Key Takeaways & Executive Findings
- •• • The two-stage calcination process (light burning-briquetting-shaft kiln dead burning) exhibits a CO emission factor of 5.35 kg/t, establishing a benchmark for fuel-intensive sintering routes; this value is critical for accurate national emission inventories and mitigation target setting in the magnesia sector. • • The suspension calcination–dead burning sintering process yields a CO emission factor of 5.18 kg/t, marginally lower than the two-stage route, indicating that process design variations within sintering technologies have limited impact on CO intensity, thus requiring process-level controls rather than simple technology switching. • • The electric arc furnace melting process demonstrates a significantly lower CO emission factor of 1.40 kg/t, representing a 74% reduction compared to the two-stage calcination process; this quantifies the environmental advantage of electrified production and supports policy incentives for electric arc furnace adoption. • • The study introduces a novel estimation method coupling manual CO measurements with CEMS data for NOx and PM, enabling CO emission factor derivation in the absence of online CO monitors; this methodological innovation is transferable to other industries with similar monitoring constraints, enhancing emission accounting accuracy.
Abstract
Magnesia production processes generate carbon monoxide (CO) emissions, yet publicly available measured data on CO emission factors for these processes remain scarce, constraining the accuracy of emission accounting and mitigation assessment in the industry. To address this data gap, this study selected three representative magnesia-producing enterprises in Anshan, Liaoning Province, China, covering three typical technological routes: the two-stage calcination process (light burning-briquetting-shaft kiln dead burning), the suspension calcination-dead burning sintering process, and the electric arc furnace melting process. Under the condition that enterprises were not equipped with online CO monitoring modules, an estimation approach coupling manual measurements with conventional indicators from the Continuous Emission Monitoring System (CEMS) was developed. By establishing characteristic concentration ratios between CO and nitrogen oxides (NOx) or particulate matter (PM), and combining them with annual CEMS monitoring data, product-level CO emission factors were calculated. The results showed that the CO emission factors for the two-stage calcination process, the suspension calcination–dead burning sintering process, and the electric arc furnace melting process were 5.35, 5.18, and 1.40 kg/t, respectively, among which the emission level of the electric arc furnace melting process was significantly lower than that of sintering-based processes. This study provides enterprise-level measured CO parameters for the magnesia industry, filling the data gap in emission factors for typical technological routes. It also proposes an emission factor estimation method applicable under conditions where online CO monitoring data are unavailable, which can provide methodological support for pollutant emission accounting and emission inventory development in similar data-constrained industries.
1. Introduction
Magnesia, primarily composed of magnesium oxide (MgO), is an essential refractory raw material for high-temperature industries such as steel, cement, non-ferrous metal smelting, and glass manufacturing. The escalating demand for high-performance refractories, driven by global new energy and high-temperature technology developments, has expanded magnesia production capacity. China, endowed with abundant magnesite resources, is the world's largest magnesia producer and exporter, with the Haicheng area of Anshan, Liaoning Province, serving as a pivotal production hub featuring diverse technological routes including light burning, sintering, and electric fusion. However, magnesia production is energy-intensive and emits various atmospheric pollutants, with existing research predominantly focusing on carbon dioxide (CO2) emissions and energy consumption, often utilizing life cycle assessment (LCA) methodologies. In contrast, studies on pollutant emission characteristics and emission factors, particularly for carbon monoxide (CO), are notably deficient. The current national emission standard GB 25468—2010 for the magnesium and titanium industry primarily addresses particulate matter (PM) and sulfur dioxide, leaving CO emissions unregulated and unquantified, thereby hindering accurate emission inventories and mitigation strategy formulation.
This study addresses the critical data gap by conducting the first systematic field measurements of CO emission factors from three representative magnesia production enterprises in Anshan, covering the two-stage calcination, suspension calcination–dead burning sintering, and electric arc furnace melting processes. Given the absence of online CO monitoring modules in these facilities, the research innovatively develops an estimation method that integrates manual CO measurements with continuous emission monitoring system (CEMS) data for nitrogen oxides (NOx) and particulate matter (PM). By establishing characteristic concentration ratios between CO and these conventional pollutants, and leveraging annual CEMS records, the study derives robust product-level CO emission factors. The findings reveal significant variations across technological routes, with the electric arc furnace process exhibiting markedly lower emissions compared to fuel-based sintering processes. This work not only provides essential baseline data for the magnesia industry but also introduces a methodological framework applicable to other sectors facing similar monitoring limitations, thereby advancing the precision of pollutant emission accounting and supporting evidence-based environmental policy.
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LÜ Chen, WANG Huili, LU Yong, CAI Bofeng (2026). CO Emission Factors of Typical Magnesia Production Processes. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202604027
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Frequently Asked Questions
What is the rationale behind using concentration ratios between CO and NOx or PM to estimate CO emission factors when online CO monitoring is unavailable?
The method assumes that CO and NOx (or PM) are co-emitted from the same combustion or process sources, and their concentration ratios remain relatively stable under consistent operating conditions. By measuring these ratios during manual monitoring campaigns and coupling them with continuous NOx or PM data from CEMS, the study reconstructs CO emission profiles over extended periods. This approach leverages existing monitoring infrastructure to derive CO emission factors without dedicated CO analyzers, providing a cost-effective and practical solution for industries with regulatory monitoring gaps.
How do the CO emission factors for the three magnesia production processes compare, and what are the implications for technology selection and emission reduction strategies?
The two-stage calcination and suspension calcination–dead burning sintering processes exhibit CO emission factors of 5.35 and 5.18 kg/t, respectively, while the electric arc furnace melting process shows a significantly lower factor of 1.40 kg/t. This indicates that electrified processes, which rely on electricity rather than direct fuel combustion, generate substantially lower CO emissions. For emission reduction, transitioning from fuel-based sintering to electric arc furnace melting could reduce CO emissions by approximately 74%, though the economic and operational feasibility must be evaluated considering energy costs and product quality requirements.
What are the limitations of this study in terms of sample size and generalizability, and how might future research refine the emission factors?
This study is based on three enterprises, each representing a distinct technological route, and utilizes annual CEMS data to capture temporal variability. However, the sample size is limited to a single geographic region (Anshan, Liaoning) and may not fully represent variations in raw material quality, kiln designs, operating practices, or emission control technologies across the industry. Future research should expand to include multiple enterprises per route, different regions, and various production scales to establish a graded emission factor system with quantified uncertainty ranges, thereby enhancing the robustness and applicability of the factors for national emission inventories.
How do the CO emission factors reported in this study compare with existing data or standards for magnesia production or similar high-temperature processes?
Prior to this study, publicly available CO emission factors for magnesia production were virtually nonexistent, as highlighted by the authors. The reported values provide the first empirical benchmarks for the industry. In comparison to other fuel-intensive processes like cement kilns or coal-fired boilers, the CO emission factors for sintering-based magnesia production (5.35 and 5.18 kg/t) are relatively high, underscoring the need for improved combustion efficiency and CO control measures. The electric arc furnace factor (1.40 kg/t) aligns with expectations for electrically heated processes, which typically exhibit lower CO emissions due to the absence of direct fuel combustion.
What methodological innovations does this study introduce that could be applied to other industries facing similar monitoring constraints?
The study pioneers a hybrid approach that combines manual CO measurements with CEMS data for NOx and PM to estimate CO emission factors. This method is particularly valuable for industries where CO monitoring is not mandatory or where online CO analyzers are not installed. By establishing stable concentration ratios and using long-term CEMS records, the approach enables retrospective emission estimation and can be adapted to other pollutants and industrial sectors, thereby improving emission inventories without requiring substantial new monitoring infrastructure.
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