CN104676574B - Supercritical CFB Boiler main steam pressure control method based on the energy balance - Google Patents

Abstract

A kind of Supercritical CFB Boiler main steam pressure control method based on the energy balance, the method comprises the following steps: S1, main steam pressure deviation signal P of unit_T‑P_TSOutput signal A after PID regulator；S2, obtains steam turbine demand heat signal S3 by steam turbine energy demand models, obtains the heat signal S4 that boiler is provided that, steam turbine demand heat signal E by i.e. firing carbon mechanism model_RThe heat signal E being provided that with boiler_BAfter subtracting each other after PID regulator output signal C；S5, steam turbine demand heat signal E_RBeing multiplied by proportional gain k after to time diffusion, obtain output signal B, B with A, C are added and another rising exports boiler master；S6, controls main steam pressure according to boiler master output regulation coal-supplying amount.The present invention can improve the regulation quality of unit, improves the stability of Supercritical CFB Boiler main steam pressure control system, adapts to the ability of unit load responding.

Description

Supercritical CFB Boiler main steam pressure control method based on the energy balance

Technical field

The present invention relates to a kind of Supercritical CFB Boiler main steam pressure control method based on the energy balance, belong to boiler main steam Pressure Control Technology field.

Background technology

Be continuously increased the raising day by day with power network schedule automation degree along with large sized unit, it is desirable to large sized unit must by from Dynamic Generation Control (Automatic Generation Control；AGC) mode is run, and Power Plant coordinated control system is just carried by this Go out new requirement.For generating set, it is desirable to big fluctuation does not occur in controlled parameter, to ensure unit safety operation, I.e. stability should be preferential；For electrical network, for maintaining the quality of electric power system, overcome the shadow that electrical network is produced by load variations Ringing, the rapidity of generating set load responding should be preferential.For adapting to the requirement of electrical network, recirculating fluidized bed (Circulating Fluidized Bed；CFB) unit generally utilizes the accumulation of heat of boiler and the rapidity of steam turbine, change rapidly Steam Turhine Adjustment door and The measures such as boiler oil amount, improve the unit load responding ability to electrical network.Owing to the heat storage capacity of boiler is limited, dynamic mistake Journey is delayed, the most necessarily causes being widely varied of main steam pressure, load, temperature etc., produces unstable factor, affects machine The safety of group, economical operation, this is all unallowed in actual production.

By analysis, find to affect unit main steam pressure control quality and the factor of unit load variation response performance, mainly have Following several respects:

(1) CFB boiler response load variations delay characteristic.Required for change fuel quantity to steam flow starts to change Time, i.e. steam produce delay time longer compared with coal-powder boiler.Owing to CFB boiler does not has coal pulverizer, only coal breaker, because of This as-fired coal particle diameter bigger 0～8mm, the pure delay time is the longest, and 300MW CFB unit is about about 10min, 600MW CFB Unit is about about 18min.This is to affect the main cause that unit main steam pressure is unstable and load-response-speed is slow.

(2) when unit operation is in the sliding pressure stage, pressure must be risen again during unit load up, be unfavorable for the utilization to boiler heat storage, Have impact on the speed of load up；When unit operation is in fixed pressure operation mode, owing to being not related to boiler storage during load change The change of heat, for sliding pressure operation, the load-response-speed of unit is slower.

(3) CFB unit puts into after AGC, often occurs adding, main steam pressure fluctuation is excessive during load shedding, exits The situation that AGC and coordination control.On the one hand, cause owing to AGC operational percentage is defective power plant examined by electrical network, cause weight Big economic loss；On the other hand, main steam pressure fluctuation is excessive easily causes boiler superpressure even chaser, has a strong impact on unit Safe operation.

Above-mentioned analysis result is also verified in the research of Supercritical CFB Boiler and debugging, i.e. during unit lifting load, There will be that main steam pressure deviation is relatively big, load wild effect, so how during unit load regulates, keep steam ginseng Stablizing of number, is the key of unit operation quality.

The basic task of CFB boiler main steam pressure control is the need that the heat making fuel combustion be provided adapts to Boiler Steam load , safe and economical boiler to be ensured runs and environment protection standard requirement.The concrete control task of every boiler combustion process and Selecting of control strategy is otherwise varied because of the difference of fuel type, combustion apparatus and Boiler Operation, combustion control system Task mainly maintain stablizing of boiler main steam pressure.Boiler operatiopn must maintain superheater outlet vapour pressure, the change of vapour pressure Represent that the steam production of boiler is incompatible with the steam consumption of load, at this moment must change the supply of fuel accordingly, thus change Become the steam supply yield of boiler.Boiler operatiopn typically uses the deviation based on actual main steam pressure with setting main steam pressure of routine Carry out Limestone control, because the main steam pressure information delay time is oversize, it tends to be difficult to obtain satisfied Control platform.Work as master When steam pressure is reduced to the 95% of setting value, the steam consumption of power generator turbine will increase about 1%, when steam pressure is too high, A large amount of steam are discharged in steam turbine safety door action, also will result in Unit Economic loss, the most also can cause main steam enthalpy and temperature Larger fluctuation, the steam quality of steam turbine is sent in impact.Therefore, main steam to be ensured in supercritical CFB unit running process The smooth change of pressure, it is considered to by the characteristic research to unit, constructs key status parameters, needs to use new control strategy, Improve the regulation quality of unit, improve the stability of main steam pressure control system, adapt to the ability of unit load responding.

Summary of the invention

It is an object of the invention to, it is provided that a kind of Supercritical CFB Boiler main steam pressure control method based on the energy balance, energy Enough improve the regulation quality of unit, improve the stability of main steam pressure control system, adapt to the ability of unit load responding.

For solving above-mentioned technical problem, the present invention adopts the following technical scheme that:

A kind of Supercritical CFB Boiler main steam pressure control method based on the energy balance, comprises the following steps:

S1, main steam pressure deviation signal P of unit_T-P_TSOutput signal A after PID (proportional-integral-differential) actuator, wherein, P_TFor main steam pressure, P_TSFor main steam pressure setting value；

S2, obtains steam turbine demand heat signal by steam turbine energy demand modelsE_RFor the demand heat of steam turbine, P₁The heat that needed for representing steam turbine, steam flow is contained, dimension is MW, is worth P₁=k*p, p are pressure after Control Stage of Steam Turbine Power, MPa, k are pressure and the correction factor of heat after Control Stage of Steam Turbine, and dimension is MW/Mpa ", physical significance is unit The heat (MW) that steam pressure (MPa) contains；

S3, obtains, by i.e. firing carbon mechanism model, the heat signal that boiler is provided thatE_BCan provide for boiler Heat signal, the heat that the steam flow that D produced by the boiler unit interval is contained, MW, Q be in burner hearth storage i.e. Combustion carbon burning caloric value, C_BcFor i.e. firing the heat storage coefficient of carbon；

S4, steam turbine demand heat signal E_RThe heat signal E being provided that with boiler_BAfter subtracting each other, after PID regulator regulates, defeated Go out signal C；

S5, steam turbine demand heat signal E_RThrough to time diffusionAfter, be multiplied by the value of proportional gain k, obtain signal B, B, A and C is added and another rising exports boiler master；

S6, controls main steam pressure according to boiler master output regulation coal-supplying amount.

In aforesaid Supercritical CFB Boiler main steam pressure control method based on the energy balance, the i.e. combustion carbon machine in described step S3 Reason model isIn formula, Q (t) is the total amount of heat of burning release, and unit is MJ/s；B(t) For i.e. firing carbon amounts, unit is kg；PM (t) is total blast volume, and unit is Nm³/s；K is model overall coefficient；M_CFor carbon mole Quality, unit is kg/kmol；k_cBurn rate constant for carbon granule；d_cFor carbon granule average diameter, unit is m；ρ_c For the density of carbon granule, unit is kg/m³；H is the unit caloric value of fuel, and unit is MJ/kg；ko₂For total blast volume PM (t) With the correlation coefficient of oxygen concentration, R_cFor i.e. firing the burn rate of carbon, unit is kg/s.

In aforesaid Supercritical CFB Boiler main steam pressure control method based on the energy balance, the heat signal that boiler is provided thatIn formula, the heat that the steam flow that D produced by the boiler unit interval is contained, MW；C_BcFor i.e. The heat storage coefficient of combustion carbon；Q is the i.e. combustion carbon burning caloric value of the interior storage of burner hearth, and unit is MJ.

In aforesaid Supercritical CFB Boiler main steam pressure control method based on the energy balance, described C_BcIt is with momentum, institute State C_BcValue is 28～30 in low load stage 200MW～400MW, is 30～32 at high load capacity stage 400MW～600MW.

In aforesaid Supercritical CFB Boiler main steam pressure control method based on the energy balance, in described step S5, ratio Gain k span is 0.8～1.2.

In aforesaid Supercritical CFB Boiler main steam pressure control method based on the energy balance, the boiler in described step S6 Master control output is coal-supplying amount, when large change occurs in the calorific value of coal, obtains according to after the calorific value after mixing burning and 4500 comparisons One ratio value K₁, by the output coal-supplying amount of former boiler master divided by ratio value K₁, obtain the coal supply value of new boiler master, from And carry out the coal amount on-line correction of current ature of coal.

Compared with prior art, the invention have the advantages that

(1) cause for factors such as the large time delay of 600MW supercritical circulating fluidized bed boiler, increasing and decreasing load, ature of coal are unstable Main steam pressure fluctuation conducts in-depth analysis greatly and studies, by burning in circulating fluid bed boiler characteristic and control-Strategy analysis, Propose based on the energy equilibrium control method i.e. firing carbon；

(2) supercritical CFB unit, owing to boiler does not has drum container, the accumulation of heat of boiler cannot be entered by effective experimental apparatus Row on-line measurement, the i.e. combustion carbon amounts that boiler heat storage stores in showing as burner hearth, construct i.e. combustion carbon mechanism model by Analysis on Mechanism, Calculate i.e. combustion carbon and i.e. combustion carbon heat and can get the heat signal of current boiler；

(3) control achieving main steam pressure based on the energy equilibrium control method i.e. firing carbon designed, gives i.e. combustion carbon and stores The span of hot figure parameters；Through practice, the method can overcome CFB boiler main steam pressure large time delay and to model essence Really property requires high shortcoming, has good stability, achieves preferable effect, and be convenient to engineer applied；

(4) it is controlled policy optimization by Analysis on Mechanism completely to complete, does not increase any hardware device, cost-effective Having reached good effect, the control for Supercritical CFB Boiler main steam pressure provides a kind of new approaches simultaneously；

(5) not only improve the regulation quality of unit, improve the stability of main steam pressure control system, adapt to unit load The ability of response, and the effectiveness of institute's tectonic model and method is demonstrated by test.

Accompanying drawing explanation

Fig. 1 is based on the Supercritical CFB Boiler main steam pressure control policy framework figure i.e. firing carbon；

Fig. 2 is based on the main steam pressure control system structural framing figure i.e. firing the carbon energy balance；

Fig. 3 is the main steam pressure control design sketch before optimal control；

Fig. 4 is main steam pressure control design sketch in system loading excursion after optimal control；

Fig. 5 is the curve chart i.e. firing carbon amounts after optimal control in system loading excursion；

Fig. 6 is the curve chart i.e. firing carbon amounts rate of change after optimal control in system loading excursion.

The present invention is further illustrated with detailed description of the invention below in conjunction with the accompanying drawings.

Detailed description of the invention

Embodiments of the invention: a kind of Supercritical CFB Boiler main steam pressure control method based on the energy balance, such as Fig. 2 institute Show, comprise the following steps:

S1, main steam pressure deviation signal P of unit_T-P_TSOutput signal A after PID (proportional-integral-differential) actuator, wherein, P_TFor main steam pressure, P_TSFor main steam pressure setting value；

S2, obtains steam turbine demand heat signal by steam turbine energy demand modelsWherein E_RDemand for steam turbine Heat, P₁The heat that needed for representing steam turbine, steam flow is contained, dimension is MW, is worth P₁=k*p, p are Steam Turhine Adjustment Pressure after Ji, MPa, k are pressure and the correction factor of heat after Control Stage of Steam Turbine, and dimension is MW/Mpa ", physical significance The heat (MW) contained for unit steam pressure (MPa)；

S3, obtains, by i.e. firing carbon mechanism model, the heat signal that boiler is provided thatE_BCan provide for boiler Heat signal, the heat that the steam flow that D produced by the boiler unit interval is contained, MW, Q be in burner hearth storage i.e. Combustion carbon burning caloric value, C_BcFor i.e. firing the heat storage coefficient of carbon；

S4, steam turbine demand heat signal E_RThe heat signal E being provided that with boiler_BAfter subtracting each other, after PID regulator regulates, defeated Go out signal C；

S5, steam turbine demand heat signal E_RThrough to time diffusionAfter, be multiplied by the value of proportional gain k, obtain signal B, B, A and C is added and another rising exports boiler master；

S6, controls main steam pressure according to boiler master output regulation coal-supplying amount.

I.e. combustion carbon mechanism model in described step S3 isIn formula, Q (t) is that burning is released The total amount of heat put, unit is MJ/s；B (t) is for i.e. to fire carbon amounts, and unit is kg；PM (t) is total blast volume, and unit is Nm³/s；K For model overall coefficient；M_CFor the molal weight of carbon, unit is kg/kmol；k_cBurn rate constant for carbon granule；d_cFor carbon Average diameter of particles, unit is m；ρ_cFor the density of carbon granule, unit is kg/m³；H is the unit caloric value of fuel, single Position is MJ/kg；ko₂Correlation coefficient for total blast volume PM (t) Yu oxygen concentration.

The heat signal that boiler is provided thatIn formula, the steam flow that D produced by the boiler unit interval is accumulate The heat contained, MW；C_BcFor i.e. firing the heat storage coefficient of carbon, for based on certain proportion relation with momentum, on underload rank Section 200MW～400MW is 28～30, is 30～32 at high load capacity stage 400MW～600MW；Q is storage in burner hearth I.e. combustion carbon burning caloric value, unit is MJ.

Described boiler master output is coal-supplying amount, when large change occurs in the calorific value of coal, according to mixing the calorific value (heat after burning Unit is card) obtain a ratio value K after 4500 (caloric unit is card) comparison₁, by the output coal-supplying amount of former boiler master Divided by ratio value K₁, obtain the coal supply value of new boiler master, thus carry out the coal amount on-line correction of current ature of coal.

1, carbon mechanism model is i.e. fired

The monitoring i.e. firing carbon introduces one group of aequum, i.e. fires the parameter of carbon stocks change in calculating optimal reflection stove.Consider into stove Coal change causes i.e. combustion carbon stocks changing value and burning in stove to cause the equilibrium relation i.e. firing carbon stocks changing value, set steady Under operating mode, i.e. the combustion carbon of i.e. combustion carbon and the combustible loss that supplement in a period of time is one group of equilibrium relation, it may be assumed that

L=∑ F-∑ R (1)

In formula: ∑ F is the i.e. combustion carbon amounts that burner hearth supplements, kg；∑ R is the i.e. combustion carbon amounts of combustible loss, and unit is kg；L is that the two is clean Difference, unit is kg.

Can consider that in actual production the system introducing i.e. concept of combustion Carbon balance and heat balance carrys out optimal control within a period of time The quality of system.In Process of Circulating Fluidized Bed Boiler, sending into the fuel of burner hearth, a part passes through combustion heat release amount, A part is accumulated at unburned in burner hearth, the expression formula of unburned i.e. combustion carbon B (t) in can obtaining burner hearth according to the conservation of mass:

$\frac{dB\left(t\right)}{dt}=F\left(t\right)-\frac{Q\left(t\right)}{H}---\left(2\right)$

In formula: B (t) is unburned i.e. to fire carbon amounts, kg；F (t) is the coal-supplying amount entering boiler from burner hearth entrance, kg/s；Q (t) is The total amount of heat of burning release, unit is MJ/s；H is the unit caloric value of fuel, and unit is MJ/kg.

The heat of Process of Circulating Fluidized Bed Boiler release is directly proportional to the fuel quantity participating in burning, participates in the fuel quantity of burning With burn rate R i.e. firing carbon_cRelevant, i.e. fire the burn rate of carbon be i.e. fire in fluid bed burner hearth the gross mass of carbon, bed temperature, The function of oxygen concentration:

$R_C=B\left(t\right)\×\left(\frac{1}{m_p}\frac{{\mathrm{dm}}_p}{dt}\right)=\frac{6M_C{k}_c{c}_{o_2}B\left(t\right)}{d_c{\mathrm{\ρ}}_c}---\left(3\right)$

In formula: M_CFor the molal weight of carbon, unit is kg/kmol；B (t) is for i.e. firing the gross mass of carbon, and unit is kg；k_cFor carbon The burn rate constant of grain；C_O2For oxygen concentration, unit is kmol/m³；d_cFor carbon granule average diameter, unit is m；ρ_c For the density of carbon granule, unit is kg/m³；

According to unit practical operation situation, control system emphasis considers the temperature impact on carbon granule burn rate, total according to practice Knot has obtained carbon granule burn rate constant k in CFB boiler_cExpression formula:

k_c=0.513Texp (-9160/T) (4)

In formula: T is burner hearth bed temperature, unit is K (Kelvin)；

Engineer applied for convenience, can become a linear function formula (5) according to the result approximate fits that formula (4) calculate:

k_c=0.0031T-2.8392 (5)

Carbon granule oxygen concentration can approximate in the controls and average, and is determined by entering stove total blast volume PM (t), and its expression formula is:

$C_{o_2}\left(t\right)=k_{o_2}PM\left(t\right)---\left(6\right)$

In formula: ko₂Correlation coefficient for total blast volume PM (t) Yu oxygen concentration；PM (t) is total blast volume, and unit is Nm³/s；

When unit steady state condition, according to formula (6) oxygen amount concentration and the correlation coefficient ko of total blast volume₂Expression formula be:

$k_{o_2}=\frac{{C^{\′}}_{o_2}}{PM}---\left(7\right)$

Oxygen mole concentrationWith volumetric concentrationRelation be:

${C^{\′}}_{o_2}=\frac{P}{RT}{Y}_{o_2}---\left(8\right)$

Convolution (7), (8), can obtain:

$k_{o_2}=\frac{P}{R_{a}TPM}{Y}_{o_2}---\left(9\right)$

In formula: P is burner hearth bed pressure；R_aFor gas constant；T is burner hearth bed temperature；Y_o2For oxygen percent by volume；Oxygen concentration Coefficient k o₂Increasing along with the rising of burner hearth bottom bed pressure, oxygen concentration increases, the beneficially burning of burner hearth, the size of its value Relevant to the setting value of burner hearth bed pressure, ko₂Span 0.0040～0.0055, ko₂=0.0050；

Burn rate R during steady working condition_cApproximate coal-supplying amount F, steady working condition can be obtained by formula (3) and i.e. fire the initial B of carbon amounts₀Take Value is:

$B_0=\frac{{\mathrm{Fd}}_c{\mathrm{\ρ}}_c}{6M_C{k}_c{C}_{o_2}}---\left(10\right)$

By formula (3), (4), (5) the heat expression formula that discharges in combustion process of boiler is:

$\begin{array}{c}Q\left(t\right)=R_{c}H=\frac{6M_c{\mathrm{Hk}}_c{k}_{o_2}}{d_c{\mathrm{\ρ}}_c}PM\left(t\right)B\left(t\right)\\ =K\left(PM\right(t))B\left(t\right)\end{array}---\left(11\right)$

In formula: B (t) is for i.e. to fire carbon amounts, and unit is kg；PM (t) is total blast volume, and unit is Nm³/s；K is model overall coefficient,According to above formula, the heat of burning release can be obtained by i.e. combustion carbon amounts and total blast volume.

2, based on the Controlling model i.e. firing the carbon energy balance

In order to utilize the thermal storage effect of boiler, make the caloric value of boiler meet the demand of steam turbine as early as possible, need to overcome pressure controlled External disturbance, the demand heat signal of steam turbine side enters steam generator system and participates in controlling.Owing to subcritical CFB boiler amount of stored heat is permissible Observed by the measured value of drum pressure and obtaining, and for supercritical CFB Once-through Boiler, due to without drum container, the accumulation of heat of boiler Cannot be obtained by drum pressure measurement.The present invention, by i.e. firing carbon hard measurement mechanism model in structure burner hearth, in calculating burner hearth is The amount of storage of combustion carbon and calory burning, indirectly obtain the amount of stored heat of boiler, the DEB DIRECT ENERGY of subcritical CFB boiler put down Weighing apparatus controls thinking, by Analysis on Mechanism, key parameter is carried out rational structure, is successfully applied to supercritical CFB unit main steam In control pressurer system.

If the heat that the steam flow entering steam turbine is contained is D, MW, main steam pressure and corresponding setting value are respectively P_TAnd P_TS, in order to meet the load needs in the external world, energy demand E of steam turbine_RFor:

$E_R=D\frac{P_{TS}}{P_T}=P_1\frac{P_{TS}}{P_T}---\left(12\right)$

E_RFor steam turbine to the required energy signal of boiler, its physical significance is: if D is the biggest, then just flow into the steam flow of steam turbine The most, illustrate that the energy that steam turbine needs to boiler is the most, the heat P that needed for general steam turbine, steam flow is contained₁With boiler The heat D approximately equal that the steam flow that unit interval produces is contained；On the other hand, if steam pressure P_TLess than setting value P_TS, steam turbine many consumption part energy is described, system occurs in that energy deficit must be requested that boiler provides more energy Pressure can be made to return to setting value, the P of steam pressure_TValue the least, then explanation unit energy deficit the most serious, the demand of energy Amount E_RJust should be the biggest.

The energy that boiler be can be provided by, most straightforward approach is the coal-supplying amount that regulation enters boiler, but for CFB boiler Caloric value be primarily not and currently enter stove coal-supplying amount, but the i.e. combustion carbon amounts of savings in burner hearth, and owing to coal-supplying amount time delay is bigger And due to ature of coal and the change of coal, even if coal-supplying amount is identical, its caloric value is the most different.Therefore, the energy letter that boiler is provided Number should be the heat signal produced after the i.e. combustion carbon burning of storage in burner hearth, although heat signal cannot directly be measured, if energy Enough according to the i.e. combustion carbon put aside in mechanism model analytical estimating burner hearth and combustion heating amount, then can obtain the heat signal of boiler.

For Supercritical CFB Boiler, the fuel quantity of feeding burns in boiler and produces heat, working medium in heating furnace, working medium in stove Total heat E_BBeing divided into two parts, a part absorbs the heat taken away for superheated steam, and another part is unlike subcritical CFB drum Boiler is stored in the steam working medium of boiler, shows as the enthalpy after saturation water absorbs heat in boiler and increases, by measuring drum pressure P_bValue be calculated, and combustion heating amount Q i.e. firing carbon in can be by CFB boiler is calculated.Its equation of heat balance can It is expressed as:

Q_r* dt=(h_g-h_s)*D*dt+B*dh_b (13)

In formula: Q_rFor the caloric receptivity that working medium in stove is total；h_gFor the enthalpy of main steam, unit is KJ/kg；h_sFor Enthalpy of Feed Water, unit For KJ/kg；h_bFor saturation water enthalpy, unit is KJ/kg；The heat that the steam flow that D produced by the boiler unit interval is contained Amount, MW；B is the i.e. combustion carbon amounts of the interior savings of boiler, and unit is kg.

According to the characteristic of thermal conduction study saturation water enthalpy, the enthalpy increasing that can obtain saturation water in boiler in formula (19) is i.e. to fire carbon burning caloric value The function of Q, i.e. h_b=f (Q), takes differential and obtains:

${\mathrm{dh}}_b=\frac{df\left(Q\right)}{dQ}dQ---\left(14\right)$

Bring formula (14) into formula (13) can obtain:

$\frac{Q_r}{h_g-h_s}=D+\frac{B\frac{df\left(Q\right)}{dQ}}{h_g-h_s}*\frac{dQ}{dt}---\left(15\right)$

IfThen formula (15) can be reduced to:

$E_B=D+C_{Bc}\frac{dQ}{dt}---\left(16\right)$

In formula: E_BThe heat signal that can provide for boiler；The heat that the steam flow that D produced by the boiler unit interval is contained, MW； Q is the i.e. combustion carbon burning caloric value of the interior storage of burner hearth；C_BcFor i.e. firing the heat storage coefficient of carbon.

The heat signal represented in formula (16) is it is understood that the heat that boiler produces is used for two aspects: one is to provide the unit interval The heat that the steam flow produced is contained, this partial heat enters steam turbine work done after flow into steam main；Another part energy Amount is stored in the burner hearth of boiler, i.e. fires combustion heating amount Q of carbon amounts B in showing as boiler, and this portion of energy can use boiler The differential the most i.e. firing carbon caloric value is multiplied by heat storage coefficient C_BcObtain.The most directly use Q as heat signal is Because relatively big in running on the lower load (200MW～400WM) Q-value error sometimes, maximum has the error of 10%～20%, but Be the differential of Q-value be that any operating mode all has higher accuracy, simultaneously C_BcSpan comparatively small.The differential of Q-value It is multiplied by the heat storage coefficient C of corresponding load_Bc, adding heat D that steam flow contained can than directly with Q-value more more accurately Obtain the heat signal of boiler.Although as heat signal, there is certain hysteresis quality than direct Q-value, but relative to CFB For the large time delay time of boiler, the heat signal being constructed such that still has certain advanced, can meet steam turbine in time Energy requirement.

3, based on the energy balance control strategy i.e. firing carbon

Due to carbon granule continuous fluidized bed combustion in CFB boiler, carbon granule burns completely needs about 8～10 minutes, the heat of boiler side Inertia is very big, and when load increase and decrease, after coal-supplying amount change, the most common coal-powder boiler of change of main steam pressure is the most delayed. Therefore boiler master uses the control mode based on boiler follow, i.e. boiler master to control main steam pressure, turbine main control control Unit generation power processed.Boiler master output mainly is controlled to be calculated by load instruction feedforward and the energy balance, is illustrated in figure 1 Based on the Supercritical CFB Boiler compressive stress control strategy i.e. firing carbon.

4, C in machine capacity of furnace balanced signal_BcThe selection of value

The heat storage coefficient C of Supercritical CFB Boiler_BcIt is the parameter weighing storage of the generator set, it is possible to know boiler heat storage coefficient and accumulation of heat energy Power fires the relation of carbon dynamics thermal change immediately.In order to meet the demand of unit dynamic characteristic, by observing steam turbine and boiler Heat signal difference, suitably changes C_BcValue, finds in different load sections C_BcValue and proportionate relationship difference is set.C_BcIt is worth Low load stage 200MW～400MW are 28～30, are 30～32 at high load capacity stage 400MW～600MW.Heat storage coefficient C_Bc Value increase along with the increase of load, this is because in the high load capacity stage, fire box temperature is higher, i.e. combustion carbon burning is abundant, single It is more that position quality i.e. fires carbon emissions heat；And at the Drum Boiler Heat Storage Coefficient C_bValue be as the increase of load and reduce, this is Because i.e. firing carbon burning Mass lost in boiler, release heat increases, and drum pressure then can accordingly increase, i.e. combustion carbon reduces Drum pressure is increasing simultaneously.When solving value and the proportionate relationship problem in different load stage, by C_BcValue is changed into by fixed amount Based on certain proportion relation with momentum, good effect can be obtained.

5, main steam pressure control based on the energy balance

For the concrete condition of actual set, devise based on i.e. firing carbon on the basis of fully realizing various control strategy pluses and minuses The energy balance of accumulation of heat regulates, with main steam pressure, the main steam pressure control system combined, and its structure is as shown in Figure 2.

Its control program is: when application of load, properly increases rapidly air quantity in burner hearth, i.e. depositing of combustion carbon deflagrate, i.e. combustion carbon Reserves reduce, and make boiler full out discharge the accumulation of heat of burner hearth, overcome the hysteresis quality of CFB boiler to greatest extent.Load instruction is first First it is applied to air supply control system, makes air output increase with instruction and quickly increase, it is achieved changing the soonest of main steam pressure, full Foot burden requirement.Steam turbine side required energy signal E_RWith boiler side energy-providing signal E_BDifference by output letter after PID regulator Number it is C, pressure divergence signal (P_T-P_TS) it is A, simultaneously steam turbine required energy signal by output signal after PID regulatorTime diffusionAfter to be multiplied by the output signal of proportional gain k be B, proportional gain k span is 0.8～1.2, General value is 1.0, can be finely adjusted according to different units；A+B+C jointly acts on boiler master instruction and controls coal-supplying amount.By In early stage excess coal supply, add that air quantity increase is relatively big, i.e. combustion carbon burns in a large number, progressively discharges the accumulation of heat energy of boiler, institute To start to need according to i.e. firing Carbon balance from mid-term, appropriate adjustment coal-supplying amount and air output.I.e. combustion carbon amounts early stage is supplemented in time, Progressively reduce the speed of coal-supplying amount and air-supply instruction change to mid-term, progressively weaken the huge energy that early stage burning is discharged, essence I.e. fire carbon amounts in really controlling burner hearth, keep i.e. firing stablizing of carbon amounts.So on the one hand, suitably control air quantity, prevent air quantity excessive, Affect burner hearth oxygen amount and bed temperature；On the other hand the too much coal-fired hearth combustion that enters it is possible to prevent to cause showing of main steam pressure superpressure As.

Transfinite it addition, ature of coal instability also results in main steam pressure fluctuation.Owing to recirculating fluidized bed adapts to various coal, because of This, general CFB boiler can mix the various low-calorie cheap coals of burning, and such as Indonesia coal, Korea's coal etc., its calorific value is generally Only less than 3500 cards.When mixed-fuel burning proportion is different, the calorific value of coal is the most different, owing to boiler master output is coal-supplying amount, During plus-minus same load, the coal-supplying amount of Coal rank is just as.If the calorific value of certain coal is higher, produce during coal combustion Heat is the biggest, is just easier main steam pressure superpressure phenomenon occur, online for introducing ature of coal in this phenomenon control system Alignment technique, through putting into practice coal caloric value 4500 blocked as benchmark, the output quantity of coal of correction boiler master.Heat when coal When there is large change in value, can be according to the calorific value (caloric unit is card) after mixing burning and 4500 (caloric unit is card) comparison After obtain a ratio value K₁, by the output quantity of coal of former boiler master divided by ratio value K₁, obtain the coal supply value of new boiler master, Thus carry out the coal amount on-line correction of current ature of coal.Accurately reflect the energy size of fire coal, it is to avoid cause because ature of coal is unstable The big situation of main steam pressure fluctuation.

6, experimental verification

Fig. 3 is the main steam pressure control quality curve chart using tradition Limestone control main steam pressure control strategy to obtain.Negative Lotus excursion is 520MW～370MW～600MW, and main steam pressure reaches with setting value deviation as can be seen from FIG. 1.1Mpa, actual power and load instruction maximum deviation are 12MW.Due to turbine main control steam pressure exceed ± 0.7MPa time, For steam turbine master control in main steam pressure boundary control mode, turbine control main task is to maintain pressure not continue to overshoot, this Time main steam pressure control in protected mode, the control accuracy of load and the speed of response will reduce.

Fig. 4-Fig. 6 is to use based on i.e. firing the main steam pressure control quality curve chart after the energy balance control strategy of carbon, system The excursion of load is 360MW～545MW～360MW.As can be seen from Figure 5, during unit load up In (360MW～545MW) boiler, the i.e. combustion carbon amounts of storage changes from 23000kg～22000kg～23500kg, negative in unit fall During lotus, in (545MW～360MW) boiler, the i.e. combustion carbon amounts of storage changes from 23500kg～19000kg～21000kg；With Sample is in 360MW operating mode, i.e. combustion carbon drops to 21000kg from 23000kg, thus can be inferred that ature of coal there occurs change, coal The coal that matter heat is higher, i.e. combustion carbon amount of storage in burner hearth is less.As shown in Figure 6, the value i.e. firing carbon heat gradient exists Being held essentially constant in steady-state process, the excursion in dynamic process is-8～15, and boiler i.e. fires carbon heat storage coefficient C_BcValue Scope is 29.60～31.45.According to i.e. firing the instruction of carbon heat balance correction boiler master, as shown in Figure 4, become on a large scale at load During change, main steam pressure and setting value deviation control within ± 0.3Mpa, and actual power and load instruction maximum deviation are 8MW, The control accuracy making main steam pressure and load makes moderate progress.

Claims (5)

1. a Supercritical CFB Boiler main steam pressure control method based on the energy balance, it is characterised in that the method include with Lower step:

S1, main steam pressure deviation signal P of unit_T-P_TSOutput signal A after PID regulator, wherein, P_TFor main steam Pressure, P_TSFor main steam pressure setting value；

S2, obtained steam turbine demand heat signal by steam turbine energy demand modelsE_RDemand for steam turbine Heat, P₁The heat that needed for representing steam turbine, steam flow is contained, dimension is MW；

S3, by i.e. combustion carbon mechanism model obtain the heat signal that boiler is provided thatE_BCan for boiler The heat signal provided, the heat that the steam flow that D produced by the boiler unit interval is contained, MW；C_BcFor i.e. firing the storage of carbon Hot coefficient；Q is the i.e. combustion carbon burning caloric value of the interior storage of burner hearth, and unit is MJ；

S4, steam turbine demand heat signal E_RThe heat signal E being provided that with boiler_BAfter subtracting each other, after PID regulator regulates, Output signal C；

S5, steam turbine demand heat signal E_RThrough to time diffusionAfter, it is multiplied by the value of proportional gain k, obtains signal B, B, A and C are added and another rising exports boiler master；

S6, according to boiler master output regulation coal-supplying amount control main steam pressure.

Supercritical CFB Boiler main steam pressure control method based on the energy balance the most according to claim 1, it is characterised in that: I.e. combustion carbon mechanism model in described step S3 is:In formula, Q (t) is burning release Total amount of heat, MJ/s；B (t) is for i.e. to fire carbon amounts, and unit is kg；PM (t) is total blast volume, and unit is Nm³/s；K is that model is total Coefficient, whereinIn formula, M_CFor the molal weight of carbon, unit is kg/kmol；H is the unit heating of fuel Amount, unit is MJ/kg；k_cBurn rate constant for carbon granule；d_cFor carbon granule average diameter, unit is m；ρ_cFor carbon The density of grain, unit is kg/m³；ko₂Correlation coefficient for total blast volume PM (t) Yu oxygen concentration；R_cFor i.e. firing the burning speed of carbon Rate,Unit is kg/s.

Supercritical CFB Boiler main steam pressure control method based on the energy balance the most according to claim 1 and 2, its feature It is: described C_BcIt is with momentum, described C_BcValue is 28～30 in low load stage 200MW～400MW, on high load capacity rank Section 400MW～600MW is 30～32.

Supercritical CFB Boiler main steam pressure control method based on the energy balance the most according to claim 1 and 2, its feature Being: in described step S5, proportional gain k span is 0.8～1.2.

Supercritical CFB Boiler main steam pressure control method based on the energy balance the most according to claim 1, it is characterised in that: Boiler master output in described step S6 is coal-supplying amount, when large change occurs in the calorific value of coal, according to mixing the calorific value after burning With obtain a ratio value K after 4500 comparisons₂, the output coal-supplying amount of former boiler master is multiplied by ratio value K₂, obtain new pot The coal supply value of stove master control, thus carry out the coal amount on-line correction of current ature of coal.