CN113167133B

CN113167133B - Method for generating electric energy and thermal energy in a power generation cycle using a working fluid

Info

Publication number: CN113167133B
Application number: CN201980067184.4A
Authority: CN
Inventors: 马泰奥·贝拉; 安东·马可·范托利尼; 萨尔瓦托雷·德里纳迪斯; 卢卡·戴维·英里士
Original assignee: Saybaum Corp
Current assignee: Saybaum Corp
Priority date: 2018-10-10
Filing date: 2019-10-10
Publication date: 2024-04-30
Anticipated expiration: 2039-10-10
Also published as: WO2020075112A1; EP3864258A1; CN113167133A; AU2019356257A1; JP2022515700A; KR20210094515A

Abstract

The present invention relates to a method for preparing a fluid with cooling properties, which is derived from mixed LNG and LPG by low temperature thermodynamic applications, and a method for generating mechanical and/or electrical and thermal energy in a power generation cycle.

Description

Method for generating electric energy and thermal energy in a power generation cycle using a working fluid

Technical Field

The invention is applicable to the field of regasification of Liquefied Natural Gas (LNG).

Background

Techniques for regasifying Liquefied Natural Gas (LNG) are known.

Liquefied natural gas is a natural gas mixture consisting essentially of methane and, to a lesser extent, other light hydrocarbons (e.g., ethane, propane, isobutane, n-butane, pentane, and nitrogen), which mixture transitions from a gaseous state (which is at ambient temperature) to a liquid state at about-160 ℃ to permit transportation.

The liquefaction plant is located near the natural gas production site, while the regasification plant (or "regasification terminal") is located near the user.

Most equipment (about 85%) is located on land, while the remainder (about 15%) is on an offshore platform or vessel.

It is common for each regasification terminal to include several regasification lines to meet lng loads or requirements, also for reasons of flexibility or technical requirements (e.g., for repair lines).

Regasification techniques typically involve storing liquefied natural gas in a rotating drum at a temperature of-160 ℃ at atmospheric pressure, and then providing the steps of compressing the gas to about 70-80bar, vaporizing and superheating to about 3 ℃.

The thermal power required for regasification 139t/h is about 27MWt and the electrical power is about 2.25MWe (4.85 MWe if other auxiliary loads of the plant are considered; the electrical load of the plant on the 4 regasification lines is a maximum of 19.4 MWe).

Of these, open rack gasifiers (ORVs) and submerged combustion gasifiers (SCVs) used in about 70% of regasification terminals are most used, alone or in combination with each other.

Open frame type gasifier (ORV)

This technique flows liquid natural gas (about 70-80bar at a temperature of-160 ℃) up inside aluminum tubes placed side by side to form a panel; as the fluid flows, vaporization occurs gradually.

The heat carrier is sea water flowing down the outer surface of the tube, providing the heat needed for vaporization due to temperature differences.

The heat exchange is particularly optimized by designing the contour and surface roughness of the tube, so that a sea water film uniformly distributed on the panel is obtained.

Submerged combustion gasifier (SCV)

The technology utilizes a softened water bath heated by a submerged flame burner as a heat carrier; in particular, the Fuel Gas (FG) burns in the combustion zone, and the flue gases produced pass through a coil (coil) of perforated pipe, from which the burnt gas bubbles are output, which heat the water bath, thereby also transferring the heat of condensation.

Liquefied Natural Gas (LNG) is gasified in another coil of stainless steel tubing immersed in the same softened hot water bath.

The water of the same bath is kept circulating to ensure a uniform temperature distribution.

The exhausted flue gas is in turn exhausted from the SCV exhaust stack.

In particular with respect to submerged combustion gasifiers (SCVs), this technology results in a fuel gas consumption equal to about 1.5% of the gas produced, which produces carbon dioxide that lowers the pH of the water bath, thus requiring treatment with caustic soda, and results in the production of CO ₂ at about 50000 t/year to regasify 139t/h.

In contrast, with open rack gasifiers, this technique can cause, in part, the freezing of seawater outside the tubes, especially in colder sections of LNG; furthermore: i) It can be utilized in geographical areas and/or seasons where the temperature of the seawater is at least 5 ℃ to 9 ℃ (mainly described as subtropical areas), ii) to pre-treat the seawater to eliminate or reduce the content of heavy metals that could corrode the zinc coating of the pipe, iii) it results in operating the seawater pump to consume more electrical energy than the geodetic level difference equivalent to the high development of ORV, with 1.2MWe being additionally consumed per regasification line, iv) at the end, the technology is quite complex, available from a limited number of suppliers, and limited in size, relative to SCV technology (total plant power equal to 24.2 MWe).

Thus, conventional techniques generally do not allow for the generation of the electrical energy required by the device, resulting in a significant amount of energy being lost in the form of cold energy.

Organic Rankine cycle (RANKINECYCLE)

Organic Rankine Cycles (ORCs) are widely used for geothermal field and biomass applications or for waste heat recovery in industrial processes.

This cycle offers the possibility of selecting the working fluid among tens of possible fluids and allows to realize a highly efficient thermodynamic cycle, also suitable for low source temperatures and small heat sources.

In addition, the choice of a low boiling point fluid allows the condensation cycle to be achieved at ultra low temperatures without causing freezing problems or excessively hard vacuum levels.

U.S. patent application US2013/0160486 (Ormat technologies limited) describes single or dual stage pressure cycles operating with a single fluid, with and without heat exchange within the cycle (regeneration) at two levels; in one embodiment, two cascaded cycles are operated with two different fluids, wherein the heat of the first cycle is used only to vaporize the second fluid and the liquefied natural gas is vaporized with the heat released by the second fluid's cycle alone.

As shown in fig. 2 and 6 of the above-mentioned patent, the cycle described by Ormat operates using pure substances as engine fluid; indeed, the vaporization/condensation curve indicates that the temperature remains constant and that the substances mentioned as examples are all pure substances.

This results in thermodynamic disadvantages, translating into less power extractable in the cycle; the configurations presented in fig. 7, 7A, 7D and 7E attempt to avoid such problems by extracting a portion of the working fluid from the expander so that the heating of the LNG can be adjusted at two heat levels near the LNG heating profile.

This operation has the effect of increasing the power that can be extracted from the ORC, but becomes unbalanced and complicates the expander, or to eliminate the problem of using two separate expanders to produce the two heat levels needed to approximate the ORC engine fluid condensation curve and LNG vaporization curve.

The prior art document JP 2016148001 describes a method for controlling the heating value of so-called urban gas (gaseous fuel) to reduce evaporation and form boil-off gas (BOG); for this, a certain amount of Liquefied Petroleum Gas (LPG) is cooled and added to Liquefied Natural Gas (LNG).

The prior art document JP S57164183 describes a process for continuously preparing engine liquid for use in a rankine power generation cycle from an ethane-rich stream obtained by distillation of Liquefied Natural Gas (LNG) to which propane and/or commercial butanes and pentanes etc. are added as correction additives.

The document JP H05271671 describes a method for continuously purifying Liquefied Petroleum Gas (LPG) by reverse osmosis in the scope of a method for correcting the heating value of urban fuel gas (gaseous fuel) by mixing a small amount of Liquefied Petroleum Gas (LPG) with Liquefied Natural Gas (LNG).

The prior art document CN 203240278 describes a continuous process for mixing liquefied natural gas and liquefied petroleum gas to increase the heating value of the fuel mixture.

The prior art document JP 2008115842 describes a method for reducing the generation of particulates in a diesel engine driven by diesel, to which a certain amount of water is added to promote the catalytic combustion of these carbon particles.

The prior art document US 4,444,015 describes a method for generating power by means of two rankine cascade cycles operating between a heat source and cold hydrazine (represented by LNG) which is vaporised; the use of a universal engine fluid represented by a mixture comprising nitrogen, hydrogen and a hydrocarbon having 1 to 6 carbon atoms or equal amounts of halogenated atoms is described.

Thus, conventional techniques generally do not allow for the generation of the electrical energy required by the device and result in a significant amount of energy being lost in the form of cold energy.

Disclosure of Invention

The inventors of the present invention have unexpectedly found that a mixture of Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) can be used as a working fluid in a power generation cycle (power GENERATING CYCLE) (PGC), the residual heat of which can be used to regasify the Liquefied Natural Gas (LNG).

Object of the Invention

In a first object, a method for preparing a working fluid (IMR) represented by a mixture of Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) is described.

The working fluid (IMR) comprising Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) obtained by this method represents a second object of the present invention.

In a third object, a method for regasifying Liquefied Natural Gas (LNG) is described, the method using the working fluid (IMR) of the present invention.

In a fourth object, a Liquefied Natural Gas (LNG) regasification line using the working fluid (IMR) of the present invention is described.

According to a fifth object, a working fluid (IMR) for use in a regasification process of Liquefied Natural Gas (LNG) is used in a power generation cycle.

In another object, a power generation cycle using the working fluid (IMR) of the present invention is described.

Drawings

FIG. 1 shows a general simplified diagram of a regasification line according to the present invention, described in more detail in FIG. 2;

FIG. 3 illustrates a small scale LNG regasification line with examples of heat sources that may be used independently of each other;

FIG. 4 illustrates an alternative embodiment of the invention wherein the heat of the flue gas generated by the gas turbine is recovered;

FIG. 5 illustrates an embodiment of an afterburner with the addition of flue gases of a gas turbine;

FIG. 6 shows a diagram of a regasification line in accordance with another embodiment of the present invention where an IMR turboexpander is not available;

FIG. 7 illustrates a regasification line that also uses combustion air of a turbine as a low temperature heat source in accordance with one embodiment of the present invention;

FIG. 8 illustrates a regasification line that uses a regenerator in accordance with another embodiment of the present invention;

FIG. 9 shows the vaporization curve of LNG and the condensation curve of IMR of the present invention;

FIG. 10 shows vaporization curves of various LNG and condensation curves of various IMRs according to the present invention, where the chemical composition of LNG is maintained constant, as the molecular weight (molecular average) varies;

FIG. 11 shows a depiction of a thermodynamic cycle of an IMR unit in accordance with the present invention;

fig. 12 shows details of the LPG ultra-low temperature filter.

Detailed Description

According to a first object of the present invention, a method for preparing a working fluid (hereinafter IMR) is described.

The working fluid is a fluid mixture.

In particular, such fluids are obtained by mixing commercial Liquefied Petroleum Gas (LPG) and commercial Liquefied Natural Gas (LNG).

The term "commercial Liquefied Petroleum Gas (LPG)" refers to a well-characterized fuel commonly used in the domestic and industrial fields, having the following characteristics:

vapor pressure at-100°f;

-a minimum temperature at which 95% by volume of the hypothetical sample is vaporized at atmospheric pressure according to a precise method (possibly by heating);

-mole percentage of molecules having a number of carbon atoms greater than 4; for the purposes of the present invention, it does also comprise hydrocarbons having 7 or >7 carbon atoms.

It is well known that Liquefied Petroleum Gas (LPG) is a part of crude oil from which they are separated by refining in a top column.

Various refining processes produce Liquefied Petroleum Gas (LPG); for example, cracking produces Liquefied Petroleum Gas (LPG) as a by-product.

For the purposes of the present invention, liquefied Petroleum Gas (LPG) is preferably defined as a combustible fluid, the characteristics of which fall within the limits defined in the following table:

(1) Obtaining a maximum temperature of the sample to be tested of 95% of the evaporation volume at atmospheric pressure;

(2) A content of molecules having at least 5 carbon atoms.

The term "commercial Liquefied Natural Gas (LNG)" refers to a predominantly liquid hydrocarbon fluid obtained by condensing natural gas at a temperature low enough to maintain it in a liquid state also at atmospheric pressure.

Natural gas is known to consist primarily of methane and very few light hydrocarbons with a carbon number > 5; it may also contain nitrogen in varying proportions.

For the purposes of the present invention, "IMR" is defined as any mixture of Liquefied Natural Gas (LNG) and Liquefied Petroleum Gas (LPG) obtained by mixing 1 volume of Liquefied Natural Gas (LNG) with an amount of Liquefied Petroleum Gas (LPG) of 0.25 to 1.2 volumes relative to the Liquefied Natural Gas (LNG).

In more detail, the method of the present invention for preparing a working fluid comprises a step I) wherein a first amount of Liquefied Natural Gas (LNG) (101) from a rotating drum (510) thereof is prepared in a first rotating drum (530) of the working fluid; in practice, a suitable amount of Liquefied Natural Gas (LNG) stream is loaded into the first drum (530, imr drum).

In step II), a suitable first amount (210) (or stream) of Liquefied Petroleum Gas (LPG) is added.

Thus, IMR formation with contact between the first Liquefied Natural Gas (LNG) and the Liquefied Petroleum Gas (LPG) occurs in the first drum (530, IMR drum).

For the purposes of the present invention, liquefied Petroleum Gas (LPG) is added to Liquefied Natural Gas (LNG) at ambient temperature.

In step III), any volatile compounds are allowed to be removed by evaporation.

This vaporization is promoted by adding Liquefied Petroleum Gas (LPG) to Liquefied Natural Gas (LNG) at ambient temperature.

In step IV), the pressure is reduced if necessary.

In a preferred aspect, the pressure is reduced to about 2bar to 20bar.

In a possible step V), one or more of steps II, III or IV are repeated until the condensing temperature of the fluid is reached, as described in further detail below.

Specifically, in step I), the volume of Liquefied Natural Gas (LNG) may be determined by one skilled in the art according to the size of the possible power generation cycles using IMR as working fluid.

With respect to Liquefied Natural Gas (LNG), the amount (100) delivered to the regasification section (590) is derived from the drum (510) in which it is stored, possibly after a high pressure pumping step with a pump (600).

As mentioned above, after the pumping step, a portion of the first amount of liquefied natural gas (101) is preferably separated and transferred to a first drum (530, imr drum) for the preparation of a working fluid.

The addition of step II) and subsequent mixing of Liquefied Petroleum Gas (LPG) and Liquefied Natural Gas (LNG) produces heating of the IMR obtained and contained in the IMR drum; this results in the removal of the most volatile compounds contained therein by evaporation (step III), thereby increasing the pressure in the IMR drum.

This advantageously allows the pressure required in the first drum (530, imr drum) to be reached to operate the power generation cycle of which it is a part.

If the pressure is too high, an exhaust valve (not shown) may be used to remove excess steam from the first drum (IMR drum) in step IV).

For the purposes of the present invention, the mixing of step II) is carried out by adding and without any mixing apparatus.

According to a particular aspect of the invention, the total amount of Liquefied Petroleum Gas (LPG) to be added to the Liquefied Natural Gas (LNG) to obtain the working fluid varies within the limits described above.

The final goal is to reach a given liquefaction point.

The amount of final addition may be determined by an optimization method; in particular, it may be optimized based on:

-manifestation of a regasification process of Liquefied Natural Gas (LNG); and/or

-Performance of a possible power generation cycle using IMR as working fluid.

For example, any volume (within the above-mentioned limits) of Liquefied Petroleum Gas (LPG) may be added to a volume of Liquefied Natural Gas (LNG) sufficient to meet the size of the power generation cycle and thus the subsequent cycle of IMR obtained in the power cycle plant.

Depending on the resulting performance, the composition of the IMR may be modified to have the desired performance.

Alternatively, the heat exchange profile of a laboratory scale LNG may be determined, as well as the heat exchange profile of various IMR samples prepared by mixing a set volume of Liquefied Natural Gas (LNG) with a volume of Liquefied Petroleum Gas (LPG) within the limits described above, over the range of possible IMR variations.

From a practical point of view, it is desirable to fix the operating pressures and associated flow rates of Liquefied Natural Gas (LNG) and IMR.

Once the mix ratio that best meets the engineering performance of the plant is determined, the process can then be transposed to an industrial scale by implementing the required modifications.

As an alternative to the two methods disclosed above, suitable simulations can be performed if chemical analysis of the Liquefied Natural Gas (LNG) and the Liquefied Petroleum Gas (LPG) to be used is available within a specific facility and a desired specific period of time.

The first two methods allow for the calculation of the pressure and temperature that an IMR in an IMR drum may have, allowing for the use of pressure indicators and temperature sensors to prepare the IMR instead of measuring volume.

The process according to the invention is preferably a batch process.

According to one aspect of the invention, in order to avoid solidification of components (e.g., water and heavy hydrocarbons) that may be present (but are not required to be) in the Liquefied Petroleum Gas (LPG), the purification step of the Liquefied Petroleum Gas (LPG) may be performed prior to mixing the Liquefied Petroleum Gas (LPG) with the Liquefied Natural Gas (LNG).

Such steps may be carried out by well known methods (e.g., using molecular sieves to separate water and hydrocarbons).

Or the ultra-low temperature filter shown in fig. 12 may be used.

The ultra-low temperature filter shown in fig. 12 consists of an external exchanger (620) at the first drum (530, imr drum) and an internal coil (610) at the first drum (530, imr drum), and possibly other solid filters (630).

In particular, the external exchanger (620) is of the shell-and-tube condenser type.

In step 1), a first purified amount (200) of Liquefied Petroleum Gas (LPG) from a third drum (520) of liquefied petroleum gas is supplied to a shell side of an external exchanger (620).

Thus, by satisfying the cold fluid flowing in the tube, the Liquefied Petroleum Gas (LPG) is cooled and allowed to remove undesirable components to solidify on the cold surface of the tube, thereby producing a second purified amount (201) of liquefied petroleum gas.

In the subsequent step 2), the Liquefied Petroleum Gas (LPG) of the second purified amount (201) output from the shell side is delivered to the inner coil (610) of the first drum (IMR drum).

Accordingly, the Liquefied Petroleum Gas (LPG) is heat exchanged with the working fluid for which cooling is performed, thereby obtaining a third purified amount (202) of liquefied petroleum gas.

In step 3), the third purified amount (202) of Liquefied Petroleum Gas (LPG) output from the inner coil (610) is supplied to a tube side in an external exchanger (620), where it constitutes a cold fluid that cools a first purified amount (200) of the above-mentioned Liquefied Petroleum Gas (LPG) flowing on the shell side, thereby obtaining a fourth purified amount (203) of liquefied petroleum gas.

It is also possible to carry out step 4) wherein said fourth purified amount (203) of Liquefied Petroleum Gas (LPG) output from the tube side of the external exchanger (620) is further filtered in a solid filter (630).

A first quantity (210) of Liquefied Petroleum Gas (LPG) is obtained from step 3) or 4) and is fed to a first drum (IMR drum) for the preparation of a working fluid.

Advantageously, such a first drum (530, imr drum) to be fed to the working fluid is used for preparing a first quantity (210) of Liquefied Petroleum Gas (LPG) of the working fluid with a reduced content of heavy, potentially curable components.

In a preferred aspect of the invention, such an amount delivered to the first drum (530, imr drum) has a reduced pentane content.

In a preferred aspect of the invention, such content is less than 0.1%.

From the foregoing, it is apparent that the Liquefied Natural Gas (LNG) and the Liquefied Petroleum Gas (LPG) involved in purifying the Liquefied Petroleum Gas (LPG) are the same as those used for preparing the working fluid (IMR), and thus no external fluid is required.

The working fluid (IMR) obtained according to the above method represents a further object of the invention.

In one aspect of the invention, such a working fluid (IMR) may have cooling characteristics (i.e., a low liquefaction point at standard pressure) depending on the temperature of the fluid with which heat is exchanged.

The invention also describes a device for preparing the working fluid.

Such an apparatus comprises a first drum (530) for adding an amount (210) of liquefied petroleum gas to a first amount of liquefied natural gas (101) to produce the working fluid (IMR), a second drum (510) for the liquefied natural gas, and a third drum (520) for the liquefied petroleum gas.

In one aspect of the invention, the apparatus further comprises an ultra low temperature filter for purifying Liquefied Petroleum Gas (LPG) as described above.

Obviously, the device comprises a delivery tube (duct), a tube (pipe) and a valve.

According to a third object, the invention describes a regasification line for Liquefied Natural Gas (LNG) comprising a liquefied natural gas regasification section (590) in which heat exchange takes place between the Liquefied Natural Gas (LNG) and the working fluid of the invention.

Although particular mention is made in this disclosure of regasification of Liquefied Natural Gas (LNG), the regasification lines, regasification terminals, and regasification methods described below are equally applicable to regasification or other liquefied fluids stored at low temperatures (less than about 0 ℃) or ultra low temperatures (cryogenic temperature) (less than-45 ℃).

Thus, the invention is also applicable to regasification or gasification of liquefied gases selected from, for example, air, nitrogen, hydrocarbon compounds such as alkanes (e.g., propane and butane) or olefins (e.g., ethylene or propylene).

In the following description, the term "liquefied gas" refers to a fluid having a general liquid composition.

The term "regasification line" refers to a portion of equipment that includes structures, devices, machines, and systems for regasifying Liquefied Natural Gas (LNG).

Such structures, devices, machines and systems particularly start with a second drum (510) storing Liquefied Natural Gas (LNG) and a third drum (520) storing liquefied petroleum gas and end with an introduction point of regasified Liquefied Natural Gas (LNG) into the distribution network of the gas itself.

In more detail, liquefied Natural Gas (LNG) in the drum (510) is stored at atmospheric pressure at a temperature of about-160 ℃;

In some cases, for example for smaller plants, at a pressure of 3 to 10bar g, at a temperature of-150 to-130 ℃.

The liquefied gas drum may in particular be located in a different place or structure than the place or structure of the regasification facility, e.g. it may be on shore or off-shore.

Once regasified in the regasification section, natural gas may be introduced into a natural gas distribution network.

According to one aspect of the invention, the LNG regasification line (base loop) is modified to integrate the LNG bypass loop.

In particular, the two loops are integrated at a traction connection (drawing connection) for the lng from the base loop and at a reintroduction connection where the lng regasified in the base loop is introduced into the distribution network.

The traction connection is preferably located downstream of the cryogenic pump, upstream of the gasification bath.

Thus, for the purposes of the present invention, the following is described:

existing conventional regasification lines, retrofitted to integrate a natural gas regasification bypass loop (retrofit) according to the present invention;

a regasification line, forming the main line of the line according to the invention, for example for the establishment of new plants.

According to a fourth object of the invention, a method for regasifying Liquefied Natural Gas (LNG) is described, comprising the step of heat exchanging between said Liquefied Natural Gas (LNG) and a working fluid as described herein.

Such a working fluid may have cooling characteristics as detailed above.

To this end, the performance limitations are to obtain Liquefied Natural Gas (LNG) which is regasified at the temperature and pressure required to operate the plant and at which IMR output from the Liquefied Natural Gas (LNG) vaporizer is fully condensed or possibly subcooled (to avoid IMR leakage) so the process can be cycled.

In particular, a method of regasifying Liquefied Natural Gas (LNG) includes the step of exchanging heat between an amount (100) of liquefied natural gas and an amount of working fluid in a regasification section (590) of the liquefied natural gas.

The amount of Natural Gas (NG) obtained from the regasification section (590) output is introduced into the natural gas's own distribution network at the required pressure and temperature (typically about 70bar and 3 ℃).

In one aspect of the invention, an IMR for regasifying an amount (300) of Liquefied Natural Gas (LNG) is from a first drum (530) of the IMR.

According to an alternative aspect of the invention, the amount of IMR used to gasify Liquefied Natural Gas (LNG) is the amount from the power generation cycle.

According to another object of the present invention, a power generation cycle using the above working fluid is described.

More specifically, such fluids undergo a series of steps in a production cycle.

According to one aspect of the invention, the amount of working fluid (IMR) used to regasify Liquefied Natural Gas (LNG) is the amount resulting from the heat exchange step between the amount (410) of working fluid (IMR) from the step in the power generation cycle and the amount (300) of working fluid (IMR) input into the power generation cycle (after output from the IMR drum).

For the purposes of the present invention, this amount of working fluid is subjected to one or more of the following steps:

-heat transfer, and/or

-Heat collection, and/or

-Expanding in a turbine (570) producing electrical and/or mechanical energy (by means of a suitable generator).

Examples of possible power generation cycles according to the invention are described in detail below, including in particular:

The engine fluid collection drum is provided with a first fluid collection drum,

One or more pumps (20, IMR pumps) for pumping the working fluid,

A turbine (570) for generating mechanical and possibly electrical energy from the expanded working fluid,

A high temperature heat exchanger (550) and a low temperature heat exchanger (540) for recovering heat by heat exchange between portions of the working fluid at different temperatures,

One or more possible heat exchangers (recuperator) for recovering heat by using low-temperature or high-temperature heat sources, which sources may be, for example, gases discharged by an internal combustion engine,

Possible pump(s) (not shown) for pumping the engine fluid.

The power generation cycle further includes a hot side of a regasification section (590) of Liquefied Natural Gas (LNG).

For the purposes of the present invention, an amount of working fluid for regasifying Liquefied Natural Gas (LNG) is obtained by a process comprising the steps of:

a) Heating;

b) Expanding in a turbine (570);

c) And (5) partially cooling.

In particular, a first amount of said working fluid (400) in the method is subjected to the following steps:

a) Heating, thereby obtaining a second quantity (430) of heated working fluid;

b) Expanding in a turbine (570) to produce mechanical energy, thereby obtaining a third amount (440) of expanded working fluid;

c) Partially cooled to thereby obtain a fourth amount of partially cooled working fluid.

For the purposes of the present invention, said step a) comprises the steps of:

a1 Wherein the first quantity of working fluid (400) is heated in a high temperature heat exchanger (550) resulting in a heated quantity (420) at a high temperature, and step a 2) heating from a high temperature heat source (560) resulting in a second heated quantity (430) of working fluid.

In one aspect of the invention, prior to step a1, step a 0) may be performed wherein the first portion (401) of the quantity of working fluid is heated by a cryogenic heat source (580) resulting in a second heated portion (402).

Then, such a second heating portion (402) is added to the first amount of working fluid (400), thereby obtaining a further amount (403) of working fluid.

According to another aspect of the invention, said step c) comprises the steps of:

c1 Wherein part of the expanded working fluid of said third quantity (440) is thermally transferred in the high temperature heat exchanger (550) into said first quantity of working fluid (400) of step a 1), thereby obtaining a fifth quantity (410) of heated working fluid, and

C2 Wherein the fifth amount (410) of working fluid is partially cooled in the cryogenic heat exchanger (540) by heat exchange with the amount (300) of working fluid output from the first rotating drum (530), thereby obtaining a second cooled amount of working fluid output from the rotating drum and a heated working fluid of the first amount (400) of working fluid.

As shown in fig. 1, possibly after the purification step described above, a first amount of Liquefied Natural Gas (LNG) (101) in a first drum (530, IMR drum) forms a mixture (IMR) with an amount (210) of liquefied petroleum gas from a third drum (520) thereof.

The amount (300) of working fluid from the first rotor (530, imr drum) may be delivered by pumping with a pump (20) to a cryogenic heat exchanger (540) where the working fluid receives heat, thereby producing a first amount (400) of working fluid for the power generation cycle.

This heat exchange occurs in particular with the amount (410) of working fluid output from the high temperature heat exchanger (550).

A quantity of working fluid (310) exits the cryogenic heat exchanger (540), is delivered to a lng regasification section (590) from which it exits and is then returned to its first drum (530, imr drum).

The first amount of working fluid (400) is delivered to the high temperature heat exchanger (550) as an output from the low temperature heat exchanger (540).

In a preferred aspect of the invention, a first portion (401) of the first quantity of working fluid is heated by a low temperature heat source (580) prior to entering the high temperature heat exchanger (550) to provide a second heated portion (402) which is then added to the first quantity of working fluid (400) to provide a further quantity (403) of working fluid.

For the purposes of the present invention, the low temperature heat source may be the heat emitted by the radiator of the internal combustion engine, or the heat obtained from the second cooling of the exhaust gases of the turbine (possibly after combustion), or a combination of the first heat recovery (580' in fig. 3) obtained from the pre-cooling of the combustion air of the turbine and the second cooling of the exhaust gases of the turbine (possibly after combustion).

Or a boiler or one or more renewable energy sources may be used, as well as combinations with each other, such as: solar energy, air/water, geothermal energy, graphite heat accumulator or molten salt.

According to one embodiment of the invention, as shown in fig. 7, a second low temperature heat source (581) may also be utilized in an additional step a 0').

In a particular embodiment of the invention, such a step a 0') replaces step a 0).

In another embodiment of the invention, step a 2) is performed due to a low temperature heat source.

Thus, a first amount of working fluid (400) or more is delivered into the high temperature heat exchanger (550).

The amount (420) of working fluid heated at high temperature is obtained as output from a high temperature heat exchanger (550) heating the working fluid, which amount of working fluid is further heated by heat recovered from a high temperature heat source (560).

According to one embodiment of the present invention, such a high temperature heat source may be replaced with a low temperature heat source (581), as shown in fig. 7.

For the purposes of the present invention, the high temperature heat source is the heat of the flue gas of an internal combustion engine, or the heat obtained from the first cooling of the exhaust gas of a turbine (possibly after combustion) (560' in fig. 3), or a boiler or one or more renewable sources, and combinations of each other (e.g. solar energy, air/water, geothermal energy, graphite heat accumulator or molten salt) (560 ").

After the heating step of the high temperature heat source (560), a second amount (430) of heated working fluid is expanded in the turbine (570) to produce mechanical (and possibly electrical) energy by partial cooling.

The working fluid of a third expansion (440) is output from the turbine (570), and the third expansion is fed to a high temperature heat exchanger (550) in which a portion of the residual heat of the third expansion is transferred to preheat the first amount of working fluid (400) or more (403).

Thus, a fifth amount (410) of working fluid cooled thereby is obtained in the high temperature heat exchanger (550), the fifth amount of cooling is fed into the low temperature heat exchanger (540), and a portion of the heat of the fifth amount of cooling is transferred inside the low temperature heat exchanger (540) in order to preheat the amount (300) of working fluid output from its first rotor (530, imr rotor) to produce a first amount (400) of working fluid intended for the high temperature heat exchanger (550).

According to one aspect of the invention, a bypass of the turbine (570) may be provided, which is useful for start-up operations and possible operations in case of a turbine stop; it is noted that the turbine may also be bypassed only partially by the bypass line described above to regulate the temperature of the third expansion workload (440).

As described above, a quantity of liquefied petroleum gas may be subjected to a filtration step prior to the introduction of the first drum (530, imr drum) of working fluid.

For this purpose, as shown in fig. 12, the liquefied petroleum gas of the first purification amount (200) outputted from the third drum (520) is subjected to a cooling step through a passage on the shell side of the external exchanger (620).

Thus, possible curable contaminants are deposited on the outside of the pipeline, which in turn is crossed by a quantity of return Liquefied Petroleum Gas (LPG) from the inner coil (610) of the first drum (530, imr drum), where the temperature of the Liquefied Petroleum Gas (LPG) is further reduced by heat exchange with the Liquefied Natural Gas (LNG) loaded therein at the beginning of the working fluid production process.

Liquefied Petroleum Gas (LPG) as the second purified quantity (201) output from the exchanger (620) passes through an internal coil (610) in the first drum (530, imr drum) to be cooled.

The thus obtained third purified amount (202) of liquefied petroleum gas is conveyed to an exchanger (620) through the above-mentioned passage in the tubes of the tube bundle, and then the thus obtained fourth purified amount (203) of liquefied petroleum gas is passed through a solid filter (630, lpgfs-LPG solid filter) to separate any entrained solids.

The operation thus performed has the advantage of not dispersing the heat of the Liquefied Petroleum Gas (LPG), which helps to vaporize the light components in the Liquefied Natural Gas (LNG).

Notably, coils (610) (ultra-low temperature coils) in the first drum (530, imr drum) can be used for this operation and to keep the working fluid at low temperature if it is traversed by a Liquefied Natural Gas (LNG) stream.

Example 1

The objective of example 1 was to regasify LNG at a flow rate equal to 6.7 t/h.

Chemical analysis of LNG of this example (at hand) was prepared as follows:

This object is achieved by the diagram of fig. 3, in which a Power Generation Cycle (PGC) and a regasification line according to a specific embodiment of the invention are described.

LPG is fed into the apparatus to produce IMR, where chemical laboratory results for LPG are available as follows:

Composition of the composition	mol％
		Methane	0.0001
Ethane (ethane)	0.0166
		Propane	71.8904
Propylene	0.0712
		Isobutane	3.8319
Tertiary butene	0.0414
		1-Butene	0.0219
Isobutene (i-butene)	0.0131
		C-2-butene	0.0287
Isopentane	0.1005
		N-pentane	0.2359
1, 3-Butadiene	0.0347

Chemical analysis of LNG and LPG is available and IMR is determined according to the method described above.

The operating pressures of the LNG and IMR in the LNG vaporizer are set.

The LNG pressure is clearly determined by the specific needs of the regasification line, which in this embodiment needs to be introduced into the Natural Gas (NG) network at 74.5bar g.

With regard to IMR pressure, it is strictly related to the design pressure of the equipment forming the power generation cycle, in particular the power generation operating machine (turbo expander).

The optimum operating pressure of the machine is 76.5bar g and the optimum expansion ratio is about 7; once the loss of load is calculated, the IMR output from the LNG vaporizer is at a pressure of 9.5bar g.

Loss of load is applied to both sides of the LNG regasifier up to 0.5bar g.

Once the LNG and IMR pressures are known, a virtual IMR sample is prepared, obtained by mixing LNG at storage temperature (and possibly also at storage pressure in the IMR drum) and LPG at ambient temperature.

The mixing process results in the formation of a series of IMR samples having different molecular weights.

A family of heat exchange curves for IMR samples and LNG to be regasified was generated, resulting in results similar to those shown in fig. 10.

The IMR samples selected maximize energy performance while limiting the exchange surface required for the regasifier to within a technically-economically viable range; in this example, the IMR will have an average molar weight equal to 30.55 u.m.a.

According to the calculation, such an IMR sample has a boiling point of-117.5 ℃ at 9.5bar g.

IMR was prepared by adding LPG to LNG at a pressure of 9.5bar g until the aforementioned temperature of-117.5 ℃ was reached.

Operationally, the illustrated diagram operates as follows: a cylinder engine generating a power of 1.55MWe and having a heat input equal to 4MW is the heat source of the PGC, operating as such:

PGC: fluid "01" (IMR) at a flow rate of 7.8t/h and a temperature of-117.5 ℃ was collected in an IMR drum and pumped at a pressure of 78.5bar g (maximum of cycle) and then heated to-27.6 ℃ in a cryogenic heat exchanger at the expense of heat transferred from IMR current "08"; IMR preheat current "03" then enters in thermal contact with a radiator of the cylinder engine (heat engine) where it receives 760kW of thermal power and is heated to 60 ℃ for subsequent preheating then in the high temperature heat exchanger at the expense of IMR output from expander "07". The "05" current thus obtained has a temperature of 135 ℃ and is ready for final heating in the exhaust gas heat exchanger, where it meets the exhaust gases of the cylinder engine and cools them to 148 ℃; it outputs "06" from the exhaust gas heat exchanger at a temperature of 280 ℃ and a pressure of 76.5bar g for entry into the IMR turboexpander (in which it operates) and outputs "07" at 11bar g and 187.5 ℃. The IMR then transfers heat in a high temperature heat exchanger where it pre-cools "08" to 80 ℃; in the cryogenic heat exchanger, the final cooling to 8 ℃ is followed by temperature adjustment in the LNG regasifier/IMR condenser to a temperature around a minimum of no less than 5 ℃.

The LNG regasifier, referred to herein as the LNG regasifier/IMR condenser, heats supercritical LNG from-145 ℃ to 3 ℃ by operating in pure countercurrent with the IMR stream.

The mechanical power generated by the IMR turboexpander is equal to 455kW, the net energy used by the IMR pump is equal to 35kW, providing 420kW of available power relative to 900kW of thermal power recovered from the combustion flue gas; this corresponds to a mechanical efficiency of 46.7%, much greater than that of a diesel engine of the same size (about 35%).

-Recovering 80% of the heat input of the cylinder engine, which is in the form of energy generated and in the form of heat for regasifying LNG.

Methods related to known technology:

Ethane recycle (a fluid that provides higher efficiency for recycle with pure components) has:

a) The efficiency of PGC was reduced from 46.7% to 32.9%;

b) The net mechanical power recovered ranges from 420kW to only 240kW;

c) 76% of total efficiency (recovered energy/energy introduced).

Based on the same heat level and the same pressure sudden change of the turboexpander, further comparing PGCs using the same structure, but wherein ethane is used instead of IMR, with the following results:

a) Efficiency decreases from 46.7% to 42.7%;

b) The net mechanical power recovered was reduced from 420kW to 375kW (-10%);

c) The overall efficiency (recovered energy/energy introduced) was reduced to 78%.

Example 2

The objective of example 2 is to regasify LNG at a flow rate of 139 t/h.

Chemical analysis of the prepared LNG:

This object is achieved by the diagram of fig. 7, which shows a Power Generation Cycle (PGC) and a regasification line according to a specific embodiment of the invention.

The LPG is fed into the apparatus to produce a working fluid, the chemical laboratory results of which are obtained as follows:

The operating pressures of the LNG and IMR in the LNG vaporizer are set.

The optimum operating pressure of the machine is 76.5bar g and the optimum expansion ratio is about 7; once the loss of load is calculated, the IMR output from the LNG vaporizer has a pressure of 9.5bar g.

Loss of load is applied to both sides of the LNG regasifier up to 0.5bar g.

Using a calculator, a virtual IMR sample is prepared, obtained by mixing LNG at storage temperature (and possibly also at storage pressure in the IMR drum) and LPG at ambient temperature.

According to the detailed description above, the mixing process results in the formation of a series of IMR samples having different molecular weights.

Again, using the calculator, a family of heat exchange curves for IMR samples and LNG to be regasified was generated, resulting in results similar to those shown in fig. 10.

At this point, the IMR sample selected maximizes energy performance while limiting the exchange surface required for the regasifier to within the limits of technical-economic viability; in this example, the IMR will have an average molar weight equal to 29.7 u.m.a.

According to the calculation, such an IMR sample has a boiling point of-123.2 ℃ at 9.5bar g.

IMR was prepared at 9.5barg until the aforementioned temperature of-123.2 ℃ was reached.

Operationally, the operation of the illustrated diagram is as follows:

24.5MWe gas turbine (with heat input equal to 75 MWt) is the heat source for PGC, operated as follows:

PGC: fluid "01" (IMR) at a flow rate of 168t/h and a temperature of-123.2 ℃ was collected in an IMR drum and pumped at a pressure of 78.5bar g (maximum of cycle) and then heated in a cryogenic heat exchanger to-38.9 ℃ at the expense of heat transferred from IMR current "08"; IMR preheat current "02" then enters in thermal contact with a cooler of the turbine's combustion air (considering, for example, 80% relative humidity and air cooled from 15 ℃ to 5 ℃) where it receives 1860kW of thermal power and is heated to-25 ℃.

The IMR then enters the first coil "03" of the exhaust gas heat exchanger, where it recovers the last portion of the heat transferred by the exhaust turbine gas; "04" is output at 60 ℃ for subsequent preheating in a high temperature heat exchanger at the cost of losing IMR output from expander "07". The resulting "04" current has a temperature of 138 ℃ and is ready for final heating in the exhaust gas heat exchanger where it meets the exhaust gas just output from the turbine; the sum of the recoveries by the off-gas heat exchanger reduces the temperature of the flue gas to 160 ℃.

IMR "06", now at a temperature of 280 ℃ and a pressure of 76.5barg, enters the IMR turboexpander (in which it operates), outputting "07" at 11bar g and 186 ℃. The IMR then transfers heat in a high temperature heat exchanger where it pre-cools "08" to 80 ℃; after final cooling to 8 ℃ in the cryogenic heat exchanger, the temperature is adjusted to a minimum vicinity maintained at not less than 5 ℃ in the LNG regasifier/IMR condenser.

The LNG regasifier shown herein heats supercritical LNG from-162 ℃ to 3 ℃ by operating in pure countercurrent with the IMR stream.

The mechanical power generated by the IMR turboexpander is equal to 10kW, the net energy used by the IMR pump is equal to 760kW, providing 9300kW of available power relative to 35.4kW of thermal power recovered from the combustion flue gas.

-Recovering 80% of the heat input of the turbine in the form of energy generated and in the form of heat for regasifying LNG.

Notably, cooling of the turbine combustion air in such a configuration is beneficial thereto, thereby improving its efficiency.

Example 3

The diagram in fig. 4 is particularly suitable for medium and large applications.

Example 4

The diagram in fig. 5 shows a variation of the diagram in fig. 4, wherein the same results are obtained by using an afterburner of the turbine exhaust gas, although a turbine with less power is installed in terms of LNG vaporization and circulation power.

The possibility of adjusting the post-combustion introduces a further flexibility which allows to adjust the minimum load of the plant without heat waste; indeed, in fig. 4, the regulation of the heat supplied to the ORC occurs by discharging a portion of the turbine exhaust gas to the atmosphere prior to heat recovery, thus wasting a portion of the heat input introduced into the system.

Those skilled in the art can appreciate the several advantages provided by the present invention from the description provided above.

First, the present invention can obtain a new mixture that can be used to regasify Liquefied Natural Gas (LNG) with excellent results in terms of energy due to the close vaporization curve of the Liquefied Natural Gas (LNG) and condensation curve of the working fluid (IMR).

Furthermore, the fact that it can be prepared from commercially available fluids significantly increases the ease of purchase and acceptability of the process.

In fact, the process of the present invention for preparing a working fluid (IMR) does not require a distillation step (e.g., for preparing the two components of the mixture).

The Liquefied Natural Gas (LNG) used may be liquefied natural gas in the plant itself, whereas Liquefied Petroleum Gas (LPG) may be imported and commercial grade.

Again, it may not be necessary to store Liquefied Petroleum Gas (LPG) at the facility because once the IMR has been formed, the mixture can be "changed" by adding Liquefied Natural Gas (LNG) (due to the natural tendency of the light components of LNG to vaporize).

Furthermore, the described system is highly flexible, considering that the composition of the IMR can be dynamically varied to optimize the cyclic performance.

The device is easy to manufacture, has a single turbine and does not require extraction in order to increase the overall reliability of the device relative to devices having several turbines or having more complex turbines.

In embodiments with an afterburner for the turbine flue gas, the turbine itself may advantageously be smaller in size.

The configuration in FIG. 6 may be particularly interesting for covering possible standby (stand-by) or start-up speeds; in the event that the turbine is not available or the plant is stopped, the circulation of lng in the first drum (530, imr drum) keeps the loop at a low temperature.

In contrast, it is worth noting that the described process produces cogeneration of electrical energy, and vaporization of lng with an efficiency greater than 75% (considering the overall efficiency), compared to conventional technologies:

(mechanical or electrical + theoretical LNG vaporization heat)/introduced thermal power.

From an environmental point of view, CO ₂ emissions are reduced, which is proportional to the reduction of consumed fuel gas to obtain the same separate generation of mechanical or electrical power and vaporization of Liquefied Natural Gas (LNG) by conventional SCV or ORV technology.

Those skilled in the art will not only understand how to apply the above-described techniques to the construction of new regasification lines or plants, but will also understand how to modify existing plants (retrofit).

The regasification terminal of the present invention allows for a variety of needs to be met (e.g., adjusting plant flow rates to accommodate the needs of regasification or stored Liquefied Natural Gas (LNG) and vice versa, adjusting plant operability to accommodate possible reductions in the amount of Liquefied Natural Gas (LNG) due to undisputed management flexibility such as technical requirements associated with routine or additional maintenance of one or more lines).

The solution proposed by the present invention is also very adaptable to seasonal or daily weather conditions.

Another undoubtedly advantage is that the system can use heat sources of different temperatures to maximize the use of energy at higher temperatures by introducing at least two heat exchangers/regenerators (regenerator) (HTS, LTS).

It is also notable that the present invention has been described in particular with respect to regasification of Liquefied Natural Gas (LNG), but that the regasification line, regasification terminal and regasification process described herein are equally applicable to regasification or vaporization of other liquefied fluids stored at cryogenic temperatures (less than 0 ℃) or ultra-cryogenic temperatures (less than-45 ℃).

For example, the invention is also applicable to regasification or gasification of other liquefied gases.

Claims

1. A method for preparing a working fluid in a first rotor (530), comprising the steps of:

i) A first amount of liquefied natural gas (101) is produced in the first drum (530),

II) adding a first amount of liquefied petroleum gas (210) to said first amount of liquefied natural gas (101),

III) evaporating a portion of the volatile compounds,

IV) the pressure is reduced and,

V) repeating one or more of steps II), III) or IV) until the condensation temperature of the working fluid is reached,

Wherein in step II) 0.25 to 1.2 volumes of liquefied petroleum gas relative to liquefied natural gas are added to 1 volume of liquefied natural gas.

2. The method of claim 1, further comprising subjecting the liquefied petroleum gas to a purification step.

3. The method of claim 2, wherein the purifying comprises the steps of:

1) Wherein the liquefied petroleum gas of the first purified amount (200) is fed to the shell side of the external exchanger (620) to obtain the liquefied petroleum gas of the second purified amount (201),

2) Wherein the second purified amount (201) of liquefied petroleum gas from step 1) is fed to the inner coil (610) of the first drum (530) of working fluid, thereby obtaining a third purified amount (202) of liquefied petroleum gas,

3) Wherein the third purified amount (202) of liquefied petroleum gas resulting from step 2) is fed to the tube side of said external exchanger (620), where the first purified amount (200) of liquefied petroleum gas flowing in step 1) on the shell side is cooled, thereby obtaining a fourth purified amount (203) of liquefied petroleum gas.

4. A method according to claim 3, further comprising the step of:

Step 4) wherein said fourth purified amount (203) of liquefied petroleum gas resulting from step 3) is further filtered in a solid filter (630).

5. A method of regasifying a liquefied natural gas stream, comprising the step of exchanging heat between the liquefied natural gas and a quantity of the working fluid obtained by the method according to any one of claims 1 to 4.

6. A method for generating mechanical and/or electrical and thermal energy in a power generation cycle using a working fluid, wherein the working fluid is obtained according to the method of any one of claims 1 to 4.

7. The method for generating mechanical and/or electrical and thermal energy in a power generation cycle using a working fluid according to claim 6, wherein the first amount of working fluid is subjected to the steps of:

a) Comprising the following steps: step a 1) wherein said first amount of said working fluid is heated in a high temperature heat exchanger (550) to obtain a heated amount (420) at a high temperature, and a heated step a 2) from a high temperature heat source to obtain a second amount (430) of heated working fluid;

8. The method according to claim 6 or 7, comprising, prior to step a), step a 0) wherein a first portion of the first amount (401) of the working fluid is heated by a cryogenic heat source (580), resulting in a heated portion (402), which is then added to the first amount of working fluid.

9. The method of claim 7, wherein said step c) comprises the steps of:

c1 Wherein in the high temperature heat exchanger (550) the expanded working fluid of the third amount (440) transfers heat partly into the first amount of working fluid of the step a 1) resulting in a fifth amount (410) of cooled working fluid, and

C2 Wherein the fifth amount (410) of cooled working fluid is partially cooled in a cryogenic heat exchanger (540) by heat exchange with a first amount of working fluid output from a first drum (530) of the working fluid, thereby obtaining a cooled amount of working fluid output from the first drum, and the first amount of working fluid.

10. The method of claim 7, wherein the high temperature heat source is selected from the group consisting of: smoke of an internal combustion engine; heat derived from the first cooling of the exhaust gas of the turbine; a boiler or one or more renewable energy sources, and combinations of each other.

11. The method of claim 7, wherein the high temperature heat source is selected from the group consisting of: heat resulting from the first cooling of the exhaust gas after combustion in the turbine.

12. The method of claim 8, wherein the low temperature heat source is selected from the group consisting of: a combination of heat rejected by a radiator of the internal combustion engine, heat derived from a second cooling of exhaust gas of the turbine, pre-cooling of combustion air of the turbine, and first heat recovery derived from a second cooling of exhaust gas of the turbine; a boiler or one or more renewable energy sources, and combinations of each other.

13. The method of claim 8, wherein the low temperature heat source is selected from the group consisting of: a combination of heat derived from the second cooling of the exhaust gas after combustion by the turbine, pre-cooling of the combustion air by the turbine, and a first heat recovery derived from the second cooling of the exhaust gas after combustion by the turbine.

14. The method of claim 9, wherein the cooled amount of working fluid output from the first drum is subsequently used in a regasification step to transfer heat to liquefied natural gas.

15. A lng regasification line comprising a regasification section (590) wherein the lng is regasified by heat exchange with an amount of working fluid obtained according to the method of claim 5.

16. A lng regasification line comprising a regasification section (590) wherein the lng is regasified by heat exchange with a fourth amount of partially cooled working fluid obtained according to the method of claim 7.