Introduction to Furnace

CONTENTS
1.Introduction
2.Applications
3.Classification
4.Types
5.Charachterstics of an Efficient Furnace
6. Economic Measure of Surnace
7. Modes of Heat Transfer in Furnaces

1. Introduction to Furnaces

2. Presented by : Hadi 16CH18 Hasnain 16CH42 Murtaza 16CH48 Fatima 16CH19 Sana 16CH13 Zain 16CH116 Rakesh 16CH104 Mumtaz 16CH36 Iftikhar 16CH47 Aashir 16CH38 Other Group Members:

3. Table on contents 1. What is a Furnace, and its Uses 2. Types and Classifications 3. Characteristics of an Efficient Furnace 4. Economic Measures in a furnace5. 5. Correct Heat Distribution 6. Heat Transfer in Furnaces

4. What are Furnaces ? A furnace is a device used for high-temperature heating. The name derives from Greek word fornax, which means oven. The heat energy to fuel a furnace may be supplied directly by fuel combustion, by electricity such as the electric arc furnace, or through induction heating in induction furnaces.

5. Uses of Furnace A furnace is an equipment to Melt the Metals for Casting. for Heating the different Materials. for Changing Shape (rolling, forging etc ) for Change Properties (Heat Treatment). They are also used Extraction of Metal from ore or in Oil Refineries for example as the heat source for fractional distillation columns.

6. Types and Classification Furnaces are classified into four general categories based on efficiency and design Natural Draft Forced- Air Forced Draft Condensing

7. Natural Draft Furnace These furnaces consisted of cast-iron or riveted-steel heat exchangers built within an outer shell of brick, masonry, or steel. Heat exchanger is vented to the chimney. Air-Circulation mostly depend upon the pitches of pipe and their material of construction. Mostly made metallic or wooden. Works on the Beyoncé Effect. The pipes would channel the warm air into floor or wall vents inside the home. This method of heating worked because warm air rises. They have been operated with wood, coke, coal, trash, paper, natural gas, and fuel oil. Furnaces that used solid fuels required daily maintenance to remove ash and "clinkers“ that accumulated in the bottom of the burner area.

8. Forced – Air Furnace These furnaces have Atmospheric Burner Style with a cast-iron or sectional steel heat exchanger. The heated air was moved by blowers which were belt driven and designed for a wide range of speeds. As compared to modern furnaces these furnaces were still big, heavy and bulky and had heavy-steel exteriors

9. Forced Draft Furnace Forced Draft Furnaces have intermediate-efficiency w.r.t to Natural and Forced Air Furnaces. These furnaces has also a steel made heat exchanger and multi-speed blower. Physically they are much more compact than the previous styles. Because they are equipped with Combustion Air Blowers that would pull air through the heat exchanger and greatly Increased fuel efficiency while allowing the heat exchangers to become smaller. These furnaces may have multi-speed blowers and were designed to work with central air-conditioning systems.

10. Condensing Furnace The fourth category of furnace is the high-efficiency, or condensing furnace. High-efficiency furnaces can achieve from 89% to 98% fuel efficiency. This style of furnace includes, - Sealed Combustion Area, -Combustion Draft Inducer -and a Secondary Heat Exchanger. Because the heat exchanger removes most of the heat from the exhaust gas, it actually condenses water vapor and other chemicals (which form a mild acid) as it operates.

11. The Classification of Furnace fired On the basis of Firing System, Furnaces can be Direct fired, Over fired, Under fired, or Side fired . -In direct fired furnaces, the heat is produced inside of the furnace chamber. -While in over, under, and side fired furnaces, heat is produced in a chamber in the respective area and flows throughout the furnace.

12. The Types of Furnaces

13. Melting Furnaces There are many types of the melting furnaces that are mostly applied in the foundry shop. This type of furnace depends upon the type of metal and the quantity of metal that is to be melted.

14. The Main types of Furnaces that are used in the foundry shop are : Cupola furnace = for cast iron. Blast Furnace = for smelting iron to produce pig iron. Open hearth furnace = for steel . Crucible furnace = for non ferrous metal. Electric furnace= dielectric and induction furnace.

15. Cupola Furnace A cupola furnace is a melting device used in foundries that can be used to melt scrap metal and pig iron (crude iron as first obtained from a furnace) for production of various cast irons and malleable cast iron. Cupola furnace consists of a large shell of steel plate lined with refractory material.

16. Parts of the Cupola Furnace Spark arrester. Charging door. Air box. Tuyeres . Tap hole. Slag hole.

17. Working of Cupola Furnace PLAY VIDEO

18. Solar Furnace A solar furnace is a structure used to harness the rays of the sun in order to produce high temperatures. This is achieved by using a curved mirror (or an array of mirrors) acting as a parabolic reflector to concentrate light (Insolation) on to a focal point. The temperature at the focal point may reach up to 3,000 degrees Celsius, and this heat can be used to generate electricity, melt steel or make hydrogen fuel.

19. How the Solar Furnace Works ( model ) The initial creator of the solar furnace designed it as a self-sufficient device. The heat collector is a black metal plate that is placed in full sun. A photovoltaic solar cell powers the fan, pushing cold air from outside into the bottom of the box. Then, as it is pushed upwards by the fan, the air starts to warm from the contact with the back of the black plate, and exits at the top of the box, in your room. The box has to be insulated at its back, to prevent heat loss to the cold side. And because it’s solar powered, when there’s enough sun outside to power the fan, there’s enough power to heat your room – it’s a self-regulating device, the simplest possible.

20. Blast Furnace Blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals and its alloys, generally iron in a blast furnace fuel (coke), ores, and flux (limestone) are continuously supplied through the top of the furnace, while a hot blast of air is blown into the lower section of the furnace The end products are usually molten metal and slag phases tapped from the bottom, and flue gases exiting from the top of the furnace. The blast furnace is built of steel case and bricks that are made of magnesia that is very much resistant to heat and it does not melt.

21. Blast Furnace PLAY VIDEO

22. Electric Arc Furnace An Electric Arc Furnace (EAF) is a furnace that heats charged material by means of an electric arc. Arc furnaces range in size from small units of approximately one ton capacity (used in foundries for producing cast iron products) up to about 400 ton units used for secondary steelmaking Industrial electric arc furnace temperatures can be up to 1,800 °C, (3272 °F) while laboratory units can exceed 3,000 °C. (5432 °F)

23. Advantages of Electric Arc Furnace This greatly reduces the energy required to make steel when compared with primary steelmaking from ores Another benefit is flexibility: while blast furnaces cannot vary their production by much and can remain in operation for years at a time

24. Disadvantages of Electric Arc Furnace Slag production Cooling water demand Heavy truck traffic for scrap, materials handling, and product Environmental effects of electricity generation

25. Characteristics of an efficient Furnace The furnace must have following Characteristics to attain maximum possible efficiency. 1.Will Heat in very less time. 2.Maximum Material could be heated. 3.Will Uniformly Raise the temperature. 4.Will consume less fuel. 5.Least possible labor. Furnace should be designed so that in a given time, as much of material as possible can be heated to an uniform temperature as possible with the least possible fuel and labor.

26. Economic Measures in Furnaces 1) Complete combustion with minimum excess air 2) Correct heat distribution 3) Operating at the desired temperature 4) Reducing heat losses from furnace openings 5) Maintaining correct amount of furnace draught 6) Optimum capacity utilization 7) Waste heat recovery from the flue gases 8) Minimum refractory losses 9) Use of Ceramic Coatings

27. Correct Heat Distribution Correct Heat Distribution is done by Avoiding High flame temperature which can also damage the Refractory. It also result in better atomization. Burner should be aligned properly so that it can’t directly touch the material for scale loss.

28. Operating at Optimal Temperature Correct temperature ensures good quality products. Temperature higher than required would spoil the products and consume more fuel.  For maintaining specified temperature, we shouldn’t leave it on operator judgment but we should use automatic  ON/OFF  controls

29. Reducing Heat Loss from Furnace Most of the Heat is lost through openings by means of Direct radiation or Combustion Gas that leaks through openings.  Keeping the doors unnecessarily open leads to wastage of fuel. Inspection doors should not kept open during operation. Broken and damaged doors should be repaired  The extent of heat losses from wall depend on: a. Emissivity of wall. b. Thermal conductivity of refractories. c. Wall thickness. D. and Whether furnace is operated continuously or batch-wise.  

30. Reducing Heat losses by Using Ceramic Coatings Use of Ceramic Coatings The benefits of applying a ceramic coating: Rapid heat-up. Increased heat transfer at steady state. Improved temperature uniformity. Increased refractory life. Elimination of refractory dust.

31. Heat Transfer in Furnaces •Heat is transferred from flame to Combustion Products, Roof and Walls by means of Radiation. -Convective Heat Transfer takes place due to the movement of hot gases over the stock surface.

32. THANKS