Hydrocarbon recovery in a fischer-tropsch process

Abstract

An integrated process for improved hydrocarbon recovery from a natural gas resource is disclosed. A methane-rich stream, an LPG stream and optionally a C5+ stream are isolated from a natural gas source in a first separation zone and desulfurized. The methane-rich stream is converted to syngas and subjected to hydrocarbon synthesis, for example, Fischer-Tropsch synthesis. The products from the hydrocarbon synthesis typically include a C4− fraction, a C5-C20 fraction, and a C20+ wax fraction. These fractions are isolated in a second separation zone. The C4− fraction is recycled through the first separation zone to provide methane for conversion to synthesis gas and an additional LPG fraction. The C4− fraction can be treated, for example, with hydrotreating or hydroisomerization catalysts and conditions before or after the separation. The C5-C20 fraction and the C20+ wax and heavy fraction are subjected to additional process steps, for example, hydro treatment, hydroisomerization, and/or hydrocracking. The products are sent to a third separation zone, and yield an additional C4− fraction, as well as higher molecular weight products. The additional C4− fraction can also be sent to the first separation zone and treated in an analogous fashion to the C4− fraction from the hydrocarbon synthesis. Any sulfur-containing compounds resulting from the additional processing of the hydrocarbon synthesis products (i.e., hydroconversion reactions) can be treated along with the sulfur-containing compounds in the natural gas, eliminating the need for a second sulfur-treatment plant.