LANTS Unit Process Pilot Plant HERMAN L. SHULMAN Clarkson College of Technology, Potsdam, N . Y .
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N T H E chemical indus-
try there are many occasionswhen it is necessary to employ small scale equipmerits common examples
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A versatile pilot plant was built
to be both suitable and available at all times for the solution of a wide variety of problems requiring small scale equipment. Equipment was installed for studying the chemical reactions and physical separation operations involved in the preparation of batches of organic chemicals on a 5- to 30-
EQUIPMENT
Because of the corrosive action of the many chemical reagents to be used, the equipment was fabricated! from are pilot plant work, prepacorrosion-resistant materials ration of samples of new prodgallon The use of a permanent but flexible installation employsuch as stainless steel, boroucts, preparation of batches ing corrosion-resistant materials saves time and installasilicate glass pipe, and glasslined steel. The units t o be of chemicals required for tion COstsfor nonproduction chemical work in l a b o r a t o r y research Work, equipment such as pilot plant investigations, preparation described in detail are shown and process improvement Or of samples of new products, and process improvement in to 5development work where it work. Ten-Gallon Glass-Lined is desirable to study effects Reaction Kettle. T h i s of certain process variables on kettle, with its accessories, a small scale rather than in an existing plant. It is possible to is the most important piece of equipment in the unit procinstall equipment so that it is suitable and available a t all times ess laboratory and may be employed for a wide variety of for a large portion of the small scale work an organization may be experiments. It is a 10-gallon Pfaudler P series, jacketed, called upon to do over a period of time. Such an installation glass-lined kettle equipped with a two-blade impeller and an must be capable of dealing with batch and continuous operations adjustable baffle, The shafts of the impeller and baffle are hollow at high and low pressures and temperatures if it is to be prepared and may be used as thermocouple wells. The discharge valve is a for the variety of problems which may arise in chemical work. 2-inch glass-lined flush valve with a porcelain valve head and The purpose of this paper is t o describe a versatile permanent seat. Two bfoot jacketed sections of 2-inch glass-lined pipe were installation capable of dealing with a wide variety of problems on joined to provide a 12-foot vertical reflux condenser. A 3-inch a pilot plant scale. Equipment which is suitable for such a glass cylinder was placed below the condenser so t h a t the rate of versatile installation has been described recently by Gwin and refluxing may be observed and controlled. The arrangement of the various fittings may be seen in Figures I , 2, and 3. Yule (2’) who covered pilot plant equipment for studying a wide variety of catalytic and continuous processing operations enA glass pipe sampling device was attached to one of the opencountered in the petroleum industry. Glasebrook and Montings in the head of the kettle for withdrawing samples during an gomery ( 1 ) have described a high pressure laboratory designed experiment. This sampler, shown in Figure 5, is best used by for general work. In addiapplying suction to a small tion, there have been appeqrflask which is placed on the ing monthly in INDUSTRIAL external end of the sampler AND ENGINEERINQ CHEMISand opening the stopcock TRY, since 1947, articles deslowly until the desired samscribing specific pilot plants ple is withdrawn. A good which present details of many sample is obtained by first pieces of equipment which blowing. through the samare suitable for general purpler t o clear the tube of the pose w o r k . T h e p r e s e n t material sampled previously. paper is limited t o a descripWhen it is necessary to tion of that portion of the unit charge a liquid t o t h e process laboratory at Clarkkettle in the course of the son College of Technology reaction a borosilicate glass which does not duplicate the pipe charging funnel may information supplied in the b e used a s i l l u s t r a t e d in references mentioned previFigures 3 and 5. If it is ously-equipment for study necessary t o add t h e of the preparation of organic liquid below the surface of chemicals by batch operation the liquid in the kettle, the on a pilot plant scale. charging funnel is fitted with Figure 1. Front View of Equipment
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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Figure 2.
Reaction Kettles and Distillation
a glass tube and short neoprene tubing sleeve to extend the tube below the stopcock. The inside diameter of the extension tube should he slightly larger than the outside diameter of the funnel tube so that the extension and neoprene sleeve slide over the funnel tube for a short distance and prevent contact of the liquid and the neoprene sleeve. Frequently it is necessary to remove one of the reaction products by distillation from the kettle. This is accomplished with the aid of a glass pipe trap placed below the reflux condenser. The total distillate may be removed or some of it may be refluxed as desired by controlling the stopcock at the base of the trap. When water is one of the products of the reaction, a heterogeneous constant boiling mixture may be formed from which the water, as the heavier layer, can be removed 11hile the organic entrainer is returned to the kettle to serve as an entrainer again. T h e n the holdup of the trap cannot he tolerated, where total reflux is desired, it is pos~ibleto replace the trap with a blank flange or replace the trap and glass-lined tee with a glass-lined elbow. The trap is shov n in Figures 3 and 5. The kcttle may he heated with steam or cooled M ith n atcr. The steam and water piping are 3/4-inch steel IT ith bronze valves. A l/,-inch bronze globe valve is installed as a bv-pass around the 3/,-inch bionze steam control valve so that the kettle map be heated rapidly to the desired temperature with the large valve and held at constant temperature with the small valve which gives close1 control. Thirty-Gallon, Jacketed, Conical-Bottomed Stainless Steel Kettle. This is a stainless steel (Type 316) open kettle equipped Rith a double propeller, variable-speed portable agitator, and a 1-inch stainless steel gate valve discharge. The tank was fabricated hy Artisan Metal Products, Inc. The jacket is designed for low pressure steam (20 pounds per square inch gage) which is obtained by means of a reducing valve from the high pressure steam line (125 pounds per square inch gage). A relief valve, set for 20 pounds per square inch gage, is connected to the jacket as a safety measure in event of failure of the reducing valve. The tank is particularly suitable for crystallizations and precipitation reactions as ell as for mixing and separating immiscible liquids. The conical-bottomed design was adopted
Vol. 43, No. 5
rather than a flat or dished bottom bccause sharper separations of immiscibl~ liquids are obtained. The piping is similar to that for the glass-lined kettle, both steam and water may he used in the jacket. This kettle is shown in Figures 1 and 2. Five-Gallon Stainless Steel Distillation Unit. A distillation unit finds many uses in organic chemical work for the separation and purification of products. The unit shown in Figures 1 and 2 war built by Artisan Metal Products, Inc., of' stainless steel (Type 304). The 5gallon still pot is jacketed for 125pound-per-square inch steam and is equipped with a 1-inch stainless steel gate valve for the discharge of residues. The head of the still pot contains a 2-iuch vapor outlet, a 2-inch flanged charging opening, a thermocouple well, and two 3-inch sight glasses. The column is a 12-foot length of 3-int2h stainless steel tubing packed with inch glass rings. A thermocouple well is located in the vapor line lpading from Unit the column to the condenser. The condenser has 5 square feet of condensing surface obtained from ten 5/s-inch tubes arranged to give five passes on the water side. The condensate passes through a small drum with piping arranged for the removal of mater from organic liquids, and then it is split into product and reflux streams by means of two matched rotameters and valves. The reflux returns to the top of the column, and the product is collected in two product receivers. The product receivers and the condenser are vented to a common line with appropriate
Figure 3. Ten-Gallon Glass-Lined Kettle and Accessories
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
M a y 1951
Figure 4,
e
Plate Filter and Centrifugal
valves and vents so that the unit may be operated under vacuum as well as a t atmospheric pressure. Vapor lines are 2-inch stainless steel pipe and liquid lines and valves are 1/2-inch stainless steel. The jacket of the still pot is piped from steam and cooling water in the same manner as the jacket of the glass-lined kettle. Stainless Steel Portable Horizontal-Plate Filter. There are many uses for filters in organic chemical work, and in the laboratory they are required for the recovery of a solid reaction product or the removal of activated carbon and filter-aid which may have been employed for the decolorization and clarification of a liquid reaction product. Although many different types of filters are available for chemical work, in small scale equipment it is desirable to employ filters which give clean and fast separations with a minimum of work required of the operators. The first filter described is the stainless steel (Type 316) Alsop sealed disk type filter shown on the left in Figure 4. This is a portable filter mounted on a base with wheels; it is supplied as a complete unit containing motor, pump, filter, and rubber hose, and it may be wheeled to the scene of operations, connected, and used in a short time. The filter employs eight 7-inch diameter filter disks which may be made of asbestos, paper, or felt as required by the particular operation. The filter disks are separated by perforated screens and cake collecting rings which have a total capacity of 200 cubic inches of wet cake. The case of the filter is jacketed so that the contents may be heated or cooled during operation. A valve in the head of the filter permits air or steam blowing of the cake a t the end of the filtration operation. ThiH type filter may be taken apart, cleaned, and reassembled for use so easily that the filtering operation A i not usually a time-controlling step in the process. Twelve-Inch, Stainless Steel Centrifugal Filter. Another useful filter is the 12-inch stainless steel (Type 304) Fletcher Laboratory centrifugal shown on the right in Figure 4. This filter is supplied with a perforated basket, solid basket and skimming nozzle, and bottle and test-tube holder. The perforated basket may be used with cotton duck filter bags for rapid filtration of coarse solids and with filter-aids for the removal of finer solids. The filter is equipped with an explosion-proof motor, starting box, and foot brake. The filter is usually hand fed from buckets, and the filtrate is collected in buckets. The centrifugal is often the first choice for the separation of solids in the laboratory.
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Six-Point Electronic Temperature Recorder. It is usually necessary to use thermocouples for temperature measurements in chemical process equipment because i t is difficult, if not impossible, to use laboratory thermometers in the many outof-the-way places where temperature measurements are required. If several temperatures are to be read a t frequent intervals it becomes a time-consuming occupation for one or two men if a potentiometer and temperature-e.m.f. tables or curves are employed. A temperature recording instrument will provide a permanent and continuous record of all temperatures required and will allow operators to devote their time to process work. The instrument described here is a Foxboro Multi-Record Dynalog recorder. This is an electronic instrument capable of recording six temperatures, one each 6 seconds; each temperature is recorded every 36 seconds. The records are in the form of colored dots on a circular chart. Each temperature is represented by a different color and when temperatures do not change rapidly the dots overlap t o form continuous colored lines providing permanent and continuous records of the temperatures. The instrument covers the 0' to 200" C. range with iron-constantan thermocouples and has a 12-hour chart rotation so that a good part of the chart is used when the laboratory is operated for the entire day.
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2" PYREX TUBING
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WATER TRAP
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10 MM.O.0.
PYREX
TUEINO
SAMPLER
Figure 5.
Glass Pipe Accessories for Glass-Lined Kettle Stopcocks are glass
+, 6-mm. bore
The instrument is mounted flush on a combination cabinet and data-recording table as shown on the left in Figure 1. Several thermocouples are permanently installed on the process equipment; spares, although connected to the recorder, are stored with coils of lead wire on the back of the panel and may be used on short notice for any type temperature measurement required. When the spares are not in use they record the room temperature continuously. ACCESSORIES
I n addition to the major pieces of equipment, many small items are required if work is to progress smoothly and rapidly.
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possible t o install transfer lines between the units when it is undesirable to employ buckets for such operations. The piping, valves, and gages are arranged to permit operation from the front side of the equipment on completion of the charging from the platform in the rear. Both cooling water and the discharge from steam traps are carried off by a 2-inch drain line equi ped with tees and funnel-shaped openings whicE make it possible t o observe and control the cooling water supply and the use of the steam traps. By-pass valves are installed around the steam traps to be used when the rapid heating of a cold charge produces condensate faster than the traps can discharge it. A color code facilitates rapid identification of the various pipelines by the operators of the equipment. The colors used are the same as those employed throughout the laboratories in the building housing the equipment: Steam = red; water = green; air = orange; gas = yellow; and drain = gray. The Toledo platform scale and the Foxboro temperature recorder are at the left of the three vessels, and the two filters are at the right.
DISTRIBUTION OF REACTION PRODUCTS THEORETICAL BY MACMULLIN EXPERIMENTAL DATA: ABENZENE B A MONOCHLOROBENZENE
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" X " = MOLES O F CHLORINE PER MOLE OF BENZENE
UNIT PROCESS STUDIES
Figure 6
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PROGRESS OF THE REACTION B Y : A ' WATER REMOVE0
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100
1 150
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200
250
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TIME IN MINUTES
Figure 7
All accessories should be available readily so that little time is lost when they are needed. For this reason the combination cabinet and data-recording table was built with shelves and doors that can be locked. Safety equipment, such as neoprene gloves and safety goggles, is always on hand. A stainless steel scoop, 4-gallon bucket, 10-inch diameter funnel, and a large glass funnel are provided for handling the raw materials and reaction products. A siphon-type pump consisting of a flexible lead tube, rubber bulb, air release valve, and adapters for various containers is used to remove liquids from carboys and drums. Solid products may be dried in laboratory ovens or dryers. Several large shallow stainless steel trays were found to be useful for drying solids by simply exposing the solids in thin layers t o air in the open laboratory for several days. For weighing materials, a Toledo direct-indicating dial-type platform scale of 0- to 500-pound range is useful and time saving. Cans and buckets of various sizes and materials of construction are required as containers for many purposes. Piping and Equipment Layout. The first three units described are mounted on a 2 X 2 X l / 4 inch angle-iron frame, 10 feet long by 30 inches wide and can be emptied into buckets placed under the discharge valves. A platform of steel grating, 10 feet long by 30 inches wide with two steps at each end, was placed between the vessels and the wall to facilitate charging the vessels. It is
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This equipment has been used for the study of unit processes such as halogenation, nitration, amination, sulfonation, esterification, diazotization, and coupling. As examples of the type of data that may be obtained with the equipment by sampling the reaction mass during the coume of a run, a chlorination and an esterification study are described briefly.
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C h l o r i n a t i o n of B e n z e n e . Benzene was chlorinated at 60" C. with a ferric chloride catalyst to check the distribution of chlorinated products as reported by hIacR.lullin (3). Six samples were withdrawn during I'the course of the run, washed with a sodium hydroxide solution, and fractionated to determine the composition. The distribution of the chlorinated products as a function of the amount of chlorine K W used is shown in Figure 6 where the lines represent the data of hIac3lullin. Preparation of Dibutyl Phthalate. The preparation of dibutyl phthalate is an example of an esterification reaction which may be followed to completion by sampling of the reaction mass or collection of the water formed during the reaction. Phthalic anhydride was esterified with an excess of n-butyl alcohol using sulfuric acid as a catalyst. The reaction mass was refluxed so that the butanol, acting as an entraining agent, removed the water of reaction which was collected in the trap a t the base of the reflux condenser. Samples of the reaction mass were withdrawn periodically for analysis by titration with sodium hydroxide in ethyl alcohol The course of the reaction may be followed to completion by plotting the acidity versus time as well as the water of reaction collected versus time [as shown in Figure 7. ACKNOW LEDGMEIiT
The author wishes to acknowledge the aid of J. J. DeGouff, J. 0. Zimmerman, and T. R. Steinberg in the installation and operation of the equipment and of Charles Hecker for suggestions in the preparation of the manuscript. LITERATURE CITED
(1) Glasebrook, A. L., a n d Montgomery, J. B., IR'D. ENG.C H m r . , 41, 2368 (1949). ( 2 ) Gwin, G. T., a n d Yule, L. T., Ibid., 41, 862 (1949) (3) MacMullin, R. B., Chem. Dag. Progress, 44, 183 (1948). RECEIVED September 15, 1950. Based on a paper presented before the Division of Industrial and Engineering Chemistry at the 118th Meeting of the AMERICAN CHEMICAL S O C I E T Y , Chicago, 111.
