EQUILIBRIUM THERMODYNAMICS

PROJECT $1$

ASSIGNED: $\frac{9}{8}\frac{?}{24}$

DUE: $\frac{9}{24}\frac{?}{24}$

Subject: Steam Power Generation

As part of a "green field" design for biofuel production, a steam plant is required to supply

medium pressure steam $($MP$)$ at $10$ barg and very low pressure $($VLP$)$ steam to heat a fermenter

at $38C.$ The flow of mps steam must be sufficient to supply $175G\frac{J}{h}$ assuming it is returned as

saturated liquid. The flow of VLP steam must be sufficient to supply $75G\frac{J}{h}$ of heating at $50C$

$($on the steam side$)$ to the fermenter. An open feedwater preheater is used except for the

regeneration loop in part $3($which must comply with the approach temperature of $12C).$ Rather

than simply generate steam, it is proposed to generate "green" electrical power from turbines

$($which can be sold into the electrical grid$)$ and use the "waste" heat to provide the required

steam. Design the best process for achieving this within the following scenarios. Compute the net

power production $($MW$),$ thermal efficiency, and boiler duty $($MW$).$

Part I

The schematic of a typical steam turbine power plant is shown in Figure $5\mathrm{.}2$ of your text, and the

figures below show modifications. The design constraints and conditions are as follows:

$($a$)$ Due to metallurgical considerations, the steam in the boiler can be heated only up to $500C.$

$($b$)$ The maximum steam pressure should be no higher than $9$ MPa $.$

$($c$)$ Excessive moisture content in the turbine reduces the turbine lifetime. The quality exiting

any turbine should be higher than $0\mathrm{.}98.$ You can include an extra $q=1\mathrm{.}0$ valve, if needed.

$($d$)$ The temperature of the available cooling water is $38C.$ A $12C$ approach $(T_{\text{a}\text{p}\text{p}})$ is allowed.

$($e$)$ The adiabatic turbine efficiencies are $100\%$ and the pumps are adiabatic with $85\%$ efficiency.

$($f$)$ You can neglect pressure losses in the heat exchangers and along the pipeline.

Your task is to design a Rankine cycle that has the best cycle efficiency within the design

constraints. You should document the calculations and design decisions.

Part II

You want to improve the cycle efficiency of the design determined in Part I. The idea is to heat

the steam in two steps: After the steam is expanded in a high$-$pressure $($T$1)$ turbine, it is reheated

and expanded again in a low$-$pressure $($T$2)$ turbine like Figure $5\mathrm{.}3.$ You must comply with the

design constraints given in Part I.

Part III $($Optional$,5$ points EC$)$

Modify part II as a regenerative Rankine cycle plant like Figure $5\mathrm{.}7.$ The mass fraction extracted

from the HP turbine is $m_1.$ To compare with part $II(2),$ use the same states through the turbines