CN106847358A - A kind of supercritical water oxidation processes the device and method of Radioactive myocardial damage - Google Patents

Abstract

The invention discloses a device and method for supercritical water oxidation treatment of radioactive organic waste liquid. The device integrates a high-pressure liquid pump, a high-pressure gas pump, a supercritical water oxidation kettle, a heating system (tube furnace), a check valve, a back The pressure valve and the radioactive operation glove box are built into a supercritical water oxidation device, which realizes the oxidation of organic waste liquid by means of continuous operation, and converts radioactive organic waste liquid into radioactive waste water and carbon dioxide quickly and efficiently. Nowadays, many radioactive organic waste liquids that need to be treated in time generally come from nuclear-related units, typically waste engine oil produced by nuclear power plants, "tributyl phosphate (TBP) + diluent" in the process of spent fuel reprocessing, and nuclear medicine Liquid scintillation fluid produced during the process, etc. The invention uses the supercritical water oxidation technology to thoroughly oxidize the organic waste liquid containing radioactive nuclides to completely convert it into carbon dioxide, water and inorganic salts. It becomes ordinary radioactive waste water, which is convenient for treatment and disposal.

Description

A device and method for treating radioactive organic waste liquid by supercritical water oxidation

technical field

The invention relates to the technical field of radioactive organic waste liquid treatment, in particular to a device and method for supercritical water oxidation treatment of radioactive organic waste liquid.

Background technique

The so-called supercritical refers to a special fluid state of matter. When the temperature and pressure of a substance in gas-liquid equilibrium are increased, the thermal expansion causes the density of the liquid to decrease, and the increase in pressure increases the density of the gas phase. When the temperature and pressure reach a certain point, the interface between the gas-liquid two phases disappears and becomes a homogeneous phase system, this point is the critical point. The critical point temperature of water is 647.3K (374.1°C), and the pressure is 22.1MPa. Water beyond the critical point becomes supercritical water. In the supercritical state, the physical and chemical properties of water have undergone tremendous changes, which are different from both liquid water and gaseous water. Chemical reactions can be controlled very conveniently and effectively by adjusting temperature and pressure. Organic matter is soluble in supercritical water, and oxygen, nitrogen, hydrogen, carbon dioxide, etc., which have very low solubility in normal temperature water, are also miscible with it. Inorganic salts have very low solubility and dissociation constants in supercritical water. In addition, the dielectric constant, ion product, heat capacity, and heat transfer coefficient of supercritical water are significantly different from those of gas and liquid.

Supercritical water oxidation uses supercritical water as a reaction medium to oxidize and decompose organic matter, and its process is similar to wet oxidation. In supercritical water, organic matter and oxidant can form a homogeneous phase, which overcomes the material transfer resistance between phases. High temperature and high pressure increase the oxidation rate of organic matter. By controlling the conditions, organic matter can be completely decomposed within a few seconds to a few minutes. . The products are small molecular substances such as carbon dioxide, water, nitrogen and inorganic salts. When the mass fraction of organic matter in the waste liquid exceeds 2%, the oxidation process can realize self-heating.

Features of SCWO technology: 1. Homogeneous reaction. SCWO converts multiple reactions between liquid or solid organic waste and gas phase into homogeneous reactions in supercritical water. Therefore, the reaction rate is fast, and the reactor structure is simple, and the equipment volume is small. 2. High processing efficiency. In the SCWO environment, because it can form a homogeneous phase of oxygen, hydrocarbons, and water system, there is no mass transfer resistance, so the oxidation efficiency is very high, and the removal rate of most organic substances can reach more than 99%. 3. Change the unprocessable organic phase into water phase. Since the reaction is carried out in a closed environment, organic components can be completely oxidized into inorganic components such as carbon dioxide, water, nitrogen and phosphate radicals under appropriate temperature, pressure and certain residence time conditions.

Currently commonly used SCWO equipment and its flow chart are shown in Figure 1.

TBP+ extractant is used in the reprocessing of spent fuel, and its radiolysis products will accumulate with the number of times of use, thereby reducing the extraction performance. Radiolysis products must be removed by washing before TBP can be reused. After multiple reuses of TBP+diluent, it finally becomes medium-level organic waste liquid. This waste liquid is mainly contaminated with uranium, plutonium and splinter elements. The TBP + diluent produced in the spent fuel reprocessing process is an organic waste liquid with high radioactivity. The uranium hydrometallurgy process also produces radioactive waste TBP+ diluent, but the radioactivity is much weaker. In addition, radioactive organic waste liquid also includes lubricating oil and vacuum pump oil in the primary circuit system of nuclear power plants, which will produce liquid scintillation liquid and other mixed waste liquids in nuclear science research.

The flammability of radioactive organic waste liquid makes it suitable for incineration treatment, and obtains a high volume reduction ratio. The products of complete combustion of organic waste liquid are theoretically oxides of various elements, carbon dioxide and water. Incineration treatment is a mature technology widely used in organic waste treatment and is applied in many countries. The products carbon dioxide, water and ash (phosphorus, sulfur and metal oxides) are all easily incorporated into immobilized substrates (such as cement, etc.) to make waste forms suitable for long-term storage or disposal. The disadvantage of the incineration method is that it is difficult to design and process the equipment, the maintenance cost is high, and the safety and public acceptance are low.

In addition to incineration, there are acid digestion, wet oxidation, electrochemical oxidation, photochemical oxidation, alkaline hydrolysis and biodegradation methods to treat radioactive organic waste.

Strictly speaking, SCWO is also a kind of wet oxidation. Due to the special physical and chemical properties of supercritical water, it provides a homogeneous and fast-reacting environment for organic matter and oxides, so that it can rapidly and thoroughly oxidize radioactive organic waste liquid. ,high efficiency.

Contents of the invention

The present invention mainly focuses on using the method of supercritical water oxidation to treat organic wastes such as radioactive waste engine oil. In view of the various defects in the prior art in the treatment of low- and medium-radioactive organic wastes, the purpose of the present invention is to adopt a new method To deal with these wastes, improve the treatment efficiency (at this stage, the treatment efficiency of organic waste template organic matter can reach more than 99%), and prepare for its large-scale treatment of radioactive organic waste.

The technical scheme adopted in the present invention is: a device for supercritical water oxidation treatment of radioactive organic waste liquid, including an oxygen cylinder, a high-pressure air pump, a glove box, a first high-pressure pump, a tube furnace, a heat exchanger, a back pressure valve, a storage A water container, a second high-pressure pump, a waste liquid tank, and an organic waste liquid container, wherein,

The oxygen bottle provides sufficient oxidation source for the whole supercritical water redox process, and the oxygen is injected into the whole system by a high-pressure air pump;

The high-pressure air pump is used to inject oxygen or air into the whole oxidation kettle body;

The glove box provides a closed environment to ensure that the operator does not leak into the environment when handling radioactive waste;

The first high-pressure pump is used to inject organic waste liquid into the oxidation kettle body;

The tube furnace provides the heating and temperature control system of the oxidation kettle to ensure that the oxidation kettle operates within the set temperature range;

The heat exchanger cools the oxidation tank and treats the liquid after the reaction, so as to reach the specified temperature and discharge the entire reaction system;

The back pressure valve controls the reaction system pressure;

The water storage container provides sufficient water source for the second high-pressure pump so that the heat exchanger partly exchanges heat and injects the water source of the reaction system;

The second high-pressure pump is used to inject the required water phase into the oxidation kettle body;

The liquid collected and processed in the waste liquid tank is to be analyzed;

The organic waste liquid container adopts special materials to hold the radioactive organic waste liquid.

Among them, the entire processing process is completed in a relatively isolated glove box, and no radioactive substances will leak during the reaction process.

Wherein, the second high-pressure pump makes full use of the waste heat of the substance oxidized in the oxidation tank during the process of injecting the water phase.

Among them, the back pressure valve can control the entire reaction system to achieve a high pressure of 25MPa to maintain the normal operation of the supercritical reaction of the supercritical oxidation kettle.

Among them, the heat supply of the tube furnace can be as high as 600 degrees Celsius, which provides a reliable guarantee for the temperature of the supercritical reaction.

The present invention also provides a method for supercritical water oxidation treatment of radioactive organic waste liquid, using the above-mentioned device, the steps of the method are as follows:

Step 1. The water phase is pumped into the heat exchanger by the second high-pressure pump, and enters the oxidation kettle after preheating. The first high-pressure pump pumps the organic waste liquid to be treated into the oxidation kettle, and the high-pressure air pump pumps oxygen into the oxidation kettle. In the oxidation kettle;

Step 2. set the reaction initial conditions (higher than the supercritical point) of the relevant oxidation kettle of the required experiment;

Step 3. The organic waste liquid is subjected to SCWO reaction in the oxidation kettle;

Step 4. Exhaust gas (CO ₂ produced) is discharged into the glove box, filtered, and discharged into the main chimney of the factory after being qualified;

Step 5. The waste water generated in the whole process is low-level radioactive waste liquid, which should be disposed or recycled.

The advantage of the present invention compared with prior art is:

(1) Compared with traditional processing equipment, the present invention has a simple device structure, a small footprint, and a compact structure, which is convenient for application in related nuclear processing plants;

(2), the final product produced by the organic waste that the present invention handles is water and carbon dioxide, does not produce secondary pollution waste;

(3) The efficiency of the present invention for treating organic waste is extremely high, and the decomposition efficiency of many organic matter can be as high as 99%.

Description of drawings

Fig. 1 is a schematic diagram of SCWO equipment and its flow chart in the prior art;

Fig. 2 is a schematic diagram of a device for supercritical water oxidation treatment of radioactive organic waste liquid according to the present invention, wherein 1 is an oxygen cylinder, 2 is a high-pressure air pump, 3 is a glove box, 4 is a first high-pressure pump, and 5 is a tube furnace. 6 is a heat exchanger, 7 is a back pressure valve, 8 is a water storage container, 9 is a second high-pressure pump, 10 is a waste liquid tank, and 11 is an organic waste liquid container;

Figure 3 is a schematic diagram of the shape of the heat exchanger.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The main steps of using supercritical water oxidation to treat radioactive organic waste are as follows:

Step (1), configure the required oxygen source (hydrogen peroxide, high-purity oxygen or O ₃ , etc.), in line with the required oxygen mass fraction ratio in the process of corresponding oxidation of organic matter;

Step (2), carry out relevant treatment on the organic waste (to meet the normal injection conditions of the high-pressure pump), this step will be different according to the different treatment methods of the treated objects, but the ultimate purpose is to allow the normal injection of organic matter;

Step (3), according to the residence time t required for each reaction, and the relevant reactor volume and oxygen mass fraction ratio, calculate the pump speed v under corresponding conditions;

Step (4), start to adjust the speed of the high-pressure pump, inject oxygen and organic matter respectively, preheat to the specified temperature through the preheater and enter the reaction reactor (temperature T is 400-600 degrees Celsius), and the core pressure of the reactor is between 24-30Mpa ;

Step (5), each reactant has optimized treatment conditions. After the treatment is completed, the temperature is lowered first, and then the pressure is reduced through the back pressure valve (back pressure valve), and finally reaches normal pressure;

In step (6), liquid phase and gas phase products are collected respectively to analyze components and removal efficiency, so as to further optimize the reaction.

The invention proposes a radioactive organic waste treatment device that adopts supercritical oxidation, has a radiation protection design, and operates continuously, and is suitable for treating radioactive organic waste liquid. The schematic diagram of the equipment is shown in Figure 2. A supercritical water oxidation treatment device for radioactive organic waste liquid of the present invention includes an oxygen cylinder 1, a high-pressure air pump 2, a glove box 3, a first high-pressure pump 4, a tube furnace 5, a heat exchange Device 6, back pressure valve 7, water storage container 8, second high pressure pump 9, waste liquid tank 10 and organic waste liquid container 11, wherein,

1. The oxygen cylinder 1 is connected to the injection end of the high-pressure air pump 2 through a pipeline, and the outlet of the high-pressure air pump 2 is connected to the mixing port of the oxidation kettle through a pipeline;

2. The water storage container 8 is connected to the injection end of the second high-pressure pump 9 through a pipeline, and the outlet end of the second high-pressure pump is connected to the heat exchanger 6 through a pipeline to take away the residual heat of the reacted liquid and simultaneously connected to the mixing port of the oxidation kettle through a pipeline;

3. Oxygen cylinder 1, high-pressure air pump 2, water storage container 8, second high-pressure pump 9, waste liquid tank 10 are placed outside the glove box 3, first high-pressure pump 4, tube furnace 5, heat exchanger 6, back pressure The valve 7 and the organic waste liquid container 11 are placed in the glove box 3;

4. The organic waste liquid container 11 is connected to the inlet of the first high-pressure pump 4 through a pipeline, and the outlet of the first high-pressure pump 4 is also connected to the mixing port of the oxidation kettle through a pipeline;

5. After passing through the mixing port of the oxidation kettle, it reacts completely under the heating action of the tube furnace 5, and then passes through the pipeline to connect the heat exchanger 6 to cool down for easy discharge, and then connects to the back pressure valve 7 through the pipeline to depressurize, and the liquid is collected into the waste liquid tank Within 10, the gas CO ₂ is expelled by itself.

In addition, the organic waste liquid container 11 is made of materials specially used for containing radioactive substances, and is specially used for containing radioactive substances.

Wherein, a) the first high-pressure pump 3 is used for adding organic waste liquid into the oxidation kettle. b) The second high-pressure pump 9 is used to add water or hydrogen peroxide and other water-phase substances to the oxidation kettle. c) High-pressure air pump 2 for adding air or oxygen to the oxidation kettle. d) Oxidation tank, where the added organic waste liquid, water and oxygen are reacted. Made of corrosion-resistant titanium or Monel alloy, the pressure resistance is above 50MPa, and the design and processing comply with the pressure vessel standard. e) The tube furnace 5 is equipped with electric heating rods or thermal resistors that are easy to replace, can be heated to above 500°C, and is covered with insulation materials. f) The back pressure valve 7 controls the pressure of the oxidation system. g) The liquid circuit system adopts corrosion-resistant alloy pipes (design and processing comply with pressure vessel standards). h) The radiation protection system is mainly a sealed box room, and the oxidation kettle, the first high-pressure pump 4, and the back pressure valve 7 are installed in the glove box.

The supercritical water oxidation treatment device for radioactive organic waste is also characterized by:

1) The first high-pressure pump 4: used to add organic waste liquid into the oxidation kettle;

2) The second high-pressure pump 9: used to add water or hydrogen peroxide and other water-phase substances to the oxidation kettle;

3) High-pressure air pump 2; used to add air or oxygen to the oxidation kettle;

4) Oxidation kettle: The added organic waste liquid, water and oxygen react in it. It is made of corrosion-resistant titanium or Monel alloy, with a pressure resistance of more than 50MPa;

5) Back pressure valve 7: control the pressure of the oxidation system;

6) Liquid system: corrosion-resistant alloy tubes are used;

7) Radiation protection system: mainly a glove box, the oxidation kettle, the first high-pressure pump 4, and the back pressure valve 7 are installed in the glove box;

8) Tube furnace 5: with a heating rod, which can be heated to above 500°C, and is covered with insulation materials.

The method of using the supercritical water oxidation treatment device for radioactive organic waste liquid is as follows:

1. The second high-pressure pump 9 adds water to the heat exchanger, and adds it to the oxidation kettle after preheating. The first high-pressure pump 4 adds organic waste liquid to the oxidation kettle, and the high-pressure air pump 2 adds oxygen to the oxidation kettle;

2. Adjust the conditions of the oxidation kettle to be above the critical point of water, the temperature is higher than 647.3K, and the pressure is higher than 30MPa;

3. The reaction of SCWO to oxidize radioactive organic waste will take place in the oxidation kettle;

4. Exhaust gas (CO ₂ produced) is discharged into the glove box, filtered, and discharged into the main chimney of the factory after passing the test;

5. The waste water generated in the whole process is low-level radioactive waste, which should be disposed or recycled.

The embodiment is introduced as follows:

A device for treating radioactive organic waste liquid by supercritical water oxidation, comprising:

1. The oxidation kettle is made of Hastelloy alloy, with a length of 60cm, an inner diameter of Φ5cm, and an outer diameter of Φ9cm.

2. Weld 4 electric heating rods with a power of 500W each, outsource 2cm heat-insulating asbestos, and then use 1mm thick stainless steel to make a sleeve seal.

3. The liquid pump is a high-pressure liquid chromatography pump with a maximum flow rate of 20mL/min, the oxygen pump is a high-pressure oxygen pump with a flow rate of 100mL/min, and the liquid pipe is a Φ8mm Hastelloy tube. The liquid path between the pump and the oxidation tank is connected with a one-way valve.

4. The heat exchanger is made of stainless steel. The shape is shown in Figure 3. The outer tube is Φ16mm, the inner tube is Φ8mm Hastelloy tube, and the total length is 50cm. The outer tube is connected to the water pump, and the inner tube is connected to the oxidation kettle.

5. The pressure limiting valve is a stainless steel digital display pressure limiting valve with a range of 50MPa.

6. The glove box is a standard glove box, and the check valve, organic phase feed pump, oxidation kettle, heat exchanger and pressure limiting valve are reasonably arranged in the glove box.

7. The water phase is added to the pump, the oxygen pump, and the oxygen cylinder are placed outside the glove box.

The method for using a device for treating radioactive organic waste liquid by supercritical water oxidation comprises the following steps:

1. Radioactive organic waste liquid is 30% TBP/kerosene, 99% industrial oxygen is the oxidant, and deionized water is the water phase.

2. The temperature of the oxidation kettle is set to 750K, and the pressure value of the digital display pressure limiting valve is preset to 30MPa.

3. Start the water phase adding pump to add deionized water, the feeding speed is 5mL/min.

4. After the temperature of the oxidation kettle reaches 750K, start the oxygen supply pump, the oxygen is 40mL/min (30MPa). Then start the organic phase feeding pump at a feed rate of 5 mL/min.

5. After the reaction stops, flush the pipeline with 500mL, 0.1mol/L dilute nitric acid.

Experimental results

1. Process 30% TBP/kerosene 2.7L in total.

2. No organic carbon was detected in wastewater by TOC analyzer, and the TBP-diluent was destroyed below the detection limit (10 ^-5 mol/L).

3. Generate about 5.2L of waste water.

4. By measuring the TOC content, it can be fully proved that the organic matter has been completely decomposed into waste water and carbon dioxide.

Claims (6)

1. A device for supercritical water oxidation treatment of radioactive organic waste liquid, characterized in that: comprising an oxygen cylinder (1), a high-pressure air pump (2), a glove box (3), a first high-pressure pump (4), a tube furnace (5), heat exchanger (6), back pressure valve (7), water storage container (8), second high pressure pump (9), waste liquid tank (10) and organic waste liquid container (11), wherein, The oxygen cylinder (1) provides sufficient oxidation source for the entire supercritical water redox process, and the oxygen is injected into the entire system by the high-pressure air pump (2); The high-pressure air pump (2) is used to inject oxygen or air into the whole oxidation kettle body; The glove box (3) provides a closed environment to ensure that the operator does not leak into the environment when handling the radioactive waste liquid; The first high-pressure pump (4) is used to inject organic waste liquid into the oxidation still body; The tube furnace (5) provides the heating and temperature control system of the oxidation kettle to ensure that the oxidation kettle operates within the set temperature range; The heat exchanger (6) cools the oxidation tank and treats the liquid after the reaction, so as to reach the specified temperature and discharge the entire reaction system; A back pressure valve (7) controls the reaction system pressure; The water storage container (8) provides a sufficient water source for the second high-pressure pump (9) so that the heat exchanger is partially heat-exchanged and injected into the water source of the reaction system; The second high-pressure pump (9) is used to inject the required water phase into the oxidation still body; The waste liquid tank (10) collects and processes the liquid to be analyzed; The organic waste liquid container (11) adopts special materials to contain radioactive organic waste liquid. 2. A device for supercritical water oxidation treatment of radioactive organic waste liquid according to claim 1, characterized in that: the entire treatment process is completely completed in a relatively isolated glove box (3), without any radioactive substances leaked during the reaction. 3. A kind of device of supercritical water oxidation treatment radioactive organic waste liquid according to claim 1, it is characterized in that: the second high-pressure pump (9) has fully utilized the oxidation tank oxidation treatment out material in the injection water phase process waste heat. 4. A kind of device of supercritical water oxidation treatment radioactive organic waste liquid according to claim 1, it is characterized in that: back pressure valve (7) can control the high pressure of whole reaction system up to 25MPa, maintain the ultra-high pressure of supercritical oxidation still. Normal operation of critical reactions. 5. A device for supercritical water oxidation treatment of radioactive organic waste liquid according to claim 1, characterized in that: the heating of the tube furnace (5) can be as high as 600 degrees Celsius, which provides a reliable guarantee for the temperature of the supercritical reaction. 6. A method for supercritical water oxidation treatment of radioactive organic waste liquid, utilizing the device according to claim 1, characterized in that: the method steps are as follows: Step 1. The water phase is pumped into the heat exchanger by the second high-pressure pump, and enters the oxidation kettle after preheating. The first high-pressure pump pumps the organic waste liquid to be treated into the oxidation kettle, and the high-pressure air pump pumps oxygen into the oxidation kettle. In the oxidation kettle; Step 2. Set the reaction initial conditions of the relevant oxidation kettle for the required experiment; Step 3. The organic waste liquid is subjected to SCWO reaction in the oxidation kettle; Step 4. Exhaust gas (CO ₂ produced) is discharged into the glove box, filtered, and discharged into the main chimney of the factory after being qualified; Step 5. The waste water generated in the whole process is low-level radioactive waste liquid, which should be disposed or recycled.