--- title: "Steam plant components and performance improvement" subject: "Power Plant Equipment" chapter: 7 key: "semester_7/power_plant_equipment:steam-components-performance" source: https://www.bctengineer.com/q/semester_7/power_plant_equipment/steam-components-performance site: BCT Engineering --- # Steam plant components and performance improvement Power Plant Equipment · Chapter 7: Thermal (Steam) Power Plant - Asked in: 2081 Bhadra, 3+5 marks - Video: [Layout of steam power plant -Full working explained in hindi |Easy EEE|](https://www.youtube.com/watch?v=bG9pQOAADpY) — Easy EEE - EEE Study Material - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/power_plant_equipment/steam-components-performance - Whole chapter: https://www.bctengineer.com/md/semester_7/power_plant_equipment/chapter-7 ## Question Sketch the main components of a Steam Turbine Power Plant. Write down the different ways for increasing the performance of the steam turbine power plant. ## Short answer Main components are boiler, turbine, condenser, and feed pump. Performance is improved by higher boiler pressure, superheating, lower condenser pressure, reheating, regenerative feed heating, and recovering flue gas heat with economizer and air preheater. ## Answer #### Main components of a steam turbine power plant A steam (thermal) power plant works on the **Rankine cycle**. Its main parts are: ```text superheated steam (1) +---------------+ -------------> +---------+ +-----+ | Boiler | | Steam |===| Gen | | (furnace, | | turbine | +-----+ | economiser, | +---------+ | superheater) | | exhaust (2) +---------------+ v ^ ^ | +-----------+ fuel| air| v flue gas | Condenser |<--cooling | | chimney +-----------+ water | | condensate (3) | feed water (4) +-----------+ | +------------------| Feed pump |<--+ +-----------+ ``` - **Boiler (steam generator):** burns coal/oil/gas and converts feed water into high-pressure steam. Includes furnace, water walls, drum, **superheater**, **reheater**, **economiser** (heats feed water by flue gas) and **air preheater**. - **Steam turbine:** expands steam and converts its heat energy into shaft work; drives the **alternator** (generator). - **Condenser:** condenses exhaust steam under vacuum using cooling water; the low back pressure increases turbine work. Cooling water is cooled in a **cooling tower** or taken from a river. - **Feed pump** (with condensate pump): returns the condensate to boiler pressure, usually through **feed water heaters** (regeneration). - **Fuel and ash handling, draught system** (FD/ID fans), **chimney**, **ESP/dust collector**. - **Water treatment plant** for make-up water. #### Ways of increasing the performance The efficiency of a Rankine (steam) cycle is $\eta = 1 - \dfrac{T_{\text{low}}}{T_{m,\text{in}}}$ roughly, so it improves by **raising the mean temperature of heat addition** $T_{m}$ or **lowering the temperature of heat rejection**. Common methods: 1. **Increasing boiler (steam) pressure** - raises the saturation temperature at which heat is added. 2. **Superheating the steam** (higher turbine inlet temperature) - raises mean temperature of heat addition and dryness at exhaust. 3. **Reducing condenser pressure** (better vacuum) - lowers heat rejection temperature. 4. **Reheating** - steam partly expanded in HP turbine is reheated in the boiler and expanded in LP turbine. 5. **Regenerative feed water heating** - steam bled from the turbine heats the feed water in feed water heaters. 6. **Using economiser and air preheater** - recover heat from flue gases. 7. **Supercritical / binary vapour and combined cycles** - use very high pressure, or a topping cycle (gas turbine) whose waste heat runs the steam cycle. 8. Reducing losses: better turbine blading, insulation, reduced throttling. Typical effect: raising boiler pressure from 40 to 160 bar, superheat to about 540 °C, one reheat and 6-7 regenerative heaters together raise a plant's efficiency from about 25% to about 38-40%. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does the economiser do in a steam plant boiler? A. Heats feed water using flue gas heat B. Superheats the steam C. Condenses exhaust steam D. Removes dust from flue gas Answer: A. The economiser recovers heat from flue gases to heat the feed water. (Key point: Economiser function) 2. Why is the condenser kept under vacuum? A. To reduce the feed pump size to zero B. The low back pressure increases turbine work C. To raise the steam temperature entering the turbine D. To prevent superheating Answer: B. A low exhaust pressure allows greater expansion and hence more work from the turbine. (Key point: Condenser purpose) 3. Which of these is NOT a method for improving steam plant performance? A. Reheating B. Regenerative feed heating C. Raising condenser pressure D. Superheating to higher temperature Answer: C. Raising condenser pressure raises the heat rejection temperature and lowers efficiency; the plant needs lower condenser pressure. (Key point: Ways to improve performance) 4. Why does increasing boiler pressure improve efficiency? A. It raises the saturation temperature at which heat is added B. It lowers the condenser temperature C. It removes the need for a pump D. It reduces the fuel calorific value needed Answer: A. Higher pressure raises the boiling temperature, so the mean temperature of heat addition increases. (Key point: Effect of boiler pressure) 5. Roughly what efficiency can a plant reach with high pressure, superheat, one reheat and several regenerative heaters, up from about 25%? A. About 28% B. About 38-40% C. About 60% D. About 90% Answer: B. These measures together raise efficiency from about 25% to about 38-40%. 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