburner is required. Any where the pressure is less than the ambient pressure.

necessary afterburning takes place immediately in the combustion. 65 This avoids the possibility of leakage of radioactive contaminants.

and calcination furnace, and not after this, or prevention of the radioactive material of the system. A suitable pressure after a subsequent treatment step in a cyclone, which pressure is maintained in the furnace 9 ......

Below, embodiments of the invention can be between 10 and 35 mmHg, preferably 28 mmHg

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Vacuum (absolute). If indicated, the screw conveyor may have an isolating valve, not shown, intended to form an airtight seal when the feeder is out of operation. The cutting device and the storage hopper 6, as well as the associated feed lines, are preferably made of carbon steel.

The flow rates of the waste feeders are mainly of size, i.e. depending on the volume of the furnace 9. For many applications, the holding volume of the furnace 9 is advantageously chosen so that between 200 and 90.9 and 136.4 kg / hour (300 pounds / hour) combustible, solid waste can be processed. Resin and sludge are introduced into the tank 3 via the line 33 and collected therein. Typical resin and sludge waste contain ion exchange resin beads, powdery resin materials as filter auxiliary layer materials (eg «Powdex»), non-resinous filter auxiliary layer materials (e.g. «Solka-floc», diatomaceous earth, etc.) and water in different amounts. Resin and sludge are fed via line 34 into a mixing and dewatering tank 4. The material is fed from the tank 4 to a measuring device with a pump 5, whereupon it is injected into the furnace 9 via the line 35. For many applications, the holding volume of the furnace 9 is advantageously chosen so that between 45.5 and 79.5 kg / hour (100 to 175 pounds / hour) resin and sludge waste can be processed. In the mixing and dewatering tank 4, the waste is mechanically stirred, which helps prevent overloading, compression and adherence to the tank walls. After dewatering, the liquid porridge preferably only contains enough water that it can still be pumped. Such chyme typically contains between 70 and 80 weight percent solids.

The water originating from the drainage can be returned to the slurry pump system as fill water, or can be pumped by the pump 5 via the line 36 into the storage tank 1 for waste liquid. The pump 5 can be a mechanical displacement pump, which at the same time measures the amount of waste injected into the incinerator. If desired, the device can be operated continuously since the drainage, measurement and injection are simultaneous operations. If indicated, the waste feed rate can also be controlled automatically.

Resin and sludge are introduced into the furnace 9 at a point where the pressure is below the atmospheric pressure. Generally, this pressure is 0.07 to 0.14 kg / cm 2 (1 to 2 psi) below atmospheric pressure. The resin and slurry mixing and dewatering device is preferably constructed of stainless steel.

Waste liquid is introduced into the tank 1 intended for this via line 37. For many applications, the holding volume of the furnace 9 is selected so that between 136.4 and 227.3 liters / hour (30 to 50 gallons / hour) of waste liquid can be processed. The waste liquid is fed by pump 2 from tank 1 via line 38 into furnace 9. The injection into the furnace 9 is preferably carried out via atomizing nozzles. The temperature of the waste liquid is preferably high enough to keep the solids in the solution. This temperature should therefore exceed the saturation temperature of the waste solids at the concentration in which they are in the waste liquid. This temperature is usually between 10 ° C (50 ° F) and 93.3 ° C (200 ° F), depending on the amount and type of solids. The result of this is that the precipitation of dissolved solids from the waste stream onto the nozzles and the conveying device is at least delayed and subsequent blockage of the process pipes, the valves, the nozzles etc. is prevented.

Typical waste liquids contain between 50 and 90% water, as well as soluble solids such as sodium sulfate, ammonium sulfate, sodium chloride, boric acid and others. A special waste liquid from an evaporator with forced circulation of a hot water reactor contains about 75% water, 22.9% sodium sulfate, 2% sodium chloride and 0.1% other components. Another waste liquid from an io evaporator with forced circulation of a pressurized water reactor contains about 73.4% water, 14.9% sodium sulfate, 9.6% ammonium sulfate, 2% sodium chloride and 0.1% other ingredients. A waste liquid containing boric acid from a forced circulation evaporator contains about 87.9% 15 water, 12% boric acid and other components. The above percentages are to be understood as percentages by weight.

It is understandable that since different processing temperatures are required for different types of waste, depending on whether calcination or incineration is to be carried out, only one waste stream can be introduced into the furnace 9 at a time and processed in it. So if one of the streams is introduced into the furnace 9, the other two streams are closed by the furnace 9.

According to the invention, it is possible to carry out both a calcination 25 and a combustion in the same furnace under different temperature conditions set accordingly. This is made possible by using a material for the fluid bed which is resistant to oxidation, sintering and attacks by chemicals such as acids 30 and bases, at least up to 1000 ° C. By using such an inert material, problems that were encountered with previous fluid bed incinerators can be eliminated.

With these it was necessary to monitor the system closely to ensure proper operation. The reason for this was that the phenomena explained earlier regarding the particle sizes and the particle size changes were not controlled sufficiently. Fluid bed materials such as Quartz, which do not have the above properties, have not been able to prove themselves in the process according to the invention.

The preferred, inert materials for the fluid bed have the following properties:

45

hardness

Specific weight dry room weight

50 coefficient of thermal expansion

Melting point

High temperature reaction 55 High heat absorption capacity Free of silicose particle size

6.0-9.0 Moh 3.2-3.9

1.60-2.00 g / cm3 (100-125 lbs / ft3) 0.0149 cm / cm / ° C (0.0083 in / in / ° F) 1260-1760 ° C (2300-3200 ° F) Basic

Between 0.5 and 1.5 mm

60

Some examples of fluidized bed materials that can possess all of the properties listed above are chrysolite, olivine, kianite, corundum and aluminum oxide. The most preferred inert fluidized bed materials are the magnesium iron silicates known as Oli-65 vin and chrysolite. A typical olivine material which is suitable as a fluidized bed material in the process according to the invention has the following chemical and physical properties:

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Olivine

hardness

6.5-9.0 Moh

Drying room weight

1.60-2.00 g / cm3

(100-125 lbs / ft3)

specific weight

3.2-3.9

Coefficient of thermal expansion

0.0149 cm / cm / ° C

(0.0083 in / in / ° F)

Apparent heat transfer

Low

Melting point

1260-1760 ° C

(2300 ° F-3200 ° F)

High temperature reaction

Basic

Wettability too

molten metal

Generally, no

Chemical reaction

Basic

Particle size

Between 0.5 and 1.5

Chemical Analysis.

Areas

MgO

45-49%

Si02

39-43%

FeO

6- 8%

Cr203

0.6-0.8%

Ni

0.2-0.3%

ai2o3

0.2-0.8%

Trace elements

0.5%

Mineralogical analysis

Olivine

92-93%

Entatite

5%

Chromite sum

1% 100%

Other properties Constant coefficient of expansion High heat absorption

High thermal conductivity at low temperatures Tough, stable grain (structure)

Insulation ability at high temperatures

The maximum temperature used in the calcination process is mainly limited by the melting point of the solids in the waste. The maximum temperature used for the combustion, however, is mainly determined by economic and practical considerations related to the strength of the construction material of the furnace 9. For the calcination, the temperature is generally between 350 ° C and 550 ° C, but preferably at s400 ° C, for the combustion of resin and sludge between 800 ° C and 1000 ° C, but preferably at 800 ° C, and for Processing of compressible solids between 900 ° C and 1200 ° C, but preferably at 1000 ° C, kept.

A gas, e.g. Air is blown into the bottom part of the furnace 9 via the blower 7 and the line 39 with the purpose of keeping the bed flowing and at the correct height. When air is used as gas, it also provides the oxygen necessary for combustion. If desired, additional air can also be blown into the furnace 9, above the bed 15, via line 39 with the purpose of bringing about complete combustion. The feed rate of the waste material is chosen with regard to the height of the furnace 9 so that the material remains above the bed during such a period of time that any necessary afterburning takes place before the entrained solid particles are evacuated into the drying cyclone. This makes any afterburner superfluous. A total height of the furnace 9 of about 4.57 m (15 ft) is suitable for processing the aforementioned amounts of material. The bed height, suitable for processing the same amount of material, is between 45.7 and 91.4 cm (18 to 36 inches). Of course, the height of the furnace and / or the bed can be changed in accordance with the material actually to be processed.

30 The heat necessary for the calcination or the combustion and for the preheating of the bed is supplied by combustion, within the bed, of a liquid carbohydrate fuel in a burner not shown in the drawing. The required heat transfer takes place due to the combustion taking place inside the bed. The fuel is fed to the burner by pump 8 via line 40. The incineration and calcining furnace is preferably made of Inconel, titanium, Hastelloy or steel, with a fire-resistant or ceramic coating. A 40 gas stream leaves the furnace 9 via the line 41 in the direction of the drying cyclone 10.

The table below shows some typical operating conditions that apply to the different operating modes of the drying cylinder 45 clone 10 having the dimensions listed:

Performance of the unit

Inlet speed

Inlet line dimensions

(the larger dimension is the vertical)

Inner diameter of the cyclone

49.6 m3 / min (1750 ft3 / min)

15.24 m / sec (50 ft / sec)

15.25 cmX30.48 cm (0.5 ftx 1.0 ft)

60.96 cm (2 ft)

Calcination of waste liquids o2 n2 co2 h2o

Solids total amount temperature pressure

Flow rate

75 kg / h 389 kg / h 107 kg / h 39 kg / h 22.7 kg / h 633 kg / h 375 ° C 0.984 kg / cm2 25.5 m3 / minute

(166 lb / hr) (858 lb / hr) (235 lb / hr) (86 lb / hr) (50 lb / hr) (1395 lb / hr)

Burning resin and filter sludge

Total quantity 479.8 kg / h (1058 lb / hr)

55 temperature 800 ° C

Pressure 0.984 kg / cm2

Flow rate 32.56 m3 / minute

14 lb / in2) (1150 ft3 / min)

Incineration of compactible waste

(14.0 lb / in2) (900 ft3 / min)

Combustion of resin and filter sludge o2

n2

co2 h2o

Solids

15.0 kg / h 328.8 kg / h 71.2 kg / h 63.9 kg / h 0.9 kg / h

(33 lb / hr) (725 lb / hr) (157 lb / hr) (141 lb / nr) (2 lb / hr)

6C-02

n2

co2

h2o

Solids 65 Total temperature pressure

Flow rate

20.0 kg / h 396.4 kg / h 133.3 kg / h 54.4 kg / h 3.6 kg / h 607.7 kg / h 1000 ° C 0.984 kg / cm2 49.56 m3 / minute

(44 lb / hr) (874 lb / hr) (294 lb / hr) (120 lb / hr) (8 lb / hr) (1340 lb / hr)

(14 lb / in2) (1750 ft3 / min)

7

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The decisive dimensions of the drying cyclone are those of the inlet line, which determine the inlet quantity, and the inlet diameter, which determines the flow rates applicable within the drying cyclone and thus the centrifugal forces developed therein. The dry cyclone is designed to remove any solids from the gas stream, preferably more than 82% of the solids contained in the gas stream. The gas flow penetrates the cyclone approximately at the level of its end on one side, so that a circular swirl movement of the gas flow occurs. The solids separated from the gas stream settle at the bottom of the drying cyclone and are fed via line 42 to the collecting container 11. The solid particles are then solidified by conventional methods for later removal, e.g. through burial. At least 82% of the radioactivity of the solid particle material is removed from the dry cyclone together with at least 17% of radioactive halogens.

The swirling movement of the air causes a centrifugal force in the dry cyclone to act on the solid particles, which thus migrate towards the wall. The air velocity is lower due to a boundary layer effect near the wall so that the particles slide down the wall to the solids outlet 42. The gas stream, on the other hand, leaves the drying cyclone 10 at the upper middle of the latter via the line 43 in the direction of the cooling tank 12. The drying cyclone can be constructed from the same materials as the calcining and incineration furnace.

In the cooling tank 12, the gas flow is cooled to approximately 70 ° C. by means of a spray, which is introduced into the cooling tank 12 via the line 44 and injection nozzles (not shown in the drawing). A turbulent gas movement is caused in the cooling tank 12, which causes close contact between the gas flow and the liquid flow. This causes both a cooling of the gas stream and a wetting of the majority of the solid particles remaining in the gas stream. The larger drops of liquid fall to the bottom of the cooling tank 12 and are returned via line 45 to scrubbing solution tank 21, taking the wetted, solid particles with them. The smaller liquid drops are swept out of the cooling tank 12 with the gas stream via the line 47. The cooling tank and scrubbing solution tank are preferably made of 300 series stainless steel, or of Inconel, Hastelloy or steel, with a glass or Teflon coating.

The liquid particles are mixed in the washer solution tank 21 with water, and preferably a halogen scavenger (i.e., with a material capable of trapping halogens). Resorzine acts as a halogen scavenger for iodine,

Cooling tank

Sodium thiosulfate, sodium sulfate, cyclohexylamine, potassium ferrocyanide, potassium carbonate and potassium hydroxide. The halogen scavenger and other pH changing materials can be introduced via line 46 into the scrubber solution tank, usually as an aqueous solution. The amount of halogen scavenger used in the scrubber solution is usually between 10 and 100 ppm (parts per million).

The gas stream leaves the cooling tank via line 47 in the direction of the venturi scrubber 13. The scrubber solution is sprayed into the gas stream via line 48 at the neck of the venturi scrubber. It is desirable to effect saturation and entrainment of water in the venturi scrubber 13 in order to facilitate the wetting of the particles which are not wetted in the cooling tank 12. The gas stream leaving the furnace 9 contains 15 amounts of water vapor in the order of 9 to 17%. When the gas stream was passed through the cooling tank 12, it also picked up water vapor in addition to the entrained water. In the Venturi scrubber, the gas stream is essentially saturated with water vapor. Saturation is ensured by injecting additional scrubber solution via line 48 into the gas stream as it passes through the neck of the venturi scrubber 13. When the gas flow passes through the neck of the 13, ensured. As the gas flow passes through the neck of the venturi scrubber 13, the pressure drops, which in turn increases the amount of moisture that the gas can retain in the form of steam. So there is evaporation. As soon as the gas stream reaches the diverging part of the Venturi scrubber, its speed drops and its pressure 30 increases, so that water vapor condensation takes place. This condensation has the effect that the existing droplets become larger and that new droplets form on non-wetted particles, which act as condensation nuclei.

35 It can be seen that the main purpose of the cooling tank and the venturi scrubber is to cool the exhaust gas in order to wet as many of the solid particles as possible and thus facilitate their removal. It is easier to remove a drop of liquid than a much smaller, solid particle. The liquid particles are then removed, whether they consist of detachable material that has gone into solution in the drop or of insoluble material that has remained in the drop as a wetted, solid particle. In both cases the solid particle moves together with the liquid droplet. The Venturi scrubber can be built from the same materials as the cooling tank. The table below lists some typical process parameters related to a cooling tank and a Venturi scrubber with the specified dimensions.

50

Venturi scrubbers

Gas flow

Inlet temperature outlet temperature inlet pressure Ap

Washer solution dimensions

25.5-51.0 m3 / min (900-1800 ft3 / min) 400-1000 ° C 60-75 ° C

0.96 kg / cm2 (13.7 psia) negligible 22.7 1 / min (5 gpm) 1.22 diam. X 2.44 m (4 ft dia X 8 ft)

14.2-25.5 m3 / min (500-900 ft3 / min) 60-75 ° C 45-65 ° C

0.96 kg / cm2 (13.7 psia) 0.14 kg / cm2 (2 psi) 50.01 / min (11 gpm) 15.24 cm diam. (6 "dia) 81.28 cm length (32 in) 6.86 cm neck (2.7 in)

A gas stream containing liquid particles is withdrawn from the Venturi scrubber via line 49 and introduced into the wet cyclone 14 near its upper end. The liquid runs down in the wet cyclone 14 on its side,

to a discharge located in its bottom. From here, the liquid is discharged via the line 50 from the cyclone 14 in the direction of the scrubbing solution tank 21.

Typical operating parameters for the wet cyclone 14 are

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listed below. Operating temperature: 45-65 ° C; The gas flow leaves the filter 17 via line 57 and leaving pressure: about 0.84 kg / cm 2 (12 psia); A p: about 0.04 kg / cm 2 is fed into a halogen adsorbent 18 which is halo- (0.5 psia); Gas flow: 11.3-21.2 m3 / min (400-750 ft3 / min). genes removed by adsorption. The halogen atoms are

A gas stream is withdrawn from the top of the wet cyclone 14 via a chemical bond with the adsorbent onto the line 51 and held to a condenser 15 against the surface of the material and decomposes into one in which the gas stream is cooled. The capacitor stable atom. Radioactive iodine breaks down e.g. to stable Xe

can be a jacket or a tube heat exchanger. In the non. As adsorbent materials e.g. Adsorption coal

Capacitor increases the size of the liquid particles up to or through solids impregnated with silver, such as silver silicates, to a point where a substantial amount of silver or silver zeolite is used.

Gas flow contained water due to gravitational or 10 The temperature of the gas flow as it passes

Impulse effects is removed. When the distance through the filter 17 is between 40 and 55 ° C, whereas the gravitational mechanism is accomplished, the throughput of the same gas flow is between 1590 and 25001 /

Drops so big that they fall to the bottom of the container. Min (250 to 550 ft3 / min). Following the iodine adsorber

If, on the other hand, the removal takes place by means of a pulse mechanism, the gas flow takes place via line 58 to a second filter, the drops are not large enough to be led out of the 15. The combination of the two filters 17 and 19 with this

Gas flow falling out; however, they are large enough for this that iodine adsorber 18 is commercially available and does not have to be described in more detail if the direction of the gas flow suddenly changes. The filter over the line

Droplets on the wall or on another solid material leaving the gas flow 59 have been released to a sufficient extent.

that caused the change of direction. is concerned that the amounts of radioactive material contained in the gas

Typical operating parameters for the capacitor 15 are 20 rials significantly below the level which, according to the

the following. Gas throughput: 11.3-22.6 m3 / min (400 permit to operate the plant is allowed and can

800 ft3 / min); Coolant flow rate: 22.7-90.91 / min (5- accordingly by means of a pump 20 and a line 60 in the

20 gpm); Inlet temperature: 45-65 ° C; AT: 10-30 ° C; Inlet atmosphere.

pressure: 0.81 kg / cm2 (11.5 psia); and Ap: 0.14 kg / cm2 (2psia). As mentioned earlier, the washer solution tank 21

The gas stream and liquid drops leave the 25 through line 46 to introduce a halogen scavenger

Condenser via line 52 towards the dehumidifier to keep the halogens in the form of ions in the solution,

16. This removes the liquid particles by means of the impulse so that they break down into a stable, non-radioactive "daughter".

effect. The gas flow is len through a woven fiber. If desired, a filter can also be passed in line 61, between the two filters, which can be seen quickly and frequently by the scrubbing tank 21 and the pump 23

Changes in direction of the gas causes. Because the liquid 30 22 are turned on to remove solid particles. However, droplets are so large that the gas particles become as quickly as possible, which then becomes a scrubber solution with a heat exchanger

To make a curve, they collide with the filter fibers. 24 supplied, in which it is cooled sufficiently so that a

The liquid drops then run along the fiber to the wall part of it via the line 62 as spray liquid that of the dehumidifier 16, and from there to the outlet and to the cooling tank 12 and the Venturi scrubber 13 are returned.

53, which can drop the liquid to the washer solution tank 21 35. The rest of the scrubber solution can then be recycled. Line 63 can be returned to the storage tank 1. Current

The gas stream leaves the dehumidifier 16 in the vicinity of the heat exchanger 24 downstream, the temperature of its upper end via the line 54 in the direction of a heat, typically about 30 ° C. The throughput of the cooling tank 12

mers 55, which brings the gas flow to a temperature of 40 and the Venturi scrubber 13 led scrubber solution

55 ° C warms up. The warmer has the function, the relative 40 typically carries about 68.2 l / min (15 gpm), and that

To control the humidity of the gas stream with the purpose of returning the scrubber solution to the scrubber solution tank

Filter 17 of about 45.51 / min (10 gpm) due to moisture overload.

To protect constipation. From the warmer 55, the gas flow is conducted via line 56 to the filter 17, in which fixed

Particles that have not been wetted or that are then formed 45 The invention makes it possible to use dry, compacted

if the droplets not removed in the dehumidifier in the solids increase the volume by a factor of at least

Warmer have evaporated to be captured. The filter is best 80, with used resin materials by at least 18, with stands from a medium with very small openings, and the concentrated liquids through at least 8 and with filter

Particles are removed by impact. reduce sludge by at least 5.

C.

1 sheet of drawings

Claims (10)

637 751 (1.60-2.00 g / cm3 (100-125 lbs / ft3) 0.0149 cm / cm / ° C (0.0083 in / in / ° F) 1260-1760 ° C (2300-3200 ° F ) Basic between 0.5 and 1.5 mm 1. A method for treating waste, characterized in that A) that a combustion and calcination furnace (9) is provided with a fluid bed, the bed material of which is resistant to oxidation, sintering and attack by chemicals at least up to 1000 ° C; B) that combustion conditions are created in the furnace (9); C) that the waste is fed to the fluidized bed area of the furnace (9); D) that the furnace (9) is supplied with oxygen-containing gas so that combustion conditions are maintained; E) the gas is supplied to the furnace (9) at a rate sufficient to keep the bed material particles in the form of flowing particles; F) that the waste is burned or calcined; G) that a gas stream is removed from the furnace (9) and fed to a drying cyclone (10) in which material particles are separated from the gas stream; H) that solid particles are removed from the drying cyclone (10) and fed to a storage container (11); I) that a gas stream is removed from the drying cyclone (10) and fed to a cooling tank (12), J) that a liquid is supplied to the cooling tank (12), with the determination of cooling and wetting the particles contained in the gas stream; K) that liquid particles are removed from the cooling tank (12) and these are fed to at least one scrubbing solution tank (21); L) that a gas stream is removed from the cooling tank (12) and fed to a venturi scrubber (13); M) that the Venturi scrubber (13) is supplied with liquid, with the determination of wetting the particles remaining in the gas stream and causing a condensation of water vapor; N) that a gas stream and wet particles are removed from the Venturi scrubber (13) and these are fed to a wet cyclone (14); O) that liquid particles are removed from the wet cyclone (14) and these are fed to said at least one scrubbing solution tank (21); P) that a gas stream is removed from the wet cyclone (14) and fed to a condenser (15) in which water vapor is condensed; Q) that a gas stream and condensed liquid particles are removed from the condenser (15) and fed to a dehumidifier (16); R) that liquid particles are removed from the dehumidifier (16) and fed to said at least one scrubbing solution tank (21); S) that a gas stream is removed from the dehumidifier (16) and fed to a warmer (55) in order to raise the temperature of the gas stream and to evaporate the remaining liquid drops; T) that the gas stream is passed through a filter (17), the remaining solid particles being removed from the gas stream, and then through an absorption container (18) in which halogen gases are removed from the gas stream. 2. The method according to claim 1, characterized in that olivine is provided as bed material. 2nd PATENT CLAIMS 3. The method according to claim 2, characterized in that the olivine has a particle size between 0.5 and 1.5 mm. 4. The method according to claim 1, characterized in that the calcining process at a temperature of about 400 ° C is carried out. 5. The method according to claim 1, characterized in that the combustion process is carried out at a temperature of about 1000 ° C. 6.0-9.0 Moh 3.2-3.9 6. The method according to claim 1, characterized in that the cooling tank (12) from said at least one washer solution tank (21) is supplied with liquid. 7. The method according to claim 1, characterized in that the Venturi scrubber (13) from said at least one washer solution tank (21) is derived from liquid io leads. 8. The method according to claim 1, characterized in that a bed material is used with the following properties: 15 Hardness Specific weight Dry room weight Coefficient of thermal expansion 20th Melting point High temperature reaction High heat absorption capacity 25 Free of silicose particle size 9. The method according to claim 8, characterized in that the bed material is selected from a group that Chry- 30 solit, olivine, kyanite, corundum, aluminum oxide and mixtures of these contains. 10. Application of the method according to claim 1 for the treatment of radioactive waste.