Sugar Processing

Sugar-Beet-Processing
Beet Sugar Tech Brief

Filtration is Key in Processing Sugar Beets Into Usable Components

Sugarbeet processing is a widely used industrial process that converts raw harvested sugarbeets into food-grade sugar and byproducts such as fertilizers and quality dried animal feeds. Industrial Filtration Technology is a key component of any sugarbeet processing operation, with Durco Filters Press units and Pressure Leaf Filters both finding applications at appropriate places in a typical sugarbeet process stream.

Sugarbeet processing involves several steps to produce quality sugar and byproducts from raw harvested sugarbeets. Typical process steps include: cleaning, slicing & cossette mixing, sucrose diffusion, juice purification, evaporation, sugar crystallization, dried-pulp manufacture, and sugar recovery from molasses.

Sugar-Beet-Process-Flow
Sugar Beet Process Diagram with Durco Filters in Key Steps

Durco Filters in the Process

Beets are typically separated from their roots and leaves, then washed to remove soil and surface debris. In order to obtain maximum surface area for extraction of sucrose the cleaned beets are then sliced into long thin strips, known as cossettes, which are mixed and fed into a continuous diffuser. In the diffuser, the cossettes are exposed to dilute disinfectant and hot water (in the range 122-176°F/50-80°C), which extracts sucrose into solution. The resulting liquid Raw Juice contains ~10-15% sucrose and is piped off for juice purification. The remaining Wet Pulp is conveyed to dried-pulp manufacturing for production of animal feed.

Animal Feed Production From Wet Pulp & De-Sugared Molasses

Wet Pulp from the diffusion process is passed through a Durco Filters Press Unit to reduce its‟ moisture content from ~95% to ~25% percent (the water may be recycled as diffusion water). After pressing, recovered molasses are added to the pressed pulp, which is then dried in a pulp dryer. The resulting product may then be cooled, pelletized, and used as quality animal feed.

Raw Juice Clarification

The raw juice from the diffuser is passed through a screen which removes entrained cossette particulates, and is then heated to 176°F (~80°C) for input to the Juice Purification step, involving 2 carbonation and filtration operations:

Durco Filters EP Filter Press
Durco Filters EP Filter Press
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First Carbonation - Filter Presses

QP1200 for sugar
Durco Filters Quadra-Press™
Automated Quadra-Press

This step creates a mud by the reaction of Milk of Lime (MOL), CO and the raw juice extracted from the cossettes. The reacted juice stream is first clarified by gravity sedimentation. Solids in this phase are large in size and quantity. The solids laden slurry discharged from the bottom of the clarifiers is dewatered using a Durco Filters Press. The filter cakes discharged from the filter press is typically in the 60-70% solids content range and has residual value as a soil pH enhancer and as lime fertilizer and is sold as such.

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Quadra-Press™ - Membrane Plates

To optimize mud dewatering and residual sugar recovery at this station the capture of residual sugar by cake washing is often employed. To achieve consistent cake washing, Membrane Plates can be used to hold the filter cake firmly in place to reduce channeling of the wash water through the filter cake captured in the filter press chambers. Membrane plates can also be used to apply a secondary pressing to the cake once it has been formed in the plate chamber.

The cake wash water used is typically in the 140ºF (60°C) range. The Sweet Water that is recovered in this operation can be piped to the slaker to produce Milk of Lime (MOL). After the cake-washing step, the filter press can be core blown with compressed air and then steamed to further drive moisture-residual juice from filter cake. Durco Filters highly automated Quadra-Press™ filter press systems can precisely control each of these filtration steps to achieve consistent predictable mud dewatering.

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Second Carbonation - Pressure Leaf Filters

While the solids laden slurry is discharged from the bottom of the clarifiers, the clarified stream out of the top of the clarifier is sent on for further purification-filtration. This is the second carbonation and safety filtration steps of juice purification.  More carbonation gas is added to the heated and filtered first step juice to precipitate residual un-reacted lime. The precipitates are removed by using Durco Filters Pressure Leaf Filters. The juice is heated to 195-200ºF (90-93°C) as it enters this step of the process. The solids that are generated in this step are small in size and require the use of filter aids to effectively capture and remove them. Diatomaceous Earth (DE), Pearlite and Cellulore materials are commonly used as pre-coat and body feed to the juice. Pressure Leaf Filters offer excellent flux rates in this application.

Durco Filters Typ V Pressure Leaf for Caro Sugar
Durco Filters Type V in Michigan Sugar Plant
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Durco Filters Type V Pressure Leaf Filter

Pre-coating of the filter leaves with a slurry of clarified thin juice and filter aid at 0.1-0.2 lbs. per square foot of filter surface area. The pre-coat fluid is recirculated until the fluid is clear. The process stream is introduced into the filters and the filtration process runs until either a predetermined differential pressure or maximum calculated volume of solids is collected on the filter leaves. If the juice is heavy with organic debris, a body feed of filter aid may be added at a one to one ratio of debris/filter aid to generate a porous cake structure to enhance capture of debris and extend filtration cycle times. The filters are typically sluiced clean with either hot wash water or thin juice to avoid dilution. Durco Filters Pressure Leaf units have our exclusive DuraSluice™ technology to minimize the amount of fluid required to clean the screens. Our engineers have extensive experience automating the operation of Pressure Leaf Filters. We can design and fabricate complete packaged Pressure Leaf Systems consisting of pre-coat, body feed and sluice cleaning systems can be fabricated by Durco Filters.

The Durco Filters Type V (vertical) Pressure Leaf filter shown at left has been in continuous operation in a Michigan Sugar Beet processing plant since its installation in 1964. This filter processes up to 250,000 lbs of liquid sugar/day, for 33.6 million individual sugar packets/day, or 1.2310 sugar packets/year. That's enough sugar packets (1964-2011) to cirle the earth 1,435 times!

Durco Filters Type HC For Larger Operations

A Durco Filters Type HC (horizontal) Pressure Leaf Filter (right) is recommended to provide higher filter surface area when a higher throughput is required.

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Durco Filters Type HC Pressure Leaf for Sugar Processing
Durco Filters Type HC for Thin Juice Clarification

Durco Filters in Other Sugar Processes

De-sugaring of molasses can be accomplished by either the Steffan Process or by Chromatographic Separation. Durco Filters are a key in both of these processes.

Steffan Process

In the Steffan Process, molasses is diluted to 10% dissolved solids content with wash water from the sweet water system. The diluted mixture is agitated while quick lime (CaO) is added. The mixture is cooled to around 50ºF and the resulting saccharate precipitation is removed in a Durco Filters Press. The filtrate from this process is heated to 200ºF to precipitate more saccharate and filtered a second time to capture more sucrose.

Chromatographic Process

When Chromatographic De-sugaring is employed, the molasses is diluted to 60-70% concentration with soft water and it is heated prior to filtration using Durco Filters Pressure Leaf Filters. Filtration is critical to this operation as it is important to not foul the surfaces of the resin beads in the chromatographic units. Pressure Leaf Filtration can achieve separation of near collide-sized debris from the process stream that can block the effective adsorption of sucrose by the resins. The high flux rates and long run times make Durco Filters Pressure Leafs the best filtration tool for this application.

Expertise

Durco Filters division of Ascension Industries incorporates over 130 years of filtration experience in every Sugar Beet filtration system we build. Founded in 1933, Ascension Industries manufactures a broad line of self-cleaning Tubular Backwashing Filters, Pressure Leaf Filters, Pressure Nutsches, Filter Presses, and Sludge Dryers.

Consult Durco Filters About Your Application Needs

Consult a Durco Filters Applications Engineer to arrange testing and analysis of your process stream and determine the optimum filtration technology for your particular operation.  You can also fill out our Filtration Fast Track Form (below) and one of our Application Engineers will get back to you right away.