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18-Env-B5 Industrial & Hazardous Waste Management · May 2018

Question 9 of 14: Incinerator Destruction/Removal Efficiency and Particulate Compliance

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

Reference texts: LaGrega, Buckingham & Evans, Hazardous Waste Management, 2nd ed.; Nemerow & Dasgupta, Industrial and Hazardous Waste Treatment, 2nd ed.; Metcalf & Eddy, Wastewater Engineering: Treatment and Resource Recovery, 5th ed.; Davis & Cornwell, Introduction to Environmental Engineering, 6th ed.; Cooper & Alley, Air Pollution Control: A Design Approach; CCME, Guidelines for the Management of Biomedical Waste in Canada (1992); Ontario Environmental Protection Act, R.S.O. 1990, c. E.19 and O. Reg. 347 (Waste Management – General); Transportation of Dangerous Goods Act, 1992 (Canada) and Regulations; Canadian Environmental Protection Act (CEPA), 1999.

Question 9: Incinerator Destruction/Removal Efficiency and Particulate Compliance (10 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Given.

CompoundInlet (lb/hr)Outlet (lb/hr)
Benzene10250.087
Tetrachlorophenol7600.056
Toluene7560.024
Particulates—20.3

Stack flow rate $Q = 37{,}500$ dscfm; required DRE $= 99.99\%$; particulate standard $= 0.08$ grains/dscf ($7000$ grains $= 1$ lb); emissions already corrected to $7.0\%$ O2 in the flue gas.

Find. Whether the destruction/removal efficiency of each organic pollutant, and the particulate emission rate, both meet the stated standards.

Approach. Compute the DRE of each organic compound from its inlet/outlet mass flow rates and compare to the 99.99% requirement; separately convert the particulate mass emission rate to a stack concentration (grains/dscf) using the stack volumetric flow, and compare to the 0.08 gr/dscf standard.

  1. Destruction/removal efficiency (DRE). For each organic compound, $\text{DRE} = \dfrac{W_{in}-W_{out}}{W_{in}}\times100\%$: $$\text{DRE}_{Benzene} = \frac{1025-0.087}{1025}\times100\% = 99.9915\%$$ $$\text{DRE}_{Tetrachlorophenol} = \frac{760-0.056}{760}\times100\% = 99.9926\%$$ $$\text{DRE}_{Toluene} = \frac{756-0.024}{756}\times100\% = 99.9968\%$$ All three exceed the required $99.99\%$ DRE.
  2. Particulate concentration in the stack gas. Convert the mass emission rate to grains per hour, then divide by the stack volumetric flow (converted to dscf/hr): $$20.3\ \text{lb/hr}\times7000\ \text{grains/lb} = 142{,}100\ \text{grains/hr}$$ $$37{,}500\ \text{dscfm}\times60\ \text{min/hr} = 2{,}250{,}000\ \text{dscf/hr}$$ $$C_{PM} = \frac{142{,}100\ \text{grains/hr}}{2{,}250{,}000\ \text{dscf/hr}} = \boxed{0.0632\ \text{grains/dscf}}$$
  3. Compare to the particulate standard. The computed concentration is below the $0.08$ gr/dscf standard: $$0.0632 < 0.08\ \text{grains/dscf}\ \Rightarrow\ \text{particulate standard is MET}$$
Final results
QuantityValueStandardMeets standard?
DRE, Benzene99.9915%≥ 99.99%Yes
DRE, Tetrachlorophenol99.9926%≥ 99.99%Yes
DRE, Toluene99.9968%≥ 99.99%Yes
Particulate concentration0.0632 grains/dscf≤ 0.08 grains/dscfYes
OverallAll emission standards are MET
Check: since the problem states the emissions are already corrected to 7.0% O2, the reported particulate mass rate (20.3 lb/hr) and stack flow (37,500 dscfm) are used directly with no further oxygen-correction factor applied; no measured (uncorrected) O2% is supplied that would call for a separate $(20.9-7)/(20.9-\text{measured})$ correction step.