Modeling the Combustion Behavior of Hazardous Waste in a Rotary Kiln Incinerator

Abstract

Hazardous wastes have complex physical forms and chemical compositions and are normally incinerated in rotary kilns for safe disposal and energy recovery. In the rotary kiln, the multifeed stream and wide variation of thermal, physical, and chemical properties of the wastes cause the incineration system to be highly heterogeneous, with severe temperature fluctuations and unsteady combustion chemistry. Incomplete combustion is often the consequence, and the process is difficult to control. In this article, modeling of the waste combustion is described by using computational fluid dynamics (CFD). Through CFD simulation, gas flow and mixing, turbulent combustion, and heat transfer inside the incinerator were predicted and visualized. As the first step, the waste in various forms was modeled to a hydrocarbon-based virtual fuel mixture. The combustion of the simplified waste was then simulated with a seven-gas combustion model within a CFD framework. Comparison was made with previous global three-gas combustion model with which no chemical behavior can be derived. The distribution of temperature and chemical species has been investigated. The waste combustion model was validated with temperature measurements. Various operating conditions and the influence on the incineration performance were then simulated. Through this research, a better process understanding and potential optimization of the design were attained.

Further Study on Ash Deposits in a Large-Scale Wastewater Incineration Plant: Ash Fusion Characteristics and Kinetics

“…Lim 38 used DSC to find that Na 3 H(SO 4 ) 2 underwent three successive phase transitions at 296, 513, and 533 K. The remarkable weight loss from 480 to 620 K was therefore mainly attributable to the phase transitions of Na 3 H(SO 4 ) 2 and further decomposition. The melting and evaporation of Na 3 Fe(SO 4 ) 3 and Na 2 SO 4 were responsible for the second continuous, fluctuating weight loss process from 910 to 1320 K. Continuous endothermic sections in the DSC curve showed that Na 3 H-(SO 4 ) 2 phase transitions also took place. When the heating temperature rose above 920 K, several endothermic processes related to the melting, decomposition, and/or evaporation of Na 3 Fe(SO 4 ) 3 and Na 2 SO 4 mentioned above all occurred.…”

“…The thermal conversion technologies of incineration and pyrolysis are well-established methods that can be used to dispose of industrial organic wastewater with high toxicity, poor biodegradability, and complex compositions . Liquid-injection incinerators, rotary kiln waste incinerators, and circulating fluidized-bed boilers , combined with heat recovery steam generators (HRSGs) are commonly used for the thermal degradation of hazardous substances containing industrial high-concentration organic wastewater, because they are easy to control and simple in structure.…”

Operating Conditions of A Locally Made Fixed-Bed Incinerator, a Case Study of Bagamoyo – Tanzania

“…The flue gas from incinerator contain particles and gases which are harmful and toxic to human and environment [21]. If the mixing level of the burnt wastes are better operated, the amount of pollutants to the environment will be reduced [22]. The emission gases from incinerator indicate the combustion behavior of the incinerator, design, operation and the mixing of waste materials in the combustion chamber [23,24].…”

Optimization of incineration process

“…The flue gas from incinerator contain particles and gases which are harmful and toxic to human and environment (Wey et al, 2001). If the mixing level of the burnt wastes are better operated, the amount of pollutants to the environment will be reduced (Yang et al, 2005). The emission gases from incinerator indicate the combustion behavior of the incinerator, design, operation and the mixing of waste materials in the combustion chamber (Glarborg, 2007;Manyele and Kagonji, 2012).…”