【Q&A Question 272】2017.09.30

The dry point of hydrogenated naphtha should not be too high, as this can affect the reforming catalyst, leading to premature coking and carbon deposition. Excessive sulfur and nitrogen contents can cause catalyst poisoning, and attention must also be paid to the water content and other components

1. High impurities reduce the hydrogen partial pressure. 2. Increasing the hydrogen circulation rate increases energy consumption；

The low purity of the reforming hydrogen leads to a decrease in the purity of the recycled hydrogen, resulting in a lower hydrogen partial pressure and increased load on the recycler. This also results in an increased amount of hydrogen waste being emitted. Reformed hydrogen contains chloride ions, which readily combine with ammonia under hydrogen-rich conditions to form ammonium chloride. This substance deposits on equipment such as compressors and heat exchangers, causing chloride stress corrosion that affects the operation of these devices. Reformed hydrogen contains a small amount of hydrocarbons, which is detrimental to the proper operation of the compressor; moreover, if the liquid from the inter-stage tanks is not drained in a timely manner, it can cause the compressor to shut down as part of an interlock mechanism.

Hydrogen sulfide is present in the reformation gas, and it can corrode the pipelines

The purity of hydrogen produced through reformation generally does not exceed 93%, which is insufficient for hydrogenation purposes; it must be purified using PSA before it can be used. Reformed hydrogen can only be used for hydrofining; 98% purity is required for hydrocracking, otherwise too much waste hydrogen is generated. Furthermore, excessive levels of CO and CO2 in the reformed hydrogen can cause poisoning of the hydrogenation catalyst

The impurity content in hydrogen, especially the level of Cl-, must not exceed specified limits. Attention should be paid to the hydrogen purity in the recycled hydrogen and the load on the recirculation unit, as well as the inlet and outlet temperatures of the new hydrogen unit; this is especially important when the proportion of reformed hydrogen is high. During the startup process, it is best not to use low-purity reforming hydrogen directly. Reforming hydrogen with a purity of less than 95% can generally be used directly in hydrofining units, while its use in hydrocracking units is relatively uncommon both domestically and internationally. Because using hydrogen with low purity will inevitably reduce the purity of the recycled hydrogen, resulting in an excessively low partial pressure of hydrogen used in the reaction as well as an excessive load on the recycler; this is detrimental to both the energy consumption associated with the reaction process and safe production. Therefore, the purity of recycled hydrogen is generally improved by removing hydrogen at the end of the process, but this inevitably increases the cost of the facility. 1. The purity of the new hydrogen decreases, with increased levels of CO and CO2; as a result, the reaction temperature rises and operations become unstable. 2. New hydrogen contains water, forcing the hydrogenation unit to shut down.

The purity of hydrogen produced through reforming generally does not exceed 93%, which is not sufficient for hydrogenation processes. As a result, the load on the recycle hydrogen compressor and the new hydrogen generator increases, leading to higher operational energy consumption

The low purity of the reforming hydrogen leads to a decrease in the purity of the recycled hydrogen, resulting in a lower hydrogen partial pressure and increased load on the recycler. This also results in an increased amount of hydrogen waste being emitted. Reformed hydrogen contains chloride ions, which readily combine with ammonia under hydrogen-rich conditions to form ammonium chloride. This substance deposits on equipment such as compressors and heat exchangers, causing chloride stress corrosion that affects the operation of these devices. Reformed hydrogen contains a small amount of hydrocarbons, which is detrimental to the proper operation of the compressor; moreover, if the liquid from the inter-stage tanks is not drained in a timely manner, it can cause the compressor to shut down as part of an interlock mechanism.

The low purity of the reforming hydrogen leads to a decrease in the purity of the recycled hydrogen, resulting in a lower hydrogen partial pressure and increased load on the recycler. This also results in an increased amount of hydrogen waste being emitted. Reformed hydrogen contains chloride ions, which readily combine with ammonia under hydrogen-rich conditions to form ammonium chloride. This substance deposits on equipment such as compressors and heat exchangers, causing chloride stress corrosion that affects the operation of these devices. Reformed hydrogen contains a small amount of hydrocarbons, which is detrimental to the proper operation of the compressor; moreover, if the liquid from the inter-stage tanks is not drained in a timely manner, it can cause the compressor to shut down as part of an interlock mechanism.