Vegetable Oil Production

VEGETABLE OIL PRODUCTION. The product of the manufacture of oil mills is vegetable oils obtained from oilseeds of various plant species. The most commonly used grades of oils produced at our oil mills are sunflower, linseed, hemp, colza, mustard, castor, and cottonseed. There are two methods of obtaining oils from seeds: pressing and extraction. In the first method, oils are obtained by pressing from seeds subjected to preliminary processing. In the extraction process, oil is extracted from the substances containing it by various chemical reagents, such as carbon disulfide, ether, benzine, etc. The most widespread and prevailing method at oil mills in the USSR is pressing; extraction is currently used in the USSR only at a few enterprises, while abroad the major part of oils (over 70%) is obtained by this method. The production process proceeds quite differently in both methods, as a result of which the occupational hazards caused by the course of the production process differ sharply between these two types of oil mills. Enterprises using the pressing method consist mainly of the following departments: 1) grain stores and elevators; 2) preparatory (cleaning, hulling-winnowing, and rolling); 3) roasting-pressing; and 4) oil-refining. Grain stores, serving to house reserves of oilseeds at more primitively constructed plants, consist of ordinary wooden or brick barns. In these premises, work is usually carried out on transferring grain to the plant premises for further processing. These operations boil down to shoveling seeds into bags, tying them up, and carrying them to carts. Working conditions in these grain stores are extremely poor. Deprived of daylight, these warehouses are moreover unheated, as a result of which temperature conditions there in winter are very unfavorable; to this is added the enormous dustiness of the air caused by transferring grain into bags or dumping it into the barn. Well-equipped plants have mechanized grain stores called elevators. They consist of a receiving department equipped with a receiving pit, a system of conveyors, and silos, i.e., receivers for storing oilseeds. Receiving departments, where seeds are fed directly after delivery to the plant territory, are small rooms, very poorly lit due to the absence of glazed surfaces and completely unheated in winter. In this department, seeds are dumped into receiving pits. This operation is associated with enormous dust generation. With various systems of pits (flat and conical, open and closed) and with different work processes, the concentration of dust in the air varies and fluctuates within the range of 130–250 mg/m³, with up to 80% of the dust consisting of inorganic substances formed by soil and sand contaminating the uncleaned seed. These impurities make the dust particularly harmful, since hard silicate particles, penetrating the upper respiratory tract, cause mechanical damage to their mucous membranes, which leads to the formation of various diseases of both an inflammatory and an atrophic character. Oilseeds are transferred from the receiving pit with the help of conveyors moving through special tunnels to silos. Tunnels, which are long, narrow basement corridors, serve as the place of stay for workers servicing the conveyors. When the latter are in operation, dust is formed in huge quantities. Its concentration in the tunnel is significantly higher than at the receiving pits and in some cases reaches a colossal figure of 725 mg/m³ of air. Such a dust content in the tunnel is usually observed during the operation of open conveyors. According to its size, the dust in the tunnels must be classified as fine dust, since 86% of dust particles do not exceed 10 µ in size. Dust of such dispersity has the ability to penetrate into the most distant parts of the lungs, which increases the danger of disease for workers inhaling such dust at work. The elevator premises proper, in which the silos are located, represent, at well-equipped oil mills, fairly spacious bright buildings with a relatively good light area, giving at some enterprises a normal light coefficient and good illumination at workplaces. Regarding temperature conditions, the elevator premises differ little from the departments described above. Thus, for example, at outside temperatures of -8° and -12°, the inside temperatures of the elevator premises turned out to be -6° and -9°, respectively. The intensity of air cooling, measured by Hill's katathermometer under given meteorological conditions, was expressed on the dry kata as 17.4 (normal average 5–7), which indicates the presence of conditions capable of causing severe cooling of the body in persons working in these premises. Dust emission during the operation of conveyors is observed in all elevators, and the nature and amount of dust fluctuate here depending on the condition of the equipment, its design, and also the degree of contamination of the oilseeds. According to its chemical composition, elevator dust contains almost equal amounts of organic (47.8%) and inorganic (43.2%) substances at its usual humidity of 9%. In the cleaning departments, oilseeds are subjected to cleaning from contaminating substances using apparatus of various systems—"shakers," trommels, bar-separators, separators, and trieurs. The processing of oilseeds after cleaning proceeds differently depending on their variety. If they have a hard shell or husk (sunflower, cottonseed), they are subjected to breaking or husking on special machines called hullers. Passing through the hulling machines, the oilseeds turn into a mixture of husk, or hull, kernel, and soft seed coat. To separate these constituent parts of the mixture from each other, the latter is passed through special devices, the so-called winnowers. The hulled kernel is subsequently subjected to grinding on rolls. Skinless seed is subjected to rolling immediately after cleaning. With this operation, all processes associated with the preparation of oilseeds for pressing oil from them are completed. All the mentioned apparatus and machines in one combination or another are usually located in common premises at oil mills in the USSR, and therefore it is more expedient to give the entire preparatory department a general sanitary and hygienic assessment. Regarding daylight, the premises of this department usually do not meet hygienic requirements, since a significant part of their glazed surface is not used due to the placement of bulky machines near the windows and a dense network of various pipelines blocking the access of daylight into the room. Due to these conditions, extremely uneven illumination is created at various points of the room. Thus, for example, with an illumination at the window of 124–540 lux, the illumination in the middle of the room turned out to be 6–26 lux, and between the machines it dropped to 0.5 lux. Despite the absence of any serious obstacles from the production point of view to maintaining a normal temperature in the preparatory departments, the latter have up to the present time in the overwhelming majority been devoid of any heating devices, as a result of which the meteorological conditions in them in winter are very close to those of the external atmosphere. At a number of plants in the North Caucasus Krai, the indoor temperature remained at +5–6° with an outdoor temperature of -4°; however, it often drops below 0° in these departments; dry kata readings fluctuated within 9–16. Another harmful factor characteristic of these departments is the strong dustiness of the air in the work rooms. Dust concentrations in the preparatory departments vary depending on the equipment used in them. The highest content was found during the operation of bar-separators (177 mg/m³) and the lowest at separators (27 mg/m³). The latter apparatus can be recognized as the most desirable from a hygienic point of view; they also give the best production effect. The seed crushed on rollers enters the roasting-pressing department for final processing, where it is heated in roasters and then pressed in presses to obtain the final product of production—oil. Roasters in our oil mills are of two types: fire-heated and steam-heated. The latter are more acceptable from a hygienic point of view than the former. Of the various types of presses, open or otherwise called Anglo-American presses are the most widespread at oil mills in the USSR; closed presses with rotating cages, the so-called "Compound" presses, are less common. Daylight illumination in these departments, due to a relatively good light coefficient and less clutter of the glazed surface than in the preparatory departments, is somewhat higher than in the latter, although the absolute values of the illumination intensity in the roasting-pressing departments are still far from sufficient from a hygienic point of view.

Regarding temperature conditions, roasting and pressing departments, in contrast to preparation departments, are characterized by high indicators of both temperature and humidity. The sources of heat radiation in these departments are roasters and presses; increased humidity is caused mainly by the evaporation of water from the surface of the roasters. In the roasting and pressing departments, a very uneven state of temperature is also observed at various points in the room. Typical in this regard can be considered the data obtained at one of the oil mills in the North Caucasus (Armavir), where in winter with an outside temperature of minus 13°, it was simultaneously observed in the middle of the room at 16°, near the presses at -23-25°, and near the roasters at -27-40° with relative humidity fluctuating within 77-83%. Work under these conditions proceeds with a fairly significant muscular strain of the workers. During the roasting processes of oilseeds, fat decomposition occurs, accompanied by the release into the air of very complex volatile organic substances in their composition, which strongly pollute the air of the pressing departments. Based on currently available data, these substances mainly consist of various hydrocarbons, volatile fatty acids, various unsaturated compounds, glycerin, and many others. Under particularly unfavorable roasting conditions, when oil scorching takes place, fat decomposition can be accompanied by the release of acrolein, which is a very strong irritant capable of causing serious occupational poisoning. Finally, in the air of the pressing departments, products of more deeper decomposition of organic substances can also be encountered, such as ammonia, hydrogen sulfide, and carbon monoxide, although these substances do not usually reach such quantities that would pose a threat to workers regarding occupational poisonings by these gases. In addition to the general irritating effect of volatile organic substances found in the air of the pressing departments, certain varieties of oilseeds (rapeseed, mustard), which contain strongly irritating essential oils, also act directly on the skin of workers. Permanent and direct contact of pressing workers with oil causes severe contamination of exposed parts of the body with fatty substances, which, in the presence of the mentioned essential oils in them, cause sharp skin diseases characterized by the appearance of small itchy red nodules, gradually merging into large red spots, which subsequently acquire the appearance of punctate hemorrhages or vesicular rashes, often causing desquamation of the superficial layer of the skin with the subsequent formation of small ulcers (erosions). The oil obtained after pressing is subjected in the oil purification department to purification from impurities (various protein, mucous, and coloring substances) either by settling in vats or by filtration on special apparatus—filter presses. The settling high tanks, which make up the main equipment of the filtration and settling rooms, usually clutter most of the glazed surface, which in most cases necessitates working there even during the day under artificial lighting. The air temperature in the oil purification departments is mostly elevated due to the presence of iron tanks with hot oil at 40-50° in them. In the absence of heating devices, even in winter, inside some filtration and settling rooms, the temperature rises to 29-36°, but mostly it stays at the level of 18-25°. At separate moments of work (when rolling barrels of oil from the room into the yard), thanks to direct communication with the outdoor air in the room, the temperature often drops even below the average norm (14-16°). The large evaporation surface of hot oil formed when it stands in open tanks, as well as the cooking of foots (dregs from settling tanks) carried out in the oil purification rooms, cause the entry of various products of evaporation and decomposition of fats into the air. In the absence of particularly harmful gases in the oil purification departments formed during the deep decay of organic substances, the air of the work rooms is nevertheless sufficiently polluted with products of the initial stages of oil decomposition (hydrocarbons, volatile fatty acids, etc.). The work of fillers and filter operators in the absence of mechanical devices for pumping oil and with a insufficiently good technical condition of the apparatus (filter presses) is associated with fairly significant physical stress, exacerbating the unfavorable working conditions in the oil purification departments. Among the main health improvement measures that can significantly reduce the hazards of vegetable oil production during the described course of the production process, it is necessary to indicate the following. Replacement of primitive grain stores with mechanized elevators equipped with closed pneumatic conveyors instead of currently used open belt conveyors and screws. Oilseeds must necessarily be subjected to preliminary drying and cleaning before putting them into processing. Cleaning departments must be equipped with the most advanced machines (separators), and during subsequent processing processes of oilseeds in the preparation departments, closed apparatus equipped with powerful exhaust devices should be used. Tightness and soundness of pipelines are of great importance in combating dust in the preparation departments. Steam roasters equipped with rational casings with appropriate exhaust devices, possible reduction of the seed roasting temperature, general properly arranged supply and exhaust ventilation can significantly improve working conditions in the pressing departments. A mechanized pump system for pumping oil from the pressing department to the tanks and from the latter to the filter presses and storage facilities for the finished product, mechanization of the foot-cooking process, rationalization of tank cleaning techniques, improvement of filter presses—this is the main list of measures that can solve the problem of health improvement in the oil purification departments. The second method of obtaining oils—their extraction with the help of various chemical substances—consists mainly in the following. Oilseeds are subjected to grinding, after which a solvent (mostly gasoline at USSR oil mills) is passed through the vessel in which they are enclosed, which at a certain optimal temperature (for gasoline 40-70°) dissolves the fat; then from the solution, by steaming it with closed or live steam, the solvent is removed, which is directed through pipes to a refrigerator, where it condenses and is subsequently used again for oil extraction. The main occupational hazard in this method of oil production is the entry of toxic volatile solvent vapors into the air of the work rooms. Most of the evaporation occurs due to the leakage of gasoline from the equipment through its looseness. For example, at the Khimzhir oil extraction plant in Krasnodar, the gasoline content in the air of the work rooms under different temperature conditions and at various moments of the production process (Bensman) ranges from 0.506 to 3.998 mg/L without ventilation and from 0.286 to 1.708 mg/L under the action of ventilation—concentrations are quite significant, often exceeding the established People's Commissariat of Labor limit norms for gasoline content in the air of work rooms (0.5 mg/L). Regarding meteorological conditions, extraction departments are characterized by a fairly high temperature (on average 30-35°) and relatively low relative humidity (within 22-54%). In accordance with these data, the indicators of dry and wet kata thermometers also fluctuate within 0.9-2.6 and 10.3-17.8. The main measures to combat occupational hazards of oil extraction production are the isolation of extractors (apparatus used for oil extraction) from other auxiliary apparatus (pumps, distillation cubes), mechanization of the loading and unloading processes of extractors, as well as equipping them with automatic agitators; complete tightness of equipment and pipelines; arrangement of local exhausts at the apparatus and places of solvent vapor release, isolation of heat-emitting installations and equipment of supply and exhaust ventilation to combat abnormal meteorological conditions.