Steam Boilers

Steam Boilers and Steam Raising Plant

Steam production has evolved into a modern fuel efficient system which underpins much of the economic development around the world.

Here in the UK steam is a key component of modern production systems. Steam boilers range in size and complexity from small units powered by gas or electricity producing small quantities of steam for point of use applications to large plant powered by natural gas, oil or a growing trend for safe sustainable biomass fuels which can supply the needs of major production centres.

Steam raising plant is ubiquitous amongst manufacturing, food production and healthcare sectors. Steam use ranges from powering plant in production processes such as corrugating and manufacturing plant, cooking food products within the food and beverage sector to sanitising and disinfection within the healthcare sector. Steam is also widely used in space heating via modern efficient plate heat exchangers. The correct treatment of water feeding steam boilers is an essential component of maintaining efficient safe and compliant energy generation thus minimising the cost and the effects of failure.

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Albion Water Treatment Ltd design and build

To sustain high-purity feedwater and make-up water flow, an optimum boiler water treatment system also includes a pre treatment system Albion Water Treatment Ltd design and build this plant.

Typically this includes filtration, water softening plant or reverse osmosis unit and some form of thermal deaeration either mechanical/chemical or a combination of both.

Throughout much of the UK the use of towns mains water serving as make-up for a steam boiler will create precipitation of limescale and other naturally forming deposits within the boiler and feedwater lines. Over time this may lead to pronounced energy losses and the need for aggressive acid descaling of the boiler internals.

This process can lead to the early attrition of metallurgy within the boiler system and should be avoided.

By softening the water through base exchange and RO plant scaling may be prevented. However bicarbonate within the raw water may pass through the softening plant unaffected.

In a boiler producing steam the bicarbonate splits into carbon dioxide (CO2) and sodium hydroxide (NaOH) creating corrosive condensate and a requirement for water to be purged from the boiler which is termed blow down. The condensate flows via steel pipework back to the hot well or feed make up tank which can create a cycle of corrosion in the plant and its material of construction.

To some extent this problem may be mitigated by removing the salt content of the make-up water via a reverse osmosis plant resulting in a pure mineral or impurity feed high quality make up water.

The use of AWT specialist chemical treat programmes will passivate steam lines and boiler surfaces with a monomolecular layer of treatment which guards against the effect of low pH condensate and subsequently the effects of acid corrosion.

A second problem is that feedwater may be saturated with oxygen. Oxygen is pivotal to corrosion resulting in pitting and metal failure in steam boiler. To remove oxygen mechanical chemical deaeration may be employed. AWT can specify the correct chemical oxygen scavengers to use in a system which will sequester oxygen molecules from the feedwater significantly reducing the potential for corrosion especially within the boiler, feedwater lines and hot well.

Boiler Efficiencies

It is recognised that the chemical treatment of steam boilers is an essential component of the protection necessary to enable them to operate efficiently.

For example, operation of a steam boiler with a passivation process following chemical cleaning, maintenance such as D patch repair or wet lay up ensures that the waterside architecture is adequately protected against secondary corrosion.

Scale deposits in steam boilers can cause serious problems including higher fuel use, increased maintenance and unexpected failure. The high costs associated with boiler scale/deposits highlights the importance of good water treatment to keep waterside surfaces clean.

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Scaled Boilers Require More Fuel

The problems associated with boiler scale largely stem from its insulating properties. In a boiler, fuel (natural gas, oil, wood, etc.) is burned to generate heat energy. From an energy efficiency standpoint, the objective is to transfer as much heat as possible from the hot combustion gases to the boiler water.

Since scale deposits are insulating, they reduce how efficiently heat is transferred through the metal boiler tubes to the water. The reduced heat transfer efficiency in a fouled boiler means more of the heat is lost via the stack instead of being converted into steam. This also means more fuel must be burned to produce the required amount of steam and as a consequence yields more greenhouse gas emissions.

The process of passivation commences with your AWT service chemist selecting the correct Albion water treatment chemical product for your system. This is then carefully metered into the boiler feedwater system at a point selected to maximise effect. Control is carefully chosen via an electronic dosing pump and the chemistry closely monitored by AWT technicians using field analytical test kits.

The passivation process provided by the treatment enables a uniform and dense protective layer to form on the inner surface of the heating side of the boiler. This protects the system against acid, alkali and oxygen corrosion at a normal temperature. Furthermore, the phenomenon of secondary rusting caused by the boiler being laid up for a period following maintenance/acid descaling etc. may be avoided, thus creating a protected environment prior to steaming operation.

Any residual intrusive hardness entering the boiler from the feedwater and make up is dealt with by the Albion transport chemical and removed during the process of blowdown.

Albion Water Treatment Ltd design and commission effective chemical water treatment programmes to match our customers needs.

Frequently Asked Questions