Solid Waste- Thermal Conversion

thermal conversion

using heat to quickly turn waste into fuels, byproducts, and/or power

benefits of thermal conversion

reduces waste volume in landfills, useful products (oil, charcoal, gas, heat) are generated, energy can be generated

hydrothermal carbonization

low temperature, uses organic materials and wet wastes to produce char and gas

pyrolysis

medium temperature required, uses organics and dry wastes (NOT inert materials) to produce char, tars/oils, and gas

gasification

medium-high temperature required, uses organics and dry wastes (NOT inert materials) to produce gas

waste to energy

high temperature required, uses combustible materials and dry waste to produce heat and results in energy recovery

proximate analysis

determines key components of waste by measuring moisture, volatility, fixed carbon, and ash

ultimate analysis

lab technique to determine composition of C, H, N, O, S, moisture, and ash in waste (shows if waste is suitable to become fuel and can predict emissions)

how is energy content found?

using a calorimeter and performing calculations based on proximate or ultimate analysis

higher heating value*

the most energy you need to break everything down (includes energy to burn off water)

lower heating value*

value of just material (don’t need to vaporize water)

why do people prefer dry waste to wet waste?

the wet waste takes extra energy to burn the water off

how does waste to energy occur?

3 T’s, time, temperature, and turbulence

air pollution control methods

dust removal, acid gas neutralization, low volatility organic compounds, nitrogen oxides

energy recovery uses

hot water for heating, process steam, and electricity or heat & power

waste to energy types of facilities

mass burn

refuse derived fuel (more homogenous)

waste to energy technologies

moving grate (moving floor)

rotary kiln (rotating)

fluidized bed (more mixing and air movement)

waste to energy pre-treatment methods

removing bulky items (large furniature/mattresses)

mixing low and high heating value waste

shredding

screening

getting rid of metallic iron (won’t burn or give off energy)

waste to energy advantages

1. volume and weight reduction

2. immediate waste reduction (doesn’t need to stay a long time)

3. CAN control air discharges

4. ash residue usually sterile, non-putrescible, and inert

5. cost can be offset by heat recovery or sale of energy

waste to energy disadvantages

1. high capital cost

2. operators need to be more skilled

3. some materials won’t combust

4. might need supplemental fuel

5. high costs for pollution control and gas cleanup

6. public disapproval