Steam turbines are expensive to maintain and run, as is the permitting process and inspections, none of which applies to electric motors. You need no permits to run electric motors, and they require very little maintenance over a long period of time. They are quiet, efficient, and pose no safety threat as far as explosions, high temperatures, or the dangers of superheated steam.. . Using a steam turbine also will involve a gear reduction where the electric motor torque will be available at very low RPM up to the running RPM of the motor. A 3 phase electric motor is also easy to start, stop, and reverse, all with off-the-shelf reasonably priced magnetic relays with built in current sensing safety devices. . . Operating a turbine requires instrumentation, warm-up periods, balancing, and adjustment/regulation of steam flow rates to it. This is far more complicated then connecting 3 phase AC power to an induction motor. The people operating or being around the turbine must also be trained and certified in the operation of such, whereas electric motors require no training or certification to operate. Wiring is also far cheaper than insulated stainless steel steam lines to the superheater replete with isolation valves and inspections. The longer the distance between the turbine and the boiler will also reduce efficiencies, whereas wiring can be 100' or more with no real loss, provided you can run at increased voltages like 480 or more if the horsepower requires it.. . The other issue is the machine management of the condensate system for the turbine. It must run on ultra-pure water to protect the turbine fins during the life of the turbine. Scale, lime, minerals, or any type of contaminant can destroy a turbine. A turbine can not just be turned off or on at the flick of a switch, which can be a real disadvantage. Also, replacements are rarely available if something goes wrong--repair is the only option and you will experience down time. Electric motors can be ordered, shipped to the company fed-ex, and be in operation in hours. . . The boiler also must be certified, fired, instrumented, and managed. . . If the steam is "free," i.e. generated as a matter of course in the plant and you want to utilize the power for some machinery, a reciprocating steam engine may be more appropriate. It can offer several horsepower that can be governed and more easily controlled, with quiet, full torque at 0RPM.. . I assume you mention petrochemical industry to indicate a surplus of combustible products. A gas turbine may be more appropriate and direct-coupled to a generator rather than bother with a boiler. I wish I knew what you needed the mechanical power for. Hope this helps