JPS6234079Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is based on the evaporative gas (BOG
This relates to a gas cooling device that cools BOG to a predetermined temperature below the compressor inlet temperature control when pressurizing (Boll Off Gas))) with a compressor and sending it as fuel gas. In this case, the inlet temperature control of the compressor is -130 to -150°C in the case of a low-temperature turbo compressor, and -80 to -150°C in the case of a reciprocating type compressor. The invention relates to a gas cooling system for cooling the machine within these temperature limits.

Conventionally, evaporative gases such as those mentioned above, such as BOG
The line spray method is used to cool liquefied natural gas, and as shown in Figure 1, a separate LNG pump (not shown) is used to cool the liquefied natural gas, which is led through pipe b into BOG line a from liquefied natural gas storage tank g. Pressurized cooling liquid, such as LNG, is cooled by spraying with another compressed gas, such as gas pressurized by a compressor, and then separated into gas and liquid by a gas-liquid separation drum c such as a cyclone, The compressor d pumps the cooled gas (cooled BOG) to the desired location, or the gas generated in the liquefied natural gas storage tank
BOG is introduced into a can body (for example, knockout drum), and LNG from the storage tank is sprayed from a spray nozzle installed in the can body and cooled by bringing it into countercurrent contact with the BOG ( (See Japanese Patent Application Laid-Open No. 55-72998) was proposed.

However, in the former method, in order to cool the BOG, heat exchange is required, that is, the injected LNG is vaporized and the BOG is cooled using the latent heat. Approximately 30 m of piping f is required, and the amount of BOG generated fluctuates widely depending on the conditions at the time. Since the LNG that has been dehydrated does not atomize well and the efficiency of heat exchange becomes extremely poor, compressed gas, that is, atomizing gas, is required to atomize the LNG. The coolant is sent to the spray nozzle e and used as the atomizing gas, and furthermore, the coolant is sprayed into the vaporized gas line a, so that the coolant does not stagnate or the heavy residual liquid does not flow back. Special consideration must be given to the piping design, some of the mist may be entrained into the compressor, causing trouble, or, as mentioned above, some of the cooled compressed BOG may be sent to the spray nozzle. As a result, there were various drawbacks such as an increase in compressor power.

In addition, in the latter method, the amount of BOG generated fluctuates widely depending on the conditions at the time, as mentioned above.
Since the BOG compressor constantly operates and stops, for example, when using a turbo compressor, it is necessary to return compressed gas to the compressor when starting up or for anti-surge purposes. , the temperature of the compressed gas returned to the compressor rises to near room temperature, and this temperature is reduced to −130°C, which is within the inlet temperature limit range.
In order to cool the BOG to ~-150°C, a huge volume of the can is required to lower the temperature to this temperature with a single spray of LNG from the liquefied natural gas storage tank. This method had major drawbacks, such as the mist not being completely separated within the can and entering the compressor, causing trouble.

The purpose of this invention is to provide a gas cooling device which can eliminate the above-mentioned drawbacks.

The structure of this gas cooling device will be explained based on the embodiment shown in FIG. A continuing truncated cone-shaped inner cylinder 4 is provided,
A filling layer 3 is provided at the lower end of the inner cylinder 4.
A cooled gas inlet pipe 5 is opened in the ceiling part of the chamber, and a cooled gas discharge pipe 7 is opened in the upper chamber wall 6 of the sealed chamber 1. A cooling liquid pipe 8 is introduced into the upper part of the inner cylinder 4 and sprayed at the end. A nozzle 9 is provided, a mist eliminator 10 is provided in the gas ascending passage A' on the outer periphery of the inner cylinder, and a coolant discharge pipe 12 is opened at the bottom 11 of the sealed chamber 1.

Since this embodiment has the configuration as described above,
In order to cool the BOG produced by natural vaporization of LGN in the LNG storage tank due to heat input, if the BOG, which is the gas to be cooled, is introduced into the gas introduction pipe 5,
BOG escapes to the gas exhaust pipe 7 through the gas passage A, but due to the provision of the truncated conical section 2, the flow velocity gradually decreases as it goes downward.
That is, the residence time becomes longer. On the other hand, coolant LNG was introduced into the coolant pipe 8 and sprayed into the gas flow from the spray nozzle 9, and was sprayed with the BOG.
The BOG is cooled by contact with LNG, but at this time, the flow velocity decreases toward the bottom of the truncated conical shape, and the residence time increases, causing the BOG and LNG to cool.
and can come into good contact with each other, increasing the cooling effect. Since the internal flows flow simultaneously, all the gas and liquid flow down to the lower packed layer 3, and sufficient heat exchange is performed on the large heat exchange surface in this packed layer.
The BOG is well cooled and moves to the ascending passage A through the turning section in the gas passage A. At this time, due to the sudden direction change, the mist is well separated, and the upward passage
It is removed by the mist eliminator installed in A′. On the other hand, the vicinity of the opening of the gas discharge pipe 7 is on the outside of the truncated conical part 2, and the cross-sectional area gradually increases, that is, a large space is formed in terms of volume, so the flow velocity gradually slows down. Even if there is residual mist, the flow velocity in the upper direction is slow in this part and the residence time is long, so it is well separated, changed direction, and discharged from the gas exhaust pipe 7.

Note that the filler layer 3 is provided at the bottom of the truncated conical portion 2 and is intended to use the widest cross-sectional area, so the layer thickness can be made the thinnest for the same contact area. This allows the passage resistance to be kept as low as possible. Furthermore, excess LNG is discharged to the outside from the liquid discharge pipe 12.

Since this device has the above-mentioned configuration, it does not require a long heat exchange pipe f of 30 m from the spray nozzle to the gas-liquid separation drum, unlike the conventional line spray method, or it requires a simple countercurrent flow. Unlike the spray method, the heat exchange rate is low, so
By using a can body with an extremely large capacity and without increasing equipment costs, we have created a truncated cone-shaped inner cylinder 4 with a direct inner cylindrical part continuing to the lower end in the vertical inner cylindrical sealed chamber 1. Because of this structure, the flow rate of BOG is gradually slowed down, allowing good contact between gas and liquid, increasing the heat exchange rate, and then leading it to the packed layer 3, which further increases the heat exchange rate. That is, by combining the inner cylinder and the packing layer, it is possible to achieve extremely compact and highly efficient heat exchange.

In addition, since the cooling liquid is not injected with atomizing gas, it can contribute to energy saving, and the direction of flow of the cooling gas is changed by 180°C, which improves the separation efficiency of gas and liquid. The mist in the gas flow is well removed by the mist eliminator 10 during the passage, and the collected mist always falls, resulting in a good mist separation effect. The residual mist is completely separated and removed because the volume is large and the upward flow velocity is reduced. Furthermore, when spray cooling is performed in a long pipe as in the past, repeated thermal stress is generated in the pipe, but in this design, cooling is carried out in a relatively short and thick inner cylinder in a closed chamber where the cooling liquid is collected at the bottom 11. Since the heat exchange is performed in the heat exchange section, there is no such drawback, and there is no possibility that the cooling liquid will remain in the heat exchange section. Furthermore, by adopting the above-mentioned configuration, this invention can dramatically increase the gas-liquid contact efficiency and the gas-liquid separation efficiency, and therefore the cooling device as a whole can be made larger. In addition, the effect of completely preventing corrosion of the compressor impeller due to mist entrainment, which was a problem with the conventional method, is extremely large. Compared to a method that attempts to cover the volume with a can body, this method has effects such as saving power costs and construction costs, and avoiding troubles around the compressor caused by entrainment of gas and liquid due to the low gas-liquid separation efficiency. In addition, with the line spray method, the spray amount is limited, so the high temperature BOG compressor recycled gas was returned to the tank for anti-surge of the compressor, but normally the tank yard and the compressor are quite far apart, for example.
Since the length is 500m, installing the necessary stainless steel recycling piping along that length would have resulted in a significant cost increase. However, since the cooling device according to this invention has a large cooling capacity, this gas can be returned directly to the cooling device without returning to the tank, and has remarkable effects such as being able to reduce construction costs.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an example of a conventional gas cooling device, and Fig. 2 is a longitudinal sectional front view of the gas cooling device according to the invention, where 1 is a vertical closed chamber, 3 is a filling layer, and 4 is a vertical sectional front view of the gas cooling device according to the invention. Inner cylinder, 5 is a cooled gas introduction pipe, 6 is an upper chamber wall, 7 is a cooled gas discharge pipe, 8 is a coolant pipe, 9
10 is a spray nozzle, 10 is a mist eliminator, A is a gas passage, and A' is a rising passage.

Claims (1)

[Scope of utility model registration request] On the center line of the vertical cylindrical sealed chamber 1, a truncated cone-shaped inner cylinder 4 with a right cylindrical part continuing from the lower end is suspended from the ceiling into the sealed chamber, and a filling layer is placed at the lower end of the inner cylinder 4. 3, a cooled gas introduction pipe 5 is opened in the ceiling part of the inner cylinder 4, and a cooled gas discharge pipe 7 is opened in the upper chamber wall 6 of the sealed chamber.
A gas passage A is formed which descends inside the inner cylinder 4 from the cooled gas inlet pipe 5, ascends the outside of the inner cylinder by turning, and exits to the gas discharge pipe 7, and at least a gas passage A is formed in the upper part of the inner cylinder. One coolant pipe 8 is introduced, a spray nozzle 9 is provided at the end of the pipe, a mist eliminator 10 is provided in the gas ascending passage A' on the outer periphery of the inner cylinder, and a coolant is provided at the bottom 11 of the sealed chamber. Discharge pipe 12
A gas cooling device characterized by having an opening.