Design og modellering af metanolanlæg til VEnzin-visionen Bilag

1 Abstract
In connection with DONG Energy’s REtrol vision 1 a methanol plant is designed to
obtain optimal energy efficiency and economy.
A key element in the design is the usage of sustainable energy sources for the
methanol production.
6 different plant configurations, each with its own syngas production method, are
compared and it is concluded that the highest methanol exergy efficiency of 74 % is
achieved for the plant which uses biogas as the primary exergy source for syngas
production.
The plant that only uses electricity as exergy source is the only plant with a significant
lower methanol exergy efficiency of 67 %.
By using the waste heat from the methanol plant for district heating the energy
efficiency is increased considerably and the methanol cost is lowered.
The lowest methanol cost of 95 kr/GJex is achieved for the plant which uses
gasification of biomass and CO2 sequestration for syngas production.
The methanol cost achieved for a number of the plant configurations can therefore
compete with the commercial methanol price (142 kr/GJex) and the petrol price inc.
duties (187 kr/GJex).
It is also shown that a duty cut on the electricity price would result in a significant
reduction in methanol cost, since 39-84 % of the total costs for the 6 plant
configurations are for electricity.
Additionally it is concluded that it is economically feasible to use underground gas
storage for hydrogen and oxygen in a buffer system in connection with an electrolysis
plant integrated in a methanol plant.
The costs are reduced by operating the electrolysis plant only when the electricity
price is low while the rest of the methanol plant is in constant operation.
Simulations based on the electricity prices from DK-WEST in the period 2000-2006
and a rate of interest of 5 % show the largest cost reductions at 5000 operation hours
per year for the electrolysis plant.
The cost reductions are up to 10.5 % and 6.1 % in average at 5000 operation hours.
These cost reductions are close to the theoretical maximum for the used electricity
prices. The maximum cost reductions are in theory up to 11.5 % and 7.7 % in average
at 5000 operation hours.
The greatest cost reductions are achieved when the calculations are based on the
electricity prices with the largest standard deviation.
Finally it is concluded that suitable locations for underground gas storage of hydrogen
and oxygen are available in Denmark.
1 Originally developed by the Danish power company Elsam.
2