The 54 MW Cogeneration Plant in Rheinberg
In November 1996 a Cogeneration Plant was commissioned at SOLVAY ALKALI GmbH in Rheinberg / Germany. MAN Turbomaschinen AG GHH BORSIG (MAN TURBO) in Oberhausen, Germany, supplied Europe’s first FT8 TwinPac gas turbine installation with 54 MW power rating. The overall plant concept was jointly developed by SOLVAY and MAN TURBO.
Anideal CHP application The gas turbine unit is provided with down-stream waste-heat recovery steam generators which replace a coal-fired boiler giving 100 t/h steam production which had been in service since 1961 and whose operating permit had expired after approx. 260,000 service hours. Shutdown of the original coal-fired boiler has reduced the output of electrical energy from the existingbackpressure steam turbines by approx. 14 MW.
The FT8 TwinPac has increased the power generation capacity by 40 MW while maintaining the same process steam production rate, hence achieving an excellent plant utilization factor.
Products from the SOLVAY Rheinberg plant include the salt-based chemicals soda ash, chlorine and PVC. Energy costs for the production of these feedstock materials are veryhigh, with a demand for both electrical energy and process steam.
Integration of gas turbine package into existing power station
The two waste-heat recovery boilers feed a total of 84 t/h of 12 bar steam to the process and to a MAN TURBO extraction condensing steam turbine. In addition, some 200 t/h of feedwater are preheated from 105 °C to 170 °C. A basic prerequisite for the project wasthat both operating costs and capital outlay should be optimized on the basis of the technical input requirements. Obviously aeroderivative gas turbines were the best choice for this application of a combined heat and power generation process. These gas turbines have the highest electric efficiency in the power range 25 to 50 MW with exhaust temperatures around 450 °C. Therefore they areparticularly suited for cogeneration processes requiring hot water or process steam with temperatures of less than 400 °C. The selected site provided an excellent infrastructure for a low-cost installation, i.e. a natural gas long-distance pipeline with a pressure of approx. 45 bar, a transformer station, and the necessary process-steam piping were already located in the immediate vicinity of the gasturbine facility. In a purpose-built pressure reduction station, the fuel gas pressure is reduced to 32 bar. The existing water treatment plant is of a sufficient capacity to provide fully demineralized water (approx. 5 m³ per hour) needed by the gas turbines to reduce their NOx emissions. As cooling water is not available on site, the lube oil systems of the gas turbines and generator are ofair-cooled type, and the generator itself is also provided with open circuit direct air cooling.
Live steam pressure 12 Live steam temperature 260 Live steam mass flow 70 Extraction pressure 1.8 Outlet pressure 0.07 Turbine speed 5,400 Power at terminals 12,280
1 MAN TURBO steam turbine
bar °C t/h bar bar rpm kW
Flow diagram of the power station
The core element ofthe plant is the FT8-30 TwinPac gas turbine unit. In this facility, two FT8 aeroderivative gas turbines, each rated for an electric power output of 27 MW, are directly connected to a centrally located synchronous generator. This particular FT8 arrangement was chosen for the first time in Europe.
The FT8 gas turbine consists of a gas generator and a free-running power turbine. The gas generatorhas been derived from the latest version of the most successfull aeroengine in commercial service, the JT8D-219 of Pratt & Whitney. For power generation with grid frequencies of 50 Hz or 60 Hz, 4-stage power turbine designs are available with design speeds of 3,000 or 3,600 rpm for CW and CCW rotation. This makes the FT8 the only gas turbine in this power range which is suitable for coupling to...