Device for utilizing lime from seashells for purifying raw sugar juice

Abstract

Device for purifying sugar cane juice (14) in sugar production from sugar beets (10) using CaCO3-containing mussel shells (2).

Description

[0001] On an industrial scale, sugar is extracted from sugar cane or sugar beets. In the production of sugar from sugar cane, the cane is ground under pressure, causing the plant cells to rupture and allowing the sugary juice (sugar cane juice) to be released.

[0002] To extract sugar from sugar beets, the beets are first cleaned of adhering soil particles (clay, sand, stones) and then shredded into small pieces called sugar beet pulp. The sugarcane juice is then extracted in an extraction tower using hot water.

[0003] The sugar cane juices obtained have a similar composition whether sugar cane or sugar beet is used, therefore the purification process can be carried out using essentially identical methods.

[0004] Sugarcane juice has an acidic character, is cloudy and dirty, and contains, in addition to the desired sugar, other components, so-called non-sugar substances, which must be separated during refining. The main undesirable components of sugarcane juice are phosphate, sulfate, citrate, and several other impurities, which preferentially form poorly soluble compounds with calcium.

[0005] Therefore, lime milk, which is made from quicklime (CaO), is used in sugar production to purify the sugar cane juice, both from sugar cane and from sugar beets.

[0006] The consumption of limestone for the production of milk of lime is high; typically, 125 to 250 kg of limestone (CaCO3) are needed to produce one ton of sugar. For this reason, most sugar factories are equipped with lime kilns in which the delivered limestone is burned with coke at approximately 900 °C. This burning process produces quicklime and releases CO2. CaCO3 + Energy → CaO + CO2

[0007] Together with water, calcium oxide (CaO) is used to produce milk of lime [Ca(OH)2], in order to first capture and then remove impurities in the sugar cane juice: CaO + H2O → Ca(OH)2

[0008] The CO2 released during lime burning is an important component required for removing non-sugar substances from the sugarcane juice and is used in the separation process to precipitate the lime milk mixed with the sugarcane juice. Introducing CO2 produces CaCO3, which precipitates and binds unwanted components of the sugarcane juice, thus enabling the separation process.

[0009] One disadvantage of the technologies known so far is that the production of lime milk requires very large quantities of limestone from quarries, which can only be made available through very extensive extraction methods.

[0010] The following focuses on the effort required to extract limestone from quarries: Once a quarry has been cleared for extraction after very extensive and lengthy testing and approval procedures, the process chain initially consists of removing overburden, which requires considerable preliminary work.

[0011] The rock is then extracted, primarily by blasting and / or wire sawing. Afterwards, the usable rock is transported to a processing plant according to its intended use. Here, the material is crushed using crushers or mills and classified using screens or, if necessary, classifiers.

[0012] The limestone is then transported to its destination (sugar factory), where, after possible further pre-selection, it is calcined in a lime kiln. It should be noted that the production of milk of lime requires calcined CaO with a particle size of < 100 µm, meaning that considerable energy is needed to grind it to the required size.

[0013] According to the invention, the use of mussel shells as a CaO carrier in the calcium cycle for purifying raw sugar juice offers a promising alternative in sugar production because mussel shells have a similar chemical composition, including CaCO3, to limestone products from quarries, but with advantageously higher porosities and specific surface areas. Furthermore, mussel shells must be treated as waste, the disposal of which is associated with considerable costs.

[0014] Parallel to the continuous increase in the world's population, the demand for shellfish products is rising, with China, India, Chile, Spain, and Italy leading the market. Global shellfish production reached approximately 2.3 million tons in 2022, with Europe accounting for around 600,000 tons. More recent publications report even higher levels of shellfish waste: "10 million tons of waste from oyster, mussel, scallop, and clam shells are produced worldwide. Discarded shells are frequently thrown into the sea or disposed of in landfills, where they alter soils, waterways, and marine ecosystems" (Appl. Sci. 2023, 13(1), 623). This immense amount of waste must be considered non-compostable, which can cause numerous environmental problems, including unpleasant odors as the organic matter decomposes.

[0015] A key advantage of mussel shells as a biomaterial is that their mineralogical component consists of approximately 96% calcium carbonate, from which calcium oxide can be produced through thermal treatment. This can then be very sustainably reacted with water to form lime milk and used to purify sugarcane juice. Utilizing this waste material offers both economic and ecological benefits, as it is abundant, increasingly available, renewable, and cost-effective.

[0016] Further advantages, details and features of the invention will also become apparent from the following description of drawing 1. This shows: Fig. 1 A simplified representation of the device for the utilization of CaO3 as a basis for the production of CaO (quicklime) and further processing of CaO with water to lime milk.

[0017] In Fig. Figure 1 shows a device for purifying raw sugar juice during sugar production by removing unwanted non-sugar substances using milk of lime, which is formed from lime derived from mussel shells. Figure 2 depicts a reservoir consisting of mussel shells. In Figure 3, the mussel shells are first processed (cleaned and ground). They are then fed into a lime kiln (6) via a feed unit (5) together with fuel / coke (4). Here, at temperatures of approximately 900 °C, the so-called calcination takes place. This means that quicklime is produced from calcium carbonate in mussel shells (2) using heat generation (coke), and carbon dioxide (7) is released during the combustion process. This quicklime is then reacted with water to form milk of lime and is available via Figure 8 for the subsequent liming process in Figure 9.

[0018] Furthermore, in Fig.Figure 1 shows a sugar beet storage facility (10). The sugar beets are first washed in (11) and then chopped into so-called beet slices.

[0019] The beet pulp is then conveyed to an extraction tower (12). Here, the cell walls of the beet pulp are opened using water heated to approximately 70 °C, and the sugar molecules are extracted. At the bottom of the extraction tower, the raw sugar juice (14), with a sugar content of approximately 15%, can flow out and be conveyed to (9) for liming.

[0020] The desugared sugar beet pulp can be discharged via (13) and used as animal feed in agriculture. The raw sugar beet juice (14), containing all its impurities, is fed into a decalcification tower (9) for liming. At this stage, the raw sugar beet juice contains not only sugar but also various organic and inorganic components from the sugar beet. These are bound by lime milk (8) and pass via (15) into the carbonation process (16). The addition of CO2 initiates the precipitation of the lime milk with the bound non-sugar substances from the raw sugar beet juice, forming CaCO3.

[0021] In the downstream filter press (17) a final separation of CaCO3 together with non-sugar substances (19) and the sugar solution (18), also called thin juice, takes place.

[0022] The thin juice (18) is then concentrated in crystallizers until, after some further known process engineering measures, crystallized sugar is obtained.

[0023] Saturated CaCO3 can be dried and is generally used for soil liming in agriculture. However, such large quantities are produced that the sugar industry worldwide is searching for other applications.

[0024] Of course, the examples described can be modified and supplemented in many ways without departing from the fundamental concept of the invention. The invention also relates to a liming and carbonation process for sugar cane juice during sugar production, regardless of whether sugar cane or sugar beets serve as the sugar source. A key component here is the use of CaCO3-containing mussel shells as the source of lime for the production of lime milk. Naturally, other CaCO3-containing waste materials, such as eggshells and / or snail shells, can also be used. Reference symbol list 1 Device for purifying sugar cane juice with lime from mussel shells 2 Reservoir for mussel shells (waste) 3. Processing of the mussel shells 4 Fuel for the production of quicklime (CaO and CO2 from CaCO3) 5. Feeding processed mussel shells and fuel into the lime kiln 6 lime kiln 7 CO2 8 Lime milk CaOH2 9 Lime tower (liming sugar cane juice) 10 Reservoir for sugar beets 11. Preparation of the sugar beets (washing & chopping) 12 Extraction unit 13 De-sugared sugar beet pulp 14 Sugar cane juice 15 Sugar cane juice & lime milk 16 Carbonator 17 Filter press 18 Sugar syrup 19 CaCO3 saturated with non-sugars QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Appl. Sci. 2023, 13(1), 623

[0014]

Claims

[1] Device for cleaning sugar cane juice (14) during sugar production from sugar beet (10) by means of CaCO3-containing mussel shells (2). [2] Device according to claim 1, characterized by that the CaCO3 from mussel shells is burned in a lime kiln (6) to produce quicklime, which also produces CO2. [3] Device according to the preceding claims, characterized by that lime milk (8) is made from quicklime and water. [4] Device according to the preceding claims, characterized by that the milk of lime (8) is used in the lime device (9) to separate non-sugar substances from the sugar cane juice (14). [5] Device according to the preceding claims, characterized by that the milk of lime (8) is used in the lime device (9) to separate non-sugar substances from the sugar cane juice (14). [6] Device according to the preceding claims, characterized bythat by adding CO2 (7) in the carbonator (16) the precipitation of lime milk (8) with bound non-sugar substances from the sugar cane juice (14) is initiated.

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