Page 29 - demo

PROCESS & TECHNOLOGY FOR METHANOL AND DME

In addition to the commercially established routes for production of syngas from natural gas
or lower hydrocarbons (up to naphtha), there are several other technologies such as Catalytic
Partial Oxidation, Dry Reforming with carbon dioxide, and Chemical Looping.

2.1.2
SYNGAS PRODUCTION FROM DIFFERENT HYDROCARBON SOURCES

While coal, coke, natural gas and biomass are the major carbon sources, there are several
other sources from which syngas can be manufactured. The solid waste from domestic origin,
food waste, agricultural waste, effluent gases, liquids and solids from different industry are very
often utilized for production of syngas. In addition to the advantage on the cost of hydrocarbon
source, the other benefits are reduction of carbon footprint and waste disposal problem.

2.1.2.1
SYNGAS FROM HEAVY RESIDUE, COAL, BIOMASS OR SOLID WASTES

While normal combustion of solid fuel will essentially produce hot gases after complete
combustion, the term gasification has a special meaning. Gasification implies that the fuel
is not completely burnt. Technically it could be termed as partial oxidation. The key is the
combustion of the fuel with less than stoichiometric ratio of oxygen to convert it to syngas.
Operating pressure used is around 30 Bar and temperature of the order of 1000 to 1500 C.
0
Regarding the basic technology for conversion of solid hydrocarbons or coal, both follow
similar chemical pathways, as also the reactor configurations. However, there are several
specific issues for coal, heavy hydrocarbon residues and biomass. Complete combustion of
coal or other residual solid hydrocarbons produces energy. Similarly, gasification also produces
energy but to a lower extent. The main difference is that complete combustion produces a large
amount of carbon dioxide while gasification produces much less carbon dioxide. The energy
is delivered in the form of a mixture of carbon monoxide and hydrogen. Power plants based
on gasification may be coupled with production of syngas and methanol or DME, to recover
a major part of the hydrocarbon in the fuel as high grade transportation fuel or chemicals. For
large scale plants it could be coupled with combined cycle to recover energy from the product
gases, before converting them into useful chemicals. The fuel efficiency of a coal gasification
power plant with combined cycle can be more than 50%. In addition to the energy efficiency,
with the use of oxygen in place of air, the produced carbon dioxide is in concentrated form
therefore, syngas cleaning or carbon sequestering is easier and the size of the gasification
equipment is lower.
The wide variation of heating value and moisture content of biomass as well as coal has to be
taken into account before estimation of expected methanol/DME production. The quantity of
feedstock is directly proportional to the heating value of the feed [118].

2.1.2.1.1
GASIFICATION TECHNOLOGIES AND REACTORS FOR GASIFIERS

Besides air or oxygen, gasification can be carried out even with steam or carbon dioxide, but
the energy requirement is too high to sustain a stand-alone facility.
Gasification is the heart of the process, and several modes of operation are possible for
gasification. Technologies for most of these variations are established, while some of them are
still in the development stage.

Methanol and DME Production: Survey and Roadmap | 2017 29