Energy-saving preheating process and system for water used for boiler

The invention specifically relates to an energy-saving preheating process and system for water used for a boiler, belonging to the technical field of alumina production. According to the invention, condensed water in an alumina production system is completely recycled, consumption of raw water is lowered, and pollution to environment caused by discharging of primary water and secondary water is avoided; the heat of the condensed water in the alumina production system is recycled, and demineralized water is heated to a temperature that meets temperature requirements on heating power, so the demand for energy during operation of the boiler is lowered, and production cost is further reduced. 本发明属于氧化铝生产技术领域，具体涉及种锅炉用水预热节能工艺及系统，实现了氧化铝生产系统中凝结水的完全回收利用，降低原水水耗，避免次水和二次水外排，污染环境；实现了氧化铝生产系统凝结水热量的回收利用，加热除盐水温度至满足热力温度要求，节约了锅炉运行能源的需求量，也进步降低了生产成本。