Control system of closed ship tail gas desulfurization device

Abstract

The invention relates to a control system of a closed ship tail gas desulfurization device, and belongs to the technical field of ship desulfurization. The system comprises a gas-liquid conveying module used for controlling the conveying process of a desulfurizing agent and ship tail gas to a desulfurization device, and an absorbent control module is used for carrying out flow control and desulfurization mode conversion on the desulfurizing agent; the spraying control module is used for conveying a desulfurizing agent into a vertical spraying column of the desulfurizing device from a liquid inlet in the bottom of the desulfurizing tower through a peristaltic pump driven by a motor; the spraying module is used for spraying through a vertical spraying column, liquid sprayed by the vertical spraying column is uniformly dispersed into fine liquid drops through a grid dispersion plate, and the fine liquid drops are in full contact with ship tail gas which rises along with time and is conveyed by a gas inlet in the bottom of the desulfurization tower; and the gas-liquid control module is used for adjusting gas-liquid distribution in the desulfurization tower according to the height distribution through the gas-liquid distribution ring. The content of sulfur oxides in ship tail gas is effectively reduced, the environment-friendly emission standard is achieved, and meanwhile energy consumption and operation cost are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of ship desulfurization, and in particular relates to a control system of a closed ship exhaust gas desulfurization device. Background Art

[0002] As a terminal treatment technology, flue gas desulfurization technology has been widely used in SO2 emission sources such as ships. Most of them now use spray desulfurization towers with relatively simple structure, low pressure drop and investment cost for desulfurization treatment. The tail gas is contacted and mixed with the absorbent through the reactor to achieve the purpose of absorbing and removing SO2 in the tail gas; because seawater is a relatively easy-to-obtain natural absorbent when ships are sailing at sea, it can greatly save operating costs, and seawater is usually used for tail gas washing. At present, most ship washing systems use hybrid systems, that is, seawater is directly obtained from the ocean for tail gas washing treatment during open operation, and switches to use the ship's own alkaline absorbent (magnesium-based, sodium-based absorbent, etc.) to absorb the tail gas during closed operation.

[0003] However, there are some problems with the traditional open scrubbing system, such as regulatory restrictions in certain sea areas, or seawater freezing in cold climates that affects the normal operation of the system. Although the closed scrubbing system can avoid these problems, its operating cost is relatively high, especially the large amount of alkaline absorbent required. Therefore, it is necessary to optimize the operating efficiency of the closed scrubbing system and reduce the consumption of alkaline absorbent while ensuring that the desulfurization efficiency is not affected. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a control system for a closed ship exhaust gas desulfurization device; The purpose of the present invention can be achieved through the following technical solutions: A control system for a closed ship exhaust gas desulfurization device, characterized in that it comprises: a gas-liquid transport module, a spray control module, a gas-liquid control module, a spray module, and an absorbent control module; The gas-liquid delivery module is used to control the delivery process of the desulfurizer and the ship exhaust gas to the desulfurization device, and the flow rate of the desulfurizer is controlled and the desulfurization mode is switched through the absorbent control module; The spray control module is used to transport the desulfurizer from the liquid inlet at the bottom of the desulfurization tower to the vertical spray column of the desulfurization device through a peristaltic pump driven by a motor; The spray module is used to spray through the vertical spray column, and the liquid sprayed by the vertical spray column is evenly dispersed into fine droplets through the grid dispersion plate to fully contact with the ship exhaust gas that rises over time and is transported by the gas inlet at the bottom of the desulfurization tower; The gas-liquid control module is used to adjust the gas-liquid distribution in the desulfurization tower according to the height distribution through the gas-liquid distribution ring.

[0005] Specifically, the vertical spray column includes a circulation layer and a spray layer. The circulation layer receives the absorbent transported from the circulation pool according to the spray control module. The spray layer evenly sprays the absorbent transported from the circulation layer onto the grid dispersion plate through a porous nozzle.

[0006] Specifically, the desulfurization mode includes a high-concentration desulfurization mode, a conventional desulfurization mode and a recovered liquid desulfurization mode; the high-concentration desulfurization mode improves the desulfurization efficiency by increasing the circulation volume and spraying density of the absorbent; the conventional desulfurization mode achieves the desulfurization requirements through standard absorbent circulation and spraying operations; the recovered liquid desulfurization mode utilizes the treated liquid for reuse.

[0007] Specifically, the gas-liquid distribution ring calculates the desulfurization model according to the continuous phase flow field and the gas-liquid mass transfer model and adjusts the distribution of the gas-liquid two-phase flow field in the desulfurization tower according to the desulfurization model; the gas-liquid distribution ring is located above the packing layer of the desulfurization tower.

[0008] Specifically, the model calculation method of the continuous phase flow field is: The turbulence model of gas-liquid flow is used to capture the average flow behavior of the continuous phase flow field and obtain the turbulent kinetic energy and dissipation rate. The calculation formula is: , , in, ρ represents the fluid density, k represents the kinetic energy per unit mass of fluid, is the local time rate of change of turbulent kinetic energy, The convection term representing the turbulent kinetic energy is used to describe the change of turbulent kinetic energy with the motion of the fluid. is the turbulent viscosity (kg / (m·s)), which is used to express the contribution of turbulence to momentum transfer, represents the diffusion term of turbulent kinetic energy, which is used to describe the diffusion and dissipation of turbulent kinetic energy in space. is the universal diffusion coefficient of turbulent kinetic energy, is the turbulent kinetic energy generation term, is the turbulent dissipation rate, which indicates the rate at which turbulent kinetic energy is converted into thermal energy. represents the dissipation of turbulent kinetic energy; is the local time rate of change of the turbulent dissipation rate, is the convective term of the turbulent dissipation rate, represents the diffusion of turbulent dissipation rate, C1 and C2 are empirical constants of the conversion rate of turbulent dissipation loss and kinetic energy.

[0009] Specifically, the calculation method of the gas-liquid mass transfer model is: based on the calculation of sodium hydroxide in the absorbent as the source phase, the mass transfer rate equation of the absorbent absorbing sulfur oxides in the tail gas is: , in, is the partial pressure of SO2 on the phase interface, is the mass transfer resistance of the gas phase when absorbing SO2, is the mass transfer resistance of the liquid phase when absorbing SO2, is the Henry constant of SO2 in water, is the concentration of hydroxide anions at the interface after sodium hydroxide is ionized in the solution, θ is the diffusion coefficient.

[0010] Specifically, the method for adjusting the gas-liquid two-phase flow field of the desulfurization tower is: The interaction between sulfur dioxide and the liquid phase in the desulfurization reaction is calculated according to the gas-liquid mass transfer model, the efficiency and rate of gas dissolution in the liquid phase are determined, the continuous phase flow field and the gas-liquid mass transfer model are combined for simulation, and the geometric parameters of the gas-liquid distribution ring and the gas-liquid flow ratio of the desulfurization tower are adjusted according to the simulation results; the geometric parameters are the aperture and the number of distributors.

[0011] The beneficial effects of the present invention are: The desulfurization efficiency is significantly improved. By accurately controlling the liquid flow direction of each branch, the full contact between the desulfurizer and the tail gas is ensured. The energy consumption management is optimized. The reasonable configuration of the circulation pump and the regulating valve reduces unnecessary energy loss. The stability and reliability of the system are enhanced. The porous structure design of the vertical spray column and the adjustable nozzle make the spraying of the absorbent more uniform, avoiding blockage and nozzle wear. The environmental performance of tail gas treatment is improved. The multi-layer structure of the grid dispersion plate effectively disperses the particles and droplets in the tail gas, reducing pollution to the environment. Intelligent control is realized. The dynamic adjustment of the gas-liquid distribution ring is based on the advanced flow field and mass transfer model, which ensures the optimal distribution of the gas-liquid two-phase flow field in the desulfurization tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0013] Figure 1 The present invention is a schematic structural diagram of a control system of a closed ship exhaust gas desulfurization device.

[0014] Figure 2 A schematic diagram of the control system of a closed ship exhaust gas desulfurization device of the present invention Description of main component symbols: On the way: 1. Motor; 2. Peristaltic pump; 3. Grid dispersion plate; 4. Gas outlet; 5. Vertical spray column; 6. Gas-liquid distribution ring; 7. Liquid outlet; 8. Tail gas inlet; 9. Liquid inlet; 10. Concentration meter; 11. Recovery tank; 12. Waste liquid tank; 13. Circulation tank; 14. Control valve; 15. Circulation pump; 16. Main desulfurizer slurry tank; 17. Lime slurry tank. DETAILED DESCRIPTION

[0015] The example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein: on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concept of the example embodiments will be fully conveyed to those skilled in the art. In addition, the described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to give a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid blurring various aspects of the present disclosure. The blocks shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices. The flowcharts shown in the accompanying drawings are only exemplary illustrations and do not necessarily include all the content and operations / steps, nor do they necessarily have to be executed in the order described. For example, some operations / steps may be decomposed, while some operations / steps may be combined or partially combined, so the actual execution order may change according to the actual situation.

[0016] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0017] See also Figure 1-2 , a control system for a closed ship exhaust gas desulfurization device, characterized in that it includes: a gas-liquid delivery module, a spray control module, a gas-liquid control module, a spray module, and an absorbent control module; The gas-liquid delivery module is used to control the delivery process of the desulfurizer and the ship exhaust gas to the desulfurization device, and the flow rate of the desulfurizer is controlled and the desulfurization mode is switched through the absorbent control module; The spray control module is used to transport the desulfurizer from the liquid inlet at the bottom of the desulfurization tower to the vertical spray column of the desulfurization device through a peristaltic pump driven by a motor; The spray module is used to spray through the vertical spray column, and the liquid sprayed by the vertical spray column is evenly dispersed into fine droplets through the grid dispersion plate to fully contact with the ship exhaust gas that rises over time and is transported by the gas inlet at the bottom of the desulfurization tower; The gas-liquid control module is used to adjust the gas-liquid distribution in the desulfurization tower according to the height distribution through the gas-liquid distribution ring.

[0018] The desulfurization tower in the desulfurization device in this embodiment is provided with a gas-liquid distribution ring, a vertical spray column, and a grid dispersion plate; the absorbent is transported from the liquid inlet at the bottom of the desulfurization tower to the vertical spray column by a peristaltic pump driven by a motor, and the absorbent is sprayed through the vertical spray column. The liquid sprayed by the vertical spray column is evenly dispersed into fine droplets through the grid dispersion plate to fully contact with the ship exhaust gas that rises over time and is transported from the gas inlet at the bottom of the desulfurization tower; the gas-liquid distribution ring is distributed in the desulfurization tower according to the height to adjust the gas-liquid distribution condition; the treated ship exhaust gas is discharged through the gas outlet at the top of the desulfurization tower, and the reacted liquid is discharged through the liquid outlet at the bottom of the desulfurization tower. The absorbent includes a main desulfurizer and an auxiliary desulfurizer. The main desulfurizer is a sodium hydroxide solution, and the auxiliary desulfurizer is a limestone slurry. The absorbent is stored in a circulation pool for peristaltic pump delivery to the vertical spray column. The circulation pool is connected to the recovery pool, the main desulfurizer slurry pool, and the lime slurry tank through the first branch, the second branch, and the third branch, respectively. The recovery pool is used to store the incompletely reacted desulfurizer liquid discharged from the liquid outlet at the bottom of the desulfurization tower; the main desulfurizer slurry pool is used to store the main desulfurizer. The lime slurry tank receives the lime powder delivered by the conveyor and dissolves it to obtain lime powder dissolved water. The lime powder dissolved water is stirred by a top-entry agitator and supplied to the circulation pool through an overflow pipe and a regulating valve. The liquid outlet is provided with a desulfurizer concentration meter to detect the concentration of the discharged liquid and preset the waste liquid recovery standard. According to the waste liquid recovery standard, the valve controls the liquid flow to the waste liquid tank and the recovery pool. The desulfurizer concentration meter is only used to detect the concentration of the main desulfurizer, and the recovery tank is only used to store the main desulfurizer that meets the waste liquid recovery standard. The first branch, the second branch, and the third branch control the liquid flow direction of the recovery tank, the main desulfurizer slurry tank, and the lime slurry tank through a circulating pump and a regulating valve. The vertical spray column sprays the absorbent evenly into the tail gas through a liquid distributor, and the liquid distributor is designed as a porous structure, and the nozzle angle and spray height are adjustable. The grid dispersion plate is arranged in the absorption tower to disperse the particles and droplets in the tail gas; the grid dispersion plate has a multi-layer structure, and staggered channels are formed between each layer of the plate. The material of the grid dispersion plate is selected from an alloy material with strong corrosion resistance. The gas-liquid distribution ring calculates the desulfurization model according to the continuous phase flow field and the gas-liquid mass transfer model and adjusts the distribution of the gas-liquid two-phase flow field in the desulfurization tower according to the desulfurization model. The continuous phase flow field adopts the Euler-Lagrange two-phase flow model, and the gas-liquid mass transfer model is calculated based on the sodium hydroxide in the main desulfurizer as the source phase.

[0019] Specifically, the vertical spray column includes a circulation layer and a spray layer. The circulation layer receives the absorbent transported from the circulation pool according to the spray control module. The spray layer evenly sprays the absorbent transported from the circulation layer onto the grid dispersion plate through a porous nozzle.

[0020] Specifically, the desulfurization mode includes a high-concentration desulfurization mode, a conventional desulfurization mode and a recovered liquid desulfurization mode; the high-concentration desulfurization mode improves the desulfurization efficiency by increasing the circulation volume and spraying density of the absorbent; the conventional desulfurization mode achieves the desulfurization requirements through standard absorbent circulation and spraying operations; the recovered liquid desulfurization mode utilizes the treated liquid for reuse.

[0021] In this embodiment, purchased lime powder is used and filled into the lime storage bin. Subsequently, the lime powder is transported to the lime slurry tank for dissolution through a feeder and a screw conveyor. The circulating slurry is directly injected into the lime slurry tank using a circulating pump branch as a dissolving medium for the lime powder. The lime slurry tank is equipped with an overflow pipe, and the amount of lime slurry supplied to the circulation pool is controlled by adjusting the valve on the overflow pipe. In addition, the lime slurry tank is also equipped with a top-entry agitator. When the main desulfurizer circulating water cannot meet the desulfurization standard, the auxiliary desulfurizer lime slurry addition system will be started. The amount of lime powder added to the circulation system will be determined based on the expected SO2 removal rate, boiler load, and pH value of the absorber slurry. The discharger of the lime powder bin adopts frequency conversion control, and the frequency of the discharger is adjusted to meet the pH value of the slurry in the absorber.

[0022] Specifically, the gas-liquid distribution ring calculates the desulfurization model according to the continuous phase flow field and the gas-liquid mass transfer model and adjusts the distribution of the gas-liquid two-phase flow field in the desulfurization tower according to the desulfurization model; the gas-liquid distribution ring is located above the packing layer of the desulfurization tower.

[0023] Specifically, the model calculation method of the continuous phase flow field is: The turbulence model of gas-liquid flow is used to capture the average flow behavior of the continuous phase flow field and obtain the turbulent kinetic energy and dissipation rate. The calculation formula is: , , in, ρ represents the fluid density, k represents the kinetic energy per unit mass of fluid, is the local time rate of change of turbulent kinetic energy, The convection term representing the turbulent kinetic energy is used to describe the change of turbulent kinetic energy with the motion of the fluid. is the turbulent viscosity (kg / (m·s)), which is used to express the contribution of turbulence to momentum transfer, represents the diffusion term of turbulent kinetic energy, which is used to describe the diffusion and dissipation of turbulent kinetic energy in space. is the universal diffusion coefficient of turbulent kinetic energy, is the turbulent kinetic energy generation term, is the turbulent dissipation rate, which indicates the rate at which turbulent kinetic energy is converted into thermal energy. represents the dissipation of turbulent kinetic energy; is the local time rate of change of the turbulent dissipation rate, is the convective term of the turbulent dissipation rate, represents the diffusion of turbulent dissipation rate, C1 and C2 are empirical constants of the conversion rate of turbulent dissipation loss and kinetic energy.

[0024] Specifically, the calculation method of the gas-liquid mass transfer model is: based on the calculation of sodium hydroxide in the absorbent as the source phase, the mass transfer rate equation of the absorbent absorbing sulfur oxides in the tail gas is: , in, is the partial pressure of SO2 on the phase interface, is the mass transfer resistance of the gas phase when absorbing SO2, is the mass transfer resistance of the liquid phase when absorbing SO2, is the Henry constant of SO2 in water, is the concentration of hydroxide anions at the interface after sodium hydroxide is ionized in the solution, θ is the diffusion coefficient.

[0025] Specifically, the method for adjusting the gas-liquid two-phase flow field of the desulfurization tower is: The interaction between sulfur dioxide and the liquid phase in the desulfurization reaction is calculated according to the gas-liquid mass transfer model, the efficiency and rate of gas dissolution in the liquid phase are determined, the continuous phase flow field and the gas-liquid mass transfer model are combined for simulation, and the geometric parameters of the gas-liquid distribution ring and the gas-liquid flow ratio of the desulfurization tower are adjusted according to the simulation results; the geometric parameters are the aperture and the number of distributors.

[0026] In this embodiment, according to the double film theory, when the gas contacts the liquid, a stable gas film and liquid film will be formed at the phase interface. The thickness and characteristics of these films determine the mass transfer efficiency. As the concentration of alkaline substances increases, the liquid phase mass transfer rate increases, and the reaction interface is closer to the phase interface, thereby reducing the mass transfer resistance. When the reaction interface coincides with the phase interface, continuing to increase the concentration of alkaline substances will no longer increase the absorption rate. Therefore, it is very important to set an optimal NaOH concentration and ensure that the NaOH concentration in the main desulfurizer does not exceed this optimal value. The mass source term, momentum source term and energy source term can be calculated by the continuous phase model, and the component mass of the desulfurizer can be dynamically adjusted according to the real-time data in the absorption process to ensure that the desulfurization efficiency is maximized while avoiding corrosion of the equipment by excessive alkaline substances. In addition, by optimizing the design of the gas-liquid distribution ring, the contact efficiency of the gas-liquid two phases can be further improved, thereby enhancing the overall performance of the desulfurization tower. In actual operation, factors such as the temperature, pressure and flow rate of the tail gas need to be considered, which will affect the desulfurization process. Therefore, the control method should include a corresponding adjustment mechanism to adapt to different operating conditions.

[0027] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A control system for a closed ship exhaust gas desulfurization device, characterized in that: include: Gas-liquid transport module, spray control module, gas-liquid control module, spray module, absorbent control module; The gas-liquid delivery module is used to control the delivery process of the desulfurizer and the ship exhaust gas to the desulfurization device, and the flow rate of the desulfurizer is controlled and the desulfurization mode is switched through the absorbent control module; The spray control module is used to transport the desulfurizer from the liquid inlet at the bottom of the desulfurization tower to the vertical spray column of the desulfurization device through a peristaltic pump driven by a motor; The spray module is used to spray through the vertical spray column, and the liquid sprayed by the vertical spray column is evenly dispersed into fine droplets through the grid dispersion plate to fully contact with the ship exhaust gas that rises over time and is transported by the gas inlet at the bottom of the desulfurization tower; The gas-liquid control module is used to adjust the gas-liquid distribution in the desulfurization tower according to the height distribution through the gas-liquid distribution ring.

2. The system according to claim 1, characterized in that The vertical spray column comprises a circulation layer and a spray layer. The circulation layer receives the absorbent transported by the circulation pool according to the spray control module. The spray layer evenly sprays the absorbent transported by the circulation layer onto the grid dispersion plate through a porous nozzle.

3. The system according to claim 1, characterized in that The desulfurization modes include high-concentration desulfurization mode, conventional desulfurization mode and recovery liquid desulfurization mode; the high-concentration desulfurization mode improves the desulfurization efficiency by increasing the circulation volume and spraying density of the absorbent; the conventional desulfurization mode achieves the desulfurization requirements through standard absorbent circulation and spraying operations; the recovery liquid desulfurization mode utilizes the treated liquid for reuse.

4. The system according to claim 1, characterized in that The gas-liquid distribution ring calculates the desulfurization model according to the continuous phase flow field and the gas-liquid mass transfer model and adjusts the distribution of the gas-liquid two-phase flow field in the desulfurization tower according to the desulfurization model; the gas-liquid distribution ring is located above the packing layer of the desulfurization tower.

5. The system according to claim 4, characterized in that The model calculation method of the continuous phase flow field is: The turbulence model of gas-liquid flow is used to capture the average flow behavior of the continuous phase flow field and obtain the turbulent kinetic energy and dissipation rate. The calculation formula is: ， ， in, ρ represents the fluid density, k represents the kinetic energy per unit mass of fluid, is the local time rate of change of turbulent kinetic energy, The convection term representing the turbulent kinetic energy is used to describe the change of turbulent kinetic energy with the motion of the fluid. is the turbulent viscosity (kg / (m·s)), which is used to express the contribution of turbulence to momentum transfer, represents the diffusion term of turbulent kinetic energy, which is used to describe the diffusion and dissipation of turbulent kinetic energy in space. is the universal diffusion coefficient of turbulent kinetic energy, is the turbulent kinetic energy generation term, is the turbulent dissipation rate, which indicates the rate at which turbulent kinetic energy is converted into thermal energy. represents the dissipation of turbulent kinetic energy; is the local time rate of change of the turbulent dissipation rate, is the convective term of the turbulent dissipation rate, represents the diffusion of turbulent dissipation rate, C1 and C2 are empirical constants of the conversion rate of turbulent dissipation loss and kinetic energy.

6. The system according to claim 4, characterized in that The calculation method of the gas-liquid mass transfer model is: based on the calculation of sodium hydroxide in the absorbent as the source phase, the mass transfer rate equation of the absorbent absorbing sulfur oxides in the tail gas is: ， in, is the partial pressure of SO2 on the phase interface, is the mass transfer resistance of the gas phase when absorbing SO2, is the mass transfer resistance of the liquid phase when absorbing SO2, is the Henry constant of SO2 in water, is the concentration of hydroxide anions at the interface after sodium hydroxide is ionized in the solution, θ is the diffusion coefficient.

7. The system according to claim 4, characterized in that The method for adjusting the gas-liquid two-phase flow field of the desulfurization tower is: The interaction between sulfur dioxide and the liquid phase in the desulfurization reaction is calculated according to the gas-liquid mass transfer model, the efficiency and rate of gas dissolution in the liquid phase are determined, the continuous phase flow field and the gas-liquid mass transfer model are combined for simulation, and the geometric parameters of the gas-liquid distribution ring and the gas-liquid flow ratio of the desulfurization tower are adjusted according to the simulation results; The geometric parameters are aperture and number of distributors.

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