SU367049A1 - - Google Patents

Description

METHOD OF GAS PRODUCTION FOR AMMIAK SYNTHESIS

I

This invention relates to the production of a gas for the synthesis of ammonia and methanol.

A method of producing gas for the synthesis of ammonia and methanol is known, which means that the original natural gas is purified from sulfur, shifted with oxidizers (water vapor, carbon dioxide, air, oxygen), the mixture is heated to and sent for conversion. in the presence of a nickel catalyst.

However, heating up to 290 ° C in tubular reactors, the upper part of the pipe is used unproductively: the relatively low temperature and high volume rates in this part of the reactor cause a low degree of hydrocarbon response. The upper portion of the tubular reactor is essentially used as an imperfect heat exchanger. Under these conditions, nickel catalysts also work unstablely — deactivation with water nars and sulfur compounds takes place. All this reduces the intensity of the process.

In addition, in the case of lary-oxygen or vapor-oxygen-air reforming in shaft reactors, low heating temperatures of the initial components, primarily a mixture of natural gas and VOD, are increased by increasing oxygen consumption, to STRONG} spreading the METANOL exo-zone

thermal reactions and deactivation of the upper catalyst layers of water by the current of steam, sulfur compounds, oxygen. As a result, an exothermic reaction zone, called the hot zone, starts to be buried in the catalyst bed, and this is accompanied by an increase in the residual methane content in the converted gas. With an increase in .m tem.nerury heating a mixture of water lars

and natural gas, pyrolysis of methane homologs contained in natural gas occurs. So, prn heated under pressure of 20-30 atm of natural gas of composition 92-94% СН, 3-4%% СНБ, 1% ССНз, 0.6%

C.iHio, 0.9-1.2 vol% CO-2, 1-1.5 vol% NaB mixture with 3-4 volumes of water vapor Iri tem. Temperature 580-620 C and 680-720 ° C are formed respectively 0.5-0.6 n 1.9-2.1 vol% olefins. This complicates the subsequent implementation of the processes of steam and vapor-oxygen conversion due to the formation and deposition on catalysts, as well as in heat exchangers of a large number of carboids (soot, coke).

They propose to predispose natural gas to purification of methane from the homologues and to heat the gas from the natural gas and oxidizer until 650-750 ° C.

Pizhe shows the composition of the pelvis after it is cleared by homologues of methane.

SY.,

Ib 3.6

Omer experience 1-2 96.4 99.7 0.3 3-4 99.8 0.2 5

In experiments 1 and 2, purification was carried out with a small excess of hydrogen compared to stoichiometry. This determined the presence of a certain amount of hydrogen in the purge gas. In experiments 3, 4, o purified natural gas from homologs of methane is subjected to an additional purification from hydrogen with copper oxide. As a result of purification, technically pure methane is obtained. The latter is mixed with water vapor in a gasket NZO / gas with a rape of 4/1 and sent to be heated to a temperature of 680-720 ° C.

The results of experiments on the heating of gas-vapor mixtures at 680-720C and a pressure of 20 aga are given in the table.

As can be seen from the table, when the vapor-gas mixture is heated under the above conditions, olefins are not formed. No soot deposits were found in the heating apparatus either. As a result of purification of methane homologs, most of the hydrogen remaining after the desulfurization stage is consumed, and the purified gas is a technically pure methane with a small (2–3 vol.%) Impurity of hydrogen. The resulting gas is mixed with steam, heated to 650-750 ° C and sent for conversion by known methods. The presence of a small amount of hydrogen in the initial gas-gas mixture contributes to the suppression of thermal expansion of methane by the reaction of Crl4 C + - | -2H2 in the presence of local overheating of the heat-exchange surfaces. Hydrogen allows the upper layers of nickel catalysts to be maintained in the active (re-entrained; state) state.

Example 1. For natural gas containing 95% CH4; 3-4 06% C2Hb; 0.8-1.0 ab% SzNv; 0.2-0.3% by volume C4Hio; 0.8-1.0% by volume N2. and 0.05-0.1% by volume of CO2, hydrogen is added (at the rate of 0.057 M of hydrogen per 1 m of the natural pelvis). The resulting mixture is compressed to a pressure of 30 aha and sent to sulfur removal.

The desulfurization is carried out in two stages. At the first stage, at a temperature of 350 ° C and a space velocity of 2000 hours, organic matter (sickle) is hydrated by a cobalt-molybdenum catalyst. to HoS, which is then absorbed by a chemisorbent based on zinc oxides of copper in the second stage of desulfurization. The second stage of desulfurization is carried out at a temperature C and a space velocity of 1000. Sulfur-free gas containing not more than 0, 3 mg of sulfur in 1 nm is then directed

for the purification of methane homologs by the method of catalytic destructive hydrogenation with a special nickel catalyst, at a temperature of 300-350 ° C and a space velocity of 1000 hours.

At this stage, gas containing practically pure methane with the addition of 2-3% hydrogen is mixed with water heated to 400 ° C.

steam to a steam / gas ratio of 3.9 / 4.0. The resulting gas-vapor mixture is heated to a temperature of 700 ° C by utilizing the heat of flue gases generated in the furnace chamber of the tube furnace and sent to the tube reactor to perform an incomplete steam reforming. At a temperature at the outlet of the tubular reactor 800 C, the maximum wall temperature is 900-910 ° C, the space velocity is 1000-1100 hours. Get converted gas containing (in terms of dry steam), about. %:

10-10.5 9-9.5 70-70.5 8.5-9.5

Example 2. Natural gas of the same composition, purified from sulfur and from methane homologues of Example 1, after reducing the pressure to 1.5-2.0 MPa, is mixed with water vapor to a vapor / gas ratio of one, heated to a temperature of 670 ° C due to the utilization of heat from the converted gas and sent to a shaft converter, where oxygen-air mixture is also supplied (at the rate of 1.10-1.15 m of air and 0.32-0.33 nm of oxygen per 1 nm of natural gas) . In the shaft Converter on the nickel catalyst is a vapor-oxygen-1 air conversion L1stan.

At the same time, the temperature under the catalyst lattice is set at 850-870 ° C. The gas leaving the converter has the following composition (in terms of dry), about. %:

5-6

14-15

42-43

18-19

0.3-0.5

Subject invention

A method of producing gas for the synthesis of ammonia and methanol by desulfurizing natural gas with subsequent mixing with an oxidizing agent, heating the resulting mixture and catalytic conversion, characterized in that, in order to increase the catalyst activity and increase the process intensity, the sulfur-free gas is subjected to preliminary purification of methane homologues and heat lead to a temperature of 650-750 ° C.