Solid Waste Management and Sustainability Technology (NOTE 3)

1. Solid Waste Management and Sustainability Technology (NOTE 3) Joonhong Park Yonsei CEE Department 2013. 10. 06.

2. Materials Flow Through Society Recovery Recycle Reuse Energy Domestic Use Waste Management Industrial Production Raw Materials Industrial Scrap A B

3. New aspect of environmental friendly materials Minimization of green house gas production Potential to use as renewable energy sources Biodegradability Long life of products (Thing is that the trend is being changing….)

4. Chapter 3: Collection Truck House Can Can To Truck Truck From House To House Truck Routing House To Can Truck To Disposal

5. House to Can Volume base fee system to pay waste program in US, not yet in Korea. Example: A family of four people generates solid waste at a rate of 2 lb/cap/day And the bulk density of refuse in a typical garbage can is about 200 lb/cubic yd. If collection is once a week, how many 30-gallon garbage cans will they need. Or alternatively, how many compacted 20-lb blocks would the family produce if they had a home compactor? How many cans would they need in that case? Solutions) 2lb/cap/day x 4 persons x 7 days/week = 56 lb refuse per week 56 lb/200lb/cubic yd = 0.28 cubic yd 0.28 cubic yd x 202 gal/cubic yd = 57 gal. => Require two 30-gallon cans Alternative: If each block of compacted refuse is 1400 lb/cubic yd. The necessary volume is 56lb/1400(lb/cubic yd) X 202 gal/cubic yd = 8.1 gal. => Need only one 30-gal can

6. Can to Truck Still one of the most dangerous jobs REVOLUTIONS(?): Green-can-on-wheels & Plastic Bags Semi-automated, Fully-automated (see Supplementary figures) Truck from House to House Compaction: improving coverage of service Example: Assume each household produces 56 lb of refuse per week. How many customers can a 20-cubic yd truck that compacts the refuse to 500 lb/cubic yd collect before it has to make a trip to the landfill? Answer: 20 cubic yd X 500 lb/cubic yd = 10,000 lb 10,000 lb/ 56lb/customer = 178 customers

7. Truck from House to House Make an equation to estimate the amount of time the crew actually works in collecting refuse (Y) using the following parameters. A: time from the garage to the route, including the marshaling time, or that time needed to get ready to get moving. B: actual time collecting a load of refuge. C: number of loads collected during the working day. D: time to drive the fully loaded truck to the disposal facility, deposit the refuse, and return to the collection route. E: time to take the final, not always full, load to the disposal facility and return to the garage. F: official breaks including time to go to the toilet. G: other lost time such as traffic jams, breakdowns, etc.

8. Truck from House to House Make an equation to estimate the number of collection vehicles needed (N) using the following parameters. S: total number of customers serviced. F: collection frequency, number of collections per week X: number of customers a single truck can service per day W: number of workdays per week N =? What assumptions are required to solve this problem?

9. Truck Routing Micro-routing: Routing of a vehicle within its assigned collection zone. Shore C A B Shore D Mission: Finishing at the starting position Without passing the same bridge twice => Not possible. C B A To make it possible: • All points must be connected. • The number of links to any node must be even D

10. Truck Routing Useful guidelines • Routes should not overlap, but should be compact and not be fragmented. • The starting point should be as close to the truck garage as possible. • Heavily traveled streets should be avoided during rush hours. • One-way streets that cannot be traversed in one line should be looped from the upper end of the street. • Dead-end streets should be collected when on the right side of the street. (Should be different in UK or Japan) • On hills, collection should proceed downhill so that the truck can coast. • Clockwise turns around blocks should be used whenever possible. • Long, straight paths should be routed before looping clockwise. • U-turns can be avoided by never leaving one two-way street as the only access and exit to the node. • For certain block patterns, standard paths, as shown in Figure 3-11, should be used.

11. Truck Routing Start Finish Start Finish Block patterns and their standard paths (Figure 3-11 in p.79 of the main TB)

12. Truck to Disposal Macro-routing: Routing to the disposal site. Necessary to use optimization techniques – Transportation algorithm (Linear programming) Collection Route centroids Disposal site 1 (k=1) i=N i = 1 2 i=3 Constraints • Landfill capacity is limited. • Amt of disposed = Amt of generated • No sink in the routes. Disposal site K (k=K)

13. Objective Function Amt of waste from i to k per time Cost per waste amt from i to k Constrain 1 For all k Number of source i Number of disposal sites k Constrain 2 For all i Disposal cost per waste at k Capacity of k disposal site Total quantity of waste at area A Constrain 3

14. Solid Waste Management and Sustainability Technology (NOTE 4) Joonhong Park Yonsei CEE Department 2013. 9. 30.

15. Combustion and Energy Recovery • Heat value of refuse • Materials and thermal balances • Combustion hardware used for MSW • Undesirable effects of combustion

16. Heat value: Unit • Amount of energy necessary to heat one unit mass of water one unit temperature degree. • British termal unit (BTU) energy amount to heat one pound of water by one degree Fo. • Calorie (Cal): energy to heat one gram of water by 1Co • Joule (J): kg m2/s2 (ML2T-2) 4.184 J = 1 Cal. • watt-hours (Wh): (kg m2/s3)* 3600(s/h) • See Table 7.1 (useful conversion factors)

17. Heat value: Determination methods • Ultimate analysis • Compositional analysis • Proximate analysis • Calorimetry

18. Heat value: Calorimetry Calorimeter: to measure energy necessary to heat 1gram of water by 1 degree C Thermometer H2O To electrical contact O2 Bumb Cell

19. Heat value: Calorimetry Thermogram Linear Part Temp oC dT Time

20. Heat value: Calorimetry U = Cv * dT / M System characteristic Here U: heat value of unknown material, cal/g Cv: heat capacity of the calorimeter dT: rise in temperature from thermogram oC M: mass of the unknown material, gram How to determine Cv? [Calibration]

21. Heat value: Calorimetry • Higher heating value (HHV): the gross calorific energy • Lower heating value (LHV): the net calorific energy • HHV = LHV + latent heat of vaporization (occurring in the bomb calorimeter) • LHV is a more realistic value for design.

22. Heat value: Calorimetry • Calorimetry is the referee method of measuring heat value of a fuel • But it does not actually simulate the behavior of that fuel in a full-scale combustor. • Reason 1: Some metals oxidize at sufficiently high temperatures to yield heat (exothermic reaction) => It happens in calorimetry but not in a full-scale combustor. • Reason 2: All organic material will oxidize in a calorimeter but this will not occur in a full- scale combustor (time dependent efficiency.)

23. Reaction - Thermodynamics Activation Energy (Barrier): activated by Catalyses/Enzymes Reactants (A and B) ΣΔGreactant Total RXT’n Chemical Free Energy, ΔGr = ΣΔGpro -ΣΔGrxt Products (C and D) ΣΔGproduct

24. Reactions Stoichiometry and Kinetics • Energetics : “thermodynamic fall” • When ΔGr is less than 0, thermodynamically favorable. • dCi = Ф (dGr) = Ф (masses of reacting constituents) • Fundamental Governing Eq. (Stoichiometry) α1 A + α2 B < = > α3 C + α4 D αi: stoichiometric coefficient; Q: unit? forward rxn const. = [C] α3 [D] α4 /[A] α1 [B] α2 • Reaction Kinetics (the Mass Law) rate = dCi/dt = Ф (masses of reacting constituents) = function of (energetics, system characteristics)

25. Combustion Stoichiometry • Production of hydrocarbons CO2 + sunlight + nutrients + H2O => (HC)x + O2 • Combustion (rapid decomposition) (HC)x + O2 => CO2 + H2O + nutrients + heat energy • Two-step reaction • C+O => CO + 10,100 J/g • CO + O => CO2 + 22,700 J/g • Stoichiometric oxygen: one mole carbon + one mole of molecular oxygen (2.67 gO2/gC)

26. Example: Stoichiometric oxygen & combustion air Problem 1: calculate stoichiometric oxygen required for the combustion of methane gas (CH4) Problem 2: Calculate the stoichiometric oxygen required for the combustion of methane gas

27. Combustion efficiency Emission Cold water Condenser Steam Combustion Turbine Fuel Generator Air Electricity

28. Combustion efficiency • Energy conservation 0 = Q0 – QU – QW Q0: energy flow in QU: useful energy out QW: wasted energy out E(%) = QU/Q0 X 100 • Carnot efficiency (Ec) Ec(%) = 100 x (T1-T0) /T1 T1: absolute temp. of the boiler, oK T0: absolute temp. of the condenser, oK

29. Thermal balance on a waste-to-energy combustor To vaporation To stack gases To steam From water To radiation From fuel To ash

30. Heat value: Calorimetry Calorimeter: to measure energy necessary to heat 1gram of water by 1 degree C Thermometer H2O To electrical contact O2 Bumb Cell

31. Heat value: Calorimetry Thermogram Linear Part Temp oC dT Time

32. Incinerators…Being too hot is not good. “Incinerator” is a facility to burn refuse without recovering energy from MSW. “Incinerators”, a name no longer used by the industry because of the sorry record of these facilities (poor design, inadequate engineering, and inept operation combined to produce an ash still high in organics and smoke that even in the days of little industrial air pollution controlled caused many communities to shut down the incinerators.) Without energy recovery, the exhaust gas from these units was too hot => causes problems in dust control (electrostatic precipitators)

33. Supercritical Fluid Soild Liquid Pressure CRITICALPOINT TRIPLEPOINT Super-cooled Liquid Saturated vapor Superheated vapor Super-cooled Vapor Temperature MELTINGPOINT BOILINGPOINT CRITICALTEMPERATURE

34. Waste-to-Energy Combustors Combination of combustion of waste with energy recovery. A typical MSW combustor Stack Overhead crane Feed hopper Steam generator Bag house Scrubber Solid Waste Storage pit Receiving area Stoker grate Ash conveyor Furnace

35. Combustion chamber Overfire air (oxygen and turbulence provider) Temperature (980-1090 oC) Grates • Reciprocating • Rocking • Traveling (functions: conveying refuse, producing turbulence, and underfire air) Q: If temp. is low? If temp. is high? Underfire air

36. Excess air and temperature relationship in MSW combustion Why not? (supercritical steam) 4000oF Why not? Operational air volume 3000oF 2000oF (1090oC) Remember Stoichiometric oxygen? 1000oF 0 50 100 150 % -50 Excess air, % above stoichiometric

37. Efficiency of energy recovery as related to quality of MSW as a fuel

38. Another types of combustors Rotary kiln: - furnace is rotating - provides excellent mixing, improving the efficiency of combustion. Modular starved air combustors - two-stage combustion system (burned by starved air mode and then by fossil fuel) - typically, no recovery of energy - good for small scale (15-100 tons per day) - mainly used for destruction of some hazardous materials such as biohazards from hospitals.

39. Pyrolysis (in principle) Destructive distillation or combustion in the absence of O2. C6H10O5+heat energy => CH4 + H2 + CO2 + C2H4 + C + H2O Produces a solid, a gas (methane), and a liquid (ethylene) Effect of temperature and heating rate in the formation of pyrolysis products. Gas 1200 Liquid Temp (oC) 800 Solid 400 100 101 102 103 104 105 106 1/heating rate (milliseconds per oC)

40. Pyrolysis (theory vs. reality) Theoretically speaking, pyrolysis and gasification is - Environmentally excellent - Producing little pollution - Resulting in the production of various useful fuels. - Gasification appears to be able to meet the air emission requirements for solid waste combustion, including the strict dioxin standards. Nevertheless, practically speaking…. - Success in pyrolysis of homogeneous and predictable fuels such as sugarcane bagasse. - Failure in pyrolysis of heterogeneous and unpredictable refuse. - Not a single unit has yet to be successfully field tested in full scale (could not convince PEOPLE). => Should we continue improving pyrolysis technology?

41. Mass Burn vs RDF Mass burn unit: no preprocessing of the MSW prior to being fed into the combustion unit. RDF (refuse-derived fuel) unit: processed prior to combustion (i) to remove noncombustible items and (ii) to reduce the size of the combustible fraction. Advantages of RDF - uniform heat value - reduction of the amount of excess air required for combustion (50% the excess air is sufficient). - less requirement for air-pollution-control devices. - some problem items (ex. Batteries) can be eliminated before combustion. - Possible to store them for a relatively long term. Disadvantages of RDF - processing of MSW is not easy. - corrosion and erosion problems (due to high temp.)

42. ASTM RDF Designations Note: RDF-6 and -7 have been tried on a pilot scale but have not been found to be successful at full-scale plants.

43. Undesirable effects of combustion Waste heat Ash Air pollution Dioxin (of particular concern)

44. Solid Waste Management and Sustainability Technology (NOTE 4) Joonhong Park Yonsei CEE Department 2013. 9. 30.

45. Combustion and Energy Recovery • Heat value of refuse • Materials and thermal balances • Combustion hardware used for MSW • Undesirable effects of combustion

46. Heat value: Unit • Amount of energy necessary to heat one unit mass of water one unit temperature degree. • British termal unit (BTU) energy amount to heat one pound of water by one degree Fo. • Calorie (Cal): energy to heat one gram of water by 1Co • Joule (J): kg m2/s2 (ML2T-2) 4.184 J = 1 Cal. • watt-hours (Wh): (kg m2/s3)* 3600(s/h) • See Table 7.1 (useful conversion factors)

47. Heat value: Determination methods • Ultimate analysis • Compositional analysis • Proximate analysis • Calorimetry

48. Heat value: Calorimetry Calorimeter: to measure energy necessary to heat 1gram of water by 1 degree C Thermometer H2O To electrical contact O2 Bumb Cell

49. Heat value: Calorimetry Thermogram Linear Part Temp oC dT Time

50. Heat value: Calorimetry U = Cv * dT / M System characteristic Here U: heat value of unknown material, cal/g Cv: heat capacity of the calorimeter dT: rise in temperature from thermogram oC M: mass of the unknown material, gram How to determine Cv? [Calibration]