Oxygen generating method and oxygen generating device

Abstract

To provide an oxygen generation method and an oxygen generation device that suppress a fall in temperature of an oxygen adsorbent in the vicinity of a wall surface in an adsorption tower.SOLUTION: An oxygen generation method according to a pressure swing adsorption system uses an adsorption tower that comprises a heat insulation material on an inner wall, and is filled with an oxygen storage agent for adsorbing and eliminating oxygen at high temperature in a central space of the heat insulation material.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an oxygen generating method and an oxygen generating device. [Background technology]

[0002] Industrial oxygen gas is produced using cryogenic separation equipment that liquefies and distills air, separating it into nitrogen gas and oxygen gas by utilizing the difference in liquefaction temperature. However, when a relatively small amount of oxygen is required, a pressure swing adsorption (PSA) type oxygen generator is used because the efficiency of cryogenic separation equipment is low. A PSA oxygen generator is a device that generates oxygen gas by removing nitrogen gas from the air using zeolite, which adsorbs nitrogen gas. A PSA oxygen generator adsorbs nitrogen at high pressure and desorbs the adsorbed nitrogen by reducing the pressure with a vacuum pump, making it possible to adsorb nitrogen repeatedly and continuously generate non-adsorbed oxygen. However, in order to adsorb nitrogen gas, which makes up 78% of the atmosphere, and desorb it with a vacuum pump, the adsorption tower is large and a large-displacement vacuum pump is required. In contrast, if a perovskite-based material capable of absorbing and desorbing oxygen at high temperatures is used, only the oxygen that makes up 21% of the atmosphere can be adsorbed and then desorbed using a vacuum pump, allowing the adsorption tower and vacuum pump to be made smaller, enabling efficient oxygen generation with reduced power consumption. For this reason, in factories and other places with heat sources, oxygen supply using PSA type high-temperature oxygen generators made of materials that can adsorb and desorb oxygen at high temperatures is beginning to be considered.

[0003] Patent Document 1 describes a method for separating oxygen and nitrogen by pressure swing adsorption (PSA), in which a mixed gas mainly composed of oxygen and nitrogen is supplied under relatively high pressure conditions to an adsorption tower equipped with a heat storage material, a mixed gas-nitrogen heat exchanger, a mixed gas heater, and a high-temperature acid adsorbent, the mixed gas is brought into contact with the heat storage material to raise the temperature of the mixed gas, the mixed gas is then heat exchanged with nitrogen at the tower outlet in the mixed gas-nitrogen heat exchanger to raise the temperature, the mixed gas is then brought into contact with the mixed gas heater to set the adsorption temperature, the oxygen is brought into contact with a high-temperature oxygen adsorbent to adsorb and separate from the nitrogen, the high-temperature oxygen adsorbent with the oxygen adsorbed is brought into relatively low pressure conditions to desorb the oxygen, and heat is recovered from the high-temperature oxygen by contacting the oxygen with the heat storage material; and a pressure swing adsorption apparatus for separating oxygen and nitrogen by supplying a mixed gas mainly composed of oxygen and nitrogen under relatively high pressure conditions. The pressure swing adsorption apparatus described herein includes, in the order of flow direction of the mixed gas, (1) a heat storage material for recovering heat from the adsorbed high-temperature oxygen and transferring the recovered heat to the mixed gas, (2) a mixed gas-nitrogen heat exchanger in which the mixed gas that has passed through the separated heat storage material flows through one side of the heat exchanger and the high-temperature nitrogen product gas flowing out of the packed tower flows through the other side of the heat exchanger, recovering heat from the high-temperature nitrogen product gas to the mixed gas and raising the temperature of the mixed gas flowing out of the heat exchanger, (3) a heater for heating the mixed gas that has been heated through the heat exchanger with nitrogen to the adsorption temperature, and (4) two or more packed towers equipped with an adsorbent bed that selectively adsorbs oxygen through the mixed gas that has passed through the mixed gas-nitrogen heat exchanger and allowing the nitrogen to pass through, in parallel, and the packed towers separate oxygen and nitrogen that are stored in an insulation cabinet to keep them warm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-012439 A Summary of the Invention [Problem to be solved by the invention]

[0005] The pressure swing adsorption device for separating oxygen and nitrogen described in Patent Document 1 is equipped with a heat storage material, a mixed gas-nitrogen heat exchanger, a mixed gas heater, and a high-temperature oxygen adsorbent inside an adsorption tower, and recovers exhaust heat to increase thermal efficiency and reduce the power consumption rate for oxygen generation. However, since various equipment is installed inside the adsorption tower, the structure of the adsorption tower is complicated and the manufacturing costs are high. The adsorbent is heated by heating the raw gas with a single heater and supplying it to each tower by switching the valves, which simplifies the equipment and significantly reduces manufacturing costs. However, with the conventional method of keeping the adsorption tower warm by applying insulation to the outside, there was a problem that the heat was dissipated through the base material of the adsorption tower, causing the temperature of the oxygen adsorbent near the wall of the adsorption tower to drop, making it impossible to adsorb and desorb oxygen.

[0006] An object of the present invention is to provide an oxygen generating method and an oxygen generating apparatus capable of suppressing a decrease in temperature of an oxygen adsorbent in the vicinity of the wall surface of an adsorption tower. [Means for solving the problem]

[0007] [1] A method for generating oxygen by pressure swing adsorption using an adsorption tower with an insulating material on its inner wall and a central space in the insulation filled with an oxygen absorbing agent that adsorbs and desorbs oxygen at high temperatures. [2] The oxygen generation method according to [1], wherein air at 250 to 450°C is brought into contact with the oxygen storage agent at 0 to 100 kPaG to adsorb oxygen, and then the pressure applied to the oxygen storage agent is reduced to desorb oxygen from the oxygen storage agent and generate oxygen. [3] The oxygen generating method described in [1] or [2], in which a plurality of the adsorption towers are used to continuously generate oxygen by sequentially repeating the adsorption of oxygen to the oxygen adsorbent and the desorption of oxygen from the oxygen storage agent. [4] A method for generating oxygen by a pressure swing adsorption system using two or more adsorption towers, each of which has an inner wall provided with a thermal insulation material and is filled with an oxygen storage agent that adsorbs and desorbs oxygen at high temperatures in a central space of the thermal insulation material, an adsorption step of contacting the oxygen occluding agent with air to adsorb oxygen to the oxygen occluding agent; a desorption step of reducing the pressure applied to the oxygen occluding agent to desorb oxygen from the oxygen occluding agent; a desorption + rinsing process in which exhaust gas from another adsorption process is introduced while the pressure applied to the oxygen occluding agent is kept reduced to promote desorption of oxygen from the oxygen occluding agent; Including, The method does not include a pressure equalization step of recovering pressure from the plurality of adsorption towers. The oxygen generating method according to any one of [1] to [3]. [5] The oxygen generating method according to any one of [1] to [4], wherein the temperature when oxygen is desorbed from the oxygen storage agent is 250 to 450°C. [6] An oxygen generation device using a pressure swing adsorption system for carrying out the oxygen generation method described in any one of [1] to [5], which uses an adsorption tower equipped with a thermal insulation material on its inner wall and filled with an oxygen storage agent that adsorbs and desorbs oxygen at high temperatures in the central space of the thermal insulation material. Effect of the Invention

[0008] According to the present invention, it is possible to provide an oxygen generating method and an oxygen generating device capable of suppressing a decrease in temperature of the oxygen adsorbent in the vicinity of the wall surface of the adsorption tower. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an oxygen generating device according to an embodiment of the present invention; [Diagram 2] 1 is a schematic diagram showing a vertical cross section of an adsorption tower used in the oxygen generation device of the present embodiment. FIG. [Diagram 3] 1 is a schematic diagram showing a cross section of an adsorption tower used in the oxygen generation device of the present embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the oxygen generating device and the oxygen generating method of the present embodiment will be specifically described with appropriate reference to the drawings.

[0011] FIG. 1 is a schematic diagram showing an oxygen generating apparatus for carrying out the oxygen generating method of the present embodiment. The oxygen generation device 1, the schematic configuration of which is shown in FIG. 1, includes a first adsorption tower 20A having an adsorption tower body 21 equipped with a thermal insulation material 23 on the inner wall thereof and having a central space of the thermal insulation material 23 filled with an oxygen storage agent 22 that adsorbs and desorbs oxygen at high temperatures, a second adsorption tower 20B having a configuration similar to that of the first adsorption tower 20A, a boost pump 11, a vacuum pump 12, a gas heater 13, gas flow paths L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14, L15, valves A1, B1, A2, B2, A3, B3, NV, and RV.

[0012] The gas flow path L1 is connected to the inlet side of the boost pump 11, and air AIR, which is a raw material gas, is fed to the gas flow path L1. IN This is a gas flow path for taking in the gas. The gas flow passage L2 is a gas flow passage that connects the outlet side of the boost pump 11 and the gas heater 13. The gas flow path L3 is a gas flow path that connects the gas heater 13, the valve A1, and the valve B1. The gas flow path L4 is a gas flow path that connects the first adsorption tower 20A and the valve A1. The gas flow path L5 connects the second adsorption tower 20B and the valve B1. The gas flow path L6 connects the first adsorption tower 20A and the valve A2. The gas flow path L7 connects the second adsorption tower 20B and the valve B2. The gas flow path L8 is a gas flow path that connects the inlet side of the vacuum pump 12, the valve A2, and the valve B2. The gas flow path L9 connects the first adsorption tower 20A and the valve NV. The gas flow path L10 connects the second adsorption tower 20B and the valve RV. The gas flow path L11 connects the first adsorption tower 20A and the valve A3. The gas flow path L12 connects the second adsorption tower 20B and the valve B3. The gas flow path L13 is connected to the outlet side of the vacuum pump 12 and supplies oxygen gas O2 OUT ... is a gas flow path that discharges The gas flow path L14 is connected to the valve A3 and the valve B3, and is a gas flow path for discharging the exhaust gas EX from the oxygen generation device 1. The gas flow path L15 is a gas flow path that connects the valve NV and the valve RV.

[0013] FIG. 2 is a schematic diagram showing a vertical cross section of the adsorption tower 20 used in the oxygen generation device 1 of this embodiment. FIG. 3 is a schematic diagram showing a cross section of the adsorption tower 20 used in the oxygen generation device 1 of this embodiment. An insulating material 23 is provided on the inner wall of the adsorption tower body 21, and the central space of the insulating material 23 is filled with an oxygen storage agent 22 that adsorbs and desorbs oxygen at high temperatures. The material of the adsorption tower body 21 is usually, but not limited to, a stainless steel alloy because it can withstand high temperatures and has good durability. In addition, it is preferable to provide a heat insulating material around the adsorption tower 20 to prevent heat radiation.

[0014] Any material that is heat resistant at the operating temperature can be used as the insulating material 23, and examples of such materials include rock wool, alumina fiber, and alkali silicate wool. Furthermore, materials that are gas impermeable are preferable as the insulating material 23, and examples of materials that can be used include an insulating board made of calcium silicate, a cement-based insulating board, and firebricks. In the case of insulating materials that are gas permeable, the volume of the insulating material becomes a dead volume, and unadsorbed nitrogen enters the product oxygen, causing a decrease in the oxygen concentration.

[0015] The oxygen storage agent 22 is not particularly limited as long as it is an oxygen storage agent that adsorbs and desorbs oxygen at high temperatures, and examples thereof include metal oxides having a perovskite structure (perovskite-based oxygen storage agents). The oxygen storage agent 22 is preferably an oxygen storage agent that adsorbs and desorbs oxygen at 250 to 450° C. If the operating temperature of the oxygen storage agent is 450° C. or lower, gas heating using a heat-resistant valve becomes possible, and the adsorption tower does not need to be equipped with a heater, which can simplify the system. If the operating temperature of the oxygen storage agent is 250° C. or higher, the speed of oxygen adsorption and desorption to the oxygen storage agent increases, and the amount of oxygen generated increases.

[0016] Hereinafter, an oxygen generating method (oxygen generating method of the present embodiment) using the oxygen generating device of the present embodiment shown in FIG. 1 will be described.

[0017] In the oxygen generation method of the present embodiment, in an oxygen generation apparatus 1 using a PSA system as shown in FIG. 1, a first adsorption tower 20A and a second adsorption tower 20B are used to continuously recover oxygen while sequentially switching between an adsorption process, a desorption process, a desorption+rinse process, and a pressurization process, which will be described later, to generate oxygen using air as a raw material gas. In the following explanation, we will explain the half cycle, which is the adsorption of oxygen to the oxygen storage agent in the first adsorption tower 20A (adsorption process) and the recovery of oxygen from the oxygen storage agent in the second adsorption tower 20B (desorption process, desorption + rinsing process, and pressurization process).

[0018] (Adsorption process) Valve A1 is open, valve A2 is closed, valve A3 is open, valve B1 is closed, valve B3 is closed, and valve NV is open. Valve B2 and valve RV are selected to be open or closed depending on the process of the second adsorption tower 20B. Using a boost pump 11, air AIR, which is a raw material gas, is pumped from a gas flow path L1. IN The air is taken in, pressurized, and sent to the gas heater 13 through the gas flow passage L2 to heat the air. The temperature of the air after heating is preferably 250 to 450°C, and more preferably 300 to 400°C. The air heated by the gas heater 13 is introduced into the first adsorption tower 20A from the lower part of the adsorption tower through the gas flow path L3. When the air passes through the first adsorption tower 20A, oxygen in the air is adsorbed by the oxygen storage agent 22, and nitrogen-enriched gas is taken out from the upper part of the first adsorption tower 20A. In the present invention, it is preferable to bring air at 250 to 450° C. into contact with the oxygen storage agent at 0 to 100 kPaG to adsorb oxygen. From the viewpoint of reducing the power required for the compressor, it is preferable that the feed air pressure is close to atmospheric pressure, but taking into consideration the pressure losses in the heater, tower, and valves, a pressure of 0 to 100 kPaG is suitable. A portion of the nitrogen-enriched gas extracted from the top of the first adsorption tower 20A is sent to the second adsorption tower 20B as a rinsing gas, and the rest is used in the desorption + rinsing process. The rest is discharged from the oxygen generator 1 to the outside of the system through gas flow path L11 and gas flow path L14 as exhaust gas EX.

[0019] (Desorption process) Valve A1 is open, valve A2 is closed, valve A3 is open, valve B1 is closed, valve B2 is open, valve B3 is closed, valve RV is closed, and valve NV is open. The vacuum pump 12 is operated to reduce the pressure in the second adsorption tower 20B, thereby reducing the pressure on the oxygen storage agent 22 and desorbing the adsorbed oxygen from the oxygen storage agent 22. The desorbed oxygen is taken out from the bottom of the second adsorption tower 20B by the vacuum pump 12 and is circulated as product oxygen O2 through gas flow path L7, gas flow path L8, vacuum pump 12, and gas flow path L13. OUT is sent out of the system of the oxygen generator 1 as

[0020] (Desorption + Rinse process) Valve A1 is open, valve A2 is closed, valve A3 is open, valve B1 is closed, valve B2 is open, valve B3 is closed, valve RV is open, and valve NV is open. With the vacuum pump 12 operating to reduce the pressure inside the second adsorption tower 20B, a portion of the nitrogen-enriched gas sent out from the top of the first adsorption tower 20A is introduced into the interior of the second adsorption tower 20B from the top of the second adsorption tower 20B as a rinse gas. The rinse gas promotes the desorption of oxygen from the oxygen storage agent 22 in the second adsorption tower 20B. Since the oxygen adsorbed in the oxygen storage agent acts on the oxygen partial pressure in the air, which is the raw material gas, the introduction of the rinse gas reduces the oxygen partial pressure in the oxygen storage agent, and oxygen is desorbed more efficiently. The oxygen desorbed from the oxygen occluding agent 22 is taken out from the bottom of the second adsorption tower 20B by the vacuum pump 12, and is circulated as product oxygen O2 through the gas flow path L7, the gas flow path L8, the vacuum pump 12, and the gas flow path L13. OUT is sent out of the system of the oxygen generator 1 as

[0021] (Pressure increase process) Valve A1 is open, valve A2 is closed, valve A3 is open, valve B1 is closed, valve B2 is closed, valve B3 is closed, valve RV is open, and valve NV is open. By introducing a rinse gas into the second adsorption tower 20B, the pressure inside the second adsorption tower 20B is increased.

[0022] By alternately repeating the adsorption step, the desorption step, the desorption + rinsing step, and the pressurization step in the first adsorption tower 20A and the second adsorption tower 20B, oxygen can be continuously generated from air.

[0023] (Pressure equalization process) In a typical PSA oxygen generation method, a pressure equalization step is introduced to recover the pressure in one adsorption tower to the other in order to reduce the power of the boost pump. However, in the oxygen generation method of this embodiment, it is preferable not to perform the pressure equalization step. This is because if the nitrogen-rich gas after oxygen is adsorbed by the oxygen storage agent in the first adsorption tower 20A is introduced into the second adsorption tower 20B to perform the pressure equalization step, a part of the oxygen extracted from the first adsorption tower 20A flows into the second adsorption tower 20B, and the amount of oxygen recovered from the second adsorption tower 20B decreases. In particular, when a perovskite-type metal oxide is used as the oxygen storage agent, the amount of oxygen generated is likely to decrease when the pressure equalization step is performed.

[0024] [Effects] The stainless steel used in adsorption towers has good thermal conductivity, so simply installing insulation on the outside of the adsorption tower will limit the insulating effect because heat will escape in the vertical direction of the tower. However, by installing insulation inside the tower, the release of heat through the stainless steel is prevented, making it possible to achieve a high insulating effect. EXAMPLES

[0025] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples described below, and various modifications are possible without departing from the gist of the present invention.

[0026] [Example 1] A stainless steel adsorption tower with an inner diameter of 300 mm and an inner wall with 50 mm of a highly gas-permeable insulating material (Isowool BSSR1300 Blanket 130, manufactured by Isolite Industries) was filled with 17 kg of perovskite-based oxygen storage agent to a filling height of 400 mm (12.5 L). The exterior of the adsorption tower, the gas heater, the piping from the gas heater to the adsorption tower, and the valves were also insulated with 50 mm thick material to prevent heat loss. Using an oxygen generator equipped with two of these adsorption towers, the schematic configuration of which is shown in Figure 1, 300 L / min of heated air was flowed at 10 kPaG, and oxygen was adsorbed into the oxygen storage agent in the center of the adsorption tower while it was heated to 340°C (adsorption process).Then, the air was evacuated to -80 kPaG using a vacuum pump to desorb the oxygen adsorbed by the oxygen storage agent, and the oxygen desorbed from the oxygen storage agent was removed from the adsorption tower (desorption process, desorption + rinsing process, pressurization process). The adsorption process, desorption + rinsing process, and pressurization process were performed alternately in two towers using the valve opening and closing sequence shown in Table 1, enabling oxygen-enriched gas with an oxygen concentration of 50% by volume to be continuously obtained at 100 L / min.

[0027] [Example 2] A stainless steel adsorption tower with an inner diameter of 300 mm and an inner wall with 50 mm of low gas permeability insulation (ISOLITE B6, manufactured by Isolite Industries Co., Ltd.) was filled with 17 kg of perovskite-based oxygen storage agent to a filling height of 400 mm (12.5 L). The exterior of the adsorption tower, the gas heater, the piping from the gas heater to the adsorption tower, and the valves were also insulated with 50 mm thick material to prevent heat loss. Using an oxygen generator equipped with two of these adsorption towers, the schematic configuration of which is shown in Figure 1, 300 L / min of heated air was flowed at 10 kPaG, and oxygen was adsorbed into the oxygen storage agent in the center of the adsorption tower while it was heated to 340°C (adsorption process).Then, the air was evacuated to -80 kPaG using a vacuum pump to desorb the oxygen adsorbed by the oxygen storage agent, and the oxygen desorbed from the oxygen storage agent was removed from the adsorption tower (desorption process, desorption + rinsing process, pressurization process). The adsorption process, desorption + rinsing process, and pressurization process were performed alternately in two towers using the valve opening and closing sequence shown in Table 1, enabling oxygen-enriched gas with an oxygen concentration of 71% by volume to be continuously obtained at a rate of 70 L / min.

[0028] [Comparative Example 1] A stainless steel adsorption tower with an inner diameter of 300 mm and no internal insulation was filled with 17 kg of a perovskite-based oxygen storage agent to a filling height of 175 mm (12.4 L). The exterior of the adsorption tower, the gas heater, the piping from the gas heater to the adsorption tower, and the valves were covered with 50 mm thick insulation to prevent heat loss. Using an oxygen generator equipped with two of these adsorption towers, the schematic configuration of which is shown in Figure 1, 300 L / min of heated air was flowed at 10 kPaG, and oxygen was adsorbed into the oxygen storage agent in the center of the adsorption tower while it was heated to 340°C (adsorption process).Then, the air was evacuated to -80 kPaG using a vacuum pump to desorb the oxygen adsorbed by the oxygen storage agent, and the oxygen desorbed from the oxygen storage agent was removed from the adsorption tower (desorption process, desorption + rinsing process, pressurization process). The adsorption process, desorption + rinsing process, and pressurization process were performed alternately in two towers using the valve opening and closing sequence shown in Table 1, enabling oxygen-enriched gas with an oxygen concentration of 38% by volume to be continuously obtained at 80 L / min.

[0029] [Table 1]

[0030] (Explanation of results) Comparing the working example and the comparative example, by placing an internal insulation material between the outer wall of the adsorption tower and the oxygen adsorbent, it was possible to suppress the temperature drop of the oxygen adsorbent near the wall surface, and the amount of oxygen generated was increased by approximately 66%. [Explanation of symbols]

[0031] 1...oxygen generator, 11...booster pump, 12...vacuum pump, 13...gas heater, 20...adsorption tower, 20A...first adsorption tower, 20B...second adsorption tower, 21...adsorption tower body, 22...oxygen storage agent, 23...insulation material, L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14...gas flow path, A1, A2, A3, B1, B2, B3, NV, RV...valve, AIR IN …Air, O2 OUT ...Oxygen gas, EX...Exhaust gas

Claims

1. 1. A method for generating oxygen by a pressure swing adsorption system using two or more adsorption towers each having an inner wall provided with a thermal insulation material and a central space between the thermal insulation material filled with an oxygen storage agent that adsorbs and desorbs oxygen at high temperatures, an adsorption step of contacting the oxygen occluding agent with air to adsorb oxygen to the oxygen occluding agent; a desorption step of reducing the pressure applied to the oxygen occluding agent to desorb oxygen from the oxygen occluding agent; a desorption + rinsing process for promoting desorption of oxygen from the oxygen storage agent by introducing exhaust gas from another adsorption process while keeping the pressure applied to the oxygen storage agent low, An oxygen generation method that does not include a pressure equalization step of recovering the pressure in the adsorption tower.

2. 2. The oxygen generating method according to claim 1, wherein the temperature when oxygen is desorbed from the oxygen occluding agent is 250 to 450°C.

3. 3. An oxygen generating apparatus for carrying out the oxygen generating method according to claim 1 or 2, comprising an adsorption tower having an inner wall provided with a thermal insulation material and a central space of the thermal insulation material filled with an oxygen occlusion agent which adsorbs and desorbs oxygen at high temperatures.

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