ENGINEERING, DESIGN, AND EQUIPMENT by weight of feed. The acetylene yield is approximately 5% by weight of feed. Two sets of runs were carried out with a feed stock containing approximately equal parts by volume of ethane and propane, a t 1810’ to 1885’ F., atmospheric pressure, and without steam addition. As expected, the propane was more reactive than ethane-for example, the ethane conversion was 48% in one run as compared with the propane conversion of 80.7%. The observed yields were not significantly different from the values calculated on the assumption that each component reacted independently. It is expected that the best yields obtainable from ethane-propane mixtures will be about 37 to 39% by weight of combined feed or within 1or 2% of the combined maximum yields when ethane and propane react individually. All yields reported here are for single-pass operation. With natural gas, where maximum acetylene yields occur in the region of 60% conversion, significant amounts of unconverted feed are found in the make gas; this suggests the possibility of recycle operation. However, the volume expansion associated with the reaction results in dilution of the unreacted methane with permanent gases from which the methane is not easily separable.
The introduction of these diluents into the reaction zone by the recycling of scrubbed product gas would result in a sharp reduction of acetylene concentration for only modest increases in over-all yield. With the other gases, by far the greatest part of the feed gas can be efficiently converted in a single pass. Literature cited (1) Bixler, G. H., and Coberly, C. W., IND. ENQ.CHEM.,45, 2596
(1953). (2) Bogart, M. J. P., Schiller, G. R., and Coberly, C. J., Petroleum Processing, 8,377 (March 1953). (3) Hasohe, R. L. (to Carbonic Development Corp.), U. S. Patent 2,622,864 (Dec. 23,1952). (4) Hasche, R. L.,Chem. & Met. Eng., 49,No.7,78 (1942); Hasche, R. L., and Hincke, Wm. B. (to Eastman Kodak Co.), U. S. Patent 2,318,688 (May 11, 1943); Hasche, R.L.,and Hincke, Wm. B. (to Wulff Process Co.), U. S. Patent 2,319,679 (May 18,1942): Am. Gas Assoc. Proc.. 1951. DD. 510-13. ( 5 ) Weaver, T..,Chem. ’ Eng. Progr., 49,’35(1955); Petroleum Refiner, 32, No.5, 151 (1953). RECEIVED for review May 6, 1955. ACCEPTED June 21, 1955. Division of Gas and Fuel Chemistry, 127th Meeting, ACS, Cincinnati, Ohio.
Coal Gasification at Louisiana, Missouri H. R. BATCHELDER’ AND L. L. HIRST2 Synfhefic Fuels Demonsfrafion Planf,
U. S.
Bureau of Mines, Louisiana, Mo.
T
H E Synthetic Fuels Demonstration Plant a t the Louisiana, Mo., station of the Bureau of Mines was built to study and demonstrate the production of synthesis gas from coal and the conversion of this gas to liquid fuels. This plant has been described (S),and the results of the work on the Koppers coal gasification unit have been published (1). These results indicated that a change in the geometry of the gasifier would be beneficial, and, after preliminary tests a t the Morgantown, W. Va., station of the Bureau of Mines had supported this belief, a new unit was constructed a t Louisiana. This article describes the gasification unit and its subsequent modifications and discusses the results obtained to the time that the Demonstration Plant was closed (June 1953). The work reported in this article was the result of the coordinated efforts of the personnel of the operating, engineering, and planning sections and is in no sense a personal accomplishment of any one individual or group. A complete description of the original gasification plant has been given in a previous report (1). The new gasifier was constructed for the following purposes:
1. Eliminating “short-circuiting” within the gasifier 2. Feeding finely ground coal without premixing with oxygen 3. Using a refractory less sensitive to temperature variations encountered during operation 4. Removing part of the ash in liquid form Severe erosion i s encountered with modifled Koppers unit using coal-oxygen feed system
Preliminary experiments a t Morgantown had been conducted in a vertical cylindrical unit, in which the reactants were intro-
* Present address, Battelle
Memorial Institute, Columbus, Ohio. Present address, Branch of Coal Gasification, U. 9. Bureau of Mines, Morgantown, W. Va. 2
1522
duced tangentially near the bottom and the product gases were removed at the top of the unit. This general design was incorporated with the new unit that was constructed a t Louisiana. After some discussion concerning refractories, a “ram mix” of high purity alumina was selected as lining. Under the terms of a cooperative agreement with the Bureau of Mines, the Aluminum Co. of America offered technical assistance and much of the necessary material. At the time, the Alcoa engineers were not willing t o recommend construction of a unit more than 6 feet in outside diameter, nor more than a 9-inch lining thickness. These limits, with the decision t o keep the volume about equal to that of the Koppers unit, led to the design shown in Figure 1. Originally, it had been planned to pump a slurry of coal in water through a heated coil t o produce a suspension of heated coal in superheated steam. This system was similar to the one that was described by Eastman (b), except that the coil discharge was to be a t substantially atmospheric pressure. Because of difficulties encountered in this feed system, the gasifier was ready for operation before any promise of satisfactory performance of the slurry heater had been obtained. Accordingly, the coal feed system of the Koppers unit, in which coal was conveyed by process oxygen, was adapted for use in the new unit, and the slurry coil was used for superheating steam. All of the coal was delivered to the gasifier by one set of screw feeders, instead of two sets, as was formerly used. This required the screw8 to operate a t twice the normal speed. Preliminary tests indicated that this could be done, but considerable operating difficulty was encountered during the runs. A horizontal, three-port water-jacketed burner was installed at A in Figure 1, tangent to a 42-inch-diameter circle, and the steam nozzle was installed at B,tangent to the same circle and 60’ from the burner. A flow diagram of the system is shown in Figure 2. Preweighed coal was dumped at intervals into the feed hopper, from which it was fed by three screws in parallel into three equal
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 8
ENGINEERING. DESIGN. AND EQUIPMENT
streams of oxygen. Coal rate was to be controlled by screw speed and oxygen rate by supply pressure. The suspension of coal in oxygen was carried through 2-inch-diametjer stainless steel tubes to the burner nozzle. Water was pumped a t a predetermined rate through the coil, and the gas firing was adjusted to maintain the desired outlet steam temperature. The steam nozzle was a 4-inch-diameter pipe, into which was fitted a 11/4-inch-inside-diameter Venturi throat.
SECT. C - C
RECYCLE
GAS IN
-3'-
13'3 COAL
STEAM
Figure 1 .
Vertical gasifier
The product gas left the top of the gasifier through the existing brick-lined pipe (18 inches in diameter) to the existing waste heat boiler, washer cooler, and gas exhauster. A valve in the gas discharge from the exhauster was actuated by a recording pressure controller connected to the gasifier outlet. By setting up the new unit in this manner, it was possible to use substantially all of the existing equipment. Coal handling, pulverization, and storage; oxygen transport control and metering; and product gas OXYGEN cooling, cleaning, metering, and handling were all unchanged from the previous system. Instrumentation and control on the gasifier proper were almost entirely adapted from those formerly used with the Koppers unit. The steam superheater, MR SPEED DRIVE the gasifier shell (salvaged from Missouri Ordnance Works), the alumina lining, and some piping were the onlv additions. Provision was made for the accumulation of molten slag a t the bottom of the gasifier and for intermittent tapping through a 6-inch-diameter port 3 inches above the floor lining. This port was plugged with a wooden cylinder with a a/,-inchthick layer of alumina over the end. The gasifier was first placed in operation in January 1951 for a trial run. This was -purelv - a test of the mechanical operation, and no data were taken. Two more of these t,ests were made, and on Feb. 6, 1951, a short run was made a t normal steam, oxygen, and coal rates. Following this test, a run of about 3 days was made during which slag deposits over the burner nozzle ports caused several shutdowns. These deposits were removed by rodding. The results of the run were gratifying, in spite of the fact that the coal screws delivered less than the planned rate of coal, so that the oxygen to coal ratio was higher than desired. Carbon conversions were calculated t o be nearly loo%, and the oxygen and coal per 1000 cubic feet of synthesis gas were measurably below those previously achieved.
August 1955
An inspection of the gasifier interior after the run, however, showed appreciable damage. Apparently the slag deposits over the end of the burner nozzles had deflected the flame, causing it to impinge on the lining. A deep groove had been melted in the lining, beginning above and behind the coal-oxygen nozzle and continuing around the gasifier in the direction of the gas flow, spiraling upward a t an angle of about 25". At the deepest point, the groove was 10 to 12 inches wide and 7 l / 2 inches deep. It became progressively wider and shallower, and substantially disappeared about three quarters of the way around the gasifier. This, and subsequent observations, and flame temperature calculations all lead to the conclusion that there is probably no practical refractory material that can withstand the direct impingement of the oxygen-coal flame. If refractories are to be used, impingement must be prevented, at. least until after the oxygen has been consumed. T o minimize the changes of recurrence of this trouble, the burner nozzle was made tangent to a 32-inch-diameter circle and extended 5 inches farther into the gasifier. The steam nozzle remained tangent to the original 42-inch circle, but a new type nozzle was used. This was a vertical slot, 1/2 inch wide and 4 inches high, cut shorter on the top side t o give the steam jet an upward slant, to promote more thorough mixing with the oxygencoal stream. After these changes, two runs were made a t lower oxygen-coal ratios. The results of these runs, from a process standpoint, were distinctly disappointing. The carbon conversions and synthesis gas yields were lower than those normally achieved on the Koppers unit a t the same oxygen-coal ratios. Gasifier temperatures were lower than had been expected, which may have caused the poor results, or the changed orientation of the nozzles may have resulted in poor mixing. At this point, the work on the gasifier was interrupted and the operation of the Synthetic Fuels Demonstration Plant as a whole was undertaken, with the Kerpely producer operating on oxygen blast to generate the necessary synthesis gas. Nearly 9 months elapsed before operations on the gasifier were resumed on Dec. 28, 1952.
RECYCLE
M S l € HEAT
muR
GASIFIER
gi
EXHAUSTER
FLARE OR HOLDER
90
__c
t
SETTLING SETTLING BASIN
Figure 2.
Flow diagram of vertical gasifier
Another run (run 9) was made with no change from the preceding ones, except that the oxygen-coal ratio was raised nearly to that used in the first good run. Again, the results were disappointing and corresponded with those of the two preceding runs. Photographs taken during the inspections indicated that the high velocity steam from the new slot nozzle was not mixing with the oxygen-coal stream. Calculated velocity was about 600 feet per second. A temporary nozzle was used that would give a lower velocity, and the run (run 10) which was made seemed to
INDUSTRIAL AND ENGINEERING CHEMISTRY
1523
ENGINEERING. DESIGN. AND EQUIPMENT show definitely improved results. A new nozzle was then used which would give a velocity of about 200 feet per second, and two more runs were made (runs 11 and 12). These showed very good results, with carbon conversions about 100% and relatively low usage of coal and oxygen. No further changes were made in the system until March 1952. An inspection made after run 20
\
7
COALHOPPER FEE0
/COAL
FEEDER
TO PREVIOUS 31C*M
SUrrLT
--m
JET PUMP
.__ -_
GAS-HANDLING SYSTEM
STEAM-COAL MIXTURE
4uu
7,
M
.\
4 -
-+PI--"
I
rawr
VERTICAL GASIFIER
Figure 3.
Steam-conveyed coal system
showed that extensive peeling of the lining had occurred in the lower section, approximately opposite the coal-oxygen nozzle. This probably had its origin in the damage inflicted on the lining during the first extended run and had been progressively aggravated by the poor mixing of the steam with coal-oxygen streams and by the intermittent operation. Extensive major repairs were required, and it was decided to make revisions in the system.
Anchor circle brick (Harbison-Walker Refractories Co.), and two Korundal impingement blocks were inserted in the area directly opposite the burner. No other changes were made. A run was made from Sept. 29 to Oct. 5, 1952, substantially without interruption. Slag was tapped without shutting down, in spite of the fact that larger taps and more viscous slag were encountered than in previous operations. Inspection after this run showed that the circle brick had disappeared almost completely. It could not be determined whether the Korundal blocks had become dislodged owing to the failure of the surrounding brick or whether they also had failed under the impact of the flame. It was believed that a second burner, opposed to the first, would prevent the attack on the opposite wall and that a denser, higherservice-temperature refractory was desirable. While preparations for these changes were being made, A new lining of Allmull brick was installed, and a grid of water-cooling coils was mounted directly behind the brick in the area opposite the burner where the greatest erosion had been encountered in previous runs. It WAS possible that this cooling might enable the brick to withstand the impact of the flame. .4 run of 7 days was made, which was satisfactory in every respect. Inspection of the interior, however, showed that there was distinct loss of refractory in all sections of the lower portion, including that in front of the cooling coils. There was definite evidence that the coils had reduced the refractory loss, but the loss still was heavy. The two-burner system was installed after this run. Extensive changes in the control system and panel board arrangement were also undertaken a t this time to eliminate, in future operations, many minor troubles that had been encountered.
OXYOEN
Superheated steam transport of coal feed with two-burner system i s successfully operated
Some preliminary tests had shown that transport of the coal with superheated steam was feasible. Accordingly, the scheme shown in Figure 3 was adopted. The Bailey feeder was equipped with a variable-speed drive and the combination was used to control the coal feed rate. The oxygen was supplied to the nozzle through a recording flow-controller. Steam was fed through a recording flow-controller to the superheater used previously and then through a jet pump into which the coal was fed. The steamcoal mixture flowed through the center pipe of the reactants nozzle; the oxygen was fed into an annular pipe and passed through 16 ports, ll/aa inch in inside diameter, set a t a 45" angle to the burner axis (Figure 4.) The damaged section of the lining was patched with castable refractory and one course of Allmull arch brick (Babcock & Wilcox Co.) inside. The internal diameter of this section was thus reduced from 4 feet 4a/, inches t o 3 feet 6 inches. The burner was pointed downward at a 45" angle, projecting about 3 inches from the wall a t the lower edge and terminating about 2'/2 feet above the floor of the gasifier. The down-shot burner was installed in deference to the belief that it was necessary to maintain the slag a t the highest possible temperature, to avoid difficulty with tapping. Also, i t was felt that impingement of the flame on the accumulated slag would minimize refractory damage. The first extended operation of this revised unit was from Sept. 2 to Sept. 11, 1952. Difficulty with the coal weighing system precluded any calculation of yields, but the mechanical operation was highly satisfactory. With four shutdowns to tap slag, the unit was in operation 210 out of 216 hours of elapsed time. The slag tapping was satisfactory. Inspection showed that the brick was almost completely cut out in a small area directly opposite the nozzle and that most of the brick in the lower section had suffered from slag attack. The damaged brick was replaced by
1524
3
- by-7
Figure 4.
&I Burner nozzle
The major features of the revised gasifier are shown in Figure 5 . All refractory material was removed from the shell to a height of approximately 6 feet. Above this the original ram mix alumina lining was still intact and in satisfactory condition. The lower section was lined with 2 1 / 2 inches of high-temperature insulating brick and 6l/2 inches of Monofrax K (Carborundum Co.). The steam was controlled and superheated aR before, then divided by means of critical flow orifices between two branches, each leading to it,s own coal jet pump. Coal was fed from two hoppers (as in the Koppers system) through Bailey feeders, each equipped with variable-speed drive. The oxygen supply was fed through two recording flow-controllers, each leading to one of the burner nozzles. The nozzles were identical to the one used previously, and, with the divided flow, all velocities were reduced to one half the former value. Because of the approaching termination of work a t Louisiana, it was necessary to limit the run to about 1 week. It was started on May 20 and continued uninterrupted until the planned shutdown on May 29, for a total of 209 hours.
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
voi. 41,
NO.
a
ENGINEERING, DESIGN, AND EQUIPMENT From every viewpoint, the operation was gratifyingly steady and trouble free. The newly installed controls were very successful, and little change in the auxiliaries would be indicated for any future continuous operation. Slag was tapped without incident at approximately 2-day intervals for a total of 5000 pounds; the largest tap was 1700 pounds.
GAS~F~ER
Figure
5. Two-burner gasification unit
Examination of the gasifier after the run showed that the refractory was, for the most part, completely unaffected. There were two areas at right angles to the plane of the burners and just above the slag level that had been definitely eroded. These areas were perhaps 12 inches wide and 18 inches high, and at the worst point were about 2 inches deep. It is postulated that the two flames intersecting would “butterfly” downward and toward the walls. There were two small areas of erosion directly under each burner and just above the slag line. These were much less severe and much less sxtensive than the two on the side walls. I n addition, there waR a shallow groove completely around the gasifier, just above the slag level. It is believed that, with a modification to reduce the sideward component of the flame, a satisfactory operation could be achieved over an appreciable length of time. The upper part of the gasifier, the duct leading to the wasteheat boiler, and the boiler itself, during all of the operations reported here, had not accumulated any significant amount of slag, and no cleaning had been done except for soot removal. I n runs where carbon conversion was low (below 8OY0), accumulations of floating coal residue on the settling basins had a definite limit on the length of the operations. Where the carbon conversion was higher (above 850J,), there was little difficulty with the settling basins. For example, in the final run only one of the two basins was used for the 9 days of operation, which would have afforded ample time t o clean another basin and return it t o service. This would indicate that continuous operation was entirely feasible from this standpoint.
tinuous change in the geometry of this part of the unit and probably affecting the degree of mixing, flow patterns, and heat transfer. It may be t h a t these changes were the more important ones, with occasional errors in coal weighing and feeding and in product gas measurement contributing to the confusion. The more important data from these runs are given in Table I. Figures 6, 7, and 8 are plots of carbon conversion, carbon, and oxygen requirements, respectively, as functions of oxygen-carbon ratio. The aberrations are apparent. Brief notes on each run, the purpose of the run, the changes that preceded it, and romments on the results, are presented in the following discussion. Run 6 (Feb. 19 to 22, 1951). First sustained run at full rate. Oxygen-coal ratio higher than planned because of difficulty with coal screws. Severe refractory damage due to slag deflection of flame. Run 7 (March 27 to 28, 1951). First run made with oxygen-coal burner and steam nozzle tangent to smaller circle. Lower oxygen-coal ratio than in run 6. Results poor. Run 8 (March 28 to 29, 1951). Same as run 7 except for higher oxygen-coal ratio. Results poor. Run 9 (Dec. 28, 1951). Same as run 8, except higher oxygen-coal ratio. Weathered coal, lower heating value. No improvement in results. Run 10 (Jan. 4, 1952). New, lower velocity Steam nozzle to Promote better mixing. Resdts apparently m $ ~ ~ ~ f ~ 1952). ~ ~ ~ New d i o , nozzle, 2oo feet per second velocity. Results apparently further improved. Run 12 (Jan. 10, 1952). Continuation of run I 1 a t changed conditions. Result8 very good. :,(
J ~ ~ n . ~ ~ i f , ! ? ~~ ~~~ &~ $
Unexplained variations in the results of the unit when operating with oxygen-conveyed coal and with t h e superheated steam introduced separately were noted. At the time, there was always the possibility that an individual deviation might be caused by some local and temporary difficulty, and many attempts were made t o explain these as they occurred. I n retrospect, however, there seems little doubt that the results of the runs on this system were completely unreliable. Several times it was felt that the differences were explainable, but in each case subsequent runs made the explanation invalid. I t is known that erosion of the lower lining was causing conAugust 1955
,
$
$ oxyh
100
Bp
i 0 90 iz e
9Z
8
z
P
E
4
80
12 CU.
Experimental data show superiority of steam-conveyed feed installation
~
Figure 6.
I3 14 15 FT. OXYGEN/LB. CARBON
16
Carbon conversion as function of oxygencarbon ratio
gen-coal ratio. Results poor. Comparable to those of rum 7, 8, 9. Run 15 (Jan. 29, 1952). Made to check runs 11 and 12. Results poor. Run 16 (Jan. 31 to Feb. 1, 1952). Planned to cover in first four parts oxygen-coal ratios of 9, 9.75, 10.75, and 11.5 cubic feet per pound. Trouble with coal screws resulted in ratios of 9.6, 10.0, 11.4, and 11.6 cubic feet per pound. Deposit over steam nozzle prevented normal steam flow. Results uniformly poor, b u t consistent with one another. Run 17 (Feb. 1, 1952). Continuation of run 16 a t changed conditions. Run made to see if air-oxvgen operation t o produce
INDUSTRIAL AND ENGINEERING CHEMISTRY
I525
~
~
ENGINEERING, DESIGN, AND EQUIPMENT Table 1. Run number
Principal Operating Results for Oxygen-Conveyed Coal
1035 9.4 12.50 0.7
1000 10.0 13.62 0.9
14.8 37.2 43.5
15.8 37.4 39.9
17.7 38.7 39.6
16.3 34.4 45.7
17.7 36.7 42.3
19.0 35.9 41.8
18.3 37.1 41.9
18.0 38.6 39.8
16.6 37.0 43.6
63.0 48.5 97.0
69.8 56.4 99.8
37.5 29.0 77.5
55.6 43.5 81.5
54.4 43.5 90.0
63.0 49.7 87.8
64.3 50.0 100
66.0 52.1 101
54.8 43.0 75.5
57.0 45.9 84.7
33.3
33.2
30.6
39.5
38.2
37.3
36.5
34.0
32.7
41.0
37.2
24.2 392
24.8 402
23.0 354
29.6 370
28.5 384
27.2 413
27.4 358
24.8 354
24.0 333
31.0 373
28.0 377
16.7 36.0 41.9
16.7 36.1 41.5
17.1 36.0 41.0
hr.a 69.2 CO HI, 1000 std. cu. ft./hr. 53.9 Carbon conversion, To 99.5 Dry coal lb./1000 std. cu. f t . (CO +'Hz) 32.9 Carbon, lb./1000 std. cu. f t . (CO Hd 24.0 Ox gen, std. cu. f t . / l O O O std. CU. 377 (CO Hzi F. Gasifier temp., ... Firing zone refractory Top refractory 2125 Outlet gas 2450 Coal Bouroe Fraction through 200-mesh 91.3 soreen, % Ultimate analysis (moisturefree basis), % Hydrogen 5.0 72.9 Carbon 1.6 Nitrogen 11.7 Oxygen 1.4 Sulfur 7.4 Ash Net heating value, 1000 B.t.u./ 12.5 Ib.
64.5 50.1 98.1
Dry coal raie, lb./hr. Oxygen rate, 1000 std. CU. ft./hr. Steam rate, lb./hr. Steam Oxygentemperature std. CU. ft.(/lb.F.dry coal Oxygen: std. CU. ft./lb. carbon Steam lb./lb. dry coal Produbt gas analysis, % Carbon dioxide Hydrogen Carbon monoxide Product gas rate, 1000 std. cu. ft./
+
+
+
A.
-
11 12 14 15 10 1/29/52 1/4/52 1/10/52 1/10/52 1/24/52 8 8 3.5 4 5 1765 1710 1810 1700 1710 16.0 17.3 17.3 17.7 17.8 1450 1440 1475 1385 1440 890 910 930 910 910 9.1 10.1 9.8 10.4 10.2 13.05 14.25 13.85 12.02 0.8 103.. 8 48 0.8 0.9 0.9
8 3/29/51 12 1660 16.7 1420
6B 2/20/51 5 1665 19.7 1560 900 11.8 16.20 0.9
Date Data period hr.
9 12/28/51 5 1625 17.9 1100 900 11.1 15.15 0.7
7 3/28/51 10 1140 10.7 810
6A 2/19/51 4 1770 20.3 1475 910 11.5 15.75 0.8
...
2150 2450
6C 6D 2/21/51 2/22/51 6 6 1610 1720 20.0 19.5 1510 1270 925 900 12.1 11.5 16.25 15.50 0.9 0.7
...
2100 2450
...
2100 2400
2500 1875 2000
2020' 2200
2650 2000 2150
2500 1850 2170
2540 1810 2180
2470 1840 2175
2300 1710 2060
2620 1900 2260
Rock Springs, Wyo.; D. 0. Clarke Mine 92.0
91.8
91.5
90.3
93.1
87.6
88.8
89.8
90.8
91.1
89.9
6.0 72.9 1.6 11.7 1.4 7.4
5.1 74.8 1.6 11.3 1.3 5.9
5.1 74.8 1.6 11.3 1.3 5.9
5.1 74.8 1.6 11.3 1.3 5.9
5.1 74.8 1.6 11.3 1.3 5.9
5.1 73.0 1.5 13.0 1.0 6.5
5.1 75.3 1.8 11.8 1.o 5.1
5.5 73.1 1.6 12.0 1.1 6.8
5.4 73.3 1.6 12.0 1.1 6.6
4.9 75.5 1.6 11.3 0.7 6.0
4.8 75.4 1.7 10.9 0.7 6.5
12.5
12.8
12.8
12.8
12.8
12.2b
12.2
12.3
12.4
12.3
12.4
16D 1/31/52 5 1540 17.9 1250 900 11.6 15.50
16E 2/1/52 4 1500 16.0 1255 900 10.7 14.50 0.8
17 2/1/52 4 760 10.5C 934 900 13.6 18.85 1.2
18A 2/12/52 5 1740 16.9 1700 880 9.7 13.35 1.0
16.9 34.0 45.9
16.3 35.5 44.9
17.0 24.7 30.8
19.7 38.5 39.0
13.0 34.9 48.9
50.0 54.2 51.7 54.5 hr." 52.4 40.2 41.3 43.6 43.5 41.4 CO Hz 1000 std. CU. ft./hr. 88.0 92.5 89.2 83.3 Carbon cdnversion % 79.6 Dry coal, lb./lOdO std. cu. ft. 37.1 37.4 39.0 35.8 40.2 (CO Hd Carbon, lb./1000 std. cu. f t . 27.4 2 7 . 9 26.5 2 8 . 4 2 9 . 4 (CO Ha) Oxygen, std. cu. ft./1000 std. cu. 398 433 408 388 386 f t . (CO Hz) Gasifier temp., F. 2580 2630 2710 2470 Firing zone refractory 2300 1980 1950 2140 1790 1690 TOPrefractory 2380 2400+ 2325 2170 2060 Outlet gas Coal -Illinois No. 6, Peabody Mine No. 17 Source Fraction through 200-mesh screen, % 89.1 92.4 90.4 90.0 90.4 Ultimate analysis (moisturefree basis), % 5.1 5.1 5.1 5.0 4.9 Hydrogen 73.5 73.0 71 4 .. 17 7 14 .. 8 7 13 .. 8 Carbon 7 7 1.7 1.7 Nitrogen 12.9 13.0 12.8 12.3 12.6 Oxygen 1 . 0 1 . 1 1 . 2 1.2 1.2 Sulfur 5.6 6.0 5.3 5.1 5.8 Ash Net heating value, 1000 B.t.u./ 12.2 12.1 12.4 12.5 12.4 lb. a Standard gas conditio,ns are 60'. F., 30 inches Hg, dry. b Weathered coal used I n succeeding runs; note reductlon ,in heating value. c 8000 std. cu. ft./hr. 0 2 2500 std. cu. ft./hr. 02 from air.
34.1 18.9 93.5
57.8 44.8 85.0
40.2 29.3
Run number Date Data period, hr. D r y coal rate lb./hr. Oxygen rate, '1000 std. cu. ft./hr. Steam rate, lb./hr. Steam temperature ' F. Oxygen std. cu. ft.)lb. dry coal Oxygen: std. cu. ft./lb. carbon Steam, lb./lb. dry coal Product gas analysis, % Carbon dioxide Hydrogen Carbon dioxide Product gas rate, 1000 std. cu. f t . /
16A 16B 1/31/52 1/31/52 4 5 1700 1655 16.0 16.9 1445 1480 900 900 10.0 9.6 13.60 13.12 0.9 0.9 17.9 38.6 40.3
17.3 37.6 42.3
16C 1/31/52 4
1550 17.7 1375 900 11.4 15.40 0.9 17.1 35.4 44.4
0.8
+
+ +
+
20B 2/28/52 4.5 1740 17.5 970 900 10.0 14.60 0.6
2/29/52 9 1605 17.5 930 900 10.9 15.75 0.6
12.5 33.5 50.7
13.0 33.4 46.5
12.3 33.7 46.7
58.5 49.0 90.3
54.7 46.1 89.1
56.8 45.4 89.3
56.2 45.2 95.2
38.9
35.2
35.5
38.5
35.6
28.3
25.9
26.6
26.5
19 18B 2/12/52 2/14/52 5 8 1730 1640 17.0 17.2 980 915 900 880 9.8 10.5 13.35 14.00 0.6 0.6
20C
24.5
548
377
348
373
387
386
2520 1920 2250
2400 1760 2200
2550 1850 2280
2550 1900 2300
2450 1725 2200
2550 1850 2300
(First run with Illinois No. 6 coal was run 20B.)
-
89.6
91.5
91.2
89.8
90.2
90.4
4.8 72.9 1.7 12.8 1.1 6.7
4.8 72.9 1.6 13.0 1.1 6.6
4.9 7 13 .. 56 12.8 1.1 6.1
4.8 71 5 .. 25 11.6 1.1 5.8
5.0 61 9 .. 04 9.3 4.2 11.1
4.9 6 19 .. 15 9.7 4.0 10.8
12.4
12.0
12.0
12.3
11.9
11.9
+
synthesis gas-nitrogen mixtures for ammonia production feasible. Air -should be preheated, no other difficulty. Results difficult to evaluate. Run 18 (Feb. 12, 1952). Run made in two parts t o test effect of lower steam-coal ratio. Improvement in results with lowered steam was more than anticipated. No explanation. Run 19 (Feb. 14, 1952). Made as check on low steam operation of run 18. Oxygen-coal ratio was higher than in run 18, but to higher conversion was no better, and steam runs. R~~ 20 (Feb, 26 to 29, 1952). First run on 1liinois N ~ 6. coal t o test slag tapping. Because of refractory damage found later 1526
and consequent inclusion of alumina in slag, tapping not successful. Coal rates probably in error, results not sound. Results with Steam-Conveyed Coal. The first test made with steam-conveyed coal (run R-1) was only of 2 hours' duration because of trouble with the electrical control system, and no results were calculated. I n the next two runs (runs R-2 and R-3) the weigh-hopper scales did not function properly, and there was no reliable measure of the coal feed rate on which t o base calculations.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 8
ENGINEERING,DESIGN, AND EQUIPMENT
2
I
400
v,
t' 5 U 0
8
r. g 350 1
B 8
5 2
4
25.
0
t:
0
"
24
5
U
300 12
13 CU. FT.
15
16
Oxygen requirement as function of oxygencarbon ratio
Figure 8.
Table I1 presents the results of the last two runs with steamconveyed coal. Run R-4 was made with the single burner, run R-5 with the duplex feed system. I n the last run (R-5), there mas reason to doubt the accuracy of the product gas flowmeter. Fortunately, this was noticed during the run, and during the last 24 hours the product gas rate mas measured by the rate of holder rise over two periods, one with the compressors operating and one with the compressors idle. The agreement between the two measurements was good, and the results reported are based on the product gas flow measured in this manner. As nearly as can be determined from only two tests, the change from Eingle to double burner had little effect on the results, although the results of run R-5 seem to be somewhat better than those of rim R-4. Comparison with Table I and Figures 6, 7 , and
14
OXYGEN/LB. CARBON
1300
1275
1250 LL
I 1225 I W
z m
1200
4
1175 v)
z n
2
1150
112s
Table It. (Illinois No. 6
Principal Operating Results for SteamConveyed Coal coal: Peabody Mine KO.17: 90% through 200-mesh screen) Run Number and Date R-4 R-5 11'2-11/9/5% 5/20-5/29/53 A B B 48 89 26 1960 1915 1920 19.1 19.1 19.1 1730 1770 1800 420 435 387 9.7 10.0 10.0 14.15 14.40 14.35 0.9 0.9 1.0 66.0 64.8 67.7 52.4 51.2 53.0 16.4 16.5 16.8
Data period, hr. Dry coal rate, Ih./hr. Oxygen rate. 1000 std. cu. ft./lir. Steam rate, Ib./hr. Temp., steam-coal to gasifier, O F. Oxygen, cu. ft./lb. dry coal Oxygen. std. cu. ft./lb. carbon Steam, lb./lb. dry coal Product gas, 1000 std. cu. ft./lir. Hz, 1000 std. cu. ft./hr. CO Product) gas analysis, yo Carbon dioxide
+
39.2 40.2 Carbon monoxide Hydrogen Carbon conversion % 87.5 Coal, lb./1000 std.'ou. f t . (CO H2) 37.6 Carbon, lb./1000 std. cu. ft. (CO Hd 25.8 Oxygen, cu. f t . / l O O O std. cu. ft. (CO H?) 366 Gasifier temp., F. Firing zone refractory 2460 Top refractory ... Outlet gas ... Cltimato analysis (moisture-free basis),
++
%
Hydrogen Carbon Nitrogen Oxygen Sulfur Ash Wet heating value, 1000 B.t.u./lb.
August 1955
+
5.2 69.0 1.2 9.5 3.2 11.9 11.9
3 48 0.8 3 88.0 37.4 25.8 373
... , . .
... 5.4 69.2 1.3 9.6
3.5 11.0 11.9
39 8. 5 8 89.8 36.1 25.1 360 1746 2040 4.8 69.8 0.8
9.8 4.9 12.3
10.0
1100 IO
II
12
13
14
15 16 17 B.T.U.
ie
IS
20 21
22 23 24 2s 26 27 28 29 30
/ 1000 CU. FT. IC0
+ H2)
Figure 9. Gasifier heat loss per unit of gas yield as function of carbon throughput and oxygen-carbon ratio
8 ehows that the results of these runs are superior to those of many of the preceding rum. It seems logical that the intimate premixing of the coal and superheated steam should preclude the possibility of any laminar flow up the gasifier, and the poor heat and mass transfer that such flow would entail. Certainly, further experimentation would be necessary before these results would be accepted as soundly established, particularly in view of the difficulties with inconsistency that were encountered previously. However, the longer periods of operation in these runs generally make the coal rates more reliable, and it is believed that, with the system described, reproducible results could be obtained. The number of runs completed with either oxygenconveyed coal or steam-conveyed coal was insufficient to yield enough reliable data to establish the effect of gasifier heat losses on gasification results. For each run, a calculation was made of the heat loss from the gasifier, using the method previously described ( 1 ) . Expressed in relation to the yield of synthesis gas, the heat loss for the runs reported in Tables I and I1 varied from 10 t o 37 B.t.u. per 1000
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
1527
ENGINEERING, DESIGN, AND EQUIPMENT cubic feet of carbon monoxide plus hydrogen. I n calculating the gasifier heat loss for each run, a “thermal balance” temperature was computed and any serious difference between this temperature and observed gasifier temperatures indicated error in the run data. The data from those runs in which the temperatures were in closest agreement has been plotted in Figure 9. The curves seem to indicate that, expressed as a function of synthesis gas yield, the heat loss from the gasifier a t constant oxygen to carbon ratio varies inversely with the carbon throughput and, a t constant carbon throughput, increases directly with increasing oxygen to carbon ratio. Conclusions and recommendations The operation of a bottom-fired vertical gasifier with two systems of reactant feed has been described. It is believed that many of the difficulties and lack of reproducibility encountered with the first unit are traceable to the method of feeding and t o the changing geometry of the gasifier The indication of i b proved results with steam-conveyed coal leads to the conclusion that thorough premixing of the steam and coal is highly desirable and that perhaps the method of oxygen admission is less important. The mechanical operation of the steam-conveyed coal feed system was highly satisfactory in every respect. There seems to be no reason why this system could not be expected to function smoothly over long periods.
The adoption of two opposed burners and the use of a very dense, high-service-temperature refractory apparently reduced refractory damage to the point where sustained operation is possible. It is believed that the impact of the flame on the slag pool does produce undesirable agitation of the slag and promotes refractory loss to some extent. Further reduction In reactant velocities might help. It might also help to have the burners pitch downward less steeply. Slag temperatures could probably be maintained high enough for satisfactory tapping without such direct flame impingement. The refractory loss and slag agitation would both b e decreased in a unit of larger diameter, so that possibly the present design might be satisfactory for larger scale operations. No matter how i t is achieved, i t is believed that a reasonable increase in refractory life would allow a gasifier of this design to operate without difficulty, substantially continuously. literature cited (1) Dressler, R. G.. Batchelder, H. R , Tenney, R. F., Wenzell, L. P., Jr., and Hirst, L. L., U. S. Bur. Mines, Rept. Invest. 5038, 1954. (2) Eastnian, D., Symposium, Gasification and Liquefaction of Coal, at Annual Meeting of the Am. Institute of Min. Met. Engrs., N. Y . ,N. Y., Feb. 20, 21, 1952. Published by The Am. Inst. of Min. Met. Engrs. N. Y., pp. 73-9, 1953. (3) Kastens, M. L., Hirst, L. L., and Dressler, R. G., IND.ENG. CHEM..44, 460-f?6 (1952).
RECEIVED for review October
16, 1954.
ACCEPTED March 9, 1955.
Vapor liquid Equilibrium Self-lagging Stills DESIGN AND EVALUATION ARTHUR ROSE
AND
EDWIN T. WILLIAMS
The Pennsylvania S t a t e University, University Park, Pa.
I
T WAS desired to select, from the apparatus described in the literature ( 3 , 6, 7 , 10, 11, 13-16, 18, 19, 21), a superior still for use a t atmospheric pressure and below. The choice was made most difficult by the disagreement in the published data for several systems which have been run in various stills. Garner ( 5 ) and Kortum, Moegling, and Woerner (8) emphasized this fact when they tested popular equilibrium stills with common mixtures and obtained considerably different results. Recognition of the importance of the boiling point measurement reduced the number of possible choices considerably. Development of self-lagging still A modification of the Gillespie still ( B ) , designed in this laboratory in 1947 by D. F. Botkin, seemed to offer the best possibilities. The apparatus is illustrated in Figure 1. The modification was the inclusion of a liquid trap to permit sampling of the liquid that was discharged from the Cottrell tube. The original Gillespie still provided for sampling the boiler liquid, rather than the liquid leaving the Cottrell tube. The fallacy of this procedure was pointed out by Fowler ( 4 ) and Othmer (10). This modified Gillespie still was tested in the preliminary stage of the present investigation using the ethyl alcohol-water binary, for the purpose of obtaining qualitative information about the possible errors. T o this end the still was run with no lagging or with heating wires on either one, or the other, or both, of two sections of the apparatus-the Cottrell tube-entrainment separa-
1528
tor section and the liquid trap section. The following results were obtained. When the Cottrell tube was unlagged, partial condensation of the binary mixture occurred. When the Cottrell tube was heated, incorrect boiling points were obtained. When the liquid trap was unlagged, the vapor above the liquid condensed and enriched the liquid sample. When the liquid trap was heated, total vaporization of some of the liquid droplets on the walls of the trap resulted in a lowering of the vapor concentration. These results were obtained by exaggeration of the underheating and overheating problems. It was felt that good results were possible if the Cottrell tube, entrainment separator, and liquid trap could be kept in an adiabatic condition, but would be hard to achieve with any of the usual types of automatically controlled heaters. Fowler ( 4 ) subsequently described this modification of the Gillespie still, and Brown and Ewald ( 2 ) employed a still modified in this way in several experimental investigations. It was decided to design a new equilibrium still, and a list of essential design features was compiled. Requirements of Equilibrium Still. The apparatus should be based on the Cottrell tube, because of its known value in determination of boiling point (18). The Cottrell tube, entrainment separator, and liquid trap should be automatically self-lagging, without the aid of complicated control mechanisms.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47,No. 8
