CARBUROS METÁLICOS HYCO PLANT IN TARRAGONA
Process description
Carburos Metálicos is a company that belongs to the Air Products Group. It has a plant in La Pobla de Mafumet, Tarragona, adjacent to Repsol´s largest refinery in Spain, for the continuous production and supply of HYDROGEN to the refinery.
The factory is active 24 hours a day 365 days a year, continuously producing and supplying hydrogen, a vital raw material for the refining of hydrocarbons.
The Problem
Despite being supplied directly from the transport line that goes directly to the Repsol refinery for the supply of the necessary electrical current, it was not free of VOLTAGE DIPS of up to 50% that occurred during the start-up of some powerful motors in the refinery. Moreover, the installations were in an area in which storms occurred in summer that, occasionally, also caused voltage dips.
The hydrogen production process is sustained by very powerful motors that work at medium voltage (6,6 kV), whose regulation systems are sensitive to dips when they drop below 12 – 15% When this happens, the motors stop for safety reasons (hydrogen is highly explosive), which stops the supply of hydrogen to the refinery and causes an emergency stop at Repsol in a domino effect.
The consequences of an unplanned stop are that Carburos Metálicos takes a whole day in returning the hydrogen supply to the refinery, but it takes some 3 days in restarting the entire process, which causes economic losses that are so high that the return on the investment (ROI of the investment in the SET DVR) has been less then two (2) years.
The Solution
For the electrical supply of the Hydrogen Production Plant, there are two feeders, each one with a medium voltage transformer with a power of 2.1 MW /6.6 KV, each one being capable of supplying all the power.
To protect the entire hydrogen generation process, including the motors supplied at medium voltage at 6.6 kV, a 2.4 MW medium-voltage SET DVR was installed which ensures a stable 6.6kV voltage (± 1%), even if the voltage dips drop to 40% of the nominal voltage value.
The medium voltage SET DVR system was designed with protection devices that can be supplied from either of the two feeders in such a way that the flexibility they had previously was not lost. The system continuously supplies practically the entire plant (except minor services and exterior lighting) and principally protects the variable frequency drives of the main medium-voltage motors of the production process.
On 25 March 2013, it will have been in operation for 4 years, and protected the plant from stoppages due to tension dips on numerous occasions.
