Abstract: The present invention provides a method and apparatus for automatically controlling product purity in a pressure swing adsorption process without risking unacceptable impurity breakthrough as the feedstock changes, yet providing rapid response and high stability. The process comprises sensing a characteristic of the effluent from cocurrent depressurization, and taking corrective action responsive thereto. Any action can be taken which is effective to vary the impurity concentration in the product gas in the direction necessary to obtain desired product purity. Among the suitable corrective actions are the following: (1) adjusting the adsorption step time to control the impurity loading of each adsorbent bed; (2) adjusting the cocurrent depressurization termination pressure to control the impurity breakthrough at the product end of each adsorbent bed; and/or (3) adjusting the amount of purging gas received by each adsorbent bed to control the extent of regeneration.

Abstract: Normal paraffins present in high concentrations in light naphtha streams are separated from non-normal paraffins in a four or more bed adsorption system employing, on a cyclic basis, the processing steps of (1) cocurrent purge/adsorption, (2) cocurrent feed/adsorption, (3) countercurrent purge and (4) countercurrent displacement. A processing sequence is employed wherein the cocurrent purge/adsorption and countercurrent purge steps are carried out on a discontinuous basis, while cocurrent feed/adsorption and countercurrent displacement steps are carried out in overlapping sequence.

Abstract: An invention is described in which a portion of one of the product streams from an adsorption system is used to wash a recycle gas stream in order to improve the quality of one of the products.

Abstract: An annunciator to indicate the presence of a truck on a weighing platform to a weigh station operator is disclosed. The apparatus includes a presence sensor operable in response to the weight of the truck on the scales. The sensor provides a signal to a discriminator circuit which, depending upon the length of the signal from the presence sensor, determines whether the truck is merely passing over the scales or has stopped on the scales to be weighed. The discriminator produces an output causing a signaling device to operate and indicate to the operator of the weigh station that a truck is on the scales and is ready to be weighed.