Novel Combustion Technology For Lower-heat-value Gas Control Using Porous Media

A large number of low calorific value gases are directly exhausted because conventional technology is difficult to achieve efficient and clean utilization,which not only causes energy waste,but also serious environmental pollution.The porous media combustion featured by large operation range,high treatment efficiency and low emissions has been attracted extensive attentions in recent years,and thus provides suitable way for clean utilization of low calorific value gases.Based on this,the combustion characteristics of low calorific value ethylene were studied by using a self-built porous media test rig from the aspects of equivalence ratio,premixed flow velocity and pellet diameter.The investigation work is as follows.1.The flammable limits and propagation characteristics of low calorific value ethylene.The flammable conditions for 3 mm and 9 mm alumina pellets burner are all at the moderate fuel-lean conditions(0.3???0.7),but the lower flammable limit of 9 mm alumina pellets is lower than that of 3 mm alumina pellets.It is stationary combustion when the equivalence ratio is ranged from0.450 to 0.550 for 3 mm alumina pellets and 0.500 to 0.550 for 9 mm alumina pellets.If the equivalence ratio is larger,the flame will spread upstream,while the equivalence ratio is smaller,the flame will spread downstream.2.The combustion temperature characteristics of low calorific value ethylene.The combustion temperature is higher when the flame spreads upstream and the highest temperature will be obtained,when the flame spreads upstream at an extremely slow combustion wave velocity,but not stationary.The temperature increases with the premixed flow velocity,especially under the condition of higher equivalence ratio.The combustion temperature for 3mm alumina pellets burner is always higher than 9 mm alumina pellets.3.The combustion wave velocity.When the flame propagates upstream,the combustion wave velocity is directly proportional to the equivalence ratio and inversely proportional to the premixed flow velocity.In contrast,as the flame propagates downstream,the combustion wave velocity is inversely proportion to the equivalence ratio and proportion to premixed flow velocity.When the flame spreads downstream,the burner stacked with 9 mm alumina pellets has a higher combustion wave velocity,whereas the circumstances are opposite as the flame spreads upstream.4.Treatment efficiency and pollutant emissions.The treatment efficiency increases with the equivalence ratio,but is conventionally insensitive to premixed flow velocity.The CO concentration decreases significantly with the equivalence ratio,but the influence of premixed flow velocity is mainly reflected in the low velocity region.In this experiment,NO_x emissions are less than 13 ppm regardless of the conditions.By the comparison,3 mm alumina pellets burner has higher superiority in treatment efficiency and pollutant emissions than 9 mm ball burner.