CN104764504A - Flow augmenting method of saturated and superheated steam - Google Patents

Abstract

The invention relates to a flow augmenting method of saturated and superheated steam. The method comprises the following steps: 1) dividing the steam into a plurality of temperature intervals according to a common temperature range, wherein each temperature interval corresponds to a temperature augmenting factor r (T, P[0])/r (T[0], P[0]); dividing the steam into a plurality of pressure intervals according to a common pressure range, wherein each pressure interval corresponds to a pressure augmenting factor r (T[0], P)/r (T[0], P[0]); 2) determining the temperature interval of the steam according to the temperature value of the practical steam, selecting the corresponding temperature augmenting factor, determining the pressure interval of the steam according to the pressure value of the practical steam, and selecting a corresponding pressure augmenting factor; calculating the augmented steam flow by using a formula: FORMULA. Compared with the prior art, the method provided by the invention has the beneficial effects: 1) an ideal gas equation density augmenting formula generally adopted by an existing steel enterprise can be completely replaced to greatly reduce the data storage amount and calculation amount, and is likely to be simply implemented to an industrial PLC (Programmable Logic Controller) or a DCS (Data Communication System) controller; 2) the steam measurement error can be reduced, and the steam metering precision can be improved.

Description

A kind of flow correction method of saturated and superheated vapor

Technical field

The present invention relates to steam flow measuring and calculating technical field, particularly relate to a kind of flow correction method of saturated and superheated vapor.

Background technology

Energy measurement is the important indicator of national economic accounting and commercial production metering.In industrial processes, conventional steam realizes generating, technological process such as insulation heating, heating etc. as medium.And the accuracy of steam measurement is related to energy settlement, energy quality and industrial processes index between level of factory, enterprise, be extremely important; On the one hand, in some process control process, as power plant boiler equipment, the flow of steam is the important parameter participating in control directly; On the other hand, user and energy producing unit usually need the use amount or the turnout that correct, check steam; Thus the metering of steam flow becomes the problem that domestic and international industry member is particularly paid close attention to.

Steam is as actual gas, its flow rate calculation and general gas flow and ideal gas completely different, carrying out correction for the steam flow recorded by flow monitoring device is a very loaded down with trivial details and complicated computation process, very big owing to calculating data volume, general controller is difficult to implement.General enterprises is for correction many employings equation for ideal gases of superheat steam flow, and superheated vapor is not ideal gas, uses existing correction method obviously unreasonable.Especially for temperature, saturated and superheated vapor that pressure is higher, the flow error adopting current correction method to calculate is very large.

Once put into effect the density criterion of IFC1967 superheated vapor in the world, but be limited to industrial computer level, do not apply in the flow correction of industrial steam, not a kind of unified standard that saturated and superheat steam flow are calculated of current domestic enterprise.

Summary of the invention

The invention provides a kind of flow correction method of saturated and superheated vapor, according to the inherent characteristic of processing medium steam and the density meter of IFC1967 water and steam, set up the two dimensional model of vapor (steam) temperature and pressure, two-dimentional segmentation correction is carried out to steam flow, computation process is simple, be easy to realize commercial Application, and the precision of steam measurement can be improved.

In order to achieve the above object, the present invention realizes by the following technical solutions:

A flow correction method for saturated and superheated vapor, comprises the steps:

1) steam is divided into multiple temperature range by conventional temperature range, each temperature range corresponding temperature augmenting factor r (T, a P ₀)/r (T ₀, P ₀); Steam is divided into multiple pressure range by wirking pressure scope, the corresponding pressure correction coefficient r (T of each pressure range ₀, P) and/r (T ₀, P ₀); Wherein r (T, P ₀) under design pressure, temperature is the vapour density of actual temperature T; R (T ₀, P) and under design temperature, pressure is the vapour density of actual pressure P; R (T ₀, P ₀) be the vapour density under design temperature, pressure;

2) determine the temperature range at its place according to the temperature value of actual steam, and select corresponding temperature augmenting factor, determine the pressure range at its place according to the force value of actual steam, and select corresponding pressure correction coefficient; Utilize formula: calculate the steam flow after correction; In formula: Fw is the steam flow after correction; Flow is the steam flow of non-correction.

Temperature augmenting factor and pressure correction coefficient are stored in DCS or PLC respectively, steam flow is revised in real time.

It is 130 DEG C ~ 310 DEG C that described steam commonly uses temperature range, is divided at least 11 temperature ranges.

Described vapor pressure usual range is 0 ~ 0.8MPa, is divided at least 9 pressure ranges.

Compared with prior art, the invention has the beneficial effects as follows:

1) the approximate ideal gas equation density correction formula that current iron and steel enterprise can be replaced completely generally to adopt, greatly reduces memory data output and calculated amount, and application is simple, is easy to implement in industrial PLC or DCS controller;

2) reduce the error of vapour survey, improve the precision of steam measurement; And can the accuracy requirement of correction and the processing power of DCS or PLC as required, expand or reduce the scope of piecewise interval, thus change the precision of correction, realize more preferably steam flow correction.

Accompanying drawing explanation

Fig. 1 is the process flow diagram that the DCS of utilization of the present invention or PLC carries out steam flow correction.

Embodiment

The flow correction method of a kind of saturated and superheated vapor of the present invention, comprises the steps:

1) steam is divided into multiple temperature range by conventional temperature range, each temperature range corresponding temperature augmenting factor r (T, a P ₀)/r (T ₀, P ₀); Steam is divided into multiple pressure range by wirking pressure scope, the corresponding pressure correction coefficient r (T of each pressure range ₀, P) and/r (T ₀, P ₀); Wherein r (T, P ₀) under design pressure, temperature is the vapour density of actual temperature T; R (T ₀, P) and under design temperature, pressure is the vapour density of actual pressure P; R (T ₀, P ₀) be the vapour density under design temperature, pressure;

2) determine the temperature range at its place according to the temperature value of actual steam, and select corresponding temperature augmenting factor, determine the pressure range at its place according to the force value of actual steam, and select corresponding pressure correction coefficient; Utilize formula: calculate the steam flow after correction; In formula: Fw is the steam flow after correction; Flow is the steam flow of non-correction.

Temperature augmenting factor and pressure correction coefficient are stored in DCS or PLC respectively, steam flow is revised in real time.

It is 130 DEG C ~ 310 DEG C that described steam commonly uses temperature range, is divided at least 11 temperature ranges.

Described vapor pressure usual range is 0 ~ 0.8MPa, is divided at least 9 pressure ranges.

A kind of flow correction method that is saturated and superheated vapor of the present invention is realized by following derivation:

One, for steam flow, the first the flow correction formula drawn by discharge orifice flowmeter calculation formula is:

$\mathrm{Fw}=k\·\sqrt{\mathrm{\ΔP}\·\mathrm{\ρ}}---(1-1)$

The wherein mass rate of Fw-actual steam; K-coefficient of colligation; Δ P-orifice plate both sides differential pressure value; ρ is vapour density.

Visible, by throttling orifice plate flow rate calculation formula flow measurement process, during by differential pressure signal reduced discharge, flow is relevant with fluid density.

Two, the Ideal-Gas Equation formula is adopted to carry out Fluid Computation density, i.e. PV=nRT; And can P be derived by equation for ideal gases R=ρ V/T and ρ=M/V ₀v ₀/ T ₀=P ₁v ₁/ T, and then derive:

ρ ₁/ρ ₀＝P ₁T ₀/P ₀T ₁(1-2)

By formula (1-2), and after same dimension uniform units:

${\mathrm{\ρ}}_1/{\mathrm{\ρ}}_0=\sqrt{\frac{P+1.01}{P_0+1.01}\·\frac{T_0+273}{T+273}}---(1-3)$

Can be obtained by hole plate calculation formula (1-1):

$F_w/\mathrm{Flow}=\sqrt{{\mathrm{\ρ}}_1/{\mathrm{\ρ}}_0}---(1-4)$

In formula: the steam flow of Flow-non-correction; (design temperature T ₀, design pressure P ₀under steam flow)

Actual steam flow after Fw-correction; (actual temperature T ₁, actual pressure P ₁under steam flow)

ρ ₀-design temperature T ₀, design pressure P ₀under vapour density;

ρ ₁-actual temperature T ₁, actual pressure P ₁under vapour density;

By formula (1-3) and (1-4), namely draw the correction of the second steam flow, i.e. equation for ideal gases correction flow formula:

$F_w=\sqrt{\frac{P+1.01}{P_0+1.01}\·\frac{T_0+273}{T+273}}\·\mathrm{Flow}---(1-5)$

Three, above formula carried out processing and derive a kind of formula being suitable for vapor quality;

Make r (T ₀, P ₀)=ρ ₀, r (T, P)=ρ, wherein ρ ₀for design density, ρ ₁for actual density;

Formula (1-5) is deformed into following formula:

$F_w/\mathrm{Flow}=\sqrt{\frac{{\mathrm{\ρ}}_1\·{\mathrm{\ρ}}_0}{{\mathrm{\ρ}}_0\·{\mathrm{\ρ}}_0}}=\sqrt{\frac{r(T_1,P_1)\·r(T_0,P_0)}{r(T_0,P_0)\·r(T_0,P_0)}}---(2-1)$

Formula (1-3) is substituted into formula (2-1) and derives:

$\sqrt{\frac{{\mathrm{\ρ}}_1\·{\mathrm{\ρ}}_0}{{\mathrm{\ρ}}_0\·{\mathrm{\ρ}}_0}}=\sqrt{\frac{r(T_1,P_1)\·r(T_0,P_0)}{r(T_0,P_0)\·r(T_0,P_0)}}=\sqrt{\frac{P+1.01}{P_0+1.01}\·\frac{T_0+273}{T+273}\·\frac{P_0+1.01}{P_0+1.01}\·\frac{T_0+273}{T_0+273}}$

By the factor (T in denominator term ₀+ 273) obtain with the factor (T+273) transposition:

$=\sqrt{(\frac{P+1.01}{P_0+1.01}\·\frac{T_0+273}{T_0+273})\·(\frac{P_0+1.01}{P_0+.1.01}\·\frac{T_0+273}{T+273})}=\sqrt{\frac{r(T_0,P)}{r(T_0,P_0)}\·\frac{r(T,P_0)}{r(T_0,P_0)}}$

Thus, final steam flow correction formula can be drawn:

$F_w=\sqrt{\frac{r(T_0,P)}{r(T_0,P_0)}\·\frac{r(T,P_0)}{r(T_0,P_0)}}\·\mathrm{Flow}---(2-2)$

R (T ₀, P) to fix for temperature one, pressure is the vapour density of actual pressure P;

R (T, P ₀) fix for pressure one, temperature is the vapour density of actual temperature T;

R (T ₀, P ₀) be the vapour density under design temperature, pressure;

P ₀, T ₀be respectively design pressure and design temperature;

Flow is the steam flow of non-correction;

F _wfor the actual steam flow after correction;

Flow augmenting factor is split as by the present invention with two coefficients are respectively to steam flow correction; Wherein r (T ₀, P) and/r (T ₀, P ₀) be pressure correction coefficient, r (T, P ₀)/r (T ₀, P ₀) be temperature augmenting factor.

With vapor (steam) temperature usual range 130 DEG C ~ 310 DEG C, vapor pressure usual range 0 ~ 0.8MPa is example, according to formula (4-2), vapor pressure is divided into 9 intervals, and vapor (steam) temperature is divided into 11 intervals and sets up two dimensional model, and by pressure correction coefficient with temperature correcting system list according to interval respectively, specifically see the following form:

Vapor pressure and the interval correction model of temperature section (pressure unit MPa; Temperature unit DEG C) (table 1)

According to upper table, the operating mode actual pressure as correction steam flow is 0.75MPa, and temperature is 300 DEG C, i.e. vapor pressure

In interval (0.7 ~ 0.8), temperature is in interval (290 ~ 310), then correction flow rate calculation formula is:

$F_w=\sqrt{\frac{r(T_0,P_{0.7-0.8})}{r(T_0,P_0)}\·\frac{r(T_{290-310},P_0)}{r(T_0,P_0)}}\·\mathrm{Flow}$

Wherein r (T ₀, p _0.7-0.8) be under design temperature, pressure is respectively vapour density linear interpolation during 0.7MPa and 0.8MPa, r (T _290-310, P ₀) be under design pressure, the linear interpolation of vapour density when temperature is respectively 290 DEG C and 310 DEG C, r (T ₀, P ₀) be the linear interpolation of the vapour density under design temperature, pressure.As can be seen here, the steam flow precision of application measured by the method for the invention is relevant to interval division fine degree, and interval division must be thinner, and namely temperature and pressure value interval is less, then the steam flow after correction is more close to actual steam flow.But by the needs of on-the-spot practical application, consider input cost, interval division can find an optimal balance point according to actual conditions simultaneously.

Seeing Fig. 1, is the process flow diagram that the DCS of utilization of the present invention or PLC carries out steam flow correction.To be stored in DCS or PLC respectively by the pressure correction coefficient after Concourse Division and temperature augmenting factor, after gathering the actual pressure value of steam and temperature value, determine pressure range and the temperature range at steam place, and inquire about pressure correction coefficient and temperature augmenting factor respectively, finally calculating correction is carried out online to the actual steam analog value collected, the steam flow after correction can be obtained.

Following examples are implemented under premised on technical solution of the present invention, give detailed embodiment and concrete operating process, but protection scope of the present invention are not limited to following embodiment.In following embodiment, method therefor is conventional method if no special instructions.

Obtained pressure correction coefficient and the temperature augmenting factor of each temperature and pressure scope by vapor (steam) temperature and pressure correction model and steam flow correction formula respectively, see the following form:

(table 2)

[embodiment 1]

Vapor pressure 0.15MPa, temperature is respectively 145 DEG C, 162 DEG C, 174 DEG C, 185 DEG C, 200 DEG C, 300 DEG C.Tabling look-up 2, can to obtain pressure correction coefficient be 0.405, in like manner can obtain temperature augmenting factor, see the following form:

[embodiment 2]

Vapor pressure 0.5MPa, temperature is respectively 145 DEG C, 162 DEG C, 174 DEG C, 185 DEG C, 200 DEG C, 300 DEG C.Tabling look-up 2, can to obtain pressure correction coefficient be 1.00, in like manner can obtain temperature augmenting factor, see the following form:

[embodiment 3]

Vapor pressure 0.75MPa, temperature is respectively 145 DEG C, 162 DEG C, 174 DEG C, 185 DEG C, 200 DEG C, 300 DEG C.Tabling look-up 2, can to obtain pressure correction coefficient be 1.432, in like manner can obtain temperature augmenting factor, see the following form:

Carry out error analysis to above three groups of data can obtain: relative to error E r=Ea/T × 100% ≈ 0.43% of the true actual density value of steam; The temperature, pressure correction precision of steam flow is higher.

Note: steam actual density value is checked in by the character of international association formulism IFC97 water and steam.

Claims (4)

1. a flow correction method for saturated and superheated vapor, is characterized in that, comprise the steps:

1) steam is divided into multiple temperature range by conventional temperature range, each temperature range corresponding temperature augmenting factor r (T, a P ₀)/r (T ₀, P ₀); Steam is divided into multiple pressure range by wirking pressure scope, the corresponding pressure correction coefficient r (T of each pressure range ₀, P) and/r (T ₀, P ₀); Wherein r (T, P ₀) under design pressure, temperature is the vapour density of actual temperature T; R (T ₀, P) and under design temperature, pressure is the vapour density of actual pressure P; R (T ₀, P ₀) be the vapour density under design temperature, pressure;

2) determine the temperature range at its place according to the temperature value of actual steam, and select corresponding temperature augmenting factor, determine the pressure range at its place according to the force value of actual steam, and select corresponding pressure correction coefficient; Utilize formula:

calculate the steam flow after correction; In formula: Fw is the steam flow after correction; Flow is the steam flow of non-correction.

2. the flow correction method of a kind of saturated and superheated vapor according to claim 1, is characterized in that, temperature augmenting factor and pressure correction coefficient are stored in respectively in DCS or PLC, revise in real time steam flow.

3. the flow correction method of a kind of saturated and superheated vapor according to claim 1, it is characterized in that, it is 130 DEG C ~ 310 DEG C that described steam commonly uses temperature range, is divided at least 11 temperature ranges.

4. the flow correction method of a kind of saturated and superheated vapor according to claim 1, it is characterized in that, described vapor pressure usual range is 0 ~ 0.8MPa, is divided at least 9 pressure ranges.