RU2254526C2 - Method and device for vortex liquefying - Google Patents

Abstract

FIELD: processes or apparatus for liquefying.

SUBSTANCE: method comprises flowing gas through one or two recuperative heat exchangers connected in series where the gas cools and low-boiling components are condensed and frozen, flowing the gas through a gas-expansion machine and/or an air throttle to the cold receiver. A part of the straight gas flow is branched into the cold and hot flows inside the energy separator made of, e.g., a two-flow vortex pipe. The cold flow is mixed with the return flow at the inlet to the heat exchanger. The hot flow is directed to the straight passage of the nonoperating recuperative heat exchanger-freezer.

EFFECT: enhanced efficiency.

2 cl, 3 dwg

Description

The invention relates to the field of creating cooling and liquefying devices operating using the properties of an expanding gas stream in vortex cooling devices in so-called vortex tubes [1].

A known method of operation of a vortex liquefaction (cooling) device, including passing gas in a direct stream through one or two successively connected recuperative heat exchangers, where gas is cooled, condensation of low-boiling components and their freezing, flow through a pneumatic throttle into a cold receiver, and part of the direct flow is diverted to a two-flow vortex tube, in which the gas is expanded and separated into cold and hot flows, while the cold stream is mixed with a reverse flow at the entrance to the heat the exchange [2].

Such a method is implemented in the design described in the patent [2], according to which the known vortex liquefaction device comprises a gas flow separator, one or two successively connected recuperative heat exchangers with direct and return channels, an air throttle, a cold receiver and an expander made in the form of one or more in series connected two-line pipes, the cold pipe of which is connected to the inlet pipe of the return flow of the regenerative heat exchanger.

Since the inlet of such a vortex liquefaction device almost always receives undrained (wet) gas, at a temperature below 273K, moisture and the associated heavy gas fractions forming solid gas hydrates will inevitably freeze inside the direct flow channel (high pressure channel) of the regenerative heat exchanger (hereinafter simply “ice”), which leads to a gradual decrease in the effective section of this channel, a decrease in the effective heat transfer area, a decrease in the specific thermal conductivity of the channel surface and, as a result, to reduce the performance of the entire device. Ultimately, if precautionary measures are not taken, clogging of such a channel may even occur.

This is a disadvantage.

Typically, ice formed inside the channel is removed by periodically heating the entire heat exchanger, for example, by blowing back the channel with uncooled gas coming from an inlet connected to a high pressure pipe. Therefore, the operation of such a vortex liquefaction device is inevitably accompanied by periodic stops to thaw the ice formed inside the channel. To reduce the time required for defrost (to reduce installation downtime), the regenerative heat exchanger is duplicated by another, exactly the same heat exchanger-freezer, included in the work for the defrost period of the first heat exchanger.

But at the same time, the gas temperature entering the device inlet from the main pipelines often does not exceed 5 ... 10 ° C, which is clearly not enough for effective thawing. In addition, using high-pressure gas for purging, we are forced to throttle it, which further reduces its temperature. Yes, in addition, such a gas has high humidity. All this further reduces the effectiveness of this method of defrosting.

This is a disadvantage.

For defrosting of any heat exchanger-freezer, it can be blown hot stream from the vortex tube included in the set of the cooling device according to the patent [2]. In this case, hot gas can be supplied either to the return or direct channel.

Although the temperature of the gas leaving the hot end of the vortex tube can be quite high (50 ... 70 ° C or more) and such a gas can melt the accumulated ice in an idle heat exchanger, but during such thawing, when hot gas is fed into the return channel , we will be forced to heat up the entire mass of metal of the heat-exchange channels (for example, the entire mass of tubes in a twisted heat exchanger), all tube plates, as well as the body, etc., i.e. virtually the entire heat exchanger. So, for example, it is known that at least 1.0 ... 1.5 hours are required for heating the heat exchanger weighing 2000 kg in this way to ambient temperature. In addition, to put into operation a heated heat exchanger, it is necessary to cool it all again, which will require a significant amount of cold, and besides, the whole process will require a significant amount of time - again, at least the specified 1.0 ... 1.5 hours .

Therefore, it is most rational to feed the hot vortex tube stream into the direct channel of the recuperative heat exchanger-freezer disconnected from operation.

The technical result of the present invention is to reduce these disadvantages.

The technical result in terms of the method is obtained due to the fact that the hot flow of the energy separator is directed into the direct channel of the recuperative heat exchanger-freezer disconnected from operation.

The technical result in terms of the device is due to the fact that the hot branch pipe of the energy separator is connected to the direct channel of the recuperative heat exchanger-freezer disconnected from operation.

Figure 1 illustrates the invention.

The inlet pipe 1 through a tee-separator 2, through a two-way valve switch 3 and a tee 4 is connected to the input of the direct channel 5 of the regenerative heat exchanger-freezer 6, which through the separator 7, through a two-way valve-switch 8 is connected to the input of the direct channel 9 of the second heat exchanger 10 The output of the direct channel 9 through the pneumatic throttle 11 is connected to the storage vessel (cold receiver) 12 having a gas and liquid cavity. The upper (gas) cavity of the cold receiver 12 through the return channel 13 of the heat exchanger 10 through the two-way valve switch 14, through the return channel 15 of the heat exchanger 6 and through the tee 16 is connected to the outlet 17 of the vortex liquefaction device. In addition, the separator 7 is connected to the fluid collector 18, also having gas and liquid cavities. The gas cavity of the fluid collector 18 is connected to a collector of heavy gas fractions (not shown in FIG. 1).

Inlet tee 2 is connected to the inlet pipe 19 of the two-stream vortex tube 20, which has still hot 21 and cold 22 ends (pipes). The hot end 21 through a two-way valve switch 23 and a tee 24, through a direct channel 25 of the second heat exchanger-freezer 26 - a backup of the heat exchanger-freezer 6, through a separator 27 is connected to a fluid collector 28, also having a gas and liquid cavity. The gas cavity of the fluid collector 28 is connected to a collector of heavy gas fractions (such a collector is also not shown in the figure).

The heat exchanger-freezer 26 is temporarily disconnected from operation by means of the corresponding two-way valve taps 3, 8, 14 and 23. Moreover, the connections of the direct and return channels of the heat exchanger-freezer 26 in FIG. 1 and the heat exchanger-freezer 6 in FIG. 2 are indicated by a dotted line. The contours of the defrosting heat exchanger-freezer 26 in figure 1 and figure 2 are also indicated by a dotted line. In addition, the dashed line shows the connection of the hot end 21 of the vortex tube with the tee 4 temporarily taken out of operation with the help of a crane switch 23.

The cold end 22 of the vortex tube 20 using a two-way valve switch 14 can be connected either to the input of the return channel 15 of the heat exchanger 6, and then through the tee 16 to the output 17 of the vortex liquefaction device or to the input of the return channel 29 of the heat exchanger 26, and then through the tee 16 also with output 17 of this device.

Consider a device for implementing the proposed method works as follows (see figure 1).

Through the inlet pipe 1, the compressed gas in the initial thermodynamic state enters the tee-separator 2.

In the tee-separator 2, the gas is divided into two streams:

- the first (direct) flow through a two-way valve switch 3 and tee 4 is fed to the input of the channel 5 of the direct flow of the regenerative heat exchanger 6;

- the second stream enters the input 19 of the vortex tube 20.

The first (direct) flow, passing through the channel 5 of the direct flow of the regenerative heat exchanger 6, is cooled from the cold return flow 15.

When the cooling device is operating in the normal cooler mode (or in the liquefier start mode), the gas temperature in the direct channel 5 does not fall below 273K, so moisture simply condenses in this channel and can be removed at the outlet from it with a conventional separator (dehumidifier or desiccant). Such a moisture separator can be mounted separately from the heat exchanger unit 7 or combined in one design with the output (lower) part of the channel 5.

When the cooling device is operating in the liquefier mode, the gas temperature in the direct channel 5 of the heat exchanger 6 drops significantly below 273K, therefore, moisture condensing from the gas immediately freezes on the internal surfaces of this heat exchanger, gradually clogging the channel 5 and reducing its cross section, which negatively affects the operation of the entire device for cooling. Therefore, the operation of such a fluidizer is inevitably accompanied by periodic stops to thaw the ice formed inside the channel 5.

To ensure the continuity of the operation of the entire device, the heat exchanger-freezer 6 is duplicated with exactly the same heat exchanger-freezer, for example, heat exchanger 26, and they are periodically switched by special fittings (two-way switch taps), giving time for thawing of the internal ice. For a period of temporary stop for the purpose of defrosting the heat exchanger-freezer 26, the direct channel 25 is blown with warm compressed gas from the hot end 21 of the vortex tube 20 through a two-way valve switch 23 and a tee 24, and the resulting moisture is collected in the moisture collector 28, preventing it from falling into main channels of the fluidizing device. Therefore, with such a purge, the direct channel 25 and the moisture separator 27 are cut off from the main part of the device using two-way valve taps 3, 8, and 14. Heavy gas fractions separated from the melting gas hydrates after the separator 27 and the moisture collector 28 are first dumped into the liquid collector 18, and then in the collection of heavy gas fractions (not shown).

After thawing, recuperative defrost heat exchangers using the system of faucets-switches 3, 8, 14 and 23 change operating modes (see figure 2). This ensures the continuity of the device for cooling.

In the case of operation in the low-temperature liquefaction mode of natural gas, the separator (external 7 or located inside the heat exchanger) operates not only during the non-working period, i.e. when defrosting the heat exchanger 6 to remove the moisture that forms, but also during the main operation, it can be useful in the presence of heavy fractions in the gas, for example, the presence of a propane-butane-pentane mixture in a cooled or liquefied natural gas, and which begin to condense earlier than the main gas (methane). Such a separator pre-separates heavy liquid fractions (including gas condensate), which are collected in the storage vessel 18, from which the gaseous fraction is removed. This allows you to improve the quality (uniformity of composition) of the gas mixture supplied to the liquefaction through the pneumatic throttle 11 in the fluid collector (cold receiver) 12.

After the separator 7, the gas direct flow passes through a two-way valve-switch 8, through the direct flow channel 9 of the heat exchanger 10 and the pneumatic throttle 11, after which it enters the cold receiver 12 (liquid gas storage vessel).

In the direct channel 9 of the heat exchanger 10, the gas is additionally cooled from the return stream 13, which is a low-temperature low-pressure stream of non-condensing gas in the vessel 12. In the pneumatic throttle 11, cold gas is throttled and strongly cooled down, therefore, two phases are formed in it - liquid and gaseous. Entering the cold receiver 12 (storage vessel), the two-phase flow is divided:

cryogenic liquid accumulates at the bottom, and a very cold gaseous phase goes up, passes through the return channel 13 of the heat exchanger 10, cools the stream 9, passes through a two-way valve switch 14, where it mixes with the cold stream from the vortex tube 20, passes through the return channel 15 of the heat exchanger 6, is heated from direct flow 5 and cools it. In this state, the return flow enters the output 17 of the vortex fluidizing device.

The second stream entering the input 19 in the vortex tube 20 is divided into two streams:

- hot 21, which has an elevated temperature and enters through a two-way valve switch 23 into a tee 24, and then enters the direct channel 25 of the heat exchanger 26 and thaws the ice inside it;

- as well as cold 22, having a reduced temperature and coming through a two-way valve switch 14 into the return channel 15 of the heat exchanger 6.

Figure 2 shows the same cooling device, but with the thaw switched off from operation of the heat exchanger-freezer 6 (shown by a dotted line), and instead its heat exchanger-freezer 26 is included in the main operation. Moreover, as a result of switching two-way valve taps 3, 23, 14 and 8, the direct flow from the inlet 1 passes in a different way: tee 2, valve 3, tee 24, channel 25 of the direct flow of the heat exchanger 26, water separator 27, valve 8, channel 9 direct flow of the heat exchanger 10 and through the pneumatic throttle 11 to the refrigerator 12, wherefrom the reverse flow through the channel 13 of the heat exchanger 10, through a two-way mixer valve 14, where it is mixed with cold flow from the vortex tube 20, through the return channel 29 of the heat exchanger 26, through the tee 16 exit 17 vortex sting device.

Warm gas from the hot end 21 of the vortex tube 20 passes through the valve 23, through the tee 4 enters the direct channel 5 of the heat exchanger 6 and thawing the ice inside it. Thawed moisture flows through the moisture separator 7 into the storage vessel 18. In this case, only ice inside the direct flow channels 5 (or 25) is heated, which significantly reduces the effect of the heat flow on other elements of the heat exchangers.

The operation of the vortex liquefaction device of FIGS. 1 and 2 is possible without a heat exchanger 10, for example, with one heat exchanger-freezer 6 (or 26) included in the operation and one exited heat exchanger-freezer 26 (or 6).

The hot stream of the vortex tube can be fed from either side of the direct channel of the heat exchanger - either from the inlet or from the outlet.

As a pneumatic expander, not only a pneumatic throttle 11 can be used, but also a combination of an expander 30 with a pneumatic throttle 11, as shown in FIG. 3. Moreover, 31 is the load of the expander.

In addition, not only one vortex tube, but also several vortex tubes connected in series can be used as an energy separator [1, p. 111].

Thus, the flow of hot flow into the direct channel of the heat exchanger-freezer allows you to reduce the time required for defrosting it, as well as reduce the time and energy required for putting it into operation after defrosting. This is the technical essence of the invention.

This technique allows for greater stability of the device for cooling (liquefaction) according to the patent [2].

Literature taken into account

1. Merkulov A.P. Vortex effect and its application in technology. M.: Mechanical Engineering, 1969.

2. Arturov S.V. and other. The method of operation of the device for cooling and the device for cooling. RF patent No. 2149324 dated March 26, 1996

Claims (2)

1. The method of operation of a vortex fluidizing device, including passing gas in a direct stream through one or two successively connected recuperative heat exchangers, where gas is cooled, condensation of low-boiling components and their freezing, flow through a pneumatic expander, for example through an expander and / or pneumatic throttle, into a cold receiver, moreover, a part of the direct flow is diverted to an energy separator (made, for example, in the form of a two-stream vortex tube), in which the gas is separated into cold and hot flows, that cold flow is mixed with return flow at the inlet of the heat exchanger, characterized in that the hot flow energorazdelitelya directed to a forward channel operation disconnected from the recuperative heat exchanger-vymorazhivatelya. 2. A vortex fluidizing device containing a gas flow separator, one or two series-connected heat exchangers, one of which is a regenerative heat exchanger-freezer equipped with a stand-in duplicator - the same recuperative heat exchanger-freezer, an energy separator (made, for example, in the form of a vortex tube) , the cold pipe of which is connected to the input of the return channel of the heat exchanger, as well as a pneumatic expander, made, for example, in the form of a throttle, and a cold receiver, distinguishing The fact is that the hot branch pipe of the energy separator is connected to the direct channel of the recuperative heat exchanger-freezer disconnected from operation.

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