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Detailed Design Calculations: Plastic to Fuel Pyrolysis Plant (10 TPD)

1. Input Data and Assumptions

Parameter	Value	Unit
Plant capacity	10,000	kg/day
Operation time	20	hours/day
Bulk density of plastic flakes	0.25	kg/L
Plastic to oil yield (avg.)	70	%
Heating value of feedstock	35	MJ/kg
Specific heat of plastic	2.0	kJ/kg·K
Target pyrolysis temp.	450	°C
Ambient temp.	30	°C

2. Material Balance

Daily Feedstock:

10,000 kg plastic/day

Estimated Product Yields:

Oil: 70% → 7,000 kg/day
Gas: 20% → 2,000 kg/day
Char: 10% → 1,000 kg/day

3. Energy Requirement for Pyrolysis

Heating Load (Q):

Q = m \cdot c \cdot \Delta T

$m = 10,000$ kg/day
$c = 2.0$ kJ/kg·K
$\Delta T = 450 - 30 = 420$ °C

Q = 10,000 \cdot 2.0 \cdot 420 = 8,400,000 \text{ kJ/day}

Convert to kWh:

8,400,000 \div 3600 = 2,333 \text{ kWh/day}

Add heat losses (assume 25%):

Q_{\text{total}} = 2,333 \cdot 1.25 = 2,916 \text{ kWh/day}

4. Reactor Sizing

Assume 4 hours residence time and 250 kg/h feeding rate

\text{Volume} = \frac{\text{Mass}}{\text{Density}} = \frac{1,000}{250} = 4.0 \text{ m}^3

Assuming horizontal cylindrical reactor:

\text{Volume} = \pi \cdot \frac{D^2}{4} \cdot L

Assume L = 4 m:

4 = \pi \cdot \frac{D^2}{4} \cdot 4 \Rightarrow D = 1.13 \text{ m}

=> Reactor Size: 4 m length x 1.13 m diameter

5. Condenser Sizing

Condense 7,000 kg/day of vapor to liquid

Vapor flow rate: 350 kg/h
Latent heat of condensation: 300 kJ/kg
Cooling water ΔT: 10°C

Q = m \cdot L = 350 \cdot 300 = 105,000 \text{ kJ/h}

Cooling water flow rate:

Q = m \cdot c \cdot \Delta T \Rightarrow m = \frac{105,000}{4.18 \cdot 10} = 2,510 \text{ kg/h} \approx 2.5 \text{ m}^3/h

6. Gas Scrubber and Flare Sizing

Combustible Gas: 2,000 kg/day (~100 kg/h)

Assume methane equivalent:

\text{Energy value} = 50 MJ/kg \Rightarrow 5,000 MJ/day = 1,389 kWh/day

Flare size estimation:

Assume 10 kg/h continuous flaring

Use flame diameter ≈ 0.3–0.5 m with vertical pipe height ≈ 3 m

7. Fuel Oil Storage

Yield = 7,000 kg/day, assume density = 0.85 kg/L

\text{Volume} = \frac{7000}{0.85} = 8,235 \text{ L/day}

For 3 days buffer:
Storage Tank = 25,000 L (use 30,000 L for contingency)

8. Char and Ash Handling

Char output = 1,000 kg/day
Assume stored in 1-ton jumbo bags or silos

Silo size (1.2 bulk density):

\text{Volume} = \frac{1,000}{1.2} = 0.83 \text{ m}^3/day

Use 3–5 m³ silo for buffer capacity.

9. Electrical Power Consumption (Estimation)

Equipment	Power (kW)	Duration (hr)	Energy (kWh)
Reactor Heater	100	20	2,000
Condenser Pumps	5	20	100
Feed System	2	20	40
Scrubber/Fan	3	20	60
Automation + Lighting	5	24	120
Total Daily			2,320 kWh

✅ Summary Table

Item	Design Value
Reactor Volume	4 m³
Reactor Dimensions	Ø1.13 m × 4 m
Energy Required	2,916 kWh/day
Condenser Water Flow	2.5 m³/h
Daily Oil Output	7,000 kg
Storage Tank Size	30 m³
Total Electric Consumption	~2,320 kWh/day

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The growing menace of plastic waste pollution has driven a wave of innovation in sustainable recycling technologies. Among the most promising methods is Plastic Pyrolysis—a thermochemical process that transforms plastic waste into fuel. This article discusses the fundamental science, engineering design, system components, safety measures, input-output balance, and environmental implications of plastic-to-fuel technology using pyrolysis.

1. Basic Scientific Principles of Pyrolysis

Pyrolysis is governed by principles of thermodynamics and chemical kinetics. It is the thermal decomposition of organic material in the absence of oxygen, preventing combustion and promoting molecular breakdown.

Key principles involved include:

First Law of Thermodynamics: Energy conservation during heat input and chemical transformation.
Second Law of Thermodynamics: Entropy increases as complex polymers are broken into smaller molecules.
Chemical Kinetics: Reaction rates depend on temperature, catalyst, and molecular structure.
Le Chatelier’s Principle: Used in catalytic pyrolysis to steer reactions toward desirable outputs (e.g., fuel oil).

Common plastic types such as polyethylene (PE), polypropylene (PP), and polystyrene (PS) are thermally cracked into smaller hydrocarbon chains that can be condensed into oil.

2. Process Flow and Technology Implementation

The plastic-to-fuel process consists of the following stages:

Feedstock Sorting and Pre-treatment
Shredding to Uniform Particle Size
Feeding into the Pyrolysis Reactor
Thermal Decomposition (200–900°C) in Oxygen-Free Environment
Condensation of Hydrocarbon Vapors into Oil
Separation of Byproducts (Gas and Char)
Oil Refining for End-Use

📌 PFD – Plastic to Fuel Process Flow Diagram

Process Flow Diagram (PFD) of the Plastic to Fuel Pyrolysis Plant

3. Key Components and Auxiliary Systems

Feed Hopper: Receives pretreated plastic waste.
Pyrolysis Reactor: Sealed chamber (SS316 or Inconel) that provides uniform heating.
Heating System: Electrical or gas-fired units for controlled temperature rise.
Catalyst Unit: Zeolite or silica-alumina to enhance cracking efficiency.
Condensers and Fractionation Units: Stainless steel heat exchangers for condensing vapors.
Gas Scrubbers and Flare Stack: For safe exhaust gas handling.
Char Collection System: For solid residue disposal or reuse.
PLC/SCADA Control Panel: For automation and safety interlock systems.

📌 Layout – Plastic to Fuel Plant Process Layout Diagram

Technical Layout of Plastic to Fuel Conversion Plant

4. Construction Materials and Standards

Reactor and Condenser: SS304, SS316, Inconel, or Hastelloy for high-temperature resistance.
Piping and Seals: PTFE or Viton-based materials.
Refractory Lining: Ceramic fiber or alumina bricks.
Safety Standards:
- ASME Section VIII – Pressure vessel standards
- API 650 – Tank fabrication standards
- ISO 14001 – Environmental compliance
- OSHA 1910 – Worker safety

5. Input Materials and Output Products

Acceptable Plastic Waste Feedstocks:

Polyethylene (PE)
Polypropylene (PP)
Polystyrene (PS)

Outputs:

Liquid Oil (TPO): Used as fuel for generators, engines, or refined into diesel.
Syngas: Recycled as heating fuel within the plant.
Char: Used in construction or pigment manufacturing.

Byproducts Applications:

Light oil: Fuel additive.
Heavy oil: Industrial heating.
Carbon black: Reinforcement filler.
Gas: Used for energy recovery within the process loop.

📌 Graph – Plastic to Fuel Output Comparison

Estimated Fuel Yield Based on Different Plastic Types

6. Environmental Impact and Mitigation

Risks:

VOC emissions
Chlorine release (if PVC is processed)
Explosion risk from syngas
Water or soil contamination

Mitigation Measures:

Oxygen sensors to ensure oxygen-free operation.
Scrubbers to capture dioxins and HCl.
Flare system for excess gas burning.
Regular PPE usage and personnel training.
Emergency shutdown systems (ESD).

Environmental Benefits:

Reduces landfill plastic burden.
Prevents ocean plastic accumulation.
Provides circular economy fuel.
Lowers dependence on fossil fuel refining.

7. International Standards and Compliance

The system should comply with:

EPA guidelines – Emission and fuel quality
ISO 45001 – Occupational safety
REACH / RoHS – Chemical content standards
Basel Convention – Waste material handling and export

8. Conclusion

Plastic pyrolysis presents a scalable and circular solution to the global plastic waste crisis. The conversion of non-recyclable plastics into usable fuel not only reduces environmental impact but also offers significant energy recovery. With proper engineering design, process control, and environmental safeguards, this technology can be safely integrated into modern waste management and renewable energy infrastructures.