According to the process feature of ammonia oxidation furnace for concentrated nitric acid plant, the ratio control system is applied to make the volume flow ratio between ammonia and air that enter into the ammonia oxidation furnace become stable. But the temperature fluctuation of catalyst layer in the ammonia oxidation furnace causes the fluctuation of NO generation rate. In the modification program, dual closed-loop variable ratio control system is introduced. The volume flow ratio of ammonia and air is changed from the former fixed ratio to adjustable ratio by the temperature controller of catalyst layer in the ammonia oxidation furnace. By adjusting this ratio, constant temperature of catalyst layer in the ammonia oxidation furnace is achieved, and the generation rate of NO is finally guaranteed to satisfy the production requirements of process, and ammonia consumption during start-up is reduced. Meanwhile, the generation of ammonium during follow-up production is decreased, and the problem of tail gas concentration that exceeds the standard is solved completely.%根据浓硝酸装置氨氧化炉工艺反应特点，应用比值控制系统使进入氨氧化炉的氨气和空气的体积流量配比稳定。但氨氧化炉触媒催化层的温度波动造成一氧化氮生成率存在波动，故在改造方案中引入了双闭环变比值控制系统。通过触媒催化层的温度控制器使氨气与空气的体积流量比值由原来的固定值变成可调值，通过调节该比值以保证氨氧催化层的温度恒定，最终保证了一氧化氮的生成率，满足工艺的生产要求，减少开车过程中氨气的消耗，同时降低后续生产过程铵盐的产生，使尾气超标的问题得到了彻底根治。
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