Sugar refinery
A sugar refinery is a refinery which processes raw sugar from cane or sugar extracted from beets into white refined sugar.
Cane sugar mills traditionally produce raw sugar, which is sugar that still contains molasses, giving it more coloration than the white sugar which is normally consumed in households and used as an ingredient in soft drinks and foods. Raw cane sugar does not need refining to be palatable. It is refined for reasons such as health, color, and the requirement for a pure sugar taste. Raw sugar is stable for transport and can be taken from mills to locations for processing into white sugar. Cane sugar mills / factories often produce a partially refined product called Plantation White for their local market, but this is inferior to white sugar made by refineries.
Beet sugar factories can also produce raw sugar, but this has an unpleasant taste. There is no separate raw sugar stage to the process; the sugar extract from the beet is, after cleaning, crystallized directly into white sugar.
History
Overview
The origins of the art of refining sugar seem to stem from Khorasan in Persia. Next, the Venetians produced refined sugar, resembling sugar candy. In 1573, the first German sugar refinery was built in Augsburg. During the 17th century, the Dutch started their refineries, which soon dominated the European market. The risks involved in large refineries stimulated developments in the insurance industry.In the early modern era the sugar refinery process consisted of some standard steps. First the raw sugar was put in a copper boiler and mixed with bullock's blood and lime-water. The mixture was then left to stand for a night in order to dissolve. In the morning, a fire was lit under the pan or boiler. The albumen of the blood then coagulated and entangled the mechanical impurities of the sugar, forming a scum that was constantly removed. The simmering was then continued till a sample of the mixture appeared transparent. It was then rapidly boiled down till such consistency that it could form threads between one's finger and thumb. At which point the fire was damped. The second step was granulation. For this, the syrup was transferred to a vessel called a cooler, where it was agitated with wooden oars till it granulated. The third step was to put the granulated sugar in molds.
The first sugar refineries were located in coastal cities throughout western Europe. They did not necessarily have to be in a port city, because at the time goods were generally transloaded from a ship onto a barge before reaching their destination. Sugar refineries are often located in heavy sugar-consuming regions such as North America, Europe, and Japan. Since the 1990s, many state-of-the art sugar refineries have been built in the Middle East and North Africa region, e.g. in Dubai, Saudi Arabia and Algeria. The world's largest sugar refinery company is American Sugar Refining with facilities in North America and Europe.
Sugar refineries as a type of building
The sugar refineries that were built from about 1500 AD to 1800 did not require purpose built buildings. Ideally, they were located on a broad street along a broad canal with a good quay, so resources could be brought in at low cost by barge and by road. The refinery also had to stand somewhat free from other buildings. It required wind to dry the produce and to keep it from sweating, especially in Summer. The chimneys also had to significantly stick out above the surrounding buildings. From about 1800 the Industrial Revolution changed the refining process by introducing steam power and all kinds of machinery. It led to the construction of specialized building that could be recognized by having a large number of very shallow floors.The pre-1800 refinery was extensively described in the Netherlands, because the Dutch Republic dominated the trade in and refining of sugar for a long time. In Holland, the ideal refinery was at least 150 Rijnland feet long and 30 feet wide. The warehouse of the refinery would be on the street/canal side. It had to be at least 30 feet wide, 40 feet long and 20 feet high, with enough natural light and two 10 feet doors to let pass 2000-3000 pound barrels. The warehouse needed a windlass for vertical transport and a scale to weigh at least 1,800 pounds. Ideally, the warehouse and the refinery were separate buildings, but with the high real estate prices in Holland, this was rare.
The refinery was often directly behind the warehouse in the same building. Closest to the warehouse was the storage for raw materials. Here, there were 4 rooms/boxes to store different kinds of raw sugar, which was fed into the boxes from the first floor. These were each 6 feet long and 12–14 feet wide, making that the raw sugar storage part of the refinery was about 30 feet long, and as wide as the total building, i.e. at least 30 feet. In the 16–18 feet of width that was left there were all kinds of tools, and things like baskets to move the scum. Near the first box, there was a hole in the ceiling and all the floors above, in order to transport goods vertically by rope. On the first floor, there was a storage for lime, which was the same size as the pans, so enough lime could be stored to operate the refinery for 3–4 months.
Behind the storage for raw materials was the drying house, also called drying stove or oven. One or two houses were for drying the sugar loaves, two more were for making candy. These drying rooms were 10 feet long, 12 feet wide and 30 feet high. Each contained an iron stove burning on coal. It was set in brick, and fed from outside the room.
The part of the refinery where the actual refining took place was behind the drying house. Here were the copper boilers called pans where the sugar was boiled. Most of the Dutch refineries had four pans, many had three, and only a few had two. If there were four, these pans occupied a length of at least 25 feet. Each pan rested on a brick vault under which was its own stove. The location of these pans was in the rear of the refinery in order to have as much light as possible, and as little draft as possible. The light came from the rear façade of the building, which ended on an open space of about 25 feet long. Here earth and coal were stored. Below the refinery was a lead tube that allowed to pump fresh water that, in Amsterdam, was brought by barge schuitwater to the rear of the building. The same part of the building that contained the pans also contained the two lime cisterns. These had to be founded at least 30 feet deep and stood 4 feet above ground level. They were 9 by 6 feet and stood opposite the pans. Behind the lime boxes were the scum boxes of 8–9 feet high. Opposite the first pans was the cleared juice cistern klaarselketel. It was about 4 feet above ground and could contain about 8-9000 pounds of cleared sugar.
The post 1800 industrial sugar refinery was characterized by using gravity to transport sugar downwards through the building as it went through several refining steps. In combination with some other features, this led a recognizable type of 19th century sugar refinery building. Examples were buildings of: the Domino Sugar Refinery, the Boston Sugar Refinery, the Amsterdamsche Stoom Suikerraffinaderij, the Wester Suikerraffinaderij and the Nederlandsche Suikerraffinaderij.
History of the refining process
The refining process was also extensively described in 1793. In 1833 another description referred to it as 'The old, or German Method, by Blood, Eggs, Clay etc. At the time refineries produced different kinds of sugar. Loaf sugar was the highest quality. Next came lump sugar, followed by bastard sugar. Bastard sugar was made from the drainings of loaf and lump sugar. It was generally ground and sold as powder sugar. Sugar candy consisted of very large crystals formed around threads. It was either white or brown, depending on the quality of the sugar that was used.The first step, roughly equal to purification, was to fill the pans with fresh water and some lime water. Next raw sugar was put into the pan. The pans had a brace, which was a part of the front of the pan which occupied between 33 and 40% of its circumference, and was about two feet high. After the lower part of the pan had been filled, the brace was fixed in place to allow further filling. The mixture would then be left to stand during the night to dissolve the sugar. On the morrow, the fire below the pan was lit, and the mixture was slowly heated. It was regularly stirred to prevent the sugar from attaching to the pan. Stirring was decreased when the sugar had completely dissolved. When the sugar had almost reached the boiling point, the fire was almost extinguished. During heating the lime bound to impurities and formed a solidified scum, which was removed with a skimmer, resembling a perforated spade, with a 6–8 feet long handle. As soon as this was done a solution of eggs in water was plunged into the sugar mixture. This was done for the egg white or albumen, which bound more impurities. This led to more scum being scraped off. This was repeated 5-6 times, till a white slimy layer appeared on the surface instead of more scum. The solution was then called klaarsel for being cleared. Here clear also meant transparent. For purifying very rough sugar, ground water was used, and more lime and more eggs. The total use of eggs could be 400 or 500 a day, costing up four guilders for 100 in the winter. Adding fresh blood of oxen could help to further clarify sugar, but it was often used when not fresh, and as an alternative to expensive eggs. This led to rotten sugar, and in Holland it led to an official, but ineffective ban of its use.
The second step was to filter and store the cleared liquor. For that it was brought to the cleared juice cistern by feeding it into a copper tube that ended above a filter that was placed over the cistern. This filter was a piece of cloth in a basket and caught things like egg scales, nails, pieces of wood etc. At the time, the cleared juice cistern, was simply called cistern. It also served to hold the cleared juice while the first two pans were cleaned.
The third step was equal to evaporation. Small portions of the clarified juice were fed to the first pan, which was brought to boil by a brisk fire. In about 12–30 minutes, evaporation would lead the liquor to attain its requisite degree of viscosity. In Holland fast evaporation was obvious only for sugar candy. The test whether the liquor could form threads between one's finger and thumb determined when the sugar was 'done'. The first option to continue refining was to drain off the remaining water by using gravity, which would result in loaf, lump or bastard sugar. The other option was to evaporate the remaining water by heat, resulting in Sugar candy.
The fourth step cooling, was not applicable to sugar candy. For loaf sugar the third or fourth pan were used as cooling pans. For lump sugar three pans were used for cooling. As soon as a pan of sugar was 'done', it was transferred to a cooling pan. when it had sufficiently cooled, the sugar would form a crust. Ideally, the next batch of boiled sugar was done at this exact moment and was then added to the cooling pan. A cooling pan could be filled with up to five batches. Also see granulation above.
Filling the molds was the fifth step. Sugar candy was made by drying the sugar by heat. For this it was brought to the drying house by transport bucket. Here the sugar was put in candy pots. The operation to put the sugar in the transport buckets and to fill the pots could take about two-three minutes. Ideally, the second pan was by then ready to fill the transport buckets. If candy sugar was made, the drying room could contain about 150 pots of candy made from the raw sugar of four pans after about 6 hours of work. The drying room was then cleaned, shut off, and the fire in its stove was lit.
If sugar loaves or lump sugar was made, the sugar was brought to the filling room, see image: Filling molds in 1793. Here, the molds were filled. These had a conical shape with a hole in the tip, which was stopped by a piece of cloth. In the filling room, the molds were filled and then placed on their pointy end, starting in a corner of the room. They were then stacked up to each other while the outer rows were supported by prefixes voorzetsels, i.e. broken molds that were not fit for any other purpose.
The day after, the molds were brought to one of the upper floors. Here the stop of the forms was removed, and over a few days syrup leaked out and was gathered into collection pots. The forms were then put on top of a box, where sugar that stuck to the outside of the form was scraped off and collected. The loaves were carefully ticked out of the molds.