CN203224099U - Isobaric liquefying apparatus for natural gas - Google Patents

Abstract

The utility model relates to an isobaric liquefying apparatus for natural gas and the apparatus comprises a pre-processing system for natural gas, a pre-cooling system, a liquefying system, a cold adding system, a storing system, a controlling system and a fire-fighting system. The cold adding system works in a way that a liquid refrigerant 20 of a refrigerant storing tank 19 becomes a refrigerant gas-liquid mixture 22 via actions of a low temperature liquid pump 21 and a cool exchanger 18; the refrigerant gas-liquid mixture enters an upper tower 10; methane in a lower tower 8 is condensed via a condensing-evaporator 9 to generate liquid methane; or methane in the upper tower is introduced to the lower tower and is condensed to form liquid methane; a low temperature refrigerant 15 from an upper tower 10 cools natural gas 1 via actions of a cool exchanger 6 and a cool exchanger 3; and the cooled natural gas 1 becomes refrigerant superheated steam 16 and goes back to the refrigerant storing tank 19 via an expansion machine 17 and a re-cooler 21, thereby forming a cold capacity of refrigerant recycling loop.

Description

The isobaric liquefying plant of a kind of natural gas

Technical field

The present invention relates to the isobaric liquefying plant of a kind of natural gas, specifically belong to the cryogenic refrigeration technical field.

Background technology

Natural gas is a kind of fossil energy of high-quality cleaning, has very consequence in national economy.The liquefaction of natural gas and storage are the key technologies of its development and use, have formed an industry at home and abroad, and be annual with average 8% speed increment, in the China energy consumption structure, increases very fast in recent years.The liquefied natural gas technology has become a high-tech technology, is subjected to the attention of more and more scientific and technical subjects.

Expect the middle of this century, if consume natural gas 5000*10 with China ⁸m ³/ a, wherein imported L NG1000*10 ⁸m ³/ a meter (being equivalent to the present import volume of Japan), it is 257*10 that available cold energy is amounted to electric energy ⁸KWh/a is equivalent to a 600*10 ⁴The annual electricity generating capacity in kW power station.Therefore how to make the breakthrough of each side such as LNG realization technology, administrative mechanism, the market promotion, strive making the energy consumption that reduces LNG significantly, obtaining huge energy-conservation and economic benefit simultaneously, promotion comprises the fast development of the large-scale cold energy industrial chain of empty branch, coal oxygen-rich gasification, in the hope of for China's round Realization circular form economy and economizing economy contribute, be worth deeply thinking.Simultaneously, fast development of Chinese economy and pattern have determined to utilize the imperative of LNG on a large scale transition, and grand user market is provided.

The liquefaction flow path of tradition natural gas mainly contains following three kinds:

1, cascade type liquefaction flow process (also claiming stepwise liquefaction flow path, superposition type liquefaction flow path or cascade evaporation condensation liquefaction flow process) is mainly used in base load type natural gas liquefaction device;

2, mix refrigerant liquefaction flow path: i.e. so-called MRC liquefaction flow path, MRC is the hydrocarbon with C1 to C5, and N ₂Be working medium Deng the multicomponent mix refrigerant more than five kinds, carry out the refrigerating capacity that condensation step by step, evaporation, throttling expansion obtain the different temperatures level, to reach the purpose of progressively cooling and liquefied natural gas.MRC had both reached the purpose of similar cascade type liquefaction flow process, and the shortcoming that has overcome its system complex is arranged.Since the eighties in 20th century, for base load type natural gas liquefaction device, newly-built with the enlarging base load type natural gas liquefaction flow process, almost adopt propane precooling mix refrigerant liquefaction flow path without any exception;

3, the liquefaction flow path of band decompressor: band decompressor liquefaction flow path, refer to utilize the cold-producing medium Cloud's circulation in the turbo-expander again, realize the flow process of natural gas liquefaction.When gas expands in decompressor and does work, reduce temperature and also reclaim merit.According to the difference of cold-producing medium, can be divided into nitrogen expansion liquefaction flow path and natural gas expansion liquefaction flow path.The advantage of this class flow process is: (1) flow process is simple, regulate flexibly, reliable operation, easily start, easy to operate, easy to maintenance; When (2) making working medium with natural gas itself, can save the expense of special production, transportation, accumulating refrigerant.Shortcoming is: the air-flow of (1) feeder needs whole depth dryings; (2) return pressure is low, and heat exchange area is big, equipment metal input amount is big; (3) be subjected to what restriction of low-voltage customer; (4) liquefied fraction is low, and as recirculation, then after increasing recycle compressor, power consumption increases greatly.Because the liquefaction flow path operation of band decompressor is fairly simple, invest moderately, be specially adapted to the less peak regulation type natural gas liquefaction device of liquefying power.

Accompanying drawing 1 is tandem type natural gas liquefaction schematic flow sheet.

Accompanying drawing 2 is APCI propane precooling mix refrigerant liquefaction flow path schematic diagrames.

Accompanying drawing 3 is natural gas expansion liquefaction flow paths, among Fig. 3: the 1-dehydrating agent, 2-carbon dioxide removal tower, the 3-water cooler, 4-returns air compressor, and 5,6, the 7-heat exchanger, 8-subcooler, 9-storage tank, 10-decompressor, 11-compressor.

Accompanying drawing 4 is nitrogen expansion liquefaction flow paths, among Fig. 4: 1-pretreatment unit, 2,4, the 5-heat exchanger, 3-heavy hydrocarbon separator, 6-nitrogen stripper, 7-turbo-expander, 8-nitrogen-methane separation tower, 9-recycle compressor.

Accompanying drawing 5 is the natural gas of the band propane precooling liquefaction schematic flow sheets that expand, among Fig. 5: 1,3,5,6, the 7-heat exchanger, 2,4-propane heat exchanger, 8-water cooler, 9-compressor, 10-brake compressor, 12,13, the 14-gas-liquid separator.

The main theoretical basis of above-mentioned traditional natural gas liquefaction flow scheme design is thermodynamics, namely adopt with the contrary cycle analysis gas deliquescence process in the Kano of the temperature difference, the economic index of circulation is coefficient of refrigerating performance, the ratio of the income that obtains exactly and the cost that expends, and with the atmospheric environment temperature T ₀With temperature be T _CAll kind of refrigeration cycle between the low-temperature heat source (as freezer), with the coefficient of refrigerating performance of reverse Carnot cycle for the highest:

${\mathrm{\ϵ}}_c={\left(\mathrm{COP}\right)}_{R,C}=\frac{q_2}{w_0}=\frac{T_c}{T_0-T_c}---\left(1\right)$

ε in the following formula _cBe coefficient of refrigerating performance, q ₂Be the refrigerating capacity of circulation, w ₀Be the net work that circulates and consume.

Actual cycle efficient adopts the coefficient of refrigerating performance of actual cycle and the ratio of theoretical circulation coefficient to be described usually, but its theoretical foundation is with the contrary circulation in Kano process of refrigerastion to be carried out cycle analysis.

In fact, the Kano is in the paper of " about thermodynamic opinion ", and the conclusion that draws is: " all hot machines of between the constant temperature thermal source of two different temperatures, working, with the efficient of reversible heat engine for the highest." namely being referred to as Carnot's theorem by the descendant, the thermal efficiency of putting the Carnot cycle that draws by the desirable equation of gas state in order is:

${\mathrm{\η}}_c=1-\frac{T_2}{T_1}---\left(2\right)$

The temperature T of the high temperature heat source in the formula (2) ₁With the temperature of low-temperature heat source be T ₂All be higher than the atmospheric environment temperature T ₀, and can draw following some important conclusion:

1) thermal efficiency of Carnot cycle only is decided by the temperature of high temperature heat source and low-temperature heat source, and the temperature when working medium heat absorption just and heat release improves T ₁And T ₂, can improve the thermal efficiency.

2) thermal efficiency of Carnot cycle can only must not equal 1 less than 1, because T ₁=∞ or T ₂=0 all can not realize.In other words, though in cycle engine in the ideal case, also heat energy all can not be converted into mechanical energy, the thermal efficiency is more impossible greater than 1 certainly.

3) work as T ₁=T ₂The time, thermal efficiency of cycle equals 0, it shows, in the system of temperature balance, heat energy can not be converted into mechanical energy, heat energy produces power must have temperature difference as thermodynamic condition, thereby has verified that the machine by the single source continuous doing work does not manufacture, or perpetual motion machine of the second kind is non-existent.

4) Carnot cycle and thermal efficiency formula thereof are significant in thermodynamic (al) development.At first, it has established the theoretical foundation of the second law of thermodynamics; Secondly, the research of Carnot cycle has been pointed out direction for improving the various heat power machine thermals efficiency, closely may improve the endothermic temperature of working medium and reduce the exothermic temperature of working medium as far as possible, and heat release is carried out when can unearned minimum temperature being atmospheric temperature approaching.What propose in the Carnot cycle utilizes adiabatic compression to improve the method for gas endothermic temperature, still generally adopts in the heat power machine that with gas is working medium so far.

5) limit point of Carnot cycle is the atmospheric environment temperature, and to being lower than the process of refrigerastion circulation of environment temperature, Carnot cycle does not provide clear and definite answer.

But use thermodynamic (al) basic theories can not make succinctly the natural gas liquefaction device cyclic process, understand, explain intuitively, the power of one ton of LNG of every production and public utility power consumption are about 850 degree, and the energy-output ratio of process is very big.

Einstein once did evaluation to classical thermodynamics: " a kind of theory, its prerequisite is more simple, and related things is more many, and its accommodation is more extensive, and it gives people's impression just more deep." basic theories of refrigerating field is explored, also should inherit and develop this advantage.

Therefore the natural gas liquefaction cyclic process is studied, really find the theoretical foundation of refrigerating plant circulation, find the correct direction of improving flow process, and organize new natural gas liquefaction device flow process in this theoretical foundation, reduce the energy consumption of natural gas liquefaction device by a relatively large margin, become the difficult point of natural gas liquefaction technical field research.

Summary of the invention

Purpose of the present invention is exactly to be applied to the imperfection that the natural gas liquefaction device Cyclical Theory is analyzed for solving Carnot's theorem, proposition is cold theory of mechanics corresponding to the new refrigerating theory of thermodynamic argument, and the isobaric liquefying plant of new natural gas of this principle design is used in proposition, overcome traditional natural gas liquefaction flow process complexity, the energy consumption height, shortcomings such as the communal facility of necessary supporting excess such as recirculating cooling water system, keep and develop the advantage of band decompressor liquefaction flow path, cut down the consumption of energy more than 30% greatly, realize the isobaric condensation of natural gas simultaneously, maintenance of equipment and materials for later use amount reduce significantly, thereby realize the change of natural gas liquefaction technology.

Corresponding to traditional hot mechanics category, the basic conception of cold mechanics is proposed: be referred to as low-temperature receiver for the environment that is lower than the atmospheric environment temperature, with respect to the thermal source that is higher than environment temperature; Corresponding to heat energy, heat, corresponding cold energy, cold concept are proposed; Described refrigerating plant, refer to consume mechanical power realizes cold energy from atmospheric environment to low temperature cold source or from low temperature cold source to the more transfer of low temperature cold source.When realizing the cold energy conversion, all need some material as the operation material of refrigerating plant, be called refrigeration working medium.

Energy conversion and law of conservation are followed in the transmission of cold energy in the process of refrigerastion.

For describing direction, condition and the limit that cold transmits in the process of refrigerastion, propose cold mechanics second law: the essence of cold mechanics second law is the same with the essence of the second law of thermodynamics, follow equally " can matter decline demote principle ", being multi-form cold energy, is the difference that " matter " is arranged in the ability of changing successfully amount; Even with a kind of cold energy of form, its existence not simultaneously, its transfer capability is also different.The real process that all cold energy transmit, always the direction that descends towards energy matter is carried out, and all cold energy are always from being sent to the conversion of atmospheric environment direction.Cold energy can matter the raising process can not be automatically, carry out individually, the process that the process of the raising of an energy matter must be accompanied by the decline of another energy matter takes place simultaneously, this process that can matter descends is exactly to realize the compensation condition of necessity that can the matter elevation process, namely with can matter drop to cost, by way of compensation promote can the matter elevation process realization.In real process, as the energy matter decline process of cost, must be enough to compensate the process that energy matter raises, to satisfy the universal law that total energy matter must descend.Therefore, under the compensation condition that certain energy matter descends, the process that energy matter raises must have a theoretical limit the highest.Only under the ideal conditions of completely reversibility, just can reach this theoretical limit, at this moment, can just in time equal the offset that energy matter descends by the matter lift-off value, make total energy quality guarantee hold constant.As seen, reversible process is the energy matter conservative process of equidimensional idealization; Energy matter total in irreversible procedure must descend; May realize making the process of the total energy matter rising of isolated blob in no instance.Here it is can matter declines and demotes the physical connotation of principle, is the essence of cold mechanics second law, also is the essence of the second law of thermodynamics, and it has disclosed the objective law of mandatory, the relevant process travel direction of all macroscopical processes, condition and limit.

The fundamental formular of describing cold mechanics second law is:

${\mathrm{\η}}_c=1-\frac{T_{c2}}{T_{c1}}---\left(3\right)$

In the formula (3), Tc2＜Tc1＜To, To is environment temperature, is Kelvin's thermometric scale.

Relative environment temperature To, the maximum cold efficient of low-temperature receiver under Tc1, Tc2 is:

${\mathrm{\η}}_c=1-\frac{T_{c1}}{T_0}---\left(4\right)$

${\mathrm{\η}}_c=1-\frac{T_{c2}}{T_0}---\left(5\right)$

Be assumed to be q ₂The refrigerating capacity of circulation, w ₀Be the net work that circulates and consume, then when sink temperature is Tc1:

$w_0=(1-\frac{T_{c1}}{T_0})q_2---\left(6\right)$

Equally, when sink temperature is Tc2:

$w_0=(1-\frac{T_{c2}}{T_0})q_2---\left(7\right)$

Be not difficult to find out to (7) that from formula (4) efficient of cold mechanics is between 0 to 1, because irreversibility inevitable in the real process, kind of refrigeration cycle efficient is always less than 1;

When environment temperature To determined, sink temperature was more low, and from the same merit of this low-temperature receiver input, the refrigerating capacity of acquisition is more many, and this has indicated direction for making up new natural gas liquefaction device flow process.

Need to prove:

(1) cold is spontaneously to transmit from low temperature cold source to environment temperature;

(2) can not pass to cold lower low-temperature receiver and not cause other variations from low temperature cold source;

When (3) cold was from the low temperature cold source transmission to environment, the merit amount that exchanges with the external world was w ₀, wherein comprise the idle work p that environment is done ₀(V ₀-V _c), p ₀Be atmospheric pressure, Vo is the volume under the environment temperature, and Vc is the volume under the sink temperature, and the maximum reversible useful work that can do is:

${\left(W_u\right)}_{\max }=W_0-p_0(V_0-V_c)=(1-\frac{\mathrm{Tc}}{\mathrm{To}})Q_0-p_0(V_0-V_c)$

When (4) cold is from the low temperature cold source transmission to environment, to the unavailable energy of environment transmission be:

Idle work to the environment transmission is: p ₀(V ₀-V _c)

Corresponding to the available energy of heat " ", unavailable energy " cinder ", understanding to heat, cold water intaking fire, the available energy for cold is named as " cold ripples ", cold is called " cold Jin " to the unavailable energy of environment transmission, " Jin " pronunciation is " using up ".

When (5) cold energy transmitted to environment temperature, outwards the optimum pattern of acting was for adopting the thermal generator of Seebeck (Seebeck) effect, i.e. cold power generator;

(6) energy must, also must meet energy conversion and law of conservation in the cold mechanics;

(7) by using for reference the thermodynamic (al) design of finite time, can develop the cold mechanics basic theories of finite time;

(8) can not break away from the grade that environment is estimated cold;

(9) cold mechanics and thermodynamics are two branches in the energetics, the one side that had both had opposition, exist unified one side again: in the cryogenic refrigeration circulation, under the prerequisite of following cold mechanics second law, the Rankine cycle principle is followed in the cyclic process of the cold-producing medium working medium of constructing under low temperature environment again, again get back to the Kano law again, meet the principle that has the positive and negative sun to help mutually in the moon in the Chinese traditional aesthetics just.

From above-mentioned viewpoint as can be seen, the cold mechanics of supposing has the theoretical frame system with the thermodynamics symmetry, meets the basic principle of the aesthetics of science, namely opposes each other and yet also complement each other, symmetry principle.

Based on above-mentioned cold mechanics basic principle, the present invention proposes to be different from the process organization of traditional natural gas liquefaction device, low energy consumption realizes the isobaric liquefaction of natural gas, and effectively reduces the energy consumption of natural gas liquefaction device, and the ratio power consumption of natural gas is reduced to about 0.24kWh/kg.

The objective of the invention is to realize by following measure:

The isobaric liquefying plant of a kind of natural gas, this liquefying plant comprises natural gas and treatment system, liquefaction system, benefit cooling system, stocking system, control system and fire-fighting system, it is the liquefaction flow path schematic diagram that the present invention only lists most important component, unspecified content is undertaken supporting by traditional mature technology, realize that the processing step of the isobaric liquefaction of natural gas is as follows:

(1) raw natural gas 1 is removed moisture, carbon dioxide through pretreatment unit 2, enters cool exchanger 3, separator 4 is isolated liquid heavy hydrocarbon component 5, becomes precooling through cool exchanger 6 again and goes into tower unstripped gas 7;

(2) precooling is gone into tower unstripped gas 7 and is entered down tower 8, and the cold methane liquid of mistake that produces through condenser/evaporator 9 refluxes and carries out rectifying, and it is LNG that isobaric condensation produces liquefied natural gas 11, and LNG sends into LNG storage tank 12;

(3) the pure methane liquid 13 that isobaric condensation produces in the condenser/evaporator is introduced liquid pure methane storage tank 14;

(4) the benefit cooling system of described device, refer to the liquid refrigerant 20 that comes out from cold-producing medium basin 19, through cryogenic liquid pump 21, the refrigerant air-liquid mixture 22 that returns cooler 18 formation enters tower 10, make down the methane gas condensation of tower 8 produce liquid methane by condenser/evaporator 9, or the methane condensation of tower forms liquid methane to make down tower 8 introduce upward, go out tower low-temperature refrigerant 15 from what last tower 10 came out, through cool exchanger 6, cool exchanger 3 cooling raw natural gas 1, form refrigeration working medium superheated steam 16, through decompressor 17, return cooler 21, return cold-producing medium basin 19, thereby form the cold power closed circuit of cold-producing medium; Can conveniently regulate the pressure of mending cooling system by the choke valve 23 that arranges.

The braking equipment 24 of described decompressor 17 adopts blower fan, motor, hydraulic pump or compressor.

The methane on following tower 8 tops also can directly be introduced tower 10 and produce liquid pure methane through scrubbing with liquid nitrogen, draws from last tower 10 bottoms and delivers to liquid pure methane storage tank 14.

Described isobaric the separation, refer to enter the raw natural gas of natural gas liquefaction system, need not as traditional natural gas liquefaction process the throttling step-down and liquefy, the raw natural gas of sending here 1 only has along the drag losses of journey equipment and pipeline, can be considered as isobaric liquefaction process.

Described liquefaction system comprises following tower 8, condenser/evaporator 9, goes up tower 10, adopts integral type or split type structure.

The boiling point of described cold-producing medium under normal pressure is less than or equal to methane, include but not limited to the mist of one or more gas compositions such as methane, nitrogen, argon gas, helium, hydrogen, safety if can be guaranteed, also hydrogen or liquid hydrogen, preferably nitrogen can be used.

Described cold-producing medium basin 19 adopts necessary cold insulation measure, as adopts cold insulation materials such as adiabatic vacuum tank, pearlife.

Described cool exchanger 6, cool exchanger 3, time cooler 18 adopt the cold-exchange of shell-and-tubes, plate-fin, microchannel or other patterns, its structure and to change shell-and-tube heat exchanger in cold element and the traditional natural gas liquefaction flow process, plate-fin heat exchanger, micro-channel heat exchanger etc. identical is just for corresponding with refrigeration system and change title accurately.

Described cool exchanger 3, cool exchanger 6, separator 4, time cooler 18 can arrange one or more.

Unaccounted equipment and back-up system thereof, pipeline, instrument, valve, cold insulation among the present invention, the mature technology with known traditional natural gas liquefaction systems of employing such as regulatory function bypass facilities carry out supporting.

Be provided with safety, the control facility supporting with natural gas liquefaction device of the present invention, make device energy economy, safety, high thermal efficiency operation, reach purpose energy-saving and cost-reducing, environmental protection.

Device of the present invention is equally applicable to the liquefaction of other gases, and the boiling point that the cold-producing medium of employing is depressed at normal atmosphere is less than or equal to the boiling point for the treatment of that accordingly liquid gas is depressed at normal atmosphere.

The present invention has following advantage compared to existing technology:

1, energy-saving effect is remarkable: the circulation compressor of cancelling traditional natural gas liquefaction system circulation, utilize the character near incompressible fluid of liquid, adopting the cryogenic liquid circulating pump to carry out supercharging mends cold, realize the equipressure liquefaction of natural gas, can effectively improve the efficient of kind of refrigeration cycle, compare with traditional natural gas liquefaction device, the fractional energy savings of identical refrigerating capacity can reach more than 30%, the more traditional advanced process of liquefied natural gas per ton economize on electricity at least 200 the degree.

2, LNG or the liquid pure methane of isobaric condensation generation can be saved the electric work of the pressurization consumption of traditional LNG or pure liquid methane.

3, can make natural gas liquefaction by low pressure, the method for liquefied natural gas supercharging be saved the gas work done during compression of traditional gas deliquescence process again, the public work power consumption supporting with natural gas liquefaction system reduces more than 80%.

4, flow setting is more succinct, and the potentiality of liquefaction system are not fully exerted, and operating flexibility is big, and operation is regulated more flexible.

5, the reserve level of equipment and material has minimizing by a relatively large margin.

6, can substitute traditional main flow base load type natural gas liquefaction device such as propane precooling mix refrigerant liquefaction flow path fully, become the main flow flow process of base type natural gas liquefaction device, peak regulation type natural gas liquefaction device.

Description of drawings

Fig. 1 is tandem type natural gas liquefaction schematic flow sheet;

Fig. 2 is APCI propane precooling mix refrigerant liquefaction flow path schematic diagram;

Fig. 3 is natural gas expansion liquefaction flow path:

Among Fig. 3: the 1-dehydrating agent, 2-carbon dioxide removal tower, the 3-water cooler, 4-returns air compressor, and 5,6, the 7-heat exchanger, 8-subcooler, 9-storage tank, 10-decompressor, 11-compressor.

Fig. 4 is the nitrogen expansion liquefaction flow path:

Among Fig. 4: 1-pretreatment unit, 2,4, the 5-heat exchanger, 3-heavy hydrocarbon separator, 6-nitrogen stripper, 7-turbo-expander, 8-nitrogen-methane separation tower, 9-recycle compressor.

Fig. 5 is the natural gas expansion liquefaction schematic flow sheet of band propane precooling:

Among Fig. 5: 1,3,5,6, the 7-heat exchanger, 2,4-propane heat exchanger, 8-water cooler, 9-compressor, 10-brake compressor, 12,13, the 14-gas-liquid separator.

Fig. 6 is the isobaric liquefying plant schematic flow sheet of a kind of natural gas of the present invention:

Among Fig. 6: 1-raw natural gas, 2-pretreatment unit, 3-cool exchanger, 4-heavy hydrocarbon separator, the liquid heavy hydrocarbon component of 5-, 6-cool exchanger, the tower unstripped gas is gone in the 7-precooling, tower under the 8-, 9-condenser/evaporator, the last tower of 10-, 11-LNG, 12-LNG storage tank, the pure liquid methane of 13-, the pure liquid methane storage tank of 14-, 15-goes out the tower low-temperature refrigerant, 16-refrigerant superheat steam, the 17-decompressor, 18-returns cooler, 19-cold-producing medium storage tank, 20-liquid refrigerant, the 21-cryogenic liquid pump, 22-refrigerant air-liquid mixture, 23-choke valve, 24-braking equipment.

The specific embodiment

Below in conjunction with the drawings and specific embodiments the present invention is described in further detail.

Embodiment 1:

As shown in Figure 6, the isobaric liquefying plant of a kind of natural gas, cold-producing medium adopts nitrogen, and specific embodiment is as follows:

(1) raw natural gas 1 is removed moisture, carbon dioxide through pretreatment unit 2, enters cool exchanger 3, heavy hydrocarbon separator 4 is isolated liquid heavy hydrocarbon component 5, becomes precooling through cool exchanger 6 again and goes into tower unstripped gas 7;

(2) precooling is gone into tower unstripped gas 7 and is entered down tower 8, and the cold methane liquid of mistake that produces through condenser/evaporator 9 refluxes and carries out rectifying, and it is LNG1 that isobaric condensation produces liquefied natural gas 11, and LNG sends into LNG storage tank 12;

(3) the pure methane liquid 13 that isobaric condensation produces in the condenser/evaporator is introduced liquid pure methane storage tank 14;

(4) liquid refrigerant 20 that comes out from cold-producing medium basin 19, through cryogenic liquid pump 21, the refrigerant air-liquid mixture 22 that returns cooler 18 formation enters tower 10, make down the methane gas condensation of tower produce liquid methane by condenser/evaporator 9, go out tower low-temperature refrigerant 15 from what last tower 10 came out, through cool exchanger 6, cool exchanger 3 cooling raw natural gas 1, form refrigeration working medium superheated steam 16, after decompressor 17 expansion step-downs cooling, again through returning cooler 21, choke valve 23, return cold-producing medium basin 19, by condenser/evaporator 9, cool exchanger 6,3 pairs of natural gas liquefaction systems of cool exchanger are mended into required cold, thereby form the cold power closed circuit of cold-producing medium; Can conveniently regulate the pressure of mending cooling system by the choke valve 23 that arranges.

The braking equipment 24 of described decompressor 17 adopts compressor, is used for raw natural gas is carried out supercharging.

Described refrigeration working medium basin 19 adopts necessary cold insulation measure, as adopts cold insulation materials such as adiabatic vacuum tank, pearlife.

Unaccounted equipment and back-up system thereof, pipeline, instrument, valve, cold insulation among the present invention, the mature technology with known traditional natural gas liquefaction systems of employing such as regulatory function bypass facilities carry out supporting.

Be provided with safety, the control facility supporting with natural gas liquefaction device of the present invention, make device energy economy, safety, high thermal efficiency operation, reach purpose energy-saving and cost-reducing, environmental protection.

Though the present invention with preferred embodiment openly as above, they are not to limit the present invention, anyly are familiar with this skill person, without departing from the spirit and scope of the invention, when doing various variations or retouching, belong to the present invention's protection domain equally certainly.Therefore protection scope of the present invention should with the application claim was defined is as the criterion.

Claims (8)

1. the isobaric liquefying plant of a natural gas, this device comprises natural gas pretreatment system, chilldown system, liquefaction system, benefit cooling system, stocking system, control system and fire-fighting system, it is characterized in that:

The benefit cooling system of described device, refer to the liquid refrigerant (20) that comes out from cold-producing medium basin (19), through cryogenic liquid pump (21), the refrigerant air-liquid mixture (22) that returns cooler (18) formation enters Shang Ta (10), make down the methane gas condensation of tower (8) produce liquid methane by condenser/evaporator (9), or make down the methane condensation of tower in tower (8) introducing form liquid methane, go out tower low-temperature refrigerant (15) from what last tower (10) came out, through cool exchanger (6), cool exchanger (3) cooling raw natural gas (1), form refrigeration working medium superheated steam (16), through decompressor (17), return cooler (21), return cold-producing medium basin (19), thereby form the cold power closed circuit of cold-producing medium.

2. device according to claim 1 is characterized in that:

Be provided with choke valve (23):

The liquid refrigerant (20) that comes out from cold-producing medium basin (19), through cryogenic liquid pump (21), the refrigerant air-liquid mixture (22) that returns cooler (18) formation enters Shang Ta (10), make down the methane gas condensation of tower (8) produce liquid methane by condenser/evaporator (9), or make down the methane condensation of tower in tower (8) introducing form liquid methane, go out tower low-temperature refrigerant (15) from what last tower (10) came out, through cool exchanger (6), cool exchanger (3) cooling raw natural gas (1), form refrigeration working medium superheated steam (16), through decompressor (17), return cooler (21), choke valve (23), return cold-producing medium basin (19), thereby form the cold power closed circuit of cold-producing medium.

3. device according to claim 1 is characterized in that:

The braking equipment (24) of described decompressor (17) adopts blower fan, motor, hydraulic pump or compressor.

4. device according to claim 2 is characterized in that:

The braking equipment (24) of described decompressor (17) adopts blower fan, motor, hydraulic pump or compressor.

5. device according to claim 1 is characterized in that:

Described liquefaction system comprises following tower (8), condenser/evaporator (9), goes up tower (10), adopts integral type or split type structure.

6. device according to claim 2 is characterized in that:

Described liquefaction system comprises following tower (8), condenser/evaporator (9), goes up tower (10), adopts integral type or split type structure.

7. device according to claim 3 is characterized in that:

Described liquefaction system comprises following tower (8), condenser/evaporator (9), goes up tower (10), adopts integral type or split type structure.

8. device according to claim 4 is characterized in that:

Described liquefaction system comprises following tower (8), condenser/evaporator (9), goes up tower (10), adopts integral type or split type structure.

Images