Waste heat recovery in industry

Waste heat recovery in industry

The energy and environmental framework to which all companies have been exposed for several years now is forcing us to look for all kinds of solutions to reduce energy consumption and the environmental impact that our activities generate.
One of the technologies that have been used for several years is waste heat recovery in industry. Do you know specifically what this energy saving concept consists of? The concept of waste heat recovery in industry refers to the fact of recovering and reusing, in different processes of a plant, the heat generated as a by-product of some of the various processes of our activity.
The main objective of this activity is to reduce the use of resources of our industry and to reduce its dependence on imported fossil energy.
There are various methods of waste heat recovery that vary depending on the type of process characteristics and heat generated. The main methods would be the following:

1. Heat exchangers

Heat exchangers are devices designed to transfer heat between two different media. There are an infinite number of possible variations when configuring a heat exchanger (material, shape, fluid medium...) The most common heat exchangers on the market are plate, coil or tube and shell.

Where are they used?

They are used in a myriad of applications in industry, from heating systems, ventilation, air conditioning, boilers, refrigeration systems, chemical processes, power generation, in flue gas ...

What is its efficiency?

The efficiency of a heat exchanger depends on several factors such as geometry, material of construction, temperature and flow of the exchange media, among others. A well calculated and optimized heat exchanger can reach transfer efficiencies of up to 95%. This makes this type of device an exceptional ally when it comes to energy optimization in our industry.


This type of equipment generates electricity from steam. The process specifically generates mechanical energy from the steam, which comes from a process, and then turns an electric generator to produce electricity. The steam is fed into the turbine at high pressure where it expands and turns the turbine blades. This turbine is connected to a shaft which in turn is connected to the rotor of an electric generator.


Where are they used?

Generally this type of heat recovery equipment is used when there is a process that consumes heat and generates steam as a by-product. It is common that this type of equipment is used in the paper industry, food, chemical or power generation.
When there is not enough energy to turn the turbine, the steam turbine is used in a Rankine cycle, which will do the following:
a.Compression: water is compressed to raise the boiling point
b. Heating: the by-product steam is heated with the feed water
c. Expansion: steam expands in the steam turbine and spins the rotor
d. Condensation: the steam is condensed back to water and can be reused elsewhere in the process.


What is its efficiency?

The efficiency of a turbine depends on several factors such as size, design, speed, pressure and operating temperature.
It is considered that the efficiency of a steam turbine working at optimum conditions can vary between 70% and 90%.


Although the two technologies mentioned above are the most widespread, there are other methods used in the industry to recover waste heat.

One of them would be the absorption refrigeration systems. This system works by means of an absorbing agent (usually lithium bromide - LiBr). 


The absorption refrigeration system consists of four main components: evaporator, absorber, condenser and generator, which are connected to form a closed refrigeration cycle.
These systems are less efficient than conventional systems, but can operate with waste heat or solar energy to generate refrigeration and can be very useful in certain applications.

Another system would be cogeneration systems, which are widely developed and spread across different industries. Cogeneration systems are characterized by generating electrical and thermal energy simultaneously, and in the context of waste heat recovery, they can be used to generate electricity from the heat generated as a by-product of an industrial process.

At SDS we have more and more inquiries every day focused on waste heat recovery projects, and due to the great competition in almost all sectors of the industry, controlling production costs is becoming a more strategic and more important point to take into account. In addition, it is expected that in the coming years most European companies will be obliged to account for and reduce the environmental impact of their activities. The reduction of energy resources will be a factor to be taken into account.