Question

A coal-fired power plant converts 40% of the coal's energy into electrical energy. The electrical output of the plant is 750 MW. The rest of the energy is converted to waste heat with 10% in the smokestack and 90% using cooling water from a stream. The river has a flow of 80 m2/s and temperature of 15°C a. What is the cooling water flow rate if the water temperature increases 10°C? b. What is the new temperature of stream just downstream of the plant? (energy balance) 2. Determine the Molarity (M) for a 2-L solution containing 45 g of magnesium hydroxide Mg(OH)2. Assuming all of it dissociates, what is the pH of the solution? (Hint: Kw) 3. 4. For a sample of water that is in equilibrium with the atmosphere which contains 400 ppm CO2, what is the pH of the rainwater assuming only atmospheric CO2 affects the pH of the water. Assume 25 °C and 1 atm. (Henry's law, carbonate system equilibrium)

Please answer all parts of the questions, and try explaining it in a simple way that is understandable.

Answer 1

Sol 2 Given (ooling water temperature rise, AT 0 C g0% oh the rest ener conver ted to s waste heat using cooling uwoterrom a stream. River temparature blow rate is 80 mys and is 15C To determine flow rate ol ce o ling water New temperature o stream just ds. b) Calculations Using csader cooling egootion, AT= (M CP) .) AT is rise in temperature ob cooling wader dissipated where, is heat (wor 3lsec) 10ad to be flow rade of cooling water m is mass Cp is specibic heat o water (186 Jam

substitu ting valves, 1000=/ m x 4.186 go o enevau thot isn't converted into eledrical energs 1012:5 mW O:4 (1o l25 X10) W 10125 X10 10 mx 4186 solving bor m (3/aec) Q41897689 5 1 density o water, fw3/am lo00k/m 2 6 lous rate oh cooling water, 000 SO, 88 mls242 ms Ans. a)

New tem perature bD stream just d/s (xT) (00ling (T), (ax1) new neuw Streom water fhis is energy balance, Cauax 2s) +(8OX15) Trew X (24a+ 80) Tnew 22.5 C Ans 2. b)