CN1314585C

CN1314585C - Auxiliarily burning reactor and its application in vapor process of preparing nano SiO2

Info

Publication number: CN1314585C
Application number: CNB031169465A
Authority: CN
Inventors: 李春忠; 张祖钧; 丛德滋; 岳群; 干路平; 胡彦杰
Original assignee: East China University of Science and Technology; Shanghai Chlor Alkali Chemical Co Ltd
Current assignee: East China University of Science and Technology; Shanghai Chlor Alkali Chemical Co Ltd
Priority date: 2003-05-16
Filing date: 2003-05-16
Publication date: 2007-05-09
Anticipated expiration: 2023-05-16
Also published as: CN1548369A

Abstract

The present invention discloses an auxiliary burning reactor and an application method for preparing nanometer silicon dioxide by a gas phase method. By changing a spray nozzle structure of the traditional auxiliary burning reactor, the reactor of the present invention overcomes the defects of the prior art for preparing nanometer silicon dioxide by a gas phase method that a temperature field and a concentration field in a burning reaction chamber are not uniform; the residence time distribution of materials in a burning reaction zone is not uniform; a spray nozzle outlet is easy to be scabbed and blocked, etc. Consequently, the quality of nanometer silicon dioxide products is enhanced.

Description

Method for preparing nano silicon dioxide by using auxiliary combustion reactor

Technical Field

The invention relates to a method for preparing nano silicon dioxide by a gas phase method, in particular to a method for preparing nano silicon dioxide by using an auxiliary combustion reactor.

Background

Nano SiO₂Is a nano-particle product with wide application, and is widely applied to the fields of rubber, paint, plastics, medicine, adhesive, printing ink, pesticide, catalysis, electronics, fine ceramics and the like.

Gas phase method for preparing nano SiO₂Is made of silicon tetrachloride (SiCl)₄) Steam is prepared by high-temperature hydrolysis in oxyhydrogen flame, and the reaction equation is as follows:

or

For preparing nano SiO by gas phase method₂The reactors of (a) are of various types, and the reactors are classified into two types, namely auxiliary combustion type reactors and pre-combustion type reactors. The prior auxiliary combustion reactor is to mix SiCl₄The gas, air and hydrogen are directly introduced into the combustion reaction zone through a pipeline (commonly called a nozzle) to carry out combustion reaction. The advantages of the reactor are simple structure and convenient manufacture and maintenance, but the existence of the reactorThe defects of uneven temperature field and concentration field in the combustion reaction zone, uneven residence time distribution of materials in the combustion reaction zone, easy scabbing and blockage at the outlet of a nozzle and the like are overcome, so that the high-quality nano SiO is difficult to prepare by adopting the conventional auxiliary combustion reactor₂And (5) producing the product.

Disclosure of Invention

The invention aims to provide a method for preparing nano silicon dioxide by using an auxiliary combustion reactor.

The idea of the invention is that:

the reasons for the phenomena of the prior auxiliary combustion reactor, such as the uneven temperature field and concentration field in the combustion reaction zone, the uneven residence time distribution of materials in the combustion reaction zone, the easy scabbing and blocking of the nozzle outlet, are manifold, and through experiments, the inventor finds that the auxiliary combustion reactor not only has the reaction product (SiCl)₄、H₂And air) and the configuration of the nozzles in the reactor. The structure of the nozzle in the existing auxiliary combustion reactor is a single-tube type, and experiments prove that when the reactant (SiCl)₄、H₂And air) is low, the tempering speed is extremely high, namely the mixed gas can be combusted in the nozzle; when the gas velocity of the mixed gas is high, the phenomena of fire dropping or flameout are easy to occur, and the flame is extremely unstable. In order to solve the problem, the inventor has invented the invention through a large number of experimentsCoaxial multitubular nozzle, the central tube of which is fed with the stoichiometrically proportioned reactant (H)₂Air and SiCl₄) Mixed gas, two rings are communicated with H₂Combustion supporting gas mixed with air. Because the combustion-supporting gas of the two rings can form stable flame and become a non-extinguishing 'long-life fire', the gas velocity of the mixed gas in the central tube can be improved safely and is far higher than the tempering velocity to prevent tempering, and the phenomenon of fire escaping or extinguishing does not need to be worried about. In addition, the stability of central flame is guaranteed by the annular flame formed by the two rings, and the central flame can be prevented from being directly contacted and mixed with cold air in a combustion reaction zone, so that the uniformity of a temperature field and a concentration field in the reaction zone is improved.

The technical scheme is as follows:

the reactor comprises a nozzle and a combustion reaction chamber with a water cooling jacket, wherein the nozzle is communicated with the combustion reaction chamber, and the combustion reaction chamber comprises a reaction product outlet, a cooling water inlet, a cooling water outlet, an ignition port and a tangential air inlet.

Drawings

FIG. 1 is a schematic view of the reactor structure of the present invention

Wherein: 1-a nozzle; 101-a central tube; 102-two loops; 103-three ring pipes; 2-a combustion reaction chamber; 3-an ignition port; 4-cooling water outlet; 5-a tangential air inlet; 6-cooling water inlet; 7-outlet of reaction product.

FIG. 2 is a sectional view taken along line A-A of FIG. 1

The invention will be further described with reference to the accompanying drawings in which:

the reactor comprises a nozzle 1 and a combustion reaction chamber 2, wherein the nozzle 1 is communicated with the combustion reaction chamber 2, the combustion reaction chamber 2 comprises a reaction product outlet 7, a cooling water inlet 6, a cooling water outlet 4, an ignition port 3 and a tangential air inlet 5, and the reactor is characterized in that the nozzle 1 is formed by arranging a central pipe 101, a double ring pipe 102 and a triple ring pipe 103 from inside to outside in a coaxial manner.

Wherein: the ratio of the diameter of the combustion chamber 2 to the diameter of the nozzle 1 is preferably: 2-5: 1.

According to the technical scheme, the defects that in the prior art, a temperature field and a concentration field in a combustion reaction chamber are uneven, materials are not uniformly distributed in a residence time in a combustion reaction zone, a nozzle outlet is easy to scar and block and the like are overcome by changing the nozzle structure of the auxiliary combustion reactor, so that the nano SiO is improved₂The quality of the product.

Detailed Description

The auxiliary combustion reactor is applied to the preparation ofnano silicon dioxide by a gas phase method:

SiCl premixed according to the theoretical ratio of reaction is introduced into the central tube 101₄、H₂And air, introducing mixed gas of air and hydrogen into the double ring pipe 102, introducing air into the three ring pipes 103, igniting and reacting by the ignition port 3 of the combustion reaction chamber under the condition that the combustion reaction chamber 2 has cooling water and tangential air, and collecting reaction products by the reaction product outlet 7.

Wherein: the total gas velocity of the gas at the outlet of the central tube 101 is 70-80 m/s, the total gas velocity of the gas at the outlet of the double ring tube 102 is 30-40 m/s, the gas velocity of the gas at the outlet of the three ring tubes 103 is 20-30 m/s, and the gas velocity at the tangential air outlet is 10-20 m/s; the reaction temperature is 1600-2000 ℃; the temperature of the cooling water is 80-100 ℃.

The invention is further illustrated by the following examples, which do not limit the scope of the invention:

examples

The liquid silicon tetrachloride is heated and vaporized electrically, the vapor and the air after drying, purification and preheating are mixed through a tee joint and enter a mixer, and meanwhile, hydrogen is also introduced into the mixer after drying and purification. After the three gases are premixed according to the reaction theoretical ratio (considering that the primary mixing is not uniform, two mixers are connected in series), the three gases are introduced into a central pipe of the reactor to be sprayed out at a high speed, the total gas velocity at the outlet of the central pipe is 76.2 m/s (hydrogen, air and silicon tetrachloride steam are in the chemical theoretical ratio), and the ignition combustion reaction is carried out. Because theflame of the mixed gas is easy to extinguish, purified air and excessive hydrogen are mixed by a tee joint and then are introduced into the two rings of the reactor, the total gas velocity at the outlet of the two rings is 33.5 m/s (the hydrogen is excessive in the air), and the long-life fire is ignited to ensure the stable combustion of the central flame. Purified air is respectively introduced into the three rings of the nozzles and the combustion reaction chamber, the reaction system is quenched, the air speed of the three ring cooling air outlet is 29.1 m/s, and the air speed of the tangential air outlet of the combustion reaction chamber is 10.4 m/s. Forming SiO after gas phase combustion₂The powder is blown out with high-speed airflow, flocculated and cooled by a flocculator made of multi-section pipelines and finally entersDeacidifying in a collecting deacidifying tower, and packing in a packing machine. The obtained fumed silica product: SiO 2₂Purity 99.8%, BET specific surface area 212.4 m²(ii) a heating loss (free moisture removed at 105 ℃) of less than 1% and a burning loss (structural moisture removed at 1000 ℃) of less than 1%.

The whole reactor, the outlet pipe of the reactor, the pipe of the flocculator and the outlet pipe of the flocculator are all cooled by constant temperature water of a jacket or a water tank. The thermostatic water bath has a separate circulating system and is controlled at about 100 ℃. When the thermostatic waterbath is started, steam is needed to preheat, once the reaction starts, the reaction heat can maintain the water temperature to be surplus, and the surplus heat can be removed by a condenser if necessary so as to prevent the water from evaporating. The cooling water is preferably deionized water.

Claims

1. A method for preparing nano-silica by means of an auxiliary combustion reactor, characterized in that the preparation method is as follows: in the central tube (101), SiCl ₄ , H ₂ pre-mixed in advance according to the reaction theoretical ratio and air, the mixed gas of air and hydrogen is passed into the second ring pipe (102), and the air is passed into the third ring pipe (103). Under the condition that cooling water and tangential air exist in the combustion reaction chamber (2), the The ignition port (3) of the reaction chamber ignites and reacts, and the reaction product is collected by the reaction product outlet (7);

Wherein: the total gas velocity of the outlet gas of the center pipe (101) is 70-80 m/s, the total gas velocity of the outlet gas of the second-ring pipe (102) is 30-40 m/s, The velocity is 20-30 m/s, the gas velocity of the tangential air outlet is 10-20 m/s, the reaction temperature is 1600-2000°C, and the temperature of the cooling water is 80-100°C.