Citric acid is one of the most indispensable and frequently used organic acids. It is in widespread use as an acidifier, a pH buffer and — in combination with other materials — as a preservative by the food processing and beverage industries. Its sequestration characteristics and its biodegradability make it a favored ingredient in detergents, pharmaceuticals and cosmetics.
Citric acid occurs naturally in various citrus fruits. To cover the industrial demand, large scale production of citric acid is based on various starch hydrolysates, cane or beet molasses, and from sugar.
Vogelbusch process for citric acid production
A proprietary strain of Aspergillus niger is used for citric acid fermentation. The product is subject to a series of isolation, purification and finishing steps.
Due to the widely differing levels of impurity of substrates, Vogelbusch has customized technologies for raw material processing which are adapted to the individual situation.
Molasses often requires hexacyanoferrate clarification, with simultaneous boiling and sterilization.
In the case of starch hydrolysates with relatively low impurity, as well as with sugar solutions, raw material preparation consists of decationization and subsequent continuous sterilization.
Vogelbusch licenses own strains of Aspergillus niger that have been selected and improved for industrial citric acid fermentation.
We match our fermentation procedures precisely to the raw material employed as to maximize yields. To start the process the fermenter is inoculated with spores, which are propagated and pilot tested on site. The well-aimed addition of nutrients, trace elements and specific inhibitors regulates the metabolic activity of the micro-organisms and thus provides for constant high production rates.
Our bubble column (air-lift) fermenter system for submerged citric acid fermentation stands out for its simple design and low energy consumption.
A precondition for an efficient microbial production process is the availability of high-quality inoculation material. In the case of citric acid synthesis, the inoculation material is added to the fermenter in the form of spores. Taking account of the demand for high quality for this material, Vogelbusch has developed appropriate technology for spore propagation, harvesting and testing. The spores are dried which improves the storage stability as well as the ease of dosage.
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Summary of process parameters achieved in the Vogelbusch fermentation process on the examples of a pure substrate (raw sugar, glucose, hydrolysate) and molasses. Depending on raw material quality and the impurity of the fermented mash, a yield of 90 to 92% is achieved in the product isolation and purification stages.
|Yield||g CAM/g DS*||min 0.84||min 0.80|
|Final concentration||g CAM/l||min 140||min 100|
*) fermentable sugars as disaccharide
The object of citric acid isolation is to obtain a largely pre-purified citric acid solution from the fermented mash. The mash is subjected to several process stages to separate the mycelium and to isolate the citric acid solution.
While most of our plants use the traditional lime-sulphuric acid process for purification this step can be substituted now by chromatographic methods.
The final purification of the citric acid is effected by treating the isolated citric acid solution with activated carbon, cation and anion exchange resins in fixed bed reactors. Thanks to their automation and reactor design concept, these process stages also meet all the demands of a modern production process.
For final processing the citric acid solution is treated in multistage falling film evaporators combining the advantages of delicate product handling with high energy efficiency. The specific energy requirement can be reduced even further by thermal vapor compression or alternatively by mechanical vapor compression.
Continuously operated forced-circulation vacuum crystallizers are used for the crystallization of the citric acid. The appropriate measuring and control strategies, and a crystallizer design matched to suit them, allow Vogelbusch plants to produce citric acid monohydrate as well as anhydrous using the same equipment. Sophisticated strategies for the recirculation of the mother liquor, separated from the crystal mash in a continuous centrifuge, allow for effective control of the quality of the final product.
Fluidized bed drying takes full account of the high demands for the quality of the final product by providing delicate product handling. Subsequent screening of the dried final product allows customer-specific fractioning according to particle size.
Citric acid is available in both powder and liquid forms. Our product purification and crystallization processes are compatible with a wide range of product grades including
and comply with international quality standards for food, industrial and pharmaceutical grades, including BP, USP and FCC.
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All figures given here are typical and can vary depending on plant configuration and equipment.
|Consumption for 1,000 kg CAM|
|Process water *||48||m³|
|Cooling water 24 °C **||470||m³|
|Cooling water 29 °C ***||260||m³|
|Steam 9 bar||7,200||kg|
|Consumption for 1,000 kg CAM|
|Sugar content *||50||%|
|Process water **||45||m³|
|Cooling water 24 °C ***||550||m³|
|Cooling water 29 °C ****||280||m³|
|Steam 9 bar||7,200||kg|
The plant of Kimia Gharb Gostar Industries Industries Co. has a capacity of 36 tons per day and is the first citric acid plant set up in Iran. It is suitable for processing of raw sugar and sugar beet molasses. The process concept allows for a choice between production of either...
Raw sugar from local production was the substrate of choice for Citro Misr Co. of Egypt. This raw material required a new approach in the fermentation process to assure the economic feasibility of the plant. The spore cultivation was adapted and the fructose utilization was optimized for the substrate. Products include...
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The minimum plant capacity for an economic production of citric acid is 10,000 tons per year.
For a 10,000 tons per year facility 3 - 5 hectare are required.
Capital expenditure always depends on plant capacity and configuration as well as local conditions. Costs for the process plant (excluding building, auxiliaries, infrastructure) are from euro 25 million upwards.
This figure is for general reference only since each project has its own particularities that need consideration.
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