Quantitative Carbon Emission Calculation and Application in Sand Casting Processes

With increasing industrialization, global CO₂ emissions reached 36.7 billion tons in 2022, where manufacturing sectors like sand casting contribute significantly. This study proposes a hybrid carbon emission quantification model for individual sand-cast components, combining input-output (IO) and process analysis (PA) methodologies under life cycle assessment (LCA) principles. We establish a systematic framework to allocate emissions across material consumption, energy usage, and waste treatment phases while validating the model through a wind turbine locking disk case study.

Sand casting process overview

1. Carbon Emission Sources in Sand Casting

Sand casting emissions originate from three subsystems:

  1. Material-related emissions: Resin sand, metal alloys, coatings
  2. Energy consumption: Melting, molding, transportation
  3. Waste treatment: Dust collection, slag disposal

The process boundary spans four stages:

$$ \text{Total Emissions } C_d = C_{M,d} + C_{E,d} + C_{U,d} $$

Where \( C_{M,d} \), \( C_{E,d} \), and \( C_{U,d} \) represent material, energy, and waste emissions for casting \( d \).

2. Mathematical Modeling

2.1 Material Emission Calculation

Resin sand consumption dominates molding-stage emissions:

$$ C_{VR,d}^1 = M_d R^1 (1-\eta) f_b $$

Parameter Description Unit
\( M_d \) Casting weight kg
\( R^1 \) Sand-metal ratio
\( \eta \) Sand recycling rate %
\( f_b \) Resin sand emission factor kgCO₂/kg

2.2 Energy Emission Model

Melting furnace electricity constitutes 60-75% of energy emissions:

$$ C_{E,d}^2 = M_d(1+MIR)E_n f_e + \sum_{m=1}^{m_0} \frac{p_m s_m}{v_m M_d} f_e $$

Equipment Power (kW) Efficiency
Induction furnace 500-800 85-92%
Sand mixer 10-15 6.3 kg/s
Crane 20-25 16 m/min

3. Case Study: Wind Turbine Locking Disk

A 6,932 kg QT500-14 ductile iron locking disk was analyzed with the following parameters:

$$ R^1 = \frac{\rho_b V_x}{\rho_m V_d} = \frac{1.48 \times 19.8}{7.08 \times 0.98} = 8.25 $$

Material Ratio (%) Emission Factor
Steel scrap 58.19 8.2 kgCO₂/kg
Pig iron 24.69 2.13 kgCO₂/kg
Carburizer 2.20 4.2 kgCO₂/kg

Emission distribution results:

Category Emission (kgCO₂) Percentage
Material 44,791.79 91.3%
Energy 4,234.82 8.6%
Waste 14.55 0.1%

4. Emission Reduction Strategies

Key measures for sand casting decarbonization:

  • Optimize sand-metal ratio through mold design
  • Increase recycled metal content (>70%)
  • Adopt high-efficiency melting technologies

$$ \Delta C = M_d \left[ \Delta R^1(1-\eta)f_b + \Delta R_g^2 f_g \right] $$

Where \( \Delta R^1 \) and \( \Delta R_g^2 \) represent optimized process parameters.

5. Conclusion

This study establishes a practical carbon accounting framework for sand casting processes, enabling emission source identification and process optimization. The hybrid IO-PA model provides granular insights while maintaining computational efficiency, serving as a foundation for low-carbon foundry operations.

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