I
R. BURGESS MASON Esso Research Laboratories, Esso Standard Oil Co., Baton Rouge, La.
Hydrodesulfurization of Coke Preoxidation of petroleum coke at low temperatures greatly enhances the rate of sulfur removal upon subsequent hydrogen treating, and satisfactory desulfurization can be achieved in reasonable periods of time
PRODUCTION
of Detroleum coke bv the fluidized solids technique has been described in the literature ( 4 , 5, 72). When high sulfur residua are used as the coking feed, sulfur content of the resultant coke is higher than desired for specialty applications such as metallurgical or electrode coke. Consequently, experimental work \vas conducted to develop effective means of the coke product other than high temperature calcination ( 9 ) . Removal of sulfur from coke is an old problem. Processes giving varying degrees of success, reviewed by Thiessen (77): include contacting with steam, air, air-steam, nitrogen, carbon dioxide, carbon monoxide, hydrogen, methane, &lorine, coke Oven gas, and producer gas, Subsequently, Brewer and Ghosh ( 2 ) found that ammonia, hydrogen, and nitrogen, especially ammonia, lowered the sulfur content of coke when used in
-
coal carbonization and in treating the coke product. Sabott ( 8 ) observed that olefinic gases such as ethylene and propylene are effective in removing the sulfur from petroleum coke, presumably from delayed ~ ~ coking operation, zielke, curran, and G~~~~~ ( 73) used hydrogen and steam at 1600' F. with the ratio varying from 0.1 to I O at pressures between I and 6 atm. They reported desulfurization as high as 90% with no more than 20% of the carbon gasified. These more recent investigations provided an incentive to study the desulfurization of petroleum coke from the fluidized solids process by contacting with an inexpensive gas at low pressures. The objective set for the present work was to reduce sulfur in the fluid coke to a level of 1%.
Procedure
Most Of the work Was at atmospheric Pressure and consisted Of passing a gas stream over a bed of 35- to 60-mesh coke (about 20 grams) from large-scale pilot plant fluidized coking operations. Ef~ i ~ reactor , fluent from the system (below) was scrubbed with 30% sodium hydroxide solution, and hydrogen sulfide in gas was determined a t intervals by titrating with silver nitrate a tentiometric technique ( 70). Sulfur content of the coke charge and the discharged sample was determined by a high-temperature sulfur method ( 7). A few runs were made at 3.5 and 6 arm.: and in such cases the reactor was a metal tube equipped with screw caps, back pressure regulator, and pressure rotameter. Gas from this operation was not scrubbed, and the effect of time at a given
A
U C
s VSR I i
2
c
li I
When operating at 3.5 and 6 atm. the
9670
Reactor t u b e 2 5 - m m . diameter, 12-inch length; insert coke-containing t u b e 19-mm. diameter, 1 0-inch length A. Metering system for Ng, H?S, etc. 6. Metering system for ethylene, Hz, or Hz-Hz0 vapor C. Saturator far adding HIO vapor for Hz-steam operation D. Insulation
silica glass reactor was replaced with a metal one E.
Thermocouple Coke charge Sintered 96% silica glass plate to support coke H. Vent 1. NoOH scrubbers for removal of HzS J. Electrical outlet
F. G.
VOL. 51, NO. 9
SEPTEMBER 1959
1027
Desulfurization of Petroleum Coke with Hydrogen and/or Steam Was Not Successful at First 2 0 - g r a m charge; 35- to 60-mesh coke; atmospheric pressure
Hz,
Temp.,
Table I
but..
F.
RWl Untreated coke
...
34 35 36 37 38 39 40 41 42 43 44
1500 1500 1500 1500 1500 1600 1600 1700 1700 1100 1100
.
Cc./Min.
Steam, Cc./Min.
Hours of
..
...
. . I
150 150 150 150 150
S on Coke,
wt. 70
Run
0
7.0 6.1 5.4 4.7 5.6 5.6 6.1 5.6 6.1 6.6 6.6 6.6
1
2
0 0
6.5 2 2
30 30
150
0
2
150 150 150 150 5
30 30
2
0 0
2 2 2
2
0
Increasing the Hydrogen Rate Improved the Rate and Degree of Desulfurization Fixed bed; atmospheric pressure, 1300' F.; 2 0 - g r a m coke charge
Run 68 69
and..
.
Gas
HP
70
Hn+Nzn H2 HzS"
67
H?
+
S on Coke After Operating Intervals, W t . %
Run
Rate, Gas
Table II
T'ol./ Time, T'ol./Hr. Min. 43 1500 1500 1500
250 110
120 350
Minutes 60 110 120
120 240
10
20
30
7.0 7.0 7.0
6.9 6.3
6.9 6.1
6.8 6.0
6.6 5.8
6.1 5.7
6.1
7.0
6.1
5.9
5.6
5.1
4.5
4.4
-
Filial-
5.3
5.2
3.7
5.7 8.0 3.5
...... .....................
50-50 ratio.
Table 111
Preoxidation of the Coke Greatly Improved Subsequent Desulfurization Atmospheric pressure
Oxidation Conditions" Surface Air area. rate, Yield, W. Temp., Time, vol./ wt. meters/ Run F. hr. vol. /hi gram %
..
15 15 17 8 8 10 2 2 2 6 a
. . . . . . ... 650 650 700 700 700
750 750 750 750 850 1100
12.5 12.5 6 17 17 2 4.5 4.5 4.5 1.5 1
..
550
550 550 660 660 660 790 790 790 790 495
Fluidized solids operation.
.. 93 93 93 62 62 94 80 80 80 91 93
5 163 163 139 339 339 98 199 199 199 83 10
Run
Temp., v0l.l ' F. vol./hr.
67 83 84 76 79A 79B 74 71 81 82 75 78
1300 1300 1400 1300 1300 1600 1300 1300 1400 1500 1300 1300
1500 1500 1500 1500 1500 1500 1500 1500 1500 1500 1500 1500
Run time, min. 350 350 330 400 220 100 395 340 350 350 450 400
S on Coke d f t e r Oueratinrr Intervals, W t . 57, ~
Initial
10
20
30
7.0 7.0 7.0 7.0 7.0 2.1 7.0 7.0 7.0 7.0 7.0 7.0
6.1 4.0 3.2 4.1 3.4
5.9 3.6 2.5 3.6 3.1
5.1 4.4 3.9 3.5 5.1 5.9
4.7 4.0 3.2 2.9 4.6 5.5
5.6 3.3 2.1 3.3 2.8 1.6 4.4 3.6 2.8 2.6 4.2 5.3
......
Minutes 60 5.1 2.6 1.4 2.9 2.4 1.6 3.8 2.8 2.2 2.1 3.6 4.6
110
120
240
Final
