Part 19 (2/2)

which is derived as follows:

The N in the flue gas is the content of nitrogen in the whole aas is that contained in the air supplied and which was not utilized in coen was accoen The total aases is (O - CO); hence N - 3782(O - CO) represents the nitrogen content in the air actually required for combustion and N (N - 3782[O - CO]) is the ratio of the air supplied to that required This ratio minus one will be the proportion of excess air

The heat lost in the flue gases is L = 024 W (T - t) (15)

Where L = B t u lost per pound of fuel, W = weight of flue gases in pounds per pound of dry coal, T = teases, t = teases

The weight of flue gases, W, per pound of carbon can be coas analysis from the formula:

11 CO_{2} + 8 O + 7 (CO + N) ---------------------------- (16) 3 (CO_{2} + CO)

where CO_{2}, O, CO, and N are the percentages by voluas analysis of carbon dioxide, oxygen, carbon as per pound of dry coal will be the weight detere of carbon in the coal from an ulti Gases--Deg Fahr

against Heat carried away by Chimney Gases--In Btu

per pound of Carbon burned[31]

Fig 20 Loss Due to Heat Carried Away by Chies of Carbon Dioxide Based on Boiler Rooen in Flue Gas = 805 Per Cent Carbon Monoxide in Flue Gas = 0 Per Cent]

Fig 20 represents graphically the loss due to heat carried away by dry chies of CO_{2}, and different teases

The heat lost, due to the fact that the carbon in the fuel is not coases, in B t u per pound of fuel burned is:

( CO ) L' = 10,150 (-----------) (17) (CO + CO_{2})

where, as before, CO and CO_{2} are the percentages by voluht of carbon which is burned and passes up the stack

Fig 21 represents graphically the loss due to such carbon in the fuel as is not completely burned but escapes up the stack in the form of carbon monoxide

[Graph: Loss in BTU per Pound of Carbon Burned[32]

against Per Cent CO_{2} in Flue Gas

Fig 21 Loss Due to Unconsumed Carbon Contained in the CO in the Flue Gases]

Apparatus for Flue Gas analysis--The Orsat apparatus, illustrated in Fig 22, is generally used for analyzing flue gases The burette A is graduated in cubic centimeters up to 100, and is surrounded by a water jacket to prevent any change in te analyzed

For accurate work it is advisable to use four pipettes, B, C, D, E, the first containing a solution of caustic potash for the absorption of carbon dioxide, the second an alkaline solution of pyrogallol for the absorption of oxygen, and the re the carbon lass tubes, to which so the absorption of the gas In the pipettes D and E, copper wire is placed in these tubes to re-energize the solution as it becomes weakened The rear half of each pipette is fitted with a rubber bag, one of which is shown at K, to protect the solution from the action of the air The solution in each pipette should be drawn up to the as is drawn into the burette through the U-tube H, which is filled with spun glass, or sias in the apparatus, the cock G is opened to the air and the bottle F is raised until the water in the burette reaches the 100 cubic centimeters mark The cock G is then turned so as to close the air opening and allow gas to be drawn through H, the bottle F being lowered for this purpose The gas is drawn into the burette to a point below the zeroopened to the air and the excess gas expelled until the level of the water in F and in A are at the zero mark This operation is necessary in order to obtain the zero reading at atmospheric pressure

The apparatus should be carefully tested for leakage as well as all connections leading thereto Simple tests can be made; for example: If after the cock G is closed, the bottle F is placed on top of the fraht to the zero mark, the level of the water in A is above the zero22 Orsat Apparatus]

Before taking a final saas and emptied once or twice, to as The cock G is then closed and the cock I in the pipette B is opened and the gas driven over into B by raising the bottle F The gas is drawn back into A by lowering F and when the solution in B has reached the mark in the capillary tube, the cock I is closed and a reading is taken on the burette, the level of the water in the bottle F being brought to the same level as the water in A

The operation is repeated until a constant reading is obtained, the nue of CO_{2} in the flue gases