🔧 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

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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

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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%):

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

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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

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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:

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

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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

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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)

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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.

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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

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✅ 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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Plastic to Fuel: Pyrolysis Technology – From Scientific Principles to Real-World Application

 

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.

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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.

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2. Process Flow and Technology Implementation

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

1. Feedstock Sorting and Pre-treatment

2. Shredding to Uniform Particle Size

3. Feeding into the Pyrolysis Reactor

4. Thermal Decomposition (200–900°C) in Oxygen-Free Environment

5. Condensation of Hydrocarbon Vapors into Oil

6. Separation of Byproducts (Gas and Char)

7. Oil Refining for End-Use

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📌 PFD – Plastic to Fuel Process Flow Diagram

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

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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.

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📌 Layout – Plastic to Fuel Plant Process Layout Diagram

Technical Layout of Plastic to Fuel Conversion Plant

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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

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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.

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📌 Graph – Plastic to Fuel Output Comparison

Estimated Fuel Yield Based on Different Plastic Types

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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.

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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

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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.

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⚙️ Anaerobic Biogas Plant

 

⚙️ Energy Balance and Automation System A Smart Approach to Efficiency, Monitoring, and Control

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🔋 1. Energy Balance of Anaerobic Biogas Plant

A well-engineered anaerobic biogas plant is designed to deliver a positive net energy yield by ensuring that the energy outputs significantly exceed the energy inputs. The energy balance is calculated by comparing the operational energy requirements (thermal, mechanical, and electrical) with the energy produced in the form of biogas.

🔢 Typical Energy Input (kWh/ton feedstock):

• Heating (Thermophilic range, 50–55°C): 30–60 kWh

• Agitation and Mixing: 10–15 kWh

• Pumps and Feedstock Transfer: 5–10 kWh

• Gas Compression (for CBG): 20–50 kWh

• Biogas Purification: 15–30 kWh

⚡ Energy Output (kWh/ton feedstock):

• Biogas Production: 180–250 Nm³/ton

• Methane Content (CH₄): ~55–65%

• Usable Energy (Electrical + Thermal): 500–650 kWh/ton

📘 Net Energy Gain: ~400–500 kWh/ton feedstock, depending on substrate quality, system insulation, and digester efficiency.

🔄 Energy Recovery Techniques:

• Combined Heat and Power (CHP) Units: Convert biogas into electricity while recovering heat for digester heating.

• Heat Integration Systems: Recover heat from CHP flue gases and engine jackets.

• Feedstock Pre-heaters: Utilize solar thermal or exhaust heat to pre-condition the input substrate, reducing load on primary heating systems.

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🖥️ 2. Automation System: SCADA and PLC Integration

Automation is an integral component for modern anaerobic digestion systems, enabling precise process control, enhanced safety, real-time monitoring, and optimized biogas yields.

🧠 Key Features of the Automation System:

• PLC (Programmable Logic Controller)

  • Local control of field devices

  • Logic-based control of pumps, agitators, heating systems, gas valves

  • Alarms and interlocks

• SCADA (Supervisory Control and Data Acquisition)

  • Graphical user interface (GUI) with real-time data

  • Control of process parameters from central or remote terminals

  • Event and trend logging with historical data storage

  • Secure remote access for monitoring and troubleshooting

📶 Communication Protocols:

• Modbus TCP/IP, Profibus for device-level communication

• Ethernet/IP for enterprise and cloud integration

• GSM or VPN modules for remote access

📍 Typical Control Points Monitored via SCADA:

• pH levels in digester (optimal range: 6.8–7.5)

• Temperature in primary digester (mesophilic or thermophilic)

• Biogas flowrate and composition (CH₄, H₂S, CO₂)

• Substrate input quantity and mixing ratios

• Agitator status and retention time tracking

• Digestate level and backpressure data

• H₂S scrubber and filter differential pressure

💻 Automation Benefits:

• Minimizes manual intervention and operator errors

• Increases process stability and overall biogas yield

• Real-time alerts reduce downtime and improve safety

• Historical data supports predictive maintenance

• Enables performance reporting for ESG and carbon credit validation

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📐 Recommended Automation and Instrumentation Standards:

• ISA-88 / ISA-95: For batch process automation and integration

• IEC 61131-3: Programming standards for PLCs

• IEC 61511: Functional safety for industrial process systems

• OPC UA: For seamless interoperability across automation systems

✅ Conclusion: A well-automated anaerobic biogas plant, designed with robust energy integration, offers superior operational efficiency, reduced OPEX, higher uptime, and compliance with modern energy and safety regulations. This smart design approach not only enhances ROI but also positions the plant for eligibility in green energy incentives and carbon market programs.

🔧 Sample of Technical Engineering Document: Anaerobic Biogas Plant – Capacity 10 Tons/Day

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📈 1. Process Flow Diagram (PFD) – Conceptual Description

A 10-ton/day anaerobic biogas plant typically processes organic feedstock (e.g., livestock manure, food/agro waste) via the following stages:

Feedstock Pre-treatment ➝ Anaerobic Digestion ➝ Biogas Collection ➝ Gas Upgrading ➝ Biogas Storage ➝ Utilization (CBG/CHP) ➝ Digestate Processing ➝ Treated Water Reuse

Main Process Units:

1. Feedstock Reception Hopper & Pre-mixing Tank
2. Primary Digester Tank (CSTR, mesophilic @ 35–40°C)
3. Gas Dome & Pressure Equalization System
4. H₂S Scrubber ➝ Moisture Trap ➝ Activated Carbon Filter
5. PSA Unit for CO₂ Separation ➝ CBG Compressor
6. Cascade Gas Cylinder Storage
7. CHP Unit or Gas Bottling Station
8. Solid-Liquid Separator for Digestate
9. Sludge Dryer ➝ Pelletizer ➝ Organic Fertilizer Storage
10. WWTP (SBR type) for effluent

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🛠️ 2. Piping & Instrumentation Diagram (P&ID) – Main Loops Description

A simplified representation of key control loops and piping structure:

• FT-101: Feedstock Flow Meter
• P-102: Feed Pump to Digester
• TIC-103: Digester Temperature Control via Jacket Heating System
• LIT-104: Digester Liquid Level Transmitter
• PIT-105: Gas Dome Pressure Indicator
• GCV-106: Gas Control Valve to Scrubber
• AIC-107: H₂S Analyzer Controller
• P-108: Booster Blower to PSA System
• FIC-109: Flow Controller to Storage Cylinders
• LIT-110: Sludge Tank Level Transmitter
• MCC Panel: Connected to SCADA with all sensor inputs

Instrumentation legend available upon request.

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📋 3. Instrumentation I/O List – Main Field Devices

Tag No.	Device Description	Type	Signal	Location
FT-101	Feedstock Flow Transmitter	AI	4–20 mA	Feed Hopper Line
TIC-103	Temperature Indicator/Controller	AI/AO	4–20 mA	Digester Heating
LIT-104	Level Indicator Transmitter	AI	4–20 mA	Digester Tank
PIT-105	Pressure Indicator Transmitter	AI	4–20 mA	Gas Dome
AIC-107	Gas Composition Analyzer (H₂S, CH₄, CO₂)	AI	RS-485	Gas Line
FIC-109	Flow Indicator Controller	AI/AO	4–20 mA	PSA Outlet
ESD-111	Emergency Shutdown Switch	DI	Dry	MCC Room
V-112	Motorized Valve	DO	Relay	Gas Header
AL-113	Gas Leak Detector	AI/DI	4–20 mA	CBG Zone

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🧠 4. Control Philosophy

The automation strategy is built upon a dual-tier structure: field-level PLC control and supervisory SCADA system.

A. PLC Logic & Control Loops:

• Controls all pumps, agitators, temperature regulation via analog/digital I/O
• Logic-based interlocks:
• High-High Pressure → PRV Open + Shutdown Biogas Line
• High Temp → Cut Heater + Activate Alarm
• Gas Leak Detected → Shutdown Blower + Close Main Valve

B. SCADA Functions:

• Graphical Interface: Real-time display of all process variables
• Trending: Biogas output, pH, H₂S concentration, energy consumption
• Alarms & Events: Set for all high/low limits and trip conditions
• Reports: Daily gas yield, energy balance, feedstock stats
• Remote Access: Optional via VPN module

C. Communication Network:

• All devices use Modbus RTU/TCP, Ethernet/IP, integrated through industrial switch to SCADA server
• Local HMI panel also installed near MCC for onsite operations

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📊 5. Energy Balance – Based on 10 Tons/day

Assumptions:

• Feedstock: Cattle manure + food waste
• Organic Loading Rate: ~2.5 kg VS/m³/day
• Biogas Yield: ~200 Nm³/ton
• Methane Content: 60%

Category	Value
Total Biogas/day	2,000 Nm³
Usable Energy	~1,200 kWh/day
Electricity Used	~150 kWh/day
Heat Used	~200 kWh/day
Net Energy Gain	~850 kWh/day

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