Some synthetic drugs are usually crystallized in organic solvents and contain a considerable amount of organic solvents. If these organic solvents are directly discharged into the atmosphere, they will seriously pollute the environment and cause energy waste. Drying and recycling various solvents for reuse are not only in line with the requirements of environmental protection, but also the requirements of the company's own development. Therefore, for the drying of these drugs and APIs, it is more appropriate to choose a closed-circuit drying system, which can effectively achieve economical, Effective unification of environmental and social benefits.
In recent years, when drying anaerobic
materials or materials containing flammable and explosive organic solvents, and
the organic solvents can be recycled and cannot be discharged into the
atmosphere, closed-circuit dryers are generally used for drying of these
special materials. , using nitrogen as the drying medium, the nitrogen is
heated and circulated in the drying system, the nitrogen in the circulating
flow process takes out the organic solvent in the material, and the gaseous
organic solvent is condensed into a liquid state by the condenser in the drying
system, and It is recycled by the recycling system to achieve the purpose of
drying the material. At the same time, due to the injection of nitrogen in the
drying system, the oxygen content is reduced. When the oxygen content is
reduced to the specified value, anaerobic materials can also be safely dried.
Based on these advantages, this vertical closed-circuit dryer is currently in
comparison. Special pharmaceutical products, chemical products and other
industries are widely used. In the process of use, there are also some
prominent problems. In response to these problems, After many technical and
process demonstrations, our company has summarized the following problems and
proposed solutions
Problem 1: The dust removal method of
closed-circuit drying equipment is not environmentally friendly
For the dust removal method of
closed-circuit drying equipment currently used by many pharmaceutical
companies, pulse backflushing is mainly used for dust removal, some materials
will adhere to the surface of the filter cartridge. In order to make the
material on the surface of the filter cartridge fall off, the backflushing
system needs to backflush the inner wall of the filter cartridge, and the gas
used for backflushing is nitrogen. Backflushing into the equipment system
causes the positive pressure in the system to increase rapidly and the oxygen
content to decrease. When the positive pressure in the system reaches a certain
level, the automatic pressure relief port begins to release pressure, and the
frequency of pressure relief is very fast. During the pressure relief process
The nitrogen and the organic solvent in the nitrogen will be released from the
pressure relief port, which will consume a large amount of nitrogen, and the
recovery of the organic solvent will be much less.
Problem 2: The surface area of the filter
cartridge affects the production efficiency
In the process of backflushing and dust removal,
due to the relatively large surface area of the filter cartridge, the pressure
and flow of backflushing nitrogen are not enough to blow back all the materials
attached to the surface of the filter cartridge, so that the material on the
surface of the filter cartridge will accumulate more and more. The resistance
on the surface of the filter cartridge will become larger and larger, resulting
in poor material boiling state, or even no boiling, which seriously affects the
production efficiency and product yield.
Problem solving
Based on the problems raised above,
combined with the specific production process of the user's materials, the
process flow 2 shown in Figure 2 is a good solution. Its main process principle
is the same as process one, using the traditional air cylinder shaking bag dust
removal method, combined with the structural characteristics of the
closed-circuit drying equipment system with high airtightness requirements, the
dust removal cloth bag is made of smooth anti-static cloth with good air
permeability. The cylinder adopts a double-stroke cylinder structure. The long
stroke is used for disassembling and assembling the cloth bag or for
maintenance and repair, and the short stroke is used for the up and down
shaking of the cloth bag. Because the cloth bag shakes up and down under the
action of the cylinder, the material attached to the surface of the cloth bag
is easily shaken off, and the cylinder is shaken up and down using compressed
air, which has nothing to do with the mixture of nitrogen and air circulating
in the system. It saves a lot of nitrogen, and the pressure in the system will
not increase frequently and is automatically released to the atmosphere, which is
conducive to the requirements of environmental protection, and is also
conducive to the complete recovery of organic solvents in materials, and also
greatly improves production efficiency.
Comparison of advantages and disadvantages
of new and old processes
Compared with the first process, the main
advantages of the second process are as follows: ① It can recover the organic
solvent better and more effectively, and reduce the production cost; ② It can
save a lot of nitrogen; ③ It can better shake the bag for dust removal and
improve the production efficiency; ④ It can better Avoid the pollution of
organic solvents to the environment; ⑤ The operation procedure is simpler, more
convenient and easier to maintain. The main disadvantage is that the height of
the user's room is higher, or the user is required to open a hole on the
ceiling (top plate) of the room to facilitate the installation of the
double-stroke cylinder.
