Век химии (Английский язык для студентов химического профиля). Учебное пособие

There are three main basic models used to estimate the most important process variables of different chemical reactors:

batch reactor model (batch),

continuous stirred-tank reactor model (CSTR), and plug flow reactor model (PFR).

Furthermore, catalytic reactors require separate treatment, whether they are batch, CST, or PF reactors, as the many assumptions of the simpler models are not valid.

Key process variables include residence time (τ, lower case Greek tau) volume (V)

temperature (T) pressure (P)

concentrations of chemical species (C1, C2, C3, ... Cn) heat transfer coefficients (h, U)

3.Make up the plan to the text.

4.Give a brief summary of the text.

TEXT D

1. Read the text and choose the most suitable title out of the given ones

a)Microfiltration membranes

b)Microfiltration

c)Membrane filters

Microfiltration is a filtration process which removes contaminants from a fluid (liquid & gas) by passage through a microporous membrane. A typical microfiltration membrane pore size range is 0.1 to 10 micrometres (µm). Microfiltration is not fundamentally different from reverse osmosis, ultrafiltration or nanofiltration, except in terms of the size of the molecules it retains.

Developed by Professor Sigmondy University of Goettingen, Germany, in 1935, membrane filters were first commercially produced by Sartorius GmbH a few years later. Membrane filters found

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immediate application in the field of microbiology and in particular in assessment of safe drinking water. Further development of microfilters in the mid 1970's led by the FDA's requirement for non-fibre releasing filters to be used in the production of injectable solutions. Microporous membranes are used by the micro-electronics industry as an integral part of water production. Membrane filters are widely used in biotechnology and food and beverage applications where sterile product is required.

Increasingly used in drinking water treatment, it effectively removes major pathogens, contaminants and large bacteria. For this application the filter has to be rated for 0.2 micrometres or less. For mineral and drinking water bottler the most commonly used format is pleated cartridges usually made from Polyethersulfone(PES) media. This media is asymmetric with larger pores being on the outside and smaller pores being on the inside of the filter media.

Microfiltration membranes were first introduced to the municipal water treatment market in 1987 and applied primarily to waters that were relatively easy to treat. These were cold, clear source waters that were susceptible to microbial contamination. Low pressure membranes were selected to remove turbidity spikes and pathogens without chemical conditioning. As low pressure membranes increased in acceptance and popularity, users began to apply the technology to more difficult waters which contained more solids and higher levels of dissolved organics. Some of these waters required chemical pretreatment, including pre-chlorination. These shifts in water quality triggered change in low pressure membrane technology. New products and processes were introduced to deal with higher solids and chemical compatibility.

2. Write out.

а) key words and terms;

b) the sentences expressing the main idea of each paragraph.

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Unit 12

GRAMMAR: Participle I, Participle II.

1. a) Translate the following words and word combinations into Russian.

beverage, processing, to recycle, target, permeate, retentate, to depend on smth., to purify, to occur, weight, prone, fouling, to cause, solute concentration, culprit, internal pore structure, aggregation, surface, flux, reverse osmosis processes, potable water.

b)Put the words in the correct order to form sentences.

1.resembles, was, The result, radiator, which, a structure, a steam-heat.

2.over, will, the planet, become, The sky, cleaner.

3.study, The, UF processing, mainly, of, in, laboratory,

occurs,.

4.help, Nowadays, power, can, the, industry, microorganisms.

5.The, known, components, that, membrane, pass, the, are, as, permeate, through.

2. Read the following sentences and translate them into Russia paying attention to the Participles. Identify the participle construction.

1.For some time bacteria must remain inactive but when container are dumped, under the action of the environment they will become activized, destroying the plastics.

2.In the future, man will be able to send enormous clouds containing earthly microorganisms.

3.Scientists have developed an original method of combating methane based on the ability of some organisms to absorb this gas.

4.The vapour emitted into the atmosphere is not harmless.

5.Air coolers functioning in many enterprises are up to date devices.

6.Water distilled in a proper way is very clear.

7.The solid separated in the filter device is called the cake.

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Text A

3. Read the text and translate it using a dictionary.

ULTRAFILTRATION

Ultrafiltration is a type of filtration. Industries such as chemical and pharmaceutical manufacturing, food and beverage processing, and waste water treatment, employ ultrafiltration in order to recycle flow or add value to later products. Ultrafiltration is commonly abbreviated to "UF."

UF's main attraction is its ability to purify, separate, and concentrate target macromolecules in continuous systems. UF does this by pressurizing the solution flow. The solvent and other dissolved components that pass through the membrane are known as permeate. The components that do not pass through are known as retentate. Depending on the Molecular Weight Cut Off (MWCO) of the membrane used, macromolecules may be purified, separated, or concentrated in either fraction.

Currently, the study of UF processing occurs mainly in laboratory setups because it is very prone to membrane fouling caused by increased solute concentration at the membrane surface (either by macromolecular adsorption to internal pore structure of membrane, or aggregation of protein deposit on surface of membrane), which leads to concentration polarization (CP)). CP is the major culprit in decreasing permeate flux. Ultrafiltration is used as a pre-treatment step in reverse osmosis processes in many Middle Eastern countries to potable drinking water, as there is little fresh water available in those areas.

4. Answer the questions.

1.What is ultrafiltration?

2.Where is ultrafiltration employed and what for?

3.What is UF's main attraction?

4.What components do we call permeate (and retentate)?

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5.What do macromolecules purification and separation de-

pend on?

6.Why does UF processing mainly occur in laboratory

setups?

7.Where is ultrafiltration used as a pre-treatment step?

8.What is CP?

5.Complete the following sentences using some active words and word combinations (see below).

1.Industries such as … employ ultrafiltration.

2.Ultrafiltration is employed in order … to later products.

3.The components that do not pass through the membrane are known as ….

4.There is a great solute … at the membrane surface.

5.Concentration polarization is the major … in decreasing permeate flux.

6.Ultrafiltration is used as a … step in many Middle Eastern countries.

chemical and pharmaceutical manufacturing, to add value, retentate, concentration, culprit, pretreatment.

6. Retell the text using the following scheme.

1.The headline of the text is…

2.The text informs on (deals with, dwells upon)…

3.At the beginning the author makes close study of (considers)…

4.Then much attention is given to…

5.The text also tells about…

6.To sum up it should be noted…

Text B

1. Match the English words and word combinations in A with their Russian equivalents in B.

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2. Read the text trying to understand its main idea.

DISTILLATION

Distillation is a method of separating mixtures based on differences in their volatilities in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction.

Commercially, distillation has a number of uses. It is used to separate crude oil into more fractions for specific uses such as transport, power generation and heating. Water is distilled to remove impurities, such as salt from seawater. Air is distilled to separate its components—notably oxygen, nitrogen, and argon—for industrial use. Distillation of fermented solutions has been used since ancient times to produce distilled beverages with a higher alcohol content. The premises where distillation is carried out, especially distillation of alcohol, are known as a distillery.

The application of distillation can roughly be divided in four groups: laboratory scale, industrial distillation, distillation of herbs for perfumery and medicinals (herbal distillate), and food processing. The latter two are distinct from the former two in that the distillation is not

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used as a true purification method but rather to transfer all volatiles from the source materials to the distillate.

The main difference between laboratory scale distillation and industrial distillation is that laboratory scale distillation is often performed batch-wise, whereas industrial distillation often occurs continuously. In batch distillation, the composition of the source material, the vapors of the distilling compounds and the distillate change during the distillation. In batch distillation, a still is charged (supplied) with a batch of feed mixture, which is then separated into its component fractions which are collected sequentially from most volatile to less volatile, with the bottoms (remaining least or nonvolatile fraction) removed at the end. The still can then be recharged and the process repeated.

In continuous distillation, the source materials, vapors, and distillate are kept at a constant composition by carefully replenishing the source material and removing fractions from both vapor and liquid in the system. This results in a better control of the separation process.

3.Divide the text into some logical parts and entitle them.

4.Translate the following sentences into English using lexical material of the text.

1.Перегонка – это физический процесс сепарации, а не химическая реакция.

2.В промышленных условиях перегонка имеет несколько назначений.

3.Воду перегоняют для удаления примесей.

4.Помещение, в котором проводят перегонку, называется перегонный цех.

5.Промышленная перегонка часто осуществляется непре-

рывно.

6.Иногда перегонка используется для переноса летучих соединений из материала-источника в дистиллят.

7.Непрерывная перегонка приводит к лучшему контролю над процессом сепарирования.

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Text C

1. Pay attention to the following words and word combinations.

due to – благодаря, из-за; solubility – растворимость;

diffusivity – коэффициент диффузии; predominantly – преимущественно; motion – движение;

polymer chains – полимерные цепи; penetrants – проникающие вещества; utmost importance – большая важность; velocity – скорость;

gas flux – поток газа; mean – средний; purpose – цель

2. Read the text and be ready to say if the following statements are true or false. Use the following phrases.

As far as I know …

It seems to be wrong (right) …

I cant’t agree with you …

I’m afraid you are mistaken …

On the contrary …

That’s right …

1.Both nonporous and porous polymeric membranes are

utilized.

2.Vapours and gases are separated due to their different solubility and diffusivity in polymers.

3.Free volume of the polymer, its distribution and local changes of distribution are of great importance.

4.The diffusivity of a penetrant depends mainly on the total amount of its molecules.

5.Porous membranes are utilized for the gas separation.

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6.Separation efficiency is moderate – oxygen passes 4 times faster than hydrogen.

7.In case the pores are larger than the limit no separation

occurs.

GAS SEPARATION

Usually nonporous polymeric membranes are utilized. There, vapours and gases are separated due to their different solubility and diffusivity in polymers. Polymers in glassy state, generally more effective for separation, predominantly differentiate in diffusivity. Small molecules of penetrants move among polymer chains according to the formation of local gaps by thermal motion of polymer segments. Free volume of the polymer, its distribution and local changes of distribution are of the utmost importance. Then diffusivity of a penetrant depends mainly on the size of its molecule.

Porous membranes can also be utilized for the gas separation. The pores diameter must be smaller than the mean free path of gas molecules. Under normal condition (100 kPa, 300 K) it is about 50 nm. Then the gas flux through the pore is proportional to molecules velocity i.e. inversely proportional to square root of the molecule mass. It is known as Knudsen diffusion. Gas flux through a porous membrane is much higher than through nonporous one – 3 to 5 orders of magnitude. Separation efficiency is moderate – hydrogen passes 4 times faster than oxygen. Porous polymeric or ceramic membranes for ultrafiltration serve the purpose. Note, in case the pores are larger than the limit then viscous flow occurs, hence no separation.

3.Make up the plan to the text.

4.Give a brief summary of the text.

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Text D

1. Read the text and choose the most suitable title out of the given ones.

a)Filtering Devices.

b)Advantages of Filtering Process.

c)Types of Separation.

The separation of comparatively small amounts of solids from larger amounts of liquids is done by settling, followed by decantation of the supernatant clear liquid, or by the use of a filtering device. The separation of very small amounts of liquids from large amounts of solids is done by draining, or by centrifuging.

Settling out the solid is the cheapest method, and is frequently used. If the operation is extensive, a large capacity in settling tanks is required: these act also as storage tanks. If the liquor is hot, the tank may be insulated by strips of wood. As a rule, this process is too slow; also the mud collected in the bottom of the tank still contains too much water, and is usually sent through a filter, a combination of settling and filtering.

Filtering devices include gravity filters, pressure filters, more commonly called filter-pressers, and suction filters. Several points must be considered when studying a filtration problem: whether the cake or the filtrate is the valuable part, whether or not washing is required, and whether the operation should be continuous or intermittent. These considerations will have weight in the choice of the device.

The suspension to be filtered is called a slurry, if its content in solids is not so high that it does not flow and cannot be pumped; slurries contain from less than 1 per cent to 40 per cent of solids are more properly called sludges. The solid separated in the filter device is called the cake, the clear liquor running off is the filtrate. Filtering devices such as filter-presses and suction filters are really frames for the support of the filtering medium, the filter cloth, which may be cotton duck of various thicknesses, muslin, paper, wool flannel, or metal wire woven into cloth, such as iron wire, and nickel wire.

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