CS258512B1 - Method of carbon oxides removal from technical hydrogen by means of methanation - Google Patents

Abstract

The solution concerns technical cleaning of hydrogen generated from the generator gas by converting from carbon oxides by methane on the catalyst, containing nickel oxide on a support, at which the purified gas is shown at catalyst bed, which is filled in the inlet or outlet port through the catalyst with a NiO content of 30 to 55 wt. in the form of surface-grooved cylindrical and the catalyst at the bottom with a NiO content of 15 to 30% in the form of tablets balls, or preferably peat rings, wherein the catalyst volume ratio is inlet to the bottom is 1: 4 to 4: 1.

Description

The invention relates to the removal of carbon oxides from industrial hydrogen, by hydrogenating them to methane by so-called methanation, predominantly on catalysts containing nickel Ni as oxygen in amounts ranging from 15 to 40% by weight, on suitable supports. However, industrial hydrogen also contains trace amounts of various catalytic poisons, such as sulfur compounds S and chlorine Cl, which reduce the activity of all catalysts used hitherto. Iron carbonyls and nickel carbonyls, in the case of non-nickel methanation catalysts, act in a similar manner. The resistance of Ni-catalysts to catalytic poisons increases partly with the content of Ni in the catalyst, but at the same time its cost increases. Usually, therefore, catalysts with a Ni content in the range of 15 to 25% by weight are used, which also determines the maximum volumetric loading of the catalyst, i.e. the power of the reactor. The increased volumetric load can be used practically only shortly after the catalyst has been driven. Under increased volumetric loads, the commonly used shape of particles, which are usually small tablets or spheres, causes a pressure drop sharply increasing with volumetric loads in axial adiabatic layer or tubular reactors.

It has now been confirmed that to eliminate or reduce the effect of the above, while increasing the reactor power, i.e. the volumetric load, it is advantageous to use a combination of nickel catalysts of differently shaped and different Ni contents suitably axially distributed in the reactor. higher volumetric velocities, i.e. higher loads on the reactor charge at the same degree of removal of carbon oxides, which may, in a particular case, eliminate the need for the construction of an additional methanization plant.

According to the invention, a process for removing carbon oxides from technical hydrogen by methanization on catalysts containing nickel oxide as the active ingredient is that the carbon-containing gas enters the catalyst bed in the inlet portion of which, if appropriate,

the nickel catalyst having a NiO content of 30 to 55 wt. in the form of surface grooved cylindrical extrusions and at the bottom thereof a catalyst with a NiO content of 15 to 30% in the form of tablets, spheres or preferably rashig rings, wherein the ratio of catalyst to inlet volume is 1: 4 to 4: 1, preferably 1: 2 to 1: 1. The lower portion of the cartridge may be further subdivided into 2 parts in a ratio of 1: 2 to 2: 1, which are filled at the top with a rashig-ring catalyst having a NiO content of 15 to 30% by weight. and at the bottom a catalyst in the form of surface grooved cylindrical extrusions having a NiO content of 30 to 55 wt. Thus, a nickel catalyst with a content of 25 to 55% NiO, preferably in the form of cylindrical extrusions longitudinally surface grooved, which has a high efficiency of activity and considerable resistance to trace catalytic poisons, is placed in the methanation reactor inlet layer. In the lower part of the combined charge of the methane reactor is charged a Ni catalyst of classical shapes, i.e., tableted or pelleted with a NiO content of 15 to 25% by weight, or a catalyst with similar NiO content, but preferably it results in an increase in the effective activity of the catalyst as well as a reduction in the pressure drop across the bed. The arrangement of the bottom layer charge substantially influences the required reactor load, the desired methanation efficiency, i.e. the degree of removal of carbon oxides from the technical hydrogen, and the optimization of the reactor charge with respect to its cost.

Therefore, under particularly demanding methanation conditions at high volumetric load, in the presence of trace poisons and with increased demands on hydrogen purity after methanation, the lower part of the charge is also divided into two layers composed of one of the last two types of catalyst and , which is preferably filled into the lowest part of the combination charge.

Due to the high effective activity of the packed catalyst located in the first layer, the methanation reaction starts rapidly in the inlet part of the charge and, consequently, due to the released heat of reaction, the temperature in the bed increases rapidly. a catalyst with a lower NiO content. At the same time, the first layer with a high content of NiO is a protective layer for the lower charges due to its high capacity for poisons and allows long-term use of their optimal activity. Reactor filling the above type can be used at virtually any operating pressure determined essentially only pressure and ^- temperature resistance of the reactor shell. While the working temperatures of the reactor packing are determined by the thermal stability of the catalysts used, catalysts active in the temperature range of 200 to 400 ° C, preferably 260 to 350 ° C, are used to achieve maximum reactor load performance. At pressures of about 3 MPa, a volumetric velocity of 3 to 5 500 has been used up to now, while a combined loading of two or more preferably three-layer catalysts, depending on the type of catalyst, achieves a volume loading of 6 to 10,000 h ^-1 , 10 ppmv. and also the pressure drop of the reactor is practically unchanged from the original values or remains within the limits of the permitted reactor grate designs. At the same time, operating cost optimization is also achieved in terms of catalyst charge cost. Advantageously, such cartridges can also be used in a situation of reduced gas offtake for methanol synthesis and, conversely, increased hydrogen demand for ammonia production in cases where both plants are operated in parallel. This also applies to any other possible consumption of pure hydrogen.

Example 1

Parallel operation of two methane reactors with a total volume of 9 m ³ with a conventional charge and a combined charge according to the invention.

Feed gas composition (mol%):

CO ₂ 0.15

CO 0.40 inerts 2.45

S 20 ppbv

97, 97

Catalytic charges:

classical combined ball catalyst diameter of balls 4 to 7 mm NiO content 25% by weight

inlet layer: 3 m cylindrical longitudinally grooved catalyst containing 40 wt. NiO backing: classic

Exploitation conditions: 55 000 3 gas inlet (m / h) 60 000 6 100 vol. velocity (h ^χ ). 6 700 300 gas temperature (° C) 300 338 outlet temperature (° C). 339 8 pressure. loss (kPa) 9 3 lifetime (years) 3 rest. content v (ppmv) 4 co ₂ 2 6 WHAT 1

Example one confirms not only the higher productivity of the combined cartridge, but also its higher activity.

Example 2

Two-layer combined charge of total volume methane reactor

Bottom layer: 4 m ^{3 of} catalyst containing 25% NiO, shape: 5 mm diameter Rashig rings

Upper layer: 5 m ^{3 of} catalyst with 40% NiO, shape: longitudinal grooved rollers

Feed gas composition as in Example 1.

Reactor power: m gas / h inlet 72 000.0 vol. Velocity (h ^-1 ) 8 000 temperature <° C) inlet 300 outlet 340 pressure. loss (kPa) 10 in gas: ppmv CO ₂ 4

CO 2 fill life (estimated ¹ year) 3

Example 3 o

Three-layer combined methane reactor total charge of 9 m.

Upper layer: as in Example 2, catalyst volume 3 m ^{2 3} o

Middle layer: as the lower layer in eg 2, volume 3 m

Bottom layer: same as the top layer, volume 3 m

Input gas composition: as in example 1.

Reactor power: m gas / h inlet 72 000.0 vol. Velocity (h ³ ) 8 000 temperature (° C) inlet 300 outlet 340 pressure. loss (kPa) 11 in gas: ppmv CO ₂ 2

CO 1

From the results given in Examples 2 and 3, said reactor packings will allow a higher volume load in the future if an increase in the carbon oxide content of up to 10 ppmv is permitted. Also the expected service life will be min. 3 years.

Claims (2)

SUBJECT OF THE INVENTION Method for removing carbon oxides from technical hydrogen by methanation on catalysts containing as an active ingredient nickel oxide on a support, characterized in that the carbon-containing gas enters the catalyst bed, in which the nickel catalyst containing NiO 30 to 55 wt. in the form of surface grooved cylindrical extrusions and at the bottom thereof a catalyst with a NiO content of 15 to 30% in the form of tablets, spheres or preferably rashig rings, the ratio of catalyst to inlet to bottom volumes being 1: 4 to 4: 1, preferably 1: 2 to 1: 1. 2. A process according to claim 1, wherein the lower part of the catalyst packing is divided into 2 parts in a ratio of 1: 2 to 2: 1, which are filled at the top with a catalyst in the form of a peat ring with a NiO content of 15 to 30 wt. and a surface-grooved cylindrical catalyst with a NiO content of 30 to 55 wt.