Case Study # 1

Heat Recovery System

Results

From the previous temperature profile and considering that the flow rate is constant and equals to the data provided by the manufacturer, and that the outlet temperature of the heat exchanger is 100°C (value obtained from the manufacturer of the heat exchanger), the following profile of the power recoverable along the day has also been set up:

Premises and assumptions:

Flow rate = 17.4 m³/min

Outlet temperature = 100°C

Calorific value and density estimated from benchmarks of CO₂

Inlet temperature given by the profile of temperature

Air at the appropriate temperatures

Efficiency of the heat exchanger of 70%

Based on these information and integrating this profile, the energy recoverable per day is 300 kWh.

Selection of a suitable heat exchanger

Equipments pre-selected

Firstly, an economiser heat exchanger designed for recovering heat from boilers' exhaust was considered.

It was supposed to be delivered within the duration of the project, but due to delays and problems with the delivery, the equipment could not be installed and the tests were not carried out.

Therefore, a different approach was considered for this case study and, a heat exchanger especially created to recover heat from generators' exhaust gas was envisaged.

More details about each one of these equipments are given below.

Expected Heat Exchanger: Totaleco from Ygnis

This equipment is a counter flow shell and tube heat exchanger. It is made up of 7 tubes and 4 passes. According to the specifications of the manufacturer, the outlet temperature of the fumes is low enough to condensate their water content. However, this heat exchanger only stands a maximum inlet temperature of 280°C; for this reason, Venturi has to be integrated between the heat exchanger and the generator in order to increase the flow rate of the heat exchanger inlet and then reduce its temperature.

Therefore, this solution implies that some energy is lost before the economiser. Nevertheless, this fact is compensated by the increase in the inlet flow rate. More specifications about this heat exchanger are available on the website of the manufacturer.

Selected Heat Exchanger: Bowman

This equipment is properly designed to recover heat from a generator's exhaust gas. Its maximum admissible inlet temperature is around 700°C. Using it implies then recovering all the heat released by the generator. For this reason, the whole installation comprising this heat exchanger will be more efficient. It is also a counter flow shell and tube heat exchanger and more information about it are available on the following website: put web link.

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