COST OF PLANT. Following is a tabulation of the cost of construction of the No. 2 plant, based on the cost of material in 1915: Cost of construction of Trumble plant No. 2, Martinez. Three inspection boxes... Six 30-inch coolers, three 6 by 18 foot separators, eight 30inch vertical condensers..... Five 48-inch heat exchangers, and six dephlegmators.. One 6 foot by 25 foot evaporator.. One 12-inch oil separator.......... One 470-barrel fuel oil tank.. Two 2,800-barrel residuum tanks..... $1,125. 83 10, 006. 95 842.50 265.00 558.50 3, 945. 90 5, 472.50 55. 45 5, 720. 34 Five 1,000-barrel distillate receiving tanks.. Miscellaneous equipment... Building and platforms. Heaters and brickwork.... Pipe and fittings.... Excavation, foundations and erecting labor.. Total....... Ten per cent for engineering and supervision.. 4, 010. 34 13,850. 84 17,591. 57 69, 178. 18 6, 917. 81 $76,095.99 The cost of construction, omitting the cost of the tankage, is approximately $8.80 per barrel of capacity, which compares favorably with the other plants described herein and is somewhat lower than that of the conventional still set when the cost of material at the time of building is considered. POSSIBLE CHANGES AND IMPROVEMENTS. In the writer's opinion a combination of these two plants would effect the most practicable operating arrangement. The crude could then be heated fractionally by operating the heaters in series in conjunction with the evaporator column, and the products fractionally cooled by the series of dephlegmators used in the second plant. With light oil this arrangement would be particularly desirable, because of the large quantity of vapors that otherwise would be superheated when running to a residual fuel oil. Also, the design and construction of the heaters undoubtedly could be improved (1) by rearranging the baffling as before mentioned to increase the velocity of the gases and make them flow countercurrent to the oil, (2) by preheating the air for combustion through absorption of some of the waste heat radiated from the setting, and, possibly (3) by supporting the coils at their center. It is not uncommon for the lower coils to sag fully a foot under fire, a condition which can not fail to weaken the tubes and invite deposits with consequent local superheating and burning. Careful firing will prevent this 131096°-19—11 trouble, but the middle support could be arranged as an oil-containing coil in series with the main coil, and thus render the heater less susceptible to damage from careless or inexperienced operation. However, on the whole, such plants are economical in operation, low in first cost, can be quickly built, and every advantage is taken of the heat recovered, as the following theoretical computations show: DISTILLATION. The approximate fractions by volume distilling over at the different boiling points are given in the following average sample: Composite sample of crude oil, gravity, 22° B. (specific gravity, 0.922). The quantity of heat required per pound of this oil to remove the above fractions, assuming that no heat loss occurred in the apparatus and considering the heat recovered by the exchangers, would be as follows: Where the specific heat of the oil is 0.45, approximately, specific heat of the vapors is 0.50, approximately, Heat 0.988 pounds of oil 225 to 250° F. (107.2 to 121.1° C.)....... Evaporate 0.013 pounds of vapors. Superheat 0.023 pounds of vapors 225 to 250° F. (107.2 to 121.1° C.)................ Heat 0.977 pounds of oil 250 to 300° F. (121.1 to 148.8° C.).............. Evaporate 0.026 pounds of vapors.. Superheat 0.049 pounds of vapors 250 to 300° F. (121.1 to 148.8° C.)..... Heat 0.951 barrels of oil 300 to 350° F. (148.8 to 176.6° C.)................. Evaporate 0.039 pounds of vapors... Superheat 0.088 pounds of vapors 300 to 350° F. (148.8 to 176.6° C.)...... Heat 0.912 pounds of oil 350 to 400° F. (176.6 to 204.4° C.)....... Evaporate 0.043 pounds of vapors. Superheat 0.131 pounds of vapors 350 to 400° F. (176.6 to 204.4° C.)........... Heat 0.868 pounds of oil 400 to 450° F. (204.4 to 232.2° C.)....... Evaporate 0.008 pounds of vapors. Superheat 0.139 pounds of vapors 400 to 450° F. (204.4 to 232.2° C.)................... Total heat required to top 1 pound of this oil at 100 per cent efficiency=120.78 or as 22° B. (0.922) gravity oil weighs 322.5 pounds per barrel, to top 1 barrel at 100 per cent efficiency would require 322.5×120.78=38951.55 B. t. u., or 9,800 calories. Actually the plant consumed 0.011 barrel of fuel for each barrel of oil topped, as shown in Table 28, or with 18° B. (0.946) gravity fuel oil, 68,325.4 B. t. u., or 17,219 calories. OVER-ALL EFFICIENCY OF THE RETORTS. Therefore the combined over-all efficiency of both batteries of 38,951.55 19,800 calories retorts is 68,325.4 17,219 calories = = 57.0 per cent. HEATER DATA. The data showing the relative transfer of heat in the different banks of coils in the heaters, is presented in Table 30. The positions of the thermometers used for these readings are shown in figure 41. The table brings out the large heat transfer in the two lower rows of pipes as compared with the small temperature rise in the top row. A countercurrent flow of oil and flue gases would result in an even temperature increment at each successive row of pipes and cool the gases more nearly to the temperature of the entering oil, which would save fuel and increase the plant efficiency. TABLE 30.-Data on heaters at Trumble plant No. 2, Martinez, Cal. August, 1916. [In each set of observations, first line shows degrees Fahrenheit; second line, degrees centigrade.] Tem Tem pera- Rise.b pera- Rise. pera- Rise.b pera- Rise. pera- Rise.b pera- Rise. pera- Rise.b pera- Rise, pera- Rise, pera- Rise. ture. ture. ture. ture. ture. ture. ture. ture. ture. ture. Tem Tem Tem Tem Thermometer No. a Tem GENERAL DATA. For location of thermometers see figure 41 (p. 143). Quantity of crude oil heated, 10,000 barrels in 24 hours, of oil of 25.7° B. (0.900) gravity. Quantity passed through one heater, 1,093 pounds per minute. Total length of pipe in one heater, 1,461 feet. Total length of pipe in one heater exposed to heat, 1,136 feet. Total area heating surface, 1,486.8 square feet. Total average rise of temperature, 197° F. (91.65° C.) Total time required for oil to travel through one heater, 6 minutes and 40 seconds. Velocity of oil, 3.66 feet per second. Percentage of total area of pipe exposed to heat, 77.75 per cent. Average square foot of heating surface for each 1° F. rise between thermom Records of the various plants are summarized in Table 31, for the purpose of comparison and to point out some of the most important items. TABLE 31.-Summary of topping-plant records showing fuel consumption and products made. a Records of water dehydrated were not available for all the plants. |