Energy Saviours: Part 3

Article by Tom Baxter CEng FIChemE

Tom Baxter shares more options for chemical engineers to boost energy efficiencies

AS STATED in my previous articles in The Chemical Engineer, I believe chemical engineers have a hugely significant role to play in decarbonising the environment and reducing other harmful gaseous emissions. Amongst the mix of decarbonisation options, energy efficiency is a key enabler. This article builds upon “Energy Saviours” parts 1 and 2, and discusses further options and considerations for energy efficiency.

Energy Recovery from Low Grade Heat

The Rankine Cycle

Figure 1: Rankine cycle components

The Rankine cycle makes use of a temperature difference to generate power. The ideal cycle is in four parts. The hot source is used to vapourise a liquid at constant pressure. The vapour is used to drive a turbine to isentropically extract work. The vapour is condensed to a liquid utilising the cold fluid at constant pressure. The liquid is returned to the vapouriser using a pump. It is the principle adopted in heat recovery steam generation systems in combined cycle power stations.

The cycle is shown in Figures 1 and 2. Figure 2 shows the Rankine path on a pressure/enthalpy plot. The plot includes isotherms (green dash) and lines of constant entropy (black dash). Starting from 1, the fluid is heated to 2 using a hot source. 

Article by Tom Baxter CEng FIChemE

Retired Senior Lecturer at Aberdeen University, Visiting Professor of Chemical Engineering at Strathclyde University, and retired Technical Director, Genesis Oil and Gas Consultants

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