CS221061B1 - Method of refining raw hydrogen - Google Patents

Abstract

The invention relates to the purification of raw hydrogen obtained by low-temperature conversion with subsequent scrubbing of carbon dioxide by methanation to a content of up to 10 ppm in the presence of a ruthenium catalyst. Methanation takes place at temperatures of 160 to 300 °C and is less energy-intensive than previous methods.

Description

The invention relates to a process for purifying crude hydrogen to a residual carbon dioxide content below 10 ppm by volume of carbon oxides by methanization.

The crude hydrogen, obtained after the high and low temperature conversions and the scrubbing of carbon dioxide, is refined by methanization to remove any carbon oxides and possibly contained oxygen.

To date, a catalyst in which the active ingredient is nickel is generally used as the methanization catalyst. Sufficient reaction rates for the methanization nickel catalyst are in the temperature range of 270 to 600 ° C, preferably in the range of 290 to 380 ° C. When polishing a raw hydrogen containing 0.1 to 0.5% carbon dioxide and 0.2 to 1% carbon monoxide is usually operated at a space velocity ranging from 2000 to 7000 m ³ of crude _N atom per 1 m ³ of catalyst per hour metanizačního. The residual carbon dioxide content is lowered to below 10 ppm by volume; at the same time, any oxygen present is removed. Reaction heat is used in part on the installed equipment to preheat the incoming raw hydrogen, and in part, due to the high temperature of 300 to 380 ° C, escapes into the environment, although the device is thermally insulated. Only a small proportion of the heat is removed in the final after-coolers of purified technical hydrogen.

The raw hydrogen after preheating in the exchanger must be preheated in the installed electric heater. Before commissioning the methanization unit, the filled nickel catalyst must be reduced and this requires additional electrical energy for 12 to 24 hours before the methanization unit is commissioned. A disadvantage of the nickel catalyst is also that at lower temperatures, for example at 100 to 160 ° C, toxic tetracarbonyl of nickel is formed and nickel escapes from the catalyst.

Metanization

Quantity of raw hydrogen m _n ³ / h volume composition of input gas (%)

CO2

WHAT

H2 inerty

Volume velocity m _n ³ / m ³ . h

Inlet temperature (° C)

Outlet temperature (° C)

Residual content in purified hydrogen (ppm by volume)

CO2

WHAT

Electricity supply per 1000 m _n ^{3 of} input gas JkWh)

Cooling water consumption in final cooler m ³ per 1000 m _n ^{3 of} output gas

The aforementioned drawbacks have no method of purifying crude hydrogen to a residual carbon dioxide content of up to 10 ppm by volume of carbon oxides by methanization in the presence of a ruthenium catalyst according to the invention, characterized in that the methanization takes place in the inlet temperature range of 160 to 200 C and an outlet temperature of 300 ° C at a space velocity of 5000 20 000 ³ _Mn crude hydrogen per 1 m ³ of catalyst per hour metanizačního.

An advantage of the method according to the invention is that in the operation of this method, the electricity demand in the installed methanization plant can be significantly reduced and the installed electric preheater almost completely taken out of operation. Heat losses to the environment are substantially reduced. With the same amount of raw hydrogen purified, fewer catalysts can be stored in existing methanization reactors or the installed equipment capacity can be increased.

The capacity of the installed equipment will be increased by 30 ° / o while maintaining the existing operating conditions, including the flow rate of purified hydrogen. If the pipe is replaced by a pipe with a larger diameter, the capacity increases by up to 100%.

When the ruthenium-based methanization catalyst is applied, the start-up time is reduced by 12 to 2.4 hours.

Example 1

In an existing methanization reactor, in which 9 m ^{3 of} nickel catalyst were charged, 5 m ^{3 of} ruthenium catalyst were charged. The installed electric preheater had a power input of 455 kW. The course of methanization with the ruthenium catalyst compared to the nickel catalyst was as follows:

Nickel catalyst Ruthenium catalyst

51 200 51 200 0.3 0.3 0.4 0.4 97.65 97.65 1.35 1.35 5688 10 240 295 190 341 237 2 under 1 1 under 1 5.86 - 2.34 1.66

2 1 5

Upon increase of amount of hydrogen to the raw inlet 62000 m ³ _N / residual content of carbon dioxide unchanged. This increase can be used operationally when there is an excess of raw hydrogen, or consumption for other purposes is reduced.

When using a nickel catalyst, it is necessary to maintain the gas throughput of the catalyst, which means that in similar cases the actual production of hydrogen and synthesis gases must be reduced.

Example 2

Into the installed methanization reactor, in which 9 m ^{3 of} nickel catalyst was charged and methanized to a maximum of 53,000 m _n ^{3 of} raw hydrogen per hour, 61 no 9 m _n ^{3 of} ruthenium methanization catalyst was charged and the heat exchange system was adjusted for changed hydraulic conditions at higher throughput , the pipe was also replaced with a larger diameter.

Input crude hydrogen had a similar composition as in Example 1. The amount metanizovaného gas was gradually increased up to 110,000 m ⁵ _N / h and without the right to supply electric power for heating. The reaction conditions were as follows:

inlet temperature 200 ° C outlet temperature 247 ° C flow rate m _n ³ / m ³ . h 12 222 CO2 content (ppm vol) 2 CO content (ppm vol) 1 in the exhaust gas

Claims (1)

SUBJECT Process for refining crude hydrogen to a residual carbon dioxide content of up to 10 ppm by volume of carbon oxides by methanization in the presence of a ruthenium catalyst, characterized in that the methanization takes place between inlet temperature of 160 to 200 ° C and outlet temperature of up to 300 ° C at volume per 1 m ^{5 of} methanization catalyst per hour.