RU2757521C1 - System and method for regulating fuel consumption for steam boiler - Google Patents

Abstract

FIELD: steam boiler units.

SUBSTANCE: invention relates to the regulation of steam boiler units and can be applied in automation systems for regulating fuel consumption for a steam boiler. An automated system and method for regulating fuel consumption, according to which they provide constant measurement of flow parameters, pressure and temperature of steam from the boiler, pressure and temperature of feed water to the boiler and pressure Psc the point of connection of each of the boilers to the general station steam collector of the TPP. Such a regulating effect on the fuel supply feeders is developed with the help of a fuel consumption regulator in order to maintain the balance of the specified and consumed heat of fuel combustion for the production of steam heat at the outlet of the boiler in the basic mode, or the balance of the specified and expended heat of fuel combustion for the production of steam heat consumed at the point of connection of the boiler to the general station steam collector of the TPP, in the regulating mode. In the basic operating mode of the boiler, the consumed heat Qpb of fuel combustion of a steam boiler is determined by the formula Q_bs = F_ds*(i_s(T_ds,P_ds)-i_fw(T_fw,P_fw)), the specified heat Q_gs of fuel combustion: Q_gs= F_gds*(i_ns(T_nds,P_nds)-i_nfw(T_nfw,P_nfw)). In the regulating mode, the consumed heat Q_rs = Fds*(i_rs1(T_ds,R_sc)-i_fw(T_fw,P_fw)), and the specified heat Q_ngs = F_ds*(i_rs2(T_nds,P_gsc)-i_nfw(T_nfw, P_nfw)).

EFFECT: higher precision of heat generation and less transport lag of the control action.

3 cl, 1 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to power engineering, in particular to the field of regulation of steam boiler units, and can be applied in automation systems for regulating fuel consumption for a steam boiler.

LEVEL OF TECHNOLOGY

In the field of management of thermal power plants (TPP) and industrial steam boiler houses, there is a relatively wide range of possible problems, such as increased fuel consumption for generating electricity and heat in heating networks; disconnection by operating personnel of proportional-integral-differentiating (PID) regulators due to the impossibility of maintaining automatic modes of changing the heat load and disconnecting automatic heat load regulators. At the same time, in order to solve these problems, in practice, it is relevant to regulate the fuel supply for a boiler or a boiler system.

Many methods known in the art to control fuel consumption for steam boilers are based on the heat balance equation of the system. So, according to one of the known methods of regulating the heat load of a steam boiler ("Automation of thermal power plants", Yu.M. Goldobin, E. Yu. Pavlyuk, Yekaterinburg: UrFU, 2017, hereinafter D1), regulation is proposed based on the difference in the current consumption of live steam and the set flow rate of live steam, corrected for the change in steam pressure in the boiler drum:

Z = F _op - (F _opz + C * dP _b / dt), where

Z - mismatch of the regulator,

F _op - current consumption of live steam,

F _opz - the specified consumption of live steam,

C - mass heat storage capacity of the steam-water mixture and metal of the evaporating part of the boiler,

P _b - steam pressure in the boiler drum.

Such a control system contains a heat load regulator, a steam flow sensor and a steam pressure sensor in the drum.

The regulator is made with the ability to generate a control action based on an indirect calculation of the heat load, in which a number of assumptions are made. So, in the balance equation, the flow rate of live steam from the boiler is taken to be equal to the flow rate of saturated steam from the boiler drum due to their approximate equality, and the system generates a regulating effect based on the "heat" signal, which is expressed in units of steam flow and does not depend on real changes in enthalpy live steam and enthalpy of feed water.

As a result of these assumptions, the regulation is carried out according to the steam flow rate and the change in pressure in the drum - values that only correlate with the true heat load and inaccurately reflect its change, which leads not only to inaccuracy of regulation, but also to an increase in transport lag. Errors in determining the heat load of the boiler due to the inaccuracy of its determination do not allow bringing the heat output of the boiler to the true value of the heat load. A significant negative factor in this case is that the temperature, pressure of the boiler feed water and the pressure in the general station steam collector of the TPP are variable quantities. Changes in these parameters and, as a consequence, changes in the enthalpy of feed water and enthalpy of steam from the boiler depend on many factors, for example, on changes in: the number of operating boilers, thermal load of TPPs, the number of feed water heaters, the number and characteristics of feed pumps, and the configuration of general station feed pipelines. Due to the fact that changes in enthalpy are not taken into account by known methods and control systems, these changes begin to be worked out by them not at the time of their occurrence. The fuel consumption to compensate for the excess or lack of produced heat begins to change with a transport delay only when the steam consumption from the boiler begins to change, and the rate of change in the steam pressure in the drum becomes higher than the sensitivity of the regulator differentiator.

Thus, a technical problem is the need to provide a system and method for regulating the fuel consumption for a steam boiler, which have a higher accuracy and the minimum possible transport delay in a wide range of changes in steam consumption for industrial and heating needs.

DISCLOSURE OF THE INVENTION

According to the present invention, a system and method for regulating the fuel consumption for steam boilers are proposed, which provide the technical result in the form of a higher accuracy of generating a control action and a smaller transport delay of the control action.

This technical result is achieved due to the fact that the proposed automated system for regulating fuel consumption for each of the steam boilers connected to the general station steam collector of the TPP, containing a microprocessor-based fuel consumption regulator and sensors for flow parameters, pressure and temperature of steam from the boiler, pressure and temperature sensors for feed water to the boiler and _{pressure sensors Р sk} at the point of connection of each of the boilers to the general station steam manifold of the TPP, and these sensors are functionally connected to the specified fuel consumption regulator, which is configured to generate such a regulating effect on the fuel supply feeders in order to maintain the balance of the specified and consumed heat fuel combustion for the production of steam heat at the outlet of the boiler in the basic operation of the boiler, or the balance of the specified and consumed heat of fuel combustion for the production of steam heat consumed at the point of connection of the boiler to the general station steam to the new collector of the TPP, in the regulating mode of the boiler. The specified or consumed heat is the product of the flow rate F _op steam from the boiler and the specified or consumed heat for the production of a unit of steam consumption, respectively. The specified or expended heat per unit of steam consumption is the difference between the enthalpy i _{p of} steam and feed water i _{pw of the} boiler, which is formed by the heat of the amount of fuel burned when the feed water is heated, vaporized and overheated.

According to the proposed invention in the basic mode of operation of the boiler

The consumed heat Q _pb of fuel combustion of a steam boiler is the product of the current flow rate F _{op of} steam from the boiler and the difference in enthalpy i _{p of} steam, calculated on the basis of the measured current temperature T _op and pressure P _{op of} steam from the boiler, and the enthalpy i _{pw of the} boiler feed water, calculated based on the measured current temperature T _pw and pressure P _{pw of} feed water: Q _pb = F _op * (i _p (T _op , P _op ) - i _pw (T _pw , P _pw )), and

the specified heat Q _pw of fuel combustion of a steam boiler is the product of the specified flow rate F _{ov of} steam from the boiler and the difference in enthalpy i _{pn of} steam, calculated on the basis of the nominal temperature T _nop and pressure P _{nop of} steam, and the enthalpy i _{pwn of the} boiler feed water, calculated on the basis of the nominal temperature T _pwn and pressure P _pwn feed water: Q _pz = F _pwn * (i _pn (T _pwn , P _pwn ) - i _pwn (T _pwn , P _pwn )), and

in regulatory mode

the heat expended Q _pr for the production of steam consumed at the point of connection of the steam boiler to the general station steam collector of the TPP is the product of the current flow rate F _op steam from the boiler and the difference in enthalpy i _pr1 steam calculated on the basis of the measured current temperature T _op steam from the boiler and pressure R _{sc of} steam in the general station steam header of the TPP, and enthalpy i _{pw of the} boiler feed water, calculated on the basis of the measured current temperature T _pw and pressure P _{pw of the} feed water: Q _pr = F _op * (i _pr1 (T _op , P _sk ) - i _pv (T _pv , P _pv )), and

the specified heat Q _pn for the production of steam consumed at the point of connection of the steam boiler to the general station steam header of the TPP is the product of the current flow rate F _{op of} steam from the boiler and the difference in enthalpy i _{pr2 of} steam, calculated on the basis of the nominal temperature T _{nop of} steam from the boiler and the specified pressure R _rms couple in common station steam header TPP, and the enthalpy i _DID boiler feed water, calculated on the basis of the nominal temperature T _DID and pressure P _DID feedwater: Q _PTZ = F _op * (i _np2 (T _ALD, R _rms) - i _MPP (T _pvn , P _pvn )).

In the standard operating scheme of a TPP with one boiler in a regulating mode, the preset steam pressure at the point of connection of the steam line from the boiler to the station header is equal to the nominal pressure _{Psc of} steam in the general station steam header of the TPP. However, if there are several boilers operating in a regulating mode and connected to the collector at different points, it can be different for these boilers due to the difference in steam flows from boilers to loads (collector effect). If necessary, equalization of the load on the control boilers is achieved by changing the P _rms for different control boilers. In this case, _Pscr decreases relative to the nominal steam pressure in the general station header for a more loaded boiler and / or increases for a less loaded one.

Due to the fact that the proposed system contains sensors for flow parameters, pressure and temperature of steam from the boiler, pressure and temperature sensors of feed water to the boiler and a pressure sensor in the general station steam manifold of the TPP, functionally connected to the fuel consumption regulator, and the control system is based on the method of direct calculation of the heat given or spent on the production of a unit of steam consumption, determined by the enthalpies of steam and feed water of the boiler together with the steam consumption at the temperature and pressure measured by the indicated sensors, it is possible to more accurately account for the specified and expended steam heat and their dynamics, which in turn allows for more accurate regulation of fuel consumption. At the same time, the change in heat due to a change in the steam consumption is taken into account in the change in the balance of the specified and consumed heat directly, based on its measured value, and changes in the temperatures and pressures of feed water and steam are taken into account in the balance indirectly, by calculating the physical characteristics (enthalpies) of these media. The proposed method, illustrated in the application for the example of a drum pulverized coal boiler in a TPP scheme with cross-links, is universal and can be successfully expanded to direct-flow boilers and boiler-turbine blocks and all types of fuels, the exact calculation of the calorific value of which is impossible due to the difficulties of measurement consumption and / or instability of the fuel composition.

BRIEF DESCRIPTION OF DRAWINGS

The description of the proposed technical solution is given below with reference to Fig., Which shows an example of the implementation of the proposed system for regulating the fuel consumption for a steam boiler.

CARRYING OUT THE INVENTION

According to the proposed technical solution, the automated system for regulating fuel consumption for a steam boiler contains sensors for the flow parameters F _op , pressure P _op and temperature T _op steam from the boiler, pressure sensors P _pv and temperature T _{pw of} feed water to the boiler and a sensor P _sc of steam pressure in the place of connection of the boiler to the general station steam manifold of the TPP, and these sensors are functionally connected to a microprocessor-based fuel flow controller, which is configured to generate a regulating effect on the fuel supply feeders. At the same time, according to the proposed technical solution, a direct calculation of the specified and consumed heat of the produced steam (heat output) of the boiler is provided.

The examples given in this description are based on the embodiments of the proposed technical solution, in which the fuel supply of the steam boiler is provided by the raw coal feeders. All the advantages of the present invention can be realized with various other features of the power supply and control of the steam boiler.

According to a preferred embodiment of the invention, the system and the corresponding method for regulating the fuel consumption operate as follows.

Microprocessor controller 1 receives signals from sensors of current parameters of pressure P _op , flow rate F _op and temperature T _{op of} live steam from the boiler and sensors of pressure P _pv and temperature T _{pv of} feed water to the boiler, as well as pressure P _{sc of} steam in the general station steam header of the TPP, calculates the enthalpy i _{p of} steam and feed i _pw water and the value of heat spent on steam production from the boiler for the basic mode according to the formula Q _pb = F _op * (i _p (T _op , P _op ) - i _pw (T _pw , P _pw ) ) or the value of the heat spent on the production of consumed steam at the point of connection of the boiler to the general station steam header of the TPP for the regulating mode according to the formula Q _pr = F _op * (i _pr1 (T _op , P _sk ) - * i _pv (T _pv , P _pv ) ). Enthalpy can be calculated using formulas known in the art.

Microprocessor-based controller 1 receives from its own virtual setpoints the set values for the flow rate F _{ov of} steam from the boiler and P _sr of the steam pressure at the point of connection of the boiler to the general station header of the TPP, the nominal pressure P _nop and the nominal temperature T _{nop of} steam from the boiler, the nominal pressure _Ppn and the nominal temperature T _pvn feed water to the boiler and performs calculation operations:

- nominal enthalpy i_Mon(T_nop, P_nop) steam from the boiler; and

- nominal enthalpy i _pwn (T _pwn , P _pwn ) feed water; and

- the current enthalpy i _pr1 (T _op , P _sk ) steam in the general station steam collector of the TPP, and

- enthalpy i _pr2 (T _nop , P _rms ) of steam for a given value of steam pressure in the general station steam collector of the TPP.

In the basic mode, the regulator calculates the value of the set heat for steam production from the boiler as Q _pz = F _opz * (i _pn (T _nop , P _nop ) - i _pvn (T _pvn , P _pvn )), and in the regulating mode, the value of the set heat at production of steam consumed at the point of connection of the boiler to the general station steam collector of the TPP as Q _pn = F _op * (i _pr2 (T _nop , R _skz ) - i _pvn (T _pvn , P _pvn )) _.

Based on the calculated values of the set or consumed heat, the discrepancy of the microprocessor controller Z is determined by the deviation from their balance: for the basic mode Z _b = Q _pz -Q _p = F _opz * (i _pn -i _pvn ) -F _op * (i _p -i _pv ), and for the regulating mode Z _p = Q _pn -Q _p = F _op * (i _pr2 -i _pvn ) -F _op * (i _pr1 -i _pv ). According to a preferred embodiment of the invention, the mismatch Z according to the standard PID control law causes the formation of an effect on the fuel supply mechanisms (raw coal feeders 2), which provides a decrease in their speed (coal supply) at negative Z or its increase at positive Z.

The proposed method and system, according to one of the embodiments, operate as follows.

In the basic mode, in the formula Z _b = Qpz-Q _p = F _opz * (i _pn -i _pvn ) -F _op * (i _p -i _pv ) at static equilibrium, a balance is observed between the specified and expended heat of fuel combustion.

An increase in the value of Q _p caused by:

- an increase in the consumed heat, in the produced unit of steam consumption due to a decrease in the temperature T _pw and / or pressure P _{pw of the} feed water, causing a decrease in the enthalpy i _{pw of the} feed water, or an increase in the temperature T _op and / or pressure P _op steam, causing an increase in enthalpy i _p pair; or

- increase in consumption F _op live steam

leads to imbalance, the value of the mismatch Z becomes negative, and the coal supply decreases, which leads to a decrease in the consumed heat of fuel combustion until the balance is restored and the static equilibrium of the regulator is restored.

A decrease in the value of Q _p caused by:

- a decrease in the consumed heat in the produced units of steam consumption due to an increase in the temperature T _pw and / or pressure P _{pw of the} feed water, causing an increase in the enthalpy i _{pw of the} feed water, or a decrease in the temperature T _op and / or pressure P _op steam, causing a decrease in the enthalpy i _n pair; or

- decrease in consumption F _op live steam

leads to imbalance, the value of the mismatch Z becomes positive, and as a result of the formation of the corresponding regulating effect, the coal supply increases, which leads to an increase in the consumed heat of fuel combustion until the balance and static equilibrium of the regulator are restored.

In the regulating mode, in the formula Z _p = Q _pn -Q _pr = F _op * (i _pr2 -i _pvn ) -F _op * (i _pr1 -i _pv ) at static equilibrium, a balance is observed between the specified and expended heat of fuel combustion.

An increase in the value of Q _pr caused by an increase in the consumed heat in units of steam consumption consumed at the point where the boiler is connected to the general station steam header of the TPP, due to a decrease in the temperature T _pw and / or pressure P _{pw of the} feed water, which causes a decrease in the enthalpy i _{pw of the} feed water or an increase temperature T _op and / or steam pressure P _sc , causing an increase in enthalpy i _pr1 steam,

leads to imbalance, the value of the mismatch Z becomes negative, and the coal supply decreases, which leads to a decrease in the consumed heat of fuel combustion until the balance is restored and the static equilibrium of the regulator is restored.

A decrease in the value of Q _pr , caused by a decrease in the consumed heat in units of steam consumption consumed at the point of connection of the boiler to the general station steam header of the TPP due to an increase in the temperature T _pw and / or pressure P _{pw of the} feed water, which causes an increase in the enthalpy i _{pw of the} feed water, or a decrease in temperature T _op and / or pressure P _{sc of} steam, causing a decrease in the enthalpy of steam,

leads to imbalance, the value of the mismatch Z becomes positive, and the coal supply increases, which leads to an increase in the consumed heat of fuel combustion until the balance and static equilibrium of the regulator are restored.

A decrease in pressure _Psc in the general station steam collector due to an increase in the thermal load of the TPP or a decrease in the flow rate F _op steam from the boiler causes a decrease in the current enthalpy i _pr1 steam in the station steam collector and leads to an imbalance, the value of the mismatch Z becomes positive, and the coal supply increases , which leads to an increase in the consumed heat of fuel combustion until the moment the balance is restored and the static equilibrium of the regulator is restored.

An increase in pressure P _ck in the general station steam collector due to a decrease in the thermal load of the TPP or an increase in the flow rate F _op steam from the boiler causes an increase in the current enthalpy i _pr1 steam in the general station steam collector and leads to a violation of the balance, the value of the mismatch Z becomes negative, and the coal supply decreases, which leads to a decrease in the consumed heat of fuel combustion until the moment the balance and static equilibrium of the regulator are restored.

Thus, according to the proposed invention, the regulation of fuel consumption is implemented, which reacts to changes in current indicators indicating a change in the internal energy of the coolant, takes into account the reduced pressure in the general station steam collector in the case of a group of boilers and is based on values directly proportional to the amount of heat.

According to the known methods and systems for regulating the heat load, the mismatch of the regulator does not contain dependencies on enthalpies, therefore, the regulating action begins to form only when the change in enthalpies leads to changes in the steam flow rate, that is, with an increased transport delay.

In this aspect, in contrast to the known methods and systems for regulating the fuel supply for steam boilers, according to the proposed invention, the direct and aggregate accounting of changing indicators from flow sensors F _op , pressure P _op and temperature T _op steam from the boiler, pressure sensors P _pv and the temperature _{Tpw of the} feed water to the boiler and the pressure _Psc at the point where the boiler is connected to the general station steam header of the TPP when forming a control action for the fuel supply devices, due to which it is possible to implement the regulation of the fuel supply with less transport lag and greater accuracy.

The embodiments of the invention presented here are only special cases given for a better explanation of the features of the proposed technical solution, and the proposed method and system for controlling the steam flow rate can be changed and modified within the scope of the claims.

Claims (17)

1. An automated system for regulating fuel consumption for each of the steam boilers connected to the general station steam manifold of the TPP, containing a microprocessor-based fuel consumption regulator and sensors for flow parameters, pressure and temperature of steam from the boiler, sensors for pressure and temperature of feed water to the boiler and pressure _{sensors Psc} at the point of connection of each of the boilers to the general station steam collector of the TPP, and these sensors are functionally connected to the specified fuel consumption regulator, characterized in that the fuel consumption regulator is configured to generate such a regulating effect on the fuel supply feeders in order to maintain the balance of the specified and consumed heat of fuel combustion for the production of steam heat at the outlet of the boiler in the basic operating mode of the boiler, or the balance of the specified and expended heat of fuel combustion for the production of steam heat consumed at the point of connection of the boiler to the general station steam collector of the TPP, in the regulating mode of the boiler, and in basic mode The consumed heat Q _pb of fuel combustion of a steam boiler is the product of the current flow rate F _{op of} steam from the boiler and the difference in enthalpy i _{p of} steam, calculated on the basis of the measured current temperature T _op and pressure P _{op of} steam from the boiler, and the enthalpy i _{pw of the} boiler feed water, calculated based on the measured current temperature T _pw and pressure P _pw feed water, and the specified heat Q _pw of fuel combustion of a steam boiler is the product of the specified flow rate F _{ov of} steam from the boiler and the difference in enthalpy i _{pn of} steam, calculated on the basis of the nominal temperature T _nop and pressure P _{nop of} steam, and the enthalpy i _{pwn of the} boiler feed water, calculated on the basis of the nominal temperature T _pwn and pressure P _pwn feed water, and in regulatory mode the heat expended Q _pr for the production of steam consumed at the point of connection of the steam boiler to the general station steam collector of the TPP is the product of the current flow rate F _op steam from the boiler and the difference in enthalpy i _pr1 steam calculated on the basis of the measured current temperature T _op steam from the boiler and pressure _Rsc steam in the general station steam header of the TPP, and enthalpy i _{pw of the} boiler feed water, calculated on the basis of the measured current temperature T _pw and pressure P _{pw of the} feed water, and the specified heat Q _pn for the production of steam consumed at the point of connection of the steam boiler to the general station steam header of the TPP is the product of the current flow rate F _{op of} steam from the boiler and the difference in enthalpy i _{pr2 of} steam, calculated on the basis of the nominal temperature T _{nop of} steam from the boiler and the specified pressure _{Rcr of} steam in the general station steam header of the TPP, and the enthalpy i _{pwn of the} boiler feed water, calculated on the basis of the nominal temperature T _pwn and pressure P _{pwn of the} feed water. 2. A method for regulating the fuel consumption for each of the steam boilers connected to the general station steam collector of the TPP, according to which provide constant measurement of parameters of flow rate, pressure and temperature of steam from the boiler, pressure and temperature of feed water to the boiler and pressure _Psc at the point of connection of each of the boilers to the general station steam header of the TPP; generate such a regulating effect on the fuel supply feeders using a fuel consumption regulator to maintain the balance of the specified and consumed heat of fuel combustion for the production of steam heat at the boiler outlet in the basic mode, or the balance of the specified and expended heat of fuel combustion for the production of steam heat consumed at the point of connection of the boiler to the general station steam collector of the TPP, in the regulating mode. 3. The method for regulating the fuel consumption according to claim 2, according to which in the basic mode The consumed heat of fuel combustion Q _{pb of the} steam boiler is the product of the current flow rate F _{op of} steam from the boiler and the difference in enthalpy i _{p of} steam, calculated on the basis of the measured current temperature T _op and pressure P _{op of} steam from the boiler, and the enthalpy i _{pw of the} boiler feed water, calculated based on the measured current temperature T _pw and pressure P _pw feed water, and The specified heat of fuel combustion _{Qpw of the} steam boiler is the product of the specified flow rate F _{ov of} steam from the boiler and the difference in enthalpy i _{pn of} steam, calculated on the basis of the nominal temperature T _nop and pressure P _{nop of} steam, and the enthalpy i _{pwn of the} boiler feed water, calculated on the basis of the nominal temperature T _pwn and pressure P _pwn feed water, and in regulatory mode the heat expended Q _pr for the production of steam consumed at the point of connection of the steam boiler to the general station steam collector of the TPP is the product of the current flow rate F _op steam from the boiler and the difference in enthalpy i _pr1 steam calculated on the basis of the measured current temperature T _op steam from the boiler and pressure _Rsc steam in the general station steam header of the TPP, and enthalpy i _{pw of the} boiler feed water, calculated on the basis of the measured current temperature T _pw and pressure P _{pw of the} feed water, and the specified heat for the production of steam consumed at the point of connection of the steam boiler to the general station steam header of the TPP, Q _pn is the product of the current flow rate F _{op of} steam from the boiler and the difference in enthalpy i _{pr2 of} steam, calculated on the basis of the nominal temperature T _{nop of} steam from the boiler and the specified pressure _{Rcr of} steam in the general station steam header of the TPP, and the enthalpy i _{pwn of the} boiler feed water, calculated on the basis of the nominal temperature T _pwn and pressure P _{pwn of the} feed water.

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