JP4978361B2 - Surplus gas type surge avoidance compressor system - Google Patents

Description

  The present invention relates to a compressor system that adds a surplus gas utilization function and a surge avoidance function and handles refrigerant or liquefied gas.

  Since LNG is a low-temperature liquid, even if the tank is covered with a heat insulating material, it naturally vaporizes in the tank due to heat from the outside. This naturally vaporized gas is called boil off gas (hereinafter abbreviated as “BOG”). Patent Document 1 below discloses a technique related to a BOG recovery method for an LNG storage facility. Specifically, after supplying BOG of the LNG storage facility to the suction drum, cooling it with LNG liquid, and sending it to the recovery facility with multiple compressors, the discharge gas from the compressor is sent to the suction drum according to its pressure. In addition to recycling, the supply amount of the cooling LNG liquid to the suction drum is controlled in accordance with fluctuations in the thermal load caused by the recycle gas.

  On the other hand, in Patent Document 2 described below, by continuously operating a prime mover that drives a compressor, it is not necessary to prepare for starting at the time of a stop, or an overload can be reduced, and the gas supply pressure is stabilized. Techniques relating to a pumping method, a pumping device, a fuel gas supply device, and a relay base for a gas transport line that can be used are disclosed. Specifically, the compressor, the fluid supply line connected to the compressor inlet, the outlet line connected to the compressor outlet, and the recycle line connecting the compressor inlet and outlet And a fluid pressure-feeding method comprising a recycle valve interposed in the recycle line, and detecting the pressure of the outlet line and feedback controlling the compressor and recycle valve, and providing an inlet fluid pressure regulating valve in the fluid supply line And detecting the pressure upstream of the inlet fluid pressure regulating valve to control the opening degree of the inlet fluid pressure regulating valve.

Further, in Patent Document 3 below, even if the unload state is continued for a long time, the inside of the cylinder can be reliably cooled to prevent overheating of the piston ring and the bull ring, and the driving power at no load can be obtained. A technique relating to a high-pressure compression facility that can be reduced and a no-load operation method thereof is disclosed. Specifically, a high-pressure compressor having a plurality of unloader-equipped intake valves, an aftercooler that cools the gas compressed by the high-pressure compressor, and a reverse discharge that prevents backflow of the pressurized gas that exits the aftercooler A recycle line communicating the stop valve, the aftercooler outlet and the gas inlet of the high-pressure compressor; an on-off valve provided on the recycle line; and a control device for controlling the on-off valve and the unloader of the high-pressure compressor. During no-load operation, part of the suction valve with unloader is unloaded, the remaining suction valve is kept in operation and the pressurized gas cooled is recycled to the gas inlet of the high-pressure compressor through the recycle line. The inside of the cylinder is circulated through the intake valve.
Japanese Examined Patent Publication No. 63-16640 JP 2006-316687 A JP 2006-115663 A

However, from the viewpoint of a surplus gas utilization type surge avoidance compressor system, there is still room for improvement in the techniques described in Patent Documents 1 to 3. In particular, there are the following problems as adverse effects of taking measures to avoid entering the surge region.
1) When a cooler is provided in the bypass line, there are problems of space and cost.
2) When the compressor is on / off controlled, there is a problem that the mechanical stress increases and the equipment life is shortened in addition to the energy loss at the start / stop.

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a surplus gas utilization type surge avoidance compressor system that solves the following problems.
1) Simplification in terms of space and cost by omitting the bypass line cooler.
2) In addition to eliminating start / stop energy loss associated with frequent on / off control of the compressor, it eliminates mechanical stress and extends equipment life.

In order to achieve the above object, the surplus gas utilization type surge avoidance compressor system according to the first invention employs the following first means. That is, a rotary compressor, a condenser connected to the discharge side of the compressor for cooling and condensing high-temperature and high-pressure fluid, a storage tank connected to the discharge side of the condenser for storing liquefied fluid, and a fluid from the inlet A suction drum connected to the suction side of the compressor for receiving the fluid mist trapped at the top and a condensate supply for supplying the condensate fluid to the bottom of the storage tank to the suction drum And a recycle line for injecting the high-temperature and high-pressure fluid diverted from the discharge side of the compressor to the bottom of the suction drum.

  According to the surplus gas utilization type surge avoidance compressor system according to the first aspect of the present invention, a gaseous fluid (gas) typified by BOG or the like, or a saturated vapor state fluid (saturated vapor) is condensed by a rotary compressor. . The condensed fluid (gas-liquid mixture) is cooled and condensed by a condenser to become a liquefied fluid (liquid).

  Further, the condensed fluid (liquid) obtained on the discharge side of the condenser is stored in a storage tank. This fluid (liquid) is pumped from the bottom of the storage tank and is used according to the application. For example, if the apparatus liquefies BOG in the liquefied gas storage / supply facility, the liquefied gas is consumed.

  On the other hand, as an application different from consumption, for example, in a refrigerant compression / expansion cycle in a refrigeration facility, liquid refrigerant stored in a storage tank at room temperature expands around a chiller (expansion / heat absorption part). -After absorbing heat, it becomes a gaseous fluid (gas) and then returned to the suction drum via the inlet. The suction drum receives the supply of fluid from the condensate supply line communicating with the bottom of the storage tank and / or the inlet and separates the steam and water.

  The fluid (gas) mist trapped by the air / water separation function of the suction drum is sucked from the suction side of the compressor. The fluid (gas) sucked into the compressor is condensed and the same thing is repeated.

  On the other hand, the high-temperature and high-pressure fluid (gas) pumped through the recycle line branched from the compressor discharge side and the condenser is stored in the fluid (liquid) stored by the injection means disposed at the bottom of the suction drum. To spray. Then, the sensible heat latent in the high-temperature and high-pressure fluid (gas) moves to the fluid (liquid) stored at the bottom of the suction drum and promotes vaporization, thereby cooling (1). (2) A new utility for cooling the recycle gas becomes unnecessary. (3) By supplying the gas to the suction drum, it is possible to avoid the danger that the compressor falls into a surge state. This leads to the following effects:

1) By omitting the cooler of the recycle line (bypass line), it is simplified in terms of space and cost.
2) In addition to eliminating start / stop energy loss associated with frequent on / off control of the compressor, it eliminates mechanical stress and extends equipment life.

  Moreover, the surplus gas utilization type | mold surge avoidance compressor system which concerns on 2nd invention employ | adopts the following 2nd means in addition to the said 1st means. That is, a sensor that is disposed on the suction drum and detects any one of internal temperature, pressure, and liquid level, and controls the flow rate of the condensate supply line and / or the recycle line based on the detection output of the sensor. And a control means for adopting.

  According to the surplus gas utilization type surge avoidance compressor system according to the second invention, the flow rate of the low temperature liquid supply line of the suction drum is controlled by the control means for controlling the liquid level to be constant. Retained. In addition to this, the flow rate of the recycle line is also controlled by the control means for controlling the pressure to be constant, so that the pressure is also kept constant. If it does so, the danger that a compressor will fall into a surge state can be avoided more reliably.

ADVANTAGE OF THE INVENTION According to this invention, the surplus gas utilization type | mold surge avoidance compressor system which solved the problem in the following points can be provided.
1) By omitting the cooler of the recycle line (bypass line), it becomes possible to simplify in terms of space and cost.
2) In addition to eliminating start / stop energy loss associated with frequent on / off control of the compressor, it is possible to extend mechanical life by eliminating mechanical stress.

  Hereinafter, with reference to the drawings, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described by appropriately interweaving the configuration and operation. FIG. 1 is a piping diagram of a surplus gas utilization type surge avoidance compressor system (hereinafter also referred to as “the present system”) E according to the present embodiment.

  As shown in FIG. 1, this system E is mainly constituted by a fluid circulation circuit of a rotary compressor 10 → a condenser 2 → a storage tank 3 → a low-temperature liquid supply line 4 → a suction drum 6 → a compressor 10, and a refrigeration facility or the like. In addition to the heat exchange cycle, it constitutes a compressor system for compressing and expanding liquefied gas. This system E circulates chlorofluorocarbon and ammonia as refrigerants in the heat exchange cycle in a closed circuit including a chiller (not shown), and stores liquefied gas LNG, liquefied nitrogen, liquefied oxygen and the like for consumption. It is the main application to handle in this way.

In particular, in the case of an LNG storage facility including a huge gas tank, condensation and liquefaction of BOG which is naturally vaporized in the tank by heat from the outside is the main application. More specifically, when BOG is introduced from the inlet 5 to the suction drum 6, it is cooled to some extent by the low temperature of the LNG liquid 1 _L stored so as to maintain a predetermined liquid level at the bottom of the suction drum 6. It is compressed by a compressor 10 communicating with the upper part of the suction drum 6. The discharge gas of the compressor 10 is divided and recycled to the suction drum 6 according to the pressure. At this time, the supply amount of the cooling LNG liquid to the suction drum is controlled in accordance with fluctuations in the heat load caused by the recycle gas.

Here, the compressor 10 has a specification capable of compressing only a fluid (hereinafter also referred to as “gas”) 1 _G in a gaseous state, and therefore, it is possible to deal with saturated steam 1 _S. If the fluid in a gas-liquid mixed state (hereinafter also referred to as “gas-liquid mixture”) 1 _M , only the gas 1 _G separated by gas-liquid (hereinafter also referred to as “mist trap”) by the suction drum 6 is used. And introduced into the suction side 12 of the compressor 10.

The condenser 2 is connected to the discharge side 11 of the compressor 10 and cools and condenses the discharged saturated steam 1 _S or gas-liquid mixture 1 _M to be liquefied. The storage tank 3 stores 1 _L of fluid (hereinafter also referred to as “liquid”) liquefied by the discharge side 21 of the capacitor 2.

The suction drum 6 is supplied with the fluid 1 _G · 1 _S · 1 _L from the cryogenic liquid supply line 4 and / or the inlet 5 connected to the bottom of the storage tank 3 and is filled with the gas-liquid mixture 1 _M. The gas-liquid mixture 1 _M is the gas-liquid separation by gravity, and is temporarily stored is separated into the liquid 1 _L of gas 1 _G and the bottom layer of the upper layer portion.

In addition, the high-temperature and high-pressure gas-liquid mixture 1 _{M which} is diverted from the discharge side 11 of the compressor 10 through the recycle line 7 and bypassed is injected into the liquid 1 _L stored in the bottom portion of the suction drum 6. 8 is injected.

Then, latent heat latent in the gas-liquid mixture 1 _M of high temperature and high pressure is, by prompting the vaporized to move to stored liquid 1 _L, since recovering waste heat generated in front of the condenser 2, the energy efficiency In addition to the improvement, the danger of the compressor 10 falling into a surge state can be avoided.

Further, the low-temperature liquid 1 _L is appropriately supplied for cooling by the low-temperature liquid supply line 4 connected to the suction drum 6 from the bottom of the storage tank 3. A control valve 41 is inserted in the low-temperature liquid supply line 4, and the opening degree of the control valve 41 is controlled by the control means LIC that controls the flow rate of the low-temperature liquid supply line 4. The control valve 41 are also subject to the control of the control means LIC based on the detection output of the sensor 9 _B for liquid level detection which is arranged to monitor the liquid level of the suction drum 6, suction drum 6 is liquid level Is held constant.

A control valve 71 is inserted in the recycle line 7, and the valve opening degree of the control valve 71 is controlled by the control means PIC that controls the flow rate of the recycle line 7. Further, it disposed in the suction drum 6, and controls the operation control unit PIC is based on the detection output of the sensor 9 _U for detecting the pressure inside the suction drum 6 the pressure is kept constant.

  In this way, the suction drum 6 is kept constant because the flow rate of the low-temperature liquid supply line 4 is controlled by the control means LIC that controls the liquid level to be constant. Furthermore, since the flow rate of the recycle line 7 is also controlled by the control means PIC for controlling the pressure to be constant, the suction drum 6 is also kept at a constant pressure. Thereby, the danger that the compressor 10 falls into a surge state can be avoided more reliably.

According to this system E, gas 1 _G represented by BOG or the like, or saturated steam 1 _S is condensed by the rotary compressor 10. A liquid 1 _{L obtained} by cooling, condensing, and liquefying the condensed gas-liquid mixture 1 _M by the condenser 2 is stored in the storage tank 3. The liquid 1 _L is made available according to the application being pumped from the bottom of the storage tank 3. For example, if the liquefied gas BOG is liquefied, it is consumed.

Alternatively, as an application different from consumption, for example, in a refrigerant compression / expansion cycle in a refrigeration facility, the gas 1 _G expanded and vaporized while circulating through the chiller passes through the inlet 5 to the suction drum. 6 is circulated through the closed circuit. That is, the gas 1 _G mist trapped by the air / water separation function of the suction drum 6 is sucked from the suction side 12 of the compressor 10. And it circulates through the following fluid circulation circuits.
Compressor 10 → condenser 2 → storage tank 3 → suction drum 6 → compressor 10

  The various shapes and combinations of the constituent members shown in the above-described embodiments are merely examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention. Further, regarding the names of the respective parts, even if they are other expressions, they can be regarded as being included in the present invention if they are substantially the same. For example, the recycle line 7 may be replaced with the bypass line 7.

In short, high temperature and high pressure fluid (gas-liquid mixture) 1 _M bypassed through the recycle line 7 branched from the discharge side 11 of the compressor 10 and the condenser 2 is injected at the bottom of the suction drum 6. The present invention includes all the techniques in which the liquid is ejected into the fluid (liquid) 1 _L stored by holding the predetermined depth (liquid level) at the bottom of the suction drum 6 by 8.

According to the present invention, the latent heat latent in the high-temperature and high-pressure fluid (gas-liquid mixture) 1 _M moves to the fluid (liquid) 1 _L stored in the bottom of the suction drum 6 to promote vaporization, thereby The exhaust heat generated in front of 2 is recovered. This not only improves energy efficiency, but also avoids the danger of the compressor 2 falling into a surge state. From this, the following effects can be derived: 1) By omitting the cooler of the recycle line (bypass line) 7, it is possible to simplify in terms of space and cost.
2) In addition to eliminating the start / stop energy loss associated with frequent on / off control of the compressor 10, it is possible to extend mechanical life by eliminating mechanical stress.

It is a piping diagram showing a schematic structure of a surplus gas utilization type surge avoidance compressor system (this system) concerning one embodiment of the present invention.

Explanation of symbols

1, 1 _G , 1 _S , 1 _M , 1 _L ... fluid 1 _G ... (gas) fluid,
1 _S (saturated steam) fluid,
1 _M (gas-liquid mixture) fluid,
1 _L (fluid) fluid,
2… Capacitor,
3 ... storage tank,
4 ... Condensate supply line 5 ... Inlet 6 ... Suction drum,
7 ... recycle line 8 ... injection means 9 _{U, 9} B ... _(disposed in the suction drum 6, to detect the internal temperature, pressure, one of the liquid level) sensor,
10: Rotary compressor,
11 ... discharge side (of the compressor 10),
12 ... suction side (of the compressor 10),
21 ... discharge side,
E ... Surplus gas utilization type surge avoidance compressor system,

Claims (2)

A rotary compressor,
A condenser connected to the discharge side of the compressor for cooling and condensing a high-temperature and high-pressure fluid;
A storage tank for storing the liquefied fluid connected to the discharge side of the capacitor;
A suction drum connected to the suction side of the compressor for receiving fluid inflow from the inlet and receiving the fluid mist trapped at the top;
A cryogenic liquid supply line connected to the bottom of the storage tank and supplying a condensate fluid to the suction drum;
A surplus gas utilization type surge avoidance compressor system comprising: a recycle line that injects the high-temperature and high-pressure fluid diverted from the discharge side of the compressor to the bottom of the suction drum. A sensor that is disposed on the suction drum and detects any of the internal temperature, pressure, and liquid level;
2. The surplus gas utilization type surge avoidance compressor system according to claim 1, further comprising: a control unit that controls a flow rate of the cryogenic liquid supply line and / or the recycle line based on a detection output of the sensor.

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