Process for producing synthesis gas
Process for the production of synthesis gas by catalytic steam reforming of a hydrocarbon containing feedstock in parallel in an autothermal steam reformer and heat exchange reformer, the heat for the steam reforming reactions in the heat exchange reformer being provided by indirect heat exchange with the combined effluent of the heat exchange reformer and a portion of the autothermal steam reformer.
1. Process for the production of synthesis gas by catalytic steam reforming of hydrocarbon feedstock by parallel arrangement of heat exchange reforming (HER) and autothermal reforming (ATR) comprising:
passing a first hydrocarbon feedstock through an autothermal reforming stage and withdrawing an effluent gas of raw synthesis gas;
dividing the raw synthesis gas into at least a first and second portion of raw synthesis gas, wherein the ratio of the volumetric flow rate of the second portion of the raw synthesis gas to the volumetric flow rate of the effluent gas of raw synthesis gas is 50-95%;
passing a second hydrocarbon feedstock through the catalyst side of a heat exchange reforming stage and withdrawing a primary reformed synthesis gas;
combining a portion or all of the primary reformed gas with the first portion of raw synthesis gas to form a synthesis gas,
passing the synthesis gas through the non-catalyst side of the heat exchange reforming stage to provide heat for the steam reforming reactions in said catalyst side by indirect heat exchange with said synthesis gas; and
withdrawing, from the heat exchange reforming stage, a cooled synthesis gas.
2. Process according to claim 1 further comprising combining all or a portion of said cooled synthesis gas with the second portion of the raw synthesis gas.
3. Process according to claim 1 , wherein said first hydrocarbon feedstock and said second hydrocarbon feedstock are split from a single hydrocarbon feedstock and, prior to split, the single hydrocarbon feedstock is subjected to pre-reforming.
4. Process according to claim 1 , wherein each individual stream in the form of first hydrocarbon feedstock, or second hydrocarbon feedstock, or both, are subjected to pre-reforming prior to passing through the autothermal reforming or heat exchange reforming.
5. Process according to claim 1 , in which tail gas from downstream synthesis of diesel, methanol or gasoline, is combined with the first or second hydrocarbon feedstock.
6. Process according to claim 1 , in which the steam-to-carbon molar ratio of the first hydrocarbon feedstock is lower than the steam-to-carbon molar ratio of the second hydrocarbon feedstock.
7. Process according to claim 6 in which the steam-to-carbon molar ratio of the first hydrocarbon feedstock is less than 1.20.
8. Process according to claim 1 , in which the volumetric flow rate of the second hydrocarbon feedstock is 1-30% of the volumetric flow rate of the first and second hydrocarbon feedstock combined.
9. Process according to claim 1 , in which carbon dioxide is removed completely or partly from the second portion of raw synthesis gas, the cooled synthesis gas, or from the synthesis gas resulting from combining said second portion of raw synthesis gas and said cooled synthesis gas.
10. Process according to claim 1 , in which catalytic partial oxidation (CPO) is used instead of autothermal reforming (ATR).
11. Process according to claim 1 , in which the ratio between the volumetric flow rate of the second portion of the raw synthesis gas stream to the volumetric flow rate of the effluent gas of raw synthesis gas is 20-49%.