Waste Management Services and Solutions | Republic Services

Question 1 

(a) In reference to Figure 4-12 (p. 145), the composites line stands for the entire waste combined into a solitary sample. The particle size of composites of several Municipal Solid Waste (MSW) components which was 100 percent and was shredded and as a result the material obtained after shredding was 20 inches and the following was its composition: 5% ferrous 2inches, 10% of miscellaneous is 2.5inches, 20% of plastic is 0.8inches, 30% of nonferrous is 2inches, 45% of garden is 0.1%, 50% of cardboard is 2.5inches, 70% of paper is 2inches, 70% of textile is 6inches, 80% of food is 0.8inches, 100% of glass is 0.3inches, 90% of wood is 2inches and 80% of sand and rock is 0.2inches ( Laurent, Bakas, Clavreul, Bernstad, Niero, Gentil ... & Christensen, 2014) . Consequently, with 6inches of textile being the major particle size of the waste categories, no particle size is huge than the composite curve. 

(b) The whole particle sizes were less than the composite which was 20 inches. Consequently, it is sufficed to say that the waste particles which have a small particle size compared to the composite curve include miscellaneous, ferrous, nonferrous, cardboard, textiles, wood, paper, plastic, food, glass, sand and rock and garden ( Laurent et al.2014) . 

(c) Tear and ware is a crucial factor which determines the size of the particle. The aims of the blades on the shredder is to decrease the material into smaller pieces ( Laurent et al.2014) . So, as the blades found on shredders commence to tear and wear the grating performance decreases and will not be able to reduce materials. Thus, the composite size of the particles would shift towards large particles. 

(d) Examining at Table 4.3 (p.148) Rosin-Rammler Exponents for Shredded Refuse Wilmington, DC has a grainier size distribution. The constant of Houston, TX, and Wilmington, DE are 0.639 and 0.629 respectively. Laurent et al. (2014) observed that Houston character size is 2.48 whereas Wilmington character size is 4.56. A wider X 0 elaborates a rougher particle size output. Consequently, Wilmington, DE, having a characteristic particle size of 4.56 shall have a rougher product emitting from the shredder. 

Question 2 

Step 1 – We will 29.30 lb./ft 3 to the same as Unit B – kg/m3. This necessitates comprehension of the conversion for lbs. to kg and vise-versa, as well as ft 3 to m 3 

1.00 lb. = 0.45400kg and 1.00 ft 3 = 0.028300 m 3 

Step 2 – Set up the calculation by beginning with the units you have 

29.3 lb./ft 3 x 1ft 3 /0.0283 x 0.454kg/1lb = 470.11 kg/m 3 

Therefore, Unit A has a better performance 

200kg/m 3 occurs at 5 meters, which is approximately 16.4 ft. 

Using the conversion table, we know that 1 meter = 3.28 ft. Therefore, 

5m x 3.28ft/1m = 16.4ft 

Physical properties such as particle size, bulk density, and angle pose are physical properties that are all affected by moisture content. The potential concern of the facility manager is that the moisture content is 60% which exceeds the 50% limit. According to Worrel et al. (2017), moisture content that exceeds 50% is hazardous and can cause high organic fraction to undergo spontaneous combustion if the material is allowed to stand undisturbed. 

Shredder Technologies 

Horizontal hammermill	Vertical hammermill
Advantages  It provides efficient grinding at the shortest time, which saves human labor as well as time.  Available in different capacities and sizes.  It consumes less electric power.  It needs less maintenance.	Advantage  Low Initial Investment and Low Operating Costs  Easy to Use and Maintain  Ability To Crush Material To Different Sizes.

Question 3 

Revenue for 25-acre portion = 2.500 x 10 6 yd 3 x 750.00lb/yd 3 x 1ton/2,000.00lb x $45.00/ton = $42,187,500.00 

Revenue for 25-acre lot = 2.50 x 10 6 yd 3 x 1350.0lb/yd 3 x 1ton/2,000.0lb x $45.00/ton = $75,937,500.00 

Therefore, additional revenue = $75,937,500.00 - $42,187,500.00 = $33,750,000.00 

Applied pressure which requires to be enforced to deliver a compressed waste to the landfill of 

500.00lb/yd 3 is 25psi 

The landfill must run the compressor at 180.00psi to obtain a substance density of 1080.00 lb/yd 3 

Question 4 

(a) The vertical hammermill is designed with a vertical shaft, and the movement of the waste material is aided by gravity down the sides of the housing (Worrel et al. 2017). There are two halves comprising the unit, the top and bottom halves. The top half serves to break the material into smaller particles. Malfunctioning of the top half results in incomplete breakage of material and larger particles conveyed to the bottom half and consequently inadequate clearance ( Laurent et al.2014) . 

(b) The bottom half has lesser clearance in comparison to the top half clearance. The bottom half serves to further break down the material conveyed from the top half as it passes through the machine. The clearance capacity is dependent on the functioning of the bottom half; as an improper functioning significantly reduces the clearance capacity between the hammer tips and the housing structure from top to bottom halves, consequently hampering the machine’s ability to break down material to finer size ( Laurent et al.2014) . 

(c) In accordance with the Rosin-Rammler model, Y= 1-exp (-x/ xo)n in which xo is the characteristic particle size and where n is a constant, the characteristic particle size can be calculated mathematically from specifications such as 90%-----------------------. The characteristic particle size can be defined as the size at which a large percentage of the particles (63.2%) are smaller by weight (Woller et al. 2017). 

(d) The characteristic size (x0) in figure 4-16 (p. 151), portrays the data from an evaluation study of a vertical hammermill shredder. The characteristic size of the data varies between 1.2 to ~1.5inches and changed with time. As the characteristic size relates directly to the exponents of processed waste, the largest size factor (~1.5inches) indicates that 9,000 tons of the 15,000 tons of waste processed have coarser product emitted from the shredder (Woller et al. 2017). The X 0 did not change significantly over the approximately 15,000 tons of waste processed. Factors such as energy requirements, moisture, speed, and loading could be the cause of the variability in the graph. Rapid loading of the shredder results in more energy requirement, thereby reducing the shredder force. As a result, the coarse particle size is produced. Higher speeds result in the production of finer particle size. Energy requirements directly affect the feed rates and efficiency of the machine. Efficiency increases with the increase in feeding rate; until the machine becomes overloaded (Worrel et al. 2017). The moisture content in the waste also influences the energy requirement and conversely the particle size. Higher moisture content in the refuse results in larger particle size 

References 

Laurent, A., Bakas, I., Clavreul, J., Bernstad, A., Niero, M., Gentil, E., ... & Christensen, T. H. (2014). Review of LCA studies of solid waste management systems–Part I: Lessons learned and perspectives.  Waste management ,  34 (3), 573-588. 

Worrel, W. A., Veslind, P.A., & Ludwig, C. (2017). Solid waste engineering: A global 

Perspective (3 rd ed.). Boston, MA: Cengage Learning.