Pilot Plant EQUIPMENT FOR OIL AND PETROCHEMICAL PROCESS

Equipment for Oil and Petrochemical Process Development H. HOOG, J. J. LEENDERTSE, N.V.

AND

H. REITSMA

d e Bafaafsche Pefroleum Maatschappii,

The Hague, Koninklijke/Shell-Laboraforium,Amsterdam, Netherlands

SI””

side with the enormous growth of industrial research throughout by the world, research in the oil and petrochemical fields has passed through a turbulent development period in the past 30 or 40 years; the laboratories of the Royal Dutch-Shell Group (one of which is established in Amsterdam) have contributed their share to this rapid growth. The activities of these laboratories are not restricted to fundamental research and to small scale basic research on new processes and products, but also include the work required for the development of such proresses and products and for the evaluation of new base materials to be used in existing processes. I n this paper, attention i s given to the process development and pilot plant activities of the Amstwdaq laboratory, with particular emphasis on equipment. Broad approach and experience are more important than specialized knowledge

Process Development. Between the discoveries made in the research laboratory and their implementation in industrial applications lies the field of process development. Considering the complicated technology of modern times, it is out of the question t,o take a new reaction worked out in the laboratory in glass-or even in small steel apparatus-and transfer it straightaway to a scale which may be as much as a thousand times larger. It is usually too difficult and too risky to assess on the strength of the laboratory data alone what the economics of a project will be, and hence an intermediate stage is called for in order t o get as near as reasonably possible to the most efficient process and equipment. Accordingly, it is the function of process development:

Figure 1.

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To find out whether the technological basis of a new process orked out in research studies on a laboratory scale is sound To make a choice among the equipment and operational alternatives for commercial realization of the process steps; this may also lead to the development of new equipment for special purposes To furnish the data necessary for economic evaluation of pro(.esse6 To furnish all further data necessary for the design of the commercial installation; this information has to cover the corrosion arid instrumentation aspects as well 11

All process development studies and pilot plant activities of the Amsterdam laboratories have, for reasons of efficiency, been combined in one department with a staff of about 200. I t s activities cover primarily the experimental phase of all oil and petrochemical process development and pilot plant work. Years of experience have shown that in tackling development problems, a broad, general approach and wide experience in handling technological questions and in designing the related equipment are factors of greater worth than specialized knowledge in some particular research field. The activities of the research departments proper are concentrated on the discovery and exploration of new process and product ventures, the building up of a fundamental background, and the working out of a preliminary laboratory process, ultimately resulting in a rough preliminary economic evaluation. After this has been found encouraging, the task of finding an economical and well operable technological form is allocated to the process development department, while product development activities belong to the domain of the reseawh departments. Katurally, product properties should never be lost sight of during the process development work, and continuous contact with the research departments is therefore imperative.

Pilot plant building

INDUSTRIAL AND ENGINEERING CHEMISTRY

Vol. 47, No. 6

’

Process development has to pass through several phases; the one following laboratory research is, of course, drafting of a preliminary flow scheme showing the various stages of the new process. It would be premature, however, to construct a pilot plant merely on the basis of such a flow diagram. First the stages in the flow scheme should be analyzed, and separate investigations will serve to find a favorable procedure and attractive conditions. The pilot plant is not necessarily the actual plant in miniature; a first requisite is ample scope for varying and accurately measuring process factors such as pressuresI velocities, and temperatures. This process development and pilot plant work is very costly. The expenses incurred by complete development of a new process are usually several times the cost of the preliminary laboratory research work, and constitute a considerable percentage of the cost of building the envisaged commercial plant. The quesFigure 2. tion therefore arises as to whether all this work is justified. The short answer is that practice has proved i t to be so. Baekeland describes the pilot plant as the instrument with whirh “to make your mistakes on a small scale, so that your profits can be on a large one” ( I ) . Process development aims a t developing a given chemical reaction or complex of reactions and occupies itself with the total process for manufacturing or refining products. Within this general scheme, however, are all types of unit operations which are by no means peculiar to the process concerned, but are encountered again and again in technology in general. Such factors as mass transfer, heat transfer, and transfer of momentum are among the basic industrial problems, and present-day industry would be unthinkable without the transport of gases, liquids, and, solids, or without distillation, filtration, and mixing. I n many cases new chemical reactions can be introduced into the industry

PILOT PLANT

Assembly for small scale continuous testing of catalysts at atmospheric pressure

only by means of a rational selection and development of constructional materials for the apparatus to be used. It is to this complex of physical, physicochemical, and physicomechanical factors that chemical engineering devotes its energies. For these reasons the Process Development Department of the Koninkli jke/Shell-Laboratorium, Amsterdam, comprises not only two main groups %Torkingon oil and petrochemical processes, but also a third group, whose task i t is to keep fully informed on and if necessary to devote experimental study to unit operations. I n many cases this results in the development of new equipment tools. The Amsterdam process development aotivities are only part of the total development work, as the process development and design group of de Bataafsche Petroleum 34aatschappij (one of the principal operating companies of the Royal Dutch-Shell Group outside the United States , + AIR. MAGNf T/C VALV f--@A . -VACUUM @ AUTOMANCALLY C O N T R U E D and Canada), contributes its ,!r - > m [ .._ fp70L.FR @ HAND CONrROLLED own share to the development i @ INDICATOR of the total project in its various aspects. The activities of the department result in the prepl“ERmocouPL aration of the ultimate process OFF and process engineering flow schemes; i t acts as a liaison among the various parties concerned in the final commercial realization of the project-e.g., Amsterdam research and deGAS S&MPLE velopment (experimental background)] economics (cost evaluation of processes and prodecures), manufacturing (availability of base materials, balances tie-in GAS BUFFER of the new processes in refineries, etc.), purchasing department (position as to raw materials to be purchased from outside), patent department] and the commercial and marketing departments. For a sound development in the experimental Figure 3. Apparatus for continuous testing of catalysts a t atmospheric pressure phase, close contacts and coSimplified flowsheet of one of seven reactor tubes shown in Figure 2 operation with the head office ?-.

-

June 1955


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ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT

Figure 4.

Assembly for small scale continuous testing medium pressure

of catalysts at

Equipment i s provided for numerous purposes The purpose for which development add pilot plant equipment is built may vary widely. This is reflected in the way in which the equipment is built. I n the case of the Amsterdam laboratory this may be illustrated by the following division of equipment:

process development and design group are indispensable in order to keep the development studies in line with optimum economic justification, the need for data of process design workers, and possible factors limiting the commercial potentialities. Service Activities. Although actual process development is the primary task of the process development and pilot plant department, part of its activities must be devoted to questions of a service character received from many sources outside the department, and which, for reasons of technological experience or availability of equipment and trained staff, are best dealt with in this department. For example, while process development work is going on, the question usually arises how to manufacture the quantities of the envisaged product necessary for a careful evaluation of its properties and for market development. Particularly in the case of chemicals market development quantities are frequently required and here the available pilot plant equipment will naturally play an important part. Another point to be considered, particularly in the oil industry, is the frequent application of new base materials for the manufacture of products already on the market (and as such object to rigid specifications). I n general, this will raise problems of how to make thelmost efficient use of existing plants and how to manu-

REACTOR INSIDE DlA34mm.

Equipment for development of new processes Accounting for various process development phases, a further distinction must be made. First orientation in the development field, laboratory phase Small pilot plants More extensive pilot plants Model experiments in unit operation studies supporting all phases of development and plant design Equipment meant as scaled-down models of commercial installations and processes, mainly to be used for evaluation of base materials, and for manufacture and evaluation of products Equipment for general routine and service purposes Figure 1 shows some of the buildings used for this work. Equipment for Process Development Studies. FIRST ORIENTATION IX DEVELOPMEKT FIELD(LABORATORY PHASE). Prior to building a pilot plant, the process to be developed and its various stages should be carefully analyzed. Apart from the economic aspects, which must not be lost sight of in any phase of development, there are at the very outset numerous questions with a technical background which in most cases have received insufficient attention in the research phase. With the available research results as a starting point and the building of a commercial plant with optimum efficiency as the ultimate goal, there are a number of points on which information must be collected.

SIGHT- GLASS

BACK PRESSURE VALVE@

Tisotg. to otm. PRESSURE

8 A H

AUTOMATfCALLY CONTROLLED HAND CONTROLLED

@

INDlCATOR ALARM

cjih v

I C O N S T A k PRESSURE)

Figure

5.

Apparatus for continuous testing of catalysts at medium pressure Simplified flowsheet of one of two sets shown in Figure

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facture the relatively large quantities of products required for a complete assessment of product properties. I n the latter case equipment available in the process development pilot plant department will have to be used. Naturally, both here and in market development the products will have to be representative of future commercial production. Apart from these questions of evaluation of base materials and products, the pilot plant may also be required for the solution of problems arising in the operation of existing commercial plants. Finally, in an all-round research laboratory a certain pilot plant activity is necessary for constantly recurring operations of a routine character-e.g., supply of base materials to other pilot plants by means of distillation, highpressure operations in batch autoclaves, etc.).

4

Optimum operating conditions-temperature, pressure, space velocity, ratio of reaction components, sensitivity of the process to variations in operating conditions and t o impurities in base materials, auxiliary materials, and intermediate products Best procedure for each process stepbatch vs. continuous procedure, filtration os. centrifuging or settling, choice of reactor type, etc. Optimum combination of process steps; material and heat balances of each process ste$uantitative data on heat and material transfer; most suitable analytical methods; best construction materials


Vol. 47, No. 6

PILOT PLANT

Figure 6.

Pilot plant for continuous sulfonation of hydrocarbon fractions

Although sometimes part of the questions can be answered on the basis of literature data, earlier experience, or calculations, i t is usually necessary to resort to experiments. As pilot plant work is time-consuming and requires expenditure of manpower and money, the obvious way is t o collect as many data as possible by means of small scale experiments. T h a t is why in this first development phase a considerable part of the experimental work is carried out on a laboratory scale. Questions referring to the process as a whole are studied by a laboratory development working group, while for questions regarding the separate stages of the process, the unit operations section can lend considerable support. This section carries out simple model experiments for selecting the procedure which technically is the most attractive, and for establishing scaling-up rules. In this phase of small scale experiments standard laboratory equipment and materials will suffice in the majority of cases. Equipment and instrumentation are here kept as simple as possible, so as to limit time of construction and enhance flexibility and simplicity of operation. Two examples illustrating the way in which this type of equipment is set up are given in Figures 2 to 5 . Figure 2 shows a continuous apparatus to be used for catalyst testing a t atmospheric pressure; Figure 4 represents an apparatus for studying catalyst activity and the inffuence of the reaction conditions for continuous catalytic proceases a t working pressures up to 50 atmospheres.

SMALLPILOTPLAXTSFOR DEVELOPMEKT PURPOSES.A careful investigation in the first exploratory development phase usually furnishes, in a comparatively short time, a wealth !of information from which emerges a general outline of the setup for the commercial plant. Another important result of this first orientation is that a- much better view is obtained of the questions-e.g., process data, alternatives in equipment, and procedure-which remain t o June 1955

be studied in more detail and on a larger scale. I n this way a sound basis is laid for the next phase of development-the design and use of a small pilot plant. The size of such pilot plants is generally of the order of 5 to 10 liters per hour intake for continuous processes and this is therefore the first opportunity for an experimental study of upscaling. I n constructing the pilot plant, as the problem in hand is better understood, more or less drastic changes may prove to be desirable. This means that the construction will have to be simple and partly of a temporary character, to facilitate building and altering. An essential point is t h a t the plant is not further extended and completed than is required for this stage. For instance, i t is often wise not to connect the reaction system of the pilot plant to working up facilities for the product envisaged, but AIR ICENSPNT &“E$MEURE,

W A T C VESSEL

FOR WATER FLOW METER

STORAGE OF OLEUM

ACID

Figure 7.

Continuous sulfonation o f hydrocarbon fractions Simplified flowsheet of installation shown in Figure 6

I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY

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ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT first to assess results by analysis. When considerable recirculation of unconverted material is involved, however, coupling to a distillation or extraction unit will be inevitable, if equilibrium in the system is to be obtained. The use of auxiliary equipment, such as control instruments, pumps, etc., is restricted to a minimum in this phase. Additional time and money can be saved by using available but not specially adapted equipment (settlers, coolers, heaters, grinding equipment) a t points which are not of vital importance for the development work proper. An example of such a small “temporary” pilot plant,, an installation for the continuous sulfonation of hydrocarbon fractions, is shown in Figures 6 and 7 . The plant is completely operated by hand control. Some detailed information is given in Table I. I n some cases it is unnecessary to build a new pilot plant, because an existing one can be easily adapted t o the purpose in view. Cases in point are pilot plants built for catalytic high-pressure processes, which after some minor alterations can be re-used for other, analogous processes. Figures 8 and 9 show a plant which, in the course of time, has been used for high-pressure hydrogenation as well as for Oxo and Fischer-Tropsch synthesis (Table 11). In several catalytic high-pressure processes the general procedures have many features in common. I n the study of processes for the batchwise production of chemicals, too, it is usually easy to build up a suitable pilot plant from available all-purpose reactors and auxiliary equipment. As soon as the process has assumed a more definite form, it is useful t o ascertain the influence of fluctuations in the process variables, and to consider how difficulties t o be expected in the instrumentation of the commercial plant can be met. Careful attention should be paid to the selection of constructional materials for the commercial plant. T o this end, corrosion test plates in standardized holders are placed in the pilot plant (see Figure 10).

The question will now arise whether and to what extent the “temporary” pilot plant should be given a more permanent character. This is very often done to enable the plant to be used as a scaledldown model of the commercial or semicommercial plant which is based on the results obtained in the small pilot plant. I n some cases the plant is dismantled or part of it used for other processes. The situation is different from case t o case and general rules cannot be given. LARGER PILOT PLANTS FOR DEVELOPMEKT PURPOSES. Where new processes are concerned which bear much resemblance to well known existing ones, the small pilot plant together with the unit operation studies usually provides a sufficient basis for the neucommercial plant, without intermediate studies in a larger pilot plant. I n other words, in such cases a high upscaling factor-say, 1000-does not involve undue risks. For a brand new process, however, even an upscaling factor of 100 is high and here it is the rule t o build a larger pilot plant. This serves primarily to confirm the conclusions reached so far as regards upscaling effects t o be expected and optimum operating conditions. I n addition, it must give further proof of the operability of process and plant on a semicommercial scale. Naturally, the upscaling factor must be considered for each case separately; when upscaling is very difficult as regards equipment, the factor must be very low-e.g., 10. A pilot plant of large dimensions naturally requires large quantities of base materials and produces large amounts of final product which must he worked up and removed. Frequently, the obvious way is to use for the large pilot plant the facilities of the refineries or the chemical production plants and to build it there and not in the Amsterdam laboratories. Sometimes it is possible to work in a slip stream of existing refinery processes. Naturally, experimenting in a semicommercial pilot plant is comparatively expensive and often interferes with the normal ac-

P

GAS RECYCLE PUMP

I I

I I

j j

OOc MAKE-UP GAS

1 zzzzq ELECTRIC h’&4TER

Figure 8.

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Pilot plant for catalytic high-pressure processes

Figure 9. Diagram of catalytic high-pressure pilot plant (up to 200 atmospheres gage) for fixed-bed reactions in upflow and downflow operation and for slurry operation


Vol. 47, No. 6

PILOT PLANT

Table 1. Type of Equipment Vessels

Detailed Information on Pilot Plant for Continuous Sulfonation of Hydrocarbon Fractions Volume (Capacity), U. S. Gal.

Purpose Storage a n d mixing of hydrocarbons Hydrocarbon feed tanks Storage of oleum Oleum feed t a n k Sulfonation

Materials of Construction Glass-lined Mild steel Mild steel

Type

60 1.50 80 50

Gasoline storage Dilution Settler

15

Mild steel

65 40 20

Stainless steel AISI 321 Mild steel Mild steel

Remarks Mild steel would have been suitable Provided with calibrated liquid level glass Provided with calibrated liquid level glass Provided with 4 baffles, bottom of cylindrical vessel slightly conical Mild steel would have been suitable Conical bottom, 4 baffles in conical part Horizontal type

Gal./Hr. Pumps

Oleum feed Hydrocarbon feed Circulation in reaction system Circulation in dilution system

0-15 0-20 Abt. 260 Abt. 200

Stirrers

I n reaction vessel I n vessel for storage and mixing of hydrocarbons I n dilution vessel

200-376 0-120 1400

Plunger Plunger Centrifugal Centrifugal

Stainless steel AISI 321 Stainless steel AISI 321 ASTM A 299-52aT Glass-lined

Packing, asbestos-graphite

Anchor Anchor Double propeller

Mild steel Glass-lined Mild steel

Coil Coil

Mild steel Mild steel

Cooling medium t a p water, heating medium steam

Mild steel Mild steel Mild steel Mild steel Mild steel Mild steel

Provided with stainless steel valves AIS1 420, s/8 inch Stainless steel AISI 321 cocks, 1 inch

R.P.M.

Cooling Area, Sq. Ft. Coolers

7

I n reaction system I n dilution system

14

Inch Diam. Lines

Oleum feed line Hydrocarbon feed line Reactor system Dilution system Overflow line from reactor to dilution vessel Overflow line from dilution vessel to settler

3/8 3/8

1

1 1

1

tivities in the refineries. This is reflected in the design Of the pilot plant, which is not nearly so flexible as its small predecessor of the first phases of the development work. As a rule the large pilot plant is built as nearly as possible as a definite unit, which, if desired, can be used for small scale production; it is also provided with all measuring and control instruments that must be used in the ultimate commercial plant. I n many cases, additional instruments are even fitted, in order to obtain a complete picture of the process in all its steps.

quired for one or more physical or physicochemical operations in the process. The procedure is fundamentally comparable to that described for the process studies. When extensive general experience of analogous cases has already been gained and good upscaling rules are available, a simple model experiment in a small laboratory

EQUIPMENT FOR M O D E L EXPERIMESTS I N UNIT OPER4TION STUDIES. The studies for development of the process as a whole run parallel t o the unit operation studies made as and when re-

L7

J

TO BE FIXED IN A SUPPORT NUT

END PLATE DlSkS OF MAT€RfAL T 0 . M TESTED

MICA fNSULATlON

STEATITE DISTANCE RINGS

Figure 10.

Cutaway view of corrosion test assembly Dimensions in inches

lune 1955

Figure 1 1 . Equipment for model experiment on transport of solid particles in gases

INDUSTRIAL AND ENGINEERING

CHEMISTRY

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ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT , Table II. Catalytic High-pressure Pilot Plant Type Gas apd liquid feed Make-up gas storage buffer

Dimensions

Cylindrical high pressure buffer

Gas recycle pump

Reciprocating plunger pump with variable number of strokes

Liquid feed tank

Cylindrical with conical bottom

Liquid feed pump

Reciprocating plunger pump with variable stroke

Preheater, reactor, condenser Prehester

Reactor

Condenser Gas-liquid separator

Electrically heated coil

Height 9 f t . ,0.d. 20.5 in. i.d. 15.4 in. Volume abt. 80 E. S. gal: Max. pressure 5700 lb./sq. in. Displacement per stroke 2.1 cu. in. Max. number of strokes 200/minute Working caoacitv 7-14 cu. ft./hr. Max. working pressure 5700 lb./sq. in. Height 4 ft., i.d. 21.6 in. Volume a b t . 80 E. S. gal.

ASTM A 29952aT

Plunger packing. Metallic (lead) rings with continuous lubrication between plunger and packing

Mild steel

For slurry operation provided with stirrer a n d gear

ASTM h 29952aT

1 6 f t . 0.62in. (0.d.) X 0.39 in. (Ld.) tube H e a t surface 2.8 sq. Et. Max. heat input 6 kw. Heat transfer, direct by radiation

ASTM -4 30152aT

Croloy 7 AISI 501 modified

Cylindrical

Mild steel

apparatus may be sufficient. I n other cases, however, tentative experiments on the smallest scale possible as well as experiments on a semitechnical, semicommercial, or even commercial scale are required to arrive at satisfactory upscaling rules or to decide on the most efficient commercial operation of the process stage under consideration. Particularly in the first phases of unit operation work the aim is rapid construction of the requisite equipment, which must be of a flexible (and very often temporary) character and must allow easy alterations without undue loss of time. Within the requirements for reliability and exactness of results the equipment will not, in the first instance, be perfected further than is absolutely necessary for the purpose in view. Wherever possible, standard parts and assembly frames are used. It has been found very important and instructive in unit operation work to use glass or another transparent material Cor the most essential sections of the process; direct observation may afford a more rapid and better understanding of the background of the phenomena. Figure 11 shows two temporary setups built on different scales and used to study the transport of solid particles in gases. Another typical example of equipment used for unit operation studies on flow and dispersion of liquids is shown in Figure 12. An apparatus to study fluid. and fluid-solid flow on a larger the scale is illustrated in Figure 13. The essential part-i.e., tower with a height of 4 meters and an inside diameter of ca. 1 meter-is made of Perspex (I.C.I. Ltd.). Experiments may even be made in scale models, as is shown in Figure 14, presenting a photograph of a n apparatus used for model experiments t o study the distribution of liquids over fixed catalyst beds. Scaled-Down Models of Commercial Installations and Procewes. Numerous small pilot plants, after having completed their task in process development, are used as scaled-down models for

pump, latter for circulating suspension on the low pressure side of t h e suction valve of feed pump Plunger. Chromium plated or nitrated. Plunger packing. Teflon with normal gasoline resisting packing

AISI 420 steel containing 0.9% carbon, 1.5% vanadium

Tubular with central Height 18 ft., 0.d. 4.5 in., i.d. 3.1 in. thermowell through- Thermowell 0.d. 0.9 in., i.d. 0.39 in. out whole length Volume abt. 7 U. 9. gal. Max. working pressure 3500 lb./sq. in. Heating electrically by two-circuit electrical furnace Max. heat input 6.5 kw. Max. temp. 300' C. Coil 80 ft. 0.91 in. (0.d.) X 0.39 in. (i.d.) tube Cooling surface 19'sq. ft. Height 5 f t . , 0.d. 13 in., i.d. 11 in. Max. working pressure 2800 lb./sq. in.

Remarks

Mild steel

Max. displacement per stroke 0.85 cu. in. Max. number of strokes 6O/min. Working capacity 2.5-13 U. S. gal./hr. Max. working pressure 2800 lb./sq. in. 0.75-in. ball valves 0.6-in. diam. sharp edged seats

Liquid release via threefold valve system

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Material

AISI 501 (mod.) (Croloy 7) Placed on scales. Liquid level kept constant by maintaining certain weight. Connection lines provided with hairpin bends, providing flexibility. Two release valves made from mild steel; regulating valve must be erosion-resistant and therefore made from special material-e.g., tungsten carbide

Figure 12. Equipment for model studies on flow and dispersion of liquids


Vol. 47, No. 6

PILOT PLANT Table 111. A.

Extraction tower Capacity Dimensions Baffles Materials of construction Heating

B.

Figure 13.

Assembly for larger scale model studies on fluid and fluid-solid flow

the commercial plant, particularly for the production of large quantities of product-e.g., for market development and evaluation-for the evaluation of new base materials, and as a stand-by in the case of operational trouble in the commercial plant. Unlike the pilot plants-and particularly the small plants in the development phase-the scaled-down models will be altered very little or not a t all, as the process is now in its final form. The scaled-down models, as a rule, have to be available for long periods up t o several years. Consequently, their construction will assume a more permanent character. Naturally, the operation of the scaled-down models can also acquire a routine character, more than in the development phase; accordingly, the pilot plant can now be provided m-ith a full set of measuring and control instruments as Tell as other facilities, in order to reduce the operating crew to a minimum. The construction of a scaled-down model is, of course, not necessarily the direct consequence of the development of a new process or a different procedure. It may also be required for processes that have been in commercial use for a long time. Thus immediately after World War 11, they were necessary in Amsterdam for the production of refined petroleum fractions from crude oils by conventional methods, one of the objects being the evaluation of new crudes. A set of continuous pilot plants was built for the normal operations in this field (crude distillation unit, single-solvent, and Duosol extraction, tower deasphalting, demaxing, acid and earth treatment). As an example, Figure 15 shows a section of the crude distillation unit; Figure 16 gives an idea of the continuous tower deasphalting unit. The intakes of these oil plants were adjusted t o give a production of 5 to 10 liters of refined lubricating oil fractions per hour. The crude distillation unit is made of mild steel. The main column (length 36 feet, diameter 4.7 inches) and the stripping column (length 5 . 7 feet, diameter 3.8 inches) are packed with 0.6 X 0.6 inch Raschig rings. I t s working pressure varies from atmospheric down to about 2 inches of mercury. Some details of the desaphalting unit are found in Table 111. The above may have conveyed the impression that there is only one scaled-down model plant for a given process. As a rule

lune 1955

Pumps Propane feed pump Type Capacity Discharge Materials of construction

Deasphalting Unit

+

2 U. 9. gal./hr. short residue 20 U. S. gal./hr. Length 33 ft., internal diameter 4 in. 50 Mild steel ToxT-er provided with jacket in 6 separate sections, each connected with separate spindle oil circulation system (circulation rate 80 U. S.gal./hr.). Temperature of circulating oil controlled automatically: oil heated electrically

Max. 8800 Pump bodj Plunger, Si Ball valves Packing, (Kobar)

Oil feed p u m p Same as for propane feed pump, except: Capacity 2.6 U. S. gal./hr. C. Columns Two colurnns for propane recovery from propane phase Simple flashing column Length 10 ft., diameter 3 . 7 in Dimensions 140 lb./sq. in. Working pressure Materials of construction Mild steel Bottom electrically heated Heating Stripping column for bottoms from column 1 Dimensions Length 13 ft.. diameter 3 . 3 in. Working pressure Atmospheric Materials of construction Mild steel Heating Stripping with superheated steam Flashing for propane recovery from asphalt phase Dimensions Length 7 it., diameter 2.6 in. Working pressure Atmospheric Materials of construction Mild steel Heating Bottom electrically heated Stripping Stripping with superheated steam

this is true, but occasionally, when a large amount of work of widely varying character has to be done for an important project, two or more scaled-down models of different size and perfection may be justified. A similar situation occurred, for example, in Amsterdam, when after World War I1 the evaluation of base

Figure 14. Scale model for studies on distribution of liquids over fixed catalyst beds


1111


Figure 15. Section of crude distillation pilot plant

materials (and design questions) called for close attention in connection with the envisaged construction of fluid-bed catalyst cracking units on the Continent and in the United Kingdom. The following units, which were erected in collaboration with American associates (and which essentially had been developed by them beforehand), were successfully used:

A small fluid fixed-bed unit A somewhat larger semicontinuous unit ( 2 ) A complete unit with an intake of 15 t o 20 liters per hour ( 3 )

Naturally, each covers a wider field of application than its predecessor. The small fluid fixed-bed reactor-which is alternately used for cracking the feed and regenerating the catalystis very simple and thus primarily suited for a rapid orientation, particularly as regards the activity and selectivity of cracking catalysts under standard conditions, using a standard base material. The semicontinuous unit (shown in Figure 17) provides considerably more possibilities and is eminently suited for evaluation of base materials, catalysts, and operating variables. I n this apparatus regenerated catalyst is continuously fed to the reactor

Figure 17. Figure 16. Tower deasphalting pilot plant

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Semicontinuous catalytic cracking pilot plant


Vol. 47, No. 6

PllLOT PLANT . _ I

Figure 19.

Figure 18.

Continuous catalytic cracking pilor’ plant

and spent catalyst continuously withdrawn from it; but there is no continuous regeneration of spent catalyst. The larger unit (parts of which are shown in Figures 18 and 19) is almost a replica of the commercial plant as far as the cracking section (reactor, regenerator, and stripper) is concerned. After the cracking section i t has a complete distillation section. The unit has

Part of panel of continuous catalytic cracking pilot plant

been designed for continuous operation and is provided with recycle facilities. Hence, this plant allows a more definite evaluation of base materials (and a final assessment of optimal process conditions): if desired, it supplies large quantities of final product for evaluation purposes. This example demonstrates that in the group of the scaleddown models there may be considerable differences both as regards flexibility and scale. A few figures given in Table IV stress the importance of collecting as many data as possible on a small scale. Equipment for General Routine and Service Purposes. A group of equipment which, without bearing on any particular process or process development study, yet constitutes a n essential part of the over-all pilot plant equipment is usually designated as “general-purpose equipmentJ’-Le., equipment suitable for the greatest possible variety of purposes and serving for the rapid solution of frequently recurring and closely related questions. These questions mag- arise not only in the process development

Figure 21.

Panel of batch distillation unit

Leff. 6-point temperature indicator controller for controlling column wall temperature b y differential temperature between vapors and column wall. 48-point temperature indicator for measuring all temperatures in units Center. Reflux ratio controllers for controlling cycle time for reflux valve. Switches and ampere indicators for heating elements

Figure 20.

Batch distillation unit

Right. &point temperature recorder with safety device for maximum 1 -point temperature indicator with alarm system for skin temperatures. cutting temperature


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Table IV.

Catalyst Cracking Units

Feed, liters per hour

About

Diameter of reactor, inches

Cost of construction, guilders

Plant operators By day only Continuous operation Plant operating tinie for experiment with one set of conditions, hours

Table V.

Figure 22.

Autoclaves for general purposes

and pilot plant sections, but often in other sections of the laboratory or outside the laboratory. Much work, mostly of a similar character, is done in this equipment, which is hence seldom altered. It is therefore fully justifiable to give its construction the utmost rigidity, and to take all measures for automatic and safe functioning. A classical instance in this field is distillation. The feed supply to the pilot plants alone means a considerable amount of distillation work and usually intermediate and final products also require distillation. Wherever possible, this is done in a central distillation section specially equipped with a multipurpose set of columns for batchwise and continuous distillation. As an example, Figures 20 and 21 show parts of one of the stainless steel batch columns (bottom capacity 1000 liters); i t is provided with the same control instruments as the most automatized scaled-down models-e.g., automatic reflux distributor, temperature control, compensation coil, control of column loadand with various safety and alarm devices, so that the equipment can work without supervision for some time (protection and alarm if cooling water supply fails, if bottom wall of boiler is overheated, or if impermissible pressure builds up across column; alarm if a predetermined top temperature is reached). More detailed information on batch distillation units of this type is given in Table V. Another example of general-purpose equipment is afforded by the autoclaves for the batchwise production of chemicals. A large number of organochemical reactions can be carried out in these autoclaves, which are GOO- L ITER GLASS -L /NED suited for a pressure of 4 to 6 kg. per sq. em. AUTOCLAVE and are fitted with a stirring device with variable rotation speed, a jacket for heating with steam or hot oil or for cooling, and a simple device for distillation and azeotropic dehydration. This set includes autoclaves of various capacities, made of various materials (stainless steel, enamel, Hastelloy, steel) (Table VI). Some are shown in Figures 22 and 23. Figure 23. Yet other examples are the autoclaves for high-pressure experiments and the equipand Optimum conditions in fixed-bed operation for high- and merit for

1114

Out

Maximum intake, bbl. Columns Diameter, inches Length, feet Packing type dimensions, inches Distillate containers, capacity, U. S. gal. Bottom heating (automatic control on differential pressure over column) hlaterials of construction Working pressure Maximum, lb./sq. in. gage Minimum, mm. €Ig

Vacuum pumps, capacity, cu. ft./hr. Vacuum buffer, capacity, cu. f t .

Fluid FixedBed

Semicontinuous

Unit

Unit

0.5

2

1 5 20,000

Continuous Unit 15 fresh feed 8 recycle

2 6 125,000 500,000

1

1

..

. ..

1.5

4

......

2 per shift

60

Batch Distilling Units 7.5 Adiahatic 8

1.6 Adiabatic

Bed saddles 0.47 X 0.47

17

16 Berl saddles 0.32 X 0.32

0.5 Adiahatic 3 13 Berl saddle8 0.2 X 0 2

25

8

4

4

Electrical stainless steel, AISI 321



44

44 1

44

1

2800

2800

2800

30

30

30

1

medium-pressure catalytic processes, Figure 24 shows a seriea of simple reactors, which, to this end, are equipped for continuous once-through operation a t high pressures. More detailed information is given in Table VII.

STA/NLESS STEEL

STAINLESS-STEEL

Simplified flow diagram of general-purpose autoclaves

Equipment i s provided with jackets that can be heated by hot water, steam, and hot oil, or cooled by water and brine. Autoclaves are provided with manhole and connections for vacuum, compressed air, water, steam, liquid feed, etc. T. Thermocouple (with recorder)


Vol. 47, No. 6

PILOT PLANT Table VI. Material of construotion of autoclave Total content, U. S. gal. Working pressure, lb./sq. in. Bottom Heating and cooling

Stirrer Type Dimensions, in. Speed, r.p.m. Place Packing of stuffing box

Column on autoclave Dimensions, in. Material Heating, cooling Working pressure, lb./sq. In. Distillate condenser Type

General Purpose Autoclaves and Auxiliaries Cast iron, glass lined

Abt. 6 5

Abt. 160

Stainless steel AISI 321 Abt. 260

85

55

85

55

55

140

Semisphere Semisphere Steam-water jacket Heating, jacket, and internal coil steam, or hot oil (surface a b t . 11 sq. Cooling, jacket, waft.) ter, or brine

Semisphere Heating, jacket, steam-water Cooling, jacket, water, or brine

Semisphere Heating, jacket, steam-water Cooling, jacket, water, o r brine

Semisphere Heating, jacket, steam or hot oil Cooling,’ jacket, water, or brine

Conical Heating, jacket, steam, or h o t oil Cooling, jacket, water, or brine

Two four-blade propellers Diameter 19 0-120 Eccentric Asbestos-graphite

Height GO, diameter 2.8 Mild steel Jacket, steam-water 85

Pipe condenser

Settler Material Mild steel Capacity, U. S. gal. 15 Working pressure, Ib./sq. in. 45 Distillate receiver Material Mild steel Capacity, U. S. gal. 13 Working pressure, lb./sq. in. 45

Abt. 5 0

Open ring

Anchor

Open ring

Open ring

Propeller

About 18 X 26 0-120 Eccentric Asbestos-graphite

Tip distance 27 0-120 Centric Asbestos-graphite

.%bout 20 X 32 0-120 Eccentric Asbestos-graphite

About 22 X 3 7 0-120 Eccentric Asbestos-graphite

Diameter 6 1000 Eccentric Asbestos-graphite Stirrer shaft cast iron lined with Hastelloy B

Height 60, diameter 2.8 Stainless steel AISI 321 Jacket, steam-water 55

Height 7 2 , diameter 6 Cast iron, glass lined

Height 63, diameter 6 Cast iron, glass lined

Height 6 5 , diameter 3 Cast iron, glass lined

Jacket, steam-water

Jacket, steam-water 55

Height 63, diameter 6 Stainless steel AISI 321 Jacket, steam-water 55

85

L___y___2

Material Mild steel Cooling area, sq. ft. 9 Working pressure, lb./sq. in. 45

i -

Jacket, steam-mater 85

Y--

Combination for two autoclaves Pipe condenser

Combination f o r two autoclaves Pipe condenser

Stainless steel AISI 321 8


Special t y p e pipe condenser Hastelloy B 3.3

45

46

1.40



No settler

45

45



Cast iron, glass lined 13

45

45

85

Remarks

Connection between condenser and receiver borosilicate glass pipe (35 in. lonn. 4 in. diameter; working pressure 45 lb./sq. in.)

Figure 24.

June 1955

Hastelloy B

Cast iron, glass lined

Abt. 160

Stainless steel A I S I 321 Abt. 65

Mild steel

Equipment for continuous fixed-bed operation in high- and medium-pressure catalytic processes


1115

ENGINEERING. DESIGN. AND PROCESS DEVELOPMENT Table VII.

Equipment for Continuous Fixed-Bed Operation in High- and MediumPressure Catalytic Processes Vapor Phase Upflow

Type of Operation Reactor dimensions Length, f t . Inner diameter, in. Outer diameter, in. Reactor design d a t a hhterial

1

2

1.9 Croloy 7 mod)

Remarks

5.1 1.2

3.8

Working pressure, lb./sq. in. Temperature, C. Catalyst loading Volume, cu. In. Pellet size, in. Catalyst bed height, in. Heating (electrical) Temperature measurement Temperature control Pressure control

Liquid Phase Downflow

(AIS1 501

Croloy 7

2800

2800 500

Max. 6 . 1 Max. 0 . 2 X 0 . 2

Feet rate, cu. in./hr.

1-circuit furnace By coaxial thermowell 6 point on-off controller By reducing valve in hydrogen supply Max. 3 0 . 5

Max. 30,5 Max. 0 . 2 X 0 . 2 29 3-circuit furnace By coaxial therinowell 6 point on-off controller By reducing valve in hydrogen supply Max. 120

Hydrogen supply, standard cu. ft.

Illax. 18

Max. 18

500

--

18

Capacity 1 and 2 kw.,resp. Outer diameter 0 . 4 3 in. Located between hydrogen storage bomb a n d unit B y plunger p u m p with adjustable sttoke

Acknowledgment

Literature cited

The authors wish to express their sincere thanks to the management of the Koninklijke/Shell-Laboratorium, Amsterdam, and the management of N.V. de Bataafsche Petroleum Maatschappij for permission to publish the above information. They are equally indebted to many colleagues for their helpful assistance in the preparation of this paper and for their valuable criticism.

(1) Killeffer, D. H., "Genius of Industrial Research," p. 203, Reinhold, New York, 1948. (2) Marshall, J. A , , and Askins, J. W., IND.ENQ.CHEM.,45, 1603 (1953). (3) Trainer, R. P., Alexander, N. W., and Kunreuther, F., Ibid., 40, 175 (1948). RECEIVBD for review December 2, 1954.

ACCEPTED April 9, 1955.

Sodium Sulfite from Caustic Cell liquor Sodium Sulfite-Sodium Chloride-Water System KENNETH A. KOBE AND

KATHERINE C. HELLWIG

U n k e r s i f y o f T e x a s , Austin, Tex.

I

N THE electrolysis of sodium chloride brine in diaphragm

electrolytic cells, the products are chlorine, hydrogen, and a solution of sodium chloride and hydroxide. A t times, the market situation has been that the sodium hydroxide was a competitive product because of the caustic soda produced by causticization of soda ash. Even when the caustic soda was surplus, i t was necessary to concentrate the electrolytic solution, separate the

I

I For times of surplus caustic soda these phase relations show that

. . . conversion of cell liquor to sodium sulfite may be feasible as an alternate for carbonating to soda ash

. . .the mother liquor can be reused in the diaphragm cell

I 1116

sodium chloride, and produce for market a caustic soda of 50, 7 3 , or 1 0 0 ~ oconcentration. It would be desirable to have a process that would avoid the evaporation of the caustic brine solution, b u t would permit i t to be used directly for the production of some chemical used in large amounts. Such a process directs attention t o the Hargreaves-Bird cell ( 1 0 )in which carbon dioxide unites with the alkali in the cathode chamber to form sodium carbonate. The recent announcement ( 1 6 ) that the Dour Chemical Co. a t Freeport, Tex., will carbonate cell liquor to produce sodium carbonate arouses new interest in this process. I n a similar manner, sulfur dioxide could be used t o form sodium sulfite. Thus, a three-component system, sodium chloride-sodium sulfite-water, would result. The necessity for separating the sodium chloride and sodium sulfite becomes apparent. T o determine the industrial feasibility of this separation, the phase relationships of the system must be known. Therefore, the phase properties of the system sodium chloridesodium sulfite-water a t O", 25", 40", 60°, 80", and 100" C. have been determined. The solubility of sodium chloride has been well established b y previous investigators. A summation of data obtained b y Mulder in 1883, Andrae in 1884, and Berkeley in 1904 is presented


Vol. 47, No. 6

'

Pilot Plant EQUIPMENT FOR OIL AND PETROCHEMICAL PROCESS

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