Please discuss how each of you dehydrates your hydrogenation feedstocks
Thread Content
Our hydrogenation feedstocks often have a high water content, sometimes reaching several thousand ppm. Catalyst suppliers claim that 500 ppm is already sufficient to cause catalyst deactivation; we are currently replacing the catalysts, and controlling the water content has become an issue. Please share how your respective plants remove water from the feedstocks, not limited to hydrogenation units. Yesterday I saw a document discussing the use of degassing machines; I’ve never seen one before and don’t know what they look like.
Our factory only installs a raw material buffer tank to remove free water from the raw materials. In the case of feeding from a tank area, multiple dehydrations are required during storage, and no free water is allowed before processing by the equipment.
Our factory carries out dehydration in the raw material tank area, and conducts moisture analysis before feeding materials into the tanks. .
Our hydrogenation unit is equipped with a feedstock buffer tank, which is used to receive the feedstock directly； If feeding from the tank area, water should first be removed from there before the material enters the raw material buffer tank; it enters the reaction system without any water.
The presence of water in the raw materials has a significant impact on the catalyst and the reaction, so it must be addressed as early as possible: 1. Maintain a constant temperature in the raw material storage area to facilitate dehydration; conduct moisture analysis before the materials enter the system, and only allow them to proceed once they meet the required standards； 2. After entering the device, a dehydration tank should be installed first: it is a horizontal tank with a higher inlet and outlet level; after that, a buffer tank comes next. The main purpose of the buffer tank is to prevent the feed pump from running dry, although its dehydration efficiency is generally average.
Our unit first undergoes dehydration in the tank area, with continuous analysis and monitoring. The material entering the unit passes through a filter and a coalescer, then goes through another dehydration tank, before reaching the material buffer tank.
Thank you to the friends who responded actively above; it seems that dehydration is carried out in the tank area, with horizontal dehydration tanks being used after the material enters the facility. I was wondering if the friends could provide more details on the following questions: 1. How is dehydration done in the tank area? 2. What is the structure of a horizontal dehydration tank? 3. What is the processing capacity of the coalescer mentioned on floors 6 and 7? How effective is it? Is it available from any manufacturers?
In fact, it’s not necessarily necessary to use horizontal tanks; it’s also possible to modify the inlet and outlet of vertical raw material buffer tanks. The inlet can be placed at the bottom, with the outlet at the top. The lowest point is for drainage, while the top part can be used for venting or nitrogen protection. Of course, the most important thing is to remove water from the oil storage area – once that is done, there will be almost no water entering the plant area.
To achieve dehydration in a tank farm, at least 3 feed tanks are required: one for receiving oil, one for discharging oil, and another for static dehydration, with a resting time of over 6 hours. Both the raw oil dehydration tank and the buffer tank inside the unit can remove water
From what you’ve described, it seems that dehydration in the tank area actually involves allowing oil and water to separate through settling. This seems to serve the same purpose as the buffer sedimentation tanks in our facility, right? Also, what should be done if oil and water emulsify? I think it should be quite difficult to let it sit.
To ensure that an anhydrous feed is supplied to the hydrogenation unit, we take the following measures: First, the feed is divided into stationary tanks and operating tanks; when switching between them, water must be removed first, and only after testing confirms that the feed is free of water can the switch be made. Second, due to the shortage of raw materials, the processing unit does not stop operating; moreover, the tanks are changed frequently, which makes it impossible to carry out dehydration in a timely manner. Therefore, another pump inlet is installed on the storage tank, at a height of 1 meter above the bottom of the tank, so as to ensure the stable operation of the unit. Secondly, in cases of severe oil-water mixing, the resting time can be increased or the mixture can be poured into a separation tank for separation.
It should be added that when oil-water emulsification is severe, heating for dehydration or the addition of demulsifiers can be employed, and the dehydrated oil can be returned to the raw material tank.
Generally, dehydration is carried out in the diesel hydrogenation tank area; for wax oil hydrogenation, it is best to connect the feed line directly to the outlet line of the upstream unit, as this is more economical and avoids the hassle of using intermediate tanks.
Very good, thank you. There are no points available today; I’ll add them to you tomorrow. Additionally, what is the appropriate temperature for heating and dehydration? What grade and type of demulsifier? Does it have an impact on the hydrogenation catalyst? Also, what is the internal structure of the horizontal tank and your static tanks respectively? This post was last edited by New Life Propositions on 2009-4-15 19:46.]
Generally, 3 raw material tanks are required: one for receiving the material, one for sedimentation and dehydration, and one for discharging the material, in order to ensure effective dehydration; it is essential to avoid drawing off the material while it is still being fed in. We have installed automatic dehydrators in our raw material tank area, and the results are good; there have been no issues with water remaining in the raw materials. If the viscosity of the oil is high, causing emulsification and making it difficult to remove water, the storage tank can be appropriately heated to improve the dehydration effect.
Automatic dehydrator – could you explain it in detail?
Hello, friends on the 9th and 15th floors. You both mentioned three tanks: the oil collection tank, the dehydration tank, and the oil discharge tank. My understanding is that the structure inside these tanks should be similar – in each case, the oil and water are allowed to separate due to gravity, and then the water layer is removed. So, if I use just one sedimentation tank and let it sit for a longer time, say 24 hours, with the oil outlet placed at the top, wouldn’t the result be the same? Please give me some advice.
If our refinery reforming unit needs to draw raw materials from the tank farm, it must first pass through the hydrocracking unit for dehydration.
This thing is mainly about the residence time in the tank area, as well as sedimentation. We usually use two containers: one for receiving and one for paying. It would be best to have three containers, but such favorable conditions are rare; two is already good enough. This post was last edited by net2002163 on 2009-4-20 22:58.]