6. Operating Conditions.
The main variables of the operation, such as pressure, temperature, space-velocity, gas composition are today practically the same, as in 1937-1938. Specifically, there was no improvement or change in the design of the ovens. Nevertheless there was no increase in the average yield expressed in gram/m3 feed gas from approximately 100 g to 130 g/m3. As Germany was faced with a serious lack of cobalt, the yield of product per ton of cobalt was of greatest importance, since this yield can be raised by keeping the space-velocity low, most plants were operated at less than 100 V/H/V (Vol feed gas/hr/unit volume catalyst).
The Essener Steinkohlen A.G. apparently had developed a somewhat improved method of operation, which resulted in a better yield based on feed, and longer catalyst life. This operation widely discussed by the FT group, was known as the “Essener Fahrweise”.
In principle, it consisted only in a rigorous control of operation, i.e.;
With these means the Essener plant obtained the following results:
Essener |
Others |
|
Yield |
160 |
130 C3+gm/m3 gas. |
Catalyst life |
2000 |
1400 hours |
Catalyst yield |
425 |
250 ton/ton catalyst |
Flexibility of Operation. In order to show the variations possible in FT plant operation, yields and product qualities for 2 conditions listed below. The data are based on a report from Brabag and refer to their Ruhland Plant:
Processing |
Case I |
Case II |
|
Absorber gasoline |
160°C EP |
140°C EP |
|
Diesel oil |
160-300°C Max |
under 325°C |
|
Gatsch |
over 325°C |
over 325°C |
|
Yield |
|||
Gasol |
5100 ton/year |
7600 ton/year |
|
Gasoline |
73800 ton/year |
83900 ton/year |
|
Diesel oil |
52500 ton/year |
35100 ton/year |
|
Gatsch |
10100 ton/year |
10100 ton/year |
|
Products |
|||
Gasoline: |
sp.gr. |
0.686 |
0.689 |
Octane No. |
56 |
62 |
|
Diesel oil: |
sp.gr. |
0.757 |
0.732 |
Pourpoint |
-20°C |
-60°C |
|
Flashpoint |
+56°C |
+25°C |
|
Vis E/20 |
1.08 |
1.022 |
|
Cetane No. |
100 |
88 |
The difference is due to a variation in the amount of thermal cracking of the distillation fraction carried out in a separate unit.