научная статья по теме THE FLUE GASES CLEANING. MODELLING OF FUMES THERMO DESTRUCTION IN A CYLINDRICAL INCINERATOR Комплексное изучение отдельных стран и регионов

Текст научной статьи на тему «THE FLUE GASES CLEANING. MODELLING OF FUMES THERMO DESTRUCTION IN A CYLINDRICAL INCINERATOR»

ЭНЕРГОЭФФЕКТИВНЫЕ СПОСОБЫ И УСТРОЙСТВА РАЗДЕЛЕНИЯ И ОЧИСТКИ АГРЕССИВНЫХ ГАЗОВЫХ СМЕСЕЙ

ENERGY EFFICIENCY METHODS AND FACILITIES FOR AGGRESSIVE GAS MIXTURE SEPARATION AND PURIFICATION

Статья поступила в редакцию 08.02.10. Ред. per. № 717 The article has entered in publishing office 08.02.10. Ed. reg. No. 717

УДК 66.074.8

ОЧИСТКА ДЫМОВЫХ ГАЗОВ. МОДЕЛИРОВАНИЕ ТЕРМИЧЕСКОГО РАЗРУШЕНИЯ ДЫМОВ В ЦИЛИНДРИЧЕСКОЙ МУСОРОСЖИГАТЕЛЬНОЙ ПЕЧИ

12 1 1 3 3

К. Палм , А. Одраго , И. Одраго , К. Чесно , Б. Жегмати

'Лаборатория органической химии и прикладной физики UFR/SEA Университет Уагадугу 03 BP 7021 Уагадугу 03, Буркина Фасо Fax: (+226) 50 30 72 42, e-mail: palm_kalifa@hotmail.com

Исследовательский институт прикладной науки и техники 03 BP 7047 Уагадугу 03, Буркина Фасо 3Лаборатория математических и физических систем университета Пепигнян 66860 Пепигнян, Франция

Заключение совета рецензентов: 26.02.10 Заключение совета экспертов: 08.03.10 Принято к публикации: 15.03.10

На протяжении многих лет переработка мусора является одной из наиболее серьезных проблем городов и пригородов. Горение мусора, даже горение пластика или бумаги, может производить токсичные загрязняющие вещества. В данной работе мы предлагаем численное моделирование термического разрушения дымов от сжигания городского мусора, состоящего из картона, дерева и пластика, в цилиндрической мусоросжигательной печи. Переносы описываются усиленными уравнениями турбулентности, связанными с уравнениями радиационного переноса и с глобальной кинетической моделью. Уравнения решаются с помощью компьютерного кода FLUENT. Таким образом, влияние массовой скорости потока поступающих дымов на тепломассоперенос в мусоросжигательной печи и эффективность очистки дымов было проанализировано для CO, CO2, CH4, C2H4, H2O, O2. Также в работе представлены преимущества этой термической обработки. Наблюдается уменьшение главной массовой доли этих загрязнителей и, наконец, выяснено, что термическое разрушение менее эффективно при увеличении числа Рейнольдса.

Ключевые слова: дымовые газы, термическое разрушение, мусоросжигательная печь, загрязнители, уравнения переноса.

THE FLUE GASES CLEANING. MODELLING OF FUMES THERMO DESTRUCTION IN A CYLINDRICAL INCINERATOR

K. Palm1'2, A. Ouédraogo1,1. Ouédraogo1, X. Chesneau3, B. Zeghmati3

'Laboratoire de Chimie Organique et Physique Appliquée UFR\SEA Université de Ouagadougou 03 BP 7021 Ouagadougou 03, Burkina Faso. Fax: (+226) 50 30 72 42, e-mail: palm_kalifa@hotmail.com 2Institut de Recherche en Sciences Appliquées et Technologies 03 BP 7047 Ouagadougou 03, Burkina Faso 3Laboratoire de Mathématiques et Physique des Systèmes Université de Perpignan 66860 Perpignan France

Referred: 26.02.10 Expertise: 08.03.10 Accepted: 15.03.10

One of the most serious problems that cities and their surroundings have been facing for years is the garbage treatment. Burning garbage, even burning plastics or paper, can release hazardous pollutants. In this paper, a numerical modelling of the thermo destruction in a cylindrical incinerator of the fumes from the combustion of municipal waste composed of cartoon, wood and plastics is proposed. Transfers are described by forced turbulent equations, associated to radiative transfer equation, and a global kinetics model. The equations are solved using FLUENT Software. Then, the influence of inlet fumes mass flow rate on heat mass transfers in the incinerator and the cleaning up of the fumes effectiveness are analyzed for CO, CO2, CH4, C2H4, H2O, O2 and the advantages of this thermal treatment presented. A reduction of the principal mass fractions of these pollutants is observed and finally the thermodestruction is less efficient when the Reynolds number increases.

Keywords: flue gases, thermodestruction, incinerator, pollutants, transfers equations.

International Scientific Journal for Alternative Energy and Ecology № 5 (85) 2010

© Scientific Technical Centre «TATA», 2010

Institut de Recherche en Sciences Appliquées et Technologies (IRSAT), Ouagadougou.

Research Engineer, 1997.

Ph. D, 2008.

Research Assitant, 2009.

Member of «Laboratoire de Chimie Organique et Physique Appliquée». Scientific interests: Environmental Science and Energy. Publications: 1 in SOACHIM; 1 in ISJAEE; 1 in JSR; 1 in ZJUS-A.

Palm Kalifa

Ouédraogo Alioune

Laboratoire de Chimie Organique et Physique Appliquée, UFR/SEA, University of Ouagadougou. Ph. D, Assistant Professor, 2002. Head of Physics Department, IMP, 1981-1984. Coordinator of Physics-Chemistry section UFR/SEA, 2004. Decoration: Chevalier des Palmes Académiques, 2002. Fullbright grant (USA) 1986-1987 at UC-Davis and Uga-Athens. CIUF grant for 3 months training (Belgium) 1999-2002 at ULB. Scientific interests: Solid State Physics; Ferroelectrics; Environmental Science. Main publications: 4 in Mechanics (BUP); 9 in Solid State (Journal de Physique, Ferroelectrics, Solid State Communications, European Physical Journal, Journal of SOACHIM, JSR, ZJUS-A...); 5 on Environment (Journal of Applied Sciences, Annals of UO, SOACHIM and ISJAEE).

Nomenclature

k: Turbulent kinetic energy (m2s-2) K: Reaction velocity constant (m3mol-1s-1) K0: Frequency or pre-exponential Factor (m3mol-1s-1) Cp: Fumes-air mixture specific heat (Jkg-1K-1) d: Incinerator diameter (m) D: Diffusion coefficient (m2s-1) E: Activation energy (Jmol-1) g: Gravity acceleration (9.81 ms-2) hair: Heat transfer coefficient by natural convection (Wm-2K-1)

H: Incinerator height (m) M: Molar Mass (kgmol-1) n: Moles number (mol) P: dynamic pressure (Pa) Q: Energy (kJ)

r: Radial co-ordinate (m)R: Gas constant (8.314 Jmol-1 K-1)

Re: Reynolds number

Rf thermal resistance (K/W)

S: Area (m2)

T: Temperature (K)

U: Radial component Velocity (m s-1)

V: Axial component Velocity (m s-1)

W : Fumes combustion global rate (s-1)

x: Molar fraction

Y: Mass fraction

z: Axial coordinate (m)

Greek letters Stream function (m2 s-1) 1: Thermal conductivity (W m-1 K-1)

Mixture dynamic viscosity (kgm-1 s-1) p: Air-fumes mixture density (kgm-3) e: Turbulent kinetic energy dissipation rate (m2 s-3)

Subscripts

amb: Ambient

in: Inlet

F: Fluid

i: Isolation type

out: outlet

pout: External wall

pin: Interior wall

rea: Combustion reaction

rad: Radiative

t: Turbulent

T: Temperature

Introduction

More and more cities pay attention to urban and suburban environmental improvement and show stronger desire in environment protection and pursuit of modern and healthy lifestyle. Domestic waste is a major problem for cities in many developing countries because in reason of the increasing of urbanization, a huge quantity of garbage cannot be processed and is found along roads, in street dustbins and on the ground, causing threat to environment and endangering public health. A method of processing domestic garbage proposed by Eldar [1], includes the steps of sorting it into two or more classes and placing each into a unified domestic container. This container is divided in several components. The containers are transferred to a garbage dumping site and

Международный научный журнал «Альтернативная энергетика и экология» № 5 (85) 2010 © Научно-технический центр «TATA», 2010

dismembered into their compartments. Each compartment is then transferred to its respective garbage class treatment location. Among techniques used for garbage treatment, thermo destruction is very widespread, although it is known to produce atmospheric pollution [2]: it is responsible for releasing pollutants in the atmosphere. Even if atmospheric pollution can have natural sources, for example, volcanic eruptions, the term is usually used to refer to the gaseous by-products from man-made processes such as energy production, waste incineration, transport, deforestation and agriculture. Incineration is a waste treatment technology that involves the combustion of organic materials and/or substances [3]. Incineration and other high temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into incinerator bottom ash, flue gases, particulates, and heat, which can in turn be used to generate electric power. The flue gases are cleaned of pollutants before they are dispersed in the atmosphere. In fact, the fumes produced by burning domestic waste include a number of pollutants, especially carbon oxides (COx), sulfur dioxide (SO2), nitrogen oxides (NOx), ammonia (NH3), acids and toxic metals such as mercury, lead, cadmium, nickel and copper particles which can be harmful to both humans, and the environment (Nammari et al., 2004) [4]. Thus, the study of Bahillo and al [5] about ignition of leather shoes waste in Spain shows that 60% of garbage can be transformed in fume including NO, NO2, NH3, SO2, NH3, SO2, Cr2O3, Cr2O2, SiO2 and carbon gas. In order to reduce the effect of fume pollutants on the environment, it is necessary to reduce the waste or the fume. Among the techniques of the treatment of fumes, the thermodestruction is effective. It can be associated for instance with an electric co-generation system [6]. The energy content of waste products can be harnessed directly by using them as a direct combustion fuel, or indirectly by processing them into another type of fuel. Recycling through thermal treatments ranges from using waste as a fuel source, for cooking or heating, to fuel for boilers to generate steam and electricity in a turbine in addition to reducing the volume. This article presents a numerical modelling of thermodestruction in a cylindrical incinerator of the fumes produced by the combustion of domestic waste. The heat, generated by chemical reactions related to the thermodestruction of the main components of the fumes (CO, CO2, CH4, C2H4, H2O) are coupled with the heat, mass and momentum transfers. The purpose of this paper is to analyze the cleaning up effectiveness of fume incineration from burning garbage and to present the advantages of this thermal treatment. The results for different

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