(WO9602614-A1)      The following stages are executed: (a) the 20-65% methane gas is withdrawn and compressed to 5-15 bar; (b) carbon dioxide and water are extracted from the gas; (c) the gas is pre-cooled, to the extent that partial condensation of the methane sets in; and (d) the gas/fluid mix is separated at low temperature into an 85% or higher methane product, and residual gas. In addition to the process described, suitable plant to accomplish it, is also claimed.    USE -   For the enrichment of low grade landfill or mine gas, containing a low methane concentration, with mainly carbon dioxide, and some nitrogen and oxygen.    ADVANTAGE -   The low quality of gas from drainage schemes means a methane content as low as 20%, which is too low for use as a fuel, or even for supplementary firing. Because the methane is sufficiently enriched, in the process described, it becomes perfectly suited for injection into a natural gas supply network. Using the divided column, it is possible to recover methane fractions of differing concentration. Gases can be enriched to over 90% methane. The gas is of sufficient purity to be used directly as a product gas. A further advantage is that the liquefaction of the residual gas is not necessary. Crystallisation of water and carbon dioxide is prevented by their removal. Low boiling nitrogen and oxygen are removed at the head of the column.    (DE4425712-C2)      The following stages are executed: (a) the 20-65% methane gas is withdrawn and compressed to 5-15 bar; (b) carbon dioxide and water are extracted from the gas; (c) the gas is pre-cooled, to the extent that partial condensation of the methane sets in; and (d) the gas/fluid mix is separated at low temperature into an 85% or higher methane product, and residual gas. In addition to the process described, suitable plant to accomplish it, is also claimed.    USE -   For the enrichment of low grade landfill or mine gas, containing a low methane concentration, with mainly carbon dioxide, and some nitrogen and oxygen.    ADVANTAGE -   The low quality of gas from drainage schemes means a methane content as low as 20%, which is too low for use as a fuel, or even for supplementary firing. Because the methane is sufficiently enriched, in the process described, it becomes perfectly suited for injection into a natural gas supply network. Using the divided column, it is possible to recover methane fractions of differing concentration. Gases can be enriched to over 90% methane. The gas is of sufficient purity to be used directly as a product gas. A further advantage is that the liquefaction of the residual gas is not necessary. Crystallisation of water and carbon dioxide is prevented by their removal. Low boiling nitrogen and oxygen are removed at the head of the column.    (EP772665-B1)      The following stages are executed: (a) the 20-65% methane gas is withdrawn and compressed to 5-15 bar; (b) carbon dioxide and water are extracted from the gas; (c) the gas is pre-cooled, to the extent that partial condensation of the methane sets in; and (d) the gas/fluid mix is separated at low temperature into an 85% or higher methane product, and residual gas. In addition to the process described, suitable plant to accomplish it, is also claimed.    USE -   For the enrichment of low grade landfill or mine gas, containing a low methane concentration, with mainly carbon dioxide, and some nitrogen and oxygen.    ADVANTAGE -   The low quality of gas from drainage schemes means a methane content as low as 20%, which is too low for use as a fuel, or even for supplementary firing. Because the methane is sufficiently enriched, in the process described, it becomes perfectly suited for injection into a natural gas supply network. Using the divided column, it is possible to recover methane fractions of differing concentration. Gases can be enriched to over 90% methane. The gas is of sufficient purity to be used directly as a product gas. A further advantage is that the liquefaction of the residual gas is not necessary. Crystallisation of water and carbon dioxide is prevented by their removal. Low boiling nitrogen and oxygen are removed at the head of the column.