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Simon Tin provides overview of heat exchangers

Published by , Editorial Assistant
World Cement,

There are three main types of heat exchangers – plate, shell and tube, and air cooled. They work in different ways and are suited to various applications, but, essentially, they all fulfil the same task: transferring heat from one fluid to another.

Heat exchangers are primarily used in the cement sector for ancillary cooling on plants and machinery, so whatever the size or location of the plant there is bound to be some sort of heat exchanger system there. Aggregate crushing, in particular, is a process that requires power levels that generate vast amounts of heat and, therefore, requires heat exchanges to cool them and keep them online and operating efficiently.

How do heat exchangers work?

Shell and tube systems function by passing a fluid through a set of tubes that is located within a sealed shell that contains another fluid. The liquids can move in the same direction (parallel flow), opposite directions (counter flow), or at right angles (cross flow).

Plate heat exchangers comprise many thin metal plates to provide a large surface area with narrow channels to transfer the heat rapidly. Air cooled heat exchangers tend to be used where ambient air is the cooling mechanism. The air is forced or drawn through a tube bundle or core by fans.

Which type of heat exchanger?

  1. Materials and coatings: The metals used in a heat exchanger must be suitable for the environment in which it is going to be installed. In the cement sector, this means that they must be robust enough to cope with the dusty and harsh environments in which they will be operating.
  2. The more a supplier understands a business, the better they will appreciate what is important to it. In the cement sector, this is most commonly the ability to supply systems designed to meet the specific needs of individual plants and their operations. For example, some heat exchange systems are fitted with metallic fins to help with cooling processes. Their performance will be compromised by the corrosive dust which is inevitably the result of cement production. Thornhill offers a range of coatings that can be applied to various sorts of heat exchangers, and fins to protect them, to increase their efficiency and longevity, as well as providing onsite cleaning to improve cooling efficiency.

  3. Supplier’s experience and location: Speed of response is vital to meet the high-performance requirements of cement companies, so it is important to ensure that the chosen supplier has sites at geographically convenient locations to service equipment off site and return it to meet demanding deadlines. It is also vital to check that they have appropriately skilled and qualified engineers to carry out onsite cleaning when required, somtimes with little advance notice. Thornhill Group has worked with leading companies in the cement sector, including Breedon and Lafarge.
  4. Servicing: To keep a heat exchanger system working at the optimum level it is vital to undertake a programme of proactive maintenance, to ensure that potential problems can be identified and plans put in place to rectify them, to minimise their cost and effect on the business. However, there may still be emergency situations that require urgent repairs, so it is good to choose a supplier who can meet these needs. It is important to be confident that a supplier totally understands a system prior to taking it apart.
  5. Spares: It is often the case that spares will need to be delivered urgently to replace parts, so choosing a supplier that not only provides the initial design and manufacture of the overall system, but also fabricates spares that can be stored onsite or held at their site can be vital in emergency situations.

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Cement news 2018