components is efficiently separated out. The acid gas removal will be done by absorption in MDEA ( N-Methyl-DiEthanolAmine). The operation of the plant will provide added insight into how the sulfur slip varies with operating conditions and CO2 rejection efficiency. This knowledge enables a more compact design of the downstream sulfur guard and gives better insight into the conditions at which an MDEA wash can be used for the AGR service.

The necessary sulfur polishing – regardless of the AGR technology used - must take place by solid absorption. This process is more efficient at increased pressure and temperature compared to the conditions that prevail at the AGR outlet. The sulfur guard is therefore installed downstream of the methanol synthesis gas compressor.

The methanol synthesis takes place in two steps.
In the first reactor the bulk of the reaction takes place
at conditions favoring a high reaction rate while
the second reactor with its unique design ensures a
sufficiently high conversion to eliminate the need for
a recycle stream around the methanol synthesis. In
both reactors the main reaction is
(B) CO + 2 H2 ↔ CH3OH
The raw methanol is sent to the DME synthesis
via an evaporator that is designed so that heavy by-
products from the methanol synthesis (particularly
wax) are simultaneously rejected.

Methanol splitter and a wastewater column. In the latter, water that is co-produced in the DME reactor is separated from the unconverted methanol that is recycled to the DME reactor to obtain essentially 100% methanol conversion.

The process described has one distinct feature, which makes it extremely attractive compared to current state-of-the-art DME processes, and that is its single-pass nature. The only recycle stream in the process described above is that comprising unconverted methanol to the DME reactor. This is a liquid recycle requiring no loop compressor and further the flow rate is very small as more than 80% of the methanol is converted in the DME reactor. The advantages of the once-through process is reduced capital and operating cost as well as process that is easier to operate and control.

Surprisingly, these advantages come without an efficiency penalty, as the overall CO and H2 conversion is higher than what is normally attained in methanol and DME processes based on a conventional methanol loop.

Another advantage of this process over conventional DME processes is the flexible distillation system. The separation process in the DME pilot contains more separation columns than the com-