The oily solid waste, which was produced from the oil mine exploiting action in Vietnam, was to be burnt in the primary chamber of the two stable chambers incinerator. The combusting gases in the primary chamber were sampled by the Testo 350 and Testo 360 gas analysers. The recorded gas compositions in the primary chamber were to be employed as a material for the prediction in this paper.
Electronics and Automation PREDICTING THE EFFECT OF RANDOM FACTORS TO THE COMBUSTION OF OILY SOLID WASTE USING FLUENT Le Anh Kien* Abstract: The oily solid waste, which was produced from the oil mine exploiting action in Vietnam, was to be burnt in the primary chamber of the two stable chambers incinerator The combusting gases in the primary chamber were sampled by the Testo 350 and Testo 360 gas analysers The recorded gas compositions in the primary chamber were to be employed as a material for the prediction in this paper The combusting gas properties were hugely varying during the progressing of incineration This paper discusses the effect of random factors of gases species and temperature at the inlet to the combustion in the two stable chambers incinerator The temperature, rate of reaction of CH4 and CO species were monitored in the entirely computing domain A mathematical model of the finite volume method (FVM) was employed to predict the three dimensional reacting flows within these modified incinerator designs Thek- submodel has been employed for turbulence, together with a combustion model of Magnussen and Hjertager A Lagrangian model was used to estimate the residence times for different cases The user-defined functions (UDFs) were created to define the boundary conditions for the modelling The FLUENT of version 6.2 was used as a solver Keywords: Two stable chambers incinerator, Oily solid waste, Incinerator modelling, Fluent INTRODUCTION Currently, due to the demand of economic development in Vietnam, the export products, which will bring the foreign currency, were especially concerned The oil exploiting industry is one of the most important industries in Vietnam For past several years, the quantity of the exploiting product was continuously increasing This caused the oily solid waste quantity increasing rapidly Because of the specific properties of this solid waste, it could not be disposed together with municipal solid waste and industrial solid waste This caused a difficulty for management and disposal work The thermal degradation method is recently taken into account as the best method for the disposal of this type of waste Most of the incinerators that were employed to incinerate oily solid waste are two stable chambers incinerators In the general incineration science, many researchers have shown that the combustion progress of solid waste, biomass was taken place with three main stages The first stage is the water vaporisation, which released moisture in solid phase The second stage is the devolatilisation that released volatile matter The third stage is the char burning that consumed char Depending on the type and properties of material, these stages can occur succeeding and overlapping together [1-5] In this study, the first stage was considered as taking place within after feeding the oily solid waste to the incinerator However, this stage has not only released most of moisture but has released vaporisable hydrocarbon in solid waste as well Furthermore, due to the large amount of mass of solid waste was released shortly, it caused the velocity of gas phase, which was transformed from solid phase, was high and the combustion reactions took place very slow and minor This stage consumed about 30% of initial feeding mass The second stage took place within 15 to 25 from the first stage This stage devolatilised about 50% of initial mass to form char and tar The volatilised products mainly comprised oil in waste and cracking products from solid waste In this stage, owing 104 L A Kien “Predicting the effect of random factors …” Research to the combustion of volatilised matter, the temperature in the incinerator was increasing The temperature and the devolatilisation of matter in this stage were to be considered as the highest and major The third stage took place within 30 to 50 from end of the second stage, consumed about 10% of initial mass of solid waste In this stage, the process was the burning up of char and forming ash The chemical reaction was the combustion of char with air to release carbon monoxide (CO) and carbon dioxide (CO2) The ratio of CO and CO2 was depending on the incidence of oxygen [6, 7] In this stage, due to the combustion rate was low and the air supplied was not reducing, the temperature of the incinerator, therefore, was dropping down toward the end of the incineration process For the above reasons, it has been assumed that the gas products from the oily solid waste combustion were quite different to the other materials Therefore, in order to have a master view about the environmental impacted assessment during the processing of oily solid waste, the mathematical modelling technique have been employed to survey concentration of the pollutants at the outlet of the rig and the technical requirements for the incineration performance Furthermore, due to the properties of incinerated products were varied in a wide range during the combustion taking place, it also affected to the burning efficiency in the secondary chamber Therefore, it influenced to the environmental atmosphere around the stack The combustion in the two stable chambers incinerator was employed in the research of Jangsawang et al (2005) This research showed the influence of secondary air on the combustion [8] Rogaume et al (2002) presented the effects of different airflows on the formation of pollutants in the incineration on fixed bed reactor [9] There have also been some researchers performed their studies on the changing of condition reaction, fuel properties, or types of initial materials [10-14] They all contributed to the understanding of combustion in different apparatus, different operating conditions, and different types of material However, there were no studies carried out on the effect of random factors at the inlet in the two stable chambers incinerator whilst the combustion taking place This paper would contribute to the understanding of the effects of species concentration variation and temperature to the prediction in the secondary chamber of the two stable chambers incinerator EXPERIMENT 2.1 Material for modelling and simulation The research was conducted on the pilot incinerator in Institute for Tropical Technology and Environment (ITE) as shown: Figure 1.The pilot incinerator (1) Primary chamber;(2) Secondary chamber; (3) Outlet pipe that the flue gas escaped; (4) Bottom of the incinerator that the primary air entered from; (5) Connected pipe between two chambers Journal of Military Science and Technology, Special Issue, No 48A, - 2017 105 Electronics and Automation At the primary chamber, oily solid fuel was fed as a batch The capacity for each batch was 5kg The primary air was set to be a constant of 936kg/m2h, and entered the incinerator from the bottom The gases in the prima primary ry chamber flew up to the secondary chamber via a connected pipe The online gas analyser Testo 360 (Germany) was conducted to measure the components of incinerated products The probe of the Testo360 was posited at the connected pipe The basis dimensions of the pilot incinerator were: the capacity of primary chamber was 54 litres The capacity of secondary chamber was 72 litres The dimension of connected pipe and outlet were 20 centimetres The mean values of temperature and species mass fraction inlet w were ere tabulated in Table 1, as: Table Temperature and gas concentrations in primary chamber chamber Time Temperature Mass fraction of species, % (min) CH4 CO CO2 O2 H2O C) (C)