1 PB389 Integrated Solid Waste ManagementNumfon Eaktasang, Ph.D. Thammasat University

2 Solid Waste Managementgeneration Waste reduction and separation at the source Collection Transportation Separation, processing & transformation Disposal

3 Disposal TechnologiesLandfill Thermal treatment Biological conversion

4 Dumping on Land

5 Burial

6 Hog Feeding

7 Thermal Treatment Solid waste Ash + Gases + Vapor Smoke + Soot + Energy (1°pollutant) (2°pollutant) “conversion of solid waste into gaseous, liquid, and solid conversion products, with the concurrent or subsequent release of heat energy”

8 Thermal Treatment Open burning Air pollution Smoke Dust Health riskRespiratory system Eye irritation GHGs

9 Thermal Treatment Agricultural waste

10 Thermal Treatment Incineration Air pollution control systemDust collection system Ash

11 Categorization of thermal processingCombustion Stoichiometric: with exactly the amount of oxygen (or air) needed for complete combustion excess-air: with oxygen in excess of the stoichiometoric requirements Gasification partial combustion of solid waste under substoichiometric conditions to generate a combustible gas containing carbon monoxide, hydrogen, and gaseous hydrocarbons. Pyrolysis thermal processing of waste in the complete absence of oxygen

12 What is incineration? Basic reaction of stoichiometric combustionFor carbon C+O2 CO2 For hydrogen 2H2+O22H2O For sulfur S+O2 SO2 However, difficult to achieve complete combustion in stoichiometric condition practically. Excess air must be used to promote mixing and turbulence The use of excess air affects the temperature and composition of combustion products (called flue gases) Excess air increase: oxygen contents increase and temperature of combustion decrease Temperature of flue gas is important for odor control. Less than 800 OC -> may occur odor problem greater than 1,000 OC -> may minimize the emission of dioxins, furans, VOCs

13 Complete Combustion 3T’s of combustion Time Temperature Turbulence

14 Complete Combustion C6H10O5 + 6O2 6CO2 + 5H2O + (Energy 5,000 Btu/Ib)Theoretical combustion air (TA) C6H10O5 1 Ib  oxygen requirement (6 × 32)/162 = 1.2 Ib Theoretical air = 1.2 × (100/23) = 5.2 Ib Excess air (EA) = excess air to complete combustion Actual combustion air (AA) = total air to complete combustion AA = TA + EA

15 Complete Combustion Ex: Excess air 50% AA = 5.2 Ib + (0.5 x 5.2) AA = AA = 7.8 Ib AA = TA + EA

16 Why is the SW incinerated?To reduce the volume and weight of SW 1/4 by weight, 1/15 by volume To remove the bad smell To decompose the hazardous materials heat of high temperature decompose the smelling and hazardous components

17 Where incinerated? Hikarigaoka Incineration plant Tokyo, Japan maishima/01_kankyo.html

18 How incinerated?

19 Incineration plant platform Incinerator NOx remover Baghouse Ash pitGas cleaner (HCl, SOx, HM) Waste pit

20 Types of combustion systemsWaste type or combustion system Commingled wastes: Mass-fired combustion systems Processed wastes: Refuse derived fuel (RDF) fired combustion system

21 Types of combustion systemsMass-Fired Combustion Systems

22 Types of combustion systemsRefuse derived fuel (RDF) fired combustion system

23 Types of Incinerators Single chamber incinerator

24 Types of Incinerators Multiple chamber incinerator

25 Types of Incinerators Incinerator type Stoker grate combustionFluidized bed combustion Rotary Kiln Small incinerator

26 Stoker grate combustionMost common in mass-fired combustion system Movement of waste through the grate system, mixing of the waste, and injection of combustion air. (RT=2hrs) Air comes from below thorough the grate. Ash falls down to the collection hopper to conveyer. Temp ,200 0 C Many variations of grates: travelling, rotating, reciprocating and rocking grates

27 Stoker grate combustion

28 Traveling Grates

29 Reciprocating Grates

30 Rocking Grates

31 Roller Grates

32 Stoker grate combustionAdvantages-Disadvantages Temp ,200 o C Commingled wastes Various composition of wastes Efficiency – 85% 1,200 ton/day High investment and maintenance costs

33 Fluidized bed combustion (FBC)Consists of a vertical steel cylinder with a sand bed, a supporting grid plate, and air injection nozzle. When air is forced up, the bed fluidizes and expands up to twice its resting volume. FBC are quite versatile and can be operated on a wide variety of fuels. The bed material: plain sand, silica or limestone (CaCO3) Limestone can contribute to decrease SO2 emission

34 Fluidized bed combustion (FBC)

35 Fluidized bed combustion (FBC)Advantages-Disadvantages Temp ,000 o C Complete combustion Processed wastes Efficiency – 90% ton/day Low investment and maintenance costs

36 Rotary kiln Rotary kiln is widely used for cement production and also used for industrial waste incineration, especially oily mud, tar, pitch, paint mud, dye waste, or plastics.

37 Rotary kiln

38 Rotary kiln Advantages-DisadvantagesTwo-chamber incinerator (Temp. 700 and 1,200°C) 480 ton/day Used for hazardous waste Commingled wastes Various composition of wastes Efficiency – 80% High investment and maintenance costs

39 Small incinerator There are many kinds of anti-dioxins emission incinerators invented in Japan. They are suitable for small scale waste treatment, not like uncontrolled combustion in open space. Typical small incinerator Dioxin-emission prevention type

40 Environmental Control SystemsGaseous and particulate emissions Solid residuals Liquid effluents

41 Air emissions Nitrogen oxides (NOx) Sulfur oxides (SOx)include NO and NO2 Source of NOx: Thermal NOx and fuel NOx Precursors of the phtochemical oxidants, acid rain and fog Sulfur oxides (SOx) formed by the combustion of fuel containing sulfur an eye, nose and throat irritant. Asthma, bronchitis, acid rain Carbon mono oxide (CO) formed when insufficient oxygen is present Headache, nausea, sudden death Particle matter (PM) Visibility reduction and effect to human lung Metals MSW usually has a higher metal concentration than coal or oil.

42 Air emissions Acid gases Dioxins (PCDDs) and Furans (PCDFs)Not only NOx and SOx, but also Hydrogen chloride (HCl), Hydrogen fluoride (HF) Iron corrosion, acid rain Dioxins (PCDDs) and Furans (PCDFs) 75 PCDD isomers and 135 PCDF isomers Some of them have been found to be among the most toxic substances in existence. (e.g. 2,3,7,8-TCDD) Polychlorinated dibenzodioxin Polychlorinated dibenzofuran 2,3,7,8-TCDD

43 Pollution control systemsParticulate Electrostatic precipitators fabric filters NOx Source separation combustion controls flue gas treatment SOx and acid gas wet or dry scrubbing CO and HC control Combustion controls

44 Electrostatic precipitatorfirst particle control device for MSW incinerators removing fine (<10mm) and very fine (<2mm) particles. Mechanism -20,000 to -100,000 V, applied to the discharge electrodes, produces a strong electric field between the electrodes. The negatively charged particles in the flue gas attract to grounded collector electrode. The collected particles are removed by mechanical vibration. Typical performance 93% removal for fine, and 99.8% for very fine particles does not meet the emission control requirement in some strict areas (countries) like Japan, California.

45 Electrostatic precipitator

46 Fabric filter technology of choice on most recently constructed combustion systems. Mechanism Filter bags are connected in parallel in a housing. Particles (>0.1mm) in the gas are trapped on a dust bed on the filter surface. The particles are removed from the filter bags by mechanical shaking, reverse air flow, and pulse-jet. Felted glass, woven glass, and Teflon have been used as fabric filters.

47 Fabric filter

48

49 NOx control Source (food and yard wastes) separationfor avoiding fuel NOx Combustion control for avoiding thermal NOx Low excess air operation and staging of combustion First stage; gasification with low-excess air, Second stage; combustion with excess air Flue gas recirculation Flue gas treatment Catalytic reduction Ammonia injection followed by a catalyst bed reaction (metals; copper, iron, chromium, nickel, molybdenum, cobalt, and vanadium). NO + NH3 + 1/4O2  N2 + 3/2H2O (at 275 – 425 oC) up to 90% removal for coal- and oil- burning applications

50 Acid gases control Source separation of chlorine and sulfur containing wastes Wet scrubbing of flue gases liquid solutions are used to scrub and neutralize Ca(OH)2 or NaOH solution added in venturi scrubber Cooling before wetting and re-heating after wetting Dry scrubbing neutralizing slurries are injected Na2CO3 or Ca(OH)2 added just before the baghouse

51 Dioxins, furans (DXNs) and metals controlSource separation is difficult for DXNs reduction, however, is working properly for metals reduction Combustion control is the principal reducing strategy for DXNs Minimum temperature in thermal system of oC with a minimum residence time of 1 sec Minimization CO emission also minimize DXNs Particulate control is also important for DXNs and metals DXNs and most metals except mercury tend to condense on flyash particles <250oC and can be removed by filters Temp of flue gas must not be kept around 300 oC (avoid De-novo)

52 Flow diagram of gas treatmentDry scrubbing (Acid gas) Boiler <850Co <2 sec Lime AC Re-heater AC Baghouse PM removal Na(OH) Cooler Re-heater Cooling tower Avoid De-novo Baghouse protect NH3 Wet scrubbing (Acid gas) Incinerator Combustion control NOx catalytic reduction

53 Ash management Solid residuals Bottom ash Fly ash Scrubber productBottom ash, fly ash and scrubber product Bottom ash contains considerable amount of metals and glass as well as unburned organics. Amount of unburned organic material in the ash is a measure of performance. (Ash Burnout Index, ABI) sometimes used as a construction material Fly ash particulates removed from the flue gases contains trace pollutants with fine particles, so careful handling is necessary. Scrubber product sludge produced by a wet scrubber

54 Ash management Heavy metals and trace organics, e.g. DXNsLeaching potential in a landfill EP toxicity test, Toxicity Characteristic Leaching Procedure (TCLP) test Recommended ash-handling Handling; Ash should be properly wetted or covered. Transport; Ash should be covered and leak-resistant. Disposal of flyash only; Disposal should be in a monofill (ash only) equipped with double liners and a leachate collection system. Combined or bottom ash only; Disposal should be in a monofill equipped with a composite or clay liner, or by codisposal in an MSW landfill equipped with a double liner.

55 Wastewater Wastewater dischargescooling and wash water from wet ash removal systems wet scrubber effluents wastewater from sealing, flushing and housekeeping wastewater from boiler feedwater production cooling tower blowdown Quantities of wastewater produced are relatively minor, but may require pretreatment before discharge into a sewer system

56 Energy recovery systemsRecovered energy electricity steam (heat) using industrial processes or building heating Principal components boilers for steam production steam or gas turbines and reciprocating engines as prime movers for mechanical energy electric generator Cogeneration systems both thermal and electricity production

57 Energy recovery systemsEfficiency of electricity production Average: 10% (overall efficiency, Japan, 2000) many efforts to improve it bigger facilities improve electricity generation system combined turbine RDF use more heat

58 Disposal method in Asia

59 Electricity production in major developed countriesTotal capacity of electricity production by SW incineration (MW) Number of SW incineration plants which produce electricity US UK Germany France Sweden Switzerland The Netherlands Japan 2,820 230 1,000 160 100 180 1,058 102 11 50 90 3 30 5 210 Source:

60 Thank You for Your Attention