Matthew Branham11-1-06ME 2.810Manufacturing ProcessesProf. GutowskiAccounting for the Environmental Impact of Sand Casting in the Manufacture of ‘Cahs’Sandcasting is unique among the manufacturing processes utilized in the manufacture of ‘cahs’ for the ME 2.810 final design project since it utilizes no electricity and is performed entirely offsite. In order to characterize the environmental impact of sand-casting the ‘cah’ chassis, we visited Burlington Foundry to better understand their process. In comparison with other casting houses, it appears that Burlington Foundry runs a relatively clean and conscientiousoperation. Their sand binder, for example, is sodium silicate (as opposed to more insidious hydrocarbon binders), they reuse the vast majority of the sand with which they cast, and their furnaces consume ~12 gallons of heating oil per 275kg of melted aluminum. After evaluating their casting process, I propose the following method of accounting for the environmental impact of sandcasting:MATERIAL CONSUMED: 1. Find the weight of the finished chassis to determine material used in car. 2. Approximate the weight of lost aluminum as 2% of the mass of your chassis.SAND CONSUMED:Although the bulk of Burlington’s sand castings are done using a sand which is almost entirely reused (they have not required new sand of this type for 15 years), our castings will be made using a different sand variety that is one use only. To calculate the amount of sand used per casting, use:volumesand = 14”x19”x5.75” = 1,530 in.3 per castTo calculate the amount of sodium silicate bonding agent used per cast, we begin with the information that about 25lbs of sodium silicate are used for every 350 lbs of sand. We do not know the density of Burlington’s sand, so we use a representative value for dry quartz sands of 1600 kg/m3. Working out the math, we find the approximate sodium silicate used per cast:€ massNa2SiO3=1,600kg /m3*2.2lbkg*1m361,024in.3*1,530in.3*25lbsNa2SiO3350lbssand=6.3lbs sodium silicate per castGASES CONSUMED:For every cast, the foundry dries the mold with CO2, pumped from a 60 psi tank for 15 seconds. If we assume an outlet cross section of 9mm2, then the mass flow will be 1.2 * 10-4kg/sec which becomes:= .002kgCO2/castingFUEL CONSUMED AND CONSEQUENT EMISSIONS: Burlington Foundry burns approximately 8 gallons of heating oil per hour in one of its furnaces, and the first melt of each pouring session is 1.5 hours (where each melt is approximately 275lbs of aluminum). Thus, Burlington uses about 12 gallons of oil per 275lbs aluminum. To find out how much oil is burned for one casting:Calculate the weight of aluminum poured. This includes the weight of the part, the gatingand risers (provided to you for one part), and the weight calculated in (2.) of the section labeled “material consumed”. Let this be total weight, W, per cast. Then oil consumed per cast is given by:volumeoil = W * (12/275)and moil = volume * 6 lb/galFinally, heating oil consists of a mixture of the hydrocarbons C14H30, C15H32, C16H34, C17H36, C18H38, C19H40, and C20H42. Taking the average molecular weight of these compounds as 240kg/kmol, which gives .0113kmol/gal. Thus, the consumption of one gallon of fuel yields approximately 17*0.0113*6.02*1023 CO2 molecules/gallon or 8.48kg/gallon. In order to calculate the CO2 released per cast:MassCO2 = 8.48kg/gallon
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