CS250398B1 - A method of low temperature carbon monoxide conversion - Google Patents

Abstract

A method for low-temperature conversion of carbon monoxide, contained together with carbon dioxide in a gas mixture in addition to mainly hydrogen and on the order of 10-1 2ppm of sulfur compounds, by water vapor into hydrogen and carbon dioxide on a low-temperature conversion catalyst containing copper Cu as an active component together with zinc oxide ZnO, in which the input gas first enters the upstream low-temperature conversion catalyst, optionally in a mixture with a ZnO sorbent, after which it enters the actual conversion catalyst, the content of which is in a ratio to the upstream layer of 8:1 to 2:1, with the conversion taking place at temperatures of 180 to 220 °C, a volume velocity of 1,000 to 3,500 h-1 of dry gas with a carbon monoxide and carbon dioxide content of up to 10% mol. and the remainder mainly hydrogen and at a steam to gas ratio below 0.35 m3/m3n

Description

The present invention relates to a process for the low temperature conversion of a carbon monoxide gas.

The low-temperature conversion of carbon monoxide-containing gases, low sulfur compounds and in the absence of chlorine compounds, is carried out industrially on catalysts whose active ingredient is Cu. The content of sulfur compounds that are poison for this catalyst can usually be up to 0.5 ppm by volume and the catalyst itself is usually protected by a pre-sorbent based on zinc oxide ZnO. The resistance of Cu-based catalysts is to some extent influenced by the ZnO content of the catalyst itself, which provides some internal protection.

In industrial practice, in the process gas produced by gasification of petroleum residues or coal, in addition to hydrogen sulfide, other sulfur compounds of the type R2S, hydrogen sulphide RSH and carbon disulphide CS2 are present which do not get trapped on the ZnO sorbent at 180 to 220 ° C. , where by increasing the temperature of the conversion reaction they decompose or become trapped at the active centers of copper, deactivating the catalyst. Regeneration of sulfur catalysts deactivated conversion catalysts is either impossible or very difficult and does not guarantee the achievement of operationally satisfactory catalyst activity. It can be seen from the above that the catalyst activity decreases both when the catalyst is protected by a ZnO sorbent layer in the reactor inlet section and when the ZnO packers are upstream of the conversion reactor itself.

Gradual deactivation reduces the volume of catalyst charge involved in the reaction, increases process steam consumption to the required gas saturation required to achieve a sufficient degree of conversion, and decreases process gas throughput. The set of these adverse effects limits the life of the catalyst charge, which has an adverse effect on fixed repair cycles of shutdown of the entire hydrogen and / or synthesis gas production line.

With a sulfur content of 0.2 to 0.5 ppm by volume in the process gas, regenerable Cu-Cr-based catalysts, which are particularly suitable for the conversion of gases containing chlorine compounds, are not suitable in industrial practice, but in which With higher sulfur compounds, deactivation of these catalysts proceeds very quickly, and a regeneration cycle consisting of thermal oxidation of these compounds with a mixture of water vapor and a defined amount of oxygen in the temperature range of 100 to 350 ° C is necessary. disproportionately often.

It has already been proposed to use operationally exloatable non-regenerable copper-based catalysts for the capture of sulfur compounds, and not only the possibility of their use for sulfur-containing compounds has been confirmed, but information on the impact of residual activity of these catalysts on productivity or The system consists of two main parallel reactors for the conversion of carbon monoxide with three upstream pre-reactors for capturing catalytic poisons, two of which are permanently connected to the production line.

Such an arrangement allows for a separate cartridge change in each of the pre-reactors whose cartridge is already deactivated, without limiting production on the process line. The advantages found could not be fully exploited economically for the relatively rapid deactivation of partially deactivated catalysts; furthermore, the repeated use of catalysts places considerable demands on their mechanical strength, which is not always satisfactory in these types.

It has now been found that these disadvantages can be overcome and the operating cycle of the low temperature carbon monoxide steam conversion process can be extended while increasing line performance or reducing the carbon monoxide output content without increasing process steam addition by the method of the invention.

The process for the low temperature conversion of carbon monoxide contained with carbon dioxide in a gas mixture in addition to predominantly hydrogen and of the order of ^10-1 ppm sulfur compounds, water vapor to hydrogen and carbon dioxide on a low temperature conversion catalyst containing Cu as the zinc oxide active component in that the feed gas first enters at least one of the two upstream parallel layers of the low temperature ZnO-containing Cu catalyst or the ZnO-containing Cu catalyst in admixture with the ZnO sorbent in a ratio of 2.5 to 4, preferably 4: 1 whereupon, after cooling, if desired, to the actual conversion catalyst, the content of which is preferably 4: 1 in relation to the upstream catalyst layer 8: 1 to 2: 1, the conversion reaction being carried out at an inlet temperature of 180 to 220 ° C up to 3500 h ^{@ -1 of} dry gas containing at most e 10 mol%. of carbon monoxide CO and carbon dioxide CO2 in sum and the remainder predominantly hydrogen and a vapor to gas ratio of 0,35 m ³ / mn ³ . In addition, the upstream layer can be used to increase the vapor to gas ratio by evaporating the steam condensate and thereby creating more favorable thermodynamic conditions in the main layer of the conversion catalyst.

The advantages of this low-temperature carbon monoxide conversion arrangement are that the higher catalyst charge u250398 makes it possible to increase process gas throughput by 5 to 20% at the same carbon monoxide conversion rate on the upstream catalyst in the form of upstream parallel reactors. Sulfur compounds are removed from the process gas, including those that are not retained on the ZnO sorbent and which have previously deactivated the main conversion reactor charge.

Depending on operating conditions and needs, the pre-reactor catalyst charge can be used either throughout the main reactor charge, or at the last stage of the main charge, when it is necessary or desirable to extend the entire production line, or can be replaced separately after deactivation the need to shut down the production line.

The pre-reactor charge exchange cycle and suitable combination of the charge can be determined and performed operatively depending on the possibly varying content of sulfur compounds. The operating cycle of the main conversion reactor is extended by 10 to 50 ° / o, i.e. up to the time allowed for the prescribed inspection of the reactor pressure vessel.

A further advantage of the process according to the invention is that when heat is removed from the gas between the pre-reactor and the main reactor by reducing the temperature of the gas entering the main reactor, the thermodynamically more advantageous two-stage conversion of carbon monoxide is achieved.

In the two-stage carbon monoxide conversion, the process steam consumption is reduced by 5 to 10% / o, or the carbon monoxide conversion is increased by 0.05 to 0.15 mol%. with the same process steam consumption, which in effect corresponds to 0.15 to 0.45 mol%, an increase in the production of hydrogen that would be consumed for the hydrogenation of carbon monoxide.

The process according to the invention is illustrated by the following examples.

Example 1

On the two low temperature carbon monoxide conversion lines, a process gas of the same composition was treated, with a pre-reactor filled with a ZnO-based sorbent on the first line, and a pre-reactor filled with a NT conversion catalyst with high sulfur compound resistance. No heat was drawn between the pre-reactor and the main reactor.

the original arrangement of the arrangement according to PV

Input gas composition: CO ₃ mol% 2.5 2.5 CO ° / omol. 5.5 5.5 H ₃ mol%. 90.5 90.5 inerts% mol. 1.5 1.5 content content S ppm vol. 0.3 0.3 content merge Cl Reactor charges: neg. neg. Pre-reactors m ³ 5 m ³ sorbent ZnO (type C7 2) 5 m ³ high-resistance NT catalyst (type ICI 52—8) charge of main reactors m ³ 20 m ³ NT catalyst (ICI 52—1) 20 m ³ NT catalyst (ICI 52—1) volume load h ^_1 process throughput 3 000 3 000 gas m _n ³ . h ^_1 60 000 75 000 output content CO mol% water vapor to gas ratio m _n ³ / m _n ³ 0.4 0.4 at the beginning of the cycle 0.25 0.25 at the end of the cycle, the gas temperature at the inlet to the pre-reactors ° C 0.31 0.31 at the beginning of the cycle 195 190 at the end of the cycle, the gas temperature at the inlet to the main. Reactor ° C 215 210 at the beginning of the cycle 195 220 at the end of the cycle Lifetime of cartridges: 215 215 předreaktor 1 year 1.5 year main reactor 2 years 3 years

250393

Example 2

On the two low temperature carbon monoxide conversion lines, a process gas of the same composition was treated with ZnO sorbent on the first line, and on the second line on the NT conversion line with high sulfur compound resistance. Steam condensate was injected to reduce the gas temperature at the inlet to the main conversion reactor.

the original arrangement of the arrangement according to PV

Feed gas composition: CO ₂ mol%.

CO mol%

H ₂ mol%

inerts% mol.

content merge With ppm vol.

content merge Cl ppm vol.

Reactor filling:

pre-reactor main reactor

2.5

5.5 90,5

1.5 0.3 neg.

m ³ sorbent ZnO (type C7.2) m ³ NT cat.

Volume loading h ^-1 3 000

Process gas throughput m _n ³ .h ¹ 60 000

Output content CO mol%. 0.4

Water vapor to gas ratio m _n ³ / m _n ³ at the start of the cycle 0.25 at the end of the cycle 0.31

Pre-reactor inlet gas temperature ° C at the beginning of cycle 195 at the end of cycle 215

2.5

5.5 90,5

1.5 0.3 neg.

m ³ NT catal. (type C 18 HCS) 20 m ³ NT catalog (type C 18 HCS)

400

000 0.25

0.25

0.31

185

210

Increase of steam to gas ratio upstream of main reactor by injection of condensate m _n ³ / _n ³ gas inlet temperature

0.02 main reactor at cycle start ° C 105 at cycle end ° C 215

Lifetime of cartridges:

pre-reactor 1 year main reactor 2 years

Reduction of H ₂ consumption for methanization at lower CO content

190

210

1.5 years

3.5 years

200.10 ³ m _n ³ per year

EXAMPLE 3 The composition of the feed gas is identical to that of Example 2, except that the pre-reactor with a combined charge of Cu containing sulfur compounds that was a catalyst and a ZnO sorbent. 0.4 ppm.

Reactor charge: pre-reactor main reactor volumetric load h ^_1 process gas m _n ³ / h output CO content mol%.

water vapor / gas m ³ / m ³ ratio at the beginning of the cycle at the end of the cycle gas temperature ° C inlet to the pre-reactor at the beginning of the cycle at the end of the cycle gas inlet temperature to the main reactor ° C reduction of H ₂ consumption for methanation at lower CO m ³ content of ZnO sorbent (C7.2) m ³ low temperature conversion cat. (type K3 - 110) m ³ NT catalyst C18 HCS

500

000

0.27

0.25

0.33

185

212

189

210

1.5

3.5 x 10 ^fi (m ^_n? 7 years)

Claims (1)

Method for low temperature conversion of carbon monoxide contained together with carbon dioxide in the gas mixture beside predominantly of hydrogen and of the order of 10 ^"1 ppm of sulfur compounds, water vapor to hydrogen and carbon dioxide at a low temperature shift catalyst containing as active component Cu together with zinc oxide ZnO characterized in that the feed gas first enters at least one of the at least two upstream layers of the ZnO-containing low temperature Cu catalyst or the ZnO-containing Cu catalyst in the mixture with OF THE INVENTION with a ZnO sorbent in a ratio of 2.5 to 4, preferably 4: 1, after which, after cooling, it enters the conversion catalyst itself, the content of which is 8: 1 to 2: 1, preferably 4: 1, relative to the precoat. a conversion reaction takes place at an inlet temperature 180-220 ° C at a space velocity of 1 000 to 3500 h ^_1 dry gas containing not more than 10 mol%. of carbon monoxide CO and carbon dioxide combined, and the remainder predominantly hydrogen and with a vapor to gas ratio below 0.35 m ³ / m _n ³ .