Industrial furnaces

A furnace or direct fired heater is equipment used to provide heat for a process or can serve as reactor which provides heats of reaction. Furnace designs vary as to its function, heating duty, type of fuel and method of introducing combustion air. However, all furnaces have some common features.

Fuel flows into the burner and is burnt with air provided from an air blower. There can be more than one burner in a particular furnace which can be arranged in cells which heat a particular set of tubes. Burners can also be floor mounted, wall mounted or roof mounted depending on design. The flames heat up the tubes, which in turn heat the fluid inside in the first part of the furnace known as the radiant section. In the chamber where combustion takes place, known as the firebox, the heat is transferred mainly by radiation to tubes around the fire in the chamber. The heating fluid passes through the tubes and is thus heated to the desired temperature. The gases from the combustion are known as flue gases. After the flue gas leaves the firebox, most furnace designs include a convection section where more heat is recovered before venting to the atmosphere through the flue gas stack. (HTF=Heat Transfer Fluid. Industries commonly use their furnaces to heat a secondary fluid with special additives like anti-rust and high heat transfer efficiency. This heated fluid is then circulated round the whole plant to heat exchangers to be used wherever heat is needed instead of directly heating the product line as the product or material may be volatile or prone to cracking at the furnace temperature.)

Task 12

Work in groups. Scan the text and find information about the main function of the stack damper. Describe principle of its operation, using the diagram.

Stack

The flue gas stack is a cylindrical structure at the top of all the heat transfer chambers. The breeching directly below it collects the flue gas and brings it up high into the atmosphere where it will not endanger personnel.

The stack damper contained within works like a butterfly valve and regulates draft (pressure difference between air intake and air exit) in the furnace, which is what pulls the flue gas through the convection section. The stack damper also regulates the heat lost through the stack. As the damper closes, the amount of heat escaping the furnace through the stack decreases, but the pressure or draft in the furnace increases which poses risks to those working around it if there are air leakages in the furnace, the flames can then escape out of the firebox or even explode if the pressure is too great.

breech – боров (дымоход)

endanger – подвергать опасности

work – механизм, конструкция

butterfly valve – дроссельный клапан

GRAMMAR

Task 13

Put the following questions into the correct order.

1. fuel, does, where, flow, into?

2. be, how, burners, can, mounted?

3. the, what, radiant, is, section, known, as, section?

4. fluid, the, does, through, pass, where, heating?

5. designs, why, most, a, section, do, convection, include, furnace?

Task 14

Translate the following sentences paying attention to italicized grammar

!!!Remember:

1. The design of the furnace depends considerably upon the fuel to be burned.

2. It is the turbulence that gives an effective combustion.

3. The heated fluid is circulated round the whole plant to heat exchangers to be used wherever heat is needed.

Task 15

Give the English equivalents to the Russian words.

1. The incoming fuel-air mixtures (должна нагреваться) above the ignition temperature.

2. Fuel (сжигается) with air provided from an air blower.

3. Burners (могут быть) floor mounted, wall mounted or roof mounted.

4. The heat (передается) mainly by radiation to tubes around the fire in the chamber.

5. The heating fluid passes through the tubes and (нагревается) to the desired temperature.

WRITING

Task 16

Date: 2014-12-29; view: 1454