BAIRD &TATLOCK (LONDON) LTD. 



4771 



4771* BI-Meter CO 2 Recorder, O.K. Patent No. 20/1906. 



Price, complete with all accessories . . . . . . . . . . . . 30 



The importance of controlling the percentage of carbon-dioxide emitted by the chimney of a power plant is now so unh 

 recognised that it is not necessary to dwell on this point at length. The engineers of all the important power stations ai 

 works in the country have installed, or are considering the installation of, instruments to enable them and their firemen to 

 exactly what is taking place in their furnaces. To the uninitiated it seems hardly credible that by properly controlli 

 dampers which admit air into a furnace, and by blocking up all cracks in the flues between the furnaces and the chimney, 

 large saving in the coal bill may be effected. Nevertheless it has been proved that in many cases from 10 to 15 per cent, per 

 can be saved by this means. When perfect combustion is secured there is present in the flue gases about 21 percent, o 

 but in practice it is impossible to obtain this percentage since it is always necessary to admit a slight amount of air in 

 in order to avoid smoking. By correctly controlling the dampers, however, the stoker should obtain 15 to 16 per cent, o 

 in the flue gases, according to tie kind of coal used and other local conditions. In many works (although not in so many i 

 formerly the case), the percentage of CO 2 is as low as 5 and in some cases only 3 per cent. If a works in which the perc< 

 is as low as 5 per cent, is able to increase its percentage to 1 5 per cent, they will obtain an over-all increase in fuel effii 

 of about 20 per cent ; that is to say, they will only burn 800 tons of coal where formerly they had to burn 1000 tons. 



A very little arithmetic will show what a large saving of money this may mean in twelve months. 



Inefficient combustion is generally due to one of two causes, either an insufficiency of air or an excess of air. In th 

 case smoke is produced, and in the second case the furnace temperature is lower than it should be, and the chimney di 

 is also reduced. 



In many large towns, owing to the vigilance of the public health officers, the number of chimneys emitting black 

 is being steadily reduced ; and, in his efforts to avoid being fined, the fireman admits a larger volume of air into the fi 

 than is really necessary. This causes a drop in the working efficiency of the boiler due to the cooling of the furnace a: 

 heating up of the excess amount of air. Thus in boiler plants the inefficiency is generally due to a large excess of air s 

 The most efficient results are obtained when the dampers are so controlled that the chimney is always just on the point ( 

 never actually, smoking. It is however unreasonable to expect a stoker to be able to work continuously at this point 

 he has some instrument to guide him. 



Although air leaking into the flues between the boiler and the chimney does not have the same direct cooling effect 

 furnace as excess of air admitted through the dampers does, yet it is frequently a cause of inefficiency. For, by reduci 

 temperature of the gases in the chimney, it reduces the draught, and therefore not only indirectly reduces the temperat 

 the fire but also prevents the maximum output being obtained from the boiler. In a case with which we have recent!; 

 brought into contact, a careful stopping of all cracks in the flues between the boilers and the chimney raised the percent \ 

 CO, in the chimney by 3j per cent. It is only by having a continuous record that a continuous control can be kept o\ 

 flue and boiler settings, which are so apt to give trouble unexpectedly and to crack in the most un-get-at-able and darkest ; 



The practice of giving a fireman a bonus on the maintenance of a certain temperature is largely growing in the in < 

 steel trade, and we believe that if a bonus is given to a fireman in a power station on the percentage of CO 2 in his chim . 

 shown by a recorder, it will be found one of the best investments that any power station engineer could make. 



In this connection the following extract from a paper by Professor A. H. Gibson, D.Sc., on " Diagnosis Based on the Ai J 

 of Flue Gases," is of interest : 





14- CROSS STREET HATTON GARDEN, E-C 



