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Spray drying technology in the application of the production of oral solid preparations

放大字体  缩小字体 Published date:2016-05-24 14:30:06   views:
Core tip:Method of spray drying technology is to use spray materials scattered in droplets form in the stream, material contact with hot gas fully, to complete the process of heat and mass transfer in an in
Method of spray drying technology is to use spray materials scattered in droplets form in the stream, material contact with hot gas fully, to complete the process of heat and mass transfer in an instant, the solvents (including water and organic solvent) quickly evaporated into gas, achieve the purpose of drying. Spray drying technology are widely used in the pharmaceutical industry in our country, in the field of oral solid preparation, often used in high heat sensitive medicines and medicines of the easy decomposition of dry material liquid enrichment process. The product particle size small, uniform, good flowability and solubility.

The characteristics and classification of spray drier


Spray dryer is the solution or suspension directly drying drying equipment for solid particles. Can be obtained directly by the material liquid and dry product, eliminating evaporation, crystallization, separation and crushing unit operations, such as continuous and automatic production, stable operation. Using this method of drying, spray drier gas solid two phase contact surface area is large, short drying time, generally the drying time is 5 ~ 30 s, is suitable for drying heat-sensitive materials. Dry the product quality is good, can obtain 30 ~ 50 microns particles, good flowability and solubility products. Defect is the volume of a dryer, heat transfer coefficient is low, lead to low thermal efficiency, power consumption is big.

Spray drier classification method has a lot of kinds, according to the gas and liquid flow can be divided into parallel flow, counterflow and mixed flow; According to the installation of the atomizer methods can be divided into the spray type, the spray type; According to the atomizer structure can be divided into centrifugal, pressure type gas flow; According to whether the heating gas cycle can be divided to open type, part of the circulating and closed.


The basic process of spray drying (closed)


Material liquid through the atomizer atomized, dispersed into tiny droplets into the drying chamber, at the same time, by the blower into heater heating gas to heat up, and then into the drying chamber. Material liquid droplets and the hot gas in drying chamber fully mixing, contact. Dry evaporating droplets of liquid to gas, materials into tiny particles. Mixture of gas-solid two phase in the induced draft fan cyclone separator, two phase separation, solid material sinking to the bottom collector, gas phase is led to the dust filter, capture the escape of the materials. Filter after condenser condensate gas phase, gas phase with solvent into liquid, can be collected to paraphrase, as a carrier gas is dry is recycled in the system.


Oral API process requirement


There are many different kinds of oral solid preparation, specific technical requirements also differ in thousands ways, in the process of spray drying machine design and manufacturing, do different designs for different varieties, best match the equipment and process in order to achieve the best state. In selecting solid preparation production of spray drying machine, often put forward some requirements listed below:


1. Clean requirements (please into the following seven little title in italics)


API production of the main processes need to comply to the level in the clean environment, the spray drying is important working procedure quality control. Spray drier parts of contact materials, should adopt stainless steel material, for acid corrosive strong material, had better choose the 316 l stainless steel. Drying chamber, cyclone separator, the filter parts, direct contact with the materials such as the lining should be smooth, no dead Angle, easy to clean, easy to disassemble, easy to clean. Spray drier tend to be huge, so cannot be in the clean area as a whole, often only will collect material parts in clean areas, sealed performance is good, this requires a system to prevent the external pollution not system.


2. Avoid wall sticking


Wall sticking phenomenon so far is still hinder the spray drying machine normal operation of a particular problem, the spray drying process of solid preparations (especially the Chinese traditional medicine). Collect of wall material viscosity is not only unfavorable to the operation, and with the extension of time, the sensitive material wall sticking happens metamorphic, unqualified material. From the perspective of process, the solution including chooses a suitable solvent, adding auxiliary materials, process parameters change, but the method can adjust the room is not very big, so we must from the perspective of equipment seeking radical solutions. Experts at home and abroad on the wall is in the process of drying and caking problem carried on the thorough research, agreed that the main reasons for wall sticking wall temperature. The following lists the possible ways to prevent the five kinds of wall sticking:

* double wall drying tower, with air cooled, keep the wall temperature under 50 ℃;


* by the tower wall spiral gas tangential introduced secondary air cooling tower wall;

* tower near the wall installation composed of a row of nozzle air broom, and turning slowly along the column wall;

* tower wall increase pneumatic hammer, through pneumatic hammer knock, materials from wall sticking force;

* to improve the accuracy of the processing of tower wall polishing can also reduce the wall sticking.


3. The control performance


Spray drying is a continuous production process, control points more. Control points such as closed circulation system including: feed concentration, feed speed, into the wind velocity, inlet air temperature, system pressure, differential pressure components, gas purity test and so on, is very difficult to rely on traditional manual adjustment. A good set of automatic control system, can make whole spray drying system run smoothly, reduce the fraction defective of the products, reduce the security hidden danger. At present domestic products, relatively backward in self-control and foreign advanced equipment, such as Denmark, lu company spray drier, in self-control technology has been very mature.


4. The drying effect


Because oral API also need to further complete the preparation process, improve the effect of preparation and its final drug taking absorption effect, the physical properties of the spray drying products put forward different requirements. First of all, the moisture content is the first indicator of dry products, general control in a certain scope, can not be too high or too low. Second, drug packaging generally according to the volume to control the load, which requires the bulk density of product stability, better liquidity of products. Oral medicine is often required instant. As a general rule, change atomization dispersion or proper operating conditions to control the drying rate, can be made with different bulk density of product, but the extent of change is limited. In improving the physical aspect it is important to note that a technology of foam spray drying, the feed liquid bubbles before spray drying. First is to increase the thermal efficiency and puts forward the method, then used to adjust the physical properties of the product. Has been proved that the product of the foam spray drying system large particle size, porous, sag, rough surface, good instant. In addition, oral API will also have some special requirements, such as particle shape. Some required spherical particle, particle size uniform. Generally speaking, by changing the way of atomization, can get a different shape of particles. API manufacturers in the choice before spray drier, the best in the equipment manufacturing enterprises, with the assistance of parameter optimization experiment, to determine an optimal parameter combination, to ensure that spewed drying effect of drugs.


5. Protection measures


Due to the different nature of drugs, the protection of equipment design are also put forward some higher requirements. Materials dissolved in organic solvent, in the whole system must meet the requirements of explosion-proof requirement when dry. In designing electrical, instrumentation, control valves and other accessories to select explosion-proof type. In addition, in order to prevent the solvent and air mixture of explosion gas, the system also can't use open, and closed circulation system must be used, and the carrier to choose an inert gas, such as nitrogen, etc. In addition, easy oxidation of some material is dry, also want to use nitrogen as the carrier of the closed loop system.


6. The environmental protection


Spray drying products for fine particles, in order to meet the requirements of environmental protection, the spray drying system with cyclone separation products, purifying exhaust gas is not enough, usually use bag filter purification, make the dust content in tail gas is lower than 50 mg/(nm) 3 gas; Or use wet scrubber, can will exhaust dust content down to 15 ~ 35 mg/(nm) 3 gas. By nitrogen as carrier, the system must pay attention to the enclosed, vent will lead to the outside.


7. To reduce costs


Hot air inlet temperature and flow operation for 250 ~ 500 ℃, countercurrent operation for 200 ~ 300 ℃, spray drying after the outlet temperature control in 60 ~ 100 ℃ in general. Spray drying heat utilization is low, the industrial scale of spray dryer, thermal efficiency is commonly 30% ~ 50%. Abroad with waste heat recovery of spray drying, the thermal efficiency can reach 70%, but this kind of equipment only if the production capacity of more than 100 kg (water)/h to have economic significance. But in nitrogen gas carrier and organic solvents are used, the closed loop system, can make the nitrogen recycling, solvent condensation to paraphrase, effectively reduces the production cost.


Domestic spray drier manufacturers are constantly improve the technical level, solve the technical problems in the field of spray drying in oral API, believe in the near future, will be able to produce more suitable, high quality and low price products, make the spray drying technology in China has reached the leading level in the world.

Keywords: Spray drying techno
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