Calculation method for the joint particulate matter removal effect of series-type flue gas wet desulfurization equipment

Abstract

To provide a method of calculating the effect of jointly removing particulate substances in a wet-type exhaust-gas desulfurization device of a serial tower type, relating to a technology field of wet-type exhaust-gas desulfurization.SOLUTION: A whole-part-whole method is employed to simulate and perform calculation in relation to a flue system, a demister, a pre-washing tower, and an absorption tower stepwise respectively. Specifically, the whole simulation of a monophase flow is employed to quickly obtain the flow velocity distribution and the temperature distribution of the inlet cross-sections of the pre-washing tower and the absorption tower, to obtain the collection efficiency curves of the pre-washing tower demister and the absorption tower demister for dust particles of different particle sizes and droplet slurry by carrying out calculation using a demister sub-model. Based on the two steps, the joint removal of the three-phase flow flowing in the tower is simulated and calculations are performed in relation to the pre-washing tower and the absorption tower, to quickly and quantitatively calculate the effect of jointly removing the particulate matter in the wet-type exhaust-gas desulfurization device of a serial two-stage tower type.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of wet flue gas desulfurization, and in particular to a method for calculating the joint particulate matter removal effect of a series column type flue gas wet desulfurization apparatus. [Background technology]

[0002] Wet flue gas desulfurization is a widely used desulfurization method, which is used at the end of the flue gas before it enters the chimney. As environmental standards become increasingly stringent, traditional single-tower desulfurization equipment can no longer meet the needs. When the efficiency of single-tower desulfurization cannot meet the emission requirements, a two-stage series configuration of a pre-scrubber and an absorber becomes an effective desulfurization method.

[0003] The dust components in the flue gas after wet desulfurization can be divided into two parts: dust particles that have not been washed away from the flue gas, and slurry droplets carried in the flue gas. Dust particles are collected to a certain extent in the spray zones and demisters in the pre-scrubber and absorption towers, but slurry droplets are mainly removed in the demister. The theories for removing dust particles and slurry droplets are different, and the process is complex, so there are no established theories or empirical formulas to refer to.

[0004] Computational fluid dynamics (CFD) is a design optimization tool that can simulate and calculate flue gas flow and gas-liquid-solid three-phase flow within a desulfurization tower. However, the tower's internal structure and removal theory are extremely complex, and the removal theory differs depending on the region. Furthermore, the removal conditions in different regions affect each other, making it impossible to directly calculate the removal effect of a desulfurization system. Therefore, the development of effective computational fluid dynamics calculations for joint particulate matter removal in a series tower desulfurization system is a technical challenge that must be resolved as soon as possible. Summary of the Invention [Problem to be solved by the invention]

[0005] To address the above-mentioned problems, an embodiment of the present invention provides a method for calculating the joint particulate matter removal effect of a series tower type flue gas wet desulfurization unit. [Means for solving the problem]

[0006] An embodiment of the present invention comprises: Step S1: establishing a whole model of a series two-stage tower flue system and collecting operating state parameters of the series two-stage tower flue system; Step S2: using the established overall model to simulate and calculate the single-phase flow of the series two-stage tower flue system to obtain the flow field distribution of the series two-stage tower flue system; Step S3: cutting out the inlet cross sections of the pre-scrubber and the absorption tower, and acquiring the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at each inlet cross section based on the obtained flow field distribution; Step S4: establishing a demister model in the pre-washing tower, and performing detailed gas-solid-liquid three-phase flow simulation and calculation to obtain collection efficiency curves for dust particles and slurry droplets of different particle sizes of the demister in the pre-washing tower; Step S5: using the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at the inlet cross section of the pre-scrubber as boundary conditions, and the collection efficiency curves for dust particles and slurry droplets of different particle sizes of the demister in the pre-scrubber as input conditions, to simulate and calculate the gas-liquid-solid three-phase flow in the pre-scrubber, thereby obtaining the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the pre-scrubber; Step S6: establishing a demister model in the absorber and performing detailed gas-solid-liquid three-phase flow simulation and calculation to obtain collection efficiency curves for dust particles and slurry droplets of different particle sizes of the demister in the absorber; Step S7: using the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at the inlet cross section of the absorber, and the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the pre-scrubber as boundary conditions, and using the collection efficiency curves of the demister in the absorber for dust particles and slurry droplets of different particle sizes as input conditions, to simulate and calculate the gas-liquid-solid three-phase flow in the absorber, thereby obtaining the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the absorber; The present invention provides a method for calculating the joint removal effect of particulate matter in a series-tower type flue gas wet desulfurization device, the method including a step S8 of determining the joint removal effect by calculating the sum of the amount of dust particles with different particle diameters flowing out from the outlet of the absorption tower and the solid content of the slurry droplets.

[0007] Compared with the prior art, the present invention has the following advantageous effects: A whole-part-whole approach is adopted to perform step-by-step simulation and calculation of the flue system, demister, pre-scrubber, and absorber. Specifically, a single-phase flow overall simulation is used to quickly obtain the flow velocity and temperature distributions at the inlet cross-section of the pre-scrubber and absorber. A demister submodel is then used for calculation to obtain the collection efficiency curves for dust particles and droplet slurries of different particle sizes for the pre-scrubber demister and absorber demister. These two steps are used to simulate and calculate the joint removal of three-phase flows flowing through the pre-scrubber and absorber. This allows for rapid and quantitative calculation of the joint particulate matter removal effect of a series two-tower wet flue gas desulfurization system. Compared with conventional overall simulation and calculation methods, the present invention enables numerical calculation of the joint particulate matter removal and obtains accurate calculation results.

[0008] Optionally, in step S1, the operating state parameters of the system include an inlet flue gas volume, an inlet flue gas temperature, a diameter of the pre-scrubbing tower, a height of the pre-scrubbing tower, the number of spray layers of the pre-scrubbing tower, a dust concentration at the inlet of the pre-scrubbing tower, a diameter of the absorption tower, a height of the absorption tower, and the number of spray layers of the absorption tower.

[0009] Optionally, in step S2, in the process of simulating and calculating the single-phase flow of a series two-tower flue system, a turbulence model and a mass transport model are selected to simulate and calculate the flue gas flow, and a Lagrangian discrete phase model is adopted to simulate and calculate the dust particles, and the calculation domain is from the fan outlet to the chimney inlet, including the connecting flue, the pre-scrubber body and the absorber body.

[0010] Optionally, in step S4, in the process of detailed gas-solid-liquid three-phase flow simulation and calculation, the Slinn formula is used to comprehensively consider the gas-liquid-solid three-phase interaction for dust particle removal, to calculate the removal efficiency of dust particles of different particle sizes in the demister in the pre-scrubber, and the water-film model is used to calculate the removal efficiency of slurry droplets.

[0011] Optionally, the formula according to Slinn is: E(D d ,d p )=E di (D d ,d p )+E it (D d ,d p )+E im (D d ,d p ) and In the formula, E di (D d ,d p ), E it (D d ,d p ), E im (D d ,d p ) are the collection efficiencies E(D d ,d p ) and the calculation formulas are: E di (D d ,d p )=4 / ReSc[1+0.4Re 1 / 2 Sc 1 / 3 +0.16Re 1 / 2 Sc1 / 2 ] E it (D d ,d p )=4φ[ω -1 +(1+2Re 1 / 2 )φ] E im (D d ,d p )=[(St-St * ) / (St-St * +0.667)] 3 / 2 (ρ p / ρ w ) 1 / 2 and During the ceremony, Re=D d U t (D d )ρ a / 2μ a Sc=μ a / ρ a D St=2U t (D d )τ a / D d φ=d p / D d ω=μ w / μ a St * =(1.2+(1 / 12ln(1+Re))) / (1+ln(1+Re)) U t (D d )=aD d b (ρ a0 / ρ a ) 0.4 Re is the Reynolds number, Sc is the Schmidt number of the fly ash particles, St is the Stokes number of the fly ash particles, and St * is the critical Stokes number, U t (D d) is the final falling velocity of the slurry, where a and b are constants, a = 842 and b = 0.8, φ is the particle size ratio of the fly ash particles to the slurry droplets, and ω is the viscosity ratio of the slurry to the exhaust gas. d p is the particle diameter of the fly ash particles, and D d is the particle size of the slurry, D is the diffusion coefficient of the fly ash particles, and μ w is the viscosity of the slurry, and μ a is the viscosity of the exhaust gas, ρ p is the particle density of fly ash, and ρ w is the density of the slurry, and ρ a is the density of the exhaust gas, and ρ a0 is the density of the standard exhaust gas, and τ a is the relaxation time of the particle, and D d b is the b-th power of the particle size of the slurry.

[0012] Optionally, in step S5, in the process of simulating and calculating the gas-liquid-solid three-phase flow for the pre-scrubbing tower, a porous medium model is adopted in the demister region, the particle size distribution of the slurry at the nozzle outlet of the spray layer is set according to the nozzle's designed particle size distribution, and the removal efficiency of dust particles in the spray layer region is calculated by comprehensively considering the interaction between the gas-liquid-solid three phases using the Slinn formula, and the removal efficiency of dust particles of different particle sizes in the spray layer region is calculated using a water-film model.

[0013] Optionally, the inlet flue gas volume includes the sum of the outlet flue gas volumes of each fan, and for an out-of-operation series tower type flue gas wet desulfurization apparatus, the inlet flue gas temperature may be obtained based on design parameters and test data from similar projects, and for an operating series tower type flue gas wet desulfurization apparatus, the inlet flue gas temperature may be obtained based on on-site monitoring data.

[0014] Optionally, for an inactive series tower flue gas wet desulfurization unit, calculations are made at a solids content of 15%, and for an active series tower flue gas wet desulfurization unit, on-site production data is actually measured and obtained. [Brief explanation of the drawings]

[0015] The drawings described herein are intended to be part of this application to provide a further understanding of the present invention and are not to be construed as limitations thereon.

[0016] [Figure 1] 1 is a flow chart of a method for calculating the joint particulate matter removal effect of a series column type flue gas wet desulfurization apparatus provided by the present invention; [Figure 2] 1 is a schematic diagram of the process of a series two-stage column type flue gas wet desulfurization apparatus provided by the present invention. [Figure 3] FIG. 1 is a schematic diagram of the overall model of a series two-stage flue system provided by the present invention. [Figure 4] 1 is a flow velocity distribution diagram of exhaust gas at the inlet cross section of the pre-scrubbing tower provided by the present invention. [Figure 5] 2 is a flow velocity distribution diagram of exhaust gas at the inlet cross section of the absorption tower provided by the present invention. FIG. [Figure 6] FIG. 1 is a schematic diagram of a demister model in a pre-scrubber provided by the present invention. [Figure 7] FIG. 1 is a schematic diagram of a grid division of a demister model in a pre-washing tower provided by the present invention. [Figure 8] 1 is a dust particle collection efficiency curve of the demister in the pre-washing tower provided by the present invention. [Figure 9] 1 is a curve showing the slurry droplet collection efficiency of the demister in the pre-wash tower provided by the present invention. [Figure 10] FIG. 2 is a diagram showing the trajectory of dust particles in the pre-wash tower provided by the present invention. [Figure 11] 1 is a diagram of the trajectory of slurry droplets in a pre-wash tower provided by the present invention; [Figure 12] 1 is a dust particle collection efficiency curve of the demister in the absorption tower provided by the present invention. [Figure 13] 1 is a curve showing the slurry droplet collection efficiency of the demister in the absorber provided by the present invention. [Figure 14] 1 is a diagram showing the trajectory of dust particles in an absorption tower provided by the present invention; [Figure 15] 1 is a diagram showing the trajectories of slurry droplets in an absorber tower provided by the present invention. [Figure 16] 2 is a particulate matter concentration distribution diagram at different positions of the series two-stage wet flue gas desulfurization apparatus provided by the present invention; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the embodiments and drawings. Hereinafter, the exemplary embodiments of the present invention and the description thereof are provided for the interpretation of the present invention, but are not intended to limit the present invention.

[0018] Referring to FIG. 1 , an embodiment of the present invention provides a method for calculating the joint particulate matter removal effect of a series column type flue gas wet desulfurization device, including: Step S1: Establish an overall model of the series two-stage tower flue system, and collect the operating state parameters of the series two-stage tower flue system.

[0019] In practice, the series two-stage tower type flue gas wet desulfurization apparatus shown in FIG. 2 includes a pre-scrubbing tower 2 and an absorption tower 4 arranged in series, and the series two-stage tower type flue system includes an inlet flue 1 of the pre-scrubbing tower, a connecting flue 3 between the pre-scrubbing tower 2 and the absorption tower 4, and an outlet flue 5 of the absorption tower; The operating state parameters of the system include the amount of exhaust gas at the inlet, the temperature of the exhaust gas at the inlet, the diameter of the pre-scrubbing tower, the height of the pre-scrubbing tower, the number of spray layers in the pre-scrubbing tower, the dust concentration at the inlet of the pre-scrubbing tower, the diameter of the absorption tower, the height of the absorption tower, and the number of spray layers in the absorption tower.

[0020] However, the inlet flue gas volume includes the sum of the outlet flue gas volumes of each fan, and for an inlet flue gas temperature desulfurization apparatus that is not in operation, the inlet flue gas temperature may be obtained based on the design parameters and test data of a similar project, where a similar project is a project with the same or similar production scale, and for an inlet flue gas temperature desulfurization apparatus that is in operation, the inlet flue gas temperature may be obtained based on on-site monitoring data.

[0021] In step S2, the established overall model is used to simulate and calculate the single-phase flow of the series two-stage tower flue system, and the flow field distribution of the series two-stage tower flue system is obtained.

[0022] In the implementation, in the process of simulating and calculating the single-phase flow of the series two-tower flue system, a turbulence model and a mass transport model are selected to simulate and calculate the flue gas flow, and a Lagrangian discrete phase model is adopted to simulate and calculate the dust particles. The calculation domain is from the fan outlet to the chimney inlet, including the connecting flue, the pre-scrubber body, the absorber body, etc.

[0023] In step S3, the inlet cross sections of the pre-scrubber and the absorber are cut out, and based on the obtained flow field distribution, the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at each inlet cross section are obtained.

[0024] In practice, the location of the truncated inlet cross section is typically a location downstream of the last elbow of the inlet flue and between the pre-scrubber (absorber).

[0025] In step S4, a demister model in the pre-washing tower is established, and detailed gas-solid-liquid three-phase flow simulation and calculation are performed to obtain collection efficiency curves for dust particles and slurry droplets of different particle sizes in the demister in the pre-washing tower.

[0026] In practice, in the process of detailed gas-solid-liquid three-phase flow simulation and calculation, a model is created according to the actual structure of the demister in the pre-scrubber. During simulation and calculation, the demister in the pre-scrubber may be grid-divided, dividing the entire demister into multiple calculation units, and calculating the data in each calculation unit to obtain the overall distribution status of the entire demister. Theoretically, the finer the grid division, the better, but if the grid is too fine, the calculation volume will be too large and the computing resources will not be able to cope. Generally, a certain level of grid fineness can fully reflect the actual state, and the specific size of the grid may be determined by verifying grid independence.

[0027] Specifically, in the simulation and calculation process, the Slinn equation is used to comprehensively consider the interaction between the gas, liquid, and solid three phases for dust particle removal, and the removal efficiency of dust particles of different particle sizes in the demister in the pre-washing tower is calculated. The water-film model is used to calculate the removal efficiency of slurry droplets. Specifically, the improved Slinn formula is: E(D d ,d p )=E di (D d ,d p )+E it (D d ,d p )+E im (D d ,d p ) and In the formula, E di (D d ,d p ), E it (D d ,d p ), E im (D d ,d p ) are the collection efficiencies E(D d ,d p ) and the calculation formulas are: E di (D d,d p )=4 / ReSc[1+0.4Re 1 / 2 Sc 1 / 3 +0.16Re 1 / 2 Sc 1 / 2 ] E it (D d ,d p )=4φ[ω -1 +(1+2Re 1 / 2 )φ] E im (D d ,d p )=[(St-St * ) / (St-St * +0.667)] 3 / 2 (ρ p / ρ w ) 1 / 2 and During the ceremony, Re=D d U t (D d )ρ a / 2μ a Sc=μ a / ρ a D St=2U t (D d )τ a / D d φ=d p / D d ω=μ w / μ a St * =(1.2+(1 / 12ln(1+Re))) / (1+ln(1+Re)) U t (D d )=aD d b (ρ a0 / ρ a ) 0.4 Re is the Reynolds number, Sc is the Schmidt number of the fly ash particles, St is the Stokes number of the fly ash particles, and St * is the critical Stokes number, U t (Dd ) is the final falling velocity of the slurry, where a and b are constants, a = 842 and b = 0.8, φ is the particle size ratio of the fly ash particles to the slurry droplets, and ω is the viscosity ratio of the slurry to the exhaust gas. d p is the particle diameter of the fly ash particles, and D d is the particle size of the slurry, D is the diffusion coefficient of the fly ash particles, and μ w is the viscosity of the slurry, and μ a is the viscosity of the exhaust gas, ρ p is the particle density of fly ash, and ρ w is the density of the slurry, and ρ a is the density of the exhaust gas, and ρ a0 is the density of the standard exhaust gas, and τ a is the relaxation time of the particle, and D d b is the b-th power of the particle size of the slurry.

[0028] The water-film model is a mathematical model built into CFD software that can calculate the situation in which discrete droplets form a continuous liquid film, and can also calculate droplets that flow out without forming a liquid film.

[0029] In step S5, the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at the inlet cross section of the pre-scrubbing tower are used as boundary conditions, and the collection efficiency curves for dust particles and slurry droplets of different particle sizes in the demister in the pre-scrubbing tower are used as input conditions, and a gas-liquid-solid three-phase flow in the pre-scrubbing tower is simulated and calculated to obtain the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the pre-scrubbing tower.

[0030] In practice, when performing CFD calculations of the overall joint removal effect of the pre-scrubber, a porous media model is used in the demister region, and the particle size distribution of the slurry at the nozzle outlet of the spray bed is set according to the nozzle's design particle size distribution, or it can be set according to the particle size distribution provided by the nozzle manufacturer. The removal efficiency of dust particles in the spray bed region is calculated by comprehensively considering the gas-liquid-solid three-phase interaction using the Slinn formula to calculate the removal efficiency of dust particles of different particle sizes in the spray bed region, and a water-film model is used to calculate the removal efficiency of slurry droplets. In addition, the collection efficiency of the demister for dust particles and slurry droplets of different particle sizes is calculated overall for the pre-scrubber using the pre-scrubber demister efficiency model as a sub-model, and the amount of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the pre-scrubber is obtained.

[0031] In step S6, a demister model in the absorber is established, and detailed gas-solid-liquid three-phase flow simulation and calculation are carried out to obtain collection efficiency curves for dust particles and slurry droplets of different particle sizes in the demister in the absorber.

[0032] In step S7, the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at the inlet cross section of the absorber, and the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the pre-scrubber are used as boundary conditions, and the collection efficiency curves for dust particles and slurry droplets of different particle sizes of the demister in the absorber are used as input conditions, and a gas-liquid-solid three-phase flow simulation and calculation are performed for the absorber to obtain the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the absorber.

[0033] In practice, the detailed simulation and calculation of the gas-solid-liquid three-phase flow using the demister model in the absorber and the process of simulation and calculation of the gas-liquid-solid three-phase flow for the entire absorber are the same as those of the pre-scrubber, so they will not be described in detail here.

[0034] In step S8, the combined removal effect is determined by calculating the sum of the amount of dust particles with different particle sizes flowing out from the outlet of the absorption tower and the solid content of the slurry droplets.

[0035] In the implementation, calculations are made with a solid content of 15% for a series tower type flue gas wet desulfurization unit that is not in operation, and on-site production data is actually measured and obtained for a series tower type flue gas wet desulfurization unit that is in operation.

[0036] (Example) Step 1: Establish an overall model of the two-stage series flue system and collect its operating parameters. Here, the three-dimensional model of the two-stage series flue system is as shown in Figure 3, with two fans installed at the inlet flue of the pre-scrubbing tower, and the operating parameters are as shown in Table 1. [Table 1]

[0037] Step 2: Simulate and calculate the single-phase flow of the series two-stage absorber flue system to obtain the flow field distribution of the series two-stage absorber flue system.

[0038] In step 3, the inlet cross sections of the pre-scrubber and the absorber are cut out, and the flue gas flow velocity distribution, temperature distribution, and dust particle size distribution are obtained, respectively. The flue gas flow velocity distribution at the inlet cross section of the pre-scrubber is shown in Figure 4, and the flue gas flow velocity distribution at the inlet cross section of the absorber is shown in Figure 5.

[0039] In step 4, a demister model in the pre-scrubber is established, and detailed gas-solid-liquid three-phase flow simulations and calculations are performed to obtain collection efficiency curves for dust particles and slurry droplets of different particle sizes in the demister in the pre-scrubber. The demister model in the pre-scrubber during the simulation and calculation process is shown in Figure 6, and the grid division is shown in Figure 7. The collection efficiency curves for dust particles of different particle sizes in the demister in the pre-scrubber are shown in Figure 8, which shows the collection efficiency curves for dust particles of different particle sizes at three speeds: 3.5 m / s, 4.0 m / s, and 4.5 m / s. The collection efficiency curves for slurry droplets of different particle sizes are shown in Figure 9, which shows the collection efficiency curves for slurry droplets of different particle sizes at three speeds: 3.5 m / s, 4.0 m / s, and 4.5 m / s.

[0040] In step 5, the gas-liquid-solid three-phase flow in the pre-scrubber is simulated and calculated to obtain the amount of dust particles and slurry droplets with different particle sizes flowing out from the outlet of the pre-scrubber. The trajectories of dust particles in the pre-scrubber in the simulation and calculation are shown in Figure 10, and the trajectories of slurry droplets are shown in Figure 11.

[0041] In step 6, a detailed gas-solid-liquid three-phase flow simulation of the sub-model for the demister in the absorber is performed to obtain collection efficiency curves for dust and slurry droplets of different particle sizes. The dust particle collection efficiency curves of the demister in the absorber in the simulation and calculation are shown in Figure 12, which shows the collection efficiency curves for dust particles of different particle sizes at three speeds of 3.5 m / s, 4.0 m / s, and 4.5 m / s. The slurry droplet collection efficiency curves are shown in Figure 13, which shows the collection efficiency curves for slurry droplets of different particle sizes at three speeds of 3.5 m / s, 4.0 m / s, and 4.5 m / s.

[0042] In step 7, the gas-liquid-solid three-phase flow in the absorber is simulated and calculated to obtain the amounts of dust particles and slurry droplets with different particle sizes flowing out from the outlet of the absorber. The trajectories of dust particles in the absorber in the simulation and calculation are shown in Figure 14, and the trajectories of slurry droplets in the absorber in Figure 15.

[0043] Step 8: Adding the predetermined percentage of solids in the slurry droplets at the outlet of the absorber and the amount of dust particles at the outlet of the absorber to obtain the solid particulate matter emission concentration at the outlet of the two-stage series absorber.

[0044] After simulation and calculation, the particulate matter concentration distribution at different positions in the series two-stage wet flue gas desulfurization equipment was statistically analyzed to obtain the distribution diagram shown in Figure 16. The calculation results showed that the dust concentration at the outlet of the absorber was 2.8 mg / Nm 3 The slurry droplet concentration was 12.2 mg / Nm 3 When calculated with a solid content of 15% in the circulating slurry, the solid concentration at the outlet of the absorber is 1.83 mg / Nm3 due to the transport of the slurry. 3 The total emission concentration of both is 4.63 mg / Nm 3 and meets emission standards.

[0045] The solution provided by the present invention employs a whole-part-whole approach to perform step-by-step simulation and calculation of the flue system, demister, pre-scrubber, and absorber. Specifically, a single-phase flow overall simulation is employed to quickly obtain the flow velocity and temperature distributions at the inlet cross-sections of the pre-scrubber and absorber. A demister submodel is then used for calculation to obtain the collection efficiency curves for dust particles and droplet slurries of different particle sizes for the pre-scrubber demister and absorber demister. These two steps are then used to simulate and calculate the joint removal of three-phase flows within the pre-scrubber and absorber, allowing for rapid and quantitative calculation of the joint particulate matter removal effect of a series two-tower wet flue gas desulfurization system. Compared with conventional overall simulation and calculation methods, the present invention enables numerical calculation of joint particulate matter removal and obtains accurate calculation results.

[0046] The above is merely a preferred embodiment of the present invention, not a limitation on the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and scope of the present invention shall be included in the protection scope of the present invention. [Explanation of symbols]

[0047] 1 Pre-wash tower inlet flue 2 Pre-wash tower 3 Connecting flue 4. Absorption tower 5 Absorption tower exit flue SP1 Spray layer in pre-wash tower ME1 Demister in pre-washing tower SP2 Spray layer inside absorption tower ME2 Demister in absorption tower

Claims

1. Step S1: establishing a whole model of a series two-stage flue system and collecting operating state parameters of the series two-stage flue system; Step S2: Using the established overall model to simulate and calculate the single-phase flow of the series two-stage tower flue system to obtain the flow field distribution of the series two-stage tower flue system; Step S3: cutting out the inlet cross sections of the pre-scrubber and the absorption tower, and acquiring the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at each inlet cross section based on the obtained flow field distribution; Step S4: establishing a demister model in the pre-washing tower, and simulating and calculating the gas-solid-liquid three-phase flow to obtain collection efficiency curves for dust particles and slurry droplets of different particle sizes of the demister in the pre-washing tower; Step S5: using the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at the inlet cross section of the pre-scrubbing tower as boundary conditions, and the collection efficiency curves for dust particles and slurry droplets of different particle sizes of the demister in the pre-scrubbing tower as input conditions, to simulate and calculate the gas-liquid-solid three-phase flow in the pre-scrubbing tower, thereby obtaining the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the pre-scrubbing tower; Step S6: establishing a demister model in the absorber and simulating and calculating the gas-solid-liquid three-phase flow to obtain collection efficiency curves for dust particles and slurry droplets of different particle sizes of the demister in the absorber; Step S7: using the flow velocity distribution, temperature distribution, and dust particle size distribution of the exhaust gas at the inlet cross section of the absorber, and the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the pre-scrubber as boundary conditions, and using the collection efficiency curves of the demister in the absorber for dust particles and slurry droplets of different particle sizes as input conditions, to simulate and calculate the gas-liquid-solid three-phase flow in the absorber, thereby obtaining the amounts of dust particles and slurry droplets of different particle sizes flowing out from the outlet of the absorber; and (S8) determining the joint removal effect by calculating the sum of the amount of dust particles of different particle diameters flowing out from the outlet of the absorption tower and the solid content of the slurry droplets.

2. The method for calculating the joint particulate matter removal effect of a series-type flue gas wet desulfurization device according to claim 1, wherein the system operating state parameters in step S1 include the inlet flue gas volume, the inlet flue gas temperature, the diameter of the pre-scrubber, the height of the pre-scrubber, the number of spray layers in the pre-scrubber, the dust concentration at the inlet of the pre-scrubber, the diameter of the absorber, the height of the absorber, and the number of spray layers in the absorber.

3. Step S2 is the process of simulating and calculating the single-phase flow of a series two-tower flue system, selecting a turbulence model and a mass transport model to simulate and calculate the flue gas flow, and adopting a Lagrangian discrete phase model to simulate and calculate the dust particles, and the calculation domain is from the fan outlet to the chimney inlet, including the connecting flue, the pre-scrubber main body, and the absorber main body. The method for calculating the joint particulate matter removal effect of a series tower flue gas wet desulfurization device described in claim 1, characterized in that

4. The method for calculating the joint particulate matter removal effect of a series-column flue gas wet desulfurization apparatus according to claim 1, wherein in step S4, in the process of simulating and calculating the gas-solid-liquid three-phase flow, the Slinn equation is used to consider the interaction between the gas-liquid-solid three-phase flow for dust particle removal, to calculate the removal efficiency of dust particles of different particle sizes in the demister in the pre-scrubber, and a water-film model is used to calculate the removal efficiency of slurry droplets.

5. The formula by Slinn is: E(D ｄ ,d ｐ )=E ｄｉ (D ｄ ,d ｐ )+E ｉｔ (D ｄ ,d ｐ )+E ｉｍ (D ｄ ,d ｐ ) and In the formula, E ｄｉ (D ｄ , d ｐ ), E ｉｔ (D ｄ , d ｐ ), E ｉｍ (D ｄ , d ｐ ) are the collection efficiencies E(D ｄ , d ｐ ) and the calculation formulas are: E ｄｉ (D ｄ ,d ｐ )\4 / Reｳc[+00.42e １／２ ｳc １／３ 00.162e １／２ ｳc １／２ ) E ｉｔ (D) ｄ ,d ｐ )=4φ[ω －１ + (1 + 2 Re) １／２ )φ] E ｉｍ (D ｄ ,d ｐ )=[(St-St ＊ ) / (St-St ＊ +0.667)] ３／２ (ρ ｐ / ρ ｗ ) １／２ and During the ceremony, 100.000 ｄ 10 ｔ (5) ｄ )ρ ａ 22μ ａ Sc=μ ａ / r ａ D 2020 ｔ (5) ｄ )τ ａ 30 ｄ φ=d ｐ / D ｄ ω=μ ｗ / m ａ St ＊ =(1.2+(1 / 12ln(1+Re))) / (1+ln(1+Re)) U ｔ (D) ｄ )=aD ｄ ｂ (p) ａ０ / r ａ ) ０．４ Re is the Reynolds number, Sc is the Schmidt number of the fly ash particles, St is the Stokes number of the fly ash particles, and St ＊ is the critical Stokes number, U ｔ (D ｄ ) is the final falling velocity of the slurry, where a and b are constants, a = 842 and b = 0.8, φ is the particle size ratio of the fly ash particles to the slurry droplets, and ω is the viscosity ratio of the slurry to the exhaust gas. d ｐ is the particle diameter of the fly ash particles, and D ｄ is the particle diameter of the slurry, D is the diffusion coefficient of the fly ash particles, and μ ｗ is the viscosity of the slurry, and μ ａ is the viscosity of the exhaust gas, ρ ｐ is the particle density of fly ash, and ρ ｗ is the density of the slurry, and ρ ａ is the density of the exhaust gas, and ρ ａ０ is the density of the standard exhaust gas, and τ ａ is the relaxation time of the particle, and D ｄ ｂ 5. The method for calculating the joint particulate matter removal effect of a series column type flue gas wet desulfurization apparatus according to claim 4, wherein is the b-th power of the particle diameter of the slurry.

6. 6. The method for calculating the joint particulate matter removal efficiency of a series-type flue gas wet desulfurization unit according to claim 5, wherein in step S5, in the process of simulating and calculating the gas-liquid-solid three-phase flow for the pre-scrubbing tower, a porous media model is adopted for the demister region, the particle size distribution of the slurry at the nozzle outlet of the spray bed is set according to the designed particle size distribution of the nozzle, the removal efficiency of dust particles in the spray bed region is calculated by taking into account the interaction of the gas-liquid-solid three-phase using the Slinn formula, and the removal efficiency of slurry droplets is calculated by using a water film model.

7. The method for calculating the joint particulate matter removal effect of a series-tower type flue gas wet desulfurization apparatus according to claim 2, wherein the inlet flue gas volume includes the sum of the outlet flue gas volumes of each fan; for an out-of-operation series-tower type flue gas wet desulfurization apparatus, the inlet flue gas temperature can be obtained based on design parameters and test data of similar projects; for an operating series-tower type flue gas wet desulfurization apparatus, the inlet flue gas temperature can be obtained based on on-site monitoring data.

8. The method for calculating the joint particulate matter removal effect of series-tower type flue gas wet desulfurization equipment according to claim 1, characterized in that for non-operational series-tower type flue gas wet desulfurization equipment, the calculation is performed with a solid content of 15%, and for operating series-tower type flue gas wet desulfurization equipment, on-site production data is actually measured and obtained.

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