Posted 15 March - AM In response to your query, i would like to add the following, picked up from literature: " Steam or inert distillation is commonly used in the following situations: 1. Posted 18 March - PM It would be very interesting if someone can give e In response to your query, i would like to add the following, picked up from literature: " Steam or inert distillation is commonly used in the following situations: 1. For example, sour water stripper 1?
I've read your comment saying that injecting steam lowers the partial vapor pressure of the process fluid. What does this mean? Does it have something to do with Dalton's Law of Partial Pressures? Posted 22 December - AM Why does we need the steam injection into crude oil column and so on? Steam is injected into crude oil column topping only for stripping reasons, ie removing of light tails from residue and heavier products. The fractionation heat is provided by furnace.
Steam has to be taken at a minimum since it has to be condensed and then it generates sour water ie additional operating costs. Posted 22 December - PM Following notes could be useful, complying with above posts. Neither of the two distillation columns has a reboiler usual ; so steam injection helps light component stripping, as mentioned in above posts and the example Process Description.
Nevertheless there is another significant reason to add steam into VDU. Most important among these are the much smaller tower and condensing equipment required. Nevertheless, the absolute pressure that is required for dry processing of most petroleum oils amounts to less than 10 mm, and such a vacuum cannot be produced at a reasonable cost in most large-scale vacuum equipment " remark: 10 mm means 10 mm Hg. Total vapor pressure is sum of vapor pressures of pure water and oil.
According to above, equipment ejectors creating a pressure of 30 mm Hg abs in the column cannot create 10 mm Hg abs in case of no steam addition. It seems so, e. Data can be also found in R. Watkins, "Petroleum Refinery Distillation", 2nd edition, Gulf - The total vapor pressure of the mixture is the sum of the individual vapor pressure of each component in the mixture proportional to their mole fractions.
Adding steam water is adding another vapor pressure component which contributes to the total vapor pressure of the mixture. A mixture starts boiling when its vapor pressure exceeds the atmospheric pressure. Thanks to the extra component water, the total vapor pressure of the mixture exceeds the atmospheric pressure sooner; in other words: it boils at lower temperature.
As water and hydrocarbons are immiscible, separating them is not an issue. Mixing water vapor with the hydrocarbon in the flash zone reduces the pressure that the hydrocarbon is influenced by.
Due to the large difference in relative quantities of hydrocarbon and steam, the flash temperature is only negligibly changed. The wastewater must be free of solid matter, which could block the heat exchanger. A stream stripper selectively removes components.
Substances that dissolve well in water, which cannot be removed with the classic stripping method, can also be separated from water. Steam stripping consumes relatively large amounts of energy because electricity is used. Further, lime residue is also left behind, which could pollute the stripping tower. The "stripability" of the compound is indicated by the Henry coefficient. Steam stripping is primarily implemented for the removal of volatile organic matter incl.
Stripping is normally carried out on the concentrated partial flow. Ammoniac can be stripped in a steam stripper. If ammoniac is interfering with other pollutants that need to be removed, this can be confirmed using neutralising substances. Flue gases and condensed fluid are released as by-products.
In most cases, these flows require further treatment. No concrete data is available about the cost price of the purification technique itself.
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