QUESTION $4$

$4\mathrm{.}1$ Explain the term, evaporation, as it pertains to a steam power plant.

$4\mathrm{.}2$ Anthracite coal with the calorific value of $31M\frac{J}{k}g$ is fed into a steam power plant which consists of a boiler at a rate of $670$ kg per hour. The plant produces steam which is $2\%$ wet at a pressure of $760$ kPa $.$ Steam production is at the rate of $5400$ kg per hour. The feed$-$water temperature is $43,8C.$

Use steam tables to determine the following:

$4\mathrm{.}2\mathrm{.}1$ The boiler efficiency and equivalent evaporation at $100C$

$4\mathrm{.}2\mathrm{.}2$ The amount of coal saved in $k\frac{g}{h}$ and as a percentage if an economiser is fitted and it raises the feed$-$water temperature to $90C$ and increases the plant's efficiency by $5\%$

$4\mathrm{.}2\mathrm{.}3$ After six months, the plant was further fitted with a super$-$heater and then it was discovered that steam was produced at $1000$ kPa and $250C.$

$?$

Determine the new plant efficiency after the installation of the economiser and the super$-$heater.