DD219952A1 - PROCESS FOR THE PARTIAL CLEANING OF GASES - Google Patents

Abstract

The invention relates to a process for the partial purification of gases, in particular of methane-containing natural gases. Cleaning principle is the adsorption. The aim and object of the invention is to provide a cost-effective, energetically and in terms of apparatus less expensive process for the separation of water vapor, sulfur compounds and ammonia from a gas mixture which still contains methane and carbon dioxide. According to the invention, this is accomplished by retaining in various layers of switchable adsorption apparatus, water vapor, sulfur compounds and ammonia. Layer proportions and composition as well as state data for adsorption and desorption are set out in connection with the type, amount and reuse of the spuelur gas.

Description

Field of application of the invention

The invention relates to the field of adsorptive gas separation, in particular methane-containing natural gases.

Characteristic of the known technical solutions. -

Methods are known for the desulfurization of gas mixtures by means of turf iron ore. This process is still liable as a wear process to the disadvantage that the residual content of sulfur compounds after the partial purification of biogas is still so high that severe corrosion phenomena occur in the downstream facilities of metallic materials.

The prior art includes the so-called gas scrubbing in connection with downstream adsorption. Disadvantages of these methods are the high process pressure required with optimum driving of the physical gas scrubbing (4 to 10 MPa), the relaxation losses caused thereby and the high energy and investment costs for the regeneration of the detergent. .

Object of the invention

It is an object of the invention to provide an economically favorable method for the adsorptive removal of impurities with the exception of carbon dioxide from methane-containing gases-in particular from biogas.

Explanation of the essence of the invention

The object of the invention is to reduce the disadvantages associated with the prior art.

This object is achieved according to the invention by methane-containing natural gas, which in addition to the methane still contains water vapor, sulfur compounds, carbon dioxide and traces of ammonia, with a temperature of about 308K and a.

Pressure of 2 to 4 kPa (Cl) is passed through an adsorber whose Adsorptionsmittelben - seen in the flow direction - from a layer of narrow-pore silica gel for binding the water vapor and from a second layer of zeolitic molecular sieve type Ca A with 58 to 64 mol percent Ca ^{2 +} ions and / or of the type Na X to take up the sulfur compounds and the NM ₃ traces, wherein the proportion of these layers as 1: 5 behaves.

In the adsorbent bed devices for indirect heat transfer are installed, which are used in the subsequent regeneration process to increase the temperature and after completion of the desorption for cooling.

The desorption is carried out in a known manner by means of temperature increase and purging with product gas in countercurrent to the loading flow direction, but according to the invention with a temperature of about 523K and a purge gas of at most three adsorber according to the purge gas pressure. Under these conditions, the flushing process should begin at the latest in the last third of the heating time and continue throughout the entire cooling phase. The proportion of purge gas flow, which is used during the cooling phase, returns to the gas storage.

Embodiments ·

A possible embodiment will be described below.

A pending in a biogas reactor gas at a pressure of 3kPa (Cl), which is water vapor saturated at 308K and essentially still out

60.0 vol. Percent CH ₄ , 0.5 vol. Percent H ₂ S, methyl mercaptan,

39.0 vol. Percent CO ₂ , dimethyl sulfide

200vpmNH ₃

is in an amount of 20 m ³ i. N./h performed by an adsorber of 0.286 m ³ content, which is operated with a second adsorber of the same size in cyclic permutation in the adsorption and desorption phases. First, the raw gas flows through a layer of narrow pore silica gel of the type KE 1, in which it is dried and then a layer of zeolitic molecular sieve of the type Na X, wherein the sulfur compounds and traces of ammonia are separated. The proportion of these layers in the total bed behaves as 1: 5 (1 share for the silica gel).

Shortly before reaching the breakthrough, which is at a loading time of about one hour, the cyclic permutation, whereby the desorption of the previously loaded adsorber begins. About the installed in the adsorbent bed devices, the bed is heated up to about 523 K. At the latest in the last third of the heating product gas is removed after the now in charge adsorber and passed in countercurrent to the loading direction through the bed. This purge gas is discharged together with the impurities from the process. However, the flushing gas fraction, which flows through the adsorber bed during cooling (which takes place with the same devices as the heating), is returned to the biogas storage tank. The total amount of purge gas is at most three times an adsorber volume at purge gas pressure 'are at 0.286m ³ and about 3kPa (Cl) about 0.3m ³ , of which - as described above - a portion is recycled.

-2- 255 249 O

Another embodiment is described for a gas of the same composition, but without organic aliphatic sulfur compounds, for a similar cleaning task. In this case, such a crude gas at 308K and under a pressure of 1 MPa in an amount of 20Om ³ i. N./h passed through an adsorber of 0.43 m ³ content, whose first layer in turn consists of narrow-pored silica gel of the type KE 1, but whose second layer consists of zeolitic molecular sieve of the type Ca A with 58 to 64 mol% Oa ² * - is formed and the proportions of the layers of silica gel and molecular sieve behave as 1: 8. t:;

The regeneration can be done either in two ways.

- By raising the temperature to about 523 K and rinsing the Bettos. ; '

- By lowering the pressure to values between 0.9MPa and ambient pressure (whereby all intermediate pressures are possible) and temperature increase aufca.523K and flushing of the bed. , ,>

With each of these Regenerierungsarten sufficient desorption is effected and for each applies that the flushing is carried out in countercurrent to Beladestromrichtung that product gas is used as the purge gas, that the amount of purge gas is at most twice the adsorber volume at purge gas pressure, that the flushing process at the beginning of last one-third of the heat-up time and continue throughout the entire cooling-down period.

So the amount of purge gas at 1 MPa is approx. 8.6m ³ iN and 0.1 MPa 0.86m ³ iN per cycle, in each case the purge gas from the cooling phase in the biogas storage (raw gas storage) is recycled. Of course, during regeneration by means of pressure reduction, the adsorber must be re-strung before it is re-charged with product gas.

Claims (3)

  ,! ''. ν. '. '' ' Invention claims: 1. A process for the partial purification of gases, in particular for the adsorptive separation of water vapor, sulfur compounds and traces of ammonia from methane-containing natural gases, in alternately operated adsorption, which are filled with different - arranged in separate layers adsorbents, which indirectly cool as a total bed of internals for heat exchange - or are heated and their regeneration by increasing the temperature and purging with product gas in countercurrent to Beladestromrichtungoder by lowering the pressure. associated with temperature increase and also rinsing, characterized in that A raw gas at its pressure of 2 to 4 kPa (Ü) first passes through a layer of narrow-pored silica gel, then a second layer of zeolitic molecular sieve of the Ca A type with 58 to 64 mol% Ca ² 'ions and / or of the Na x type flows through, wherein the proportions of these layers in the above order on the total bed as 1 ^ Behavior - And that the regeneration of the entire bed at a temperature of about 523 K with flushing, the latest in _. last third of the heating is started and stops on the cooling phase is carried out with a purge gas amount that is at most three times an adsorber volume at purge gas pressure and this amount is fed back from the cooling phase the process. 2. The method according to item 1, characterized in that at pressures greater than 0.5 to 2 MPa, the proportions of the layers of the total bed behave as 1: 8. 3. Method according to items 1 and 2, characterized in that the desorption temperature is 510 to 530K.