The Application Of Screw Compressors For Processes In The Chemical And Petrochemical Industries

Abstract

The name of the event that has kept us all in suspense for three days is "Turbomachinery Symposium." We have been fed a wealth of interesting information on turbines and turbo compressors-mostly radial machines but also axial compressors. The machines referred to were, without exception, flow machines which transform kinetic energy into potential energy (or vice versa), machines that is to say that work dynamically. I have been asked to give you an account of the uses screw compressors are put to in the processes met with in the chemical and petrochemical industries. Screw compressors are not turbo machines: they do not compress dynamically but by positive displacement, exactly like the piston compressor. Nevertheless it would appear reasonable to discuss screw compressors like these within the context of a symposium otherwise devoted exclusively to the subject of turbo machines. Of all known rotary piston machines the screw compressor surely represents the best attempt at uniting the advantages of a turbo and a piston machine while at the same time eliminating their disadvantages. The speeds, for example, with which the rotors do their oil-free compression work are in the range otherwise reserved for turbo machines. This is perhaps why even today-almost 20 years after the screw machine made its way on to the compressor market-we still occasionally come across users with the notion that the screw compressor is similar in its characteristics to the flow machine. To avoid misunderstandings of this sort and to explain as clearly as I can the workings of the screw machine as a process gas compressor, I shall, with your permission, briefly deal with the peculiarities of this machine's modus operandi-even at the risk of covering familiar ground once again.