CN112090221A - Method for purifying raw gas for ammonia synthesis and ammonia synthesis process based on method - Google Patents
Method for purifying raw gas for ammonia synthesis and ammonia synthesis process based on method Download PDFInfo
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- CN112090221A CN112090221A CN202010815062.3A CN202010815062A CN112090221A CN 112090221 A CN112090221 A CN 112090221A CN 202010815062 A CN202010815062 A CN 202010815062A CN 112090221 A CN112090221 A CN 112090221A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- 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
- B01D53/14—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 by absorption
- B01D53/1456—Removing acid components
- B01D53/1481—Removing sulfur dioxide or sulfur trioxide
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/025—Preparation or purification of gas mixtures for ammonia synthesis
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
- C01B3/56—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/30—Sulfur compounds
- B01D2257/302—Sulfur oxides
Abstract
The invention relates to the technical field of synthetic ammonia, in particular to a method for purifying raw material gas for synthetic ammonia, which comprises the following steps: 1) enabling the sulfur-free methanol-rich liquid at the outlet of the methanol washing tower to pass through a sulfur-free flash evaporation tank to obtain sulfur-free flash evaporation steam I; 2) enabling sulfur-containing methanol-rich liquid at the outlet of the methanol washing tower to pass through a sulfur-containing flash evaporation tank to obtain sulfur-containing flash evaporation steam, enabling the sulfur-containing flash evaporation steam to enter a washing section for desulfurization, and then carrying out deep desulfurization on the sulfur-free flash evaporation steam by using a desulfurizing agent to obtain sulfur-free flash evaporation steam II; 3) the sulfur-free flash steam I and the sulfur-free flash steam II are converged and then enter a fuel gas header pipe to enter the next processAnd (4) section. The sulfur content in the flash steam without sulfur can be reduced to be not higher than 0.05mg/Nm after the modified silica gel is subjected to deep desulfurization3The method avoids the situation that the production safety is possibly endangered due to the existence of sulfide in the subsequent working section, and obviously reduces the total energy consumption and the total investment cost of the operation of the synthetic ammonia system in the prior art.
Description
Technical Field
The invention relates to the technical field of synthetic ammonia production, in particular to a synthetic ammonia raw material gas purification method and a synthetic ammonia process based on the same.
Background
The synthetic ammonia refers to ammonia directly synthesized by nitrogen and hydrogen under high temperature and high pressure and in the presence of a catalyst, and is a basic inorganic chemical process. In the modern chemical industry, ammonia is the main raw material for the fertilizer industry and for basic organic chemicals. The synthetic ammonia industry was developed in the early 20 th century, ammonia was used as a raw material in the explosive industry for war service, and after world war for the first time, the industry was turned to agricultural and industrial service. With the development of scientific technology, the demand of ammonia is increasing.
In the production of synthetic ammonia, the raw material gas is firstly desulfurized and decarbonized to obtain the nitrogen-hydrogen mixed gasDirectly synthesizing ammonia under the conditions of high temperature and high pressure and in the presence of a catalyst. The sulfur in the raw material gas for synthesizing ammonia is present in different forms of sulfide, and the raw material gas of semi-water gas generally contains 0.6g/Nm3The presence of the above hydrogen sulfide and organic sulfide, is liable to cause catalyst poisoning in the production of methanol and synthetic ammonia, causing metal corrosion, blocking equipment and pipelines and affecting product quality. In the purification of raw gas for producing synthetic ammonia, the methanol washing process is a common desulfurization and decarburization process, in the conventional design, sulfur-containing methanol-rich liquid and sulfur-free methanol-rich liquid at the outlet of a methanol washing tower are respectively subjected to flash evaporation through a flash evaporation tank, and the main components of flash evaporation gas are carbon dioxide and hydrogen. The two flash evaporation gases are combined and then sent to a circulating compressor for pressurization and then recovered by a methanol-removing raw material gas washing system. The operation has the problems that the load of decarburization is increased in the system circulation by the flash evaporation gas taking carbon dioxide as the main component, and the circulating compressor always works, so that a large amount of electric energy is consumed, and the energy conservation and consumption reduction of the production of synthetic ammonia are not facilitated (figure 1).
The above background disclosure is only for the purpose of assisting understanding of the inventive concept and technical solutions of the present invention, and does not necessarily belong to the prior art of the present patent application, and should not be used for evaluating the novelty and inventive step of the present application in the case that there is no clear evidence that the above content is disclosed at the filing date of the present patent application.
Disclosure of Invention
In view of the above, one of the objectives of the present invention is to provide a method for purifying raw material gas for ammonia synthesis, which significantly reduces the total energy consumption and total investment cost of the operation of the ammonia synthesis system in the prior art, reduces the nitrogen addition amount in the coal grinding system, and reduces the consumption of nitrogen in the production, and the sulfur content in the sulfur-free flash steam can be reduced to not more than 0.05mg/Nm after deep desulfurization is performed on the modified silica gel of the present invention3The situation that the production safety is possibly endangered due to the existence of sulfide in the subsequent working section is greatly avoided.
The invention also aims to provide a synthetic ammonia process, which has the advantages of simple process flow, fewer high-temperature and high-pressure working sections, easy operation and management, lower process flow operation cost, easy maintenance, less waste water and waste gas discharge, low energy consumption and easy large-scale popularization and application.
In order to achieve the above object, the present invention provides the following technical solutions.
[1] A method for purifying raw gas for synthesizing ammonia comprises the following steps:
1) enabling the sulfur-free methanol-rich liquid at the outlet of the methanol washing tower to pass through a sulfur-free flash evaporation tank to obtain sulfur-free flash evaporation steam I;
2) enabling sulfur-containing methanol-rich liquid at the outlet of the methanol washing tower to pass through a sulfur-containing flash evaporation tank to obtain sulfur-containing flash evaporation steam, and enabling the sulfur-containing flash evaporation steam to enter a washing section for desulfurization to obtain sulfur-free flash evaporation steam II;
3) the sulfur-free flash steam I and the sulfur-free flash steam II are converged and then enter a fuel gas main pipe and enter the next working section;
the washing section uses methanol liquid without sulfur as washing liquid.
In some preferred embodiments of the invention, the washing-stage desulfurization is carried out so that the sulfur content in the sulfur-free flash steam II is less than a preset content threshold value of 10mg/Nm3And collecting sulfur-containing liquid and crystallizing.
In some preferred embodiments of the present invention, the sulfur-containing liquid comprises sodium thiosulfate and ammonium sulfate, which are introduced into a sodium thiosulfate crystallizer, and vacuum evaporation is performed after the solution is full, wherein the vacuum degree is 0.094-0.096 MPa, the vacuum evaporation temperature is 55-65 ℃, and the evaporation is performed until the solution density is 1290kg/m3And extracting crystals when the volume ratio of the crystal liquid is 45-48%.
In the method, on the basis that the original sulfur-containing and sulfur-free methanol-rich liquid is respectively subjected to flash evaporation by a flash evaporation tank, is combined and then is pressurized by a circulating compressor and then is recycled by a methanol-removing washing raw material gas system, the rear section of the flash evaporation tank of the sulfur-containing methanol-rich liquid is added into a washing section, and the sulfur-free methanol liquid is used as the washing liquid to desulfurize the sulfur-containing flash steam, so that the flash steam at the outlet of the sulfur-free flash tank is ensured not to contain sulfur, the two flash steam flows are converged and enter the next working section without decarburization, the load of methanol decarburization is reduced, in addition, the method of the invention does not need to utilize a circulating compressor to pressurize and apply work to convey the flash steam to a methanol washing raw material gas system, thereby reducing the power consumption and investment cost of the device, ensuring that the flash steam entering the fuel gas main pipe does not contain sulfur or has extremely low sulfur, and ensuring that the fuel gas does not cause the new environmental pollution problems of standard exceeding of sulfur dioxide and the like after being used. The conventional design of the fuel gas main pipe is that the pressure of gas with about 3.0MPa is reduced to 0.4MPa of the fuel gas main pipe, but the pressure of flash gas in the method is about 1.0MPa, and the flash gas can be directly sent into the fuel gas main pipe, thereby avoiding the problem of pressure reduction and utilization of the original high-pressure gas and reducing the total energy consumption of the operation of the synthetic ammonia system.
In some preferred embodiments of the present invention, the desulfurization of the washing section in step 2) of the purification method of the synthesis ammonia raw material gas further comprises deep desulfurization of the sulfur-free flash steam with a desulfurizing agent, wherein the desulfurizing agent is a silica gel desulfurizing agent modified by dinitrosalicylic acid.
In other preferred embodiments of the present invention, the desulfurizing agent is prepared in particular by a process comprising the steps of:
1) refluxing and activating silica gel with the particle size not higher than 100 mu m by using 8-10 mol/L hydrochloric acid, and completely drying after washing to be neutral;
2) mixing the silica gel, an amination reagent and toluene according to a weight-volume ratio of 1g: 1.0-1.5 mL: 15-20 mL, refluxing and stirring at 70-75 ℃ for at least 12h, leaching and washing with toluene, ethanol and diethyl ether in sequence after the reaction is finished, and drying in vacuum to obtain the amination silica gel;
3) adding the silicon amide glue obtained in the step 2) and 3, 5-dinitrosalicylic acid and N, N-dicyclohexyl diimine into sufficient tetrahydrofuran according to the weight ratio of 1: 0.05-0.06: 0.1-0.12, and reacting at room temperature for at least 24 hours under stirring;
4) and 3) leaching and washing the product obtained in the step 3) by using 4-6 mol/L hydrochloric acid and deionized water in sequence until the difference between the absorbance of the eluate and the absorbance of a blank detergent is lower than 0.5%, and drying in vacuum to obtain the detergent.
In other preferred embodiments of the present invention, in the step 1) of preparing the desulfurizing agent, thorough drying means drying in a drying oven at 110 to 120 ℃ for not less than 12 hours.
In other preferred embodiments of the inventionIn the step 2) of preparing the desulfurizing agent, the amination reagent is gamma-aminopropyltriethoxysilane and (3-mercaptopropyl) triethoxysilane in a weight ratio of 2.5-3.0: 1. The inventor surprisingly found that the silica gel is modified by 3, 5-dinitrosalicylic acid after the amination reaction is carried out on the silica gel by using the silane coupling agent with the special proportion, the obtained modified silica gel can deeply remove sulfur compounds in flash steam, and the sulfur content in the flash steam without sulfur is reduced to be not higher than 0.05mg/Nm3The deep desulfurization section of the silica gel desulfurizer can endow the purification process with excellent desulfurization performance, which is far superior to the prior art.
The structural formulas of the gamma-aminopropyltriethoxysilane and the (3-mercaptopropyl) triethoxysilane are respectively shown as the following formulas (1) and (2):
in other preferred embodiments of the present invention, in the step 2) of preparing the desulfurizing agent, vacuum drying means vacuum drying at a temperature of 80 to 90 ℃ for at least 24 hours.
In other preferred embodiments of the present invention, in step 3) of preparing the desulfurizing agent, the stirring rate is not less than 600 r/min.
In other preferred embodiments of the present invention, in step 3) of preparing the desulfurizing agent, room temperature means 25 ± 1 ℃.
In other preferred embodiments of the present invention, in the step 4) of preparing the desulfurizing agent, vacuum drying means vacuum drying at 25 to 35 ℃ to a constant weight.
In the method, firstly, the silica gel acid is activated and then aminated, and then the aminated silica gel is modified by dinitrosalicylic acid, so that the prepared silica gel desulfurizer can be used in the section of the purification method of the raw material gas for ammonia synthesis in the application, and sulfur in flash steam which does not contain sulfur and is desulfurized in a washing section can be added into the flash steam which does not contain sulfurThe amount is reduced to not more than 0.05mg/Nm3The deep desulfurization section of the silica gel desulfurizer can endow the purification process with excellent desulfurization performance, which is far superior to the prior art, thereby greatly avoiding the occurrence of the conditions of influencing the product yield and quality and the like in the production of methanol and synthetic ammonia, such as catalyst poisoning, metal corrosion, equipment and pipeline blockage and the like possibly caused by the existence of sulfides in the subsequent section, and ensuring the safe production.
In some preferred embodiments of the invention, the next section comprises a flare pilot lamp, a coal grinding system, or a synthetic ammonia feed gas treatment process. In the process of using the gas in the fuel gas main pipe in the coal grinding procedure, in order to ensure the production safety, inert gas nitrogen is required to be added, but the feed gas treated by the method of the invention contains a large amount of inert gas carbon dioxide, so the adding amount of nitrogen in a coal grinding system can be obviously reduced, and the consumption of nitrogen in production is reduced.
[2] A process for synthesizing ammonia, which comprises decarbonizing the raw material gas treated by the purification method in item [1] and then synthesizing ammonia.
In some preferred embodiments of the invention, the ammonia synthesis process comprises:
1) the raw material gas treated by the purification method in the item [1] enters a coke filter and an oil remover for oil-gas separation treatment, and then is transformed by adopting a medium-temperature-low-temperature three-section transformation process with a saturated hot water tower;
2) step 1), sending the gas into a first-stage pressure swing adsorption tower for decarburization, and then sending the gas into a second-stage pressure swing adsorption tower for obtaining hydrogen;
3) supplementing nitrogen into the purified hydrogen in the step 2), and compressing to 10-15 MPa to synthesize ammonia to obtain ammonia with the purity not lower than 99.5% in weight percentage.
In other preferred embodiments of the present invention, the medium temperature in the medium-temperature-low-temperature three-stage conversion process in step 1) of the ammonia synthesis process is 400 to 550 ℃, and the low temperature is 200 to 250 ℃.
In other preferred embodiments of the present invention, the compression in step 3) of the ammonia synthesis process may be performed by a reciprocating compressor or a centrifugal compressor.
The method comprises the steps of washing and desulfurizing the raw material gas by using a sulfur-free methanol solution, deeply desulfurizing by using a dinitrosalicylic acid modified silica gel desulfurizing agent, and then synthesizing ammonia with nitrogen after decarburization to obtain the ammonia with higher purity.
The invention has the beneficial effects that:
1) the method reduces the load of methanol washing decarburization, and because the method does not need to utilize a circulating compressor to pressurize and do work to convey the flash steam to a methanol washing raw material gas system, the power consumption and the investment cost of the device are reduced, the flash steam entering a fuel gas main pipe does not contain sulfur or contains extremely low sulfur, and the fuel gas is ensured not to cause the new environmental pollution problems of over standard sulfur dioxide and the like after being used;
2) the conventional design of the fuel gas main pipe is that the gas with about 3.0MPa is decompressed to 0.4MPa of the fuel gas main pipe, but the pressure of flash gas in the method is about 1.0MPa, and the flash gas can be directly sent into the fuel gas main pipe, thereby avoiding the problem of decompression utilization of the original high-pressure gas and reducing the total energy consumption of the operation of the synthetic ammonia system;
3) in order to ensure the production safety in the use of the gas of the fuel gas header pipe in the coal grinding process, inert gas nitrogen is required to be added, but the process contains a large amount of inert gas carbon dioxide, so that the adding amount of the nitrogen in a coal grinding system can be reduced, and the consumption of the nitrogen in the production is reduced;
4) the inventor finds that the silicon amide gel modified by dinitrosalicylic acid is used in the section of the purification method of the raw material gas for synthesizing ammonia in the application, and can reduce the sulfur content in the flash steam without sulfur after being desulfurized in the washing section to be not higher than 0.05mg/Nm3The deep desulfurization section of the silica gel desulfurizer can endow the purification process with excellent desulfurization performance which is far superior to the prior art, and greatly avoids catalyst poisoning, metal corrosion, equipment and pipelines in the production of methanol and synthetic ammonia possibly caused by the existence of sulfide in the subsequent sectionThe occurrence of conditions such as blockage and the like which influence the yield and the quality of products ensures safe production;
5) the process flow for synthesizing ammonia is simple, the number of high-temperature and high-pressure working sections is small, the operation and management are easy, the operation cost of the process flow is low, the maintenance is facilitated, the discharge of waste water and waste gas is small, the energy consumption is reduced, and the large-scale popularization and application are facilitated.
The invention adopts the technical scheme for achieving the purpose, makes up the defects of the prior art, and has reasonable design and convenient operation.
Drawings
The foregoing and/or other objects, features, advantages and embodiments of the invention will be more readily understood from the following description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic diagram of purification of a conventional ammonia synthesis feed gas according to the background of the invention;
FIG. 2 is a schematic diagram of the purification of a feed gas for ammonia synthesis according to the present invention;
FIG. 3 is a schematic diagram of another purification of a feed gas for ammonia synthesis according to the present invention;
FIG. 4 is a structural formula of gamma-aminopropyltriethoxysilane according to the present invention;
FIG. 5 shows the structural formula of (3-mercaptopropyl) triethoxysilane according to the present invention.
Description of reference numerals: 1. a sulfur-free methanol-rich liquid; 2. a sulfur-free flash tank; 3. sulfur-containing methanol-rich liquid; 4. a sulfur-containing flash tank; 5. a recycle compressor; 6. the next working section; 7. a washing section; 8. and (4) deep desulfurization.
Detailed Description
Those skilled in the art can appropriately substitute and/or modify the process parameters to implement the present disclosure, but it is specifically noted that all similar substitutes and/or modifications will be apparent to those skilled in the art and are deemed to be included in the present invention. While the products and methods of making described herein have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the products and methods of making described herein may be made and utilized without departing from the spirit and scope of the invention.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The present invention uses the methods and materials described herein; other suitable methods and materials known in the art may be used. The materials, methods, and examples described herein are illustrative only and are not intended to be limiting. All publications, patent applications, patents, provisional applications, database entries, and other references mentioned herein, and the like, are incorporated by reference herein in their entirety. In case of conflict, the present specification, including definitions, will control.
All percentages, parts, ratios, etc., are by weight unless otherwise indicated; additional instructions include, but are not limited to, "wt%" means weight percent, "mol%" means mole percent, "vol%" means volume percent.
When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5(1 to 5)" is described, the described range is understood to include ranges of "1 to 4(1 to 4)", "1 to 3(1 to 3)", "1 to 2(1 to 2) and 4 to 5(4 to 5)", "1 to 3(1 to 3) and 5", and the like. Where numerical ranges are described herein, unless otherwise stated, the ranges are intended to include the endpoints of the ranges, and all integers and fractions within the ranges.
When the term "about" is used to describe a numerical value or an end point value of a range, the disclosure should be understood to include the specific value or end point referred to.
Furthermore, "or" means "or" unless expressly indicated to the contrary, rather than "or" exclusively. For example, condition a "or" B "applies to any of the following conditions: a is true (or present) and B is false (or not present), a is false (or not present) and B is true (or present), and both a and B are true (or present).
In addition, the indefinite articles "a" and "an" preceding an element or component of the invention are intended to mean no limitation on the number of occurrences (i.e., occurrences) of the element or component. Thus, "a" or "an" should be understood to include one or at least one and the singular forms of an element or component also include the plural unless the singular is explicitly stated.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation. The use of the phrase "comprising one of the elements does not exclude the presence of other like elements in the process, method, article, or apparatus that comprises the element.
The materials, methods, and examples described herein are illustrative only and not intended to be limiting unless otherwise specified. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.
The present invention is described in detail below.
Example 1: a method for purifying raw material gas for ammonia synthesis comprises the following steps:
as shown in fig. 1, the present embodiment provides a method for purifying raw material gas for ammonia synthesis, which specifically includes the following steps:
1) enabling the sulfur-free methanol-rich liquid at the outlet of the methanol washing tower to pass through a sulfur-free flash evaporation tank to obtain sulfur-free flash evaporation steam I;
2) the sulfur-containing methanol-rich liquid at the outlet of the methanol washing tower firstly passes through a sulfur-containing flash evaporation tank to obtain sulfur-containing flash evaporation steam, the sulfur-containing flash evaporation steam enters a washing section which takes the sulfur-free methanol liquid as washing liquid for desulfurization, and the sulfur content is obtained to be less than 10mg/Nm threshold value3The flash steam II without sulfur;
3) and the sulfur-free flash steam I and the sulfur-free flash steam II are converged and then enter a fuel gas header pipe to enter the next working section.
Example 2: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
as shown in fig. 2, this embodiment provides another method for purifying raw gas for ammonia synthesis, which specifically includes the following steps:
1) enabling the sulfur-free methanol-rich liquid at the outlet of the methanol washing tower to pass through a sulfur-free flash evaporation tank to obtain sulfur-free flash evaporation steam I;
2) the sulfur-containing methanol-rich liquid at the outlet of the methanol washing tower firstly passes through a sulfur-containing flash evaporation tank to obtain sulfur-containing flash evaporation steam, the sulfur-containing flash evaporation steam enters a washing section which takes the sulfur-free methanol liquid as washing liquid for desulfurization, and the sulfur content is obtained to be less than 10mg/Nm threshold value3Then deeply desulfurizing by using a desulfurizing agent to obtain sulfur-free flash steam II;
3) and the sulfur-free flash steam I and the sulfur-free flash steam II are converged and then enter a fuel gas header pipe to enter the next working section.
In this embodiment, the desulfurizing agent is a silica gel desulfurizing agent modified by dinitrosalicylic acid, and is specifically prepared by a method including the following steps:
a) refluxing and activating silica gel with the particle size of 80 mu m by using 10mol/L hydrochloric acid, cleaning to be neutral, and completely drying in a drying oven at 120 ℃ for 24 hours;
b) compounding gamma-aminopropyltriethoxysilane and (3-mercaptopropyl) triethoxysilane as amination reagents according to the mass ratio of 3:1, mixing the silica gel, the amination reagents and toluene according to the weight volume ratio of 1g:1.2mL:20mL, refluxing and stirring for 15h at 75 ℃, leaching and washing with toluene, ethanol and diethyl ether in sequence after the reaction is finished, and drying in vacuum to obtain the aminated silica gel;
c) adding the silicon amide glue obtained in the step b), 3, 5-dinitrosalicylic acid and N, N-dicyclohexyldiimine into sufficient tetrahydrofuran according to the weight ratio of 1:0.06:0.12, and reacting for 36 hours at room temperature under stirring;
d) and c) leaching and washing the product obtained in the step c) by using 5mol/L hydrochloric acid and deionized water in sequence until the difference between the absorbance of the washing liquid and the absorbance of a blank detergent is lower than 0.5%, and drying in vacuum to obtain the detergent.
Example 3: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another method for purifying a feed gas for synthesis of ammonia, which comprises the same steps as those in example 2, except that silica gel particles having a particle size of 80 μm are subjected to deep desulfurization without any modification.
Example 4: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another process for purifying a feed gas for synthesis of ammonia, which comprises the same steps as those in example 2, except that in this example, the desulfurizing agent is subjected to deep desulfurization without performing steps c) and d).
Example 5: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another process for purifying a feed gas for synthesis of ammonia, which comprises the same steps as those of example 2 except that 3, 5-dinitrosalicylic acid is not added in step c) of preparing the desulfurizing agent.
Example 6: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another process for purifying a feed gas for synthesis of ammonia, which comprises the same steps as those in example 2 except that 3-amino-5-nitrosalicylic acid is used instead of 3, 5-dinitrosalicylic acid in step c) of preparing the desulfurizing agent.
Example 7: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another process for purifying a feed gas for synthesis of ammonia, which comprises the same steps as those in example 2, except that in this example, salicylic acid is used instead of 3, 5-dinitrosalicylic acid in step c) of preparing the desulfurizing agent.
Example 8: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another purification method of raw material gas for synthesis of ammonia, which comprises the same steps as those of example 2, except that in step b) of preparing the desulfurizing agent, the amination reagent is gamma-aminopropyltriethoxysilane and (3-mercaptopropyl) triethoxysilane at a mass ratio of 1: 1.
Example 9: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another purification method of raw material gas for synthesis of ammonia, which comprises the same steps as those in example 2, except that in step b) of preparing the desulfurizing agent, the amination reagent is gamma-aminopropyltriethoxysilane and (3-mercaptopropyl) triethoxysilane at a mass ratio of 5: 1.
Example 10: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another purification method of raw material gas for ammonia synthesis, which comprises the same steps as those of example 2, except that in step b) of preparing the desulfurizing agent, the amination reagent is gamma-aminopropyltriethoxysilane and (3-mercaptopropyl) triethoxysilane at a mass ratio of 2.5: 1.
Example 11: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another purification method for raw gas for ammonia synthesis, which comprises the same steps as those in example 2, except that in step b) of preparing the desulfurizing agent, the amination reagent is gamma-aminopropyl triethoxysilane, i.e. the amination reagent does not contain (3-mercaptopropyl) triethoxysilane.
Example 12: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another purification method of raw material gas for synthesis of ammonia, which comprises the same steps as those in example 2, except that in step b) of preparing the desulfurizing agent, the amination reagent is gamma-aminopropyltriethoxysilane and vinyltriethoxysilane at a mass ratio of 3: 1.
Example 13: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another method for purifying a feed gas for synthesis of ammonia, which comprises the following steps substantially the same as example 2, except that in step b) of preparing the desulfurizing agent, the following silane coupling agents are used in a weight ratio of 1:1 in place of the amination reagent:
silane coupling agent a:
silane coupling agent B:
example 14: the other method for purifying the raw material gas for synthesizing ammonia comprises the following steps:
this example provides another method for purifying a feed gas for synthesis of ammonia, which comprises the following steps, except that in this example, the desulfurizing agent is prepared by the following steps:
a) soaking silica gel with the particle size of 80 mu m in sufficient tetrahydrofuran, and polarizing for 4 hours at the temperature of 70 ℃ at 120 r/min;
b) drying the polarized silica gel in the step a) for 1h at the temperature of 100 ℃ in a nitrogen atmosphere with the purity of more than 99%;
c) the dried silica gel in the step B) is placed in the silane coupling agent A and the silane coupling agent B with the weight ratio of 1:1 in the embodiment 13, and is modified for 3 hours at the temperature of 70 ℃ at the speed of 120 r/min;
d) and c) drying the modified silica gel in the step c) for 3 hours at the temperature of 100 ℃ in a nitrogen atmosphere with the purity of more than 99 percent to obtain the desulfurizer.
Experimental example 1: and (3) measuring the sulfur content:
the sulfur content of the sulfur-containing flash steam and the sulfur content of the sulfur-free flash steam II in each of the ammonia synthesis raw materials of examples 1 to 14 were measured, and the measurement results are shown in table 1.
TABLE 1 sulphur content
As can be seen from the above table, in the embodiment 1 of the present application, after the sulfur-containing flash steam is washed and desulfurized by using the sulfur-free methanol solution as the washing solution, more than 98.6% of sulfur can be removed, and the desulfurization effect is significant; as a further improvement to the embodiment 1, the preferable embodiments 2 and 10 in the application can further reduce the sulfur content in flash steam to not more than 0.5mg/Nm due to the addition of a dinitrosalicylic acid modified silica gel deep desulfurization section3Endows the purification process with excellent desulfurization performance which is far superior to the prior art. In example 3, silica gel particles were not aminated, aminated silica gel was not modified with dinitrosalicylic acid in example 4, 3, 5-dinitrosalicylic acid was not added in example 5, and salicylic acid was used in place of 3, 5-dinitrosalicylic acid in example 7, the ratio of the amination reagent was changed in examples 8 and 9, and the composition of the amination reagent was changed in examples 11 and 12, all of which significantly affect the desulfurization effect in the deep desulfurization stage, and it is particularly noted that the aminated silica gel was modified with 3-amino-5-nitrosalicylic acid in example 6, and the desulfurization effect was substantially the same as that of 3, 5-dinitrosalicylic acid-modified silica gel. Further, the silica gel particles modified with the silane coupling agent of the prior art instead of the amination reagent (example 13) could not significantly reduce the sulfur content, and the desulfurization effect of the present invention could not be achieved by desulfurization with the modified silica gel of the prior art. Therefore, the technical scheme of the application has excellent desulfurization effect, can greatly avoid the occurrence of the conditions that the yield and the quality of products are influenced by catalyst poisoning, metal corrosion, equipment and pipeline blockage and the like in the production of methanol and synthetic ammonia possibly caused by the existence of sulfide in the subsequent working section, and ensures safe production.
Experimental example 2: the ammonia synthesis process comprises the following steps:
the method for synthesizing ammonia by taking the purified raw material gas of each of the embodiments 1 to 14 as a raw material comprises the following specific steps:
1) the raw material gas treated by the purification method enters a coke filter and an oil remover to be subjected to oil-gas separation treatment, and then is converted by adopting a medium-temperature (500 ℃) to low-temperature (240 ℃) to low-temperature (220 ℃) three-section conversion process with a saturated hot water tower;
2) step 1), sending the gas into a first-stage pressure swing adsorption tower for decarburization, and then sending the gas into a second-stage pressure swing adsorption tower for obtaining purified hydrogen;
3) supplementing nitrogen into the purified hydrogen in the step 2), and compressing the hydrogen to 12MPa by using a centrifugal compressor to synthesize ammonia to obtain the ammonia.
The purity of ammonia obtained by synthesizing ammonia from the purified raw material gas of each of examples 1 to 14 was counted, and the results are shown in table 2.
TABLE 2 Ammonia purity
| Examples | Ammonia purity (vol%) | Examples | Ammonia purity (vol%) |
| 1 | 98.65 | 8 | 99.44 |
| 2 | 99.78 | 9 | 99.38 |
| 3 | 99.06 | 10 | 99.75 |
| 4 | 99.12 | 11 | 99.30 |
| 5 | 99.18 | 12 | 99.10 |
| 6 | 99.82 | 13 | 98.90 |
| 7 | 99.24 | 14 | 98.52 |
As can be seen from table 2, the raw material gases in preferred embodiments 2, 6 and 10 of the present application have high purity, which can reach a purity of not less than 99.75 vol%, and the process flow is simple, and ammonia synthesis can be performed without re-desulfurization to obtain high-purity ammonia gas; comparative analysis in the remaining examples, the final product, ammonia, was not pure enough due to the high sulfur content as an impurity.
In the above embodiment and the alternatives thereof, the weight ratio of the γ -aminopropyltriethoxysilane to the (3-mercaptopropyl) triethoxysilane in the amination reagent may be any one of 2.5 to 3.0:1, 2.6 to 3.0:1, 2.7 to 3.0:1, 2.8 to 3.0:1, 2.9 to 3.0:1, 2.5 to 2.9:1, 2.6 to 2.9:1, 2.7 to 2.9:1, 2.8 to 2.9:1, 2.5 to 2.8:1, 2.6 to 2.8:1, 2.7 to 2.8:1, 2.5 to 2.7:1, 2.6 to 2.7:1, 2.5 to 2.6:1, or 2.5:1, 2.55:1, 2.6:1, 2.65:1, 2.7:1, 2.5 to 2.6:1, 2.5:1, 2.55:1, 2.6:1, 2.65:1, 2.7:1, 2.75:1, 2.8:1, and 3.8: 1.
Conventional techniques in the above embodiments are known to those skilled in the art, and therefore, will not be described in detail herein.
In view of the numerous embodiments of the present invention, the experimental data of each embodiment is huge and is not suitable for being listed and explained herein one by one, but the contents to be verified and the final conclusions obtained by each embodiment are close. Therefore, the contents of the verification of the respective examples are not described herein, and the excellent points of the present invention will be described only by representative examples 1 to 14 and experimental examples 1 to 2.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or method illustrated may be made without departing from the spirit of the disclosure. In addition, the various features and methods described above may be used independently of one another, or may be combined in various ways. All possible combinations and sub-combinations are intended to fall within the scope of the present disclosure. Many of the embodiments described above include similar components, and thus, these similar components are interchangeable in different embodiments. While the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and obvious modifications and equivalents thereof. Accordingly, the invention is not intended to be limited by the specific disclosure of preferred embodiments herein.
Claims (8)
1. A method for purifying raw gas for synthesizing ammonia is characterized by comprising the following steps:
1) passing the sulfur-free methanol-rich liquid (1) at the outlet of the methanol washing tower through a sulfur-free flash evaporation tank (2) to obtain sulfur-free flash evaporation steam I;
2) enabling sulfur-containing methanol-rich liquid (3) at the outlet of the methanol washing tower to pass through a sulfur-containing flash evaporation tank (4) to obtain sulfur-containing flash evaporation steam, and enabling the sulfur-containing flash evaporation steam to enter a washing section (7) for desulfurization to obtain sulfur-free flash evaporation steam II;
3) the sulfur-free flash steam I and the sulfur-free flash steam II are converged and then enter a fuel gas main pipe and enter the next working section (6); the washing section uses methanol liquid without sulfur as washing liquid.
2. The process according to claim 1, wherein: the washing section (7) is used for desulfurizing so that the sulfur content in the flash steam II without sulfur is less than a preset content threshold value of 10mg/Nm3And collecting sulfur-containing liquid and crystallizing.
3. A process for purifying a feed gas for synthesis ammonia as claimed in claim 1 or 2, wherein: and 2) carrying out deep desulfurization (8) on the flash steam without sulfur by using a desulfurizing agent after desulfurization of the washing section (7), wherein the desulfurizing agent is a silica gel desulfurizing agent modified by dinitrosalicylic acid.
4. The process according to claim 4, wherein: the desulfurizing agent is prepared by a method comprising the following steps:
1) refluxing and activating silica gel with the particle size not higher than 100 mu m by using 8-10 mol/L hydrochloric acid, and completely drying after washing to be neutral;
2) mixing the silica gel, an amination reagent and toluene according to a weight-volume ratio of 1g: 1.0-1.5 mL: 15-20 mL, refluxing and stirring at 70-75 ℃ for at least 12h, leaching and washing with toluene, ethanol and diethyl ether in sequence after the reaction is finished, and drying in vacuum to obtain the amination silica gel;
3) adding the silicon amide glue obtained in the step 2) and 3, 5-dinitrosalicylic acid and N, N-dicyclohexyl diimine into sufficient tetrahydrofuran according to the weight ratio of 1: 0.05-0.06: 0.1-0.12, and reacting at room temperature for at least 24 hours under stirring;
4) and 3) leaching and washing the product obtained in the step 3) by using 4-6 mol/L hydrochloric acid and deionized water in sequence until the difference between the absorbance of the eluate and the absorbance of a blank detergent is lower than 0.5%, and drying in vacuum to obtain the detergent.
5. The process according to claim 4, wherein: in the step 2) of preparing the desulfurizing agent, the amination reagent is gamma-aminopropyltriethoxysilane and (3-mercaptopropyl) triethoxysilane in a weight ratio of 2.5-3.0: 1.
6. A process for synthesizing ammonia, which comprises decarbonizing the raw material gas treated by the purification method according to any one of claims 1 to 5, and then synthesizing ammonia.
7. The ammonia synthesis process according to claim 6, characterized in that: the ammonia synthesis process comprises the following steps:
1) the raw material gas treated by the purification method in the item [1] enters a coke filter and an oil remover for oil-gas separation treatment, and then is transformed by adopting a medium-temperature-low-temperature three-section transformation process with a saturated hot water tower;
2) step 1), sending the gas into a first-stage pressure swing adsorption tower for decarburization, and then sending the gas into a second-stage pressure swing adsorption tower for obtaining hydrogen;
3) supplementing nitrogen into the purified hydrogen in the step 2), and compressing to 10-15 MPa to synthesize ammonia to obtain ammonia with the purity not lower than 99.5% in weight percentage.
8. The ammonia synthesis process according to claim 7, characterized in that: the medium temperature in the medium-temperature-low-temperature three-stage conversion process is 400-550 ℃, and the low temperature is 200-250 ℃.
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| CN104107730A (en) * | 2014-07-02 | 2014-10-22 | 淮海工学院 | Functionalized silica gel containing quaternary ammonium cations and salicylaldehyde chelation groups on surface |
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| GB1014955A (en) * | 1962-05-26 | 1965-12-31 | Siemens Ag | Improvements in or relating to the desulphurisation of gases |
| US6911189B1 (en) * | 1999-10-29 | 2005-06-28 | Philip Morris Usa Inc. | Filter for selective removal of a gaseous component |
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