Amine liquid defoaming device and defoaming process

Abstract

The present invention discloses an amine liquid defoaming device and a defoaming process thereof, which solves the technical problem in existing amine liquid purification processes that a large amount of waste liquid is generated during the purification process of removing heat-stable salts and / or foaming substances, which is detrimental to environmental protection and increases the number of subsequent waste liquid treatment steps. The present invention comprises a foaming tube, an adsorption tube, and a suction device. The lower end of the foaming tube is provided with a nitrogen inlet and a foaming amine liquid inlet. The top of the foaming tube is connected to the adsorption tube. The side wall of the foaming tube is provided with a suction device connection port, and the suction device is connected to the foaming tube through the suction device connection port. The suction device connection port is located above the nitrogen inlet and the foaming amine liquid inlet. The present invention has the advantages of good defoaming effect and reduces the amount of waste liquid generated during amine liquid purification.

Description

Technical Field

[0001] The invention relates to the technical field of desulfurization solution treatment, and in particular to an amine solution defoaming device and a defoaming process thereof. Background Art

[0002] Foaming of the desulfurization solution in natural gas purification plants is a common problem encountered during daily production. There are two main causes for this foaming: first, the oxidative degradation of the amine solution itself, which produces metamorphic products that alter the solution's physical and chemical properties (such as surface tension and viscosity), increasing its foaming tendency. Second, surfactants (such as long-chain alkanes and carboxylic acids) in the drilling and completion fluids, reservoir stimulation fluids, and gathering and transportation chemicals used in upstream natural gas wells can enter the desulfurization solution with the gas flow through the separation equipment, causing the amine solution to foam. The consequences of foaming range from fluctuations in the unit's liquid level and unstable operation to excessive product gas quality, requiring a plant shutdown.

[0003] Natural gas in my country generally contains no oxygen, so under normal operation, oxidative degradation of alcoholamines rarely or never occurs in natural gas purification equipment. Tracking the content of heat-stable amine salts in desulfurization solutions at over a dozen natural gas purification plants in the Sichuan and Chongqing regions revealed that these levels are generally low, below 1% (see Table 1). Furthermore, statistics indicate that foaming caused by increased levels of heat-stable amine salts is rarely a problem. In most cases, foaming is caused by the influx of foreign contaminants carried by the natural gas into the solution. These contaminants, in addition to inorganic salts, are mostly organic substances, typically surfactants.

[0004] Table 1 Content of heat-stable salt in desulfurization solution of natural gas purification plants in Sichuan and Chongqing (Unit: w, 10 -6 )

[0005]

[0006] Conventional amine solution purification processes typically include filtration and heat-stable salt removal. This process removes suspended solids and heat-stable salts (including organic and inorganic salts) from the amine solution. While removing these salts reduces the foaming properties of the desulfurization solution, the wide variety and complex composition of foaming substances, particularly those caused by external contamination, prevents conventional amine solution purification processes from completely addressing this issue. Furthermore, after desalination, regeneration is typically performed with a 3% NaOH solution, which generates a certain amount of waste liquid. Typically, processing one volume of amine solution produces one to two volumes of waste liquid (the amount of waste liquid is related to the content of heat-stable salts in the amine solution; higher salt content results in greater waste liquid). This waste liquid requires separate treatment, incurring additional processing costs and increasing production costs. Yan Xiaoqin et al. developed a foaming substance remover for amine solution and applied it to the amine solution purification process. However, some waste liquid is still generated, increasing the subsequent waste liquid treatment process.

[0007] Therefore, based on the problems existing in the existing amine liquid purification process, it is necessary to improve it. Summary of the Invention

[0008] The technical problem to be solved by the present invention is that in the existing amine liquid purification process, a large amount of waste liquid is generated during the purification process of removing heat-stable salts and / or foaming substances, which is not conducive to environmental protection and increases the subsequent waste liquid treatment process.

[0009] The present invention is achieved through the following technical solutions:

[0010] An amine liquid defoaming device comprises a foaming tube, an adsorption tube and a suction device, wherein the lower end of the foaming tube is provided with a nitrogen inlet and a foaming amine liquid inlet, the top of the foaming tube is connected to the adsorption tube, and the side wall of the foaming tube is provided with a suction device connection port, the suction device is connected to the foaming tube via the suction device connection port, and the suction device connection port is located above the nitrogen inlet and the foaming amine liquid inlet.

[0011] Foaming in the desulfurization solution at a natural gas purification plant is primarily caused by foreign contaminants in the desulfurization solution. These contaminants are primarily surfactants (such as long-chain alkanes and carboxylic acids) in drilling and completion fluids, reservoir stimulation fluids, and gathering and transportation chemicals used in upstream natural gas wells. These substances can enter the desulfurization solution with the gas flow through the separation equipment, causing foaming in the amine solution. Furthermore, heat-stable salts can also increase the foaming of the amine solution. Conventional amine purification processes can remove these foaming substances. While this can reduce the foaming of the desulfurization solution to a certain extent, due to the wide variety and complex composition of foaming substances, it cannot completely solve the foaming problem. Furthermore, after desalination, regeneration with 3% NaOH solution is generally performed, which generates a certain amount of waste liquid. Typically, processing one volume of amine solution generates one to two volumes of waste liquid. The amount of waste liquid is related to the content of heat-stable salts in the amine solution, with higher salt content resulting in greater waste liquid. This waste liquid requires separate treatment, adding processing steps and incurring additional processing costs, increasing production costs. Even with the use of foaming substance removers, a large amount of waste liquid is still generated.

[0012] In fact, whether the foaming is caused by degradation of amine solution or by foreign pollutants, it is due to the action of foaming substances (surfactants). Most of these substances are in the foam layer on the surface of the solution. If these foaming substances can be enriched and their content in the solution can be reduced, it will indirectly play a role in defoaming. Based on this principle, the present invention provides a defoaming device before amine solution purification, which is used as a pretreatment before amine solution purification. Specifically, the foaming amine solution is loaded into a foaming tube and nitrogen is introduced for bubbling. The foaming amine solution will be stratified in the foaming tube, with the lower layer being the clear liquid layer and the upper layer being the foaming layer. For amine solution without foreign pollutants, during the foaming process, During the process, through experimental observation, conventional desulfurization solution that is not polluted by foreign matter will produce a certain volume of foam, and will not increase with the increase of ventilation time. In order to stabilize the foaming amine liquid with high foaming capacity, at this time, the foam layer is directly collected into a container by a suction device, left to stand, and the foam dissipates before the next step is carried out. For the amine liquid containing foreign pollutants, the foam in the foaming tube will continue to spread, generating high foam, which is called high-foaming amine liquid. The high-foam is removed by the adsorption effect of the adsorption tube to remove the foaming substances. In the process of foam removal, the foaming substances mixed in the foam, including surfactants and heat-stable salts, will be reduced due to adsorption. The present invention performs two defoaming methods according to the actual amount of foam generated and the different heights in the foaming tube. The amine liquid after defoaming is enriched and collected by two foam separation methods. This greatly reduces the foam in the amine liquid, reduces the burden of the amine liquid in the later treatment, and greatly reduces the generation of waste liquid.

[0013] The present invention preferably provides an amine liquid defoaming device, wherein the nitrogen inlet is located at the bottom of the foaming tube, and the foaming amine liquid inlet is located between the nitrogen inlet and the suction device connection port.

[0014] The nitrogen inlet is arranged at the bottom and is located below the foaming amine liquid inlet. After the foaming amine liquid is injected into the foaming tube, the nitrogen introduced from below can better bubble the foaming amine liquid and spread it upward.

[0015] Furthermore, when foaming is low, a suction device connection port is provided on the side wall 1-2 cm above the top layer of the clear liquid layer, and is connected to the suction device, which is a negative pressure device.

[0016] The present invention takes into account that the main function of the suction device is to suck away the low-foaming section. Since the foaming tube is installed upright, when the foam below is sucked away, the foam above will fall. Therefore, the suction device is set at a position below the low-foaming section to suck away more low-foaming.

[0017] The present invention preferably provides an amine liquid defoaming device, wherein the adsorption tube is an inverted U-shaped tube, one end of the inverted U-shaped tube is connected to the top of the foaming tube, and the adsorption tube is filled with activated carbon.

[0018] The present invention configures the foaming tube into an inverted U-shaped structure. The U-shaped slope provides shear and centrifugal forces, as well as a buffer zone, making it easier to break up high-expansion foam and aggregate it into droplets. The activated carbon filling absorbs foam-causing impurities in the foam carried by the airflow. After the foam overflows into the inverted U-shape, the shear and centrifugal forces of the airflow act on the inverted U-shaped slope to gather the amine droplets adsorbed by the activated carbon, which then flows back into the foaming tube under the action of gravity. Regardless of whether the foam height overflows the top of the inverted U-shaped tube, the surfactant in the foam will be adsorbed on the tube wall of the adsorption tube. When the foam overflows the middle of the adsorption tube, the amine or water it carries will flow back into the amine collection tank at the outlet end of one side of the U-shaped tube.

[0019] The present invention preferably provides an amine liquid defoaming device, wherein the adsorption tube includes an inlet end and an outlet end, the inlet end is connected to the foaming tube, the inlet end is provided with an inlet filter, the outlet end is provided with an outlet filter, and the side wall of the outlet end is also provided with a nitrogen outlet.

[0020] The inlet filter and the outlet filter together confine the activated carbon in the adsorption tube, and the nitrogen outlet arranged on the side wall of the outlet end of the adsorption tube and the nitrogen inlet arranged at the bottom of the foaming tube form a nitrogen flow from the bottom of the foaming tube upward into the adsorption tube, and finally discharged from the side wall of the outlet end of the adsorption tube. The generated nitrogen flow has a driving effect on the foam, which is more conducive to the removal of the foam.

[0021] The present invention preferably provides an amine liquid defoaming device, wherein the suction device is connected to a storage tank for the amine liquid to be treated, the outlet end of the adsorption tube is connected to an amine liquid collecting tank, and the amine liquid collecting tank is connected to the storage tank for the amine liquid to be treated.

[0022] The present invention preferably provides an amine liquid defoaming device, wherein the inlet end of the adsorption tube is further provided with a washing water inlet. When the activated carbon reaches adsorption saturation, activated carbon washing water can be introduced through the washing water inlet to activate the activated carbon.

[0023] The present invention preferably provides an amine liquid defoaming device, wherein the nitrogen inlet is connected to a nitrogen input pipe, and the foaming amine liquid inlet is connected to a foaming amine liquid storage tank.

[0024] The present invention preferably provides an amine liquid defoaming device, wherein the adsorption tube and the foaming tube are detachably connected. When the adsorption tube needs to be activated, only the saturated adsorption tube needs to be taken out and a new adsorption tube needs to be installed, which is simple and efficient.

[0025] An amine liquid defoaming process comprises the following steps:

[0026] Step 1: Add foaming amine solution into the foaming tube;

[0027] Step 2: introducing nitrogen into the foaming tube;

[0028] Step 3: When the amine liquid is a foaming amine liquid with a stable high foaming rate, the suction device is turned on to pump the foam in the low foaming section into the amine liquid storage tank to be treated. When the amine liquid is a high foaming amine liquid, the foam continues to spread into the adsorption tube to adsorb the foaming substance;

[0029] Step 4: The amine liquid in the amine liquid storage tank to be treated flows into the amine liquid purification process at the back end.

[0030] The present invention preferably provides an amine liquid defoaming process, which also includes an adsorbent treatment step: soaking adsorption-saturated activated carbon with low-pressure steam or desalted water.

[0031] The present invention preferably adopts an amine liquid defoaming process, wherein the waste liquid obtained after the activated carbon treatment flows into the amine liquid storage tank to be treated and is used to recover part of the amine liquid in the activated carbon.

[0032] As a pretreatment method for foaming amine liquid, the present invention greatly reduces the amount of waste liquid recovered by conventional amine liquid purification, thereby saving production costs.

[0033] The present invention has the following advantages and beneficial effects:

[0034] 1. The present invention enriches and removes foaming substances in the amine solution, thereby reducing the content of foaming substances in the amine solution, thereby reducing foam, greatly alleviating the burden of subsequent amine solution purification treatment, reducing the amount of waste liquid generated, and saving costs.

[0035] 2. The present invention takes into account the different types and contents of foaming substances in the amine solution and designs a double-foam separation defoaming device. For the stable high-foam amine solution without foreign pollutants, a suction device is used for mechanical treatment, and the low-foam liquid is sucked into a storage tank and placed for defoaming. For the high-foaming amine solution containing foreign pollutants, the foam spreads to the inverted U-shaped adsorption tube, and is enriched through adsorption in the adsorption tube, thereby reducing the foaming substances in the amine solution.

[0036] 3. The present invention sets the adsorption tube into an inverted U shape and utilizes the shear force and centrifugal force of the foam at the slope to break the foam and produce droplets, while the foaming substances are adsorbed by the adsorption tube to achieve better enrichment and removal effect.

[0037] 4. The adsorbent of the present invention adopts activated carbon for adsorption and is activated after saturation. The liquid generated by the activated carbon activation enters the amine liquid storage tank to be treated, and the amine liquid in the adsorption tube is further recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural schematic diagram of the present invention.

[0039] Markings and corresponding parts names in the accompanying drawings:

[0040] 1-foaming tube, 10-nitrogen distributor, 11-foaming amine liquid inlet, 12-clear liquid outlet, 13-suction device connection port, 2-adsorption tube, 20-inlet filter, 21-outlet filter, 22-nitrogen outlet, 3-foaming amine liquid storage tank, 4-amine liquid collecting tank, 5-suction device, 6-amine liquid storage tank to be treated, 7-nitrogen input pipe. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0042] Example 1

[0043] An amine liquid defoaming device comprises a foaming tube 1, an adsorption tube 2 and a suction device 5. A nitrogen inlet is provided at the bottom of the foaming tube 1, and the nitrogen inlet is provided with a nitrogen distributor 10. A foaming amine liquid inlet 11 and a clear liquid discharge port 12 are provided at the lower end of the side wall of the foaming tube 1. The foaming amine liquid inlet 11 is located between the nitrogen inlet and the suction device connection port 13. The top of the foaming tube 1 is connected to the adsorption tube 2. The side wall of the foaming tube 1 is provided with a suction device connection port 13. The suction device 5 is connected to the foaming tube 1 through the suction device connection port 13. The suction device connection port 13 is located above the nitrogen inlet and the foaming amine liquid inlet 11.

[0044] The adsorption tube 2 is an inverted U-shaped tube, one end of which is connected to the top of the foaming tube 1. The adsorption tube 2 is filled with activated carbon. The adsorption tube 2 includes an inlet end and an outlet end. The inlet end is connected to the foaming tube 1. The inlet end is provided with an inlet filter 20, and the outlet end is provided with an outlet filter 21. The side wall of the outlet end is also provided with a nitrogen outlet 22.

[0045] The present invention configures the foaming tube 1 into an inverted U-shaped structure. The U-shaped slope provides shear and centrifugal forces, as well as a buffer zone, making it easier to break up high-expansion foam and aggregate it into droplets. The activated carbon filling absorbs foam-causing impurities in the foam carried by the airflow. After the foam overflows into the inverted U-shape, the shear and centrifugal forces of the airflow act on the inverted U-shaped slope to gather the amine droplets adsorbed by the activated carbon, which then flows back into the foaming tube 1 under the action of gravity. Regardless of whether the foam reaches the top of the inverted U-shaped tube, the surfactant in the foam is adsorbed on the wall of the adsorption tube 2. Once the foam overflows the middle of the adsorption tube 2, the amine or water it carries flows back into the amine collection tank 4 at the outlet end of one side of the U-shaped tube.

[0046] A suction device connection port 13 is provided on the side wall 1-2 cm above the top layer of the clear liquid layer, and is connected to the suction device 5, which is a negative pressure device.

[0047] The nitrogen inlet is connected to the nitrogen input pipe 7, and the foaming amine liquid inlet 11 is connected to the foaming amine liquid storage tank 3.

[0048] The negative pressure device is connected to the amine liquid storage tank 6 to be treated, the outlet end of the adsorption tube 2 is connected to the amine liquid collecting tank 4 , and the amine liquid collecting tank 4 is connected to the amine liquid storage tank 6 to be treated.

[0049] The suction device 5 is connected to a storage tank 6 for the amine liquid to be treated, and the outlet end of the adsorption tube 2 is connected to an amine liquid collecting tank 4 , and the amine liquid collecting tank 4 is connected to the storage tank 6 for the amine liquid to be treated.

[0050] Example 2

[0051] The difference between this embodiment and embodiment 1 is that a washing water inlet is further provided at the inlet end of the adsorption tube 2. When the activated carbon reaches adsorption saturation, activated carbon washing water can be introduced through the washing water inlet to activate the activated carbon. The adsorption tube 2 is detachably connected to the foaming tube 1. When the adsorption tube 2 needs to be activated, it is only necessary to take out the saturated adsorption tube 2 and install a new adsorption tube 2. This is simple and efficient.

[0052] In the specific experiment:

[0053] Foaming tube 1 is designed with a diameter of 30 mm and a total length of 500 mm. A foaming amine solution with a stable foam height is used, with the bubble height within the foaming tube ranging from 200 to 500 mm and the clear liquid layer at 100 mm. A suction connection port 13 is provided 1-2 mm above the clear liquid layer for extracting the foam. When the foam height exceeds 500 mm, it is considered a high-foaming amine solution, and the foam spreads to adsorption tube 2 for adsorption.

[0054] Example 3

[0055] An amine liquid defoaming process comprises the following steps:

[0056] Step 1: introducing foaming amine liquid into the foaming tube 1;

[0057] Step 2: Nitrogen is introduced into the foaming tube 1 for bubbling. According to the industry standard SY / T 6538-2002 "Formulated Selective Desulfurization Solvent", the gas rate is 250 mL / min;

[0058] Step 3: When the amine liquid is a foaming amine liquid with a stable high foaming rate, the suction device 5 is turned on to pump the foam in the low foaming stage into the amine liquid storage tank 6 to be treated. When the amine liquid is a high foaming amine liquid, the foam continues to spread into the adsorption tube 2 to adsorb the foaming substance.

[0059] Step 4: The amine liquid in the amine liquid storage tank 6 to be treated flows into the amine liquid purification process at the rear end.

[0060] The activated carbon that is saturated with adsorption can be activated. The treatment process of the activated carbon is as follows: the activated carbon that is saturated with adsorption is soaked in low-pressure steam or desalted water above 80°C. The waste liquid obtained after the activated carbon treatment flows into the amine liquid storage tank 6 to be treated, and is used to recover part of the amine liquid in the activated carbon.

[0061] As a pretreatment method for foaming amine liquid, the present invention greatly reduces the amount of waste liquid recovered by conventional amine liquid purification, thereby saving production costs.

[0062] The identification of activated carbon deactivation is:

[0063] When the foaming test results of the amine liquid discharged through the activated carbon exceed the internal industry standards, which are: bubble height <200mm, defoaming time <60s, it indicates that the foaming trend is increasing, and it is judged that the activated carbon adsorption is close to saturation. The adsorption tube 2 is replaced, and the adsorption saturated activated carbon is soaked with low-pressure steam or desalted water above 80°C to fully dissolve the adsorbed impurities and increase their solubility. The cleaning liquid flows into the amine liquid storage tank 6 to be treated, and part of the amine liquid is recovered.

[0064] This process saves the operating cost of the traditional amine liquid purification process, improves its processing capacity, and saves the amount of regeneration liquid used in the amine liquid purification and defoaming tower.

[0065] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An amine solution defoaming process, characterized in that: The defoaming device adopted comprises a foaming tube (1), an adsorption tube (2) and a suction device (5), wherein the lower end of the foaming tube (1) is provided with a nitrogen inlet and a foaming amine liquid inlet (11), the top of the foaming tube (1) is connected to the adsorption tube (2), the side wall of the foaming tube (1) is provided with a suction device connection port (13), the suction device (5) is connected to the foaming tube (1) through the suction device connection port (13), and the suction device connection port (13) is located above the nitrogen inlet and the foaming amine liquid inlet (11), the adsorption tube (2) is an inverted U-shaped tube, one end of the inverted U-shaped tube is connected to the top of the foaming tube (1), the adsorption tube (2) is filled with activated carbon, the suction device (5) is connected to the amine liquid storage tank (6) to be treated, the outlet end of the adsorption tube (2) is connected to the amine liquid collecting tank (4), and the amine liquid collecting tank (4) is connected to the amine liquid storage tank (6) to be treated; The amine solution defoaming process comprises the following steps: Step 1: introducing foaming amine liquid into the foaming tube (1); Step 2: introducing nitrogen into the foaming tube (1); Step 3: When the amine liquid is a foaming amine liquid with a stable high foaming rate, the suction device (5) is turned on to pump the foam in the low foaming section into the amine liquid storage tank (6) to be treated. When the amine liquid is a high foaming amine liquid, the foam continues to spread into the adsorption tube (2) to adsorb the foaming substance. Step 4: The amine liquid in the amine liquid storage tank (6) to be treated flows into the amine liquid purification process at the rear end.

2. The amine solution defoaming process according to claim 1, characterized in that: The nitrogen inlet is located at the bottom of the foaming tube (1), and the foaming amine liquid inlet (11) is located between the nitrogen inlet and the suction device connection port (13).

3. The amine solution defoaming process according to claim 1, characterized in that: The adsorption tube (2) comprises an inlet end and an outlet end, the inlet end is connected to the foaming tube (1), the inlet end is provided with an inlet filter (20), the outlet end is provided with an outlet filter (21), and the side wall of the outlet end is also provided with a nitrogen outlet (22).

4. The amine solution defoaming process according to claim 3, characterized in that: The inlet end of the adsorption tube (2) is also provided with a washing water inlet.

5. The amine solution defoaming process according to claim 1, characterized in that: The nitrogen inlet is connected to the nitrogen input pipe (7), and the foaming amine liquid inlet (11) is connected to the foaming amine liquid storage tank (3).

6. The amine solution defoaming process according to claim 1, characterized in that: It also includes an adsorbent treatment process: using low-pressure steam or desalted water to soak the adsorption-saturated activated carbon.

7. The amine solution defoaming process according to claim 1, characterized in that: The waste liquid obtained after the activated carbon treatment flows into the amine liquid storage tank (6) to be treated, and is used to recover part of the amine liquid in the activated carbon.

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