Lactic acid production

ZAVKOM-ENGINEERING designs and supplies equipment for lactic acid producing companies.

Lactic acid is an organic acid often found in nature. It is metabolism product of many plants and animals (including humans), it participates in the metabolism of almost all living organisms.

Lactic acid is purposefully produced by lactic acid bacteria, for which it is one of the main metabolic products (for example, as alcohol for yeast). This process is called lactic acid fermentation, and it has been widely used since ancient times to produce lactic acid products, as well as in the processing of vegetables and fruits (for example, sauerkraut, etc.).

Lactic acid is widely used in the food industry, beverage production, public catering, medicine and cosmetology, animal husbandry and many other industries. A fairly large amount of lactic acid is used to produce biodegradable polymers — polylactides due to rising prices for oil and other fossil resources, as well as due to stricter environmental regulations and requirements in many countries. Polylactides decompose quite quickly (from 1 month to 1 year) under natural conditions having almost all the properties of traditional polymer materials (polyethylene, polypropylene, etc.), carbon dioxide and water are the final products of their decomposition. Currently, polylactides are used to produce disposable tableware, packaging and containers for food, as well as medical materials (suture materials, implant parts, etc.).

Annual global increase in polylactides production, and accordingly, the need for lactic acid, is 5-7%.

In General, there are two main stages in lactic acid and its polymers production:

  1. Production of lactic acid itself;
  2. Production of polymer materials based on lactic acid.

1. Lactic acid production

Lactic acid production from grain raw materials can be divided into several main stages.

  1. Grain raw materials acceptance and cleaning.
  2. Starch suspension obtaining.
  3. Starch to sugars hydrolysis.
  4. Lactic acid fermentation.
  5. Fermented solution processing with slaked lime.
  6. Filtering.
  7. Calcium lactate crystallization.
  8. Calcium lactate cleavage with sulfuric acid.
  9. Lactic acid cleaning, filtration and concentration.

The first two stages are generally similar to those used in gluten from grain production. Starch suspension hydrolysis is performed in continuously operating reactors using enzyme preparations, or can be combined with the fermentation stage.

Lactic acid fermentation is carried out periodically or continuously in special apparatus-reactors. The necessary medium temperature and pH are maintained in the apparatus, the medium is constantly mixed and aerated (if necessary) during lactic acid fermentation. The process takes from 3 to 5 days (periodic fermentation method), lactic acid concentration can reach 20% in the fermented substrate.

Further stages of lactic acid production (processing with slaked lime and acid, filtration, crystallization, purification and evaporation) are more typical for the chemical industry than for the food one.

2. Lactic acid based polymers production

In General, the process of lactic acid biopolymer obtaining can be divided into two main stages:

  1. Lactide preparation (a chemical consisting of two lactic acid molecules).
  2. Polylactic acid preparation (polylactide-PLA).

Both stages are connected with catalytic chemical reactions conducting. The reactions take place at relatively low temperatures (150-200 оС), in a vacuum, using zinc and tin catalysts, the polymer yield is at least 70% of the initial lactic acid mass.

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