Plenary Lecture, ENERGY & ENVIRONMENT (EE'09), Cambridge, UK, February 21-23, 2009

Plenary Lecture

Cooling Water and the Environment

Professor T. Reg. Bott
College of Engineering and Physical Sciences
School of Chemical Engineering
University of Birmingham, Edgbaston
Birmingham B15 2TT.
United Kingdom

In the Industrial Revolution particularly in respect of the invention of the steam engine used to drive machinery, the use of heat energy derived from the combustion of fossil fuels was greatly intensified. Combustion technology was later adapted for the production of electricity through the use of steam turbines. In order to maximise the conversion of the pressure energy in the steam into electricity water-cooled condensers were incorporated into the power plant design, to maximise the pressure drop across the turbines, Large quantities of water were required to remove the latent heat in the steam. In order to satisfy this demand water was, and still is taken from natural resources such as lakes, rivers and the sea depending on the location of the power plant. The choice of location may often be dictated by the availability of large quantities of water. The water may be “once through” or recycled through cooling towers to reduce the cooling water temperature, although “make up” water will be required to replace evaporative losses and to maintain the quality of the circulating water. The use of this “natural” resource can have serious implications for the environment in a number of ways not least in combating the fouling problem in the condensers and associated equipment.
The conversion efficiency will depend at least in part. on the design and operation of the steam condensers. In addition during operation the heat transfer surfaces are likely to become fouled, thereby impeding heat removal that ultimately reduces the electrical energy obtained for a given quantity of fossil fuel. A deposit is also likely to present a rough surface to the water flow, with an attendant increase in pressure drop and hence a higher pumping energy requirement with the increase in greenhouse gas emission linked to that additional energy requirement.
The fouling can arise from a number of causes such as particulate deposition, salt precipitation, corrosion and particularly biofouling – the accumulation of micro-organisms originally contained in the water, principally bacteria although fungi and algae may be involved in some circumstances. Some species can initiate corrosion. It is probably true that the accumulation of living matter makes the largest contribution to inefficiency. There are a number of ways by which the problem can be overcome or its effects reduced. Amongst the methods available the most common way of combating biofouling is the use of chemical additives to act either as biocides to kill the micro - organisms or acting as surface - active agents to reduce their adhesion to the heat exchanger surface.
From the review of the use of cooling water taken from, and returned to, a natural source, in the production of electrical power, it is evident that there are a number of environmental implications including water above ambient temperature and water containing chemicals. Many governments have introduced legislation to control these environmental risks, representing a challenge to plant designers and operators alike. The paper discusses techniques available to meet this challenge.

Brief biography of the speaker:
After graduating in chemical engineering Reg. Bott carried out large-scale development work in the plastics and gas industries before being invited to join the staff and the University of Birmingham. During a period as the Institution of Chemical Engineers Industrial Fellow in Heat Transfer he was able to carry out a survey of industrial heat exchanger usage. He discovered that very little was known about the fouling of heat exchangers except its effect on performance! It was clear that this would be a very worthwhile topic for research. As a result the rest of his academic career has been devoted to aspects of this topic. He has been author or co-author of some 300 papers and written two books on heat exchanger fouling and editor of four others.
Reg. Bott has been presented with a number of awards including the Arnold Greene and Brennan Medals from The Institution of Chemical Engineers, the Donald Q, Kern award from The American Institute of Chemical Engineers. He was made a Grand Commander of the Order of Prince Henry the Navigator, by the President of Portugal for services to higher education in Portugal. For his contribution to chemical engineering and energy management he was awarded the M.B.E, by Her Majesty Queen Elizabeth.
In addition Reg, is also a fully ordained priest in the Church of England serving in a parish in Birmingham.


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