Characteristics Research On Mixed Combustion Of Dissociated Methanol In Boiler

In recent years,energy conservation and environmental protection have become urgent.The idea that green water and green mountains are the golden mountains and silver mountains is deeply rooted in the hearts of the people.Carbon peaks and carbon emissions reduction have a long way to go.The use of coal in boilers pollutes the environment,and natural gas is a non-renewable energy source,and my country’s dependence on natural gas has exceeded 43%.The energy crisis has become increasingly prominent.As a renewable clean energy,methanol has always been favored by people.In view of this,this paper studies the combustion and emission characteristics of small vertical boilers burning natural gas,methanol and its cracked gas;and then studies the combustion and emission characteristics of large industrial boilers burning methanol and mixed methanol cracking gas.First,simulate the burning of natural gas,methanol and its cracked gas in a vertical boiler.By changing the excess air coefficient,the gas velocity,temperature and component concentration changes in the furnace are explored.Studies have shown that when the excess air coefficient is 1.2,the combustion state of the boiler using methanol and natural gas is the best.When the methanol cracking gas blending ratio is 0%,10%,30%,50% and 80%,as the blending ratio increases,the average boiler temperature increases,and the outlet CO2 is basically stable around 14%～15%,The amount of outlet CO increases,and the concentration of formaldehyde at the outlet of the boiler decreases.By changing the height of the boiler,it is found that as the height of the boiler increases,the average temperature in the furnace first increases and then slowly decreases,the concentration of CO2 at the outlet increases,and the concentration of CO and formaldehyde decreases.Under the condition of30% blending ratio and 0.8m boiler outer diameter,the boiler with a height of 1.2m has the best combustion characteristics.Second,study the combustion and emission characteristics of large-scale boilers that are converted to methanol and mixed with methanol pyrolysis gas.The results showed that with the increase of the mixing ratio of methanol cracking gas,the average temperature of the furnace increased.When burning methanol,the average furnace temperature is 1255K;when the blending ratio is 10%,the temperature increases by 200 K,indicating that a small amount of methanol cracking gas has a strong promotion effect on boiler combustion.When the blending ratio is increased from 50% to 80%,the temperature increase is not obvious.As the blending ratio increases,the CO concentration increases slowly and the formaldehyde concentration decreases.This is consistent with the emission characteristics of small boilers,but the amount of harmful gas emissions is more than that of small boilers.Considering the influence of combustion and emission characteristics on boiler life,performance,and economy,when large-scale boilers use methanol and its cracked gas,it is best to choose a ratio of 30% to 50% for the combustion of cracked gas.Finally,based on the characteristics of the boiler mixed with methanol cracked gas,a method of catalytically cracking part of methanol fuel using boiler flue gas waste heat to further improve efficiency and reduce emissions is proposed,which can theoretically increase the calorific value of fuel by 21%.