CN108305700A - A kind of startup method of radwaste cold crucible curing process - Google Patents

Abstract

The invention belongs to the technical field of radioactive waste treatment, and relates to a starting method for cold crucible solidification treatment of radioactive waste. The method comprises the following steps: (1) adding starting glass in the cold crucible, and then placing the starting material titanium wire on the starting glass; (2) starting the power supply, selecting a suitable power to start heating the titanium wire and gradually increasing the power, so that the titanium wire is gradually heated to combustion; (3) feed oxygen into the cold crucible to accelerate the combustion of the titanium wire until it burns out; (4) stop feeding oxygen into the cold crucible, keep the power of the power supply, and make the cold crucible The glass in the crucible is continuously melted until it is completely melted. Utilizing the method of the present invention, when used for the start-up of cold crucible solidification treatment of radioactive waste, the starting material placement method is simple, the start-up speed is high, no radioactive leakage, and no influence on the quality of solidified products, and the method is not only suitable for cold crucible solidification Routine start-up of treatment, also applies to emergency start-up of cold crucible solidification treatment.

Description

A start-up method for radioactive waste cold crucible solidification treatment

technical field

The invention belongs to the technical field of radioactive waste treatment, and relates to a starting method for cold crucible solidification treatment of radioactive waste.

Background technique

Cold crucible vitrification technology is a glass melting technology transplanted from the industrial high-temperature metallurgy industry. It uses high-frequency induction heating. The furnace body made of ordinary stainless steel is a water-cooled jacket and a high-frequency induction coil. Through high-frequency (105 -106Hz) induction heating to melt the glass. Since the cooling water passes through the water-cooling jacket continuously during the operation of the furnace body, a thin layer of solid glass shell is formed near the jacket to protect the crucible wall from corrosion by the high-temperature molten body, so the life of the furnace can be very long. At the same time, because it is not limited by the material of the furnace body, the temperature of the molten body in the furnace can also be higher, up to 2000 ° C or more. Because the cold crucible has the incomparable advantages of these other solidification technologies, it has become an internationally recognized advanced solidification technology for high-level liquid waste treatment, and has a good application prospect (see: Gu Zhongmao, nuclear waste treatment Technology [M], Beijing: Atomic Energy Press, 2009: 369-377; Liu Lijun et al., Analysis on the development of radioactive waste cold crucible vitrification technology, Atomic Energy Science and Technology [J], 2015, 49(4): 589-596; Hu Tanghua, et al. , Application of cold crucible technology in nuclear waste treatment, Nuclear Technology [J], 2001, 24(6): 521-528).

The prerequisite for induction heating of cold crucible is that the substance to be heated must be conductive, while glass is non-conductive at room temperature, and only conductive at high temperature in a molten state. Therefore, the process of heating the glass from room temperature to the molten state is the "starting" process of the cold crucible. When cold crucible solidification treatment technology is used to treat radioactive waste, it is very necessary to establish a start-up technology that is simple, efficient, has no radioactive leakage, and has no impact on the quality of solidified products.

The applicant's prior Chinese patent application with application number 201710177161.1 conducts research on the starting method of the cold crucible, and discloses the starting method of the graphite ring as the starting material of the cold crucible. Although this method has a good start-up effect, it is more suitable for the initial start-up during operation. In case of emergency treatment during operation, this method is often not applicable. However, in the actual production process, there may be equipment failures and a short-term shutdown. If the glass in the furnace is unloaded at this time, the raw materials added may not be completely melted, and the quality of the glass will not meet the requirements; And if the unmelted glass remains in the melting furnace, once the crucible lid is opened to place the graphite ring when restarting next time, radioactive leakage will be caused.

Therefore, it is necessary to study a start-up method for radioactive waste cold crucible solidification treatment that is based on high start-up speed, no radioactive leakage, and no impact on the quality of solidified products. of.

Contents of the invention

The purpose of the present invention is to provide a start-up method for the cold crucible solidification treatment of radioactive waste, so that when it is used for the start-up of the cold crucible solidification treatment of radioactive waste, the starting material placement method is simple, the start-up speed is high, and there is no radioactive leakage. There is no impact on the quality, and this method is not only suitable for the routine start of the cold crucible solidification treatment, but also for the emergency start of the cold crucible solidification treatment.

To achieve this purpose, in a basic embodiment, the present invention provides a method for starting radioactive waste cold crucible solidification treatment, and the method for starting includes the following steps in sequence:

(1) Add starting glass in the described cold crucible, then place the starting material titanium wire on the described starting glass;

(2) Start the power supply, select the appropriate power to start heating the titanium wire and gradually increase the power so that the titanium wire is gradually heated to burn;

(3) Feed oxygen into the cold crucible to accelerate the burning of the titanium wire until it burns out, during which a certain glass melting zone is formed in the cold crucible;

(4) Stop feeding oxygen into the cold crucible, keep the power of the power supply, so that the glass in the cold crucible is continuously melted until completely melted.

In the above-mentioned steps (1), during routine start-up, start-up glass is pre-added in the described cold crucible, and then the start-up material titanium wire is placed on the described start-up glass; There is a certain amount of vitreous body in the original, in order to ensure the starting speed, it is also necessary to add several kilograms of starting glass.

In the above step (3), the titanium wire is completely converted into TiO ₂ after burning. Since TiO ₂ is one of the components of the glass, a small amount of TiO ₂ will not significantly affect the quality of the vitrified product.

In a preferred embodiment, the present invention provides a start-up method for cold crucible solidification treatment of radioactive waste, wherein in step (1), the added start-up glass has a high-temperature resistivity of 1-10Ω at 1100-1200°C cm.

In a preferred embodiment, the present invention provides a start-up method for radioactive waste cold crucible solidification treatment, wherein in step (1), the height of the start-up glass added into the cold crucible is controlled at the position of the induction coil 1/3-3/4 of the height H.

In a more preferred embodiment, the present invention provides a start-up method for radioactive waste cold crucible solidification treatment, wherein in step (1), the height at which the start-up glass is added into the cold crucible is controlled at 0.5- 0.6H position.

In a preferred embodiment, the present invention provides a method for starting solidification treatment of radioactive waste in a cold crucible, wherein in step (1), the titanium wire has a diameter of 2-4 mm and a length of 2-5 cm. Due to the small size of such titanium wire, it can be added through the feeding tube without opening the crucible lid of the cold crucible to feed.

In a preferred embodiment, the present invention provides a start-up method for radioactive waste cold crucible solidification treatment, wherein in step (1), the addition amount of the titanium wire is such that it can be placed in the cold crucible The diameter of the formed effective melting zone is not less than 1/2 of the diameter of the cold crucible.

In a preferred embodiment, the present invention provides a method for starting solidification treatment of radioactive waste in a cold crucible, wherein in step (1), the amount of titanium wire added is 100-200 g.

In a preferred embodiment, the present invention provides a start-up method for radioactive waste cold crucible solidification treatment, wherein in step (2), the start-up power of the power supply is greater than or equal to 30kW, so that in a very short time Heat the starting material titanium wire to a burning state.

In a preferred embodiment, the present invention provides a method for starting radioactive waste cold crucible solidification treatment, wherein in step (3), the flow rate of oxygen fed into the cold crucible is controlled at 5-10m ³ /h , so that the burning time of this step lasts 15-30 minutes. This operation of controlling the amount of oxygen inflow can prevent the titanium wire from burning too fast, and prevent the glass melting zone from being formed, which is not conducive to its next expansion.

The beneficial effect of the present invention is that, using the start-up method of the radioactive waste cold crucible solidification treatment of the present invention, when used for the start-up of the radioactive waste cold crucible solidification treatment, the starting material placement method is simple, the start-up speed is efficient, and there is no radioactive leakage. The quality of the cured product is not affected, and this method is not only suitable for the routine start of the cold crucible solidification treatment, but also for the emergency start of the cold crucible solidification treatment.

The beneficial effects of the present invention are embodied in:

(1) The start-up material is titanium wire, and the large amount of heat released by its combustion can realize fast start-up, so that the start-up process is simple and efficient, and the start-up time only takes 2-3h.

(2) The substance produced by the combustion of the starting material is TiO ₂ . Since TiO ₂ is one of the components of glass, a small amount of TiO ₂ will not significantly affect the quality of vitrified products.

(3) The starting material is small-sized titanium wire, which is easy to process and convenient to feed. It can be directly fed from the feed pipe without deliberately positioning it at a certain position on the glass surface.

(4) The starting material can be completely burnt out, and the problem of taking out the remaining starting material from the cold crucible is not involved, which greatly improves the safety of the operation in the hot chamber.

(5) The starting method can be used not only for conventional starting, but also for emergency starting.

Description of drawings

FIG. 1 is a schematic diagram of the placement positions of the starting glass and the starting material in the cold crucible before starting in Example 1.

Fig. 2 is a schematic diagram showing that the glass in the cold crucible has melted into a glass melt after the start-up in Embodiment 1 and Embodiment 2 is completed.

Fig. 3 is a schematic diagram of the start-up glass and start-up material placement positions in the cold crucible before start-up in Example 2.

In the above Figures 1-3, the induction coil 1 is located outside the side wall of the cold crucible 2, and the bottom of the cold crucible 2 is connected with a discharge pipe 5; in Figures 1 and 3, the starting glass 4 is laid on the bottom of the cold crucible 2, and the titanium wire 3 is placed On the upper surface of the starting glass 4, wherein in Fig. 3, a layer of remaining glass body 8 is formed between the starting glass 4 and the bottom of the cold crucible 2; in Fig. 2, after the starting glass 4 is melted, molten glass 7 is formed inside the cold crucible 2 A cold wall 6 is formed adjacent to the side wall and bottom of the cold crucible 2 .

Detailed ways

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

Example 1:

Put 15kg of start-up glass 4 into Φ300mm cold crucible 1, and then put 100g of Φ4×30mm titanium wire 3 (see Figure 1). The high-frequency power supply starts at 25kW and increases by 5kW every ten minutes until it reaches 50kW. After the titanium wire 3 starts to burn, oxygen is introduced at a rate of 10m ³ /h, and the titanium wire 3 burns to release a large amount of heat to melt the surrounding glass. After 30 minutes, the titanium wire 3 is basically completely burned, stop feeding oxygen, and continue to maintain this power until the added starting glass 4 is completely melted (see Figure 2), which takes 2.5 hours in total.

Example 2:

Put 7kg starting glass 4 into Φ300mm cold crucible 1 with glass body 8 of about 10kg in advance, and then put 100g, Φ4×30mm titanium wire 3 (see Figure 3). The high-frequency power supply starts at 25kW and increases by 5kW every ten minutes until it reaches 50kW. After the titanium wire 3 starts to burn, oxygen is introduced at a rate of 10m ³ /h, and the titanium wire 3 burns to release a large amount of heat to melt the surrounding glass. After 30 minutes, the titanium wire 3 is basically completely burned, stop feeding oxygen, and continue to maintain this power until the starting glass 4 added is completely melted (see Figure 2), which takes a total of 3 hours.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies, the present invention also intends to include these modifications and variations. The above-mentioned embodiments or implementations are only examples of the present invention, and the present invention can also be implemented in other specific ways or other specific forms without departing from the gist or essential features of the present invention. Accordingly, the described embodiments should be considered in all respects as illustrative and not restrictive. The scope of the present invention should be described by the appended claims, and any changes equivalent to the intention and scope of the claims should also be included in the scope of the present invention.

Claims (9)

1. a start-up method of radioactive waste cold crucible solidification treatment, it is characterized in that, described start-up method comprises the following steps successively: (1) Add starting glass in the described cold crucible, then place the starting material titanium wire on the described starting glass; (2) Start the power supply, select the appropriate power to start heating the titanium wire and gradually increase the power so that the titanium wire is gradually heated to burn; (3) feed oxygen into the cold crucible to accelerate the burning of the titanium wire until it burns out; (4) Stop feeding oxygen into the cold crucible, keep the power of the power supply, so that the glass in the cold crucible is continuously melted until completely melted. 2. The start-up method according to claim 1, characterized in that: in step (1), the high-temperature resistivity of the added start-up glass at 1100-1200° C. is 1-10 Ω·cm. 3. The start-up method according to claim 1, characterized in that: in step (1), the height at which the start-up glass is added into the cold crucible is controlled at 1/3-3/3 of the height H of the induction coil 4 positions. 4. The start-up method according to claim 3, characterized in that: in step (1), the height at which the start-up glass is added into the cold crucible is controlled at a position of 0.5-0.6H. 5. The starting method according to claim 1, characterized in that: in step (1), the diameter of the titanium wire is 2-4mm, and the length is 2-5cm. 6. The starting method according to claim 1, characterized in that: in step (1), the addition amount of the titanium wire is such that the diameter of the effective melting zone formed in the cold crucible is not less than 1/2 of the diameter of the cold crucible. 7. The start-up method according to claim 1, characterized in that: in step (1), the addition amount of the titanium wire is 100-200g. 8. The start-up method according to claim 1, characterized in that in step (2), the start-up power of the power supply is greater than or equal to 30kW. 9. The start-up method according to claim 1, characterized in that: in step (3), the oxygen flow rate passed into the cold crucible is controlled at 5-10m ³ /h, so that the burning time of this step lasts for 15 -30 minutes.