CN106477627A - A kind of alkali fusion method of continuous decomposition zircon sand - Google Patents

Abstract

The invention relates to an alkali fusion method for continuously decomposing zircon sand. According to the molar ratio of zircon sand and alkali of 1:4 to 1:7, zircon sand and alkali are respectively prepared. First, zircon sand, solid alkali or liquid The alkali is preheated to a certain temperature respectively. Among them, solid alkali or liquid alkali is completely dehydrated, and continues to heat up to become liquid. Then add the heated zircon sand and liquid caustic soda into the vertical reactor to mix and evenly mix, and carry out preliminary alkali fusion reaction to generate solid materials. The solid material is transferred to a rotating cylindrical reactor, and the deep alkali fusion reaction is further completed under the solidified state, and the alkali fusion reaction product is obtained by slow cooling, and the alkali fusion reaction product is washed with water to obtain sodium zirconate and Na ₂ SiO ₃ . The invention proposes a continuous process for decomposing zircon sand by an alkali fusion method, which realizes industrial continuous production, improves production efficiency, reduces the cost of producing zirconium oxychloride, and improves the production environment.

Description

Alkali fusion method for continuously decomposing zircon sand

technical field

The invention relates to a method for decomposing zircon sand by alkali fusion, in particular to a method for continuously decomposing zircon sand by alkali fusion in the process of producing zirconium oxychloride by an acid-alkali method.

Background technique

As a scarce strategic resource, zirconium has excellent characteristics such as high melting point, corrosion resistance, plasticity and nuclear performance, and is widely used in military and civilian industries, among which nuclear grade zirconium is an important basic material in nuclear energy applications. Zircon sand is a concentrate obtained by beneficiating zircon (ZrSiO ₄ ) minerals, and its theoretical composition is 67.21% ZrO ₂ and 32.79% SiO ₂ . Since zirconium and hafnium belong to the same subgroup and have similar chemical properties, zircon sand often contains a certain proportion of hafnium minerals. Due to the high bond strength between the [SiO ₄ ] tetrahedron and the [ZrO ₈ ] dodecahedron in zircon sand (ZrSiO ₄ ), the chemical stability is very high, so it is necessary to use a certain process to make Zr , Si separation, currently used separation methods mainly include NaOH alkali fusion method, Na ₂ CO ₃ sintering method, CaCO ₃ sintering method, carbonation chlorination method and boiling chlorination method.

The melting and sintering of zircon sand and NaOH is the most important step in the process of preparing zirconium oxychloride by alkali fusion method. The purpose is to make the zircon sand in the zircon sand Zr and Si are separated and converted into easy-to-handle Na ₂ ZrO ₃ and related silicates, so as to achieve the purpose of recovering zirconium. The main reactions between zircon sand and NaOH are shown in formulas (1) to (3).

ZrSiO ₄ +2NaOH(l)=Na ₂ ZrSiO ₅ +H ₂ O(g) (1)

ZrSiO ₄ +4NaOH(l)=Na ₂ ZrO ₃ +Na ₂ SiO ₃ +H ₂ O(g) (2)

ZrSiO ₄ +6NaOH(l)=Na ₂ ZrO ₃ +Na ₄ SiO ₄ +H ₂ O(g) (3)

The above reaction process and product composition vary with the reaction temperature, raw material ratio, and particle size of zircon sand. The reaction between zircon sand and NaOH can be divided into two processes: liquid-solid reaction and solid-solid reaction. In the initial stage of the reaction, NaOH is sufficient, zircon sand and NaOH first react on the surface of zircon sand particles according to formula (3), and produce Na ₂ ZrO ₃ and Na ₄ SiO ₄ , which cover the surface of zircon sand particles. Along with the massive consumption of NaOH, may carry out by the reaction of formula (1) and formula (2). At the same time, reactions of formula (4) to formula (7) may occur.

ZrSiO ₄ +Na ₄ SiO ₄ ＝Na ₂ ZrSiO ₅ +Na ₂ SiO ₃ (4)

ZrSiO ₄ +Na ₂ ZrO ₃ ＝Na ₂ ZrSiO ₅ +ZrO ₂ (5)

Na ₂ ZrSiO ₅ +NaOH=Na ₂ ZrO ₃ +Na ₂ SiO ₃ +H ₂ O(g) (6)

2NaOH+ZrO ₂ ＝Na ₂ ZrO ₃ +H ₂ O(g) (7)

In the current production process of producing zirconium oxychloride by alkali fusion method, alkali fusion decomposition is intermittent operation, which cannot form continuous production, which leads to problems such as low production efficiency, high production cost and high energy consumption. , During the sintering process, there will be a problem of uneven heating of the sintering pot, resulting in unstable product quality. In addition, during the production process, there are certain production safety issues in the transportation of high-temperature sintering pots.

Contents of the invention

Based on the in-depth analysis of the reaction of zircon sand decomposed by alkali fusion method, this process proposes an alkali fusion decomposition process of zircon that is more energy-saving, environmentally friendly, easy to operate, environmentally friendly, and can greatly improve labor productivity. Melting and decomposing zircon sand continuous production process.

The present invention is an alkali fusion method for continuously decomposing zircon sand; comprising the following steps:

step one

Preheat the solid alkali or liquid alkali and zircon sand to 550°C-750°C respectively, and the solid alkali will melt into a liquid state;

step two

Add the molten lye into the swirl hopper of equipment B along the tangential direction, add the preheated zircon sand into the swirl hopper from the axial direction of the center of the swirl hopper, and carry out the zircon sand lye in the swirl hopper Wetting, mixing and mixing, and starting alkali fusion reaction to obtain a mixed product; in terms of molar ratio, zircon sand: molten alkali = 1:4 to 1:7, preferably 1:6;

step three

The mixed product is sent to the vertical reactor through the bottom of the swirl hopper to continue heating and alkali fusion reaction; the gas reaction product in the vertical reactor is discharged from the upper exhaust port of the vertical reactor and recycled; The solidified or semi-solidified alkali fusion reaction product is transported to the rotating cylinder reactor for deep alkali fusion reaction under the solidified state and slowly cooled to obtain the alkali fusion reaction product;

step four

The alkali fusion reaction product obtained in Step 3 is washed with water to obtain sodium zirconate and Na ₂ SiO ₃ .

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; the equipment B used in it includes alkali fusion equipment (15), high-temperature hot gas transport pipe (4), zircon sand heating cylinder (5), vertical Type reactor (6), molten lye inlet (7), swirl hopper (8), zircon sand feeder (9), baffle plate (13), rotating cylinder reactor (14);

The alkali melting equipment (15) is provided with a feeding port (1) and a molten soda outlet (3), and the molten soda outlet (3) is connected to the molten lye inlet (7) through a pipeline, and the molten lye The inlet (7) is arranged on one side of the swirl bucket (8);

The vertical reactor (6) is located above the swirl hopper (8), and it is connected to the zircon sand feeder (9) through a pipeline, and the zircon sand feeder (9) is arranged on the swirl hopper (8), and be positioned at the top of swirl bucket (8);

The discharge port of the swirl hopper (8) is positioned above the first baffle plate, and the baffle plate (13) is arranged in the vertical reactor (6); the vertical reactor (6) The discharge port of the tube is connected with the rotary cylinder reactor (14) through a pipeline.

As a preferred solution, an insulation layer (11) is provided outside the vertical reactor (6) and the rotating cylindrical reactor (14).

As a preferred solution, a heating chamber (10) is further provided on the side of the vertical reactor (6); an air outlet is provided on the top of the heating chamber (10). The top of the vertical reactor (6) is also provided with a discharge port. The top of the heating chamber (10) is provided with an air outlet connected to the high-temperature hot gas transport pipe (4) and the zircon sand heating cylinder (5) through pipes.

In order to supplement the heat of the vertical reactor (6), a combustion chamber (12) is provided outside the vertical reactor (6).

As a preferred solution, the zircon sand feeder (9) is arranged in the swirl hopper (8) and close to the side of the molten lye inlet (7). This is conducive to the uniform mixing of zircon sand and molten lye.

As a preferred version, the alkali melting equipment (15) is composed of a solid alkali or liquid alkali feed port (1), an alkali melting and heating tank (2), and a molten alkali outlet (3); the alkali melting and heating tank (2 ) is provided with a baffle plate to achieve alkali melting and heating step by step to ensure that the molten alkali enters the temperature of the swirl hopper (8).

The alkali fusion equipment (15) is located above the high-temperature hot gas transportation pipe (4); the hot gas brought out by the high-temperature hot gas transportation pipe (4) adds heat to the alkali fusion equipment (15).

As a preferred solution, the present invention relates to an alkali fusion method for continuously decomposing zircon sand; the molten alkali in step 2 is a molten alkali solution with a mass percentage of sodium hydroxide greater than or equal to 95%.

As a preferred version, the present invention is an alkali fusion method for continuously decomposing zircon sand; the molten alkali is prepared through the following steps:

Using solid alkali or liquid alkali as raw material, first heat and dehydrate at 100°C to 300°C, then heat up at 450°C to 550°C to melt it into a liquid state, and continue to heat up to 550°C to 750°C, preferably 600 to 750°C, to obtain Molten lye; the mass percentage of sodium hydroxide in the solid alkali is greater than or equal to 95%; the liquid caustic soda is an aqueous solution of sodium hydroxide; in the aqueous sodium hydroxide solution, the mass percentage of sodium hydroxide is greater than or equal to 30%.

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; the molten alkali is prepared through the following steps: using solid alkali or liquid alkali as raw material, using waste heat as heat source, and first heating at 100°C to Heating and dehydration at 300°C, and then using the high-temperature tail gas (650°C-750°C) discharged from the vertical reactor as a heat source for heating and liquefaction, so that the lye continues to heat up to 550°C-750°C to obtain molten alkali; the waste heat is Use the vertical reactor (650°C-750°C) as the heat source to carry out the residual heat carried by the tail gas after the temperature rise and liquefaction.

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; the zircon sand is zircon sand concentrate, and the mass percentage of ( _ZrHf )O in the zircon sand concentrate is greater than or equal to 63%; the zircon sand is heated to more than 600° C. to obtain the preheated zircon sand.

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; in step 1, molten alkali is added into the swirl hopper along a tangential direction at a speed of 4-10 m/s. The adding speed of molten lye is realized by adjusting the height difference, and the height difference is 1m-5m.

As a preferred solution, the present invention provides an alkali fusion method for continuously decomposing zircon sand; adding zircon sand to a cylindrical preheater, using waste heat from tail gas (650°C to 750°C) after heating the vertical reactor, natural gas, Gas is heated to over 600°C to obtain preheated zircon sand.

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; the vertical reactor is vertically installed in a heating furnace, and natural gas, coal gas or electricity is used as a heat source.

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; the exhaust gas and alkali-containing fine dust generated by the vertical reactor and the rotating cylinder reactor are collected and recycled.

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; in step 2, the mixture A is sent into the vertical reactor through the bottom of the swirl hopper and continues to be heated to 650-750°C, preferably 700-750°C And carry out alkali fusion reaction; the gas reaction product in the vertical reactor is discharged from the upper exhaust port of the vertical reactor and used as a heat source for zircon sand preheating, solid alkali or liquid alkali heating dehydration and temperature rise liquefaction;

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; the solidified or semi-solidified alkali fusion reaction product in the vertical reactor is transported to a rotating cylinder reactor at 650-750°C, preferably 700- Carry out deep alkali fusion reaction under condensate condition at a temperature of 750°C and slowly cool to obtain an alkali fusion reaction product;

As a preferred solution, the present invention is an alkali fusion method for continuously decomposing zircon sand; under better decomposition conditions, the decomposition rate of zircon sand is greater than 97%, preferably 98.05%, and more preferably 98.5%.

Advantage

Compared with the existing alkali fusion method of zircon sand, the present invention has the following obvious advantages: the alkali fusion process of zircon sand is compact and reasonable, and the alkali fusion decomposition of zircon sand can be carried out continuously and efficiently to obtain alkali fusion reaction products. The decomposition rate obtained after washing with water and acid decomposition is greater than 97%. At the same time, it is a zircon alkali fusion decomposition process that is more energy-saving and environmentally friendly, easy to operate, environmentally friendly, and can greatly improve labor productivity.

Description of drawings

Fig. 1 is a schematic diagram of a device used in an alkali fusion method for continuously decomposing zircon sand according to the present invention.

Among them, 1 is the solid alkali or liquid alkali feeding port, 2 is the alkali melting and heating tank, 3 is the molten alkali outlet, 4 is the high-temperature hot gas transportation pipe, 5 is the zircon sand heating cylinder, 6 is the vertical reactor, 7 8 is the swirl hopper, 9 is the zircon sand feeder, 10 is the heating chamber, 11 is the insulation layer, 12 is the combustion chamber, 13 is the baffle plate, 14 is the rotating cylinder reactor . ① is the heat provided by the combustion chamber, ② is the high-temperature tail gas discharged from the vertical reactor, ③ is the waste heat discharged from the heating chamber, and ④ is the tail gas. Ⅰ is the molten lye, Ⅱ is the zircon sand before preheating, Ⅲ is the zircon sand after preheating, Ⅳ is the mixture A, Ⅴ is the solid mixture, and Ⅵ is the final product.

detailed description

The present invention will be further described below in conjunction with embodiment. The raw material is zircon sand, the main components are ZrO ₂ and SiO ₂ with mass fractions of 65.72% and 28.93% respectively.

Example 1

Heat the solid alkali and zircon sand to 600°C and 700°C respectively, then add the zircon sand and alkali with a molar ratio of 1:6 to the ore alkali respectively into the alkali fusion reaction device for continuously decomposing zircon sand, vertical reaction The reaction temperature in the reactor is 650°C, the reaction time is 1.5min, and the residence time is 30min in a rotating cylinder reactor with a temperature of 700°C, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after washing and acid decomposition is 96.56%.

Example 2

Heat the solid alkali and zircon sand to 600°C and 700°C respectively, then add the zircon sand and alkali with a molar ratio of 1:6 to the ore alkali respectively into the alkali fusion reaction device for continuously decomposing zircon sand, vertical reaction The reaction temperature in the reactor is 700°C, the reaction time is 1.5min, and the residence time in the rotating cylinder reactor with a temperature of 750°C is 30min, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after water washing and acid decomposition is 97.15%.

Example 3

Heat the solid alkali and zircon sand to 600°C and 700°C respectively, then add the zircon sand and alkali with a molar ratio of 1:6 to the ore alkali respectively into the alkali fusion reaction device for continuously decomposing zircon sand, vertical reaction The reaction temperature in the reactor is 750°C, the reaction time is 1.5min, and the residence time in the rotating cylinder reactor with a temperature of 750°C is 30min, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after water washing and acid decomposition is 98.08%.

Example 4

Heat the solid alkali and zircon sand to 550°C and 600°C respectively, then add the zircon sand and alkali with a molar ratio of 1:6 to the ore alkali respectively into the alkali fusion reaction device for continuously decomposing zircon sand, vertical reaction The reaction temperature in the reactor is 750°C, the reaction time is 3.5min, and the residence time in the rotating cylinder reactor with a temperature of 750°C is 30min, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after water washing and acid decomposition is 96.88%.

Example 5

Heat the solid alkali and zircon sand to 600°C and 700°C respectively, then add the zircon sand and alkali at a molar ratio of 1:4 to the alkali fusion reaction device for continuous decomposition of zircon sand, and vertical reaction The reaction temperature in the reactor is 750°C, the reaction time is 3.5min, and the residence time in the rotating cylinder reactor with a temperature of 750°C is 30min, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after water washing and acid decomposition is 95.78%.

Example 6

Heat the solid alkali and zircon sand to 600°C and 700°C respectively, then add the zircon sand and alkali with a molar ratio of 1:7 to the ore alkali respectively into the alkali fusion reaction device for continuous decomposition of zircon sand, vertical reaction The reaction temperature in the reactor is 750°C, the reaction time is 3.5min, and the residence time in the rotating cylinder reactor with a temperature of 750°C is 30min, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after water washing and acid decomposition is 98.15%.

Example 7

Heat the solid alkali and zircon sand to 600°C and 700°C respectively, then add the zircon sand and alkali with a molar ratio of 1:6 to the ore alkali respectively into the alkali fusion reaction device for continuously decomposing zircon sand, vertical reaction The reaction temperature in the reactor is 750°C, the reaction time is 3.5min, and the residence time in the rotating cylinder reactor with a temperature of 750°C is 40min, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after washing and acid decomposition is 98.75%.

Example 8

Heat the solid alkali and zircon sand to 600°C and 700°C respectively, then add the zircon sand and alkali with a molar ratio of 1:7 to the ore alkali respectively into the alkali fusion reaction device for continuous decomposition of zircon sand, vertical reaction The reaction temperature in the reactor is 750°C, the reaction time is 1.5min, and the residence time in the rotating cylinder reactor with a temperature of 700°C is 30min, and the alkali fusion decomposition product is obtained. The decomposition rate of zircon sand after water washing and acid decomposition is 97.68%.

Claims (10)

1. an alkali fusion method for continuously decomposing zircon sand; it is characterized in that, comprising the following steps: step one Preheat the solid alkali or liquid alkali and zircon sand to 550°C-750°C respectively, and the solid alkali will melt into a liquid state; step two Add the molten alkali into the swirl hopper of equipment B along the tangential direction, add the preheated zircon sand into the swirl hopper from the axial direction of the center of the swirl hopper, and carry out the alkali liquid wetting of the zircon sand in the swirl hopper. Wet, mix and mix, and start alkali fusion reaction to obtain a mixed product; in terms of molar ratio, zircon sand: molten alkali = 1:4 ~ 1:7; step three The mixed product is sent to the vertical reactor through the bottom of the swirl hopper to continue heating and alkali fusion reaction; the gas reaction product in the vertical reactor is discharged from the upper exhaust port of the vertical reactor and recycled; The solidified or semi-solidified alkali fusion reaction product in the vertical reactor is transported to the rotating cylinder reactor for deep alkali fusion reaction under the solidified state and slowly cooled to obtain the alkali fusion reaction product; step four The alkali fusion reaction product obtained in Step 3 is washed with water to obtain sodium zirconate and Na ₂ SiO ₃ . 2. A kind of alkali fusion method for continuously decomposing zircon sand according to claim 1; it is characterized in that: said equipment B comprises alkali fusion equipment (15), high-temperature hot gas transport pipe (4), zircon sand heating circle Cylinder (5), vertical reactor (6), molten lye inlet (7), swirl hopper (8), zircon sand feeder (9), baffle plate (13), rotating cylinder reaction device (14); The alkali melting equipment (15) is provided with a feeding port (1) and a molten soda outlet (3), and the molten soda outlet (3) is connected to the molten lye inlet (7) through a pipeline, and the molten lye The inlet (7) is arranged on one side of the swirl bucket (8); The vertical reactor (6) is located above the swirl hopper (8), and it is connected to the zircon sand feeder (9) through a pipeline, and the zircon sand feeder (9) is arranged on the swirl hopper (8), and be positioned at the top of swirl bucket (8); The discharge port of the swirl hopper (8) is positioned above the first baffle plate, and the baffle plate (13) is arranged in the vertical reactor (6); the vertical reactor (6) The discharge port of the tube is connected with the rotary cylinder reactor (14) through a pipeline. 3. a kind of alkali fusion method of continuously decomposing zircon sand according to claim 1; It is characterized in that; The side of described vertical reactor (6) is also provided with heating chamber (10); The top of described heating chamber (10) is provided with air outlet; The top of described vertical reactor (6) is also provided with outlet ; The top of the heating chamber (10) is provided with an air outlet connected to the high-temperature hot gas transport pipe (4) and the zircon sand heating cylinder (5) through a pipeline. 4. a kind of alkali fusion method of continuously decomposing zircon sand according to claim 1, is characterized in that the alkali of described fusion is prepared by following steps: Using solid alkali or liquid alkali as raw material, first heat dehydration at 100°C-300°C, then heat at 450°C-550°C to melt it into a liquid state, and then continue to heat up to 550°C-750°C to obtain molten alkali ; The mass percentage of sodium hydroxide in the solid alkali is greater than or equal to 95%; the liquid alkali is an aqueous solution of sodium hydroxide, and the mass percentage of sodium hydroxide is greater than or equal to 30%. 5. A kind of alkali fusion method for continuously decomposing zircon sand according to claim 4, characterized in that the molten alkali is prepared through the following steps: using solid alkali or liquid alkali as raw material, using waste heat as heat source , first heating and dehydrating at 100°C to 300°C, then using part of the high-temperature tail gas discharged from the vertical reactor as a heat source for heating and liquefaction, and then continuing to heat up to 550°C to 750°C to obtain molten alkali; the waste heat is a vertical Part of the high-temperature tail gas discharged from the reactor is used as a heat source to heat up the residual heat carried by the tail gas after liquefaction. 6. The alkali fusion method for continuously decomposing zircon sand according to claim 1, characterized in that: the zircon sand is zircon sand concentrate, and ( _ZrHf )O in the zircon sand concentrate The mass percentage content is greater than or equal to 63%; the zircon sand is heated to greater than 600° C. to obtain preheated zircon sand. 7. A kind of alkali fusion method for continuously decomposing zircon sand according to claim 1 or 2; it is characterized in that: in step 2, the molten alkali is added into the cyclone hopper along the tangential direction with the speed of 4-10m/s middle. 8. An alkali fusion method for continuously decomposing zircon sand according to claim 1 or 2; it is characterized in that: the zircon sand is added to the cylinder preheater, and the waste heat of the heating chamber of the heating vertical reactor is used , natural gas, and coal gas are heated to more than 600°C to obtain preheated zircon sand. 9. A kind of alkali fusion method for continuously decomposing zircon sand according to claim 1 or 2; it is characterized in that: the vertical reactor is vertically installed in the heating furnace, with natural gas, coal gas or electricity as the heat source, the temperature At 650-750°C; the rotating cylinder is placed horizontally and has a certain angle to the horizontal plane for material transportation. The temperature of the material maintains the temperature at which the zircon sand is decomposed. The part with insufficient heat is supplemented by natural gas, coal gas or electricity as a heat source. The temperature range is 650- 750°C. 10. An alkali fusion method for continuously decomposing zircon sand according to claim 1 or 2; it is characterized in that: the exhaust gas and alkali-containing dust produced by the vertical reactor and the rotating cylinder reactor are collected in a concentrated manner And recycle.