Boiler surface (1) ____________ as the tubes and drum shells that are part of the steam-water circulation system, and that are in contact with the hot gases (flue gas). Although the term boiler now frequently (2) _______________ the overall steam generating system, the term boiler surface (3) _______________ the economizer, superheater, reheater, or any component other than the steam-water circulation system itself.
While boilers (4) __________broadly _________as fire tube and water tube types, modern high capacity boilers are of the water tube type. In the water tube boiler, the water and steam flow inside the tubes and the hot gases flow over the outside surfaces. The boiler circulation system (5) ______________ of tubes, headers, and drums joined in an arrangement that provides water flow to generate steam while cooling all parts. The water tube construction (6) ____________ greater boiler capacity and higher pressure than shell or fire tube designs. The water tube boiler also (7) ______________ greater versatility in arrangement; this
(8) ______________ the most efficient use of the furnace, superheater, reheater, and other heat recovery components.
Modern high capacity boilers come in a variety of designs, sizes, and configurations to suit a broad range of applications. Sizes (9) ________________ 1000 to 10,000,000 lb/h (0.13 to 1260 kg/s) and pressures range from one atmosphere to above the critical pressure.
The combustion system, fuel, ash characteristics, operating pressure, and total capacity largely
(10) ____________________ the boiler configuration.
WRITING
Ways of linking ideas
When we write, we may have to describe, explain, argue, persuade, complain, etc. In all these forms of writing, we use ideas. To make our writing effective, we have to make sure our readers can follow our ideas. One way of helping our readers is to make the links between the ideas in our writing.
What are the links between these pairs of ideas? What words can we use to mark the links?
1 Mechanisms are important to us.
2 They allow us to travel.
3 Mechanisms deliver the power to do work.
4 They play a vital role in industry.
5 Friction is sometimes a help.
6 It is often a hindrance.
Sentence 2 is a reason for sentence 1. We can link 1 and 2 like this:
Mechanisms are important to us because /since /as they allow us to travel
Sentence 4 is the result of sentence 3. We can link 3 and 4 like this:
Mechanisms deliver the power to do work so they play a vital role in industry. Mechanisms deliver the power to do work; therefore they play a vital role in industry.
Sentence 6 contrasts with sentence 5. We can link 5 and 6 like this:
Friction is sometimes a help but it is often a hindrance.
Task 15
Show the links between these sets of ideas using appropriate linking words.
1. Once-through boiler is widely used.
It has many advantages.
2. The costly drum is eliminated.
Capital costs are lower.
3. Steam temperature is related to enthalpy.
Steam temperature will depend on the ratio of heat input to throughput.
4. Such steam generating units are called the once-through generating units.
Water passes through the whole aggregate without multiple circulation.
Task 16
Write an abstract of the text “Boilers” according to the plan. Writing an abstract use the following linking devices: firstly, first of all, furthermore, in addition to, moreover, finally, in conclusion and so on.
1. The definition of boiler surface.
2. Classification of boilers, their advantages.
3. Boiler configurations.
UNIT 2
FUEL
Tuning in
Task 1
List the different types of fuel.
Task 2
Study the diagram below. Answer these questions using the diagram and your own knowledge.
1. In what regions are there the largest reserves of crude oil, natural gas and coal?
2. What regions have the smallest reserves of crude oil, natural gas and coal?
3. How do you think, what countries are the principal exporters of these fossil fuels?
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