Thermofluids and Sustainable Energy – Level5 – Assignment 2015-16

Case Study - estimation of Fawley power station efficiency & conversion to renewable fuel source

Background

Fawley power station was an oil-fired power station located on the western shore of Southampton water in Hampshire, and reported to be one of the most efficient oil fired power stations in the UK. In 2013 it stopped producing power from fossil fuels in line with the EU Large Combustion Plant Directive.

The heat produced in the boiler furnace converted pure water to superheated steam, which left the boiler at up to 165 times atmospheric pressure and at a temperature of 541°C.

The steam from the boiler passed through the high pressure section of the steam turbine, turning the blades and shaft at 3,000 revolutions per minute. The steam returned to the boiler for reheating, and then to the turbine intermediate pressure stage, and then passed to the three low pressure stages.

As the steam left the turbine, it was cooled back to water by large condensers before passing back to the boiler. The condensers were cooled by sea water, pumped from Southampton Water, which was then returned to the Solent through tunnels.

Specification

4 x 500MW turbo gen sets – Oil fired

Turbines: HP inlet 165bar / 541degC

IP inlet 40bar / 541degC

3 x LP in parallel

Alternator: 3000rpm (22kV)

Condensers: Press 0.037bar (27degC sat)

Cooling water 51x106 gal/hr

Feedwater heaters: 3 low press (mixing), 6 high press (closed)

Tasks

You are required to analyse the performance of the steam cycle, and comment on the feasibility of converting to alternative fuel sources. Making suitable approximations where required, and referencing sources of additional information (books, technical papers, on-line resources), complete the following tasks:

(1) Draw a schematic of the steam turbine power-plant (one of the four generating sets), indicating system states around the cycle (limit the quantity of FWH’s included in your system to one (open), or remove altogether, and assume the 3xLP turbines behave as 1xLP turbine to simplify the analysis). ie. there are two possible schematics for the steam power-plant.

(10marks)

(2) Draw the steam cycle to scale on A3 graph paper, indicating system states and key property values around the cycle. Assume isentropic expansion and compression for turbine and pumps. Produce a table of steam property values at states around the cycle and show your working.

Calculate the steam cycle efficiency.(30marks)

(3) Estimate through literature review isentropic efficiency for turbines and pumps. State your sources. Plot this on a Mollier (h-s) diagram (A4 size) for the key turbine stages.

Re-calculate the steam cycle efficiency including the turbine and pump isentropic efficiencies.

(25marks)

(4) Calculate the mass flow of steam in the cycle for rated power output, the heat input rate to the steam, and by making assumptions for boiler efficiency (determine from literature review).

Compare the mass flow rate of the following different fuels if used to fuel the boiler: Fuel oil Biomass

Discuss briefly the pro’s and con’s of the two different fuel types (engineering and environmental considerations, commenting on the European Union ‘Large Combustion Plant Directive’).

(25marks)

Assessment:

The solution must be presented in a professional report format & typed, but concise. Each element of the “Engineering Problem Solving Method” must be clearly listed. 10 marks are for clarity of your work and report presentation.

Submission deadline: Friday 5pm 23rd-Oct-2015

Format: Electronic copy via Moodle only