## center72209Chapter necessary for a gas to be

center72209Chapter 100Chapter 11571171256086Introduction00IntroductionIntroductionLiquefaction of Gases:Change of state of any substance form gaseous state to the liquid state is called liquefaction. As the different states of matter has different quantity of energy of molecules which makes up the substance. So this energy must be given or supplied to or from a substance in order to make its state change. To change the gas to the liquid the heat must be removed. For liquefaction of gases, its molecules must be brought closer because liquids occupy less volume than gases. So, to bring them closer we need to increase the pressure on the gas and lower its temperature to reduce the speed of higher energy molecules. In order to achieve these conditions, we need to know the critical temperature and pressure of the gases.

1Critical temperature:Critical temperature of gas is the temperature which is minimum required to liquefy a gas. The pressure alone will not liquefy a gas until this critical temperature is achieved. It depends upon three factors (size of molecules, shape of molecules & intermolecular forces between the molecules) 1Critical pressure:Critical pressure is the at least pressure which is necessary for a gas to be liquefied at the critical temperature. 1Critical volume:The volume occupied by a unit mole of the gas at its critical temperature & critical pressure.There are generally four methods adopted to liquefy a gas , which are following:CompressionMaking a gas work against an external forceJoule Thomson effect1Purification of gases:The process in which the impurities from industrial gaseous streams are removed is called purification of gases. The impurities are needed to remove because they not only pollute the atmosphere but also disturbs the efficiency of the production process. Generally the purification methods are: Mechanical, Electrical & physiochemical methods. Mechanically, by centrifugal force, scrubbing the gas with water, by filtration through fibrous & porous material.

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Electrically, by action of forces of high voltage, non uniform electric field like electrical filtersPhysiochemical, for removal of gaseous impurities by scrubbing with solvent (absorption), by chemical absorption, by adsorption, physical separation2History of Purification & Liquefaction of gases:Initial work on the liquefaction of gases was done by English scientist Michael Farady in the initial era of 1820. He liquefied gases at high critical temperatures like chlorine, carbon dioxide, hydrogen bromide and hydrogen sulfide by utilization of pressure only. After this era the scientist found other ways to liquefy the gases.

Then in 1869, Thomas Andrews found that every gas has a specific temperature which is its critical temperature, which is minimum required to liquefy it, without the consideration of pressure applied on it. That’s why it is necessary to cool the gas lower to its critical temperature to liquefy it. Before the start of 19th century many scientists had performed experiments on this process. The first to achieve the success were, Davy ; Farady. The mass production of liquefied gases in bulk quantities was done by efforts of Z.F.Wroblewski ; K.

S.Olszewski, the two well-known scientists. Sir James Devware has performed liquefaction of air. Many advanced processes of liquefaction of gases were developed by Lind and many others gave the basic information that is now used in advanced refrigeration systems.

Importance of LiquefactionLiquefaction is a process in which gas or solid is converted into the liquid form. Liquefaction is of great importance in many industrial and chemical processes. Many important gases are converted to liquid form which are used in wide range of useful applications. One of the major use of liquefaction is the liquefaction of air to separate it into its constituents like oxygen, nitrogen and other noble gases. It also finds its application in conversion of hard coal into a liquid form which then used as a replacement to liquid fuels. Liquefaction is also very useful in analysis of basic properties of gas molecules like intermolecular forces. It is used on large scale for storage of gases and for their easy handling as well.

Many important gases are liquefied on vast scale for special purposes like liquid oxygen is used in hospitals for artificial respiration, liquid nitrogen is also used utilized in cryosurgery. Liquid chlorine is vastly used in purification of water, sanitation of industrial wastes, sewage and swimming pools, in pulp bleaching and textiles and manufacture of carbon tetrachloride, glycol and numerous other organic compounds as well as phosgene gas. Liquefied carbon dioxide is also used on large scale in food and beverages and also in oil refinery for extraction of more quantity of crude oils and has many used in food industry.History of Carbon DioxideCarbon dioxide (CO2) was the primary gas to be represented as a distinct substance. In regarding 1640,3 the Flemish chemist Baptist van Helmont discovered that once in a closed vessel he burned charcoal, the mass of the ensuing ash was abundant lower than that of the initial charcoal.

His conclusion was that the remainder of the charcoal had been transfigured into imperceptible substance he named a “gas” or “wild spirit”.4 The possessions of carbon dioxide (CO2) were studied carefully in the 1750s, by the J. Black, carefully found that the limestone (calcium carbonate) could be treated with acids to produce a gas, called “fixed air.” He experiential that the fixed air was denser than air and supported neither flame nor animal life. He also carefully found that when it bubbled through limewater, it precipitated in CaCO3. Utilized this wonder to demonstrate that CO2 is yielded by animal respiration and microbial fermentation. 5 In 1772, Chemist J.

Priestley from England, printed a paper authorised Impregnating Water with fastened Air within which he delineates a method of dripping acid on chalk so as to provide dioxide of carbon, and forcing gas to dissolve by provocative a bowl of water in touch with the gas. 6 CO2 was 1st liquefied (at elevated pressures) in 1823 by H. Davy and Faraday. The earliest description of solid CO2 was given by A.

J. P. Thilorier, who opened a controlled instrumentation of liquid CO2 storage in 1835, solely to seek out that cooling made by quick evaporation of liquid produces a “snow” of solid CO2. Union Carbide and Dow Chemical produced inhibited, thirty wt.

% MEA solution processes for efficient recovery of CO2 present in gases in 1970’s and 1980’s mostly for EOR (Economical-Oil-Recovery) marketplace. As rate of crude oil fall abruptly in 1986, EOR market vanished, these licensors died out. In 1989, Dow Chemical, sold its GAS/SPEC FT1TM Technology to “Fluor Daniel, Inc.” 7World’s utmost unconventional and complete industrial programs of R&D (started in 1990 and continuing) by “Mitsubishi Heavy Industries, Ltd”. MHI’s patented CO2 capturing from flue gas technology commercially practical since 1999. 8Physical Properties of Carbon Dioxide1160007560693300StructureThermochemistry Critical PointTriple PointCO2 Normal LevelCO2 Levels-Dangerous and ExtremeApplication of CO2 Chemical’s Precursor In Industry, CO2 is for the most part devoured as a fixing in generation of CH3OH and urea. Few carboxylic-acids subsidiaries (e.g.

, sodium salicylate), metal bicarbonates and carbonates, set up from CO2. Foods CO2 is sustenance added substance utilized as a charge and acridity controller in food Industries, affirmed for utilization in EU (recorded as E-Number E290), Australia, New Zealand and USA (recorded with INS-Number 290). CO2 pressurization of Pop Rocks, a candy, done at around 580.0 psia. At the point, as set in mouth, breaks down (simply alike other solid confection), discharges gas rises by a discernible pop.

Raising operators make batter ascend by creating CO2. Bread cook’s yeast produces CO2 by maturation of sugars inside the mixture, while substance liveners, for example, preparing powder and preparing pop discharge CO2 when presented to acids or warmed.BeveragesCO2 is utilized to deliver carbonated sodas and pop water.

Customarily, the carbonation in lager and shimmering wine occurred through common maturation, however numerous makers carbonate these beverages with CO2 recuperated from the aging procedure. On account of packaged and egged brew, reused CO2 carbonation is the most widely recognized strategy utilized. Except for British Real Ale, draft lager is normally moved from barrels in an icy chamber or basement to apportioning-taps on bar utilizing compressed CO2, once in a while blended with N2Wine MakingCO2 as dry ice is regularly utilized as a part of the wine making procedure to chill off packs of grapes rapidly in the wake of picking to help avoid unconstrained maturation by wild yeast. The primary favourable position of utilizing dry ice over customary water ice is that it cools the grapes without including any extra water that may diminish the sugar fixation in the grape must, and subsequently likewise diminish the liquor focus in the completed wine.

Dry ice is additionally utilized amid the frosty drench period of the wine making procedure to keep grapes cool. The CO2 that outcomes from the sublimation of the dry ice tends to settle to the base of tanks since it is heavier than air. The settled CO2 makes a hypoxic situation which keeps microorganisms from developing on the grapes until the time has come to begin the maturation by coveted yeast’ strain. CO2, likewise utilized to make hypoxic situation for carbonic maceration, procedure utilized to deliver Beaujolais-wine.Inert GasStandout amongst most ordinarily utilized compacted gasses for pneumatic (pressurized gas) frameworks in convenient weight apparatuses. CO2 additionally discovers use as atmosphere for welding, despite the fact that in welding circular segment, responds to oxidize generally metal. Utilized in car business, regular in spite of critical, prove by the fact, weld completed in CO2 is extra fragile than that complete in extra inactive environments, and such welds joints crumble after some period on account of Production of H2CO3.

Utilized as welding gas principally on the grounds that it is a great deal more affordable than more latent gasses, for example, argon or helium.Fire ExtinguisherCO2 quenches flame, some fire dousers, particularly those intended for electrical flames, contain fluid CO2 underweight. CO2 quenchers function admirably on little combustible fluid and electrical flames, yet not on normal flammable flames, on the grounds that in spite of the fact that it prohibits oxygen, it doesn’t cool the consuming substances essentially and when the CO2 scatters they are allowed to burst into flames upon introduction to air oxygen. CO2 has likewise been broadly utilized as a smothering specialist in settled fire security frameworks for neighborhood use of particular risks and aggregate flooding of an ensured space. Worldwide Maritime Organization principles additionally perceive CO2 frameworks for flame assurance of motor room and ship holds.

CO2 built fire security framework has been connected to a few casualties, since it doesn’t bolster life in the fixations used to douse fire (40% or something like that), be that as it may, it is not thought to be harmful to people. A survey of CO2 frameworks recognized 51 accidents in the vicinity of 1975, triggering 72 casualties and 145 were injured. Solvent CO2 (Super Critical)Fluid CO2 is decent dissolvable for some lipophilic natural mixes and, utilized to expel caffeine through espresso. CO2 has pulled in consideration in pharmaceutical and substance handling ventures as less harmful contrasting option to extra conventional solvents, for example, organo chlorides. Also, utilized by some laundry. Applications in Biology and AgricultureAt high conc.

(100 times concentration at atmospheric condition, or more prominent), CO2 is lethal to creature life, raising fixation to 10,000.0 ppm or greater for a few hrs will dispose of nuisances, for example, whiteflies and creepy crawly parasites in a Green House-GH. CO2 is utilized as a part of nurseries as fundamental carbon hotspot for Spirulina green growth. For medication, CO2 up and about to 5.0 % (130 times concentration at atmospheric condition) is mixed with O2 for incitement of breathing after apnea, to balance out CO2/O2 adjust in lifeblood. Recommended that CO2 from control era be risen to lakes, to develop green growth, later changed over to biodiesel-fuel.

Recovery of OilCO2 is utilized for EOR, give a jab into producing-oil reservoir, typically underneath supercritical-conditions. This sort of generation can expand unique oil recuperation by 7 for every penny to 23 for each penny promote from essential extraction. It goes about as both a pressurizing specialist and, when disintegrated into the underground raw petroleum, essentially decreases its thickness, empowering the oil to stream all the more quickly by earth to evacuation well. For develop oil fields, broad pipe systems are utilized to convey CO2 to infusion focuses. RefrigerantSolid and Fluid CO2 are essential refrigerant, particularly for food industries, where utilized amid capacity of dessert, transportation and other solidified sustenance.

Solid CO2 is named “dry ice”, utilized for little shipments, wherever refrigeration hardware is costly. Strong CO2 is dependably underneath ?78.5 °C, at customary pressure(atmospheric), paying little mind to the air temperature. Fluid CO2 (industry classification R-744 or R744), utilized as refrigerant preceding disclosure of R-12, may appreciate renaissance because of way, R-134a adds to environmental change. Physical properties, profoundly positive for refrigeration, cooling and warming activities, having large volumetric cooling limit. Because of its high-pressure operation up to 1880 psia, CO2 frameworks require exceedingly safe segments which now been created for large scale manufacturing for numerous segments.

In vehicle aerating and cooling, in over 90% of every single driving condition for scopes higher than 50°, R744 works more productively than frameworks utilizing R-134a. Its ecological favourable circumstances (GWP of 1, non-ozone draining, non-lethal, noncombustible) in future, could make it working liquid to supplant momentum HFCs in autos, stores, boiling water warm pumps, among others. Coca-Cola has handled CO2-based refreshment coolers and the U.S. Armed force is keen on CO2 refrigeration and warming innovation.

The worldwide car industry is required to settle on the cutting-edge refrigerant in auto aerating and cooling.Market SurveyFigure SEQ Figure * ARABIC 1. market surveyPAKISTAN LCO2 MARKET CO2 is mostly liquefied in order to lessen its concentration in atmosphere. This is achieved in compliance with the environmental regulations.LCO2 PRODUCTIONPakarab 192TPDLinde Gas 83TPDChitral oil and Ghee 75TPDHabib Sugar Mills 49TPDColony Sugar Mills 45TPD United Gases 20TPDLCO2 CONSUMERCoca Cola 63000TPYPepsi37000TPYOther Beverages 25000TPYOther Industry 18000TPYFood Industry 10000TPYOil Refinery5000TPYSeasonal Consumption of LCO250% of the total LCO2 produced is sold in months of May, June, July and August35% LCO2 in Oct, Sep, March,April10% LCO2 in Nov, Dec, Jan, FebCapacity of PlantCapacity selection basically depends upon the demand for that particular object.

We have selected the capacity of plant as 200TPD. LCO2 Temperature = -20 C Pressure = 21 barPlant LocationFollowing factors should be considered while selecting the plant site.Raw Materials Availability. The source of raw material plays a most important role while selecting plant site. If the location of raw material source is near to the plant site it will reduce the transportation and storage cost. Markets. The cost of the product distribution and the time required for shipping that product greatly depends upon the market.

Plant should be situated in that area which is near to the market because buyer purchase product from nearby market. By-product and major final product requires market.Energy Availability Power and steam are the most vital need of every industry. Plant site should be near to large hydroelectric installation.

Energy supply should readily and easily available to plant this will reduce various cost.Climate. The plant site should be selected where climate is favorable. Cold areas are mostly not suitable for plant. Excess of humidity and extreme of hot and cold weather can affect the plant operation and may enhance the cost of operation.

Transportation facilities. Most of the large industries transport their final products using water, railroads and highways. Plant site should be selected in such a way that at least two of the transport facilities should be available to plant site. This will save transportation cost. Transportation facilities should be available for workers also.Water Supply A large quantity of water for cooling, washing, steam generation and as a raw material is used by most of the process industries. Therefore, plant should be located in that area where water is readily available.

Plant site should be near large river or lake so that water is easily available. Waste Disposal In past industries have to face legal restrictions for disposing of waste materials. Therefore, plant site selected should have adequate capacity and facilities for properly disposing waste material.

While selecting plant site various waste disposal methods should be considered. Waste should be disposed of in a proper way.Labor Supply Plant site should be selected by considering the factor that type and supply of labor is easily available.

It should be noted that the site chosen for plant should be that area where labor is easily available and at lowest wages.Taxation and Legal Restriction Site should be selected by considering the factor that like tax rates and various legal restriction. In some areas there are many restrictions imposed by Govt. Sometimes property taxes are high. So while selecting plant site it should be consider that tax rates and legal restrictions should be minimum.Site Characteristics There are some characteristics of site that should be consider while selecting plant site like topography of land, soil structure, construction cost, living conditions and future changes.Flood and Fire Protection It should be considered that site selected should be protected from flooding and fire. Sometimes industrial plants are located near large rivers so there is a risk of flood.

Regional history of the site should be studied carefully.Community Factors Community factors effect location of plant. Cultural facilities of the community plays important role in growth. Different recreational activities should be available near plant site.

It these facilities are not available it becomes burden for plant site to provide such facilities.Selection of Plant Site There are various factors involved in selecting the plant site which are as followRaw MaterialsMarketsEnergy SupplyClimateTransportationWater SupplyFor initial survey for selecting plant site first four factors should be taken into account. Thus on the basis of these factors like raw material, markets, energy supply and climate acceptable location can easily be selected. 2035629241028Chapter 200Chapter 238100020683Process Selection and Process Description00Process Selection and Process DescriptionProcess Selection and Process DescriptionMethods of LiquefactionIn general gases can be liquefied by one of the three general methods: By compressing the gas at temperatures less than its critical temperature.

By making the gas do some kind of work against an external source, causing the gas to lose energy and change to liquid state. By Joule-Thomson effect. In the first approach, the application of pressure alone is sufficient to cause a gas to change to a liquid. For example, ammonia has a critical temperature of 406K (271.4 F 133 C).

This temperature is well above room temperature, so it is relatively simple to convert ammonia gas to the liquid state simply by applying sufficient pressure. At its critical temperature, that pressure is 112.5 atmospheresA simple example of the second method for liquefying gases is the steam engine. The principle on which a steam engine operates is that water is boiled and the steam produced is introduced into a cylinder. Inside the cylinder, the steam pushes on a piston, which drives some kind of machinery. As the steam pushes against the piston, it loses energy. That loss of energy is reflected in a lowering of the temperature of the steam.

The lowered temperature may be sufficient to cause the steam to change back to water.In this method the gas is first pumped into a container under high pressure. The container is fitted with a valve with a very small opening. When the valve opened, the gas escapes from container and expands quickly. At same time its temperature drops. In some cases, the cooling that occurs during this process may not be sufficient to cause liquefaction of the gas.

However, the process can be repeated more than once. Here, we have made use of compression process for liquefaction of CO2. Polytropic compression is being employed.Basically there are two technologies that are being employed for liquifaction of co2.American technologyGerman technologyThe standard for liquefaction of CO2 is 99.

99 % pure .In selection of any process the first most important aspect is purity of product. The more the purity the more consistent is the product.We have selected American technology for the following reasonsPurityThe final purity level through this technology is 99.997% pure which makes this technology very better than others.

As main concern of any industry is purity so we have selected it as it provides better purity than others.Advance technologyThe american technology is designed on latest parametes. It is the most latest technology for liquefaction of co2 around the world.12FeaturesMultistage compressionThis employs multistage compression. The benefit of this is that it makes it easily possible to reach the critical pressure which is required for liquefaction.Polytropic compressionIt employs polytropic compression which is very efficient. As it compresses than cools then again compresses.

So makes it efficient compressionDryerThe other main feature of this technology is that it employs the dryer that is of latest technology and is efficient upto 95% . It is of dessicant type dryer.12Process Introduction Product: LCO2 for food and industrial use CO2 is stored and transported in liquid form. CO2 must be purified to meet product specifications that will allow its use in food and other applications.Feedstock: VCO2 with various impuritiesTo produce LCO2, the raw gas must be compressed (19 bar), dried (to prevent the formation of water ice), and refrigerated (cooled to –28C). To remove impurities from the feedstock, the raw gas is scrubbed with water and passed over adsorbents. In addition, the LCO2 is stripped of dissolved gases.

To produce LCO2: The feedstock is: Chilled in the low pressure precooler to condense water vapor from the gas stream so that the water does not condense out in the oil of the low or high stage CO2 compressors. Passes through the low pressure knock out drum to separate the condensate (liquid water) from the gas so liquid water does not enter the low stage compressors. Compressed in the low stage compressors (5.9 bar). This is the first of two stages of compression up to 19 barg. Cooled in the intercooler to permit efficient compression in the high stage compressor. Passes through the interstage knock out drum to separate any condensate (liquid water) from the gas so liquid water does not enter the high stage compressor Compressed in the high stage compressor (19 barg) the pressure desired for liquefaction.

Purified in the scrubber Chilled in the high pressure precooler to condense water vapor from the gas stream so that water vapor removal requirement of the dryer is reduced. Passes through the high pressure knock out drum to separate the condensate (liquid water) from the gas so liquid water does not enter the dryer. Has water removed in the dryer to prevent the formation of water ice in the CO2 condenser. Refrigerated and partially condensed in the CO2 condenser to produce LCO2. ? Passes through the disengaging chamber to separate entrained vapor CO2 and non- condensable impurities from the condensed liquid and provides a liquid head for the stripper tower feed pump LCO2 is pumped through the stripper to be purified The liberated gases, along with CO2 vapor, pass through the reflux condenser where a portion of the CO2 is re-condensed. The remaining CO2 and non-condensable gases exit the top of the stripper. This impure vapor stream then flows through the non-condensable purge assembly and then to atmosphere.

The pure CO2 vapor which enters below the packed bed is generated in the reboiler pure liquid CO2 flows by thermosyphon action from the stripper’s flooded sump to the reboiler. The reboiler vaporizes the liquid CO2 by a flow-regulated stream of refrigerant to create a constant minimum supply of stripping CO2. Purified LCO2 product is pumped through to the storage tank. NH3 evaporating at two different temperatures is used to chill (+1oC) and refrigerate (-28oC) the system. These temperatures correspond to intermediate and low pressure sections 0f the NH3 system: +1oC NH3 (intermediate pressure section) is obtained by flashing LNH3 from the receiver down to approximately 3.5 barg in the low and high pressure precoolers -28oC NH3 (low pressure section) is obtained by flashing LNH3 from the intermediate pressure system to approximately 0 barg in the CO2 condenser and reflux condenser Purification of the CO2 is accomplished by: Once through (water is not re-used) scrubbing of the CO2 with deaerated water for bulk removal of alcohols (methanol and ethanol) and aldehydes (acetaldehyde ). Activated alumina and molecular sieve media in the dryer towers to adsorb water.

The dryer consists of two towers. One tower is on line purifying CO2 while the other tower is being thermally regenerated. Removing the small quantities of non-condensible gases (H2, N2, O2) which dissolve in the LCO2 exiting the CO2 condenser by stripping these gases from the LCO2 in the stripping tower. PROCESS ; EQUIPMENT OVERVIEW Raw gas is delivered to the plant at 1.07 bar and 60C. The gas is chilled in the low pressure precooler and the resultant process condensate is removed in the suction knock out drum. The vapor is then compressed, in two stages, to approximately 19 bar.

Oil lubricated screw compressors utilizing food grade oil are used. Two low stage CO2 compressors operate in parallel. The gas exiting the low stage compressors passes through a common intercooler and knocks out drum prior to entering the single high stage compressor. The gas exiting the high stage CO2 compressor passes through an external coalescing filter for oil removal before entering the structured packed scrubber where the condensate drops out and water soluble impurities are removed from the gas by a deaerated make up water stream. The gas exiting the scrubber is then chilled in the high pressure precooler and the condensate removed in a knock out drum to reduce the quantity of water to be removed in the dryer. The dryer contains both activated carbon and desiccant to remove certain oxygenated hydrocarbons and water vapor.

CO2 gas from the head space of the static liquid CO2 storage tanks is utilized for dryer purge gas. The dry gas exiting the dryer then passes through a dust filter and enters the CO2 condenser. The gas entering the CO2 condenser is partially condensed.

The liquefied CO2 gravity flows to the liquid inlet of the Disengaging Chamber vessel while the non-condensable gas is directed to the inlet / bottom of the Reflux CO2 condenser mounted at the top of the stripper tower. Non-condensibles dissolved in the LCO2 entering the stripper are stripped utilizing pure CO2 vapor generated in the reboiler. LCO2 exiting the stripper is pumped to the static liquid CO2 tanks at approximately –21C and line pressure up to 21.4 bar. The screw compressor oil coolers are water cooled whereas the gas chilling and condensing is done with NH3.The water cooling heat load is rejected to the customer supplied water cooling system, whereas the NH3 heat load is rejected through the evaporative type condenser. Nominal 1C coolant for use in the precoolers and nominal –31C coolant for use in the CO2 condenser and reflux condenser are provided by mechanical refrigeration utilizing oil lubricated NH3 screw compressors with a side port which accepts 1C vapor NH3.Process ; Equipment Detailed DescriptionLow Pressure Cooling SkidLp Precooler:The feed gas coming from ammonia plant goes to LP precooler.

It is a shell and tube exchanger with CO2 in tubes and ammonia in the shell side.Purpose:The main purpose of LP precooler is to remove sufficient water vapour from CO2 stream so that water will not condense in CO2 compressors.Working of LP precoolerNH3 at 1C is used to cool feed gas to 7C. The temperature of NH3 is maintained above 0C to prevent formation of water ice on CO2 side of exchanger. Heat transfer takes place and CO2 is cooled. Ammonia comes from storage.

Expansion occurs but properly expansion takes place in LP precooler shell.So high level of ammonia may trip compressors to stop entry of ammonia in LP precooler.Effect:If it happens these vapors may condense in compressors and cause corrosion.PCV:On top of receiver there is a PCV and pressure gauge. They control the ammonia pressure of 3.

5 bar. Then ammonia is send back to compressors.Oil Pot:Ammonia has some oil drops from compressor. There this oil is removed.

The oil starts to settle at the bottom which increases liquid level in shell that can cause less expansion of ammonia.It’s having a heater which removes entrapped ammonia from oil. Then it goes to receiver and then to compressors. The oil may sent back to compressor or if not clear then drained.Knock Out Drum:Its main function is to remove of liquid from gas so that it does not goes to compressor.

The water condensed in LP precooler is collected in sump and drained to sewer through LCV. At the top the moisture is removed from the gas stream in demister pad as gas stream exits the tower and enters low stage compression. Its having LSLL and LSHH to indicate water level in drum.

Low Stage Co2 CompressorsThese are single stage oil lubricated screw compressors.Working Mechanism:The gas from knock out drum inters at suction of compressor with constant injection of oil. Gas is compressed between a driven and undriven rotor. There the gas is compressed to 5.8 bar at 180°F then the oil is separated from the gas as it passes through the separator and a demister and gas goes to intercooler.Oil Purpose:1 Seal the gap between the rotors to permit compression2 Cool the gas as it is compressed3 lubricate the compressorOil Nature:Food grade oil is used so it could not affect product quality. Oil circuit of low stage compressor:The oil is separated in separator by action of gravity and mists of oil is removed in demister.

Then from bottom line it passes through a ball valve and a bucket type strainer. Then there are two lines one is of NRV and one is pump. Pump:At start the oil is circulated by pump which is gear type.NRV: When pump makes enough discharge pressure the pump trips and oil is circulated by NRV.PSV:There is a PSV line with the NRV line. If discharge pressure increases the PSV opens and sends the oil back to suction of pump in this way it maintains it.

MOV:Now it plays main role in the oil circuit. Its function is to maintain the oil temperature at 65C. So if required MOV sends some oil to oil cooler.Oil Cooler:The oil cooler is a shell and tube heat exchanger having oil in shell and water in tubes. It cools the oil to maintain temperature of 65C.Then the oil stream from separator and oil cooler are mixed to form 65C and passes through filter.Oil Filter:After mixing the oil passed through filter and is filtered there and goes to the suction of compressor and this cycles continues like this.

There are 5 PSV’s, 5 TE’s and 4 PT’s on compressor to control excess pressure, temperature and pressure.IntercoolerGas leaving low stage compressor is cooled in intercooler. It is shell and tube heat exchanger having CO2 in tubes and water in the shell side.

Heat transfer takes place and CO2 is cooled and moisture is reduced so that it does not enter the High stage compression. The gas leaving the intercooler has temperature of 43CKnock Out Drum:Its main function is to remove of liquid from gas so that it does not goes to compressor.The water condensed in intercooler is collected in sump and drained to sewer through LCV. At the top the moisture is removed from the gas stream in demister pad as gas stream exits the tower and enters high stage compression.

It’s having LSLL and LSHH to indicate water level in drum.High Stage Co2 CompressorsThese are single stage oil lubricated screw compressors.Working Mechanism:The gas from knock out drum inters at suction of compressor with constant injection of oil. Gas is compressed between a driven and undriven rotor. There the gas is compressed to 19.3 bar at 180°F then the oil is separated from the gas as it passes through the separator and a demister and gas goes to intercooler.

Oil Purpose:1 Seal the gap between the rotors to permit compression2 Cool the gas as it is compressed3 lubricate the compressorOil Nature:Food grade oil is used so it could not affect product quality. Oil Circuit Of Low Stage Compressor:The oil is seperated in seperator by action of gravity and mists of oil is removed in demister. Then from bottom line it passes through a ball valve and a bucket type strainer.

Then there are two lines one is of NRV and one is pump.Pump:At start the oil is circulated by pump which is gear type.NRV:When pump makes enough discharge pressure the pump trips and oil is circulated by NRV.PSV:There is a PSV line with the NRV line. If discharge pressure increases the PSV opens and sends the oil back to suction of pump in this way it maintains it.MOV:Now it plays main role in the oil circuit.

Its function is to maintain the oil temperature at 65C. So if required MOV sends some oil to oil cooler.Oil Cooler:The oil cooler is a shell and tube heat exchanger having oil in shell and water in tubes. It cools the oil to maintain temperature of 65C.Then the oil stream from separator and oil cooler are mixed to form 65C and passes through filter.Oil Filter:After mixing the oil passed through filter and is filtered there and goes to the suction of compressor and this cycles continues like this.There are 5 PSV’s, 5 TE’s and 4 PT’s on compressor to control excess pressure, temperature and pressure.

Coalescing Filter:Gas leaving HS Compressor passes through this filter to remove any traces of oil and make the gas completely oil free. Then it goes to scrubber.ScrubberIt uses the technique of scrubbing which is a separation technique. With the help of potable water the water soluble impurities are removed in the scrubber.Principle Involved:The principle applied in scrubber is absorption as water absorbs water soluble impurities.

Mechanism:The scrubber is a structured packed bed. The water enters from the top while the gas enters from bottom. Counter current action takes place and water absorbs impurities like ethanol, methanol, aldehydes and ketone etc and gas then leaves at 85C.

There is FCV to control water rate so that it can contact to gas according to set point because if water level reduces it may not remove the required level of impurities and it also has a LCV to maintain level then it goes to HP precooler.High Pressure Cooling SkidHp Precooler:It is a shell and tube exchanger with CO2 in tubes and ammonia in the shell side.Purpose:The main purpose of HP precooler is to remove sufficient water vapour from CO2 stream to minimize the duty of dryerWorking Of Hp PrecoolerNH3 at 1C is used to cool feed gas to 7C. The temperature of NH3 is maintained above 0C to prevent formation of water ice on CO2 side of exchanger. Heat transfer takes place and CO2 is cooled. Moreover its working is same as LP precooler.Oil Pot:Ammonia has some oil drops from compressor. There this oil is removed.

The oil starts to settle at the bottom which increases liquid level in shell that can cause less expansion of ammonia.It’s having a heater which removes entrapped ammonia from oil. Then it goes to receiver and then to compressors.The oil may sent back to compressor or if not clear then drained.Knock Out Drum:Its main function is to remove of liquid from gas so that it does not goes to dryer.The water condensed in HP precooler is collected in sump and drained to sewer through LCV. At the top the moisture is removed from the gas stream in demister pad as gas stream exits the tower and enters high stage compression.

It’s having LSLL and LSHH to indicate water level in drum.Coalescing PrefilterIts function is to remove the final trace amounts of liquid water present in the gas exiting the high pressure knock out drum. This prevents the desiccant in the dryer from loading with liquid water instead of water vapor. It also prolongs the life of desiccant.DryerType:It is thermal type dryerMain Components:1 Pre Filter2 Dryer Vessels3 After FilterPre Filter:Gas passes through pre filter which removes water droplets from gas . These droplets can reduce dryer efficiency and increase dew point of final product.

Dryer Vessels:There are two dryer vessels one is in use while the other is thermally regenerated.Principle:This works on principle of adsorption.Mechanism:The vessel consists of three bed 1 Activated carbon2 Activated Alumina3 Molecular sieveThe gas first passes through the activated car which adsorbs higher weight hydrocarbons and the odour as well.

Then it passes through the activated alumina and molecular sieve which removes the moisture and they preferentially adsorb water over other compounds.After Filter:Then it passes through the after filter which removes dust from gas or desiccant particles.Regeneration It is of prime importance for proper functioning of the dyer. It takes 8 hours to regenerate the dryer1 minute depressurization160 minutes heating50 minutes cooling/sweeping19 minutes repressurization250 minutes standbyDepressurizing:Prior to thermal regeneration the tower must be depressurized.

Gas from the offline tower flows through the depressurization valve, across orifice to atmosphere. Failure in this step prevents the next step from taking place.Heating:Heating is done by electric heaters placed inside the dryer at the bottom. The desiccant is heated to drive off the adsorbed moisture contents. The heating is terminated as temperature rises to 200°F.Cooling:After heating, cooling starts.

Cooling is done naturally. During cooling sweeping is also done in dryer by passing CO2 gas from the bottom to the top. This gas is drained from the top because of larger moisture contents.

Repressurization:This is also very important to repressurize the system because the coming stream is at 270 PSI. This is done to avoid1 Thermal shock2 Mass transfer shockThese can damage the desiccants that’s why it is necessary to repressurize the system.Stand By:Then the system is on stand by for next 250 minutes and regeneration completes and ready to be used.Co2 CondensorPurpose:The purpose of CO2 condenser is to recover liquid CO2 from feed gas .

This is a shell and tube exchanger with refrigerant accumulator vessel.It works same like LP and HP precoolers. Ammonia leaving reboiler and reflux condenser is taken as the inlet of CO2 condenser. Ammonia leaves at -28C and goes to compressorDue to sudden decrease in temperature CO2 gas is partially condensed and goes go disengaging chamber CO2 temperature is -27C.The vapour exiting the CO2 condenser will contain CO2 and and high concentration of non-condensable gases which should be removed in order to get product specifications that’s why it is further processed in stripper sectionOil Pot: It also has oil pot which works similar to LP and HP oil potsDisengaging ChamberPurposr:It separates liquid and vapour CO2 through the action of gravity and provides liquid head for stripper tower feed pumps.

Mechanism:The feed enters the chamber and through the action of gravity liquid falls down in sump while vapours are at top. There are two sliding vane pumps one is in working while one is standby they are used to send the liquid to stripper and back to disengaging chamber. Then both liquid and vapour streams enter the stripper section.LCo2 StripperStripper is the last step of purification and liquefaction of CO2 plant. There the non-condensable gases like H2, N2, and O2 are removed.

This system consists of a wire mesh structured packed bed tower, CO2 reboiler and LCO2 product pumps.Principle:It strips off the non-condensable through the action of adsorption.Mechanism:The vapor CO2 and liquid CO2 enters the stripper. Due to gravity liquid falls in sump and maintains a level of 50% while vapors go to reflux condenser. Reflux condenser is a shell and tube exchanger. Ammonia is in tubes while vapor CO2 is in shell side. The liquid from sump enters the reboiler. Reboiler is also a shell and tube exchanger mounted vertically.

The ammonia comes from compressor line and when leaves the reboiler it enters the condenser. The ammonia is in tubes while CO2 in shell side. As liquid CO2 at -28C enters the reboiler it vaporizes and temperature becomes -22C and leaves the reboiler and enters the stripper and moves upward making counter current contact with coming CO2 and strips off the non-condensable gases by adsorbing them and then passes through reflux condenser which will condense the CO2 vapors and let the non condensible to escape from vent. The ammonia comes from HP precooler in reflux condenser and after use goes to condenser. Product LCO2 exiting the stripper sump is transferred to the LCO2 storage tank by the LCO2 product pump which are sliding vane type. There are also solenoid valves used to prevent cavitation at start up.Storage TanksTwo storage tanks are there to store and deliver LCO2. Each storage tank has the capacity of 250MT.

Two refrigerant units are used to cool down compressed CO2 to keep it in liquid form.Refrigeration CycleThe ammonia refrigeration cycle consists of these main components1 Compressors2 Evaporative Condenser 3 Receiver4 Expansion valves5 EvaporatorMechanismCompressors:The ammonia from CO2 condenser, LP and HP comes the ammonia compressors that are single stage screw compressor. They compress the ammonia gas to use for refrigeration in LP, HP precooler and CO2 condenser. The ammonia leaves the compressor at 70 to 70C at 10 to 12 bar. These vapors go to evaporative condenser.

These compressors work on the same principle as the CO2 compressors discussed previously.Evaporative Condenser:Ammonia is condensed in this prior to returned to the ammonia receiver. It comprises of 2 cells with a separate water basins. Each cell has one ammonia coil and one fan, water pump, water make up fload valve, over flow, drain, and electric pan heater. Mechanism:The ammonia refrigerant vapor from the compressors is circulated through the coil of the evaporative condenser.

Heat from the refrigerant is dissipated through the coil tubes to the water cascading downward over tubes. Air is drawn in through the air inlet louvers at the base of condenser and travels upward over the coil opposite the water flow. A small portion of water is evaporated which removes the heat, condensing the vapor ammonia to liquid. The warm moist air is drawn to the top of the evaporative condenser by fan and is discharged to the atmosphere. The remaining water falls to the sump and recirculated by pump.

The condensed liquid flows to the liquid receiver vessel.Nh3 ReceiverLNH3 is drawn from the receiver to the LP and HP precoolers.Expansion Valves:After receiver ammonia expands from three vales to achieve final temperature of 1C. First expansion occurs through solenoid valve on top of receiver then through LCV and then through manual valve.Evaporator:When it enters the receiver of LP precooler evaporation takes place and again returned to the compressors. This is how ammonia refrigeration cycles works.Design BasisTable SEQ Table * ARABIC 1. Design basisCOMPONENT FEED GAS (%) PRODUCT LIQUID (%)Carbon Dioxide 78.

92 99.94Water 18.74 0Carbon Monoxide 0.004063 0.

000204Niterogen0.879 0.012Argon 0.15 0.046415Hydrogen 1.3 0Acetaldehyde 0.004 0Methanol 0.

0055 0Benzene 0.000001 0Figure SEQ Figure * ARABIC 2. PFD of CO2 Liquefaction Plant Description of Process Flow Diagram of CO2 liquefaction plant Table SEQ Table * ARABIC 2. Description of PFDStream no.

Description 1 Raw CO2 gas from NH3 plant 2 CO2 gas to LP knock out drum 3 CO2 gas to low stage compressors 4 CO2 gas to intercooler 5 CO2 gas from high stage compressor 6 CO2 gas from scrubber 7 CO2 gas from HP precooler 8 CO2 gas to dryers 9 CO2 gas to CO2 condenser 10 Non condensable gases to reflux condenser 11 CO2 liquid to scrubber 12 CO2 liquid for pressure balance 13 CO2 liquid to reboiler 14 CO2 gas from reboiler 15 CO2 product for pressure balance 16 CO2 product 17 Non condensable gases to atmosphere 18 NH3 liquid to LP precooler 19 NH3 liquid to HP precooler 20 NH3 gas to compressor inlet 21 NH3 gas to compressor inlet 22 NH3 liquid to reflux condenser 23 NH3 liquid to CO2 condenser 24 NH3 gas to reboiler 25 NH3 liquid to CO2 condenser 26 NH3 gas to compressor inlet 27 NH3 liquid to evaporative condenser 28 To drain 29 To drain 30 Potable water inlet 31 Potable water outlet 32 To drain 33 Water to evaporative condenser 34 Water from evaporative condenser 35 Cooling water inlet 36 Cooling water outlet 37 Oil back to high stage compressor 38 NH3 liquid to storage 186145785906Chapter 300Chapter 3947058171994Material and Energy Balance00Material and Energy BalanceMaterial and Energy Balance: Material Balance On LP Cooler4895850857250 10608 kg/hr08 kg/hr00 10608 kg/hr08 kg/hr-180975924560 10608 kg/hr08 kg/hr00 10608 kg/hr08 kg/hrFigure SEQ Figure * ARABIC 3. LP CoolerIt is a shell and tube heat exchanger with CO2 in the tubes and ammonia in the shell side. The main purpose of LP cooler is to remove sufficient water vapour from CO2 stream so that water will not condense in CO2 compressor. Input=Output Feed=ProductTotal Flow rate= 10608 kg/hrMolar flow rate=241 kmol/hrInput StreamTable SEQ Table * ARABIC 3.

Material Balance On LP CoolerComponent Kg/hrKmol/hrMol. Frac.CO2 8274.24 188.

05 0.789H2O 1986.87 110.38 0.1873C6H6 1.0608*10^-4 1.36 * 10-6 1 * 10-8H2 137.904 68.

95 0.013Ar16.36 0.409 1.543 * 10-3CH4O 0.69 0.

021 6.51 * 10-5N2 92.18 3.29 8.69 * 10-3CO 0.424 0.015 4 * 10-5C2H4O 0.

430 0.0097 4.06 * 10-5Output StreamComponent Kg/hrKmol/hrMol. Frac.

CO2 8274.24 188.05 0.789H2O 1986.87 110.

38 0.1873C6H6 1.0608*10^-4 1.36 * 10-6 1 * 10-8H2 137.904 68.95 0.013Ar16.

36 0.409 1.543 * 10-3CH4O 0.69 0.

021 6.51 * 10-5N2 92.18 3.

29 8.69 * 10-3CO 0.424 0.

015 4 * 10-5C2H4O 0.430 0.0097 4.06 * 10-5Total Material In = 10608 Kg/hrTotal Material Out= 10608 Kg/hr Material balance on compressorsright1400175 9758 kg/hr08 kg/hr00 9758 kg/hr08 kg/hr-47625781050 9758 kg/hr08 kg/hr00 9758 kg/hr08 kg/hrFigure SEQ Figure * ARABIC 4. CompressorsCompressors are single stage screw compressor. They compress the ammonia gas to use for refrigeration in LP, HP precooler and CO2 condenser.Input=OutputFeed=ProductTotal Flow rate= 9758.

02 kg/hrMolar flow rate=241 kmol/hrCompressor 1= 4879.01 kg/hrCompressor 2= 4879.01 kg/hrInput StreamTable SEQ Table * ARABIC 4. Material balance on compressorsComponent Kg/hrKmol/hrMol. Frac.CO2 94116.4 214 0.

965H2O 96.6 5.36 0.0099C6H6 9.75*10^-5 1.25*10^-6 1 * 10-8H2 146.3 73.

18 0.015Ar18.34 0.

45 0.00188CH4O 0.77 0.

024 7.9 * 10-5N2 102.4 3.65 1.

05 * 10-2CO 0.483 0.017 4.

951 * 10-5C2H4O 0.478 0.10 4.9 * 10-5Output StreamComponent Kg/hrKmol/hrMol. Frac.CO2 94116.4 214 0.965H2O 96.