Process for hydrogenation of coal

Details Process for hydrogenation of coal Process for hydrogenation of coal

1983-06-08

1984-12-11

Dees, Carl F.

Mineral oils: processes and products

Products and compositions

Lubricating oils

C10G 106

Patent

active

044876840

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a process for hydrogenizing coal whereby the finely ground coal is pumped under pressure, heated to the temperature at which hydrogenation is initiated and hydrogenized with hydrogen in a reaction zone in the presence of a substance which acts as a catalyst, the process being such that at least part of the heat required for the heating process is fed to the coal in a mixing stage by direct heat-exchange with hot product vapors.
German Pat. DT-PS No. 669 660 discloses a process for producing liquid hydrocarbon oils by hydrogenizing solid carbon-containing substances, the process being such that vaporous and gaseous products are brought into intimate contact with starting materials in the form of a slurry. The aim of this process is to bind the acidic substances entrained in the vaporous and gaseous products by the alkaline constituents contained in the solid starting materials, whereby, due to the neutralization of their alkaline constituents, the starting materials should be simultaneously put into a more suitable form for the pressure-hydrogenizing process.
At the same time, part of the low boiling point constituents contained in the coal slurry can be separated from the latter, while the high boiling point constituents of the hot product vapors condense and arrive again in the hydrogenizing reactor along with the coal slurry.
The heating of the coal slurry which occurs as a result of mixing the said slurry with the vapor and gaseous products is not always sufficient to initiate the hydrogenizing reactions. It then becomes necessary additionally to heat the coal slurry to the reaction-initiating temperature in a separately heated heat exchanger.
However, heating the coal slurry in a heat exchanger is found to be extremely difficult because, due to the viscosity of the slurry, it is impossible to obtain uniform loading of the heat exchanger surfaces. In addition, at the high temperatures present in the heat exchanger, the coal suspended in the slurry swells. This leads to an additional increase in the viscosity and, in turn, to a pulsating throughput of the coal slurry through the heat exchanger with concomitant pressure surges and high material wear.
In addition, the gases and vapors, which are first formed during the further heating of the coal slurry in the heat exchanger, arrive in the reactor, thus leading, in particular, to a dilution of the hydrogen in the reactor and, because of the space required to accommodate these gases and vapors, the result is a worsening in the degree of filling of the reactor with coal slurry.
The gases and vapors entrained by the coal slurry must be heated, along with the latter, to the temperature of the initiation of the hydrogenation resulting in an additional heat requirement.
Low boiling point oils, which arrive with the coal slurry in the reactor where they vaporize on the further increase of the temperature, do not, on account of their vapor state, participate in the actual coal hydrogenizing process but undergo, instead, a further cracking on account of the high temperature and whereby, with the consumption of hydrogen, additional undesirable compounds are produced.
The basic objective of this invention is to provide a process of the above-mentioned type which obviates these drawbacks and which ensures better heating as well as the optimum conditioning of the coal slurry to be hydrogenated.
This objective is attained, in accordance with the invention, by bringing the coal slurry in the mixer region in contact with an additional stream of hot gas.
With the process of the invention, it is possible to dispense entirely with the use of heat exchangers to heat the coal slurry, and thus avoid the problems associated with them. Furthermore, heating the gas stream can be effected in the usual way in a heat exchanger or in a furnace and gives rise to no difficulties.
Both the gas stream and the uncondensed part of the product vapors, along with the gases and vapors driven out of the coal slurry, are separated again from the slurry before the latter

REFERENCES:
patent: 4152244 (1979-05-01), Raichle et al.
patent: 4189375 (1980-02-01), Kirby et al.
patent: 4222844 (1980-09-01), Nizawoff

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