Citric Acid Fermentation Centrifuge

Citric acid is one of the world's most widely produced organic acids, with annual production exceeding 2 million tons for use in food and beverages (acidulant, preservative), pharmaceuticals (effervescent formulations, anticoagulant), detergents (builder, chelating agent), and cosmetics. The industrial production of citric acid is achieved through submerged fermentation of carbohydrates (molasses, corn syrup, dextrose) using the fungus Aspergillus niger. After 5-8 days of fermentation, the broth contains 10-15% citric acid along with biomass (mycelium), insoluble oxalates, gypsum (from calcium hydroxide neutralization), and other impurities. The recovery of citric acid requires efficient separation of these solids from the broth before downstream purification (precipitation, filtration, ion exchange, crystallization). Traditional separation methods including rotary vacuum filters, filter presses, and conventional centrifuges each present significant limitations. Rotary vacuum filters produce wet cake (30-40% solids) and require high maintenance on the filter cloth. Filter presses are batch operations requiring labor-intensive cake discharge. Conventional centrifuges may not provide the high G-force needed to separate fine particles or the corrosion resistance needed for the acidic broth (pH 1.5-3.0). Our Citric Acid Fermentation Centrifuge has been specifically engineered to overcome these limitations through high-speed, continuous centrifugation that efficiently removes biomass (mycelium), calcium sulfate (gypsum), and other solids from fermentation broth, producing clarified citric acid solution for downstream processing. The disc stack design provides an exceptionally large effective settling area within a compact footprint, enabling processing of fermentation broth at flow rates from 5,000 to 100,000 liters per hour. The high-G design (up to 10,000 x g) provides the driving force needed to separate fine mycelial fragments (5-50 micrometers) and gypsum particles (1-20 micrometers). The low-shear inlet prevents mycelial breakage, which would create fines that are difficult to separate. All product-contact surfaces are manufactured from corrosion-resistant materials (Hastelloy C22, Duplex stainless steel, or rubber-lined carbon steel) to withstand the aggressive acidic environment (pH 1.5-3.0, 30-40°C) and the presence of chlorides and sulfates. The system is fully enclosed with CIP capability. The centrifuge has been validated for all stages of citric acid recovery including fermentation broth clarification (removal of mycelium and gypsum), calcium citrate precipitation (separation of precipitated calcium citrate from mother liquor), and acidulation step (separation of gypsum from citric acid solution). For each application, the operating parameters including G-force, feed rate, disc stack configuration, and ejection interval can be optimized to achieve maximum solids removal and product recovery. The control system continuously monitors key parameters including feed rate, bowl speed, discharge cake solids, and centrate clarity, providing real-time feedback for process optimization.

The disc stack design at the heart of our citric acid centrifuge is specifically optimized for the challenging characteristics of fermentation broth. The disc stack consists of precision-engineered conical discs stacked vertically, with gap spacing optimized for mycelial and gypsum separation (0.5-1.5 mm). The disc angle (40-55 degrees) has been optimized to facilitate solids sliding while preventing plugging from sticky mycelium. The bowl is manufactured from corrosion-resistant materials; for high-chloride applications (using hydrochloric acid for acidulation), Hastelloy C22 or titanium bowls are recommended. The partial ejection mechanism removes accumulated solids (mycelium, gypsum) while the bowl continues to rotate. For broth clarification, ejection cycles may be required every 10-30 minutes. The recovered solids (mycelium + gypsum) are typically dewatered and processed for animal feed or disposed. The clarified broth (<0.1% solids) proceeds to downstream recovery (lime precipitation or solvent extraction). For the calcium citrate precipitation step, the centrifuge separates the precipitated calcium citrate (Ca3(C6H5O7)2) from the mother liquor. This step requires careful control of pH and temperature to maximize yield. For the acidulation step, the centrifuge separates gypsum (CaSO4·2H2O) from the citric acid solution after treatment with sulfuric acid. The gypsum cake is washed and discharged, while the clarified citric acid solution is sent to carbon treatment, ion exchange, and crystallization.

Our Citric Acid Fermentation Centrifuge incorporates several advanced features specifically designed for citric acid processing. The feed system includes a low-shear pump to prevent mycelial breakage. The control system provides comprehensive monitoring, automation, and data logging capabilities, built around a Siemens S7-1500 or Allen-Bradley ControlLogix PLC with a 15-inch full-color touchscreen HMI. The user interface presents key parameters including bowl speed, feed rate, discharge cake solids, centrate clarity, and pH. The system supports recipe management for different process stages (broth clarification, calcium citrate separation, acidulation). The combination of robust mechanical design and advanced process control makes our centrifuge the preferred choice for citric acid manufacturers worldwide.