A WORKING MODEL BY-PRODUCT COKE PLANT. A CHEMISTRY PROJECT FOR A STUDENT AT THE SECONDARY LEVEL* HOWARD WILLIAMS, WESTERNRESERVE ACADEMY, HUDSON, OHIO One day a boy came to me and said, "I am interested in the by-product coke plant. Would i t be possible for me to build one in the laboratory that would have all the parts and do all the things that the commercial plant does?' I reminded him that we had performed the usual laboratory exercise on the destructive distillation of coal, but he was not satisfied with that. He said that the apparatus we had used-a couple of test tubes and a beakerwas only a toy. What he wanted was to build a real, working-model coke plant. The result of the conference was that he went to the library with some suggestions and a great deal of enthusiasm. He took notes on everything that he could find about the destructive distillation of coal. He then brought his notes in for a second conference, and we mapped out a working plan. Fist, he wrote a letter to the manager of the coke plant of the American Steel and Wire Co., Cleveland, Ohio. This plant is about twenty-five miles from our school. The letter was a request for permission to visit the coke plant. The permission was graciou~lygranted, and the boy made a trip through the plant. He saw the process from start to finish. He had a conference with the head chemist. He was shtwn the blue prints of a small experimental coke plant, similar in many ways to the one he wished to build, which was then being built by the company for use in research. He came back full of ideas and burning to get to work. Next, working together, we made a diagram of the plant that he wished to build. I gave him a table about two feet wide and six feet long upon which to build the plant, and he started to work. Many problems arose before the task was finished, but together we ironed them out. Finally, after about four weeks of the most interesting work that I have ever seen done a t the secondary level, he had a very complete little coke plant that worked. He built two ovens or retorts so as to be able to run the plant continuously. These were made of two pieces of ordinary 2" black steam pipe, 9" long. One end was threaded and fitted with a 2' cap. The other end was closed by having a piece of flattened pipe welded onto the retort. The welding was done by a local garage man at a cost of fifty cents. Two inches * T h e apparatus herein described was on display at the conference of the Progressive Education Association, Hotel Jefferson, St. Louis, Mo.. February 21. 22. 23, 1929.
from the closed end of this retort, a bole was drilled with a standard A'' drill and tapped to receive a 8" pipe nipple. This was the outlet for the gases. The retorts and their connections were then assembled with 8'' pipe fittings as shown in Figure 1. A 8" globe valve with two female threads was used in the gas line from each of the retorts so that one could be shut off for cleaning and recharging while the other one was being heated. A heat-insulating jacket was placed around the retorts so as to prevent the loss of heat and make it possible to attain within the retorts a tempera-
twe high enough to coke the coal. These jackets were composed of a mixture of two parts asbestos fiber and one part plaster of Paris. Each jacket was supported on a sheet iron lining which was placed around the retort so as to leave about 4" between the jacket and the retort. A long slot was left in the under side of the jacket for the entrance of the flames from the burners used to heat the reto*ts. Fow round holes about 4" in diameter were also left in the top of each jacket for the escape of burned gas fumes, and also to allow the flames to circulate completely around the retorts. Figure 1 also shows a cross-section of the retort and jacket, and will give a clear idea of the assembly.
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At a distance of about 6" from the tee where the gas lines from the two retorts joined, the steel piping was discontinued and glass tubing was used from there on. This made it possible to observe any action that took place in the rest of the apparatus. Figure 2 shows the assembly of the entire plant. The gas line from the retorts was rnn into three coolers to condense the tar from the hot gases. These were made from three large test tubes immersed in a pneumatic trough through which a circulation of cold water was maintained. The tarry material gathered in the tubes, and the gases passed on and out through the tube, "T." The tar was brown in color when first condensed, but upon standing for a few days it became black and separated from the ammoniacal liquor with which it had been emulsified.
FIGUREENTIRE ASSEMBLY OR THE COKEPLANT
Following the coolers was a small bubbler bottle which was used as a tell-tale. So long as gas was being given off from the retorts the bubbling in the bottle would indicate its passage. When the bubbling slowed down the second retort was started and by the time the bubbling had entirely ceased-showing the first retort to be out-gassed-the second one was ready to deliver gas. The first retort was then shut off, allowed to cool, the coke removed, and the retort recharged for the next heating. The tell-tale was about half full of a 10% solution of sulfuric acid, which helped to remove ammonia gas as well as acting as an indicator of gas flow. From the tell-tale the gas was led into the bottom of the first scrubbing tower. Each of these towers was made of an 18'' section of the la" glass tubing usually used in the physics laboratory for depth-pressure measure-
ments. Each tower was filled with broken glass in pieces about i" in diameter. This was to give plenty of surface for contact of the gas with the scrubbing liquid introduced a t the top of the tower. Both ends of the towers were fitted with two-holed rubber stoppers. The gas entered through one of the holes in the bottom stopper, and the used scrubbing liquid was removed through the other by means of a short piece of glass tubing to which was fixed a sbort piece of rubber tubing and a pinch-cock. The scrubbing fluid was introduced through one of the holes in the upper stopper through a glass dropper tip. A glass funnel was coupled to this
'rll~3l
M COKE ~ PLANT ~ AND ~ TH ~E BOYWHOB u m IT
tip by means of a sbort piece of rubber tubing. A screw pinch-cock was placed on the rubber tubing to regulate the speed of dropping of the scrubbing liquid. The second bole in the upper stopper was used for the outlet gas tube to the next tower. From the third or last scrubbing tower, the gas was led to the reserve gas tank, and also by means of a glass tee tube to a small micro burner where the gas could be used. The reserve gas tank was a container for unused gas, and also a means of keeping a constant supply and pressure of gas for the micro burner which
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represented the consumer. It was made of two large tin cans. The inner can was the bottom half of a five-gallon denatured alcohol can. The outer can was of the same depth as the inner one, but had a diameter about two inches greater. This allowed free motion between the two cans. The outer can was about ten inches deep. A piece of copper tubing about 20" long was soldered through the center of the bottom of the outer can so that the end inside the can was about 3" below the level of the top of the can. The copper tube below the bottom of the can was then bent a t right angles over a round form and attached to the gas line from the last scrubbing tower. Both cans were painted with heavy black roofing paint to prevent rusting. The lower can was filled with water to within 1i" of the top, and the upper can inverted into it. The upper can was counterweighted by means of a piece of string, a couple of pulleys, and a weight, so thatit exerted a pressure of about two ounces to force the gas out of the tank. It was found that a very convenient counterweight was made of a glass bottle with some water in it. By adding or removing a little water from t h e b o t t l e the counterweight could be quickly and easily adjusted. A SECTION On UNBROKEN COKEPROM THE The coal for the retort was RETORT ground in an iron mortar so that it Note the concentric circular structure of pores showing the progress of the coking would pass through a twenty-mesh the from the outside toward the center of the sieve. I t was afterward sifted in a charge If the center of this structure is sixty-mesh sieve to remove fine displaced to one side of the center of the charge it means that the heating is not coal dust which would cake and uniform from all sides. cause trouble in the retorts. The retorts were then charged with the clean ground coal. They were filled about half full so as to allow for expansion when the charge was heated, and for slight frothing when the gas was coming off rapidly. Before placing the cap on the retort, the threads on both the cap and the retort were generously painted with a mixture of heavy lubricating oil and graphite. This served the double purpose of helping to make the retort gas tight, and also of preventing sticking when the cap had to be removed to take out the coke of the spent charge. The firing was started slowly and gradually increased to a maximum just as the coal was about out-gassed. The scrubbing liquid used in the first tower was a lo'% solution of sulfuric acid. This removed uncombined ammonia. The combined ammonia was
found in the ammoniacal liquor which collected on the top of the tar in the tar coolers. The saubbing liquid used in the second tower was a very light lubricating oil. This removed the benzene vapors from the gas, they being soluble in light oils. The liquid used in the third tower was a 10% solution of sodium hydroxide. This caught the hydrogen cyanide and hydrogen sulfide in the gas, and removed them as sodium cyanide and sodium sulfide, respectively. The ammoniacal liquor upon treatment with a little sodium hydroxide gave off strong fumes of ammonia, thus showing the presence of combined ammonia in the liquor. The sulfuric acid from the first tower and from the tell-tale gave a small mass of crystals of ammonium sulfate npon evapora-
S o ~ SAMPLES e OP TEE F a w MATERIALS AND THE PRODUCTS OF THE MODELCOKE PLANT 1. The coal before grinding. 2. The coal after being ground. 3. The coke from the retorts. 4. Some of the coal tar. 5. The washings from the ammonia tower. These scrubbing liquids were run through the towers several times so as to
nearly saturate them. 6. The oil from the benzene scrubber. 7. The washings from the cyanide-sulfide tower.
tion. These crystals were grayish in color due to impurities. The addition of sodium hydroxide to these crystals gave unmistakable evidence of their ammonia content. The light oil from the second tower yielded two or three cubic centimeters of benzene oils npon very careful distillation with a small condenser. The sodium hydroxide from the third tower was treated with ferrous sulfate solution. A heavy black precipitate of iron sulfide gave evidence of the presence of sulfides in the gas. This sulfide precipitate was filtered off, and the filtrate boiled with a little more ferrous sulfate. If cyanides were present, this treatment would yield sodium ferrocyanide. A few drops of
ferric chloride were then added. A faint blue color due to the presence of Prussian blue proved the presence of traces of cyanides in the coal gas. The plant had worked. Everything the boy had started out to do was accomplished. He was overjoyed, and so was I. It was a real bit of secondary-school research, planned and carried out by a boy of high-school age. It had proved beyond doubt that such projects in high-school chemistry are not only possible but intensely interesting and profitable adjuncts to the usual high-school course. The boy had not received all the benefit from the project. His work and the plant attracted the attention and interest of other members of the class, and I immediately began to get requests from others to be allowed to do
some similar piece of work along the lines of their special interests. The result was that several other remarkable bits of work were done. The interest also spread to the rest of the school and resulted in a rather widespread and general interest in the chemistry course. The final step in bringing this project to a well-rounded conclusion was the preparation of a carefully written report of the work. This report was typewritten on 53" X 83" paper (half letter head size), and hand-bound in attractive board covers. The booklet also included blueprint drawings of the apparatus used, and a photograph of the boy and his apparatus. The drawings for the blueprints were made by the boy himself, the photograph was made by a classmate who was interested in photography, and the booklet was bound and decorated by the boys in the art department of
the school. The booklet was typed and bound in triplicate. One copy became the property of the boy. A second copy was given to the school and placed on the reference shelves of the school library for the benefit of any one who might wish to repeat the work another year. The third copy went to the instructor who, I can assure you, was delighted to have this memento of the project in his personal files. The idea of substituting this type of project and report for the usual obnoxious-to both student and instructor-semester paper was a very happy outgrowth of this piece of work. I have now completely discarded the old type of semester paper drudgery in favor of this new, live-interest method of getting a student to go somewhat beyond the textbook and regular course of study in the field of chemistry. It do? all and more than was ever accomplished by the semester paper by bringing real interest and enthusiasiasm into the work. The drudgery of reading the usual uninteresting, technical material, the painful note-taking, and the distressing composition of dead material is all supplanted by intriguing work leading to a goal desired by the pupil, and followed by living composition of actual interest material gathered a t first hand by the student.
