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Application of supercritical fluid technology(3)——Fine particle device

I. Overview:

The development of ultra-fine particles, especially nano-sized particles, has become a hot area in the current high-tech fields and has been widely used in the fields of materials, chemicals, light industry, metallurgy, electronics, and biomedicine. There are many methods for the preparation of ultrafine particles. Supercritical fluid deposition technology is a high technology that can more accurately control the crystallization process, can produce fine particles with a very small average particle size, and can also control the distribution of their particle size. Therefore, deposition from a supercritical solution is a promising new technique.

Gas anti-solvent crystallization (GAS process) is a new crystallization technology, and its process principle is as follows: When the high-pressure gas is dissolved in the solution phase containing solute, the solvent therein is swelled, thus decreasing the solubility of the solute therein, resulting in The solute crystals are precipitated.

The GAS process is used to crystallize the solute and must satisfy the following two conditions: first, the solute is insoluble or slightly soluble in the solvent-resistant gas; and second, the solvent-resistant gas has a relatively large solubility in the liquid phase.

 

Ⅱ. The flow chart

The following figure shows the application of the GAS process. It is a continuous GAS process and its flow is as follows:

 

Ⅲ. The composition of the structure

The device consists of the following components: a solvent-resistant gas (CO2) supply system, a solution feed system containing solute, a visible crystallizer, a pressure relief device, and a temperature control system (incubator air bath heating).

When GAS operation is performed, CO2 is sent to the top of the crystallizer by high-pressure pump II. The pressure of the crystallizer is controlled by adjusting the outlet valve of the crystallizer, and the excess CO2 is circulated back to the front of the refrigeration system. The temperature is controlled by an air bath heated by a thermostat. When the system is stable, the solution containing the solute is introduced into the crystallizer through the fine nozzle with the high-pressure pump I. The pressure at the outlet of the nozzle is higher than the pressure in the crystallizer, so that CO2 and the solution containing the solute flow down from the top of the crystallizer. The sub-millimeter droplets ejected from the nozzle are dispersed in a continuous medium composed of solvent-resistant gas. Due to the expansion and evaporation of the droplets, solute fine particles are crystallized, and a glass plate and a metal powder metallurgy filter plate are provided at the bottom of the crystallizer. To collect solute fine particles. The fluid mixture (and the solvent that dissolves the solute) exits the crystallizer and enters the pressure relief tank. After enough fine particles have been collected, the supply of the solution is stopped, CO2 is continuously fed, and CO2 is removed in the crystallizer. Residual solvent on the microparticles. This drying process takes about 2 hours.

 

Ⅳ. configuration instructions

1. The filter volume is 0.5L, the maximum design pressure is 16Mpa, and the interior is filled with molecular sieve or silica gel. It can filter impurities and moisture, and the quantity is 2 in parallel. It is easy to replace the desiccant.

2. Refrigeration system

a core chiller adopts the imported French Melosure closed compressor.

b The cold box is equipped with an automatic control system for the cooling temperature. The required cooling temperature can be freely set. The cold box is divided into inner liner, insulation layer, CO2 coil and stainless steel decorative layer.

3, storage tank: for liquid CO2 storage, volume 1L, the maximum design pressure up to 10MPa.

4, CO2 pump II; flow rate is selected as appropriate, the maximum discharge pressure is 40MPa, FM control flow, flow adjustment range of 15% -100%, the pump head cooling in the cold box cooling.

5. Solution pump I: The flow rate is selected as appropriate. The maximum discharge pressure is 40 MPa. The frequency control flow is controlled. The flow adjustment range is 15%-100%. The pump head is cooled by the coolant in the cold box.

6. Mold: It is a pressure-receiving visual container with a capacity of 0.3L. The inlet is connected with a nozzle, the nozzle is made of stainless steel, and the laser perforation has a ratio of length to inner diameter of 15:1. The diameter of the nozzle is 20μ and 40μ. 60, 80μ, 100μ. The autoclave can be used to make visible windows to observe the formation of fine particles.

The following figure shows the structure of the crystallizer, the main component of the supercritical fine particle device. With a visible window, one can observe the formation of internal fine particles. In order to consider the convenience and quickness of disassembly, the kettle uses a typical clamp type. Open structure form. Both are equipped with single and multiple concentric nozzles. Single head nozzles can be used for nozzles with different fine inner diameters. Multi-headed concentric nozzles are made of concentric nozzles using special processes with three different fine inner diameters. Both types of nozzles can be used to produce nanometer-sized particles.

 



1Pressure Cap 2Stainless Steel Cover 3Perfluoroelastomer Seal 4Pressure Glass

Figure 1, the structure of the crystallizer

 

7. Pressure relief tank: volume specification is 0.2L, design pressure 20MPa Fly is mainly used to separate CO2 from solvent.

8. Incubator: The size of the studio is 400mm (long) × 400mm (deep) × 500mm (high). The temperature controller is used to control the temperature. The incubator contains the heater and circulating fan. The heat exchange adopts convection and radiative heat transfer. The rooms are all made of stainless steel liners with novel design, beautiful appearance and compact and reasonable structure.

9, electric contact pressure gauge: mainly used for carbon dioxide pressure source safety protection, can be set in advance a safety pressure, when the working pressure due to special reasons to reach the safety pressure, (such as the error of the valve) electric contact pressure gauge will automatically cut off the pressure Source power supply, implement security protection. Under normal circumstances, the working pressure is far below the safety pressure.

10. Flowmeter: The measurement of the flow of carbon dioxide at the outlet of a device for the preparation of a fine-limbed particle by a GAS method is measured using a dry flow meter and a gold-period rotameter.