Master thesis - DiVA portal

Mohammad Parsamehr. Environmental Engineering Department. Mid Sweden University. Master thesis (30 credits). Supervisor. Dr. Nils Nilsson. Autumn 2012 ...
702KB Sizes 106 Downloads 367 Views
Heat generation by cow dung incineration in the north of Iran

Mohammad Parsamehr

Environmental Engineering Department Mid Sweden University Master thesis (30 credits) Supervisor Dr. Nils Nilsson Autumn 2012 I

Abstract

The main objective of this thesis was to design an incinerator which was fuelled by cow dung. The purpose of this study was to investigate if the designed incinerator can provide the heat needs of a medium size farm in the north of Iran. This project was conducted to study local energy sources accessible in a farm to cut the costs of fossil fuels in one hand and reduction of environmental impacts caused by use of those fuels in the other hand. The whole system was composed of heating elements inside the farm building and an incineration system to heat generation by combusting dry cow dung outside the farm building. The wet manure contained 40% moisture that should be dried by passing through two dryers in series before entering the incinerator. An appropriate water-tube boiler has been designed to boil water which condensed in a condenser so that the latent heat of steam has used for heating the building. A shell and tube heat exchanger has been designed for condensing the steam in the shell side and warming up water flow circulated through heating elements in the tube side. Therefore there are two water cycles one within the heat generation system and the other cycle through heating elements which are designed to exchange heat inside a condenser. About the dryers it is attempted to use recoverable heat of flue gas so that the heat required for the drying section is supplied by the stack of incinerator. As the result of the project, proposed system is evaluated in terms of heat balance and thermal efficiency. Calculation shows that the system is quite sufficient to supply heat needs of the farm and the theoretical thermal efficiency of the system is about 78%.

Key words Incineration, cow dung, drying, heat recovery, heating system II

Table of content 1. Introduction………………………………………………………………………….1 1.1 Background………………………………………………………………………1 1.2 Design criteria……………………………………………………………………5 2. Purpose of the thesis………………………………………………………………...8 3. Method………………………………………………………………………………..9 4. Theory………………………………………………………………………………....9 4.1.Heat transfer modes……………………………………………………………..9 4.1.1. Conduction……………………………………………………………….9 4.1.2. Convection………………………………………………………………..10 4.1.3. Radiation………………………………………………………………….10 4.1.4. Rate of heat transfer……………………………………………………...11 4.1.5. LMTD method…………………………………………………………….11 4.1.6. NTU-effectiveness method………………………………………………11 4.2.Combustion……………………………………………………………………….12 4.2.1. Calorific value…………………………………………………………….12 4.2.2. Excess air………………………………………………………………….12 4.2.3. Flue gas…………………………………………………………………....13 4.2.4. Adiabatic combustion temperature…………………………………….13 4.2.5. Water-tube boiler design…...…………………………………………....13 4.3.Drying……………………………………………………………………………..13 4.3.1. Rate of drying…………………………………………………………….14 4.3.2. Types of dryers…………………………………………………………...14 5. Results………………………………………………………………………………....14 5.1.Heat demand……………………………………………………………………...14 5.2.Heating system…………………………………………………………………...15 6.

Discussion…………………………………………………………………………….24 6.1.Process description……………………………………………………………….24 6.2.Alternatives for use of cow dung in a farm………………………………….…27 6.3.Advantages of the system………………………………………………………..27 6.4.Disadvantages of the system…………………………………………………….27 6.5.Future prospect…………………………………………………………………..28

7. Conclusion…………………………………………………………………………….28 III

8. References……………………………………………………………………………..29 9. Appendices……………………………………………………………………………32 Appendix A……………………………………………………………………………32 Appendix B…………………………………………………………………………….34 Appendix C…………………………………………………………………………….39

IV

1. Introduction 1.1 Background Vast pastures together with an appropriate climate have made the northern provinces of Iran as a region of high potential for devel