Abstract: A method of withdrawing landfill gas from a landfill without drawing air into the landfill comprising providing a well in the landfill and withdrawing landfill gas from the well at a plurality of different withdrawal rates. The pressure at a selected region within the landfill is detected while the landfill gas is being withdrawn. A relationship is then established between the withdrawal rate and the pressure at the selected regions. This relationship is utilized to establish a maximum withdrawal rate, and this maximum rate occurs at approximately zero gauge pressure. Landfill gas is then withdrawn from the well at no more than about the maximum withdrawal rate.

Abstract: A process for purifying a fluid stream which includes an impurity and a product fluid comprising providing three adsorption zones, cycling each of the adsorption zones on stream for the adsorption of the impurity from the fluid stream in a predetermined sequence to provide a substantially uninterrupted flow of the product fluid from the adsorption zones, desorbing the impurity from each of the adsorption zones in a predetermined sequence by sequentially reducing the pressure within each of the adsorption zones sufficiently to desorb the impurity, and repressurizing each of the adsorption zones subsequent to the desorption of such adsorption zone to make such adsorption zone ready for subsequent use for on stream adsorption of the impurity. The duration of the period of desorption for each of the adsorption zones is at least as great as about the duration of the period of on stream adsorption of the impurity.