A technology of rational beet pulp usage

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A TECHNOLOGY OF RATIONAL BEET PULP USAGE

Kravchenko R.А.,

Chernikov A.M.

The increase in profitability of beet sugar production depends on several factors. These include production modernization, introduction of energy-saving and waste-free technologies, allowing to fully recycle all the waste including beet pulp which is a demanded commodity product.

Food processing industry is in dire need of pectin substances and beet pulp, which contains them in great amounts, can become a valuable source.

However, raw beet pulp is often taken to the fields and ploughed into the soil. Wasting livestock forage and substratum for pectin production is not only thriftless, but also harmful. Application of beet pulp into the natural environment on a large scale in the autumn-winter period can disrupt the safe sanitary and epidemiological situation.

The main factor destabilizing sanitary and epidemiological situation in the ecosystems is the number of rodents which can increase as a result of leaving beet pulp in the fields and thus creating a food potential for rodents' nutrition and reproduction.

Several factories remove pulp to fields and disseminate it there instead of drying it. In the spring they plough the remains of beet pulp and thus create the illusion of solving the problem of pulp utilization.

Removal of the pulp to the fields and disseminating it there in the autumn-winter period allows rodents to pass the winter successfully and reproduce more actively in the spring. A great number of rodents often results in increasing the population of mites - transmitters of dangerous illnesses. Rodents are also hosts to ectoparasite insects (fleas, lice, mites) whose reproduction threatens with a “renaissance” of medieval epidemics. Therefore, the increase of food potential for rodents must be avoided by all means. However, it is also necessary to utilize the beet pulp.

Special mention should be made to the danger, posed by removal beet pulp mixed with defecate (filtration sludge) to fields. Pure defecate can be removed to fields as it is a fertilizer, does not present a food source for rodents and does not constitute a threat to sanitary and epidemiological safety. However, mixed with pulp it becomes even more attractive for rodents.

Beet pulp has been thrown into cloughs and ravines, which inflicted great damage on the environment. Such actions destroy natural ecosystems. Rotting biomass leads to the demise of soil invertebrate animals. Beet pulp water runoff poisons water fauna, primarily fish.

The problem of beet pulp usage and technologies of its recycling in theory in practice is a topical issue and a number of studies is dedicated to it [1], [2], [3] etc.

Beet pulp composition and properties

Beet pulp is a byproduct of beet sugar production with the following volume of generation: raw - 80-83% of beet weight, dried - 5, 5 - 6, 5% of beet weight.

In its structure pulp is a complex colloid capillary-porous material, cells and intercellular space of which are filled with water with a low content of saccharose. The bond between moisture and beet pulp can be categorized as physico-chemical (adsorptive and endocellular) and physico-mechanical (capillary and wetting). When pressing the pulp mainly physico-mechanical moist is removed. If we take the content of moisture in raw pulp as 100%, then it falls into two categories according to the possibility of mechanical removal: not removable mechanically (adsorptive, endocellular) - 20%; removable mechanically, i.e. by pressing (capillary and wetting moisture) - 80% [5, P. 120].

If stored for long periods, raw pulp sours. 25-50% of dry solids (including all the sugar and nearly all the pectin substances) are lost in sour pulp as a result of biochemical and microbiological processes of souring. Sugar and pectin substances transform to lactic, acetic, oleic and other acids. [5, P. 122]

The properties of beet pulp are mainly defined by those of pectin substances, which constitute approximately 50% of dry solids of dried pulp. Apart from that, it contains about 47% of cellulose and hemicellulose, 2% of protein, 1% of alkali, saccharose, organic acids, vitamins, microelements [5, P. 120]. 1 kg of dried beet pulp contains 0, 84 of a food unit. 100 kg contain 4 kg of digestible protein.

Pectin substances or pectins are polysaccharides formed with the remains of galacturonic acid. The term “pectin” derives from an ancient Greek notion meaning “coagulated, frozen”. It is worth while noting the origin of the word for it is a real prompt from the past.

Dried beet pulp is the primary product for pectin production. Pectin is widely used in food processing industry.

The traditional technology of beet pulp drying

Fresh pulp, coming out of the diffuser, is pressed until solids content is 12 - 25 %, which allows to return the press pulps water for diffusion, reduce the cost of fresh pulp transportation and spend less fuel on its drying. The pulp intended for feeding to cattle in raw state is pressed until solids content is 12 - 14 %, and the pulp intended for drying - until solids content is 22 - 25 % [5, P. 119].

Under the conditions of a sugar factory the cost of heat energy is many times greater than that of mechanical energy, so usually manufacturers aspire for fully mechanical pulp dehydration thus reducing the fuel spending for its drying [5, P. 120].

However, there are several factors determining theimpracticality of drying beet pulp according to the traditional technology. These include high humidity of the pulp passed for drying (approx. 75%), high energy capacity and length of drying, damage to the environment. 300 mі of natural gas is spent to produce 1 t of dry beet pulp, while all the combustion gases are released into the atmosphere.

42-46 million t of sugar beet is grown in Russia every year. Theoretical volume of dry beet pulp can reach the level of 3, 5 million t. Assuming that we will dry all the beet pulp according to the traditional technology, the gas expenditure will constitute an amount, comparable to that of gas export to certain countries of Western Europe.

Let us consider the problem using the Kursk region as example. This region has its own ancient traditions of sugar refining. Nowadays up to 4, 5 million t of sugar beet is grown here yearly, and this number can be bigger. Hypothetically sugar industry in the region could produce up to 300 000 t of dry beet pulp (which is 250 000 t of grain in fodder equivalent). But that would require burning 90 000 000mі. Using traditional high-temperature drying means that approx. 300mі of carbon dioxide per 1 t of dry pulp would have to be released into the atmosphere.

In April of 2016 Russian Federation joined the Paris Agreement of combat against climate change. This agreement is aimed at reducing greenhouse gas emission into the atmosphere, including carbon dioxide.

Every year beet sugar industry in Russian Federation possesses an amount of raw beet pulp, enough for producing more than 3, 5 million t of dry pulp.

Beet pulp drying according to the traditional technology would require burning 10, 5 billion m³ of natural gas yearly and releasing the same amount of gas into the atmosphere. That is a great damage for the environment, but there is an alternative technology.

An alternative technology

An alternative technology of beet pulp drying using forced ventilation reduces the expenditure of natural gas and emission of carbon dioxide into the atmosphere by 18, 9 times. Other advantages of this technology include:

· ecological cleanliness (with traditional technology dry beet pulp is contaminated with combustion gases)

· high productivity and economic efficiency.

Production of dry beet pulp using forced ventilation [4] allows to fully recycle this byproduct of beet sugar production into a valuable commodity product while reducing its prime cost by two or three times.

The suggested technology includes four stages: 1) pressing-out; 2) granulating; 3) forced ventilation; 4) drying.

After the pressing-out on the deep-pressing machine the beet pulp is granulated on rotatory press. Then most of moisture is removed from the grains using forced ventilation until the humidity is 20 - 25 %, after which the grains proceed to the drying units, where they are dried until the humidity is less than 13%.

Previously it was thought impossible to use forced ventilation for beet pulp drying. Experts were convinced that the air for ventilation has to be heated. However, beet pulp should be ventilated with cold air, not heated (remember: pectin - “coagulated, frozen”). This is so because of pectin substances' properties. These substances dissolve well in hot water, but are virtually indissoluble in cold water. Beet pulp pectins are water-saturated, but when the temperature is lowered, the three-dimension structure of its molecules changes, which leads to water disengagement. During forced cold air ventilation pectin gives associated water into intergranular space, from where it is removed by the air flow. Humidity of ambient air should also be considered during forced ventilation. The less it is, the easier it will be to remove the moisture.

Removing the basic mass of water from beet pulp allows for tremendous economy of natural gas (by 18, 9 times) during final drying, reduces the time of drying and increases the productivity of drying equipment [4].

It is reasonable to ventilate beet pulp on an open platform under a canopy (a canopy is needed in order to prevent precipitation reaching the pulp) in virtually unlimited amounts. This way the humidity of beet pulp reduces to 20-25%, while mass and volume reduce by several times.

Ventilated pulp with humidity 20-25% is not intended for long-term storing, but endures short-term storing without souring or losing nutritional value. This allows using it fully as forage for livestock animals or primary product for producing pectin substances.

When ventilated, beet pulp conglutinates because of pectin substances polymerization, this is why in order to be used for cattle forage it has to be shattered and also steamed for better nutrient availability.

Transportation of ventilated pulp (solids content - 75-80%) is more than four times as cost-efficient as transportation of pressed pulp (solids content - 15-18%). 1 t of ventilated pulp contains 750-800 kg of nutritional substances, while the same mass of pressed pulp only contains 150-180 kg, therefore, one trip of a freight vehicle with ventilated pulp delivers as much nutritional substances to a farm as 4-5 trips of the same vehicle with pressed pulp would.

The expenditure of natural gas on drying a unit of dried beet pulp decreases by 15-20 times, and although power consumption increases by approx. 2 times, the general energy capacity reduces many-fold because of gas economizing.

A complex of ecological problems is solved: products of combustion gases, used for pulp drying, are emitted into the atmosphere in much smaller amounts, pulp water disposal into the environment is eliminated as well as littering fields with sugar beet byproducts, disturbance of phytosanitary and sanitary and epidemiological condition of fields and removal of raw pulp to unauthorized landfill sites.

sugar beet pulp drying

Список литературы

1. Бабенко Д. С. Разработка способа обезвоживания свекловичного жома методом прессования в поле вибрационного воздействия: дис. … канд. тех. наук: 18.12 / Бабенко Денис Сергеевич. - Воронеж, 2008. - 179 с.

2. Дыганова Р. Я. Технология переработки свекловичного жома с использованием биоэнергетической установки / Р. Я. Дыганова, З. Р. Зайнашева // Ученые записки Казанской государственной академии ветеринарной медицины им. Н.Э. Баумана. - Выпуск № 1, том 221. - С. 64 - 67

3. Мхитарян Г.А. Современные технологии переработки свекловичного жома / Г.А. Мхитарян, А.П. Леснов, В.М. Ткаченко // Сахарная свекла. - - №2. - С. 33 - 35

4. Патент на изобретение РФ № 2542530 Способ получения сушеного свекловичного жома. - Бюл. - 2015 - № 5

5. Сапронов А.Р. Технология сахарного производства / А.Р. Сапронов. - М.: Колос, 1999. - 495 с.

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