CN106248133A - A kind of heater full working scope upper end difference and lower end difference should reach the On-line Estimation method of value - Google Patents

Abstract

The invention provides a kind of poor On-line Estimation method that should reach value with lower end difference in heater full working scope upper end, step is: 1, obtain the real time data of relevant measuring point under given time；2, the mass flow On-line Estimation value of drawing gas of each heater of acquisition is calculated；3, the outer steam of calculating heat exchanger tube is to the coefficient of heat transfer of aqueous phase working medium heat exchanging tube wall in the coefficient of heat transfer and heat exchanger tube of heat exchange tube wall, and then obtains when in heater, heat exchanging pipe wall dirtiness resistance is zero, heater Composite Walls theoretical maximum；4, calculate heater condensate outlet temperature theoretical value, and then defined by lower end difference, obtain heater lower end difference and should reach value；5, calculate heater aqueous phase sender property outlet temperature theoretical value, and defined by upper end difference, obtain heater upper end difference and should reach value.The present invention can analyze heater upper end difference and the impact on unit heat economy of the lower end difference, provides supporting condition for regenerative steam system thermal economy real-time assessment.

Description

A kind of heater full working scope upper end difference and lower end difference should reach the On-line Estimation method of value

Technical field

The present invention relates to firepower power station running optimizatin and control technical field, concrete, relate on a kind of heater full working scope End difference and lower end difference should reach the On-line Estimation method of value.

Background technology

Economy and reliability that power station is run by the various auxiliary equipments of firepower power station play very important effect.Add Hot device is one of most important auxiliary equipment of steam turbine, utilizes steam turbine regenerative steam heat-setting water and feedwater, it is possible to reduce Cold source energy, improves the thermal efficiency of cycle of unit, and therefore the heat-economy of whole unit is had directly by the running status of heater Connect impact.In unit running process, heater upper end difference and lower end difference are the important indicators of monitoring operating states of the units.Upper end Difference is defined as saturated-steam temperature and aqueous phase sender property outlet temperature difference under this grade of heater extraction pressure；Lower end difference is defined as adding The hydrophobic outlet temperature of hot device and the difference of aqueous phase working medium inlet temperature.Heater upper end difference or lower end difference are the biggest, to unit operation Economic influence is the biggest.Generally power station collection control operating standard can be given heater upper end difference under declared working condition should reach value and under End difference should reach value as reference frame.But when operating mode changes, unit operation parameter all can change accordingly, carries out unit During Thermal Efficiency Analysis, upper end difference during declared working condition should reach value and lower end difference should to reach value the most applicable, it is therefore desirable to obtain Heater upper end difference under different operating modes should reach value and lower end difference should reach value, and on this basis assessment heater upper end differ from The impact on unit heat economy of the lower end difference.

Through the retrieval to prior art, Chinese Patent Application No. 201310142718.X, publication number 103267539A, public affairs Open a day 2013-08-28, describe a kind of horizontal syllogic feed-water heater upper end difference and the measuring method of lower end difference.The method Parameter, respectively hydrophobic cooling section, condensation section and the superheated steam cooling to heater can be surveyed based on dimensional analysis principle and operation Section is fixed the test under operating mode, obtains each section of number of transfer units and a certain parameter (extraction flow, feedwater by data matching Flow, saturation pressure etc.) simplification linear functional relation, be used for calculating under other operating mode heater and import and export each thermal parameter, Thus it is poor with lower end to obtain upper end difference.Substantially, under above-mentioned linear functional relation is only applicable to operating condition of test upper end difference and under End difference is estimated, in addition to operating condition of test under conditions of calculating error be to be greatly little to become uncontrollable factor.Additionally, the method is only Relate to heater upper end difference and the measuring and calculating of lower end difference, it is impossible to value should be reached for heater upper end difference and lower end difference should reach estimating of value Meter, it is impossible to analyze heater upper end difference and the impact on unit heat economy of the lower end difference, also cannot be regenerative steam system thermal warp Ji property real-time assessment provides supporting condition.

Summary of the invention

For deficiency of the prior art, it is an object of the invention to provide a kind of heater full working scope upper end difference and lower end is poor The On-line Estimation method of value should be reached.

For realizing object above, the technical solution used in the present invention: in the case of first obtaining the true heat exchange of each heater The On-line Estimation value of mass flow of drawing gas, then obtains heater Composite Walls theoretical value in the case of preferable heat exchange, Jin Ergen According to the theoretical value of the heat exchanger efficiency Equation for Calculating heater condensate outlet temperature in the case of preferable heat exchange, according to heater self-energy Equilibrium relation, obtains aqueous phase sender property outlet temperature theoretical value in heater, and obtains upper end according to upper end difference and lower end difference definition Difference should reach value and lower end difference should reach value.The present invention can analyze heater upper end difference and the impact on unit heat economy of the lower end difference, Supporting condition is provided for regenerative steam system thermal economy real-time assessment.

Concrete, a kind of heater full working scope upper end difference and lower end difference should reach the On-line Estimation method of value, and the method is concrete Comprise the following steps:

Step one, obtain under given time from the dcs DCS real-time data base of operating unit and respectively heat Device inlet steam pressure, temperature, drain temperature, aqueous phase sender property outlet temperature, condense water quality flow, pressure, temperature, economizer Entrance feed-water quality flow, pressure, temperature；

Step 2, combine working medium physical parameter storehouse, draw gas according in the energy balance relations in each heater, i.e. heater The heat of the heat of release+absorb from the heat=aqueous phase working medium of the hydrophobic release of a upper heater, calculates to obtain and respectively adds The mass flow On-line Estimation value of drawing gas of hot device, calculates thermal capacity flow rate ratio in step 4；

The outer steam side convection transfer rate α of heat exchanger tube in the case of step 3, the calculating true heat exchange of heater₁With in heat exchanger tube The coefficient of heat transfer α of aqueous phase working medium heat exchanging tube wall₂, and obtain heat exchanging pipe wall dirtiness resistance R in heater_bIt it is heating when zero Device Composite Walls theoretical value K_lx, in step 4, calculate the theoretical maximum of number of transfer units；

Step 4, based on thermal capacity flow rate ratio and the theoretical maximum of number of transfer units, add in the case of setting up preferable heat exchange Hot device heat exchanger efficiency equation, calculates heater condensate outlet temperature theoretical value, and then is defined by lower end difference, be calculated online and add Hot device lower end difference should reach value；

Step 5, according to the energy balance relations in the case of heater ideal heat exchange, in the case of i.e. preferable heat exchange, heater Inside draw gas the heat of the heat of release+absorb from the heat=aqueous phase working medium of the hydrophobic release of a upper heater, and calculating adds Hot device aqueous phase sender property outlet temperature theoretical value, and defined by upper end difference, it is calculated heater upper end difference online and should reach value.

Preferably, in step 2, the energy balance relations in heater is:

D_cq(h_cq-h_ss)+D_sspre(h_sspre-h_ss)=D_w(h_outs-h_ins) (1)

Wherein, D_wIt is aqueous phase working medium mass flow, kg/s；D_cqIt is mass flow of drawing gas, kg/s；h_cqIt it is heater extraction entrance Specific enthalpy, kJ/kg；h_ssIt is the hydrophobic specific enthalpy of heater outlet, kJ/kg；D_sspreBe a upper heater flow to this heater dredge The mass flow of water, kg/s；h_sspreIt is the upper heater specific enthalpy that flows to this heater condensate, kJ/kg；D_wIn being heater Aqueous phase working medium mass flow, kg/s；h_outsIt is aqueous phase working medium specific enthalpy at heater outlet, kJ/kg；h_insIt is aqueous phase working medium Specific enthalpy at calorifier inlets, kJ/kg.Calculate the heater each heater that mass flow flows through that draws gas according to aqueous phase working medium suitable Sequence is carried out, and wherein before oxygen-eliminating device, the aqueous phase working medium of low-pressure heater is main condensate, the water of high-pressure heater after oxygen-eliminating device Phase working medium is feedwater；

Preferably, in step 3, calculate the outer steam side convection transfer rate α of heat exchanger tube₁Time, plunder staggered tubes owing to steam is horizontal Bundle, steam side reynolds number Re_sWith adjacent tube bank Transverse tube pitch d_hWith longitudinal pipe spacing d_v, determine α₁Computing formula for (to see Yang Shiming, inscription on pottery select. thermal conduction study (fourth edition). Higher Education Publishing House, 2010,259-262):

${\mathrm{\α}}_1=k_1{\left(\frac{d_h}{d_v}\right)}^{k_2}{\mathrm{Re}}_s^{k_3}{\mathrm{Pr}}_s^{0.36}{\left(\frac{{\mathrm{Pr}}_s}{{\mathrm{Pr}}_w}\right)}^{0.25}---\left(2\right)$

In formula, k₁, k₂, k₃It is that the ratio by steam side Reynolds number and adjacent tube bank Transverse tube pitch and longitudinal pipe spacing is true Fixed coefficient, Pr_sAnd Pr_wIt is steam side and the Prandtl number of aqueous phase working medium.Fluid Reynolds number and the computational methods of Prandtl number For:

$\mathrm{Re}=\frac{\mathrm{\ρ}du}{\mathrm{\μ}}---\left(3\right)$

$\mathrm{Pr}=\frac{c\mathrm{\μ}}{\mathrm{\λ}}---\left(4\right)$

In formula, ρ is the density of fluid, kg/m³；U is the flow velocity of fluid, m/s；μ is the viscosity of fluid, Pa s；λ is stream The thermal conductivity of body, W/ (m DEG C)；C is the specific heat capacity of fluid, kJ/ (kg DEG C)；

Due to the reynolds number Re of aqueous phase working medium in heat exchanger tube_wMeet turbulent-flow conditions, therefore aqueous phase working medium side heat convection system Number α₂Computational methods for (see Yang Shiming, inscription on pottery select. thermal conduction study (fourth edition). Higher Education Publishing House, 2010,259- 262):

${\mathrm{\α}}_2=0.023\frac{\mathrm{\λ}}{d_i}{\mathrm{Re}}_w^{0.8}{\mathrm{Pr}}_w^{0.4}---\left(5\right)$

In formula, d_iIt is heat exchanger tube internal diameter, m；

In heater in the case of true heat exchange, when heater pipe wall of heat exchange pipe dirtiness resistance is R_bTime, the total heat exchange of heater COEFFICIENT K is:

$K=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+R_b+\frac{1}{{\mathrm{\α}}_2}}---\left(6\right)$

Therefore, when heater pipe wall of heat exchange pipe cleans, i.e. dirtiness resistance R_bWhen being zero, heater Composite Walls theoretical value K_lxFor:

$K_{lx}=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+\frac{1}{{\mathrm{\α}}_2}}---\left(7\right)$

Preferably, in step 4, due to thermal capacity flow rate ratio0≤R≤1, so changing according to heater The definition of thermal efficiency ε, can derive the heat exchange efficiency of heater in the case of true heat exchange is:

$\mathrm{\ϵ}=\frac{D_{cq}{c}_{ph}(t_{cq}-t_{ss})}{D_{cq}{c}_{ph}(t_{cq}-t_{ins})}=\frac{t_{cq}-t_{ss}}{t_{cq}-t_{ins}}---\left(8\right)$

Wherein, c_phIt is the mean specific heat of the outer steam of heater heat exchanger tube, kJ/ (kg DEG C)；t_cqIt is that calorifier inlets is taken out Stripping temperature, DEG C；t_ssIt is heater condensate outlet temperature, DEG C；t_insIt is calorifier inlets aqueous phase Temperature of Working, DEG C；

Make heater number of transfer unitsWherein, A is that heater surface amasss, m².Set up heater to change Thermal efficiency ε and number of transfer units NTU and the thermal capacity flow rate relation than R:

$\mathrm{\ϵ}=\frac{1-\exp \[-NTU(1-R)\]}{1-R\exp \[-NTU(1-R)\]}---\left(9\right)$

According to ε Yu R, the relation of NTU, owing in the case of true heat exchange situation and preferable heat exchange, R is constant, therefore when NTU Time big, ε is maximum.In heater actual motion, heater also exists certain performance degradation, such as heater heat exchange tube wall knot Dirt, the reason such as heater heat exchanger tube blocking, make heater Composite Walls K and heat exchange area A less than theoretical value or design load.Cause This, in the case of preferable heat exchange, i.e. heater heat exchanger tube wall surface is clean, i.e. dirtiness resistance R_b=0, and heater truly changes Hot side is long-pending equal to design load A_sjTime, the theoretical maximum of NTU is:

${\mathrm{NTU}}_{max}=\frac{K_{lx}{A}_{sj}}{D_w{c}_{pc}}---\left(10\right)$

Therefore, heater heat exchanger efficiency equation in the case of preferable heat exchange is set up:

${\mathrm{\ϵ}}_{lx}=\frac{t_{cq}-t_{ss\_lx}}{t_{cq}-t_{ins}}=\frac{1-\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}{1-R\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}---\left(11\right)$

Wherein, t_{ss_lx}It is heater condensate outlet temperature theoretical value, DEG C.Can solve:

$t_{ss\_lx}=t_{cq}-\frac{1-\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}{1-R\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}(t_{cq}-t_{ins})---\left(12\right)$

According to the definition of lower end difference, should reach value in line computation heater lower end difference is:

t_dt=t_{ss_lx}-t_ins (13)

Preferably, in step 5, in the case of heater ideal heat exchange, heater self-energy equilibrium relation is:

D_cq(h_cq-h_{ss_lx})+D_sspre(h_sspre-h_{ss_lx})=D_wc_pc(t_{outs_lx}-t_ins) (14)

Wherein, h_{ss_lx}It is according to t_{ss_lx}Calculated heater outlet hydrophobic specific enthalpy theoretical value, kJ/kg；t_{outs_lx}It it is heating Device aqueous phase sender property outlet temperature theoretical value, DEG C.Can solve:

$t_{outs\_lx}=\frac{D_{cq}(h_{cq}-h_{ss\_lx})+D_{sspre}(h_{sspre}-h_{ss\_lx})}{D_w{c}_{pc}}+t_{ins}---\left(15\right)$

According to upper end difference definition, i.e. upper end poor=extraction pressure under saturated-steam temperature-aqueous phase sender property outlet temperature, Line computation heater upper end difference should reach value and be:

t_tt=t_bq-t_{outs_lx} (16)

Compared with prior art, the present invention has a following beneficial effect:

The present invention is based on heater Composite Walls theoretical value in the case of preferable heat exchange, by changing in the case of preferable heat exchange The theoretical value of thermal efficiency Equation for Calculating heater condensate outlet temperature, then by heater self-energy equilibrium relation, obtain heater Interior aqueous phase sender property outlet temperature theoretical value, and finally obtain upper end difference according to upper end difference and lower end difference definition and should reach value and lower end is poor Value should be reached.The present invention can utilize the art of this patent On-line Estimation heater complete under conditions of not increasing existing measuring point hardware Operating mode upper end difference should reach value and lower end difference should reach value, for analyzing heater upper end difference and the lower end difference shadow to unit heat economy Ring, provide supporting condition for regenerative steam system thermal economy real-time assessment.

Accompanying drawing explanation

By the detailed description non-limiting example made with reference to the following drawings of reading, the further feature of the present invention, Purpose and advantage will become more apparent upon:

Fig. 1 is one embodiment of the invention regenerative steam system structure schematic diagram；

Fig. 2 is one embodiment of the invention heater structure schematic diagram；

Fig. 3 is difference value of calculation t in certain unit 2# high-pressure heater true heat exchange situation upper end in one embodiment of the invention_tAnd reason Think that heat exchange situation upper end difference should reach value t_ttResult of calculation；

Fig. 4 is difference value of calculation t in certain unit 2# high-pressure heater true heat exchange situation lower end in one embodiment of the invention_dAnd reason Think that heat exchange situation lower end difference should reach value t_dtResult of calculation.

Detailed description of the invention

Below in conjunction with specific embodiment, the present invention is described in detail.Following example will assist in the technology of this area Personnel are further appreciated by the present invention, but limit the present invention the most in any form.It should be pointed out that, the ordinary skill to this area For personnel, without departing from the inventive concept of the premise, it is also possible to make some deformation and improvement.These broadly fall into the present invention Protection domain.

The present embodiment relates to the horizontal heater upper end difference being suitable for full working scope of certain ultra supercritical 1000MW firepower power station and should reach Value and lower end difference should reach value method of estimation.The high-pressure heater of this crew qiting is Horizontal U-shaped tube-surface heater.Fig. 1 is real Execute example unit regenerative steam system structure schematic diagram.Main condensate sequentially pass through No. 8, No. 7, No. 6, after No. 5 low-pressure heaters, Become feedwater in oxygen-eliminating device after deoxygenation heating, then sequentially pass through No. 3, No. 2, No. 1 high-pressure heater entrance boiler side economizer.Figure 2 is No. 1 high-pressure heater structural representation.In aqueous phase working medium is entered heater by aqueous phase working medium entrance, heat exchanger tube changes with steam Heat, discharges heater from aqueous phase sender property outlet after being heated to uniform temperature and enters next heater；At different levels draw gas by drawing gas Entrance enter heater, and from a upper heater hydrophobic together with aqueous phase working medium heat exchange in heat exchanger tube, be cooled to supercool Water is discharged by hydrophobic outlet.

Now it is described as a example by No. 1 high-pressure heater, said method comprising the steps of:

Step one, obtain from the real-time data base running No. 2 unit DCS control systems and obtain given time given time Under each high-pressure heater and low-pressure heater extraction entrance steam pressure, temperature, drain temperature, aqueous phase sender property outlet temperature, solidifying Bear water mass flow, pressure, temperature, the flow of economizer entrance feedwater, pressure and temperature；

Step 2, combine working medium physical parameter storehouse, according to each heater water side and the energy balance relations of vapour side, it is thus achieved that each The mass flow On-line Estimation value of drawing gas of heater.The energy balance relations of each heater water side and vapour side is:

D_cq(h_cq-h_ss)+D_sspre(h_sspre-h_ss)=D_w(h_outs-h_ins) (1)

Wherein, D_cqIt is mass flow of drawing gas, kg/s；h_cqIt is the specific enthalpy of heater extraction entrance, kJ/kg；h_ssIt it is hydrophobic outlet Specific enthalpy, kJ/kg；D_sspreIt is the mass flow of a upper heater condensate, kg/s；h_sspreIt it is the ratio of a upper heater condensate Enthalpy, kJ/kg；D_wIt is the aqueous phase working medium mass flow by heater, kg/s；h_outsIt is that aqueous phase working medium is at heater outlet Specific enthalpy, kJ/kg；h_insIt is aqueous phase working medium specific enthalpy at calorifier inlets, kJ/kg.Calculate heater draw gas mass flow according to Each heater order that aqueous phase working medium flows through is carried out, and wherein before oxygen-eliminating device, the aqueous phase working medium of low-pressure heater is main condensate, After oxygen-eliminating device, the aqueous phase working medium of high-pressure heater is feedwater.

Step 3, for No. 1 high-pressure heater, plunder staggered tubes bundle owing to steam is horizontal, according to steam side reynolds number Re_sAnd phase Adjacent tube bank Transverse tube pitch d_hWith longitudinal pipe spacing d_v, the outer steam side convection transfer rate α of heat exchanger tube₁Computational methods for (to see Yang Shiming, inscription on pottery select. thermal conduction study (fourth edition). Higher Education Publishing House, 2010,259-262):

${\mathrm{\α}}_1=0.35{\left(\frac{d_h}{d_v}\right)}^{0.2}{\mathrm{Re}}_s^{0.6}{\mathrm{Pr}}_s^{0.36}{\left(\frac{{\mathrm{Pr}}_s}{{\mathrm{Pr}}_w}\right)}^{0.25}---\left(2\right)$

In formula, Pr_sAnd Pr_wIt is steam side and the Prandtl number of aqueous phase working medium.Fluid Reynolds number and the calculating side of Prandtl number Method is:

$\mathrm{Re}=\frac{\mathrm{\ρ}du}{\mathrm{\μ}}---\left(3\right)$

$\mathrm{Pr}=\frac{c\mathrm{\μ}}{\mathrm{\λ}}---\left(4\right)$

In formula, ρ is the density of fluid, kg/m³；U is the flow velocity of fluid, m/s；μ is the viscosity of fluid, Pa s；λ is stream The thermal conductivity of body, W/ (m DEG C)；C is the specific heat capacity of fluid, kJ/ (kg DEG C)；

Owing in heat exchanger tube, the reynolds number Re of aqueous phase working medium meets turbulent-flow conditions, therefore aqueous phase working medium side convection transfer rate α₂Computational methods for (see Yang Shiming, inscription on pottery select. thermal conduction study (fourth edition). Higher Education Publishing House, 2010,259-262):

${\mathrm{\α}}_2=0.023\frac{\mathrm{\λ}}{d_i}{\mathrm{Re}}_w^{0.8}{\mathrm{Pr}}_w^{0.4}---\left(5\right)$

In formula, λ is the thermal conductivity of feedwater, W/ (m DEG C)；d_iIt is heat exchanger tube internal diameter, m；

In the case of true heat exchange, if heater pipe wall of heat exchange pipe dirtiness resistance is R_b, heater Composite Walls is:

$K=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+R_b+\frac{1}{{\mathrm{\α}}_2}}---\left(6\right)$

Therefore, when heater pipe wall of heat exchange pipe dirtiness resistance R_bWhen being 0, heater Composite Walls theoretical value K_lxFor:

$K_{lx}=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+\frac{1}{{\mathrm{\α}}_2}}---\left(7\right)$

Step 4, due to thermal capacity flow rate ratio0≤R≤1, according to the definition of heater heat exchange efficiency ε, can Deriving the heat exchange efficiency of heater in the case of true heat exchange it is:

$\mathrm{\ϵ}=\frac{D_{cq}{c}_{ph}(t_{cq}-t_{ss})}{D_{cq}{c}_{ph}(t_{cq}-t_{ins})}=\frac{t_{cq}-t_{ss}}{t_{cq}-t_{ins}}---\left(8\right)$

Wherein, D_cqIt is mass flow of drawing gas, kg/s；c_phAnd c_pcIt is the flat of the outer steam of heater heat exchanger tube feedwater interior with pipe All specific heat capacity, kJ/ (kg DEG C)；t_cqIt is calorifier inlets extraction temperature, DEG C；t_ssIt is heater condensate outlet temperature, DEG C；t_ins It is calorifier inlets feed temperature, DEG C；

Make heater number of transfer unitsWherein, A is that heater surface amasss, m².Set up heater to change Thermal efficiency ε and number of transfer units NTU and the thermal capacity flow rate relation than R:

$\mathrm{\ϵ}=\frac{1-\exp \[-NTU(1-R)\]}{1-R\exp \[-NTU(1-R)\]}---\left(9\right)$

Owing in the case of true heat exchange situation and preferable heat exchange, R is constant, according to ε Yu R, the relation of NTU, when NTU maximum, ε is maximum.In heater actual motion, heater also exists certain performance degradation, and such as heater heat exchange tube wall incrustation, adds The reasons such as hot device heat exchanger tube blocking, make heater Composite Walls K and heat exchange area A less than theoretical value or design load.Therefore, exist In the case of preferable heat exchange, i.e. heater heat exchanger tube wall surface is clean, i.e. dirtiness resistance R_b=0, and the true heat-transfer surface of heater Long-pending equal to design load A_sjTime, the theoretical maximum of NTU is:

${\mathrm{NTU}}_{max}=\frac{K_{lx}{A}_{sj}}{D_w{c}_{pc}}---\left(10\right)$

Therefore, heater heat exchanger efficiency equation in the case of preferable heat exchange is set up:

${\mathrm{\ϵ}}_{lx}=\frac{t_{cq}-t_{ss\_lx}}{t_{cq}-t_{ins}}=\frac{1-\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}{1-R\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}---\left(11\right)$

Wherein, t_{ss_lx}It is heater condensate outlet temperature theoretical value, DEG C.Can solve:

$t_{ss\_lx}=t_{cq}-\frac{1-\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}{1-R\exp \[-{\mathrm{NTU}}_{max}(1-R)\]}(t_{cq}-t_{ins})---\left(12\right)$

According to lower end difference definition, i.e. lower end poor=heater condensate outlet temperature-heater aqueous phase working medium inlet temperature, Should reach value in line computation heater lower end difference is:

t_dt=t_{ss_lx}-t_ins (13)

Step 5, in the case of preferable heat exchange, heater self-energy equilibrium relation is:

D_cq(h_cq-h_{ss_lx})=D_wc_pc(t_{outs_lx}-t_ins) (14)

Wherein, h_{ss_lx}It is according to t_{ss_lx}Calculated heater outlet hydrophobic specific enthalpy theoretical value, kJ/kg；t_{outs_lx}It it is heating Device feedwater outlet temperature theoretical value, DEG C.Can solve:

$t_{outs\_lx}=\frac{D_{cq}(h_{cq}-h_{ss\_lx})}{D_w{c}_{pc}}+t_{ins}---\left(15\right)$

According to upper end difference definition, i.e. upper end poor=extraction pressure under saturated-steam temperature-aqueous phase sender property outlet temperature, Line computation heater upper end difference should reach value and be:

t_tt=t_bq-t_{outs_lx} (16)

Use the present invention above-mentioned heater full working scope upper end difference and lower end difference should reach the On-line Estimation method of value, obtain and implement Upper end difference under No. 1 high-pressure heater of example unit different load on August 2nd, 2013 should reach value.Fig. 3 is on No. 1 high-pressure heater End difference t_tIndirect measurement and upper end difference should reach value t_ttEstimated result.From the figure 3, it may be seen that owing to heater exists certain property Can degenerate, make the number of transfer units of heater be unable to reach theoretical maximum, aqueous phase sender property outlet temperature is unable to reach theoretical value, Cause upper end difference slightly above upper end difference should reach value.Fig. 4 is No. 1 high-pressure heater lower end difference t_dIndirect measurement and lower end difference should Reach value t_dtEstimated result.In like manner, as shown in Figure 4 due to the performance degradation of heater, hydrophobic outlet temperature is unable to reach theory Hydrophobic outlet temperature, causes heater lower end difference slightly above lower end difference should reach value.

Present invention achieves full working scope heater upper end difference and should reach value and lower end difference should reach the On-line Estimation of value, and then can divide Analysis heater upper end difference and the impact on unit heat economy of the lower end difference, provide for regenerative steam system thermal economy real-time assessment Supporting condition.

Above the specific embodiment of the present invention is described.It is to be appreciated that the invention is not limited in above-mentioned Particular implementation, those skilled in the art can make various deformation or amendment within the scope of the claims, this not shadow Ring the flesh and blood of the present invention.

Claims (4)

1. a heater full working scope upper end difference and lower end difference should reach the On-line Estimation method of value, it is characterised in that described method Comprise the following steps:

Step one, from the DCS dcs real-time data base of operating unit scene, obtain each heater under given time The pressure of extraction entrance, temperature, drain temperature, aqueous phase sender property outlet temperature, condense water quality flow, pressure, temperature, economizer Entrance feed-water quality flow, pressure, temperature；

Step 2, combine working medium physical parameter storehouse, draw gas in the energy balance relations of working medium, i.e. heater according in each heater The heat of release is equal to, plus the heat of the hydrophobic release from a upper heater, the heat that aqueous phase working medium absorbs, it is thus achieved that respectively add The mass flow On-line Estimation value of drawing gas of hot device, calculates thermal capacity flow rate ratio in step 4；

In the case of step 3, the calculating true heat exchange of heater, the outer steam side convection transfer rate α of heat exchanger tube₁With aqueous phase in heat exchanger tube Working medium side convection transfer rate α₂, and obtain heat exchanging pipe wall dirtiness resistance R in heater_bIt it is heater when zero total heat exchange system Number theoretical value K_lx, in step 4, calculate the theoretical maximum of number of transfer units；

Step 4, based on thermal capacity flow rate ratio and the theoretical maximum of number of transfer units, set up heater in the case of preferable heat exchange Heat exchanger efficiency equation, calculates heater condensate outlet temperature theoretical value, and then is defined by lower end difference, be calculated heater online Lower end difference should reach value；

Step 5, according to the energy balance relations in the case of heater ideal heat exchange, in the case of i.e. preferable heat exchange, take out in heater The heat of vapour release is equal to, plus the heat of the hydrophobic release from a upper heater, the heat that aqueous phase working medium absorbs, and calculating adds Hot device aqueous phase sender property outlet temperature theoretical value, and defined by upper end difference, it is calculated heater upper end difference online and should reach value.

2. the On-line Estimation side of value should be reached according to a kind of heater full working scope upper end difference described in claim 1 and lower end difference Method, it is characterised in that in step 3, according to the outer steam side convection transfer rate α of heater heat exchanger tube₁With aqueous phase work in heat exchanger tube Matter side convection transfer rate α₂, calculate in the case of true heat exchange, when heater pipe wall of heat exchange pipe dirtiness resistance is R_bTime, add Hot device Composite Walls K is:

$K=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+R_b+\frac{1}{{\mathrm{\α}}_2}}---\left(1\right)$

Therefore, when heater pipe wall of heat exchange pipe dirtiness resistance R_bWhen being zero, heater Composite Walls theoretical value K_lxFor:

$K_{lx}=\frac{1}{\frac{1}{{\mathrm{\α}}_1}+\frac{1}{{\mathrm{\α}}_2}}---\left(2\right).$

3. the On-line Estimation side of value should be reached according to a kind of heater full working scope upper end difference described in claim 1 and lower end difference Method, it is characterised in that in step 4, thermal capacity flow rate ratio0≤R≤1, according to determining of heater heat exchange efficiency ε Justice, in the case of deriving true heat exchange, heater heat exchange efficiency ε is:

$\mathrm{\ϵ}=\frac{D_{cq}{c}_{ph}(t_{cq}-t_{ss})}{D_{cq}{c}_{ph}(t_{cq}-t_{ins})}=\frac{t_{cq}-t_{ss}}{t_{cq}-t_{ins}}---\left(3\right)$

Wherein, D_wIt is aqueous phase working medium mass flow, kg/s；D_cqIt is mass flow of drawing gas, kg/s；c_phAnd c_pcIt it is heater heat exchanger tube The mean specific heat of aqueous phase working medium, kJ/ (kg DEG C) in outer steam and pipe；t_cqIt is calorifier inlets extraction temperature, DEG C；t_ssIt is Heater condensate outlet temperature, DEG C；t_insIt is calorifier inlets aqueous phase Temperature of Working, DEG C；

Make heater number of transfer unitsWherein, A is that heater surface amasss, m²；Heater heat exchange efficiency ε with Number of transfer units NTU and the thermal capacity flow rate relation than R be:

$\mathrm{\ϵ}=\frac{1-\exp \[-NTU\left(1-R\right)\]}{1-R\exp \[-NTU\left(1-R\right)\]}---\left(4\right)$

According to ε Yu R, the relation of NTU, owing in the case of true heat exchange situation and preferable heat exchange, R is constant, therefore when NTU maximum, ε is maximum；In heater actual motion, heater also exists certain performance degradation, makes the Composite Walls K of heater and changes Hot side amasss A and is less than theoretical value or design load, and therefore, in the case of preferable heat exchange, i.e. heater heat exchanger tube wall surface is clean, dirt Thermal resistance R_bSituation without exception in=0, and heater, true heat exchange area is equal to design load A_sjTime, the theoretical maximum of NTU For:

${\mathrm{NTU}}_{max}=\frac{K_{lx}{A}_{sj}}{D_w{c}_{pc}}---\left(5\right)$

K_lxFor heater Composite Walls theoretical value, now, in the case of preferable heat exchange, calculated heater upper end difference is i.e. Value should be reached for upper end difference；

Heater heat exchanger efficiency equation in the case of the preferable heat exchange of foundation:

${\mathrm{\ϵ}}_{lx}=\frac{t_{cq}-t_{ss\_lx}}{t_{cq}-t_{ins}}=\frac{1-\exp \[-{\mathrm{NTU}}_{\max }\left(1-R\right)\]}{1-R\exp \[-{\mathrm{NTU}}_{\max }\left(1-R\right)\]}---\left(6\right)$

Wherein, t_{ss_lx}It is heater condensate outlet temperature theoretical value, DEG C, solve:

$t_{ss\_lx}=t_{cq}-\frac{1-\exp \[-{\mathrm{NTU}}_{\max }\left(1-R\right)\]}{1-R\exp \[-{\mathrm{NTU}}_{\max }\left(1-R\right)\]}\left(t_{cq}-t_{ins}\right)---\left(7\right)$

According to lower end difference definition, i.e. lower end poor=heater condensate outlet temperature-heater aqueous phase working medium inlet temperature, obtain Heater lower end difference should reach value t_dtFor:

t_dt=t_{ss_lx}-t_ins (8)。

4. the On-line Estimation side of value should be reached according to a kind of heater full working scope upper end difference described in claim 1 and lower end difference Method, it is characterised in that in step 5, in the case of preferable heat exchange, heater self-energy equilibrium relation is:

D_cq(h_cq-h_{ss_lx})+D_sspre(h_sspre-h_{ss_lx})=D_wc_pc(t_{outs_lx}-t_ins) (9)

Wherein, h_{ss_lx}It is according to t_{ss_lx}Calculated heater outlet hydrophobic specific enthalpy theoretical value, kJ/kg；t_{outs_lx}It it is heating Device aqueous phase sender property outlet temperature theoretical value, DEG C, D_sspreIt is a upper heater condensate mass flow, kg/s；h_sspreIt it is upper one Heater condensate specific enthalpy, kg/s；

Solve:

$t_{outs\_lx}=\frac{D_{cq}(h_{cq}-h_{ss\_lx})+D_{sspre}(h_{sspre}-h_{ss\_lx})}{D_w{c}_{pc}}+t_{ins}---\left(10\right)$

According to upper end difference definition, i.e. upper end poor=extraction pressure under saturated-steam temperature-aqueous phase sender property outlet temperature, can obtain Should reach value to heater upper end difference is:

t_tt=t_bq-t_{outs_lx} (11)。