阅读说明：本技术 天然气处理装置以及天然气处理方法 (Natural gas processing device and natural gas processing method ) 是由 中山彻 于 2018-07-24 设计创作，主要内容包括：本发明提供下述技术,即：用于在天然气的供给量减少的情况下,也稳定地进行天然气所含有的杂质的除去。天然气处理装置中,在天然气的液化前进行杂质除去处理,接下来进行烃分离工序25,使分离后的甲烷的一部分回收再利用于杂质除去设备群20的入口侧。因此,当井口的天然气的产出量变少而天然气的供给量变少时,也可使供给至杂质除去设备群20的气体的量增加。因此,可抑制伴随杂质除去处理群20中的被处理气体的减少的、处理效率的降低。(The present invention provides the following technology: for stably removing impurities contained in natural gas even when the supply amount of the natural gas is reduced. In the natural gas processing apparatus, impurity removal processing is performed before liquefaction of the natural gas, and then the hydrocarbon separation step 25 is performed, so that a part of the separated methane is recovered and reused on the inlet side of the impurity removal equipment group 20. Therefore, when the output of the natural gas at the wellhead becomes small and the supply amount of the natural gas becomes small, the amount of the gas supplied to the impurity removal facility group 20 can be increased. Therefore, a decrease in the process efficiency associated with a decrease in the gas to be processed in the impurity removal process group 20 can be suppressed.)

1. A natural gas processing plant characterized by comprising:

an impurity removal facility group including at least one pretreatment facility selected from an adsorption facility for adsorbing and removing impurities contained in natural gas using an adsorbent and an adsorption facility for removing impurities contained in natural gas by bringing natural gas into contact with an absorption liquid, and removing impurities contained in natural gas supplied through a supply line;

a distillation facility that distills and separates the natural gas treated by the impurity removal facility group into methane and heavy hydrocarbons having 2 or more carbon atoms, and sends the methane to a gas supply line; and

and a recovery/reuse gas line for splitting a part of the methane supplied through the supply line and merging the split methane with the natural gas supplied from the supply line to the impurity removal facility group.

2. A natural gas processing plant characterized by comprising:

a liquefaction apparatus for liquefying methane fed from the distillation apparatus.

3. The natural gas processing plant of claim 1,

the distillation apparatus performs the distillation separation of a gas-liquid mixture obtained by reducing the temperature of the natural gas by decompressing and expanding the natural gas, and

the gas supply line includes a compressor for pressurizing the methane, and the recycle gas line is provided at a position where a part of the methane is branched from an outlet side of the compressor.

4. The natural gas processing plant of claim 1, comprising:

a gas-liquid separation facility that separates condensate that is a liquid component contained in the natural gas before being supplied to the impurity removal facility group, and supplies the natural gas after the condensate separation to the impurity removal facility group via the supply line;

a vapor pressure adjusting device which is supplied with the condensate through a condensate supply pipeline and adjusts the vapor pressure of the condensate by distilling and separating the light hydrocarbon contained in the condensate; and

and a condensate recovery/reuse line for branching a part of the condensate from which the light hydrocarbons have been separated by the vapor pressure adjusting device and joining the part of the condensate with the condensate supplied from the condensate supply line to the vapor pressure adjusting device.

5. The natural gas processing plant of claim 4,

the condensate recovery/reuse line is detachably provided between the condensate extraction line for extracting the condensate from the vapor pressure adjustment throttle device and the condensate supply line.

6. The natural gas pretreatment device according to claim 1,

the impurity removal equipment group and the distillation equipment are provided on a floating body floating in the ocean.

7. The natural gas processing plant of claim 6,

the floating body is provided with a liquefaction device for liquefying methane fed from the distillation device.

8. A natural gas treatment method is characterized by comprising the following steps:

removing impurities contained in natural gas supplied through a supply line using an impurity removal facility group including at least one pretreatment facility selected from an adsorption facility that adsorbs and removes impurities contained in natural gas using an adsorbent and an absorption facility that removes impurities contained in natural gas by bringing natural gas into contact with an absorption liquid;

distilling and separating the natural gas treated by the impurity removal facility group into methane and heavy hydrocarbons having 2 or more carbon atoms, and feeding the methane through a gas feed line; and

a part of the methane fed through the gas feed line is branched and merged with the natural gas supplied from the supply line to the impurity removal facility group.

Technical Field

The present invention relates to a natural gas processing apparatus for processing natural gas.

Background

A Natural Gas processing apparatus for processing Natural Gas, which is hydrocarbon Gas produced from a wellhead, is provided with a pretreatment facility for performing pretreatment for removing various impurities from the Natural Gas before liquefaction, and a liquefaction facility for liquefying the Natural Gas after the pretreatment to obtain liquefied Natural Gas (L acquired Natural Gas, L NG).

As an example of the pretreatment equipment, patent document 1 describes an absorption equipment which, when liquefied natural gas (L NG) is produced from natural gas or Coal bed gas (CSG), causes the natural gas before liquefaction to come into contact with N-Methyldiethanolamine (MDEA) to absorb and remove hydrogen sulfide or carbon dioxide, and an adsorption equipment which causes the natural gas to flow through a dehydration equipment (adsorption tower) including a molecular sieve (adsorbent) vessel to adsorb and remove water and the like.

In addition, in a natural gas field, the gas production amount from the development to the exhaustion gradually increases after the natural gas starts to be produced, and enters a stable period (plateau) in a state where the production amount is high. Then, a decline period in which the output gradually decreases is entered following the plateau period, and finally the production of natural gas ends.

With such a change in the output of natural gas, the supply amount of natural gas to each facility in the natural gas processing apparatus changes. In another aspect, the pretreatment device for removing impurities, which comprises the absorption device or adsorption device, is designed to: in general, when natural gas is processed at a supply amount in a plateau stage, the processing efficiency is high. Therefore, there is a problem that: if a fall-off period in which the throughput is gradually reduced is entered, the treatment efficiency is deteriorated.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made under the above-described background, and an object of the present invention is to provide a technique for stably removing impurities contained in natural gas even when the supply amount of the natural gas is reduced.

Means for solving the problems

The natural gas processing apparatus of the present invention comprises: an impurity removal facility group including at least one pretreatment facility selected from an adsorption facility for adsorbing and removing impurities contained in natural gas using an adsorbent and an adsorption facility for removing impurities contained in natural gas by bringing natural gas into contact with an absorption liquid, and removing impurities contained in natural gas supplied through a supply line;

a distillation facility that distills and separates the natural gas treated by the impurity removal facility group into methane and heavy hydrocarbons having 2 or more carbon atoms, and supplies the methane through a gas supply line;

and a recovery/reuse gas line for splitting a part of the methane in the feed gas and merging the split methane with the natural gas supplied from the supply line to the impurity removal facility group.

The natural gas processing plant may also include the following features.

(a) The natural gas processing apparatus includes: a liquefaction apparatus for liquefying methane fed from the distillation apparatus.

(b) The distillation apparatus performs the distillation separation of a gas-liquid mixture obtained by reducing the temperature by decompressing and expanding the natural gas,

the gas supply line includes a compressor for pressurizing the methane, and the recycle gas line is provided at a position where a part of the methane is branched from an outlet side of the compressor.

(c) The natural gas processing apparatus includes: a gas-liquid separation facility that separates condensate that is a liquid component contained in the natural gas before being supplied to the impurity removal facility group, and supplies the natural gas after the condensate separation to the impurity removal facility group via the supply line;

a vapor pressure adjusting device for adjusting the vapor pressure of the condensate by supplying the condensate through a condensate supply line and distilling and separating the light hydrocarbons contained in the condensate; and

and a condensate recovery/reuse line for branching a part of the condensate from which the light hydrocarbons have been separated by the vapor pressure control device and joining the condensate supplied from the condensate supply line to the vapor pressure control device.

(d) The condensate recovery/reuse line is detachably provided between the condensate extraction line for extracting the condensate from the vapor pressure adjustment throttle device and the condensate supply line.

(e) The impurity removal equipment group and the distillation equipment are provided on a floating body floating in the ocean.

(f) The floating body is provided with a liquefaction device for liquefying methane fed from the distillation device.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, when natural gas is treated, before liquefaction of the natural gas, impurity removal treatment is performed by a plurality of pretreatment facilities, and then the natural gas is separated into methane and heavy hydrocarbons, and a part of the separated methane is recovered and reused on the inlet side of the impurity removal treatment. Therefore, even when the amount of the treated natural gas is small, the amount of the treated natural gas in each pretreatment facility can be maintained, and efficient and stable treatment can be performed.

Drawings

Fig. 1 is a process diagram showing various treatment steps performed by a natural gas treatment apparatus.

Fig. 2 is a schematic diagram of a hydrocarbon separation facility provided in the natural gas processing apparatus.

Fig. 3 is a view showing a configuration of a condensate vapor pressure adjusting device provided in the natural gas processing apparatus.

Detailed Description

First, a flow of processing the natural gas in the natural gas processing apparatus of this example will be described with reference to fig. 1. The natural gas processing apparatus of this example is a natural gas liquefaction apparatus that separates and liquefies methane contained in natural gas (also referred to as NG in the figures).

The NG processed by the natural gas liquefaction apparatus of this example contains at least hydrogen sulfide or carbon dioxide, and also contains moisture, mercury, or oxygen.

As shown in fig. 1, the natural gas from which the liquid has been separated in the gas-liquid separation step 21 is subjected to removal of impurities as a pretreatment before liquefaction, the natural gas from which the liquid has been separated is first subjected to removal of carbon dioxide, hydrogen sulfide, or the like (which may be collectively referred to as "acid gas") in the acid gas removal step 22, and the equipment of the acid gas removal step 22 includes, for example, an absorption facility including an absorption tower for bringing an absorption liquid that absorbs acid gas into counter-current contact with the natural gas, and the carbon dioxide or hydrogen sulfide that is an acid gas that may be solidified in L NG at the time of liquefaction is absorbed and removed from the natural gas into the absorption liquid.

The natural gas treated in the acid gas removal step 22 is further subjected to moisture removal in a moisture removal step 23. Further, the natural gas treated in the moisture removal step 23 is subjected to mercury removal in a mercury removal step 24.

The facilities for performing the moisture removal step 23 and the mercury removal step 24 include, for example, adsorption towers each filled with an adsorbent for adsorbing moisture and a mercury adsorbent for adsorbing mercury. These adsorption towers allow natural gas to pass through the adsorption towers, thereby allowing the natural gas to pass through gaps between adsorbents filled in the adsorption towers, thereby allowing the natural gas to contact the adsorbents. At this time, the natural gas is brought into contact with the adsorbent, and water or mercury as an adsorption object is adsorbed by the adsorbent, whereby water or mercury in the natural gas is removed. The mercury removal step 24 may be performed before the acid gas removal step 22. The group of facilities including the pretreatment facilities for performing the acid gas removal step 22, the water removal step 23, and the mercury removal step 24 is referred to as an impurity removal facility group 20.

Next, the natural gas from which the impurities have been removed is separated into methane and heavy hydrocarbons having 2 or more carbon atoms in the hydrocarbon separation step 25. In the hydrocarbon separation step, for example, a distillation apparatus (demethanizer) is used. A detailed description of the hydrocarbon separation apparatus including the demethanizer will be provided below.

The methane separated in the hydrocarbon separation step 25 is liquefied in the liquefaction step 26 to become liquefied natural gas (L NG). for L NG, the steps such as a terminal flash gas step 27 of adjusting the temperature of L NG by vaporizing a part of L NG (terminal flash), a step 28 of storing L NG, and the like are performed, and the product is shipped to a L NG tanker, for example.

Further, a part of the liquid component (condensate) obtained by Gas-liquid separation from the natural Gas in the Gas-liquid separation step 21 is stored 32 as condensate after the vapor pressure adjustment step 31 for removing light hydrocarbons is performed, and then shipped, further, the unfrozen liquid containing water is phase-separated from the condensate after the Gas-liquid separation, and the unfrozen liquid is subjected to an unfrozen liquid regeneration treatment 30. regarding the unfrozen liquid, monoethylene glycol (MEG) or the like can be used, and the regenerated unfrozen liquid is supplied to the well head of the natural Gas again, and the pressure increase treatment 29 is performed on the end flash Gas or the Boil-Off Gas (Boil Off Gas, BOG) evaporated from L NG in the L NG storage step 28 to be mainly used as combustion Gas, and when a surplus is generated, the surplus Gas can be liquefied again by returning to the front stage of the liquefaction step 26.

Further, the present embodiment includes: the recovery/reuse gas line 10 returns the methane separated in the hydrocarbon separation step 25 to the supply line 100 that supplies the natural gas to the acid gas removal step 22, and merges with the natural gas supplied from the gas-liquid separation step 21 side. The gas recovery/reuse line 10 will be described together with the description of the facility for performing the hydrocarbon separation step 25.

Next, a hydrocarbon separation facility included in the natural gas processing apparatus and performing the hydrocarbon separation step 25 will be described.

Fig. 2 shows an example of the configuration of a hydrocarbon separation facility constituting a natural gas processing apparatus. A hydrocarbon separation apparatus comprising: a natural gas supply line 101 for supplying the natural gas treated in the mercury removal step 24; a cold box (cold box)11 and a cold box 12 for cooling the natural gas supplied from the natural gas supply line 101; a feed separator (feed separator)13 for performing gas-liquid separation of a part of the liquefied natural gas cooled by the cold box 11 and the cold box 12; and a methane fractionator 17 for distilling the natural gas and separating the natural gas into methane and heavy hydrocarbons having 2 or more carbon atoms.

The natural gas supplied from the natural gas supply line 101 is cooled by the cold boxes 11 and 12, and is subjected to gas-liquid separation by the feed separator 13. Then, a part of the gas component is decompressed and expanded by an expander (expander)14, and supplied to a methanator 17 as a gas-liquid mixture at-50 ℃ to-80 ℃. Fig. 2 shows a Joule-Thomson (JT) valve 15 at 15. The remaining gas component in the natural gas subjected to gas-liquid separation in the feed separator 13 is cooled in the cold box 16, and then decompressed and expanded by the decompression valve 104, and supplied to the methanator 17 as a gas-liquid mixture at-70 ℃ to-100 ℃. The liquid component obtained by gas-liquid separation in the feed separator 13 is used as a refrigerant in the cooling box 12, and then supplied to the methanator 17.

Further, the methane fractionator 17 separates methane by distilling the gas-liquid mixture of the supplied natural gas, and discharges the methane through the gas feed line 105 provided at the top of the column. Also, heavier hydrocarbons heavier than ethane (C2+) were made to flow out from the bottom of the column. In fig. 2, reference numeral 171 denotes a reboiler.

The hydrocarbon separation facility of the present embodiment uses methane discharged from the methanator 17 or a liquid component in the natural gas separated by the feed separator 13 as a refrigerant for the cold box 11 or the cold box 12. That is, the methanator 17 of the present embodiment is configured as a self-cooling type distillation apparatus.

Further, the methane flowing out of the methane fractionator 17 is used as a refrigerant of the cooling tank 11, and is pressurized by a compressor 311 and a booster compressor (booster compressor)312, and further cooled by an air cooler 320, and then supplied to the equipment for performing the liquefaction step 26.

One end of the recovery/reuse gas line 10 is connected to the downstream side of the compressor 311 in the gas supply line 105. As shown in fig. 1, the other end of the recovery/reuse gas line 10 is connected to the inlet side of the impurity removal facility group 20, in this example, to a supply line 100 on the inlet side of the acid gas removal step 22. As shown in fig. 2, a pressure regulating valve V10 may be provided in the recycling gas line 10.

Here, the change in the output between the development and exhaustion of the natural gas field and the influence on the natural gas processing apparatus accompanying the change in the output will be described. As described above, in the natural gas field, the production amount gradually increases after the production of natural gas from the gas field starts, and a period (plateau) is reached in which the high production amount is maintained. Further, over the years, the natural gas eventually enters a decline period in which the production of natural gas is gradually reduced.

In other words, in the fall-down period, for example, even if the amount of processing is reduced, the energy required for liquefaction of methane gas per unit weight, end flashing of L NG, or storage does not change greatly.

On the other hand, as described above, the impurity removal equipment group 20 uses an absorption tower in the acid gas removal step 22 and uses adsorption towers in the moisture removal step 23 and the mercury removal step 24.

For example, in the absorber in the acid gas removal step 22, if the amount of the natural gas to be supplied is less than the design flow rate, the amount of the absorbed liquid is also reduced by the amount of the natural gas, and therefore, the vapor load and the liquid load are both lower than those in the appropriate operation region, the absorbed liquid and the natural gas cannot be brought into sufficient contact, and the absorber cannot exhibit the predetermined performance, and as a result, the absorber may be difficult to continue the operation.

Further, if the amount of the natural gas supplied to the adsorption towers in the moisture removal step 23 and the mercury removal step 24 is less than the variation range suitable for the operation, an uneven flow (channeling) may occur: the natural gas supplied to the adsorption tower passes only through a portion of the packed adsorbent, which is relatively easy to pass through. When such channeling occurs, the natural gas comes into contact with only a part of the adsorbent filled therein, and the adsorption efficiency of the adsorbed component (moisture or mercury) contained in the gas is deteriorated. Further, if the operation at a low flow rate such as the generation of the channeling is constantly performed, the short-circuit path may be fixed. As a result, even if the natural gas flow rate returns to the appropriate flow rate, the natural gas does not uniformly contact the entire adsorbent, but preferably flows through the short-circuit path, and therefore, not only the adsorption efficiency deteriorates, but also only the adsorbent in the vicinity of the short-circuit path contributes to adsorption, and therefore, the life of the adsorbent may be extremely short compared to the design life based on the entire adsorbent.

Further, the demethanizer 17 in the hydrocarbon separation step 25 is a distillation column, and even in the distillation column, if the amount of the supplied gas is reduced, the steam load and the liquid load are reduced by that amount, and thus the distillation efficiency is lowered. In addition, since the methane fractionator is a process of separating heavy hydrocarbons by self-cooling the supplied natural gas by introducing the heat and cold generated in the expander 14 into the cold box 11, the cold box 12, and the cold box 16, the heat and cold obtained by the expander 14 are also reduced when the amount of gas supplied is reduced, and the separation efficiency of heavy hydrocarbons is reduced.

As exemplified above, the influence accompanying the supply of natural gas from the wellhead being lower than the design flow rate becomes conspicuous mainly in the impurity removal equipment group 20 or the methanator 17 which is a distillation equipment of the hydrocarbon separation process 25.

In this respect, it is preferable to design each facility in the natural gas processing plant so that efficient processing can be performed in a plateau period where the production amount is large and is longer than the production start period or the decline period. Therefore, in each processing facility of the natural gas processing apparatus, the design flow rate of the natural gas in each facility is often set based on the supply flow rate of the natural gas in the plateau period.

However, even in small and medium-sized gas fields, the plateau period is relatively short, and the gas fields enter the decline period in a short period of several years to about 10 years. Therefore, the period of time during which the natural gas processing apparatus exhibits the performance as designed for the flow rate is shortened, and the production efficiency is sometimes deteriorated.

Therefore, in the natural gas processing apparatus of the present embodiment, when the gas field at the wellhead enters the decline period and the supply amount of natural gas decreases, a part of the methane gas is recovered and reused on the inlet side of the impurity removal facility group 20 via the recovery and reuse gas line 10. For example, when the supply flow rate of the natural gas supplied to the acid gas removal step 22 through the supply line 100 is lower than a preset flow rate, the recovery/reuse gas line 10 is brought online. The amount of methane gas recovered and reused is adjusted by the adjustment valve V10 shown in fig. 2 so that the supply flow rate of the natural gas supplied to the acid gas removal step 22 is, for example, approximately the same as the plateau period.

According to the above configuration, on the inlet side of the impurity removal equipment group 20, the natural gas supplied from the wellhead side merges with a part of the methane gas discharged from the methanator 17, and is then supplied to the impurity removal equipment group 20. As a result, for example, natural gas is supplied to the absorber in the acid gas removal step 22 at the same flow rate as in the plateau phase.

By recovering and reusing the methane gas, the supply flow rate of the natural gas supplied to the impurity removal facility group 20 and the hydrocarbon separation facility, that is, the flow rate of the natural gas flowing through each facility can be maintained at the same level as that in the plateau stage.

As a result, the steam load due to the shortage of the flow rate of the natural gas can be maintained at the operable flow rate in the absorption tower in the acid gas removal step 22, and the state in which the acid gas can be absorbed can be efficiently maintained.

In addition, in each of the adsorption towers in the subsequent moisture removal step 23 and the subsequent mercury removal step 24, generation of channeling due to a shortage of the flow rate of the natural gas can be suppressed, and the state in which moisture or mercury can be adsorbed can be efficiently maintained.

Further, in the methane fractionator (distillation apparatus) 17 in the hydrocarbon separation apparatus, the distillation separation of methane gas can be efficiently performed while suppressing a decrease in the amount of heat and cold generated and a decrease in the steam load in the distillation column due to a shortage of the supply flow rate of liquefied natural gas.

Even if the amount of natural gas produced in the fall-off period is decreased and the amount of natural gas supplied is further decreased, the flow rate of natural gas supplied to the impurity removal facility group 20 and the hydrocarbon separation facility can be maintained by increasing the amount of methane gas recovered and reused.

The amount of methane gas recovered and reused is not limited to the following cases: the pressure on the inlet side of the impurity removal equipment group 20 is adjusted to be maintained at the same level as the plateau pressure. For example, it is also possible to set an appropriate value according to the plant capacity or the like, considering setting of the suppliable flow rate of the recycling gas line 10 such that the pressure is maintained at a value of 80% or more of the plateau period, or the like.

Further, the high-pressure methane gas can be recovered and reused by connecting the recovery and reuse gas line 10 to the methane gas supply line 105 downstream of the compressor 312. As a result, the flow rate on the inlet side of the impurity removal device group 20 can be easily adjusted, and the number of compressor devices required for increasing the pressure can be reduced.

According to the above embodiment, in the natural gas liquefaction device, the impurity removal process is performed before the liquefaction of the natural gas, and then the hydrocarbon separation step 25 is performed to recover and reuse a part of the separated methane on the inlet side of the impurity removal equipment group 20. Therefore, when the output of the natural gas at the wellhead is reduced and the supply amount of the natural gas is reduced, the amount of the natural gas supplied to the impurity removal facility group 20 can be maintained at the same level as the plateau. Therefore, in the pretreatment equipment (the absorption tower for acid gas, the adsorption tower for moisture or mercury) provided in the impurity removal equipment group 20 and the demethanizer 17 provided in the hydrocarbon separation equipment, it is possible to perform stable treatment while suppressing a decrease in treatment efficiency associated with a decrease in the supply amount of natural gas.

Next, an embodiment in which the recovery/reuse line is provided in the facility for performing the vapor pressure adjustment step 31 of the condensate will be described.

As shown in fig. 3, the apparatus for performing the vapor pressure adjusting step 31 includes a condensate distillation column (stabilizer) 131, and the condensate separated in the gas-liquid separation step 21 described above is supplied through a condensate supply line 106.

An extraction line 108 for extracting the light gas separated by distillation of the condensate is connected to the top of the stabilizer 131, and the extracted light gas is compressed by, for example, a compressor 41 and then merged with the supply line 100 leading to the acid gas removal step 22.

Further, a condensate extraction line 107 for extracting the condensate separated from the light gas accumulated at the bottom of the column is connected to the bottom of the stabilizer column 131, and the extracted condensate is discharged to the condensate storage step 32. Further, reference numeral 43 provided in the condensate extraction line 107 denotes a cooler.

Further, a branch line 109 branches from the condensate extraction line 107. A reboiler 42 is inserted into the branch line 109, and the extracted condensate containing the heavy component is heated and returned to the stabilizer column 131.

On the downstream side of the cooler 43 in the condensate take-off line 107, one end of a condensate recovery and reuse line 110 is connected, and the other end side of the condensate recovery and reuse line 110 is connected to the condensate supply line 106. In fig. 3, reference numeral 44 denotes a pump.

In the vapor pressure adjusting step 31, when the amount of condensate supplied to the stabilizer 131 is decreased as the amount of natural gas produced from the wellhead is decreased, the liquid load is decreased, and the treatment efficiency is decreased. Therefore, by returning the condensate containing the heavy component to the inlet side through the condensate recovery and reuse line 110, the amount of the condensate supplied to the stabilizer column 131 can be maintained at the same level as the plateau period. Thus, even when the gas production amount at the wellhead becomes low due to the fall-off period, the stabilizer 131 can suppress the reduction of the treatment efficiency due to the reduction of the condensate amount.

Also, when the supply amount of natural gas from the wellhead is sufficiently large, the condensate recovery reuse line 110 does not need to be used.

Therefore, the condensate recovery and reuse line 110 may be detachably provided to the condensate supply line 106 and the condensate extraction line 107. According to the configuration, the condensate recovery and reuse line 110 may be installed during a decline period in which the output of natural gas into the wellhead is reduced. In addition, the stabilizer 131 may be installed from the beginning of construction in order to quickly start up.

Further, the above-described methane gas recovery/reuse gas line 10 shown in fig. 2 has a large diameter and a long pulling distance, and thus is difficult to be configured to be detachable. Therefore, the following can be exemplified: the natural gas liquefaction plant is set in advance at the time of construction of the natural gas liquefaction plant, and is started to be used according to the timing of the decrease in the production amount of natural gas.

The embodiments described are not limited to the case of application to a natural gas liquefaction plant including a natural gas liquefaction plant. For example, in a natural gas processing apparatus that keeps methane gas obtained in the hydrocarbon separation step 25 in a gaseous state and directly delivers the methane gas to a pipeline, a recycle gas line 10 that recycles a part of the methane gas on the inlet side of the impurity removal equipment group 20 may be provided.

In recent years, small and medium-sized gas fields on the sea bottom have been developed, but a natural gas processing apparatus including a recovery and reuse gas line 10 may be installed on a floating body floating on the ocean.

Description of the symbols

10: supply line

17: methane distilling remover

22: acid gas removal step

23: water removal step

24: mercury removal step

25: hydrocarbon removal process

26: liquefaction Process

31: steam pressure adjusting step

100: gas pipeline for recycling

101: pretreatment apparatus

102: liquefaction plant

131: distillation column for condensate

311: compressor with a compressor housing having a plurality of compressor blades