CN104992026A - Method for calculating mass flow rate of fired coal based on model - Google Patents

Abstract

The present invention discloses a method for calculating a mass flow rate of fired coal based on a model. The method comprises the specific steps: (a) pre-processing a coal feeding signal, i.e. preprocessing a belt weighing signal of a coal feeder by utilizing a moving average method; (b) establishing a pulverized coal bunker model; (c) carrying out balance calculation on the mass flow rate, i.e. determining the mass flow rate of the fired coal under variable working conditions and dynamic conditions according to values of a dynamic air-to-coal ratio and a primary air mass flow rate; and (d) verifying the model. According to the present invention, a coal pulverizing system of a boiler and the mass flow rate of the fired coal are calculated through three links, i.e. signal preprocessing and two modeling processes, the whole process is analyzed from mechanism, the established model is accurate and effective, and the modeling process is automatically fed back and updated by comparing the mass flow rate with the actual mass flow rate of the fired coal and correcting model parameters, so that a reliable data resource is provided for the calculation of the caloric value of the fired coal and the analysis of boiler combustion optimization.

Description

A kind of as-fired coal mass flow calculation method based on model

[technical field]

The technical field that the as-fired coal burning quality flow optimization that the present invention relates to boiler combustion control technology field, particularly boiler controls.

[background technology]

Industry standard " fuel-burning power plant Combustion System Design computing technique code " defines the design and calculation method of heat power plant boiler combustion system, comprise the coal analysis of pulverized coal preparation system, ranking, define boiler actual use coal-fired calorific value and design coal calorific value between deviate within 0.4MJ/kg-2MJ/kg (generally getting 1.26MJ/kg), but along with the diversification of China's coal supply, this requirement seldom can be satisfied in actual production.

Industry standard gives the method that back balance method calculates boiler efficiency, and also suggestion calculates the appropriate to the occasion contract guarantee value with reference to boiler factory under design coal of boiler efficiency.But the thermodynamic computing error of carrying out accordingly when as-fired coal fluctuation will strengthen.And, before calculating as-fired coal calorific value, first accurately must calculate the mass rate of as-fired coal, just obtain the calorific value of coal by boiler side whole process quality and energy balance model.

Also the computing method to boiler coal-ash mass rate are had at present, as CN200810044158, soft measuring method for power boiler breeze concentration mass flow, mainly utilize fuzzy mathematics, the non-linear soft-sensing model of multi-model average weighted solid phase mass rate based on local behavior is proposed, based on the soft-sensing model of electrostatic sensing technique and fuzzy rule, but consider that fuzzy control needs manual intervention, expertise and test, and soft-sensing model is set up not easily, and the mass flow calculation effect of coal dust is unsatisfactory.Based on this, the present invention is the mass budget model by omnibearing analysis as-fired coal, and each model of divided piece to establish, drastically increases the precision of model, for the mass flow calculation of coal dust lays the foundation.

[summary of the invention]

Object of the present invention solves the problems of the prior art exactly, a kind of as-fired coal mass flow calculation method based on model is proposed, three parts are divided to set up the mass rate model of raw coal to as-fired coal powder, improve modeling accuracy, thus be the calculating of as-fired coal calorific value, ensure reliably for burning optimization improves.

For achieving the above object, the present invention proposes a kind of as-fired coal mass flow calculation method based on model, is that account the mass rate of as-fired coal, concrete steps comprise on the basis that the mechanism model based on coal is set up:

A coal supply Signal Pretreatment: utilize the signal that the method pre-service belt conveyer scale of coal feeder of running mean is heavy;

B powder storehouse model is set up: utilize the method for Model Distinguish to rest on the time modeling in powder storehouse to raw coal, model is thought of as single order purely retarded;

C mass rate is accounted: according to the value of dynamic air-to-coal ratio and First air mass rate, determine the mass rate of as-fired coal under variable working condition;

D model checks: carry out scene checking computations to the model set up, compare, make error analysis, correct model parameter with actual as-fired coal mass rate.

As preferably, in described (a) step, coal supply Signal Pretreatment process, it is the method that make use of running mean, consider that running mean method has the advantage of variable point numeral and weighted number in process random noise, better to the filter effect of signal, computing method are simple to operation.

As preferably, in described (b) step, the foundation of powder storehouse model is on the basis of identification, and rest on point estimation of storehouse time to raw coal, the Model Distinguish of single order purely retarded is representative.

As preferably, in described (c) step, accounting of as-fired coal mass rate model, is in variable working condition, dynamic situation, calculates the overall process of coal dust.

Beneficial effect of the present invention:

The present invention is by three links, i.e. Signal Pretreatment and two modeling process, calculating has been done to the pulverized coal preparation system of boiler and the mass rate of as-fired coal, from mechanism analysis overall process, the model set up is accurately effective, and by the contrast with actual as-fired coal mass rate, calibration model parameter, make modeling process have self-feedback and renewal process, thus provide reliable Data Source for the calculating of as-fired coal calorific value, the analysis of boiler combustion optimization.

[embodiment]

A kind of as-fired coal mass flow calculation method based on model of the present invention, concrete steps comprise:

Step one, the signal utilizing the method pre-service belt conveyer scale of coal feeder of running mean to weigh;

Step 2, utilize the method for Model Distinguish to rest on the time modeling in powder storehouse to raw coal, model is thought of as single order purely retarded;

Step 3, value according to dynamic air-to-coal ratio and First air mass rate, determine the mass rate of as-fired coal in variable working condition, dynamic situation;

Step 4, the model set up carried out to scene checking computations, compare with actual as-fired coal mass rate, make error analysis, model parameter is corrected.

Enter in the process of coal pulverizer at raw coal, powder process control system comprises two closed loops: First air damper opening control system and coal pulverizer powder storehouse material level control system.Wherein, the setting input variable of damper aperture closed-loop control system is load instruction signal.The change of the pulverized coal mass flow that First air carries is a disturbing signal for material level (differential pressure) close loop control circuit in coal pulverizer powder storehouse, after disturbance produces, the actual differential pressure signal in powder storehouse can depart from its setting value, Level control loop with feeder belt slewing rate for powder storehouse material level is controlled to setting value by manipulated variable.

In order to obtain as-fired coal mass rate, need to three links of fire coal process in pulverized coal preparation system (feeder transports, coal pulverizer grinding and First air carry) respectively Modling model: the heavy Signal Pretreatment model of belt conveyer scale of coal feeder, powder storehouse residence time model and enter the coal-fired dynamic mass flow of stove and accounts model.

1, the heavy Signal Pretreatment of belt conveyer scale of coal feeder

Feeder belt weighing measuring point signal noise level is very high, needs to adopt suitable method to make noise suppression preprocessing to original signal, intends the method denoising choosing running mean.

2, raw coal is at the residence time model in powder storehouse

Graininess raw coal, after feeder belt enters coal pulverizer powder storehouse, just generate the qualified coal dust of fineness, therefore there is phase differential in qualified coal dust generating rate and coal supply speed through certain stop grinding in time domain.For calculating this phase differential, need to set up the residence time model of raw coal in powder storehouse.Consider that thickness divides the effect of separation vessel, model can adopt first-order plus time delay transport function structure, and expression formula is as follows:

$D_{pul}=\frac{D_{raw}}{(Ts+1)}{e}^{-\mathrm{\τ}s}$

In formula, D _pulfor qualified coal dust generating rate (mass rate), kg/s; D _rawfor the feeder mass rate after Denoising disposal, kg/s; T, τ are model parameter, are determined by the geometry in feeder and powder storehouse, need to exert oneself electric current in addition preliminary identification in conjunction with feeder.

3, enter stove coal quantity flow and account model

Calculate qualified coal dust generating rate in real time with powder storehouse residence time model, and then calculate dynamic air-to-coal ratio, recycling primary air flow signal calculates into stove coal quantity flow, can realize the calculating of as-fired coal mass rate.Ignore the obvious delay of qualified coal dust in coal pulverizer, the coal dust dynamic mass balance equation in coal pulverizer is:

${\∫}_{t_0}^{t_0+\mathrm{\Δ}t}\frac{{\mathrm{dM}}_{pul}}{dt}={\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{D}_{pul}\·dt-{\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{D}_{fur}\·dt$

In formula, M _pulfor the accumulation of coal dust in powder storehouse, kg; D _pulfor qualified coal dust generating rate (mass rate), kg/s; D _furfor First air carries pulverized coal mass flow, namely enter stove coal quantity flow, kg/s; Within load variations amplitude less time period and moderate time, ignore the obvious delay of qualified coal dust in coal pulverizer, even above formula left end is 0:

${\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{D}_{pul}\·dt={\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{D}_{fur}\·dt$

So dynamic air-to-coal ratio average R is:

$R=\frac{{\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{F}_{pa}\left(t\right)\·dt}{{\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{D}_{fur}\left(t\right)\·dt}=\frac{{\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{F}_{pa}\left(t\right)\·dt}{{\∫}_{t_0}^{t_0+\mathrm{\Δ}t}{D}_{\mathrm{pul}}\left(t\right)\·dt}$

In formula, F _pat () is First air mass rate, kg/s; D _furfor entering stove coal quantity flow, kg/s; D _pulfor qualified coal dust generating rate (mass rate), kg/s.

At load without the period significantly changed, the calculating formula entering stove coal quantity flow is:

D _fur＝F _pa/R

In the fast-changing process of load coal-air ratio obviously and load value be inverse relation.Utilize this inverse relation, can coal-air ratio during calculated load Rapid Variable Design:

$R=R_0\frac{P_0}{P}$

In formula, P ₀for the load value that load Rapid Variable Design start time is corresponding, MW; R ₀for the coal-air ratio of varying load process start time; P is the load instantaneous value in load Rapid Variable Design process, MW.

The course of work of the present invention:

The present invention is by three links, i.e. Signal Pretreatment and two modeling process, calculating has been done to the pulverized coal preparation system of boiler and the mass rate of as-fired coal, from mechanism analysis overall process, the model set up is accurately effective, and by the contrast with actual as-fired coal mass rate, calibration model parameter, make modeling process have self-feedback and renewal process, thus provide reliable Data Source for the calculating of as-fired coal calorific value, the analysis of boiler combustion optimization.

Above-described embodiment is to explanation of the present invention, is not limitation of the invention, anyly all belongs to protection scope of the present invention to the scheme after simple transformation of the present invention.

Claims (4)

1. the as-fired coal mass flow calculation method based on model, it is characterized in that: described computing method are on the basis that the mechanism model of coal is set up, three parts are divided to set up the mass rate model of raw coal to as-fired coal powder, account the mass rate of as-fired coal, improve modeling accuracy, concrete steps comprise:

A coal supply Signal Pretreatment: utilize the signal that the method pre-service belt conveyer scale of coal feeder of running mean is heavy;

B powder storehouse model is set up: utilize the method for Model Distinguish to rest on the time modeling in powder storehouse to raw coal, model is thought of as single order purely retarded;

C mass rate is accounted: according to the value of dynamic air-to-coal ratio and First air mass rate, determines the mass rate of as-fired coal in variable working condition, dynamic situation;

D model checks: carry out scene checking computations to the model set up, compare, make error analysis, correct model parameter with actual as-fired coal mass rate.

2. a kind of as-fired coal mass flow calculation method based on model as claimed in claim 1, it is characterized in that: in described (a) step, coal supply Signal Pretreatment process, it is the method that make use of running mean, consider that running mean method has the advantage of variable point numeral and weighted number in process random noise, better to the filter effect of signal, computing method are simple to operation.

3. a kind of as-fired coal mass flow calculation method based on model as claimed in claim 1, it is characterized in that: in described (b) step, the foundation of powder storehouse model, on the basis of identification, rest on point estimation of storehouse time to raw coal, the Model Distinguish of single order purely retarded is representative.

4. a kind of as-fired coal mass flow calculation method based on model as claimed in claim 1, it is characterized in that: in described (c) step, accounting of as-fired coal mass rate model, is in variable working condition, dynamic situation, calculates the overall process of coal dust.