| The Democratic People’s Republic of Korea（DPR Korea）is rich in anthracite resources and lacking in oil resources.Some utility boilers,as opposed combustion mode,are equipped with volute burners,which consume a large amount of heavy fuel oil（HFO）during cooled start-up and low-load stable combustion.Therefore,by transforming the volute burner into a swirl burner with good flame stability,the HFO consumed to eliminate flame instability due to low-load and changes in operating condition can be saved.At the same time,to save the HFO consumed during the cooled start-up of the boiler,it is of great practical significance to combine various oil-saving technologies.Because of the above problems,in order to develop a new type of swirl burner with axial swirl vanes combining tiny-oil ignition technology,oxygen-enriched ignition technology,and swirl combustion technology,this thesis has carried out basic experimental research and theoretical analysis.An experimental study on the application of oxy-fuel combustion technology which can reduce air pollution emissions,has been carried out.At the end,a numerical simulation calculation was conducted to develop a swirl burner with axial swirl vanes.The main contents of this thesis are as follows:1)As transform the swirl combustion technology developed and utilized in China into a swirl burner suitable for DPR Korea’s anthracite（KA）,in order to explain the change of combustion characteristics caused by the difference in quality between China’s anthracite（CA）and KA,the combustion characteristics of two coals were firstly studied and compared by combustion experiment.The combustion performance of KA was weaker than that of CA based on the ignition,burnout,and comprehensive combustion indexes.And according to the Kissinger-Akahira-Sunose（KAS）method,KA had 112.13 kJ/mol of average apparent activation energy,whereas that of CA was 81.51 kJ/mol.The activation energy of KA was higher than that of CA.For KA,A3/2,R3,and A1 were the most consistent reaction models（A（n）:Avrami-Erofeev（nucleation and growth）reaction mechanism,R（n）:Contracting（phase boundary）reaction mechanism,n:reaction order）,and for CA,they were A3,A2,and A3/2,respectively,while the reaction order of KA was lower than that of CA.2)In order to understand the synergistic combustion characteristics of heavy fuel oil（HFO）and KA during the co-combustion process of boiler start-up ignition,relevant co-combustion experiments were carried out.The combustion stage of HFO-KA mixtures was divided into five stages,namely moisture dehydration（MD）,low-temperature oxidation（LTO）,fuel decomposition（FD）,high-temperature oxidation（HTO）,and fixed carbon burnout（CB）stage.When the mixing ratio changed,as the KA content increased,the DTG and DSC peak values in the LTO and HTO stages of the HFO-KA mixtures decreased,while the DTG and DSC peak values in the CB stage increased.Comparative analysis was conducted on the experimental and predicted values of 75%HFO/25%KA,50%HFO/50%KA,and 25%HFO/75%KA samples.The experimental values of the 25%HFO/75%KA mixture were superior to the predicted values,and the synergistic effect was more obvious.3)The combustion characteristics of KA under oxygen-enriched conditions（O2/N2 atmosphere）were tested and analyzed.The results indicated that the higher the oxygen concentration,the more improvement was made in the combustion characteristics and combustion performance indexes of KA,especially in the ignition index.The result of apparent activation energy with various oxygen concentrations showed that among the apparent activation energy under 21%O2/79%N2,3 0%O2/70%N2,50%O2/50%N2 atmosphere,the apparent activation energy when oxygen concentration was 30%was the smallest.Using the model-free integral master plot method to estimate combustion reaction models with various oxygen concentrations,the nucleation and growth reaction mechanisms were mainly followed when the oxygen concentrations were 21%and 30%.In 50%of cases,the combustion reaction model mainly followed the phase boundary reaction mechanism.4)In order to reduce the greenhouse gas emissions of KA boilers by using carbon capture and storage（CCS）technology,the combustion process of anthracite under oxy-fuel（O2/CO2 atmosphere）conditions were investigated.The results indicated that the higher the oxygen concentration,the better the combustion characteristic parameters and combustion performance indexes of KA.The combustion characteristics parameters of oxy-fuel condition with an oxygen concentration of 30%were mainly similar to those of general air（21%O2/79%N2）,and the kinetics reaction model was completely consistent.Under the same oxygen concentration,the combustion characteristic index of KA in the oxy-fuel condition（O2/CO2 atmosphere）was significantly lower than that in the oxygen-enriched condition（O2/N2 atmosphere）.In O2/N2 and O2/CO2 atmospheres,when the oxygen concentration was 30%,the average apparent activation energy of KA was the lowest.The combustion reaction models at different heating rates were estimated based on oxygen concentration using the model-free integral master plot method.5)The numerical simulation at cooled state was conducted on the modification of the existing volute burner to a swirl burner with axial swirl vanes.The simulation results showed that compared with the volute burner,the swirl burner with axial swirl vanes had more obvious recirculation characteristics,and had greater advantages in the flow field and pulverized coal concentration distribution in the combustion chamber.The optimized structure of the swirl burner was provided,with a large size and velocity of the central recirculation zone,and a high concentration distribution of pulverized coal near the burner outlet. |
