2.3.1. Steam boiler
The horizontal return tubular boiler is one of the most commonly used steam generation boilers in the world. The
heating in this type of boiler takes place inside the flame tube and flue gas pipes. Within the flame tube and the
subsequent flue gas pipes, flue gases formed during combustion are led through a series of changes in direction
within reversing chambers along the cylindrical axis of the outer shell.
Conventional systems for steam generation feed supply water to the boiler via thermal water treatment and a
pumping station (Figure 2b). The heating and vaporization of the feed water takes place in the outer shell of the shell
boiler. The approach of this research is to use a shell boiler for its traditional purpose of steam generation, in
addition to replacing the steam drum of the solar collector and acting as a volume reservoir for the feed water supply
to the collector. Thus, thermal water treatment for the entire system will be centralized. Operating such a hybrid
system requires a complex control system.
The complex control system is a technical challenge. It must control the boiler water level with no detectable
measure of the precise collector output quality. Furthermore, the boiler firing activation controls are pressure
dependent. The individual operating conditions of both steam producers will play a crucial role in the proposed
commercial use. The primary criteria for commercial acceptance from the consumer are fluctuations in steam
demand, security and quality of steam, of course the cost relative to conventional systems.
Currently, the different operating conditions of the two systems – the boiler and the Fresnel collector – are being
determined and evaluated. An initial understanding of the reactions of the two steam generators with different
operating conditions is currently underway.