How to adjust the light gasoline extraction ratio in the fractionation tower (for V-series blended gasoline produced by gasoline hydrodesulfurization units)
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Currently, my plant is producing Grade V blended gasoline. During production adjustments, the proportion of material drawn from the fractionation tower is reduced (from 38% wt to around 33% wt), and the bed temperatures in the two reactors of the hydrodesulfurization system are increased, in order to meet the requirements for reducing olefins. The difficulty encountered was that, while keeping the feed temperature, bottom temperature, top temperature, and top pressure essentially constant, reducing the amount of light gasoline product drawn from the 9th stage of the distillation column increased the amount of fluid discharged by the top reflux pump. The sum of this outward flow amount and the amount of light gasoline extracted remains essentially unchanged; then, by adjusting the bottom and top temperatures of the tower, it is attempted to see whether the proportion of light gasoline extracted can decrease or increase. This is quite troublesome: Q fails to achieve the goal of precise adjustment. Question: How can the extraction ratio of a distillation column be adjusted more accurately? For example, to reduce the extraction ratio from 33% wt to 32% wt, which parameters need to be adjusted?
1. Reduce the feed temperature of the distillation column appropriately, without affecting the distillation accuracy. 2. Reduce the top temperature of the tower: a) Increase the heat absorbed by the mid-section reflux; b) Increase the flow rate of reflux at the tower top.
The fractionation tower for gasoline hydrogenation should be operated in conjunction with a pre-hydrogenation system to control the diene value, right? The desulfurization reactor is used to control desulfurization, while the octane recovery reactor is responsible for adjusting the octane level. I’m not sure what technology is used in your facility However, pre-hydrogenation and distillation column operations are merely fine-tuning steps; for National V blended gasoline, adjusting the desulfurization reaction temperature as well as the temperature in the subsequent reactors is sufficient to achieve the required standards. Adjusting the light gasoline extraction volume from the fractionation tower is the main reason for the increased external carryover. I’m not familiar with the design of your device, so this is just a preliminary assessment that there’s an issue with the parameters you’re adjusting; it may not be accurate
I really don’t understand these issues; I hope we can learn together once we find an answer. They are very practical problems.
Hello, I would like to ask some questions. We need to produce National V blended fuel here, and it involves a gasoline hydrogenation unit. I am an instrumentation technician; there are no operators available here. If I am to operate the equipment, what aspects do I need to pay attention to? All I know for now is that the sulfur content in the feed oil varies, and I’m not sure how to adjust the hydrogen-to-oil ratio; it’s something I really have no idea about. Knowing only the oil feed rate FT, recycled hydrogen rate FT, and fresh hydrogen rate FT – is it possible to carry out commissioning in this case? I asked for advice, thank you! ! !
:Oh, really? Operators and instrument technicians are two distinct job roles. Starting up a plant is when accidents are most likely to occur; there are strict procedures for this process, and it also needs to be coordinated with the overall startup efforts of the entire plant. Each step has key points and important considerations. Regardless of the process, there are not many differences when starting up a gasoline hydrogenation unit or a hydrogenation plant – the differences lie mainly in the details. According to what you’re saying now, it’s not suitable for being an operator
Adjustments between National Standard IV and National Standard V are made quite frequently, mainly in response to market demands. Our factory has to make such adjustments roughly once a week. Taking the adjustment of the ratio between light gasoline and heavy gasoline as an example when switching from National Standard V to National Standard IV: 1. Calculate the amount of light gasoline that needs to be extracted based on the desired ratio. 2. Gradually reduce the temperature at the bottom of the tower; simultaneously, reduce the amount of light gasoline extracted, as well as the amount of heavy gasoline extracted from the bottom of the tower (in our facility, there is no external reflux at the top of the tower, nor any intermediate reflux, so the feed temperature cannot be adjusted easily. The temperature at the bottom of the tower is controlled using a reboiler located there). 3. Eventually, a new balance is reached. There is only a general range within which the temperature at the bottom of the tower can be maintained; the key is to ensure that the reflux flow rate at the top of the tower remains above a certain level, thereby ensuring proper separation of light and heavy gasoline. When switching from National Standard V to National Standard IV, it is necessary to lower the temperature at the bottom of the tower. If this temperature is not reduced and only the amount of light gasoline extracted is decreased, the load on the top of the tower will increase significantly, the liquid level in the reflux tank will rise rapidly, the pressure at the top of the tower will increase as well, and the volume of gas coming from the top of the tower will also increase. This leads to large fluctuations in operation, posing a risk of overflow, and it also increases energy consumption, which is unnecessary.
Your company is going a bit overboard here – having instrument technicians involved in the initial startup process. Have enough leadership