https://doi.org/10.1016/j.egypro.2017.03.1376
“2.1 Overview of pilot plants
This study is based on three pilot plant campaigns namely at TNO’s capture plant at Maasvlakte, The
Netherlands (TNO), ENEL’s capture plant at Brindsi, Italy (ENEL) and EnBW’s capture plant at Heilbronn,
Germany (EnBW). The details of the plant and techniqu es for analysis are already reported in [14,15,16]. Hence
these pilot plants are discussed briefly in this study and description is focused on highlighting the differences in
equipment in an otherwise typical absorber- desorber setup of the plant. The process flow schemes for the pilot
plants are shown in Figure 1.
An inter-cooler section is available at EnBW’s CO2 capture pilot plant between the lowest two beds as shown in
Figure 1(a). The absorber tower includes two packed beds at th e top to act as water washing section and an acid
wash section. Along with the absorber and stripper sumps, the solvent is stored in a tank in the inter-cooling line. It also has an option for different entry heights for the lean solvent, however only the top most inlet point was used.
The absorber section is made up of FRP pipes with polypropylene in liner. The rest of the plant is made up of
SS316L.
At TNO’s CO2 capture pilot plant, a BDU is installed downstream the SO 2 scrubber and prior the absorber in
order to remove particles from the flue gas to avoid ex cessive amine aerosol based emissions, as in Figure 1(b).
BDU units are made up of a polypropylene filter which removes particles larger than 1-2 μm[17]. The absorber
tower has a section at the top which acts as a water wash. Another wash section, an acid wash is installed
downstream the water wash. The principal material for equipment of pilot plant are SS 304L and SS 316L.
The pre-treatment section (Figure 1(c)) at ENEL’s CO2 capture pilot is constituted of flue gas desulphurization
(DeSOx) unit based on limestone and two wet electrostatic precipitators in series to capture particulate matter but
these were not operational for most part of the campaign. The absorber section in ENEL too has multiple inlet points
for the lean solvent (Figure1(c)), however only the top most inlet line was used for this campaign. A conventional
pump around type of water wash is located in the absorber tower. In addition to sump, storage tank of 36m3 capacity
was also used to hold the solvent. The material of the columns and equipment is SS 316L.”
“2.2 Comparison of operating conditions
All the pilot plant campaigns were based on MEA (30 wt.%). One refilling of 760 kg of MEA was done at 952
hours of operation in EnBW’s campaign. At the end of EnBW campaign, water was added to the system resulting in
a decrease of the concentration to around 25 % wt. In ENEL’s campaign, additionally 40 m3 of 30 wt.% MEA was
added midway in the campaign. This additional solvent was used till the end of the campaign. No fresh MEA or
solvent was added in TNO’s MEA campaign.
All the three campaigns received their flue gas from coal based power plants. As flue gas quality plays an important
role in carbon capturing process, Table 1 compares the typical values of flue gas quality observed at absorber inlet.”
“The temperatures in different sectio ns of the plant are important from the point of view of solvent
degradation. Table 2 summarizes the process temperatures at the equipment which were prone to oxidative
degradation in the solvent loop. The temperatures in TNO’s and ENEL’s plants were quite similar, while EnBW’s
pilot plant was operated with a relatively lower absorber sum p temperature. EnBW had an inter-cooling section
operating at 32°C , which resulted in a lower rich solvent temperature.”
“Table 3 summarizes the holdup volumes and corresponding residence time in each process equipment
based on a typical solvent flow rate. Depending on the design of the plant, the solvent inventory could vary even for
plants of similar CO 2 capture capacity as seen between TNO’s and EnBW’s CO2 capture plants. This impacts the
residence time of the solvent in each process equipment. Since different operating conditions, i.e. temperature and
CO2 loading, exists at different sections of the plant, a different residence time in equipment can have a significant
impact on the solvent degradation. The main hold up/residence time of the solvent at TNO and EnBW’s plant was in
the sumps, while for ENEL the main hold up/residence time of the solvent was in the storage tanks.
Another important aspect for comparison is the ratio of solvent in ventory to the flue gas flow rate
inventory. Table 4 shows the solvent inventory at the three pilot plants with respect to the flue gas flow rate. The
ratio at TNO’s pilot plant is much lower, however, EnBW’s and ENEL’s ratio are quite similar in standard
operation.”
