The benzine from (4) is run into the agitator (8) where it is treated with sulphuric acid. The benzine is agitated by air blasts to give good mixing. The sulphuric acid eats the im purities and imparts a white color to the benzine. The next procedure is to neutralize the acid with soda ash and wash it with water. The neutralized oil is next pumped into storage tank (9) from where it is pumped into the steam still (10). It passes from the steam still to the condenser box and then into the receiving house (12). The first cut from the benzine is high grade gasoline which goes to the gasoline tank No. 1 (13). The second cut is low-grade gasoline which is run to tank No. 2 (13).
The. kerosene cut is carried to another tank. The gasoline is then run to the storage tank (14) from which it is carried to the tank cars (23).
II, Chart following the F. W. distillate cut in tank (5), the condensate is run to the re-run still (15) and goes through the condenser box (16) to the receiv ing house (17). The first product is run to the running tank (19), and from there is carried to agitator (20) where it is purified much like the gasoline cut. It is next run to the bleacher tank (21) where it is allowed to settle, and is then pumped to the kerosene storage tank (22) from which it is run to the tank cars (23). This completes the operation.
Refining of Wax and Lubricating II, Chart 2.— The general procedure for refining wax and lubricating oil is illustrated in Chart 2. (Fig. 95.) The procedure follows that in Chart 1, up to the treatment of the wax distillate.
The wax distillate is shown coming off from the receiving house and going into tank (8). It is pumped into the storage tank and from there through' the refrigerating tank (9) and (10), where it is chilled. The chilled wax goes to the wax filter press (11) where it is forced under heavy pressure (300 lb. per square inch) through canvas filters that catch the wax. The pressed distillate (12) includes the lubricating stock and is treated as described later. The slack wax which contains considerable oil is freed from the filter press and is carried off to the sweat pans (14). The sweating takes place in a square brick building filled with pans, placed one above the other with some space between. These pans have frames swung in the upper part. The pans are first partly filled with water. The slack wax from the filter press is melted and then pumped into the pans where it settles on the frames above the water. The water chills the wax, and also leaves it suspended on the frame. The water is next drawn off from the pans, the sweating room is then closed tight and steam is turned into the steam coils under the pans. The wax becomes soft and melts very slowly. The oil with the wax runs into the pans, carrying a little wax with it.
The sweated wax cakes are then melted and filtered through Fuller's earth at (17) to take out impurities. It is then pumped to the storage tank and from there is carried to the molding press (19) or is caused to drop on revolving chilled plates. As the wax chills it is removed by a set of stationary knives which cut the wax from the revolving plate. This is the wax of commerce which is then barreled and sent out to market.
Pressed II, Chart pressed dis tillate (12), which comprises the principal lubricating stock for cylinder oil, is carried to the reducing still (20) and is redistilled there. Part of the oil goes off as gas oil and non-viscous neutral oil, and is run into tanks (23) and (24).
The remaining residue in the still is the lubricating stock. This is cooled and then stored in tank (25). It is next filtered (26) and then barreled in the barrel house (27). This is the lubricating oil of commerce.
The schemes just outlined are modified with oils of different character, but the elementary principles hold good for oil of any kind. The types of stills, of agitators, of condensers, of filters, and of wax presses may all vary, but the simple refining scheme follows those outlined above.
Steam stills equipped with closed steam coils are used only for the distillation of the lighter volatile products. They are used particularly for distilling gasoline. The highest temperature attained is 212°F.
Capacity of range in size from 75 to 1300 bbl. capacity. Large stills have diameters of 14 to 15 ft. and lengths of 42 to 45 ft.
Many small companies prefer four small stills of 250 bbl. capacity each to one large 1000–bbl. still, as they can use the con tinuous system with four smaller stills. Large concerns use batteries of stills of the 14 by 42 ft. size, or even larger.
Topping or practice of only separating into their groups the light constituents from the heavy in a contin uous operation or by intermittent distillation is called topping or skimming.
Topping is generally used with oils to separate the lighter fractions containing the gasoline and naphtha contents from the heavier fuel oil. Three or four cuts are made. The lighter products are then shipped to a refinery where they go through the operations outlined before. The residue of lower fractions is sold as fuel oil.
Topping is often employed by oil companies that do not care to build a complete refining system. By separating the lighter parts of the oil from the heavier they can obtain a higher price for the light products, and generally sell their fuel oil at a good figure. Topping or skimming will, in this way, give a larger profit than selling the crude alone.
Refinery of refineries vary greatly. Topping plants may treat 1000 to 10,000 bbl. of oil per day. Some of the big refineries have capacities of 20,000 to 60,000 bbl.
Refinery Profits.—The idea is quite general that refineries make tremendous profits. On the contrary many refineries are failures. In good periods the 'profit on refined products obtained from a barrel of crude oil may range as high as $2 per barrel and as low as 30 to 50˘ per barrel. One dollar per barrel is a fair profit.
However, the fair way to determine profits is on the amount of capital invested in a refinery. A refinery having an invest ment of a million dollars and on a good market may pay 20 to 30 per cent per year on the investment, or even higher. Refinery profits, however, vary with the market and with the different products obtained from the crude oil, which vary in every field. No set scale of profits can be announced as conditions are so different in every part of the country.