A sugar mill in Florida has been disposing of the bagasse us
A sugar mill in Florida has been disposing of the bagasse (used sugar cane) by open-air burning. You, as a new chemical engineer, determine that by using the dried bagasse as boiler fuel in the mill, you can generate 5000 kg/hr of surplus steam at 20 bar and 600oC. You propose to your supervisor that the mill invest in a steam turbine–electrical generator assembly to generate electricity that can be sold to the local power company.
If you purchase a new, state-of-the-art adiabatic and isentropic steam turbine, and the turbine exit pressure is 1 bar, what is the temperature of the exit steam, how much electrical energy (in kW) can be generated, and what fraction of the steam exiting the turbine is vapor?
Instead, a much cheaper used turbine is purchased, which is adiabatic but not isentropic, that at the same exit pressure of 1 bar produces 90 percent of the work produced by the state-of-the-art turbine. What is the temperature of the exit steam, what fraction of the steam exiting the turbine is vapor, and what is the rate of entropy generation?
Solution
