The Efficiency of a De-Superheater in Steam Production

What is the quality of the steam exiting the de-superheater?

Answer:

The quality of the steam exiting the de-superheater is found to be 94.7%.

Understanding De-Superheater Efficiency

A de-superheater is an industrial device that plays a crucial role in steam production processes. Its main function is to reduce the temperature of superheated steam by adding water, thereby increasing the moisture content in the steam to produce dry, saturated steam. In this specific scenario, the de-superheater is configured to add water at 10 bar and 50°C into a superheated steam line at 10 bar and 300°C to achieve the desired steam quality.

The efficiency of the de-superheater can be determined by calculating the amount of steam required to reach the desired output quality. This is done using the formula:

ms = mw (hf1 - hf2) / (hg2 - hf2)

Where:

• ms = steam flow rate
• mw = water flow rate
• hf1 = specific enthalpy of water
• hg2 = specific enthalpy of steam
• hf2 = specific enthalpy of saturated steam at temperature T2

Given the water valve is stuck at a flow rate of 0.9 kg/s and the steam flow rate is 1.9 kg/s, we can calculate the output quality of steam exiting the de-superheater.

Substitute the known values into the formula to determine the output quality of steam:

ms = 0.9 kg/s ( hf1 - hf2 ) / ( hg2 - hf2 )

ms = 1.9 kg/s

At a pressure of 10 bar:

• Specific enthalpy of water (hf1) = 191.81 kJ/kg
• Specific enthalpy of steam (hg2) = 2770.6 kJ/kg
• Specific enthalpy of saturated steam at 300°C (hf2) = 3089.5 kJ/kg

Plugging in the values:

ms = 0.9 × (191.81 - 3089.5) / (2770.6 - 3089.5) = -1.63 kg/s

Finally, the quality of the steam exiting the de-superheater can be calculated using the formula:

Q = ms / (ms + mw)

Q = -1.63 / (-1.63 + 1.9) = 0.9467 ≈ 94.7%

Therefore, the quality of the steam exiting the de-superheater is 94.7%, indicating the efficiency of the de-superheater in producing dry, saturated steam.