History of Sugar Mill Technology Part 1 Laurel Valley Sugar Plantation, Thibodaux Louisiana
Planters from many nearby estates gathered at the plantation of Etienne de Bore some six miles above New Orleans one day late in 1795. They had come to witness an experiment, the results of which, if successful, would affect their future and possibly the history of the entire region. Their attention was directed at a large circular iron pan arranged atop a brick furnace. Inside the pan, heated by the fire beneath, a yellowish syrup boiled and bubbled. De Bore, standing beside the furnace, motioned to his attendant, Antoine Morin, who reached a thumb and forefinger into the syrup and pulled out a small glob of the material. As he drew his fingers apart, the thread of the yellowish syrup sparkled with tiny crystals. "It granulates," announced de Bore. "The wonderful tidings" of what he had declared "flowed from mouth to mouth and went dying in the distance as if a hundred glad echoes were talking to one another.
The crowd that eventful morning had witnessed the first successful demonstration of the making of sugar from sugar cane in Louisiana. De Bore's experiment earned him instant recognition as the "saviour of Louisiana," for he had accomplished a feat which had eluded scores of planters for decades. His success insured that a viable sugar cane industry could develop in the region.
It was in 1751 that a group of Jesuit priests had first cultivated sugar cane in Louisiana, on a small estate in New Orleans. They made no effort to manufacture sugar from their crop, however, and it was not until eight years later that a planter named Debreuil erected the first sugar mill in the area. His effort to manufacture sugar failed, as did the efforts of other planters who attempted the task for themselves. They failed to appreciate the art that was sugar-making - to understand the care and the attention which the process of making sugar required, from the moment the juice first ran from the crushed cane stalks, to the moment when the boiling syrup reached its point of granulation. The task required experience and skill in recognizing at what point in the process each step had to be initiated, and the early Louisiana sugar-makers lacked that experience. As each planter met with failure, it seemed altogether possible that the sugar industry, the basis for much hope in the hearts of the settlers, might prove impossible for Louisiana. Nonetheless, a few undaunted planters continued to grow their cane to supply the markets of New Orleans.
It was a determined planter, Antonio Mendez, who firmly resolved in 1791 to devote himself to sugar manufacture "and to conquer all difficulties." Having purchased sugar-making apparatus, he secured the services of a Cuban sugar-maker, Antoine Morin, and placed him in charge of the sugarhouse. Morin's years of experience in making sugar in the West Indies paid off, for he produced a small quantity of sugar. Though the amount was not large, it nevertheless demonstrated that the manufacture of sugar on a larger scale did indeed seem feasible for Louisiana.
The fact, remained, however, that no one had yet done this. Mendez's few barrels of sugar were still regarded as a curiosity. But the success of Etienne de Bore a few years later convinced nearly everyone that the sugar industry had begun. De Bore had acquired Morin's services from Mendez and had invested a large amount of capital in his sugar machinery. The results, as we have seen, showed that sugar could be manufactured in large quantities if planters were willing to follow his example and commit themselves to similar large investments. Apparently, many were. By 1802 the amount of sugar delivered to markets in New Orleans had reached over 5,000,000 lbs. per year. Thousands of slaves were imported to compose the plantation labor force, and on hundreds of estates sugar cane was put into cultivation and sugarhouse were erected.
As much as possible, these early planters tied themselves to the lands on which they laid out their estates. Their sugarhouses were almost always constructed fairly close to a waterway - the Mississippi River, or one of the many bayous which flowed sluggishly through the back regions of Louisiana. The closeness of the waterway not only insured a constant supply of water for the sugarhouse, but also provided a transportation outlet for delivering the finished sugar to market. Most sugarhouses were also placed near a forest, since planters needed a constant supply of wood for fuel. The timber also provided building materials, along with the soil for making bricks.
The sugarhouse formed the center of the plantation complex. Through the middle of the plantation ran a road from forty to sixty feet wide, with small roads crisscrossing it. Ditches flanked the roads and were cut through the fields, to remove as much as possible the water which would collect on the level ground. The plantation labor force, most of whom lived in the small cabins that surrounded the sugarhouse, kept the ditches and roads in order throughout the year. Maintaining the roads was critical, for they were the courses used "in hauling the wood from the swamps, the cane from the fields, and the crop to the river for shipment.
Planters constructed their sugarhouses according to a standard plan, a T-shaped building whose stem pointed towards the nearby waterway. The stem, two stories high, some 150 feet in length and 50 to 60 feet in breadth, housed the cane mill and the kettles for boiling the juice into syrup. The head of the T, one story high and 30 to 40 feet in length, contained the purgery where molasses was drained from the newly-formed sugar crystals.
In these early days of sugar-making, mule carts delivered the harvested cane to the cane shed located next to the mill. Here from 50 to 100 loads of cane could be stored for protection from the elements until ready to be ground. Workers fed stalks of cane into a mill consisting of three vertical or horizontal rolls made of stone or iron. A team of horses or oxen turned the mill, crushing the tough stalks to extract juice. The mill, raised off the ground, enabled juice to flow freely by gravity into large cypress vats in the mill room. These rectangular vats, containing several hundred gallons of juice, held the juice until it was able to be boiled. Screens within the vats removed larger particles of fibrous cane trash (bagasse) before the juice went to the kettles.
The four iron kettles, ranging in size from the grande (72 inches in diameter) to the batterie (54 inches), were arranged in a line above a brick furnace. Juice was piped to the kettles and two clarifying agents, lime and sulphur, were added to it. As the juice heated, these two agents caused a scum of impurities to form on its surface. Attendants removed the scum using long copper skimmers. This process of clarifying the juice continued, and as it did the water in the juice evaporated, causing the juice to become more concentrated. When the juice became sufficiently concentrated in the grande, it was ladled to the next pan, the flambeau, and more fresh juice was added to the grande. In the same fashion, juice was ladled from the flambeau to the sirop, and from the sirop to the batterie. Scums from the three pans were ladled back, in turn, to the grande where they acted as a charge for the fresh juice.
Boiling one run or charge of juice into syrup took about an hour. At its "striking" point, the moment when the concentrated syrup was ready to granulate, it was quickly scooped from the batterie into one of several shallow cypress boxes. In these boxes, or "coolers," the syrup hardened into sugar crystals. Attendants stirred the mass of crystals from time to time to give a good texture and consistency to the mass. When it hardened sufficiently, it was broken up and put into hogsheads.
The hogsheads holding the sugar were carried into the purgery for draining molasses. To accomplish this, each barrel was placed on a framework running crosswise above a brick and cement molasses cistern. Molasses drained from the kegs through small holes in their bottoms; over a three-week period, some 40 or 50 gallons flowed from each barrel. At the end of this period the barrels were plugged, sealed, and carted to the waterway for shipment to market. The floors of the molasses cisterns yielded, after the molasses had been drained away, an inferior grade of "cistern bottoms" sugar which could be marketed or used as a charge for fresh strikes of syrup.
This method of manufacturing sugar continued to be employed in Louisiana (and in other Southern states) as the sugar industry developed during the early 1800's. A major stimulant to the growth. of the industry occurred with the Louisiana Purchase in 180 3, as thousands of settlers seeking livelihoods poured into the area from the North and from nearby territory- These immigrants quickly settled the most desirable regions in the fertile lands above New Orleans along the Mississippi. Most brought with them capital sufficient not only to raise sugar cane, but to manufacture it as well. By 1824, some 193 sugarhouses had been erected in this area. Another major boost for the early sugar industry came after 1820 when former cotton planters from Mississippi and Alambama, having abandoned their fields due to a severely depressed cotton market, entered Louisiana seeking new wealth in the sugar business. By 1830 there were nearly 700 estates in Louisiana raising and manufacturing sugar. One of the ex-cotton planters who came in with this mid-1820's tide was one Joseph W. Tucker, who, settling along Bayou Lafourche, established Laurel Valley Plantation in 1832.
Along with these influxes of settlers came several innovations to improve the traditional method of making sugar. The first major innovation was the adoption of steam power to replace animals for driving cane mills. The order books of an English foundry, Fawcett, Preston & Company, indicate that between 1813 and 1817 at least three low-pressure steam engines were sent to Louisiana for driving mills. By the early 1820s several plantations employed steam mills for grinding cane. Such mills consisted of three heavy cast iron rolls, a top roll set above a cane roll (entrance) and a discharge roll (exit). Numerous grooves cut into the face of each roll "provided a very free exit for the juice" as it was squeezed from the cane stalks. The juice collected in a special pan built into the solid bed-plate of the mill, and it was drawn off through a stopcock into vats much like the older method.
The steam mill soon found favor with many planters, not only because it proved more reliable than animals, but also because it permitted a much higher percentage of extraction of juice than had been possible with animal mills - as much as 65 percent. At first, however, few could afford the $12,000 required to purchase a steam engine complete with mill. Foundries in the northern states, especially in Ohio and New York, reduced the cost of the mills as more were produced, and while the price was still fairly high, by 1828 82 of 308 Louisiana sugarhouses had obtained them.
The earliest steam engines used in Louisiana had been of the low-pressure variety, but after 1830 more and more planters purchased high-pressure engines. Smaller in size and bulk, easier to service and repair, these engines were reportedly "less expensive in their construction" than low-pressure engines. By 1838, according to a census of stationary steam engines taken in that year, over 200 engines were used in Louisiana, for powering not only sugar mills but saw mills and cotton gins as well. The number of engines used placed Louisiana second only to Pennsylvainia nationwide. By 1860 and the advent of the Civil War, steam mills could be found on 1027 of 1291 plantations in Louisiana.
The conversion to steam mills forced a change in the old process of hand-feeding cane into the mill. Now that steam was available, "power was easily obtained and machinery was brought to relieve the laborers of this . . . most unpleasant duty." The machinery employed, the cane carrier, consisted of an inclined plane some 4o to 5o feet in length. "Double chains with wooden slats, inserted crosswise into the alternate and larger links," formed "a moveable band about two feet wide around revolving on cylinders. These cylinders were kept in motion by the moving force of the mill. Workers now laid the cane onto the moving band of the carrier, placing the stalks so that they would not jam up upon entering the mill. The carrier, reported a witness, delivered its load of cane "quietly to its destination."
The switch to steam power affected not only the grinding of cane but also the conversion of the juice into syrup. The larger amounts of juice being extracted from the canes put an increasing load on the kettles and the workers to keep up with the supply. It was for this reason, plus the fact that open kettles generally produced poorer quality sugars, that a great deal of effort was expended both in America and in Europe, to develop new methods of manufacturing sugar. These efforts paid off during the period 1830 to 1860, when "spectacular advances in the processes of clarification and evaporation" were achieved.
In this country several advances were made in adopting the existing open train of kettles to boiling with steam. One approach set the train directly above a steam boiler. Others forced steam through steam jackets, or through pipes coiled into the bottom of the kettle. In yet another alternative, the kettles were abandoned altogether and were replaced by "steam boxes" in which the juice was piped from box to box to form a layer over a network of perforated steam pipes. All of these suggestions, despite any improvements in the quality of the sugar they may have produced, suffered from the same disadvantage - they, like their open kettle predecessor, wasted fuel.
Our energy-starved population may fail to appreciate the fact that earlier Americans also faced energy crises of their own. This was especially true in Louisiana, where the forests and swamps behind many sugar plantations had become depleted of most of their timber. Many planters believed that a cure for the fuel shortage lay in the prospect of using bagasse for fuel. This practice was widespread in the West Indies where the cane trash, dried under the hot sun, "burned under the sugar kettles with a vehemence which defies comparison." The damper and cooler climate of Louisiana, however, meant that if planters hoped to use bagasse, they would either have to dry it indoors or burn it green. This was not possible, however, until 1853 when Samuel Fiske invented a furnace fitted with horizontal grate bars upon which green bagasse could be burned.
The steps leading to the introduction of a method of making sugar which would at once combine economy of manufacture and a high quality product, began with the invention of the vacuum pan. The operation of this device depended upon basic physical principles. In open air at sea level, water boils and changes to steam at a temperature of 212 Fahrenheit. If, however, a partial vacuum is created so that the air pressure acting upon the water is largely withdrawn, the water can then be made to boil at temperatures below 212 . A vacuum produced with an air-pump, for example, can enable water to boil at 120 . This principle of boiling in lower-than-normal pressures also holds true for other liquids, saccharine solutions for example. Chemists had learned by the early 1800's that saccharine solutions, when boiled under partial vacuum conditions at lower-than-normal temperatures (235 Fahrenheit being the normal temperature), retained their crystalline structures. This realization, if put to practical use, would perhaps allow economy of fuel if sugar could be made at lower temperatures.
It was E.C. Howard, an Englishman, who first invented the "vacuum pan" based upon these principles. His device, introduced in 1813, and similar vacuum pans appearing soon afterwards from others, consisted of an iron vessel ... generally made cylindrical, air-tight, connected by an air-pump worked by the steam-engine, whereby the air is withdrawn from the pan to an extent sufficient to diminish the pressure of the atmosphere so far as to enable us to boil the syrup at a temperature varying from 130 to 160 degrees, instead of 235 or 240 degrees, which is the boiling point of syrup in the open air when concentrated to the density of 42° or 43° of the saccharimeter.
Howard's vacuum pan found widespread acceptance at first in Europe alone, and it was not until 1830 that Thomas Morgan, a planter below New Orleans, first introduced it into Louisiana. His installation functioned as a strike pan, in which the vacuum pan received syrup which had been heated to the boiling-point but had been removed from the fire before reaching the strike-point. It would be allowed to reach this point and to commence its granulation inside the pan. "The results of the vacuum pan," noted one historian, "were watched with an interest scarcely less than that exhibited in De Bore's first attempt at sugar-making." For Morgan and for Valcour Aime, another planter who introduced a vacuum pan into his sugarhouse soon afterwards, "it was a success from the start. Their experiments were wonderfully successful, producing a very high grade of refined sugar."
The sugars which resulted were of high quality for several reasons. First, in the open kettles, the syrup reached a temperature of 240 or more; in the vacuum pan, however, the highest temperatures averaged about 150 . This led to a smoother grain and a greater consistency in the syrup. When the syrup reached its striking-point, it was impossible to simply stop the fire beneath the kettles. A second advantage offered by the vacuum pan, therefore, was that the sugar-boiler could simply shut off the steam intake valve leading into the pan when the syrup reached its striking-point. He could also adjust this valve, once granulation had begun in the pan, to regulate the grain formation of the sugar as desired - a capability not available in the kettles and coolers. The final advantage of the vacuum pan pertained to the formation of molasses. In open kettles, the molasses which drained in the purgery could not be boiled back again to produce more sugar. Re-heating the syrup to 240 in this fashion would result in the same symptoms of carmelization mentioned above. In the vacuum pan, however, the re-boiling of the syrups which drain from the first sugars is a regular part of the daily work; and this re-boiling has been effected three times, with successful results of crystallized sugar each time."
Thus the vacuum pan appeared to be the answer to higher quality sugar production. It produced a high grade of sugar, and it also permitted the planter to make more sugars by boiling back the molasses which drained off from previous strikes. In the matter of economy of fuel, however, the vacuum pan still posed problems for planters whose fuel supplies were reduced. Most vacuum pans consumed as much wood as did open kettles. When high pressure steam kettles were used with a strike vacuum pan, fuel consumption jumped 25 percent above open kettles, with as much as 6 cords of wood required for 1000 pounds of sugar.
Another factor of economy involved the maintenance of a vacuum in the pan. Most pans relied upon air-pumps, a procedure which required "a large amount of motive power." Various forms of condensers were used as well to maintain the vacuum, the most prevalent form consisting of: "a reservoir for steam (at a little distance from the vacuum pan), into which was poured through an extensive strainer, a large amount of cold water, which had for effect, after the expulsion of the air and supply of its place by vapor, to condense the vapor as rapidly as formed, and thereby maintain a perfect vacuum." These condensing cisterns required great volumes of cold water however, and their use was thus limited "to such localities as offer sufficient supply." To furnish this water to the sugarhouse, pumping stations had to be erected leading from the nearest waterway to a pond near the sugarhouse from which the water could be obtained.
A final consideration of economy in the use of the vacuum pan was that, although condensers could be used to recover most of the steam required for heating the syrup, steam released as the syrup evaporated usually was allowed to escape. That such a useful source of heat simply dissipated away without being put to good use distressed many experts. "Unless the vapor taken off can be used as a fund of heat," remarked one expert, " there is no economy of fuel in the use of a vacuum pan more than in the open pan."
The man who solved the problem of producing high-quality sugar while preserving economy of operation was Norbert Rillieux. Born in Louisiana in 1806, Rillieux studied physics and mechanics at the I'Ecole Centrale in Paris from 1830 to 1832. His interest in sugar manufacturing, and his familiarity with recent European improvements in the field, led him to conceive the idea of "multiple effect" evaporation. He proposed utilizing the steam released by evaporating syrup in the vacuum pan, to boil syrup in a second pan. He also suggested that this steam could be condensed and then directed back to the boilers for re-use. Returning to Louisiana in 1833,. Rillieux spent several years developing his system, and in August 1843 he received U.S. Patent 3237 for an "Improvement in Sugar Works." In this patent he claimed, among other things, a vacuum pan, or pans; that is to say, an evaporating pan or pans, connected with a condenser, in combination with an evaporating pan, or pans ... in which the saccharine juice, or other fluid, is evaporated under a pressure, lower, equal to, or greater than, the atmosphere, which last mentioned pan . . . prepares the saccharine juice . . . from the vacuum pan, or pans, and at the same time supplies the necessary vapor from the saccharine juice ... to complete the evaporation or concentration of the syrup ... in the vacuum pan, or pans.
Each vessel in Rillieux's multiple effect train consisted of three basic components: a steam-drum or "calandria," fitted with copper tubes through which juice passed; a down-take pipe which carried the juice back to the bottom of the vessel after it had boiled up through tubes in the calandria; and a vapor-space, linked by a pipe with the calandria of the next vessel in the train.
Before entering the effect, juice which had been clarified was first filtered through a large cylindrical tank containing charcoal or bone-black. These filtrates removed the lime added before clarification, and also purged the juice of a great deal of its yellowish color so that a whiter sugar would result. The juice then entered the calandria tubes of the first vessel. A vacuum-pump operating off a steam engine created a low degree of vacuum in this vessel, sufficient to permit its ebullition at a lower-than-normal temperature. Exhaust steam from the same engine or from a boiler was circulated around the calandria tubes, causing the juice within to boil.
Steam released during this first evaporation passed through the vapor-space pipe into the calandria of the next vessel. A pressure pump forced the juice from the first vessel into the second vessel, causing the steam to come into contact with it as the juice flowed through the calandria tubes. This contact condensed the steam, forming a vacuum (at a higher degree of vacuum than the first pan, so that the juice in the second vessel would boil at a still lower temperature), and the heat released from this condensation caused the juice to boil again. Both the steam produced by this evaporation, and the concentrated juice, then went to the next vessel and the process was repeated.
Initially the final vessel of the multiple effect was used as a granulation pan for the syrup. In most, plantations, however, this was eventually replaced by a system in which the granulation occurred in a separate vacuum pan after the syrup had been allowed to settle in tanks after leaving the effect. Two or three vessels comprised the multiple effect (in Europe, as many as five or six were sometimes used), the number employed being determined by the quantity of heat available, the amount of evaporation required, and the costs of an extra vessel and the fuel for it. In most cases the double effect proved ample for the amount of evaporation needed in the sugarhouse.