Could someone with experience in diesel and gasoline hydrotreating units that use direct feedstock please share their insights? What measures need to be taken in various areas?

For the direct feeding of raw materials into diesel and gasoline hydrorefining units, direct feeding of coker gasoline is generally chosen to prevent catalyst gumming. 1. The upstream unit should be operated as smoothly as possible. 2. Appropriate dehydration measures must be in place before material enters the unit. 3. Larger buffer tanks should be installed, along with a backup process using an oil storage tank.

1. Water must be removed from the raw material dehydrating tank and the buffer tank; it is strictly prohibited to allow water to enter the system. Therefore, the hot feed temperature and pressure must be carefully calculated. 2. It is advisable to install a temporary storage tank to prevent disruptions in supply from upstream units, which could lead to shutdown of the facility

Our diesel feed is supplied directly; if its level is too high, it is returned to the reservoir for regulation. A pre-filter is located before the raw material tank

Indeed, as the others above have said, in order to make full use of energy and achieve energy savings and reduced consumption, many diesel and gasoline hydrogenation processes opt for direct supply； Typically, a hydrogenation unit is equipped with a filter before the feed enters the storage tank; thereafter, it is heated (if necessary), pressurized, and pumped into the reactor. Direct supply requires operational balance of the upstream units, with certain control parameters such as the diesel dry point being maintained stable, in order to ensure stable operation of the hydrogenation unit.

Experience with direct feeding: 1. Install a raw material buffer tank and filter for feeding, to remove moisture and mechanical impurities in a timely manner； ⒉A raw material return line is provided to allow excess material to be sent back to the tank area ； ⒊There is a transfer line in the tank area; the temperature of the material fed directly is relatively high, which results in poor cavitation suppression performance by the feed pump. In such cases, it is necessary to have the tank area supply the material in order to lower its temperature and increase the processing capacity ； ⒋The raw material tank is equipped with pressure control to reduce cavitation in the raw material pump.

Due to the operating characteristics of coking units, the gasoline, diesel, and wax oil distilled from the fractionation towers typically exhibit large flow rate fluctuations, and are prone to containing coke particles and water (in the case of gasoline). Based on production experience, when supplying materials to downstream units, both direct supply and indirect supply have their own advantages and disadvantages. During design, it is necessary to choose between these two supply methods appropriately, taking into account the specific production conditions and requirements of each enterprise, as well as the production characteristics of the downstream units. I. Direct feeding method 1. Advantages: It allows for the full utilization of the low-temperature heat source from upstream products, thereby saving energy and reducing consumption. 2. Disadvantages: (1) The coke powder present in the upstream products is carried to the downstream hydrogenation units, which causes an excessive increase in the pressure drop across the bed of the hydrogenation reactors; as a result, the catalysts need to be periodically cleaned. The use of automatic backwash filters can extend the headspace time of the catalyst bed. (2) Flow fluctuations affect the stable operation of the hydrogenation unit, as the buffer tanks for hydrogenation feedstocks cannot be designed to be too large; this is especially important when the hydrogenation unit switches from intermittent feeding to continuous feeding. (3) When changing from intermittent supply to direct supply through technical upgrades, attention must also be paid to the impact of the temperature of upstream products on the existing equipment (buffer tanks, filters, pumps). II. Intermittent feeding method 1. Advantages: The small amount of coke powder contained in the coking products has sufficient time to settle in the tank area, which helps to reduce the amount of coke powder that reaches the hydrogenation unit. 2. Disadvantages: (1) Increased energy consumption, as the low-temperature heat in the coking products is not fully utilized. (2) If the coking products remain in the tank area for too long, gums will be formed, which increases the pressure drop in the heat exchangers of the hydrogenation unit; accordingly, more scale inhibitors need to be injected. III. Precautions (1) Use a nitrogen-sealed tank. Minimize the contact time between coking products and air to prevent the formation of gums. (2) Reasonably control the residence time of coking products in the storage tank to improve its utilization rate; experience suggests that this time should generally be no less than 24 hours. The above is for reference only. What was said on the 6th floor is also correct and can be used as a reference. This post was last edited by liant on 2009-4-18 15:20]