Document XRKjOZwk2VdZ0n28qvGXKM3QR

% # .'+ t;r j.'.--: Mr: summer . POWERFAX 939 trie power requirements revealed the interesting possibility of gen erating the electric power needed along with steam for process. A tabulation of process steam and electric power requirements for normal plant operation was made. Department 90-lb. Pressure Process Steam lbs. kw.-hre. "A" "B" "C" D" Heat Special Depts. Lights Power Plant Total 30,000 13,000,000 760,000 3,500,000 300,000 200,000 200,000 140,000 30,000 86,000 80,000 160,000 26,000 26,000 17,980,000 636,000 .Fig. 1--Tabulation of process steam and electric power requirements for normal operation. Requirement of newprocesses esii- moled. Fig. 1 shows a normal operating month with estimated increased usage for the proposed installa tion. The graph. Fig. 2, shows actual daily relationship of elec tric power and process steam re quirements for the factory in No vember, 1927. The maximum de mand for electric power was found to be 1000 kw. Process steam was used at 20 lbs. and 80 lbs. gauge, 750,000 lbs. being used at 80 lbs. pressure and the balance at 20 lbs. pressure. This tabulation showed that the installationiofa back-pressure gen erating unit should be considered. In the analysis, it was estimated that thelow-press lire process steam demand would range from 24 to 36 lbs. for every kilowatt-hour of electrical energy used. Against back-pressure of 25 lbs., 1500-kw. generating units wore available, with water rates varying from 21 to 36 lbs. per kilowatt-hour. With steam at an initial pressure of 200 lbs. and 60 superheat, the water rate would be 36 lbs. per kilowatthour; 24 lbs. with steam at 400-lb. pressure and 170 superheat; and 21 lbs. at 600-lb. pressure and 200 superheat. A 1500-kw. generating unit with a water rate of 25 to 30 lbs. was selected. A tabulation of electric power loads indicated that such a unit would exhaust 13,700,000 to 16,500,000 lbs. of steam per month for process work. It was figured that a unit with a back pressure of 25 lbs., generating all electric power required, would ex haust an amount of steam winch could be used at all times for proc ess heat. An estimate of the cost of the new proposed plant was made to determine the saving which could be expected. A comparison of costs of steam and electric power when generating process steam and pur chasing power, and when gen erating steam for turbo-gener ator and using exhaust steam for process, was made. Since all ex haust steam fromthe turbine would be used for process, cost records for the old plant could be com pared with estimated costs for the proposed plant. As the existing steam plant was inadequate, $80,000.00 would have been required for changes and additions in any event. The additional investment toinstallthe more economical plant was $140,000.00. The saving of $30,665.00 represented a return of 22% on the investment. In addi tion to the saving in power, the expenditure provided for a sub stantial allowance for expansion and increased power demand. Having selected a generating unit requiring steam at 420-lb. pressure and 180 superheat, ' and having sufficient information about steam demands, the steam plant was planned. Two Babcock & Wilcox 500-hp. cross-drum wa ter tube boilers were purchased. Combustion Engineering Type E heavy - duty, single - retort under feed stokers were selected. A forced draft fan having a capacity of 30,780 cu. ft. per minute at 4J^" static pressure was provided for each boiler. These stokers were de signed and guaranteed to burn Pennsylvania bituminous coal passing through a 1J^" round screen. The flue gas temperature at the outlet of the boilers was specified as 500 F. at 100% rating and 550 F. at 200% rating. The two existing 100-ft. steel [4] CRIMDEBN00000363