CN113046137B - Method for capturing and extracting ammonia in low-temperature methanol washing system - Google Patents
Method for capturing and extracting ammonia in low-temperature methanol washing system Download PDFInfo
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- CN113046137B CN113046137B CN202110271487.7A CN202110271487A CN113046137B CN 113046137 B CN113046137 B CN 113046137B CN 202110271487 A CN202110271487 A CN 202110271487A CN 113046137 B CN113046137 B CN 113046137B
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
- C10K1/00—Purifying combustible gases containing carbon monoxide
- C10K1/002—Removal of contaminants
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
- C10K1/00—Purifying combustible gases containing carbon monoxide
- C10K1/08—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors
- C10K1/16—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with non-aqueous liquids
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
- C10K1/00—Purifying combustible gases containing carbon monoxide
- C10K1/20—Purifying combustible gases containing carbon monoxide by treating with solids; Regenerating spent purifying masses
Abstract
The invention discloses a method for capturing and extracting ammonia in a low-temperature methanol washing system, and belongs to the technical field of ammonia recovery. The method comprises the following steps: s1, adding NH3The acid gas is introduced into the ammonia extraction and capture device through an air inlet pipe, and a filler layer and an ammonia capture layer in the ammonia extraction and capture device capture ammonia in the acid gas; s2, discharging residual NH in the ammonia extraction and collection device3An acid gas; s3, taking out the ammonia trapping layer in the ammonia collecting and trapping device, collecting and enriching ammonia crystals on the ammonia trapping layer; or desalted water is introduced into the ammonia collecting and trapping device, the ammonia crystal enriched on the ammonia trapping layer is dissolved in the desalted water, then the desalted water containing ammonia is discharged, and the ammonia is collected and treated. The method effectively solves the problem of the bottleneck of ammonia crystallization of the acid gas pipeline of the low-temperature methanol washing system, fills the blank of the method for solving the problems in China, abroad and in the field of industrial application, and provides reference for the same type of enterprises.
Description
Technical Field
The invention relates to the technical field of ammonia recovery, in particular to a method for capturing and extracting ammonia in a low-temperature methanol washing system.
Background
In the chemical production using coal as raw material, the transformed gas after CO sulfur-tolerant transformation contains a large amount of redundant CO2A small amount of H2S, COS, which are very harmful to downstream production, especially if the sulphides poison the catalyst in downstream production, and therefore must be treatedAnd removing. The low-temperature methanol washing process takes cold methanol as an absorption solvent, and utilizes the methanol to treat acid gas (CO) at low temperature2、H2S, COS, etc.) and the acidic gas in the converted gas is removed by a physical absorption method so as to meet the use requirement of the subsequent section. At present, more process packages such as German low-temperature methanol washing, Luqi low-temperature methanol washing, Dalianjia pure low-temperature methanol washing and the like are used.
The shift gas entering the low temperature methanol wash from the shift unit contains a trace amount of NH3According to the solubility of each component in the conversion gas in low-temperature methanol under the same pressure and temperature, the dissolving capacity of each component in the methanol is obtained as follows: NH (NH)3＞H2S＞COS＞CO2＞CH4＞CO＞N2＞H2Therefore, under the same conditions, the most soluble of the components of the raw material gas in methanol is NH3. In a low-temperature methanol washing system, the methanol cannot be effectively separated from methanol through a reduced-pressure flash evaporation and gas stripping area, and only incomplete analysis can be carried out in a methanol thermal regeneration tower area; along with the methanol recycling of the low-temperature methanol washing system, NH in the methanol3Gradually accumulate and concentrate, and when a certain degree is reached, at the existing temperature and pressure, CO is added2And H2Ammonia crystallization can form in the acid gas pipeline with S as the main component, blocking the pipeline and equipment, which has the main effect: (1) the overpressure or pressure of the acid gas pipeline of the low-temperature methanol washing system fluctuates greatly, the balance of the temperature, the flow, the liquid level and the like of the methanol thermal regeneration tower is broken, the regeneration effect of methanol is threatened, the desulfurization effect of the low-temperature methanol washing on the converted gas is deteriorated, and H in the purified gas discharged from the top of the methanol washing tower is seriously caused2The S content exceeds the standard, so that the poisoning and inactivation of the synthetic catalyst are caused; (2) the byproduct acid gas of the low-temperature methanol washing system cannot be sent out and can only be discharged to an acid gas flare system through a nearby pipeline for pipeline dredging, so that the load of a sulfur recovery system is reduced or the gas is cut, and certain environmental pollution is caused.
In order to achieve the above-mentioned objects, those skilled in the art generally adopt a partial displacement methanol method, an acid gas pipeline hot washing method, and an acid gas pipeline setting ammonia crystallization prevention hand valve method;
partial displacement methanol method: when ammonia crystallization occurs in the acid gas pipeline of the low-temperature methanol washing system, NH in methanol in the low-temperature methanol washing system3High concentration of NH is discharged at the highest place3Methanol, and fresh refined methanol (without NH) is supplemented to the low-temperature methanol washing system from the tank field3) To the NH in the methanol of the low-temperature methanol washing system3The content is diluted, and the phenomenon of ammonia crystallization in an acid gas system is avoided. Through long-term operation data statistics, the conversion process gas enters a 7-tower full barren solution flow of a Germany Linde low-temperature methanol washing system under the pressure of 7.5MPaG, corresponds to a 180 wt/synthetic methanol device, and is partially replaced and discharged by low-temperature methanol washing to contain NH3Methanol (component: H)2O 1.03％；NH3 4.08g/l；H25.6 percent of S; pH 8.3) in an amount of about 150t to 200 t/month. The method wastes a large amount of refined methanol and simultaneously discharges NH-containing gas3Methanol has no treatment process related to industrial application at present, and the discharged NH is replaced3The risk of methanol storage is extremely high.
The hot washing method of the acid gas pipeline comprises the following steps: when ammonia crystallization occurs in the acid gas pipeline of the low-temperature methanol washing system, the acid gas is cut into an acid gas torch to be combusted and discharged, and ammonia crystals are decomposed into CO by a method of increasing the temperature of the acid gas2And NH3The aim of eliminating ammonia crystallization is achieved, and simultaneously, a large amount of methanol can enter an acid gas flare system along with an acid gas pipeline. The method does not produce NH3Methanol off, but rich in H2SO generated after S acid gas is discharged to a torch for combustion2Certain pollution is caused to the atmospheric environment, and the methanol consumption of a low-temperature methanol washing system is increased; containing NH3After the acid gas enters a flare pipeline, ammonia crystallization may be generated in an acid gas flare system, and the safe and stable operation of the acid gas flare is affected.
The method for setting the ammonia crystallization prevention hand valve on the acid gas pipeline comprises the following steps: an ammonia crystallization prevention hand valve (namely a hot acid gas cross-line valve) is arranged on the cold and hot acid gas heat exchanger of the acid gas line of the low-temperature methanol washing system. When the ammonia crystallization phenomenon occurs in the acid gas pipeline of the low-temperature methanol washing system, the hand valve for preventing ammonia crystallization of the acid gas pipeline is openedTo decompose ammonia crystals of the acid gas pipeline into CO2And NH3So as to achieve the purpose of eliminating ammonia crystallization. The method does not produce NH3The methanol can not cause the release of the acid gas to affect the environment, but the use of the valve can lead the methanol-containing acid gas which is not separated to be brought into a sulfur recovery system through an acid gas pipeline, and easily causes a large amount of carbon deposition in a sulfur recovery Claus reactor under the high-temperature reaction, thereby causing the activity of the catalyst of the sulfur recovery Claus reactor to be deteriorated, the pressure difference of the Claus reactor to be increased and affecting the sulfur recovery rate; in severe cases, the tail gas SO2The emission of the indexes exceeds the standard; affecting the quality of the sulfur product.
Therefore, the method for capturing and extracting ammonia in the low-temperature methanol washing system has important social significance and economic value.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a method for capturing and extracting ammonia in a low-temperature methanol washing system. By washing NH in methanol in the system with low-temperature methanol3Collecting and extracting NH in methanol in a low-temperature methanol washing system3The content is effectively controlled without generating NH3The method has the advantages that the consumption of refined methanol is reduced, the environment is protected without using an acid gas pipeline hot washing method, the consumption of methanol in a low-temperature methanol washing system is reduced, the stable operation of the sulfur recovery working condition is effectively maintained without using an ammonia crystallization prevention valve, the ammonia crystallization phenomenon of the acid gas pipeline of the low-temperature methanol washing system is avoided, and the bottleneck problem of ammonia crystallization of the acid gas pipeline of the low-temperature methanol washing system is effectively solved.
The invention aims to provide a method for collecting and extracting ammonia in a low-temperature methanol washing system, which adopts an ammonia collecting and collecting device to collect NH in the ammonia3Collecting and extracting ammonia in the acid gas;
the ammonia extraction and trapping device comprises:
a collecting container, and
at least one packing layer and at least one ammonia trapping layer are alternately arranged in the trapping container from bottom to top in sequence, the bottommost layer is the packing layer, and the topmost layer is the ammonia trapping layer;
the trappingThe lower part of the packing layer positioned at the bottommost layer on the container is communicated with a pipeline for introducing NH3An inlet pipe for acid gas;
an exhaust pipe is communicated above the ammonia trapping layer positioned at the topmost layer on the trapping container;
the specific ammonia trapping and extracting method comprises the following steps:
s1, adding NH3Acid gas is introduced into the ammonia extraction and capture device through the gas inlet pipe, the ammonia in the acid gas is captured by the filler layer and the ammonia capture layer in the ammonia extraction and capture device, and NH is stopped to be contained when the difference between the gas outlet pipe and the gas inlet pipe reaches a certain pressure difference value3Introducing acid gas into the ammonia production catching device;
s2, discharging residual NH in the ammonia extraction and collection device3An acid gas;
s3, taking out the ammonia trapping layer in the ammonia collecting and trapping device, collecting and enriching ammonia crystals on the ammonia trapping layer;
or desalted water is introduced into the ammonia collecting and trapping device, the ammonia crystal enriched on the ammonia trapping layer is dissolved in the desalted water, then the desalted water containing ammonia is discharged, and the ammonia is collected and treated.
Preferably, the top of the collecting container is also communicated with an output pipe for outputting gas or liquid; the output pipe is provided with a control valve;
the bottom of the collecting container is communicated with a nitrogen or inert gas filling pipe, and a gas control valve is arranged on the filling pipe;
three packing layers and three ammonia trapping layers are alternately arranged in the trapping container from bottom to top in sequence; a sieve plate is arranged between the middle packing layer and the ammonia trapping layer; the sieve plate comprises at least three layers of sieve nets which are laminated from bottom to top, and the mesh number of the sieve nets from bottom to top is increased in sequence;
a water inlet pipe for introducing desalted water is communicated with one side of the sieve plate on the trapping container, and a water control valve is arranged on the water inlet pipe;
an overflow valve is arranged at the upper part of the ammonia trapping layer at the topmost layer on the trapping container;
the bottom of the collecting container is communicated with a spray guide pipe, and a liquid discharge control valve is arranged on the spray guide pipe.
More preferably, the ammonia extraction and capture device is introduced into the device containing NH3Before the acid gas is cooled, the acid gas is pre-cooled to-32 to-25 ℃.
More preferably, the residual NH-containing gas in the ammonia extraction and collection device is discharged3The acid gas is specifically carried out according to the following steps:
and opening a control valve arranged on the output pipe, introducing nitrogen or inert gas into the ammonia extraction and capture device through a nitrogen or inert gas filling pipe for gas replacement, and discharging the residual acid gas in the ammonia extraction and capture device to an acid gas torch system.
More preferably, it is a mixture of more preferably,
after ammonia crystals enriched on the ammonia trapping layer are dissolved in desalted water, the desalted water containing ammonia is discharged specifically according to the following steps:
step one, detecting the temperature and H in the ammonia extraction and capture device before introducing desalted water into the ammonia extraction and capture device2S content, when the temperature is more than or equal to 5 ℃, H2When the S content is less than or equal to 6.5ppm, injecting desalted water into the ammonia extraction and trapping device from a water inlet pipe until water overflows from an overflow valve, and stopping injecting water;
step two, introducing nitrogen or inert gas into the ammonia extraction and trapping device through a nitrogen or inert gas filling pipe to stir and wash the ammonia trapping layer, dissolving ammonia crystals enriched in the ammonia trapping layer into the desalted water,
step three, discharging the desalted water containing ammonia into a collecting barrel through a guide shower pipe;
and step four, repeating the steps one to three until the ammonia crystal trapped in the ammonia extraction and trapping device is completely washed.
More preferably, in S1, the pressure drop value of the exhaust pipe with respect to the intake pipe is not greater than 110 to 150 kPa.
More preferably, the ammonia collected in the ammonia collecting and collecting device is washed by the ammonia crystalWashing to NH in the washing liquid4 +The content is less than or equal to 10mg/l, and the washing is stopped.
More preferably, the ammonia collected in the ammonia collecting and trapping device is completely washed, and after the ammonia collecting and trapping device is cleaned and dried, NH is introduced again3The acid gas is used for capturing and extracting ammonia.
Compared with the prior art, the invention has the beneficial effects that:
the invention is based on that an ammonia trapping and extracting device is added on an acid gas concentration pipeline in a low-temperature methanol washing system, and NH in methanol in the low-temperature methanol washing system is treated by alternately arranging at least one packing layer and at least one ammonia trapping layer on a trapping container from bottom to top in sequence3Collecting and extracting NH in methanol in a low-temperature methanol washing system3The content is effectively controlled without generating NH3The methanol reduces the consumption of refined methanol, does not use an acid gas pipeline hot washing method to protect the environment, reduces the consumption of the methanol of a low-temperature methanol washing system, does not use an ammonia crystallization prevention valve to effectively maintain the stable operation of the sulfur recovery working condition, avoids the ammonia crystallization phenomenon of the acid gas pipeline of the low-temperature methanol washing system, and effectively solves the bottleneck problem of the ammonia crystallization of the acid gas pipeline of the low-temperature methanol washing system.
The method provided by the invention enables the methanol in the low-temperature methanol washing system to contain NH3Effective extraction is carried out, and NH in methanol in the low-temperature methanol washing system is washed3The content is effectively controlled to be that the crystallization concentration c1 is less than or equal to 10mg/l (or NH in methanol at the bottom of a reflux tank of a methanol thermal regeneration tower)3Content is less than or equal to 0.5 percent), thereby avoiding the ammonia crystallization phenomenon of the acid gas pipeline of the low-temperature methanol washing system.
Drawings
FIG. 1 is a schematic diagram showing the structure of an ammonia trapping apparatus used in the ammonia trapping and withdrawing method in the low-temperature methanol washing system in the example.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.
The filler layer, the ammonia trapping layer and the sieve plate used in the following examples were made of stainless steel.
The ammonia trap/extraction device used in the following examples, as shown in fig. 1, includes:
a collecting container 1, and
at least one packing layer 11 and at least one ammonia trapping layer 12 are alternately arranged in the trapping container 1 from bottom to top in sequence, the bottommost layer is arranged to be the packing layer, and the topmost layer is arranged to be the ammonia trapping layer;
a filling layer 11 for introducing NH is communicated with the lower part of the bottommost layer on the collecting container 13An inlet pipe 101 for acid gas;
an exhaust pipe 102 is connected to the trap container 1 above the ammonia trap layer 12 located at the uppermost layer.
For this purpose, a device for collecting and extracting ammonia in the low-temperature methanol washing system is communicated with an acid gas concentration pipeline in the low-temperature methanol washing system through an air inlet pipe and an air outlet pipe, and NH is contained3Acid gas is introduced into a collecting container through a gas inlet pipe, the collecting container can be a tank body, at least one packing layer 11 and at least one ammonia collecting layer 12 are alternately arranged in sequence, ammonia in the gas and the packing layer generate throttling effect respectively to crystallize the ammonia, and the crystallized ammonia is enriched on the ammonia collecting layer, so that ammonia is collected and extracted; effectively solves the problem of the bottleneck of ammonia crystallization of the acid gas pipeline of the low-temperature methanol washing system.
In order to judge whether ammonia is extracted or not, a first pressure gauge 111 and a second pressure gauge 112 are respectively arranged on the gas inlet pipe 101 and the gas outlet pipe 102; judging the collection of ammonia in the trapping container by judging the difference between the first pressure gauge 111 and the second pressure gauge 112, when the pressure drop value of the exhaust pipe relative to the air inlet pipe is 110-150 kPa, and NH in the exhaust pipe3The content is accumulated to a lower concentration which is less than or equal to 50mg/l (or NH in methanol at the bottom of a reflux tank of a methanol thermal regeneration tower)3Content is less than or equal to 1.0 percent), the ammonia crystal is formed in the ammonia trapping and extracting device, thereby further defining the successful trapping and extracting of ammonia in the trapping container. In order to further increase the pressure of the gas stream flowing into the collecting container, a booster pump is also provided in the gas inlet pipe 101.
To be capable of introducing NH-containing gas through an inlet pipe3Acid gas is uniformly dispersed below the packing layer at the lowest layer, and a gas distributor 10 is arranged in the trapping container 1; the gas distributor 10 is disposed below the packing layer 11 at the lowermost layer and above the portion where the collecting vessel 1 communicates with the gas inlet pipe 101.
To containing NH3Ammonia in the acid gas can be collected and extracted better, and three packing layers 11 and three ammonia collecting layers 12 are alternately arranged in the collecting container 1 from bottom to top in sequence; a sieve plate 13 is arranged between the packing layer 11 and the ammonia trapping layer 12 in the middle; the sieve plate comprises at least three layers of sieve nets which are laminated from bottom to top, and the mesh number of the sieve nets from bottom to top is increased in sequence; each packing layer consists of two layers of structured packing layers which are arranged in a laminated manner, and the size of an opening on each layer of structured packing layer is 1-2 mm; each ammonia trapping layer is composed of 3-4 filter screens arranged in a laminated manner, and the mesh size of each filter screen is 10 mu m. Therefore, ammonia in the gas can be further crystallized after throttling effect is generated between the ammonia and the packing layer, and the crystallized ammonia is enriched on the ammonia trapping layer, so that ammonia is trapped and extracted; effectively solves the problem of the bottleneck of ammonia crystallization of the acid gas pipeline of the low-temperature methanol washing system.
After completion of ammonia capture, the NH content is stopped3Introducing the acid gas into a collecting container, and communicating a gas or liquid output pipe 106 at the top of the collecting container 1 in order to discharge the redundant gas in the collecting container; the output pipe 106 is provided with a control valve. Meanwhile, the bottom of the collecting container 1 is communicated with a nitrogen or inert gas filling pipe 104, and the filling pipe 104 is provided with a gas control valve.
It should be noted that, during the collection, the control valve provided in the outlet pipe 106 and the gas control valve provided in the inlet pipe 104 are in the closed state, and for this reason, when the pressure drop value of the exhaust pipe in the trap container reaches a certain value, the supply of NH-containing gas is stopped3Introducing acid gas into the collecting container, closing control valves on the gas inlet pipe and the gas outlet pipe in order to discharge excessive gas in the collecting container, opening a control valve on a gas or liquid outlet pipe 106 communicated with the top of the collecting container 1, and collecting the acid gasAnd (3) discharging redundant gas through an output pipe 106 while releasing pressure, communicating with a branch pipe 1061, conveying the redundant gas to a torch for combustion treatment, communicating a nitrogen or inert gas filling pipe 104 with the bottom of the collecting container 1 in order to further discharge the gas in the collecting container, arranging a gas control valve on the filling pipe 104, opening the gas control valve on the filling pipe 104, introducing nitrogen or inert gas into the collecting container, and conveying the residual acid gas in the ammonia collecting and collecting device to an acid gas torch system through the output pipe 106.
After the residual gas in the collecting container is discharged, a water inlet pipe 107 for introducing desalted water is communicated with one side of the collecting container 1 positioned on the sieve plate 13 so as to discharge the collected ammonia, and a water control valve is arranged on the water inlet pipe 107;
an overflow valve 105 is arranged at the upper part of the ammonia trapping layer 12 at the topmost layer on the trapping container 1;
the bottom of the collecting container 1 is communicated with a spray guide pipe 103, and a liquid discharge control valve is arranged on the spray guide pipe 103. In addition, the output pipe 106 is also communicated with a liquid separation tank 2 through a second branch pipe 1062, and the second branch pipe 1062 is provided with a control valve;
therefore, desalted water is filled into the collecting container through the water inlet pipe 107, and along with continuous filling of desalted water, whether the desalted water in the collecting container soaks the ammonia collecting layer is judged through the overflow valve 105, once the desalted water is discharged from the overflow valve 105, the overflow valve is closed, the control valve body arranged on the branch pipe 1061 is closed, the control valve arranged on the second branch pipe 1062 is opened, meanwhile, nitrogen or inert gas is filled into the collecting container through the gas control valve arranged on the filling pipe 104, the desalted water in the collecting container is continuously stirred, the nitrogen or the inert gas enters the output pipe 106 after the desalted water, the nitrogen or the inert gas containing liquid is conveyed into the liquid separating tank 2 through the second branch pipe 1062, gas-liquid separation is carried out through the liquid separating tank 2, and the separated gas is introduced into the torch system for combustion treatment.
After the desalted water after gas stirring dissolves the ammonia crystals trapped on the trapping layer, the effluent control valve arranged on the lead sprinkling pipe 103 is opened, the desalted water containing ammonia is drained through the lead sprinkling pipe 103, and subsequent treatment is carried out, so that the ammonia trapped in the trapping container is dissolved and drained, and then the trapping device is subjected to cleaning agent drying treatment and is thrown into the trapping and extracting process of ammonia again. Therefore, the problem of the bottleneck of ammonia crystallization of the acid gas pipeline of the low-temperature methanol washing system is effectively solved.
In addition, in order to ensure the safe operation of the whole process, each pipe body provided with the control valve is provided with a double control valve.
Examples
A method for capturing and extracting ammonia in a low-temperature methanol washing system, as shown in fig. 1, comprising the following steps:
s1, adding NH3Acid gas is introduced into the ammonia extraction and capture device through the gas inlet pipe 101, the filler layer 11 and the ammonia capture layer 12 in the ammonia extraction and capture device capture ammonia in the acid gas, and when the difference between the exhaust pipe 102 and the gas inlet pipe 101 reaches a certain pressure difference value, the process of capturing ammonia containing NH stops3Introducing acid gas into an ammonia extraction and capture device; introducing NH into the ammonia extraction and trapping device3Pre-cooling the acid gas to-32-25 ℃ before the acid gas; the pressure drop value of the exhaust pipe 102 relative to the intake pipe 101 is 110-150 kPa.
S2, collecting residual NH in the device for collecting the discharged ammonia3An acid gas; the method specifically comprises the following steps:
and opening a control valve arranged on the output pipe 106, introducing nitrogen or inert gas into the ammonia extraction and capture device through a nitrogen or inert gas filling pipe 104 for gas replacement, and discharging the residual acid gas in the ammonia extraction and capture device to an acid gas flare system.
S3, taking out the ammonia collecting layer 12 in the ammonia collecting and trapping device to collect ammonia crystals enriched on the ammonia collecting layer 12;
or through introducing desalted water into the ammonia collecting and trapping device, dissolving the ammonia crystal enriched on the ammonia trapping layer 12 in the desalted water, discharging the desalted water containing ammonia, and collecting the ammonia;
after ammonia crystals enriched on the ammonia trapping layer 12 are dissolved in desalted water, the desalted water containing ammonia is discharged specifically according to the following steps:
step one, detecting the temperature and H in the ammonia extraction and capture device before introducing desalted water into the ammonia extraction and capture device2S content, when the temperature is more than or equal to 5 ℃, H2When the S content is less than or equal to 6.5ppm, injecting desalted water into the ammonia extraction and collection device from the water inlet pipe 107 until water overflows from the overflow valve 105, and stopping injecting water;
step two, nitrogen or inert gas is filled into the ammonia extraction and trapping device through a nitrogen or inert gas filling pipe 104 to stir and wash the ammonia trapping layer 12, ammonia crystals enriched in the ammonia trapping layer 12 are dissolved in the desalted water,
step three, discharging the desalted water containing ammonia into a collecting barrel through a draining pipe 103;
step four, repeating the steps one to three until the ammonia collected in the ammonia collecting and collecting device is completely crystallized and washed; washing the ammonia crystal trapped in the ammonia extraction and trapping device to NH in the washing liquid4 +The content is less than or equal to 10mg/l, and the washing is stopped.
The ammonia crystal trapped in the ammonia extraction and trapping device is completely washed, and after the ammonia extraction and trapping device is cleaned and dried, NH is introduced again3The acid gas is used for capturing and extracting ammonia.
By using the method, NH in methanol in a low-temperature methanol washing system can be washed3Effective extraction is carried out, and NH in methanol in the low-temperature methanol washing system is washed3The content is effectively controlled to be less than or equal to 10mg/l of crystallization concentration or NH in methanol at the bottom of a reflux tank of a methanol thermal regeneration tower3The content is less than or equal to 0.5 percent, thereby avoiding the ammonia crystallization phenomenon of the acid gas pipeline of the low-temperature methanol washing system.
In conclusion, the method effectively solves the bottleneck problem of ammonia crystallization of the acid gas pipeline of the low-temperature methanol washing system, fills the blank of the method for solving the problems in China, China and other countries in the field of industrial application, and provides reference for the same type of enterprises.
The method replaces the current methanol replacement method flow, and effectively reduces the methanol consumption of the low-temperature methanol washing system; effectively restrains the replaced NH from the source3And (5) risk of later-stage storage and treatment of methanol.
The invention replaces the prior acid gas emptying hot washing process, and effectively ensures the safe operation of the acid gas flare pipeline; the methanol consumption of the low-temperature methanol washing system is effectively reduced; ensures that the acid gas is sent to the sulfur recovery as much as possible for treatment, and greatly protects the environment.
The invention replaces the current flow of the ammonia crystallization prevention valve, and effectively reduces the methanol consumption of the low-temperature methanol washing system; the sulfur recovery section can omit a methanol washing tower before the acid gas enters the sulfur recovery thermal reactor, thereby effectively reducing the sulfur recovery investment; because the carbon deposition frequency of the sulfur recovery Claus reactor is reduced, the service cycle of the sulfur recovery Claus catalyst is greatly prolonged.
The above disclosure is only for the specific embodiment of the present invention, but the embodiment of the present invention is not limited thereto, and any variations that can be made by those skilled in the art should fall within the scope of the present invention.
Claims (8)
1. A method for collecting and extracting ammonia in a low-temperature methanol washing system is characterized in that an ammonia collecting and collecting device is adopted to collect NH-containing ammonia3Collecting and extracting ammonia in the acid gas;
the ammonia extraction and trapping device comprises:
a collecting container (1), and
at least one packing layer (11) and at least one ammonia trapping layer (12) are alternately arranged in the trapping container (1) from bottom to top in sequence, the bottommost layer is arranged to be the packing layer, and the topmost layer is arranged to be the ammonia trapping layer;
the lower part of the packing layer (11) positioned at the bottommost layer on the trapping container (1) is communicated with a device for introducing NH3An inlet pipe (101) for acid gases;
an exhaust pipe (102) is communicated above the ammonia trapping layer (12) positioned at the topmost layer on the trapping container (1);
the specific ammonia trapping and extracting method comprises the following steps:
s1, adding NH3The acid gas is introduced into the ammonia production and capture device through an air inlet pipe (101), and a filler layer (11) and an ammonia capture layer (12) in the ammonia production and capture device are used for acid gasAmmonia in the gas is collected, and when the difference between the exhaust pipe (102) and the inlet pipe (101) reaches a certain pressure difference value, the NH is stopped3Introducing acid gas into the ammonia production catching device;
s2, discharging residual NH in the ammonia extraction and collection device3An acid gas;
s3, taking out ammonia crystals collected and enriched on the ammonia collecting layer (12) from the ammonia collecting layer (12) in the ammonia collecting and trapping device;
or desalted water is introduced into the ammonia collecting and trapping device, the ammonia crystal enriched on the ammonia trapping layer (12) is dissolved in the desalted water, and then the desalted water containing ammonia is discharged and the ammonia is collected and treated.
2. The method for capturing and extracting ammonia in a low-temperature methanol washing system according to claim 1, characterized in that an output pipe (106) for outputting gas or liquid is communicated with the top of the capturing container (1); a control valve is arranged on the output pipe (106);
the bottom of the trapping container (1) is communicated with a nitrogen or inert gas filling pipe (104), and a gas control valve is arranged on the filling pipe (104);
three packing layers (11) and three ammonia trapping layers (12) are alternately arranged in the trapping container (1) from bottom to top in sequence; a sieve plate (13) is arranged between the middle packing layer (11) and the ammonia trapping layer (12); the sieve plate comprises at least three layers of sieve nets which are laminated from bottom to top, and the mesh number of the sieve nets from bottom to top is increased in sequence;
one side of the trapping container (1) positioned on the sieve plate (13) is communicated with a water inlet pipe (107) for introducing desalted water, and the water inlet pipe (107) is provided with a water control valve;
an overflow valve (105) is arranged at the upper part of the ammonia trapping layer (12) at the topmost layer on the trapping container (1);
the bottom of the collecting container (1) is communicated with a spray guide pipe (103), and a liquid discharge control valve is arranged on the spray guide pipe (103).
3. The method according to claim 2, wherein the ammonia extraction and collection device is introduced into the system containing NH3Before the acid gas is cooled, the temperature is precooled to-32 to-25 ℃.
4. The method according to claim 3, wherein the residual NH content in the ammonia extraction and collection device is discharged3The acid gas is specifically carried out according to the following steps:
and opening a control valve arranged on the output pipe (106), introducing nitrogen or inert gas into the ammonia extraction and trapping device through a nitrogen or inert gas filling pipe (104) for gas replacement, and discharging the residual acid gas in the ammonia extraction and trapping device to an acid gas flare system.
5. The method for capturing and withdrawing ammonia in a low-temperature methanol washing system according to claim 2,
after ammonia crystals enriched on the ammonia trapping layer (12) are dissolved in desalted water, the desalted water containing ammonia is discharged according to the following steps:
step one, detecting the temperature and H in the ammonia extraction and capture device before introducing desalted water into the ammonia extraction and capture device2S content, when the temperature is more than or equal to 5 ℃, H2When the S content is less than or equal to 6.5ppm, injecting desalted water into the ammonia extraction and trapping device from a water inlet pipe (107) until water overflows from an overflow valve (105), and stopping injecting water;
step two, introducing nitrogen or inert gas into the ammonia extraction and trapping device through a nitrogen or inert gas filling pipe (104) to stir and wash the ammonia trapping layer (12), dissolving ammonia crystals enriched in the ammonia trapping layer (12) into the desalted water,
step three, discharging the desalted water containing ammonia into a collecting barrel through a draining pipe (103);
and step four, repeating the step one to the step three until the ammonia crystal trapped in the ammonia extraction and trapping device is completely washed.
6. The method for capturing and extracting ammonia in a low-temperature methanol washing system according to claim 5, wherein in S1, the pressure drop value of the exhaust pipe (102) relative to the inlet pipe (101) is less than or equal to 110-150 kPa.
7. The method according to claim 5, wherein the ammonia crystals trapped in the ammonia trap device are washed into NH in the washing liquid4 +The content is less than or equal to 10mg/l, and the washing is stopped.
8. The method for capturing and extracting ammonia in a low-temperature methanol washing system according to claim 7, wherein the ammonia captured in the ammonia capturing and extracting device is completely washed, cleaned and dried, and then introduced again with NH3The acid gas is used for capturing and extracting ammonia.
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| CN114887456A (en) * | 2022-03-07 | 2022-08-12 | 蒲城清洁能源化工有限责任公司 | Ammonium bicarbonate crystallization prevention system for low-temperature methanol washing process |
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| CN203593735U (en) * | 2013-11-22 | 2014-05-14 | 上海国际化建工程咨询公司 | Device for treating low temperature methanol washing ammonium crystallization and purifying barren liquor methanol |
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