And Packings

Based OH RULES OF THUH 6 PORTER fl 4D JENKINJ ( ) AN FRANK (sj I 3est results for replacing trays with packings are obtained at lev I values cf flow parameters, i.e. low liquid loads and low vapor densities, such as those experienced ir. vacuum and atmospheric pressures, particularly if the trays operate at a relatively low ' efficiency (Figure 9.3 and 9.4). Another case where replac-r.g trays with packings is effective is systems which tend to foam 'section .5.1), as packings can handle these...

Distillation Column Troubleshooting

A further hike in vapor rate may trigger flooding by expanding the liquid holdup to the point at which the phases begin to invert, with the liquid phase becoming the continuous phase. After flooding has begun, the liquid can continue to build up above the fioodpoint m the column. Vapor, being the continuous phase in a packed column, does not bubble through the liquid, as in a trayed column. Because of this and the absence of vapor-flow orifices (as in a tray), packed columns operate at much...

Random Packings

OBJECTIVES In order to compare the capacity of structured packings to the capacity of trays and random packings, a chart, such as Figure 9.5 can be used. The construction of such a chart requires that several assumptions are made. The assumptions made in developing Figure 9.5 may be a poor approximation for many applications, and this diagram is therefore only suitable for defining very general guidelines. The user is therefore strongly encouraged to develop his own chart, similar to Figure 9.5...

Column Startup

France, Giitscn, inc. Distillation-column troubleshooting' begins with the recognition that the expected separation or capacity is not being delivered, and ends with action that restores performance. The tasks of the troubleshooter are first, to identify the problem next, to determine its cause and lastly, to recommend a remedy. Because the economic loss from reduced column performance or extended downtime can be significant, the pressure to restore column...

Estimating Separation Efficiency Part 2 Vital Grossel Olsen

Pract al Tips on Tower . fee. 7. 1987. pp. 101- AIChE. Trav Distillation Columns. AIChE Equipment testing Procedure.' America.-. Inst, of Chem. Engrs New York. 19 , . 2. Anderson. A. E and Jubin. J. C Case Histories of the Distillation Practioner. Chew. Eng. Prog October 1964. pp. tiO-63. 3. Bolles. W. L Estimating Valve Tray Performance. Chem. Eng. Prog September 1976. pp. 43-49. 4. Jamison. R. H Internal Design Techniques. Chem. Eng. Prog March 196 . pp. 46-51. 5. Kister. H. Z Design and...

Non Condensibles Beer Column

Vertical Thermosiphon Reboiler

FIGURE 8.1.18 TEfifERftTUftE CyCLE , CASE 1 CASE STUDY No. 2 Heavies in Inlet Line Reference 2 author had similar experience . INSTALLATION A vertical thermosyphon reboiler, processing a mixture of two components - a high boiler and a low boiler Figure 8.1.2 . PROBLEM Heat transfer and circulation rate deteriorated with time. Neither fouling nor composition variations appeared to be the cause. The problem was diagnosed to a lack of outlet for residue. It accumulated at the base of the reboiler...

Even if a multicomponent system falls outside the methods normal limits it may be possible to get useful vaporliquid

Wilcox, Jacobs Engineering Group, Inc. The UNIFAC group-contribution method outlined in the preceeding article is a means of calculating multi-component vapor-liquid equilibrium VLE data. Experimental data are always preferred, but UNIFAC can prove useful if they are unavailable, or if they are available only for binary mixtures and not the multicomponent ones of interest. There are, however, limits on where UNIFAC can be applied Pressure no more than a few i.e., 3 4 atmospheres All...

Figure

Distillation Column Internals

Gamma scanner helps pinpoint locations of abnormal hydraulics in distillation column Heavily laden trays with high absorption in vapor spaces increments of from 0.5 to 2 in. The amount of gamma radiation absorbed and transmitted indicates the quantity and nature of the substance between the emitting source and detector. The gamma absorption of the column wall and insulation is constant except where wall thickness changes. This absorption profile can be translated into a density profile that...

Info

Substituting the above in equation 4-1 gives Equation 4-2 shows that the ratio W QR can be expressed I the log of the pressure ratio. iEither the temperature difference, or the pressure ratio, can be used to measure the potential of applying the heat pump technique. Compared to the relationship in equation 4-1, the relationship of equation 4-2 is more complex and more difficult to express in terms I of readily available parameters such as column top and bottom temperatures for this reason, the...

Product

Distillation Alcohol

CONVENTIONAL CONDENSATION In a conventional distillation column, heat is applied in the bottom reboiler and removed in the top condenser. Commonly, heat is applied by steam in the reboiler and rejected to cooling water or air in the condenser. This represents an energy degradation from the temperature of the heating medium generation system in case of steam, the combustion temperature to ambient temperature. This system owes its existence to simplicity, low investment,...

Trouble Shooting Distillation Columns

Distillation Trays Operation

France, Glitsch. Inc. ' For information about the authors, see p. 123 of the first article o this series. .Marc 19S9. p. 116. Overall, trayed columns operate via countercurrent liquid and vapor flow, with staged contacting for heat and mass transfer. Each stage is often modeled as a mixer-separator, with liquid-vapor contacting followed by the separation of liquid and vapor for transport to, respectively, the stages below and above Figure 1 . This description...

Vapor Blanketing Reboiler Corrective Actions

Product that crystallized during the shutdown of a distillation column decorate the fouled finned tubes of a reboiter steam-condensate-seal blowing, film boiling, heating-medium inadequacy, boiling-point elevating, foaming, inert blanketing, leaking and undersizing. Fouling The vaporization of process fluids at tube walls can precipitate dissolved solids onto the tubes. Tar-like materials in the feed may plate out on metal surfaces. Tube-wall temperatures which are higher than bulk-fluid...

Columns

Liquid Holdup Trays Distillation Column

The first step identifying the problem will usually be simpler if column performance has suddenly deteriorated than if capacity or efficiency declined gradually. Except when related to auxiliary equipment or instrumentation, most distillation problems arise from flooding impeded liquid flowpath , excessive pressure drop impeded vapor flowpath , or inefficiency insufficient liquid and vapor contact . Of course, these problems do not usually occur independently. After attempts to stabilize column...

Internal Hardware Revamps

Distillation Dual Tray

WHEN EFFECTIVE A quick browse through Sections 5.2.3 and 6.3.4, which list factors affecting capacity and efficiency, can define the effectiveness of this technique. Changing layout may be used effectively to increase column capacity, but the technique is rather limited in its ability to significantly improve column efficiency. It is thus suitable for capacity revamps only. METHODS The methods commonly used depend on the flooding mechanism which restricts capacity, and can simply be deduced...

Bc

Demethanizer

Figure 4 ko thermal coupling BRuc-na's scheme Figure 4 ko thermal coupling BRuc-na's scheme FIGURE 4.12 RNRL TICflL DiftGftAM 0F THE 4.2.9 Other Common Heat Integrations DIFFERENT COLUMNS One of the most straight-forward energy saving schemes is thdt of direct heat integration between different columns. Such a scheme can be implemented whenever one column rejects energy at a temperature sufficiently high to be utilized for heatir.c in another column. Figure 4.13 shows a typical example. Energy...

Comparing The Capacity Of Trays And Packings

OBJECTIVES In order to compare the capacity of trays and packings, a chart such as Figure 9.3 can be used. The construction of such a chart requires that several assumptions are made. The assumptions made in developing Figure 9.3 may be a poor approximation for many applications, and this diagram is therefore only suitable for defining very general guidelines. The user is therefore strongly encouraged to develop his own chart, similar to Figure 9.3, whenever an alternative set of assumptions...

What Is Distilation And Show In Practical

Mole Fraction And Distillation

While the overhead product consists of a mixture of spent C4s butanes, butenes, butadienes that passed through the reaction step as inerts. The overhead composition depends on the composition of the feedstock, which is generally a C4 cut from a catalytic cracker or steam cracker. C2B, one of the heavier C4s, is characteristic of the overhead stream. The other system is diethanolamine DEA and trietha-nolamine TEA . Ethanolamines, including monoethanol-amine MEA , are used to scrub sour acid...

Cf

The group-contribution methods consider a liquid mixture to be a mixture of functional groups, rather than a mixture of molecules. Table I lists the groups currently included in the UNIFAC model. The properties of a mixture, then, are determined by the properties of the groups rather than of the molecules. This is like scaleup to molecules from smaller elements. For example, the mixture of dimethyl ether CHsOCHs and benzene QHe can be considered a mixture of CHS, CHsO and aromatic CH groups....

P s IT y

Pall Ring Capacity Parameter Graph

Figure 9.3 indicates that at this flow parameter, 1 IMTP is the most likely choice. This will be used as a first Capacity Factor of sieve trays at 18 inch tray spacing Capacity Factor of 1-inch IMTP 0.22 Figure 9.3 STEP 2 Mccify the above capacity factors as per Appendix 9A. 1 Correct sieve tray capacity factor for the smaller tray spacing. From Figure 5.10, this correction for the capacity factor is roughly at a flow parameter of 0.16 0.21 0.23 0.91 2 Allow a greater safety factor for the...

References

1 Davies, J A, Chem Eng Prog 61 9 , 74, 1965 2 Gilmour, C H, Chem Eng, June 19, p 221, 1967 3 Moore, J A in Rubin, F L Chairman and P Minton, Heat Exchangers That Did Not Work, Panel Discussion, AIChE Meeting, June 6-10, 1982 4 Bell, K J in Rubin, F L Chairman and P Minton Heat Exchangers That Did Not Work, Panel Discussion, AIChE Meeting, 5 Bell, K J, Chem Eng Prog 79 7 , 54, 1983 6 Kister, H Z, and T C Hower, Plant Operations Prog 6 3 , 151, 1987 7 Steinmeyer, D E and Mueller A C, Chem Eng...

Charts

Blood Pressure Nomogram

No 1 16 Nomogram for predicting equilibrium ratios of hydrocarbons in the low-pressure range. From Cajander el al., J. Chem. Eng. Data, 5 25 I960 . Reproduced by permission of C. F. Broun and Company. M. Van Winkle, Distillation, 1967, by courtesy, McGraw-Hill Book Company.

Appendix 9a Appendix 9b References

9.1 REVAMP TECHNIQUES 9.1.1 Objectives of Revamp Some of the common reasons for revamps are ii Reducing reflux and reboil - energy savings. j iii Accomodating new process conditions - new product 1 specifications, new feed composition. iv Reducing bottom pressure vacuum applications - decreasing j polymerization. TYPES For the purpose of discussion, most revamp objectives can be classified into three types A Capacity revamps - the objective of this type of revamp is to increase unit throughput....

Energy Saving In Distillation

Interreboiler

J 4.1.1 Classification of Energy Saving Techniques j Energy saving techniques can be classified into two categories 1 Techniques that involve a considerable amount of capital i expenditure. These techniques are generally capable of achieving large energy savings, and are mainly suitable for new i plants or major revamps. j 2 Techniques that involve a relatively small amount of capital i expenditure. These techniques generally but not always are capable of achieving smaller savings than those...

A A 1 A

Distillation Overhead Compressor

This exchanger superheats the column overhead while subcooling the reflux. Subcooling the reflux reduces the vapor flash generated upon expansion of the reflux stream. The lower vapor flash reduces vapor recycle through the compressor and therefore lowers compressor power consumption. This power reduction is somewhat offset by the higher compressor suction temperature and lower suction pressure because of exchanger pressure drop . The higher compressor...

Pr026h002000

Reformer General Arrangement

iv Trim condenser or trim reboiler are often used because the condensing and boiling- duties of- the column are net perfectly matched. These devices are also very helpful for startup. A trim condenser is more common when the product is withdrawn as liquid, while a trim reboiler is more common when the product is withdrawn as vapor, but other factors such as presence of a discharge cooler and the feed conditions are also important in determining which one of these if any is needed. v Discharge...

Spillover Distillation

Pumparound

One means of generating such a low-grade heating medium is by I applying the hot liquid belt technique. The equipment that is j usually needed is heat exchangers, a drum, a pump, and a heat j transfer liquid suitable for the temperature range of up to about ' j 200 F. Ideally, this liquid should be non-fouling, non-corrosive, I not excessively viscous and non-toxic. Cooling water is rarely suitable, because it tends to cause accelerated fouling at i temperatures greater than about 150 F, but...

Energy Saving Operation

Reflux and reboil rates are adjusted to produce or.-spec products. Product impuriry levels well below their specifications represent overrefluxing and cverreboiling, and waste energy. Operators tend to overreflux in the interest of smooth operation, and in order to maintain safe margin in case of upset. To minimize joverrefluxing, plant supervision must provide the operators with the jappropriate tools and incentives. These include INSTRUMENTATION Overrefluxing tends to be a greater problem in...

SE On REf a

Deethanizer Processes

8.3 Control Systems That Did Not Work CASE STUDY No. 1 Analyzer Located in the Next Column Product Line INSTALLATION An absorption-refrigeration gas plant. Rich absorption oil contained absorbed hydrocarbons from C_ to gasoline. In order to regenerate the absorption oil, the deethanizer stripped out the C. and C2 hydrocarbons. Gasolines, LPG C.-C. , and C, impurities from the bottom of the deethanizer were recovered ifl the still overhead product Figure 8.3.1A . There was an economic incentive...

Lp

FIGURE 4.10 hi iTi-EFFECT i TllLftTION continued FIGURE 4.10 hi iTi-EFFECT i TllLftTION continued In the forward-feed arrangement Figure 4.10c , all the feed enters j the HP column. When the feed, is rich in the less volatile component, this arrangement produces a pure bottom stream and an impure Icistillate stream as shown in Figure 4.10c. The impure overhead i stream is further separated into a distillate stream ar.c a second bottom stream. when the feed is rich in the more volatile...

Solution

Demethanizer Design

1 Install a vent above the bottom liquid level in the heating side of the reboiler. This was difficult to implement in the field and was not done. 2 Install a vent in the horizontal leg of the condensate line upstream of the vertical leg. FIGURE 8.1.4 RCBOILEft flftRfWGEMENT, CASE 4 QASEO OH R F 4 FIGURE 8.1.4 RCBOILEft flftRfWGEMENT, CASE 4 QASEO OH R F 4 CASE STUDY No. 5 Reboiler Condensate Seal Reference 6 INSTALLATION Vertical thermosyphon reboiler on a demethanizer, using refrigerant vapor...

Xha

1 Floating pressure strategy or control is a technique pioneered by I Shir.skey 4,5 in which the column is trimmed or controlled to operate at the minimum possible pressure. This technique achieves significant energy savings during periods of favorable ambient i conditions. For most systems, relative volatility increases as pressure is i reduced, making separations easier the ensuing reduction in reflux ratio accounts for a lower reboiler duty as pressure reduces. This lower duty benefit is...

Cox Vapor Pressure Charts

Cox Chart Vapor Pressure

The most important term in both K values and the relative volatility j equation is the vapor pressure term. EFFECT OF TEMPERATURE This effect can be illustrated with the aid of j a Cox chart Figure 1.5, Reference 8 . This chart shows a steep increase of vapor pressure with temperature. For this reason, the K value for each component increases steeply with temperature. The Cox chart also shows that in general, for members of a homologous series, vapor pressure of the less volatile component...

Ypq

Rasmusser. and M.L. Michelsen, Paper presented at the A.I.Ch.E. 87th National Meeting, 3oston, Ma., August, 1979. I 19. Soave, G.S., I.Chem. E. Syrap. Ser. 56_, p. 1.2 1, London, 1979. 20. Peng. D.Y. and D.B. Robinson, Ind. Eng. Chem. Fund., 15, 59 1976. 21. Benedict, M., G.B. Webb and L.C. Rubin, Chem. Enc. Prog., 47 3 , 419, 1951. 22. Orye, R.V., Ind. Eng. Chem. Proc. Des. Dev., 8, 579, 1969. 23. Starling, K.E., Hydroc. Proc., 5 3 , 101, 1971. 24. Edmister, W.C., and...

Kvalue Calculation

1.2.L rLa.ssificaticn of Prediction Methods K-Value prediction methods are often classified into hydrocarbon-type methods and chemical-type methods 10,11 . In hydrocarbon-type systems, effects of molecular interactions are relatively small, because the nature of the components is similar. On the other hand, it is most important to obtain good correlation at varying temperature and pressure, since many separations are carried out at high pressures. The approach used in hydrocarbon-type systems...

J

When a significant portion of the column product is vapor, the achievable energy recovery from the product is diminished, because j the dew point of vapor leaving the reflux drum in the two-stage j system is lower than the dew point of vapor leaving the column j overhead in the conventional scheme. As a result, the savings from I condensing reflux at a higher temperature are offset by having to j condense the product at a lower temperature. Further, the reflux drum temperature drops as...

Estimating vaporliquid equilibria with UNIFAC

When experimental vapor-liquid equilibrium data are not available, you may be able to estimate them via the UNIFAC method. Gus K. Georgeton and Jude T. Sommerfeld, Georgia Institute of Technology Q Chemical engineers use vapor-liquid equilibrium VLE data in designing many types of separation processes and equipment. Experimental VLE data are of course the best, but when such data are not available the engineer has to make a choice run an experiment, or try an estimation method. This article...

Henry Kister Seminar

KISTER BROWN amp ROOT BRAUN, ALHAMBRA, CALIFORNIA COPYRIGHT BY H. Z. KISTER, MAY 26, 1983 No part of this publication may be reproduced without prior permission. The opinions expressed at this program are those of the seminar leader and not necessarily McGraw-Hill's. The seminar leader makes no representation, warranties or guarantees expressed or implied, as to the application or fitness of the ideas, suggestions, or recommendations, presented herein or during seminar discussions, for...

I

1.2.2 Hand Calculation Methods for Hydrocarbon-Type Systems K CHARTS Several charts giving K-values for hydrocarbons are available in tiie literature. Perhaps the easiest to use are the De Priester charts 47 , shown in Figure 1.11. These charts are a simplification of the Kellogg Charts 49 , and include experimental data not coverred by the Kellogg Charts. The Kellogg Charts 40 , and therefore the De Priester Charts 47 , are based on the Benedict-Webb-Rubin equation Section 1.2.3 . Edmister and...