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US 4,064,156 AGranted
Methanation of overshifted feed
AssigneeUnion Carbide Corporation
InventorHenry William McRobbie
Life of this patent
Estimating the term…
Abstract
A process for the production of methane from feed gas comprising H.sub.2 and CO wherein prior to methanation of feed gas fractions in a series of at least two primary, fixed bed, adiabatic, catalytic reactors, the ratio of H.sub.2 to CO in the feed gas is over-shifted to greater than about 4 to 1 and then the ratio of H.sub.2 and carbon oxides in the over-shifted feed gas is adjusted by removing a predetermined amount of CO.sub.2 from the feed gas in order to moderate the temperature rise in the first methanation reactor in conjunction with steam. In addition, after the effluent gas from each primary reactor is cooled, by controlling the ratio of adjusted feed gas fraction to cooled effluent gas from the preceding primary reactor, the temperature rise in each succeeding primary reactor is moderated.
Claims21
A process for the production of methane from a feed gas comprised of hydrogen and carbon oxides in a series of at least two primary and at least one secondary wet, fixed bed, adiabatic, catalytic reaction zones each of which is separated by a cooling zone except the last zone wherein the effluent gas from each of the primary reaction zones is passed through a cooling zone and into the succeeding reaction zone, which process comprises:
- a. providing said feed gas, the molar ratio of H.sub.2 to CO in said feed gas being greater than about 4 to 1;
- b. removing a portion of said CO.sub.2 from said feed gas to adjust the ratio of H.sub.2 and carbon oxides therein substantially according to the formula:
- R.sub.3 = x(R.sub.2 -(1/4) (R.sub.0 -3R.sub.1))
- wherein, x = a number between about 0.95 and about 1.07, R.sub.0 = the fraction of hydrogen in said feed gas which is available for methanation of CO and CO.sub.2, R.sub.1 = the molar ratio of CO/H.sub.2 in said feed gas, R.sub.2 = the molar ratio of CO.sub.2 /H.sub.2 in said feed gas, and R.sub.3 = the moles CO.sub.2 removed from said feed gas per moles H.sub.2 in said feed gas;
- c. splitting said feed gas into a plurality of fractions;
- d. introducing a first mixture comprised of steam and a first one of said fractions into said first primary reaction zone at a first inlet temperature above about the minimum initiation temperature of the catalyst therein, the amount of steam in said first mixture being sufficient to prevent both (1) carbon formation on the catalyst in each of said reaction zones and (2) overheating of said catalyst in said first primary reaction zone;
- e. adiabatically reacting said first mixture in said first primary reaction zone to produce an effluent gas the steam, carbon oxides and hydrogen molar content in said first mixture being sufficient to moderate the temperature rise upon methanation from said first inlet temperature to a first outlet temperature below about the maximum operating temperature of said catalyst in said first primary reaction zone;
- f. introducing the effluent gas from said first and each succeeding primary reaction zone into a cooling zone wherein its temperature is regulated from the outlet temperature of the preceding primary reaction zone to a temperature sufficient to raise the inlet temperature of a second mixture and each succeeding mixture fed into the next primary reaction zone above about the minimum initiation temperature of the catalyst in the primary reaction zone to which the mixture is fed, said second mixture and each succeeding mixture comprised of one of said fractions and the cooled effluent gas from the primary reaction zone preceding the one to which the mixture is fed;
- g. forming said second mixture and each of said succeeding mixtures, the molar ratio of each of said fractions to the cooled effluent gas in each of said mixtures being sufficient to moderate the temperature rise upon its methanation from said inlet temperature above about the minimum initiation temperature to an outlet temperature below the maximum operating temperature of the catalyst in the reaction zone to which the mixture is fed;
- h. introducing said second mixture and each of said succeeding mixtures into the primary reaction zone succeeding the one whose effluent gas is employed to form the mixture;
- i. adiabatically reacting said second mixture and each of said succeeding mixtures to produce an effluent gas having said outlet temperature specified in step (g);
- j. introducing the effluent gas from the last of said primary reaction zones and each succeeding secondary wet reaction zone into a cooling zone wherein its temperature is regulated from an outlet temperature below about the maximum operating temperature of the catalyst in the preceding reaction zone to an inlet temperature above about the minimum initiation temperature of the catalyst in the succeeding reaction zone;
- k. adiabatically reacting the cooled effluent gas from step (j) in the succeeding secondary, wet reaction zone to produce a product gas rich in methane having a temperature below about the maximum operating temperature of the catalyst in the last of said secondary, wet reaction zones, the temperature rise in each of said secondary, wet reaction zones moderated by the steam, carbon oxides and hydrogen molar content in the cooled effluent gas from step (j);
- and
- m. condensing a substantial portion of the steam present in said product gas to water which is removed from said product gas.
12 more elements
A process for the production of methane from a feed gas comprised of hydrogen and carbon oxides in a series of at least two primary and at least one secondary wet, fixed bed, adiabatic, catalytic reaction zones each of which is separated by a cooling zone except the last zone wherein the effluent gas from each of the primary reaction zones is passed through a cooling zone and into the succeeding reaction zone, which process comprises:
- a. providing said feed gas, the molar ratio of H.sub.2 to CO in said feed gas being greater than about 4 to 1;
- b. removing a portion of said CO.sub.2 from said feed gas to adjust the ratio of H.sub.2 and carbon oxides therein substantially according to the formula:
- R.sub.3 = x(R.sub.2 - (1/4) (R.sub.0 -3R.sub.1))
- wherein x = a number between about 0.95 and about 1.07, R.sub.0 = the fraction of hydrogen in said feed gas which is available for methanation of CO and CO.sub.2, R.sub.1 = the molar ratio of CO/H.sub.2 in said feed gas, R.sub.2 = the molar ratio of CO.sub.2 /H.sub.2 in said feed gas, and R.sub.3 = the moles CO.sub.2 removed from said feed gas per moles H.sub.2 in said feed gas;
- c. splitting said feed gas into a plurality of fractions;
- d. admixing steam with a first one of said fractions to form a first mixture having a temperature above the dew point of the steam in the mixture, the amount of said steam being sufficient to prevent both (1) carbon formation on the catalyst in each of said reaction zones and (2) overheating of the catalyst in the first primary reaction zone;
- e. preheating said first mixture to a first inlet temperature above about the minimum initiation temperature of the catalyst in the first primary reaction zone;
- f. adiabatically reacting said first mixture in said first primary reaction zone to produce an effluent gas, the steam, carbon oxides and hydrogen molar content in said first mixture being sufficient to moderate the temperature rise upon methanation from said first inlet temperature to a first output temperature below about the maximum operating temperature of said catalyst in said first primary reaction zone;
- g. introducing the effluent gas from said first and each succeeding primary reaction zone into a cooling zone wherein its temperature is regulated from the outlet temperature of the preceding primary reaction zone to a temperature sufficient to raise the inlet temperature of a second mixture and each succeeding mixture fed into the next primary reaction zone above about the minimum initiation temperature of the catalyst in the primary reaction zone to which the mixture is fed, said second mixture and each succeeding mixture comprised of one of said fractions and the cooled effluent gas from the primary reaction zone preceding the one to which the mixture is fed;
- h. forming said second mixture and each of said succeeding mixtures, the molar ratio of each of said fractions to the cooled effluent gas in each of said mixtures being sufficient to moderate the temperature rise upon its methanation from said inlet temperature above about the minimum initiation temperature to an outlet temperature below the maximum operating temperature of the catalyst in the reaction zone to which the mixture is fed;
- i. introducing said second mixture and each of said succeeding mixtures into the primary reaction zone succeeding the one whose effluent gas is employed to form the mixture;
- j. adiabatically reacting said second mixture and each of said succeeding mixtures to produce an effluent gas having said outlet temperature specified in step (g);
- k. introducing the effluent gas from the last of said primary reaction zones and each succeeding secondary wet reaction zone into a cooling zone wherein its temperature is regulated from an outlet temperature below about the maximum operating temperature of the catalyst in the preceding reaction zone to an inlet temperature above about the minimum initiation temperature of the catalyst in the succeeding reaction zone;
- m. adiabatically reacting the cooled effluent gas from step (j) in the succeeding secondary, wet reaction zone to produce a product gas rich in methane having a temperature below about the maximum operating tempera- of the catalyst in the last of said secondary, wet reaction zones the temperature rise in each of said secondary, wet reaction zones moderated by the steam, carbon oxides and hydrogen molar content in the cooled effluent gas from step (j);
- and
- n. condensing a substantial portion of the steam present in said product gas to water which is removed from said product gas.
13 more elements
Dependencies are inferred from the claim text.