VOCABULARY

Task 6

Work in pairs. Read the following definition and try to express the following notions in one word or phrase.

1.The equipment whose purpose is to convert the energy of fuel into heat energy carried by steam.

2 The basic aggregate of the steam-generating equipment.

3 The device in which fuel is burnt.

4. The closed metallic vessel in which steam is generated from water by means of application of heat.

5. The device in which the high pressure steam is generated.

6. The fan which forces the air into the furnace.

7. The steam-generating unit which has no drum.

Task 7

Match the words with the synonyms.

Task 8

Match these words with their opposites.

Task 9

Give the English equivalents of the phrases below.

выработка энергии; паровая турбина; пар высокого давления; потеря энергии; паровой котел; уровень воды; горячие продукты горения; теплопередающая поверхность; пучок труб; теплообменник; питательная вода котла; воздухонагреватель; комнатная температура; вытяжной вентилятор; дутьевой вентилятор; система труб; пылевой коллектор.

TASK 10

Give the English equivalents to the Russian words in the sentences below.

1. Steam (используется) for space heating.
2. The boiler (состоит) a drum and a bank of tubes (связанных) the drum.
3. (Так как) the gaseous products of combustion (покидающие) the boiler tank are (при относительно высокой температуре) and their discharge (привел бы) a large loss in energy, an economizer (может использоваться) to recover part of the energy (в этих газах).
4. An air (подается) to the air heater (при нормальной комнатной температуре).
5. (Различие) between the steam-generating unit with natural circulation and the once-through steam-generating unit is that (последний из упомянутых) has no drum, and water from the economizer passes directly (к поверхностям теплопередачи).

TASK 11

Match each of these components to its function, and then describe its function in a sentence.

SPEAKING PRACTICE

Task 12

Work in pairs.

Study and comment on questions below.

Share your ideas with other students in your group.

1. What are the advantages of the once-through boiler?

2. What is necessary to obtain the lowest operating costs?

3. What can be used to vary the pressure level and control the steam flow?

4. How can steady state be maintained?

ONCE-THROUGH - BOILER CONTROL

To design a control system, or to understand it, a basic knowledge of the process is necessary. Hence we will look first at some of the basic principles of the once-through boiler. To begin with, its acceptance is growing rapidly because it offers certain advantages over the drum type, such as:

1. lower operating costs, and

2. lower capital costs.

Greater efficiency is made possible by operating at supercritical pressures and by maintaining full desired steam temperature over a wider load range. Obviously, to obtain maximum benefits from these factors and to obtain lowest operating costs, a highly advanced control system is required. Capital costs are lower because the costly drum is eliminated. In its simplest form, the once-through boiler can be pictured as a single tube. Feedwater flows in at one end, heat is applied along its length, and superheated steam is discharged at the other end. The enthalpy, or energy content, of the fluid leaving the tube is directly related to the ratio of the heat input to the total throughput. Dividing heat absorbed (Btu/hr) by throughput (lb/hr) yields enthalpy (Btu/lb).A valve placed at the discharge of this simplified boiler can be used to vary the pressure level and control the steam flow. For any given pressure, steam temperature is related to enthalpy; hence, if pressure is held constant, steam temperature will depend on the ratio of heat input to throughput (water flow).

Thus for steady state operation, pressure can be maintained at the desired value by equating flow into the tube to flow leaving the tube. Steam temperature can be held as desired by providing the proper ratio of heat input (fuel and air) to throughput (water flow).

Date: 2014-12-29; view: 1278