RU2513623C1 - Superdispersed powder production plant - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates in chemical industry for production of sorbents and catalyst carriers, in powder metallurgy and pharmaceutics for production of active ingredient carriers and encapsulated preparations. Ultrasound powder atomiser is arranged at drying chamber bottom. Atomiser discharge pipe is located above gas-distributing plate with higher density of orifices nearby the atomiser and lower density nearby the chamber. Atomiser inlet is connected with syringe pump to feed initial stock and with peristaltic pump to feed water as coolant. Drying agent inlet pipe is located below gas-distributing plate and communicated with heat-exchanger-heater outlet the inlet of which is connected to adsorption drier outlet. Drier is connected via main line filter with compressor. Drying chamber top tap is communicated via connection pipe with cyclone connected in its turn with electric filter.

EFFECT: simplified design, expanded range of powders, continuous operation.

2 cl, 5 dwg

Description

The invention relates to the production of ultrafine powders with a narrow particle size distribution, which can be used in the chemical industry for the production of sorbents and catalyst supports, in powder metallurgy, and also in pharmaceuticals for the production of carriers for active ingredients and encapsulated preparations.

Known installation for freeze-drying of biologically active substances, described in the patent of the Russian Federation for utility model No. 98672, publ. 10.27.2008, in which the solution to be treated is sprayed through an ultrasonic nozzle in a freezing chamber with liquid nitrogen. In the sublimation chamber, drying is carried out in a gushing layer. Air is pumped by a compressor, drained in a drying column and cooled in a non-contact heat exchanger. Particles obtained in this setup have good flowability, regular spherical shape and do not stick together. The disadvantage of this installation is the use of low-temperature equipment.

A known installation for producing porous material from biocompatible metals of alloys, ceramics and polymers by spray drying them is described in US patent No. 7163715, publ. 01/16/2007, in which the spraying is carried out using an ultrasonic nozzle. The compressed gas is heated before being fed into the nozzle, and the sprayed powder is mixed with a portion of the compressed gas. However, this installation is intended for spraying on a substrate, and not for obtaining powder.

Known installation for producing particles from at least partially liquid material, followed by freeze drying, described in US patent No. 6584782, publ. 07/01/2003, which includes three fluidized bed apparatus with working chambers for dispersion. The spray nozzle can be made in the form of an ultrasonic nozzle into which dispersing gas is supplied through one line and a heating liquid through the other. However, this installation is difficult, because contains low temperature equipment and bulky fluidized bed apparatus.

A device for dispersing and drying is also known, described in Japanese Patent No. 56-026501, publ. 03/14/1981, containing an ultrasonic nozzle, into the outer cylinder of which gas is introduced, and the liquid into the guide tube. This device provides effective drying and fine dispersion. However, the introduction of the drying agent through the annular gap of the nozzle does not allow to obtain a uniform flow in the entire volume of the cylinder-conical drying chamber. This document also does not describe a pretreatment system for a drying agent.

The closest analogue of the proposed installation is a device for producing ultrafine particles that can be used in pharmaceuticals, medicine, electric power, described in US patent No. 5874029, publ. 02/23/1999. This installation contains a line for supplying near- or supercritical fluid, including a cylinder with liquid carbon dioxide, a syringe pump, a two-way valve, and a heat exchanger. The compressed liquid or solution is introduced into the ultrasonic nozzle, at the exit of which ultrafine particles are obtained, which are collected in the lower part of the thermostatically controlled cell. This installation is complicated because contains means for creating a flow of near- or supercritical fluid and for temperature control. The formation of the solid phase of the powder occurs due to a change in the solubility of the substance in the mixture being formed and precipitation in the anti-solvent, which in this case is carbon dioxide, which, ultimately, leads to the formation of irregular particles. In addition, it is impossible to obtain powders from materials soluble in carbon dioxide and from complex mixtures, the components of which have different solubilities, in this installation.

The technical result of the proposed invention is to simplify the design by eliminating low-temperature, cryogenic and special equipment, expanding the range of powders obtained in it through the use of single-component liquids, true solutions and suspensions, both thermolabile and insensitive to high temperature, eliminating particle agglomeration, clogging of nozzles drying chamber and sticking to its walls. The expansion of the assortment is also provided with the possibility of obtaining solid, hollow, and encapsulated particles with a narrow fractional composition and an average diameter of less than 20 microns in the proposed installation. An additional advantage of the proposed installation is its continuous operation.

This is achieved by the fact that the proposed installation for producing ultrafine powders includes pumps, a heat exchanger and a drying chamber with an ultrasonic nozzle located in the lower part along its axis, the outlet pipe of which is located above the gas distribution plate, which has a higher density of holes near the nozzle and a smaller one near the chamber walls, moreover, the input of the ultrasonic nozzle is in communication with a syringe pump for supplying raw materials and with a peristaltic pump for supplying water as a cooling agent, and not on the same side of the gas distribution plate there is an inlet pipe for a drying agent in communication with the output of the heat exchanger-calorifier, the input of which is connected to the output of the adsorption dryer communicated through a main filter with a compressor, while the upper part of the drying chamber is connected to the cyclone connected in turn, in turn , with an electrostatic precipitator.

The location of the ultrasonic nozzle in the lower part of the drying chamber and the uneven density of the openings of the gas distribution plate provide such a gas-dynamic regime in the drying chamber in which wet, i.e. non-dried particles do not interfere with the internal surfaces of the drying chamber, gas distribution plate and ultrasonic nozzle. This prevents particles from sticking inside the drying chamber. At the same time, such a gas-dynamic regime promotes optimal drying and the formation of spherical particles, eliminating their irregular shape and agglomeration.

The installation is shown in figure 1 and contains the following elements:

1 - compressor

2 - main filter

3 - adsorption dryer

4 - air heater

5 - generator ultrasonic nozzle

6 - syringe pump

7 - peristaltic pump

8 - ultrasonic nozzle

9 - drying chamber

10 - cyclone

11 - electrostatic precipitator

12 - gas distribution plate.

The proposed installation works as follows.

The supply of the drying agent to the installation is carried out using an oil-free compressor 1, which allows to obtain products that require a very low content of impurities. The compressor is powered from a 380 V network, all other consumers of electricity from a network of 200 V. Additional cleaning of the drying agent is carried out using the main filter 2. To achieve maximum driving force of the drying process and independence from constantly changing environmental conditions, the drying agent is passed through a dryer 3.

The moisture removal in the desiccant 3 is carried out by the physical method by sorption on silica gel using two chambers that are switched on alternately. At the moment when one chamber is in working condition, the sorbent is regenerated in the second chamber. Thus, a continuous mode of operation of the desiccant 3 and a continuous supply of the drying agent through the air heater 4 in the drying chamber 9. This ensures that the dew point of the drying agent decreases to -50 ° C.

Heater 4 is used to achieve the required temperature of the drying agent. The voltage supplied to the heater 4 is regulated using a laboratory autotransformer. The temperature of the drying agent can be controlled in the range from ambient temperature to + 250 ° C. The flow rate of the drying agent can be controlled by valves installed on the reinforcing agent supplying the drying agent.

After the heater 4, the drying agent is fed into the drying chamber 9, which consists of steel inlet and outlet parts, the central glass part and the gas distribution unit, through the inlet pipe located below the gas distribution plate 12. The ultrasonic nozzle 8 is fixed by means of a fastener, which allows it to be changed if necessary location. An electrical signal of a given frequency, supplied to the ultrasonic nozzle 8, is created using a generator 5.

The initial raw material mixture in the drying chamber 9 is supplied using syringe pumps 6, which are operated alternately. A single syringe pump 6 is a batch equipment, but the use of several syringe pumps provides a continuous supply of the raw material mixture due to the fact that when one pump is working to supply the mixture to the nozzle 8, the second one takes it from the buffer tank. Syringe pumps provide high precision control and low (less than 5 ml / min) volumetric flow rate of the raw material mixture. All this allows you to expand the range of powders obtained both through the use of various raw materials, and through the production of solid, hollow or encapsulated particles of the spherical shape depicted in figure 2.

Since ultrasonic nozzles are very sensitive to heat, it is necessary to supply a cooling agent inside the metal body of the nozzle. As the cooling agent, water was used, which was supplied by means of a peristaltic pump 7. The flow rate of the cooling agent is controlled on the basis of data recorded using a thermocouple integrated in the ultrasonic nozzle 8 and attached to a piezoelectric crystal.

The formed and dried particles are discharged on top of the drying chamber 9 through the connecting pipe into a cyclone 10, in which large particles are deposited larger than 1 μm. The gas leaving the cyclone 10 containing small particles smaller than 1 μm in size is subjected to final purification on the electrostatic precipitator 11 before being released into the atmosphere.

The use of cyclone 10 and electrostatic precipitator 11 allows to obtain powders with a narrow fractional rate.

The metal parts of the drying chamber 9 are covered with a removable layer of thermal insulation material to reduce heat loss. The linear velocity of the drying agent at the entrance to the drying chamber 9 was measured using a hot-wire anemometer, and the humidity was measured with a hygrometer.

The proposed installation uses only standard and manufactured equipment and does not use special low-temperature and cryogenic equipment, which simplifies its design and operation.

At the developed installation, ultrafine powders based on dextran and powders consisting of microencapsulated particles of polyvinylpyrrolidone were obtained.

An experiment to obtain ultrafine powders based on dextran was carried out using a single-stream nozzle with an operating frequency of 48 kHz. The mass concentration of dextran in the feed mixture was 4%. Samples were obtained at various values of the flow rate of the raw mix, which ranged from 4 to 10 ml / min. The temperature of the drying agent at the entrance to the drying chamber 9 was 80 ° C. The linear velocity of the drying agent is 4 m / s. The relative humidity of the drying agent at the entrance to the drying chamber 9 was 0.229% at 20 ° C. The power of the electrical signal supplied to the ultrasonic nozzle 8 is 1.3 watts.

An experiment on the production of powders based on microencapsulated particles was carried out under the following conditions: the operating frequency of the ultrasonic nozzle was 8-60 kHz, the mass concentration of polyvinylpyrrolidone was 4%, the flow rate of the raw material mixture was 5 ml / min, the temperature of the drying agent at the inlet of the drying chamber was 9-80 ° C, the linear velocity of the drying agent at the entrance to the drying chamber is 9-4 m / s, the relative humidity of the drying agent at the entrance to the drying chamber 9 at 20 ° C is 0.229%, the electric signal supplied to the ultrasonic nozzle 8 is 3.8 W.

Pictures of particles obtained using a scanning electron microscope are shown in figure 3 (a, b, c).

Claims (2)

1. Installation for producing ultrafine powders, including pumps, a heat exchanger and a drying chamber with an ultrasonic nozzle located on its axis, characterized in that the ultrasonic nozzle is located in the lower part of the drying chamber, while the output nozzle of the ultrasonic nozzle is located above the gas distribution plate having a high density holes near the nozzle and a smaller one near the walls of the chamber, and the inlet of the ultrasonic nozzle is in communication with a syringe pump for supplying feedstock and peristal an inlet pipe for a drying agent, in communication with the output of the heat exchanger-heater, the inlet of which is connected to the output of the adsorption dryer, communicated through the main filter with the compressor, and the upper part of the drying chamber by means of a pump for supplying water as a cooling agent, and below the gas distribution plate the connecting pipe is connected with a cyclone, which, in turn, is connected with an electrostatic precipitator. 2. Installation for producing ultrafine powders according to claim 1, characterized in that it includes several syringe pumps.

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