Startup And Energy Utilization Of Porous Media Built-in Swiss-roll Burner

Ventilation air methane (VAM), which has a great amount of emission, has to be emitted to the air, because the CH4 concentration of VAM is about 0.1-1%, is far less than the lean-combustible limit of CH4, which is 5%. This results in a waste of energy, and on the other hand, methane is a serious greenhouse gas, its Global Warming Potential (GWP) is 21 times of CO2. Therefore, the rational use of the methane mixed in the ventilation air methane, has a double significance, energy conservation and environmental protection.Both porous medium burner and Swiss-roll burner can achieve excess enthalpy combustion, decreasing the fuel lean-combustible limit. Moreover, we can get a stable flame in porous media. In this article, we filled porous media into center of a conventional size Swiss-roll burner. And the ignition process, lean-combustible limit, thermal energy utilization were studied on a self designed combustion experiment platform. On this basis the clean development mechanism (CDM) analysis was carried out.A combustion experiment platform is built, which consists of four parts:the precise supply system of fuel and oxidizer, testing instruments and equipments, the computer integrated display and record system of operating parameters, combustion reactor. For different reactors and study subjects, the experiment platform can provide a common interface, qualitative and quantitative measurements can be carried out on the reaction products and the reactor's operating parameters (such as temperature, pressure). In addition, the experiment platform's functions can be expanded.The ignition method and the combustion characteristics of start-up process of the burner were studied. Because the center of the combustion zone is filled with porous medium, the surface quenching effect is great in cold state, making ignition difficult. First, the ignition theory of methane was analyzed, and on this basis two different ignition methods were designed:1) ignite in porous media center with a single-tube diffusion burner; 2) left a gap of about 10mm in porous media center, and use electric spark or heating wire to ignite. When ignition starts, with the porous medium temperature and combustion efficiency increased, unburned CH4 and CO concentrations decreased gradually, and NOx emissions is very low in the whole process. The nature of porous media and the flow rate of pre-mixed gas have a great effect on the starting characteristics. When premixed gas flow is 3.49L/s, when the CH4 concentration dropped to 1.3%, the unburned CH4 increased, and CO emissions up to 1000 mg/m3, and the combustion efficiency decreased to 70%. This indicates that the Swiss-roll burner with built-in porous media has achieved counter-current heat exchange between high temperature flue gas and inlet gas, and pre-mixed gas is further heated in the central area of the porous medium, the fuel lean-combustible limit is significant expanded.We use FLUENT6.3 to simulate the methane/air igniting process in porous media built-in Swiss-roll burner. The cold flow field, the flame fronter evolvement process of the start process, and the temperature changes of burner when CH4 concentration decreased are obtained. The temperature distribution evolvement process, got from numerical simulation, has a good agreement with experiments, but the overall temperature distribution is higher than the experiment.A heat exchanger is placed in porous media. The energy conversion and transfer relations of the porous media built-in Swiss-roll burner and its heat energy utilization system were analyzed. And based on this, a heat balance model of the system was built. The effect of heat extraction on the combustion characters and heat extraction and thermal efficiency under different conditions were studied. In this basis, the control system was designed, to avoid extinction for low concentration ventilation air methane and over heating of burner for high concentration ventilation air methane. Experiment result shows that the position of heat exchanger in porous media is very important, because the movement of flame front in porous media. In addition, while excess heat is continuously removed, the flame front will be backward, and the combustion efficiency will decline.The projects based on this device can decrease CO2 equivalent emissions, and is qualified as a Clean Development Mechanism (CDM) project, because it's in accordance with ACM0008 (version 6) methodological requirements. Taking a coal mine in northern Anhui for example, the supererogatory, baseline and emissions of the project was analyzed and calculated, and a technical economic analysis was carried out.