Sugar is one of the most widely consumed foods in the world, mainly derived from sugarcane and sugar beets. Producing high-quality sugar is a complex process involving multiple stages: extraction, clarification, evaporation, crystallization and refining. At each stage of sugar processing, the quality and purity of the sugar juice need to be precisely controlled. Natural impurities, such as colloidal particles, proteins, pigments and microorganisms, can seriously affect the efficiency of clarification, filtration and crystallization.
Chemicals play a crucial role in modern sugar-making processes. Without proper chemical control, these impurities can cause scaling, color problems and output loss. Sugar-making chemicals not only enhance efficiency and output, but also improve product quality, reduce energy consumption, and help factories meet environmental protection standards. These chemicals can:
- Improve clarification efficiency and solid-liquid separation effect.
- Prevent the growth of microorganisms in fruit juice and syrup.
- Enhance the decolorization effect of high-purity white granulated sugar.
- Control the formation of foam and scaling in the evaporator and vacuum evaporator.
This article takes sugarcane as an example to comprehensively summarize the sugar-making process. It also explained how different chemicals - flocculants, disinfectants, decolorizing agents and defoamers - were applied at each stage to ensure smooth operation and high-quality sugar production.
Raw Material Preparation
The production of sugar begins with the harvesting and preparation of raw materials. The sugarcane is washed and chopped to remove soil, stones and leaves. At this stage, if the juice is left standing for a long time, it will start to breed microorganisms. To reduce the microbial load on the surface of raw materials, prevent sugar juice contamination or spoilage during the saccharification process, disinfectants are sometimes applied to the surface of sugarcane, storage water or cleaning equipment.
| Disinfectant Type | Recommended Concentration | Application Method | Main Functions | Precautions | Advantages |
| Sodium Hypochlorite (NaClO) | 50–200 ppm free chlorine | Spraying or soaking the sugarcane surface for 5–10 minutes | Broad-spectrum sterilization, reduces microbial load | Control concentration (generally 50–200 ppm free chlorine). Avoid excessive chlorine residual in juice to prevent color or crystallization issues. Rinse or drain after use if needed. | Broad-spectrum sterilization; low cost. |
| Sodium Dichloroisocyanurate (SDIC) | 50–150 ppm free chlorine | Spraying or soaking the sugarcane surface for 5–10 minutes | High stability, strong sterilization efficiency | Control free chlorine to avoid affecting juice crystallization and color. | More stable than sodium hypochlorite; high efficiency; controlled residual chlorine; widely used in food processing environments. |
| Hydrogen Peroxide (H₂O₂) | 0.1%–0.5% | Added into cleaning water or surface spraying | Sterilization, no residue, environmentally friendly | Control concentration; generally 0.1–0.5% for surface treatment. Handle with care during operation. | Decomposes without residue; safe and environmentally friendly. |
| Hot Water / Steam | Hot water at 80–90°C or steam at 100°C | Rinsing with hot water or steam treatment for 2–5 minutes | Sterilization without chemical addition | High energy consumption; requires appropriate equipment; observe safety precautions. | No chemical additives; reduces chemical residues. |
| Plant / Facility Cleaning Water Disinfection | SDIC, 50–100 ppm | Cleaning of equipment, transport vehicles | Prevents secondary contamination | Regularly replace and monitor free chlorine concentration. | — |
Recommended Practice
When sugarcane enters the factory, it undergoes an initial wash with clean water to remove soil and impurities.
Then, surface disinfection is carried out by spraying low-concentration SDIC or sodium hypochlorite according to the conditions.
The water sources and cleaning equipment of the sugar factory should also be disinfected regularly to ensure the overall hygienic environment.
Juice Extraction
After the first step of cleaning and disinfection. The next step is to extract sugarcane juice. The juice is usually extracted by mechanical pressing or diffusion systems. This step involves breaking the hard structure of sugarcane and extracting the juice from it.
In most cases, a sugarcane juicer consists of three roller mills in combination with a chopper or rotating blades. After sugarcane is processed on one conveyor belt, it will be conveyed to another conveyor belt to extract more juice. However, before transportation, water will be sprinkled first to further extract the juice. The residue left after juicing is called bagasse.
Juice contains soluble and suspended impurities, including plant fibers, proteins and even soil particles that have been completely washed away. These impurities must be treated to enhance the efficiency of subsequent clarification and crystallization.
Clarification of Sugarcane Juice
Juice clarification is the most crucial step in the early stage of the sugar-making process. The aim is to remove impurities (such as soil, protein, colloid, organic acid, etc.) from sugarcane juice and improve its purity. Generally, the Lime Process is adopted, combined with the phosphorus flotation method or the carbonation method.
Chemical use
Lime (CaO)/lime milk ( Ca(OH)2 ) : Neutralizes acidic substances and precipitates impurities.
Carbon dioxide (CO2 ) (used in the carbonation method) : Reacts with lime to form calcium carbonate precipitate, which adsorbs impurities.
Flocculant/coagulant aid: Helps suspended solids settle rapidly.
Commonly used: Polyaluminium chloride (PAC), polyacrylamide (PAM), etc.
Sulfur (SO2 ) or sodium sulfite: It plays a role in bleaching, decolorization and sterilization in phosphorus flotation.
Filtration and Preheating
After clarification, the juice needs to be filtered to remove sediment. Preheating the juice before evaporation is crucial, as it helps reduce the juice's viscosity and prevents microbial growth.
Evaporation and Concentration
The fruit juice is then concentrated into a syrup using a multi-effect evaporator, reducing the moisture content from approximately 85% to 30-40%. Vacuum evaporation helps maintain the quality of the sugar, but it also presents some operational challenges:
- Dissolved proteins and surfactants cause foam formation.
- Scale buildup on the evaporator surface.
Chemical Applications:
Defoamers: Silicone-based defoamers for high-temperature foam suppression. Polyether and fatty alcohol-based defoamers suitable for medium-foam fruit juice systems.
Scale Inhibitors/Dispersants: Prevent the formation of calcium carbonate or sulfate scale in the evaporator.
Impact: Efficient foam control and scale prevention ensure smooth evaporation, higher heat transfer efficiency, and less downtime.
Crystallization
The crystallization process in sugar production (often referred to in the industry as boiling) is a crucial step in converting concentrated sugar syrup into solid sucrose crystals. The concentrated syrup is boiled in a vacuum kettle to initiate sugar crystallization. Proper crystallization is essential for sugar yield, crystal size, and color. This is a complex physicochemical process designed to control the size and uniformity of the precipitated sucrose crystals.
Defoamers are often used in this process. Defoamers control foam formation during boiling, preventing syrup overflow.
Stable crystallization increases sugar yield and reduces losses during centrifugation.
Centrifugation & Separation
After crystal formation, the crystals are separated from the molasses using a centrifuge and then dried through hot pipes. The molasses can be further processed for the production of ethanol, animal feed, or other uses.
Decolorization and Refining
Decolorization and refining is the final stage in the sugar-making process, primarily used in the production of high-purity, white refined sugar (such as granulated sugar or rock sugar). This stage requires the use of large quantities of chemicals and adsorbents.
Commonly used chemicals include:
Activated carbon (powder or granules): Adsorbs polyphenols, caramel, and other pigments.
Decolorizing resins/ion exchange resins: Remove ionic and non-ionic colored compounds.
Hydrogen peroxide (H₂O₂): Oxidizes remaining pigments, further lightening the syrup color.
Decolorizing agents: Ensure low ICUMSA values and high visual quality.
The above outlines the main processes and chemical applications in the sugar industry.
How is wastewater from the sugar industry treated? What chemicals are needed?
Sugar factories generate wastewater during the sugar production process. This wastewater is complex in quality and has a high pollution load, requiring systematic water treatment before discharge.
The wastewater mainly comes from raw material washing, equipment cleaning, sugar production process wastewater, cooling water/condensate, and boiler blowdown. These wastewaters are characterized by very high COD and BOD (due to sugar content), high suspended solids content, strong biodegradability, and sometimes contain oil and silt. Therefore, a combination of processes—pretreatment + coagulation and sedimentation + biological treatment + advanced treatment—is typically used to treat this wastewater. Common treatment methods include physical treatment (such as sedimentation and filtration), chemical treatment (such as coagulation and neutralization), and biological treatment (such as activated sludge processes and constructed wetlands).
The specific steps and chemical applications are as follows:
| Treatment Stage | Purpose | Recommended Chemicals | Main Functions |
| 1. Raw Material Washing & Primary Pretreatment | Remove sand, mud, fibers, suspended solids | PAC (Polyaluminum Chloride) | Rapid coagulation, removal of SS and turbidity |
| PAM (Polyacrylamide) – Anionic/Nonionic | Floc formation, enhances settling | ||
| Defoamer | Controls foam generated during cane washing and juice extraction | ||
| 2. Equalization & pH Adjustment | Stabilize influent quality, adjust pH for downstream processes | Lime (CaO / Ca(OH)₂) | Raises pH, partial hardness removal |
| Sodium Hydroxide (NaOH) | Precise pH adjustment | ||
| Sulfuric Acid / Hydrochloric Acid | Lowers pH | ||
| Defoamer | Reduces foam in the equalization basin | ||
| 3. Coagulation & Flocculation (Primary Sedimentation) | Remove suspended solids, colloids, color; reduce COD | PAC / PolyDADMAC / Polyamine | Primary coagulants for turbidity and color removal |
| PAM (Anionic) | Improves floc strength and settling velocity | ||
| Coagulant Aids (e.g., Magnesium Silicate) | Enhances clarity and settling performance | ||
| 4. Anaerobic Biological Treatment (UASB, EGSB) | Reduce high organic load (COD, BOD) | Nutrient Additives (N & P sources) | Maintain microbial activity and healthy biomass |
| pH Adjusters | Keep optimal pH (6.8–7.2) for anaerobic bacteria | ||
| Defoamer | Suppresses biogas-related foam | ||
| 5. Aerobic Treatment (Activated Sludge, SBR) | Further reduce COD, BOD, ammonia | Nutrient Additives (N & P) | Provide balanced nutrients to microorganisms |
| Defoamer | Controls foam during aeration | ||
| Bio-enzymes / Microbial Cultures | Enhances biological degradation efficiency | ||
| 6. Advanced Treatment (If strict discharge standards apply) | Improve clarity, remove residual COD, SS, color | Polyamine / PolyDADMAC | Strong decolorization and turbidity removal |
| PAC | Additional SS and colloid removal | ||
| PAM (High Molecular Weight) | Final flocculation and polish | ||
| Activated Carbon | Removes color, odor, and organic residues | ||
| 7. Disinfection & Water Reuse | Ensure microbial safety for discharge or reuse | Calcium Hypochlorite | Powerful disinfection |
| Sodium Hypochlorite | Common online dosing disinfectant | ||
| SDIC (Sodium Dichloroisocyanurate) | Stable, long-lasting chlorine release | ||
| TCCA (Trichloroisocyanuric Acid) | High chlorine content, slow-release chlorination |
Sugar production is a complex industrial process requiring precise control at every stage—from raw material preparation and juicing to clarification, evaporation, crystallization, refining, and wastewater treatment. Each stage presents its own challenges, including suspended solids, color, microbial activity, foam formation, and scale buildup. By integrating appropriate chemicals into each stage of the sugar production process, sugar mills can increase output, improve crystal quality, enhance color, reduce losses, and minimize downtime. Simultaneously, optimized chemical solutions contribute to environmental protection through more efficient wastewater treatment and reduced chemical waste.
Choosing the right chemical partner allows sugar mills to improve production efficiency, ensure consistent product quality, extend equipment lifespan, and achieve long-term operational excellence.