Biogas upgrading – Review of commercial technologies - SGC

SGC Rapport 2013:270
2.1.3 Investment and consumables
To be able to get up-to-date information regarding consumables, investment cost
and supplier interface with customers a supplier of amine-based biogas purification
systems has been interviewed. The supplier has three standard sizes that
they offer to the Swedish market and two that they offer to the German market.
The differences between the markets are mainly on the feed used for the fermentation,
resulting in a significantly higher CO2 level in the German digester gas. But
there are also differences with respect to supply pressure requirements etc.
The systems have a nameplate capacity of 600, 900 and 1 800 Nm 3 /h of inlet
raw biogas for the Swedish market and 700 and 1 400 Nm 3 /h of inlet raw biogas
for the German market. The design value with respect to CO2 concentration in the
inlet gas is 60% in the Swedish case and 50% in the German case. The systems
are designed to have a certain turndown as per Table 8. These values are of
course dependent on the inlet conditions such that they depend on the inlet level
of CO2, as an example the Swedish systems accept a methane content ranging
from 55% to 70%. The systems are designed to handle a maximum 300 ppm H2S
in the incoming gas.
Table 8 Turndown ratio of standard amine scrubbing units for biogas upgrading
available at the Swedish market.
Capacity raw biogas
(Nm 3 Lowest flow rate
/h)
(Nm 3 Highest flow rate
/h)
(Nm 3 /h)
600 100 700
900 300 1 000
1 800 800 2 000
In the delivery, there are certain guarantee values with respect to water consumption,
electricity, methane slip and chemicals. The water consumption is specified to
0.00003 m 3 /Nm 3 raw biogas. Electricity is slightly dependent on where in the operating
window the units are operating, with the lowest consumption at the highest
load (0.12 kWh/Nm 3 raw biogas) and the highest at the lowest load (0.14 kWh/Nm 3
raw biogas). Further, the stripper column requires heat to regenerate the amine,
this heat demand is approximately 0.55 kwh//Nm 3 raw biogas. The methane slip
based on third party measurements is 0.06% (99.94% of the inlet methane exit as
product) and the guarantee value is set to 0.1%. With respect to chemicals (antifoam,
amine make-up) the consumption is guaranteed at 0.00003 kg/Nm 3 raw biogas
With respect to the investment cost, the systems vary with size and there is an 8
MSEK difference between the smallest and the largest system. In the investment
cost the gas purification unit including transport, commissioning, heat recovery
system, analysis equipment and a guaranteed 96% availability is included. Service
contracts are offered, but at an additional cost (annually around 3% of the investment
cost). The specific investment costs may be viewed in Figure 5. In 2008 the
purification systems were redesigned to modular construction and the investment
cost has not increased since.
20 Svenskt Gastekniskt Center AB, Malmö – www.sgc.se