Research is being done to utilize microbial cells found in common soil or the oc

Question

Research is being done to utilize microbial cells found in common soil or the ocean floor to produce usable fuels, such as propane, from CO2 that has been sequestered from flue gases from power plants (a major source of CO2 emissions). The challenge here to make the process useful is to be able to produce large quantities of propane from these cells at a reasonable cost. In a first attempt to this, a company (GASBUGS INC.) attempts to mass produce propane by employing a simple continuously stirred tank reactor (CSTR). GASBUGS INC. found that keeping the reactor at 25 oC provides conditions in the reactor where the rate of death and growth of cells are equal. On a molar basis, when CO2 (density = 0.00197 g/cm3) is bubbled into the reactor at a flow rate of 1680 L/hr., complete conversion to propane is achieved in 10% excess of water, and no bacteria are lost in the output flow stream.

A. Find how much feed water is required in mol/hr

B. Find the Daily output of propane

Explanation / Answer

During off peak months, propane will be used by cooking appliances, water heaters, clothes dryers and the maybe pool heaters. If the gas range, dryer and water heaters are used at a rate of 25% capacity 2 hours per day, the gas usage will be about 1.2 gallons per day.
220,000 BTU/hr ÷ 91,547 = 2.4 gal/hr • 2.4 gallons x .25 = .6 gallons • .6 gallons x 2 hours = 1.2 gallons of propane

Using the same calculation above, the usage rates will differ as capacity and length of use change.
25% capacity for 2 hours - 1.2 gallons per day
25% capacity for 6 hours - 3.6 gallons per day
50% capacity for 2 hours - 2.4 gallons per day
50% capacity for 6 hours - 7.2 gallons per day

If the pool heater (425,000BTU/hr) is used for one hour per day at 75% capacity, add 3.5 gallons per day to the numbers above (425,000BTU/hr ÷ 91,547 = 4.64 gal/hr • 4.64 x .75 = 3.48 gallons). As you can see, pool heaters use a lot of gas and playing with these numbers, you can get an idea of normal off peak propane usage rates.

The winter months bring more usage of all energy sources for heating so the usage numbers above will drastically change as heating requirements increase. For instance, let's take an unseasonably cold week with the same appliances above and compute the propane gas usage with the same hours of use adding the use of the furnaces for heating. If the furnaces are used at 50% capacity for 12 hours, the daily gas usage will increase by about 26 gallons. Note that does not include the two fire places.
400,000 BTU/hr ÷ 91,547 = 4.4 gal/hr • 4.4 gallons x .5 = 2.2 gallons • 2.2 gallons x 12 hours = 26.4 gallons

Using the same calculation above, the usage rates (during heating) will differ as capacity and length of use change.
50% capacity for 18 hours - 39.6 gallons/day or 277.2 gallons/week
75% capacity for 06 hours - 19.8 gallons/day or 138.6 gallons/week
75% capacity for 12 hours - 39.6 gallons/day or 277.2 gallons/week
25% capacity for 12 hours - 13.2 gallons/day or 92.4 gallons/week
25% capacity for 18 hours - 19.8 gallons/day or 138.6 gallons/week
25% capacity for 24 hours - 26.4 gallons/day or 184.8 gallons/week

If you add the propane consumption of a pool heater, the numbers really start to climb. Pool heaters are high capacity appliances that can consume more than 4.5 gallons of propane per hour (425,000 BTU/hr ÷ 91,547 = 4.64 gal/hr). If it takes 4 hours to heat the pool on a cool day, the pool heater may use 18.5 gallons. We bring pool heaters up because they are such high demand appliances that can really cause consumers to think they have a gas leak...when in reality, they just need to be mindful of not leaving the pool heater on for an extended period of time. The pool heater in the above example will consume 100 gallons of propane in less than a day if left running at capacity. If you're heating your pool, keep an eye on the gas gauge.

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