Closing the active carbon cycleREGENERATION OF SPENT ACTIVATED CARBON FOR RESOURCE OPTIMISATION

Jumoke Oladejo

PhD, MSc, BEng

New Materials Institute4th June 2018

Outline

Overview

Methodology

Results

Conclusion

Activated Carbon and Use

What is Activated Carbon

Bituminous coal

Lignite

Wood residues

Coconut shell

Physical or Chemical

activation

Granular activated carbon

Powder activated carbon- Carbonization (pyrolysis at 600 – 900°C)

- Oxidation (oxidized at 600 – 1200°C)

- Chemical activation (acid , base or salt, then carbonized at 450

– 900°C)

Use of Activated Carbon

The wide and diverse application of activated carbon in all aspects of industrial

and agricultural production would consequentially lead to increase in its demand

Use of Activated Carbon

The wide and diverse application of activated carbon in all aspects of industrial

and agricultural production would consequentially lead to increase in its demand

Doubt me?

Imagine everyone

decides to add active

carbon to their shelves

for these……

Why Regenerate Activated Carbon

- China, U.S and western Europe make up >50% of annual demand

- Water and air treatment are currently the largest market users

- Market forecasted to rise by ~300% by 2024 (grand view research)

- Major increase in water and waste water applications

Why Regenerate Activated Carbon

So... What happens to “spent“ activated carbon afterwards?

Incineration

Industrial Landfill(non-hazardous) Reactivation

Need for cost-effective

and quality restoring approach

- Growing waste management issues

- Hindering policies and regulations for carbon disposals

- Increasing price of activated carbon

- Pollutants considerations

Common Methods of Regeneration

Other methods....

- Electrochemical Regeneration

- Microwave Regeneration

First principle of circular economy:

“Waste is food” … or money

“no waste and pollution”

Microwave heating versus Conventional heating

Microwave Technology

Conventional

Heat transfer from surface

to center by convection,

conduction and radiation

Microwave

Transfer of electromagnetic

energy to thermal energy.

-Microwaves penetrate

materials, deposit energy

and heat is generated

throughout the volume

Microwave Technology Benefits

- Rapid heating

- Selective heating

- Enhanced chemical reactivity

- Energy Efficient

- Portability of system

- Ease of control

- Flexibility of process

Reactivation of ‘spent activated carbon’

Carbon from

Methodology

Regeneration Process

Material

Spent activated carbon from

Sewage treatment facility

Drying at 105°C

for 12 hours

Microwave and Conventional

Reactor

Powdered size <150µm

Schematic diagram of regeneration process

Methodology

- Gas flow (200ml/min)

- K-type thermocouple with Nb alloy tube

- Iodine sorption value(mg/g) –

GB/T 12496.8 (measure of microporosity)

- Methylene cyanine adsorption value(mg/g) –

GB/T 12496.10 (measure of mesoporosity )

Results

- Coconut activated carbon has Iodine value (900- 1250 mg/g) and Methylene value (135 – 210 mg/g)

- Iodine Value (IV) of spent AC was 70.9% of the lower limit

- Methylene Value (MV) of spent AC was 37.5% of the lower limit

- Negligible difference in IV and MV after drying (<2% reduction)

Activity Parameters of Activated Carbon

Regeneration of Activated Carbon at 500°C

- IV(0.01 – 1.9%) and MV (68.8 – 78.2%) increase in conventional reactor

- IV(3.2 – 8.3%) and MV (87.4 – 100.5%) increase in microwave assisted reactor

- Higher improvement in CO₂ atmosphere at 2 hours reaction time

Regeneration of Activated Carbon at 600°C

- IV(0.5 – 1.8%) and MV (99 – 119%) increase in conventional reactor

- IV(7.3 – 17.1%) and MV (97– 141%) increase in microwave assisted reactor

- Higher improvement in CO₂ atmosphere at 2 hours reaction time

Microwave Assisted Regeneration of Activated Carbon at 600 and 700°C

- IV(11.4 – 17.1%) and MV (124 – 145%) increase at 600°C

- IV(9.8 – 15.5%) and MV (101.5 – 116%) increase at 700°C

- Optimal improvement in both parameters was at 600°C (IV at 2hr/5hrs and MV at 3hrs)

- Best operating condition = 600°C at 2hrs (83% IV and 90.37% MV of Reference AC)

Concluding Remarks

Concluding Remarks

• MAP is an attractive technology for activated carbon regeneration applications at

lower temperature.

• Higher Iodine and Methylene Value from microwave compared with conventional

systems

• Optimal activity obtained at 600°C after 2 hours or 5hrs

• Scalability potential for in-house regeneration at various usage facilities

Merci

Thank you

Xie Xie

Gracias

Danke sha

Questions???

Proximate Analysis

- Reduction in moisture and volatile content with increase in regeneration time and temperature- Increase in Fixed carbon content with regeneration time