Question

In Boston, due to the large amount of snowfall during winter of 2014-2015, the city has brought in several "snow dragons" to melt the snow.  
Model SND5400 is rated at:

•180 ton rated capacity per hour (Based on Latent Heat of Ice)
•No. 2 Fuel Oil or Diesel Fuel Type, Jet A Fuel
•Propane, and Natural Gas available for stationary units
•Fuel storage capacity of 3,000 US gallons
•Burner Output at 54,000,000 btu/hr  
•Measures 68' long x 11'6" wide x 12'4" high  


The USEPA states that there are 22,300 lb CO₂ emitted per 1000 gal of No. 2 fuel oil burned (AP-41 Table 1.3-12). The heat content of No. 2 fuel oil is 140 MMBtu/10³ gal (AP-42 Chapter 1.3).
(a) How many lbs of CO₂ are generated per hour when operating at maximum capacity?

(b) Calculate the lbs of CO₂ are generated per ton of snow melted.

(c) If the snow has a density of 24.97 lb/ft³, calculate the lbs of CO₂ are generated per ft ³ of snow melted.

(d) If the snow is 78 inches deep, and the road is 30 ft in width, calculate the lbs of CO₂ that are generated in clearing the snow from a length of road 10 ft.

(e) Based on the weighted average combined fuel economy of cars and light trucks in 2011, the amount of CO₂ emitted per mile driven was 0.92594 lbs CO₂/mile. Calculate the "equivalent miles" driven in clearing the snow from a length of road 10 ft (as in part (d)).

Answer 1

(a)

Burner output = 54000000 Btu/hr

140 MMBtu = 140000000 Btu

140000000 Btu heat is given out when 103 gallons of fuel oil is burned.

Hence, 54000000 heat will be given out when = (103/140000000)54000000 = 39.73 gallons of fuel oils is burned

When 1000 gallons of fuel oil is burned, 22300 lb of CO₂ is emitted.

So when 39.73 gallons of fuel oil will be burned = (22300/1000)39.73 = 885.98 lb of CO₂ will be emitted.

Therefore, 885.98 lb of CO₂ will be emitted per hour when operating at maximum capacity.

(b)

180 ton of snow is melted when 54000000 Btu/hr is the burner output

1 ton of snow will be melted when = 54000000/180 = 3000000 Btu/hr is the burner output.

140000000 Btu heat is given out when 103 gallons of fuel oil is burned.

Hence, 3000000 heat will be given out when = (103/140000000)3000000 = 2.207 gallons of fuel oils is burned

When 1000 gallons of fuel oil is burned, 22300 lb of CO₂ is emitted.

So when 2.207 gallons of fuel oil will be burned = (22300/1000)2.207 = 49.22 lb of CO₂ will be emitted.

That is, when 1 ton of snow is melted, 49.22 lb of CO₂ will be emitted

(c)

11'6" = 11.5'

12'4" = 12.33'

Volume of snow = 68 11.5 12.33 = 9642.06 ft³

Density of snow 24.97 lb/ft³

Mass of snow = 24.97 9642.06 = 240762.24 lb = 120.38 ton

When 1 ton of snow is melted, 49.22 lb of CO₂ is emitted

Hence, When 120.38 ton of snow is melted = 120.38 49.22 = 5925.10 lb of CO₂ will be emitted

(d)

78" = 6.5'

Volume of snow = 6.5 10 30 = 1950 ft³

Density of snow = 24.97 lb/ft³

Mass of snow = 24.97 1950 = 48691.5 lb = 24.34 ton

When 1 ton of snow is melted, 49.22 lb of CO₂ is emitted

Hence, When 24.34 ton of snow is melted = 24.34 49.22 = 1198.01 lb of CO₂ will be emitted

(e)

Amount of CO₂ emitted per mile driven was 0.92594 lbs CO₂/mile

When the snow is removed from a road length of 10 ft, 1198.01 lb of CO₂ is emitted

0.92594 lbs is emitted CO₂ when 1 mile is driven

1198.01 lb of CO₂ will be emitted when = (1/0.92594)1198.01 = 1293.83 mile is driven