1. Prof. Jiakuan Yang Huazhong University of Science and Technology Air Pollution Control Engineering

2. Lecture 7-1 General ideas in air pollution control Ⅰ Three alternative for air pollution control Ⅱ air pollution control systems and equipment Ⅲ Fluid velocities in air pollution control equipment Ⅳ Minimizing volumetric flow rate and pressure drop Ⅴ Efficiency, penetration, nines

3. Questions for the Last Lecture 1. 1. What are three alternatives for air pollution control? 2. 2. Please give three logical approaches to improving dispersion. 3. 3. How to deal with the collected pollutants in down-stream pollution control device?

4. Answer (1) Process change and pollution prevention Down-stream control device Improving dispersion

5. Answer (2) Tall stack Intermittent control schemes Relocate the plant

6. Answer (3) Reuse the collected pollutants if the concentration is high enough to recovery, such as, raw materials, fuels Ultimate disposal of the rest pollutants by landfill or combustion.

7. Ⅴ Efficiency, penetration, nines Downstream control device C0C0 Q1C1Q1C1 Q0C0Q0C0 C1C1 Q0C0Q0C0 Mass flow rate of contaminant into the device Q1C1Q1C1 Mass flow rate of contaminant out of the device

8. Ⅴ Efficiency, penetration, nines Efficiency penetration nines 99% 99.9% 90%

9. Ⅴ Efficiency, penetration, nines Q1C1Q1C1 Q3C3Q3C3 Q2C2Q2C2 Q0C0Q0C0

10. In the terms of penetration

11. Ⅵ Homogeneous and non-homogeneous pollutants CO, SO 2 are homogeneous Every CO molecule is identical to every other CO molecule. Particles are not homogeneous different particle with various sizes.

12. Ⅶ combustion Most air pollutants are created and released in processes involving combustion, transportation, fuel combustion, industrial processes, solid wastes incineration, miscellaneous.

13. Ⅶ combustion (1) basic combustion equation (2) Heat of combustion In combustion, we will have removed a finite amount of energy in the form of heat, called the heat of combustion. The higher heating value, water is condensed. The lower heating value, water as gas less than the higher heating value by the amount of that latent heat of condensation.

14. Ⅶ combustion (3) Explosive or combustible limits Too rich to burn Flammable y methane T, 0 F 0.0 0.4 0.3 0.2 0.1 0.5 2000 Too lean to burn 1000 3000 4000 0 UEL LEL Stoichiometric

15. Ⅶ combustion 1 mol CH 4 need 2 mol O 2. O 2 in air is about 21%, so the needed air is 2/0.21. Stoichiometric mixture ( 理论完全燃烧混合物 ) The mixture of air and combustible gases in the state of complete combustion. 12 (3) Explosive or combustible limits (volume % methane ) mol % methane == 0.095 = 9.5%

16. Ⅶ combustion LEL (Lower Explosive Limit), leans limit A lower limit value, less than which mixture will not burn, expressed as the concentration of the combustible gas. UEL (Upper Explosive Limit ),rich limit (3) Explosive or combustible limits

17. Ⅶ combustion LEL and UEL often are expressed in the ratio of the mole percent of methane in the limit mixture to that in the stoichiometric mixture. (3) Explosive or combustible limits

18. Ⅶ combustion Two types expressions = volume%, in the limit mixture, in the stoichiometric mixture Fig. 7.4, Page 181 Table 7.1, Page 179 (3) Explosive or combustible limits

19. Ⅶ combustion (3) Explosive or combustible limits Mass of air Mass of fuel

20. Ⅶ combustion products change (4) The volume and composition of combustion products volume change Fuel (C x H y ) Air(O 2 、 N 2 ) Products of combustion

21. (4) The volume and composition of combustion products The faction of excess air humidity Product of CO 2 Product of H 2 O Humidity N2N2 Excessive of Oxygen

22. Ⅷ Changing Volume Flow rate Air flow in Air flow out m · =100lbm/min T = 500 0 F =260 ℃ 1atm m · =100lbm/min T = 300 0 F = 148.9 ℃ 1atm Q=?

23. Ⅷ Changing Volume Flow rate m · Q (1) Standard International Units, SI, metric Units

24. Ⅷ Changing Volume Flow rate (1) Standard International Units, SI, metric Units =0.627 scms =0.627 scm / s =0.627 Nm 3 /s Standard Cubic Meters per Second Normal Cubic Meters per Second Standard flow rate

25. Ⅷ Changing Volume Flow rate (1) Standard International Units, SI, metric Units Actual flow rate =1.14 acms =1.14 acm/s =1.14 am 3 /s Actual Cubic Meters per Second

26. Ⅷ Changing Volume Flow rate (2) British Units Standard flow rate

27. Ⅷ Changing Volume Flow rate (2) British Units Actual flow rate

28. This Lecture and the Next Lecture  This Lecture:  Chapter 7 Page 160~196 Page 202~205  The Next Lecture:  Chapter 8 Page 209~246

29. Exerciser Page 203, 7.5 Page 204, 7.12 Page 205, 7.19, 7.21 1. Please explain a typical air pollution control system.

30. 2. The below table shows the Lean Limit and Rich Limit of Toluene(C 7 H 8 ). What are the stoichiometric mixture, LEL, and UEL for the combustion of Toluene in air, expressed in y Toluene (volume percentage of Toluene in air) respectively? Fuel Molecular Weight Explosive Limit % stoichiometric Lean Rich Toluene9243322

31. Some device Air flow Air flow out m=10 kg/s T=227 ℃ Q=? m=10 kg/s T=127 ℃ Q=? 3. The following figure shows some kind of device with a gas flow in and out. The gas has the properties of air, and a flow rate of 10 kg/s. The pressure is close to atmospheric(1 atm). At standard conditions the temperature is 20 ℃. What are the volumetric flow rates in and out? The results should be expressed as four types in scms, acms, scfm and acfm respectively.

32. 3. A typical coal has the following ultimate analysis by weight: H, 6.0%; C, 60.0%; N, 1.0%; S, 2.0%; O, 7.0%; ash 10.0%. It is burned with 20% excess air with humidity 0.0116 mol/mol dry air, and combustion is complete. (1) Determine SO 2 concentration (ppm) in the gases of combustion products. (2) A rate of 1000 kg/h of dry coal is used in combustor, and the temperature of the gases of combustion products is 100 0 C. What is the gas flow rate of the gases of combustion products in actual cubic meter per second (acms) at the actual conditionings (100 0 C and 1 atm)?

33. DISCUSSION Topics about Air pollution:  Introducing yourself  Interesting news or information about air pollution your having read or heard  Your opinions on this Air Pollution course  Your suggestions for Chinese Air Pollution  Other familiar issues about Air Pollution