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Module 1: Impurità e Residui

    Study Reminders

    Hi friends, now we will discuss on the residue upgradation part.In the previous lecture, we have discussed on the removal of sulphur, nitrogen and metalsfrom the liquid fuels.Now we will concentrate how the vacuum residue or the residual part can be upgraded to liquidfuels through different upgradation routes to make the product and the process more cleaner.So, the content of this topic, Petroleum residue and its upgradation then residue Upgradationroutes, the solvent deasphalting.Visbreaking, delayed coking and gasification.So, these are different routes which are normally used.In this class we will cover up to solvent deasphalting and the rest will be coveredin the next part.So, now, we know that when we process petroleum crude in the atmospheric distillation, itlefts some residue.And then that atmospheric distillation column residue is processed in vacuum distillationcolumn and again vacuum residue is formed.And so what we are getting crude oil then atmospheric residue and then we are gettingvacuum residue.So, if we go from crude oil to different ratio, then we see the quality is degraded.So viscosity increases, sulphur increases, nitrogen increases, asphaltenes increases,H/C ratio decreases and API decreases, CCR increases.So, this clearly indicates that the quality of VR is much poor than the crude oil andrefinery is not that much interested with this VR to properly manage it, because thisof low value or negative value product for them.So, we need to convert these VR, so that the; it will be managed properly, and environmentalpollution will be reduced.On the other way, the refinery can also add some value addition to the whole process.So, from this table, it is clear to us that residue is having higher viscosity, high sulphur,high average boiling point and, H/C ratio is low and CCR is high.So if we want to upgrade it, obviously, the scope is there, we have to improve the hydrogenH/C ratio.So H/C ratio we need to improve.So for doing this, there are number attempts, people tried to do it, and like say solvent,deasphalting, and then thermal processes, hydro treatment etc.So now we will see, what, how the solvent the deasphalting and other process will helpto improve it.And to understand that, we have to understand the residue, what the residual oil is?So, Residual oil is a high viscuous oil, in which we have asphaltenes and resins as wellas some oil part.So oil part is called say Maltenes says one here.So, this is a maltene part, this is the emulsion.In this emulsion, we are getting asphaltene and resins in the disperse state and in thecontinuous phase we are getting the Maltenes.Now, if we can remove asphaltenes and resins from this whole system, then we can get themaltenes which is desirable and we can recover that oil for our applications.So, how we can do it?Obviously, because the presence of these asphaltenes and resins and other presence of metals arealso there.So, it gives here higher viscosity and higher salt content, higher heavy metal content,higher sulphur and nitrogen content and higher naphthenic acid content.So, this content, this is the properties of this now, we need to remove these things,the asphaltenes from this.So, how it can be done?We can use some solvent.So, that solvent will take these maltenes from this whole emulsion and it will be brokenand some maltenes can come to the solvent.So that is one way of solvent deasphalting.Otherwise you can apply thermal heat here.So, heat will break or crack the molten molecules and after a certain extent of cracking thisemulsion may break and then that broken emulsion under the conditions the asphaltenes can beseparated from the oil.And hydro processing can also take place to hydrogen addition.So, this maltenes will be converted and then this will be separated.So, these three major routes which can be applied for the removal of this asphaltenesfrom the maltenes and to get pure quality oil from the residual part.So, on the basis of this, the methods which are developed one is solvent deasphaltingand there is thermal conversion based process that is cracking and gasification and hydroprocessing based process, hydro cracking.Now, thermal and hydrocracking maybe catalytic or non catalytic type and some thermal crackingroutes are visbreaking, delayed coking, fluid cooking Flexi coking, hydro visbreaking donorsolvent cracking and hydropyrolysis.So, these are the different routes people have applied for the upgradations of the residue.So, the total upgradation technologies we can classify into three major category.One is hydrogen addition method, another is carbon rejection method and another is theother method.So, in hydrogen addition method, we add hydrogen.So, hydro desulfurization and hydro cracking these are two and different types of reactorshave been used that is fixed bed, ebullated bed and slurry bed reactor.Now the carbon rejection method, one is thermal cracking, catalytic cracking and solvent extractionswe can apply.So, these thermal cracking visbreaking and delayed coking and coker, it is mentionedhere and catalytic cracking FCC, RFCC.Residual Fill Catalytic cracking, FCC is fluid catalytic cracking RFCC, residual fill catalyticcracking and solvent extraction also that will reject carbon.So, carbon rich molecules are settled in the extractor.So, when get separated later on, so, then other techniques are the gasification.So, these are different techniques.Now first we will discuss this one solvent deasphalting process.Before that, we see around the world what type of techniques are used?And if you see this figure, coking is mostly use that is 40.29% then, visbreaking or crackingthat is 33.89%, the you see here hydrotreating and then hydro cracking and then the deasphaltingis 3.62%.So, these are different technologies which have been applied around the world to upgradethe residual part.So, now, we will be conducting this one.Before that we will see how we can select this technology which is always selected forwhat type of feedstocks.This slide shows with reference to some properties of 343 degrees centigrade residues.So, various crudes if we take and then we can measure the nickel and vanadium and wecan measure the CCR.So, carbon residue, CCR carbon residue Condensed Carbon Residue and nickel and vanadium concentration.Both amounts can guide us what process will be more suitable.So if more metal is there then more carbon is also there, we can go for carbon rejection.So these are carbon rejection zone metal is also more and carbon is also more.But if we have carbon is less, metal is also less, we can go for fluid catalytic crackingand hydro processing range are the, in between one or more preferable.So this way we can select a particular route which will be more suitable for a particularfeedstock.Now we are coming to solvent deasphalting.So, the term itself says the solvent de asphalting.So, we will be adding some solvent so maltenes will come into the solvent and asphalt willbe separated from the feedstock.So, that is the main objective.So, vacuum residue we are using in the SDA process.So, so, asphaltene will be separated at the bottom.So, we are getting asphaltene so pitch we are getting and then solvent plus oil.So that is called deasphalted oil.So, after the deasphating the oil which are getting that is deasphalted oil plus solventis coming here.So that can be used for different FCC for further purification or improvement of quality.FCC, Hydro crackers, Thermal cracking, as a Lubes, we can use it as a lube base stock.And pitch or asphaltene spot which you are getting that can be used for Bitumen or roadmaking that can be used in circulatory fluidized based combustor for power production or steamgeneration.And that can also be gasified, and that steam gas can be used for power applications forSteam, or production hydrogen production petrochemicals or as the fuel itself.So, these are the overall concept of solvent deasphalting process.Now we will see this flowsheet which explains this SDA process.So here we are getting feed then feed has to be mixed with some solvent.So solvent we are getting initially we add then we get the recovered solvent.So, solvent plus feed we are mixing here.So it is going to extractor.Extractor has certain conditions: temperature pressure is maintained and RPM etc propermixing is provided.Then we get to phase.It is allowed to settle we get two phases.One phase we are getting asphalting phase as it is going there and then heat recoverytakes place and then it is coming to pitch stripper.So we get pitch here so again some flashing tap arrangement so it is coming here and thenflashing we are getting some liquid part, if solvent comes here, so that can also goesoff and it is coming here and then it is going to mixer and condenser.After condenser this solvent is recycled.And here we are getting the pitch which we are having.And from the extractor, the upward deasphalted oil along with the solvent it is going andin it heat exchange is taking place here then it is going to boiler and then DAO separator,so DAO and deasphalted oil and solvent.We have to separate it now solvent has boiling point and deasphalted oil components alsohave boiling point.So those are not similar so if we apply heat and then the solvent will be in vapor phasethat we can go there and it can mix here and can be added here extractor.And then deasphalted oil along with some solvent it comes then it will be coming to here.So deasphalted oil will be separated in the stripper section and then solvent will alsobe come through these routes and then it will be recycled.So solvent is this it can from the bottom is also recycled, recovered and recycled andfrom the DAO separator also solvent is recycled and is recovered and recycled.So that way a solvent is recovered and recycled.That recovery of solvent is very, very important.Now people have used two routes for its recovery, what is use of evaporators, sequential andthen another is the operation separation of solvents at supercritical conditions of thesolvent.So DAO plus solvent this mixture is it is heated to supercritical conditions of thesolvent and then solvent is recovered from it and in that process the efficiency is more.So, now, we will be making some discussion on that line.Before that, we will see the properties of the solvent and the deasphalting solvents.So, what can be the good solvent obviously, the liquid hydrocarbons, low molecular weighthydrocarbons.Like say propane, it may butane, it may be pentane.So, normally it may be hexane also, but normally, these propane, butane and pentane have beenreported in literature and have been used for the separation.So, once we use low molecular weight hydrocarbon, then the maltene part which will come to thisbecause the density is less here, all the asphaltenes will be removed.And lighter solvent propane and isobutane that are the higher selectivity that theyare having and reject all resins and asphaltenes suitable for production of lube oils.And heavier solvents we use pentane and n-butane, then light naphtha can also be used in thatcase less selective than lighter solvents and then produce higher yields of DAO andDMO.So, Deasphalted oil production is higher.So produce higher yields of DAO, so if we use more butane and pentane, it will be ableto take more maltenes because its condition changes, it takes it operates at higher temperature.So high temperature means more maltenes can come here.So now we will see the general properties of the solvents.So, solubility of oil decreases with the increase in temperature, then more selective at highertemperatures exhibit lower critical solution temperature.So, lower the critical temperature that recovery part will be easy.Now, process variables for this process so what is the, we are interested to get theoil part from the residue?So, solvent, how much solvent we are using that will play a role, solvent to feedstockratio and the solvent composition, solvent to feedstock ratio.So selectivity improves by increasing solvent to feedstock ratio at constant DAO yield.And economically, we have to optimise it.Obviously if we say more solvent, more purity of the product will get and but we have tooptimise about with the economy and the solvent composition blends of light hydrocarbon solventcan be used and then its increased operating flexibility.If we use the blends, then flexibility will increase and temperature also important becausethis temperature gradient will help the transfer of the oil phase from the residue to our solventwhile solubility in solvent decreases with increase in temperature and temperature gradientimproved separation between DAO asphalt phases.And pressure also maintained above the vapour pressure of the solvent.Now, we will see the comparison of some solvent and that DAO and deasphalting process.So, so, if we have some SR that we have, we have feed then we have propane, we have propane,butane or we have butane we have pentane.So different solvents we are using in the deasphalting process, then will be gettingDAO as well as you will be getting asphaltenes.Then we will see how the properties of DAO asphaltenes are changing with the variationof this solvents.So, here yield, DAO yield let us say 29% and then we are fine it is propane is used, ifwe use propane butane 46.8, if we use butane against 67.3 if it is pentane then 82.8.So, with the increase in carbon number, we are getting more DAO.We are getting more DAO but the same time we will be getting lower quality.So, higher solvent recovery is possible here higher oil recovery is possible by this way.And then but the quality you see the API gravity is decreased here 21, here 16, here 12.1,here 10.3.So, we are getting more oil, but we are compensating we are compromising with the quality, we areusing higher carbon number in the solvent.So, viscosity is also similar way increases.That means more oil is coming to the solvent.And then CCR, it also increased and the oil part which is coming to the solvent are havinghigher carbon than its so that is why CCR has also increased in this case.And sulphur content also increased because the bottom which is going to the VR that iscoming to the DAO part that is why sulphur is also increasing.The metal content is also increased with the increase of the carbon number in the solvent.Then we see this asphaltene then also softening point, if we see softening point increasesand then penetration point decreases.It is not that soft.So penetration is not possible in this case.And specific gravity also increases.Why it is?Because more denser particles or molecules are coming to the DAO part with their useof heavier hydrocarbon or hydrocarbon with more carbon number.So, this is the comparison of different types of solvents when it is used for deasphaltingpurpose.And now we will compare the about the operating conditions if we use propane, butane and pentane.Then extraction temperature is different for propane it is 50 to 80, butane it is 100 to130 and pentane is 170 to 210.So that is one reason why we are getting more heavier part in the in the in the solvent,in the DAO part and then pressure range we are getting 3.5 to 4 mega Pascal, in caseof propane, Butane is 4 and pentane is 4.And solvent ratio is higher.So butane solvent ratio is lesser, Pentane is further lesser.So higher the solvent than the feedstock higher solvent to feedstock ratio will be gettingmore pure quality product or better quality product so that propane when we use, then,we can use the feedstock for lube oil based off production.Then we are coming to solvent recovery.So evaporative mode and supercritical mode already we have discussed.So, in case of you have evaporative mode we can use multiple effect evaporation up tothree stages and series of progressively lower pressure flashes followed by stripping.Just in the flow sheet also we have seen some stripping is there, flashing was there andthen stripping was there.So, supercritical mode if it is used then it becomes more energy efficient say phaseseparation at above critical temperature of solvent above critical temperature up or atthe critical temperature solvent can is possible and 85 to 90% solvent recovered as lighterphase for heat exchange and recycle in the process and recovered solvent has very lowDAO content, that the purity of the recovered solvent is higher if we use the supercriticalmode of operation.And then, remaining solvent from DAO is recovered by flashing and stripping.So, solvent recovery is higher quality is higher, but we have to optimise with the costalso economic factor also.Now, we see the comparison of different process.If Supercritical unit Triple effect evaporator, double effect evaporator and single effectevaporator, if we use single effect that 280 unit say energy cost and it is double it is170 triple effect 150 and for supercritical 100.So, if we use supercritical unit, the relative energy cost is less and it also more energyefficient approach and utilities saving up to 40% with heavier solvents, more compactunit, this one and savings in capital investment for grass root plants is 15 to 25%.So, this is the advantage of applying super critical condition.Now, we will discuss on deasphalting tower for the extractor which we had in this caseextractor.So, here we can get some internals.So, column internal internals may be Baffle trays, it may contain rotating disc contractor.It may have packing or it may have parallel interceptor plate.So, these different types of options are available.So, baffle plates baffles are, mostly used in PDA plants in India and that RDC and PIPthat UOP and foster wheeler, they offer the choice for the PIP or RDC.And structure packing used for rose units that is called residual oil supercriticalextraction unit ROSE unit.So, currently used in all ROSE units are packing.And the advantage of this is that better quality of DAO and higher circulating solvent purity,higher capacity for existing solvent deasphalting units and the lower operating cost.And PIP assemblies if it is used that I have mentioned that UOP and foster wheeler hasgiven their options which are PIP or rotating disc contractor.But it has some advantage that PIP has some advantage that increased separation efficiencyand reduce size of extraction vessel and reductions in the capital and operating costs.So, these are the comparison of different deasphalting design column design.Now we will see the processing of DAO and asphaltene.So, what we can do with the DAO and asphaltene.So, once we can get DAO we can get lube oil and lube production increased by approximately20% and that due to the use of this deasphalted oil and cracking one third of catalytic crackingfeed in a refinery can be of DAO and hydro cracking economical consumes less hydrogenless investment.So, we see that that if we can produce DAO so that can improve the economics of the plantalso because it will give more products which are available in market.Then asphalts can be used as a blending, it can be used as a bitumen or fuel oil or roadmaking and it can be going to visbreaking so that many ways minimise the need of cutterstock and then it can be gasified also.Here, we will see some technology licences.So, if we Kellogg brown and root, they are giving the technology rose, residuum oil supercriticalextraction.And more than 33 supercritical units are used in commercial scale with this capacity.And UOP, Foster wheeler solvent deasphalting process, they are also 50 units and IFP Francethere are 7 unit and then IIP Dehradun and EIL in India they have 2 conventional plantsand RIPP China they have 5.So, these are some basis of 2002 data also it is a very old data, but Exxon Mobil offersPDA technology.So, in India we are having the conventional PDA technology.And we will see the what that PDA is Propane deasphalting.Propane Deasphalting use propane as a solvent for the removal of asphalting from the vacuumresidue or any heavy lube oil base stock can be produced from this process.And cylinder oil can also be produced and the operating condition is 50 to 80 degreescentigrade and 6 to 10 solvent to feed ratio and pressure more than the vapour pressureof the propane.So, these are the conditions.And we see the IOC Haldia, CPCL and HPCL.They are producing DAO with this quality the kinetic viscosity and CCR.So, these values are provided here.So, obviously, you see the viscosity is reduced and the CCR is also reduced.So, by this process and good amount of DAO is recovered from the vacuum residues whichare cleaner in nature.Now, we see the propane deasphalting status.So we shall see HPCL, Mumbai, CPCL, Chennai, IOC Haldia.So, their capacity is this 5,48,000 MMT per annum and for this CPCL it is 5,74,000 MMTper annum and this is for 6,50,000 MMT per annum.And these are the technology licenser IIP/EIL and this is in case Romanian, expansion byEIL, ROSE.So, these are the some deasphalting technology which is implemented in the country.So all plants produce Lube oil based stock and solvent recovery, evaporation mode orsupercritical a supercritical mode, IIP and EIL have developed a knowhow on this process.So, so far we have discussed on the Solvent deasphalting part and next class we will discussthe other part of the vacuum residual Upgradation.So thank you very much for your patience.