The Design, Application, And Operation Of High Efficiency Turboexpanders In Process Plants.

Abstract

Turboexpander thermal efficiency is an important parameter in the process design of hydrogen purification plants. When a process requires low flow and high head, expander thermal efficiency can only be improved by increasing rotational speed. This trend towards higher speeds is often limited by the stability and rotordynamic characteristics of the rotor-bearing system. High rotational speeds necessitate the use of smaller diameter bearings to maintain acceptable surface speeds. Conventional tilt pad bearings cannot achieve the required clearance and preload due to the stackup of manufacturing tolerances inherent in their multi-piece design. A new style of tilting pad bearings which are manufactured using wire EDM technology, offered a solution to the size and stability problem. Herein, the authors present an application of high-speed turboexpanders in a hydrogen purification process. The thermal efficiency of this system is approximately 20 percent better than the equipment it replaced. Some problems of a minor nature were experienced during the commissioning of these units and will be discussed along with the approach and solutions used to solve these problems.