| Zero carbon energy system is the fundamental means to achieve carbon neutrality,so H2,NH3 and other zero carbon energy sources are of great concern.However,at this stage,the combustion equipment and piping system are designed for NG.If H2 is used as the fuel for direct supply,the combustion equipment will need to be replaced and the H2 transmission pipeline and piping system will need to be relayed and replaced.Mixing H2 in NG is an important transition scheme to establish a fully hydrogen energy society.However,H2 incorporation can have a significant effect on the combustion characteristics of existing combustion equipment designed for NG,and this effect has not been fully investigated.To address the current situation that the combustion efficiency and NOx emission after NG doping with H2 are less studied,this thesis conducts a numerical simulation study on the current widely used MILD combustion method,and optimized the JHC burner.The simulations used Species Transport model,Eddy Dissipation Concept,Do radiation model,combined with DRM-22 chemical mechanism,to analyze the effect of adding H2 to NG and different H2 content on combustion,and verified the accuracy of the burner and numerical model by comparing with related experimental results.The results show that with the increase of H2 content,the mixing degree of fuel and oxidizer increases gradually,the internal temperature of the burner increases,the Thermal NOx concentrates on the rear end of the burner;The increase of fuel inlet velocity leads to incomplete combustion in the burner,lower temperature at the outlet;In addition,the hydrogen enriched natural gas is more favorable to achieve MILD combustion conditions than NG.The optimized swirl burner can effectively reduce NOx concentration.With carbon capture-oxygen combustion technology,CO2 is used instead of N2 in the oxidizer to burn in the burner,and as O2 in the oxidizer mixture decreases（CO2 increases）,the reaction intensity,flame speed and flame temperature decrease.The volumetric energy density of H2 is very low,and the high-pressure or low-temperature hydrogen storage and transportation solutions currently used in industry are costly and highly prone to leakage.NH3,which has good storage and transportation safety,is gaining increasing attention.In addition to being a hydrogen carrier,NH3 can also be used as a fuel for direct combustion.Therefore NG blended with NH3 for mixed combustion is also an important transition solution to reduce carbon emissions at present.In addition,due to the slow flame speed and low flame temperature characteristics of NH3,it needs to be mixed with a combustion aid to assist combustion,NG can be used as a combustion aid,NH3 and NG mixed combustion is also of great concern.In this study,the emission characteristics of ammonia enriched natural gas combustion with different NH3 contents in a swirl burner were analyzed and compared with the combustion temperature and NOx emissions of hydrogen enriched natural gas in conjunction with the GRI Mech 3.0 chemical reaction mechanism.The results show that as the NH3 content increases,the laminar flow rate and exothermic rate of the ammonia enriched natural gas combustion monotonically decreases,the internal temperature of the burner decreases,and less CO and CO2 are generated and the NH3at the exit of the burner increases,which is mainly due to the incomplete combustion of the fuel;NOx emission tends to increase and then decrease with increasing NH3content,and NOx emission is higher than that of hydrogen-doped natural gas combustion.In this thesis,the combustion characteristics of the hydrogen enriched natural gas and the ammonia enriched natural gas under MILD combustion and swirl combustion conditions are investigated,and the results can be used to guide the design and optimization of relevant combustion systems,which will make positive guidance for the advancement of hydrogen and ammonia combustion technologies. |
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