DE3433058A1 - METHOD AND DEVICE FOR PRODUCING NITROGEN - Google Patents

Abstract

A process for adsorptive separation of gas mixtures which in addition to nitrogen contain at least oxygen, by the cyclic charging and discharging of carbon-containing molecular sifted coke, in which the pressurized gas mixture is fed to an adsorber and in which the procedure is as follows: a) production of a pressure balance between the previously-decompressed adsorber and another pressure vessel; b) constant build-up of pressure in the adsorber to a final pressure by passing the pre-compressed gas mixture through it (production stage) and c) desorption of the adsorbed gas components by decompressing the adsorber. The product gas production takes place in only one adsorber. The product gas is then fed to a product gas store. The pressure balancing in the adsorber is effected with product gas from the product gas storage. The subsequent pressure build-up in the adsorber takes place in two stages, namely a first relatively rapid pressure-build-up stage to an intermediate pressure and a second relatively slow stage in which the pressure builds up to its final value.

Description

The invention relates to a method for adsorptive separation

of gas mixtures containing at least oxygen in addition to nitrogen by cyclic loading and unloading of carbonaceous Mblekularsiebkokse, whereby the pressurized gas mixture is applied to an adsorber and the procedure comprises the following process steps: a) Establishing a pressure equalization between the previously relaxed adsorber and another pressure vessel; b) constant pressure build-up in the adsorber up to the final pressure by passing the pretensioned gas mixture through (Production step) and c) Desorption of the adsorbed gas components by decompression of the adsorber.

The generic method known from DE-OS 26 52 486 for Generation of nitrogen works with two or more adsorbers, which alternate pressurized and relaxed again.

Such multiple adsorber systems are comparatively large and accordingly expensive to manufacture.

The invention is based on the object of the method of the opening paragraph mentioned genus so that the dimensions of such systems for Process implementation is reduced and the manufacturing costs of such systems are minimized will.

This object is achieved according to the invention in a method of the opening paragraph mentioned genus by the characteristics laid down in the label of the claim solved.

By using the method according to the invention, the production costs of systems for its implementation are significantly reduced, since the investment for a single adsorber system is much lower than for a multiple adsorber system.

The invention is explained below with reference to the drawing and the examples explained in more detail.

The drawing shows in FIG. 1 a process scheme of the invention Single adsorber system.

In Figure 2 is a diagram of the valve position in the individual Process steps shown as a function of time.

In FIG. 3, the pressures are dependent on a further diagram applied by the process steps.

As Figure 1 shows, there is the single adsorber pressure swing system according to the invention from an adsorber 9 and a product gas storage 10, which several Lines 11, 12, 13, 14, 15, 16, 17 and 18 as well as valves 1, 2, 3, 4, 5, 6, 7 and 8 are assigned. The air compressed in a compressor, not shown, from which the nitrogen content is to be separated off, passes through line 11 via the throttle valve 3 and the valve 2 into the line 13 and from there into the Adsorber 9. In the adsorber 9, which is filled with carbon molecular sieves, is preferentially adsorbs oxygen. The nitrogen content leaves the adsorber 9 with it a given purity, which is preferably between 97 and 99.9% N2 can. The nitrogen passes via line 14 into line 15 in which the valve 7 and the throttle valve 4 are arranged. From the Line 15 arrives the product via the line 17 into the product gas storage 10. The adsorber 9 is with the product gas storage 10 additionally via the line 16, the valve 8 and the Check valve 5 connected. From the product gas storage 10 he can via the throttle valve 6, which is housed in the line 8, withdrawn and fed to the end user will.

In Figure 2 is a diagram of the valve position in the individual Process steps shown as a function of time. An open valve is indicated by a dash.

When the system is started up, the valves are first operated via line 11 2 and 3 and the line 13 of the adsorber 9 is charged with air and via the line 14, the valve 7, the throttle valve 4 and the lines 15 and 17 in the product gas reservoir 10 a pressure built up. The valves 6, 8 and 1 are closed, while the Valves 4 and 3 are slightly throttled, so that even with the initially reduced The desired nitrogen purity is achieved.

It now follows: Step 1: Pressure equalization between adsorber and nitrogen storage.

By opening the valve 8, the pressure between the adsorber is equalized 9 and product gas storage 10 via lines 17 and 16, non-return valve 5, Valve 8 and line 14 instead. The adsorber is thereby with already produced Product gas preloaded to e.g. 5.5 bar. The preload pressure of the adsorber depends essentially depends on the size ratio of adsorber to product gas storage. The valves 1, 2 and 7 are closed.

Step 2: building up pressure with compressed air.

By opening valve 2 - valve 8 closes again - overflows Line 11 and throttle valve 3 compressed air from the compressor, not shown into the pretensioned adsorber 9 and brings it to an intermediate pressure of e.g.

6 bar.

Step 3: producing nitrogen.

After opening valve 7, product gas leaves the adsorber 9 via line 14 and reaches the product gas reservoir via valve 7, throttle valve 4 and lines 15 and 17 10. The product gas can be collected in the storage unit 10 or from the storage unit 10 via a throttle valve 6 and line 18 are fed to a consumer.

Step 4: Desorption of the adsorber.

After completion of the production step, valves 2 and 7 close, Valve 1 opens and directs the desorption of the adsorber 9 via line 13 and line 12 outdoors. The oxygen-enriched gas can also be used for other suitable purposes are fed.

After the regeneration time has elapsed, valve 8 opens again and conducts repeat the pressure equalization step for a new cycle.

By repeating the inflow described above, the system will be as long as driven until the pressure equalization level at e.g.

5.5 bar. Then the desired amount of product gas is applied to the throttle valves 3, 4 and 6 adjusted and the production of the product gas takes place according to the described Cycle.

About half of the total cycle time is used, for example 60 seconds, for pressure build-up and adsorption and the other half for desorption, The times for pressure equalization and pressure build-up (steps 1 and 2) are variable (Step 1: z, R. 0.5 - 4 s, Step 2: e.g. 1 - 4.5 s).

In FIG. 3, the pressures are as they are in line 11 (P1), adsorber 9 (P2), product gas storage 10 (P3) and line 18 (P4) were measured, depending on applied by the process steps. The following process conditions are for example given: The adsorber 9 has a volume of 4 1, while the product gas storage 10 has a volume of 36 1. In line 11 (P1) there is air at a medium pressure of approx. 8.2 bar. This pressure remains during the individual process steps constant.

After the desorption, a pressure of 1 bar prevails in the adsorber 9 (P2). During the pressure equalization between adsorber 9 and product gas storage 10 (process step 1) there is a pressure of 5.5 bar when the product gas reservoir 10 has a Has a storage pressure of 6 bar. During the pressure build-up (step 2), line 11, Throttle valve 3, valve 2 and line 13 air passed into the adsorber 9 until a Pressure of 6 bar is reached.

The subsequent production step (step 3) then takes place successively the further pressure build-up with air up to 8 bar. During the desorption (step 4) the adsorber 9 is expanded to 1 bar.

In the product gas storage 10 (P3) results from the pressure equalization with the adsorber 9 (step 1) a pressure drop to 5.5 bar. During the pressure build-up in the adsorber 9, the pressure in the memory 10 remains constant. In the production phase it rises to 6.2 bar. During the desorption step, the pressure in the storage tank is reduced 10 back to 6 bar.

Due to the throttle valve 6, there is a for P4 in line 18 0.1 bar lower pressure than in accumulator 10.

With the single adsorber system, the same production quantities can be achieved with the same Purity (preferably 97 to 99.9%) as with multi-adsorber systems but with the opposite higher compressed air requirements can be achieved. This does result in somewhat higher operating costs, the investment costs are j however lower.

From the exemplary embodiment for the generation of 6 m i.N./h nitrogen with a purity of 98%, a carbon molecular sieve amount of 40 l was required. A carbon molecular sieve according to DF-PS 21 19 served as adsorbent 829 has been manufactured.

3.

The air requirement was 17.5 m / h at a process pressure of 8 bar.

The discharge pressure of the nitrogen was 5.9 bar. Thereby were for the process steps shown in FIG. 2 require the following times: 1. Pressure equalization time: 1 s, 2nd pressure build-up: 2 s, 3rd production time: 57 s and desorption time: 60 s.

Claims (1)

Method and device for generating nitrogen Patent claim Process for the adsorptive separation of at least oxygen containing nitrogen in addition to nitrogen Gas mixing through cyclic loading and unloading of carbonaceous molecular sieve cokes, wherein the pressurized gas mixture is given to an adsorber and the The procedure comprises the following procedural steps: a) Establishing a pressure equalization between the previously relaxed adsorber and another pressure vessel; b) steadily Pressure build-up in the adsorber up to the final pressure by passing the preloaded Gas mixture (production step) and c) Desorption of the adsorbed gas components by relaxing the adsorber, characterized in that the product gas generation takes place in just one adsorber and the product gas is fed to a product gas reservoir the pressure equalization in the adsorber - step a) - with product gas from the product gas storage is carried out and the pressure build-up in the adsorber - step b) - takes place in two stages, namely in a first, relatively fast pressure build-up stage up to an intermediate pressure and in a second, relatively slow pressure build-up stage up to the final pressure.