At the heart of any steam generation system is the boiler/steam drum. Although it comes in many sizes, its primary and peripheral functions are as follows: providing ample surface area for the efficient separation of water and steam; providing storage capacity to meet immediate boiler feed water requirements; and facilitating the introduction of chemicals for treatment purposes, as well as the removal (blowdown) of impurities. Measuring boiler/steam drum level is therefore crucial for the success of the steam generation cycle.
Magnetrol® has recently released a new, updated white paper on level instrumentation for the steam generation and condensate recovery cycle. This blog post, part of a series based on this white paper, explores one of the most essential components of the steam generation cycle and discusses how level instrumentation can increase the efficiency of this process.Boiler Steam Drum
A boiler presents an extremely dynamic environment with respect to level control regardless of the control strategy— single-, two-, or three-element. The common denominator in each of these strategies is the level measurement itself.
Applying a technology that improves on this variable in the equation will most certainly aid in controlling the normal water level (NWL) in the boiler/steam drum, allowing it to better serve its primary function of separating water and steam for improved steam quality.
This becomes more important when fluctuations in demand can have dramatic effects on an instrument’s performance during “shrink” and “swell” conditions resulting from pressure changes in the boiler/steam drum.
In larger-scale steam production, such as that required for commercial power generation, (water tube boilers), disruptions in boiler/steam drum level control can have adverse affects on the natural circulation of the process and a plant’s ability to respond to market demand.
Although corrections can be applied to mitigate the effects, the variables that need to be accounted for in those corrections typically increase the level control’s installation, hardware and calibration complexity, which has the unintended consequence of introducing new avenues for error. Eliminating potential sources of error (including human error) as related to an instrument’s fundamental technology is the first step in optimizing boiler/steam drum level control.
Level technologies historically used on boilers rely on inference or buoyancy to determine the level. This in itself leaves them vulnerable to process dynamics (specific gravity, pressure, temperature, etc.) and can limit their ability to precisely manage the level for improved fuel economy.