Catalytic cracking reaction operation issues
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The quantity and properties of the catalytic raw materials are unstable; the following issues have occurred. Please help me analyze the reasons: 1. Before overheating, the temperature of the self-pumped raw material dropped from 120°C to 113°C. 2. After superheating, the temperature of the raw material rises from 220°C to 236°C. 3. The flow rate at the feed nozzle fluctuates significantly, by as much as ten tons; under normal conditions the nozzle operates stably. 4. The regeneration temperature was increased from 695°C to 730°C, and the dilute-phase temperature reached up to 800°C. 5. The thermocouple at the riser feed point drops by about 5°C. 6. The reaction pressure fluctuates significantly, showing an overall upward trend. 7. There is no problem with the on-site raw material pump. Solution: 1. Contact for oil dehydration and tank replacement. 2. Change the feed nozzle to manual mode to significantly increase the processing capacity and reduce the air flow, while controlling the reaction pressure; once stability is achieved, quickly restore the processing capacity and air flow levels. Additional note: There were two sources of raw material supplied to our equipment, and the volume coming from these two sources fluctuated greatly at that time. The oil supplier insisted that their raw material was free of water; these fluctuations persisted for over an hour, until normal conditions were restored half an hour after the oil was transferred to another tank. Is this situation caused by moisture in the raw material? It seems there are many issues that don’t meet the requirements. Could everyone help me analyze the reasons?
1. It’s possible to contain water; the oil products simply do not accept it. 2. The supply from the two sources is unstable; could it be that the oil was transferred between tanks earlier, resulting in a change in the properties of the raw material? What caused the increase in light components?
Various phenomena indicate that the crude oil is likely to contain water.
Based on the reaction pressure and feed fluctuations in the nozzle, it can be determined that the raw material contains water. However, if it’s just water present, shouldn’t the temperature of the overheated crude oil decrease? And the regeneration temperature shouldn’t be that high either, right? I think when considering water content in crude oil, we should also take into account the issue of high levels of heavy metals in the oil, as well as the problem of increased water content in steam or liquid content in dry gas As a newcomer, I’m just sharing my own opinion.
Typical water content in crude oil. Water in the raw material causes a certain gas resistance after heat exchange, which prolongs the heat exchange time and raises the preheating temperature; fluctuations in the raw material flow rate further affect changes in the reaction pressure. As for the increase in regenerator temperature, it is caused by fluctuations in the amount of feed entering the lift column, which disrupts the balance between coke formation and coke burning.
A fairly obvious phenomenon of moisture in the raw materials. Has the raw material become heavier? However, the regeneration temperature increased from 695°C to 730°C, and the dilute-phase temperature reached up to 800°C. I think this issue is simply caused by fluctuations in the amount of feed entering the lift pipe, which disrupts the balance between the amount of char formed and the amount that burns away. ”Is this reason sufficient? Please ask an expert for advice!
In the treatment method, ‘significantly increasing the treatment capacity and reducing air volume’ – what is the device regeneration method?
”The regeneration temperature was increased from 695°C to 730°C, and the temperature in the dilute phase reached up to 800°C. Could this be caused by large fluctuations in reaction pressure, which in turn lead to large fluctuations in the level of material in the settler?
I wonder what the quality of the steam was at that time, and whether there were any fluctuations in pressure. I suspect it is the result of light components in the raw material belt, low steam pressure, and the combined effect of water.
Thank you all for your answers. hlytyy’s analysis is excellent; it’s likely that water was present in the raw materials. These days, there have also been leaks in the heat exchangers used for the crude oil slurry, and this might be caused by the water leading to gas blockages. Additional note: The steam flow remains stable during the water addition process. Our system features two stages of burning, and the regeneration temperatures referred to are both those of the second regeneration stage. The temperature for repeated regeneration also increases by 10°C. Although there were fluctuations in the nozzle flow, overall, the processing volume increased by nearly 10 tons at that time, while the air volume decreased by about 100 nm³; otherwise it would not have been possible to maintain stability. It took 20 minutes for the air volume and processing volume to return to normal levels, in order to prevent carbon buildup.
Oh, I see. I learned a lot of knowledge that can’t be found in books through Hai Chuan.