Investigation on the preheating temperature of heavy oil catalytic feedstock?
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Brothers, the feedstocks we use for catalytic processes are becoming increasingly heavy. I’d like to find out what the preheating temperatures of those heavy oil catalytic feedstocks are for each of you Because there is a trade-off between the preheating temperature of the feed oil and the oil-to-agent ratio: increasing the preheating temperature of the feed oil can reduce its viscosity and improve atomization, but as the preheating temperature rises, the oil-to-agent ratio decreases, which may have an adverse effect on the product distribution. Has anyone conducted experiments in this area? What is the highest preheating temperature that is most beneficial?
At the start of operation here, the preheating temperature of the feedstock was 220 degrees, but it has gradually decreased over time as the unit has been in operation; now it’s below 200 degrees, and the heat exchange between the feedstock and the slurry is not effective! As for the optimal preheating temperature, I think it depends on the properties of your feedstock. Currently, there are significant variations in the characteristics of different catalytic feedstocks, making it difficult to determine the ideal preheating temperature
It’s usually around 200 degrees! The raw material temperature should be appropriate to the coking tendency of the raw material. Put simply, good raw materials allow for a higher preheating temperature; 220 degrees is certainly fine as well. For heavy feedstocks that are of poor quality and high in nitrogen, requiring high-intensity cracking, the preheating temperature can be lower, but it should not be below 150 degrees; otherwise, it will affect atomization!
We are part of a local refinery; the crude oil we use is of very poor quality – with a residue content of over 6, a density of over 92, an alkaline nitrogen level of over 1100, and high levels of heavy metals and sulfur. Additionally, I heard that the feedstock for heavy catalytic cracking at Daqing Petrochemical, with a capacity of 1.4 million tons per year, is not of high quality either; yet it manages to achieve its designed processing capacity, which is really impressive. The preheating temperature of that feedstock is usually maintained at 270 degrees. I would like to mention the preheating temperature as well, in order to match the standards set by those more experienced companies, but I’m not quite sure if I should do so. Could anyone give me some encouragement? Thank you!
Our plant uses the MIP process, with a preheating temperature of around 195 degrees; increasing the preheating temperature is not a solution to the problem of poor quality of the crude oil
I have now increased the preheating temperature from 207 degrees to 237 degrees, and it indeed had an effect: the dense-phase temperature in the regenerator dropped by about 6 degrees. But I’m also worried that if the oil-to-agent ratio is too low, the temperature in the settler will become too high, leading to coking; this in turn can cause the temperature at the bottom of the distillation tower to rise as well, resulting in coking and blockages in the slurry-feed oil heat exchanger. Please help me analyze this further, and give me some encouragement too!
It can range from 150 to 390; this value varies depending on the structure of each device and the properties of the materials used. This post was last edited by ** the years on 2007-12-17 04:34】
The heavier the feedstock, the higher the preheating temperature required, as confirmed by an increasing amount of practical experience. Although lowering the preheating temperature leads to an increase in the heat balance, the oil-to-fuel ratio during vaporization in the nozzle section does not necessarily increase. In the nozzle area, the probability that each oil droplet comes into contact with catalyst is limited; the oil-to-fuel ratio in the riser is 6, while in the vaporization stage it may be 3 for some oil droplets. Therefore, the better the vaporization of the feedstock in a device with a lower oil-to-fuel ratio, the worse it is in a device with a higher oil-to-fuel ratio. For the reaction of the vaporized gaseous oil and gas with the catalyst, a higher catalyst-to-oil ratio is preferable; these two factors are opposite to each other. There is an optimal value for the preheating temperature in the past – it’s not the case that the lower the temperature, the better. Practice has shown that increasing the temperature from 200 degrees to 260 degrees reduces the oil-to-agent ratio, yet the degree of conversion increases, while the amounts of dry gas, coke, and slurry decrease. So I feel that the preheating temperature of heavy oil can be increased to 220–280 degrees; try it out depending on the conditions of your setup, and you’ll make some discoveries!
The guy on the 8th floor said it very well; I tried it as well. At 240 degrees, it was possible to increase the processing volume a bit, but the yield of recycled oil was very high, and the tank became full. Later, I reduced the preheating temperature to 230 degrees, and things improved – the level of recycled oil decreased. So there is an optimal temperature! It is certain that the atomization effect of the raw materials in my device is already satisfactory at 230 degrees; otherwise, even if the preheating temperature is reduced, that is, if the fuel-to-oil ratio increases, it would be impossible to enhance the depth of reaction. I’m not sure if this analysis is correct!
Hello! As you mentioned, practice has shown that by raising the temperature from 200 degrees to 260 degrees, the oil-to-agent ratio decreases, yet the depth of conversion increases, while the amounts of dry gas, coke, and slurry decrease. ”What does the depth in it refer to? Conversion rate or something else? Your approach of raising the preheating temperature comes at the cost of processing capacity, as the experiments on the 9th floor clearly illustrate this. Raising the preheating temperature led to a decrease in the agent-oil ratio, which in turn reduced the conversion rate. As a result, less dry gas coke was produced, but more reprocessed oil was generated and the tank became full; therefore, it was necessary to lower the preheating temperature again, otherwise the amount of fresh feed would have to be reduced. I know your understanding that, in theory, catalysis is a gas-phase reaction while in practice it is a liquid-phase reaction is absolutely correct; this is indeed something that many people have not considered carefully! However, under the current catalytic processes, increasing the catalyst-to-oil ratio remains the method to enhance the degree of heavy oil cracking. What you say, that \"the lower the oil-to-catalyst ratio, the better the gasification in a unit; the higher the oil-to-catalyst ratio, the worse the gasification\", is not correct. The phenomenon you observed merely indicates that the catalyst in the pre-raising section at the bottom of the riser experiences increased mixing due to the higher oil-to-catalyst ratio, which results in a deterioration of the flow pattern and prevents the maintenance of an ideal plug flow pattern. At this point, one should consider how to improve the fluidization at the bottom of the riser, rather than reaching the conclusion you mentioned. Over a decade ago, my friend and I discussed the idea that increasing the oil-to-agent ratio does not improve the contact between the agent and the oil, and as a result, vaporization does not occur effectively ； It will also affect the flow pattern at the bottom of the riser, leading to premature coking of the catalyst. The method we came up with is to attach a regenerating inclined tube to the riser; the catalyst in the first tube serves only for vaporization, while the catalyst in the second tube performs catalytic cracking. This actually shares the same way of thinking as the two lift pipe technologies at the Petroleum University ten years later. It’s just that his patent adds another set of centrifuges in the middle of the riser.
I didn’t understand what the original poster meant. Raising the preheating temperature from 207 degrees to 237 degrees did indeed have an effect: the dense-phase temperature in the regenerator dropped by about 6 degrees. ”What’s strange about that? With a decrease in the oil-to-agent ratio, isn’t it inevitable that the coking rate will drop as well? But when you say, “Yet there’s a concern that the oil-to-fuel ratio might be too low, causing the temperature in the settler to rise and leading to coking,” I don’t understand. By your logic, would a higher oil-to-fuel ratio actually lower the temperature in the settler? It’s unbelievable; could you please explain it?