CN114093431B - Operation performance evaluation method of limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis - Google Patents
Operation performance evaluation method of limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis Download PDFInfo
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- 238000012546 transfer Methods 0.000 title claims abstract description 107
- 238000006477 desulfuration reaction Methods 0.000 title claims abstract description 91
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Abstract
The invention discloses an operation performance evaluation method of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis, which comprises the steps of constructing a relation between a SO 2 gas-phase mass transfer rate and a gas-phase SO 2 partial pressure, calculating an effective mass transfer specific surface area of a gas-liquid interface, calculating a spray droplet terminal sedimentation rate of a laminar flow area, a sliding area, a transition area and a turbulent flow area, obtaining a desulfurization slurry spray atomization particle size by adopting an on-line laser measurement method, obtaining a Sotel average diameter d SMD, calculating a SO 2 gas-phase mass transfer coefficient K g,i, and realizing on-line evaluation of the operation performance of the limestone-gypsum wet desulfurization system according to real-time analysis of each spray layer SO 2 gas-phase mass transfer coefficient K g,i and Sotel average diameter d SMD of the limestone-gypsum wet desulfurization system. The assessment method has universal applicability and can accurately assess the operation performance of the limestone-gypsum wet desulfurization system of the coal-fired power generating unit on line.
Description
Technical Field
The invention relates to the technical field of limestone-gypsum wet desulfurization of coal-fired generator sets, in particular to a method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis.
Background
The performance evaluation of the existing limestone-gypsum wet desulfurization system can only be carried out through an offline performance test, the offline detection result can only represent the performance of the desulfurization system in a test period, the general applicability is lacking, meanwhile, the time hysteresis exists in the diagnosis process of abnormal operation of the desulfurization system, and the requirements of on-line fault diagnosis and rapid defect elimination on-line lean management cannot be met. Therefore, in order to accurately evaluate the performance of the limestone-gypsum wet desulfurization system of the coal-fired power generation unit on line, the evaluation method of the limestone-gypsum wet desulfurization system needs to be further optimized, and the online evaluation method of the limestone-gypsum wet desulfurization system with general applicability is fully constructed, so that the operation and maintenance performances of environmental protection facilities of the coal-fired power generation unit are effectively improved.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art, and provide the operation performance evaluation method of the limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis, which has universal applicability, can effectively improve the operation and maintenance performance of environmental protection facilities of the coal-fired power generator unit, and can accurately evaluate the operation performance of the limestone-gypsum wet desulfurization system of the coal-fired power generator unit on line.
In order to solve the technical problems, the invention adopts the following technical scheme.
A limestone-gypsum wet desulphurization system operation performance evaluation method based on gas-liquid mass transfer analysis comprises the following steps: the method comprises the steps of constructing SO 2 gas phase mass transfer rate (the relation between N SO2)g and partial pressure P SO2,g of gas phase SO 2), calculating effective mass transfer specific surface area of a gas-liquid interface, calculating spray drop terminal sedimentation rates of a laminar flow area, a sliding area, a transition area and a turbulent flow area, obtaining spray atomization particle size of desulfurization slurry by adopting an on-line laser measurement method, obtaining the average diameter d SMD of the SOT according to the principle of keeping the total surface area of original liquid mist unchanged, calculating SO 2 gas phase mass transfer coefficient K g,i according to the result of the steps, and realizing on-line evaluation of the operation performance of a limestone-gypsum wet desulfurization system according to real-time analysis of each spray layer SO 2 gas phase mass transfer coefficient K g,i and the average diameter d SMD of the SOT of the limestone-gypsum wet desulfurization system.
In the above method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis, preferably, the process of constructing the gas-phase mass transfer rate of SO 2 (the relationship between N SO2)g and the partial pressure P SO2,g of gas-phase SO 2 is as follows: firstly, constructing the relationship between the partial pressure of gas-phase SO 2 and the pH value and concentration of liquid-phase SO 3 2- according to the liquid-phase dissociation equilibrium principle, then calculating the partial pressure P SO2,g of gas-phase SO 2 according to the concentration of SO 2 in the gas-phase, and then calculating the gas-phase mass transfer rate of SO 2 (N SO2)g:
KW＝[H+][OH-],pH＝-log[H+]
Wherein (N SO2)g) is a gas phase mass transfer rate, kmol/(m 2·s),PSO2,g) is a gas phase SO 2 partial pressure, pa, P SO2,aq is a liquid phase SO 2 partial pressure, pa, C SO2 is a gas phase SO 2 partial pressure, mg/m 3,Kg is a gas phase mass transfer coefficient, kmol/(Pa.m 2.s).
According to the limestone-gypsum wet desulfurization system operation performance evaluation method based on gas-liquid mass transfer analysis, preferably, the process of calculating the effective mass transfer specific surface area in each layer of absorption area of the desulfurization system is as follows:
Wherein V g is the flue gas tower speed, m/s, Q g is the flue gas flow, m 3/h, phi is the diameter of the desulfurizing tower, m, tau g,i is the effective residence time of flue gas in the ith spray layer, s, h i is the effective absorption section height of the ith spray layer of the desulfurizing tower, m, V i is the effective volume of the ith spray layer, m 3,RStr,i is the effective mass transfer specific surface area of the gas-liquid interface of the ith spray layer, m 2/m3,Str,i is the effective gas-liquid mass transfer area of the effective absorption section of the ith spray layer, and m 2.
According to the limestone-gypsum wet desulfurization system operation performance evaluation method based on gas-liquid mass transfer analysis, preferably, the process of calculating the sedimentation rate of the spray droplet terminal of the laminar flow zone, the sliding zone, the transition zone and the turbulent flow zone is as follows: the drop terminal settling rate in the laminar flow zone is:
Wherein: u s is the gravity settling end speed of the liquid drop, the unit m/s, dp is the diameter of the liquid drop, the unit m, ρ p is the density of the liquid drop, the unit kg/m 3, g is the gravity acceleration, the unit m/s 2, mu is the air viscosity, and the unit Pa.s;
the drop terminal settling rate of the sliding zone is:
Wherein: u s is the gravity settling end velocity of the liquid drop, the unit m/s, d p is the liquid drop diameter, the unit m, ρ p is the liquid drop density, the unit kg/m 3, g is the gravity acceleration, the unit m/s 2, μ is the air viscosity, the unit Pa.s, C is the Canning Han correction coefficient, dimensionless, kn is the Knudsen number, dimensionless, λ is the gas molecular mean free path, the unit m, ρ is the air density, the unit kg/m 3, The unit of the arithmetic average speed of gas molecules is M/s, R is a general gas constant, 8.314 J.mol -1·K-1, T is gas temperature, unit K and M is gas molar mass, and unit kg/mol;
the drop terminal settling rate in the transition zone is:
Wherein u s is the gravity settling end speed of the liquid drop, the unit m/s, d p is the liquid drop diameter, the unit m, ρ p is the liquid drop density, the unit kg/m 3, g is the gravity acceleration, the unit m/s 2, μ is the air viscosity, the unit Pa.s, ρ is the air density, and the unit kg/m 3;
the drop terminal settling rate in the turbulent zone is:
Where u s is the end speed of gravity settling of the droplet, m/s, d p is the droplet diameter, m, ρ p is the droplet density, kg/m 3, g is the gravitational acceleration, m/s 2, ρ is the air density, kg/m 3.
According to the limestone-gypsum wet desulfurization system operation performance evaluation method based on gas-liquid mass transfer analysis, preferably, before the spray droplet terminal sedimentation rates of a laminar flow zone, a sliding zone, a transition zone and a turbulent flow zone are calculated, the droplet motion state is judged according to the Reynolds number:
Wherein Re p is the Reynolds number, d p is the droplet diameter, m is the air density, p is the air density, kg/m 3 is the droplet movement speed, m/s is the air viscosity, mu is the air viscosity, pa.s is the dry air viscosity at 293K and 101325Pa is 1.81× - 5 Pa.s, and the dry air density is 1.205kg/m 3;
Laminar flow region: re p is less than or equal to 1, sliding region: re p is less than or equal to 1, and the transition area is: 1 < Re p < 500, turbulence zone: re p＜2×105 is less than 500.
In the above method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis, preferably, the average diameter of the cable too is:
Wherein D j represents a particle size of the jth size in μm; n j represents the number of droplets of particle size D j in units of one.
The operation performance evaluation method of the limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis preferably comprises the following process of calculating the gas-phase mass transfer coefficient K g,i of SO 2:
Wherein Q L,i is the flow rate of the spraying slurry of the ith layer, the unit L/min, tau d,i is the effective residence time of the liquid drop on the ith spraying layer, the unit S, u s,i is the average gravity sedimentation end speed of the liquid drop of the ith layer, the unit m/S, L i is the effective liquid holdup of the ith spraying layer, the unit m 3,hi is the effective absorption section height of the ith spraying layer of the desulfurizing tower, the unit m, d SMD,i is the Sotel average diameter of the ith spraying layer, the unit mu m, S tr,i is the effective absorption section gas-liquid mass transfer area of the ith spraying layer, and the unit m 2;
Wherein, (N SO2)g,i is the gas phase mass transfer rate of the i-th spraying layer, kmol/(m 2·s),Qg) is the flue gas flow, m 3/h,CSO2,i is the concentration of an inlet SO 2 of the i-th spraying layer, mg/m 3,CSO2,i+1 is the concentration of an inlet SO 2 of the (i+1) -th spraying layer, mg/m 3,Str,i is the gas-liquid mass transfer area of the effective absorption section of the i-th spraying layer, m 2,PSO2,g,i is the partial pressure of the gas phase SO 2 of the i-th spraying layer, pa, P SO2,aq,i is the partial pressure of the liquid phase SO 2 of the i-th spraying layer, pa, K g,i is the gas phase mass transfer coefficient of the i-th spraying layer, and kmol/(Pa.m 2.s).
According to the limestone-gypsum wet desulfurization system operation performance evaluation method based on gas-liquid mass transfer analysis, preferably, the limestone-gypsum wet desulfurization system operation performance real-time analysis mode is as follows:
When the load of the coal-fired generator set is stable, a spraying pump of a limestone-gypsum wet desulfurization system keeps normal mode operation, the pH value of slurry of an absorption tower is in a normal range of 5.2-5.8, the concentration of SO 2 at an outlet of the desulfurization system shows an ascending trend, and a system analyzes that the gas-phase mass transfer coefficient K g,i of the ith layer SO 2 is reduced, and meanwhile, the ascending of the ith layer d SMD is detected, SO that the system analyzes that the ith spraying layer has nozzle falling and pipeline breakage and leakage abnormality, the pressure of the ith layer nozzle is obviously reduced, the atomization effect is poor, and shutdown maintenance is required to be carried out;
When the load of the coal-fired generator set is stable, a spray pump of a limestone-gypsum wet desulfurization system maintains the normal mode operation, the slurry supply flow of limestone slurry is stable, the system detects that the pH value of the slurry of an absorption tower is in a descending trend and can not be effectively stabilized within a normal range of 5.2-5.8, and meanwhile, each spray layer d SMD is in a normal range, and the gas phase mass transfer coefficient K g,i of each spray layer SO 2 is lower than a long-period experience value range, SO that the system analyzes the slurry poisoning of the absorption tower, the dissolution of limestone in a slurry liquid phase is influenced, the slurry replacement is needed to be carried out in time, and the continuous deterioration of the slurry quality is avoided;
When the load of the coal-fired generator set is stable, a spray pump of the limestone-gypsum wet desulfurization system maintains the normal mode operation, the slurry supply flow of limestone slurry is stable, the system detects that the pH value of the slurry of the absorption tower is in a normal range of 5.2-5.8, and meanwhile, each spray layer d SMD is in the normal range, and the gas phase mass transfer coefficient K g,i of each spray layer SO 2 is lower than the long-period experience value range, SO that the system analyzes that the slurry of the absorption tower has liquid phase mass transfer resistance, gas phase SO 2 mass transfer is prevented from entering the liquid phase slurry, and the liquid phase mass transfer of SO 2 is enhanced by adding a desulfurization synergistic mode.
The above method for evaluating the operation performance of the limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis is preferably suitable for evaluating the purification performance of the limestone-gypsum wet desulfurization system SO 2 with multiple spray layers.
The operation performance evaluation method of the limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis is preferably suitable for a desulfurization absorption tower with a multi-spray-layer empty tower structure, and is not suitable for an absorption tower type with a tray and grid reinforced mass transfer structure in the absorption tower.
The operation performance evaluation method of the limestone-gypsum wet desulfurization system based on gas-liquid mass transfer comprises the following steps: ① The on-line evaluation method of SO 2 purification performance of the spraying layer of the desulfurization system based on gas-liquid mass transfer analysis comprises the following steps: the method is used for evaluating the real-time online evaluation of the SO 2 purification performance in the limestone-gypsum wet desulfurization system; ② The particle size distribution characteristics of spray slurry of the desulfurization system are uniformly characterized as d SMD (Sotel average diameter), the terminal sedimentation rate of the liquid drops is analyzed in a partitioning way according to the movement state of the spray liquid drops in the desulfurization absorption tower, and the evaluation method of the average sedimentation rate of the spray slurry liquid drops based on d SMD is used for evaluating the sedimentation migration characteristics of the spray slurry liquid drops in an SO 2 absorption area in the limestone-gypsum wet desulfurization system.
Compared with the prior art, the invention has the advantages that:
According to the limestone-gypsum wet desulfurization system operation performance evaluation method based on gas-liquid mass transfer analysis (namely, the SO 2 purification performance online evaluation method), firstly, according to the liquid phase dissociation balance of a desulfurization system, the relation between the partial pressure of gas phase SO 2, the pH value of the liquid phase and the concentration of liquid phase SO 3 2- is constructed, meanwhile, the effective mass transfer specific surface area in each layer of absorption area of the desulfurization system is analyzed, the spray atomization liquid drop Sotel average diameter d SMD is monitored based on an online laser measurement method, and the spray liquid drop movement state and the terminal sedimentation rate are analyzed on the basis. Based on the analysis content and the gas-liquid mass transfer principle, the gas-liquid mass transfer coefficient K g,i of each spraying layer region SO 2 is calculated, and the desulfurization performance index of the ith spraying layer region is represented, SO that the on-line evaluation of the desulfurization performance of the limestone-gypsum desulfurization system is realized.
The performance evaluation of the existing limestone-gypsum wet desulfurization system is generally carried out by referring to the test Specification for the performance acceptance test of limestone-gypsum wet flue gas desulfurization devices (DL/T998-2016), the method is an off-line test mode (test period is 3-6 days), hysteresis exists in test results, the lean management requirement of the real-time evaluation of the running state of the current environmental protection facilities cannot be met, the method adopts an on-line measurement means, and the on-line evaluation of the running state and the on-line diagnosis of the running fault of the limestone-gypsum wet desulfurization system can be realized by analyzing the variation trend of the mass transfer performance of SO 2 in a desulfurization tower.
Drawings
Fig. 1 is a schematic diagram of an online evaluation flow of the operation performance evaluation method of the limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis in embodiment 1 of the present invention.
FIG. 2 is a schematic diagram showing the equilibrium of the liquid phase H 2SO3---HSO3 ----SO3 2- in example 1 of the present invention.
Fig. 3 is a schematic diagram of on-line evaluation of SO 2 purification performance based on gas-liquid mass transfer analysis in example 1 of the present invention.
Detailed Description
The invention is further described below in connection with the drawings and the specific preferred embodiments, but the scope of protection of the invention is not limited thereby. The materials and instruments used in the examples below are all commercially available.
Example 1:
The invention relates to a limestone-gypsum wet desulphurization system operation performance evaluation method based on gas-liquid mass transfer analysis, which is shown in figure 1 and comprises the following steps:
s1, constructing SO 2 gas phase mass transfer rate Partial pressure with gas phase SO 2 ]Relationship between:
firstly, according to the liquid phase dissociation equilibrium principle, the relation between the partial pressure of the gas phase SO 2 and the pH value of the liquid phase SO 3 2- concentration is constructed. As shown in fig. 2, which is a schematic diagram of the equilibrium of the liquid phase H 2SO3---HSO3 ----SO3 2- in this embodiment, a specific workflow is as follows:
In the gas-liquid mass transfer process of SO 2, the main ion balance equation and the reactive ion balance equation are shown in formulas (1) - (4).
KW＝[H+][OH-],pH＝-log[H+] (4)
The partial pressure of the SO 2 liquid phase P SO2,aq (kPa) can be obtained according to the above formula:
Combining the SO 2 concentration in the gas phase, the partial pressure P SO2,g (kPa) of SO 2 in the gas phase can be obtained:
Wherein C SO2 is the concentration of gas-phase SO 2 in mg/m 3; 22.4L/mol is the ideal gas mole volume; 64g/mol is SO 2 molecular mass; 101.325kPa is 1 normal atmospheric pressure value at normal temperature and pressure.
Then in the desulfurization spray system, the mass transfer rate of SO 2 (i.e., the absorption rate, kmol/(m 2·s))NSO2,g) is:
Wherein (N SO2)g) is the gas phase mass transfer rate, kmol/(m 2·s),PSO2,g) is the partial pressure of gas phase SO 2, pa, P SO2,aq is the partial pressure of liquid phase SO 2, pa, K g is the gas phase mass transfer coefficient, kmol/(Pa.m 2.s).
S2, analyzing the specific surface area of effective mass transfer in each layer of absorption area:
For the i-th spray layer, in the effective absorption area,
In the formula, h i is the height of the effective absorption section of the ith spray layer of the desulfurizing tower, m; phi-diameter of desulfurizing tower, m; q g - -flue gas flow, m 3/h;τg,i - -effective residence time of flue gas in the ith spray layer, s; v g - -flue gas tower velocity, m/s.
In the formula, S tr,i -i spraying layer effective absorption section gas-liquid mass transfer area, m 2;RStri,i -i spraying layer gas-liquid interface effective mass transfer specific surface area, m 2/m3;Vi -i spraying layer effective volume, m 3.
S3, the terminal sedimentation rate of the liquid drops is a decisive parameter for determining the residence time and the liquid holdup of the liquid phases in a spraying area, so that the important analysis of the terminal sedimentation rate of the liquid drops is particularly necessary, and the terminal sedimentation rate level of the liquid drops is distinguished according to the movement state of the liquid drops. First, the droplet motion state is analyzed according to the Reynolds number:
Wherein: re p - -Reynolds number; d p - -droplet diameter, m; ρ - -air density, kg/m 3; u- -droplet velocity, m/s; mu- - -air viscosity, pa.s, dry air viscosity at 293K and 101325Pa, dry air density 1.81X 10 -5 Pa.s, dry air density 1.205kg/m 3.
Laminar flow region: re p is less than or equal to 1.
Sliding region: re p is less than or equal to 1, the droplet size is very small, and the average free path of the droplet is almost the same as that of gas molecules.
Transition zone: re p is more than 1 and less than 500.
Turbulence zone: re p＜2×105 is less than 500.
According to different partition motion states of the liquid drops, analyzing the sedimentation velocity of the liquid drops:
1. Laminar flow region
Wherein: u s - -the end speed of gravity settling of the droplet, m/s; dp- - -droplet diameter, m; ρ p —drop density, kg/m 3; g-gravity acceleration, m/s 2; mu- - - -air viscosity, pa.s.
The calculation accuracy of the formula (13) is within + -10% for the droplets having a particle diameter of 1.5-75 μm and a unit density (ρ p＝1000kg/m3).
2. Sliding region
Wherein: u s - -the end speed of gravity settling of the droplet, m/s; d p - -droplet diameter, m; ρ p —drop density, kg/m 3; g-gravity acceleration, m/s 2; mu-air viscosity, pa.s; c- - -Canning Han correction coefficient; kn- - -Knudsen number; lambda- - -gas molecular mean free path, m; ρ - -air density, kg/m 3; -arithmetic mean velocity of gas molecules, m/s; r-general gas constant 8.314 J.mol -1·K-1; t-gas temperature, K; m- -molar mass of gas, kg/mol.
3. Transition zone
Wherein: u s - -the end speed of gravity settling of the droplet, m/s; d p - -droplet diameter, m; ρ p —drop density, kg/m 3; g-gravity acceleration, m/s 2; mu-air viscosity, pa.s; ρ - -air density, kg/m 3.
4. Turbulence zone
Wherein: u s - -the end speed of gravity settling of the droplet, m/s; d p - -droplet diameter, m; ρ p —drop density, kg/m 3; g-gravity acceleration, m/s 2; ρ - -air density, kg/m 3.
S4, analyzing the spray atomization particle size characteristics of the desulfurization slurry by adopting an on-line laser measurement method, and providing basic technical parameters for the derivation of mass transfer specific surface area of a subsequent spray atomization layer. The average diameter most commonly used at present is the cable average diameter d SMD. The average diameter, the average diameter of the Sotel (Sauter MEAN DIAMETER, abbreviated as SMD), is determined on the principle of keeping the total surface area of the original mist constant and reflects the ratio of the volume occupied by the liquid to the total surface area of the liquid.
Volume-surface area average diameter:
Wherein D j represents a particle size of the jth size, μm; n j represents the number of droplets having a particle size of D j.
S5, as shown in FIG. 3, is a schematic diagram for on-line evaluation of SO 2 purification performance based on gas-liquid mass transfer analysis. Based on the gas-liquid mass transfer principle, calculating a SO 2 gas-liquid mass transfer coefficient K g,i, and representing the desulfurization performance index of the i-th layer spraying region:
Wherein, the flow rate of the spraying slurry of the (i) th layer Q L,i (0 if the spraying of the layer is not started) L/min; τ d,i - -effective residence time of the droplet in the ith spray layer, s; u s,i - -average gravity settling terminal velocity of layer i droplets, m/s; l i - -effective liquid holdup of the ith spray layer, m 3;
The gas phase mass transfer rate of the i-th spray layer SO 2 is:
In the formula, (N SO2)g,i is the gas phase mass transfer rate of the i-th spraying layer, the unit kmol/(m 2·s);Qg) is the flue gas flow, the unit m 3/h;CSO2,i is the SO 2 concentration of the i-th spraying layer inlet, the unit mg/m 3;CSO2,i+1 is the SO 2 concentration of the i+1th spraying layer inlet, the unit mg/m 3;Str,i is the gas-liquid mass transfer area of the effective absorption section of the i-th spraying layer, and the unit m 2.
The i-th spray layer SO 2 gas phase mass transfer coefficient K g,i(kmol/(m2.s.kPa)) is:
wherein P SO2,g,i is the partial pressure of the gas phase SO 2 of the i-th spraying layer, and the unit Pa; p SO2,aq,i is the partial pressure of the liquid phase SO 2 of the i-th spraying layer, and the unit Pa; k g,i is the gas phase mass transfer coefficient of the i-th spraying layer, and the unit kmol/(Pa.m 2.s).
S5, according to real-time analysis of the gas phase mass transfer coefficient K g,i of each spray layer SO 2 of the limestone-gypsum desulfurization system, online evaluation of desulfurization performance of the limestone-gypsum desulfurization system can be realized, and a core reference basis is provided for online diagnosis of operation faults of a follow-up desulfurization system. Based on the long-period monitoring of the core parameters of the desulfurization system, the variation trend of various core parameters under different stable working conditions can be counted. When the core parameters are obviously deviated, the abnormity of the desulfurization system can be evaluated on line, and the on-line diagnosis of the operation fault of the desulfurization system is realized. The desulfurization system operation performance evaluation examples are as follows:
1. When the load of the coal-fired generator set is stable, the spray pump of the limestone-gypsum wet desulfurization system keeps normal mode operation, the pH value of slurry in the absorption tower is in the normal range of 5.2-5.8, and the concentration of SO 2 at the outlet of the desulfurization system shows an ascending trend. The system analyzes that the gas phase mass transfer coefficient of the ith layer SO 2 is reduced, and meanwhile, the rise of the ith layer d SMD (the increase reaches more than 30%) is detected, SO that the system analyzes that the ith layer spraying layer is abnormal in that the nozzles fall off, the pipelines are damaged and leaked, and the like, SO that the pressure of the ith layer of nozzles is obviously reduced, the atomization effect is poor, and shutdown maintenance is required to be carried out in time.
2. When the load of the coal-fired generator set is stable, a spray pump of the limestone-gypsum wet desulfurization system maintains the normal mode operation, the slurry supply flow of limestone slurry is stable, the system detects that the pH value of the slurry in the absorption tower is in a descending trend and can not be effectively stabilized within a normal range of 5.2-5.8, and meanwhile, each spray layer d SMD is in a normal range, and the gas phase mass transfer coefficient K g,i of each spray layer SO 2 is lower than a long-period experience value range, SO that the system analyzes the slurry poisoning of the absorption tower, the dissolution of limestone in the slurry liquid phase is influenced, the slurry replacement is needed to be carried out in time, and the continuous deterioration of the slurry quality is avoided.
3. When the load of the coal-fired generator set is stable, a spray pump of the limestone-gypsum wet desulfurization system keeps normal mode operation, the slurry supply flow of limestone slurry is stable, the pH value of slurry of an absorption tower is in a normal range of 5.2-5.8, meanwhile, each spray layer d SMD is in a normal range, and the gas phase mass transfer coefficient K g,i of each spray layer SO 2 is lower than a long-period experience value range, SO that the system is analyzed to form liquid phase mass transfer resistance of the slurry of the absorption tower, gas phase SO 2 mass transfer is prevented from entering the liquid phase slurry, and the liquid phase mass transfer of SO 2 is enhanced by adding a desulfurization synergist and other synergistic modes.
The above description is only of the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. While the invention has been described in terms of preferred embodiments, it is not intended to be limiting. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention or equivalent embodiments using the method and technical solution disclosed above without departing from the spirit and technical solution of the present invention. Therefore, any simple modification, equivalent substitution, equivalent variation and modification of the above embodiments according to the technical substance of the present invention, which do not depart from the technical solution of the present invention, still fall within the scope of the technical solution of the present invention.
Claims (8)
1. The operation performance evaluation method of the limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis is characterized by comprising the following steps of: constructing SO 2 gas phase mass transfer rate (the relation between N SO2)g and gas phase SO 2 partial pressure P SO2,g), calculating effective mass transfer specific surface area of a gas-liquid interface, calculating spray drop terminal sedimentation rates of a laminar flow area, a sliding area, a transition area and a turbulent flow area, adopting an on-line laser measurement method to obtain spray atomization particle size of desulfurization slurry, obtaining a Sotel average diameter d SMD according to the principle of keeping the total surface area of the original liquid mist unchanged, calculating SO 2 gas phase mass transfer coefficient K g,i according to the result of the steps, and realizing on-line evaluation of the operation performance of a limestone-gypsum wet desulfurization system according to real-time analysis of each spray layer SO 2 gas phase mass transfer coefficient K g,i and Sotel average diameter d SMD of the limestone-gypsum wet desulfurization system;
The process of constructing the SO 2 gas phase mass transfer rate (the relationship between N SO2)g and the partial pressure P SO2,g of the gas phase SO 2 is as follows: firstly, according to the liquid phase dissociation equilibrium principle, constructing the relationship between the partial pressure of the gas phase SO 2 and the pH value and concentration of the liquid phase SO 3 2-, then according to the concentration of the SO 2 in the gas phase, calculating the partial pressure P SO2,g of the gas phase SO 2, and then calculating the gas phase mass transfer rate of the SO 2 (N SO2)g:
KW＝[H+][OH-],pH＝-log[H+]
Wherein (N SO2)g) is the gas phase mass transfer rate, kmol/(m 2·s),PSO2,g) is the gas phase SO 2 partial pressure, pa, P SO2,aq is the liquid phase SO 2 partial pressure, pa, C SO2 is the gas phase SO 2 partial pressure, mg/m 3,Kg is the gas phase mass transfer coefficient, kmol/(Pa.m 2.s);
the real-time analysis mode of the operation performance of the limestone-gypsum wet desulfurization system is as follows:
When the load of the coal-fired generator set is stable, a spraying pump of a limestone-gypsum wet desulfurization system keeps normal mode operation, the pH value of slurry of an absorption tower is in a normal range of 5.2-5.8, the concentration of SO 2 at an outlet of the desulfurization system shows an ascending trend, and a system analyzes that the gas-phase mass transfer coefficient K g,i of the ith layer SO 2 is reduced, and meanwhile, the ascending of the ith layer d SMD is detected, SO that the system analyzes that the ith spraying layer has nozzle falling and pipeline breakage and leakage abnormality, the pressure of the ith layer nozzle is obviously reduced, the atomization effect is poor, and shutdown maintenance is required to be carried out;
When the load of the coal-fired generator set is stable, a spray pump of a limestone-gypsum wet desulfurization system maintains the normal mode operation, the slurry supply flow of limestone slurry is stable, the system detects that the pH value of the slurry of an absorption tower is in a descending trend and can not be effectively stabilized within a normal range of 5.2-5.8, and meanwhile, each spray layer d SMD is in a normal range, and the gas phase mass transfer coefficient K g,i of each spray layer SO 2 is lower than a long-period experience value range, SO that the system analyzes the slurry poisoning of the absorption tower, the dissolution of limestone in a slurry liquid phase is influenced, the slurry replacement is needed to be carried out in time, and the continuous deterioration of the slurry quality is avoided;
When the load of the coal-fired generator set is stable, a spray pump of the limestone-gypsum wet desulfurization system maintains the normal mode operation, the slurry supply flow of limestone slurry is stable, the system detects that the pH value of the slurry of the absorption tower is in a normal range of 5.2-5.8, and meanwhile, each spray layer d SMD is in the normal range, and the gas phase mass transfer coefficient K g,i of each spray layer SO 2 is lower than the long-period experience value range, SO that the system analyzes that the slurry of the absorption tower has liquid phase mass transfer resistance, gas phase SO 2 mass transfer is prevented from entering the liquid phase slurry, and the liquid phase mass transfer of SO 2 is enhanced by adding a desulfurization synergistic mode.
2. The method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis according to claim 1, wherein the process for calculating the effective mass transfer specific surface area in each layer of absorption area of the desulfurization system is as follows:
Wherein V g is the flue gas tower speed, m/s, Q g is the flue gas flow, m 3/h, phi is the diameter of the desulfurizing tower, m, tau g,i is the effective residence time of flue gas in the ith spray layer, s, h i is the effective absorption section height of the ith spray layer of the desulfurizing tower, m, V i is the effective volume of the ith spray layer, m 3,RStr,i is the effective mass transfer specific surface area of the gas-liquid interface of the ith spray layer, m 2/m3,Str,i is the effective gas-liquid mass transfer area of the effective absorption section of the ith spray layer, and m 2.
3. The method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis according to claim 1, wherein the process of calculating the sedimentation rate of spray droplet terminals in a laminar flow zone, a sliding zone, a transition zone and a turbulent flow zone is as follows: the drop terminal settling rate in the laminar flow zone is:
Wherein: u s is the gravity settling end speed of the liquid drop, the unit m/s, dp is the diameter of the liquid drop, the unit m, ρ p is the density of the liquid drop, the unit kg/m 3, g is the gravity acceleration, the unit m/s 2, mu is the air viscosity, and the unit Pa.s;
the drop terminal settling rate of the sliding zone is:
Wherein: u s is the gravity settling end velocity of the liquid drop, the unit m/s, d p is the liquid drop diameter, the unit m, ρ p is the liquid drop density, the unit kg/m 3, g is the gravity acceleration, the unit m/s 2, μ is the air viscosity, the unit Pa.s, C is the Canning Han correction coefficient, dimensionless, kn is the Knudsen number, dimensionless, λ is the gas molecular mean free path, the unit m, ρ is the air density, the unit kg/m 3, The unit of the arithmetic average speed of gas molecules is M/s, R is a general gas constant, 8.314 J.mol -1·K-1, T is gas temperature, unit K and M is gas molar mass, and unit kg/mol;
the drop terminal settling rate in the transition zone is:
Wherein u s is the gravity settling end speed of the liquid drop, the unit m/s, d p is the liquid drop diameter, the unit m, ρ p is the liquid drop density, the unit kg/m 3, g is the gravity acceleration, the unit m/s 2, μ is the air viscosity, the unit Pa.s, ρ is the air density, and the unit kg/m 3;
the drop terminal settling rate in the turbulent zone is:
Where u s is the end speed of gravity settling of the droplet, m/s, d p is the droplet diameter, m, ρ p is the droplet density, kg/m 3, g is the gravitational acceleration, m/s 2, ρ is the air density, kg/m 3.
4. The method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis according to claim 3, wherein before calculating the sedimentation rate of spray droplet terminals of a laminar flow zone, a sliding zone, a transition zone and a turbulent flow zone, the state of droplet motion is judged according to the Reynolds number:
Wherein Re p is the Reynolds number, d p is the droplet diameter, m is the air density, p is the air density, kg/m 3 is the droplet movement speed, m/s is the air viscosity, mu is the air viscosity, pa.s is the dry air viscosity at 293K and 101325Pa is 1.81× -5 Pa.s, and the dry air density is 1.205kg/m 3;
Laminar flow region: re p is less than or equal to 1, sliding region: re p is less than or equal to 1, and the transition area is: 1 < Re p < 500, turbulence zone: re p＜2×105 is less than 500.
5. The method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis according to claim 1, wherein the cable of mean diameter is:
Wherein D j represents a particle size of the jth size in μm; n j represents the number of droplets of particle size D j in units of one.
6. The method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis according to claim 1, wherein the process of calculating the SO 2 gas-phase mass transfer coefficient K g,i is as follows:
Wherein Q L,i is the flow rate of the spraying slurry of the ith layer, the unit L/min, tau d,i is the effective residence time of the liquid drop on the ith spraying layer, the unit S, u s,i is the average gravity sedimentation end speed of the liquid drop of the ith layer, the unit m/S, L i is the effective liquid holdup of the ith spraying layer, the unit m 3,hi is the effective absorption section height of the ith spraying layer of the desulfurizing tower, the unit m, d SMD,i is the Sotel average diameter of the ith spraying layer, the unit mu m, S tr,i is the effective absorption section gas-liquid mass transfer area of the ith spraying layer, and the unit m 2;
Wherein, (N SO2)g,i is the gas phase mass transfer rate of the i-th spraying layer, kmol/(m 2·s),Qg) is the flue gas flow, m 3/h,CSO2,i is the concentration of an inlet SO 2 of the i-th spraying layer, mg/m 3,CSO2,i+1 is the concentration of an inlet SO 2 of the (i+1) -th spraying layer, mg/m 3,Str,i is the gas-liquid mass transfer area of the effective absorption section of the i-th spraying layer, m 2,PSO2,g,i is the partial pressure of the gas phase SO 2 of the i-th spraying layer, pa, P SO2,aq,i is the partial pressure of the liquid phase SO 2 of the i-th spraying layer, pa, K g,i is the gas phase mass transfer coefficient of the i-th spraying layer, and kmol/(Pa.m 2.s).
7. The method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis according to any one of claims 1 to 6, wherein the evaluating method is suitable for evaluating the purification performance of a limestone-gypsum wet desulfurization system SO 2 having multiple spray layers.
8. The method for evaluating the operation performance of a limestone-gypsum wet desulfurization system based on gas-liquid mass transfer analysis according to any one of claims 1 to 6, wherein the evaluating method is applicable to a desulfurization absorption tower of a multi-spray-layer hollow tower structure, and is not applicable to an absorption tower type with a tray and a grid enhanced mass transfer structure in the absorption tower.
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