In recent years, as the copper smelting industry's requirements for energy conservation, environmental protection, and stable oxygen supply continue to rise, traditional air separation processes have gradually demonstrated problems with high energy consumption, insufficient production capacity, and high maintenance costs. To address these challenges, Yantai Guorun Copper Co., Ltd. has introduced a dual-downstream oxygen-enriched cryogenic air separation process in its copper smelting process. After years of operational verification, the process has demonstrated excellent results.
Previously, the company employed a "side-blown furnace smelting + side-blown blowing" process, with a blister copper production capacity of approximately 60,000 tons/year and an associated sulfuric acid production capacity of approximately 200,000 tons/year. This level was lower than the industry entry requirement of 100,000 tons/year, and the overall energy consumption was relatively high. To address capacity and energy efficiency challenges, the company collaborated with China ENFI Engineering Technology Co., Ltd. to develop a three-furnace production process combining "oxygen-enriched side-blowing smelting + multi-lance top-blowing continuous blowing + pyrometallurgical anode refining." This process was accompanied by an advanced oxygen production system. The oxygen purity requirement was primarily 85%, while a limited supply of high-purity oxygen and nitrogen was also required.
After equipment research and demonstration, the company selected the Fusda KDON-18800 air separation unit in 2016, which began operation in 2017. This system utilizes a dual-downstream process with one downstream tower and one auxiliary tower, consistently producing 85% pure oxygen. A supplementary pure oxygen tower can be used to meet 99.6% high-purity oxygen requirements.
Oxygen-enriched cryogenic air separation offers significant advantages over conventional air separation processes. Conventional cryogenic air separation (CASA) consumes a high amount of energy when producing high-purity oxygen, typically consuming 0.42-0.45 kWh/Nm³ of electricity. However, oxygen-enriched CSA reduces this to 0.3627 kWh/Nm³ by modifying the distillation process, adding auxiliary towers, and reducing operating pressure, resulting in energy savings of 15%-20%. Compared to pressure swing adsorption (PSA), oxygen-enriched CSA, while having similar energy consumption, avoids the capacity reduction caused by molecular sieve degradation and offers greater operational stability. Furthermore, while providing oxygen for smelting, this process also produces nitrogen and liquid products as byproducts, enhancing overall economic benefits.
In terms of operational performance, the unit boasts an oxygen recovery rate of 99.1%, demonstrating extremely low oxygen losses and meeting the goal of high efficiency and energy conservation. Statistics from 2018 to 2019 show that the unit produced nearly 120 million Nm³ of oxygen and approximately 1.17 million Nm³ of liquid oxygen annually, with a utilization rate exceeding 93%, stable operation, and minimal maintenance. The equipment features an integrated air compressor and booster structure, with the remainder consisting of small motors and static equipment. It is easy to operate and has operated without a single breakdown or downtime for over three years. Maintenance costs primarily focus on the replacement of consumable parts.
However, the process encountered some initial operational challenges, such as excessive summer chiller load, insufficient expander cooling capacity, inadequate compressor oil cooling, and noise control. These issues have been gradually addressed through a series of modifications and optimizations. For example, the company added a small chiller in the summer to ensure temperature control of the purifier inlet air; added a heat exchanger at the expander outlet to prevent summer overtemperature alarms; modified the oil cooler water supply system to improve the stability of water and oil temperatures; and implemented soundproofing materials to reduce noise levels at the plant boundary, meeting environmental standards. Furthermore, optimized electrical programming has prevented grid surges during the purifier furnace heating process, resulting in more stable operation.
Notably, to meet the high-pressure oxygen demand for smelting cylinders, the company installed a liquid oxygen pump on the liquid oxygen storage tank to directly deliver high-pressure oxygen to the smelting process, significantly reducing cylinder oxygen consumption. This transformation has reduced bottled oxygen usage to one-tenth of its original level, further improving operational economics.
Overall, the oxygen-enriched cryogenic air separation process offers the copper smelting industry a new path that balances energy conservation, efficiency, and stability. It not only reduces energy consumption and investment costs, but also simplifies operation and maintenance, improves oxygen recovery, and enhances plant stability. With continued process optimization, the advantages of this technology will become even more pronounced, and it is expected to be widely adopted in more oxygen-using industries.
This practical case demonstrates that copper smelters can effectively improve production efficiency, reduce overall energy consumption, and enhance environmental compliance by introducing advanced gas separation technology. The application of oxygen-enriched cryogenic air separation also offers valuable insights for other industries requiring large-scale oxygen supply, such as the steel, chemical, and new energy sectors.
