Responsiveness to Load Changes

Generally, load changes from 5 to 100% should be tolerated by a fuel processor [11]. However, this is of course a more crucial issue for drive train applications than for APUs. Micro structured devices offer benefits concerning the load-change behavior of fuel processors owing to the small fluid volumes applied [12, 13]. 

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This fuel is then introduced to the boiler furnace by an air jet, which casts the fuel out over the stoker grate in a thin, even layer.1 The advantage of this type of boiler configuration is that it has a fast response to load changes, has improved combustion control, and can be operated with a variety of fuels.1... 

An integrated heat exchanger-reactor for methanol steam reforming was developed by Hermann et al. [65] at GM/OPEL for a 50 kW methanol fuel processor. The system specifications included a volumetric power density of more than 5 kW dm, a gravimetric power density of more than 2.5 kWkg and a transient response to load changes from 10 to 90% in milliseconds. 

Robbins recommended using a proportional gain of 0.3 UG for minimum variability in the process response. The recommended integral time constant is 1.0 times UTP for good response to load change and 2.0 times UTP for minimum lAE (integral of absolute error) in response to a step change in setpoint. 

This will give an excellent response to load changes. Generally, no derivative action is desired for distillation controllers, because any noise in the signal for the controlled process variable can be translated into controller output and valve movement. Smooth controller output to a control valve is usually desired for distillation. When derivative action is used, the recommended setting is 0.10 to 0.15 times the response time. 

Figure 9.7 Control loop response to load change.

Robbins, L. A., Setpoint tuning method gives excellent response to load changes. Hydrocarbon Proc., September 2002. 

Dynamic simulations for a single couple of microcharmels performed by Petrachi et al. revealed a fast response to load changes of the microchannels due... 

Pulverized-coal-fired boilers are more responsive to load change. 

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