Research On Key Issue Of Replace Coal With Natural Gas As A Boiler Fuel

China has a huge number of industrial boilers;they are the main consumers of coal.Because of a large proportion of small and medium capacity boilers,distribution of scattered and difficult to control emissions,these boiler has become a major source of air pollution."Coal to gas" means "Using natural gas?Or other clean gaseous fuel?instead of coal as a fuel of boiler",so as to achieve the purpose of energy conservation.There are many ways to achieve "coal to gas",and this paper is based on a "coal to gas" project of a boiler?Model:SHL20-1.25?.We proposed a scheme without changing the main structure of the boiler body and pressure parts,but only transforming the combustion system,and researched the key issues in the project.The main contents of this paper as follows:?1?We analyzed the influence of coal to gas on radiation heat transfer process in the boiler.After replace coal with natural gas,its furnace gas blackness is 0.28;the blackness range of coal-fired boiler gas is between 0.6 and 0.7;If do not consider the impact of the carbon particles,different excess air ratio made little effect to the furnace gas blackness.?2?We analyzed the influence of coal to gas on convective heat transfer process in the boiler.Due to the change of fuel and combustion conditions,the combustion efficiency improve by 16%,and reduction of the combustion products reducing the flow rate of the smoke in the channel,so that the convective heat transfer coefficient is reduced by about 19%?3?For these conditions above,we made some changes in the structure such as:increasing a wall,so it can strengthen the radiation and increasing the number of deflector,so it makes the smoke flowing faster,In order to reduce the impact caused by "Coal to gas".?4?Compare with "Overall removal","Partial reconstruction" can greatly reduce the cost in the project of "Coal to gas"."Coal to gas" improved the efficiency of a boiler from 73%to almost 90%,at the same time,the emission of CO₂ and No_x are reduced by 70%and 14%,the emission of SO₂ is almost 0.