Abstract:

The feed plate heat exchanger of a certain disproportionation unit experiences fouling on both sides of the plate after multiple cycles of operation, resulting in a significant decrease in heat transfer efficiency and an abnormal increase in fuel gas consumption. The cold end pressure difference of the plate heat exchanger reaches 98% of the design value, which can not continue to improve the load of the unit, seriously restricting the long-term stable operation of the device. In order to reduce the pressure difference of the plate heat exchanger and restore its heat transfer efficiency, it is necessary to clean or scorch it. This paper introduces a treatment technology of alkali washing, rinsing and controllable combustion scorching. The salts existing in the reaction feed heat exchanger of the disproportionation unit are removed by chemical cleaning, avoiding the corrosion risks that may be caused in the process of scorching and internal inspection. By controlling the amount of low concentration of air in the scorching process, the intensity of the scorching is controlled to remove the coke inside the plate heat exchanger. The cold end pressure difference of the plate heat exchanger under the same load decreases from 188 kPa to 45 kPa, the hot end temperature difference decreases from 51.9 ℃ to 31.0 ℃, and the fuel gas consumption of the reaction heating furnace decreases by more than 50%. It can achieve the effect of restoring the design capacity of the plate heat exchanger by more than 95%, reducing the energy consumption of the device, and eliminating the bottleneck of the device operation.

Key words: disproportionation unit, plate heat exchanger, cleaning, scorching, alkali cleaning, rinsing, vacuum airtight

摘要：

某歧化装置反应进料板式换热器经过多个周期的运行后，板片两侧结垢，换热效率大大下降，燃料气消耗量异常增加。板式换热器冷端压力降达到设计限值的98%,无法继续提高装置负荷，严重制约了装置的长周期稳定运行。为降低板式换热器压力降、恢复其换热效率，有必要对其进行清洗或烧焦。文中介绍了一种碱洗、漂洗及可控燃烧除焦的处理技术，通过化学清洗除去了歧化装置反应进料换热器内存在的盐类，避免了烧焦和开盖内部检查过程中可能出现的腐蚀风险。烧焦过程中通过通入较低浓度的空气来控制烧焦的强度，实现板式换热器内部除焦。处理后，板式换热器在相同负荷下的冷端压力降由188 kPa下降至45 kPa,热端温差由51.9℃下降至31.0℃,反应加热炉燃料气消耗下降50%以上，降低了装置能耗，消除了装置运行瓶颈。

关键词: 歧化装置, 板式换热器, 清洗, 烧焦, 碱洗, 漂洗, 真空气密