JPS6355633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for operating a nitrogen production device using cryogenic separation, and particularly in a nitrogen production device that mainly performs liquid nitrogen sampling operation, it is suitable for operating a gaseous nitrogen sampling operation. It is about the method.

When performing liquid nitrogen collection operation using conventional nitrogen production equipment, in order to operate automatically, maximum load is applied to the expansion turbine, which is the source of cold generation in the equipment, and liquid nitrogen is automatically controlled to compensate for the surplus cold. It was taken out through a mechanism. Therefore, during a gas nitrogen sampling operation in which liquid nitrogen is not sampled, it is necessary to operate the expansion turbine by reducing the load on the expansion turbine by performing operations such as throttling the expansion turbine inlet valve using a remote controller or the like. In this case, if there is an imbalance between the refrigeration generated by the expansion turbine and the refrigeration losses required by the equipment, the liquid air (or liquid nitrogen) in the equipment will increase or decrease, and the tendency of long-term operating conditions , adjustment operations were required to optimize the load on the expansion turbine.

An object of the present invention is to enable operation switching in a nitrogen production apparatus by simply pressing the operation switching button, whether during liquid nitrogen sampling operation or gaseous nitrogen sampling operation, and
The object of the present invention is to provide a driving method that can automatically perform stable driving.

In the present invention, raw air is cooled by exchanging heat with low-temperature return gas in an air heat exchanger, and then introduced into a rectification column.
Nitrogen is collected by separating it into liquid air rich in nitrogen and oxygen in a rectification column, and the liquid air is introduced into a condenser at the top of the rectification column to liquefy the gaseous nitrogen, and the liquid air is gasified in the condenser. In a nitrogen production device that introduces nitrogen into an expansion turbine to compensate for the coldness of the device, a signal from a condenser liquid level controller controls a liquid nitrogen sampling valve via a switching mechanism, and the switching mechanism is switched to reduce the temperature of the condenser liquid. By controlling the expansion turbine inlet valve with the signal from the surface controller, it is possible to easily switch between liquid nitrogen sampling operation and gaseous nitrogen sampling operation, and to automatically ensure stable operation. be.

An embodiment of the present invention will be described below with reference to the drawings. The raw material air is pressurized to a predetermined pressure (approximately 8 kg/cm ² G) by a raw material air compressor (not shown), and after moisture and carbon dioxide are adsorbed and removed in an adsorption tower (not shown), it is passed through a conduit 13. It is introduced into the cold storage layer 5, cooled by exchanging heat with the low-temperature return gas in the air heat exchanger 1, and introduced into the rectification column 2 in a partially liquefied state.
In the rectification column 2, the feed air is separated by rectification into high-purity nitrogen and oxygen-rich liquid air. The air is cooled and taken out after recovering its temperature, and the liquid nitrogen is passed from the liquid reservoir at the top of the rectification column 2 to the conduit 1.
6. The liquid nitrogen is taken out through the liquid nitrogen collection valve 10. On the other hand, the oxygen-rich liquid air accumulated at the bottom of the rectification column 2 is introduced into the condenser 3 installed at the top of the rectification column 2 via a conduit 18, and the nitrogen gas at the top of the rectification column 2 is liquefied. The liquid nitrogen becomes a reflux liquid in the rectification column 2, and the gasified liquid air is taken out from the condenser 3 through the conduit 14 as waste gas. Most of the waste gas taken out from the condenser 3 cools the raw air in the air heat exchanger 1, and after the temperature has recovered to about -150°C, it is transferred to the conduit 15 and the expansion turbine inlet valve 11.
The waste gas is then introduced into the expansion turbine 4 where it undergoes adiabatic expansion and generates cold. The low-temperature waste gas passes through the air heat exchanger 1 again and exchanges heat with the feed air to restore the flow rate to room temperature. After that, it is removed via conduit 19. In this case, in order to maintain the pressure in the condenser 3 constant regardless of the load on the expansion turbine 4, the bypass valve 9 is automatically controlled by the pressure gauge 6, and all the waste gas is removed.

In the nitrogen production apparatus described above, 7 is the condenser 3
8 is a condenser liquid level controller that detects the liquid level and sends a signal; 8 is a remote-controlled expansion turbine inlet valve 11;
A remote controller 12 for opening and closing is a switching mechanism that is operated by an operation switching button (not shown) and switches the signal from the condenser liquid level controller 7 to the liquid nitrogen sampling valve 10 side and the expansion turbine inlet valve 11 side. When the switching mechanism 12 is switched to the liquid nitrogen sampling valve 10 side, the expansion turbine inlet valve 11 is fully opened, and when the switching mechanism 12 is switched to the expansion turbine inlet valve 11 side, the signal from the condenser liquid level controller is transmitted to the remote controller The signal is transmitted to the expansion turbine inlet valve 11 with priority over the signal.

During the liquid nitrogen sampling operation, the expansion turbine inlet valve 11 is fully opened by switching the switching mechanism 12 to the liquid sampling operation using the operation switching button, and the expansion turbine inlet valve 11 is fully opened by the signal from the condenser liquid level controller 7 via the switching mechanism 12. Liquid nitrogen sampling valve 10 is automatically controlled so that liquid nitrogen is sampled via conduit 16 to match the excess refrigeration within the apparatus. In addition, when performing gas nitrogen sampling operation, by switching the switching mechanism 12 to gas sampling operation, the signal from the condenser liquid level controller 7 is used via the switching mechanism 12 in priority to the signal from the remote controller 8. Since the expansion turbine inlet valve 11 is automatically controlled, it is possible to stably collect gaseous nitrogen.

Note that when the liquid nitrogen storage tank (not shown) becomes full during liquid nitrogen collection operation, by detecting this and operating the switching mechanism 12, the switching mechanism 12 is automatically activated. It is possible to switch to gas sampling operation.

As described above, in the present invention, raw air is cooled by exchanging heat with low-temperature return gas in an air heat exchanger, and then introduced into a rectification column, where it is separated into liquid air rich in nitrogen and oxygen. Nitrogen production involves collecting nitrogen through a distillation tower, introducing liquid air into a condenser at the top of the rectification column to liquefy the gaseous nitrogen, and introducing the gasified liquid air in the condenser into an expansion turbine to compensate for the cooling of the equipment. In the apparatus, a liquid nitrogen sampling valve is controlled via a switching mechanism by a signal from a condenser liquid level controller, and the switching mechanism is switched to control an expansion turbine inlet valve by a signal from a condenser liquid level controller. Because of this, it is possible to easily switch between liquid nitrogen sampling operation and gaseous nitrogen sampling operation with the operation switch button, and during liquid nitrogen sampling operation, all excess cold in the device can be automatically collected as liquid nitrogen. In addition, during the gas nitrogen collection operation, the load on the expansion turbine can be automatically adjusted according to the required cooling of the device, and the operation operation can be simplified and automatic operation can be performed.

[Brief explanation of the drawing]

The drawing is a system diagram showing an example of an apparatus implementing the method of operating a nitrogen production apparatus according to the present invention. 1... Air heat exchanger, 2... Rectification column, 3... Condenser, 4... Expansion turbine, 5... Cold storage tank, 6...
... Pressure gauge, 7 ... Condenser liquid level controller, 8 ... Remote controller, 9 ... Bypass valve, 10 ... Liquid nitrogen sampling valve, 11 ... Expansion turbine inlet valve, 12 ... Switching mechanism, 13 ~19... Conduit.

Claims (1)

[Claims] 1. Feed air is cooled by exchanging heat with low-temperature return gas in an air heat exchanger, and then introduced into a rectification column, where it is separated into liquid air rich in nitrogen and oxygen. The nitrogen production equipment collects liquid air, introduces it into a condenser at the top of the rectification column to liquefy the gaseous nitrogen, and introduces the liquid air gasified in the condenser into an expansion turbine to compensate for the cooling of the equipment. In the operating method, during the liquid nitrogen collection operation, the switching mechanism that can switch the operation is switched to the liquid sampling operation, and the expansion turbine inlet valve is fully opened via the switching mechanism in response to a signal from the condenser liquid level controller, and the liquid nitrogen is removed. In addition, during the gas nitrogen sampling operation, the switching mechanism is switched to fully close the liquid nitrogen sampling valve based on the signal from the condenser liquid level controller, and the expansion turbine inlet valve is controlled. Characteristic operating method of nitrogen production equipment.