Ikelic - Alliance Digital Repository

COAL
The Coal Hydrogenator
A reactor for coal hydrogenation must provide
rapid heating of the coal to promote devolatiliza-
tion and avoid agglomeration of the particles.
The reactor (Figure 1) achieves this using a spe
cial high velocity injector which subjects the pul
verized coal and hot hydrogen to intense mixing
as they
enter the reactor. The injector also
provides the driving force to recirculate the hot
product gases which further raises the tempera
ture of the inlet reactants. This feature of internal
recirculation and reactant preheating avoids the
need for oxygen addition and for high hydrogen
preheat temperatures. This leads to a high over
all process thermal efficiency.
The coal reacts within the central draught tube
yielding a char, which can then be used to
produce the hydrogen.
At reactor temperatures above 900C the
products are mostly methane and char while at
temperatures between 800 and 900C significant
quantities of hydrocarbon liquids can be
produced.
Coal
Temperature (C)
Pressure (bar)
H2/Coal Ratio (wt/wt)
Gas Residence Time (s)
%Carbon Conversion to
Methane
Other Gases
Benzene
Heavy Aromatics
Total
TABLE 1
Pilot Plant Trials
Six runs were carried out during 1990-1991.
Three coals, two United Kingdom bituminous
(Kiveton Park and Markham Main) and a
Japanese subbituminous coal (Taiheiyo), were
gasified. A total of 53 tonnes of coal were fed to
the reactor over a cumulative coal feeding time of
429 hours.
Taiheiyo coal gave the highest total conversion.
Selected results are given in Table 1 .
The relative yields of benzene and higher
aromatics varied with coal type and operating
conditions. Liquid yields were highest at lower
temperatures with up to 18 percent liquids yield
being achieved. In all cases, benzene has com
prised the major proportion of the total liquid
yield. The sulfur content in the liquids ranged
from only 0.01 to 0.26 weight percent.
Commercial Plant
PILOT PLANT PERFORMANCE
An engineering design and costing study was
carried out for a full-size commercial plant
Manvers Taiheivo Pittsburgh 8
865
62
4-31
0.4
12
27.0
3.0
8.6
4.6
43.2
846
62
0.4
12
35.7
6.6
12.3
3.8
58.4
872
62
11
0.4
29.6
1.9
6.8
8.2
46.5
THE SYNTHETIC FUELS REPORT, JANUARY 1995