Small-scale natural gas drag reduction indoor loop evaluation device and method

Abstract

The invention relates to the field of gas anti-drag conveying methods and evaluation thereof, and discloses a small-scale natural gas anti-drag indoor loop evaluation device and a small-scale natural gas anti-drag indoor loop evaluation method. The device comprises a nitrogen purging system, a drag reducer atomization injection system, a drag reducer turbulence testing system and a gas emptying combustion system. Wherein the drag reducer atomization injection device comprises a shell sleeve, jet atomization and rotary atomization; the jet atomization comprises a drag reducer storage tank, a booster pump and a jet pipe with micropores, and primary atomization of the drag reducer is achieved; the rotary atomization device comprises a rotary disc, a connecting rod and a porous nozzle, the rotary disc achieves secondary atomization, and the porous nozzle achieves third-time atomization and enables the atomized drag reducer to be sprayed into the pipeline more evenly at the same time. The atomization effect of the drag reducer is enhanced through the combined action of jet flow and rotation, drag reducer molecules are more evenly distributed in the pipeline, then the drag reduction performance of the natural gas drag reducer is evaluated, and the drag reducer can be applied to drag reduction and transportation increase of the natural gas pipeline according to the evaluation result.

Description

Technical Field

[0001] The invention relates to a gas drag reduction transportation method and the field of evaluation thereof, and in particular to a small-scale natural gas drag reduction indoor loop evaluation device and method. Background Art

[0002] Turbulence shows strong irregularity in the pipeline. Due to high Reynolds number turbulent flow, the gas will generate a large amount of energy dissipation in the pipeline. In order to reduce the energy loss of natural gas in the pipeline flow process, it is proposed to use atomized injection of natural gas drag reducers in the pipeline to reduce the turbulence intensity, thereby reducing the friction loss of natural gas in the pipeline transportation process, so as to achieve drag reduction and increased transportation of long-distance natural gas. At present, the method of drag reduction by adding agents to natural gas transportation is still in the laboratory research and exploration stage and has not been put into industrial application. It can be seen that the establishment of a natural gas drag reduction indoor loop evaluation device and method is crucial to accelerate the industrial application of this technology. There are several problems with the evaluation method of natural gas drag reduction effect:

[0003] (1) Lack of suitable indoor evaluation equipment for natural gas drag reduction. The actual pipeline operation on site is complicated and expensive, and the performance evaluation of drag reducers is not easy to achieve. Therefore, it is particularly necessary to establish a suitable indoor evaluation equipment for natural gas drag reduction. However, due to the flammable and explosive nature of natural gas, there is currently no indoor pipeline that can evaluate the performance of natural gas drag reducers;

[0004] (2) Lack of reasonable evaluation methods for natural gas drag reduction performance. At present, there is little experience in the application of natural gas drag reduction indoor loop technology, and there is a lack of evaluation methods for small-scale natural gas drag reduction indoor loops. In addition, a unified natural gas drag reduction performance evaluation system standard has not yet been formed.

[0005] It can be seen that in order to meet the application of natural gas drag reducers in pipelines and evaluate the drag reduction performance of drag reducers, it is urgent to design a small-scale natural gas turbulent drag reduction indoor loop evaluation device. This device can study the turbulent drag reduction flow law of natural gas in the pipe, provide an evaluation method for the drag reduction performance of different natural gas drag reducers, and provide an experimental basis for the application of drag reducers in actual long-distance natural gas transmission pipelines. Summary of the invention

[0006] The purpose of the present invention is to provide a small-scale natural gas drag reduction indoor loop evaluation device and method, so that the drag reducer can be tested for turbulent drag reduction in an indoor loop, thereby realizing the evaluation of the drag reduction performance of the drag reducer in the flow of natural gas pipelines.

[0007] The invention comprises a nitrogen purge system, a drag reducer atomization injection system, a drag reducer turbulence test system and a gas venting and combustion system.

[0008] The nitrogen purge system is used to remove gas and impurity particles in the exhaust pipeline and dry the loop, and comprises a nitrogen bottle (5), a gate valve (6), (11-3), (11-4), (13-1), (13-2), (13-3), (13-4), pressure gauges (9-1), (9-2), (9-3), (9-4), (14-1), (14-2), a check valve (12-1), (12-2), a temperature gauge (7), a gas circulation pump (4), an orifice flowmeter (15), an exhaust burner (1) and an experimental loop (16), see Figure 1 shown.

[0009] The drag reducer atomizing injection system is used to inject the natural gas drag reducer into the experimental loop in the form of atomization, and comprises a drag reducer atomizing injection device (2), gate valves (8), (13-1), (13-2), (13-3), (13-4), pressure gauges (9-1), (9-2), (14-1), (14-2), check valves (12-1), (12-2), a temperature gauge (7), a gas circulation pump (4), an orifice flowmeter (15), and an experimental loop (16).

[0010] The drag reducer turbulence test system is used to evaluate and test the drag reduction effect of atomized injection of drag reducer, and comprises a natural gas injection port (3), gate valves (11-1), (11-2), (13-1), (13-2), (13-3), (13-4), a gas compressor (10), pressure gauges (9-1), (9-2), (14-1), (14-2), a thermometer (7), a gas circulation pump (4), an orifice flowmeter (15) and an experimental loop (16).

[0011] The gas venting and combustion system is used to discharge the gas in the purging process and to vent and burn the natural gas after the test, and comprises a venting combustion port (1), a gate valve (6), (13-1), (13-2), (13-3), (13-4), a gas compressor (10), pressure gauges (9-1), (9-2), (9-3), (14-1), (14-2), a thermometer (7), a gas circulation pump (4), an orifice flowmeter (15) and an experimental loop (16).

[0012] The main parameters of the equipment are: gas compressor: 565L / min, 1MPa; orifice flowmeter: 6.3MPa, accuracy ±0.75%; gas circulation pump: 3MPa, accuracy ±0.25FS; experimental loop: Φ25×2.5mm, roughness: h0=0.01;

[0013] Determination of the natural gas circulation flow state in the evaluation of the natural gas turbulent drag reduction indoor loop: During the natural gas drag reduction cycle test, since the pressure provided by the circulation pump can be adjusted, the natural gas flow state must be ensured to be in the turbulent complete square zone during the test, and its Reynolds number can be calculated according to the following formula:

[0014]

[0015] When the gas circulation pump is enabled during the circulation process, the Reynolds number of the natural gas flowing in the pipeline is:

[0016]

[0017] The maximum pressure provided by the gas circulation pump is 3MPa, Re=236104, and its flow is in the perfect square area; if the gas circulation pump is not enabled, the pressure of the natural gas flow is 1MPa, and its Reynolds number in the pipeline is: Re=136315, and its flow is also in the perfect square area. Therefore, the flow of natural gas has been in the turbulent perfect square area throughout the entire circulation test loop.

[0018] The natural gas drag reducer atomizing injection device comprises two parts: the upper part is jet atomizing, including a drag reducer injection tank (17), a booster pump (18) (which can provide a maximum pressure of 1 MPa), and a microporous jet tube (19); the lower part is rotary atomizing, including a rotary disc (20), a connecting rod (22), a porous nozzle (23), and a shell (21), see Figure 2 As shown. The diameter of the microporous jet tube is 25mm, the length deep into the rotating device is 250mm, and its surface has 120 micropores with a diameter of 0.6mm (the micropores are arranged in 20 rows, 6 in each row). The jet atomization part pressurizes the drag reducer through a booster pump. When the high-pressure drag reducer passes through the micropores of the jet tube, the liquid is sprayed out and torn to achieve initial atomization. The initially atomized drag reducer particles will further contact the rotating disc for secondary atomization. The rotary atomization part is driven by a motor to achieve rotary atomization. It is connected to the porous nozzle through a connecting rod. The rotating disc rotates and drives the porous nozzle to rotate at the same time. Due to the centrifugal force, the drag reducer is atomized again at the nozzle outlet and the atomized particles can be sprayed into the pipeline more evenly.

[0019] Evaluation of atomization effect of natural gas drag reducer atomization injection device: In order to make the separated droplets reach micron level, the linear velocity of the droplets at the edge of the disc separation must reach v=50m / s or more. Considering safety, cost and other factors, the rotating device is connected to an external 220V power supply to power the AC motor, providing a speed of n=2800r / min. The radius of the rotating disc can be calculated by the following formula:

[0020]

[0021] w=2πn

[0022] To meet the requirement that the atomized particles are micron-sized, the radius of the disc is at least 170 mm. The drag reducer atomization device has five levels of rotating discs with radii of 170, 175, 180, 185, and 190 mm respectively, and the interval between the discs is 50 mm.

[0023] The atomized particle size of the drag reducer can be calculated using the empirical formula:

[0024]

[0025] Where: d av is the arithmetic mean diameter of the droplets, μm; N is the disk speed, r / min; σ is the surface tension of the drag reducer solution, N / m, taken as 50×10 -3 N / m; D is the disk diameter, m; ρ is the density of the drag reducer solution, about 1.13 g / cm 3 The arithmetic mean diameter of the atomized particles during the atomization process was calculated to be 58.6 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Purpose of the drawings: In order to more clearly illustrate the examples and technical solutions of the present invention, the drawings required for the examples will be simply marked and introduced below.

[0027] Figure 1 It is an indoor loop evaluation device for small-scale natural gas turbulence drag reduction.

[0028] Figure 2 It is a natural gas drag reducer atomization injection device. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of the specification, not all of the embodiments. Based on the embodiments of the specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the implementation scheme of this specification.

[0030] Implementation 1: Evaluation of turbulent drag reduction performance of natural gas drag reducer under constant flow conditions

[0031] The small-scale natural gas drag reduction indoor loop evaluation device is used to evaluate the turbulent drag reduction performance of natural gas drag reducers. Using the experimental device, the pressure difference change at both ends of the test pipe section before and after the addition of the drag reducer is measured under the condition of constant flow controlled by a flow meter, so as to calculate the natural gas drag reducer's turbulent drag reduction efficiency. The calculation expression of the drag reduction efficiency is:

[0032]

[0033] Wherein, ΔP1 and ΔP0 are the pressure differences of natural gas with and without drag reducer at the same flow rate, Pa.

[0034] The method for evaluating the drag reducing performance of the drag reducing agent on natural gas turbulence has the following specific implementation steps:

[0035] First, close the natural gas inlet (3), the drag reducer atomizing injection device (2) and valves (6), (8), (11-1), (11-2), slowly open the nitrogen bottle (5) for purging, and control the gas circulation pump (4) to purge the nitrogen pressure. Observe the readings of the pressure gauges (9-1), (9-2), (14-1), (14-2) in the loop at this time, and adjust the valves at the venting position to make the readings of the pressure gauges close. Then repeat the above operation and use the gas circulation pump (4) to slowly increase the pressure to 1MPa, 1.5MPa, 2MPa, 2.8MPa and continue for 5-10 minutes. Then open the valve (6) before venting to discharge the gas, and then complete the purging of the experimental loop before the experimental test.

[0036] After the purging is completed, valves (11-1) and (11-2) are opened, valves (11-3), (11-4) and (8) are closed, and the gas compressor (10) is turned on and on. The rotation speed of the gas compressor (10) is adjusted to inject natural gas into the ring channel at a relatively high flow rate, so that the natural gas circulates in the ring channel device. Then, valve (8) is opened to inject the atomized drag reducer into the circulation pipeline. During the experiment, the readings of flow meters (14-1) and (14-2) are monitored to keep them constant. The pressure gauge readings before and after the drag reducer is injected at both ends of the experimental ring channel (16) are read respectively to obtain the pressure differences ΔP1 and ΔP0 generated by the natural gas containing the drag reducer and the natural gas without the drag reducer flowing through the test pipe section at a constant flow rate. The turbulent drag reduction efficiency of the drag reducer on the natural gas is calculated, thereby evaluating its turbulent drag reduction performance.

[0037] Implementation 2: Evaluation of turbulent drag reduction performance of natural gas drag reducer under constant pressure difference conditions

[0038] The small-scale natural gas drag reduction indoor loop evaluation device can be used to evaluate the impact of natural gas drag reducer on turbulent drag reduction flow rate. The evaluation of the impact of natural gas drag reducer on turbulent drag reduction flow rate is to use the small-scale indoor loop experimental device to test the change of flow rate in the experimental loop before and after adding the agent under constant pressure difference conditions, so as to calculate the turbulent drag reduction efficiency of the drag reducer on natural gas before and after adding the agent. The calculation expression of the drag reduction efficiency is:

[0039]

[0040] Among them, Q1 and Q0 are the flow rates of natural gas with and without drag reducers at the same pressure drop, L / min.

[0041] The specific example steps of the evaluation of the turbulent drag reduction flow rate of the natural gas drag reducer are as follows:

[0042] When conducting the experiment, the steps of implementation mode 1 are followed. First, the experimental loop is purged. After the purging is completed, natural gas is connected to the experimental loop, and valves (6), (8), and (11-4) are closed at the same time. Valve (11-1), (11-2) and gas compressor (10) are opened. After a certain amount of natural gas is injected, valve (11-1), (11-2) and gas compressor (10) are closed. The speed is adjusted by the gas circulation pump (4) to keep the natural gas in the loop flowing stably. The difference ΔP0 between the pressure gauges (14-1) and (14-2) on the test loop under stable flow and the reading Q0 of the orifice flowmeter (15) are recorded. Then, the valve (8) is opened to inject the drag reducer in the drag reducer atomizing injection device (2) into the loop. After the drag reducer is injected, the valve (8) is closed and the rotation speed of the gas circulation pump (4) is continuously adjusted to make the difference ΔP1 between the pressure gauges (14-1) and (14-2) on the test loop close to ΔP0 without adding the drag reducer, and the reading Q1 of the orifice flow meter (15) is recorded at this time. Thus, the turbulent drag reduction efficiency of the drag reducer on the natural gas before and after adding the drag reducer is calculated, and then its turbulent drag reduction performance is evaluated.

[0043] Compared with the prior art, the present application provides a small-scale natural gas drag reduction indoor loop evaluation device and method, which has the following beneficial effects:

[0044] 1. The small-scale natural gas drag reduction indoor loop evaluation device evaluates the drag reduction performance of the natural gas drag reducer in the indoor loop. According to the evaluation results, the drag reducer can be used to reduce drag and increase transportation of natural gas pipelines;

[0045] 2. The atomization injection device for the natural gas drag reducer includes primary atomization by high-pressure jet and secondary atomization by rotary atomization. The atomization degree of the drag reducer is improved by the two atomizations, so that the atomized particles of the drag reducer reach the micron level;

[0046] 3. The natural gas drag reducer atomizing injection device, the porous nozzle of the atomizing outlet is connected to the atomizing rotating device through a connecting rod, which can not only make the drag reducer form three atomizations at the nozzle outlet, but also make the drag reducer atomized particles more uniform, and achieve the beneficial effect of uniformly spraying the atomized particles into the pipeline.

Claims

1. A small-scale natural gas drag reduction indoor loop evaluation device and method, characterized in that: The evaluation device for the natural gas drag reduction indoor loop includes a nitrogen purge system, a drag reducer atomization injection system, a drag reducer turbulence test system and a gas venting and burning system; the nitrogen purge system mainly includes a nitrogen bottle and a gas circulation pump, which are used to remove gas and impurity particles in the exhaust pipe and dry the loop; the drag reducer turbulence test system mainly includes a natural gas injection port, a gas compressor, a pressure gauge, an orifice flowmeter, a gas circulation pump and an experimental loop, and the drag reduction effect of the drag reducer atomization injection is evaluated and tested by the pressure difference or flow difference of the natural gas at both ends of the experimental loop before and after the addition of the agent; the gas venting and burning system mainly includes a gas circulation pump, a venting combustion port and an experimental loop, which are used to discharge the gas and impurity particles in the purge process and to vent and burn the natural gas after the test; the drag reducer atomization injection system includes a drag reducer atomization injection device, a gas circulation pump and an experimental loop, which are used to inject the natural gas drag reducer into the experimental loop in the form of atomization; The drag reducer atomization injection device includes a shell, jet atomization, and rotary atomization; the jet atomization includes a drag reducer storage tank, a booster pump, and a jet tube with micropores; the rotary atomization includes a rotating disc, a connecting rod, and a porous nozzle.

2. According to claim 1, a small-scale natural gas drag reduction chamber internal loop evaluation device and method is characterized in that: The atomization injection process of the drag reducer atomization injection system is as follows: the drag reducer first enters the microporous jet tube through a booster pump, the high-pressure drag reducer passes through the micropores, and the liquid is sprayed out and torn to achieve initial atomization, and the initial atomized particles contact the high-speed rotating disk in the rotary atomization device to achieve secondary atomization, wherein the rotary atomization device is driven by a motor, the rotating disk is connected to the multi-hole nozzle by a connecting rod, and the rotation of the disk drives the multi-nozzle nozzle to rotate, so that the already rotary atomized drag reducer forms a third atomization at the nozzle, and at the same time, due to the action of centrifugal force, the atomized particles can be sprayed into the pipeline more evenly.

3. The small-scale natural gas drag reduction chamber internal loop evaluation device and method according to claim 1, characterized in that: The drag reducer atomizing injection device is composed of a high-pressure jet primary atomizing, a rotating disc secondary atomizing, and a rotating nozzle tertiary atomizing, so that the arithmetic mean diameter of the natural gas drag reducer molecular particle size is 58.6 μm.

4. The small-scale natural gas drag reduction chamber internal loop evaluation device and method according to claim 1, characterized in that: The jet tube with micropores in the jet atomization system of the drag reducer atomization injection device has a diameter of 25 mm, a length of 250 mm deep in the rotating device, and 120 micropores with a diameter of 0.6 mm on its surface (the micropores are arranged in 20 rows, with 6 micropores in each row).

5. The small-scale natural gas drag reduction chamber internal loop evaluation device and method according to claim 1, characterized in that: The rotary atomization system in the drag reducer atomization injection device has five rotating discs with radii of 170, 175, 180, 185 and 190 mm respectively. The interval between the rotating discs is 50 mm, and the linear speed of the smallest disc is 50 m / s. The rotating device is connected to an external 220V power supply to power the AC motor, providing a disc rotation speed of 2800 r / min.

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