Experimental set up of CO2 absorption from flue gas using MEA

2.1 Laboratory Setup
For continuous CO2 removal from flue gas, a special laboratory unit was constructed. The most important parameters of
the unit are given in Table 2. The basic elements of the setup were absorber, stripper and main heat exchanger. The columns were built from metal and glass and were filled with glass Raschig rings 6×6×0.5 mm (Raschig GmbH) with an option to replace with another type
of packing [23]. Glass walls enabled the observation of distributor liquid sprinkling and liquid flow distribution over the
packing. The main heat exchanger was necessary to exchange heat between the hot lean solution and the cooler rich solution. The main heat exchanger was used to reduce the overall stripper size. When necessary, the rich solution could be cooled to a lower temperature in the final water cooler. The solution was additionally filtered through an activated carbon bed to remove solid contaminants and some of the products of amine degradation. The heat needed for the CO2 desorption from the solution was delivered to the system using an adjustable electric heater. That solution is convenient under laboratory conditions and simplifies the calculations. Despite having the column stripper and piping insulated, the ambient heat loss was so high that the heat loss strongly affected the value of the reboiler heat duty. Transferring the heat duty values directly to the industrial process would be inappropriate but still sufficient to allow the comparison of different solvents.
The laboratory setup described here has been equipped with approximately 30 measuring points and controlled by a
supervisory control and data acquisition system (SCADA). The installation has the possibility of controlling parameters of the gas and solvent solution by Intergaz gas metersand Tecfluid M21 flowmeters. The temperature is controlled by Limatherm PT-100 sensors and the pressure by pressuretransducers from Wika. The amount of electricity to the stripper heater is regulated by Aplisens PMS-200 electric current. The CO2 volume fraction both at the inlet and at outlet is measured with Siemens Ultramat 23 and Sick-Maihak S700 gas analyzers.


“2.2 Process Flow Description
A schematic diagram and a picture of the laboratory setup to investigate the CO2 removal process are presented in Fig. 1.
According to the schematic diagram, air is compressed in an air blower to the discharge pressure of 130−150 kPaabs. After
drying, air is directed to the gas mixer where the gas mixture is combined with carbon dioxide. The composed gas mixture
is next directed to the absorber where the CO2 absorption process takes place. Cleaned gas is evacuated from the column through the gas meter and discharged outside.



“Fig. 1 Schematic diagram and a picture of the laboratory unit to investigate the CO2 capture process [24]”

“In the absorption column, the packing gas mixture comes into contact with the lean amine solution from stripper in
a countercurrent way. The rich solution with the absorbed carbon dioxide is pumped from the bottom of the absorber
and passed through the main heat exchanger to the top of the stripper. In the stripper, thermal carbon dioxide regeneration
takes place. In next step, the lean solution is pumped back to the absorber top from the bottom of the stripper.
Losses of water/sorbent are supplemented periodically from the solvent tank.
2.3 Materials and Media
The gas mixture was prepared from ambient air and carbon dioxide (purity 4.0) delivered by Linde AG. Carbon dioxide
in gas composition oscillated at 13 vol% level. To simplify the experiment, ambient air instead of nitrogen was used.
This simplification brought the experiment to more real conditions. Due to the relatively short time tests, solvent oxygen
degradation was negligible. Baseline studies were conducted using 30 wt% monoethanolamine solution. Concentrated monoethanolamine (MEA, CAS #000141-43-5) was obtained from Acros Organics. For solvent comparison studies, the following solutions were also used:
• 30 wt% 2-amino-2-methyl-1-propanol with 10 wt% piperazine. Both reagents—2-amino-2-methyl-1-propanol
(AMP, CAS #000124-68-5) and piperazine (PZ, CAS #000110-85-0)—were obtained from Sigma-Aldrich. • Multicomponent solution 2—developed at the Institute for Chemical Processing of Coal—contains 15 wt% of first-order amine, 20 wt% of AMP, 2 wt% of activator, 63 wt% of organic solution and water [25].
Distilled water was used during solvent preparation.
2.4 Testing Procedure
The performance of the 30 wt% MEA was evaluated to estimate its ability to capture carbon dioxide and to minimize
the reboiler heat duty under laboratory conditions as well as to obtain baseline performance for solvent comparison.
Table 3 describes the range of process conditions applied in the laboratory setup during the studies that we conducted.
The measurements presented in this paper were selected from the database of trends recorded in the SCADA system.
The tests were considered of value only when the period of the steady state lasted at least 1 h. For better balancing or performance estimation, the average of the chosen parameters from the steady-state period was used for further calculations.
The lines at presented figures were used to connect experimental data, and these lines serve only to join the data points.
2.5 Error Determination
After conducting the appropriate calculations, which included inlet gas parameters and mass balance, an estimation of
the maximum absolute error was made (Table 4). Based on several measurement cycles, the precision of the test method
was also established. Repeatability of the results was determined within the range of the measurement errors.”

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