A simulation calculation method for a spray deaerator based on the clustering of feed water droplets

Abstract

The object of the present invention is to provide a simulation calculation method for a spray type deaerator based on the grouping of feed water droplets, comprising the following steps: calculating the grouping of feed water droplets to obtain the characteristic diameters, total number of droplets, heat transfer area and mass transfer area of different feed water droplet groups; calculating the heat transfer process of the deaerator to obtain parameters such as the mass, density, enthalpy value and temperature of the steam and feed water in the spray zone and bubbling zone of the deaerator; calculating the mass transfer process of the deaerator to obtain the oxygen partial pressure and thereby calculating the oxygen content in the feed water outlet. On the basis of the partition calculation of the deaerator, the present invention adopts the droplet diameter distribution relationship widely used in the existing droplet spray theory, and makes the droplet distribution in the deaerator conform to the actual working condition of the atomizing nozzle of the deaerator through the method of droplet grouping, and performs a refined calculation on the heat transfer and mass transfer areas in the spray zone of the deaerator, reduces the simulation calculation error of the heat transfer and mass transfer areas, and further improves the refined calculation ability of the deaerator equipment.

Description

Technical Field

[0001] The present invention relates to a simulation method for deaerator equipment, specifically a refined simulation calculation method for a spray deaerator based on the grouping of feed water droplets. Background Art

[0002] The deaerator is an important equipment in a power plant. Its main function is to heat and deaerate the feed water, discharge the non-condensable gases in the feed water to the condenser or the atmospheric environment, and supply the feed water with an oxygen content meeting the operation standard to the boiler of a thermal power plant or the steam generator of a nuclear power plant. The spray deaerator is widely used in power plants. During operation, the feed water is sprayed through atomizing nozzles to form fine droplets and dispersed downward from the top of the deaerator. The steam extracted from the steam turbine of the deaerator is introduced from the bottom of the deaerator through a distribution pipe and flows in a reverse direction to directly contact and exchange heat with the feed water droplets, heating the feed water droplets to the saturation temperature and causing the dissolved oxygen in the feed water to escape.

[0003] In the existing simulation calculations of spray deaerators, in the literature [Zhao Yunyun, Zhang Yanping, Huang Shuhong, etc. Research on the sectional simulation model of an in-built deaerator [J]. Thermal Power Generation, 2012, 41(1): 5.] and the literature [Cong Rixue, Yu Xiaohui, Meng Xiangyu, etc. Research on the dynamic characteristics of a deaerator during the rapid load rejection process of a thermal power unit [J]. Journal of Northeast Electric Power University, 2018, 38(2): 6.], the zoning calculation method of the deaerator is adopted, and the deaerator is divided into two zones, namely the spray zone and the bubbling zone, for calculation. The distribution of the feed water droplets of the atomizing nozzles of the deaerator can reflect the actual working performance of the nozzles, and the heat transfer area and mass transfer area are important basic parameters in the simulation calculation of the deaerator, which have an important impact on the simulation calculation of parameters such as the heat exchange amount and the oxygen content. In the existing methods for calculating the spray zone, the calculation models established in the literature [Sun Jilin. Simulation research on a hybrid heat exchanger with steam condensation phenomenon [D]. Harbin Engineering University, 2016.] and the literature [Gong M, Peng M, Zhu H. Research of quasi 2-D refined simulation and modeling for deaerator in nuclear power plant [J]. Annals of Nuclear Energy, 138.] both consider that after the feed water droplets in the spray zone are sprayed through the atomizing nozzles, there is no difference in the droplet diameters, that is, the diameter of the feed water droplets is regarded as a fixed value, and the working performance of the nozzles during the operation of the deaerator cannot be shown through the research on the droplet distribution relationship of the atomizing nozzles, and the heat transfer area and mass transfer area of the deaerator are calculated according to the same droplet diameter value.

[0004] The problems existing in the existing simulation calculation methods are as follows: First, from the perspective of liquid spray science, the atomizing nozzles of deaerators cannot generate feed water droplets with a uniform diameter during actual operation. The generation process of feed water droplets from the nozzles follows a probability distribution relationship rather than a single diameter value. This method overuses the homogenization concept in calculations and uses the homogenization method to solve probability distribution problems. Second, from the perspective of refined calculation of deaerator equipment, in the spray area during normal operation of the deaerator, the feed water droplets are dispersed in the continuous-phase steam in the form of a dispersed phase. The calculation of the diameter of the dispersed-phase droplets affects the calculation of the heat transfer area and mass transfer area of the droplets in this area. Considering all the feed water droplets as having the same diameter will inevitably lead to errors in the calculation of the heat transfer and mass transfer areas and cannot meet the refined simulation requirements of the deaerator. Summary of the Invention

[0005] The purpose of the present invention is to provide a simulation calculation method for a spray-type deaerator based on the grouping of feed water droplets, which makes the droplet distribution of the deaerator conform to the actual working conditions of the atomizing nozzles of the deaerator through the method of droplet grouping, and performs refined calculations on the heat transfer and mass transfer areas in the spray area of the deaerator, reduces the simulation calculation errors of the heat transfer and mass transfer areas, and further improves the refined calculation ability of the deaerator equipment.

[0006] The purpose of the present invention is achieved as follows:

[0007] A simulation calculation method for a spray-type deaerator based on the grouping of feed water droplets according to the present invention is characterized in that:

[0008] Step 1: Calculate the grouping of feed water droplets. Use the Rosin-Rammler distribution relationship to describe the atomization performance of the feed water droplets of the atomizing nozzles of the deaerator, and thus calculate the characteristic diameters, total number of droplets, heat transfer area, and mass transfer area of different groups of feed water droplets.

[0009] Step 2: Calculate the heat transfer process of the deaerator. Use the calculation method of establishing and solving the mass and energy conservation equations of steam and feed water in the spray area and bubbling area of the deaerator, and iteratively solve to obtain parameters such as the mass, density, enthalpy value, and temperature of steam and feed water in the spray area and bubbling area of the deaerator.

[0010] Step 3: Calculate the mass transfer process of the deaerator. By solving the mass transfer deaeration flow in the spray area and bubbling area of the deaerator and establishing and calculating the oxygen mass conservation equation in the spray area of the deaerator, iteratively calculate to obtain the partial pressure of oxygen and thus calculate the oxygen content at the outlet of the feed water.

[0011] The present invention may further include:

[0012] 1. Specifically, Step 1 is as follows:

[0013] (1) Set the number of droplet groups N s , N s= 1, 2, 3, ……, and the adopted distribution relation is the Rosin-Rammler distribution relation:

[0014]

[0015] In the formula, R is the cumulative volume percentage of droplets with a diameter less than d i , d i is the droplet diameter corresponding to R, N is the droplet uniformity index, is the characteristic diameter of the droplet, which is calculated by the following formula:

[0016]

[0017] In the formula, d is the aperture of the atomizing nozzle, q m is the feed water flow rate, σ is the surface tension of the feed water droplets, and μ is the dynamic viscosity of the feed water droplets;

[0018] (2) Calculate the cumulative volume percentage R of droplets corresponding to the Rosin-Rammler distribution relation for each droplet group: According to the number of groups Ns, determine the cumulative volume percentage R of droplets in the i-th group in the Rosin-Rammler distribution relation as R = i / N s , 1 ≤ i ≤ N s ;

[0019] (3) Calculate the boundary diameter of each droplet group: According to the R value of each droplet group, solve the corresponding d in the Rosin-Rammler distribution relation i , N s groups, a total of N s +1 boundary diameter values of the droplet groups are calculated;

[0020] (4) Calculate the characteristic diameter D k , 1 ≤ k ≤ N s of each droplet group: Take the median value of the adjacent droplet group boundary diameter values d i as the characteristic diameter D s of the k-th droplet group; k ;

[0021] (5) Calculate the total number of droplets N d in each droplet group: According to the relationship between the characteristic diameter value D k of each droplet group and the feed water parameters, calculate the total number of droplets N d in each droplet group;

[0022] (6) Calculate the heat transfer area and mass transfer area of each droplet group: According to the characteristic diameter D k of each droplet group and the total number of droplets N d , calculate N by the sphere area calculation formula Ak = N d πD k 2 for N sThe heat transfer area and mass transfer area of each droplet group are obtained, and the sum is used to obtain the total heat transfer area and total mass transfer area of the spray zone;

[0023] (7) Record the parameters in the above steps: Record the characteristic diameter D of each droplet group k , the total number of droplets N of each droplet group d , the heat transfer area and mass transfer area of the droplets in each droplet group, and the total heat transfer area and total mass transfer area of the spray zone, which are used as the basic parameters for the simulation calculation of the spray zone of the deaerator.

[0024] 2. Step 2 is specifically as follows:

[0025] (1) For the spray zone of the deaerator, by solving the steam mass conservation equation of the spray zone:

[0026]

[0027] In the formula, m s,pw is the steam mass in the spray zone; W s,in,pw is the steam inlet flow rate in the spray zone; W s,cond,pw is the steam condensation flow rate in the spray zone;

[0028] The feed water mass conservation equation of the spray zone:

[0029]

[0030] In the formula, m w,pw is the feed water mass in the spray zone; W w,in,pw is the feed water inlet flow rate in the spray zone; W w,out,pw is the feed water outlet flow rate in the spray zone;

[0031] Iteratively calculate the mass and density of the steam and feed water droplets in the spray zone;

[0032] (2) For the spray zone of the deaerator, by solving the steam energy conservation equation of the spray zone,

[0033]

[0034] In the formula, h s,pw is the steam enthalpy value in the spray zone; h s,in,pw is the steam inlet enthalpy value in the spray zone; h s,cond,pw is the steam condensation enthalpy value in the spray zone; Q s,pw is the steam heat transfer amount in the spray zone;

[0035] The feed water energy conservation equation of the spray zone:

[0036]

[0037] In the formula, h w,pw is the feed water enthalpy value in the spray zone; h w,in,pwis the enthalpy value of the water supply inlet in the spray zone; h w,out,pw is the condensation enthalpy value of the water supply in the spray zone;

[0038] Iteratively calculate the enthalpy values and temperatures of the steam and water droplets in the spray zone. In the calculation of the heat exchange amount in the energy conservation equation, calculate the heat transfer coefficient of each droplet group for different droplet groups, calculate the heat transfer area and mass transfer area of each droplet group, and through Q k = α k A k ΔT k Calculate the heat exchange amount of each droplet group. In the formula, Q k is the heat exchange amount of the k-th group; α k is the heat transfer coefficient of the k-th group; A k is the heat transfer area of the k-th group; ΔT k is the heat exchange temperature difference of the k-th group;

[0039] (3) For the bubbling zone of the deaerator, by solving the steam mass conservation equation of the bubbling zone:

[0040]

[0041] In the formula, m s,gp is the steam mass in the bubbling zone; W s,in,gp is the steam inlet flow rate in the bubbling zone; W s,out,gp is the steam outlet flow rate in the bubbling zone; W s,cond,gp is the steam condensation flow rate in the bubbling zone;

[0042] The water supply mass conservation equation of the bubbling zone:

[0043]

[0044] In the formula, m w,gp is the water supply mass in the bubbling zone; W w,in,gp is the water supply inlet flow rate in the bubbling zone; W w,out,gp is the water supply outlet flow rate in the bubbling zone;

[0045] Iteratively calculate the mass and density of the steam and water supply in the bubbling zone;

[0046] (4) For the bubbling zone of the deaerator, by solving the steam energy conservation equation of the bubbling zone:

[0047]

[0048] In the formula, h s,gp is the steam enthalpy value in the bubbling zone; h s,in,gp is the steam inlet enthalpy value in the bubbling zone; h s,out,gp is the steam outlet enthalpy value in the bubbling zone; h s,cond,gp is the steam condensation enthalpy value in the bubbling zone; Q s,gp is the steam heat exchange amount in the bubbling zone;

[0049] Mass conservation equation of feed water in the bubbling zone:

[0050]

[0051] In the formula, h w,gp is the enthalpy value of feed water in the bubbling zone; h w,in,gp is the inlet enthalpy value of feed water in the bubbling zone; h w,out,gp is the outlet enthalpy value of feed water in the bubbling zone;

[0052] Iteratively calculate the enthalpy values and temperatures of steam and feed water in the bubbling zone.

[0053] 3. Step 3 is specifically as follows:

[0054] (1) Through the mass transfer calculation of the spray zone of the deaerator:

[0055] W ox,pw = K pw A pw Δc pw

[0056] In the formula, W ox,pw is the mass transfer deaeration flow rate of the spray zone of the deaerator; K pw is the mass transfer coefficient of the spray zone of the deaerator; A pw is the mass transfer area of the spray zone of the deaerator; Δc pw is the mass transfer concentration difference of the spray zone of the deaerator;

[0057] Calculate the mass transfer deaeration flow rate of the spray zone of the deaerator, where the mass transfer area of the spray zone is calculated using the obtained droplet group area;

[0058] (2) Through the mass transfer calculation of the bubbling zone of the deaerator:

[0059] W ox,gp = K gp A gp Δc gp

[0060] In the formula, W ox,gp is the mass transfer deaeration flow rate of the bubbling zone of the deaerator; K gp is the mass transfer coefficient of the bubbling zone of the deaerator; A gp is the mass transfer area of the bubbling zone of the deaerator; Δc gp is the mass transfer concentration difference of the bubbling zone of the deaerator;

[0061] Calculate the mass transfer deaeration flow rate of the bubbling zone of the deaerator;

[0062] (3) Establish the oxygen mass conservation equation for the spray zone of the deaerator:

[0063]

[0064] In the formula, m ox is the mass of oxygen; W ox,in is the oxygen input flow rate; S ox,in is the oxygen content corresponding to the oxygen input flow rate; W pw,sum is the total flow rate of steam condensation and feed water entering the bubbling zone from the spray zone; S o is the oxygen content at the feed water outlet of the deaerator; W ox,out is the oxygen flow rate discharged from the vent at the top of the deaerator;

[0065] Calculate the oxygen mass and density in the spray zone, and thus calculate the partial pressure P of oxygen in the spray zone ox ;

[0066] (4) Calculate the oxygen content at the feed water outlet of the deaerator from the calculation relationship between the partial pressure of oxygen and the oxygen content in the deaerator:

[0067]

[0068] In the formula, P ox is the partial pressure of oxygen in the deaerator; T is the temperature at the feed water outlet of the deaerator.

[0069] The advantages of the present invention are as follows:

[0070] (1) The present invention realizes the simulation calculation for the atomizing nozzle of the deaerator by calculating the grouping of the feed water droplets in the deaerator, and further reflects the working performance of the atomizing nozzle during the operation of the deaerator;

[0071] (2) The feed water droplets obey the distribution relationship rather than the same value, making the calculation of the spray zone of the deaerator fit the actual atomization working condition of the atomizing nozzle;

[0072] (3) This method is more accurate than the existing deaerator calculation methods, can accurately calculate the heat transfer area and mass transfer area of different droplet groups, improve the refined calculation ability of the deaerator equipment model, and further provide refined calculation information of different droplet groups;

[0073] (4) Under the condition of the change of the deaerator working conditions, this method can well reflect the change of the heat transfer area and mass transfer area of different droplet groups due to the change of the working conditions of the atomizing nozzle, and further lead to the change of the heat transfer and mass transfer deaeration capacity of the deaerator. Description of the Drawings

[0074] Figure 1 is the flow chart of the present invention;

[0075] Figure 2 is the droplet grouping mode diagram of the present invention;

[0076] Figure 3 is the result diagram of the feed water droplet temperature in the spray zone of the deaerator in the embodiment of the present invention. Detailed implementation mode

[0077] The present invention will be described in more detail with reference to the accompanying drawings as follows:

[0078] Combined with Figures 1-3 , the specific steps of the present invention are as follows:

[0079] Step 1: Calculate the clustering of feed water droplets. The Rosin-Rammler distribution relationship is used to describe the atomization performance of the feed water droplets of the deaerator atomizing nozzle. From this, the characteristic diameters, total number of droplets, heat transfer area, and mass transfer area of different feed water droplet groups are calculated.

[0080] Specifically, it includes:

[0081] (1) Set the number of droplet clusters N s (N s = 1, 2, 3,...), and the adopted distribution relationship is the Rosin-Rammler distribution relationship (Literature [Hou Lingyun, Hou Xiaochun. Nozzle Technology Handbook [M]. China Petrochemical Press, 2002, 74-76.]):

[0082]

[0083] In the formula, R is the cumulative volume percentage of droplets with a diameter less than d i , %, d i is the droplet diameter corresponding to R; N is the droplet uniformity index, taken as 4, which is a known quantity; is the characteristic diameter of the droplet, which is a known quantity and is calculated by the following formula (Literature [Cai Xizong, Cai Wengang. Deaerator in Thermal Power Plants [M]. China Electric Power Press, 2007, 31-33.]):

[0084]

[0085] In the formula, d is the aperture of the atomizing nozzle, which is a known quantity; q m is the feed water flow rate, which is a known quantity; σ is the surface tension of the feed water droplets, which is a known quantity; μ is the dynamic viscosity of the feed water droplets, which is a known quantity.

[0086] (2) Calculate the cumulative volume percentage R of droplets corresponding to the Rosin-Rammler distribution relationship for each droplet group: According to the number of clusters Ns in step 1, determine the cumulative volume percentage R = i / N of the i-th group in the Rosin-Rammler distribution relationship s (1 ≤ i ≤ N s );

[0087] (3) Calculate the boundary diameter of each droplet group: According to the R values of each droplet group in (2), solve the corresponding d i , N sThe group calculation obtains N s +1 boundary diameter values of the droplet groups;

[0088] (4) Calculate the characteristic diameter D of each droplet group k (1 ≤ k ≤ N s ): For the adjacent droplet group boundary diameter values d in (3) i take the median as the characteristic diameter D of the N s group droplet groups; k ;

[0089] (5) Calculate the total number of droplets N of each droplet group d : According to the characteristic diameter values D of each droplet group in (4) k and the relationship between the feed water parameters, calculate the total number of droplets N of each droplet group d ;

[0090] (6) Calculate the heat transfer area and mass transfer area of each droplet group: According to the characteristic diameter D of each droplet group in (4) and (5) k and the total number of droplets N d , from the sphere area calculation formula A k = N d πD k 2 calculate the heat transfer area and mass transfer area of the N s droplet groups, and sum them up to obtain the total heat transfer area and total mass transfer area of the spray zone.

[0091] (7) Record the important parameters in the above steps: Record the characteristic diameter D of each droplet group k , the total number of droplets N of each droplet group d , the heat transfer area and mass transfer area of the droplets in each droplet group, the total heat transfer area and total mass transfer area of the spray zone, as the basic parameters for the simulation calculation of the deaerator spray zone.

[0092] Step 2: Calculation of the heat transfer process of the deaerator. Adopt the calculation method of establishing and solving the mass and energy conservation equations of the steam, feed water in the spray zone and bubbling zone of the deaerator, and iteratively solve to obtain the mass, density, enthalpy value and temperature and other parameters of the steam, feed water in the spray zone and bubbling zone of the deaerator. Specifically include:

[0093] (1) For the spray zone of the deaerator, by solving the steam mass conservation equation in the spray zone:

[0094]

[0095] In the formula, m s,pw is the steam mass in the spray zone; W s,in,pw is the steam inlet flow rate in the spray zone; W s,cond,pw is the steam condensation flow rate in the spray zone;

[0096] Mass conservation equation of feed water in the spray zone:

[0097]

[0098] Where, m w,pw is the mass of feed water in the spray zone; W w,in,pw is the inlet flow rate of feed water in the spray zone; W w,out,pw is the outlet flow rate of feed water in the spray zone;

[0099] Iteratively calculate the mass and density of steam and feed water droplets in the spray zone;

[0100] (2) For the spray zone of the deaerator, by solving the energy conservation equation of steam in the spray zone,

[0101]

[0102] Where, h s,pw is the enthalpy value of steam in the spray zone; h s,in,pw is the inlet enthalpy value of steam in the spray zone; h s,cond,pw is the condensation enthalpy value of steam in the spray zone; Q s,pw is the heat transfer amount of steam in the spray zone;

[0103] Energy conservation equation of feed water in the spray zone:

[0104]

[0105] Where, h w,pw is the enthalpy value of feed water in the spray zone; h w,in,pw is the inlet enthalpy value of feed water in the spray zone; h w,out,pw is the condensation enthalpy value of feed water in the spray zone;

[0106] Iteratively calculate the enthalpy value and temperature of steam and feed water droplets in the spray zone. In the calculation of the heat transfer amount in the energy conservation equation, calculate the heat transfer coefficient of each droplet group for different droplet groups. According to the heat transfer area and mass transfer area of each droplet group calculated in (6) of step 1, through Q k = α k A k ΔT k Calculate the heat transfer amount of each droplet group. In the formula, Q k is the heat transfer amount of the k-th group; α k is the heat transfer coefficient of the k-th group; A k is the heat transfer area of the k-th group; ΔT k is the heat transfer temperature difference of the k-th group;

[0107] (3) For the bubbling zone of the deaerator, by solving the mass conservation equation of steam in the bubbling zone:

[0108]

[0109] where m s,gp is the steam mass in the bubbling zone; W s,in,gp is the steam inlet flow rate in the bubbling zone; W s,out,gp is the steam outlet flow rate in the bubbling zone; W s,cond,gp is the steam condensation flow rate in the bubbling zone;

[0110] Mass conservation equation of feed water in the bubbling zone:

[0111]

[0112] where m w,gp is the feed water mass in the bubbling zone; W w,in,gp is the feed water inlet flow rate in the bubbling zone; W w,out,gp is the feed water outlet flow rate in the bubbling zone;

[0113] Iteratively calculate the mass and density of steam and feed water in the bubbling zone;

[0114] (4) For the bubbling zone of the deaerator, by solving the energy conservation equation of steam in the bubbling zone:

[0115]

[0116] where h s,gp is the enthalpy value of steam in the bubbling zone; h s,in,gp is the inlet enthalpy value of steam in the bubbling zone; h s,out,gp is the outlet enthalpy value of steam in the bubbling zone; h s,cond,gp is the condensation enthalpy value of steam in the bubbling zone; Q s,gp is the heat transfer amount of steam in the bubbling zone;

[0117] Energy conservation equation of feed water in the bubbling zone:

[0118]

[0119] where h w,gp is the enthalpy value of feed water in the bubbling zone; h w,in,gp is the inlet enthalpy value of feed water in the bubbling zone; h w,out,gp is the outlet enthalpy value of feed water in the bubbling zone;

[0120] Iteratively calculate the enthalpy value and temperature of steam and feed water in the bubbling zone.

[0121] Step 3: Calculation of the mass transfer process of the deaerator. By calculating the mass transfer deaeration flow rates in the spray zone and bubbling zone of the deaerator, and establishing and calculating the calculation method of the oxygen mass conservation equation in the spray zone of the deaerator, iteratively calculate the partial pressure of oxygen and thus calculate the oxygen content in the outlet feed water, specifically including:

[0122] (1) Through the mass transfer calculation of the spray zone of the deaerator:

[0123] W ox,pw = Kpw A pw Δc pw

[0124] In the formula, W ox,pw is the mass transfer deoxidization flow rate in the spray zone of the deaerator; K pw is the mass transfer coefficient in the spray zone of the deaerator; A pw is the mass transfer area in the spray zone of the deaerator; Δc pw is the mass transfer concentration difference in the spray zone of the deaerator;

[0125] The mass transfer deoxidization flow rate in the spray zone of the deaerator is calculated, where the mass transfer area in the spray zone is calculated using the droplet group area obtained in (6) of Step 1;

[0126] (2) By performing mass transfer calculation on the bubbling zone of the deaerator:

[0127] W ox,gp = K gp A gp Δc gp

[0128] In the formula, W ox,gp is the mass transfer deoxidization flow rate in the bubbling zone of the deaerator; K gp is the mass transfer coefficient in the bubbling zone of the deaerator; A gp is the mass transfer area in the bubbling zone of the deaerator; Δc gp is the mass transfer concentration difference in the bubbling zone of the deaerator;

[0129] The mass transfer deoxidization flow rate in the bubbling zone of the deaerator is calculated;

[0130] (3) Establish an oxygen mass conservation equation for the spray zone of the deaerator:

[0131]

[0132] In the formula, m ox is the oxygen mass; W ox,in is the oxygen input flow rate; S ox,in is the oxygen content corresponding to the oxygen input flow rate; W pw,sum is the total flow rate of steam condensation and feed water entering the bubbling zone from the spray zone; S o is the oxygen content at the deaerator feed water outlet; W ox,out is the oxygen flow rate discharged from the deaerator top vent;

[0133] Calculate the oxygen mass and density in the spray zone, and thereby calculate the oxygen partial pressure P ox ;

[0134] (4) Calculate the oxygen content in the feed water outlet of the deaerator from the calculation relationship between the oxygen partial pressure and the oxygen content in the deaerator (literature [Tromans, Desmond. Modeling oxygen solubility in water and electrolyte solutions[J]. Ind. eng. chem. res, 2000, 39(3): 805 - 812.]):

[0135]

[0136] In the formula, P ox is the oxygen partial pressure of the deaerator; T is the temperature of the feed water outlet of the deaerator.

[0137] Example

[0138] Step 1, perform droplet grouping calculation:

[0139] (1) Set the number of droplet groups N s of the feed water in the deaerator. Based on the operating parameter specifications of the deaerator of a certain 900MW nuclear power plant, set the number of groups N s = 3 in this example;

[0140] (2) According to the number of feed water droplet groups N s , calculate the cumulative volume percentage R of the droplets corresponding to the Rosin - Rammler distribution relationship for each droplet group;

[0141] (3) According to the R values of each droplet group in (2), solve for the corresponding d i in the Rosin - Rammler distribution relationship. The calculation results in this example are:

[0142]

[0143] (4) Take the median value of the adjacent droplet group boundary diameter values d i in (3) as the characteristic diameter D s of the N k group of droplets;

[0144] (5) According to the characteristic diameter values D k of each droplet group in (4) and the feed water flow rate relationship, calculate the total number of droplets N d of each droplet group;

[0145] (6) According to the characteristic diameter D k and the total number of droplets N d of each droplet group in (4) and (5), calculate the total area of the N s droplet groups to obtain the heat transfer area and mass transfer area of the spray zone;

[0146] (7) Record the characteristic diameter d of each droplet group k and the total number N of droplets in each droplet group d , as well as the heat transfer area and mass transfer area in the spray zone, which are used as the basic parameters for the simulation calculation of the spray zone of the deaerator.

[0147] According to the above steps, for this embodiment, the characteristic diameter D of 3 groups of feed water droplet groups can be calculated k , the total number N of droplets d , the heat transfer area and mass transfer area:

[0148]

[0149] If calculated using the existing non-grouping method, the droplet-related parameters obtained are:

[0150] Parameter Droplet diameter / mm <![CDATA[Heat transfer area and mass transfer area of droplets / m 2 > Area calculation deviation from clustering method / % Value 0.868 90.699 10.45

[0151] Step 2, perform the heat transfer process calculation of the deaerator:

[0152] (1) Iteratively solve the mass conservation equations of steam and feed water in the spray zone to calculate the mass and density of steam and feed water in the spray zone;

[0153] (2) Iteratively solve the energy conservation equations of steam and feed water in the spray zone to calculate the enthalpy and temperature of steam and feed water in the spray zone. Among them, for the calculation of the heat exchange amount between steam and feed water in the spray zone, the heat transfer area of each droplet group obtained in step 1 (6) is used to calculate the heat exchange amount of different droplet groups;

[0154] (3) Iteratively solve the mass conservation equations of steam and feed water in the bubbling zone to calculate the mass and density of steam and feed water in the bubbling zone;

[0155] (4) Iteratively solve the energy conservation equations of steam and feed water in the bubbling zone to calculate the enthalpy and temperature of steam and feed water in the bubbling zone;

[0156] Step 3, perform the mass transfer process calculation of the deaerator:

[0157] (1) Perform mass transfer calculation on the spray zone of the deaerator to obtain the mass transfer deaeration flow rate in the spray zone of the deaerator, where the mass transfer area is calculated using the droplet group mass transfer area obtained in step 1 (6);

[0158] (2) Perform mass transfer calculation on the bubbling zone of the deaerator to obtain the mass transfer deaeration flow rate in the bubbling zone of the deaerator;

[0159] (3) Iteratively solve the oxygen mass conservation equation in the spray zone to calculate the oxygen mass and density in the spray zone, and thus calculate the oxygen partial pressure in the spray zone;

[0160] (4) Calculate the oxygen content at the outlet of the deaerator feed water from the oxygen partial pressure and oxygen content calculation relationship of the deaerator.

[0161] Table 1 lists the original operation data of the deaerator in this embodiment, and Table 2 lists the deaerator parameters calculated by applying this method after the above steps and their errors. Attached Figure 3 The result graph of the deaerator droplet temperature change curve calculated by applying this method is given.

[0162] Table 1 Original operation data of the deaerator

[0163] Serial number Parameter Value Unit 1 Deaerator operating pressure 0.7515 MPa 2 Feed water inlet flow rate 1211.61 kg / s 3 Feed water inlet temperature 143.93 ℃ 4 Steam inlet flow rate 64.7 kg / s 5 Steam inlet temperature 169.54 ℃ 6 Drain water inlet flow rate 337.09 kg / s 7 Drain water inlet temperature 176.08 ℃ 8 Feed water outlet temperature 167.84 ℃ 9 Oxygen content in feed water outlet 5 ppb

[0164] Table 2 Deaerator parameters and errors after calculation using this method

[0165]

[0166] After performing the above calculations using this method, the main parameters of different feed water droplet groups of the deaerator can be obtained, which are used as important basic parameters for further simulation calculations of the deaerator equipment, enabling the simulation calculation of the deaerator to fit the actual working conditions of the atomizing nozzle, keeping the calculation error of the calculation results small, and effectively improving the refined simulation ability of the deaerator equipment to meet the engineering requirements of the refined simulation calculation of the deaerator.

[0167] From the Figure 3 results of the feed water droplet temperature in the spray area of the deaerator in the attachment, it can be seen that by applying this method to calculate the grouping of the feed water droplets of the deaerator, the temperature change differences of different diameter droplet groups during the operation of the deaerator can be obtained, showing that the present invention has good adaptability to the refined calculation ability of the deaerator model and is of positive significance for improving the refined simulation calculation ability of the deaerator model.

Claims

1. A simulation calculation method for a spray deaerator based on the grouping of feed water droplets, characterized in that: Step 1: Calculate the grouping of feed water droplets. Use the Rosin-Rammler distribution relationship to describe the atomization performance of the feed water droplets of the atomizing nozzle of the deaerator, and thus calculate the characteristic diameters, total number of droplets, heat transfer area, and mass transfer area of different groups of feed water droplets. (1) Set the number of droplet clusters N s , N s = 1, 2, 3, ……, and the adopted distribution relationship is the Rosin-Rammler distribution relationship: wherein, R is the cumulative volume percentage of droplets with a diameter less than d i , d i is the droplet diameter corresponding to R, N is the droplet uniformity index, is the characteristic diameter of the droplet, which is calculated by the following formula: where d is the aperture diameter of the atomizing nozzle, q m is the feed water flow rate, σ is the surface tension of the feed water droplets, and μ is the dynamic viscosity of the feed water droplets; (2) Calculate the Rosin-Rammler distribution relationship droplet cumulative volume percentage R corresponding to each droplet group: According to the number of groups Ns, determine the droplet cumulative volume percentage R = i / N of the i-th group in the Rosin-Rammler distribution relationship s , 1 ≤ i ≤ N s ; (3) Calculate the boundary diameter of each droplet group: According to the R value of each droplet group, solve for the corresponding d in the Rosin-Rammler distribution relationship i , N s For a total of N s +1 boundary diameter values of droplet groups are calculated; (4) Calculate the characteristic diameter D of each droplet group k , where 1 ≤ k ≤ N s : Take the median of the boundary diameter values d of adjacent droplet groups i as the characteristic diameter D of the N s -th droplet group k ; (5) Calculate the total number of droplets N in each droplet group d : Calculate the total number of droplets N in each droplet group according to the characteristic diameter value D of each droplet group k and the relationship between the feed water parameters d ; (6) Calculate the heat transfer area and mass transfer area of each droplet group: According to the characteristic diameter D of each droplet group k and the total number of droplets N d , from the sphere area calculation formula A k = N d πD k 2 Calculate the heat transfer area and mass transfer area of N s droplet groups, and sum them up to obtain the total heat transfer area and total mass transfer area of the spray area; (7) Record the parameters in the above steps: Record the characteristic diameter D of each droplet group k , the total number of droplets N of each droplet group d , the heat transfer area and mass transfer area of the droplets in each droplet group, and the total heat transfer area and total mass transfer area of the spray area, as the basic parameters for the simulation calculation of the spray area of the deaerator; Step 2: Calculate the heat transfer process of the deaerator. Adopt the calculation method of establishing and solving the mass and energy conservation equations of steam, feed water in the spray zone and bubbling zone of the deaerator, and iteratively solve to obtain parameters such as the mass, density, enthalpy value, and temperature of steam, feed water in the spray zone and bubbling zone of the deaerator. Step 3: Calculate the mass transfer process of the deaerator. By solving the mass transfer deaeration flow rates in the spray zone and bubbling zone of the deaerator, and establishing and calculating the oxygen mass conservation equation in the spray zone of the deaerator, iteratively calculate to obtain the partial pressure of oxygen and thus calculate the oxygen content at the outlet of the feed water.

2. The simulation calculation method of a spray deaerator based on the clustering of feed water droplets according to claim 1, characterized in that: Specifically, Step 2 is as follows: (1) For the spray zone of the deaerator, by solving the steam mass conservation equation in the spray zone: Where, m s,pw is the steam mass in the spray area; W s,in,pw is the steam inlet flow rate in the spray area; W s,cond,pw is the steam condensation flow rate in the spray area; The feed water mass conservation equation in the spray zone: Where m w,pw is the water quality of the water supply to the spray area; W w,in,pw is the inlet flow rate of the water supply to the spray area; W w,out,pw is the outlet flow rate of the water supply to the spray area; Iteratively calculate the mass and density of steam and feed water droplets in the spray zone. (2) For the spray zone of the deaerator, by solving the steam energy conservation equation in the spray zone, Where h s,pw is the enthalpy value of the steam in the spray zone; h s,in,pw is the inlet enthalpy value of the steam in the spray zone; h s,cond,pw is the condensation enthalpy value of the steam in the spray zone; Q s,pw is the heat exchange amount of the steam in the spray zone; The feed water energy conservation equation in the spray zone: where h w,pw is the enthalpy value of the feed water in the spray zone; h w,in,pw is the inlet enthalpy value of the feed water in the spray zone; h w,out,pw is the condensation enthalpy value of the feed water in the spray zone; Iteratively calculate the enthalpy and temperature of the steam and feed water droplets in the spray zone. In the calculation of the heat transfer amount in the energy conservation equation, calculate the heat transfer coefficient of each droplet group for different droplet groups, calculate the heat transfer area and mass transfer area of each droplet group, and through Q k = α k A k ΔT k Calculate the heat transfer amount of each droplet group. In the formula, Q k is the heat transfer amount of the k-th group; α k is the heat transfer coefficient of the k-th group; A k is the heat transfer area of the k-th group; ΔT k is the heat transfer temperature difference of the k-th group; (3) For the bubbling zone of the deaerator, by solving the steam mass conservation equation in the bubbling zone: where m s,gp is the steam mass in the bubbling zone; W s,in,gp is the steam inlet flow rate in the bubbling zone; W s,out,gp is the steam outlet flow rate in the bubbling zone; W s,cond,gp is the steam condensation flow rate in the bubbling zone; The feed water mass conservation equation in the bubbling zone: where m w,gp is the feed water quality in the bubbling zone; W w,in,gp is the feed water inlet flow rate in the bubbling zone; W w,out,gp is the feed water outlet flow rate in the bubbling zone; Iteratively calculate the mass and density of steam and feed water in the bubbling zone. (4) For the bubbling zone of the deaerator, by solving the steam energy conservation equation in the bubbling zone: where h s,gp is the enthalpy value of the steam in the bubbling zone; h s,in,gp is the inlet enthalpy value of the steam in the bubbling zone; h s,out,gp is the outlet enthalpy value of the steam in the bubbling zone; h s,cond,gp is the condensation enthalpy value of the steam in the bubbling zone; Q s,gp is the heat transfer amount of the steam in the bubbling zone; The feed water energy conservation equation in the bubbling zone: where h w,gp is the enthalpy value of feed water in the bubbling zone; h w,in,gp is the inlet enthalpy value of feed water in the bubbling zone; h w,out,gp is the outlet enthalpy value of feed water in the bubbling zone; Iteratively calculate the enthalpy value and temperature of steam and feed water in the bubbling zone.

3. A simulation calculation method for a spray deaerator based on the clustering of feed water droplets according to claim 1, characterized in that: Specifically, Step 3 is as follows: (1) Through the mass transfer calculation of the spray zone of the deaerator: W ox,pw = K pw A pw Δc pw Where, W ox,pw is the mass transfer deaeration flow rate in the spray zone of the deaerator; K pw is the mass transfer coefficient in the spray zone of the deaerator; A pw is the mass transfer area in the spray zone of the deaerator; Δc pw is the mass transfer concentration difference in the spray zone of the deaerator; Calculate the mass transfer deaeration flow rate in the spray zone of the deaerator. Among them, the mass transfer area in the spray zone is calculated using the obtained droplet group area. (2) Through the mass transfer calculation of the bubbling zone of the deaerator: W ox,gp = K gp A gp Δc gp Where, W ox,gp is the mass transfer deaeration flow rate in the bubbling zone of the deaerator; K gp is the mass transfer coefficient in the bubbling zone of the deaerator; A gp is the mass transfer area in the bubbling zone of the deaerator; Δc gp is the mass transfer concentration difference in the bubbling zone of the deaerator; Calculate the mass transfer deaeration flow rate in the bubbling zone of the deaerator. (3) Establish an oxygen mass conservation equation for the spray zone of the deaerator: where m ox is the mass of oxygen; W ox,in is the oxygen input flow rate; S ox,in is the oxygen content corresponding to the oxygen input flow rate; W pw,sum is the total flow rate of steam condensation and feed water entering the bubbling zone from the spraying zone; S o is the oxygen content at the feed water outlet of the deaerator; W ox,out is the oxygen flow rate discharged from the vent at the top of the deaerator; Calculate the oxygen mass and density in the spray area, and calculate the partial pressure P of oxygen in the spray area from this ox ; (4) Calculate the oxygen content at the outlet of the feed water of the deaerator from the calculation relationship between the partial pressure of oxygen and the oxygen content of the deaerator: where P ox is the oxygen partial pressure of the deaerator; T is the outlet temperature of the feed water of the deaerator.

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