A Experimental Study On Combustion Characteristic For Dimethyl Ether

With the rapid and sustained growth of economy, China also exhibits an increasingdemand for energy consumption. However, due to the coal-dominated energy structureof China, the mining and utilization processes associated with coal have caused severedamage to the ecological environment and human beings in the past years. Additionally,the coal of limited reserves can not satisfy the sustainable development of social andeconomy. As a result, an effective way for solving this problem is exploration andutilization of clean fuels, such as the natural gas and oils. However, the effectiveness ofthese conventional fuels is rather limited because of the high price as well as the narrowaccess to them. In addition, the national security problem is often associated with largeimportation of these energy sources.Dimethyl ether (DME) is kind of clean fuel developed in the recent years, and ithas behaviors of high combustion efficiency, high adiabatic temperature, and nearlynone pollution emission etc. Meanwhile, it can be produced from the coal chemicalindustry and the methanol synthesis process in large amounts. Therefore, thecoal-derived DME is fairly conductive to the clean utilization of coal, and it is feasiblerecently. The development and application of DME as a fuel can release the pollutionproblem as well as the energy shortage significantly.By far, DME has been extensively and successfully applied in the chemicalindustry and auto-motives. However, its applications in other combustion systems, forexample, the industrial boilers, were not studied as thoroughly, which reduced its cleanpotentials considerably. The objective of this paper is to introduce DME into the field ofindustrial boilers and to investigate its combustion characteristics by means ofexperiment, and finally, to develop appreciate technologies for its application in theindustrial boilers. In the present study, an medium-scaled gas combustion test platformwas designed and constructed for experiments. The DME flame behaviors were testedon it. The main findings of this paper are as follows:(1) Under the thermal load of120kW, the gas temperatures within the radial ranger=0-50mm slightly reduced along the axial direction until x=750mm, after which thegas temperature fell sharply. At the furnace outlet, temperature was nearly950℃. In theradial range of r=100mm, the gas temperatures remained nearly unchanged along theaxial direction. In the radial range r=100-200mm, gas temperatures increased with the axial distance.(2) At each axial position, gas temperatures decreased with radius of the cylindricalfurnace. Within the range r=0-50mm, temperatures decreased slowly along the radialdirection. Within the range r=50-100mm, they dropped rapidly towards1000℃. Withinthe range r=100-200mm, temperatures dropped rather slightly. Within the ranger=200-250mm, temperatures decreased quickly under the effect of water-cooled wall,falling down to about200℃at the water-cooled wall.(3) Under equal thermal load condition, the excess air coefficient did not changethe flame size. The temperature distributions under different excess air coefficients wererather similar, and the transition point of the centerline temperature profiles alwaysoccurred at the axial position of x=750mm. Moreover, gas temperatures inside theflame zone decreased with the increase of excess air coefficient significantly. the globalgas temperatures in the furnace under the high loads were higher than those under thelow loads.(4) Under the same excess air coefficient, if the thermal load was increased, thetransition point for the centerline temperature curve moved downstream to x=1030mm.Besides, the high temperature area inside the furnace became wide, the dropping pointfor the radial profiles moved outwards to the position of r=150mm.(5) Under the low load condition, the mole fraction of O2increased firstly, and thenreduced gradually along the radial direction. The O2content peaked at about r≈60mm.The CO2content varied inversely with that of O2, reducing firstly, and then increasinggradually along the radius r.(6) According to the measured data, it was inferred that the flame diameter was200mm; the length was750mm under the low load condition. At the high load condition,the flame diameter was300mm, and the flame length was1030mm.Finally, it was analyzed that DME was prior to the traditional fuels in the industrialboilers, in terms of environmental benefits, combustion efficiency, and pricecompetitiveness.The present studies on combustion characteristics and prospect of DME mayprovide referential materials for the application of DME on the industrial boilers in thefuture.