ITMI20101923A1 - PROCESS AND PLANT FOR THE TREATMENT AND ENHANCEMENT OF MILK SERUM - Google Patents

Description

DESCRIPTION

"PROCESS AND PLANT FOR THE TREATMENT AND ENHANCEMENT OF WHEY"

The present invention relates to a process for the treatment and enhancement of whey. More specifically, the present invention relates to a process for the treatment and enhancement of whey through an integrated plant which produces, on the one hand, a protein concentrate in liquid form and intended for zootechnical feeding and, on the other, thermal and electrical energy through the production of biogas.

Whey, the main by-product of the dairy industry, represents one of the major problems of the production cycle. In fact, it has a high load of organic pollutant (COD equal to about 70,000 ppm / liter) and, apart from a small amount destined for the production of ricotta, it is normally considered a waste to be destined for animal feed or to be sent to an aerobic waste treatment plant.

The main component of whey is lactose, a disaccharide formed by a glucose molecule and a galactose molecule that gives the milk a slightly sweet taste (its sweetening value is about 1/6 of the sucrose). Protein normally amounts to 7-8 grams per liter.

Characteristic of whey is the high percentage of water, which exceeds 93% by weight. The nutritional values are therefore all highly diluted and the transport costs are an element not to be overlooked in relation to any process of enhancement or disposal of the whey. The high percentage of lactose and the tendency to acidify due to the degradation of lactose into lactic acid by the lactobacilli constitute a further problem in the storage phase, imposing maintenance times as short as possible.

The zootechnical use of whey, although traditionally widespread in particular for pig breeding, in turn generates various problems mainly due to the high dilution and is not to be considered as an optimal solution. The aerobic treatment for disposal, on the other hand, is expensive from an energy and plant engineering point of view, as it requires large surfaces and a significant use of energy.

Among the other possible options for the use of whey, in recent years it has become possible to use it as a protein source for the extraction of whey-protein powder, to be used as an ingredient for the production of foods or supplements. for both zootechnical and human use. However, this solution does not solve the problem of disposal, as the wastewater resulting from the protein extraction process is in any case very voluminous and rich in lactose and fats, therefore with a high polluting load. The extraction of whey proteins in dry form also involves significant investment and energy costs, with returns that are not always certain.

Another option considered is that of using whey for the production of biogas through anaerobic digestion. Anaerobic digestion is a complex biological process by which, in the absence of oxygen, the organic substance is transformed into biogas, a mixture consisting mainly of methane and carbon dioxide. In the case of whey, the anaerobic digestion process, in optimal conditions, allows to obtain about 23 liters of methane from each liter of raw whey used, also obtaining a reduction of COD around 90%: at the end of the cycle the resulting sludge can be used for agricultural purposes.

However, the use of whey for energy purposes presents some obstacles, which have so far blocked its diffusion at a practical level if not in limited quantities together with other substrates: (1) the energy efficiency of whey is lower than to that of other easily available substances; (2) the high level of dilution involves transport and storage costs that are not negligible; (3) the level of acidity of the whey and the presence of various substances not useful for the aerobic process can hinder the fermentation process; (4) the existence of an economic value, albeit theoretical and discontinuous over time, makes whey less interesting than other wastewater as an energy substrate.

The European patent application EP 1 553 059 A1 describes a process and relative plant for the transformation and use of the by-products of the dairy industry for the production of biogas, which allows to overcome some of the limitations existing up to now. energetic use of whey, ensuring greater stability of the process and the possibility of using whey as the only substrate and not in connection with other substances. This process involves a fermentation phase of the above by-products for anaerobic degradation with the production of biogas, and a subsequent phase of use of the biogas for the production of electrical and / or thermal energy. Before carrying out the fermentation, the above by-products are subjected to a preliminary phase of reducing the concentration of dissolved substances, in particular calcium, magnesium and phosphate, and of isolating the protein components present in the by-products to be treated. This preliminary phase can be carried out by microfiltration, ultrafiltration or liquid chromatography.

The Applicant has now proposed to take a further step forward with respect to the state of the art through the creation of a single integrated plant for the processing of whey aimed at the production, on the one hand, of a protein concentrate kept in liquid form. and intended for zootechnical feeding and, on the other hand, for thermal and electrical energy through the production of biogas. This plant can be built in an area with a significant presence of dairy production and cattle farms, possibly in the immediate vicinity of a dairy, so as to minimize the economic-logistical problems linked on the one hand to transport costs. and storage of whey (given the level of dilution of the product in question and therefore the high volumes that must be considered) and on the other hand to the high variability of the whey-protein market, which is strongly conditioned by a limited number of large operators.

In a first aspect, the present invention therefore relates to a process for treating whey, which comprises:

subjecting the incoming whey to a phase of analysis and selection in order to separate any whey not suitable for carrying out the subsequent phases;

subject the whey to a sanitizing phase;

subjecting the whey to a degreasing step so as to obtain a fat concentration not higher than 0.5% by weight, preferably not higher than 0.3% by weight, with respect to the dry substance;

concentrating the whey thus degreased to obtain a water-based wastewater and a concentrate, said concentration phase being preferably carried out by means of a reverse osmosis process; subjecting the whey concentrate thus obtained to a membrane filtration process, to obtain a permeate containing lactose and a retentate containing whey-proteins;

subject the permeate to an anaerobic digestion process for the production of biogas;

use the retentate as a protein concentrate for the production of a processable livestock food in liquid form.

In a second aspect, the present invention relates to an integrated plant for the treatment of whey, which comprises:

at least one station for analyzing and selecting the incoming whey in order to separate any whey not suitable for carrying out the subsequent steps;

at least one storage tank for the selected whey;

at least one whey sanitizing system;

at least one device for degreasing the whey arriving from said at least one storage tank;

at least one device for concentrating the whey thus defatted to obtain a water-based wastewater and a concentrate;

at least one membrane filtration device of the concentrate, so as to obtain a permeate containing lactose and a retentate containing whey-proteins;

at least one anaerobic digester fed with said permeate for the production of biogas;

at least one device for emulsifying the retentate with other components for the production of a processable zootechnical food in liquid form.

Preferably, the plant according to the present invention further comprises at least one device for homogenizing and cooling the emulsion thus obtained.

The present invention is further illustrated below, also with reference to the attached Figure 1, which shows a flow diagram of the process according to the present invention.

The incoming whey is subjected to a preliminary phase of analysis and selection, in order to verify the quality and characteristics of the raw material, separating the different types of whey on the basis of their characteristics, in particular pH, presence of cheese-making residues, dry matter content, etc. This selection allows you to separate any unsuitable serum for subsequent processing. Preferably, the incoming whey is selected in order to separate any whey having a pH value lower than 5.8.

The whey separated as it is not suitable for carrying out the subsequent phases can be sent to other processes or, preferably, it can be added to the zootechnical food subsequently produced, as better illustrated below.

The selected whey is then stored at a temperature from 2 ° C to 10 ° C, preferably at about 5 ° C. The cooling of the whey has the purpose of blocking bacterial fermentation processes that can develop inside the product. In this way, two results are achieved:

guarantee the healthiness of the product, considering that it will then be used for zootechnical feeding and possibly for the extraction of components also destined for human use;

avoid the formation of lactic acid, which hinders the extraction of proteins and reduces the energetic power of the whey.

The cooling and subsequent maintenance of the whey at a controlled temperature allows the whey to be stored for a few days, thus allowing the decoupling of the different production phases according to the processing and organizational needs.

The low temperature storage phase can be carried out in at least one tank, preferably a plurality of tanks, where the whey is stored and possibly a mixing of the whey coming from the adjacent dairy and possibly from external suppliers is carried out. The whey coming from the dairy adjacent to the plant can be received at a temperature up to 55-58 ° C and will be rapidly brought to a temperature from 2 ° C to 10 ° C, preferably equal to about 5 ° C, for example by passage through a heat exchanger fed by a primary circuit coming from a water-cooled refrigeration unit. If whey coming from external suppliers is used, this will reach at least one storage tank already at low temperature, and can be previously stored in stainless steel tanks with external insulation.

The total capacity of the storage tanks is preferably such as to allow the tanks to be emptied in a period not exceeding 24 hours.

The degreasing phase has the purpose of bringing the concentration of fats in the whey from about 0.8% by weight on the dry matter (s.s.) (value typically present in the whey) to a value not exceeding 0.5% on the s.s. , preferably not higher than 0.3% on s.s. The percentage on the s.s. it is expressed as weight / weight.

The degreasing phase can be carried out before storage at low temperature or later, when the whey is introduced into the treatment plant. In any case, the whey degreasing phase is carried out before the concentration phase, as the fat molecules are larger than the other particles of interest and would obstruct the membranes used for the concentration phase, decreasing their size. ™ effectiveness.

The degreasing step is preferably carried out by skimming, in particular by centrifugation.

As indicated above, the whey is also subjected to a sanitization phase, which can be carried out on all the whey or only on some batches according to the analyzes, depending on the needs. This eventual sanitation phase has the purpose of blocking the natural fermentation of the whey through the inactivation of bacteria (both exogenous and endogenous).

The sanitization phase can be carried out at different moments of the process, for example immediately before the degreasing phase or immediately after said phase, or even after the concentration phase.

Sanitization can be carried out by pasteurization, ie heating the whey up to about 70 ° C, and subsequent rapid cooling. Alternatively, the sanitization phase can be carried out by microfiltration, ie passage of the whey through membranes having a porosity of such dimensions as to retain the bacteria and leave the other molecules unaltered.

If microfiltration is used, the sanitizing phase must be carried out after the degreasing phase, as the presence of grease is contraindicated in all membrane processes.

In the process according to the present invention, the concentration step is preferably carried out by reverse osmosis, and allows to reduce the volume of the whey being processed thanks to the extraction of the water, without altering the other components. As is known, in reverse osmosis the passage of the solvent molecules (water) from the more concentrated solution to the less concentrated solution is forced, applying a pressure greater than the osmotic pressure to the more concentrated solution.

The water-based wastewater obtained from the concentration phase is preferably used for the dilution of the permeate for the subsequent biogas production phase. Optionally, this wastewater can also be initially used in the washing processes of the plant and any attached dairy, so as to reduce water consumption by the plant.

The concentration step is preferably carried out by reverse osmosis at a temperature from 15 ° C to 35 ° C, in order to increase the efficiency of the process. In fact, carrying out reverse osmosis on still cold whey, that is around 5 ° C, would significantly reduce the efficiency of the process. Alternatively, the concentration phase can be carried out with effect evaporators (low pressure evaporation).

The whey concentrate thus obtained is then subjected to a membrane filtration process, which allows to separate the protein fraction to be used for the production of zootechnical food from the lactose to be used for the production of biogas. In particular, the membrane filtration process can be an ultra-filtration or nano-filtration process, mainly as a function of the average pore size of the membranes used.

By exploiting the different dimensions of the molecules that are passed through membranes with predetermined porosity, the membrane filtration step allows to separate the protein components (retentate) from the other parts of the whey (permeate).

The retentate obtained from the process according to the present invention is a liquid protein concentrate preferably having a concentration from 15% to 20% s.s. and a protein share from 25% to 60% by weight with respect to the weight of the s.s ..

The retentate thus obtained is eventually subjected to a second concentration process, for example by means of an effect evaporator (evaporation in low pressure) in order to further reduce its volume and facilitate its workability and transportability. In this case the retentate obtained is a liquid protein concentrate preferably having a concentration from 25% to 35% of s.s. and a protein share from 25% to 60% by weight with respect to the weight of the s.s ..

The permeate obtained from the process according to the present invention is an aqueous phase preferably having a concentration from 15% to 20% s.s., containing high quantities of lactose. It is a product with little or no economic value in itself, which would be difficult to dispose of as it keeps the COD present in the starting whey almost unchanged. In accordance with the present invention, the permeate can be effectively used as a substrate for the production of biogas and therefore of electrical and thermal energy. It will then be collected and channeled to the anaerobic digestion plant.

Downstream of the membrane filtration phase, the permeate is sent to a collection tank, which also acts as a system compensator. In this tank, the permeate is preferably diluted in such a way as to obtain a concentration of s.s. preferably from 2% to 5% with respect to the total volume. For dilution, the aqueous wastewater obtained from the concentration phase can preferably be used, possibly after having used it in the washing processes. In the event that the volume available is not sufficient, this wastewater can be integrated with the wastewater coming from the dairy (washing water and the like) and possibly with water taken from the well or recovered at the end of the digestion process. In this way, water flows that come from other processes are completely reused.

The diluted permeate is then introduced into the anaerobic digester where, under controlled pH and temperature conditions, the biogas formation process takes place. The capacity of the digester is determined as a function of the working time of the bacteria involved in the process. The efficiency of the system is equal to about 90% of the organic component "digested" with a production of biogas of about 0.5 Nmc for each kilogram of dry matter treated. A fluid with a much lower organic pollutant load than the initial one comes out of the digester, a load that allows direct disposal into the sewer system or, after adequate pre-treatment, reuse for dilution of the permeate entering the digester. Separately, the saline-looking digestate sludge is separated for agricultural use as soil improvers. Further details on the biogas production process are reported in the aforementioned patent application EP 1 553 059 A1.

The biogas leaving the digester is generally subjected to a desulphurisation treatment, and sent to a collection tank and then to the cogeneration group. This group supplies electricity with an efficiency of approximately 38% of the primary energy introduced while 45% can be recovered in the form of thermal energy.

The electricity quota, after transformation, can be used for self-consumption or sold to third parties. This is electricity from renewable sources which, if all other possible conditions envisaged by the legislation in force are met, will be able to benefit from the relative concessions. As far as thermal energy is concerned, it can be partly used directly at the whey processing plant for the production of calories and refrigeration, at the dairy in the vicinity of which it is suggested to build the plant, or possibly be transferred to third parties.

The retentate containing whey-proteins has a preferred destination in the formulation of a zootechnical food to be processed, stored, transported and administered always in the liquid phase.

The heart of the zootechnical food production process is the emulsification phase, i.e. mixing the retentate obtained according to the invention described in the previous steps with a mixture of animal and vegetable fats and at least one emulsifier, so ¬ to obtain an emulsion.

Preferably, the retentate is previously enriched by adding whey, for example concentrated whey obtained from the above concentration step and / or whey as it is, including any whey having a pH value lower than 5. , 8 ("not sweet" serum). Dairy by-products such as buttermilk, unsuitable excess or expired milk, etc. can also be added.

Other components can also be added to the emulsion such as: soy lecithin, trace elements, vitamins, amino acids, cereals or their derivatives, and other useful supplements for zootechnical nutrition, based on the final formulation desired by the nutritionist.

The emulsification phase is carried out hot, in particular at a temperature between 54 ° C and 58 ° C, so as to keep the fats in the liquid phase and obtain an optimal and homogeneous mixing.

The emulsion thus obtained is then subjected to a homogenization phase for one or more cycles at a high pressure (200 bar). During the homogenization operation, the fat particles present in the mixture fragment into very small droplets, and their stability in emulsion with water increases.

The zootechnical food thus obtained in liquid form is rapidly cooled, preferably at 3-5 ° C and stored at a temperature not exceeding 8 ° C. The cooling phase allows to obtain the crystallization of the fat droplets for their optimal digestibility, in addition to improving the shelf life of the product.

The optimization of the formula and the specific mixture of fats and the emulsification and above all homogenization phases allow not only to add the nutrients necessary for the correct feeding of the animals to the protein substrate, but also to increase digestibility and above all the duration of the food thus produced, which can be stored - if kept below 8 ° C - up to 10-12 days. This is an innovative element compared to other experiences of feeding calves with feed based on whey proteins processed in the liquid phase, which are normally carried out only for self-consumption and therefore do not require particular measures to increase their storage times.

The zootechnical food thus obtained is particularly suitable for feeding calves. Before use, it can be suitably diluted and mixed with other ingredients according to the rationing plans formulated by the reference nutritionists.

It should be noted that, according to the process in accordance with the present invention, it is possible to allocate to the two main uses (biogas and zootechnical food) not the entire production of retentate and permeate but only a part, withholding a quota for alternative uses. , such as in particular the extraction of proteins and / or other fractions to be used for other purposes (ingredients for the food, pharmaceutical, cosmetic, chemical sectors; food supplements; etc.).

The part of the plant intended for food production preferably includes a series of storage tanks for the protein concentrate and various other ingredients (vegetable fats, animal fats, cereals, supplements), in order to decouple the food processing compared to the previous production phases and being able to vary the mixtures according to the different breeding needs. From the tanks, the different ingredients will first be sent to an emulsifier, where the supplements are mixed with the protein concentrate obtained from membrane filtration. Subsequently, the product is homogenized and possibly pasteurized at about 70 ° C, to be then cooled and pumped into the storage tanks from where it can be taken for shipment to end users.

The food thus obtained has greater nutritional and traceability characteristics of the product than the foods normally used for feeding the calf, thanks to the fact that the whey is always kept in the liquid phase and that all processing, from harvesting of the whey to its transformation and then the zootechnical use, take place in a circumscribed and easily identifiable and traceable geographical area.

By avoiding the complete drying phase of the whey-proteins, it is also possible to obtain a considerable saving in the processing and production costs of the food, given the significant energy consumption of the drying phase and the subsequent need to re-dilute the product for the administration.

Finally, it should be noted that the process in accordance with the present invention is suitable for small-medium scale realizations (with 250 tons / day of incoming whey, about 23.3 tons / day of protein concentrate and 500 kW of electricity are obtained biogas) and therefore lends itself well to the use of even that whey which, due to dimensional or organizational aspects of the dairies, does not enter the dried product circuit. It will also be possible to insert a certain quantity of buttermilk and milk into the process, thus offering an alternative outlet, for zootechnical use, to excess or unsuitable products for traditional uses.

Claims (16)

CLAIMS 1. Process for treating whey, which includes: subjecting the incoming whey to a phase of analysis and selection in order to separate any whey not suitable for carrying out the subsequent phases; subject the whey to a sanitizing phase; subjecting the whey to a degreasing step so as to obtain a fat concentration not higher than 0.5% by weight, preferably not higher than 0.3% by weight, with respect to the dry substance; concentrate the whey thus defatted to obtain a water-based wastewater and a concentrate; subjecting the whey concentrate thus obtained to a membrane filtration process, to obtain a permeate containing lactose and a retentate containing whey-proteins; subject the permeate to an anaerobic digestion process for the production of biogas; use the retentate as a protein concentrate for the production of a processable livestock food in liquid form. Process according to claim 1, wherein the selected whey is stored at a temperature from 2 ° C to 10 ° C, preferably at about 5 ° C. Process according to any one of the preceding claims, in which the sanitizing step is carried out immediately before the degreasing step or immediately after said step, or also after the concentration step. Process according to any one of the preceding claims, in which the concentration step is carried out by reverse osmosis. 5. Process according to claim 4, wherein the reverse osmosis is carried out at a temperature from 15 ° C to 35 ° C. Process according to any one of claims 1 to 3, in which the concentration step is carried out with effect evaporators. 7. Process according to any one of the preceding claims, in which the retentate obtained from the membrane filtration step is a liquid protein concentrate having a concentration from 15% to 20% s.s. and a protein share from 25% to 60% by weight with respect to the weight of the s.s. Process according to any one of the preceding claims, in which the water-based wastewater obtained from the concentration step is used for the dilution of the permeate for the subsequent biogas production step. Process according to any one of the preceding claims, in which the retentate is subjected to a second concentration process. 10. Process according to claim 9, wherein after the second concentration process a liquid protein concentrate is obtained having a concentration of from 25% to 35% of s.s. and a protein share from 25% to 60% by weight with respect to the weight of the s.s .. Process according to any one of the preceding claims, in which the production of the zootechnical food comprises an emulsification step by mixing the retentate with a mixture of fats of animal and vegetable origin and at least one emulsifier, so as to obtain an emulsion. 12. Process according to claim 11, in which the retentate is previously enriched by adding whey. 13. Process according to claim 11 or 12, in which the emulsification step is carried out hot, in particular at a temperature between 54 ° C and 58 ° C. 14. Process according to any one of claims 11 to 13, in which the emulsion thus obtained is subjected to a step of homogenization and subsequent rapid cooling. 15. Integrated plant for the treatment of whey, which includes: at least one station for analyzing and selecting the incoming whey in order to separate any whey not suitable for carrying out the subsequent phases; at least one storage tank for the selected whey; at least one whey sanitizing system; at least one device for degreasing the whey arriving from said at least one storage tank; at least one device for concentrating the whey thus defatted to obtain a water-based wastewater and a concentrate; at least one membrane filtration device of the concentrate, so as to obtain a permeate containing lactose and a retentate containing whey-proteins; at least one anaerobic digester fed with said permeate for the production of biogas; at least one device for emulsifying the retentate with other components for the production of a processable zootechnical food in liquid form. 16. Plant according to claim 15, further comprising at least one device for homogenizing and cooling the emulsion thus obtained.