Controlling operation of steam reformer, comprises producing synthesis gas having e.g. hydrogen from hydrocarbon-containing input, and guiding nitrogen steam as cool stream through the reformer in first and second temperature regions

摘要

The method for controlling the operation of steam reformer (14), comprises producing a synthesis gas comprising carbon monoxide and hydrogen from a hydrocarbon-containing input and water vapor, and guiding nitrogen stream as cool stream through the steam reformer in a first temperature region below the first predetermined temperature, where the specific heat capacity of the cool stream is kept above the predetermined temperature limit value, which is a first constant value during the cold start of the steam reformer. The method for controlling the operation of steam reformer (14), comprises producing a synthesis gas comprising carbon monoxide and hydrogen from a hydrocarbon-containing input and water vapor, guiding nitrogen stream as cool stream through the steam reformer in a first temperature region below the first predetermined temperature, where the specific heat capacity of the cool stream is kept above the predetermined temperature limit value, which is a first constant value during the cold start of the steam reformer, and guiding nitrogen and/or water vapor containing cool stream through the steam reformer in a second temperature region between the first predetermined temperature and second predetermined temperature, which is higher than the first predetermined temperature, where the specific heat capacity of the cool stream is maintained above the predetermined temperature limit value, which is a second constant value during the cold start of the steam reformer. The temperature limit of the specific heat capacity of the cool stream increases linearly with the temperature at specific value in the first temperature region. The first predetermined temperature is 550[deg] C and the second predetermined temperature is 750[deg] C. The first value of the specific heat capacity of the cool stream is 40 kJ/hour[deg] C. The flow-rate of the nitrogen in each reformer tube of the steam reformer is maintained at 30 Nm 3/hour in the first temperature region. The second value of the specific heat capacity of the cool stream is 200 kJ/hour[deg] C. The flow-rate of water vapor stream in each reformer tube of the steam reformer is maintained at 95 kg/hour in a third temperature region. The nitrogen of the process stream is withdrawn downstream of the steam reformer and again led back to the upstream of the steam reformer over a compressor (46). The cool stream in the first temperature region comprises nitrogen and the cool stream in the third temperature region comprises water vapor.