In the context of global industrialization, carbon emissions, primarily from carbon dioxide, have escalated, with industrial activities being a major contributor. As a foundational sector in traditional manufacturing, sand casting processes are significant sources of resource consumption and environmental pollution. The energy utilization rate in sand casting is notably low, and emissions of waste sand, slag, and exhaust gases are substantial, highlighting considerable potential for carbon reduction. Addressing this, I focus on developing a quantitative calculation method for carbon emissions specifically for individual sand casting parts. Traditional approaches often assess overall casting process emissions, but there is a lack of methods tailored to single castings. Therefore, in this study, I propose a hybrid model combining input-output and process analysis methods, grounded in lifecycle theory, to quantify carbon emissions throughout the sand casting process for sand casting parts. This model enables detailed分摊 of emissions to each production stage, providing a foundation for low-carbon strategies in batch production. The application of this model is demonstrated through a case study involving a wind power component, showcasing its practicality for emission reduction in sand casting parts manufacturing.
The sand casting process involves multiple stages, each contributing to carbon emissions through material consumption, energy use, and waste generation. Based on lifecycle assessment principles, I define the system boundaries for carbon emission calculation in sand casting parts production. The process is divided into four key stages: molding, melting, recycling, and finishing. Emissions are categorized into three types: material carbon emissions (indirect emissions from material consumption), energy carbon emissions (from equipment operation), and waste carbon emissions (from waste treatment). This classification allows for a comprehensive analysis of carbon sources in sand casting parts production. For instance, in molding, emissions arise from resin sand use; in melting, from molten metal ingredients; and across stages, from electricity consumption and waste handling. The goal is to allocate these emissions to individual sand casting parts, facilitating precise carbon footprint assessment for each unit produced.
To quantify carbon emissions for sand casting parts, I develop a calculation model that integrates both macroscopic and microscopic perspectives. The model uses input-output methods for fixed materials and process analysis for variable materials, ensuring accuracy and detail. The total carbon emission \( C_d \) for a sand casting part \( d \) is expressed as the sum of material emissions \( CM_d \), energy emissions \( CE_d \), and waste emissions \( CU_d \), calculated across all stages. This holistic approach captures the entire lifecycle of sand casting parts within the casting phase, enabling targeted emission reduction strategies. For example, material emissions depend on factors like sand-to-metal ratio and recycling rates, while energy emissions relate to equipment power and operating times. By incorporating these variables, the model adapts to different production scenarios for sand casting parts, from small batches to large-scale manufacturing.
In the molding stage, material carbon emissions for sand casting parts are driven by resin sand consumption. The variable emissions depend on the sand-to-metal ratio \( R^1 \) and recycling rate \( \eta \). The sand-to-metal ratio is defined as the ratio of sand weight to casting weight, influenced by sand density and mold volume. For a sand casting part \( d \) with weight \( M_d \), the variable material carbon emission \( C^1_{VR,d} \) is given by:
$$ R^1 = \frac{\rho_b V_x}{\rho_d V_d} $$
$$ C^1_{VR,d} = M_d R^1 (1 – \eta) f_b $$
where \( \rho_b \) is the density of resin sand, \( V_x \) is the mold volume, \( V_d \) is the part volume, \( \rho_d \) is the density of the casting material, and \( f_b \) is the carbon emission coefficient of resin sand. Fixed material emissions in molding, such as from coatings or binders, are allocated based on output, calculated as:
$$ C^1_{ST,d} = \sum_{c=1}^{c_0} \frac{I^1_c}{O_d} f_c $$
where \( I^1_c \) is the consumption of fixed material \( c \) over a period, \( O_d \) is the output of sand casting parts \( d \), and \( f_c \) is its emission coefficient. Thus, total material emissions in molding \( CM^1_d \) for sand casting parts are:
$$ CM^1_d = M_d R^1 (1 – \eta) f_b + \sum_{c=1}^{c_0} \frac{I^1_c}{O_d} f_c $$
This formulation highlights how sand casting parts’ emissions are affected by design parameters like weight and mold size, emphasizing the need for optimization in early production stages.
In the melting stage, material carbon emissions for sand casting parts originate from molten metal ingredients like scrap steel, pig iron, and additives. These are variable emissions, as their consumption can be directly calculated from the molten metal mass. For sand casting part \( d \), the material carbon emission \( CM^2_d \) is:
$$ CM^2_d = M_d (1 + MIR) \sum_{g=1}^{g_0} R^2_g f_g $$
where \( MIR \) is the ratio of pouring surplus to part weight, \( R^2_g \) is the proportion of ingredient \( g \) in the molten metal, and \( f_g \) is its carbon emission coefficient. This stage is critical for sand casting parts, as melting often contributes significantly to overall emissions due to high-energy inputs and material processing. Energy emissions in melting come from furnace operation and handling equipment. The energy carbon emission \( CE^2_d \) for sand casting parts is calculated as:
$$ CE^2_d = M_d (1 + MIR) E_n f_e + \sum_{m_2=1}^{m_2^0} \frac{p_{m_2} s_{m_2}}{v_{m_2} O_d} f_e $$
where \( E_n \) is the electricity consumption per ton of molten metal, \( p_{m_2} \) is the power of handling equipment, \( s_{m_2} \) is travel distance, \( v_{m_2} \) is speed, and \( f_e \) is the carbon emission coefficient of electricity. These formulas enable precise tracking of emissions for each sand casting part, aiding in process improvements.
The recycling and finishing stages also contribute to carbon emissions for sand casting parts, primarily through energy use and waste treatment. In recycling, material emissions are fixed, related to sand recovery systems, while energy emissions come from sand processing lines. For sand casting part \( d \), energy carbon emission \( CE^3_d \) in recycling is:
$$ CE^3_d = M_d R^1 E_o f_e + \sum_{m_3=1}^{m_3^0} \frac{p_{m_3} s_{m_3}}{v_{m_3} O_d} f_e $$
where \( E_o \) is the electricity consumption per ton of sand processed. In finishing, emissions arise from equipment like shot blasters, with energy carbon emission \( CE^4_d \) given by:
$$ CE^4_d = \sum_{u=1}^{u_0} p_u t_u f_e + \sum_{m_4=1}^{m_4^0} \frac{p_{m_4} s_{m_4}}{v_{m_4} O_d} f_e $$
where \( p_u \) is the power of finishing equipment, and \( t_u \) is operating time. Waste carbon emissions across stages result from treating by-products like dust and slag. For sand casting parts, waste carbon emission \( CU_d \) is expressed as:
$$ CU_d = \sum_{a=1}^{4} \left( M_d \frac{M^a_{U1} p_{w_a}}{v_{w_a}} f_e \right) + M_d \frac{M^2_{U2} p_{i_2} s_{i_2}}{M_{i_2} v_{i_2}} f_e $$
where \( M^a_{U1} \) is waste generation per ton in stage \( a \), \( p_{w_a} \) is waste treatment equipment power, \( v_{w_a} \) is treatment speed, \( M^2_{U2} \) is solid waste in melting, and \( p_{i_2} \), \( s_{i_2} \), \( M_{i_2} \), \( v_{i_2} \) relate to waste handling equipment. These components ensure a comprehensive emission profile for sand casting parts.
To summarize the model, the total carbon emission \( C_d \) for a sand casting part \( d \) is:
$$ C_d = CM_d + CE_d + CU_d $$
with detailed terms as above. This model integrates all stages, providing a scalable tool for emissions quantification in sand casting parts production. Key parameters are listed in Table 1 for clarity, aiding in practical application.
| Parameter | Description | Unit |
|---|---|---|
| \( M_d \) | Weight of sand casting part \( d \) | kg |
| \( R^1 \) | Sand-to-metal ratio | dimensionless |
| \( \eta \) | Resin sand recycling rate | % |
| \( f_b \) | Carbon emission coefficient of resin sand | kg CO₂/kg |
| \( MIR \) | Ratio of pouring surplus to part weight | dimensionless |
| \( R^2_g \) | Proportion of molten metal ingredient \( g \) | % |
| \( f_g \) | Carbon emission coefficient of ingredient \( g \) | kg CO₂/kg |
| \( f_e \) | Carbon emission coefficient of electricity | kg CO₂/kWh |
| \( E_n \) | Electricity consumption per ton of molten metal | kWh/t |
| \( E_o \) | Electricity consumption per ton of sand processed | kWh/t |
| \( p_{m_a} \) | Power of handling equipment in stage \( a \) | kW |
| \( s_{m_a} \) | Travel distance of handling equipment in stage \( a \) | m |
| \( v_{m_a} \) | Speed of handling equipment in stage \( a \) | m/min |
| \( M^a_{U1} \) | Waste generation per ton in stage \( a \) | kg/t |
Applying this model, I analyze a case study of a locking disk sand casting part used in wind power systems. The part is made of ductile iron QT500-14, with a weight of 6,932 kg. Production parameters include a sand-to-metal ratio \( R^1 = 8.25 \), recycling rate \( \eta = 93\% \), and pouring surplus ratio \( MIR = 0.1 \). The molten metal composition is detailed in Table 2, showing the mix of scrap steel, pig iron, and other materials. Carbon emission coefficients for key materials and energy are provided in Table 3, derived from literature and industry data. For sand casting parts like this, accurate coefficients are essential for reliable calculations.
| Ingredient \( g \) | Proportion \( R^2_g \) (%) |
|---|---|
| Scrap Steel | 58.19 |
| Pig Iron | 24.69 |
| Return Material | 14.26 |
| Carbon Additive | 2.20 |
| Silicon Carbide | 0.49 |
| Ferrosilicon | 0.17 |
| Material/Energy | Coefficient | Unit |
|---|---|---|
| Resin Sand | 0.02543 | kg CO₂/kg |
| Refractory Coating | 6.0232 | kg CO₂/kg |
| Methanol | 2.5 | kg CO₂/kg |
| Scrap Steel | 8.2 | kg CO₂/kg |
| Pig Iron | 2.13 | kg CO₂/kg |
| Return Material | 2.67 | kg CO₂/kg |
| Carbon Additive | 4.2 | kg CO₂/kg |
| Silicon Carbide | 14.68 | kg CO₂/kg |
| Ferrosilicon | 2.3 | kg CO₂/kg |
| Electricity | 0.93 | kg CO₂/kWh |
Using the model, I calculate the carbon emissions for this sand casting part. Material carbon emissions \( CM_d \) are computed as:
$$ CM_d = M_d R^1 (1 – \eta) f_b + \sum_{a=1}^{4} \sum_{c=1}^{c_0} \frac{I^a_c}{O_d} f_c + M_d (1 + MIR) \sum_{g=1}^{g_0} R^2_g f_g $$
Substituting values, for the locking disk sand casting part, material emissions amount to 44,791.79 kg CO₂. Energy emissions \( CE_d \) are:
$$ CE_d = \sum_{l=1}^{l_0} \frac{p_l M_d R^1}{v_l O_d} f_e + M_d (1 + MIR) E_n f_e + M_d R^1 E_o f_e + \sum_{a=1}^{4} \sum_{m_a=1}^{m_a^0} \frac{p_{m_a} s_{m_a}}{v_{m_a} O_d} f_e + \sum_{u=1}^{u_0} p_u t_u f_e $$
With equipment parameters: handling power \( p_{m_a} = 20.5 \) kW, travel distances \( s_{m_1} = 0 \) m (for molding), \( s_{m_2} = 70 \) m, \( s_{m_3} = 40 \) m, \( s_{m_4} = 110 \) m, speed \( v_{m_a} = 16 \) m/min, mixer power \( p_l = 11.5 \) kW, mixing efficiency \( v_l = 6.2855 \) kg/s, furnace energy \( E_n = 500 \) kWh/t, sand processing energy \( E_o = 0.0119 \) kWh/t, shot blaster power \( p_u = 80 \) kW, and time \( t_u = 20 \) min. This yields energy emissions of 4,234.82 kg CO₂ for the sand casting part. Waste emissions \( CU_d \) are calculated from waste generation rates: 0.586 kg/t for dust in molding, 0.500 kg/t in melting, 1.050 kg/t in recycling, 0.011 kg/t in finishing, and 0.054 kg/t for slag in melting, with treatment equipment power \( p_{w_a} = 7.5 \) kW and speed \( v_{w_a} = 14.2515 \) kg/h. Waste emissions total 14.552 kg CO₂. Thus, the total carbon emission for this sand casting part is:
$$ C_d = 44,791.79 + 4,234.82 + 14.552 = 49,041.162 \text{ kg CO}_2 $$
Results are summarized in Table 4, breaking down emissions by stage and type for the sand casting part. This detailed analysis reveals that material carbon emissions dominate, accounting for over 90% of the total, with melting stage contributions being the largest. For sand casting parts, this underscores the importance of optimizing material usage and配方 in melting to reduce emissions.
| Emission Type | Stage | Emission (kg CO₂) | Percentage (%) |
|---|---|---|---|
| Material Emissions | Molding | 101.75 | 0.21 |
| Melting | 44,963.76 | 91.68 | |
| Recycling | 0.00 | 0.00 | |
| Finishing | 0.12 | 0.00 | |
| Energy Emissions | Molding | 27.03 | 0.06 |
| Melting | 3,545.72 | 7.23 | |
| Recycling | 632.91 | 1.29 | |
| Finishing | 24.80 | 0.05 | |
| Waste Emissions | Molding | 3.97 | 0.01 |
| Melting | 10.51 | 0.02 | |
| Recycling | 0.07 | 0.00 | |
| Finishing | 0.002 | 0.00 | |
| Total | All | 49,041.16 | 100.00 |
Discussion of these results emphasizes strategies for reducing carbon emissions in sand casting parts production. For instance, lowering the sand-to-metal ratio through optimized mold design can decrease resin sand use. Improving recycling rates enhances material efficiency. In melting, adjusting the molten metal配方 to include more low-carbon materials like return material or reducing pouring surplus can significantly cut emissions for sand casting parts. Energy savings can be achieved by upgrading to efficient equipment or optimizing handling routes. Waste minimization through better process control also contributes. This model enables manufacturers of sand casting parts to simulate different scenarios, such as changing material sources or adopting renewable energy, to identify the most effective减排 measures. By integrating carbon footprint as a parameter in product design, similar to cost or weight, sand casting parts can be developed with lower environmental impact from the outset.
In conclusion, the quantitative carbon emission calculation model for sand casting parts, based on a hybrid lifecycle approach, provides a robust framework for assessing and reducing emissions in sand casting processes. By allocating emissions to individual sand casting parts, it supports precise carbon management in batch production. The case study of the locking disk sand casting part demonstrates the model’s applicability, revealing that material emissions, particularly from melting, are the primary carbon source. Future work could expand this model to include upstream and downstream lifecycle stages, such as raw material extraction and product use, for a full carbon footprint of sand casting parts. Additionally, incorporating real-time data from IoT sensors could enhance accuracy. This research contributes to the green transformation of the casting industry, offering a practical tool for achieving carbon reduction goals in the manufacturing of sand casting parts. As global emphasis on sustainability grows, such methodologies will be crucial for developing low-carbon sand casting parts and advancing circular economy principles in manufacturing.