The new expander technology regulates the mass flow through it by controlling the port opening duration, allowing the expander to operate at maximum pressure available at the inlet for the entire turn down.
FREMONT, CA: If the unpredictability in steam pressure and flow can be corrected, waste steam from industrial operations could be a significant source of power. Scientists have created a new technique that allows them to fix pressure and flow irregularities. This can save a lot of energy that would otherwise be wasted as steam in industrial processes, which helps with energy efficiency.
While major thermal power plants are improving their power generation efficiency, the process industry's steam efficiency has gotten little attention. Steam in process industries can also be used to generate electricity; however, one of the main challenges is the variability of steam pressure and flow.
One research group has developed a steam expander (power generator) technology to correct steam pressure and flow irregularities. The new expander technology regulates the mass flow through it by controlling the port opening duration, allowing the expander to operate at maximum pressure available at the inlet for the entire turn down. The mass flow rate of a conventional expander is typically controlled by throttle governing. This reduces admission and, as a result, steam's energy (energy available for use) before admission in the expander.
The method developed in the lab prevents throttling ahead of admission for variable load operation by dynamically modifying the port opening time based on the process load. As a result, the expander's efficiency may be maintained for a wider variety of turndown conditions.
Admission volume is constantly regulated to maximize steam energy use in the steam expander. This is accomplished by moving the revolving inlet valve back and forth with the help of a spline mounted cam to change the valve profile (which is a 3D geometry offering smooth and continuous motion of the mechanism regulating the valve motion). Then, using timing gears, the valve moves in synchrony with the crankshaft. The process pressure is used as a signal to a piston positioned on the backside of the valve, which automates the valve's operation.
Due to the application of Pressure Release Valve (PRV) for pressure decrease from boiler pressure to process pressure, approximately 15 GW of power generation potential is largely untapped in process industries. This is roughly equivalent to adding 75–100 GW of solar PV installed capacity and is available at a fraction of the cost of Rs1.1/kWh. In addition, the boiler's incremental fuel consumption is negligible, allowing this technology to reduce its carbon footprint.
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