In the project TKS CSA Rio de Janeiro, two GT of type GT11N2-LBTU are installed in two separate single-shaft power trains. Each power train (Figure 1) consists of: GT, High Pressure Fuel Gas Compressor (HP-FGC), Low Pressure Fuel Gas Compressor (LP-FGC) and Generator. Each GT is followed by a diverter damper, a by-pass stack and a Heat Recovery Steam Generator (HRSG). The power plant also includes a Steam Turbine (ST), which receives both the steam produced by the two HRSG’s (downstream of the gas turbines) and the steam produced by the coking plant in the steel mill.
The main FGC components consist of:
- Intercooler, located between LP and HP compressors (controlled by DCS)
- Recirculation Cooler, downstream of the BCV (controlled by DCS)
- LP- and HP-FGC anti-surge valves (both controlled by the anti-surge controller supplied by MAN)
- Bypass Control Valve (BCV)
- Variable Stator Blades (VSB), located at the LP-FGC inlet
The main fuel is the Blast Furnace Gas (BFG) produced in the blast furnace of the steel production process in the adjacent steel mill. MAN Turbo gas compressors (LP- and HP-FGC) are used to compress the BFG fuel to a sufficient pressure so it can be injected in the combustor chamber. The BFG pressure is controlled by the GT control system with the BCV and the FGC VSB.
Natural Gas (NG) operation is used for starting purpose and also used for special operation modes, but at low load only. After start-up on NG a fuel change over to BFG can be done.
Mixed Fuel Operation (MFO) allows to substitute a certain amount of the BFG heat input with NG, for a defined the load range. Within these limits, loading and de-loading is possible with stable operation behaviour.
MFO offers a clear benefit for the customer, since it allows to increase the GTs power output in situations were not enought BFG is produced, for example during an outage or forced shutdwon of one blast furnace.
Final implementation on both units has been completed in July 2015.
