Patent ID: 12208354

EXAMPLES

The following examples present tests of adsorption of CO2included in a CO-rich gas stream, according to a VPSA type method, utilising different adsorbents.

The adsorbents tested are listed below:Sample a: A2AW® silica gel from the KD Corporation in the form of beads of size 2-5 mm.Sample B: zeolitic agglomerate of mesoporous volume equal to 0.065 cm3·−1, and the mesoporous volume fraction is equal to 0.31 comprising about 20% attapulgit binder and about 80% type FAU zeolite with a Si/AI ratio of 1.19, the zeolitic agglomerate being in the form of beads with a granulometry of 1.6-2.5 mm.Sample C: zeolitic agglomerate similar to sample B, but in which the agglomeration binder is sepiolite

The charge in the adsorption column of a pilot installation is identical with each sample and is equal to 379 g. The column of the adsorption pilot has a diameter of 2.2 cm and a height of 2 m. The height of the charge in the column varies for each sample, depending on the density of each sample:height for sample A: 1.45 m;height for sample B: 1.59 m;height for sample C: 1.49 m.

The gas mixture that feeds the adsorption column has a volume composition of 35% CO, 35% CO2, 10% N2and 20% H2. The feed flow rate is set at 8 NL·min−1and 16 NL·min−1at a temperature of 40° C. and a pressure of 300 kPa.

Upon completion of the adsorption step, the regeneration is performed for 100 seconds while reducing the pressure to a vacuum level of 20-30 kPa, including a purge step of 50 seconds under vacuum by means of a gas of volume composition of around 62% CO, 2.7% CO2and the remainder to 100% of N2.

Example 1

The total adsorption capacities of CO2of sample A and sample B are compared in order to study the difference between a silica gel and a zeolitic agglomerate. The gaseous mixture that feeds the column is as described above. The feed flow rate is set at 8 NL·min−1at a temperature of 40° C. and a pressure of 300 kPa. As previously indicated, the same quantity of adsorbent of 379 g is used for each sample.

The adsorption phase is stopped when the samples are completely saturated with CO2, i.e. the concentrations of the constituents of the incoming gas stream are identical with those of the outgoing gas stream. The adsorption time required for each sample to obtain the total saturation thereof is as follows:Sample A: 450 seconds;Sample B: 1055 seconds.

The breakthrough time to reach a volume concentration of 0.1% of CO2, for each sample is:Sample A: 63 seconds;Sample B: 747 seconds.

These results clearly show that, in equal quantity, sample B (zeolitic agglomerate according to the invention) has a total adsorption capacity of CO2more than twice what was observed with sample A (silica gel, comparative sample). If the adsorption is stopped at the beginning of the breakthrough, the performance of sample B is about 12 times better than that of sample A.

This example clearly shows that the use of sample B (zeolitic agglomerate according to the invention) leads to a much longer use than when a silica gel is used, if the same quantity of adsorbent is used. Moreover, the adsorption unit can be made more compact by using a zeolitic agglomerate rather than a silica gel, which makes it possible to reduce both investment and operational costs.

Example 2

Under the same operating conditions as in the example 1, this example compares the dynamic adsorption capacities of CO2of samples A and C in order to study the differences between a silica gel and a molecular sieve. The feed flow rate is set at 16 NL·min−1at a temperature of 40° C. and a pressure of 300 kPa. The quantity of each sample used is 379 g.

The adsorption phase is stopped when the volume concentration of CO2of the outgoing gas stream reaches 2.6% (breakthrough concentration).

Upon completion of the adsorption step, the regeneration is performed for 100 seconds while reducing the pressure to a vacuum level of 20 kPa, including a purge step of 50 seconds under vacuum by means of a gas of volume composition of around 62% CO, 2.7% CO2and the remainder to 100% of N2. Fifteen (15) adsorption/desorption cycles are performed to reach a stable breakthrough time for each sample.

The breakthrough time to reach a volume concentration of 2.6% of CO2, for each sample is:Sample A: 15 seconds;Sample C: 38 seconds.

These results clearly show that, in equal quantity, sample C (zeolitic agglomerate according to the invention) has a performance 2.5 times better than sample A (silica gel, comparative sample) and therefore by using a zeolitic agglomerate the time of use will be longer than with a silica gel if the same quantity of the adsorbent is used, due to the possibility of reducing the number of regeneration cycles.

Example 3

Under the same operating conditions as in the example 1, this example compares the dynamic adsorption capacities of CO2of samples A and C in order to study the differences between a silica gel and a molecular sieve. The feed flow rate is set at 16 NL·min−1at a temperature of 40° C. and a pressure of 300 kPa. The quantity of each sample used is 379 g. The regeneration of each of samples A and C is compared in order to study the differences between a silica gel and zeolitic agglomerate. The gas mixture entering the adsorption column has a volume composition of 35% CO, 35% CO2, 10% N2and 20% H2. The feed flow rate is set at 8 NL·min−1at a temperature of 40° C. and a pressure of 300 kPa. The quantity of adsorbent is identical for each sample and is 379 g.

The adsorption phase is stopped when the volume concentration of CO2reaches 2.6% (breakthrough concentration). Upon completion of the adsorption step, the regeneration is performed for 100 seconds while reducing the pressure to a specific vacuum level, including a purge step of 50 seconds under vacuum by means of a gas of volume composition of around 62% CO, 2.7% CO2and the remainder to 100% of N2. The specific vacuum level mentioned above varies depending on the sample in order to obtain the same breakthrough time of 36 seconds (stable after a multitude of cycles) in order to obtain an output volume concentration of 2.6% CO2for each sample. Fifteen (15) adsorption/desorption cycles are performed to reach a stable breakthrough time for each sample.

The vacuum level for each sample is:Sample A: 20 kPa;Sample C: 40 kPa.

These results clearly show that, with an equal quantity of adsorbent and identical adsorbent performance, sample C, zeolitic agglomerate according to the invention, requires one half the amount of vacuum required for sample A (silica gel, comparative sample) and therefore by using a zeolitic agglomerate (sample C), operational costs can be reduced during regeneration.