Liquid ammonia impurity removal method and system based on selective oxidation

Abstract

The invention provides a selective oxidation-based liquid ammonia impurity removal method and system. The method comprises the following steps: acquiring impurity composition data of to-be-treated liquid ammonia to determine a catalyst type, an oxygen content control range and a reaction temperature required by the selective oxidation process of the liquid ammonia; based on the catalyst type and the oxygen content control range, establishing a selective oxidation reaction zone corresponding to the pretreated liquid ammonia in the reactor; setting an oxygen content control value of the selective oxidation reaction zone in the oxygen content control range, controlling the reaction temperature, and carrying out selective catalytic oxidation reaction on the pretreated liquid ammonia in the selective oxidation reaction zone; and carrying out gas-liquid separation on the reacted mixed product to obtain target liquid ammonia. According to the scheme, non-selective oxidation of the liquid ammonia body can be inhibited to the maximum extent, efficient removal of impurities is achieved, and energy conservation and environmental protection are achieved.

Description

Technical Field

[0001] This invention relates to a method and system for removing liquid ammonia impurities based on selective oxidation, belonging to the field of energy-saving and environmentally friendly industrial gas purification technology. Background Technology

[0002] As the application of liquid ammonia in high-purity agricultural nitrogen fertilizers, pharmaceutical intermediates, fine chemicals and electronics industries continues to expand and deepen, its purity requirements are becoming increasingly stringent. In particular, the trace amounts of hydrocarbons and sulfur impurities remaining in it will not only reduce the quality of the final product, but also cause problems such as catalyst poisoning and increased side reactions in subsequent catalytic processes, thereby directly reducing production efficiency and increasing operating costs.

[0003] Patent CN105523570A discloses a method for preparing PPT-grade ultrapure ammonia water, including the following steps: vaporization; purification filtration; resin adsorption; washing; water-gas separation; multi-stage absorption; and ultrafiltration. The ultrapure ammonia water obtained by this method has a particle concentration of less than 3 p / ml for particles larger than or equal to 0.5 μm, a particle concentration of less than 30 p / ml for particles larger than or equal to 0.2 μm, and a single metal ion content of less than 30 ppt. However, this invention has a simple process flow, but the specific implementation process and control parameters are unclear, resulting in unsatisfactory impurity removal.

[0004] Current methods for removing impurities from liquid ammonia mostly employ catalytic oxidation technology. By using supported or composite catalysts in an oxygen-containing atmosphere, impurities such as hydrocarbons are oxidized into harmless substances. Although this method can achieve high removal efficiency under suitable conditions, due to unreasonable control parameters, existing catalysts lack selective adsorption capacity for target impurities. As a result, it is difficult to selectively remove specific impurities in liquid ammonia in environments where multiple impurities coexist. Summary of the Invention

[0005] This invention provides a method and system for removing impurities from liquid ammonia based on selective oxidation. By employing intelligent data analysis and combining multiple catalysts, it can maximally suppress non-selective oxidation of the liquid ammonia and achieve efficient removal of impurities.

[0006] To achieve the above objectives, the present invention provides a method for removing liquid ammonia impurities based on selective oxidation, comprising: The impurity composition data of the liquid ammonia to be treated is obtained, and the liquid ammonia to be treated is subjected to desulfurization pretreatment to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the liquid ammonia in the selective oxidation process. The pretreated liquid ammonia is introduced into the corresponding reactor, and a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor based on the catalyst type and the oxygen content control range. Based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, the oxygen content control value of the selective oxidation reaction zone is set within the oxygen content control range. Based on the oxygen content control value and the reaction temperature, the pretreated liquid ammonia undergoes a selective catalytic oxidation reaction in the selective oxidation reaction zone to obtain a mixed product after the reaction. After gas-liquid separation of the mixed product, the target liquid ammonia is obtained.

[0007] Optionally, based on the catalyst type and the oxygen content control range, a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor, including: The copper oxide-cobalt oxide composite catalyst of the aforementioned catalyst type is loaded into the fixed bed of the reactor to form a catalyst bed; An oxygen-containing carrier gas is introduced into the catalyst bed to keep the oxygen concentration in the catalyst bed within the oxygen content control range. When the oxygen concentration in the catalyst bed reaches the oxygen content control range, the bed temperature of the catalyst bed is simultaneously controlled at the preset reaction temperature to form the selective oxidation reaction zone.

[0008] Optionally, an oxygen-containing carrier gas is introduced into the catalyst bed to keep the oxygen concentration within the controlled oxygen content range, including: A mixed carrier gas, consisting of an inert gas and oxygen, is introduced into the inlet end of the catalyst bed. An oxygen concentration sensor is deployed at the inlet end of the catalyst bed to monitor the oxygen concentration in the mixed carrier gas in real time. Based on the oxygen concentration, the mixing ratio of the mixed carrier gas is dynamically adjusted so that the oxygen concentration in the catalyst bed is within the oxygen content control range.

[0009] Optionally, based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, the oxygen content control value of the selective oxidation reaction zone is set within the oxygen content control range, including: Based on the characteristics of the components, the impurity components with the lowest oxidation reactivity in the hydrocarbons are extracted; Identify the selective oxidation activity window corresponding to the catalyst type, and based on the catalyst type, determine the minimum oxygen concentration required for the impurity component to achieve a preset removal rate; Within the oxygen content control range, a value between the minimum oxygen concentration and the upper limit of the selective oxidation activity window is selected as the oxygen content control value.

[0010] Optionally, based on the component characteristics, the impurity component with the lowest oxidation reactivity in the hydrocarbon is extracted, including: The molecular structure of each impurity component in the component characteristics is analyzed to determine the activation energy of the oxidation reaction corresponding to each impurity component; The impurity component corresponding to the highest oxidation activation energy among the oxidation reaction activation energies is determined to be the impurity component with the lowest oxidation reaction activity in the hydrocarbon.

[0011] Optionally, the mixed product is subjected to gas-liquid separation to obtain the target liquid ammonia, comprising: The mixture is passed into a gas-liquid separator for separation to obtain a gaseous product and preliminarily separated liquid ammonia. The pre-separated liquid ammonia is fed into a flash evaporation device to remove the gaseous components from the pre-separated liquid ammonia, thereby obtaining flash-evaporated liquid ammonia; The flash-evaporated liquid ammonia is passed into a distillation column for purification to remove volatile impurities and obtain distilled liquid ammonia. The distilled liquid ammonia is condensed to obtain the target liquid ammonia.

[0012] Optionally, the distilled liquid ammonia is condensed to obtain the target liquid ammonia, comprising: The distilled liquid ammonia is passed into a condenser, and the distilled liquid ammonia is cooled to below the preset liquid ammonia condensation temperature by the circulating cooling medium in the condenser, so that the distilled liquid ammonia is completely liquefied; The fully liquefied distilled ammonia is introduced into a pressure stabilizing tank to release trace amounts of non-condensable gases from the distilled ammonia. After the release of the trace amount of non-condensable gas is completed, the liquid ammonia in the pressure stabilizing tank is collected as the target liquid ammonia.

[0013] Optionally, based on the oxygen content control value and the reaction temperature, a selective catalytic oxidation reaction of the pretreated liquid ammonia occurs in the selective oxidation reaction zone to obtain a mixed product after the reaction, comprising: The pretreated liquid ammonia is introduced into the selective oxidation reaction zone at a preset flow rate; Simultaneously adjust the oxygen concentration and reaction temperature in the selective oxidation reaction zone to the corresponding oxygen content control value and reaction temperature; Under the conditions of maintaining the oxygen content control value and the reaction temperature, the pretreated liquid ammonia is continuously passed through the catalyst bed of the selective oxidation reaction zone to undergo catalytic oxidation reaction; The gas-liquid mixture after the reaction is collected synchronously from the outlet of the selective oxidation reaction zone as the mixed product.

[0014] Optionally, the liquid ammonia to be treated is subjected to desulfurization pretreatment to obtain pretreated liquid ammonia, including: The liquid ammonia to be treated is introduced into a prepared desulfurization tower so that the sulfides in the liquid ammonia to be treated undergo a selective adsorption reaction in the desulfurization tower to obtain primary purified liquid ammonia. The primary purified liquid ammonia is passed into a pre-installed activated carbon adsorption device, and the activated carbon adsorption device is used to remove trace amounts of organic sulfur components from the primary purified liquid ammonia to obtain the pretreated liquid ammonia.

[0015] To address the above problems, the present invention also provides a liquid ammonia impurity removal system based on selective oxidation, the system comprising: The raw material processing module is used to acquire the impurity composition data of the liquid ammonia to be treated and to perform desulfurization pretreatment on the liquid ammonia to be treated to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the selective oxidation process of the liquid ammonia. An environmental configuration module is used to introduce the pretreated liquid ammonia into the corresponding reactor, and to establish a selective oxidation reaction zone for the pretreated liquid ammonia in the reactor based on the catalyst type and the oxygen content control range. The parameter setting module is used to set the oxygen content control value of the selective oxidation reaction zone within the oxygen content control range according to the catalyst type and the composition characteristics of hydrocarbons in the pretreated liquid ammonia. The separation and purification module is used to selectively catalytically oxidize the pretreated liquid ammonia in the selective oxidation reaction zone based on the oxygen content control value and the reaction temperature, to obtain a mixed product after the reaction, and to separate the mixed product into gas and liquid to obtain the target liquid ammonia.

[0016] Compared with existing technical solutions, the advantages of the method and system of this invention are as follows.

[0017] This invention pre-treats the liquid ammonia to be treated with desulfurization, obtaining pre-treated liquid ammonia. This pre-treatment removes sulfide impurities from the liquid ammonia, preventing them from entering the subsequent selective oxidation reaction zone and causing poisoning and deactivation of the catalyst's active sites. Furthermore, by employing intelligent data analysis and combining multiple catalysts, based on the catalyst type and the oxygen content control range, a selective oxidation reaction zone corresponding to the pre-treated liquid ammonia is established in the reactor. This allows hydrocarbon impurities in the pre-treated liquid ammonia to undergo selective oxidation within this zone, while simultaneously suppressing non-target oxidation of the liquid ammonia itself, thereby achieving highly efficient removal of target impurities.

[0018] This invention, through setting the oxygen content control value of the selective oxidation reaction zone within the oxygen content control range based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, can match the most suitable oxygen content for a specific catalyst and target impurity combination. This effectively oxidizes hydrocarbons while avoiding excessive ammonia oxidation due to excessive oxygen content or incomplete impurity removal due to insufficient oxygen content. Furthermore, based on the oxygen content control value and the reaction temperature, this invention allows for the selective catalytic oxidation of the pretreated liquid ammonia within the selective oxidation reaction zone, yielding a mixed product. This maximizes the suppression of non-selective oxidation of the liquid ammonia, achieving efficient impurity removal and high-purity retention of the product liquid ammonia. Finally, by performing gas-liquid separation on the mixed product, the target liquid ammonia is obtained. This efficiently removes hydrocarbons while preventing excessive oxidation of the liquid ammonia, resulting in high-purity target liquid ammonia. This overcomes the problems of incomplete and unstable impurity removal caused by insufficient selectivity in traditional catalytic oxidation technologies. Therefore, this invention can suppress non-selective oxidation of liquid ammonia to the greatest extent, achieving efficient removal of impurities while saving energy and protecting the environment. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of a liquid ammonia impurity removal method based on selective oxidation, provided in an embodiment of the present invention. Figure 2 A schematic diagram of equipment connection for a liquid ammonia impurity removal method based on selective oxidation, provided in an embodiment of the present invention; Figure 3 A functional block diagram of a liquid ammonia impurity removal system based on selective oxidation is provided in one embodiment of the present invention; Figure 4 A schematic diagram of a computer device for a liquid ammonia impurity removal method based on selective oxidation, provided in an embodiment of the present invention; Detailed Implementation

[0020] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The objectives, functional characteristics, and advantages of the invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0021] This application provides a method for removing liquid ammonia impurities based on selective oxidation. The executing entity of this method includes, but is not limited to, at least one electronic device configured to execute the method provided in this application, such as a server or a terminal. In other words, the method for removing liquid ammonia impurities based on selective oxidation can be executed by software or hardware installed on a terminal device or a server device. The server includes, but is not limited to, a single server, a server cluster, a cloud server, or a cloud server cluster.

[0022] Reference Figure 1 The diagram shown is a schematic flowchart of a liquid ammonia impurity removal method based on selective oxidation according to an embodiment of the present invention. In this embodiment, the liquid ammonia impurity removal method based on selective oxidation includes: Step S1: Obtain the impurity composition data of the liquid ammonia to be treated, and perform desulfurization pretreatment on the liquid ammonia to be treated to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the selective oxidation process of the liquid ammonia.

[0023] By acquiring the impurity composition data of the liquid ammonia to be treated, this invention provides a direct basis for catalyst selection, oxygen content control, and temperature parameter setting in the subsequent selective oxidation process. Optionally, the impurity composition data of the liquid ammonia to be treated can be separated and qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry, such as GC-MS, to determine the types and concentrations of hydrocarbons in the sample.

[0024] Furthermore, in this embodiment of the invention, by performing desulfurization pretreatment on the liquid ammonia to be treated, pretreated liquid ammonia can be obtained, which can remove the sulfide impurities contained in the liquid ammonia in advance, and prevent them from entering the subsequent selective oxidation reaction zone and causing poisoning and deactivation of the catalyst active center.

[0025] As an embodiment of the present invention, the liquid ammonia to be treated is subjected to desulfurization pretreatment to obtain pretreated liquid ammonia, including: The liquid ammonia to be treated is introduced into a prepared desulfurization tower so that the sulfides in the liquid ammonia to be treated undergo a selective adsorption reaction in the desulfurization tower to obtain primary purified liquid ammonia. The primary purified liquid ammonia is passed into a pre-installed activated carbon adsorption device, and the activated carbon adsorption device is used to remove trace amounts of organic sulfur components from the primary purified liquid ammonia to obtain the pretreated liquid ammonia.

[0026] Specifically, the desulfurization tower can adopt a vertical fixed-bed adsorption tower structure. The tower is equipped with a gas distributor and a desulfurizing agent support structure, and is filled with a desulfurizing agent with zinc oxide as the main active ingredient. The zinc oxide content is not less than 90% by mass, the particle size is 3-5mm, the bulk density is 0.8-1.0g / cm³, and the sulfur capacity is not less than 20% (by mass fraction). During operation, the sulfides in the liquid ammonia undergo a chemical adsorption reaction with the desulfurizing agent. When the sulfur capacity of the desulfurizing agent tends to be saturated, it can be regenerated by hot nitrogen purging or replaced with fresh desulfurizing agent. The activated carbon adsorption device can adopt a horizontal dual-tank switchable design. The tanks are filled with coconut shell activated carbon to form a fixed bed. The ratio of bed height to diameter is controlled within the range of 1.5-2.0. The activated carbon used has an iodine adsorption value of not less than 1000 mg / g, a specific surface area of ​​not less than 1000 m² / g, and a total pore volume of not less than 0.6 cm³ / g. It is used to further remove trace organic sulfur components remaining in liquid ammonia. After the activated carbon is saturated, it can be regenerated by low-pressure steam at 150-200℃, or switched to a standby adsorption tank to continue operation.

[0027] Specifically, the sulfides refer to inorganic sulfur compounds in the liquid ammonia to be treated, either in a dissolved or suspended state, such as hydrogen sulfide, carbon oxysulfide, and soluble sulfates; the trace organic sulfur components refer to trace organic sulfur compounds that may still remain in the liquid ammonia after treatment by the desulfurization tower, such as thiols, thioethers, thiophene, and their derivatives.

[0028] The catalyst type can be selected based on the types and concentrations of hydrocarbons in the impurity data. For example, when the impurity data indicates a methane concentration of 150 ppm, an ethane concentration of 80 ppm, and no higher hydrocarbons are detected, a copper oxide-cobalt oxide (CuO-CoO) composite catalyst is selected. The oxygen content control range can be determined based on the total carbon content of hydrocarbons in the impurity data, by calculating the theoretical oxygen demand through a preset oxygen-carbon stoichiometric ratio, and then combining this with the selective oxidation activity window of the selected catalyst to determine the actual oxygen content control range. The reaction temperature can be determined based on the composition of the hydrocarbons in the impurity data, identifying the most difficult-to-oxidize component, and using the oxidation reaction kinetics experimental data of this component on the selected catalyst to determine the reaction temperature range required to meet the target removal rate.

[0029] Step S2: The pretreated liquid ammonia is introduced into the corresponding reactor, and a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor based on the catalyst type and the oxygen content control range.

[0030] In this embodiment of the invention, by introducing the pretreated liquid ammonia into a corresponding reactor, a controlled reaction environment can be provided for the liquid ammonia that has been desulfurized. The reactor is a container device for selective catalytic oxidation reaction, specifically a fixed-bed catalytic reactor. Its structure includes a corrosion-resistant and high-pressure-resistant cylinder, a catalyst bed filled with a copper oxide-cobalt oxide composite catalyst with a particle size of 3-5 mm, an oxygen distributor set at the front of the bed for uniformly distributing oxygen-containing carrier gas, a temperature control structure including a preheater and a cooling quench line to control the reaction temperature, and an inlet and an outlet for introducing the pretreated liquid ammonia and discharging the reaction mixture, respectively.

[0031] Furthermore, based on the catalyst type and the oxygen content control range, this embodiment of the invention establishes a selective oxidation reaction zone corresponding to the pretreated liquid ammonia in the reactor. This allows hydrocarbon impurities in the pretreated liquid ammonia to undergo selective oxidation within this zone, while suppressing non-target oxidation of the liquid ammonia itself, thereby achieving efficient removal of target impurities. The selective oxidation reaction zone is a localized area established within the reactor based on the oxygen content control range and catalyst activity characteristics, for the purpose of achieving selective oxidation of hydrocarbons.

[0032] As an embodiment of the present invention, based on the catalyst type and the oxygen content control range, a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor, including: The copper oxide-cobalt oxide composite catalyst of the aforementioned catalyst type is loaded into the fixed bed of the reactor to form a catalyst bed; An oxygen-containing carrier gas is introduced into the catalyst bed to keep the oxygen concentration in the catalyst bed within the oxygen content control range. When the oxygen concentration in the catalyst bed reaches the oxygen content control range, the bed temperature of the catalyst bed is simultaneously controlled at the preset reaction temperature to form the selective oxidation reaction zone.

[0033] The copper oxide-cobalt oxide composite catalyst refers to composite metal oxide particles prepared by co-precipitation method with copper oxide and cobalt oxide as the main active components; the fixed bed refers to the reaction zone filled with granular catalyst and through which the reactants pass in a fixed flow manner, specifically including: the reactants continuously pass through the catalyst bed at a preset space velocity under constant pressure, and the catalyst particles maintain a static flow and contact form during the reaction; the oxygen-containing carrier gas refers to the gas medium formed by mixing nitrogen and oxygen at a preset volume ratio; the oxygen concentration refers to the volume percentage of oxygen in the gas phase of the catalyst bed.

[0034] Optionally, the oxygen-containing carrier gas is uniformly dispersed by a distributor located at the inlet end of the catalyst bed, the distributor being a porous tubular gas distribution device; the bed temperature of the catalyst bed is controlled by a preheater and a quenching sub-line in the reactor, the preheater being a shell-and-tube heat exchanger located in the feed section of the reactor for preheating the raw materials; the quenching sub-line is a rapid cooling pipeline system connected in the middle of the reactor for introducing a low-temperature medium to regulate the reaction temperature.

[0035] In another embodiment of the present invention, an oxygen-containing carrier gas is introduced into the catalyst bed to keep the oxygen concentration in the catalyst bed within the oxygen content control range, including: A mixed carrier gas, consisting of an inert gas and oxygen, is introduced into the inlet end of the catalyst bed. An oxygen concentration sensor is deployed at the inlet end of the catalyst bed to monitor the oxygen concentration in the mixed carrier gas in real time. Based on the oxygen concentration, the mixing ratio of the mixed carrier gas is dynamically adjusted so that the oxygen concentration in the catalyst bed is within the oxygen content control range.

[0036] The oxygen concentration sensor is an online oxygen analyzer installed in the gas pipeline at the inlet end of the catalyst bed, used to acquire the oxygen concentration signal of the mixed carrier gas introduced into the bed in real time.

[0037] Optionally, the specific process for dynamically adjusting the mixing ratio of the mixed carrier gas based on the oxygen concentration is as follows: obtaining the oxygen concentration monitoring value collected in real time by the oxygen concentration sensor; comparing the oxygen concentration monitoring value with the oxygen content control range: if the monitoring value is lower than the lower limit of the range, increasing the oxygen supply ratio in the mixed carrier gas through the regulating valve; if the monitoring value is higher than the upper limit of the range, decreasing the oxygen supply ratio in the mixed carrier gas through the regulating valve.

[0038] Step S3: Based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, set the oxygen content control value of the selective oxidation reaction zone within the oxygen content control range.

[0039] This invention, by setting the oxygen content control value of the selective oxidation reaction zone within the oxygen content control range according to the catalyst type and the component characteristics of hydrocarbons in the pretreated liquid ammonia, can match the most suitable oxygen content for a specific catalyst and target impurity combination. This effectively oxidizes hydrocarbons while avoiding excessive oxidation and loss of liquid ammonia due to excessive oxygen content, or incomplete impurity removal due to excessive oxygen content.

[0040] Wherein, the hydrocarbons refer to alkane, olefin, or aromatic hydrocarbon organic impurities that exist in dissolved state in the pretreated liquid ammonia; the component characteristics include the species composition and concentration distribution characteristics of the hydrocarbons; the oxygen content control value is used to establish an oxidation atmosphere in the selective oxidation reaction zone that matches the catalyst activity and the reaction kinetics of the target impurities, so as to ensure that the hydrocarbon impurities are selectively oxidized at this oxygen concentration.

[0041] As an embodiment of the present invention, based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, the oxygen content control value of the selective oxidation reaction zone is set within the oxygen content control range, including: Based on the characteristics of the components, the impurity components with the lowest oxidation reactivity in the hydrocarbons are extracted; Identify the selective oxidation activity window corresponding to the catalyst type, and based on the catalyst type, determine the minimum oxygen concentration required for the impurity component to achieve a preset removal rate; Within the oxygen content control range, a value between the minimum oxygen concentration and the upper limit of the selective oxidation activity window is selected as the oxygen content control value.

[0042] The selective oxidation activity window refers to the range of oxygen concentrations within which the catalyst can operate effectively while maintaining high selective oxidation. The preset removal rate refers to the target removal efficiency set for the impurity component with the lowest oxidation reactivity within the selective oxidation reaction zone. For example, if the catalyst is a copper oxide-cobalt oxide composite catalyst and the impurity component with the lowest oxidation reactivity is methane, then the selective oxidation activity window can be 7.5% to 8.5%, and the preset removal rate can be above 90%.

[0043] Optionally, the selective oxidation activity window corresponding to the catalyst type can be identified by selective oxidation experiments at different oxygen concentrations. For example, under fixed catalyst and reaction temperature conditions, the oxidation removal rate of the target hydrocarbon and the oxidation loss rate of the liquid ammonia at different oxygen concentrations can be tested, and the range of oxygen concentrations with high hydrocarbon removal rate and low liquid ammonia oxidation loss rate can be determined as the selective oxidation activity window corresponding to the catalyst.

[0044] For example, the minimum oxygen concentration required for the impurity components to achieve the preset removal rate is calculated using the following formula. It should be noted that this calculation method is only one possible method and does not affect the implementation of the basic scheme above: in, Indicates the minimum oxygen concentration. Indicates the stoichiometric oxygen consumption ratio. This indicates the initial molar concentration of the target impurity component in the pretreated liquid ammonia. Indicates the preset removal rate. Indicates the oxygen utilization selectivity coefficient. This indicates the total molar concentration of the gas phase within the reactor. Indicates the carrier gas dilution factor. This represents the oxygen concentration safety redundancy factor.

[0045] In detail, the stoichiometric oxygen consumption ratio This refers to the number of moles of oxygen required for the complete oxidation of each mole of the target hydrocarbon impurity to carbon dioxide and water on the selected catalyst; the oxygen utilization selectivity coefficient S refers to the number of moles of oxygen required for the complete oxidation of each mole of the target hydrocarbon impurity to carbon dioxide and water on the selected catalyst, and its value ranges from 0 to 1. A higher value indicates a stronger selective oxidation ability of the catalyst for the target impurity; the carrier gas dilution factor... This refers to the ratio of the molar flow rate of the inert gas component in the oxygen-containing carrier gas introduced into the reactor to the molar flow rate of the vaporized liquid ammonia; the oxygen concentration safety redundancy factor. It is a multiplier coefficient set to ensure that there is always sufficient oxygen in the selective oxidation reaction zone and to avoid insufficient oxygen concentration. It can be set based on engineering experience and is usually in the range of 1.1 to 1.3.

[0046] Optionally, the oxygen utilization selectivity coefficient can be determined by comparing the oxidation rates of the target impurity and liquid ammonia; the formula for calculating the total molar concentration of the gas phase in the reactor is: =P / (RT), where P represents the operating pressure of the selective oxidation reaction zone, R represents the universal gas constant, and T represents the absolute reaction temperature of the reaction zone.

[0047] As an optional embodiment of the present invention, based on the component characteristics, the impurity component with the lowest oxidation reactivity in the hydrocarbon is extracted, including: The molecular structure of each impurity component in the component characteristics is analyzed to determine the activation energy of the oxidation reaction corresponding to each impurity component; The impurity component corresponding to the highest oxidation activation energy among the oxidation reaction activation energies is determined to be the impurity component with the lowest oxidation reaction activity in the hydrocarbon.

[0048] The molecular structure includes the chemical formula, chemical bond type, and spatial configuration of the impurity component; the activation energy of the oxidation reaction refers to the minimum energy threshold that the reactant molecules must reach when the impurity component undergoes an oxidation reaction under the action of the catalyst. The higher the value, the more difficult it is for the impurity to be oxidized and removed.

[0049] Optionally, the activation energy of the oxidation reaction corresponding to each impurity component can be determined by quantum chemical calculation methods, such as calculating the transition state energy of each impurity component undergoing oxidation reaction on the catalyst surface using density functional theory, thereby obtaining the activation energy of the oxidation reaction corresponding to each impurity component.

[0050] Step S4: Based on the oxygen content control value and the reaction temperature, the pretreated liquid ammonia undergoes a selective catalytic oxidation reaction in the selective oxidation reaction zone to obtain a mixed product after the reaction. After gas-liquid separation of the mixed product, the target liquid ammonia is obtained.

[0051] Based on the oxygen content control value and the reaction temperature, this invention embodiment involves the selective catalytic oxidation of pretreated liquid ammonia within the selective oxidation reaction zone, yielding a mixed product. This process maximizes the suppression of non-selective oxidation of the liquid ammonia, thereby achieving efficient removal of impurities and high-purity retention of the liquid ammonia product. The mixed product includes oxidized gaseous products and preliminarily separated liquid ammonia. The oxidized gaseous products mainly consist of carbon dioxide (CO2) and water vapor (H2O) generated after the oxidation of hydrocarbon impurities, as well as excess oxygen, carrier gas (such as nitrogen), and trace amounts of side reaction gases that did not participate in the reaction. The preliminarily separated liquid ammonia refers to the unreacted liquid ammonia bulk, in which the hydrocarbon impurity content has been significantly reduced.

[0052] As an embodiment of the present invention, based on the oxygen content control value and the reaction temperature, a selective catalytic oxidation reaction of the pretreated liquid ammonia occurs in the selective oxidation reaction zone to obtain a mixed product after the reaction, comprising: The pretreated liquid ammonia is introduced into the selective oxidation reaction zone at a preset flow rate; Simultaneously adjust the oxygen concentration and reaction temperature in the selective oxidation reaction zone to the corresponding oxygen content control value and reaction temperature; Under the conditions of maintaining the oxygen content control value and the reaction temperature, the pretreated liquid ammonia is continuously passed through the catalyst bed of the selective oxidation reaction zone to undergo catalytic oxidation reaction; The gas-liquid mixture after the reaction is collected synchronously from the outlet of the selective oxidation reaction zone as the mixed product.

[0053] It should be noted that the selective oxidation reaction is carried out in a fixed-bed reactor packed with a copper oxide-cobalt oxide composite catalyst. The catalyst bed provides the reaction site for the selective oxidation reaction zone. When the pretreated liquid ammonia flows through the catalyst bed, the hydrocarbon impurities therein are selectively oxidized into carbon dioxide and water at the controlled oxygen content and the reaction temperature.

[0054] Furthermore, in this embodiment of the invention, the target liquid ammonia is obtained by gas-liquid separation of the mixed product. This can efficiently remove hydrocarbons while avoiding excessive oxidation of the liquid ammonia itself, thereby obtaining high-purity target liquid ammonia. This overcomes the problem of incomplete and unstable impurity removal caused by insufficient selectivity in traditional catalytic oxidation technology.

[0055] As an embodiment of the present invention, the target liquid ammonia is obtained by gas-liquid separation of the mixed product, comprising: The mixture is passed into a gas-liquid separator for separation to obtain a gaseous product and preliminarily separated liquid ammonia. The pre-separated liquid ammonia is fed into a flash evaporation device to remove the gaseous components from the pre-separated liquid ammonia, thereby obtaining flash-evaporated liquid ammonia; The flash-evaporated liquid ammonia is passed into a distillation column for purification to remove volatile impurities and obtain distilled liquid ammonia. The distilled liquid ammonia is condensed to obtain the target liquid ammonia.

[0056] The gaseous components refer to carbon dioxide dissolved in liquid ammonia, unreacted oxygen, and inert carrier gas; the volatile impurities refer to low-boiling-point hydrocarbons, water, and trace amounts of ammonia decomposition products distilled off with the liquid ammonia.

[0057] As an optional embodiment of the present invention, the distilled liquid ammonia is condensed to obtain the target liquid ammonia, including: The distilled liquid ammonia is passed into a condenser, and the distilled liquid ammonia is cooled to below the preset liquid ammonia condensation temperature by the circulating cooling medium in the condenser, so that the distilled liquid ammonia is completely liquefied; The fully liquefied distilled ammonia is introduced into a pressure stabilizing tank to release trace amounts of non-condensable gases from the distilled ammonia. After the release of the trace amount of non-condensable gas is completed, the liquid ammonia in the pressure stabilizing tank is collected as the target liquid ammonia.

[0058] The circulating cooling medium refers to a low-temperature fluid that exchanges heat with gaseous distilled liquid ammonia in the condenser, causing it to condense into a liquid state. Specifically, industrial circulating cooling water or low-temperature ethylene glycol aqueous solution can be selected. The liquid ammonia condensation temperature refers to the liquid ammonia saturation temperature corresponding to the operating pressure at the top of the distillation column, which is usually 10°C to 30°C. The trace non-condensable gas refers to residual gas components that have not been liquefied in the condenser, such as nitrogen, hydrogen, and trace amounts of unreacted oxygen. The liquid ammonia refers to ammonia that has completed phase change and is in a stable liquid state.

[0059] It should be noted that the gas-liquid separator is a vertical gravity settling separator or a cyclone separator, used to achieve preliminary separation by utilizing the density difference between the gas and liquid phases; the flash evaporator is a reduced-pressure flash tank, used to cause dissolved gases to precipitate from liquid ammonia by reducing pressure; the distillation column is a plate column or a packed column, used to remove residual volatile impurities in liquid ammonia through distillation operations; the condenser is a shell-and-tube or plate heat exchanger, used to condense gaseous ammonia into liquid state through a cooling medium; and the pressure stabilizing tank is a pressure-bearing storage tank with an exhaust valve, used to remove trace amounts of non-condensable gases remaining in liquid ammonia under stable pressure.

[0060] See Figure 2 The diagram shown is a schematic diagram of the equipment connection for implementing the liquid ammonia impurity removal method based on selective oxidation, as provided in an embodiment of the present invention. The solid arrows in the diagram clearly indicate the flow path of the material, and the equipment is connected in sequence, thus fully realizing the entire process from raw material processing to product collection. Specifically: The liquid ammonia selective oxidation removal system described in this scheme starts with the raw liquid ammonia storage tank. The desulfurization pretreatment tower first desulfurizes the liquid ammonia, and then the liquid ammonia is adjusted to the reaction temperature by the preheater. At the same time, the oxygen-containing gasification equipment produces a mixed carrier gas of oxygen and nitrogen. The pretreated liquid ammonia and the carrier gas enter the selective oxidation reactor together, where a selective oxidation reaction occurs in the bed filled with CuO-CoO catalyst. The temperature and oxygen concentration in the reaction zone are precisely controlled by the temperature controller TIC-101 and the oxygen concentration controller AIC-201, respectively. The mixture after the reaction undergoes preliminary gas-liquid separation by the gas-liquid separator. The resulting liquid phase is then passed through a flash degassing tank to remove dissolved gases, a distillation column to remove volatile impurities, and a condenser to liquefy the liquid phase. Finally, the target liquid ammonia is collected in a high-purity liquid ammonia storage tank.

[0061] The advantages of this invention are that by pre-treating the liquid ammonia to be treated with desulfurization, the pre-treated liquid ammonia can be obtained, which can remove the sulfide impurities contained in the liquid ammonia in advance, avoiding their entry into the subsequent selective oxidation reaction zone and causing poisoning and deactivation of the catalyst active center. Furthermore, based on the catalyst type and the oxygen content control range, this embodiment of the invention establishes a selective oxidation reaction zone corresponding to the pre-treated liquid ammonia in the reactor, which allows the hydrocarbon impurities in the pre-treated liquid ammonia to undergo selective oxidation reaction in this zone, while inhibiting non-target oxidation of the liquid ammonia itself, thereby achieving efficient removal of target impurities.

[0062] This invention, through setting the oxygen content control value of the selective oxidation reaction zone within the oxygen content control range based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, can match the most suitable oxygen content for a specific catalyst and target impurity combination. This effectively oxidizes hydrocarbons while avoiding excessive ammonia oxidation due to excessive oxygen content or incomplete impurity removal due to insufficient oxygen content. Furthermore, based on the oxygen content control value and the reaction temperature, this invention allows for the selective catalytic oxidation of the pretreated liquid ammonia within the selective oxidation reaction zone, yielding a mixed product. This maximally suppresses non-selective oxidation of the liquid ammonia, achieving efficient impurity removal and high-purity retention of the product liquid ammonia. Finally, by performing gas-liquid separation on the mixed product, the target liquid ammonia is obtained. This efficiently removes hydrocarbons while preventing excessive oxidation of the liquid ammonia, resulting in high-purity target liquid ammonia. This overcomes the problems of incomplete and unstable impurity removal caused by insufficient selectivity in traditional catalytic oxidation technologies. Therefore, this invention can maximally suppress non-selective oxidation of the liquid ammonia, achieving efficient impurity removal.

[0063] like Figure 3 The diagram shown is a functional block diagram of a liquid ammonia impurity removal system based on selective oxidation according to the present invention.

[0064] The liquid ammonia impurity removal system 400 based on selective oxidation described in this invention can be installed in an electronic device. Depending on the functions implemented, the liquid ammonia impurity removal system based on selective oxidation includes a raw material processing module 401, an environment configuration module 402, a parameter setting module 403, and a separation and purification module 404. The module described in this invention can also be called a unit, which refers to a series of computer program segments that can be executed by the processor of an electronic device and can perform a fixed function, and are stored in the memory of the electronic device.

[0065] In this embodiment of the invention, the functions of each module / unit are as follows: The raw material processing module 401 is used to acquire the impurity composition data of the liquid ammonia to be treated, and to perform desulfurization pretreatment on the liquid ammonia to be treated to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the liquid ammonia in the selective oxidation process. The environmental configuration module 402 is used to introduce the pretreated liquid ammonia into the corresponding reactor, and to establish a selective oxidation reaction zone corresponding to the pretreated liquid ammonia in the reactor based on the catalyst type and the oxygen content control range. The parameter setting module 403 is used to set the oxygen content control value of the selective oxidation reaction zone within the oxygen content control range according to the catalyst type and the composition characteristics of hydrocarbons in the pretreated liquid ammonia. The separation and purification module 404 is used to selectively catalytically oxidize the pretreated liquid ammonia in the selective oxidation reaction zone based on the oxygen content control value and the reaction temperature, to obtain a mixed product after the reaction, and to obtain the target liquid ammonia after gas-liquid separation of the mixed product.

[0066] In detail, the modules in the liquid ammonia impurity removal system 400 based on selective oxidation described in this embodiment of the invention employ the same methods as described above. Figure 1 The method described herein is the same as the liquid ammonia impurity removal method based on selective oxidation, and can produce the same technical effect, so it will not be repeated here.

[0067] In one embodiment, a computer device is provided, which may be a server or a client, and its internal structure diagram may be as follows: Figure 4 As shown. The computer device includes a processor, memory, network interface, and database connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile and / or volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface is used for communication with external clients via a network connection. When the computer program is executed by the processor, it implements functions or steps on the server or client side of a selective oxidation-based liquid ammonia impurity removal method.

[0068] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to perform the following steps: The impurity composition data of the liquid ammonia to be treated is obtained, and the liquid ammonia to be treated is subjected to desulfurization pretreatment to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the liquid ammonia in the selective oxidation process. The pretreated liquid ammonia is introduced into the corresponding reactor, and a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor based on the catalyst type and the oxygen content control range. Based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, the oxygen content control value of the selective oxidation reaction zone is set within the oxygen content control range. Based on the oxygen content control value and the reaction temperature, the pretreated liquid ammonia undergoes a selective catalytic oxidation reaction in the selective oxidation reaction zone to obtain a mixed product after the reaction. After gas-liquid separation of the mixed product, the target liquid ammonia is obtained.

[0069] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program performing the following steps when executed by a processor: The impurity composition data of the liquid ammonia to be treated is obtained, and the liquid ammonia to be treated is subjected to desulfurization pretreatment to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the liquid ammonia in the selective oxidation process. The pretreated liquid ammonia is introduced into the corresponding reactor, and a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor based on the catalyst type and the oxygen content control range. Based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, the oxygen content control value of the selective oxidation reaction zone is set within the oxygen content control range. Based on the oxygen content control value and the reaction temperature, the pretreated liquid ammonia undergoes a selective catalytic oxidation reaction in the selective oxidation reaction zone to obtain a mixed product after the reaction. After gas-liquid separation of the mixed product, the target liquid ammonia is obtained.

[0070] It should be noted that the functions or steps that can be implemented by the computer-readable storage medium or computer device described above can be referred to the relevant descriptions on the server side and client side in the foregoing method embodiments. To avoid repetition, they will not be described one by one here.

[0071] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0072] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

Claims

1. A method for removing liquid ammonia impurities based on selective oxidation, characterized in that, The method includes: The impurity composition data of the liquid ammonia to be treated is obtained, and the liquid ammonia to be treated is subjected to desulfurization pretreatment to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the liquid ammonia in the selective oxidation process. The pretreated liquid ammonia is introduced into the corresponding reactor, and a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor based on the catalyst type and the oxygen content control range. Based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, the oxygen content control value of the selective oxidation reaction zone is set within the oxygen content control range. Based on the oxygen content control value and the reaction temperature, the pretreated liquid ammonia undergoes a selective catalytic oxidation reaction in the selective oxidation reaction zone to obtain a mixed product after the reaction. After gas-liquid separation of the mixed product, the target liquid ammonia is obtained.

2. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 1, characterized in that, Based on the catalyst type and the oxygen content control range, a selective oxidation reaction zone corresponding to the pretreated liquid ammonia is established in the reactor, including: The copper oxide-cobalt oxide composite catalyst of the aforementioned catalyst type is loaded into the fixed bed of the reactor to form a catalyst bed; An oxygen-containing carrier gas is introduced into the catalyst bed to keep the oxygen concentration in the catalyst bed within the oxygen content control range. When the oxygen concentration in the catalyst bed reaches the oxygen content control range, the bed temperature of the catalyst bed is simultaneously controlled at the preset reaction temperature to form the selective oxidation reaction zone.

3. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 2, characterized in that, Introducing an oxygen-containing carrier gas into the catalyst bed to keep the oxygen concentration within the controlled oxygen content range includes: A mixed carrier gas, consisting of an inert gas and oxygen, is introduced into the inlet end of the catalyst bed. An oxygen concentration sensor is deployed at the inlet end of the catalyst bed to monitor the oxygen concentration in the mixed carrier gas in real time. Based on the oxygen concentration, the mixing ratio of the mixed carrier gas is dynamically adjusted so that the oxygen concentration in the catalyst bed is within the oxygen content control range.

4. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 1, characterized in that, Based on the catalyst type and the compositional characteristics of hydrocarbons in the pretreated liquid ammonia, the oxygen content control value of the selective oxidation reaction zone is set within the oxygen content control range, including: Based on the characteristics of the components, the impurity components with the lowest oxidation reactivity in the hydrocarbons are extracted; Identify the selective oxidation activity window corresponding to the catalyst type, and based on the catalyst type, determine the minimum oxygen concentration required for the impurity component to achieve a preset removal rate; Within the oxygen content control range, a value between the minimum oxygen concentration and the upper limit of the selective oxidation activity window is selected as the oxygen content control value.

5. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 4, characterized in that, Based on the characteristics of the components, the impurity components with the lowest oxidation reactivity in the hydrocarbons are extracted, including: The molecular structure of each impurity component in the component characteristics is analyzed to determine the activation energy of the oxidation reaction corresponding to each impurity component; The impurity component corresponding to the highest oxidation activation energy among the oxidation reaction activation energies is determined to be the impurity component with the lowest oxidation reaction activity in the hydrocarbon.

6. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 1, characterized in that, After gas-liquid separation of the mixed product, the target liquid ammonia is obtained, comprising: The mixture is passed into a gas-liquid separator for separation to obtain a gaseous product and preliminarily separated liquid ammonia. The pre-separated liquid ammonia is fed into a flash evaporation device to remove the gaseous components from the pre-separated liquid ammonia, thereby obtaining flash-evaporated liquid ammonia; The flash-evaporated liquid ammonia is passed into a distillation column for purification to remove volatile impurities and obtain distilled liquid ammonia. The distilled liquid ammonia is condensed to obtain the target liquid ammonia.

7. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 6, characterized in that, The distilled liquid ammonia is condensed to obtain the target liquid ammonia, comprising: The distilled liquid ammonia is passed into a condenser, and the distilled liquid ammonia is cooled to below the preset liquid ammonia condensation temperature by the circulating cooling medium in the condenser, so that the distilled liquid ammonia is completely liquefied; The fully liquefied distilled ammonia is introduced into a pressure stabilizing tank to release trace amounts of non-condensable gases from the distilled ammonia. After the release of the trace amount of non-condensable gas is completed, the liquid ammonia in the pressure stabilizing tank is collected as the target liquid ammonia.

8. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 1, characterized in that, Based on the oxygen content control value and the reaction temperature, a selective catalytic oxidation reaction of the pretreated liquid ammonia occurs in the selective oxidation reaction zone to obtain a mixed product after the reaction, comprising: The pretreated liquid ammonia is introduced into the selective oxidation reaction zone at a preset flow rate; Simultaneously adjust the oxygen concentration and reaction temperature in the selective oxidation reaction zone to the corresponding oxygen content control value and reaction temperature; Under the conditions of maintaining the oxygen content control value and the reaction temperature, the pretreated liquid ammonia is continuously passed through the catalyst bed of the selective oxidation reaction zone to undergo catalytic oxidation reaction; The gas-liquid mixture after the reaction is collected synchronously from the outlet of the selective oxidation reaction zone as the mixed product.

9. The method for removing liquid ammonia impurities based on selective oxidation as described in claim 1, characterized in that, The liquid ammonia to be treated is subjected to desulfurization pretreatment to obtain pretreated liquid ammonia, comprising: The liquid ammonia to be treated is introduced into a prepared desulfurization tower so that the sulfides in the liquid ammonia to be treated undergo a selective adsorption reaction in the desulfurization tower to obtain primary purified liquid ammonia. The primary purified liquid ammonia is passed into a pre-installed activated carbon adsorption device, and the activated carbon adsorption device is used to remove trace amounts of organic sulfur components from the primary purified liquid ammonia to obtain the pretreated liquid ammonia.

10. A liquid ammonia impurity removal system based on selective oxidation, characterized in that, The system employs a liquid ammonia impurity removal method based on selective oxidation as described in any one of claims 1-9, wherein the system comprises: The raw material processing module is used to acquire the impurity composition data of the liquid ammonia to be treated and to perform desulfurization pretreatment on the liquid ammonia to be treated to obtain pretreated liquid ammonia. The impurity composition data is used to determine the catalyst type, oxygen content control range and reaction temperature required for the selective oxidation process of the liquid ammonia. An environmental configuration module is used to introduce the pretreated liquid ammonia into the corresponding reactor, and to establish a selective oxidation reaction zone for the pretreated liquid ammonia in the reactor based on the catalyst type and the oxygen content control range. The parameter setting module is used to set the oxygen content control value of the selective oxidation reaction zone within the oxygen content control range according to the catalyst type and the composition characteristics of hydrocarbons in the pretreated liquid ammonia. The separation and purification module is used to selectively catalytically oxidize the pretreated liquid ammonia in the selective oxidation reaction zone based on the oxygen content control value and the reaction temperature, to obtain a mixed product after the reaction, and to separate the mixed product into gas and liquid to obtain the target liquid ammonia.

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