304 ANNUAL REPORT 
the zone of high temperature is too short to allow of the complete com- 
bustion of the fine organic matter surrounded by the cement mixture. 
The addition of water to typically dry materials like limestone and 
clay for the purpose of bringing about more intimate blending and more 
complete control of the mixture is not justified in principle. 
Use of Waste Gases.—2. The idea of a long rotary kiln and the 
use of the waste heat has long been realized by inventors and engineers. 
The kiln proposed by De Navarro in 1891 employed the heat of the waste 
gases for preheating the air used in combustion, using also the heat of 
the cooling clinker. At Warners, N. Y., the waste gases were used for 
drying the clay and marl in a separate cylinder. The Stokes system 
of England does practically the same thing. Giron, in 1893, suggested the 
setting up of a boiler at the discharge end of the kiln, an idea which 
has recently again been taken up and carried out on a large scale by 
Prot.) Carpenter ‘of Cornell University; Aw verticals watereruibe spotlen 
was installed for each two kilns of a cement plant, the boiler having a 
heating surface of 3,000 square feet. ach boiler, however, was provided 
with furnaces for direct firing, if necessary. An elaborate and exhaustive 
boiler test developed the fact that two kilns generated 264 boiler horse- 
power. Another test showed that 254 horsepower were generated 
by the two kilns. During these tests the two kilns produced 8,018 pounds 
of clinker and consumed 1,888 pounds of coal per hour. ‘The temperature, 
as measured by the Noel optical pyrometer, varied from 2350 
to 2960° F. The gases left the boiler at 560° F., and the economizer at 
SO. ld, IDohsiaver WKS Wese Alnor oO jer Cea, OF ime aie Smiacime 
the kiln was heated 480° F., restoring to the kilns 2,000,000, B. 
i OU. per hour) or. perm Cent Ole teiecatmaprodtcedmm yy gmatinc 
combustion of the coal. Some difficulty was experienced by the settling 
of kiln dust on the boiler tubes, about 4 pounds per hour, which was 
blown off every five hours. By the use of dust chambers as applied in 
blast furnace practice this slight difficulty should be entirely removed. 
In several other plants this difficulty is being overcome. The temperature 
in the burning zone of the kiln was about 2850° F. 
Over one-half of the heat is discharged into the flue, of which 7o 
per cent. is utilized in steam, about one-sixth leaves with the clinker and 
about one-twelfth is lost by radiation. 
Prof. Carpenter gives the following data which are very useful for 
purposes of reference: 
*Oement, Vol. V, No. 3. 
