Real Boiler Research Articles

층류 반응기를 이용한 수분함량에 따른 석탄 휘발분의 점화 특성에 관한 연구

The main objective of this study is to investigate the variation in the ignition characteristics of coals as a function of moisture content in a laminar flow reactor (LFR) equipped with a fuel moisture micro-supplier designed by the Pusan Clean Coal Center. The volatile ignition position and time were observed experimentally when a pulverized coal with moisture was fed into the LFR under burning conditions similar to those at the exit of the pulverizer and real boiler. The reaction-zone temperature along the centerline of the reactor was measured with a , R-type thermocouple. For different moisture contents, the volatile ignition position was determined based on an average of 15 to 20 images captured by a CCD camera using a proprietary image-processing technique. The reaction zone decreased proportionally as a function of the moisture content. As the moisture content increased, the volatile ignition positions were 2.92, 3.36, 3.96, and 4.65 mm corresponding to ignition times of 1.46, 1.68, 2.00, and 2.33 ms, respectively. These results indicate that the ignition position and time increased exponentially. We also calculated the ignition-delay time derived from the adiabatic thermal explosion. It showed a trend that was similar to that of the experimental data.

Examination of flame length for burning pulverized coal in laminar flow reactor

Because there has been a recent increase in the use of low calorific coal compared to standard coal, it is crucial to control the char flame length governing the burning life-time of coal in a coal-fired utility boiler. The main objective of this study is to develop a simplified model that can theoretically predict the flame length for burning coal in a laboratory-scale entrained laminar flow reactor (LFR) system. The char burning behavior was experimentally observed when sub-bituminous pulverized coal was fed into the LFR under burning conditions similar to those in a real boiler: a heating rate of 1000 K/s, an oxygen molar fraction of 7.7 %, and reacting flue gas temperatures ranging from 1500 to 2000 K. By using the theoretical model developed in this study, the effect of particle size on the coal flame length was exclusively addressed. In this model, the effect of particle mass was eliminated to compare with the experimental result performed under a constant mass feeding of coal. Overall, the computed results for the coal flame length were in good agreement with the experimental data, particularly when the external oxygen diffusion effect was considered in the model.

CFD Based Ash Deposition Prediction in a BFBC Firing Mixtures of Peat and Forest Residue

Combustion of biofuel mixtures for heat and power production is often combined with ash related operational problems. Their reliable prediction is therefore essential in order to improve boiler performance and availability. In this work, an ash behavior prediction tool based on computational fluid dynamics and advanced fuel analysis is used to predict the ash deposition tendencies in a 295 MWth bubbling fluidized bed boiler fired with mixtures of peat and forest residue. The work focuses especially on two new modeling approaches for fuel distribution and bubbling bed. The overall combustion and deposition prediction results agree well with conditions in a real boiler.

Potential formation of PCDD/Fs and related bromine-substituted compounds from heating processes for ashes

Thermal experiments were conducted using real boiler ash and fly ash samples from three types of municipal or industrial solid waste incineration plants to understand the formation reactions of polychlorinated dibenzo- p-dioxin and furans (PCDD/Fs) and related bromine compounds that were chlorinated–brominated dibenzodioxins and furans (PXDD/Fs) and polybrominated dibenzo- p-dioxin and furans (PBDD/Fs). The results obtained were as follows: The formation of PCDD/Fs was clearly shown, and fly ash containing abundant carbon matter had a significant potential for de novo synthesis. The homologous distribution change apparently showed that the formation of PXDD/Fs occurred from the substitution of a bromine atom with a chlorine atom in the PCDD/F molecules. This suggests that PXDD/Fs are usually formed with PCDD/Fs on the ash. PBDD/Fs might be formed from any reaction mechanism different from that of PXDD/Fs. The existence of carbonaceous matters always does not mean the potential formation of PCDD/Fs. However, any addition of catalytic copper may influence the nature of ash to increase the formation potential. The findings suggest that there are many instances that result in the unintended production of trace hazardous pollutants in the incineration process and show that careful and sophisticated control is required to prevent the formation of pollutants.

A new approach for function approximation in boiler combustion optimization based on modified structural AOSVR

In the scheme of boiler combustion optimization, a group of optimal controller settings is found to provide recommendations to balance desired thermal efficiency and lowest emissions limit. Characteristic functions between particular objectives and controlling variables can be approximated based on data sets obtained from field tests. These relationships can change with variations in coal quality, slag/soot deposits and the condition of plant equipment, which can not be sampled on-line. Thus, approximation relationships based on test conditions could have little applicability for on-line optimization of the combustion process. In this paper, a new approach is proposed to adaptively perform function approximation based on a modified accurate on-line support vector regression method. Two modified criteria are proposed for selection of the unwanted trained sample to be removed. A structural matrix is used to process and save the model parameters and training data sets, which can be adaptively regulated by the on-line learning method. The proposed method is illustrated with an example and is also applied to real boiler data successfully. The results reveal their validity in the prediction of NOx emissions and function approximation, which can correctly be adapted to actual variable operating conditions in the boiler.

Hidden corrosion detection in thick metallic components by transient IR thermography

The classic inversion formula available from the literature for detecting corrosion in a plate is extended onto cylinder and sphere. Errors due to inappropriate algorithms are evaluated, theoretically. The experimental results obtained on a real boiler section are discussed. The multidimensional heat flux due to the shape, finite size of defects and heating are taken into account in detecting material loss of massive metallic components.

Highly sensitive determination of hydrazine ion by ion-exclusion chromatography with ion-exchange enhancement of conductivity detection

An ion-exclusion chromatography method with ion-exchange enhancement of conductivity was developed for the selective separation and sensitive determination of hydrazine ion from alkali/alkaline earth metal cations and ammonium ion. Hydrazine ion was separated by ion-exclusion/penetration effect from other cations on a weakly basic anion-exchange column in the OH − form (TSKgel DEAE-5PW). Moreover, two different ion-exchange resin columns were inserted between the separating column and conductimetric detector in order to improve the sensitivity of hydrazine ion. The first enhancement column packed with a strongly basic anion-exchange resin in the SO 4 2− form (TSKgel SAX) for hydrazine ion can convert from N 2H 5OH to (N 2H 5) 2SO 4. Moreover, the second enhancement column packed with a strongly acidic cation-change resin in the H + form (TSKgel SCX) can convert to H 2SO 4. As a result, the sensitivity of hydrazine ion using two conductivity enhancement columns could be 26.8-times greater than using the separating column alone. This method was effectiveness also for the enhancement of ammonium ion (6.1-times) and sodium ion (1.2-times). The calibration graph of hydrazine ion detected as H 2SO 4 was linear over the concentration range of 0.001–100 ppm ( r 2=0.9988). The detection limit of hydrazine ion in this system was 0.64 ppb. Therefore, hydrazine ion in real boiler water sample could be accurately determined, avoiding the interference of other cations.

Engineering Simulators for Fossil Power Plant

Abstract The paper generally describes a creation of models for engineering simulator and particularly the way and possibilities of work with the own simulation programme CADCS when creating simulation models. The CADCS is determined for analysis of dynamic properties of systems. This programme is block-oriented simulation system with graphical user environment. The paper issue one concrete model of real boiler. This is linear model of OPATOVICE drum pulverized - fuel fired steam boiler. The first example of Simulators is OPATOVICE Power Plant Engineering Simulator. The second example is VŘEsOVA Combined Cycle Plant Operator Training Simulator.

Evaluation of the coke formation potential of residual fuel oils

Previously, engineering control and prediction of coke particulate emission has been hampered by the apparent inadequacy of the existing heavy fuel tests that were used as coking indicators, specifically: asphaltene contents (heptane and pentane), viscosity, specific gravity, and the Ramsbottom and Conradson Carbon Residues. A new measurement, the Coke Formation Index (CFI) has been established as a more accurate measure of the coke particulate formation propensity of residual oils. This parameter, combined with previously reported results concerning particle diameter dependence on initial droplet conditions, will allow more accurate prediction of heavy oil combustion particulate emissions than was previously possible. This improved understanding of the factors affecting cenospheric coke formation and oxidation will increase the potential for control of coke particulate emission. The CFI is measured using a free, isolated droplet combustion apparatus, closely simulating the conditions experienced by droplets in a real boiler and yet separating the coke formation and oxidation processes. The CFI has been evaluated for 41 different residual fuels. From these experiments the Coke Formation Index (CFI), or ratio of the particulate mass to the initial droplet mass, has been established as principally related to fuel properties. Correlation exists between the CFI and the fuel asphaltene content or the Ramsbottom or Conradson Carbon Residues, however there is also considerable variation. Close similarity to the carbon formation results reported by others using electrically heated foils is observed; however, the CFI technique also provides particle size, morphology and composition information not generated by other coke formation tests. Results suggest that, from a single experiment with only a small mass of fuel, the resultant particle size and mass distribution can be predicted for the spray distribution of full scale burners firing the same fuel.