CN108553929B - Atomizing nozzle for airflow type spray dryer - Google Patents

Abstract

The invention discloses an atomizing nozzle for an airflow spray dryer. It includes: a material and liquid channel arranged at the center of the nozzle axis and gradually decreasing. Multiple gas channels are symmetrically arranged along the center of the nozzle axis to form a conical structure in the circumferential direction of the material and liquid channel. The cross-sectional area of the cone gradually decreases along the flow direction. , while each gas channel converges in the flow direction, it has the same twist angle along the radial direction of the cone surface; the end of each gas channel is connected with the annular nozzle cavity and forms an annular gas nozzle at the end, and the annular gas nozzle is arranged around the material liquid nozzle and On the same plane as the top of the material liquid nozzle. The present invention optimizes the atomizing nozzle used in the airflow spray drying technology to separate the gas channel and the material liquid channel. The air flow flowing through the gas channel with the above geometric structure of the invention is converted into a high-speed rotating air flow at the gas nozzle, and the material liquid nozzle is The throttled fine-strand material liquid sprayed out from the machine is fully atomized, and spherical dry powder with a particle size of less than 20 microns can be stably produced in one step.

Description

Atomizing nozzle for airflow spray dryer

Technical field

The invention belongs to the technical field of mechanical structure design, and specifically relates to a two-fluid atomizing nozzle used in spray drying equipment.

Background technique

Integral catalytic converters are commonly used for vehicle exhaust gas purification or industrial flue gas post-treatment. The porous oxide carrier or other oxide additives loaded with catalyst active components are coated in a coating-like manner on a metal or honeycomb ceramic carrier with hundreds of regular 10-1000 micron pores, and then undergo subsequent processing to obtain the overall type catalytic converter. The particle size of the oxide is an important indicator that affects the degree of bonding between the catalyst and the carrier. For vehicle exhaust gas purification catalytic converters, the particle size of the oxide powder is generally required to be less than 20 microns.

Spray drying technology can realize the two processes of granulation and drying at the same time, and is used in many industries to manufacture powder materials.

Nozzle drying equipment mainly includes air heating devices, blowers, hot air distributors, nozzles, drying towers, cyclones, induced draft fans and other parts. When the equipment is running, the blower introduces hot air into the drying tower through the hot air distributor at the top of the drying tower to form a spiral flow; at the same time, the nozzle at the top of the drying tower sprays the material liquid into the drying tower to atomize it, causing the water to quickly evaporate to form a dry Powder; finally the separation of gas and powder is achieved in the cyclone separator. Among them, the non-blocking and continuous spray process is the core part of spray drying. To achieve continuous and unblocked spray, the key is the nozzle.

Spray drying is often divided into two methods: air flow (or air pressure) type and centrifugal type. Centrifugal spray drying technology adjusts the particle size and particle size distribution of the product by changing the rotation speed of the centrifugal disk. Use it to prepare the oxide powder required for motor vehicle exhaust gas purifiers. The particle size of the powder is distributed between 5-50 microns. Only through subsequent sorting or grinding and sorting can the powder particle size be less than 20 microns.

The motor vehicle exhaust gas purification catalyst precursor powder has a certain viscosity, and air flow spray drying technology can handle materials with higher viscosity. Therefore, the air flow spray drying method can also be selected to meet the particle size requirements for manufacturing motor vehicle exhaust gas purification catalytic converters. of powder.

Patent CN202097053U discloses an airflow sprayer that can handle high-viscosity liquid or paste fluid. The gas nozzle and the material liquid nozzle are coaxial, and the high-pressure material liquid wraps the compressed gas. The material liquid flows through the expansion chamber in the atomizer, and the density and viscosity are reduced, and then contacts the high-pressure gas at the nozzle and is atomized.

Patent CN203874940U further points out that this nozzle can handle high solid content liquids, and the nozzle is not easily clogged.

Patent CN1320485A discloses an air-assisted nozzle assembly. The material liquid flows along the axis of the assembly, and the gas flows along the outer edge of the nozzle. There is a material liquid expansion chamber in the nozzle. The material liquid entering the expansion chamber is pre-atomized by the compressed air partially introduced into the expansion chamber. , and is atomized again in contact with the pressurized air flowing from the outer air duct through the specially designed diversion and pressurizing structure at the central fluid outlet. It can effectively generate a wide flat jet shape with relatively low air flow and pressure, and enhance the crushing of liquid particles.

Patent CN104772244A discloses a two-fluid atomization nozzle. The material liquid flows along the axis of the nozzle to the front end of the nozzle, and then flows into the gas channel from several distribution holes evenly distributed in the direction perpendicular to the axis of the nozzle. The gas flows along the annular shape of the outer edge of the nozzle. Channel flow, after flowing through the gas channel distributed along the conical surface in the distribution seat, becomes a vortex through the thin-layer gas distributor with fan blades in the nozzle perpendicular to the direction of the air flow, and then contacts and mixes with the material liquid flowing out from the distribution hole. Atomization, the mixture is sprayed into the drying tower from an adjusting block that can adjust the injection angle of the material liquid.

Patent CN2341721Y discloses a pneumatic atomizing nozzle that can perform two-stage atomization of material liquid. A vortex chamber is specially designed in the nozzle. The material liquid flowing along the axis of the atomizer is partially removed from the vortex chamber. The external air channel is injected into the vortex chamber along the biased air inlet hole on the vortex chamber to form a primary atomization of the compressed gas vortex. The initially atomized droplets are secondary atomized by the remaining air in the external air channel at the nozzle outlet.

Patents CN1320485A, CN2341721Y and CN104772244A are all airflow atomization nozzles. The material and liquid channels are coaxial with the center line of the nozzle assembly, and the gas channels are evenly and symmetrically distributed on the outer edge of the nozzle assembly. All three types of nozzles contain a two-stage atomization process, with the first stage of atomization occurring inside the nozzle.

Atomization in the nozzles of patents CN234172Y and CN104772244A is achieved by generating vortexes. The former vortex is generated from the outer edge gas channel in the nozzle along the biased air inlet channel entering the vortex chamber inside the nozzle. In the middle, there may be problems with the distribution of gas between the two stages of atomization and the matching of gas and material liquid pressure; the latter The vortex is achieved by adding a sheet-shaped gas distributor with fan blades that is smaller than the channel size in the external air flow channel of the nozzle. The gas distributor does not occupy the entire gas channel.

The nozzle structures disclosed in the aforementioned patents are either too simple or too complex, and the particle size distribution of the products produced by the spray drying method using nozzles with similar structures or commercial atomization nozzles on the market cannot reach the level of the production of motor vehicle exhaust gas purification catalytic converter powder. body material requirements.

Contents of the invention

In order to solve the above problems, we designed an airflow atomization nozzle by improving the airflow in the nozzle. Combined with the improved usage method, we used the airflow atomization drying equipment to produce 20 microns or less in one step, which can meet the requirements of manufacturing motor vehicle exhaust gas purification. Oxide powder material for catalytic converters.

The present invention is realized through the following technical solutions:

The atomizing nozzle for airflow spray dryer includes the material liquid channel and the material liquid nozzle at the end, the gas channel and the gas nozzle. It is characterized by:

The material and liquid channel is arranged in the center of the nozzle axis, and the cross-sectional area of the material and liquid channel gradually decreases along the flow direction; the above structure can increase the ejection speed of the material liquid and promote the dispersion of the material liquid.

There are multiple gas channels. The multiple gas channels are symmetrically arranged along the center of the nozzle axis and form a conical structure in the circumferential direction of the material liquid channel. The cross-sectional area of the cone gradually decreases along the flow direction, and each gas channel converges in the flow direction. At the same time, they have the same twist angle along the radial direction of the cone surface; the ends of each gas channel are connected with the annular nozzle cavity; the above-mentioned unique structural design can effectively ensure that the airflows of various flow rates and forms are turned into convergent The rotating air flow makes the high-speed rotating air flow fully contact and collide with the material liquid at the nozzle, which is beneficial to the dispersion of the material liquid into smaller material liquid particles and controls the particle size of the powder material to less than 20 microns.

The cross-sectional area of the annular nozzle cavity gradually decreases along the flow direction and forms an annular gas nozzle at the end. The annular gas nozzle is arranged around the material liquid nozzle. The center lines of the annular gas nozzle and the material liquid nozzle are coaxial and the top ends are on the same plane. The design helps the material liquid form uniform spherical material liquid particles.

The inner wall of the annular nozzle cavity has an arc-shaped structure in the axial direction, forming an arc-shaped cone ring with a cross-sectional area that gradually decreases in an arc along the flow direction.

The number of gas channels is 4 to 8.

While the gas channels converge in the flow direction, they have the same twist angle θ in the radial direction of the cone surface, ranging from 5 to 45 degrees.

The nozzle of the present invention is installed at the top, side, bottom or middle position of the drying tower of the spray drying equipment.

Further, the nozzle is installed at the axis position of the bottom of the drying tower column.

When in use, the material liquid flows along the material liquid channel that runs through the middle of the nozzle. The gas flows in the gas channel arranged in the circumferential direction and rejoins in the nozzle cavity. The gas and the material liquid contact at their respective nozzles and enter the drying tower.

The present invention optimizes the atomizing nozzle used in the airflow spray drying technology, uses the atomizing nozzle used in the airflow spray drying technology of the present invention to process the material liquid, separates the gas channel and the material liquid channel, and flows through the gas channel with the above geometric structure of the present invention. The air flow is converted into a high-speed rotating air flow at the gas nozzle, which fully atomizes the throttled fine stream of material liquid ejected from the material liquid nozzle, and can stably produce spherical dry powder with a particle size of less than 20 microns in one step. The nozzle of the invention is used in spray drying equipment, and is particularly suitable for manufacturing oxide powder materials for motor vehicle exhaust gas purification catalytic converters. It can also be used in pharmaceuticals, coatings, food and other chemical industries.

Description of the drawings

Figure 1 is a structural diagram of the main body of the nozzle of the present invention;

Figure 2 is a partial enlarged view of the nozzle of the present invention;

Figure 3 is a structural diagram of the nozzle cap of the present invention;

Figure 4 is a schematic cross-sectional view of the distribution seat AA in Figure 1;

Figure 5 is a schematic cross-sectional view of the distribution base BB in Figure 1 .

Names of components in the picture: 1 is the nozzle base, 2 is the distribution seat, 3 is the nozzle head, 4 is the nut, 5 is the nozzle cap, 6 is the nozzle chamber, 7 is the gas nozzle, 8 is the material liquid nozzle, 9a is Thread one, 9b is thread two, G is the gas channel, L is the material and liquid channel, and θ is the twist angle.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. The specific embodiments are further explanations of the principles of the present invention and do not limit the present invention in any way. The same or similar technologies as the present invention do not exceed the scope of protection of the present invention.

Combined with the accompanying drawings.

The atomizing nozzle used for the airflow spray dryer includes the material liquid channel L and the material liquid nozzle 8 at the end, the gas channel G and the gas nozzle 7; the material liquid channel L is arranged in the center of the nozzle axis, and the cross-sectional area of the material liquid channel L flows along the direction gradually decreases.

There are multiple gas channels G. The multiple gas channels G are symmetrically arranged along the center of the nozzle axis to form a conical structure in the circumferential direction of the material liquid channel L. The cross-sectional area of the cone gradually decreases along the flow direction. Each gas channel G is in the flow direction. While converging on the cone surface, there is the same twist angle θ along the radial direction of the cone surface; the end of each gas channel G is connected with the annular nozzle cavity 6;

The cross-sectional area of the annular nozzle cavity 6 gradually decreases along the flow direction and forms an annular gas nozzle 7 at the end. The annular gas nozzle 7 is arranged around the material liquid nozzle 8. The tops of the annular gas nozzle 7 and the material liquid nozzle 8 are on the same plane.

The inner wall of the annular nozzle cavity 6 of the present invention has an arc-shaped structure in the axial direction, forming an arc-shaped cone ring whose cross-sectional area gradually decreases in an arc along the flow direction.

The present invention adopts 4 to 8 gas channels G. While each gas channel G converges in the flow direction, it has the same twist angle θ in the radial direction of the cone surface, ranging from 5 to 45 degrees.

The nozzle of the present invention is installed at the top, side, bottom or middle position of the drying tower of the spray drying equipment. The best installation position of the nozzle is on the axis of the bottom of the drying tower column.

The specific processing structure will be described below. In this example, the specific processing structure is realized by two parts: the nozzle body and the nozzle cap 5 .

The structure of the nozzle is shown in Figures 1, 2, 3, 4 and 5, which consists of a nozzle body and a nozzle cap 5. The nozzle body includes a nozzle base 1, a distribution seat 2, and a nozzle head 3. The nozzle base 1 is fixed to the rear end of the feed pipe through thread one 9a, and the nozzle cap 5 is fixed to the rear end of the distribution seat 2 through nut 4 and thread two 9b. The material liquid channel L is on the axis of the nozzle body, and its size begins to shrink at the tail part of the distribution seat, and continues to shrink along the cone surface in the material liquid nozzle to the size of the material liquid nozzle 8. The space between the outer wall of the nozzle base 1 and the inner wall of the feed pipe is an annular gas channel at the front end of the nozzle body. There are several equal-diameter cylindrical gas channels evenly distributed along the fluid flow direction in the distribution seat 2. Along the fluid flow direction, the axial distance between each gas channel and the nozzle body gradually decreases. In addition, there is a radial angle between the axis of each gas channel and the axis of the nozzle body, as shown in Figures 4 and 5. The space between the inner wall of the nozzle cap 5 and the top of the nozzle body forms a vortex nozzle chamber 6, and the outer periphery of the material liquid nozzle 8 at the top of the nozzle cap 5 forms a gas nozzle 7 with an annular narrow hole structure. The outlet edges of the gas nozzle 7 and the material liquid nozzle 8 are flush.

The material liquid flows along the material liquid channel L, is compressed step by step in the nozzle body, and is sprayed into the drying tower body from the material liquid nozzle 8. The gas passes through the feed pipe, flows along the annular channel in the nozzle base 1 part to the front end of the distribution seat 2, and enters the nozzle chamber 6 through the gas channel G in the distribution seat 2. The multiple gas channels G distributed and gathered along the conical surface in the distribution seat 2, and the existence of the radial angle between the gas channel G and the material liquid channel L, make the gas flow through the gas channel L in the distribution seat not only along the nozzle It merges axially into the nozzle cavity 6 and also moves along the radial direction of the nozzle, forming a rotating airflow in the nozzle cavity 6 . The total cross-sectional area of the gas channel G in the distribution seat 2 is smaller than the cross-sectional area of the annular channel in the nozzle base 1, and the cross-sectional area of the gas nozzle 7 is much smaller than the cross-sectional area of the gas channel in the distribution chamber, so the gas is partially compressed in the distribution chamber. A primary accelerated vortex is formed in the nozzle cavity 6 , and after the smaller diameter gas nozzle 7 is fully compressed, the vortex ejects the gas nozzle 7 in the form of a high-speed rotating airflow. This high-speed jet gas vortex can fully contact, crush and atomize the material liquid coming out of the material liquid nozzle 8.

The nozzle of the present invention is installed at the bottom of the axis of the drying tower column, and the direction of the nozzle's nozzle is vertically upward, so that the flow direction of the material liquid and the hot air flowing downward from the top of the drying tower flow in opposite directions, which is not only beneficial to increasing the atomized mixture The contact area with the hot air will also increase the residence time of the material in the drying tower, thereby increasing the heat energy exchange efficiency between the atomized material and the hot air.

When the nozzle of the present invention is used, when the gas nozzle 7 throttles out and ejects, the high-speed vortex airflow surrounds the material liquid nozzle 8. The pressure at the outlet of the nozzle is relatively small, which will increase based on the static pressure difference between the material liquid inlet liquid level and the material liquid nozzle. Introduce additional pressure difference, which is beneficial to the flow of feed liquid. When the position of the material liquid nozzle 8 installed on the drying tower is lowered, it will further facilitate the flow of the material liquid. Tests have shown that the present invention sets the nozzle on the axis of the bottom of the drying tower column. Even if the liquid level at the inlet of the feed liquid is lower than the position of the nozzle, there is no need to apply additional pressure to the feed liquid or require the position of the feed liquid storage tank to be higher than the position of the nozzle. The liquid material can be atomized and dried by the airflow spray drying equipment into a powder below 20 microns.

As shown in Figures 1, 2, and 3, Figure 1 is a structural diagram of the main body of the nozzle, Figure 2 is a partial enlarged view of the nozzle, and Figure 3 is a structural diagram of the nozzle cap; the upper part of Figure 1 is a cross-sectional view, and the lower part is an outline structural diagram. The outer shape of the nozzle cap 5 is not shown in the lower part. The upper part of Figure 3 is a cross-sectional view, and the lower part is an outer structural diagram. The lower part includes the outer shape of the nozzle cap 5. In this illustration, a threaded connection structure is used to connect the nozzle base 1, the distribution seat 2 and the nozzle head 3. The gas channel G, the material liquid channel L, the nozzle chamber 6, the gas nozzle 7, the material liquid nozzle 8 and other structures of the present invention are arranged therein. The nozzle chamber 6 is formed by connecting the nut 4 to the nozzle cap 5 and the distribution seat 2 . The gas channel G and the material liquid channel L are arranged in the nozzle base 1 and the distribution seat 2. An annular gas nozzle 7 and a material liquid nozzle 8 are formed on the same plane on the top surface of the front part of the nozzle.

As shown in Figures 4 and 5, Figure 4 is a schematic cross-sectional view of the distribution seat AA, and Figure 5 is a schematic cross-sectional view of the distribution seat BB. In this illustration, the material and liquid channel L is located at the center of the axis. The diameter of the material and liquid channel L at the center of the axis of the distribution seat 2 gradually becomes smaller along the flow direction. The diameter of the material and liquid channel L in Figure 4 is larger than the diameter of the material and liquid channel L in Figure 5; the gas channel There are 6 groups of G. Along the flow direction, the 6 gas channels G form a tapered structure. The layout circle in Figure 4 is larger than the layout circle in Figure 5, and the torsion angle θ is twisted.

Claims (4)

1. The utility model provides an atomizing nozzle for air current formula spray dryer, includes feed liquid passageway and terminal feed liquid spout, gas channel and gas spout, its characterized in that:

the feed liquid channel is arranged at the center of the axis of the nozzle, and the cross-sectional area of the feed liquid channel is gradually reduced along the flowing direction;

the multiple gas channels are symmetrically arranged on the circumference of the feed liquid channel along the axis center of the nozzle to form a conical surface structure, the cross section area of the conical surface is gradually reduced along the flow direction, and the gas channels are converged in the flow direction and have the same torsion angle along the radial direction of the conical surface, and the torsion angle theta is 5-45 degrees; the tail end of each gas channel is communicated with the annular nozzle cavity;

the cross-sectional area of the annular nozzle cavity is gradually reduced along the flowing direction, an annular gas nozzle is formed at the tail end, the annular gas nozzle is arranged around the feed liquid nozzle, and the annular gas nozzle and the top end of the feed liquid nozzle are on the same plane; the inner wall of the annular nozzle cavity is of an arc-shaped structure in the axial direction, and an arc-shaped cone ring with the cross section area gradually reduced in an arc shape along the flowing direction is formed.

2. The atomizing nozzle for an air-flow type spray dryer according to claim 1, wherein: the number of gas channels is 4 to 8.

3. The atomizing nozzle for an air-flow type spray dryer according to claim 2, wherein: the nozzles are arranged at the top, side, bottom or middle position of the drying tower of the spray drying equipment.

4. An atomizing nozzle for an air-flow type spray dryer as set forth in claim 3, wherein: the nozzle is arranged at the axis position of the bottom of the drying tower body.