continuous continuous form ongoing separation mixture continuously fed process separated removed continuously output streams separation partial separation liquid feed mixture components selective boiling process produces output include volatile fraction boiled separately captured condensed liquid practically bottoms fraction volatile separately captured condensed alternative continuous batch mixture added unit start taken time remaining bottoms fraction removed end taken different times exit point location needed batch switched different receiver fraction collecting container batch smaller quantities continuous fraction streams taken simultaneously operation separate exit point needed fraction practice multiple exit points located different heights column bottoms fraction taken column unit taken connected column fraction contain components types chemical compounds crude oil similar fraction contains components similar properties possible run small scale laboratory continuous continuous large scale industrial process industrial application unit operations chemical engineering continuous widely chemical process industries large quantities industries natural gas processing production coal tar processing liquor production air separation production similar industries finds widest application petroleum crude oil complex mixture separated yields pure chemical compounds expected groups compounds relatively small range boiling points called origin term worthwhile separating components based product requirements economics industrial typically performed large vertical cylindrical columns shown images known towers columns ranging centimeters meters heights ranging meters meters principle principle continuous normal liquid mixture heated composition liquid differs liquid composition separated condensed liquid richer lower boiling point component original mixture happens continuous column mixture heated routed column entering column feed starts flowing component lower boiling point rises rises continues enriched volatile component begins descend image depicts simple continuous tower separating feed stream overhead product bottoms product products lowest boiling point highest exit columns heaviest products bottoms highest boiling point exit column overhead stream cooled condensed water cooled air cooled bottoms steam heated hot oil heated heat gas oil fired continuous system kept steady state approximate steady state steady state means quantities related process change time passes operation constant quantities include feed input rate output stream rates heating cooling rates ratio temperatures pressures compositions point location process disturbed changes feed heating ambient temperature steady state normally maintained main attraction continuous apart minimum easily surveillance feed rate feed composition kept constant product rate quality constant variation conditions occurs modern process control methods commonly able gradually return continuous process steady state continuous unit fed constantly feed mixture filled like batch continuous unit need sizable pot vessel reservoir batch fill instead mixture fed directly column actual separation occurs height feed point column vary situation designed provide optimal results method continuous vacuum steam design operation design operation column depends feed desired products given simple component feed methods method equation assist design multi component feed simulation models design subsequently operation column modeling erected columns equipment originally designed continuous column operation closely monitored changes feed composition operating temperature product composition tasks performed advanced computer control equipment column feed column fed different ways feed source pressure higher column pressure simply column feed pumped compressed column feed saturated partially liquid mixture saturated liquid liquid boiling point column pressure sub cooled liquid feed liquid higher pressure column pressure flows pressure let valve ahead column immediately expand undergo partial flash resulting liquid mixture enters column improving separation small size units glass laboratories industrial units large vertical steel vessels images known towers columns improve separation tower normally provided inside horizontal plates shown image column packed packing material provide heat required involved compensate heat loss heat added column purity product improved recycling externally condensed product liquid depending purpose columns liquid outlets intervals length column shown image large scale industrial towers use achieve efficient separation products refers portion condensed overhead liquid product tower returned upper tower shown images inside tower liquid provides cooling partial increasing tower provided better tower separation lower boiling higher boiling components feed balance heating column cooling condensed column maintains temperature gradient gradual temperature difference height column provide good conditions feed mixture flows middle tower called changing combination changes feed product withdrawal improve separation properties continuous column operation contrast adding plates changing packing minimum require significant plates towers images use liquid contacting methods provide required number stages devices commonly known plates plates different temperature pressure stage tower highest pressure temperature progressing upwards tower pressure temperature decreases succeeding stage liquid feed component tower unique way different pressure temperature conditions stages means component establishes different concentration liquid phases stages results separation components example depicted image detailed expanded image seen theoretical plate article acts additional stage physical plate efficient number physical needed given separation equal number stages theoretical plates seldom case column needs plates required number theoretical liquid stages packing way improving separation column use packing material instead offer advantage lower pressure drop column compared plates beneficial operating vacuum tower uses packing instead number necessary theoretical stages determined packing height equivalent theoretical stage known height equivalent theoretical plate determined total packing height required number theoretical stages multiplied packing material random dumped packing rings structured sheet metal tend wet surface packing pass surface mass transfer takes place unlike conventional represents separate point liquid liquid curve packed column continuous modeling packed columns useful number theoretical plates denote separation efficiency packed column respect traditional differently shaped different surface areas void space factors affect packing performance factor addition packing shape surface area affects performance random structured packing liquid distribution entering packed bed number theoretical stages required given separation calculated specific liquid ratio liquid evenly distributed superficial tower area enters packed bed liquid ratio correct packed bed required separation achieved packing appear working properly height equivalent theoretical plate greater expected problem packing distribution entering packed bed liquid distribution frequently problem design liquid distributors introduce feed packed bed critical making packing perform maximum efficiency methods evaluating effectiveness liquid distributor found references overhead system arrangements images assume overhead stream totally condensed liquid product water air cooling cases tower overhead easily condensed totally drum include vent gas outlet stream cases overhead stream contain water feed stream contains water steam injected tower case crude oil towers oil cases product water drum contain condensed liquid phase condensed water phase non gas phase makes necessary drum water outlet stream examples continuous crude oil petroleum crude contain hundreds different compounds organic compounds organic nitrogen compounds oxygen containing crude generally contain formed processes petroleum crude oil produce products having single boiling point produces having boiling ranges example crude oil produces overhead fraction called gasoline component processed remove reformer reform molecules complex molecules higher rating value cut fraction called contains different compounds initial boiling point final boiling point cut produced columns different boiling range distance overhead cut withdrawn column usually jet fuel cut known cut boiling range cut initial boiling point final boiling point contains different cut tower diesel oil cut boiling range boiling ranges cut cut overlap perfectly sharp come heavy fuel oil cuts finally bottoms product wide boiling ranges cuts processed subsequent processes
Continuous distillation