DE19602450C1 - Vacuum pressure swing adsorption method and device - Google Patents

Abstract

The invention concerns a vacuum pressure alternating adsorption process for the separation of at least one component from a crude gas mixture with at least two components, including at least the absorption, vacuum regeneration and pressure build-up process stages, where these process stages are effected in offset cycles in at least two adsorbers connected in parallel. The process is effected as follows: a) in the final stage of the adsorption of a first adsorber, the supply of the crude gas mixture is interrupted and; b) at least a part of the gas mixture drawn from the first absorber during the absorption cycle is supplied to a second adsorber that is already prepressurized for the purpose of further pressure build-up in this second adsorber; c) until a pressure between 650 and 800 mbar, especially between 700 and 750 mbar, is reached, and d) then follows an evacuation of the first adsorber. Vacuum-pressure alternating adsorption device comprising at least two adsorbers arranged in parallel together, at least a vacuum pump assembly and gas lines to, from and between the adsorbers and the vacuum pump, said vacuum pump assembly consisting of at least a Roots vacuum booster and at least a turbocompressor.

Description

The invention relates to a vacuum pressure swing adsorption process for separation at least one component from at least two components standing raw gas mixture, comprising at least the process steps adsorption, Vacuum regeneration and pressure build-up, these process steps cyclically ver expires in at least two adsorbers connected in parallel.

The invention further relates to a vacuum pressure swing adsorption device, comprising send at least two adsorbers arranged parallel to each other, at least one Vacuum pumping station and gas supply lines to, from, and between the adsorbers and the vacuum pumping station.

Vacuum pressure swing adsorption processes or devices are e.g. B. Ge Extraction of oxygen and / or nitrogen from air or for the separation of carbon dioxide from carbon dioxide-containing, hydrogen and carbon monoxide-rich synthesis gases used. Such vacuum pressure swing adsorption processes have at least two adsorbers connected in parallel, the one of the separation or separation at least serve two-component raw gas mixture.

In the following, the term "adsorber" is one, at least one adsorbent layer containing container to understand. The choice of the ad (s) used sorbent is of the intended use of the respective vacuum pressure change sorption process dependent.

Such a vacuum pressure swing adsorption process basically includes the Process steps adsorption, vacuum regeneration and pressure build-up. You can also further process steps, such as. B. pressure equalization or rinsing steps will.

In such vacuum pressure swing adsorption processes, the certain gas compo the skilled person strives to deliver nenten in defined purities and yields reduce energy consumption as much as possible. Especially in the extraction  of oxygen and / or nitrogen from air, where the raw gas mixture air is free is available, the operating costs of a vacuum pressure swing adsorb tion system essentially determined by its required energy requirements.

The energy requirement of such a vacuum pressure swing adsorption process It has already been proposed to lower one before evacuating an adsorber Pressure equalization between the ad to be evacuated and an already evacuated ad perform sorber. However, such a pressure equalization leads to a clear one Reduction of the capacity of the vacuum pressure swing adsorption process.

The object of the present invention is a vacuum pressure swing adsorption drive of the type mentioned to indicate that without leading to a capacity deterioration comes, a better energy balance than conventional vacuum pressure has alternating adsorption.

This is achieved according to the invention in that

• a) in the final phase of the adsorption cycle of a first adsorber Feed of the raw gas mixture interrupted and
• b) at least part of the first from the adsorption cycle Adsorber withdrawn product gas (mixture) it a second, already prestressed, adsorber for the purpose of further pressure build-up in this second adsorber is supplied until a pressure in the first adsorber is set between 650 and 800 mbar, and
• c) the first adsorber is then evacuated.

In contrast to the vacuum mentioned above, which belongs to the prior art Transfer pressure adsorption process takes place in the vacuum according to the invention pressure swing adsorption process in the final phase of the adsorption cycle pressure equalization with a second, already covered adsorber. This pressure equalization between the two adsorbers is according to the Invention Vacuum pressure swing adsorption process continued until  first adsorber a pressure between 650 and 800 mbar, in particular between 700 and 750 mbar, is set or reached. Only then is the evacuation of the first adsorber started. The negative pressure value, that by means of the pressure compensation between the first and the second adsorber is achieved by the Ausle determination of the pumping station used for the evacuation.

An advantageous embodiment of the vacuum pressure swing adsorb according to the invention tion process is characterized in that

• a) after the supply of a part of that in the adsorption cycle first adsorber withdrawn product gas (mixture) it into a second, already preloaded adsorber for the purpose of further pressure build-up, if the supply of the raw gas (mixture) continues to be interrupted in the first Adsorber, at least part of that withdrawn from the first adsorber Product gas (mixture) es, a third, which is in an evacuation cycle Adsorber supplied for the purpose of rinsing this third adsorber until a pressure between 650 and 800 mbar is reached in the first adsorber is set, and
• b) the first adsorber is then evacuated.

The two processes mentioned have in common that the second adsorber, a partial flow of the product gas (mixture) it for the purpose of further Pressure equalization is supplied, is already (pre) covered. This biasing of the Adsorbers particularly affects the life of the Adsorbent compared to known Vacuum pressure swing adsorption process with pressure equalization steps clearly is exposed to lower pressure surges, positive.

According to a further embodiment of the vacuum pressure change according to the invention Adsorption process takes place by preloading an adsorber using the product gas (mixture) it.  

It has been shown that an advantageous embodiment of the invention Vacuum pressure swing adsorption process consists of evacuation a combination of Roots blower and turbopump.

The low starting pressure associated with the procedure according to the invention the evacuation step means that the use of a turbopump due to the The fact that the turbopump can operate in the range of favorable efficiencies, makes sense over the entire pressure range of the evacuation step.

Roots blower and turbo can be used at the beginning of the evacuation process pump connected in parallel and only after a pressure of 400 to 800 mbar has been reached, in particular from 500 to 700 mbar, can be connected in series.

In an alternative embodiment of the vacuum pressure according to the invention change adsorption process, the evacuation takes place in such a way that the Wälzkol blower and the turbopump are connected in series.

In principle, with correspondingly elaborate pumping stations, you can do almost anything reach low final pressures during the evacuation cycle. Energetically sensible however, final pressures are between 150 and 450 mbar, in particular between 250 and 350 mbar.

As already mentioned at the beginning, the invention further relates to a vacuum pressure change adsorption device.

A vacuum pressure is used to solve the problem also mentioned at the beginning removable adsorption device of the generic type proposed, in which the Vacuum pumping station consisting of at least one Roots blower and at least one Turbopump exists.

It has been shown that a combination of Roots blower and turbopump represents an optimal solution. This combination makes it possible to cope with large ones Volume flows with comparatively low energy requirements.

The vacuum pressure swing adsorption device according to the invention is further developed proposed that the Roots blower and the turbopump interconnected  be the realization of both a parallel and a serial connection tion of the Roots blower and the turbopump.

The vacuum pressure swing adsorption method according to the invention, the vacuum pressure swing adsorption device according to the invention and further refinements since that are the subject of dependent claims are explained in more detail with reference to the following FIGS . 1 to 3. Here show:

Fig. 1 process schematic of the vacuum pressure swing adsorption process according to the invention with three adsorbers,

Fig. 2 clock Scheme 1,

Fig. 3 clock Scheme 2.

Here, the abbreviations used in the timing diagrams of FIGS . 2 and 3 mean:
A: Adsorption
E1: Pressure reduction, with simultaneous pressure compensation with an adsorber that is in the covering or pressure build-up cycle R1
PP: Pressure reduction with purge gas delivery to an adsorber that is in the evacuation and purge cycle EVP
EV: Evacuate
EVP: Evacuation with simultaneous (counterflow) flushing
R0: Pretensioning with product gas (mixture)
R1: Covering via the pressure compensation with an adsorber that is in the pressure reduction cycle E1
RF: Covering with a raw gas mixture

The vacuum pressure swing adsorption method according to the invention will first be described with reference to the two FIGS. 1 and 2. Here, FIG. 1 shows three parallel arranged adsorbers A1 to A3. The raw gas mixture is fed to one of the three adsorbers A1 to A3 at the inlet end, if necessary after a pressure increase in the compressor V1, via line 1 and the correspondingly opened valve 11 , 21 or 31 . At the outlet end of the adsorbers A1 to A3, with the valve 13 , 23 or 33 open, the product gas (mixture) is drawn off via line 2 and, if appropriate, compressed in the compressor 2 . The adsorbers A1 to A3 are evacuated via line 3 and vacuum pumping station V3 if the valve 14 , 24 or 34 is opened accordingly.

For a more detailed explanation of the vacuum pressure swing adsorption method according to the invention, the cycle diagram shown in FIG. 2 is now used. Here, the solid lines within a cycle mean that the corresponding valve is fully open, while an interrupted line stands for a partially open valve.

With valves 11 and 13 open, the raw gas (mixture) is fed to the adsorber A1 via line 1 . The component or components not adhering to the adsorbent are drawn off via line 2 . The valve 23 of the adsor bers A2 is already partially open, so that the adsorber A2 is biased by means of a partial flow of the product gas (mixture) flowing out of the adsorber via line 2 from its outlet end, that is to say in countercurrent. At the beginning of the second cycle, valve 11 is closed so that the supply of the raw gas mixture into adsorber A1 is interrupted. Since the valve 23 is now fully open, a partial flow of the product gas (mixture) continues to flow from the line 2 into the adsorber A2. This leads to a pressure increase in the previously evacuated adsorber A2, while the pressure in the adsorber A1 drops to 650 to 800 mbar, preferably 700 to 750 mbar.

As soon as this desired pressure level in adsorber A1 is reached or set, valve 13 is closed and valve 14 is opened. The adsorber A1 is now evacuated via line 3 and vacuum pumping station V3. After the evacuation cycle in adsorber A1 has ended, valve 14 is closed again and valve 13 is partially opened. Now there is a pressure equalization between the adsorber A3 previously in the adsorption phase, in which the product gas (mixture) flows out via the open valve 33 , and the adsorber A1, in which a partial flow of this product gas (mixture) in the partially open valve 13 it flows.

The cycle diagram shown in FIG. 3 already shows an embodiment of the vacuum pressure swing adsorption method according to the invention. Here, the adsorber A1 first runs through its adsorption phase, analogously to the cycle diagram 1 shown in FIG. 2, with the valves 11 and 13 open. Again, valve 11 is closed at the end of the adsorption cycle, so that the pressure equalization between adsorber A1 and A2, whose valve 23 is now fully open, results in a pressure drop in adsorber A1. During the third cycle, valve 23 of adsorber A2 is closed and valve 33 of adsorber A3 is partially opened. The adsorber A3 is evacuated at this time with the valve 34 open, via line 3 and vacuum pumping station V3. The now flowing through line 33 into the adsorber A3 partial flow of the product gas (mixture) it thus serves as a purge gas for the adsorber A3 in the evacuation phase.

After this purge gas delivery cycle has ended, valves 11 and 13 of adsorber A1 are closed and valve 14 is opened. In cycles 4 and 5 , the adsorber A1 is evauated with the valve 14 open via line 3 and the vacuum pumping station V3. In cycle 6 - the adsorber A1 is still being evacuated - valve 13 is partially opened so that a partial flow of the product gas (mixture) emerging from the adsorber A2 via the open valve 23 can flow into the adsorber A1 as a purge gas.

After the end of the evacuation cycles, valve 14 is closed and product gas (mixture) flows out of line 2 via partially open valve 13 for the purpose of covering into adsorber A1. In the penultimate cycle valve 13 is opened completely, so that there is a further pressure increase in the adsorber A1 by the incoming partial flow of the product gas (mixture). After closing the valve 13 and opening the valve 11 , the adsorber A1 is stretched to adsorption pressure with the raw gas (mixture) flowing in via line 1 .

In practice, the cycle times of the cycles described in cycle diagram 2 ( FIG. 3) are in the order of 15 to 30 s for cycles 1 , 4 and 7 , while the cycle times for cycles 2 , 5 and 8 are in the order of 2 up to 5 s and the cycle times for bars 3 , 6 and 9 are in the order of 2 to 10 s.

The advantages of the vacuum pressure swing adsorption method according to the invention in terms of energy are illustrated by the following table. This compares three different 3-adsorber pressure swing adsorption processes for the production of oxygen. Method A is a standard vacuum pressure change adsorption method in which no pressure equalization is provided and the evacuation start pressure is approximately 1 bar. The method B includes a conventional pressure equalization between the adsorber to be relaxed and the already evacuated, but not yet (pre) strung. The evacuation start pressure is 750 mbar. The method C is a method as it is shown in the timing diagram 2 ( FIG. 3). The evacuation start pressure is also 750 mbar.

The values given in the table apply to a product concentration of 93% Oxygen when using a Roots blower. It is clearly recognizable that with the method C according to the invention the same amount of product with the same energy needs how can be achieved with the standard method A.

In contrast to method A, method C according to the invention performs the low desorption pressure when using a combination of a Roots piston blower and turbopump for energy savings of about 10%, so that with the Method C according to the invention a specific energy requirement of 0.34 kWh / Nm³O₂ can be achieved. Process B also enables conventional printing compensate for the energetically favorable use of the combination of Roots blower and turbopump, but for this process the energy requirement is inherent too high to achieve an improvement over Method A. could.

table

Claims (8)

1. Vacuum pressure swing adsorption process for separating at least one component from a crude gas mixture comprising at least two components, comprising at least the process steps adsorption, vacuum regeneration and pressure build-up, these process steps being cyclically offset in at least two adsorbers connected in parallel, characterized in that

• a) in the final phase of the adsorption cycle of a first adsorber, the supply of the raw gas mixture is interrupted and
• b) at least a part of the product gas (mixture) drawn off from the first adsorber in the adsorption cycle is fed to a second, already biased adsorber for the purpose of further pressure build-up in this second adsorber until a pressure between 650 and 800 in the first adsorber mbar is set, and
• c) the first adsorber is then evacuated.

2. Vacuum pressure swing adsorption process according to claim 1, characterized in that

• a) after supplying part of the product gas (mixture) drawn off from the first adsorber in the adsorption cycle, it into a second, already biased adsorber for the purpose of further pressure build-up, with the supply of the raw gas (mixture) still interrupted, at least in the first adsorber a part of the product gas (mixture) drawn off from the first adsorber, a third adsorber located in an evacuation cycle for the purpose of purging this third adsorber until the pressure in the first adsorber is between 650 and 800 mbar, and
• b) the first adsorber is then evacuated.

3. Vacuum pressure swing adsorption method according to claim 1 or 2, characterized ge indicates that evacuation using a combination of Roots blower and turbopump takes place at the beginning of the evacuation  Roots blower and turbopump are connected in parallel and only after Reaching a pressure of 400 to 800 mbar can be connected in series. 4. Vacuum pressure swing adsorption method according to claim 1 or 2, characterized ge indicates that evacuation using a combination of Roots blower and turbopump takes place while being evacuated Roots blower and turbopump are connected in series. 5. Vacuum pressure swing adsorption method according to one of the previous ones Claims, characterized in that the prestressing of an adsorber by means of the product gas (mixture) it is done. 6. Vacuum pressure swing adsorption method according to one of the previous ones Claims, characterized in that the final pressure during the Evacuation cycle is between 150 and 450 mbar. 7. Vacuum pressure swing adsorption device for performing the method according to one of claims 1 to 6, comprising at least two in parallel mutually arranged adsorbers, at least one vacuum pumping station and Gas supply lines to, from, and between the adsorbers and the vacuum Pumping station, characterized in that the vacuum pumping station is off there is at least one Roots blower and at least one turbopump. 8. Vacuum pressure swing adsorption device according to claim 7, characterized shows that the Roots blower and the turbopump are connected that both a parallel and a serial connection of the Roots piston blower and the turbopump can be realized.