Nitrogen filling and oxygen removal process
Close the corresponding pipeline control
valve, the system is in a completely closed state, open the air exhaust pump,
and pump out the air in the system, so that the system reaches a micro-negative
pressure state, when the system pressure gauge shows a certain value, close the
corresponding emptying valve, and at the same time Turn off the exhaust air
pump. At this time, the nitrogen filling control valve is opened, and nitrogen
is filled into the system. When the online oxygen detection device detects that
the residual oxygen in the system is less than the required value, the system
is in a slightly positive pressure state. At this time, the nitrogen filling
control valve is closed and the next step is entered. process.
Drying process
Turn on the circulating fan to make the
material in a good boiling state; turn on the radiator to heat the temperature
in the system to the required temperature, and the heat will take away the
moisture and organic solvent in the material through nitrogen transfer, and
take away a small amount of fine powder; in the system, the fine powder is
passed through the dust collector. (filtered to 2~μm) and collected, the hot
and humid gas condenses the solvent and organic solvent into a liquid state by
the condenser and is collected by the liquid storage tank; the dry nitrogen
after condensation and dehumidification is circulated in the system through the
action of the fan.
System nitrogen protection
Nitrogen protection is mainly controlled by
an online oxygen detector. When the oxygen content exceeds the required value,
the nitrogen filling device is automatically opened and nitrogen is filled into
the system. When the oxygen content in the system meets the requirements, the
nitrogen filling device is automatically closed.
System overvoltage protection
When the pressure in the system exceeds the
set value, the pressure detection device will act to automatically drain and
release the pressure; when the system pressure meets the requirements, the
automatic drain valve will be closed and the system will operate normally.
Practical application analysis
1) The laboratory vertical closed-circuit
dryer (model FGBX-5) has been rectified according to the structure in Figure 2
and can be put into use.
2) Prepare 5 kg of starch material
containing about 30% ethanol for use.
3) After the equipment is completely
sealed, start the air exhaust pump to pump out the air in the system. After the
system reaches a certain negative pressure value, turn off the air exhaust
pump, open the filling nitrogen valve at the same time, and input nitrogen into
the system. When the pressure is positive and the oxygen content in the system
reaches a certain requirement, close the valve for filling nitrogen; during
this process, if the system is in a state of slight positive pressure, but the oxygen
content has not yet reached the standard, nitrogen should continue to be filled
into the system. When the positive pressure in the system exceeds the safe set
pressure of the automatic pressure relief valve on the equipment, the automatic
pressure relief valve will open to release the pressure. When the pressure is
released, the mixed gas of nitrogen and air in the system will be discharged,
and the oxygen content in the system will continue. When the pressure in the
system reaches the safe set value, the automatic pressure relief valve will
automatically close, and this cycle will continue until the oxygen content in
the system reaches the set value.
4) Start the condensation recovery device,
and inject the chilled water of about 3° into the chilled water inlet of the
condenser. Then start the closed induced draft fan and set the fan frequency to
about 20 Hz.
5) Using the material level difference and
the principle of double butterfly valve, the material is put into the system
which is mainly nitrogen circulation.
6) Start the steam heater and control the
inlet air temperature at about 60°.
7) The material is in a boiling state
during the nitrogen circulation movement. The organic solvent ethanol and a
small amount of water in the material are taken out by nitrogen and condensed
into a liquid state by the condenser and flow into the recovery box. The dust
removal bag is shaken up and down under the action of the shaking bag cylinder,
and the material attached to the bag is shaken into the silo to continue
drying. Without any other gas entering the system, the micro-positive pressure
state in the system will not be very fast. Increase and open the automatic
pressure relief device, the mixed gas of nitrogen and organic solvent will not
be discharged from the system frequently, so that the nitrogen content in the
system is stable, nitrogen will not be replenished into the system frequently,
and the organic solvent will not be discharged.
It pollutes the environment and is
conducive to the recovery of organic solvents in good condition. If the process
shown in Figure 1 is used, due to the pulse backflushing method used in the
dust removal system of the upper cylinder during the drying process, a certain
pressure of nitrogen must be used for each backflushing, so that the pressure
in the system will increase rapidly and the pressure will be automatically
released. The valve will be opened frequently to release pressure, which will
take away a large amount of nitrogen and organic solvents, which will not only
pollute the environment, consume a large amount of nitrogen, but also have a
very low recovery rate of organic solvents. At the same time, in the drying
process, since the system only needs a slight positive pressure during
operation, the required air volume is small, which can not only reduce the
boiling height of the material, but also make it difficult for the material
dust to come into contact with the dust removal bag of the upper cylinder,
which will reduce the cloth
The bag resistance will also improve the
yield of materials, and the frequency of the induced draft fan can also be
reduced, saving energy consumption and reducing noise.
8) After the material is dried for 10
minutes, take samples through the sampler to confirm that the product has met
the requirements.
9) The weighing result of the product after
drying shows that the starch material is 3.45 kg, and the ethanol in the
recovery box of the condensation recovery device is 1.4 kg. meet the
experimental requirements.