CN117210701A - Sodium slag recovery method and device - Google Patents

Abstract

The invention relates to the field of sodium metal production, and discloses a sodium slag recovery method and a sodium slag recovery device, wherein the sodium slag recovery method comprises the following steps: (1) Carrying out first roasting on the liquid sodium slag to obtain first roasting slag; (2) Crushing the first roasting slag, and then performing second roasting to obtain second roasting slag; (3) Leaching the second roasting slag by using water or sodium hydroxide solution to obtain sodium hydroxide solution and calcium hydroxide; the method optionally further comprises: the liquid sodium slag is mixed with a dispersant prior to the first calcination. The sodium slag roasting-leaching recovery method and device provided by the invention are safe and controllable, so that the sodium slag is converted into valuable sodium hydroxide solution and calcium hydroxide solid, and the high-value utilization of the sodium slag is realized.

Description

A method and device for recovering sodium slag

Technical field

The present invention relates to the field of metallic sodium production, and specifically to a method and device for recovering sodium slag.

Background technique

Metal sodium is a common alkali metal, mainly used in the production of leaded gasoline additives and petroleum desulfurizers, oxidants, bleaches, dyes, pesticides, pharmaceutical intermediates, catalysts, and sodium compounds for the production of organic compounds. At present, the production technology of sodium metal adopts the salt fusion electrolysis method to produce sodium metal. In order to lower the melting point of the electrolyte during the electrolysis process, calcium chloride and barium chloride need to be added to the electrolyte to form a ternary molten salt to lower the temperature of the molten salt. After the above steps, a certain amount of electrolytic slag, namely sodium slag, will remain after the electrolytic cell separates the metallic sodium. With the improvement of the refined sodium purification process, the current amount of sodium slag generated is 1.5-3% of the metallic sodium production. The sodium slag contains up to 60-86% of metallic sodium components and 14-40% of metallic calcium components. According to statistics, my country's current annual output of metallic sodium reaches 110,000 tons, and the process of producing metallic sodium produces approximately 1,650-3,300 tons of sodium slag. Sodium slag is cheap and difficult to store. And because metallic sodium and calcium are prone to chemical reactions in air or water, sodium slag treatment is difficult and poses major safety risks. Therefore, how to safely dispose and recycle sodium slag has been a long-standing problem for sodium metal production companies.

Existing sodium slag treatment methods mainly include alcoholysis, vacuum distillation and melt filter press. However, these methods are rarely used in production due to technical difficulties or safety issues. At present, factories that produce metallic sodium still sell sodium slag at low prices. Developing a process for safely disposing of sodium slag and recovering soda-calcium resources has become an urgent problem for the sodium metal industry to be solved.

Contents of the invention

In view of the shortcomings of the existing technology, the present invention provides a method and device for recovering sodium slag. The method and device for recovering sodium slag provided by the present invention are safe and controllable.

In order to achieve the above object, on the one hand, the present invention provides a method for recovering sodium slag, which method includes the following steps:

(1) Perform the first roasting of the liquid sodium slag to obtain the first roasted slag;

(2) Grind the first roasting slag and then perform the second roasting to obtain the second roasting slag;

(3) Use water or sodium hydroxide solution to leach the second roasting residue to obtain sodium hydroxide solution and calcium hydroxide;

The method also optionally includes mixing the liquid sodium slag with a dispersant before performing the first roasting.

Preferably, the dispersant in step (1) is an organic solvent, preferably at least one of alkyl silicone oil, stearic acid, polyethylene, polystyrene and benzyl alcohol.

Preferably, based on the total amount of liquid sodium slag, the amount of dispersant is 0.1-5% by weight, preferably 0.3-2% by weight.

Preferably, the first roasting is oxygen-controlled roasting, which allows the liquid sodium slag to be converted into sodium peroxide, sodium oxide, calcium oxide and residual soda-calcium slag while ensuring safe operation.

A second aspect of the present invention provides a device for recovering sodium slag, which device includes a stirring reaction kettle, a first roasting unit, a pulverizer, a second roasting unit and a reaction kettle that are connected in sequence;

Wherein, the stirring reaction kettle is used to mix and stir liquid sodium slag and dispersant;

The reaction kettle is used for leaching the second roasting residue obtained from the second roasting unit with water or sodium hydroxide solution.

The inventor of the present invention discovered during the research process that the agglomeration between liquid sodium slag makes it difficult for the sodium slag to be completely oxidized into oxides during the roasting process. Further research found that by mixing the liquid sodium slag with the dispersant before roasting, the dispersant molecules are adsorbed on the surface of the liquid sodium slag, and the liquid sodium can be dispersed into small paste-like particles, thus greatly increasing the separation between the liquid sodium slag and the air. The contact area effectively increases the oxidation depth of liquid sodium slag.

The sodium slag roasting-leaching recovery method and device provided by the invention are safe and controllable, convert the sodium slag into valuable sodium hydroxide solution and calcium hydroxide solid, and realize high-value utilization of the sodium slag.

Description of the drawings

Figure 1 is a process flow diagram of the recycling method provided by the present invention;

Figure 2 is a schematic diagram of a recovery device according to a specific embodiment of the present invention;

Figure 3 is a morphology diagram of calcium hydroxide provided by the present invention;

Figure 4 is a SEM image of calcium hydroxide provided by the present invention;

Figure 5 is an XRD pattern of calcium hydroxide provided by the present invention.

Explanation of reference signs

1-Stirring reactor 2-First roasting unit

3-Pulverizer 4-Second roasting unit

5-leaching reactor 6-solid-liquid separation device

Detailed ways

The endpoints of ranges and any values disclosed herein are not limited to the precise range or value, but these ranges or values are to be understood to include values approaching such ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges. These values The scope shall be deemed to be specifically disclosed herein.

In the description of the present invention, it should be understood that the terms "center", "longitudinal direction", "transverse direction", "length", "width", "thickness", "upper", The orientation or positional relationship indicated by "down", "left", "right", "vertical", "horizontal", "top", "bottom", "axial", "radial", "circumferential" etc. The orientation or positional relationships shown in the drawings are only for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot It should be understood as a limitation of the present invention. In addition, "inside and outside" refer to the inside and outside with respect to the outline of each component itself.

Unless explicitly stated otherwise, terms referring to connections, such as "connected" and "interconnected," refer to relationships between structures that are fixed or connected to each other, either directly or indirectly through intermediate structures, as well as to relationships that are movable or rigidly connected.

As used herein, when an element or component or unit is described as being "connected to," "coupled to," or "in contact with" another element, component or unit, that element or component or unit can be directly connected to, directly Coupled to, directly in contact with a specific element or part or unit, or connected, coupled or in contact with a specific element or part or unit through an intermediate element or part or unit. When an element is referred to as being "directly connected to", "directly coupled to" or "directly contacting" another element, there are no intervening elements or components or units present.

The term "ambient temperature" as used herein will be understood to mean temperature under ambient conditions, for example room temperature of 20-25°C.

The terms "first" and "second" used in this article are only used to distinguish materials used or operations performed in different steps or stages, and do not limit specific materials or operations.

In this disclosure, when a value is expressed as an approximation by use of the antecedent "about," it should be understood that the specific value forms another embodiment. As used herein, "about X" (where X is a numerical value) preferably means ±10% of the recited value, inclusive. For example, the phrase "about 8" preferably refers to a value in the range of 7.2 to 8.8, inclusive. When present, all scopes are inclusive and composable. For example, when a range of "1 to 5" is recited, the recited range should be construed to include the ranges "1 to 4", "1 to 3", "1-2 and 4-5", "1-3 and 5", "2-5", etc. Furthermore, when a list of alternatives is provided, the list may be interpreted to mean that any alternative may be excluded, for example, by a negative limitation in the claim. For example, when a range of "1 to 5" is recited, the recited range may be construed to include instances in which any of 1, 2, 3, 4, or 5 is negatively excluded; therefore, for "1 to 5" The statement could be interpreted as "1 and 3-5, but not 2", or simply as "which excludes 2". It is intended that any component, element, attribute or step expressly recited herein may be expressly excluded from the claims, regardless of whether such parts, elements, attributes or steps are listed as an alternative or whether they are individually recited.

Unless expressly stated otherwise, the terms "substantially" or "substantially the same" as used herein will be understood to encompass having a parameter fluctuate within a suitable range, for example having a ±10% or ±15% fluctuation of the parameter. In some embodiments, the fluctuation range is within ±10%.

In the present invention, when it comes to gas concentration, for example, "oxygen concentration" refers to the volume concentration of the gas unless otherwise specified.

A first aspect of the present invention provides a method for recovering sodium slag, as shown in Figure 1. The method includes the following steps:

(1) Perform the first roasting of the liquid sodium slag to obtain the first roasted slag;

(2) Grind the first roasting slag and then perform the second roasting to obtain the second roasting slag;

(3) Use water or sodium hydroxide solution to leach the second roasting residue to obtain sodium hydroxide solution and calcium hydroxide;

The method also optionally includes mixing the liquid sodium slag with a dispersant before performing the first roasting.

The method provided by the invention is suitable for the safe disposal of sodium slag in most industries, which can be directly obtained industrial sodium slag, preferably hazardous waste sodium slag produced by the electrolysis of sodium chloride to prepare sodium metal, or can be processed through existing technology Treated sodium residue.

According to a preferred embodiment of the present invention, the liquid sodium slag contains Na and Ca; preferably, based on the total amount of the liquid sodium slag, the content of Na is 60-86% by weight, and the content of Ca is 14-40% by weight. In addition to Na and Ca, the sodium slag described in the method provided by the present invention may also contain trace amounts (for example, no more than 2%) of other metal elements, including but not limited to barium, magnesium, and iron. In addition, the present invention does not specifically limit the existence form of Na and Ca in the liquid sodium slag. Na and Ca-containing sodium slag existing in various forms are suitable for the recovery method provided by the present invention.

In step (1) of the present invention, the liquid sodium slag can be directly roasted for the first time, or the liquid sodium slag can be mixed with a dispersant, and then the first roasting can be performed. Preferably, step (1) includes: The liquid sodium slag is mixed with the dispersant, and then the first roasting is performed to obtain the first roasted slag. The inventor of the present invention discovered during the research process that the agglomeration between liquid sodium slag makes it difficult for the sodium slag to be completely oxidized into oxides during the roasting process. Further research found that by mixing the liquid sodium slag with the dispersant before roasting, the dispersant molecules are adsorbed on the surface of the liquid sodium slag, and the liquid sodium can be dispersed into small paste-like particles, thus greatly increasing the separation between the liquid sodium slag and the air. The contact area effectively increases the oxidation depth of liquid sodium slag. The present invention has a wide selection range of the type of dispersant, as long as it can achieve the above purpose. Preferably, the dispersant is selected from at least one of organic solvents, preferably alkyl silicone oil, stearic acid, polyethylene , at least one of polystyrene and benzyl alcohol.

The source of the dispersant is not particularly limited in the present invention and can be obtained commercially. Preferably, the number average molecular weight of the polyethylene is 2,000-10,000. Preferably, the number average molecular weight of the polystyrene is 4000-5000.

Preferably, based on the total amount of liquid sodium slag, the amount of dispersant is 0.1-5% by weight, preferably 0.3-2% by weight. In the present invention, only a small amount of dispersant can be used to greatly increase the contact area between liquid sodium slag and air, effectively improving the oxidation depth of liquid sodium slag.

According to a preferred embodiment of the present invention, the mixing in step (1) includes: physically stirring the liquid sodium slag and the dispersant, the stirring speed is 5-100r/min, preferably 10-50r/min; the stirring time is 1-120min, preferably 3-60min. The inventor of the present invention discovered during the research process that by adding a small amount of dispersant to the liquid sodium slag before roasting, the dispersant molecules are adsorbed on the surface of the liquid sodium, and combined with appropriate stirring, it is more conducive to making the liquid sodium slag Dispersed into small paste-like particles, this further increases the contact area between sodium slag and air, and more effectively increases the oxidation depth of sodium slag.

According to a preferred embodiment of the present invention, the first roasting is oxygen-controlled roasting, which allows the liquid sodium slag to be converted into sodium peroxide, sodium oxide, calcium oxide and Residual sodium calcium slag. The controlled oxygen roasting mentioned in the present invention means that the supply amount and concentration of oxygen are controllable through various means, and the controlled conditions are such that they can meet the safe operation and maximize the conversion of liquid sodium slag into sodium peroxide and oxidation. Sodium, calcium oxide and residual sodium calcium slag shall prevail.

The inventor of the present invention found during the research process that segmented control of the first roasting is more conducive to controlling the stable release of combustion heat of liquid sodium slag and preventing bumping and splashing of metal sodium droplets in the liquid sodium slag.

Preferably, the first roasting includes an initial stage of roasting, a stationary stage of roasting and an end stage of roasting, and the temperature of each stage satisfies the following conditions: initial stage of roasting < stationary stage of roasting < end stage of roasting.

More preferably, the conditions for the initial stage of roasting include: oxygen flow rate is 1-30m ³ /t·min, more preferably 2-10m ³ /t·min, for example, 2m ³ /t·min, 3m ³ /t·min. min, 4m ³ /t·min, 5m ³ /t·min, 6m ³ /t·min, 7m ³ /t·min, 8m ³ /t·min, 9m ³ /t·min, 10m ³ /t·min , or any value between any two, the roasting temperature is 220-750°C, preferably 260-450°C, such as 240°C, 260°C, 300°C, 350°C, 400°C, 450°C, or any two Any value between, the oxygen concentration is 3-22%, preferably 5-20%, such as 5%, 10%, 15%, 20%, or any value between any two, the roasting time is 3-20%, 180min, preferably 10-60min, such as 10min, 20min, 30min, 40min, 50min, 60min, or any value between any two. Further preferably, in the initial stage of roasting, the oxygen input amount is 20-60% of the theoretical oxygen consumption of the sodium slag, preferably 25-50%.

More preferably, the conditions for the stable stage of roasting include: oxygen flow rate is 0.5-30m ³ /t·min, more preferably 0.5-15m ³ /t·min, such as 0.5m ³ /t·min, 1m ³ /t ·min, 2m ³ /t·min, 3m ³ /t·min, 4m ³ /t·min, 5m ³ /t·min, 6m ³ /t·min, 7m ³ /t·min, 8m ³ /t· min, 9m ³ /t·min, 10m ³ /t·min, 11m ³ /t·min, 12m ³ /t·min, 13m ³ /t·min, 14m ³ /t·min, 15m ³ /t·min , or any value between any two, the roasting temperature is 240-750°C, preferably 280-500°C, such as 300°C, 350°C, 400°C, 450°C, 500°C, or any value between the two Any value, the oxygen concentration is 5-25%, preferably 10-25%, such as 10%, 15%, 20%, 25%, or any value between any two, the roasting time is 10-180min, preferably It is 10-60min, for example, it is 10min, 20min, 30min, 40min, 50min, 60min, or any value between any two. Further preferably, in the steady stage of roasting, the oxygen input amount is 20-50% of the theoretical oxygen consumption of the sodium slag, preferably 25-40%.

More preferably, the conditions at the end of roasting include: oxygen flow rate is 0.5-30m ³ /t·min, more preferably 0.5-20m ³ /t·min, for example, 0.5m ³ /t·min, 1m ³ /t ·min, 2m ³ /t·min, 3m ³ /t·min, 4m ³ /t·min, 5m ³ /t·min, 6m ³ /t·min, 7m ³ /t·min, 8m ³ /t· min, 9m ³ /t·min, 10m ³ /t·min, 11m ³ /t·min, 12m ³ /t·min, 13m ³ /t·min, 14m ³ /t·min, 15m ³ /t·min , 16, 17m ³ /t·min, 18m ³ /t·min, 19m ³ /t·min, 20m ³ /t·min, or any value in between, the roasting temperature is 260-750°C, preferably is 300-550°C, such as 300°C, 350°C, 400°C, 450°C, 500°C, or any value between any two, and the oxygen concentration is 15-40%, preferably 20-30%, such as 20%, 22%, 24%, 26%, 28%, 30%, or any value between any two, the roasting time is 5-180min, preferably 10-60min, such as 10min, 20min, 30min, 40min , 50min, 60min, or any value in between. Further preferably, in the end stage of roasting, the oxygen input amount is 10-40% of the theoretical oxygen consumption of the sodium slag, preferably 15-30%.

The inventor of the present invention discovered during the research process that the primary roasting slag (the product after the first roasting) is often mixed with a small amount of residual sodium-calcium metal, which causes the sodium-calcium metal to easily react with water during the leaching process, resulting in a violent hydration process and The production of small amounts of hydrogen increases the hazards of the disposal process. In order to improve the safety of the roasting slag leaching process, the present invention performs a primary crushing, secondary roasting and leaching process on the primary roasting slag through steps (2) and (3) to achieve safe leaching of the roasting slag.

In the present invention, in step (2), the first roasting slag is pulverized to obtain roasting slag with uniform particle size, thereby improving the safety of the roasting slag leaching process. The method of crushing is not particularly limited in the present invention, and may be mechanical crushing, for example.

Preferably, the first roasting slag in step (2) is crushed to obtain a particle size of 10-160 mesh, preferably 20-80 mesh, and more preferably 20-60 mesh.

As long as the pulverized slag with the above particle size can be obtained, the specific rotation speed, time and frequency of pulverization are not particularly limited.

Preferably, the method also includes recovering the tail gas in the roasting process (such as the first roasting), and providing the recovered tail gas (referred to as the first roasting tail gas) with or without supplementary air or oxygen (according to the oxidation state) to The crushing process may provide a subsequent roasting atmosphere for subsequent roasting. The tail gas obtained during the first roasting process is mainly nitrogen. After being collected and cooled, it can be used as protective gas for the subsequent crushing process or for diluting the oxygen concentration in the air, which not only ensures the safety of the roasting process but also reduces costs.

Preferably, the crushing is performed under a protective atmosphere, the protective atmosphere being provided by at least one of roasting exhaust gas (eg, first roasting exhaust gas), nitrogen, helium, argon and neon. In order to reduce the cost of using a protective atmosphere during the crushing process, it is preferable to use the first roasting tail gas to provide the protective atmosphere.

According to the method provided by the present invention, each roasting can be controlled in sections, or one of the roastings can be controlled in sections. As long as one of the roastings is subject to segmented control, it will be more conducive to achieving the above purpose. The specific segmented control conditions for the two roastings can be the same or different. The present invention has no special limitations on this, and it is based on the premise that safe production can be achieved. . That is, preferably, segmented control may or may not be performed. When controlling in stages, the specific control conditions may be such as the first roasting, which will not be described again here.

According to a preferred embodiment of the present invention, the temperature of the second roasting in step (2) is 220-750°C, preferably 240-450°C, such as 240°C, 250°C, 300°C, 350°C, 400°C ℃, 450℃, or any value in between.

According to a preferred embodiment of the present invention, the second roasting time in step (2) is 5-180min, preferably 10-90min, such as 10min, 20min, 30min, 40,min, 50min, 60min, 70min , 80min, 90min, or any value in between.

Preferably, during the second roasting process in step (2), the oxygen concentration is 5-40%, preferably 10-30%, such as 10%, 15%, 20%, 25%, 30%, or any Any value in between.

Preferably, during the second roasting process in step (2), the oxygen flow rate is 0.5-200 m ³ /t·min, and further preferably the oxygen flow rate is 1-50 m ³ /t·min.

In step (3) of the present invention, the secondary roasting slag can be leached safely by using the water or sodium hydroxide solution to leach the second roasting slag.

Preferably, in step (3), relative to 1 kg of the second roasting slag, the amount of water or sodium hydroxide solution is 0.8-15.0L, preferably 1.1-8.0L.

Preferably, in step (3), when sodium hydroxide hydrate is used as the leaching agent relative to 1kg of the second roasting slag, calcium oxides are more likely to precipitate under alkaline conditions, so that sodium-calcium production can be achieved more efficiently separation.

According to a preferred embodiment of the present invention, the concentration of the sodium hydroxide solution is 20-100% by weight, preferably 20-80% by weight. Using high-concentration sodium hydroxide solution to leach the secondary roasting residue can achieve safe leaching and maximize its conversion into a mixture of sodium hydroxide solution and calcium hydroxide.

Preferably, the reaction temperature of the leaching is -18°C to 45°C, preferably -15°C to 30°C, and more preferably -15°C to 10°C. Adopting this preferred embodiment is more conducive to improving the safety of the roasting residue leaching process.

Preferably, the reaction time of the leaching is 10-300 min, preferably 15-60 min, for example, 15 min, 20 min, 30 min, 40 min, 50 min, 60 min, or any value between any two.

According to the present invention, preferably, the method also includes solid-liquid separation of the mixed material obtained by leaching to obtain liquid (sodium hydroxide solution) and solid (calcium hydroxide). It is further preferred that the method further comprises recycling at least part of said liquid back to the leaching process for providing at least part of the sodium hydroxide solution. Specifically, part of the concentrated sodium hydroxide solution can be used as a by-product, and the other part of the sodium hydroxide solution can be recycled after supplementing with water, and can be used again for the leaching process of the next batch of second roasting residue.

According to the present invention, preferably, when the step (1) does not include the use of a dispersant, at least one operation of appropriately extending the first roasting time, crushing time, leaching time, and lowering the leaching temperature can be used, to make the roasting more complete.

A second aspect of the present invention provides a device for recovering sodium slag. As shown in Figure 2, the device includes a stirring reaction kettle 1, a first roasting unit 2, a pulverizer 3, a second roasting unit 4 and a leaching reactor that are connected in sequence. 5;

Wherein, the stirring reaction kettle 1 is used to mix and stir liquid sodium slag and dispersant;

The leaching reaction kettle 5 is used for leaching the second roasting slag obtained from the second roasting unit 4 with water or sodium hydroxide solution.

According to the device provided by the present invention, preferably, the stirred reaction kettle 1 is provided with a liquid sodium slag inlet, a dispersant inlet and a mixed material outlet.

According to the device provided by the present invention, preferably, the device further includes a liquid sodium slag supply unit and a dispersant supply unit, and the liquid sodium slag supply unit and the dispersant supply unit are respectively connected with the stirring reaction kettle 1 . Preferably, the mixture outlet of the stirring reaction kettle is connected with the inlet of the first roasting unit. The liquid sodium slag and the dispersant are mixed and stirred in the stirred reactor 1, and the obtained mixed material is sent to the first roasting unit 2.

The liquid sodium slag and dispersant undergo first roasting in the first roasting unit. The present invention has no particular limitation on the equipment of the first roasting unit. Preferably, the first roasting unit 2 includes a first roasting furnace for performing first roasting, preferably a tube furnace or a rotary kiln.

Preferably, the first roasting furnace is equipped with a first flow meter and/or a first oxygen concentration meter for controlling the oxygen supply amount of the first roasting furnace. The present invention has no particular limitation on the specific arrangement of the first flow meter and the first oxygen concentration meter. As mentioned above, the purpose of these two detection devices is to perform controlled oxygen roasting in the first roasting unit. Therefore, the first flow meter and the first oxygen concentration meter can be arranged as long as they can realize controlled oxygen roasting in the first roasting unit. Specifically, flow meters can be installed at both the inlet and outlet of the first roasting furnace. and oxygen concentration meter.

Preferably, the pulverizer 3 is equipped with an inert gas pipeline for providing inert gas to the pulverizer 3 to provide a protective atmosphere for pulverization in the pulverizer 3 . The types of the inert gas are as mentioned above and will not be described again here.

Preferably, the second roasting unit 4 includes a second roasting furnace for performing second roasting, preferably a tube furnace or a rotary kiln. Preferably, the second roasting furnace is equipped with a second flow meter and/or a second oxygen concentration meter for controlling the amount of oxygen supplied to the second roasting furnace. The arrangement and considerations of the second flow meter and the second oxygen concentration meter are as described above and will not be described again here.

Preferably, the leaching reactor 5 is provided with a liquid inlet. Further preferably, the liquid inlet is connected to a water or sodium hydroxide liquid supply unit.

Preferably, the device also includes a solid-liquid separation device 6 connected in series with the leaching reaction kettle 5. The solid-liquid separation device 6 is used to perform solid-liquid separation on the material leached out of the leaching reaction kettle 5 to obtain solid and liquid. . The outlet of the leaching reactor 5 is connected with the inlet of the solid-liquid separation device 6 . Specifically, the solid-liquid separation device is provided with a liquid outlet and a solid outlet.

Preferably, the liquid outlet of the solid-liquid separation device 6 is connected with the inlet of the leaching reactor 5 . Using this preferred embodiment, the recovered liquid can be recycled back to the leaching process to provide at least part of the sodium hydroxide solution. The remaining liquid can be used as a by-product and the solid as a by-product.

According to a preferred embodiment of the present invention, the gas outlet of the first roasting unit is connected with the gas inlet of the pulverizer and/or the second roasting unit. Using this preferred embodiment, the tail gas generated in the first roasting process can be recovered, and the recovered tail gas can be supplemented with air or oxygen (depending on the oxidation state) to provide a protective atmosphere for the crushing process or an atmosphere for the second roasting.

Through the above-mentioned method and device, the present invention can secondary develop the hazardous waste sodium slag produced by electrolyzing sodium chloride to prepare metallic sodium, thereby realizing high-value utilization of liquid sodium slag.

The present invention will be described in detail below through examples.

Example 1

(1) Mix 1kg of liquid sodium slag with a temperature of 180°C (85% by weight of metallic sodium, 14% by weight of metallic calcium, and the remaining 1% by weight is sodium oxide and calcium oxide produced by surface oxidation) and 10g of methane at 180°C. Silicone-based oil is stirred and mixed, the stirring speed is 30 rpm, and the stirring time is 10 min;

(2) Put the dispersed sodium slag into the first roasting furnace (equipped with a first flow meter for controlling the oxygen supply of the first roasting furnace) for controlled oxygen roasting. The temperature in the initial stage of roasting is 250°C. The time is 40min, the flow rate of oxygen is controlled to 6L/kg·min, and the oxygen concentration is 22% at this time; the temperature in the stable stage of roasting is 320°C, the roasting time is 40min, the flow rate of oxygen is controlled to 4L/kg·min, and the oxygen concentration is 22% at this time. The concentration is 18%; the temperature at the end of the roasting stage is 400°C, the roasting time is 30min, the flow rate of oxygen is controlled to 3L/kg·min, and the oxygen concentration is 21% at this time; sodium peroxide, sodium oxide, calcium oxide and residual sodium are obtained Calcium residue.

(3) Pulverize the roasted slag through a pulverizer. The crushing speed is 150 rpm and the crushing time is 15 minutes. After screening, the roasted slag with a particle size of 60 mesh is obtained. Then the roasted slag is put into the second roasting furnace (useful for assembly). Secondary oxygen-controlled roasting is performed using a second flow meter that controls the oxygen supply of the second roasting furnace. The roasting temperature is 250°C, the roasting time is 20min, the flow rate of oxygen is controlled to 12L/kg·min, and the oxygen concentration is 15%. , obtaining a mixture of sodium oxide and calcium oxide of about 1.35kg.

(4) In the leaching reactor, use 3.6L of water to perform directional leaching of the roasted product in step (3) (temperature is 0°C, time is 15min) and separated in a solid-liquid separation device to obtain approximately 3 liters of 30% sodium hydroxide solution and 0.26kg calcium hydroxide. The morphology, SEM and XRD patterns of the recovered calcium hydroxide are shown in Figure 3, Figure 4 and Figure 5 respectively.

Example 2

According to the method of Example 1, the difference is that no dispersant is added, the liquid sodium slag is directly roasted for the first time, and the roasting time is extended, specifically including:

First roasting: the temperature in the initial stage of roasting is 260°C, the roasting time is 60min, the flow rate of oxygen is controlled to 6L/kg·min, and the oxygen concentration is 22% at this time; the temperature in the stable stage of roasting is 350°C, the roasting time is 40min, controlled The flow rate of oxygen is 4L/kg·min, and the oxygen concentration is 18% at this time; the temperature at the end of the roasting stage is 500°C, the roasting time is 60min, and the flow rate of oxygen is controlled to 3L/kg·min, and the oxygen concentration is about 20% at this time. ; Obtain sodium peroxide, sodium oxide, calcium oxide and residual sodium calcium slag.

The roasted slag is crushed through a pulverizer, the crushing speed is controlled to 150 rpm, the crushing time is 30 minutes, and the roasted slag with a particle size of 60 mesh is obtained through screening, and then the roasted slag is put into the second roasting furnace (equipped with a control unit The second flow meter for the oxygen supply of the second roasting furnace) performs secondary oxygen-controlled roasting. The roasting temperature is 250°C, the roasting time is 20min, the flow rate of controlled oxygen is 15L/kg·min, and the oxygen concentration is 15%. We get The mixture of sodium oxide and calcium oxide is about 1.35kg.

In the leaching reactor, use 5.9 liters of water to perform directional leaching of the roasted product in step (3). At this time, it is necessary to lower the leaching temperature and extend the leaching time. Control the leaching temperature to -10°C and the time to 30 minutes, and separate about 5.8 liters of 20% sodium hydroxide solution and 0.25kg of calcium hydroxide in the solid-liquid separation device.

Example 3

(1) Take 2kg of the same liquid sodium residue as in Example 1 and stir and mix with 0.02kg of benzyl alcohol. The stirring speed is 30 rpm and the stirring time is 15min;

(2) Place the dispersed sodium slag into the first roasting furnace (equipped with a first flow meter for controlling the oxygen supply of the first roasting furnace) for controlled oxygen roasting. The temperature in the initial stage of roasting is 260°C, the roasting time is 30min, the controlled oxygen flow rate is 8L/kg·min, and the oxygen concentration is 22% at this time; the temperature in the stable stage of roasting is 320°C, the roasting time is 30min, and the controlled oxygen flow rate is 15L/kg·min, the oxygen concentration is 19% at this time; the temperature at the end of the roasting stage is 400°C, the roasting time is 20min, the flow rate of oxygen is controlled to 20L/kg·min, the oxygen concentration is about 26% at this time; peroxidation is obtained Sodium, sodium oxide, calcium oxide and residual soda-calcium residue;

(3) The above-mentioned roasting slag is ball milled through a pulverizer, the crushing speed is 150 rpm, the crushing time is 15 minutes, and the roasted slag with a particle size of 60 mesh is obtained through screening, and then the roasted slag is put into the second roasting furnace ( Equipped with a second flow meter for controlling the oxygen supply of the second roasting furnace) for secondary roasting, controlled oxygen roasting is carried out under an oxidizing atmosphere, the flow rate of oxygen is controlled to 5L/kg·min, the roasting temperature is 250°C, and the roasting time is 20min, the oxygen concentration is 10%, and the sodium oxide and calcium oxide mixture is about 2.62kg;

(4) In the leaching reactor, use 7.3L of water to perform directional leaching of the roasted product in step (3) (temperature: 5°C, time: 20 minutes) and separate in a solid-liquid separation device to obtain approximately 7 liters of 30 wt% hydrogen Sodium oxide solution and calcium hydroxide 0.53kg.

Example 4

(1) Take 200g of the same liquid sodium residue as in Example 1 and stir and mix with 2g of benzyl alcohol. The stirring speed is 50 rpm and the stirring time is 10 min;

(2) Place the dispersed sodium slag into the first roasting furnace (equipped with a first flow meter for controlling the oxygen supply of the first roasting furnace) for controlled oxygen roasting. The temperature in the initial stage of roasting is 250°C, the roasting time is 15min, the flow rate of controlled oxygen is 3L/kg·min, and the oxygen concentration is 21%; the temperature in the stable stage of roasting is 320°C, the roasting time is 20min, and the flow rate of controlled oxygen is 10L/ kg·min, the oxygen concentration is 15%; the temperature at the end of the roasting stage is 450°C, the roasting time is 20min, the oxygen flow rate is controlled to 20L/kg·min, and the oxygen concentration is 25%; sodium peroxide, sodium oxide, and calcium oxide are obtained and residual soda-calcium slag;

(3) Crush the above-mentioned roasting slag through a pulverizer. The crushing speed is 10,000 rpm and the crushing time is 2 minutes. After screening, the roasted slag with a particle size of 40 mesh is obtained. Then the roasted slag is put into the second roasting furnace (assembly). There is a second flow meter used to control the oxygen supply of the second roasting kiln) for secondary controlled roasting, the roasting temperature is 320°C, the roasting time is 10min, the flow rate of controlled oxygen is 10L/kg·min, and the oxygen concentration is 20% , obtaining about 268g of sodium oxide and calcium oxide mixture;

(4) In the leaching reactor, use 2.0L of 20 wt% sodium hydroxide solution to perform directional leaching of the roasted product in step (3) (temperature: 0°C, time: 20 minutes) and separate in a solid-liquid separation device to obtain approximately 2 liters of 30% by weight sodium hydroxide solution and 52g of calcium hydroxide.

Example 5

(1) Take 500g of the same liquid sodium slag as in Example 1 and stir and mix 10g of polyethylene (average number average molecular weight: 4000), the stirring speed is 20 rpm, and the stirring time is 20 min;

(2) Put the dispersed sodium slag into the first roasting furnace (equipped with a first oxygen flow meter for controlling the oxygen supply of the first roasting furnace), and perform controlled oxygen roasting. The temperature in the initial stage of roasting is 270°C. , the roasting time is 15min, the controlled oxygen flow rate is 5L/kg·min, and the oxygen concentration is 13%; the temperature in the stable stage of roasting is 380°C, the roasting time is 15min, the controlled oxygen flow rate is 15L/kg·min, and the oxygen concentration is 19%; the temperature at the end of the roasting stage is 510°C, the roasting time is 15 minutes, the flow rate of controlled oxygen is 20L/kg·min, and the oxygen concentration is 26%; sodium peroxide, sodium oxide, calcium oxide and residual sodium calcium slag are obtained;

(3) The above-mentioned roasting slag is ball milled through a pulverizer. The crushing speed is 200 rpm and the crushing time is 15 minutes. After screening, the roasted slag with a particle size of 80 mesh is obtained. The roasted slag is then put into the second roasting furnace (assembly). There is a second flow meter used to control the oxygen supply of the second roasting kiln) for secondary roasting, the roasting temperature is 300°C, the roasting time is 20min, the flow rate of oxygen is controlled to 20L/kg·min, and the oxygen concentration is 18%, we get The mixture of sodium oxide and calcium oxide is about 670g;

(4) In the leaching reaction kettle, use 5.2L of 20 wt% sodium hydroxide solution to perform directional leaching of the roasted product (temperature is -8°C, time is 20 minutes) and separated in a solid-liquid separation device to obtain approximately 5 liters of 30 % by weight sodium hydroxide solution and 130g calcium hydroxide.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, many simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the disclosed content of the present invention. All belong to the protection scope of the present invention.

Claims (11)

1. A method for sodium slag recovery, the method comprising the steps of:

(1) Carrying out first roasting on the liquid sodium slag to obtain first roasting slag;

(2) Crushing the first roasting slag, and then performing second roasting to obtain second roasting slag;

(3) Leaching the second roasting slag by using water or sodium hydroxide solution to obtain sodium hydroxide solution and calcium hydroxide;

the method optionally further comprises: the liquid sodium slag is mixed with a dispersant prior to the first calcination.

2. The method of claim 1, wherein the liquid sodium slag contains Na and Ca;

preferably, the content of Na is 60-86 wt% and the content of Ca is 14-40 wt%, based on the total amount of the liquid sodium slag.

3. The method of claim 1, wherein the dispersant of step (1) is an organic solvent, preferably at least one of alkyl silicone oil, stearic acid, polyethylene, polystyrene, and benzyl alcohol;

preferably, the dispersant is used in an amount of 0.1 to 5 wt.%, preferably 0.3 to 2 wt.%, based on the total amount of the liquid sodium slag.

4. The method of claim 1, wherein the mixing comprises: physically stirring the liquid sodium slag and the dispersing agent at a stirring speed of 5-100r/min, preferably 10-50r/min; the stirring time is 1-120min, preferably 3-60min.

5. The method of any of claims 1-4, wherein the first roasting is a controlled oxygen roasting that converts liquid sodium slag to sodium peroxide, sodium oxide, calcium oxide, and residual sodium calcium slag while meeting safe operation.

6. The method according to any one of claims 1 to 5, wherein the first firing includes a firing initiation phase, a firing plateau phase, and a firing end phase, each phase temperature satisfying firing initiation phase < firing plateau phase < firing end phase;

preferably, the conditions of the initial stage of firing include: the oxygen flow is 1-30m ³ Preferably from 2 to 10m ³ The roasting temperature is 220-750 ℃, preferably 260-450 ℃, the oxygen concentration is 3-22%, preferably 5-20%, and the roasting time is 3-180min, preferably 10-60min;

the conditions for the bake-out plateau include: the oxygen flow is 0.5-30m ³ Preferably 0.5 to 15m ³ The roasting temperature is 240-750 ℃, preferably 280-500 ℃, the oxygen concentration is 5-25%, preferably 10-25%, the roasting time is 10-180min, preferably 10-60min;

the conditions of the baking finish stage include: the oxygen flow is 0.5-30m ³ Preferably 0.5 to 20m ³ The roasting temperature is 260-750 ℃, preferably 300-550 ℃, the oxygen concentration is 15-40%, preferably 20-30%, and the roasting time is 5-180min, preferably 10-60min.

7. The method according to any one of claims 1 to 6, wherein the first roasting residue of step (2) is crushed to obtain crushed residue having a particle size of 10 to 160 mesh, preferably 20 to 80 mesh, more preferably 20 to 60 mesh;

preferably, the pulverization is performed under a protective atmosphere provided by at least one of roasting tail gas, nitrogen, helium, argon and neon, and further preferably, the protective atmosphere is provided by roasting tail gas.

8. The method of any of claims 1-7, wherein the conditions of the second firing comprise: the roasting temperature is 220-750 ℃, and the oxygen flow is 0.5-200m ³ The oxygen concentration is 5-40% per t.min, and the roasting time is 5-180min;

preferably, the conditions of the second firing include: the roasting temperature is 240-450 ℃, and the oxygen flow is 1-50m ³ And/t.min, the oxygen concentration is 10-30%, and the roasting time is 10-90min.

9. The method according to any one of claims 1-8, wherein in step (3) water or sodium hydroxide solution is used in an amount of 0.8-15.0L, preferably 1.1-8.0L, relative to 1kg of the second roasting slag;

preferably, the concentration of the sodium hydroxide solution is 20-100 wt%, preferably 20-80 wt%;

preferably, the reaction temperature of the leaching is from-18 ℃ to 45 ℃, preferably from-15 ℃ to 30 ℃, more preferably from-15 ℃ to 10 ℃;

preferably, the reaction time of the leaching is between 10 and 300min, preferably between 15 and 60min.

10. The device for recycling sodium slag comprises a stirring reaction kettle (1), a first roasting unit (2), a pulverizer (3), a second roasting unit (4) and a leaching reaction kettle (5) which are sequentially communicated;

wherein the stirring reaction kettle (1) is used for mixing and stirring liquid sodium slag and a dispersing agent;

the leaching reaction kettle (5) is used for leaching the second roasting slag obtained by the second roasting unit (4) with water or sodium hydroxide solution.

11. The apparatus according to claim 10, wherein the first roasting unit (2) comprises a first roasting furnace for carrying out a first roasting, preferably the first roasting furnace is equipped with a first flow meter for controlling the oxygen supply to the first roasting furnace;

preferably, the pulverizer (3) is equipped with an inert gas line for providing an inert gas to the pulverizer (3) to provide an inert atmosphere in which the pulverization is carried out in the pulverizer (3);

preferably, the second roasting unit (4) comprises a second roasting furnace for carrying out a second roasting, preferably the second roasting furnace is equipped with a second flowmeter for controlling the oxygen supply to the second roasting furnace;

preferably, the device further comprises a solid-liquid separation device (6) connected in series with the leaching reaction kettle (5), wherein the solid-liquid separation device (6) is used for carrying out solid-liquid separation on the materials obtained by leaching of the leaching reaction kettle (5) to obtain solids and liquid;

preferably, a liquid outlet of the solid-liquid separation device (6) is communicated with an inlet of the leaching reaction kettle (5).