Учебное пособие 1908

Упражнение 8. Переведите текст, пользуясь словарем.

There are three main types of gasifier - fixed bed, fluidised bed, and entrained flow - which together represent the most promising methods to gasify biomass and waste.

Fixed bed gasifiers are suitable for small-scale processes, i.e., less than 10 MW. Feedstock flows by gravity, while the gas flow can be either updraft or downdraft. Ideally, the feedstock should be piece-like and fairly homogeneous to flow smoothly in the reactor. In practice, however, it contains fines and fibrous material, which cause problems in the fuel flow leading to operational problems. The flow problems can be avoided by applying a new type of technology (‘Novel’ fixed bed gasifier) in which the flow is forced.

Fluidised bed reactors could solve the problems related to nonhomogeneity of the feedstock, but they are too expensive in small scale. In fluidised bed technology, the feedstock must be crushed to millimetre size before it is gasified in either bubbling or circulating mode. These gasifiers are suitable for scales up to hundreds of megawatts. Recently, fluidised bed technology was applied for wastes where the product gas is combusted in a pulverised coal-fired boiler. The same method has been used to recover aluminium from the reject produced in liquid packaging board. The circulating fluidised bed has been demonstrated to be particularly suited for fuels containing high contents of alkali metals, where ash sintering problems can be avoided by using limestone and special arrangements with the feeds.

In the third type of gasifier, the entrained flow gasifier, pulverised fuel is gasified at high temperature. This is regarded as one of the optional processes for liquid fuel manufacture from biomass and wastes. High pressure gasification based on the entrained flow process can be applied to improve the energy recovery from black liquor.

Упражнение 9. Составьте аннотацию текста «The

BGL Slagging Gasifier».

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Упражнение 10. Подготовьте небольшие сообщения по следующим вопросам:

1.Характеристика различных типов газогенераторов.

2.Сущность технологических процессов с генераторным

газом.

3.Сущность процесса сухого золоудаления Лурджи.

4.Характеристика шлакоудаляющего газогенератора.

UNIT 8

Упражнение 1. Прочтите слова и словосочетания и постарайтесь запомнить их русские эквиваленты.

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Упражнение 2. Переведите слова, обращая внимание на суффиксы и префиксы.

Dehydrate – dehydrator - dehydration, absorb – absorber – absorption, adsorb – adsorption, down – downward, up – upward, exchange – exchanger, cool – cooling, compress – compression, sufficient – sufficiently, advantage – disadvantage, transmit – transmission, objection – objectionable.

Упражнение 3. Прочтите и переведите интернациональные слова.

Method, temperature, hydrate, antifreeze, agent, methanol, glycol, industry, category, principle, injection, process, material, line, cubic, sulphide, carbon dioxide, physical, technique.

Прочтите и переведите текст, а затем выполните следующие упражнения.

DEHYDRATION SYSTEMS

Several methods can help prevent hydrates from forming in a gas line:

Heat the gas stream so that gas temperature will not drop to the level at which hydrates form.

Add an antifreeze agent such as methanol or glycol to the gas stream.

Remove the water vapour by using a glycol dehydrator, which consists of a vertical pressure vessel (a glycol absorber) that allows the glycol to flow downward as the gas flows upward.

Dehydrate using drying agent such as alumina, silica gel, silicon alumina beads, or a molecular sieve.

Expand the gas and refrigerate using heat exchangers. Dehydration systems used in the natural gas industry fall into

four categories in principle: (a) direct cooling, (b) compression followed by cooling, (c) absorption, and (d) adsorption.

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Dehydration in the first two methods does not result in sufficiently low water contents to permit injection into a pipeline. Further dehydration by absorption or adsorption is often required.

Absorption is a process in which water vapour is removed from natural gas by bubbling the gas counter-currently through certain liquids that have a special attraction or affinity for water. Water vapour in the gas bubbles is entrained in the liquid and carried away by the liquid. Adsorption is a process in which gas flows through a bed of granular solids that have an affinity for water. The water is retained on the surface of the particles of the solid material. The vessel that allows either the absorption or adsorption process to take place is called the contactor or sober. The liquid or solid that has affinity for water and is used in the contactor in connection with either of the processes is called the desiccant. Two major types of dehydration equipment in use today are the liquid desiccant dehydrator and the solid desiccant dehydrator. Each type of dehydrator has its advantages and disadvantages. These two types of dehydrators dehydrate practically all the natural gas moved through transmission lines.

Most dehydrated gas contains no more than 7 pounds of water vapour per million cubic feet of gas (lbs/ MMcf).

Other objectionable impurities that are found are hydrogen sulphide and carbon dioxide. These impurities may be removed using chemical reactions, physical solutions, or absorption. The technique used depends on how free of impurities the gas must be before a gas company will purchase it.

Упражнение 4. Найдите в тексте данные ниже слова и словосочетания и напишите их русские эквиваленты.

Natural gas industry, expand, gas temperature, carbon dioxide, result in, physical solutions, impurities, water vapour, sufficiently low water contents, gas line, liquid, dehydration systems, chemical reactions, a bed of granular solids, hydrogen sulphide, the surface of the particles, heat exchangers, gas stream, solid material, dehydration equipment, the liquid desiccant

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dehydrator and the solid desiccant dehydrator, vertical pressure vessel, transmission lines, refrigerate, objectionable impurities.

Упражнение 5. Найдите в тексте ответы на следующие вопросы.

1.What should be done to prevent hydrates from forming in a gas line?

2.What types of dehydration systems are used in the natural gas industry?

3.What is absorption?

4.What is adsorption?

5.What is called the contactor?

6.What is called the desiccant?

7.What types of dehydration equipment are in use today?

8.What objectionable impurities can be found in dehydrated

gas?

9.How may the impurities be removed?

10.What does the technique used depend on?

Упражнение 6. Подберите из правой колонки соответствующие окончания предложений из левой колонки.

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Упражнение 7. Переведите текст, пользуясь словарем.

DEHYDRATION OF NATURAL GAS

The term dehydration means removal of water vapor. All natural gas downstream from the separators still contains water vapor to some degree. Water vapor is probably the most common undesirable impurity found in untreated natural gas. The main reason for removing water vapor from natural gas is that water vapor becomes liquid water under low-temperature and/or high

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pressure conditions. Specifically, water content can affect longdistance transmission of natural gas due to the following facts:

Liquid water and natural gas can form hydrates that may plug the pipeline and other equipment.

Natural gas containing CO2 and or H2S is corrosive when liquid water is present.

Liquid water in a natural gas pipeline potentially causes slugging flow conditions resulting in lower flow efficiency of the pipeline.

Water content decreases the heating value of natural gas being transported.

Solubility of water in natural gas increases with temperature and decreases with pressure. Salt’s presence in the liquid water reduces the water content of the gas. Water content of untreated natural gases is normally in the magnitude of a few hundred pounds of water per million standard cubic feet of gas

(lbm/MMscf); while gas pipelines normally require water content to be in the range of 6-8 lbm/MMscf and even lower for pipelines in deep water.

The water content of natural gas is indirectly indicated by the dew point, defined as the temperature at which the normal gas is saturated with water vapor at a given pressure. At the dew point, natural gas is in equilibrium with liquid water; any decrease in temperature or increase in pressure will cause the water vapor to begin condensing. The difference between the dew point temperature of water-saturated gas stream and the same stream after it has been dehydrated is called dew-point depression.

It is essential to accurately estimate the saturated water vapor content of natural gas in the design and operation of dehydration equipment. Dalton’s law of partial pressures is valid for estimating water vapor content of gas at near-atmospheric pressures.

Упражнение 8. Переведите предложения на английский

язык.

1. Термин “осушка” означает удаление водяного пара.

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2. Используя влагопоглотители, дегидратационные установки могут удалять практически всю воду из природного газа.

3.В газовой промышленности используется четыре типа дегидратационных систем: непосредственное охлаждение; сжатие с последующим охлаждением; абсорбция и адсорбция.

4.Растворимость воды в природном газе повышается с увеличением температуры и понижается с увеличением

давления.

5.Вода удерживается на поверхности частиц твердого материала.

6.Сегодня используется два основных типа дегидратационного оборудования: дегидратор с жидким поглотителем

идегидратор с твердым поглотителем.

7.Наличие в жидкой воде соли снижает водосодержание газа.

8.На водосодержание газа косвенно указывает температура конденсации.

9.Такие примеси, как сероводород и углекислый газ, можно удалить, используя химические реакции, физические растворы или абсорбцию.

10.Водяной пар является самой распространенной нежелательной примесью в неочищенном газе.

Упражнение 9. Составьте сообщение по тексту «Dehydration Systems», используя в качестве плана ответы на вопросы упражнения 5.

Упражнение 10. Представьте, что:

1.Вы – лектор, читающий лекцию о способах обработки газа. Расскажите о существующих типах дегидратационных систем и процессах, применяемых для осушки газа.

2.Вы проводите экскурсию для студентов на предприятии, производящем осушку газа. Расскажите, почему необходимо производить осушку газа.

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UNIT 9

Упражнение 1. Прочтите слова и словосочетания и постарайтесь запомнить их русские эквиваленты.

Упражнение 2. Переведите слова, обращая внимание на суффиксы.

To adsorb – adsorption – adsorbent – adsorber, to dehydrate

–dehydration – dehydrator, to separate – separator, to disturb – disturbance, to heat – heater, to arrange – arrangement, direct – indirect, to generate – to regenerate, up – upward, down – downward, to use – usable, to contaminate – contaminant, normal

–normally – abnormally.

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Упражнение 3. Прочтите и переведите интернациональные слова.

A substance, to concentrate, silicate, molecular, natural, efficiency, gas, a filter separator, regeneration, to contact, to condense, to activate, normal, effective, degradation, blockage, capillary, corrosion, inhibitor, cycle, sulfide.

Прочтите и переведите текст, а затем выполните следующие упражнения.

DEHYDRATION BY ADSORPTION

Adsorption is defined as the ability of a substance to hold gases or liquids on its surface. In adsorption dehydration, the water vapour from the gas is concentrated and held at the surface of the solid desiccant. Solid desiccants have very large surface areas per unit weight to take advantage of the surface forces. The most common solid adsorbents used today are silica, alumina, and certain silicates known as molecular sieves. Dehydration plants can remove practically all water from natural gas using solid desiccants. Because of their great drying ability, solid desiccants are employed where higher efficiencies are required.

The incoming wet gas should be cleaned by a filter separator to remove solid and liquid contaminants in the gas. The filtered gas flows downward during dehydration through one adsorber containing a desiccant bed. The down-flow arrangement reduces disturbance of the bed caused by the high gas velocity during the adsorption. While one adsorber is dehydrating, the other adsorber is being regenerated by a hot stream of inlet gas from the regeneration gas heater. A direct-fired heater, hot oil, steam, or an indirect heater can supply the necessary regeneration heat. The regeneration gas usually flows upward through the bed to ensure thorough regeneration of the bottom of the bed, which is the last area contacted by the gas being dehydrated. The hot regenerated bed is cooled by shutting off or bypassing the heater. The cooling gas then flows downward through the bed so that any water

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