CN111482087A - Low-temperature marine urea aqueous solution and preparation method thereof - Google Patents
Low-temperature marine urea aqueous solution and preparation method thereof Download PDFInfo
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- CN111482087A CN111482087A CN202010436820.0A CN202010436820A CN111482087A CN 111482087 A CN111482087 A CN 111482087A CN 202010436820 A CN202010436820 A CN 202010436820A CN 111482087 A CN111482087 A CN 111482087A
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
- B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
- B01D53/9404—Removing only nitrogen compounds
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Abstract
The invention discloses a low-temperature marine urea aqueous solution and a preparation method thereof, wherein the urea aqueous solution comprises 25-45% of urea solution, 10-30% of ammonium acetate and/or 1-10% of ammonium carbamate, and the balance is tertiary water for balancing the total mass fraction. The invention adds the low-temperature improver into the urea aqueous solution, and simultaneously optimizes the blending process, so that the freezing point of the urea aqueous solution for the ship is reduced from 2 ℃ to about-20 ℃, compared with the traditional urea reducing agent, the product obtained by the invention can be used in the environment of about-20 ℃, and the normal work of an SCR system is completely met.
Description
Technical Field
The invention relates to the technical field of reducing agents for purifying tail gas of marine diesel engines, in particular to a low-temperature marine urea aqueous solution and a preparation method thereof.
Background
The exhaust emission of ships is one of the important factors of air pollution. Particularly, in port cities, a large amount of carbon dioxide, carbon monoxide, nitrogen oxides, sulfur oxides and the like generated by ship emission seriously pollute the air and harm the health of residents in the port cities. To control ship pollution, the International Maritime Organization (IMO) regulates that three-stage (Tier iii) emission limits are implemented globally from 1/2016, according to which the emissions of nitrogen oxides are reduced by about 80% in one stage and about 75% in two stages. Including east coast of the united states, coastal canada, etc., have joined this Emission Control Area (ECA) where ship pollutant emission limits are enforced, and the mediterranean, tokyo bay, singapore, hong kong, korea, etc., are joining. At this time, the regional ship nitrogen oxide emission also needs to meet the requirement of the IMO Tier III emission limit, and a diesel engine tail gas purification device SCR (Selective catalytic reduction) system is additionally arranged, so that the method is undoubtedly a means for effectively reducing the emission, and the system currently needs to use urea as a reducing agent. Compared with the urea aqueous solution for vehicles, the urea aqueous solution for ships has larger demand, and the urea aqueous solution with higher concentration needs to be used to reduce the volume of the urea tank, so the urea aqueous solution with the mass fraction of 40wt% is generally adopted as the reducing agent.
However, the freezing point of the 40wt.% urea aqueous solution is 2 ℃, and for the storage and use of the ship in winter and the ship sailing in oceangoing in large latitude, the urea aqueous solution has the phenomena of poor fluidity and even solidification due to the high freezing point, so that the SCR system cannot work normally, and the urea tank and the conveying pipeline are burst, and other serious consequences. Some ships currently adopt a mode of arranging a heater near a urea tank to ensure the use temperature of urea for the situations, or storing solid urea on a ship and temporarily allocating urea aqueous solution when the solid urea is needed. However, these methods generally have the problems of additional equipment, inconvenient storage, additional workload on the crew, and the like.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a low-temperature marine urea aqueous solution to solve the problems that the existing marine urea has a high freezing point, is easy to generate poor fluidity and even solidification, so that an SCR (selective catalytic reduction) system cannot work normally when a ship sails in winter, and the existing marine urea is inconvenient to store and increases extra workload for sailors.
Further, the invention also provides a preparation method of the low-temperature marine urea aqueous solution, which solves the problems that the quality of the marine urea product prepared by the prior art is unstable and the freezing point of the marine urea product changes greatly when the marine urea product is stored for a long time.
In order to solve the technical problems, the invention adopts the following technical scheme:
the low-temperature marine urea aqueous solution is characterized by comprising the following raw materials in percentage by mass: 25-45% of urea solution, 10-30% of ammonium acetate and/or 1-10% of ammonium carbamate, and the balance of tertiary water for balancing the total mass fraction.
The invention improves the marine urea with the concentration of 40wt.%, and adds ammonium acetate to solve the problem of mutual dissolution of all components in the system. The ammonium carbamate is added, and after being dissolved in water, the ammonium carbamate can generate ammonium bicarbonate and ammonia hydrate, wherein the ammonium bicarbonate can generate decomposition reaction by heating to generate carbon dioxide, ammonia and water, so that nitrogen elements in a system can be supplemented. Meanwhile, the different proportions and concentrations of ammonium acetate and ammonium carbamate in the aqueous solution can affect the freezing point index of the marine urea solution, the higher the concentrations of the ammonium acetate and the ammonium carbamate are, the lower the freezing point of urea is, but the freezing points can be increased when the concentrations of the ammonium acetate and the ammonium carbamate reach a certain value. Therefore, the ratio and concentration of the two components need to be strictly controlled. The three-stage water is prepared by single distillation, deionization, ultrafiltration or reverse osmosis and meets the corresponding grade, namely, the three-stage water meets the definition of 3-stage water in ISO 3696 standard.
Further, the material comprises the following raw materials in percentage by mass: 30-35% of urea solution, 18-25% of ammonium acetate and/or 1-4% of ammonium carbamate, and the balance of tertiary water for balancing the total mass fraction.
Further, the material also comprises 0.1% -5% of glycol. The addition of the glycol in the invention enables the aqueous solution system to have a lower freezing point and be suitable for a wider environment temperature, and the glycol enables the storage performance of the urea aqueous solution system of the invention to be more stable compared with other low molecular alcohols, but the concentration is not too high, otherwise the product quality is unqualified.
Further, the material also comprises 3% -5% of glycol.
Further, the invention also provides a preparation method of the low-temperature marine urea aqueous solution, which comprises the following steps:
s1: heating the third-stage water, adding the weighed special urea, ammonium acetate and/or ammonium carbamate and glycol into the third-stage water for mixing, and stirring until the urea, ammonium acetate and/or ammonium carbamate and glycol are completely dissolved;
s2: and (5) preserving the heat of the solution obtained in the step (S1) to obtain a finished product.
Further, in the step S1, the tertiary water is heated to 30-35 ℃, and the temperature of the mixture until the dissolution process is kept at 30-35 ℃.
Further, the heat preservation time in step S2 is 1-1.5 hours.
On the basis of the prior art, the invention improves the water temperature when the product is prepared, and needs to be kept warm for a period of time, and mainly aims to ensure that the product quality is more stable through the process, particularly the freezing point can be further reduced, so that the index of the freezing point changes less in the storage process.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention reduces the freezing point of the marine urea aqueous solution from 2 ℃ to about-20 ℃ by adding the low-temperature improver into the urea aqueous solution and optimizing the preparation process. Compared with the traditional urea reducing agent, the product obtained by the invention can be used in the environment of about-20 ℃, and the normal work of an SCR system is completely met.
2. The invention improves the preparation method of the marine urea to a certain extent, improves the quality of the product by improving the water temperature during product preparation and carrying out heat preservation operation for a certain time, and ensures that the product is more stable, especially can further reduce the freezing point, and the index of the freezing point changes less in the storage process.
3. The marine urea provided by the invention is more convenient to store and use, the urea cabin is not required to be additionally improved, the product quality is more stable, extra workload cannot be added to crews in use, the freezing point cannot be greatly changed in the long-time storage process, and the marine urea is more suitable for long-time sailing of ships.
Detailed Description
The present invention will be further described with reference to the following examples.
A low-temperature marine urea aqueous solution is prepared from the following raw materials in parts by weight: 25-45% of urea solution, 10-30% of ammonium acetate and/or 1-10% of ammonium carbamate, and the balance of tertiary water for balancing the total mass fraction. In the present invention, ammonium acetate, ammonium carbamate and ethylene glycol all meet the chemical purity and above grade.
TABLE 1 (unit: wt%)
| Examples | Urea solution | Ammonium acetate | Ammonium carbamate | Ethylene glycol | Three-stage water | Freezing point | Others |
| 1 | 33% | 18% | 1% | 1% | 47% | -16℃ | Freezing points for 10 days, 20 days and 30 days of storage are respectively as follows: 16 ℃ below zero, -14 ℃ below zero, -16 ℃ below zero |
| 2 | 35% | 24% | 2% | 1% | 38% | -20℃ | Freezing points for 10 days, 20 days and 30 days of storage are respectively as follows: 22 ℃ below zero, 18 ℃ below zero and 19 ℃ below zero |
| 3 | 28% | 31% | 0 | 0.5% | 40.5% | -22℃ | Freezing points for 10 days, 20 days and 30 days of storage are respectively as follows: -20 ℃, -19 ℃, -20 ℃ |
| Comparative example 1 | 40.5% | 0 | 0 | 0 | 59.5% | 2℃ | Guangzhou company |
| Comparative example 2 | 41% | 0 | 0 | 0 | 59% | 3℃ | Beijing Corp Ltd |
Wherein the urea adopts AUS32 special urea (the mass fraction of urea in the solution is 32.5 percent and 67.5 percent of deionized water), the ammonium acetate adopts the chemical purity and above grade, the ammonium carbamate adopts the chemical purity and above grade, and the ethylene glycol adopts the chemical purity and above grade. The tertiary water is water which is prepared by single distillation, deionization, ultrafiltration or reverse osmosis and meets the corresponding grade, namely 3-grade water meeting the ISO 3696 standard.
Second, preparation method of low-temperature marine urea aqueous solution
Example 1:
s1: heating the third-stage water to 35 ℃, adding the weighed special urea, ammonium acetate, ammonium carbamate and glycol into the third-stage water according to the embodiment 1, and stirring until the special urea, the ammonium acetate, the ammonium carbamate and the glycol are completely dissolved;
s2: and (5) preserving the heat of the solution obtained in the step S1 for 1h to obtain a finished product.
Since the dissolution of urea in water is an endothermic reaction, the actual blending process is carried out in a temperature-controllable heating reactor for precise temperature control. And detecting the freezing point of the prepared urea aqueous solution, wherein the freezing point is-16 ℃. And the obtained low-temperature marine urea aqueous solution meets the product performance quality requirements of GB/T35176.1-2017 ships and the 1 st part of the marine technology ship nitrogen oxide reducing agent AUS 40.
At present, two production methods are available for the marine urea solution, one is that the marine urea solution is produced according to the production method of the vehicle urea solution, and the marine urea solution is directly filled and used after being purchased by a user; the other is to store the solid urea on board the ship for use by crew on-site on board the ship. In the research on the urea solution product for the vehicle, the phenomena of large freezing point change and unstable product quality exist in the storage process of the low-freezing-point product. The marine urea freezing point product prepared by the method has small change of the freezing point and stable product quality.
The comparative examples 1 and 2 are marine urea solutions commonly used in the current market, are prepared according to a production method of the marine urea solutions, and are directly added for use after purchase. Through comparison, the freezing point of the marine urea prepared by the invention is far lower than that of comparative examples 1 and 2, the product quality is more stable, and the marine urea can be well suitable for long-time sailing of ships.
Wherein the freezing point is measured by an engine coolant freezing point measuring method SH-T0090-1991 (2000).
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.
Claims (7)
1. The low-temperature marine urea aqueous solution is characterized by comprising the following raw materials in percentage by mass: 25-45% of urea solution, 10-30% of ammonium acetate and/or 1-10% of ammonium carbamate, and the balance of tertiary water for balancing the total mass fraction.
2. The low-temperature marine urea aqueous solution according to claim 1, comprising the following raw materials in percentage by mass: 30-35% of urea solution, 18-25% of ammonium acetate and/or 1-4% of ammonium carbamate, and the balance of tertiary water for balancing the total mass fraction.
3. The low-temperature marine urea aqueous solution according to claim 1, further comprising 0.1% -5% of ethylene glycol.
4. The low-temperature marine urea aqueous solution according to claim 3, further comprising 3-5% of ethylene glycol.
5. A method for preparing a low-temperature marine urea aqueous solution, which is characterized by comprising the following steps of:
s1: heating the third-stage water, adding the weighed special urea, ammonium acetate and/or ammonium carbamate and glycol into the third-stage water for mixing, and stirring until the urea, ammonium acetate and/or ammonium carbamate and glycol are completely dissolved;
s2: and (5) preserving the heat of the solution obtained in the step (S1) to obtain a finished product.
6. The method for preparing a low-temperature marine urea aqueous solution according to claim 5, wherein the tertiary water is heated to 30 to 35 ℃ in step S1, and the temperature of the mixing until the dissolution process is maintained at 30 to 35 ℃.
7. The method for preparing a low-temperature marine urea aqueous solution according to claim 5, wherein the temperature maintaining time in step S2 is 1-1.5 hours.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114478322A (en) * | 2021-12-30 | 2022-05-13 | 江苏艾德露环保科技有限公司 | Anti-crystallizing agent of urea solution for vehicle and preparation method thereof |
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| CN104128090A (en) * | 2014-08-03 | 2014-11-05 | 长春市永畅实业有限责任公司 | Reducing agent satisfying low temperature removal of nitrogen oxides of vehicles |
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| CN107587922A (en) * | 2017-10-13 | 2018-01-16 | 锦西天然气化工有限责任公司 | A kind of ultralow temperature urea for vehicle solution and preparation method thereof |
| CN108619907A (en) * | 2018-04-28 | 2018-10-09 | 南京工业大学 | A kind of urea for vehicle reducing agent solution |
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- 2020-05-21 CN CN202010436820.0A patent/CN111482087A/en active Pending
Patent Citations (6)
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| JP2009035644A (en) * | 2007-08-02 | 2009-02-19 | Denso Corp | Antifreeze urea solution for urea selective catalytic reduction (scr) system and urea scr system |
| CN102895874A (en) * | 2011-07-29 | 2013-01-30 | 迪尔公司 | Diesel exhaust fluid formulation having a high ammonium content and a low freezing point |
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| CN114478322A (en) * | 2021-12-30 | 2022-05-13 | 江苏艾德露环保科技有限公司 | Anti-crystallizing agent of urea solution for vehicle and preparation method thereof |
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Application publication date: 20200804 |