Treatment of starch production wastewater. Starch production technology. Wastewater from hydrolysis and biochemical plants

Application area:

Deep grain processing
Bioethanol production
Distilleries
Starch production, including modified starch
Production of syrups, molasses
Processing of gluten and pentosans
Obtaining organic semi-finished products for further processing

During deep processing of grain, industrial wastewater with a high content of organic substances is generated, which must be disposed of. Wastewater treatment after deep grain processing is carried out using biological treatment facilities based mainly on the use anaerobic reactor.

Company EnviroChemie one of the first to develop and successfully implement for enterprises in the starch industry. It is important to note, biological treatment plants must take into account not only the composition and quantity of incoming wastewater, but also the specifics of the production itself. This will make treatment facilities more efficient and reliable, and will ensure the required quality of treatment.

One example would be anaerobic treatment plants for a manufacturing enterprise modified starch in eastern Germany.

Company EnviroChemie carried out technology design, supplied, installed and successfully launched biological treatment facilities. One of the main requirements of the enterprise was maximum education biogas and its use in an installation for generating thermal and electrical energy. The quality of treatment must meet the requirements for discharge into the local sewerage system.

Anaerobic treatment facilities provide the following treatment stages:

Preliminary mechanical cleaning
Biological acidification stage
Anaerobic treatment using 2 methane reactors Biomar ASBx

Particularly noteworthy is the peculiarity of wastewater processing at enterprises where there is production of modified starch. Wastewater is characterized by a high content of not only organic substances (up to 15,000 mg/l COD), but also has a significant salt content. Therefore, the supplier and designer of wastewater treatment plants must have some special experience and provide measures for the preparation and further treatment of wastewater. Use corrosion-resistant materials (pipelines, fittings, measuring instruments, building construction etc.).

To achieve the special requirements of discharge into a sewer or reservoir, a separate stage of post-treatment is required using systems that allow the removal of biologically persistent organic compounds, for example, the use of an ozonation unit.

Anaerobic activated sludge to launch anaerobic treatment facilities is imported by the company EnviroChemie(at the Customer's request) from similar anaerobic reactors.

Company EnviroChemie performs design of treatment facilities, provides support for construction of treatment facilities, delivers and installation of equipment, carries out commissioning work followed by commissioning.

Corn starch technology with pre-soaking grain

The technology for the production of corn starch with pre-soaking of corn grains, intended for the “wet” removal of the grain shell and germ, competes with the technology for “dry” extraction of these components.

Starch technology with pre-soaking of grain includes a number of processes: diffusion (soaking of grain), grinding, separation, dehydration, drying, storage, which are characterized by large product flows, product returns, and multi-stage processing.

The stages are discussed in detail here technological process production of corn starch, each of which is accompanied by side technological operations. For example, soaking the grain can continue after crushing it, and the release of the remaining germ can continue at the stage of isolating and washing the pulp; The separation of protein and remaining fine pulp from starch is additionally carried out at the stage of washing the starch. So:

Calculation of a drum vacuum filter for gluten dehydration

Let's look at an example. Let’s assume that for a plant with a capacity of A = 360 tons of absolutely dry corn per day, it is necessary to install a drum vacuum filter for gluten dehydration.
C" = 10 * 1004 / 100 - 10 = 111.5 kg/m3

Weight of dry residue deposited when receiving 1 m3 of filtrate

C = 115.5 * 1004 * (100 - 60) / 1004 * (100 - 60) - 111.5 * 60 = 135 kg/m3

Volumetric weight of dehydrated gluten

y0 = 100 * y1 * y2 / 100 * y1 + (y2 - y1) * w = 100 * 1004 * 1180 / 100 * 1004 + (1180 - 1004) * 60 = 1100 kg/m3

Filtration time

z1 = 140 / n * 360 = 140 / 0.5 * 360 = 0.78 min

Volume of filtrate that deposits sediment whose resistance is equal to that of the fabric

V1 = r * y0 / r * C = 1.6 * 10 11 * 1100 / 200 * 10 11 * 135 = 0.0653 m3

Filtering constant

b = 1.67 * 10 -6 * (135 * 200 * 10 11 / 1100 * 2 * 6000) = 342 min/m3

The amount of filtrate obtained from 1 m2 of surface during time z

V = (100 * y1 * y2 / 100 * y1 + (y2 - y1) * w = 100 * 1004 * 1180 / 100 * 1004 + (1180 - 1004) * 60 = 0.0155 m2/m3

The minute amount of filtrate can be determined as follows

The amount of gluten suspension produced per minute in the plant is

A * b"" / 24 * 60 * 100, tons

where b"" is the amount of gluten suspension in % of the weight of corn; b""=103%

If the suspension contains b"% gluten, then the amount of gluten per minute will be

A * b"" * b" / 24 * 60 * 100 * 100, tons

At a gluten moisture content of w%, the amount of wet gluten removed from the drum vacuum filter will be equal to

A * b"" * b" *100 / 24 * 60 * 100 * 100 * (100 - w), tons

Therefore, the minute amount of filtrate

V" = (A * b"" / 24 * 60 * 100) - (A * b"" * b" *100 / 24 * 60 * 100 * 100 * (100 - w)), tons

V" = (A * b"" / 24 * 60 * 100) * (1 - (b" / 100 - w) * 1/y, m3/min

After substitution we get:

V" = (360 * 103 / 24 * 60 * 100) * (1 - (10 / 100 - 60) * 1/1.004 = 0.192 m3/min

Active filtration surface:

F = 0.192 * 0.78 / 0.0155 = 9.67 m2

Total filtration surface:

F = (9.67 / 140) * 360 = 27 m2

Filter cake thickness:

l= V * 100 * C / Y0 * (100 - w) = 0.0155 * 135 * 100 / Y0 * (100 - 60) = 0.00475 m

The extract taken from the key battery contains 5 - 8% dry substances, depending on the method of operation of the key station and technological scheme production. The extract is of great value as a feed product, as well as a raw material for the production of ethyl alcohol, dried feed yeast or antibiotics.

To thicken the extract after preliminary filtration, it is evaporated in an evaporation unit. About 100% of the liquid extract goes to evaporation. The evaporation station consists of 2 or 3 buildings. The product being boiled has high acidity, so evaporators are made of acid-resistant austenitic steel AISI 304. The extract after thickening contains 45-46% dry matter and has an acidity of about 4 - 5% in terms of HCl

When the extract is evaporated, excessive foaming is observed, which can lead to the transfer of liquid into the steam chamber of the subsequent housing of the evaporator. Therefore, the liquid level in the apparatus must be low; the apparatus must be equipped with defoamers and foam traps.

Extract from soaking vats and collection 25 supplied to settling tank 6 to remove suspended particles by continuous settling, and from it to collection 62, from which it is sent for heating with steam to the heat exchanger 63 to a temperature of 75-80"C. Then it is boiled in evaporators (three-effect evaporator 64 ), enters the collection 72, is weighed on strain gauge scales 71 and is packed into the tank by pump 73.

The extra steam formed during boiling of the extract is condensed in a surface condenser 75 and through a barometric collector 76 pump 676 is pumped to the cooling tower. To condense the steam, recycled water from the cooling tower is supplied to the condenser pipes. Air contained in water and steam from the condenser 75 is pumped out by vacuum pump 77 and removed into the atmosphere. As necessary, the heating surface of evaporators is chemically cleaned to remove scale and other contaminants.

Calculation of an evaporation station for extract

To calculate the evaporation station, a thermal and material balance of each building is compiled. If the density of the solution entering and leaving the evaporation is known, then the amount of water evaporated can be determined using the following formula

W = S * (CB2 - CB1 / CB2),

where S is the quantity liquid solution entering the residue,

where CB1 and CB2 are the content of dry substances in the solution before and after evaporation in%,

Example. The plant processes 450 tons of absolutely dry corn per day. It is necessary to determine the steam consumption for extract evaporation and the heating surface of each housing. It is known that the amount of extract entering the evaporation is equal to 100% of the weight of corn. The extract temperature is 35"C. Juice steam from the evaporation is used to heat the extract before evaporation in heat exchangers of the first group. The initial content of dry substances in the extract is 7.5%, the final content is 40%. The heat capacity of the condensed extract is 0.93 kcal/kg "C

Heat consumption for heating the extract from 35 to 75"C, taking into account 5% losses

Q = 100 * 1 * &75 - 35) * 1.05 = 4200 kcal

Secondary steam consumption of the first body of the installation for heating the extract in the heat exchanger

E1 = Q / l - tk = 4200 / 638 - 94 = 7.7 kg

where l is the heat content of steam

where tk is the condensate temperature

Amount of water evaporated from 100 kg of extract

W = 100 (40 - 7.5 / 40) = 81.5 kg kg

We design an evaporation plant consisting of three buildings with the same heating surface. Under this condition, useful temperature differences in the enclosures should be directly proportional to the relative thermal loads and inversely proportional to the heat transfer coefficients of the individual enclosures

Let's skip some calculations

Thus, the heating surface of the housings

F1 = 204 m2

F2 = 204 m2

F3 = 204 m2

Main characteristics of raw materials and finished products for corn processing

Modern technical equipment of corn-starch enterprises makes it possible to obtain high rates of extraction and quality of starch when processing high-yielding corn varieties and hybrids with a high content of starch and low protein.

When processing corn grain we get:
To produce dry corn feed, by-products are used: extract, gluten, pulp, corn germ, and two types of feed are obtained - with and without extract.

Dry mixed corn feed with a mass fraction of 88% DM contains, %: carbohydrates - 86, protein and fiber - 76; Moreover, 100 kg of commercial feed is equivalent to 125-135 feed units. Dry corn feed is used for feeding animals in various mixtures and animal feeds. Feed must meet the following quality indicators:
Technological schemes for the production of starch from corn from Alfa-Laval

Production of starch from corn (Option 1) - without flow grinder and homogenizing separator:

Production of starch from corn (Option 2) - using an averaging separator:

Production of starch from corn (Option 3) - using a flow grinder:

When working even with the most advanced technologies for the production of corn starch in a closed circuit, a fresh water consumption of more than 2 m 3 per 1 ton of corn grain, or 3.2 m 3 per 1 ton of dry starch is required.

Due to countercurrent washing of starch and its accompanying substances with recirculating process water, fresh water consumption can be reduced to 1.8 m 3 per 1 ton of grain, but with a further decrease in it, the washing of starch from soluble substances that appear at the very beginning of the process flow worsens - when soaking grain.

The main conditions for the effective functioning and development of the starch production process flow are:

Purpose of the study: to study the fertilizing value of food industry wastewater. This category of wastewater is very diverse; enterprises are located throughout Russia. To produce their products (sugar, starch, molasses), these enterprises consume large amounts of water. Unlike many enterprises, sugar factories are concentrated in the southern and southwestern parts of the country, in the zone of chernozem soils. Wastewater treatment is carried out at most plants on filtration fields. But wastewater treatment there is carried out unsatisfactorily.

The peculiarity of sugar production is that the resulting wastewater has a high content of suspended sediment and is acidic with a high content of sodium salts. Sugar factories have two types of wastewater: conditionally clean and industrial chemically contaminated wastewater.

The first of them are discharged into open reservoirs (rivers), the second are sent to treatment facilities (filtration fields or artificial-biological treatment facilities). The fertilizing value of unclarified wastewater is average, phosphorus is almost absent.

A huge amount of earthy-calcareous sediment is formed when lime is used in production technology (clarification of sugar syrup); it easily settles, the water is clarified, and its composition improves. Clarification of wastewater from sugar factories is carried out in earthen ponds - settling tanks. After clarification, wastewater is directed and accumulated in filtration field cards. After settling in the filtration fields, the wastewater becomes alkaline, the reaction of the medium approaches neutral or slightly alkaline. The content of suspended sediment decreases slightly, and the concentration of dissolved substances reaches optimal values.

Wastewater from starch and starch factories

These plants are located in all soil and climatic zones, ranging from the zone of soddy-podzolic soils to chernozems and chestnut soils. The raw materials for production are potatoes and corn. To date, the treatment and disposal of wastewater at these plants has not been fully resolved. Most factories discharge untreated or poorly treated water into rivers, as a result of which they pollute surface and groundwater. At the same time, wastewater from starch factories is a source of fertilizers and in this regard is of interest to agriculture.

Wastewater from the production of potato starch is characterized by a high content of sediment of various organic substances, including organic acids. This wastewater quickly turns sour. In the production of corn starch, sulfuric acid and sometimes sodium alkali are used to hydrolyze corn grains. As a result, the wastewater from corn starch factories is acidic. Wastewater from starch factories and combines is divided into two types, taking into account the technological process: conveyor-washing and juice-washing. At a number of enterprises they are combined into a common stock.

As a rule, wastewater from starch factories is slightly acidic and acidic, and is characterized by a high content of dissolved substances and a bicarbonate composition. The composition of salts is dominated by calcium salts, but in the production of corn starch by the alkaline method - sodium salts.

All types of wastewater from starch factories, except for conveyor-washing and re-washing, are characterized by a high content of organic substances. Fertilizer value is high in potassium and nitrogen. The general runoff and conveyor-washing waters contain significantly less nutrients. The composition of wastewater from starch factories varies significantly throughout the day and between days. Wastewater is suitable for irrigation after averaging and dilution with clean water or conveyor-washing water. The total plant effluent is usually of a better composition for regular irrigation purposes.

Wastewater from hydrolysis and biochemical plants.

Hydrolysis and biochemical plants produce feed yeast. The starting materials for their production are agricultural waste (corn cobs, husks) and forestry waste (wood waste). Hydrolysis plants are located throughout Russia, including the eastern and northern, western and southern regions of the country.

The wastewater from these plants is very unique. They are distinguished by high color (brown-brown color), the presence of fine suspended sediment, acidic and slightly acidic reaction of the environment, high content of ammonia nitrogen, sulfates and organic substances. These features are determined by production technology. To obtain biomass, agricultural waste is hydrolyzed with sulfuric acid. Neutralization of acidic wastewater from the main stages of the technological process is carried out with ammonia water. High color, the presence of fine sediment, and a high content of organic substances are caused by the effect of sulfuric acid on biomass.

The wastewater of these enterprises in its initial state (before treatment) is characterized by an acidic reaction of the environment, a significant content of suspended sediment, a high concentration of dissolved substances, and a sulfate-bicarbonate composition. The composition of salts is dominated by calcium salts. Wastewater has a high concentration of dissolved substances, which varies widely. More than 50% of the dissolved substances are organic substances.

The reaction of the environment becomes less acidic, the content of dissolved substances in suspended sediment, organic substances, including sulfates and nutrients, decreases by more than 50%. This pattern appears under the influence of artificial biological treatment. At some enterprises, artificial-biological treatment facilities do not ensure that the composition of wastewater is brought to a condition suitable for discharge into water bodies. The cleaning effect reaches 60%. Color remains, high content of nutrients, organic substances and sulfates. After biological and mechanical treatment, wastewater from hydrolysis plants becomes suitable for irrigating agricultural crops.

Wastewater from creameries and creameries

Enterprises for the production of butter, cheese and primary milk processing are mainly concentrated in the non-chernozem zone of Russia, covering such regions as the central regions, as well as the southern regions of the non-chernozem zone of Russia. The bulk of these enterprises are located in the zone of soddy-podzolic, gray forest and leached chernozem soils.

Dairy industry enterprises are extremely diverse in capacity and, therefore, in the volume of wastewater generated. Medium and small enterprises predominate. Medium-sized enterprises annually discharge about 200-250 thousand m 3 /year of untreated or poorly treated wastewater into water bodies.

Small enterprises discharge up to 50-70 thousand m3/year of wastewater. Wastewater from milk processing plants is very unique. They contain a lot of organic substances, including many protein compounds, which quickly rot and lead to air pollution. Wastewater is characterized by a high content of fertilizer elements (nitrogen, potassium). Therefore, they are of interest to agriculture as a source of fertilizers.

The production technology does not use any toxic substances. A certain danger is posed by wastewater from the salting of cheeses, where a highly concentrated solution of sodium chloride (No. 01) of 20-25% is used. These wastewater are generated at creameries and are periodically discharged in small volumes into the general wastewater collector. As a result of these discharges, the overall flow noticeably deteriorates in many agro-reclamation indicators. It is advisable to isolate these wastewater from the total volume of wastewater from a number of dairy industry enterprises.

Tables 1 and 2 present data on the chemical composition and fertilizing value of wastewater from a number of dairy industry enterprises. Using the example of JSC Nadezhda of the Kovylkinsky butter and cheese plant of the Republic of Mordovia, which is a typical enterprise for the production of butter and cheese, data on the chemical composition of wastewater is provided for the main cycles of the technological process and the total flow of the plant. At all stages of the technological process, the resulting wastewater (fresh) has an acidic reaction and a high content of organic substances and nutrients.

The content of organic matter (COD) varies from 6.5 to 7.7 mgO/l, total nitrogen from 105 to 216 mg/l, potassium from 56 to 223 mg/l (excluding drainage from salt pools), the amount of phosphorus 18-60 mg /l. Aggressive drains are typical for salt baths. These effluents are highly concentrated. Contains 25 g of dissolved salts, a lot of sodium salts (25.3 g/l) and organic compounds (3 g/l). Such effluents must be removed from the total volume of wastewater.

A study of the chemical composition of wastewater from the Kovylkinsky Butter and Cheese Plant showed that the total wastewater of the plant from storage ponds, where wastewater is stored and settled for a long time, is characterized by a more favorable composition. It has a neutral or alkaline reaction, a lower concentration of dissolved substances (1.4 g/l), and a bicarbonate-chloride composition. The composition of salts is dominated by sodium salts. The fertilizing value and content of organic substances decreases, and the water becomes suitable for irrigation of agricultural crops. At this facility, wastewater from salt baths is removed by mobile transport, therefore, isolated from the total volume of wastewater.

Table 1. Chemical composition of wastewater from Nadezhda OJSC of the Kovylkinsky butter and cheese plant of the Republic of Mordovia by main technological cycles, mg/l

Weigh it. sediment

Dry residue

Fired. remainder

Nitrogen total.

Ammonium nitrogen.

Wastewater from equipment washing

Effluent from the boiler room

Effluent from cheese salting pools

Total flow within the plant area

Total drain pump.st. on the territory of the plant

Accumulator (general plant flow)

Average data for

general drain (storage)

Table 2. Chemical composition and fertilizing value of wastewater from dairy industry enterprises

Enterprises

Weigh it. sediment

Dry residue

Proca-lostat

Total nitrogen

Ammonia nitrogen.

Torbeevsky

creamery

Krasnoslobod-

Sky Creamery

Atashevsky Creamery

Stavrovsky Dairy Plant

Table 2 presents data on wastewater from other oil and cheese factories. The table shows the composition of the total runoff from creameries in the Republic of Mordovia and factories in the Vladimir region.

The table data shows that wastewater in its initial state (before cleaning) is characterized by an increased content of suspended sediment and dissolved substances, including organic compounds and sodium salts. Wastewater requires preparation for irrigation before use. During the treatment process, wastewater should not have a high content of suspended sediment, organic compounds and fertilizer elements. Water requires averaging, settling, and isolation of sodium salts. Considering that the waters of creameries have a high fertilizing value, it is advisable to use them for irrigation of agricultural crops and, first of all, fodder.

Having considered chemical composition main categories and types of wastewater, taking into account production technology, we can conclude that wastewater from the food industry in its initial state is characterized by a high content of suspended sediment, dissolved substances, organic compounds, an increased content of nutrients and some substances, the release of which into wastewater is undesirable .

All types and categories of wastewater, to one degree or another, require preparation for irrigation. The nature and features of their preparation for irrigation are determined by the composition of wastewater, production technology, and the peculiarities of the natural conditions of the irrigation zone. With the help of treatment, wastewater must be brought to a condition suitable for irrigation.

Until 1945, the need for starch and its products in Germany was met through the operation of 200 factories, which in the 1942/1943 season. gave about 400,000 tons of products.[...]

Most of the factories, which were 90% consumers of agricultural products and 10% of industrial products, were located in the eastern parts of the country and processed mainly potatoes. Only a few industries used cereals as raw materials.[...]

In the 1949/1950 business year in Germany there were 12 small industries processing 1C9,000 tons of potatoes, about 10 industries processing 85,000 tons of corn, rice and millet, and about 6 industries processing 19,000 tons of wheat.[...]

Since in the West there is a shortage of potatoes for starch, it must be replenished by importing from other countries.[...]

A. Potato starch factories. Processing and drying of potatoes occupy a large place, especially in the following areas: Brandenburg, Mecklenburg-Pomerania, Lower Saxony, Saxony-Anhalt.[...]

Processing of potatoes begins immediately after harvesting, since when storing potatoes, losses occur due to drying, freezing and rotting, which takes from 5 to 10%. It should be noted that if frozen, potatoes become unsuitable for starch production. All of the above led to the fact that potato processing began to be carried out seasonally (September - January).[...]

According to Maizen's patent, potatoes, processed into starch, are ground and enter the tank in the form of a thick paste. Chemical additives prevent the decomposition and saccharification of starch. Processing of this slurry is successfully carried out even in the month of May.[...]

The work process for all types of starch production is basically the same. After dry cleaning on shaking screens, the potatoes are transported by hydraulic transport to the factory. Here the potatoes are washed in drums operating on the countercurrent principle, in which, through mutual friction and excess water under pressure, they are cleaned of adhered dirt. This generates wastewater from hydraulic conveyors and from potato washing. The potatoes are then mashed in a rapidly rotating cylinder equipped with teeth. There it is thoroughly washed with water. The resulting mass is crushed in brush machines or mills. The aqueous suspension containing the bulk of the potatoes is separated on sieves from the starch milk, which is sent for re-sifting, and then into settling tanks, where the starch, having a higher specific gravity, is separated from the water, which is called “fruit water”.[...]

As a result of subsequent thorough washings, the starch is completely cleaned. During this operation, as well as during the subsequent dehydration of starch in centrifuges, wash “starch waters” are formed, having a starch concentration of up to 25C0 mg/l. With high centrifuge power, this concentration can be reduced to 25 mg/l.[...]

After drying the centrifuged material, the finished product is obtained. At new enterprises, instead of sieves, hydrocyclones are used, which ensure rapid extraction of potato starch and, moreover, with almost no losses. In this method, washing is carried out during operation, and the starch is concentrated to such an extent that it is removed from the centrifuge and can be directly sent to drying.

Due to the diversity of its properties and the ability to change them, starch is used in various food industries (confectionery, bakery, sausage, etc.), in cooking, for the production of starch products, in non-food industries (perfumery, textiles, etc.).

Caloric content of 100g of starch is 350 kcal. In plant cells, starch is found in the form of dense structures called starch grains. Starch grains of different plants are characterized by a certain shape, structure, and size. Based on these characteristics, the type of starch can be determined. Starch can be made using various plant materials. However, the production technology is slightly different. In this article we will describe the technology for producing starch from potatoes and corn.

Potato starch production

The potatoes are washed to remove dirt and foreign inclusions in a potato washer, then served for chopping. The more it is crushed, the more complete the release of starch from the cells will be, but it is important not to damage the starch grains themselves. First, the potatoes are crushed twice on high-speed potato graters. The principle of their operation is to abrade the tubers between the working surfaces formed by saws with fine teeth mounted on a rotating drum. On the first grinding graters, the files protrude above the surface of the drum by 1.5...1.7 mm, on the second grinding graters - no more than 1 mm. During the second grinding, an additional 3...5% of starch is extracted. The quality of chopping also depends on the condition of the potatoes (fresh potatoes shred better than frozen or limp ones).

After crushing the tubers, ensuring the opening of most of the cells, a mixture is obtained consisting of starch, almost completely destroyed cell membranes, a certain amount of undestroyed cells and potato juice. This mixture is called potato porridge. Starch remaining in unbroken cells is lost as a by-product of production - potato pulp. This starch is usually called bound, and that isolated from potato tubers is called free. The degree of potato grinding is assessed reduction ratio, which characterizes the completeness of cell destruction and the amount of starch extraction. It is determined by the ratio of free starch in the porridge to the total starch content in potatoes. During normal operation it should not be less than 90%. To improve the quality of starch, its whiteness and prevent the development of microorganisms, sulfur dioxide or sulfurous acid is added to potato porridge.

The nitrogenous substances in juice include tyrosine, which is oxidized under the action of the enzyme tyrosinase to form colored compounds that can be sorbed by starch grains and reduce the whiteness of the finished product. Therefore, the juice is separated from the porridge immediately after grinding. Hydrocyclones are used to separate sand from the starch suspension and separate the pulp from potato juice. The principle of their operation is based on the centrifugal force generated during rotation. As a result of processing, a starch suspension with a concentration of 37...40% is obtained. They call her raw potato starch.

Continuous pneumatic dryers are most often used to dry starch. different designs. Their work is based on the principle of drying loosened starch in a moving stream of hot air. The yield of finished starch depends on its content in the processed potatoes and on the loss of starch with by-products and wastewater. In this regard, the starch content in potatoes supplied for processing is standardized by the standard and should be at least 13...15%, depending on the cultivation zone.

When producing starch, it is produced in two forms: dry and raw potato starch. The amount of raw potato starch is determined in accordance with OST 10-103-88. There are raw starch grade A and grade B with a moisture content of 38 and 50%, respectively. Depending on the quality (color, presence of inclusions, foreign odor), raw starch is divided into three grades - first, second and third. Raw starch is a perishable product and cannot be stored for long periods; 0.05% concentration of sulfur dioxide can be used for preservation.

Dry starch is packaged in bags and small packages. Potato starch is packaged in double fabric or paper bags, as well as bags with polyethylene liners weighing no more than 50 kg. In terms of quality, starch, in accordance with the requirements of GOST 7699-78 “Potato starch” is divided into the following grades: “Extra”, highest, first and second. Starch moisture content should be 17...20%, ash content 0.3...1.0%, acidity 6...20° depending on the variety. The content of sulfur dioxide is not more than 0.005%. An important indicator characterizing the purity and whiteness of starch is the number of specks per 1 square dm when viewed with the naked eye. For “Extra” - 80, for the highest - 280, for the first - 700, for the second it is not standardized. Second grade starch is intended only for technical purposes and industrial processing. The guaranteed shelf life of starch is 2 years from the date of production at a relative air humidity of no more than 75%.

Corn starch production

In general terms, the corn processing process can be described as follows: shelled corn is softened in hot water containing sulfur. At coarse The germ is separated, and when thin, the fiber and starch are separated. The mill effluent is cleared of gluten and washed repeatedly in hydrocyclones to remove the last traces of protein and obtain high-quality starch.

CLEANING.The raw material for wet grinding is threshed corn. The grain is inspected and cobs, straw, dust and foreign materials are removed. Typically cleaning is done twice before grinding. After the second cleaning, the corn is divided into portions by weight and placed in bins. From the bunkers it is hydraulically fed into the locking vats.

SOAK.Proper soaking is a necessary condition high yield and good quality starch. Soaking is carried out in a continuous counter-current process. The shelled corn is loaded into a battery of large locking containers (tanks), where it swells in hot water for about fifty hours. In fact, soaking is a controlled fermentation, and adding 1000-2000 ppm of sulfur dioxide to the steep water helps control this fermentation. Soaking in the presence of sulfur dioxide directs fermentation by accelerating the growth of beneficial microorganisms, preferably lactobacilli, while inhibiting harmful bacteria, molds, fungi and yeasts. The soluble substances are extracted and the grains are softened. The grains more than double in volume and their moisture content increases from approximately 15% to 45%.

Scheme of grain soaking at a plant with a capacity of 150 tons of corn per day

EVAPORATION OF SOAP WATER. The steep water is drained from the grain and condensed in a multi-stage evaporation plant. Most organic acids formed during fermentation are volatile and evaporate along with the water. Consequently, condensate from the first stage of the evaporation plant must be neutralized after heat recovery by heating the water supplied for soaking. The depleted steep water, containing 6-7% dry matter, is continuously withdrawn for subsequent concentration. The steep water is condensed into a self-sterile product - a nutrient for the microbiological industry, or concentrated to approximately 48% solids and mixed and dried with fiber.

SO2 PRODUCTION.Sulfurous acid is used to soak and soften the corn grain and control microbiological activity during the process. Sulfur dioxide is produced by burning sulfur and absorbing the resulting gas with water. Absorption occurs in absorption columns where the gas is sprayed with water. Sulfurous acid is collected in intermediate containers. Sulfur dioxide can also be stored in pressurized steel cylinders.

SEPARATION OF THE EMBER . The softened grains are destroyed in abrasive mills to remove the shell and destroy the bonds between the germ and the endosperm. Water is added to support the wet grinding process. Good soaking ensures free separation of the intact germ from the grains during the soft grinding process without releasing oil. Oil constitutes half the weight of the embryo at this stage, and the embryo is easily separated by centrifugal force. Light embryos are separated from the main suspension using hydrocyclones designed to separate the primary embryo. For complete separation, the product stream with the remaining germ is subjected to re-grinding, followed by separation on hydrocyclones, which effectively removes the residual - secondary - germ. The germs are washed repeatedly in countercurrent on a three-stage sieve to remove starch. Clean water is added at the last stage.

Separating the germ at a plant with a capacity of 150 tons of corn per day

Treatment of starch production wastewater. Starch production technology. Wastewater from hydrolysis and biochemical plants

Corn starch technology with pre-soaking grain

Calculation of a drum vacuum filter for gluten dehydration

Calculation of an evaporation station for extract

Main characteristics of raw materials and finished products for corn processing

Technological schemes for the production of starch from corn from Alfa-Laval

Wastewater from starch and starch factories

Wastewater from hydrolysis and biochemical plants.

Wastewater from creameries and creameries