Method for controlling liquefaction of natural gas

FIELD: machine engineering.

SUBSTANCE: invention relates to methods for controlling liquefaction of natural gas (LNG), and can be used for liquefaction and supercooling of natural gas. Method of controlling liquefaction of natural gas by means of a plant operating on mixed refrigerant consists in periodical measurement of actual parameters of said process and controlling the composition of refrigerant fed to the main cryogenic heat exchanger in order to achieve optimal process parameters. The Carnot factor is used as a criterion for optimal process parameters. The composition of refrigerant is controlled by direct calculation based on actual process parameters and equations of state of substance components quantity of mixed refrigerant (for example, equations of state of Penga-Robinson) necessary to achieve temperature profile in the main cryogenic heat exchanger corresponding to the optimal parameters of the process and introducing said components in calculated quantity in the main cryogenic heat exchanger.

EFFECT: invention makes it possible to increase efficiency of natural gas liquefaction cycle and thereby minimize the specific power of the compressor required for production of liquefied natural gas.

2 cl, 2 dwg



Same patents:

FIELD: process engineering.

SUBSTANCE: invention relates to cryogenic gas separation of associated oil gases. Process of complex drying and cleaning of associated oil gas comprises gas-dynamic separation and membrane technology of removal of acid compounds. Fed associated oil gas is subjected to two-step drying and cleaning. Main amount of water and heavy hydrocarbon fractions C5 and higher are removed at multistage primary rotary separator at low pressure of 0.3-0.5 MPa. Then, cleaned light hydrocarbon fraction is compressed to 3.0-6.0 MPa and after-purified in extra rotary separator and, then, subjected to cleaning by membrane process from acid compounds H2S and CO2. Cleaned fraction of light hydrocarbons is subjected to vortex power separation in three-flow vortex tube wherefrom produced cold flow is directed for cold recuperation for cooling of initial flow of associated oil gas and discharged as a commercial fraction of C3-C4. Separated fraction of vortex tube cold flow is directed for compression recycling with pre-separated light hydrocarbon fraction. Hot vortex tube flow is discharged as the commercial fuel gas.

EFFECT: optimised separation, drying and cleaning.

1 dwg

FIELD: machine building.

SUBSTANCE: method of partial natural gas liquefaction under option 1 switches on the pre-cooling of direct HP gas flow. After cooling the direct flow is throttled and separated in the rectifier to liquid phase and steam phase. The steam phase is supplied for re-condensation with further supply of part of re-condensed product flow to the rectifier as reflux, and throttling of the other part of the re-condensed product and separation to the liquid phase being finished product, and steam phase sent as back flow for the direct flow cooling. The liquid phase from the rectifier is expanded and due to re-condensation of the steam phase from the rectifier it is evaporated, then it is heated by the direct flow, and after re-throttling is sent to the back flow. In contrast to the option 1 during the partial natural gas liquefaction method under option 2 part of the direct flow after cooling is expanded and mixed with back flow.

EFFECT: suggested group of inventions ensures production of the liquefied natural gas with low content of high boiling components, including carbon dioxide having increased operation characteristics, upon power consumption decreasing for its production.

2 cl, 2 dwg

FIELD: oil and gas industry.

SUBSTANCE: liquefied natural gas production method according to which incoming gas flow is treated from impurities and compressed until it is separated into process and production flows. The process flow is passed through a reducer valve equipped with gas turbine, which torque is used for compression of the incoming gas flow until it is separated into process and production flows. The process flow is treated from impurities of heavy hydrocarbons by their condensation in a nozzle block of the reducer valve, which is made of heat-conductive material. Liquid phase is supercooled before pumping to the consumer's tank.

EFFECT: improved productivity at reduced energy consumption.

7 cl, 1 dwg

FIELD: energy industry.

SUBSTANCE: pre-purified and dried natural gas is cooled and condensed in heat exchanger of pre-cooling, and then it is separated by separating the liquid ethane fraction which is directed to fractionation, and the gas flow from the first separator is successively cooled in heat exchanger of liquefaction using the mixed refrigerant, overcooled with gaseous nitrogen in heat exchanger of overcooling, the pressure of the overcooled LNG is reduced in the liquid expander, and the overcooled LNG is directed to separation, then the liquefied gas is directed to the LNG storage tank, the separated gas is directed into the fuel gas system. The unit for liquefying gas comprises heat exchanger of pre-cooling, five separators, two throttles, the heat exchanger of liquefaction, three compressors designed to compress the mixed refrigerant, five air coolers, two pumps, liquid expander, a heat exchanger of overcooling, a turbo expanding assembly comprising an expander and a compressor, two compressors of nitrogen cycle.

EFFECT: reduction of energy consumption required to carry out the process of gas liquefaction.

2 cl, 1 dwg

FIELD: oil and gas industry.

SUBSTANCE: method is intended for the distribution of low-pressure natural gas to consumers with the production of liquefied gas. The method lies in the extraction of a gas flow from the high-pressure main pipeline, its expansion in a multistage turbine with the production of mechanical energy, heat exchange in a heat exchanger and distribution of the received low-pressure gas to the consumer, at that the gas from the high-pressure main pipeline is directed to an input of a heat carrier loop in a heat exchanger and cooled, while at the loop output it is directed to a multistage turbine where the cooled gas flow is expanded up to a pressure less than the preset distribution pressure in the low-pressure pipeline, at which the fed flow of the liquefied natural gas changes its parameters and aggregative state, transiting from a single-phase state at the multistage turbine input to a double-phase state at the turbine output; at that a liquid phase is separated from the latter and sent for distribution to the liquefied gas pipeline while the remaining part upon separation is sent to the input of the cold carrier loop in the heat exchanger to heat it up for heat exchange with the flow of the liquefied natural gas fed from the high-pressure main pipeline, and further this part is compressed in a bootstrap system up to a pressure equal to the pressure in the low-pressure pipeline, heating it up simultaneously up to positive temperature values, and then it is sent for distribution to the low-pressure pipeline; at that for the compression of this gas part in the compressor mechanical expansion energy is used, which is received at the multistage turbine; moreover, the separation of the liquefied natural gas part takes place after each stage of the turbine.

EFFECT: development of a highly-efficient method of natural gas distribution with simultaneous maximum output of liquefied gas due to mechanical energy produced in result of expansion when pressure drop occurs in the high-pressure main pipeline and low-pressure pipeline.

3 cl, 1 dwg

FIELD: oil and gas industry.

SUBSTANCE: method and system are intended to optimise carbon dioxide cut-off operations and are oriented towards control of operating parameters for a ground-based installation for carbon dioxide compression (CO2) or pipeline for maintenance of CO2 flow in liquid or supercritical state during transportation to the cut-off point. The methods and installation use sensors to determine whether the flow is single-phase or double-phase, and feedback coupling to regulate pressure and/or temperature at the pipeline input.

EFFECT: reduced losses of useful capacity generated by the power plant at separation and compression of CO2 flow passing through the pipeline.

14 c, 16 dwg, 1 tbl

FIELD: machine building.

SUBSTANCE: method of gas liquefaction includes the following stages. The supplied flow is supplied into liquefier, containing, at least, warm expander and cold expander. The supplied flow is compressed in the liquefier up to the pressure above critical one and the compressed supplied flow is cooled down to the temperature below the critical temperature for formation of dense phase high-pressure flow. Dense phase high-pressure flow is taken from liquefier and the pressure of dense phase high-pressure flow is decreased in the expansion device for formation of resulting two-phase flow. Then the resulting two-phase flow is immediately supplied to the storage tank. The selected part of the resulting two-phase flow is merged instantly with boiling out vapour of the liquid in the storage tank for formation of integrated steam flow. And the temperature of dense phase high-pressure flow is lower, than the temperature of output flow of the cold expander. The system of atmospheric gas liquefaction is also described.

EFFECT: development of simple and inexpensive liquefaction method with effective and beneficial extraction of vapours instantly escaped from tanks.

15 cl, 4 dwg, 2 tbl

FIELD: oil-and-gas industry.

SUBSTANCE: invention relates to liquefying of natural or associated oil gas, i.e. propane-butane fraction. Initial flow is cooled, separated to isolate light portion of low-molecular hydrocarbon stock to be liquefied with extraction of liquid propane-butane fraction in power vortex separator. Said vortex separator is composed of three-section vessel accommodating vortex tube to divide the latter into three sections, top, mid and bottom, by horizontal walls. Note here that top section accommodates cold end with vortex tube coil heat exchanger, mid-section accommodating hot end. Bottom section houses hot flow rate regulator and separator of liquid phase from said flow equipped with the valve.

EFFECT: higher yield of pure hydrocarbon stock.

2 dwg

FIELD: oil-and-gas industry.

SUBSTANCE: set of invention relates to liquefaction of high-pressure natural gases and mixes thereof. In compliance with this method, cooled straight gas flow is throttled to divide it into production and process flows. Production flow is cooled, throttled and fed to fractionator to get liquid and vapour fractions. Vapour fraction is fed for recondensation with subsequent fed of a portion of recondensed production flow to fractionator as a reflux irrigation. Another portion of recondensed production flow is throttled and divided into liquid phase, a finished product, and vapour phase to be directed as a return flow for cooling of straight flow. Pre-cooled process flow is throttled, evaporated by production flow recondensation and, after repeated throttling, directed to return flow. Invention covers also a version of natural gas partial liquefaction.

EFFECT: low content of high-boiling components including carbon dioxide, enhanced performances, lower costs.

6 cl, 6 dwg

FIELD: heating.

SUBSTANCE: after associated petroleum gas is cooled in a recuperative heat exchanger, it is separated in a multistage centrifugal separator from oil-petroleum liquid fractions, water condensate and mechanical impurities, which are removed for further processing to a gas fractionation unit, and a gaseous fraction is supplied for two-stage compression. To the first stage together with the separated gaseous fraction there supplied is vapour phase from an above-surface isothermal storage for repeated liquefaction, and gas compressed after the first stage is supplied for liquefaction to a three-flow vortex tube so that cold, hot gaseous and liquid flows are formed. To the second compression stage there supplied is a mixture of a hot flow from the vortex tube and a cold flow after recuperative heat exchangers. Gas flow compressed at the second stage is supplied to the separator after recuperative cooling; after that, the gaseous fraction is supplied to a main gas line or a fuel network, and liquefied gas together with liquid phase separated from hot flow of the vortex tube is supplied to the above-surface isothermal storage.

EFFECT: use of the invention will allow improving efficiency of processes for separation of target hydrocarbon fractions.

1 dwg

FIELD: equipment for gas liquefaction.

SUBSTANCE: method involves separating gas flow from gas pressure reducing plant inlet into two streams; feeding one stream to expansion turbine of expansion-and-compression apparatus; supplying another stream to compressor of above apparatus; directing cold gas from turbine outlet into tube space of one of two switchable freezing heat-exchangers and then to gas pressure reducing plant outlet. Pressurized gas from gas compressor outlet is also separated into two parts. The first part is fed in one of two switchable freezing heat-exchangers and then in recuperative heat-exchanger. Then the first part is divided into two streams. Each stream is expanded and one stream is fed to moisture collector means, another one is mixed with low-pressure gas exiting from moisture collector. The second part of compressed gas flow is directed from gas compressor outlet to vortex tube which generates low pressure hot gas for heating freezing heat-exchanger removed from operation and cold gas used for additional cooling of compressed gas flow moving through operative preliminary freezing heat exchanger.

EFFECT: increased efficiency.

1 dwg

FIELD: the invention refers to the mode of liquefaction of a flow of compressed gas rich in methane.

SUBSTANCE: at the first stage of the process the first fraction of the flow of the compressed fed gas is set aside preferably at the pressure more than 11000 kPa and its entropic expansion until to more lower pressure is made for cooling and at least to partial liquefaction of the set aside first fraction. The multistep expansion of the second fraction is made until to more lower pressure. At that at least partially the second fraction of the gas flow is liquefied. The liquefied second fraction is removed out of the process as a flow of compressed air at the temperature of more than -112°C and the pressure equal to the pressure at the point of beginning of boiling and higher.

EFFECT: the invention allows to improve the mode of liquefaction of natural gas.

24 cl, 6 dwg, 1 tbl, 1 ex

FIELD: processes or apparatus for liquefying.

SUBSTANCE: method comprises flowing gas through one or two recuperative heat exchangers connected in series where the gas cools and low-boiling components are condensed and frozen, flowing the gas through a gas-expansion machine and/or an air throttle to the cold receiver. A part of the straight gas flow is branched into the cold and hot flows inside the energy separator made of, e.g., a two-flow vortex pipe. The cold flow is mixed with the return flow at the inlet to the heat exchanger. The hot flow is directed to the straight passage of the nonoperating recuperative heat exchanger-freezer.

EFFECT: enhanced efficiency.

2 cl, 3 dwg

FIELD: cryogenic engineering; liquefaction of natural gas and low-boiling multi-component gases.

SUBSTANCE: proposed method includes delivery of natural gas for liquefaction, increasing the pressure of natural gas for forming direct flow which is cooled in at least one cooling stage where liquid phase of high-0boiling components is separated and throttling it into reverse flow. Direct flow is throttled after cooling stage, thus forming gas-and-liquid mixture which is separated in separator into target liquid and vapor phase forming the reverse flow; target liquid is directed to consumer. Reverse flow is directed for cooling the direct flow and mixing with starting natural gas. Prior to delivery of direct flow to cooling stage, it is cooled, working flow is separated from direct flow, pressure of direct flow is decreased, thus forming vapor-and-liquid mixture before separation of liquid phase of high-boiling components. After separation of liquid phase of high-boiling components, pressure of direct flow is increased by means of ejector due to energy of expansion of working flow; vapor-and-liquid flow escaping from ejector is divided into vapor which is directed to direct flow and liquid forming circulating flow which is throttled and mixed with reverse flow. Preliminary cooling of direct flow is performed due to cold of reverse flow.

EFFECT: increased coefficient of liquefaction; low cost of procedure.

4 cl, 4 dwg

FIELD: cryogenic engineering.

SUBSTANCE: invention relates to process of liquefaction of natural gas for automobile gas-filling compressor. According to proposed method, natural gas from mean pressure mains at pressure of (p≤7.6 MPa) is compressed in high-pressure of p≤25 MPa and then is successively cooled in first and second recuperative heat exchangers, throttled and delivered into service storage where gas is separated into liquid and gaseous phases. Gaseous phase is returned to compressor inlet through second and first heat exchangers. Gas of high pressure, (p≤25 MPa), additionally cooled in first heat exchanger by cold flow from preliminary cooling circuit in which at least one stage is used as additional refrigerating source. Said stage consists of recuperative heat exchanger and vortex tubes operating on high pressure gas,(p≤7.5 MPa)getting from inlet of gas-distributing station. "Cold" flow of first vortex tube is fed to mean pressure line of heat exchanger of preliminary cooling circuit. High pressure gas,(p≤7.5 MPa), cooled in said heat exchanger is supplied to inlet of second vortex tube, its "cold" flow is mixed with reverse flow of gas non-liquefied in cycle from outlet 0f second heat exchanger and is directed to inlet of mean pressure line(p≤1.6 MPa) of first heat exchanger where direct flow of high pressure gas(p≤25 MPa) is cooled to temperature T<245 K) and then gets into second and following recuperative heat exchangers. "Hot" flows of vortex tubes are united and directed into outlet mains of gas-distributing station.

EFFECT: improved reliability and reduced cost of process of liquefaction.

4 cl, 4 dwg

FIELD: processes or apparatus for liquefying or solidifying gases or gaseous mixtures.

SUBSTANCE: apparatus comprises body with inner partially cylindrical surface, cylindrical rotor installed into the body and rotating around an axis offset from central axis of inner body surface. Apparatus also has feeding unit for liquid CO2 supplying and expanding communicated with the body and rotor. Liquid CO2 is supplied from high-pressure source to feeding unit and turns into gas and dry ice. Gas is then discharged. The rotor has a row of blades movable in radial direction and extending between rotor and inner body surface so that pockets for dry ice receiving from feeding unit are formed. During rotor rotation about its axis pockets and dry ice are circumferentially displaced, pocket volumes decrease and dry ice is pressed to form tablets. The body has unloading zone communicated with the pockets having minimal volumes to unload solid tablets from the body.

EFFECT: increased output along with reduced time for solid carbon dioxide tablet production, increased density of the tablets, reduced power inputs, possibility of in-situ solid carbon dioxide tablet production.

23 cl, 20 dwg

FIELD: gas-filling compressor stations for automobiles.

SUBSTANCE: proposed gas-filling compressor station includes natural gas compression system for filling the automobile reservoirs with natural gas. Part of high-pressure air compressed in compressor is directed through preliminary recuperative heat exchanger. Then gas is additionally cooled in heat exchanger-evaporator by evaporating coolant, Freon or propane for example and is divided into two flows after low-temperature recuperative heat exchanger in vapor compression refrigerating machine. One flow is fed through throttle valve to receiver-separator where finished product-liquefied natural gas- is separated in form of liquid phase and then to storage reservoir and technological reservoir. Second flow after passing the throttle valve is combined with cold vapor escaping from receiver-separator in form of return flow giving cold to direct flow in recuperative heat exchangers and returns to compressor suction end to which vapor of liquefied natural gas is fed from drainage lines of storage reservoir and technological reservoir. Both reservoirs are equipped with individual supercharging systems for supercharging the reservoirs from compressor.

EFFECT: maximum loading of equipment.

2 cl,, 1 dwg

FIELD: processes or apparatus for liquefying or solidifying gases or gaseous mixtures.

SUBSTANCE: method involves cooling direct flow of compressed gas in one or two serially connected recuperative heat-exchangers; expanding thereof in expander and separating liquid phase from gaseous one; supplying gaseous phase to recuperative heat-exchanger as reverse flow. Initial gas flow before cooling is directed in vortex tube from which hot and cold flows are discharged. Cold flow is mixed with direct recuperated flow before expanding thereof or with reverse flow after liquid phase separation. Reverse flow from recuperative heat-exchanger is fed to liquefier outlet. Hot flow is cooled in outer heat-exchanger. Outer heat-exchanger is composed of two sections connected in series one to another, wherein one section is immersed in flowing water, another one is blown over with air flow.

EFFECT: increased efficiency of gas liquefaction.

13 cl, 6 dwg

FIELD: gas-processing industry, cryogenic equipment engineering, possible use for liquefaction of natural gas.

SUBSTANCE: plant for partial liquefaction of natural gas includes serially positioned along direct flow source of high pressure gas, heat exchanger for preliminary cooling, main heat exchanger, filter-separator for hard particles, expanding device, at input connected to direct flow line, and at output connected to reverse flow line, throttling valve of production flow, and separator-accumulator of liquefied gas. Prior to input into expanding device filter and cutting valve are mounted. Expanding device is made in form of turbo gas expansion machine, wherein as break on one shaft turbo-compressor is mounted. Output from turbo gas expansion machine is connected to reverse flow after accumulator-separator for liquefied gas. Temperature indicator mounted at output from turbo gas expansion machine through control block, is interconnected to throttling valve of production flow. High pressure gas source through cleaning block, filter and cutting valve is connected to input of turbo-compressor. Output of turbo-compressor through reverse valve and cooling device is connected to input of preliminary heat exchanger. Input of preliminary heat exchanger by rounding line through bypassing valve is connected to input of turbo-compressor. Bypassing valve is interconnected through control block with turbo gas expansion machine revolution number indicator.

EFFECT: 20-25% increased liquefaction of natural gas, improved stability of plant operation, improved personnel and equipment safety.

2 cl, 2 dwg

FIELD: processes or apparatus for liquefying or solidifying gases or gaseous mixtures.

SUBSTANCE: floating plant comprises barge, natural gas liquefaction system installed on the barge, natural gas receiving means and natural gas accumulation and delivery means. Natural gas liquefaction system includes heat-exchanger, which transmits heat absorbed during gas liquefaction operation to water. The barge additionally has receiver, water intake pipeline having opened end and suspended to barge so that inlet pipeline end is arranged below receiver, connection pipeline extending from outlet water intake pipeline end to receiver inlet orifice, pump adapted to supply water from receiver through supply pipeline into heat-exchanger and water discharge system adapted to discharge water from heat-exchanger. The connection pipeline is shaped as reversed "U" and has upper part located over the receiver.

EFFECT: simplified water delivery and discharge.

5 cl, 1 dwg