Pressure Reduction

The Opportunity:

Many of the Industrial steam boiler plants produce steam at a higher pressure than is required by downstream processes and let down the pressure through pressure reduction valves (PRV) generating waste heat. A non condensing steam turbine can be used instead of the PRV to generate electricity out of the pressure drop.

How it Works:

The over-pressurization of the steam serves to run the boiler more efficiently but implies introducing more energy into the steam than necessary for the production process, hence burning more fuel and letting that extra energy get wasted.

When the high pressurized steam reaches low-pressure steam distribution networks, a pressure reduction valve (PRV) typically lets down the steam pressure to a more suited pressure for the end process transforming pressure energy into heat produced by frictional dissipation, this heat is the extra energy that was consumed in the boiler to produce the high-pressure steam in the first place.

Making the waste even higher the set pressure for the end process is commonly set well above the real heat requirement of the process to provide a cushion, this cushion means that more energy than needed is delivered to the end process performing no useful work and just being wasted.

Because the pressure of the steam and the energy content go together, its possible to take advantage of the pressure drop of the steam (isentropic enthalpy change) to generate electric power, by installing a non condensing steam turbine to work as a pressure reduction valve. In this set up the high pressure steam flows though the turbine where it is accelerated as the pressure drops to the desired level for the production process. The steam spins the rotor of the turbine driving the electricity generator. The outcomes are steam at the required pressure and clean electricity out of the already existing need for heat on the plant.