RU2163323C1 - Method of nonheated pressure reduction of main-line natural gas and device for its embodiment - Google Patents

Abstract

FIELD: transportation and use of natural gas. SUBSTANCE: main-line gas is divided into two flows. One flow is passed through assembly 1 of continuous control of common gas consumption and directed to power division apparatus - heat exchanger formed as a tube with separate inlets for subsonic and supersonic gas flows. Gas passes from separation chamber 10 to pressure reducing member of power division apparatus which represents bunch of supersonic channels 4 each of which is made in the form of Leontiev tube with supersonic nozzles 3 and diffusers 6 where it is accelerated up to M number = 2-5 and pressure is reduced, and then it is supplied to consumer. Other part of gas taken off down to continuous control assembly passes into intertube space 5 and then into cold utilization apparatus after which it is supplied to consumer. Relative length of supersonic channels is

= 30-90 gauges. In supersonic channels gas is heated up to temperature T $\genfrac{}{}{0ex}{}{\text{s}}{\text{o}}$ ^upersonic/T $\genfrac{}{}{0ex}{}{\text{s}}{\text{1}}$ ^upersonic = 0.8-1.1. EFFECT: higher efficiency. 3 cl, 1 dwg

Description

 The invention relates to means of transportation and use of natural gas, in particular to the reduction of main natural gas.

 Known methods for reducing natural gas from a high-pressure line (RU, 2091682, C1, 1997), including cooling the direct flow of natural gas, separating precipitated upon cooling of the crystalline hydrates and subsequent throttling of the gas. The natural gas reduction unit for implementing the method comprises filters alternately attached to the high pressure gas stream.

 Filters are connected by additional lines through shut-off valves with return flow channels.

 The main disadvantage of this method is its "low technology", the need to reverse the gas flow, which greatly complicates the operation of the reduction unit.

 The closest technical solution to the invention is a method of reducing natural gas (US, 5582012, 1996, class F 25 B 9/02), in which the main gas reduces its pressure in the vortex tube, then the cooled stream after the vortex tube passes through a heat exchanger, where the cold is somehow disposed of and after the heat exchanger this stream is mixed with the heated stream after the vortex tube and supplied to the consumer.

The disadvantages of this method are:
- the impossibility of wide regulation of the range of gas flow, because in this case, the operation mode of the vortex tube may be violated;
- the chilled gas after the vortex tube is also expanded, and this limits the possibility of utilization of the resulting cold, for example, to produce liquefied gas.

 The technical result of the method according to the invention is a seamless reduction of natural gas in a bundle of supersonic channels of the heat exchanger with the removal of the resulting cold (chilled gas) from the annular space of the heat exchanger - pipe.

 The subject of the invention is also a device for unattended reduction of the main gas.

 The technical result achieved by using this device consists primarily in the possibility of implementing a method for unattended reduction of natural gas at gas distribution stations (gas distribution stations) with the removal and further utilization of the resulting cold, either using part of an unexpanded gas or a liquid coolant.

To achieve this technical result in a method for unattended reduction of natural gas, which includes gas expansion during energy separation in an energy separation apparatus — a heat exchanger and removal of the resulting cold (cooled gas) for utilization (in particular, liquefaction); one part of the gas after the stepless flow control unit (1) is fed into the separation chamber and then passed through the reducing organ of the energy separation apparatus - heat exchanger (16) in the form of a pipe having separate inlets for subsonic and supersonic gas flows; the reducing organ is a bunch of supersonic channels (4) with profiled supersonic nozzles (3) and diffusers (6), (similar to the Leontief pipe in accordance with RU 2106581), but with separate inputs for subsonic and supersonic gas flows), where the gas is accelerated using shaped nozzles to Mach number M = 2-5, the gas is reduced due to friction, heat transfer and shock waves and goes to the consumer. The other part of the gas is taken to the flow control unit and fed into the annulus (5) of the supersonic channel bundle. In supersonic channels (4), the gas is heated by restoring the temperature to T ₀ ^sz / T ₁ ^sz = 0.8-1.1, (where T ₀ ^sz is the initial (input) temperature at the entrance to the beam of supersonic channels; T ₁ ^cz - the final (outlet) temperature at the outlet of the supersonic channels, and in the annular space (5) the gas is cooled for the same reason, then the unexpanded cooled gas from the annular space enters the cold utilization system (8), for example, in the liquefaction unit (apparatus) natural gas, after which it is mixed with gas from supersonic channels and is supplied to the consumer through line (14).

= 30-90 калибров, при этом каждый канал начинается профилированных соплом (3) и заканчивается диффузором (6), расположенными на двух трубных досках (9 и 7), а каждое сопло имеет отсекающий клапан (2) для дискретного регулирования общего расхода редуцируемого газа.To implement this method, a device for reducing natural gas containing an energy separation apparatus, a cold recovery apparatus (8) and a gas supply and exhaust line (11, 15) is additionally equipped with a smooth gas flow control unit (1), the energy separation apparatus (16) represents It is a shell-and-tube heat exchanger in the form of a pipe and has separate inlets for subsonic and supersonic gas flows, the heat exchanger itself has a separation chamber (10) for receiving gas and a reducing organ, which is a approx supersonic channels (4) having a relative length

= 30-90 calibers, with each channel starting profiled by a nozzle (3) and ending with a diffuser (6) located on two tube plates (9 and 7), and each nozzle has a shut-off valve (2) for discrete control of the total flow rate of the reduced gas .

 The cooled agent can be either natural gas taken to the flow control unit or a liquid coolant in the circulation circuit (for example, antifreeze).

 At the entrance to each nozzle there is a shut-off valve for discrete control of the total flow rate of the reduced gas.

 No other technical solutions are known, having in aggregate features similar and identical to those of the claimed invention.

 The invention is illustrated as follows. In a supersonic flow of natural gas in a supersonic channel, it decelerates due to friction, heat transfer, and shock waves, as well as the heating of the inhibited gas (in the diffuser) due to the restoration of temperature in the supersonic flow. The tests showed that the gas flow rate is well regulated by changing the pressure at the inlet to the channel with a valve. Large flow rates are achieved by closing and opening the valves in front of the nozzles. When the Mach number M <2, braking is poor, the static pressure in the diffuser is large enough and the effect of temperature recovery is also small. At M> 5, the gas pressure drop in the shock waves is too large and the efficiency of the device will be low.

In a supersonic flow of natural gas in a heat exchanger pipe, it is simultaneously heated due to the effect of temperature recovery in a supersonic flow (actually due to heat removal from the annulus) and is cooled due to the Joule-Thomson effect, so that the ratio of the initial and final temperature T ₀ ^cz / T ₁ ^cz is the result of the interaction of these processes. At a ratio of T ₀ ^cz / T ₁ ^cz <0.8, hydrates may precipitate and blockage in pipelines, at a ratio of T ₀ ^cz / T ₁ ^cz > 1.1, an increase in hydraulic resistance occurs and gas supply to the consumer may decrease.

When using a liquid heat carrier, the ratio of water equivalents of gas and liquid (G _gas · C _p / G _liquid C _p , where G _gas is the mass of the gas component (mass flow rate); G _liquid is the mass of the liquid component (mass flow rate); C _p is the heat capacity at constant pressure.

When the ratio of G _gas · C _p / G _z.t. C _p <0.7 - temperature differences are too small and further removal of cold is difficult, at G _gas / G _z.t. > 1.1 increases heat loss during pumping of the liquid coolant.

 The drawing shows a diagram of a device according to the invention.

 This device contains a node for smoothly controlling the total gas flow (1) after the gas distribution system, a shell-and-tube heat exchanger (16) in the form of a pipe with separate inlets of subsonic and supersonic gas flows (subsonic flow enters through line (12), supersonic gas flow enters through line (13) containing a separation chamber (10), in which a tube plate (9) is installed, on which a bundle of supersonic channels (4) is placed, starting with nozzles (3) and ending with diffusers (6) located on the tube plate (7); annular space ( 5) nozzle hav e shut-off valve (2).

 The heat exchanger (energy separation apparatus) is connected by an exhaust line (11) to the cold utilization apparatus (8) (utilization system).

 The device has gas supply lines (12) and (13) to the heat exchanger, gas exhaust lines (14) and (15) to the consumer.

 The device operates as follows.

 Natural gas from the main gas pipeline enters the smooth gas flow control unit (1), which is configured according to the required flow rate and pressure of the gas going to the consumer. Then the gas through line (13) enters the separation chamber (10) containing the tube plate (9) with profiled nozzles (3) of supersonic channels (4), where it is accelerated to supersonic speed with the help of profiled nozzles, heats up, and passes through a jump system, one direct jump or jumpless diffuser (the gas velocity in the supersonic channel can decrease smoothly, without jumps and after diffusers (6) it enters the line (14) of gas consumers. Into the annular space (5) gas is taken along line (12) from the main pipeline through adjusting of its unit (1), and at the exit from the annular space, the refrigerated gas through line (11) passes through a cold recovery device (for example, a natural gas liquefaction system, after which part of the gas in liquid form is removed from the system) (8), after which line (15) together with gas from supersonic channels enters the consumer through line (14).

<30 газ не успевает нагреться, при

>90 теплообменник (аппарат энергоразделения) - труба начинает работать вхолостую как теплообменное устройство из-за практически нулевого перепада температур.With the relative length of the supersonic channel

<30 gas does not have time to heat up, at

> 90 heat exchanger (energy separation apparatus) - the pipe starts to work idle as a heat exchanger due to the almost zero temperature difference.

With the expansion of natural gas in supersonic channels (4), the Joule-Thomson effect has a large effect on the change in gas temperature (while maintaining enthalpy). It can be calculated and the effect on the temperature change taken into account by the formula of the total temperature effect ΔT = μΔP, where ΔP is the pressure drop, ΔT is the temperature drop, μ is the Joule-Thomson coefficient. Its value is related to the temperature coefficient of volume expansion (β) and the heat capacity of the gas at constant pressure (C _p ) as μ = V (βT-1) / Cp, where V is the volume; T is the temperature.

For natural gas in a wide range of pressures and temperatures, the value μ> 0
Device (8) is a gas liquefaction system with a liquefaction coefficient of 0.1 (output of liquefied gas 140 kg / h). The total gas flow after the gas distribution system is 9800 nm ³ / h with a temperature of 265 K and a pressure of 0.3 MPa.

Claims (3)

1. The method of unheated reduction of the main natural gas, including gas expansion during energy separation and the removal of the forming cold for utilization, characterized in that the gas is divided into two parts, one part is passed through a smooth gas flow control unit and fed to the reducing organ of the shell-and-tube heat exchanger in the form of a pipe , which is a bunch of supersonic channels, each of which is made in the form of a Leontief pipe, with profiled supersonic nozzles and diffusers, where the gas accelerates to a number aha M = 2 - 5 and is reduced due to friction, heat transfer and shock waves, and then the consumer receives another part of the main gas, selected to the smooth gas flow control unit, is fed into the annular space of the supersonic channels of the reducing organ, and the gas is heated in the supersonic channels due to the restoration of the temperature determined by the ratio of T _o ^sz / T ₁ ^sz = 0.8 - 1.1, where T _o ^sz and T ₁ ^sz, respectively, the initial and final temperatures at the inlet and outlet of supersonic channels, then not expanded cooled gas is supplied from the annulus to the cold recovery system, after which it is mixed with gas from supersonic channels and supplied to the consumer. 2. The method according to claim 1, characterized in that in the annular space of the supersonic channels to remove the cold serves a liquid coolant at a ratio of water equivalents equal to G _gas C _p / G _z.t. C _p = 0.7 - 1.1, where G is _gas and G _is , respectively, the mass flow rates of gas and liquid coolant, C _p - heat capacity at constant pressure. 3. Device for unheated reduction of the main natural gas, comprising an energy separation apparatus, an apparatus for disposing of the generated cold and a gas supply and exhaust line, characterized in that it is additionally equipped with a stepless control unit for the total gas flow connected by a gas supply line to the energy separation apparatus, which is shell-and-tube heat exchanger in the form of a pipe having separate inlets for subsonic and supersonic gas flows, a gas outlet line to the consumer and a ha supply line and recycling apparatus of the cold heat exchanger, the heat exchanger itself comprises a separation chamber for receiving gas and a reducing body formed as a supersonic beam channels, each of which is formed as a tube having a relative length Leontyeva

30 - 90 calibres, with each channel starting with a profiled supersonic nozzle and ending with a diffuser located on two tube plates, and each nozzle has a shut-off valve for discrete control of the total flow rate of the reduced gas.