CHEMICAL ENGINEERING 341 DESIGN FOR ENVIRONMENT
FINAL EXAM
Short Answer Section (Closed book)
l.) (10 points) In class and in your text, five tiers of costs that are relevant to the evaluation of the environmental benefits of projects were identified. Identify these five tiers of costs, describe the nature of the costs, give an example associated with each tier and describe the level of uncertainty associated with estimating the costs.a) Tie-R 1 —e D zze-er- C05TS
2. (5 points) Draw a typical cycle used in a heat pump. the inlet enthalpy, outlet enthalpy, and work input. Label appropriate temperatures and define the coefficient of performance.
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3. (5 points) (5 points) Draw a typical combined heat and power configuration, labeling the electricity generation and heat output. Compare the CHP configuration to a conventional electric power generating facility. Describe factors that limit the ability to implement combined heat and power applications.
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4. (5 points) Lurmann, et al. (1999) have estimated the costs associated with ozone and fine particulate matter concentrations above the National Ambient Air Quality Standards (NAAQSs) in Houston. They estimated that the economic impacts of early mortality and morbidity associated with elevated fine particulate matter concentrations (above the NAAQS) are approximately $3 billion/year. Hall, et al. (1992), performed a similar assessment for Los Angeles. In the Houston study, Lurmann et al examined the exposures and health costs associated with a variety of emission scenarios. One set of calculations demonstrated that a decrease of approximately 300 tons/day of fine particulate matter emissions resulted in a 7 million person-day decrease in exposure to particulate matter concentrations above the proposed NAAQS for fine particulate matter, 17 less early deaths per year, and 24 fewer cases of chronic bronchitis per year. Using estimated costs of $300,000 per case of chronic bronchitis and $6,000,000 per early death, estimate the social cost per ton of fine particulate matter emitted.
Net Cost Reduction = (17 less early deaths/yr)( $6,000,000 per early death) + (24 chronic bronchitis cases per year)($300,000 per case of chronic bronchitis) = $109.2x106/yr.
Social Costs Per Ton Emitted: ($ tons/day)(365 days/yr)] $997.26/ton.
5. (5 points) A chemical manufacturing facility buys raw material for $0.60 per pound and produces 90 million pounds per year of product, which is sold for $0.75 per pound. The process is typically run at 90% selectivity and the raw material that is not converted into product is disposed of at a cost of $0.80 per pound (by incineration). A process improvement allows the process to be run at 98% selectivity, allowing the facility to produce 98 million pounds per year of product. What is the net revenue of the facility (product sales - raw material costs - waste disposal costs) before and after the change? How much of the increased net revenue is due to increased sales of product and how much is due to decreased waste disposal costs?
Original Process: 90% selectivity.
Net Revenue (per 1b product) = selling price - raw matls. cost - waste treatment costs ($0.75/lb prod.) - prod. prod.
($0.75/lb product - $0.667/lb product - $0.089/lb product $-0.006/lb product
Improved Process: 98% Selectivity.
Net Revenue (per 1b product) = selling price - raw matls. cost - waste treatment costs ($0.75/lb prod.) - feed) waste)
= ($0.75/lb product - $0.612/lb product - $0.016/1b product $0.122/1b product
6. (10 points) Water use and treatment in a polyester yarn dyehouse, described by Wenzel, et al, (2002), will be used as a case study of water reuse design methods. The first task in the analysis is to define the current uses (sinks) of water in the process. For each stream, the flow rate, and the inlet and outlet concentrations of suspended solids (a key contaminant) are required. Data for the yarn facility are shmvn in Table 1.
Table 1. Water use and total solids (TS) contamination levels (entering and exiting each
rocess ina 01 ester arnd ehouse is described in the data below. |
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Process |
Flow m3/ ear |
TS m I |
D ebath |
1 oo,ooo |
1,000-2000 |
Reductive rinse |
10,000 |
|
Hot rinse |
100,000 |
600-2,000 |
Cold rinse |
200,000 |
|
Yarn lubrication |
100,000 |
600-1,000 |
a.) There are 4 concentration regions:
Region 1: |
400-600 mg/L One stream in this region (Cold rinse) Total flow rate of 200,000 m3/yr Total mass exchanged of 40,000 kg/yr |
Region 2: |
600-1000 mg/L Two streams in this region (Hot rinse and Yarn lube) Total flow rate of 200,000 m3/yr Total mass exchanged of 80,000 kg/yr |
Region 3: |
1000-2000 mg/L Two streams in this region (Dyebath and Hot rinse) Total flow rate of 200,000 m3/yr Total mass exchanged of 200,000 kg/yr |
Region 4: |
2000-5000 mg/L One stream in this region (Reductive rinse) Total flow rate of 10,000 m3/yr Total mass exchanged of 30,000 kg/yr |
b.)
6000 5000 4000 3000 2000 1000 O |
50000 |
100000 150000 200000 250000 Mass exchanged (kg/yr) |
300000 350000 400000 |
aao
Problems
(Open book)
Yin (rich) or Xin (lean) Yin (rich) or Xin (lean) flow rate
(mass fraction) (mass fraction) (kg/s)
.04 .0 3
.09 .04 3
.05 6
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