JP7586126B2 - Nitrogen and oxygen supply equipment and nitrogen and oxygen supply method - Google Patents

Description

The present invention relates to an equipment and method for supplying nitrogen and oxygen to a nitrogen and oxygen-using facility by cryogenic separation of feed air.

One example of a facility for producing large quantities of high-purity nitrogen and oxygen is the cryogenic separation method described in Patent Document 1. The majority of the power consumption in the cryogenic separation method is consumed by the feed air compressor. Therefore, the amount of power consumed by the nitrogen and oxygen supply facility is largely determined by the amount of feed air to be processed. Therefore, processing excess feed air results in a loss of power consumption. The feed for the cryogenic separation method is air, and a fixed ratio of oxygen and nitrogen is produced relative to the amount of feed air to be processed, based on the composition of the air. In general, the amount of feed air processed is adjusted to obtain an oxygen supply equal to the oxygen demand.

The amount of nitrogen that can be produced using the amount of feed air required to meet the oxygen demand is often in excess of the nitrogen demand, and its use as a refrigerant, etc., contributes to reducing the electricity consumption of nitrogen and oxygen supply facilities.

For example, Patent Document 2 discloses a method for supplying nitrogen and oxygen that adjusts the supply amount by adjusting the number of operating units of multiple nitrogen and oxygen supply facilities, taking into account changes in supply and demand forecasts over time and restart times.

Furthermore, Patent Document 3 discloses an operation method that includes a temporary storage facility in addition to adjusting the amount of feed air processed up to the reduction limit of the nitrogen and oxygen supply facilities according to the oxygen demand.

Patent No. 6086272 Japanese Patent Application Publication No. 8-189759 Patent No. 5407661

The above-mentioned conventional techniques have the following problems.
In the techniques of Patent Documents 1 to 3, in order to reduce the amount of power required for producing nitrogen and oxygen, the amount of feed air processed is increased or decreased according to the oxygen demand. If the amount of feed air processed is reduced as the operating rate of the oxygen-using equipment decreases, the amount of nitrogen supplied will also decrease. In the conventional method for determining the amount of feed air processed, there was a problem that even if the operating rate of the oxygen-using equipment decreases, the amount of nitrogen supplied that matches the nitrogen demand becomes the rate limiting factor, and the amount of feed air processed cannot be reduced. The reason for this is that the oxygen demand of the oxygen-using equipment is proportional to the equipment operating rate, whereas the nitrogen demand is not proportional to the equipment operating rate. This is because there is a constant demand for nitrogen, regardless of the equipment operating rate, as an inert gas for sealing in anti-oxidation gas and for gas replacement in piping, etc.

In addition, nitrogen is often used as a refrigerant to reduce the operating power of air separation units. In that respect, too, when the equipment operating rate drops, the nitrogen used as a refrigerant must be diverted to meet demand, which goes against the goal of energy conservation.

On the other hand, nitrogen gas is used as an inert gas for gas replacement in emergencies. The demand for nitrogen is calculated taking into account not only the normal steady-state demand for nitrogen, but also the amount used in emergencies. Nitrogen is used for gas replacement in emergencies, so it is for a short period of time. However, a stable supply is required to deal with sudden increases and decreases in demand for nitrogen-using equipment. This is because any interruption in the supply of nitrogen for gas replacement could pose the risk of explosions and other dangers.

The present invention aims to solve the problems of the conventional technology and provide a nitrogen and oxygen supply equipment and a nitrogen and oxygen supply method that reduce energy consumption regardless of changes in equipment operating rate. In addition, the present invention aims to provide an apparatus and method that can stably supply nitrogen even when there is a sudden increase or decrease in nitrogen demand.

The nitrogen and oxygen supply equipment of the present invention, which solves the above problems and achieves the above objects, comprises an air separation unit that produces nitrogen and oxygen by cryogenic separation of feed air, and a supply means that supplies the produced nitrogen and oxygen to a use facility. The air separation unit has a cooling section that cools the feed air, a nitrogen gas refrigerant pipe that supplies a portion of the produced nitrogen as a refrigerant to the cooling section, a liquid nitrogen tank that stores a portion of the surplus nitrogen as liquid nitrogen, a liquid nitrogen pipe that connects the liquid nitrogen tank to the cooling section and the supply means, an external refrigerant supply pipe that supplies an external refrigerant to the cooling section, and a control means that selects the refrigerant for the cooling section. The air separation unit is configured to adjust the oxygen supply amount according to the demand of the oxygen-using facility, and the control means is configured to compare the demand of the nitrogen-using facility with the nitrogen supply amount of the air separation unit, and adjust the type and amount of refrigerant used in the cooling section so as to reduce the energy used by the air separation unit.

The nitrogen and oxygen supply equipment according to the present invention is
(A) the supply means is connected to the use equipment by a plurality of annular pipes;
(a) an accumulator is provided in each of the annular pipes;
This is thought to be a more preferable solution.

The nitrogen and oxygen supply method of the present invention, which solves the above problems and achieves the above objects, produces nitrogen and oxygen by cryogenic separation of feed air, and supplies the nitrogen and oxygen to an oxygen-using facility, using or not using a part of the produced nitrogen as a refrigerant for cooling the feed air, adjusting the oxygen supply amount in accordance with the demand of the oxygen-using facility, and comparing the demand of the nitrogen-using facility with the nitrogen supply amount to reduce energy use:
(a) storing surplus nitrogen as liquid nitrogen;
(b) supplying the stored liquid nitrogen to nitrogen-using equipment;
(c) using stored liquid nitrogen as a refrigerant for cooling the feed air;
(d) cooling the feed air with an externally cooled refrigerant;
The present invention is characterized in that one or more selected from the following is selected.

The method for supplying nitrogen and oxygen according to the present invention is as follows:
(c) Supplying nitrogen and oxygen by connecting the nitrogen-using equipment and the oxygen-using equipment with multiple circular pipes,
(D) Installing an accumulator in each of the annular pipings to adjust the pressure fluctuation to a predetermined level;
This is thought to be a more preferable solution.

According to the nitrogen and oxygen supply equipment and nitrogen and oxygen supply method of the present invention, when the equipment operating rate is high, the surplus nitrogen is used as a refrigerant to cool the air and is stored as liquid nitrogen, and when the equipment operating rate is low, the nitrogen shortage is made up by supplying stored liquid nitrogen, and the refrigerant to cool the air is selected to reduce energy usage, so that it is possible to keep energy usage low regardless of the equipment operating rate, which is extremely useful in industry.

In addition, by using multiple circular pipes as the nitrogen and oxygen supply means and installing accumulators, it is possible to provide a stable supply of nitrogen and oxygen even in the event of a temporary sudden increase or decrease in demand.

1 is a schematic diagram showing the configuration of a nitrogen and oxygen supply facility according to an embodiment of the present invention; 1 is a graph conceptually showing the operation index of nitrogen- and oxygen-using facilities, the demand for nitrogen and oxygen, and the supply amounts of nitrogen and oxygen of an air separation unit matched to the demand for oxygen. FIG. 1 is a conceptual diagram showing a schematic configuration of an air separation unit.

The following is a detailed description of the embodiments of the present invention. Note that the drawings are schematic and may differ from the actual ones. The following embodiments are intended to exemplify equipment and methods for embodying the technical ideas of the present invention, and are not intended to specify the configuration as described below. In other words, the technical ideas of the present invention can be modified in various ways within the technical scope described in the claims.

Figure 1 is a schematic diagram of a nitrogen and oxygen supply facility according to one embodiment of the present invention. The nitrogen and oxygen supply facility of this embodiment comprises an air separation unit 100 that produces nitrogen and oxygen by cryogenic separation of feed air, and a supply means 200 that supplies the produced nitrogen and oxygen to a user facility 16. The air separation unit 100 has a cooling section 2 for cooling the raw air compressed by the air compressor 1, a gas separation section 3 for separating nitrogen, oxygen, argon, etc., a nitrogen gas supply valve 4 and a pipe 5 for using the produced nitrogen as a refrigerant for the cooling section 2, a pipe connecting the produced nitrogen to a nitrogen supply means 200, a liquid nitrogen tank 9 for storing a part of the surplus nitrogen as liquid nitrogen LN2, a pipe connecting to the nitrogen supply means 200 via a liquid nitrogen supply pump 10, a liquid nitrogen switching valve 11, and a liquid nitrogen evaporator 12 to supply liquid nitrogen LN2 from the liquid nitrogen tank 9, a liquid nitrogen pipe for sending liquid nitrogen LN2 as a refrigerant from the liquid nitrogen switching valve 11 to the cooling section 2, and an external refrigerant supply valve 8 and a pipe 7 for supplying the refrigerant cooled externally to the cooling section 2. In addition, it has a refrigerant supply regulator 13 as a control means for selecting the refrigerant to be supplied to the cooling section 2 and adjusting the supply amount. The refrigerant supply regulator 13 controls the nitrogen gas refrigerant supply valve 4, the external refrigerant supply valve 8, and the liquid nitrogen switching valve 11 to select the refrigerant to be passed through the cooling unit 2. The nitrogen supply means 200 has a nitrogen gas compressor 6 that compresses the produced nitrogen gas, a plurality of annular pipes 14 connected to each other that distribute the nitrogen gas to the nitrogen-using equipment 16, and a pipe for supplying liquid nitrogen LN2. In addition, in the example of FIG. 1, each annular pipe 14 has a nitrogen gas accumulator 15 for adjusting the pressure.

Figure 3 shows a schematic diagram of a specific example of an air separation unit 100. The air separation unit 100 has an air filter 101, a feed air compressor 1, a water wash cooling tower 103, a pretreatment adsorber 106 (MS adsorber), and a rectification tower such as a main heat exchanger 121, a lower tower 122, and an upper tower 123 in an outer tank 112 (gas separation section). The feed air compressor 1 sucks in and compresses atmospheric air, which is the feed air, through the air filter 101. The air filter 101 removes, for example, dust particles from the air. The compressed feed air is, for example, at about 60°C.

The water-wash cooling tower 103 introduces the raw air compressed by the raw air compressor 1, and sprays cooling water onto the raw air from the top of the tower to wash and cool it. The raw air is cooled to, for example, about 10°C by the cooling in the water-wash cooling tower 103. The cooling water sprayed in the water-wash cooling tower 103 passes through the cooling tower 110 and various heat exchangers 131, and is circulated by the water pump 111 through the cooling water tower 104 and the freon refrigerator 105, etc., to be cooled.

The pretreatment adsorber 106 removes moisture and carbon dioxide from the cooled feed air. Two sets of pretreatment adsorber 106 are usually prepared. While one pretreatment adsorber 106 is adsorbing moisture and carbon dioxide, the adsorbent in the other pretreatment adsorber 106 is supplied with heated nitrogen by the pretreatment adsorbent regeneration heater 107, and the adsorbed components (moisture and carbon dioxide) are released into the atmosphere and removed. The dried, cleaned, and pressurized feed air is introduced into the outer tank 112 (gas separation section).

The main heat exchanger 121 then exchanges heat between the raw air from which impurities have been removed and the product gas, thereby cooling the raw air to a predetermined temperature. For example, the main heat exchanger 121 cools the air to nearly -200°C. The cooled raw air is introduced into the bottom of the lower tower 122. The lower tower 122 performs low-temperature distillation on the raw air cooled by the main heat exchanger 121, separating it into nitrogen gas concentrated at the top of the lower tower 122 and oxygen-enriched liquid concentrated at the bottom of the tower.

The upper tower 123 performs low-temperature distillation of the collected gas and liquid, separating them into nitrogen gas concentrated at the top of the tower and liquid oxygen concentrated at the bottom of the tower. The crude argon tower 124 performs low-temperature distillation of the gas extracted from the middle of the upper tower 123, separating Ar gas, nitrogen gas from the top of the tower, and oxygen-enriched liquid from the bottom of the tower.

The nitrogen, oxygen, and argon in the raw air are separated by utilizing the difference in boiling points of each gas and are extracted as gas or liquefied. The separated oxygen, nitrogen, and argon gas are each extracted through individual supply lines. Each supply line extends to its respective destination via the main heat exchanger 121. In other words, the separated oxygen GO2, nitrogen GN2, and argon gas GAr become low-temperature product gases that are heat exchanged. Here, the surplus nitrogen gas GN2 is sent to, for example, the cooling tower 104 and used to cool the cooling water that cools the raw air.

In this embodiment, the excess product gas is liquefied (LN2, LO2), and for example, liquid nitrogen LN2 is stored in a liquid nitrogen storage tank 9.

Next, a method of supplying nitrogen and oxygen using the nitrogen and oxygen supply equipment of this embodiment will be described. The nitrogen and oxygen supply equipment of the above embodiment is capable of calculating the demand for nitrogen and oxygen during normal operation of the equipment using the equipment and the demand for nitrogen and oxygen during a long-term and significant decrease in operation, and changing the operation according to the increase or decrease in the operating rate of the equipment using the equipment. In other words, when producing nitrogen and oxygen by cryogenic separation of the feed air and supplying them to the equipment using the equipment, a part of the produced nitrogen is used as a cooling refrigerant for the feed air, or is not used, and the oxygen supply amount is adjusted to match the demand of the oxygen-using equipment, and the demand of the nitrogen-using equipment 16 and the nitrogen supply amount of the air separation unit 100 are compared to operate so as to reduce the energy used. In supplying nitrogen and oxygen, one or more of the following is selected for operation: (a) storing surplus nitrogen as liquid nitrogen, (b) supplying the stored liquid nitrogen to nitrogen-using equipment, (c) using the stored liquid nitrogen as a refrigerant for cooling the feed air, and (d) cooling the feed air with an externally cooled refrigerant.

Figure 2 shows the operation index and nitrogen and oxygen demand for nitrogen and oxygen-using equipment, as well as the nitrogen supply when oxygen demand is added to oxygen supply. The operation index corresponds to the number of operating equipment and the operation rate of production volume when there are multiple using equipment, for example. As shown in Figure 2, the demand for oxygen gas is roughly proportional to the operation index of the using equipment. However, the demand for nitrogen gas is not proportional to the operation index. This is because there is a constant demand for nitrogen gas as an inert gas for sealing in anti-oxidation gases and for gas replacement in pipes, etc., regardless of the equipment operation rate.

In this embodiment, for example, when the operating rate of the oxygen-using equipment becomes higher than normal, excess nitrogen is produced in excess of what is needed as a refrigerant for cooling the feed air. That portion can be stored in the liquid nitrogen storage tank 9 as liquid nitrogen LN2. When the operating rate of the oxygen-using equipment becomes lower than normal, the liquid nitrogen LN2 stored in the liquid nitrogen storage tank 9 can be converted into nitrogen gas at a predetermined pressure via the liquid nitrogen evaporator 12 and introduced into the nitrogen gas supply means. This allows the amount of oxygen supply to be reduced without reducing the product nitrogen gas GN2 required as a refrigerant for cooling the feed air. Therefore, the amount of feed air used can be reduced, and the amount of electricity required by the feed air compressor can be reduced.

In addition, instead of using the product nitrogen gas GN2 as the cooling refrigerant for the feed air, liquid nitrogen LN2 can be used as the cooling refrigerant for the feed air. This ensures a supply of nitrogen and oxygen that satisfies the demand for nitrogen and oxygen while reducing the amount of feed air used and reducing the amount of electricity required by the feed air compressor.

Furthermore, if there is a shortage of liquid nitrogen (LN2), for example, a refrigerant cooled externally using a freon refrigerator can be used to cool the feed air. This reduces the amount of feed air used and the power consumption of the feed air compressor.

As described above, when selecting a refrigerant for cooling the feed air, the refrigerant supply regulator 13 adjusts the selection and amount of refrigerant so as to reduce the overall energy usage of the nitrogen and oxygen supply equipment. The refrigerant supply regulator 13 can be configured with a computer, sequencer, etc. Based on a prediction of long-term demand trends for the nitrogen and oxygen use equipment, adjustments may be made so as to reduce the total energy consumption over a specified period. It is preferable to minimize energy usage.

In the nitrogen and oxygen supply method of this embodiment, it is preferable to supply nitrogen and oxygen by connecting the nitrogen-using equipment and oxygen-using equipment with multiple annular pipes. In the example of FIG. 1, a double annular pipe is used as the nitrogen gas supply means to supply nitrogen to the nitrogen-using equipment 16. When the nitrogen-using equipment is connected in series and supplied, if the amount of nitrogen used on the upstream side (the side closer to the nitrogen production equipment) increases suddenly, the pressure on the downstream side (the side farther from the nitrogen production equipment) will drop, and it may not be possible to supply the required amount of demand. By using multiple annular pipes, the nitrogen supply pressure can be stabilized. The same applies to the oxygen supply means.

In the nitrogen and oxygen supply method of this embodiment, it is preferable to install an accumulator in each of the annular piping that supplies nitrogen and oxygen, and adjust the pressure fluctuation to a predetermined level. This makes it possible to suppress fluctuations in the supply pressure of nitrogen and oxygen even if there is a sudden change in the demand of the equipment used. For example, it is preferable to calculate the capacity and capability of the accumulator used as the nitrogen gas supply means based on the total volume of the equipment and piping that require nitrogen replacement and the final required nitrogen concentration as the amount of nitrogen required in an emergency.

The nitrogen and oxygen supply facility may have multiple air separation units. In that case, depending on the operating status of the facilities used, if reducing the number of operating air separation units results in a reduction in energy consumption, it is preferable to reduce the number of operating air separation units.

Tests were conducted to supply nitrogen and oxygen using the nitrogen and oxygen supply equipment of the configuration shown in Figure 1. In Test No. 1 in Table 1, the index was set to 100 based on the air processing volume during normal operation. In addition, the oxygen gas supply volume and the nitrogen gas supply volume are shown as indexes based on volume. In Test No. 2 in Table 1, a specified amount of product nitrogen gas was used as a refrigerant for cooling the feed air based on the conventional operation method, and operation was performed to minimize the amount of electricity used. In Test No. 3 in Table 1, based on the above embodiment, operation was performed using the refrigerant and its amount for cooling the feed air to minimize the amount of electricity used. In Test No. 2, even though the operation index was reduced to 70, only an index of 80 was required for feed air processing to satisfy the demand for nitrogen gas with a nitrogen gas supply index of 22. In Test No. 3, the feed air processing volume could be reduced to an index of 70 in proportion to the operation index of 70.

The nitrogen and oxygen supply equipment and method of supplying nitrogen and oxygen according to the present invention make it possible to keep energy consumption low regardless of the operating rate of the equipment that uses nitrogen and oxygen, and are extremely useful in industry.

1 Feed air compressor 2 Cooling section 3 Gas separation section 4 Nitrogen gas supply valve for refrigerant 5 Nitrogen gas supply piping for refrigerant 6 Nitrogen gas compressor 7 External refrigerant supply piping 8 External refrigerant supply valve 9 Liquid nitrogen storage tank 10 Liquid nitrogen supply pump 11 Liquid nitrogen switching valve 12 Liquid nitrogen evaporator 13 Refrigerant supply regulator 14 Circular piping 15 Nitrogen gas accumulator 16 Nitrogen-using equipment 100 Air separation unit 101 Air filter 103 Water-wash cooling tower 104 Cooling tower 105 Fluorine refrigerator 106 Pretreatment adsorbent 107 Pretreatment adsorbent regeneration heater 110 Cooling tower 111 Water pump 112 Outer tank (gas separation section)
121 Main heat exchanger 122 Lower column 123 Upper column 124 Crude argon column 131 Heat exchanger 200 Supply means LN2 Liquid nitrogen LO2 Liquid oxygen GN2 Nitrogen gas GO2 Oxygen gas GAr Argon gas

Claims (6)

an air separation unit which produces nitrogen and oxygen by cryogenic separation of feed air;
A supply means for supplying the produced nitrogen and oxygen to a facility that uses the produced nitrogen and oxygen;
The air separation unit includes a cooling section for cooling the feed air, a nitrogen gas piping for refrigerant for supplying a portion of the produced nitrogen as a refrigerant to the cooling section, a liquid nitrogen tank for storing a portion of the surplus nitrogen as liquid nitrogen, a liquid nitrogen piping for connecting the liquid nitrogen tank to the cooling section and the supply means, an external refrigerant supply pipe for supplying an external refrigerant to the cooling section, and a control means for selecting a refrigerant for the cooling section;
The air separation unit is configured to adjust the amount of oxygen supplied in accordance with the demand of the oxygen-using facility,
The control means is configured to compare the demand of the nitrogen-using equipment with the nitrogen supply amount of the air separation unit, and adjust the type and amount of refrigerant used in the cooling section so as to reduce the energy consumption of the air separation unit.
Here, a reduction in energy usage means a reduction in the feed air throughput, based on the feed air throughput when only surplus nitrogen gas is used as a refrigerant for the feed air. The nitrogen and oxygen supply system of claim 1, wherein the supply means is connected to the use equipment by a plurality of annular piping. The nitrogen and oxygen supply system of claim 2, wherein an accumulator is installed in each of the annular pipes. The nitrogen and oxygen supply system according to claim 1 is used to produce nitrogen and oxygen by cryogenic separation of feed air and supply the nitrogen and oxygen to a use facility,
A part of the produced nitrogen is used as a refrigerant for cooling the feed air, or not used,
Adjust the amount of oxygen supplied according to the demand of the oxygen-using equipment.
By comparing the demand and supply of nitrogen at the nitrogen-using facility, the energy consumption is reduced.
(a) storing surplus nitrogen as liquid nitrogen;
(b) supplying the stored liquid nitrogen to nitrogen-using equipment;
(c) using stored liquid nitrogen as a refrigerant for cooling the feed air;
(d) cooling the feed air with an externally cooled refrigerant;
A method for supplying nitrogen and oxygen, comprising: selecting one or more of the following:
Here, a reduction in energy usage means a reduction in the feed air throughput, based on the feed air throughput when only surplus nitrogen gas is used as a refrigerant for the feed air. The method for supplying nitrogen and oxygen according to claim 4, in which the nitrogen-using equipment and the oxygen-using equipment are connected by multiple annular pipes to supply nitrogen and oxygen. The method for supplying nitrogen and oxygen according to claim 5, in which an accumulator is installed in each of the annular pipes to adjust the pressure fluctuation to a predetermined value.

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