One of the biggest problems with kettles of all sizes is damage done by scale (top picture) and corrosion (lower picture). These pictures show the inside of a locomotive boiler after a period in service. This can eventually stop the boiler from working properly and it could even lead to failure and loss of life. Consequently, boilers have to be inspected and often completely rebuilt - in Britain the period is every seven years. This is one of the things that makes steam locomotive hopelessly uneconomic.
But with the Porta system of water treatment, the inside of the boiler develops a protective coating of oxide and the scale remains in suspension instead of building up as a layer of lime (below). The result, it is claimed, is a reduction in maintenance costs of 90%
One of the claims in the porta document makes no sense: Section 6.2 "However, as any chemist will tell you, it is not the pH of a solution which is the hazard, rather, it is the concentration of ions within a solution. In this case the bulk of ions present in the boiler water are carbonate ions, which are low risk even in large concentrations. If the pH were based on caustic soda, and thus hydroxide ions, it would be a different matter."
ReplyDeleteCarbonate solutions produce high concentrations of hydroxide, the real concentration of hydroxide will be high. (ie the statement is plain wrong) I have no idea about "hydroxide embrittlement" - maybe the description is a simplification.
An other major issue in general with steam locomotives is emissions - kettle fans need to take seriously this topic. Can a standard boiler produce low particulate emission without the use of scrubbers?
Yes, I thought that statement about hydroxide ions sounded odd. It sounds as if the system works in a similar way to the Fernox treatment for domestic central heating installations.
ReplyDelete"Can a standard boiler produce low particulate emission without the use of scrubbers?"
It depends on the fuel. Where light oil or diesel fuel has been used ie simply burnt, tests have shown lower emissions than with internal combustion (and lower consumption as well). These figures do not mention particulates but the NOx emissions are lower. External combustion can be better controlled and takes place at a lower temperature.
DLM website
The gas producer combustion system for solid fuel gives a much improved performance when coal is used as the fuel, compared to conventional combustion. The principle is that primary air is restricted, exhaust steam is blown over the firebed to cause the water gas reaction, and the combustion chamber is provided with tuyeres to introduce secondary air is introduced over the top of the firebed. This, it is claimed, gives more complete combustion, clinker formation is prevented and spark emission is reduced or eliminated.
I have said "it is claimed". I do think these should be properly investigated. If the improvements are even half as good as their advocates suggest, then an efficient and cost-saving technology is going by the board.