Study of Desorption Agent for LADS Process Study of Desorption Agent for LADS Process

Study of Desorption Agent for LADS Process

  • 期刊名字:中国石油加工与石油化工技术
  • 文件大小:790kb
  • 论文作者:Zhang Xiaojing,Qin Ruyi,LIU Ji
  • 作者单位:LPEC Refining Research Institute
  • 更新时间:2020-11-10
  • 下载次数:
论文简介

Advances in Refining TechnologyStudy of Desorption Agent for LADS ProcessZhang Xaojing; Qin Ruyi; Liu Jinlong(LPEC Refining Research Institute, Luoyang 471003)Abstract: This article refers to the procedure for selection, evaluation and development of the LADS-Ddesorption agent associated with the LADS-A adsorbent used in the non-hydroprocessing adsorptive des-ufurization (LADS) process for FCC naphtha developed by LPEC Refining Research Institute. The LADS-Ddesorption agent can effectively remove the sulfides adsorbed on the LADS-A adsorbent. The saturatedLADS-A adsorbent can be instantly regenerated by the LADS-D desorption agent to recover its adsorptionactivity. The LADS-D desorption agent can not only effectively remove all impurities adsorbed on theadsorbent, but also has strong ability to dissolve the impurities to keep a stable desorption efficiency ofadsorbent to be basically commensurate with fresh adsorbent after extended use.Key words: catalytic cracking; gasoline material; adsorbent; desorption agent; desulfurization; regeneration1 Introductionalso significantly increase the investment in production unitand operating difficulties along with increase in energy con-The LADS process is a patented non-hydroprocessing pro-sumption of the unit. It is very important to look for andcess of desulfrization1-3) through adsorption of FCC gaso-develop a desorption agent that could efctively desorb andline developed by LPEC Refining Research Institute, takingregenerate the deactivated adsorbent for sulfur removal.into account the characterstics of sulfides contained in FCC Hence the LPEC Refining Research Institute in parallel withgasoline in order to avoid the shortcomings of current soliddevelopment of the LADS- A adsorbent for sulfur removaladsorbents. This process adopts the fixed-bed adsorptionhas carried out the selection and investigation of the desorp-unit to adsorb on the adsorbent the mercaptans, disulfides,ion agent that can secure a functional coordination to thethioethers, and thiophenes contained in gasoline in order toadsorbent developed.reduce the sulfur content in gasoline. The adsorbing agentadopted in this process is the LADS-A adsorbent developed2 Experimentalby the LPEC Refining Research Instiute.2.1 Feedstock propertyThe specifics of FCC distillates determine the special fea-tures of organic sulfides contained in the disilates. The prop-The feedstock used in the experiments is the FCC naphtha,erties of organic sulfides contained in FCC ditillates are simi-the property of which is presented in Table 1. .lar to those of the hydrocarbons constituting the FCCditillates. So it is very difficult to find an appropriate adsor-It can be seen from Table 1 that the FCC naphtha is character-bent that can selectively adsorb the sulfides contained in theized by high sulfur and olefin contents and short inductionhydrocarbons, and moreover due to strong adhesion of sul-period. The result of ASTM ditllation shows that the tem-fides on the solid adsorbent the resins are also adsorbed onperature at which 30% is recovered is 53"C, and 50% of frac-the solid adsorbent and cannot be recovered by conven-tion is recovered at 70'C, and the EBP is 159C. The gasolinetional desorption method. Application of once -through ad-fraction is quite light, whereas the content of existen gum issorbent is not practical and uneconomical. Regeneration of中国煤化工have derimental efetsaturated adsorbent through frequent coke buning wouldMYHCNMHG31China Petroleum Processing and Petrochemical TechnologyNo.4, December 2003Table 1 Property of FCC naphthathe desorption agent for adsorptive desulfurization is 700 mmItemDatahigh with an inner diameter of 28 mm. The heighudiameterDensity, kg/m3707.1 iratio of the adsorption tower is 25:1, and the tower is flldCopper strip test (50C, 3h), classlaiawith 300 grams of the LADS-A adsorbent. The adsorber, de-Existent gum, mg./100mL15sorption tower, and fumnace for feed oil and desorption agentSulfur, ppmare all heated by external heating source with temperaturesMercaptan sulfur, ppm0controlled by smart meters. The sketch of process flow dia-Nitrogen, ppm55gram is shown in Figure 1. The feed oi after being measuredInduction period, min104by electronic balance is routed through oil pump into theRON924furnace and is heated to the required temperature prior toDisillation,Centering the adsorber overhead for adsorptive purification,IBP24where the sulfides with strong polarity are retained on the10%/30%42/53adsorbent predominantly, and the refined oil not retained by50%170%70/ 104the adsorber is delivered from the tower bottom and is col-90% /EBP135/159lected after condensation and cooling. The adsorption pro-| Hydrocarbon group analysis, v%cess terminates after the adsorbent is saturated and the sys-Saturates35.4tem is switched to the intermediate purging stage, which canOlefinssweep the feed oil and refined oil (alled aggregately as theAromatics11.8intermediate oil) remaining on the surface of adsorbent, in thevoids between adsorbent particles, and in the space of2.2 Test equipment and test methodadsorber. Nitrogen or dry gas can be used as the purginggas. Then the desorption agent to be asessed after beingThe pilot-scale adsorber for screening and investigation of measured by electronic balance is routed into the furnaceand is heated to the required termperature prior to entering theadsorber/desorption tower where the desorption test is car-ried out. The impurities removed from the adsorbent are col-lected after condensation and are called the desorbed liquid.After termination of desorption the purge gas is used to sweep515日the desorption agent remaining in the adsorber bed to com-bine with the desorbed liquid.. The adsorbent after beingsubjected to desorption and purging then takes part in thenext cycle of adsorption test. The operation is then repeated.The sulfur content in the purified oil treated by fresh adsor-bent and regenerated adsorbent can be used to determine the4desorption capability of the adsorbent under assessment.11i3也3 Selection and Development of Des-orption Agent for LADS ProcessFigure 1 Process configuration of test unit3.1 Selection of desorption agent for LADS1,2,3, 6, 7- Condenser, 4- Cross valve; 5- Adsorber;,process8, 9一0il/desorption agent fumnace; 10, 11- -Oildesorp-tion agent pump; 12, 13- Oil/desorption agent feedingToc中国煤化工ADS-A desufurizar.tank;14 - -Purge gas tank;15- Purge gas flowmetertion:YHC N M H Gydrogen, light disel32Advances in Refining Technologyfuel, rffinate from reformer gasoline and the LADS-D des- gasoline could not be fully regenerated by steam in the courseorption agent were investigated on their desorption efciencyof desorption. The adsorption activity and service life of ad-with the results presented in Table 2. It can be seen from sorbent would be gradually slackened after repeated adsorp-Table 2 that the desorption ability of nitrogen, hydrogen, tion and desorption, resulting in a sharp drop in service life oflight diesel fuel, and raffinate from reformer gasoline was adsorbent. However, the LADS-D desorption agent not onlyworse, whereas steam and the LADS-D desorption agent had has good ability to remove impurities, but also has excellentexcellent desorption ability. Tests have verified that the ad- ability to solve the impurities. Hence the LADS-D desorptionsorbent after having adsorbed the existent gum contained in agent is selected as the dominating desorption agent neededby the LADS process. The property of theTable 2 Effect of different desorption agents to restore theLADS-D desorption agent is presented inability of the LADS-A desulfurization adsorbentTable 3.Sulfur content in refined product, ppmItemFresh LADS-A RegeneratedLADS-A3.2 Investigation on consumptionLADS-D desorption agent180: 180of desorption agent for LADSSteam250processNitrogenHydrogen70It is necessary to reduce the consumption ofLight diesel850desorption agent as far as possible while se-Raffinate from reformer gasoline801200curing the product quality, because the con-sumption of desorption agent is one of the important con-Table 3 Property of LADS-D desorption agentsumption indicators of the adsorptive desulfurization process.The infuence of the LADS-D desorption agent consumptionItermDataon the desorption efficiency is presented in Table 4. It can beDensity, kg/m3780.0-810.0seen from Table 4 that after desorption for 60 min at a spaceBoiling range,“60-80velocity of 1.0 hr', over 85% of sulfides (based on the totalKinematic viscosity (20"C),mm2/s0.60--1.20sulfides removed) had been discharged from the adsorbent,Table 4 Investigation on consumption of LADSDD desorption agentDuration of effluent fromRelative amount of sulfur (based ondesorption cycle, mins, ppmtotal sulfur removed), %; Desorption agent /adsorbent mass ratio| 0--1552.260.3615- -3082467380.6130-4555977.620.8645- 6044085.691.1160- -7527390.691.3675- 9019694281.6190- -10512396.541.86105--1209698.312.11120--1352798.802.36| 135- -1502299202.61150- -16599.602.86| 165- -180<22100.003.11Note:adsorption temperature..80C ;desorption temperature: 70C;中国煤化工; space vlocityof desorption: 1.0 h'.YHCNMHG33China Petroleum Processing and Petrochemical TechnologyNo.4, December 2003whereas about 95% of sulfides had been purged from the average sulfur content in refined gasoline reaching 210 ppm.adsorbent after desorption for 90 min. Further increase in When 100- 400 adsorption/desorption/regeneration cyclesdesorption duration could not apparently enhance the des- were conducted, the average sulfur content in refined gaso-orption eficiency. Thus the consumption of desorption agent line reached 320 ppm. When 400- - 1000 adsorption/desorp-at a desorption duration of 60- 90 min (with the ratio of des- tion/regeneration cycles were conducted, the average sulfurorption agent/adsorbent equating to 1.1- -1.61) is appropriate. content in refined gasoline reached 380 ppm. It is evidentthat the LADS-D desorption agent has excellent ability to4 Investigation of the LADS-D Des-desorb and regenerate the LADS-A adsorbent and make theorption Agent Used in the LADS Pro-adsorbent retain a stable sulfur removal efficiency after ex-cesstended service.Table 5 lists the results of investigation on the desorption Since a definite amount of existent gum is contained inperformance of the LADS-D desorption agent used in the gasoline, this kind of existent gum is also retained on theLADS process. It can be seen from Table 5 that tests on adsorbent in the course of application of the adsorbent. Con-desorption and regeneration of the LADS-A adsorbent for ventional method can hardly remove this gum from thesulfur removal were conducted in the presence of the LADS- adsorbent, which can affect the desulfurization efficiency ofD desorption agent. When 1000 adsorption/desorption/re- the adsorbent. Frequent coke burning and regeneration ofgeneration cycles were conducted, the LADS-A adsorbent the adsorbent must be applied to keep the high eficiency offor desulfurization still kept a relatively high adsorptive ac- adsorbent for sulfur removal, resulting in an increase in equip-tivity in termns of sulfur removal. At an adsorption tempera- ment investment and operating cost. Application of the LADS-ture of 80C, a desorption temperature of 60C, a space veloc-D desorption agent can not only remove the sulfur com-ity of 1.0 h', an adsorbentoil mass ratio of 1:1, and an adsor- pounds retained on the LADS-A adsorbent, but also canben/desorption agent mass ratio of 1:1, one hundred ad- effectively remove the gum on the adsorbent, which is thesorption/desorption/regeneration cycles had resulted in an key to sustain the high efficiency of adsorbent in terms ofTable 5 Investigation on the performance of the LADS-D desorption agent used in LADS processNumber of adsorption/desorption/regeneration cycles I0--100100- 400400- 1000Material distribution, %91391.6919Refined oil5.05.75.9Intermediate oil3.73.0Desorption oilProduct (refined oi)propertyContent of desorptionagent,%0.72: 0.68。0.6Density, kg /m'698.1! 699.46999Refractive index, mD201.40401.40411.4043S, ppm210320380N, ppm6RON: 92292.592Hydrocarbon group analysis, v%Saturates36.936.736.5Olefins53.853.9Aromatics93949.6Note:adsorption temperature: 80C ;desorption temperature: 70C ;spa中国煤化工space velocity ofdesorption: 1.0 h';adsorbentoil mass ratio=1: l; adsorbent/desorptioCNMHG34Advances in Refining Technologysulfur removal. It can be seen from Table 5 that the adsorp- adsorbent is basically equivalent to that of fresh adsorbent.tion performance of the adsorbent is commensurate with thatof the fresh adsorbent after successive 1000 cycles of ad- (3) Since the LADS process operates at low temperature, the .sorption/desorption/regeneration procedures. Thus the fre- coke buildup on the adsorbent is relatively small. Thequent coke burning of the adsorbent can be avoided to re- LADS _D desorption agent can fully restore the activity of theduce the investment in the LADS process and related operat- adsorbent, resulting in avoidance of adsorbent regenerationing cost.through coke burning to reduce equipment investment andoperating cost.5 ConclusionsReferences(1) Results of study on the effect of consumption of the [1]Zhang Xiaojing, Qin Ruyi, Liu Jinlong, et al,“New Non-LADS- D desorption agent on desorption efficiency have Hydroprocessing Technology for Desulfurization of FCCshown that about 85%- 95% of total sulfur can be released Naphtha", Petroleum Refining Technology and Engineering,from the adsorbent if the amount of the desorption agent 20.31),11-14.1usedis 1.1-1 .61 times the adsorbent applied.[2]Zhang Xiaojing, Qin Ruyi, Liu Jinlong, et al, "Technologyfor Desulfurization of FCC Naphtha- -The LADS Process",(2) The LADS-D desorption agent can not only efectively Natural Gas and Petroleum, 2003,21).39- 41.desorb the impurities adsorbed on the adsorbent, but also [3]Zhang Xiaojing, Qin Ruyi, Liu Jinlong, et al,“Study onhas strong ability to dissolve the impurities so that the adsor- Process for Desulfuization of FCC Naphtha", Petroleum Pro-bent is fully regenerated and the desulfurization ficiency is cessing and Petrochemicals,2003, 34(3), 24 -27.maintained at a stable level. The property of the regenerated800 kt/a Ethylene Revamp Project inMaoming Approved by the StateThe 800 kUa ethylene revamp project at SINOPEC Maoming to 800 kta, and increase its synthetic resins output from 440Petrochemical Branch Company has been approved by the kt/a to 1.02 Mt/a. The total amount of marketable productsState Couneil. The total investment in this project, which will increase from the original level of 1.10 MUa to 2.30 M/acovers three grassroots units and seven revamp units, is ex- to boost the annual sales revenues from 5.0 billion RMB topected to reach 4.354 bllion RMB.more than 10 bllin RMB coupled with the incremental out-put value resulted from ethylene after-processing to stimu-The three grassroots units include a 420 kUa steam cracking late the development of regional economy. Currently theunit, a 350 kt/a HDPE unit and a 200 kt/a PP homopolymer preparations for this revamp project are taking place at fullunit. The revamped facilities include the pyrolysis gasoline steam, and the overall design will be completed by the end ofhydrotreating unit, the aromatics extraction unit, the LLDPE this year. The construction work will be ofiallyl commencedunit, the butadiene extraction unit, the glycol unit, the MTBEin the second quarter of 2004, and the construction projectunit and the 1-butene unit. After completion of construction will be handed over to the owner for comissioning in theof these revamp and grassroots units Maoming Petrochemi- first quarter of 2006.cal Company will expand its ethylene capacity from 380 kta中国煤化工MHCNMHG35

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