1/14/2017. Treatment options: thermal EST 3201 Waste Management. Chapter outline. Main objectives of treatment. Chapter References

Transcription

1 Treatment options: thermal EST 3201 Waste Management Integrated Sustainable Waste Management Framework (ISWM) 2 R E Z A U L K A R I M A S S I S T A N T P R O F E S S O R D E P T. O F E N V I R O N M E N T A L S C I E N C E & T E C H N O L O G Y J E S S O R E U N I V E R S I T Y O F S C I E N C E & T E C H N O L O G Y Two Pathways for biomass-to-energy conversion Chapter outline 3 4 Incineration Mechanical Biological Treatment (MBT) Refuse-Derived Fuel (RDF) Thermochemical Conversion of Biomass Pyrolysis Gasification Combustion Chapter References Main objectives of treatment Jacqueline Vaughn (2009) Waste management : a reference handbook, ABC-CLIO, Inc. gen/sandec/e- Learning/Moocs/Solid_Waste/W1/MSW_Incinerati on_technical_guidance_report_1999.pdf 5 Waste quantities reduction Use of the value of materials and energy Environmental impact reduction 6 1

2 Incineration plant Lausanne (CH) Towards a greener future with Swedish Waste -to-energy The world s best example Incineration Applicability of Incineration Advantages recovered energy for heat or power consumption reduce the original volume of combustibles by 80 to 95 % a lack of suitable sites or long haulage distances 9 Disadvantages heavy investments and high operating costs requires skilled staff The residues from the flue gas cleaning 10 A mature and well-functioning waste management system Solid waste is disposed of at controlled and well operated landfills. The supply of combustible waste - at least 50,000 metric tons/year. The lower calorific value must on average be at least 7 MJ/kg, and must never fall below 6 MJ/kg in any season. The community is willing to absorb the increased treatment cost through management charges, tipping fees, and tax-based subsidies. Skilled staff can be recruited and maintained. The planning environment of the community is stable enough to allow a planning horizon of 15 years or more. Incineration Technology 11 Incineration Technology 12 Pretreatment Combustion system Energy recovery Flue gas cleaning 2

3 Technological Overview 13 MSW incineration flue gases 14 Incineration Residues 15 The main residue from MSW incineration is slag. The amount generated depends on the ash content of the waste. In the combustion process, the volume of waste from high income cities will by experience be reduced by approximately 90% and the weight by 70 to 75 %. For low income areas the amount of ash in the waste can be high for example, in areas using coal, wood, or similar for heating. Key Criteria for Incineration Technology 16 The technology based on the mass burning principle The furnace must be designed for stable and continuous operation and complete burnout of the waste and flue gases (CO<50 mg/nm3, TOC<10 mg/nm3). The flue gases be cooled to 200 C or lower The flue gas cleaning equipment must be at least a two-field ESP (basic emission control, dust<30 mg/nm3. A controlled landfill The annual amount of waste for incineration should not be less than 50,000 metric tons. The stack should be twice the height of the tallest building within 1.0 km, or at least 70 meters high. Typical cost of an incineration plant/ton 17 MBT: Mechanical Biological Treatment 18 3

4 Efficiency of recuperation 19 Mechanical Treatment of construction waste 20 metallic parts => recycling fine material => landfill (where are generally concentrated the main pollutants) large material, stone, concrete => re-use other material => incinerated or landfilled RDF : Refuse Derived Fuel 21 What is a thermochemical conversion? 22 four main thermochemical routes 23 Pyrolysis, Gasification and combustion 24 direct combustion gasification pyrolysis liquefaction oldest way of using biomass accounts for over 97% forming carbon dioxide and water vapour solid carbonaceous fuel into combustible gases less oxygen relatively high temperatures low temperature, high pressure thermochem ical process, using a catalyst thermally degraded in the absence of oxygen/air an independ ent process Each differs in temp, heating rate, and the O 2 level present during treatment 4

5 Pyrolysis, Gasification and combustion Terminology: Char vs Charcoal vs Biochar 27 Etymologically pyrolysis derives from the Greek words pyr (= fire) and lysis (= loosening, separating, breaking apart). Pyrolysis refers to the thermal decomposition of biomass into primarily a carbon-rich solid residue (char), and secondarily into gases and liquids. characterized by a slow heating rate (5-7 K/min), long solid and gas residence times, and relatively low temperatures ( C) in a largely inert, i.e., oxygen-deficient environment. Terminology: Char vs Charcoal vs Biochar 28 Terminology: Char vs Charcoal vs Biochar 29 The term char is generally used for the solid product that arises from the thermal decomposition of any organic material charcoal is the solid, carbon-rich residue left when organic solids, mostly woods, are heated in an environment with limited oxygen. Charcoal is intended for use as a fuel (e.g., for cooking or industrial purposes), Bio-char is carbonized biomass intended for use as a soil amendment. Differences between wood charcoal and charcoal briquettes 30 5

6 Final products from biomass 31 Carbonization, or char-making Carbonization, or char-making, is a slow pyrolysis process, which has been used since the dawn of civilization. The earliest known example of the use of charcoal, produced as an unintentional residue from cooking fires, can be found on the cave drawings of Cro-Magnon man approximately years ago. 32 Bio-waste: raw materials 33 Biomass - any organic materials derived from plants /animals. Biomass is a complex mixture of organic materials, i.e., carbohydrates, fats and proteins, along with small amounts of minerals, such as sodium, phosphorus, calcium and iron. Plant biomass can roughly be divided into food supplies (rich in starch, fat and protein), < 20% by mass lignocellulosic, non-food biomass - > 80% products, residues and waste from agriculture, forestry and related industries Municipal solid waste is an important source of waste biomass and much of it comes from food scraps, lawn clippings, leaves and papers. Criteria for assessing biowaste suitability for char production 34 The suitability of each type of biomass as feedstock for pyrolysis is dependent on its nature and chemical composition, as well as on environmental, economic and logistical factors. Availability and accessibility aspects Total amount generated Annual/seasonal variation Pre-existing and competing uses Cost of waste Degree of centralization Physical-chemical properties Bulk density Particle size and uniformity Moisture content Fixed carbon content Ash content Charring process 35 Van Krevelen diagram 36 6

7 The carbonization process: four stages Biomass is heated to C water is completely removed CO2, acetic acid and formic acid are driven out. Between 220 and 280 C pyrolytic degradation volatiles are released, emitting more CO2, acetic acid and formic acid. From 280 to 400 C biomass self-decomposes strong exothermic reaction, a rise in the temperature Above 500 C, the initial biomass is almost totally degraded the already charred layers, forming inflammable gases, such as CO and H indicators 38 Different reactors 39 Combustion open burning 40 7