Steam Boilers & Generators

Use of Industrial Steam

Even though steam might be the oldest high-performance heat carrying energy source in the industry, this saturated steam is still today widely used for high temperature process heating. Typically produced on electrical heated or oil/gas-fired steam boilers, or steam generators.

In these heating systems a high temperature level is often a necessity for achieving the required high efficiency and output in the process.

Necessity of Pressurizing Steam

Water and steam are typically used as heat carriers in industrial process heating systems. But since fluid temperatures above 100°C always correspond to a higher pressure in saturated condition, the steam systems and hot water systems with temperature level of for instance 215°C consequently required pressurizing of 20 bar. So, when using steam (or water) these high process temperatures can only be achieved by significant pressurizing of the saturated steam (or water ).

The Advantages of Steam

It is important to emphasize a major advantage using saturated steam – the fact that this dry saturated steam is both extremely efficient to carry heat and to deliver, and to transfer the heat eventually through to a secondary fluid / media / material. Saturated steam has a very high specific heat content (kJ per kg steam) and thereby delivers a large amount of heat by a modest steam flow. Steam at saturating point also very efficiently finds way to all part of colder surfaces (so-called heat surface), and finally it transfers the heat efficiently to the secondary fluid / media / material. So, steam generally means an extremely large heat transfer coefficient in the thermal design.

This indeed makes steam very attractive to use for process heating. On top of this, it is also a well-defined medium from which engineers worldwide have a lot of experience working with.

Different Steam Boiler Designs

When it comes to units for production of steam, there are many types on the market including large power plant boilers and boilers for turbines. Likewise, also a large range of the steam consumers that utilize the steam heating – for instance process air heat exchangers.

In this we will focus only on small and medium-sized steam boilers for process heating. For the types using burners (oil/gas-fired), there are typically two models available – the steam generator and the classic fire-tube steam boiler.

The principle in the fire-tube steam boiler, is that from the surface of a large volume of feed water, steam is evaporated. This boiling process is heated by the wall of the combustion chamber (the radiant part) and by the exhaust gases passing through a bundle of so-called firetubes or smoke-tubes forming the convection part of the boiler.

The principle is basically the same for electric steam boilers – only is the heating of the pool of water made by submerged electric heating element.

In the so-called steam generator boiler the operation is quite different. This type only comes with oil/gas-fired burners, it is never an electrical type (although the steam generator term is wrongly used by many as generally small boilers including electric steam boilers). The feed water and steam are in principle passing through one long tube – designed as a number of winded-up tube coils that are being serially connected.

In this long tube of tube coil assembly, the feed water is heated up to the evaporation temperature in the first part of the tube coil and then evaporated in the second part.

Where the Steam is Used

Saturated steam produced by small and medium-sized boilers is mainly used for process heating  – for instance process air  heat exchangers. But steam is also used for other applications than process heating including disinfection, creating reactions (injection) and others. For these purposes a special line of electric modular steam boilers from AB&CO offering high quality at attractive prices for moderate steam capacities and steam working pressure. Today it is the most sold type in northern Europe.