chemical physics of discharges - Argonne National Laboratory
chemical physics of discharges - Argonne National Laboratory chemical physics of discharges - Argonne National Laboratory
367 used as blnders, with different producers and consumers using entirely different standards, so the electrode quality tests were used to help evaluate the effective- ness of thermal cracking of the lignite pitch. EQUIPMENT The thermal cracking system is shown in figures 1 and 2. The feed tank (figure 2, A) is made from a 13-in. length of 10-in. diameter schedule 40 pipe, to which a cone has been added for the bottom. The tank is heated by commercial electric heaters. The feed pump (B) is a small gear pump with a variable speed drive. The thermocracker (D) is a 4-1/2 ft-length of 2-1/2-in. diameter schedule 40, type 304, stainless-steel pipe, heated by external electric heaters. The heaters are controlled by outside surface thermocouples welded to the reactor. The receiver (E) is a 20-in. length of 4-in. diameter schedule 40 pipe. The receiver is flanged so that it can be bolted to the bottom of the reactor. The condenser (F') is a 30-in. length of 6-in. diameter pipe, swaged at the bottom end to I-in. diameter and flanged at the top. The top flange supports a water-cooled tube which inserts into the condenser body in the manner of a cold finger. The knockout (G) is a 34-in. length of a 2-in. diameter pipe having a tangential gas inlet about 8-in. from the bottom. The scrubber (H) is a 30-in. length of a 4-in. diameter pipe having a water-spray nozzle near the top. The water from the scrubber drains into a standpipe water-seal tank (I). The water-seal tank is a piece of 6-in. dlameter pipe. The gas meter (J) is a laboratory-type wet-test meter capable of metering 1,000 cu ft of gas at standard conditions. PR OC E DURE Lignite pitch at 200" C was pumped from the feed tank through electrically heated lines into the top of the thermocracker. The temperature of the thermocracker was maintained at approximately 790" C as indicated by the outside surface thermocouples. At the end of a run, the flow of pitch was stopped and the pump was' flushed with a low-boiling tar fraction to keep the impeller of the pump from freezing. Reactions within the cracker produced coke, cracked pitch, oil, and gas. Both the top and bottom of the cracker were removed, and coke was removed from the sides and weighed. Cracked pitch caught in the receiver was weighed and analyzed. The oil removed by the condenser and knockout chamber was weighed and then distilled to 400" C, leaving a pitch residue. This pitch residue was analyzed and, if found to have the desired carbon-to-hydrogen atomic ratio (1. 20 to 1.80), was used as a binder for electrodes. Distillate from the oil may be oxidized to phthalic and maleic anhydrides or separated into acids, bases, and neutral oils. Gas from the cracker was cooled and scrubbed, then metered, sampled, and analyzed by gas chromatography. RESULTS AND DISCUSSION Results of the thermal cracking tests are given in tables 1 to 4. Of the four major products obtained from the pitch--coke, cracked pitch, oil, and gas--the coke averaged about 15 to 25 percent of the feed to the cracker, the cracked pitch amounted to about 20 to 40 percent, the oil was about 20 to 30 percent, while the balance of the feed to the cracker consisted of gas.
Distribution and yield rates of products (figures 3 to 6) are as expected considering the reaction within the cracker at different crude,pitch.feed rates. As the pitch is heated it begins to vaporize, and the turbulenc'e of the vapors splashes some of the iluid onto the hot wall where it sticks and is coked. If enough heat is available, the rest of the pitch is vaporized and cracked. ' As the cracked materiais leave the hot zone, heavy high-b
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- Page 370 and 371: 369 ' i 1. REFERENCES Berber, John
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367<br />
used as blnders, with different producers and consumers using entirely different<br />
standards, so the electrode quality tests were used to help evaluate the effective-<br />
ness <strong>of</strong> thermal cracking <strong>of</strong> the lignite pitch.<br />
EQUIPMENT<br />
The thermal cracking system is shown in figures 1 and 2. The feed tank<br />
(figure 2, A) is made from a 13-in. length <strong>of</strong> 10-in. diameter schedule 40 pipe,<br />
to which a cone has been added for the bottom. The tank is heated by commercial<br />
electric heaters. The feed pump (B) is a small gear pump with a variable speed<br />
drive. The thermocracker (D) is a 4-1/2 ft-length <strong>of</strong> 2-1/2-in. diameter schedule<br />
40, type 304, stainless-steel pipe, heated by external electric heaters. The<br />
heaters are controlled by outside surface thermocouples welded to the reactor.<br />
The receiver (E) is a 20-in. length <strong>of</strong> 4-in. diameter schedule 40 pipe. The<br />
receiver is flanged so that it can be bolted to the bottom <strong>of</strong> the reactor. The condenser<br />
(F') is a 30-in. length <strong>of</strong> 6-in. diameter pipe, swaged at the bottom end to<br />
I-in. diameter and flanged at the top. The top flange supports a water-cooled<br />
tube which inserts into the condenser body in the manner <strong>of</strong> a cold finger. The<br />
knockout (G) is a 34-in. length <strong>of</strong> a 2-in. diameter pipe having a tangential gas<br />
inlet about 8-in. from the bottom. The scrubber (H) is a 30-in. length <strong>of</strong> a 4-in.<br />
diameter pipe having a water-spray nozzle near the top. The water from the<br />
scrubber drains into a standpipe water-seal tank (I). The water-seal tank is a<br />
piece <strong>of</strong> 6-in. dlameter pipe. The gas meter (J) is a laboratory-type wet-test<br />
meter capable <strong>of</strong> metering 1,000 cu ft <strong>of</strong> gas at standard conditions.<br />
PR OC E DURE<br />
Lignite pitch at 200" C was pumped from the feed tank through electrically<br />
heated lines into the top <strong>of</strong> the thermocracker. The temperature <strong>of</strong> the thermocracker<br />
was maintained at approximately 790" C as indicated by the outside<br />
surface thermocouples. At the end <strong>of</strong> a run, the flow <strong>of</strong> pitch was stopped and the<br />
pump was' flushed with a low-boiling tar fraction to keep the impeller <strong>of</strong> the pump<br />
from freezing. Reactions within the cracker produced coke, cracked pitch, oil,<br />
and gas. Both the top and bottom <strong>of</strong> the cracker were removed, and coke was<br />
removed from the sides and weighed. Cracked pitch caught in the receiver was<br />
weighed and analyzed. The oil removed by the condenser and knockout chamber<br />
was weighed and then distilled to 400" C, leaving a pitch residue. This pitch<br />
residue was analyzed and, if found to have the desired carbon-to-hydrogen atomic<br />
ratio (1. 20 to 1.80), was used as a binder for electrodes. Distillate from the oil<br />
may be oxidized to phthalic and maleic anhydrides or separated into acids, bases,<br />
and neutral oils. Gas from the cracker was cooled and scrubbed, then metered,<br />
sampled, and analyzed by gas chromatography.<br />
RESULTS AND DISCUSSION<br />
Results <strong>of</strong> the thermal cracking tests are given in tables 1 to 4. Of the four<br />
major products obtained from the pitch--coke, cracked pitch, oil, and gas--the<br />
coke averaged about 15 to 25 percent <strong>of</strong> the feed to the cracker, the cracked pitch<br />
amounted to about 20 to 40 percent, the oil was about 20 to 30 percent, while the<br />
balance <strong>of</strong> the feed to the cracker consisted <strong>of</strong> gas.