Seeking advice on the issue of increased main steam pressure in turbines affecting power generation

Increasing the pressure increases the total amount of steam entering the turbine. Enthalpy is the sum of internal energy and the product of pressure and volume; \"increasing pressure results in a decrease in enthalpy,\" which is a conclusion drawn under the condition that volume remains constant. On the turbine, increasing the pressure also raises the volumetric flow rate of steam entering the turbine. That is, the steam is compressed, resulting in an increase in pressure and internal energy per unit volume.

Thank you for your response. After the capacity upgrade of our company’s boilers, their evaporation capacity increased. However, due to the limitations of the diameter of the main steam outlet pipe, the increase in flow rate led to a drop in pressure. The original design called for a steam flow rate of 22.6 at a main steam pressure of 4.0 bar at 400 degrees Celsius, with the main steam pipe having a diameter of DN150. After the upgrade, the steam flow rate increased to 29, and the temperature remained at 400 degrees Celsius; yet the main steam pressure dropped to around 3.5 bar, with a pressure drop from the steam drum to the superheater being 1 MPa. Currently, the pressure before the turbine’s main steam valve is around 3.2–3.3 MPa (the rated value being 3.8 MPa). Although power generation has indeed increased due to the higher flow rate, the steam consumption has also increased, exceeding 5 kg. May I ask, with the temperature remaining constant, which operation method – increasing the pressure (by closing the throttle valve) or reducing the pressure (to around 3.2 as currently) – will result in higher power generation, lower steam consumption, and better economic efficiency?

A steam turbine is essentially an energy converter that converts pressure energy into mechanical energy. Mechanical energy is then converted into electrical energy by the motor. It’s better to consider it from an energy perspective. Additionally, just follow the equipment parameters strictly. Going beyond the limits will cause problems. Safety, stability, and a long operational lifespan are the best ways to save energy. For reference.

"Which operation mode generates more power – increasing pressure (by closing the throttle valve) or reducing pressure (at around 3.2 currently)? Which one results in lower steam consumption? And which is more economical? "After the capacity upgrade, it is necessary to find new parameter settings for operation; since we are a waste incineration power plant, the parameters change significantly. All of the above methods remain within safe limits, with no deviations from those limits.

The results of this on-site experimental tuning are the most reliable. As long as the turbine remains unchanged, its operating conditions must be met. The same is true for variable load operation. The energy conversion efficiency should be optimal to meet the requirements of the turbine. Reducing the throttle opening and lowering the pressure both lead to insufficient air intake, preventing optimal production capacity. It is uneconomical for the equipment not to be in its optimal operating condition. If it is merely a relative load variation operation, which is nothing but a last resort, then there’s no talk of finding a more economical way to adjust it. Also, the safe range is not equivalent to reasonable normal production. Less gas consumption means a lower energy conversion rate, which in turn reduces economic efficiency. The turbine rotor has its inherent shaft power; if that isn’t sufficient, then there’s no talk of efficiency at all. For reference.

In the former case, reducing the valve opening increases throttling losses; although gas consumption rises as a result of the reduced pressure, it is more economical compared to keeping the valve fully closed