Desulfurization method

Abstract

The application discloses a desulfurization method, and belongs to the technical field of desulfurization. The method comprises the following steps: obtaining the residual activity of a desulfurizer in a desulfurization tower and the total sulfur content of raw material gas at the inlet of the desulfurization tower; determining a target water supplementing flow rate according to the residual activity and the total sulfur content; injecting water into the raw material gas at the inlet side of the desulfurization tower at the target water supplementing flow rate, and vaporizing the injected water before entering the desulfurization tower; and inputting the humidified raw material gas into the desulfurization tower for desulfurization. The method combines the residual activity of the desulfurizer to adjust the water supplementing flow rate, matches the water supplementing strategy with the actual attenuation degree of the desulfurizer, can delay the breakthrough of the desulfurizer under the working condition of high sulfur impact, and prolongs the service life of the desulfurizer.

Description

Technical Field

[0001] This invention belongs to the field of desulfurization technology, and specifically relates to a desulfurization method. Background Technology

[0002] In carbon dioxide recovery and purification processes, the carbon dioxide feed gas from upstream ammonia synthesis units typically contains trace amounts of sulfide impurities such as hydrogen sulfide. Industrially, fixed-bed dry desulfurization processes are commonly used, employing specialized iron- or zinc-based desulfurization adsorbents to remove sulfides through chemical adsorption or catalytic oxidation reactions.

[0003] The process faces the following technical bottlenecks in actual operation: Firstly, when the operating conditions of the upstream ammonia synthesis unit fluctuate, the total sulfur content of the feed gas may suddenly rise from the design value of 0.2 ppm to 3 ppm or even higher, exceeding the instantaneous adsorption capacity of the desulfurizing agent, resulting in excessive sulfur content at the outlet.

[0004] Secondly, after long-term operation, the active components of the desulfurizer are gradually consumed, and the specific surface area decreases, making it more prone to penetration when facing high sulfur loads.

[0005] Third, increasing the amount of desulfurizing agent requires increased equipment investment, and frequent replacement of desulfurizing agent leads to equipment shutdown and increased hazardous waste treatment costs.

[0006] Fourth, existing humidification control typically adjusts the amount of water added only linearly based on the inlet sulfur content, i.e., increasing the amount of water added when the sulfur content is high and decreasing the amount of water added when the sulfur content is low, without considering the degree of decay of the desulfurizing agent itself.

[0007] For humidifying the inlet feed gas, existing technologies have proposed atomizing and humidifying the feed gas before it enters the desulfurization tower, and controlling the relative humidity of the feed gas within a suitable range. This utilizes water molecules to form a water film on the surface of the desulfurizing agent, promoting the dissolution and diffusion of hydrogen sulfide and its participation in the reaction process. However, current makeup water flow control is usually based on parameters such as inlet sulfur content or feed gas humidity, without considering the remaining activity of the desulfurizing agent as a factor in determining the makeup water flow rate. When the desulfurizing agent enters the final stage of its use, its adsorption and reaction capacity has decreased. If makeup water is still added at a fixed flow rate or only based on the inlet sulfur content, it may lead to insufficient or excessive makeup water, making it difficult to simultaneously prevent penetration and prevent desulfurizing agent agglomeration.

[0008] Therefore, it is necessary to provide a desulfurization method that, based on the total sulfur content at the inlet, further combines the residual activity of the desulfurizing agent to determine the target makeup water flow rate, and switches to a moisturizing flow rate when the inlet sulfur load is normal, so as to make full use of the residual activity of the desulfurizing agent at the end of its use period and delay penetration. Summary of the Invention

[0009] The purpose of this invention is to provide a desulfurization method that obtains the residual activity of the desulfurizing agent and the total sulfur content of the raw gas at the inlet of the desulfurization tower, and determines the target water replenishment flow rate based on both, so that the water replenishment strategy matches the actual attenuation degree of the desulfurizing agent and the sulfur load, thereby optimizing the surface reaction environment of the desulfurizing agent and extending the service life of the desulfurizing agent.

[0010] To achieve the above objectives, the present invention provides a desulfurization method, comprising: obtaining the residual activity of the desulfurizing agent in the desulfurization tower and the total sulfur content of the feed gas at the inlet of the desulfurization tower; determining a target makeup water flow rate based on the residual activity and the total sulfur content; wherein, when the total sulfur content is greater than a preset sulfur content threshold, the target makeup water flow rate increases as the residual activity decreases when the total sulfur content is the same, and the target makeup water flow rate increases as the total sulfur content increases when the residual activity is the same; when the total sulfur content is less than or equal to the preset sulfur content threshold, the target makeup water flow rate is determined based on the range of the ratio of the residual activity to the initial activity of the desulfurizing agent; injecting water into the feed gas at the inlet side of the desulfurization tower according to the target makeup water flow rate, and vaporizing the injected water before it enters the desulfurization tower; and inputting the humidified feed gas into the desulfurization tower for desulfurization.

[0011] In some implementations, determining the target makeup water flow rate based on the remaining activity and the total sulfur content includes: when C is greater than C0, determining the target makeup water flow rate according to the following formula: Q = Q0 + k×(C-C0)×(1+α×(1-A / A0)); when C is less than or equal to C0 and A / A0 is less than or equal to 0.35, setting the target makeup water flow rate to 5 L / h to 15 L / h; when C is less than or equal to C0 and A / A0 is greater than 0.35, setting the target makeup water flow rate to Q0, i.e., maintaining 20 L / h to 40 L / h. The basic humidification rate is L / h, without entering the low-flow humidification mode; where Q is the target water replenishment flow rate in L / h; Q0 is the baseline water replenishment flow rate in L / h; k is the sulfur load response coefficient in L / h / ppm; C is the total sulfur content in ppm; C0 is the preset sulfur content threshold in ppm; α is the desulfurizing agent attenuation compensation coefficient; A is the remaining activity of the desulfurizing agent in percentage; A0 is the initial activity of the desulfurizing agent in percentage.

[0012] In some implementations, Q0 is 20 L / h to 40 L / h; C0 is greater than 0.2 ppm and less than 1 ppm; k is 15 L / h / ppm to 25 L / h / ppm; and α is 0.3 to 0.8.

[0013] In some implementations, k and α are selected according to the remaining activity: when A / A0 is greater than or equal to 0.35, k is 15 L / h / ppm and α is 0.3; when A / A0 is less than or equal to 0.25, k is 25 L / h / ppm and α is 0.8; when A / A0 is greater than 0.25 and less than 0.35, k is determined by linear interpolation between 15 L / h / ppm and 25 L / h / ppm, and α is determined by linear interpolation between 0.3 and 0.8.

[0014] In some implementations, obtaining the residual activity of the desulfurizing agent includes: sampling and measuring the dynamic penetration sulfur capacity of the desulfurizing agent, and taking the ratio of the measured dynamic penetration sulfur capacity to the initial dynamic penetration sulfur capacity of the desulfurizing agent as the residual activity.

[0015] In some implementations, the desulfurization method further includes: measuring the actual water supply flow rate in real time, calculating the deviation between the actual water supply flow rate and the target water supply flow rate, and adjusting the water supply flow rate of the water injection device according to the deviation using a PID control algorithm or a model predictive control algorithm.

[0016] In some embodiments, the feed gas is carbon dioxide feed gas; the desulfurizing agent is an iron-based desulfurizing agent or a zinc-based desulfurizing agent.

[0017] In some embodiments, injecting water into the feed gas includes: pressurizing the water to 6 MPa to 10 MPa, atomizing it into droplets with an average particle size of 20 μm to 50 μm, and then spraying the droplets into the feed gas.

[0018] In some embodiments, the temperature of the feed gas is 60°C to 100°C, the pressure is 1.5 MPa to 3.0 MPa, and the flow rate is 10,000 Nm³. 3 / h to 20000 Nm 3 / h.

[0019] In some implementations, the temperature of the injected water is between 20°C and 40°C.

[0020] Compared with the prior art, the present invention has at least one of the following significant beneficial effects: by using the residual activity of the desulfurizer and the total sulfur content as variables to determine the makeup water flow rate, the makeup water strategy adapts to the performance changes of the desulfurizer throughout its entire life cycle; since the target makeup water flow rate is larger when the residual activity is lower than the sulfur content is greater than the threshold, the water film effect on the surface of the desulfurizer is enhanced, which compensates for the insufficient reaction driving force caused by the reduction of active sites. Therefore, it can delay penetration and extend the service life of the desulfurizer under high sulfur impact; when the sulfur content is normal and the residual activity is low, a moisturizing flow rate of 5 L / h to 15 L / h is used to maintain the necessary wet state of the desulfurizer and avoid excessive humidification that leads to agglomeration and increased pressure drop; by high-pressure atomization and vaporization of water before entering the tower, it is ensured that the water is uniformly mixed with the raw gas in gaseous form, avoiding direct contact of liquid water with the bed and causing local over-wetting. Detailed Implementation

[0021] The invention will be described in more detail below to aid in understanding it.

[0022] It should be understood that the terms or words used in this specification and the appended claims should not be construed as limited to their general or dictionary meanings, but rather interpreted based on their meanings and concepts corresponding to the technical aspects of the invention, on the basis of the principle that the inventors are allowed to define terms appropriately for the best explanation.

[0023] It should be further understood that, unless otherwise expressly stated, when used in the specification, "comprising" or "including" indicates the presence of the said element and does not exclude the presence or addition of one or more other elements.

[0024] As used herein, a range is used as a shorthand to describe the individual values ​​within the range and each value. Any value within the range can be chosen as an endpoint of the range. Thus, the ranges 1 to 5 specifically include 1, 2, 3, 4, and 5, as well as subranges such as 2 to 5, 3 to 5, 2 to 3, 2 to 4, 1 to 4, etc.

[0025] As used herein, the term "feed gas" refers to the gas input into the desulfurization tower for desulfurization treatment, such as carbon dioxide feed gas. The term "desulfurization tower inlet feed gas" refers to the feed gas located upstream of the desulfurization tower inlet and about to enter the desulfurization tower.

[0026] As used in this article, the term "total sulfur content" refers to the total concentration of sulfur-containing components such as hydrogen sulfide in the feed gas, expressed as C, and the unit is ppm.

[0027] As used herein, the term "desulfurizing agent" refers to a solid desulfurizing agent, such as an iron-based or zinc-based desulfurizing agent, that is packed inside a desulfurization tower to remove sulfides from the raw gas.

[0028] As used herein, the term "residual activity" refers to the percentage of the current actual desulfurization capacity of the desulfurizing agent compared to its initial desulfurization capacity, denoted as A. Residual activity can be expressed as the ratio of dynamic breakthrough sulfur capacity, or it can be estimated based on the desulfurizing agent's operating time and cumulative sulfur treatment volume. Residual activity is one of the core parameters for determining the target makeup water flow rate in this application.

[0029] As used in this article, the term "initial activity" refers to the initial desulfurization capacity of the desulfurizing agent before it is used, denoted as A0 in this article.

[0030] As used in this article, the term "dynamic penetration sulfur capacity" refers to the sulfur capacity of a desulfurizing agent under specific operating conditions, from the initial introduction of sulfur-containing gas to the point where the outlet sulfur content reaches the specified penetration value.

[0031] As used herein, the term "target makeup water flow rate" refers to the flow rate of water injected into the inlet feed gas of the desulfurization tower, determined based on the total sulfur content of the inlet feed gas and the remaining activity of the desulfurizing agent. It is denoted by Q and the unit is L / h. Specifically, when the total sulfur content is greater than a preset sulfur content threshold, the target makeup water flow rate increases with increasing total sulfur content and decreases with decreasing remaining activity. When the total sulfur content is less than or equal to the preset sulfur content threshold and the remaining activity of the desulfurizing agent is in the late stage of use, the target makeup water flow rate is adjusted to a moisture retention flow rate. When the total sulfur content is less than or equal to the preset sulfur content threshold and the remaining activity of the desulfurizing agent is not in the late stage of use, the target makeup water flow rate remains at the baseline makeup water flow rate.

[0032] As used in this article, the term "moisturizing flow rate" refers to the water replenishment flow rate set to maintain the necessary wetness of the desulfurizer surface when the total sulfur content is normal and the remaining activity of the desulfurizer is at the end of its use. The value ranges from 5 L / h to 15 L / h.

[0033] As used in this article, the term "preset sulfur content threshold" refers to the sulfur content threshold used to determine whether the total sulfur content of the inlet feed gas exceeds the design capacity of the desulfurizer, and is denoted as C0 in this article.

[0034] As used in this article, the term "baseline makeup flow rate" refers to the baseline flow rate used to determine the target makeup flow rate, denoted as Q0 in the text, with units of L / h.

[0035] As used in this paper, the term "sulfur load response coefficient" refers to the coefficient of change in makeup water flow corresponding to the deviation of total sulfur content from a preset sulfur content threshold, denoted as k in this paper.

[0036] As used in this article, the term "desulfurizing agent attenuation compensation coefficient" refers to the coefficient for nonlinear compensation of the makeup water flow rate based on the remaining activity of the desulfurizing agent. It is represented by α in this article, and the value of α is larger when the remaining activity is lower.

[0037] As used in this article, the term "actual makeup water flow" refers to the actual flow rate of water injected into the feed gas at the inlet of the desulfurization tower.

[0038] As used herein, the term "water injection device" refers to a device used to inject water into the feed gas at the inlet of the desulfurization tower.

[0039] As used in this article, the term "vaporization" refers to the process by which injected water changes from a liquid state to a gaseous state before entering the desulfurization tower.

[0040] This invention provides a desulfurization method, comprising: obtaining the residual activity of the desulfurizing agent in the desulfurization tower and the total sulfur content of the feed gas at the inlet of the desulfurization tower; determining a target makeup water flow rate based on the residual activity and the total sulfur content; wherein, when the total sulfur content is greater than a preset sulfur content threshold, the target makeup water flow rate increases as the residual activity decreases when the total sulfur content is the same, and the target makeup water flow rate increases as the total sulfur content increases when the residual activity is the same; when the total sulfur content is less than or equal to the preset sulfur content threshold, the target makeup water flow rate is determined based on the range of the ratio of the residual activity to the initial activity of the desulfurizing agent; injecting water into the feed gas at the inlet side of the desulfurization tower according to the target makeup water flow rate, and vaporizing the injected water before entering the desulfurization tower; and inputting the humidified feed gas into the desulfurization tower for desulfurization.

[0041] To obtain the residual activity of the desulfurizing agent, any of the following methods can be used. Method one is the sampling and determination method: Samples are taken from the upper, middle, and lower parts of the desulfurization tower bed and mixed evenly. Under the same temperature, pressure, and gas composition conditions as industrial plants, the dynamic breakthrough sulfur capacity of the mixed sample is measured. The dynamic breakthrough sulfur capacity is divided by the nominal initial breakthrough sulfur capacity of the desulfurizing agent at the time of manufacture; the resulting percentage is the residual activity. The determination of dynamic breakthrough sulfur capacity can refer to conventional methods in the art. For example, a certain amount of desulfurizing agent sample is loaded into a fixed-bed reactor, and a simulated feed gas containing a known concentration of hydrogen sulfide is introduced. The change in outlet sulfur content over time is recorded under set temperature and pressure. When the outlet sulfur content reaches the breakthrough threshold, the total amount of sulfur adsorbed per unit mass of desulfurizing agent is calculated, which is the dynamic breakthrough sulfur capacity. The initial dynamic breakthrough sulfur capacity can be determined using the same batch of fresh desulfurizing agent using the same method. Sampling should cover different heights of the bed to reflect the overall activity distribution of the bed. Method two is the online estimation model method: Based on the operating data of the desulfurizer, such as its operating time, cumulative sulfur treatment volume, and historical changes in inlet sulfur load, combined with the life decay curve or empirical model provided by the desulfurizer supplier, the remaining activity of the desulfurizer is estimated in real time. This estimation model can be periodically calibrated using the laboratory analysis results from Method one to ensure estimation accuracy. In actual control, Method one or Method two can be used preferentially to obtain the remaining activity, or a combination of both can be used.

[0042] To obtain the total sulfur content, a sulfur content detection device installed on the main inlet pipeline of the desulfurization tower can be used to detect the total sulfur content in the raw gas in real time and transmit the detection signal to the control system. Simultaneously, the flow rate, temperature, and pressure of the raw gas can also be detected for closed-loop control of the subsequent makeup water flow and vaporization state judgment. The target makeup water flow is determined based on the remaining activity and the total sulfur content, specifically including the following control strategy: Let the total sulfur content be C (in ppm); let the preset sulfur content threshold be C0 (in ppm); let the remaining activity of the desulfurizing agent be A, and the initial activity be A0, all expressed as percentages. When A / A0 is less than or equal to 0.35, the desulfurizing agent is considered to be at the end of its service life. When C is greater than C0, the target makeup water flow is determined according to the following formula: Q = Q0 + k×(C-C0)×(1+α×(1-A / A0)). When C is less than or equal to C0 and A / A0 is less than or equal to 0.35, the target makeup water flow is set to 5 L / h to 15 L / h. When C is less than or equal to C0 and A / A0 is greater than 0.35, the target makeup water flow rate is set to Q0, i.e., maintaining a basic humidification rate of 20 L / h to 40 L / h without entering the low-flow humidification mode. The significance of this setting is that when the desulfurizer's remaining activity is still acceptable (A / A0 > 0.35) and the inlet sulfur content does not exceed the threshold, the desulfurizer itself still possesses sufficient desulfurization capacity. There is no need to switch to the low-flow humidification mode; maintaining the basic humidification rate is sufficient to ensure the desulfurizer surface is in a suitable hydration state, while avoiding control disturbances caused by frequent switching.

[0043] In the above formula, Q0 is the baseline makeup water flow rate, expressed in L / h, ranging from 20 L / h to 40 L / h, preferably 23 L / h to 30 L / h. Physically, Q0 represents the minimum makeup water flow rate required to maintain basic humidification capacity when the sulfur content is close to the threshold and the desulfurizer activity is acceptable. If Q0 is too low, it may result in insufficient water film on the desulfurizer surface under low-sulfur conditions, affecting the reaction rate; if it is too high, it may cause unnecessary humidification under low-sulfur conditions, increasing the risk of agglomeration. Therefore, Q0 can be determined based on the feed gas flow rate, temperature, pressure, and basic humidification requirements of the desulfurizer bed. In some implementation schemes, Q0 can be 20 L / h, 22 L / h, 23 L / h, 25 L / h, 28 L / h, 30 L / h, 32 L / h, 35 L / h, 38 L / h, or 40 L / h.

[0044] C0 is a preset sulfur content threshold, expressed in ppm, with a value ranging from greater than 0.2 ppm to less than 1 ppm, preferably from 0.3 ppm to 0.8 ppm, and more preferably 0.5 ppm. Physically, C0 serves as the criterion for initiating humidification compensation. In some embodiments, C0 can be 0.22 ppm, 0.3 ppm, 0.4 ppm, 0.5 ppm, 0.6 ppm, 0.7 ppm, 0.8 ppm, 0.9 ppm, or 0.98 ppm.

[0045] k is the sulfur load response coefficient, measured in L / h / ppm, ranging from 15 to 25 L / h / ppm, preferably 15 to 20 L / h / ppm. k represents the amount of makeup water required to compensate for a unit change in sulfur content. The value of k is related to the residual activity of the desulfurizing agent: when the residual activity is high, the desulfurizing agent's own desulfurization capacity is sufficient, and excessive humidification is unnecessary, so k takes a lower value; when the residual activity is low, it is necessary to compensate for insufficient activity by enhancing the surface water film effect, so k takes a higher value. Specifically, when A / A0 is greater than or equal to 0.35, k is 15 L / h / ppm; when A / A0 is less than or equal to 0.25, k is 25 L / h / ppm; when A / A0 is greater than 0.25 and less than 0.35, k is determined by linear interpolation between 15 L / h / ppm and 25 L / h / ppm. For example, when A / A0 = 0.30, k = 15 + (25-15)×(0.35-0.30) / (0.35-0.25) = 20 L / h / ppm. In some implementations, k can be 15 L / h / ppm, 16 L / h / ppm, 17 L / h / ppm, 18 L / h / ppm, 19 L / h / ppm, 20 L / h / ppm, 21 L / h / ppm, 22 L / h / ppm, 23 L / h / ppm, 24 L / h / ppm, or 25 L / h / ppm.

[0046] α is the desulfurizer attenuation compensation coefficient, ranging from 0.3 to 0.8, preferably from 0.3 to 0.5. α is used for nonlinear compensation of the decrease in reaction rate caused by the attenuation of desulfurizer activity. When the residual activity of the desulfurizer is high, its kinetic performance declines slowly and is not sensitive to the need for humidification compensation, so α takes a lower value; when the residual activity is low, its pore structure deterioration and reduction of active sites lead to accelerated performance attenuation, requiring a higher value to significantly enhance the surface water film effect. Specifically, when A / A0 is greater than or equal to 0.35, α is 0.3; when A / A0 is less than or equal to 0.25, α is 0.8; when A / A0 is greater than 0.25 and less than 0.35, α is determined by linear interpolation between 0.3 and 0.8. For example, when A / A0 = 0.30, α = 0.3 + (0.8 - 0.3) × (0.35 - 0.30) / (0.35 - 0.25) = 0.55. In some implementations, α is 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, or 0.8.

[0047] In another optional implementation, when C is greater than C0, the target makeup water flow rate can also be determined using a tiered approach. When C is greater than C0 and less than 1.0 ppm, the target makeup water flow rate is 30 L / h to 50 L / h; when C is greater than or equal to 1.0 ppm and less than or equal to 3.0 ppm, the target makeup water flow rate is 50 L / h to 90 L / h; and when C is greater than 3.0 ppm, the target makeup water flow rate is 90 L / h to 120 L / h. This tiered approach can serve as a simplified control method; when it is necessary to further improve the anti-penetration ability of the final desulfurizing agent, it is advisable to use the aforementioned formula that includes residual activity for compensation.

[0048] After determining the target water supply flow rate, water is injected into the feed gas at the inlet side of the desulfurization tower according to the target water supply flow rate. The preferred water injection method is high-pressure atomization injection. Specifically, industrial water is pressurized to 6 MPa to 10 MPa, preferably 8 MPa, using a high-pressure plunger pump; fine water mist with an average particle size of 20 μm to 50 μm, preferably 30 μm to 40 μm, is formed in the main pipeline of the feed gas, such as carbon dioxide feed gas, through an atomizing nozzle. The atomizing nozzle can be a dual-fluid recirculation spray gun, using compressed air or the feed gas itself as the atomizing medium to improve the atomization effect. The water mist is fully mixed with the high-speed flowing feed gas in the main pipeline and rapidly evaporates into water vapor before entering the desulfurization tower. The gas velocity in the main feed gas pipeline is 5 m / s to 15 m / s, preferably 8 m / s to 12 m / s.

[0049] In some embodiments, the temperature of the feed gas is 60 to 100°C, the pressure is 1.5 to 3.0 MPa, and the flow rate is 10,000 to 20,000 Nm³.3 / h. Further, the temperature can be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, or 100℃; the pressure can be 1.5 MPa, 1.8 MPa, 2.0 MPa, 2.2 MPa, 2.5 MPa, 2.8 MPa, or 3.0 MPa; the flow rate can be 10000 Nm³. 3 / h, 12000 Nm 3 / h, 15000 Nm 3 / h, 18000 Nm 3 / h or 20000Nm 3 / h. The temperature of the injected water is controlled between 20°C and 40°C, preferably between 25°C and 35°C, to accelerate the evaporation and mixing process.

[0050] After humidification, the relative humidity of the feed gas is controlled within a wide range of 5% to 70% RH. Specifically, under normal humidification mode, the relative humidity is controlled at 40% to 70% RH, preferably 50% to 65% RH, and further preferably 55% to 60% RH; under low-flow humidification mode, the relative humidity is controlled at 5% to 15% RH; and under basic humidification mode, the relative humidity is controlled at 15% to 40% RH. The basic humidification mode corresponds to the operating condition where the inlet sulfur content is not higher than C0 and A / A0 is greater than 0.35, at which time the target makeup water flow rate is maintained at Q0.

[0051] During the water injection process, closed-loop feedback regulation can also be implemented. For example, the actual water supply flow rate can be measured in real time and compared with the target value. The output of the plunger pump can be adjusted through a control algorithm to stabilize the actual water supply flow rate near the target value. Specifically, the actual water supply flow rate is measured in real time, the deviation between the actual water supply flow rate and the target water supply flow rate is calculated, and a PID control algorithm or a model predictive control algorithm is used to adjust the water supply flow rate of the water injection device according to the deviation. For example, the pump output can be controlled by adjusting the frequency of the inverter of the high-pressure plunger pump to stabilize the actual water supply flow rate near the target value, with the absolute value of the deviation not exceeding 2 L / h, preferably not exceeding 1.5 L / h. The proportional, integral, and derivative parameters of the PID control algorithm can be tuned according to the system response characteristics, and the model predictive control algorithm can be continuously optimized based on historical data and process models. Closed-loop control can ensure the accuracy of the water supply and avoid water supply deviations caused by pump characteristic fluctuations or pipeline pressure changes.

[0052] The humidified feed gas enters the fixed-bed desulfurization tower and reacts with either an iron-based or zinc-based desulfurizing agent. The main active component of the iron-based desulfurizing agent is Fe2O3, and the main active component of the zinc-based desulfurizing agent is ZnO. In some embodiments, the desulfurizing agent is an iron-based desulfurizing agent, and the operating time has been 24 to 36 months. When the residual activity of the desulfurizing agent drops to 25% to 35% of its initial value, it is considered to have entered the end of its service life. The residual activity of the desulfurizing agent gradually decreases with operating time. Under design conditions, after 24 months of operation, its residual activity typically drops to 50% to 60% of its initial value; after 30 months of operation, the residual activity is approximately 35% of its initial value; and after 36 months of operation, the residual activity is approximately 25% of its initial value. However, if the unit is frequently subjected to high sulfur load shocks, the consumption rate of the desulfurizing agent will accelerate significantly, and its residual activity may drop to a lower level in a shorter operating time. Therefore, in actual process control, laboratory analysis or online estimation models should be used first to obtain accurate residual activity values, and running time should only be used as an auxiliary reference.

[0053] During the desulfurization reaction, water vapor forms a water film on the surface of the desulfurizing agent. The solubility of H2S molecules in the water film is much higher than their physical adsorption on the dry solid surface. The water film acts as a medium for the transport of gaseous H2S to the active sites of the desulfurizing agent, significantly reducing mass transfer resistance. Simultaneously, the protons (H2S) provided by water molecules... + / OH - It can catalyze the dissociation of H2S, generating HS. - More easily with surface Fe³ + or Zn² + Electron transfer occurs, thereby lowering the reaction activation energy. Furthermore, an appropriate amount of water vapor maintains the hydration state of the microporous structure within the desulfurizer, delaying pore blockage and preserving the specific surface area. However, too low a moisture content will prevent these promoting effects, while too high a moisture content will lead to desulfurizer agglomeration, increased bed pressure drop, and even channeling. Therefore, the amount of makeup water must be controlled within an appropriate range.

[0054] If the inlet sulfur content returns to normal levels (i.e., not higher than C0) and A / A0 is less than or equal to 0.35, the system automatically switches from the normal sulfur load response humidification mode to a low-flow humidification mode of 5 L / h to 15 L / h to maintain the necessary moisture on the surface of the desulfurizer, delay its performance degradation, and prevent the collapse of the pore structure due to excessive drying. If the inlet sulfur content returns to normal levels (i.e., not higher than C0) and A / A0 is greater than 0.35, the system maintains the baseline makeup water flow rate Q0 and does not switch to the low-flow humidification mode.

[0055] Example

[0056] The effects and functions of the invention will be described in more detail below through specific embodiments. However, these embodiments are for illustrative purposes only, and the scope of the invention is not defined thereto.

[0057] Example 1

[0058] A carbon dioxide feedstock gas desulfurization unit has a DN250 main inlet pipe for the desulfurization tower. The medium inside the pipe is carbon dioxide feedstock gas at a temperature of 60℃ and a pressure of 2.0 MPa. The normal flow rate is 15000 Nm³. 3 / h. The desulfurizer is an iron-based desulfurizer, with Fe2O3 as the main active component. It has been running for 30 months and is at the end of its service life. The measured remaining activity is about 35% of the initial activity, i.e., A / A0=0.35.

[0059] Due to an upstream unit malfunction, the total sulfur content in the feed gas increased from the design value of 0.2 ppm to 3.0 ppm. The specific steps are as follows: a. Real-time detection parameters: Gas flow rate 15000 Nm 3 / h, temperature 60℃, pressure 2.0 MPa, inlet total sulfur content 3.0 ppm, the residual activity of desulfurizing agent A / A0 is about 35%. The residual activity of desulfurizing agent is determined as follows: samples are taken from the upper, middle and lower parts of the desulfurization tower bed and mixed evenly. The dynamic breakthrough sulfur capacity of the mixed sample is measured in a CO2 simulated gas containing a known concentration of H2S at 60℃ and 2.0 MPa. This value is divided by the initial dynamic breakthrough sulfur capacity of the same batch of fresh desulfurizing agent to obtain A / A0≈0.35.

[0060] b. Based on the total sulfur content at the inlet and the remaining activity of the desulfurizing agent, determine the target makeup water flow rate according to the following formula.

[0061] Q = Q0 + k×(C-C0)×(1+α×(1-A / A0)), where Q is the target makeup water flow rate in L / h; Q0 is the baseline makeup water flow rate in L / h; k is the sulfur load response coefficient in L / h / ppm; C is the total sulfur content in ppm; C0 is the preset sulfur content threshold in ppm; α is the desulfurizing agent attenuation compensation coefficient; A is the remaining activity of the desulfurizing agent in percentage; A0 is the initial activity of the desulfurizing agent in percentage. When the total sulfur content C is less than or equal to C0 and A / A0 is less than or equal to 0.35, the target makeup water flow rate is adjusted to 5 L / h to 15 L / h.

[0062] In this embodiment, Q0 is taken as 23 L / h, C0 as 0.5 ppm, k as 15 L / h / ppm, α as 0.3, and A / A0 as 0.35. Substituting into the formula, Q = 23 + 15×(3.0-0.5)×(1+0.3×(1-0.35)) = 67.81 L / h, approximately 68 L / h. Therefore, the target makeup water flow rate in this embodiment is determined to be 68 L / h.

[0063] c. Inject water into the feed gas at the inlet of the desulfurization tower according to the target water replenishment flow rate. Industrial water is pressurized to 8 MPa using a high-pressure plunger pump and atomized into a fine water mist with an average particle size of approximately 30 μm through an atomizing nozzle, then sprayed into the main pipeline of the carbon dioxide feed gas. The water mist mixes and vaporizes with the feed gas before entering the tower. The water replenishment flow rate is controlled in a closed loop using a PID control algorithm or a model predictive control algorithm, and the actual water replenishment flow rate is stabilized at 68 ± 1.5 L / h.

[0064] d. The measured relative humidity of the feed gas after humidification is approximately 56% RH. The humidified feed gas enters the fixed-bed desulfurization tower and comes into contact with the iron-based desulfurizing agent to carry out the desulfurization reaction.

[0065] Thermodynamic verification: at 60℃, 2.0 MPa, and 15000 Nm 3 Under the operating condition of 68 L / h, the water vapor mole fraction corresponding to the makeup water is 0.561%, and the water vapor partial pressure is 11.22 kPa; the saturated vapor pressure of water at 60℃ is 19.92 kPa. The calculated relative humidity RH≈56.3%, which is consistent with the measured relative humidity of the feed gas after humidification in Example 1, which is approximately 56% RH.

[0066] e. The sulfur content at the desulfurization tower outlet was continuously monitored for 72 hours and remained below 0.1 ppm, with no breakthrough phenomenon observed.

[0067] Example 2

[0068] When the upstream unit returned to normal, the total sulfur content of the feed gas dropped to 0.2 ppm. In this embodiment, the desulfurizing agent was from the same batch as in Example 1, and it was also at the end of its use, with a remaining activity A / A0 = 0.35.

[0069] At this point, the total sulfur content C = 0.2 ppm ≤ C0 and A / A0 = 0.35 ≤ 0.35, satisfying the switching conditions. The system automatically adjusts the target water replenishment flow rate to a low-flow humidification mode, which is 8 L / h in this embodiment, maintaining only the surface of the desulfurizing agent in a moist state. After humidification, the relative humidity of the raw gas is approximately 7% RH, and the pressure drop of the desulfurizing agent bed does not increase significantly.

[0070] The specific steps are as follows: a. Real-time detection parameters: Gas flow rate 15000 Nm3 / h, temperature 60℃, pressure 2.0 MPa, inlet total sulfur content C=0.2 ppm, desulfurizer residual activity A / A0=0.35.

[0071] b. Based on the total sulfur content and remaining activity, the target water replenishment flow rate is determined to be 8 L / h, which is within the moisturizing flow rate range of 5 to 15 L / h.

[0072] c. Inject water into the feed gas at the inlet of the desulfurization tower according to the target water replenishment flow rate. Industrial water is pressurized to 8 MPa using a high-pressure plunger pump and then sprayed into the main carbon dioxide feed gas pipeline through an atomizing nozzle to form a fine water mist. The water mist mixes and vaporizes with the feed gas before entering the tower. Through closed-loop control of the water replenishment flow rate, the actual water replenishment flow rate is stabilized at 8 ± 1.5 L / h.

[0073] d. The humidified raw gas enters the fixed-bed desulfurization tower and comes into contact with the iron-based desulfurizing agent to carry out the desulfurization reaction.

[0074] Thermodynamic verification: at 60℃, 2.0 MPa, and 15000 Nm 3 Under the condition of 8 L / h makeup water, the water vapor mole fraction is 0.066%, and the water vapor partial pressure is 1.33 kPa; the saturated vapor pressure of water at 60℃ is 19.92 kPa. The calculated relative humidity RH≈6.7%, which is consistent with the measured relative humidity of the feed gas after humidification in Example 2, which is approximately 7% RH.

[0075] e. During operation, the sulfur content at the desulfurization tower outlet was consistently below 0.1 ppm, and the pressure drop in the desulfurizing agent bed did not increase significantly. This low-flow moisturizing mode effectively prevented the desulfurizing agent from becoming excessively dry and cracked due to long-term operation, maintaining the integrity of the pore structure.

[0076] Comparative Example 1

[0077] Using the same desulfurization device and the same iron-based desulfurizer as in Example 1 (residual activity A / A0=0.35), the total sulfur content of the raw gas was also 3.0 ppm, but the atomization humidification system was not started, i.e. the target water replenishment flow rate was 0 L / h.

[0078] The specific steps are as follows: a. Real-time detection parameters: Gas flow rate 15000 Nm 3 / h, temperature 60℃, pressure 2.0 MPa, inlet total sulfur content 3.0 ppm, desulfurizer residual activity A / A0=0.35.

[0079] b. Do not inject water into the raw gas.

[0080] c. The raw gas directly enters the fixed-bed desulfurization tower for desulfurization reaction.

[0081] The result was that the sulfur content at the outlet of the desulfurization tower exceeded 0.1 ppm after about 8 hours of operation, resulting in a breakthrough and forcing the unit to be shut down to replace the desulfurizing agent.

[0082] Comparative Example 2

[0083] The conditions are the same as in Example 1, but the target water supply flow rate is artificially increased to 120 L / h.

[0084] The specific steps are as follows: a. Real-time detection parameters: Gas flow rate 15000 Nm 3 / h, temperature 60℃, pressure 2.0 MPa, inlet total sulfur content 3.0 ppm, desulfurizer residual activity A / A0=0.35.

[0085] b. Determine the target water supply flow rate as 120 L / h.

[0086] c. Inject water into the feed gas at the inlet of the desulfurization tower according to the target water supply flow rate. Industrial water is pressurized to 8 MPa by a high-pressure plunger pump and then sprayed into the main pipeline of the carbon dioxide feed gas through an atomizing nozzle to form a fine water mist. The water mist mixes with the feed gas before entering the tower, but some atomized droplets are not completely vaporized. By implementing closed-loop control of the water supply flow rate, the actual water supply flow rate is stabilized at 120 ± 1.5 L / h.

[0087] d. The humidified raw gas enters the fixed-bed desulfurization tower for desulfurization reaction.

[0088] Thermodynamic verification: at 60℃, 2.0 MPa, and 15000 Nm 3 Under the operating condition of 120 L / h of makeup water, the water vapor mole fraction is 0.988%, and the water vapor partial pressure is 19.76 kPa; the saturated vapor pressure of water at 60℃ is 19.92 kPa. Theoretically calculated relative humidity RH≈99.2%, which is close to saturation. In actual operation, due to factors such as incomplete vaporization of atomized droplets, local condensation on the pipe wall, and system errors of the online hygrometer, the measured relative humidity of the feed gas after humidification is approximately 85% RH. This humidity is still far higher than the upper limit of 70% RH, which is sufficient to cause desulfurizing agent agglomeration and increased bed pressure drop.

[0089] The results showed that although the sulfur content at the desulfurization tower outlet was below 0.1 ppm in the initial stage, after 24 hours of operation, the desulfurizing agent showed obvious agglomeration, the bed pressure drop increased by 35%, and some of the desulfurizing agent was pulverized due to water immersion, which accelerated the failure of the desulfurizing agent.

[0090] Results and Discussion

[0091] In Example 1, under high-sulfur shock conditions, the desulfurizer was at the end of its service life. Using the method of this invention to determine the target makeup water flow rate, the outlet sulfur content remained within the standard for a relatively long period, and no breakthrough occurred. This indicates that increasing the makeup water flow rate after introducing residual activity correction can enhance surface water film mass transfer and delay desulfurizer breakthrough at the end of its service life.

[0092] In Example 2, after the total sulfur content at the inlet of the same batch of desulfurizing agent returned to normal, switching to a low-flow moisturizing mode maintained the outlet sulfur content within the standard, and the bed pressure drop did not increase significantly. This indicates that limiting the amount of makeup water under low-sulfur conditions can maintain the necessary moisture state of the desulfurizing agent without causing agglomeration.

[0093] In Comparative Example 1, under the same high-sulfur conditions, without humidification, the outlet sulfur content quickly exceeded the standard, resulting in breakthrough. In Comparative Example 2, excessive humidification caused the desulfurizing agent to clump, significantly increasing the bed pressure drop. This indicates that insufficient or excessive makeup water is detrimental to desulfurization.

[0094] In summary, this invention determines the target makeup water flow rate based on the residual activity of the desulfurizing agent and the total sulfur content at the inlet, so that the makeup water strategy matches the degree of desulfurizing agent attenuation. This can delay penetration under high sulfur impact and avoid excessive humidification under low sulfur conditions, thus balancing desulfurization efficiency and bed stability.

[0095] While several embodiments of the invention have been described and illustrated herein, those skilled in the art will readily contemplate a variety of other ways and / or structures for performing the functions described herein and / or obtaining the results described herein and / or one or more advantages, and each such variation and / or modification is considered to be within the scope of the invention.

Claims

1. A desulfurization method, comprising: The remaining activity of the desulfurizing agent in the desulfurization tower and the total sulfur content of the feed gas at the inlet of the desulfurization tower are obtained; The target makeup water flow rate is determined based on the remaining activity and the total sulfur content; wherein, when the total sulfur content is greater than a preset sulfur content threshold, the target makeup water flow rate increases as the remaining activity decreases when the total sulfur content is the same, and the target makeup water flow rate increases as the total sulfur content increases when the remaining activity is the same; when the total sulfur content is less than or equal to the preset sulfur content threshold, the target makeup water flow rate is determined based on the range of the ratio of the remaining activity to the initial activity of the desulfurizing agent. Water is injected into the raw gas at the inlet of the desulfurization tower according to the target water replenishment flow rate, and the injected water is vaporized before entering the desulfurization tower. The humidified raw gas is fed into the desulfurization tower for desulfurization.

2. The desulfurization method according to claim 1, characterized in that, Determining the target makeup water flow rate based on the remaining activity and the total sulfur content includes: When C is greater than C0, the target water supply flow rate is determined according to the following formula: Q = Q0 + k×(C-C0)×(1+α×(1-A / A0)); When C is less than or equal to C0 and A / A0 is less than or equal to 0.35, the target water replenishment flow rate is set to 5 L / h to 15 L / h. When C is less than or equal to C0 and A / A0 is greater than 0.35, the target water replenishment flow rate is set to Q0; Wherein, Q is the target makeup water flow rate in L / h; Q0 is the baseline makeup water flow rate in L / h; k is the sulfur load response coefficient in L / h / ppm; C is the total sulfur content in ppm; C0 is the preset sulfur content threshold in ppm; α is the desulfurizing agent attenuation compensation coefficient; A is the remaining activity of the desulfurizing agent in percentage; and A0 is the initial activity of the desulfurizing agent in percentage.

3. The desulfurization method according to claim 2, characterized in that, Q0 is 20 L / h to 40 L / h; C0 is greater than 0.2 ppm and less than 1 ppm; k is 15 L / h / ppm to 25 L / h / ppm; α is 0.3 to 0.

8.

4. The desulfurization method according to claim 3, characterized in that, k and α are selected according to the remaining activity: When A / A0 is greater than or equal to 0.35, k is 15 L / h / ppm and α is 0.3; When A / A0 is less than or equal to 0.25, k is 25 L / h / ppm and α is 0.8; When A / A0 is greater than 0.25 and less than 0.35, k is determined by linear interpolation between 15 L / h / ppm and 25 L / h / ppm, and α is determined by linear interpolation between 0.3 and 0.

8.

5. The desulfurization method according to claim 1, characterized in that, Obtaining the residual activity of the desulfurizing agent includes: sampling and measuring the dynamic penetration sulfur capacity of the desulfurizing agent, and taking the ratio of the measured dynamic penetration sulfur capacity to the initial dynamic penetration sulfur capacity of the desulfurizing agent as the residual activity.

6. The desulfurization method according to claim 1, characterized in that, Also includes: The actual water supply flow rate is measured in real time, the deviation between the actual water supply flow rate and the target water supply flow rate is calculated, and the water supply flow rate of the water injection device is adjusted according to the deviation using a PID control algorithm or a model predictive control algorithm.

7. The desulfurization method according to claim 1, characterized in that, Injecting water into the feed gas includes: pressurizing the water to 6 MPa to 10 MPa, atomizing it to form droplets with an average particle size of 20 μm to 50 μm, and then spraying the droplets into the feed gas.

8. The desulfurization method according to claim 1, characterized in that, The raw material gas is carbon dioxide; the desulfurizing agent is an iron-based desulfurizing agent or a zinc-based desulfurizing agent.

9. The desulfurization method according to claim 1, characterized in that, The feed gas has a temperature of 60°C to 100°C, a pressure of 1.5 MPa to 3.0 MPa, and a flow rate of 10,000 Nm³. 3 / h to 20000 Nm 3 / h.

10. The desulfurization method according to claim 1, characterized in that, The temperature of the injected water is between 20°C and 40°C.