JPH04155175A - Air separation equipment air cooler air outlet temperature control method - Google Patents

Abstract

PURPOSE:To permit the stabilization and automatic control of the air outlet temperature of an air cooler by a method wherein the range of limit is determined in the outlet temperature of fluorocarbon based on the air outlet temperature of the air cooler to set the set value of a fluorocarbon outlet temperature regulating meter automatically. CONSTITUTION:The air outlet pipe of an air cooler 4 is provided with a temperature regulating meter 36 while the set value of a lower limit temperature, higher than an evaporation saturation temperature, and an upper limit temperature of evaporation saturation temperature +10 deg.C are provided in the set values of a temperature regulating meter 33 attached to the outlet pipe 23 of fluorocarbon. When there is no condensation of oil, an air outlet temperature becomes lower than an object by 5 deg.C or more and the set value of a fluorocarbon outlet temperature regulating meter 33 is increased by a temperature regulating meter 36 to the temperature of saturating temperature +10 deg.C in accordance with a difference of the consentration of outlet air while the outlet air is sucked into a fluorocarbon compressor 25 as perfect heating vapor and the compressor is operated under the best condition. When the load of the refrigerant is fluctuated and the condensation of oil is generated in the air cooler 4, the air outlet temperature is increased by 5 deg.C or more than an objective value. The set value of the fluorocarbon outlet temperature regulating meter 33 is set lower than the set value of an air outlet temperature regulating meter 36 automatically Whereby oil in the tube of the cooler 4 is contained in the mist of fluorocarbon liquid and is accompanied to return a normal condition.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to the freezing of fluorocarbons, etc. in a feed air pretreatment device for removing moisture and carbon dioxide from feed air in an air cryogenic separation device using an adsorption tower. This invention relates to a method for controlling the air outlet temperature of an air separation device air cooler that uses a refrigerant to cool air by direct heat exchange.

[Conventional technology]

In air liquefaction cryogenic separation equipment, in order to remove impurities such as moisture and carbon dioxide from the feed air, instead of a reversible heat exchanger, an adsorption column filled with adsorbent is used to remove impurities such as moisture and carbon dioxide from the air that enters the cryogenic separator. Methods are often used to remove these impurities.

In feed air pre-treatment equipment that uses an adsorption tower, it is necessary to cool the feed air to approximately 5°C in order to reduce the water charge in the adsorption tower. A method of cooling the air directly with an air cooler is often used. An important point in the direct cooling method using air with a fluorocarbon refrigerant is that when the air is cooled with an air cooler, if the tia degree of the fluorocarbon is lower than O'C, the moisture in the air will freeze in the air cooler and the air will cool. This is to prevent clogging of the cooler and liquid compression caused by the Freon returning to the refrigerator in liquid form without being completely evaporated in the air cooler.

Therefore, in the conventional method, the evaporation temperature of CFC is o'cu.
In order to avoid overheating, the evaporation pressure must be controlled at a constant level, and the air cooler freon outlet temperature must be detected in order to prevent liquid bubbling into the cooling unit. Temperature I! 1Ii5 meter uses a method of controlling the Freon supply expansion valve. In addition, related devices of this type include, for example, Japanese Patent Publication No. 64-10756.
The number is mentioned.

[Issues that Komei is trying to solve]

In the above conventional technology, the effect of oil contained in the fluorocarbon gas compressed by the refrigeration compressor is considered only as a problem in the design of the air cooler, and in terms of temperature control, the effect of oil contained in the fluorocarbon gas that has been completely compressed by the refrigeration compressor is considered as a problem in the design of the air cooler. 11B
The problem was considered to be only the adjustment of the meter settings and the sensitivity of the meter, and the problem of oil concentrating in the air cooling fi was not checked at all in terms of temperature control. For this reason, in actual operation, oil condenses in the air cooler due to refrigeration load conditions such as increase/decrease operation of unit 2, resulting in poor heat transfer performance, an increase in air outlet temperature, and a rise in the freon outlet. Continuing liquid back-up for a long time often had an adverse effect on the refrigeration compressor.

In the past, when such a malfunction occurred, the setting value and sensitivity of the controller were manually adjusted for the Freon outlet temperature and Freon outlet pressure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method that solves these problems and completely automates the purpose of the cooler body to stabilize the air outlet temperature of the air cooler.

[Means to solve the problem]

In order to achieve the above object, the present invention takes into consideration the material balance between the amount of oil brought into the air cooler and the amount of oil taken out. Utilizing this, a limit range is set for the freon outlet 2i degrees based on the air outlet temperature of the air cooler, and the setting position of the freon outlet temperature controller is automatically set.

Generally, fluorocarbon gas compressed by a refrigeration compressor is led to an oil separator together with the lubricating oil of the compressor, where the fluorocarbon gas and oil are separated. However, it is technically impossible to completely remove oil from fluorocarbon gas with an oil separator, and 100 ppm is contained in 70 nogas separated by an ordinary oil separator.
Contains some amount of oil.

The oil contained in this gas is dissolved in the fluorocarbon liquid condensed in the condenser.

A small amount of oil dissolved in the fluorocarbon liquid is heated in an air cooler, but at this time the oil in the fluorocarbon liquid does not evaporate but is concentrated in the heat exchanger.

This oil concentration reduces the heat transfer performance of the air cooler. To prevent this oil from condensing, a heat exchanger is designed to increase the gas velocity of the evaporated fluorocarbon gas in the air cooler and take out the oil together with the gas. , Suction II culture independent playback at startup, season! 5
4 Due to changes in temperature, etc., the load on the refrigerator will have to be reduced by about 20% between the maximum and minimum load, making it impossible to remove the oil with just the flow rate of fluorocarbon gas. . This oil concentration is due to the degree of heating on the Freon side, that is, the outlet is 70! ! If the setting value of the temperature controller is increased, it becomes even more difficult to remove the oil.

Since the evaporation temperature of the air cooler is close to 0°C, the viscosity of the oil increases, which also makes it difficult to take out the oil using just the fluorocarbon gas fi.

In the present invention, this phenomenon is clarified, and by utilizing the principle that a large amount of oil is IBM in the Freon liquid, when oil concentration occurs in the air cooler, the heat transfer performance decreases, so the air outlet +
Since the air temperature rises by 1 degree, this increase in air outlet temperature is detected, and the set temperature of the freon outlet temperature controller is lowered, allowing some of the oil-dissolved mist to be brought out from the outlet and the oil content removed from the heat exchanger. It is an attempt to do so.

If the oil content in the fluorocarbon liquid brought into the air cooler is 100 ppm of the refrigerant circulation amount, the oil content in the fluorocarbon mist is about 2.5% of the 2-stroke amount, so calculating the oil mass balance: This means that the amount of mist in the freon gas emitted from the air cooler should be 1% or less. This small amount of mist does not have a bad effect on the liquid bag of the refrigeration compressor unless it continues for a long time. By removing the oil in this way, the air cooler can maintain its original heat transfer performance, so that when the air outlet temperature reaches the specified 1 degree, the set value of the freon outlet temperature can be automatically raised again.

At this time, if the set value of the freon outlet temperature is increased too much and the refrigeration load is small, the mass balance of the oil will be disrupted, causing oil concentration. Therefore, an upper limit is set for the freon outlet temperature and stable operation can be performed within this range. .

[For production]

As described above, in view of the acquisition of oil in the air cooler, the present invention detects the influence of oil concentration at the air outlet temperature of the air cooler, and sets an upper limit at the fluorocarbon outlet at a temperature equal to or higher than the evaporation saturation temperature of the fluorocarbon. The cascade control method that automatically sets the temperature controller setpoint allows you to balance the oil concentration in the air cooler, resulting in air separation! Fully automatic control of refrigeration load fluctuations such as 1M1t increase/decrease operation is possible.

〔Example〕

Hereinafter, one embodiment of the present invention will be described using Freon R-22 as a refrigerant.
The temperature control of the air cooler of an air separation device using the air cooler will be explained using FIG. 1 as an example.

In the figure, air compressed to about 54/mG per milliliter of raw air is cooled to about 40° C. by water in an aftercooler 2 and led to an air cooler 4 through a conduit 3. The air cooler 4 is a heat exchanger that flows fluorocarbons inside the tubes and air outside the tubes, and uses the latent heat of vaporization of the fluorocarbons to cool the air to about 5°C.

After the air cooled to 5°C has lost moisture, it is filled with two sets of adsorbents from the conduit 5 through the switching valve 6 at the air inlet.
The air passes through one side of the tower 7, and in the process of passing through the adsorption tower 7, impurities such as remaining moisture and carbon dioxide contained in the air are adsorbed and removed.

The air that has become a completely dry gas in the adsorption tower 7 is guided from one side of the air outlet switching valve 8 through the conduit 9 to the air cryogenic separator IO, where it is cooled and uses the boiling point difference between oxygen and nitrogen. It is separated into product gas and waste nitrogen gas through rectification separation. The separated products oxygen and nitrogen are transferred to conduit 11 after heat exchange. L! is extracted through the The remaining magic gas is led to the regeneration heater 14 through the conduit 13 after heat exchange.

The regeneration heater usually uses an electric heater, and the waste nitrogen gas heated to 150°C in the regeneration heater 14 is transferred to the other adsorption tank, which absorbs air impurities for a certain period of time, using a nitrogen switching valve. It passes through column 7 and is used as regeneration gas for the adsorbent. Adsorption 1: The regeneration gas from which impurities have been desorbed with N7 is discharged to the atmosphere from one side of the output nitrogen switching valve 16 through the conduit 18.

In order to remove impurities from the air in the adsorption tower 7, the S absorption tower 7 is used.
The moisture content of the entering air must be below the specified amount.

For this reason, it is necessary to keep the air outlet temperature of the air cooler 4 always below the target temperature and to suppress the saturated moisture content to a minimum.

Freon for cooling the air in the air cooler 4 is held in the receiver port, and the refrigerant 70 is returned as a saturated liquid at 40°C from the conduit I through the Freon cooling n4 and evaporated.
It is supercooled with no gas and depressurized to the saturation pressure of about 0°C by the Freon supply expansion valve n and air cooled! ′! 4 is guided into the tube.

The fluorocarbon liquid inside the tube exchanges heat with the air outside the tube, cools the air, and evaporates itself into a vaporized state.The fluorocarbon liquid in the tube is led to the fluorocarbon cooling n4 through the 70 outlet pipe of the air cooler 4, and is turned into heated steam and sent to the conduit. The gas is compressed to the specified pressure using freon compression*25. The compressed 70 NO gas is led to the oil separator n through the conduit 5, where the oil in the fluorocarbon gas is separated, and the separated oil is pressurized from the conduit area in the oil pot 31, cooled with water in the oil cooler β, and passed through the fluorocarbon compressor. It is used as a lubricating oil in No. 5. On the other hand, the fluorocarbon gas from which oil has been removed in the oil separator n is guided through a conduit to the condenser 4, cooled with water, turned into a fluorocarbon liquid, and returned to the original liquid receiver W. Conventionally, the air outlet temperature of the air cooler 4 was controlled by a temperature controller installed at the fluorocarbon outlet 01FZ3, and the fluorocarbon supply expansion valve n.On the other hand, the evaporation temperature of the fluorocarbon was controlled by the pressure node installed for the conduit. A system is used in which the evaporation saturation temperature is controlled at a constant level via a pressure control valve in the meter.

In the conventional system, the temperature controller installed in the Freon outlet pipe only controlled the Freon supply expansion valve n, so the trace amount of oil contained in the Freon gas due to oil content IIIFg27 was mixed into the Freon liquid. Depending on the temperature setting value of the temperature controller vane in the air cooler 4, the oil quality balance may be disturbed.
Oil condensation often occurs in the air cooler 4, requiring manual operations such as changing the set value by 1 iL each time. There were also some influences.

In the present invention, in order to eliminate such adverse effects, the air cooler 4
A temperature controller I is installed on the air outlet pipe of the fluorocarbon outlet pipe. A limit value was set. As a result, if there is no condensation of normal oil, the heat transfer performance is not inhibited, so the air outlet temperature is below the target of 5℃, and the setting value of the Freon outlet temperature controller (of the temperature controller I) is the saturation temperature + lθ℃. Until then, the air temperature rises in accordance with the variable temperature of the air outlet Ii, and the freon compressor 5 is sucked into the completely heated vapor, and the compressor is operated under the best conditions.

When the load of the refrigerant fluctuates due to the load fluctuation of the separation device and oil condensation occurs in the air cooler 4, the air outlet temperature decreases to the target of 5°C.
It increases as above. In this case, since the set value of the freon outlet temperature controller is automatically lowered by the air outlet temperature controller, the drop in the freon outlet temperature creates a condition in which mist is entrained in the outlet pipe, and the oil in the air cooler's four pipes increases. is included in the Freon solution mist and is entrained, returning it to normal.

The fluorocarbon heat exchanger is installed for the purpose of heating and evaporating a small amount of mist entrained by the air cooler 4, and prevents the liquid from backing up to the fluorocarbon compressor.

According to this embodiment, it is now possible to control the temperature of a system that directly cools air with Freon using an air cooler, which has not been possible to fully automate up to now, and allows stable operation at all times even when there are load fluctuations.

In this embodiment, when Freon is used as the refrigerant, it is necessary to set the limit range 4 of the Freon outlet temperature to an optimum range depending on the design conditions of the air cooler.

〔Effect of the invention〕

According to the present invention, the influence of oil concentration is detected by the air outlet temperature of the air cooler, and the setting value of the 70 outlet temperature controller is automatically set with an upper limit set at 2i degrees or more at the evaporation saturation of Freon. This makes it possible to balance the oil concentration within the air cooler, making it possible to stabilize the air outlet temperature of the air cooler and perform self-control.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of the present invention. l... Air compressor, 4... Air cooler, 7... Adsorption tower, lO... Air fractionator, 14...・Regeneration heater, 19...Liquid receiver, n...Freon supply expansion valve, δ...bent fluorocarbon compressed mold, n...oil separator,...・・・Frono exit fiff-#gain measure, I...Air outlet-＼ Agent Patent attorney Masaru Ogawa

Claims (1)

[Claims] 1. Air cooling in which the raw air is directly cooled with a refrigerant from a refrigerator such as chlorofluorocarbons before the adsorption tower in order to remove moisture and carbon dioxide from the raw air using an adsorption tower filled with an adsorbent. In the air outlet temperature control method of an air separation device air cooler equipped with a device, a temperature controller is provided at the air outlet of the air cooler, and a refrigerant liquid supply expansion valve is automatically controlled by the temperature controller provided in the refrigerant gas outlet piping. A limit value above the saturation temperature of the refrigerant evaporation pressure is set in the setting range of this refrigerant gas outlet temperature controller, and the refrigerant gas outlet temperature is automatically adjusted within this limit value by the temperature controller at the air cooler outlet. A method for controlling an air outlet temperature of an air cooler of an air separation device, characterized by setting a set value of a meter.