A method and system for treating waste water from tail gas oxidation absorption process in a natural gas purification plant for recycling

Abstract

This invention provides a method and system for treating and reusing wastewater from the tail gas oxidation absorption process of a natural gas purification plant. The system includes: neutralizing pre-washing wastewater and amine purification wastewater generated from the tail gas oxidation absorption process of the natural gas purification plant to obtain neutralized wastewater to be treated; wherein the neutralization is achieved by mixing the pre-washing wastewater and amine purification wastewater and adjusting the pH value to 6-7; subjecting the neutralized wastewater to aeration oxidation to obtain aeration-oxidized wastewater; subjecting the aeration-oxidized wastewater to adsorption treatment using carboxylated activated carbon to obtain adsorbed wastewater; subjecting the adsorbed wastewater to reverse osmosis membrane treatment to obtain concentrated water and desalinated water; subjecting the concentrated water to evaporation desalination to obtain crystalline salt and evaporation condensate; and reusing the evaporation condensate and desalinated water together as greywater.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology for natural gas purification, specifically relating to a method and system for the reuse and treatment of wastewater from the tail gas oxidation and absorption process in a natural gas purification plant. Background Technology

[0002] Natural gas, as a green, efficient, and low-carbon fossil energy source, plays a vital role in energy security and the green transformation of the energy structure. However, natural gas often contains sulfides during its geological formation. While natural gas purification plants can perform deep desulfurization, they also produce and emit SO2. SO2 is an air pollutant that seriously harms human health and can easily combine with water to form acid rain, damaging plants and buildings. Therefore, it is necessary to intensify the treatment of exhaust gas from natural gas purification plants to reduce SO2 emissions.

[0003] The principle of the tail gas oxidation absorption process in natural gas purification plants is to directly burn various sulfides in the tail gas from the sulfur recovery unit of the natural gas purification plant, converting them into SO2. After cooling, the SO2 is absorbed by a highly selective di-tertiary amine solution (functional components R1R2N-R3-NR4R5 or R1R1N-R3-NR2R2, where R1, R2, R3, R4, and R5 are alkyl groups). The di-tertiary amine solution can be regenerated at high temperatures and recycled, while the high-concentration SO2 gas released is returned to the sulfur recovery unit. This process is simple, the equipment is small, the process is stable, easy to operate, and has technological advantages. However, this process also generates and discharges a large amount of process wastewater, mainly including: acidic wastewater generated in the Venturi tower and wet electrostatic precipitator during pre-washing (referred to as pre-washing wastewater) and alkaline organic amine wastewater generated from the regeneration of the di-tertiary amine solution (referred to as amine purification wastewater). This wastewater contains sulfuric acid, sulfurous acid, and organic amines, which have certain biological toxicity and will pollute the environment if they enter water bodies.

[0004] Organic amine wastewater is difficult to biodegrade. Currently, chemical precipitation, adsorption, stripping, Fenton-like oxidation, and ozone combined oxidation are commonly used for the treatment of organic amine wastewater. Under acidic conditions, organic amines are removed by reacting with water-soluble inorganic substances containing heteroacids and heteroatoms to form precipitates; however, this method generates new hazardous solid waste. Inorganic adsorbents such as zeolite, activated carbon fiber, and alumina are used to adsorb and remove amines from organic amine wastewater; however, conventional zeolite, activated carbon fiber, and alumina adsorbents are only suitable for treating low-concentration organic amine wastewater. For high-concentration organic amine wastewater, the volatility of organic amines can be utilized to remove amines through high-temperature steam stripping. This is effective for removing poorly water-soluble and volatile amines (such as aliphatic amines), but less effective for removing well-soluble and less volatile amines (such as alkanolamines). Using Fenton-like oxidation to remove organic amines from wastewater can reduce the impact and toxicity of high concentrations of organic amines on the microorganisms in the biochemical treatment system, which is beneficial for subsequent biochemical treatment. However, this treatment method uses a large amount of hydrogen peroxide, which is an easily explosive chemical, and its transportation and storage pose safety risks.

[0005] Currently, there is no effective treatment technology for wastewater containing sulfuric acid, sulfurous acid, and organic amines. In other words, there is no effective wastewater treatment technology to treat wastewater from the tail gas oxidation and absorption process of purification plants and to achieve wastewater recycling.

[0006] Therefore, new wastewater treatment technologies are still needed to achieve the regeneration and reuse of wastewater from the tail gas oxidation and absorption process of purification plants, which contains sulfuric acid, sulfurous acid, and organic amines. Summary of the Invention

[0007] The purpose of this invention is to provide a technical solution for the regeneration and reuse of wastewater from the oxidation and absorption process of tail gas from a purification plant, which contains sulfuric acid, sulfurous acid, and organic amines.

[0008] To address the above problems, the present invention provides the following two technical solutions.

[0009] In a first aspect, the present invention provides a method for treating and reusing wastewater from the tail gas oxidation absorption process of a natural gas purification plant, wherein the method includes:

[0010] The pre-washing wastewater and amine purification wastewater generated from the tail gas oxidation and absorption process of the natural gas purification plant are neutralized to obtain neutralized wastewater to be treated; wherein, the neutralization process is achieved by mixing the pre-washing wastewater and amine purification wastewater and adjusting the pH value to 6-7.

[0011] The neutralized wastewater to be treated is subjected to aeration oxidation treatment to obtain aeration oxidized wastewater.

[0012] The wastewater after aeration and oxidation is treated with carboxylated activated carbon for adsorption to obtain the adsorbed wastewater.

[0013] The adsorbed wastewater is then treated with a reverse osmosis membrane to obtain concentrated water and fresh water.

[0014] The concentrated water is evaporated and desalted to obtain crystalline salt and evaporated condensate.

[0015] The condensate from the evaporation is reused along with fresh water as greywater.

[0016] According to a preferred embodiment of the first aspect, sodium hydroxide is used to adjust the pH value to 6-7; in a specific embodiment, a sodium hydroxide solution with a sodium hydroxide mass concentration of 30% is used to adjust the pH value to 6-7.

[0017] According to a preferred embodiment of the first aspect, during the neutralization process, the wastewater is stirred at a speed of 50-100 r / min.

[0018] Furthermore, the neutralization process takes 15-30 minutes.

[0019] According to a preferred embodiment of the first aspect, the method further includes: cooling the neutralized wastewater before aeration oxidation treatment;

[0020] Further, cool it down to 25-35℃.

[0021] According to a preferred embodiment of the first aspect, the aeration oxidation is carried out by aeration oxidation.

[0022] Furthermore, the air injection rate for aeration oxidation is 30 L / min - 50 L / min;

[0023] Furthermore, the aeration oxidation treatment time is 30-60 minutes.

[0024] According to a preferred embodiment of the first aspect, in the process of adsorption treatment of the wastewater after aeration and oxidation using carboxylated activated carbon, carboxylated activated carbon microspheres with a diameter of 300-500 μm are used.

[0025] Furthermore, the mass ratio of carboxylated activated carbon microspheres to the volume of wastewater after aeration and oxidation is 1-10 g:L;

[0026] Furthermore, the adsorption treatment time is 30-60 minutes.

[0027] According to a preferred embodiment of the first aspect, the carboxylated activated carbon microspheres are prepared by the following method:

[0028] (1) Under nitrogen protection, the polystyrene resin microspheres are heated to the first target temperature and then cooled to room temperature; the first target temperature is 700-900℃ (e.g., 800℃).

[0029] (2) Under carbon dioxide protection, the product obtained in step (1) is heated to the second target temperature and then cooled to room temperature to obtain activated carbon microspheres; wherein the second target temperature is 750-950℃ (e.g. 850℃) and is greater than the first target temperature;

[0030] (3) The prepared activated carbon microspheres were mixed with hydrogen peroxide and heated to react. The product after reaction was washed and dried to obtain carboxylated activated carbon microspheres.

[0031] Further, heating the polystyrene resin microspheres to the first target temperature includes: heating the polystyrene resin microspheres to 250-350℃ (e.g., 300℃) at a heating rate of 1-2℃ / min (e.g., 1.5℃ / min) and holding them at that temperature for 1-2 hours (e.g., 1.5 hours); then heating them to 550-650℃ (e.g., 600℃) at a heating rate of 1.5-3℃ / min (e.g., 2℃ / min) and holding them at that temperature for 2 hours; and then heating them to the first target temperature at a heating rate of 1.5-3℃ / min (e.g., 2℃ / min) and holding them at that temperature for 0.5-1.5 hours (e.g., 1 hour).

[0032] Further, heating the product obtained in step (1) to the second target temperature includes: heating the product obtained in step (1) to the second target temperature at a heating rate of 1.5-3℃ / min (e.g., 2℃ / min) and holding it at that temperature for 10-20 min (e.g., 15 min);

[0033] Furthermore, taking the total mass of hydrogen peroxide as 100, the concentration of hydrogen peroxide in the hydrogen peroxide is 5-15 (e.g., 10%).

[0034] Furthermore, based on the total mass of activated carbon microspheres, the amount of hydrogen peroxide added is 3-8 mL / g (e.g., 5 mL / g);

[0035] Furthermore, the temperature for heating the reaction is 60-70℃ (e.g., 65℃);

[0036] Furthermore, the heating reaction time is 1-3 hours (e.g., 2 hours);

[0037] Furthermore, the heating reaction is carried out under stirring conditions at a stirring rate of 50-150 r / min (e.g., 100 r / min);

[0038] Furthermore, drying is achieved by drying at 100°C for 2 hours.

[0039] According to a preferred embodiment of the first aspect, the reverse osmosis membrane is an aromatic polyamide reverse osmosis membrane, such as a DTRO type aromatic polyamide reverse osmosis membrane.

[0040] According to a preferred embodiment of the first aspect, during the reverse osmosis membrane treatment of the adsorbed wastewater, the operating temperature of the reverse osmosis membrane is 25-35°C and the operating pressure is 30-75 Bar.

[0041] According to a preferred embodiment of the first aspect, the evaporation is carried out at a pressure of -80 to -90 kPa and a temperature of 35 to 55°C during the concentrated water evaporation desalination process.

[0042] According to a preferred embodiment of the first aspect, the method further includes: dehydrating the crystalline salt to obtain industrial sodium sulfate crystalline salt;

[0043] Furthermore, the crystalline salt is dehydrated by drying at 100-120°C.

[0044] Secondly, the present invention provides a wastewater reuse treatment system for the tail gas oxidation absorption process of a natural gas purification plant. This system is used to implement the wastewater reuse treatment method for the tail gas oxidation absorption process of a natural gas purification plant provided in the first aspect. The system includes:

[0045] Neutralization tank, aeration oxidation tower, adsorption tank, reverse osmosis unit, evaporation desalination unit and water quality conditioning tank;

[0046] The outlet of the neutralization tank is connected to the inlet of the aeration oxidation tower, the outlet of the aeration oxidation tower is connected to the inlet of the adsorption tank, the outlet of the adsorption tank is connected to the inlet of the reverse osmosis unit, the concentrate outlet of the reverse osmosis unit is connected to the inlet of the evaporation desalination unit, and the inlet of the water quality conditioning tank is connected to the outlet of the evaporation desalination unit and the freshwater outlet of the reverse osmosis unit, respectively. The neutralization tank is equipped with a pre-washing wastewater inlet, an amine purification wastewater inlet, and a pH adjuster inlet.

[0047] According to a preferred embodiment of the second aspect, the system further includes a plate heat exchanger disposed on the connecting pipeline between the outlet of the neutralization tank and the inlet of the aeration oxidation tower.

[0048] According to a preferred embodiment of the second aspect, the system further includes a drying and dehydration device, the inlet of which is connected to the crystallization salt outlet of the evaporation and desalination device.

[0049] The technical solution provided by this invention, based on the characteristics of pre-washing wastewater (containing sulfurous acid and sulfuric acid waste) and amine purification wastewater (containing sodium hydroxide, sodium sulfate, and organic amines), involves mixing the pre-washing wastewater and amine purification wastewater, adjusting the pH to neutral, and then employing a treatment approach of "aeration oxidation + carboxylated activated carbon microsphere adsorption + reverse osmosis membrane concentration + negative pressure evaporation desalination." This achieves wastewater regeneration and reuse, fully recovering water and sodium sulfate crystals. In the technical solution provided by this invention, the mixing of pre-washing wastewater and amine purification wastewater, followed by aeration oxidation and carboxylated activated carbon microsphere adsorption, effectively oxidizes sulfite to sulfate and retains sulfate while effectively removing organic amines. The technical solution provided by this invention enables the regeneration and reuse of wastewater from the tail gas oxidation and absorption process of purification plants containing sulfuric acid, sulfurous acid, and organic amines, offering advantages such as low cost and ease of operation. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the wastewater reuse treatment system of the tail gas oxidation absorption process in the natural gas purification plant in Example 1.

[0051] Figure 2 This is a sample image of the carboxylated activated carbon microspheres from Example 2.

[0052] Figure 3 The image shows a full-scan X-ray photoelectron spectrum of the carboxylated activated carbon microspheres in Example 2.

[0053] Figure 4 This is a high-resolution C1s X-ray photoelectron spectrum of the carboxylated activated carbon microspheres in Example 2.

[0054] Figure 5 The image shows a high-resolution O1s X-ray photoelectron spectrum of the carboxylated activated carbon microspheres in Example 2.

[0055] Figure 6 The images show samples of pre-washing wastewater (left) and amine purification wastewater (right) from Example 2.

[0056] Figure 7 This is a sample image of the water from Example 2. Detailed Implementation

[0057] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0058] Example 1

[0059] This embodiment provides a wastewater reuse treatment system for the tail gas oxidation absorption process in a natural gas purification plant, such as... Figure 1 As shown, the system includes:

[0060] Neutralization tank 1, plate heat exchanger 2, aeration oxidation tower 3, adsorption tank 4, high-pressure reverse osmosis unit 5, negative pressure evaporation desalination unit 6, water quality conditioning tank 7, and drying and dehydration unit ( Figure 1 (not shown in the image);

[0061] The outlet of neutralization tank 1 is connected to the inlet of plate heat exchanger 2, the outlet of plate heat exchanger 2 is connected to the inlet of aerated oxidation tower 3, the outlet of aerated oxidation tower 3 is connected to the inlet of adsorption tank 4, the outlet of adsorption tank 4 is connected to the inlet of high-pressure reverse osmosis device 5, the concentrate outlet of high-pressure reverse osmosis device 5 is connected to the inlet of negative pressure evaporation desalination device 6, the inlet of water quality conditioning tank 7 is connected to the outlet of negative pressure evaporation desalination device 6 and the fresh water outlet of high-pressure reverse osmosis device 5 respectively, and the feed inlet of drying and dehydration device is connected to the crystallized salt outlet of negative pressure evaporation desalination device 6; neutralization tank 1 is equipped with a pre-washing wastewater inlet, an amine purification wastewater inlet, and a pH adjuster inlet.

[0062] Example 2

[0063] This embodiment provides a method for reusing and treating wastewater from the tail gas oxidation absorption process in a natural gas purification plant. The method uses the wastewater reuse and treatment system for the tail gas oxidation absorption process in a natural gas purification plant provided in Embodiment 1. The method includes:

[0064] Step 1: The pre-washing wastewater and amine purification wastewater generated by the tail gas oxidation absorption process of the natural gas purification plant are transported to neutralization storage tank 1. Under stirring conditions, alkaline solution is added to the wastewater in neutralization storage tank 1 to carry out a neutralization reaction and adjust the pH to 6.8 to obtain neutralized wastewater to be treated. The stirring speed is 80 r / min, the alkaline solution is a 30% NaOH sodium hydroxide solution, and the stirring time for the neutralization reaction is 20 min.

[0065] See water samples of pre-washing wastewater and amine purification wastewater. Figure 6 Water quality indicators are shown in Table 1;

[0066] Table 1

[0067]

[0068] Step 2: The neutralized wastewater is cooled to 25-35℃ using plate heat exchanger 2.

[0069] Step 3: The wastewater cooled in Step 2 is transported to the aeration oxidation tower 3 for aeration oxidation treatment to obtain aerated oxidized wastewater; wherein, the air blowing rate in the aeration oxidation tower 3 is 40L / min, and the residence time of the wastewater in the aeration oxidation tower 3 is 40min.

[0070] Step 4: The wastewater after aeration and oxidation is transported to adsorption tank 4 and treated with carboxylated activated carbon microspheres with a diameter of 400 μm for adsorption, resulting in adsorbed wastewater. The mass ratio of the carboxylated activated carbon microspheres to the volume of the aeration-oxidized wastewater is 2 (g:L), and the residence time of the wastewater in adsorption tank 4 is 40 min. A sample image of the carboxylated activated carbon microspheres is shown below. Figure 2 As shown, its full-scan X-ray photoelectron spectrum, high-resolution C1s X-ray photoelectron spectrum, and microsphere high-resolution O1s X-ray photoelectron spectrum are respectively as follows: Figure 3 , Figure 4 , Figure 5 As shown;

[0071] The carboxylated activated carbon microspheres were prepared by the following method: (1) Under nitrogen protection, polystyrene resin microspheres were heated to 300°C at a heating rate of 1.5°C / min and kept at that temperature for 1.5 h; then heated to 600°C at a heating rate of 2°C / min and kept at that temperature for 2 h; then heated to 800°C at a heating rate of 2°C / min and kept at that temperature for 1 h; and cooled to room temperature; (2) Nitrogen was replaced with carbon dioxide, and under carbon dioxide protection, the microspheres were heated to 850°C at a heating rate of 2°C / min and kept at that temperature for 15 min, and then cooled to room temperature to obtain activated carbon microspheres; (3) The obtained activated carbon microspheres were transferred to a reactor, 10% hydrogen peroxide was added to them at a dosage of 5 mL / g, and the mixture was stirred at 65°C for 2 h at a stirring rate of 100 r / min. Then the microspheres were washed three times with deionized water and finally dried at 100°C for 2 h to obtain carboxylated activated carbon microspheres.

[0072] Step 5: The adsorbed wastewater is transported to the high-pressure reverse osmosis unit 5 for reverse osmosis membrane treatment to obtain concentrated water and desalinated water; wherein, the operating temperature of the reverse osmosis membrane treatment is 30℃ and the operating pressure is 70Bar; wherein, the reverse osmosis membrane is a DTRO type aromatic polyamide reverse osmosis membrane, specifically the ST-5DTRO-P01 membrane purchased from Chengdu Shuote Technology Co., Ltd.

[0073] Step 6: The concentrated water is transported to the negative pressure evaporation desalination device 6 for evaporation desalination treatment to obtain crystalline salt and evaporation condensate; wherein, the operating temperature of the evaporation desalination treatment is 40℃ (heated by steam), the operating pressure is -85KPa, and the temperature of the circulating cooling water used to condense the steam to form evaporation condensate is 25-35℃.

[0074] Step 7: Dry and dehydrate the crystalline salt using a drying and dehydration device to obtain industrial sodium sulfate crystalline salt; wherein, the drying and dehydration temperature is 105℃;

[0075] The quality indicators of the obtained industrial sodium sulfate crystals are shown in Table 2, which meet the Class III standard for industrial sodium sulfate.

[0076] Table 2

[0077]

[0078] In Table 2, “—” indicates that the standard does not require it.

[0079] Step 8: After the evaporation condensate and fresh water are transported to the water quality equalization tank 7 for equalization, the resulting reclaimed water meets the standards for reuse and can be reused.

[0080] See the sample of the obtained reclaimed water. Figure 7 Water quality indicators are shown in Table 3.

[0081] Table 3

[0082]

[0083] In Table 3, “—” indicates that the standard does not require it.

[0084] As can be seen from the data in Table 2, the present invention can effectively remove various pollutants from the wastewater of the tail gas oxidation absorption process in natural gas purification plants, and can meet the reuse standards of the wastewater of the tail gas oxidation absorption process in natural gas purification plants. At the same time, as can be seen from the data in Table 3, the by-product crystalline salt can meet the requirements of Class III qualified industrial sodium sulfate.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for treating and reusing wastewater from the tail gas oxidation absorption process of a natural gas purification plant, wherein, The method includes: The pre-washing wastewater and amine purification wastewater generated from the tail gas oxidation and absorption process of the natural gas purification plant are neutralized to obtain neutralized wastewater to be treated; wherein, the neutralization process is achieved by mixing the pre-washing wastewater and amine purification wastewater and adjusting the pH value to 6-7. The neutralized wastewater to be treated is subjected to aeration oxidation treatment to obtain aeration oxidized wastewater. The wastewater after aeration and oxidation is treated with carboxylated activated carbon for adsorption to obtain the adsorbed wastewater. The adsorbed wastewater is then treated with a reverse osmosis membrane to obtain concentrated water and fresh water. The concentrated water is evaporated and desalted to obtain crystalline salt and evaporated condensate. The condensate from the evaporation is reused along with fresh water as greywater.

2. The method according to claim 1, wherein, Adjust the pH to 6-7 using sodium hydroxide.

3. The method according to claim 1, wherein, During the neutralization process, the wastewater is stirred at a speed of 50-100 r / min for 15-30 min.

4. The method according to claim 1, wherein, The method also includes: before the neutralized wastewater is subjected to aeration oxidation treatment, it is first cooled to 25-35℃.

5. The method according to claim 1, wherein, Aeration oxidation uses air aeration oxidation; The air injection rate for aeration oxidation is 30L / min-50L / min, and the aeration oxidation treatment time is 30min-60min.

6. The method according to claim 1, wherein, In the process of adsorption treatment of wastewater after aeration and oxidation using carboxylated activated carbon, carboxylated activated carbon microspheres with a diameter of 300-500μm are used. The ratio of the mass of carboxylated activated carbon microspheres to the volume of the wastewater after aeration and oxidation is 1-10 g:L, and the adsorption treatment time is 30-60 min.

7. The method according to claim 1 or 6, wherein, Carboxylated activated carbon microspheres were prepared by the following method: 1) Under nitrogen protection, the polystyrene resin microspheres are heated to the first target temperature and then cooled to room temperature; the first target temperature is 700-900℃. 2) Under carbon dioxide protection, the product obtained in step 1) is heated to the second target temperature and then cooled to room temperature to obtain activated carbon microspheres; wherein, the second target temperature is 750-950℃ and is higher than the first target temperature; 3) The prepared activated carbon microspheres were mixed with hydrogen peroxide and heated to react. The product after reaction was washed and dried to obtain carboxylated activated carbon microspheres.

8. The method according to claim 1, wherein, The reverse osmosis membrane is an aromatic polyamide reverse osmosis membrane.

9. The method according to claim 1, wherein, During the reverse osmosis membrane treatment of the adsorbed wastewater, the operating temperature of the reverse osmosis membrane is 25-35℃ and the operating pressure is 30-75 Bar.

10. The method according to claim 1, wherein, During the evaporation and desalination process of concentrated water, evaporation is carried out at a pressure of -80 to -90 kPa and a temperature of 35 to 55°C.

11. The method according to claim 1, wherein, The method also includes: dehydrating the crystalline salt to obtain anhydrous sodium sulfate crystalline salt.

12. A wastewater reuse and treatment system for the tail gas oxidation and absorption process of a natural gas purification plant, the system being used to implement the wastewater reuse and treatment method for the tail gas oxidation and absorption process of a natural gas purification plant as described in any one of claims 1-11, wherein... The system includes: Neutralization tank, aeration oxidation tower, adsorption tank, reverse osmosis unit, evaporation desalination unit and water quality conditioning tank; The outlet of the neutralization tank is connected to the inlet of the aeration oxidation tower, the outlet of the aeration oxidation tower is connected to the inlet of the adsorption tank, the outlet of the adsorption tank is connected to the inlet of the reverse osmosis unit, the concentrate outlet of the reverse osmosis unit is connected to the inlet of the evaporation desalination unit, and the inlet of the water quality conditioning tank is connected to the outlet of the evaporation desalination unit and the freshwater outlet of the reverse osmosis unit, respectively. The neutralization tank is equipped with a pre-washing wastewater inlet, an amine purification wastewater inlet, and a pH adjuster inlet.

13. The system according to claim 12, wherein, The system also includes a plate heat exchanger, which is installed on the connecting pipeline between the outlet of the neutralization tank and the inlet of the aeration oxidation tower.

14. The system according to claim 12, wherein, The system also includes a drying and dehydration device, the inlet of which is connected to the crystallization salt outlet of the evaporation and desalination device.

Images