A new desulfurization reaction tower

Abstract

The present application relates to desulfurization tower technical field, specifically to a kind of novel desulfurization reaction tower, including tower body, flue gas import, flue gas export, slurry pool and spraying layer, the inside of tower body is equipped with the flow uniform tube mass transfer component arranged above slurry pool liquid level, flow uniform tube mass transfer component includes porous substrate and multiple vertically arranged flow uniform tubes, several through holes are opened in porous substrate, each through hole is upwardly fixed with a flow uniform tube, flow uniform tube is the hollow straight tube with both ends through, flue gas export is arranged at the top of tower body, the position of flue gas import access inside tower body is set at the elevation position of slurry pool liquid level, flue gas enters inside tower body by flue gas import and flows into each flow uniform tube, after flowing out from flow uniform tube upper end, into spraying layer;The present application can realize that flue gas is quickly and evenly distributed in tower under the premise of reducing tower height, reduce mass transfer component resistance, reduce the dependence on upstream flue flow field optimization, reduce desulfurization system investment and operating energy consumption.

Description

Technical Field

[0001] This invention relates to the field of desulfurization tower technology, and specifically to a novel desulfurization reaction tower. Background Technology

[0002] Wet limestone-gypsum desulfurization process for coal-fired power generating units is the mainstream technology for SO2 removal from power plant flue gas. The distribution of flue gas flow field inside the desulfurization tower directly determines the desulfurization absorption efficiency and slurry spray utilization rate. At the same time, the height of the tower body directly affects the project investment and civil engineering costs.

[0003] The existing mainstream desulfurization towers generally adopt BFI (Boiling) Foam Integration (BFI) technology is used to fabricate flow equalization components within the tower, namely the integrated boiling-foam BFI tray. The BFI tray is a perforated plate structure with a wind cap. After the flue gas enters the tower laterally, it is easily affected by the inlet flow deviation, resulting in large-scale swirling and backflow phenomena within the tower. The cross-sectional velocity distribution is uneven, and the velocity relative standard deviation is high. The uneven flow field will cause insufficient contact between the sprayed slurry and the flue gas in some areas, resulting in a decrease in desulfurization efficiency. To improve the flow field, the existing solution can only rely on increasing the tower height and extending the flue gas mixing path to weaken the flow field distortion caused by the inlet flow deviation. However, the increase in tower height leads to a significant increase in equipment, steel structure, and civil engineering investment.

[0004] Therefore, there is an urgent need for a desulfurization tower that can achieve rapid and uniform distribution of flue gas inside the tower while reducing the tower height, thereby reducing the resistance of mass transfer components, reducing reliance on upstream flue gas flow field optimization, and lowering the investment and operating energy consumption of the desulfurization system. Summary of the Invention

[0005] The present invention aims to provide a novel desulfurization reaction tower that can achieve rapid and uniform distribution of flue gas inside the tower while reducing the tower height, thereby reducing the resistance of mass transfer components, reducing reliance on upstream flue gas flow field optimization, and reducing investment and operating energy consumption of the desulfurization system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A novel desulfurization reaction tower includes a tower body, a flue gas inlet, a flue gas outlet, a slurry pool, and a spray layer. Inside the tower body, a flow equalization tube mass transfer component is arranged above the liquid surface of the slurry pool. The flow equalization tube mass transfer component includes a porous substrate and multiple vertically arranged flow equalization tubes. Several through holes are opened on the porous substrate, and each through hole is fixed downwards to a flow equalization tube. The flow equalization tube is a hollow straight tube with both ends connected. The flue gas outlet is located at the top of the tower body, and the flue gas inlet is located at the elevation of the liquid surface of the slurry pool. Flue gas enters the tower body through the flue gas inlet and flows upwards into each flow equalization tube. After flowing out from the upper end of the flow equalization tube, it enters the spray layer. Based on computational fluid dynamics, a Realizable k-ε turbulence model combined with a two-way coupled discrete phase model is used to predict the gas-liquid two-phase flow field inside the tower.

[0007] Furthermore, the continuous phase of the flue gas inside the tower is described in the Euler coordinate system. The flue gas adopts the assumption of a steady-state incompressible ideal gas, and the continuity conservation equation, momentum conservation equation, energy conservation equation and component transport equation are solved for the flue gas.

[0008] Furthermore, the droplet particles formed after the slurry in the slurry pool are atomized are carried by the flue gas and undergo heat exchange and movement. After analyzing the force on the droplet particles, the particle motion equation is solved, and a particle random walk model and a droplet evaporation model are introduced.

[0009] Furthermore, the flue gas inside the tower is pressure-velocity coupled using the SIMPLEC algorithm, and the relative standard deviation of cross-sectional velocity (RSD) is used as the evaluation index of the flow field uniformity of the flue gas inside the tower.

[0010] Furthermore, the through holes are arranged in an equilateral triangle, with a diameter of 10mm to 240mm, and the spacing between adjacent holes is 1.5 times their own diameter.

[0011] Furthermore, the height-to-diameter ratio of the flow equalization tube is 7.5 to 12.5, the lower end of the flow equalization tube is aligned and connected with the through hole of the porous substrate, the upper end of the flow equalization tube is a free outlet, and the tube wall is closed without lateral openings.

[0012] Furthermore, the spray layer includes bidirectional hollow cone nozzles and eccentric solid cone nozzles installed on the inner wall of the tower. The slurry in the slurry pool is pumped to the spray layer and sprayed downwards, where it comes into countercurrent contact with the flue gas flowing out from the upper end of the equalization pipe to complete the desulfurization reaction.

[0013] The beneficial effects of this plan are: The mass transfer component employing a combination of a porous substrate and a vertical flow equalization tube achieves self-balancing of flow rates in each channel by relying on the tube resistance itself, effectively mitigating the uneven flow distribution problem caused by inlet flue gas deviation. Simulation results show that the relative standard deviation (RSD) of the cross-sectional velocity can be reduced to approximately 12% under small-scale testing conditions. Furthermore, flue gas mixing is achieved without relying on tower height; compared to traditional desulfurization towers of the same processing capacity, the tower height can be reduced by approximately 15m, significantly lowering engineering investment in equipment manufacturing, steel structure support, and civil engineering foundations.

[0014] Under the same flue gas conditions, compared with the traditional BFI tray, the flow equalization tube mass transfer component of this invention can effectively reduce system pressure loss and mass transfer section resistance, directly reducing the operating load of the induced draft fan, reducing the unit's power consumption, and achieving energy-saving operation of the desulfurization system.

[0015] It is equipped with a complete CFD numerical simulation design process, and uses a Realizable k-ε turbulence model combined with a two-way coupled DPM discrete phase model to fully cover the physical processes of continuous phase turbulent flow of flue gas, droplet motion, turbulent diffusion, and droplet evaporation phase change. Through grid independence verification and velocity relative standard deviation (RSD) evaluation index, it can quantitatively evaluate the impact of different opening arrangements, apertures, height-to-diameter ratios, and opening ratios on component performance. It can complete parameter iterative optimization in the design stage, reduce the workload of physical testing, and reliably guide the engineering design of desulfurization towers for large-capacity units. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention. Figure I ; Figure 2 This is a schematic diagram of the structure of the present invention. Figure II ; Figure 3 This is a cross-sectional view of the present invention; Figure 4 This is a schematic diagram of pipe resistance and flow distribution under different diameter-to-height ratios in this invention; Figure 5 This is a velocity distribution cloud map of the BFI tower and the flow equalization tower without spraying in this invention; Figure 6 This is a cloud map of the flue gas velocity traces in the BFI tower and the flow equalization tower without spraying in this invention; Figure 7 This is a cloud map of the flue gas velocity trace in the flow equalization tower without spraying and without heat exchanger installed in this invention; Figure 8 This is a velocity distribution cloud map of the BFI tower and the flow equalization tower under spraying in this invention; Figure 9 This is a cloud map of the flue gas velocity traces in the BFI tower and the flow equalization tower under spraying in this invention; Figure 10 This is a schematic diagram of the porous substrate structure in this invention.

[0017] The following detailed description illustrates the specific implementation method: The reference numerals in the accompanying drawings include: 1. Tower body; 2. Flue gas inlet; 3. Flue gas outlet; 4. Slurry pool; 5. Spray layer; 6. Flow equalization pipe; 7. Porous substrate; 8. Through hole. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] The basic implementation examples are as follows: Figure 1-6 As shown in the attached document Figure 1-4 The novel desulfurization reaction tower shown includes a tower body 1, a flue gas inlet 2, a flue gas outlet 3, a slurry pool 4, and a spray layer 5. Inside the tower body 1, a mass transfer component consisting of flow equalization pipes 6 arranged above the liquid surface in the slurry pool 4 is provided. The flow equalization pipes 6 include a porous substrate 7 and multiple vertically arranged flow equalization pipes 6. The porous substrate 7 has several through holes 8, and each through hole 8 is fixed downwards to a flow equalization pipe 6. The flow equalization pipes 6 are hollow straight pipes with both ends open. The flue gas outlet 3 is located at the top of the tower body 1, and the flue gas inlet 2 is positioned at the point where it enters the interior of the tower body 1. At the elevation of the liquid level in the slurry pool 4, the flue gas enters the tower body 1 through the flue gas inlet 2 and flows upward into each equalization pipe 6. After flowing out from the upper end of the equalization pipe 6, it enters the spray layer 5. The diameter of the through hole 8 is 10mm to 240mm, and the spacing between adjacent holes is 1.5 times its own diameter. The height-to-diameter ratio of the equalization pipe 6 is 7.5 to 12.5. The lower end of the equalization pipe 6 is aligned and connected with the through hole 8 of the porous substrate 7. The upper end of the equalization pipe 6 is a free outlet, and the pipe wall is closed without lateral openings. As a preferred embodiment, the through holes are arranged in an equilateral triangle.

[0021] In this embodiment, the above-described structure is used to form a flow equalization tower on an existing 330MW unit desulfurization tower. Taking the 330MW unit desulfurization tower as an example, a method for flow field simulation is provided. The experimental steps of the method are as follows: Step 1: Based on computational fluid dynamics (CFD), the gas-liquid two-phase flow field in tower 1 is predicted by using a realizable k-ε turbulence model combined with a two-way coupled discrete phase model. A full-size three-dimensional computational domain is established according to the scale of the pilot desulfurization tower and the 330MW unit desulfurization tower.

[0022] Step 2: The continuous phase of flue gas inside tower 1 is described in the Euler coordinate system. The flue gas adopts the assumption of a steady-state incompressible ideal gas, and its physical properties change dynamically with temperature and composition. As the continuous phase, the continuity conservation equation, momentum conservation equation, energy conservation equation and component transport equation are solved. The equations are as follows.

[0023] Continuity conservation equation:

[0024] In the formula: The density of the flue gas (continuous phase) is kg / m³. Let the time be s; Spatial coordinate components ( =1, 2, 3 respectively correspond to x, y, z (direction), m; For the flue gas velocity at The directional component in m / s; The mass source term per unit volume (positive for droplet evaporation into the gas phase, negative for condensation) is kg / (m³·s.

[0025] Momentum conservation equation:

[0026] In the formula: The flue gas in direction and The velocity component in the direction (m / s); The static pressure of the flue gas is Pa. Effective dynamic viscosity (molecular dynamic viscosity) With turbulent dynamic viscosity (sum of) Pa·s; The difference between the density of the flue gas and the reference density (buoyancy term) is expressed in kg / m³. The gravitational acceleration component is in m / s². For the first Density of the discrete phase (droplet) in kg / m³; Its velocity component is m / s; Let s be the momentum relaxation time of the discrete phase; The interphase momentum exchange source term per unit volume is N / m³; The momentum source term due to the phase transition is N / m³; The Magnus force component per unit volume is N / m³.

[0027] Energy conservation equation:

[0028] Component transport equations:

[0029] In the formula: The specific heat capacity of flue gas at constant pressure is J / (kg·K); The flue gas thermodynamic temperature is K; The Prandtl number for energy transport turbulence (often taken as 0.85 in engineering) is dimensionless; for Component mass production rate per unit volume (kg / (m³·s)); For unit mass Enthalpy change of phase transition or reaction of components (J / kg); The heat released (absorbed) by the fluid phase per unit volume (W / m³). The value represents the radiative heat loss per unit volume in W / m³. For the first The discrete phase number density, units / m³; The heat transfer rate between a single droplet and the gas phase is expressed in W / droplet. For interphase heat transfer source terms per unit volume, W / m³. For the gas phase due to phase transition (mass source) The enthalpy source term generated by introducing enthalpy, W / m³.

[0030] Step 3: The fluid flow within industrial equipment is mostly in a turbulent state, which is essentially an unsteady random motion formed by the superposition of countless vortices of different scales, exhibiting strong nonlinearity, multi-scale characteristics, and diffusion. Based on different methods of handling turbulent vortices, turbulence numerical simulation methods can be divided into three categories: Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), and Reynolds-Averaged Navier-Stokes (RANS). Direct Numerical Simulation (DNS) has very high computer requirements and is only suitable for basic academic research at low Reynolds numbers. It cannot be applied to industrial scenarios such as desulfurization towers with meter-scale scales and Reynolds numbers on the order of (10^5). LES still has a much higher computational cost than RANS and requires extremely high-quality near-wall meshes. For full-scale simulation of a 20m-scale desulfurization tower, the computational cost is prohibitive, and it is only suitable for detailed studies of local structures. The RANS method has a moderate computational cost and acceptable engineering accuracy, making it the mainstream method for industrial CFD simulation. RANS turbulence models can be categorized into zero-equation models, single-equation models, and two-equation models based on the number of transport equations introduced. Among these, the two-equation model, by introducing transport equations for two turbulent characteristic quantities, achieves spatially adaptive calculation of turbulent viscosity, offering the best adaptability and accuracy, and is the most widely used in engineering applications. Mainstream two-equation models include Standard k-ε, RNG k-ε, Realizable k-ε, and k- Series of models.

[0031] The experimental subject was the desulfurization tower of a 330MW unit, with a focus on the flow pattern of flue gas ejected at high speed through the small holes of the BFI tray's air cap, forming a dense jet of small holes that impacted the air cap. The air cap's position was described in [reference needed]. Figure 3As shown, there are large-scale macroscopic backflows and velocity gradients within the tower, and the airflow distribution exhibits significant non-uniformity along both the radial and axial directions. Therefore, the model needs to have high simulation accuracy for jets, backflows, and shear flows, while also having controllable computational load and good steady-state convergence.

[0032] Standard k-ε provides insufficient accuracy in simulating jet and recirculation, failing to accurately capture the development and mixing processes of the jet in the wind cap. The k-ω SST near-wall mesh y+ is generally no more than 1 (y+ is the wall unit, meaning the distance and velocity near the wall are dimensionless, and the near-wall behavior under different geometries and incoming flow velocities is compared using the same scale), resulting in an excessively large overall mesh size. Similar to RSM, the computational cost is too high, and the accuracy improvement for this specific working condition is limited, making it extremely cost-effective. RNG k-ε exhibits strong numerical rigidity but generally poor convergence. Therefore, this experiment ultimately chose the Realizable k-ε turbulence model, employing the non-equilibrium wall function method for the near-wall region. Compared to the standard wall function method, this approach is more accurate in calculating large pressure gradients (boundary layer separation) near the wall, and it maintains computational accuracy even when y+≤15, making it suitable for complex flows involving flue gas impacting and separating from the wind cap.

[0033] In wet desulfurization towers, the spray slurry is dispersed in the flue gas as droplets, with the droplet volume fraction typically accounting for only about 2.5% of the gas phase, classifying it as a dilute-phase gas-liquid two-phase flow. For dilute-phase discrete systems, the Eulerian-Lagrangian method is the most efficient simulation method. This involves solving the continuous phase flue gas in Eulerian coordinates, while tracking the motion, temperature, and mass changes of individual droplets in Lagrangian coordinates. The two are bidirectionally coupled through interphase forces, heat transfer, and mass transfer.

[0034] Step 4: The atomized droplets undergo heat exchange and motion under the influence of the flue gas. Force analysis of the droplet particles reveals that, under the influence of the flue gas, the moving particles experience forces including gravity, drag, virtual mass force, Basset force, Magnus force, electrostatic force, Brownian force, and Saffman lift generated by the shear layer flow due to the lateral velocity in the additional force. Although the particles experience numerous forces, there are primary and secondary forces. The force balance equation for the particles in the flow field is:

[0035] In the formula: m p The mass of the droplet is in kg. u p The velocity of the droplet particles is m / s; t Let the time be s; F D For drag force, FA For virtual mass force, F B For Bassetley, F S For Saffman lift, F M For Magnus force, F C The force of collision between particles. F G The force is the gravitational force acting on the particle. The unit of each force is N. The physical meaning and expression are detailed below.

[0036] F D Let be the drag force of the fluid on the atomized droplet particles. For spherical particles, its expression is:

[0037] In the formula: m The mass of the droplet is in kg. μ The dynamic viscosity of the flue gas is expressed in Pa·s. ρ p The density of the droplet particles is kg / m³; d p Where m is the diameter of the droplet; C D is the drag force coefficient (dimensionless); Re is the Reynolds number (dimensionless) of the droplet particle relative to the flue gas motion.

[0038] F A Virtual mass force: When flue gas carries atomized liquid droplets, and these droplets are accelerated by a force, the fluid viscosity causes the droplets to accelerate the surrounding fluid, thus consuming some kinetic energy. At this point, the original force acting on the droplet is greater than the acceleration force; this excess force is called the virtual mass force, expressed as:

[0039] In the formula: ρ The density of the flue gas is kg / m³. V p Let m be the volume of the droplet. u The flue gas velocity is m / s; u p The velocity of the droplet particles is m / s; t Let s be the time interval.

[0040] F B Baset force: When a particle undergoes arbitrary, variable-speed linear motion in a flow field, due to the viscosity of the fluid, in addition to the added mass force acting on the particle, there is also a sudden increase in drag due to the particle's variable-speed motion in the viscous fluid. If The starting time, Then it is the integral variable.

[0041] Saffman force: When particles move in a non-uniform velocity field, the difference in flow velocity on both sides of the particle leads to a velocity gradient, especially large within the boundary layer. Within the boundary layer, particles experience lift from the low-velocity region to the high-velocity region; this force is called the Saffman force, and its expression is:

[0042] In the formula: d p Where m is the diameter of the droplet; ρ g The density of the flue gas is kg / m³; μ g The dynamic viscosity of the flue gas is Pa·s; v g The velocity of the flue gas is m / s; v p The velocity of the droplet particles is m / s; y Let m be the normal coordinate of the wall. The velocity gradient s of the flue gas along this direction - ¹.

[0043] Magnus force: When a particle moves and rotates in a flow field, due to the difference in fluid velocities on both sides, a force is generated perpendicular to the flow direction, pointing from the counter-current side to the downstream side. This force is called the Magnus force, and its expression is:

[0044] In the formula: ρ g The density of the flue gas is kg / m³; w ω is the angular velocity of the droplet particle's spin in rad / s; d p Where m is the diameter of the droplet; v g , v p The velocities are the flue gas velocity and the droplet velocity, respectively, in m / s.

[0045] The collision force between Fc particles is caused by the random motion of the particles, resulting in collisions between particles and between particles and the wall. The force is related to the speed of the particles.

[0046] F G The gravity of a particle acts on it constantly, always perpendicularly downwards. The formula for calculating gravity is:

[0047] In the formula: d p Let be the diameter of the droplet, in meters (m). ρ p The density of the droplet is kg / m³. g ρ is the acceleration due to gravity, in m / s².

[0048] After atomization, the droplets enter the desulfurization tower. Since the droplets are in a dilute phase flow, inter-particle collisions and droplet rotation are neglected. Therefore, F can be ignored as the atomized droplets flow with the tail-end flue gas. C and F M The atomizing effect of the atomizing nozzle on droplets with a diameter greater than 20 μm is significant. The diameter of the atomized and evaporated droplets is much larger than that of submicroscopic particles (1~10 μm). Therefore, in the above formula, F... A F B F S All forces are negligible. In summary, the particle motion equations of the atomized droplets in the tail flue mainly consider drag and gravity. Therefore, the simplified expression of the droplet particle motion equation is:

[0049] In the formula: t Let the time be s; u p The velocity of the droplet particles is m / s; u The flue gas velocity is m / s; C D is the drag force coefficient (dimensionless); ρ The density of the flue gas is kg / m³; ρ p The density of the droplet particles is kg / m³; d p Where m is the diameter of the droplet; g The acceleration due to gravity is m / s².

[0050] Step 5: The droplet particles entering the desulfurization tower will be subject to the interaction between the droplet particles and the discrete vortices (continuous generation and destruction) of the flue gas. The turbulent diffusion of the droplet particles is considered in the stochastic trajectory model. In this model, it is assumed that the fluctuating velocity of the fluid is a piecewise function of time. Within the characteristic life interval of the fluid vortex, this velocity fluctuation remains constant. The characteristics of the turbulent vortex are mainly determined by the duration of the vortex (…). The motion of the particle is described by the random fluctuating velocity (u') of the turbulent flow. Therefore, after adding the fluctuating velocity (u'), the equation of motion of the particle becomes:

[0051] At this point, in the principal coordinate system, the second moment of the turbulence is a diagonal matrix, and for the large eddy model, the characteristic survival time of the eddy can be defined as a constant:

[0052] In the formula: τ e The characteristic survival time (s) of the turbulent vortex; T L s is the time scale for the Lagrange turbulence integral (i.e., the large eddy time scale).

[0053] The evaporation of droplet particles follows the same mechanism as that of a single droplet. The spherical droplet particles, atomized by the nozzle, are heated by the flue gas, undergoing both preheating and steady-state heating. The heat and mass transfer of the droplet particles satisfy the laws governing droplet heating, evaporation, and boiling.

[0054] (1) The droplet particles just come into contact with the high-temperature flue gas, at which point the droplet temperature is... Less than the critical evaporation temperature During this stage, the temperature difference between the gas and liquid is large, and all the heat absorbed by the droplet is used for heating; no mass exchange occurs between the gas and liquid. The heat balance equation for the droplet in the first stage is:

[0055] In the formula: m p The mass of the droplet is in kg. c p Specific heat capacity of the droplet (J / (kg·K)); t Let the time be s; A p Let m be the surface area of ​​the droplet; T ∞ Let K be the flue gas temperature. T p The temperature of the droplet particles is K; h The convective heat transfer coefficient between gas and liquid is W / (m²·K).

[0056] The gas-liquid convective heat transfer coefficient is:

[0057] In the formula, Nu For Nusselt number (dimensionless); h The convective heat transfer coefficient between gas and liquid is W / (m²·K); d p Where m is the diameter of the droplet; k ∞ The thermal conductivity of the flue gas is W / (m·K); Re d The particle Reynolds number (dimensionless) is characterized by the droplet diameter.Pr The Prandtl number for flue gas (dimensionless).

[0058] (2) Temperature of the droplet particles Less than boiling temperature At this stage, the equilibrium equation for the droplet particles is:

[0059] In the formula: m p The mass of the droplet is in kg. c p Specific heat capacity of the droplet (J / (kg·K)); t Let the time be s; h The convective heat transfer coefficient between gas and liquid is W / (m²·K); A p Let m be the surface area of ​​the droplet; T ∞ , T p These are the flue gas temperature and the droplet particle temperature, respectively, in K. dm p / dt denoted as the rate of change of droplet mass over time (i.e., evaporation rate, which is negative during evaporation) in kg / s; h fg The latent heat of vaporization of the droplet is J / kg.

[0060] The equation related to the droplet evaporation rate at this stage is:

[0061] The mass transfer coefficient related equation is:

[0062] In the formula: N i Let be the vapor molar flow rate of component i, in kg·mol / (m²·s). k c The convective mass transfer coefficient is m / s; C i,s , C i,∞ , respectively, are the vapor concentrations (kg·mol / m³) of component i on the droplet surface and in the bulk flue gas; Sh is the Sherwood number (dimensionless). h i The convective mass transfer coefficient is m / s; d p Where m is the diameter of the droplet; D i,m Let m² / s be the diffusion coefficient of component i vapor in the flue gas. Re dis the particle Reynolds number (dimensionless); Sc is the Schmidt number (dimensionless). The convective mass transfer coefficient is... k c and h i They have the same physical meaning, both describing the intensity of convective mass transfer at the gas-liquid interface.

[0063] (3) When the temperature of the droplet particles Exceed At this point, the droplet absorbs a large amount of heat, primarily undergoing boiling and heat transfer processes. The boiling rate equation for the droplet at this time is:

[0064] In the formula: d p Let be the diameter of the droplet, in meters (m). t For time, s; k ∞ The thermal conductivity of the flue gas is W / (m·K); ρ p The density of the droplet particles is kg / m³; c p,∞ The specific heat capacity of flue gas is J / (kg·K); Re d is the particle Reynolds number (dimensionless); T ∞ , T p These are the flue gas temperature and the droplet particle temperature, respectively, in K. h fg The latent heat of vaporization of the droplet is J / kg.

[0065] Step Six: The structure of the desulfurization tower for the 330MW unit is shown in the attached figure. Figure 3 As shown in the figure, as an example, the desulfurization tower of the 330MW unit has a tower diameter of 11.734m, a tower top elevation of 39.55m, a slurry pool 4 liquid level elevation of 15.23m (considered as the bottom wall of the tower), a demister height of 6.9m, and is considered as a porous medium along with the inlet and outlet flue gas heat exchangers; the inlet boundary condition is defined as a mass inlet, the outlet is defined as a pressure outlet, the flue gas is considered as an incompressible ideal gas, the physical properties are calculated using the mixing law of incompressible ideal gases, the mass flow rate is 456kg / s, and the pressure-velocity coupling method is the SIMPLEC method.

[0066] The spray layer 5 includes bidirectional hollow cone nozzles and eccentric solid cone nozzles installed on the inner wall of the tower body 1. The slurry in the slurry tank 4 is pumped to the spray layer 5 and sprayed downwards, making countercurrent contact with the flue gas flowing out from the upper end of the flow equalization pipe 6 to complete the desulfurization reaction. The tower body 1 is regarded as an adiabatic wall, and the collision between the droplets and the spray pipe and the wall during the falling process is regarded as an ideal elastic collision. The wall boundary condition is set as reflect, the liquid surface and inlet and outlet of the slurry tank 4 are set as Escape, and the mass transfer components and wind caps are set as trap. The breakage between droplets is not considered. The actual spray parameters are used for the spray layer 5. The selection of the spray layer 5 is shown in Table 1 below: Table 1 Spraying parameters of the spray layer

[0067] Step 7: In the wet sulfurization process, the uniformity of the flue gas flow field distribution within the tower is a key factor affecting the desulfurization effect. To quantitatively describe the velocity distribution within the desulfurization tower, the relative standard deviation of velocity (RSD) and the relative standard deviation of flue gas velocity (S) are used. The formula for calculating the relative standard deviation of velocity (RSD) is as follows:

[0068] In the formula: X is the standard deviation of velocity (m / s); X0 is the cross-sectional average velocity (m / s); x m Let m be the velocity of the m-th node in the cross section (m / s), and n be the total number of nodes in the cross section.

[0069] The velocity distribution and resistance of the mass transfer components under different height-to-diameter ratios were investigated using a small-scale flow equalization tower model arranged in an equilateral triangle, as shown in Table 2 below: Table 2. Velocity distribution and mass transfer component resistance of BFI and flow equalization tower structures under different height-to-diameter ratios.

[0070] As attached Figure 4 As shown, the changes in resistance and velocity distribution are very small, and the change in resistance of the mass transfer component matches the change in pipe resistance. This indicates that when the height-to-diameter ratio decreases from 12.5 to 7.5, the effect of pipe length on the resistance of the mass transfer component is only reflected in the pipe resistance. Using the average flow velocity in each pipe to characterize the flow rate, as the height-to-diameter ratio decreases from 12.5 to 7.5, the pipe resistance decreases from 35 Pa to 21 Pa, and the flow distribution deviation in the pipe increases from 15.2% to 18.9%. Furthermore, as the height-to-diameter ratio continues to decrease, the rate of increase increases, indicating a weakening of the flow equalization effect.

[0071] Based on the desulfurization tower of a 330MW unit, a densely perforated scheme with an equilateral triangular arrangement was adopted to simulate the flow within the equalization tower, and the simulation was compared with that of a traditional BFI tower. The perforation diameter is 240mm, the perforation spacing is 360mm, the tube length is 1.8m, and the perforation rate is approximately 38% (908 perforations). The flue gas enters the equalization tower at the same position as the liquid level in the original desulfurization tower, as shown in the attached diagram. Figure 1 As shown, the spray layer 5 has four layers. Monitoring surfaces (1-4) are set 1m below the four spray layers 5 to examine the distribution of flue gas and droplet particles in the tower. The outlet of the inlet flue gas heat exchanger and the monitoring surface 1 of the bottom spray layer 5 are used as pressure monitoring surfaces to examine the resistance of the mass transfer components.

[0072] The velocity distribution cloud maps of each monitoring surface inside the tower for both mass transfer components are shown below when there is no spraying. Figure 5 As shown, (a) is a BFI tower and (b) is a flow equalization tower. From left to right, they are monitoring surface 1, monitoring surface 2, monitoring surface 3 and monitoring surface 4. The flue gas uniformity inside the flow equalization tower is much better than that of the traditional BFI tower. Its velocity distribution inside the tower is mainly affected by the spray pipe, while a large area of ​​low velocity zone can be clearly observed in the traditional BFI tower. The resistance characteristics of both are also consistent with those of the small tower. The flow equalization tower reduces the pressure loss by 69 Pa.

[0073] The smoke trails inside the two towers are shown in the attached image. Figure 6 and 7 As shown, attached Figure 6 The left side of the middle section shows the BFI tower, and the right side shows the flow equalization tower equipped with a heat exchanger. Figure 7 The middle BFI tower has no heat exchanger. The flue gas traces in the spray zone of the flow equalization tower are evenly distributed. The BFI tower forms a large area of ​​reflux on the inlet side, consistent with the velocity distribution. However, compared with the small tower, no obvious swirl is observed. There are two main reasons for this: (1) The presence of the front-end flue gas heat exchanger greatly increases the uniformity of the flue gas entering the tower. After the inlet flue gas heat exchanger is removed, the average flow velocity in the tower increases from 4.4 m / s to 6 m / s, and the swirling flow reappears, but the intensity is much lower than that of the small tower.

[0074] (2) The two towers are geometrically similar and have the same internal flow velocity. The increase in characteristic scale leads to a corresponding increase in the Reynolds number of the larger tower. The two tower types do not satisfy strict dynamic similarity. For swirling flow in a confined space, there is a critical upper limit of the Reynolds number: the Reynolds number of the small test tower is relatively low, the swirling flow can be maintained stably, and the turbulent dissipation is insufficient to destroy the rotating structure; the Reynolds number of the industrial tower is more than 50 times that of the small tower, the swirling flow is broken by turbulent dissipation and is difficult to rebuild. Macroscopically, the small tower has a clear global swirling flow while the large tower has no obvious overall swirling flow. This difference mainly stems from the flow regime migration caused by scale expansion.

[0075] The velocity distribution and resistance of mass transfer components below each spray layer 5 of the BFI tower / flow equalization tower are shown in Table 3 below. Table 3. Velocity distribution and resistance of mass transfer components below each spray layer in the BFI tower / flow equalization tower.

[0076] When spraying is in effect, the flow rate inside tower 1 is approximately 14 L / m³. 3 Spraying is carried out at a certain density, with the lower three layers having a spray volume of 5000m³. 3 / h, mainly using bidirectional hollow cone nozzles, with a top-level spray volume of 9300m³ / h. 3 / h, mainly using unidirectional hollow cone nozzles, while the tower walls are all unidirectional solid cone nozzles. The velocity distribution on each monitoring surface inside the tower under the two mass transfer components is shown in the attached figure. Figure 7 As shown, (a) is a BFI tower and (b) is a flow equalization tower. From left to right, they are monitoring surface 1, monitoring surface 2, monitoring surface 3 and monitoring surface 4. The droplet distribution of the two tower types tends to be consistent. In monitoring surface 4, the droplet particles are obviously distributed in a network shape due to the large amount of spraying at the top layer.

[0077] After the spray system was activated, the spray pipe features disappeared from the velocity cloud map of the monitoring surface inside tower 1, and the velocity distribution uniformity was dominated by the spray uniformity. The velocity distributions of the two towers became consistent both morphologically and numerically, as shown in the attached figure. Figure 7 Appendix Figure 8 Appendix Figure 9 As shown in Table 3, Appendix Figure 9 To visualize the flue gas traces within the two towers after spraying, the left tower is the BFI tower, and the right tower is the flow equalization tower. The high-speed region and low-droplet concentration region in monitoring surface 4 correspond, and due to the large spray volume from the solid nozzles on the top tower wall, a distinct low-speed zone appears on both tower walls. Therefore, under actual spraying conditions, the uniformity of flue gas distribution in the two towers is not significantly different. However, the flow equalization tower directly reduces the tower height by 15m compared to the traditional BFI tower, thus lowering the system investment cost.

[0078] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A novel desulfurization reaction tower, characterized in that: The system includes a tower body, a flue gas inlet, a flue gas outlet, a slurry pool, and a spray layer. Inside the tower body, there is a flow equalization tube mass transfer component arranged above the liquid surface of the slurry pool. The flow equalization tube mass transfer component includes a porous base plate and multiple vertically arranged flow equalization tubes. Several through holes are opened on the porous base plate, and a flow equalization tube is fixed upward to each through hole. The flow equalization tube is a hollow straight tube with both ends open. The flue gas outlet is located at the top of the tower body, and the flue gas inlet is located at the elevation of the liquid surface of the slurry pool. The flue gas enters the tower body through the flue gas inlet and flows upward into each flow equalization tube. After flowing out from the upper end of the flow equalization tube, it enters the spray layer.

2. The novel flow equalization desulfurization reaction tower according to claim 1, characterized in that: Based on computational fluid dynamics, a Realizable k-ε turbulence model combined with a two-way coupled discrete phase model is used to predict the gas-liquid two-phase flow field inside the tower. The continuous phase of the flue gas inside the tower is described in the Euler coordinate system. The flue gas adopts the assumption of a steady-state incompressible ideal gas. The continuity conservation equation, momentum conservation equation, energy conservation equation and component transport equation are solved for the flue gas.

3. The novel flow equalization desulfurization reaction tower according to claim 2, characterized in that: After the slurry in the slurry tank is atomized, the resulting droplet particles undergo heat exchange and movement under the influence of flue gas. The equations of motion for the droplet particles are solved after force analysis. By introducing a random walk model and a droplet evaporation model, the equations of motion for the droplet particles are: In the formula: t Let the time be s; u p The velocity of the droplet particles is m / s; u The flue gas velocity is m / s; C D is the drag force coefficient (dimensionless); ρ The density of the flue gas is kg / m³; ρ p The density of the droplet particles is kg / m³; d p Where m is the diameter of the droplet; g The acceleration due to gravity is m / s².

4. The novel flow equalization desulfurization reaction tower according to claim 3, characterized in that: The flue gas inside the tower is pressure-velocity coupled using the SIMPLEC algorithm, and the relative standard deviation of cross-sectional velocity (RSD) is used as the evaluation index of the flow field uniformity of the flue gas inside the tower. The formula for calculating the relative standard deviation (RSD) of speed is: In the formula: X is the standard deviation of velocity (m / s); X0 is the cross-sectional average velocity (m / s); x m Let m be the velocity of the m-th node in the cross section (m / s), and n be the total number of nodes in the cross section.

5. A novel desulfurization reaction tower according to claim 1, characterized in that: The through holes are arranged in an equilateral triangle, with a diameter ranging from 10mm to 240mm, and the spacing between adjacent holes is 1.5 times their own diameter.

6. A novel desulfurization reaction tower according to claim 5, characterized in that: The height-to-diameter ratio of the flow equalization tube is 7.5 to 12.

5. The lower end of the flow equalization tube is aligned and connected with the through hole of the porous substrate, and the upper end of the flow equalization tube is a free outlet. The tube wall is closed and has no lateral openings.

7. The novel flow equalization desulfurization reaction tower according to claim 6, characterized in that: The spray layer includes bidirectional hollow cone nozzles and eccentric solid cone nozzles set on the inner wall of the tower. The slurry in the slurry pool is pumped to the spray layer and sprayed downwards, and comes into countercurrent contact with the flue gas flowing out from the upper end of the flow equalization pipe to complete the desulfurization reaction.

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