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Über dieses Buch

Many cooling systems use water as cooling medium. They are found in public buildings, industrial production systems or power plants. Almost every cooling system using water is degraded by deposition, corrosion and microbiological fouling.

This book identifies the whole bunch of problems due to water cooling systems and proposes specific solutions to all of them. The authors have an expertise of over 20 years solving cooling water problems. In this book, they advise all practitioners which need to plan, buy or operate cooling systems.

Inhaltsverzeichnis

Frontmatter

FIRST PART

Frontmatter

A – Natural Water

Pure Water

Abstract
It seems to be useful to remind the physical and chemical characteristics of water, and indicate its variation depending on certain parameters.
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Natural Water

Various Natural Waters
The liquid water which is formed by the condensation at high altitude is relatively pure and, before reaching the ground, it dissolves gases and absorbs soluble and insoluble compounds present in the air. This water is generally saturated with oxygen, contains the carbon dioxide and can be contaminated by gases issued from industry: nitrogen oxide, hydrogen sulphide, sulphurous gas. It can also contain organic matters and minerals coming from the ground in the form of dust.
When it reaches the ground, many components of the Earth’s crust can be dissolved in rain water during the trickling or infiltration into the permeable geological layers, and this is connnected with the content of the gas dissolved, which helps the dissolving of the minerals, in particular, the carbon dioxide.
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Analysis of Natural Water

Units Chosen
We have seen in the list of dissolved salts, besides halogens found also among dry solids in water, the bicarbonates which exist only in solution: these are, for instance, calcium bicarbonate, magnesium bicarbonate and ferrous bicarbonate. These salts are not insoluble, and they are found in dry matter in the form of carbonate, as for magnesium and calcium, according to the reaction:
Ca(HCO3) →CaCO3 + CO2 + H2O
Mg(HCO3)2 →MgCO3 + CO2 + H2O
The ferrous carbonate is found in the form of ferric hydroxide by carbonate removal followed by oxydation.
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B – Water Treatment

Generalities

Abstract
In general, natural water that we have at our disposal is not ready for a desired end-use, thus, its treatment is necessary.
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Pretreatment

Abstract
Raw water used by industries is, in general, issued from one of the following two sources: runoff water and underground water. The runoff water includes water of rivers and lakes, and the underground water comes from wells or drillings/boreholes.
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SECOND PART

Frontmatter

Cooling Water

Conservation of the Raw Material: Water

Abstract
The quantities of water involved in human activities are very significant. The demand of using water has only been increasing, whereas fresh water resources do not vary, being associated to the meteorological phenomenon which remains statistically more or less constant in most of the countries.
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Conservation of Energy

Abstract
By this term we should understand not the thermodynamic principle of energy conservation, but energy savings, whatever the form, and the prevention of energy loss.
Conservation of energy may depend on the type of energy concerned, but at whatever point of an industrial production line, there is a need to ensure the energy management.
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Conservation of Water and Treatment

Abstract
Water is the element common to these circuits and therefore, logically, the most apparent and often most immediate source of energy savings, that could be introduced. This is first applied to the open recirculating systems with cooling tower, but may also be entirely true of the open circuits with single passage, as well as the completely closed circuits.
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History of the Cooling Water Treatment

Abstract
Let us to remind that the oldest use (that we know) of a corrosion inhibitor dates back to the year 1905, when it was found that arsenic was capable to prevent the dissolving of iron in the hydrochloric acid. The first mention concerning an inhibitor for water dates from 1922: some ppm of sodium silicate was added to water of domestic use in order to avoid corrosion of the piping made of lead. The first mention concerning cooling water treatment dates back to 1924, when 200 ppm of sodium dichromate and 50 ppm of sodium hydroxide were used in a refrigeration plant. Thus, as we can see it, the history of the cooling water treatment covers less than 100 years. Most of the significant developments in this field occured in the course of the professional career of many chemical engineers which are still in office.
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Cooling Circuits

Composition of the Circuits
Its great availibility and its remarkable thermodynamic properties make water an ideal fluid for realizing heat transfer necessary to the good functioning of the industrial processes.
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Fundamental Principles of Cooling Towers

Operation Principles
We have seen that an atmospheric cooling tower is a heat exchanger, in which the water to be cooled flows in contact with the ambient air, making it trickle on pi les of superimposed screens or plates (dispersion area). It is the packing that constitutes the heat exchanger. It is closed in a tower ensuring the best possible air circulation.
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Deposits and Their Treatment

Abstract
We have seen that the deposits found in a cooling system are of two types:
– hard and adhesive deposits which all are scale of mineral origin;
– clogging deposits which can be powdery and can give silt or sludge, when the circulation velocity of the water is not sufficient for keeping them suspended. They are mostly of the mineral origin. These deposits can be more or less adhesive and more or less soft, but, when they are of the biological origin, they can take any kind of appearance.
In fact, they are often constituted by a mixture of the elements of organic, mineral and biological origin.
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Corrosion and Its Treatment

Abstract
The prevention of corrosion in the open recirculating cooling systems is a field, in which enormous progress has been made during the last twenty years.
It has widely been demonstrated that the total costs of anticorrosion treatment are very low compared to the savings realized by the reduction or absence of operating losses due to the stops and prolongation of the service time of the equipement.
In fact, the anticorrosion treatments are as important as the scale-preventing treatments, since it is the service life of the cooling unit itself that is at stake. The corrosion control ensures the durability of the equipment.
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Microbiological Fouling and Its Treatment

Abstract
Microorganisms are present everywhere in nature, be it in the air, in water or in the soil, and they play a fundamental role in the permanent recycling of matters there, which constitutes the life of our planet.
The microbial life is subject of interest for many industrial processes.
It is used, deliberately, in the agri-food industries, the pharmaceutical industries and some chemical industries, for producing the molecules having resisted, until present, to the attempts of chemical synthesis. It has increasingly been used for the water purification, where it consumes the by-products undesirable for our activity.
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Start-Up of Cooling Installations

Introduction
The start-up of new recirculating water cooling tower system is an important operation which must be implemented with care.
In fact, the result of a bad procedure of start-up may be a considerable reduction of heat exchanger service life and difficulties in maintaining the heat transfer initially considered.
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Backmatter

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