Formation and Growth Behavior Analysis of Slagging Rings in Rotary Kiln-Type Hazardous Waste Incineration Systems

Rotary kiln incineration technology has the advantages of strong material adaptability and a simple treatment process and has been widely used in hazardous waste treatment. However, the actual incineration process has caused problems such as ring formation in the treatment system due to the lack of research on the slagging mechanisms. In this paper, slagging phenomena occurring in the second half of the rotary kiln, the exit flue of the secondary combustion chamber, and the wall of the quench tower are analyzed and discussed in detail through characterization methods. The results indicate that the adhesion of low-melting alkali metal salts on the refractory surface in the second half of the rotary kiln is the key factor in forming the initial slagging layer. In the growth process of the slagging ring, the formed liquid phase can bond incineration residues of different sizes together and form a dense embryo body through liquid phase sintering. The deposition and solidification of molten/semi-molten fly ashes cause slagging formation in the exit flue of the secondary combustion chamber. The slagging phenomenon occurring in the inner wall of the quench tower belongs to the “crystalline-coalesce-hardening” process of the inorganic salts precipitating out of the high-salt wastewater.

Numerical analysis of exhaust jet secondary combustion in hypersonic flow field

The interaction effect between jet and control surface in supersonic and hypersonic flow is one of the key problems for advanced flight control system. The flow properties of exhaust jet secondary combustion in a hypersonic compression ramp flow field were studied numerically by solving the Navier–Stokes equations with multi-species and combustion reaction effects. The analysis was focused on the flow field structure and the force amplification factor under different jet conditions. Numerical results show that a series of different secondary combustion makes the flow field structure change regularly, and the temperature increases rapidly near the jet exit.

Numerical Study of Air Distribution in Combustion Chamber

The main goal of this article is to analyze the distribution of primary and secondary combustion air in a combustion chamber. The fuel for the combustion chamber is biomass and the main characteristics the combustion chamber must meet is to be simple, reliable, cheap and ecological. A brief summary of the importance of primary and secondary air is made and then it is compared with the results from the numerical model. The numerical model is based upon a simplified chamber geometry and the results are computed for laminar and turbulent flow. From the comparison are determined flaws of the design of the combustion chamber and outlined possible solutions for their removal and further direction of the study.

Operability and Performance of Central (Pilot) Stage of an Industrial Prototype Burner

An investigation on the central-pilot stage of a Siemens Industrial Turbomachinery 4th Generation DLE prototype test burner has been performed to understand the emission performance and operability. The core section, which is defined as RPL (Rich premixed lean) plays an important role for full burner combustion operation by stabilizing the main and pilot flames at different operating condition. Optimal fuel-air flow through the RPL is critical for multiple stages mixing and main flame anchoring. Heat and radical production from the central stage provides the ignition source and required heat for burning the main flame downstream of the RPL section. Surrounding the RPL outside wall cooling air has been blown through an annular passage. The cooling air protects the RPL wall from overheating and provides the oxygen source for the secondary combustion downstream of the RPL. At rich operation unburned hydrocarbon/radicals can pass the RPL and burns by the co-flow air entrainment. To determine the flame stabilization and operability, an atmospheric pressure test has been accomplished using methane as a fuel. Primary flame zone can be identified by a thermocouple placed outside the RPL wall and secondary combustion zone at the exit has been examined by chemiluminescence imaging. Emission measurement and LBO (Lean blow out) limits have been determined for different equivalence ratios from 1.8 to LBO limit. Co-flow air temperature was changed from 303 K to 573 K to evaluate the secondary combustion and RPL wall heat transfer effect on flame stability/emission. It is found that equivalence ratio has strong effect on the RPL flame stabilization (primary/secondary flame). Emissions/radical generation were also influenced by the chemical reaction inside the RPL. It can be noticed that co-flow air temperature has a significant role on emission, LBO and flame stabilization for the central-pilot stage burner due to the heat loss from the flame zone and RPL wall. A chemical kinetic network (Chemkin™) and CFD modelling approaches (Fluent) are employed to understand in detail the chemical kinetics, heat transfer effect and flow field inside the RPL (combustion and heat loss inside and emission capability). Experiment shows that the low CO and NOx levels can be achieved at lean and rich condition due to lower flame temperature. Present experimental results by changing equivalence ratio, residence time and co-flow temperature, creates a complete map for the RPL combustion, which is key input for full 4th Generation DLE burner design.