12. CALORIFIC TESTS AND ANALYSES OF COAL
The quality of the fuel should be determined by calorific tests and analysis of the coal sample above referred to.[70]
13. ANALYSES OF FLUE GASES
For approximate determinations of the composition of the flue gases, the Orsat apparatus, or some modification thereof, should be employed. If momentary samples are obtained the analyses should be made as frequently as possible, say, every 15 to 30 minutes, depending on the skill of the operator, noting at the time the sample is drawn the furnace and firing conditions. If the sample drawn is a continuous one, the intervals may be made longer.
14. SMOKE OBSERVATIONS[71]
In tests of bituminous coals requiring a determination of the amount of smoke produced, observations should be made regularly throughout the trial at intervals of [Pg 274] 5 minutes (or if necessary every minute), noting at the same time the furnace and firing conditions.
15. CALCULATION OF RESULTS
The methods to be followed in expressing and calculating those results which are not self-evident are explained as follows:
(A) Efficiency. The “efficiency of boiler, furnace and grate” is the relation between the heat absorbed per pound of coal fired, and the calorific value of one pound of coal.
The “efficiency of boiler and furnace” is the relation between the heat absorbed per pound of combustible burned, and the calorific value of one pound of combustible. This expression of efficiency furnishes a means for comparing one boiler and furnace with another, when the losses of unburned coal due to grates, cleanings, etc., are eliminated.
The “combustible burned” is determined by subtracting from the weight of coal supplied to the boiler, the moisture in the coal, the weight of ash and unburned coal withdrawn from the furnace and ashpit, and the weight of dust, soot, and refuse, if any, withdrawn from the tubes, flues, and combustion chambers, including ash carried away in the gases, if any, determined from the analysis of coal and ash. The “combustible” used for determining the calorific value is the weight of coal less the moisture and ash found by analysis.
The “heat absorbed” per pound of coal, or combustible, is calculated by multiplying the equivalent evaporation from and at 212 degrees per pound of coal or combustible by 970.4.
Other items in this section which have been treated elsewhere are: