Disclosure of Invention
An object of the present invention is to provide a new solution for the formation of propane hydrate.
According to a first aspect of the invention, a propane hydrate generation system is provided, which comprises a generation device and a refrigeration device, wherein the generation device comprises a reaction kettle and a propane gas tank, the propane gas tank is communicated to the reaction kettle through a delivery pump, a pressure reducing valve and a gas flowmeter are arranged between the propane gas tank and the delivery pump, the delivery pump is communicated to the top of the reaction kettle, a silica sand layer is laid at the bottom of the reaction kettle, and the silica sand layer is immersed in a cyclopentane mixed solution; refrigerating plant is including the LNG storage tank, LNG pump, heat exchanger and the recovery bottle that connect gradually, heat exchanger is arranged in gasifying LNG and becomes the natural gas and retrieves in the recovery bottle.
Through this scheme, utilize the cold energy of LNG itself to provide the refrigerating output to reation kettle, greatly reduced the energy consumption in the traditional refrigeration process, reduced propane hydrate's formation cost, be fit for industrial production and use.
Preferably, the top of the reaction kettle is communicated with a gas collecting bottle, and a gas flowmeter is arranged between the gas collecting bottle and the reaction kettle.
Through this scheme, the gas collection bottle can retrieve unnecessary propane gas in the reation kettle, keeps the pressure balance among the reation kettle.
Preferably, the bottom of the inner wall of the reaction kettle is provided with a micro-rib structure, and the height of the micro-rib structure is not less than the thickness of the silica sand layer.
Through this scheme, the contact area of little rib structure can double increase and silica sand layer, increases the double-phase contact area of gas-liquid, increases heat transfer and mass transfer between gas and the silica sand layer, forms favorable nucleation structure, accelerates hydrate nucleation, shortens induction time.
Preferably, the heat exchanger includes a refrigeration box, an output pipe of the LNG pump is communicated to a refrigeration pipe of the refrigeration box, the refrigeration pipe is coiled into the refrigeration box, the refrigeration pipe is communicated to the recovery bottle, and the reaction kettle is located in the refrigeration box.
Through this scheme, utilize a large amount of cold energy of LNG self to provide the refrigeration volume to the refrigeration case to reach and carry out refrigerated effect to reation kettle, let in after the refrigeration and retrieve in the recovery bottle.
Preferably, a monitoring device is arranged on the reaction kettle, and the monitoring device at least comprises a pressure sensor and a temperature sensor.
According to a second aspect of the present invention, there is provided a method for producing a propane hydrate using the above-described system for producing a propane hydrate, comprising the steps of:
the method comprises the following steps: mixing cyclopentane with a salt solution to form a cyclopentane mixed solution, wherein the mole mass percentage of cyclopentane in the cyclopentane mixed solution is 1.0-5.0 mol%;
step two: injecting the cyclopentane mixed solution into a reaction kettle and enabling the cyclopentane mixed solution to immerse a silica sand layer of the reaction kettle, wherein the thickness of the silica sand layer is 1.5-5.0cm, and the particle size of silica sand in the silica sand layer is 100-500 mu m;
step three: opening a pressure reducing valve and a delivery pump to inject the propane gas into the reaction kettle until the pressure in the reaction kettle reaches a set pressure, wherein the set pressure is 0.5-2 MPa;
step four: and opening the LNG pump to enable the LNG to provide refrigerating capacity for the reaction kettle through the refrigerating box, and monitoring the temperature and the pressure in the reaction kettle in real time until the temperature and the pressure in the reaction kettle are within a stable range.
Preferably, after the cyclopentane mixed solution is prepared, the molar mass percentage of cyclopentane is 3.0 mol%.
Preferably, the filling thickness of the silica sand layer is 1.5cm, and the particle size of the silica sand used in the silica sand layer is 100 μm.
According to one embodiment of the disclosure, the generation system or the generation method of the propane hydrate can greatly shorten the induction time of the propane hydrate, improve the gas absorption rate and increase the generation amount of the hydrate within a certain time;
the invention adopts LNG cold energy as a cold source to provide refrigerating capacity for the reaction kettle, and compared with the traditional refrigerating mode, the invention can greatly reduce energy consumption and reduce the generation cost of the propane hydrate.
Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.
Detailed Description
Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
Example one
As shown in fig. 1 to fig. 2, the generation system of propane hydrate in the present embodiment includes a generation device and a refrigeration device, the generation device includes a reaction kettle 1 and a propane gas tank 111, the propane gas tank 111 is communicated to the reaction kettle 1 through a delivery pump 114, a pressure reducing valve 112 and a gas flow meter 113 are disposed between the propane gas tank 111 and the delivery pump 114, the delivery pump 114 is communicated to the top of the reaction kettle 1, a silica sand layer 12 is laid at the bottom of the reaction kettle 1, and the silica sand layer 12 is immersed in a cyclopentane mixed solution; the refrigeration device comprises an LNG storage tank 131, an LNG pump 132, a heat exchanger 133 and a recovery bottle 134 which are connected in sequence, wherein the heat exchanger 133 is used for gasifying LNG to change the LNG into natural gas and recovering the natural gas into the recovery bottle 134.
According to the scheme of the embodiment, the LNG self cold energy is used as the cold source to provide the refrigerating capacity for the reaction kettle, so that the energy consumption in the traditional refrigerating process is greatly reduced, the generation cost of the propane hydrate is reduced, and the method is suitable for industrial production.
In this embodiment or other embodiments, a gas collecting bottle 121 is communicated with the top of the reaction kettle 1, and a gas flowmeter 122 is disposed between the gas collecting bottle 121 and the reaction kettle 1. The gas collecting bottle 121 can recover redundant propane gas in the reaction kettle 1, and the pressure balance in the reaction kettle 1 is kept.
In this embodiment or other embodiments, the bottom of the inner wall of the reaction kettle 1 is provided with a micro-rib structure 11, and the height of the micro-rib structure 11 is not less than the thickness of the silica sand layer 12. The micro-rib structure 11 can multiply increase the contact area with the silica sand layer 12, increase the contact area of gas-liquid two phases, increase the heat transfer and mass transfer between the gas and the silica sand layer, form a favorable nucleation structure, accelerate the nucleation of the hydrate and shorten the induction time.
The micro-rib structure 11 in this embodiment surrounds the inner wall of the reaction kettle 1 and is distributed over the inner wall of the reaction kettle 1, the cross section of the micro-rib structure 11 is in a wave shape, that is, a plurality of annular protrusions and grooves are uniformly and alternately distributed on the inner wall of the reaction kettle 1, wherein the widths of the protrusions and the grooves are both larger than the particle size of silica sand in the silica sand layer 12.
In this or other embodiments, the heat exchanger 133 includes a refrigeration box 135, the output pipe of the LNG pump 132 is connected to a refrigeration pipe (not shown) of the refrigeration box 135, the refrigeration pipe is coiled into the refrigeration box 135, the refrigeration pipe is connected to the recovery bottle 134, and the reaction kettle 1 is located in the refrigeration box 135. Utilize a large amount of cold energy of LNG self to provide the refrigeration volume to refrigeration case 135 to reach and carry out refrigerated effect to reation kettle 1, let in after the refrigeration and retrieve in retrieving bottle 134 and retrieve. This refrigeration case 135 is, for example, a water bath case or a water bath jacket, and performs refrigeration using water as a medium, and since the specific heat capacity of water is large, the utilization rate of cold energy can be greatly improved, and it is helpful to keep the temperature constant.
In other embodiments, the heat exchanger 133 includes a vaporizer and a refrigeration box, two ends of the vaporizer are respectively connected to the LNG pump 132 and the recovery bottle 134, the vaporizer is connected to the refrigeration box, LNG is vaporized by the vaporizer to become natural gas, and the natural gas is recovered to the recovery bottle, and the reaction kettle 1 is placed in the refrigeration box, so as to achieve the effect of refrigerating the reaction kettle. LNG is introduced to release a large amount of cold energy, so that a better refrigeration effect is achieved.
In other embodiments, this refrigeration case can also be water bath and press from both sides the cover, and the water bath is pressed from both sides the cover in reation kettle 1 periphery, lets in LNG through the LNG pump, utilizes the LNG cold energy to provide the refrigerating output to reation kettle to reach the effect of carrying out the refrigeration to reation kettle 1.
The recovery bottle 134 in this embodiment is used to collect the gasified natural gas, and may also be used to directly connect the gasified natural gas to a domestic natural gas pipeline.
In this embodiment or other embodiments, the reaction kettle 1 is provided with a monitoring device 151, and the monitoring device 151 at least includes a pressure sensor and a temperature sensor (both shown in the figure).
The monitoring device 151 in this case also comprises a data processing device (not shown in the figures) which processes the data collected by the pressure sensor and the temperature sensor, converts them into readable data and displays them. The data processing device is a device having data processing capability, such as a microcomputer, a mobile phone, or an industrial personal computer.
According to the present embodiment, the system and the method for producing propane hydrate can greatly shorten the induction time of propane hydrate, improve the gas absorption rate, and increase the amount of hydrate produced in a certain period of time.
Example two
According to a second aspect of the present invention, there is provided a method for producing a propane hydrate using the above-described system for producing a propane hydrate, comprising the steps of:
the method comprises the following steps: mixing cyclopentane with a salt solution to form a cyclopentane mixed solution, wherein the mole mass percentage of cyclopentane in the cyclopentane mixed solution is 1.0-5.0 mol%;
step two: injecting the cyclopentane mixed solution into a reaction kettle and enabling the cyclopentane mixed solution to just submerge a silica sand layer of the reaction kettle, wherein the height of the cyclopentane mixed solution is consistent with the thickness of the silica sand layer, the thickness of the silica sand layer is 1.5-5.0cm, and the particle size of silica sand in the silica sand layer is 100-500 μm;
in the step, the reaction kettle needs to be evacuated in advance, and then the cyclopentane mixed solution is injected into the reaction kettle, so that the formation of the hydrate is prevented from being influenced by the existence of other gas impurities in the reaction kettle.
Step three: opening a pressure reducing valve and a delivery pump to inject the propane gas into the reaction kettle until the pressure in the reaction kettle reaches a set pressure, wherein the set pressure is 0.5-2 MPa;
step four: and opening the LNG pump to enable the LNG to refrigerate the reaction kettle through the refrigeration box, monitoring the temperature and the pressure in the reaction kettle in real time, keeping the temperature range between 2 ℃ and 5 ℃ until the temperature and the pressure in the reaction kettle are stabilized to be within the generation range, and completing the generation of the propane hydrate.
And B, adding cyclopentane into a 3 wt% salt solution for sufficient mixing in a blending process to obtain a cyclopentane mixed solution with the mole mass percent of cyclopentane being 1.0mol-5.0 mol%.
In the embodiment, cyclopentane is a good hydrate accelerant, is insoluble in water, can generate a hydrate under the atmospheric pressure above the freezing point, the required generation condition is easy to reach, and the cyclopentane is added in the generation process of the propane hydrate to make the phase equilibrium condition of the hydrate move towards the low pressure and high temperature direction. The existence of silica sand increases the contact between gas and water molecules, and the water molecules are dispersed among silica sand particle pores during the generation of the hydrate, thereby promoting the migration and capillary movement of water in the silica sand and accelerating the nucleation of the hydrate. Because the pore diameter of the silica sand particles is smaller, the smaller particles have larger edges and surfaces, and therefore more sites are provided to further promote hydrate nucleation and shorten the induction time.
EXAMPLE III
In the embodiment, the filling thickness of the silica sand layer is 1.5cm, and the particle size of the silica sand used in the silica sand layer is 100 μm. After the cyclopentane mixed solution is prepared, the molar mass percentage of cyclopentane is 1.0 mol%, 3.0 mol% and 5.0 mol%, and through experimental comparison, the influence of the molar mass percentage of cyclopentane on the formation of propane hydrate is shown in the following table:
table 1: influence of the molar mass percentage of cyclopentane on the formation of propane hydrate
As can be seen from table 1: under the condition of keeping other parameters unchanged, when the mole mass percent of cyclopentane is 3.0 mol%, the induction time is shortest and the gas absorption rate is best. When the molar mass of cyclopentane is 1 mol%, the hydrate induction time is long, the gas absorption rate is low, hydrate crystals suitable for experiments cannot be obtained, and the generated hydrate crystals are not enough. When the molar mass of the cyclopentane is 5 mol%, hydrate crystals aggregate to form slurry similar to a solid phase, further generation of the hydrate is hindered, and the generation amount of the hydrate is reduced.
Example four
In this embodiment, after the cyclopentane mixed solution is prepared, the molar mass percentage of cyclopentane is 3.0 mol%, and the particle size of silica sand used in the silica sand layer is 6 μm. The effects on the formation of propane hydrate when the packing thickness of the silica sand layer was 1.5cm, 3.5cm and 5cm, respectively, are shown in the following table:
table 2: effect of silica sand pack thickness on propane hydrate formation
As can be seen from table 2: under the condition of keeping other parameters unchanged, when the thickness of the silica sand layer is 1.5cm, the induction time is shortest, the gas absorption rate is optimal, water dispersed among the silica sand is absorbed into a gas phase to a hydrate growth area, the hydrate nucleation can be accelerated, the hydrate growth is accelerated, and a large amount of hydrates are generated. When the filling thickness is 3.0cm and 5.0cm, water molecules dispersed in the silica sand with lower depth do not participate in the generation of hydrate, and the generation amount of the hydrate is not greatly increased; when the thickness of the silica sand layer is less than 1.5cm, the hydrate generation amount is less because the water dispersed among the silica sand is less, and the requirement of large-scale production cannot be met.
EXAMPLE five
In this embodiment, after the blending of the cyclopentane mixed solution, the molar mass percentage of cyclopentane is 3.0 mol%, the filling thickness of the silica sand layer is 1.5cm, and when the particle size of the silica sand used in the silica sand layer is 50 μm, 100 μm, 300 μm, 500 μm, the effect on the formation of propane hydrate is shown in the following table:
table 3: influence of particle size of silica sand used for silica sand layer on formation of propane hydrate
As can be seen from table 3: when the particle size of the silica sand used in the silica sand layer is 100 μm, the induction time is shortest, the gas absorption rate is optimal, the pore diameter of the silica sand particles is smaller, the smaller particles have larger edges and surfaces, the surface contact area of the gas phase and the liquid phase is further increased, and therefore more positions are provided for further promoting hydrate nucleation and shortening the induction time.
As the silica sand particle size increases, the surface contact area of the gas phase and the liquid phase decreases, the sites required for hydrate nucleation decrease, and thus the induction time becomes longer. And with the particle size less than 100 μm, gas and solution cannot effectively and completely permeate into the silica sand layer due to the undersized gaps among the silica sand particles, so that the induction time and the gas absorption rate are influenced.
Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustrative purposes only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.