JPH0212355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for restarting an air separation device using a reversible heat exchanger.

When restarting the air separation device after a temporary stop, if air is supplied to the rectification column before the reversible heat exchanger has cooled down, the holes in the rectification plate will become clogged. This is because the heat exchanger is not cooled, so impurities such as moisture and carbon dioxide in the air are introduced into the rectification column without being removed, and the liquid air remaining outside the condenser tube causes This is because the introduced air liquefies and the impurities solidify to block the holes in the rectifying plate.

For this reason, conventionally a valve was installed in the rectification tower air inlet pipe, and this valve was fully closed to supply air to the rectification tower until the reversible heat exchanger was recooled and carbon dioxide gas could be removed. I was trying not to.

However, installing a valve on the rectifier air inlet pipe complicates the piping and causes heat loss.
Moreover, when manufacturing and assembling everything up to the cold box in a factory, it was also a hindrance to being able to make it compact enough to be conveniently transported.

Therefore, the present invention was developed in view of the above points. When restarting the equipment after a temporary stop, the expansion turbine inlet valve is throttled until the heat exchanger is recooled and the carbon dioxide gas in the feed air is removed. It is characterized by raising the external pressure to the same level as the raw material air pressure, and its purpose is to:
The above-mentioned drawbacks are eliminated by eliminating the valve on the rectifier air inlet pipe.

An example illustrated in the drawings will be described below.

First, to explain steady operation, compressed raw air of 5 to 7 kg/cm ² entering from pipe 1 is transferred to automatic switching valve 2.
is cooled to approximately -170°C in a reversible heat exchanger 3, and then enters the lower part of a rectification tower 7 through a pipe 4, a return valve 5a, and a rectification tower inlet pipe 6, where it is rectified and separated. The nitrogen thus produced is led out from the top condenser 8, enters the liquefier 10 through a pipe 9, enters the heat exchanger 3 through a pipe 11, exchanges heat with the compressed raw air, and then passes through a pipe 12 and a valve 13.
It is collected through the process.

On the other hand, the liquid air accumulated at the bottom of the rectification tower 7 is transferred to the pipe 14
After passing through an acetylene adsorber 15 and a subcooler 16 and expanding to 1.5 to 2 kg/cm ² at a valve 17, it enters the condenser tube outside 18 of the rectification column 7. The liquid air supplied to the condenser tube outside 18 undergoes heat exchange with the nitrogen, and the vaporized air enters the liquefier 10 from the top of the condenser tube outside 18 of the rectification column 7 via a tube 19 and passes through a tube 20. After being introduced into the reheating section of the heat exchanger 3, it is taken out through a pipe 21, and introduced into an expansion turbine 23 via an expansion turbine inlet valve 22. The air that has entered the expansion turbine 23 undergoes adiabatic expansion to a pressure of approximately 0.15 Kg/cm ² , and the air passes through the pipe 24, subcooler 16, pipe 25, check valve 5b, and pipe 26.
After passing through the heat exchanger 3 and exchanging heat with the compressed raw material air, the temperature reaches room temperature, and then the pipe 27 and the automatic switching valve 2
It is then released into the atmosphere from the pipe 28.

Next, the case of restart will be explained.

The equipment may be temporarily stopped for reasons such as production adjustments or power outages, but after about 10 hours of this stoppage, the cold end (top in the figure) of the heat exchanger 3 will warm up, and the heat exchanger 3 will restart to supply raw air to the target. Even if the air is cooled by the vessel 3, impurities in the air cannot be removed, and when this outlet air is introduced into the rectifying column 7, the impurities adhere to the rectifying plate and cause clogging, as described above.

Therefore, the expansion turbine inlet valve 22 is throttled and the pressure on the outside of the condenser pipe 18 is increased so that the temperature exceeds the liquefaction temperature of air -174℃ (pressure 5Kg/cm ² ). Make sure you have nothing to do.
That is, this expansion turbine inlet valve 22 is used as a pressure regulating valve on the outside of the condenser pipe 18, and at the time of restart, the setting is kept at the same level as the air pressure in the rectifying column 7, so that the reversible heat exchanger 3 is sufficiently cooled. After that, open this.

As described above, when the air separation device is temporarily stopped and restarted, the present invention throttles the expansion turbine inlet valve to increase the external pressure of the condenser pipe so that liquid air is not produced in the rectification column. This eliminates the rectifier inlet valve that was previously provided, making the piping more compact, and also makes the expansion turbine inlet valve an automatic valve so that the external pressure of the condenser pipe is equal to the air pressure at startup. If the setting is set to , the operation will be simple and other effects will be achieved. In addition, since the piping from the return valve to the rectification column can be connected at a slope, there is no possibility that impurities will stagnate during this process.
Since the valve is no longer necessary, its cost can be reduced and heat loss that enters the device via the valve stem can be eliminated. Furthermore, there are other effects such as convenience when transporting the device after assembly.

[Brief explanation of drawings]

The figure is a system diagram showing an embodiment of the method of the present invention. 3 is a reversible heat exchanger, 7 is a rectification column, 8 is a condenser, 22 is an expansion turbine inlet valve, and 23 is an expansion turbine.

Claims (1)

[Claims] 1 After cooling the compressed feed air in a reversible heat exchanger, it is introduced into a single rectification column to be rectified, and liquid air is supplied to the outside of the rectification column condenser tube, where the vaporized air is upon restarting the air separation device introduced into the expansion turbine to generate refrigeration, by controlling the inlet valve of the expansion turbine until the reversible heat exchanger is recooled; A method for restarting an air separation apparatus, characterized in that the pressure outside the rectification column condenser tube is maintained at the same level as the pressure of air introduced into the rectification column.