Study On The Causes Of Yellow Smoke Formation In The Start-up Process Of Heavy-duty Gas Turbine Combined Cycle

The gas-steam combined cycle power generation system is an efficient power generation system integrating a gas turbine Brayton Cycle and a steam turbine Rankine Cycle.The combined cycle power generation system has the advantages of high speed starting and stopping,high thermal efficiency,and low pollutant emissions.It is an important means for the peak-load adjustment of power network.During the start-up process of a large number of combined-cycle units,the waste heat boiler's chimneys have light or heavy yellow smoke.Studies have shown that the main reason for the yellow smoke emitted from the combined-cycle chimney is that the smoke contains a certain amount of NO2.Generally speaking,the NOx produced in the combustion chamber of the gas turbine is mainly NO.Some studies have considered that NO has generated a certain concentration of NO2 in the NO-NO2 conversion reaction during the exhaust process,resulting in a yellowish flue gas.In this thesis,reaction simulation,experimental verification and on-site testing are used to study the effects of concentrations of components such as carbon monoxide,oxygen,nitric oxide,and water vapor,and the temperature and residence time on the conversion of NO-NO2.The details are as follows:1)Plunge flow reactor(PFR)calculation was used to research the effect of composition and temperature on the conversion of NO-NO2 through chemkin calculations and experiments.Studies have shown that under the typical components of gas turbine exhaust,the presence of CO will cause the NO to NO2 conversion in the exhaust gas,600-700 ? is the temperature range of highest NO conversion.At temperatures below 400? or above 800?,the conversion of NO to NO2 is very low.At the same time,a certain amount of water vapor and oxygen are the necessary conditions for the conversion reaction.When the oxygen volume fraction is within 5%,the effect on the conversion rate of NO is large,and after 5%oxygen concentration,the NO conversion rate tends to be stabilized by the oxygen concentration.2)The sensitivity analysis method was used to analyze the elementary reactions and high activity radicals that have a great influence on the NO-NO2 conversion reaction.Studies have shown that,at 450?-650?,CO oxidation and NO oxidation are coupled to each other to form a chain reaction and can promote oxidation.With the increase of temperature,the chain reaction is gradually decoupled.When the temperature is higher than about 800?,the dependence of CO on the oxidation reaction with NO in the oxidation process is greatly weakened,and the NO-NO2 conversion rate is reduced.The conversion rate of NO first reaches a maximum with increasing temperature,and then falls.3)By measuring the exhaust components in the start-up process of the 6FA gas turbine combined cycle unit,the NO-NO2 conversion law of the combined cycle unit during actual operation is analyzed.The results show that the NO2 of the 6FA gas engine during the start-up process consists of two parts,one is the combustion chamber exhaust,and the other is the conversion of NO into the waste heat boiler.