关键词: 煤制尿素, 流程模拟, 新能源, 能量, 经济, 环境

Abstract:

This study focuses on a commercial-scale, one-million-ton-per-year coal-based urea production process. By integrating process-wide simulation, techno-economic analysis, and life cycle assessment (LCA) methods, the energy efficiency, economic performance, and environmental impact of the system were systematically evaluated. The results indicate that the coal-based urea process has a substantial heat demand; through process heat integration, the internal heating requirements of cold process streams can be fully met. A total of 271 MW of waste heat was recovered across the system, completely satisfying the heating demand of cold streams and increasing the overall energy utilization efficiency from 44.7 % to 52.9 %. Nevertheless, the gasifier still requires 1340 MW of external high-temperature heat input. The techno-economic analysis shows that the investment in coal gasification and the cost of utilities are the dominant contributors to total capital and operating expenses, each accounting for more than 60 %. The prices of coal feedstock and the investment cost of the air separation unit were identified as the key factors influencing the production cost of coal-based urea. The life cycle assessment results further reveal that the global warming potentials (GWP) of coal-derived hydrogen, ammonia, and urea are 21.77 t CO₂-eq/t H₂, 4.725 t CO₂-eq/t NH₃, and 2.374 t CO₂-eq/t urea, respectively. Carbon emissions associated with the coal feedstock contribute 53.2 % of the total, followed by indirect emissions from heat and power generation, suggesting that raw material substitution and the integration of green electricity and green heat are essential for emission reduction. Furthermore, considering the substitution of green electricity, green hydrogen, and green heat, the study explored the techno-economic and environmental advantages of green-hydrogen-based urea synthesis compared with the conventional coal-based route. The results show that the total capital investment of the green hydrogen process is 1.81 times that of the coal-based process, with electrolyzer costs accounting for 72.73 %. The production costs of urea using grid electricity, renewable electricity, and renewable cogeneration are 1.61, 1.22, and 1.35 times those of the conventional process, respectively. Finally, the evolution of production cost was analyzed under varying electrolyzer investment and green electricity price conditions, providing threshold criteria for economically viable substitution of the coal-based route. In terms of carbon emissions, the global warming potentials of three decarbonization scenarios - (i) electricity substitution only, (ii) coal feedstock replacement with green electricity, and (iii) combined utilization of green electricity and green heat, are 2.29 t CO₂-eq/t urea, 0.61 t CO₂-eq/t urea, and 0.29 t CO₂-eq/t urea, respectively. This work not only provides a quantitative analytical framework for the low-carbon transition and sustainable development of coal-based urea and related coal chemical industries but also offers practical guidance for cost reduction, energy efficiency improvement, and emission mitigation strategies in industrial applications.

Key words: coal-to-urea, process simulation, renewable energy, energy, economics, environment