The present invention was developed at 1ST, in the waste recovery field, with applicability in the brewing industry and in the use of membrane filter presses for waste dehydration.

This invention consists in the development of a dehydration process of BSG, as it proceeds from the beer production process, with moisture content between 72% and 85%, for a stabilized BSG, and with a moisture content of 15%, maintaining the protein, fibre and lipid content of the initial BSG.

The BSG, a brewing industry by-product, is the solid fraction (72%- 85% moisture) obtained during the lautering (or mash separation) stage that occurs after the mashing.

This by-product is rich in proteins, fibres and lipids, besides several organic compounds as vitamins and antioxidants polyphenols.

The BSG, due to its moisture content, is easily degraded at temperatures greater than 2 °C by microorganisms, and the process is accelerated by temperature increase. The degradation process causes the destruction of proteins and other organic compounds, forming butyric acid and other compounds with intense bad odours , and the development of fungi .

In Europe, the BSG is used, as it proceeds from the beer production process, in cattle feed, ensuring that its consumption occurs within 3 to 4 days after production. Anyway, this is a non stabilized product, with minimal commercial value.

After conducting a state of the art search, it has been found that the BSG dehydration processes currently available are the following: a) BSG dehydration to levels of 10% - 15% with a fluidized bed or rotary dryer using hot air in countercurrent . This is an expensive process due to high energy demand, even using energy from co-generation units. b) BSG dehydration first using a screw conical press with sieve (worm extruder) or a travelling screen press for mechanical dewatering followed by thermal dehydration in a convection dryer or through the use of solar energy (U.S. Pat. No. 6,167,736). This process becomes more economical than the above mentioned in a) , however, the mechanical dehydration generates an exudate with a high organic load (COD) , which corresponds to the loss of much of the organic content, especially protein content. It has the advantage that the mechanically removed water reduces energy costs in the stage of thermal drying, but the produced BSG' s nutritional value is impaired. c) More recently, a process has been developed that consists in the separation of the BSG protein and fibrous fractions by making a dilution until the content is 95% moisture followed by a passage through a vibrating sieve which retains the fibrous fraction. The protein fraction is dehydrated in a centrifugal settler to a maximum content of 30% solids. An extra step of drying, using a spray thermal dryer, a paste dryer or an extrusion dryer, allows the increase of the solids content to about 80%. This fraction can then be used as a valuable component for the feed production for non-ruminants animals.

The fraction rich in fiber is processed in a screw-press, increasing its dry matter content up to 40%, and then burned to produce vapour.

This process is interesting in very hot countries, without immediate acceptance of produced BSG. However, it involves the use of several relatively complex equipments for the two lines in which the BSG is separated and requires high energy consumption. The actual incineration of the fibrous fraction implies high energy expenditure resulting from the energy that is necessary to provide for the evaporation of high water content that still exists. This also means the emission of large amounts of water vapour in the burning process. The present invention, in relation to the equipment used, differs from the previous ones due to the use of an integrated unit of filtration, compression and vacuum drying, using a filter press with significant changes in order to respond effectively to the BSG specifications. The following table identifies the main differences between the three presented processes and the present invention process .

Equipment

The filter press is a device used since the mid-nineteenth century which has undergone numerous developments until reaching the state of the modern membrane filter presses, but has never been applied to the dehydration of BSG, as it proceeds from the beer production process .

A filter press consists of a series of plates held in contact through the action of a fixed head plate and a mobile tail plate usually acted by one or more hydraulic cylinders. The modern filters generally use recessed plates, in which a concavity allows the formation of an empty space (filtration chamber) between two consecutive plates. More recently, plates have been developed, in which the surface area that forms the filtration chamber is not made of a rigid material, but of a flexible membrane (also called a diaphragm) . Thus, by placing interspersed rigid plates and membrane plates, or just membrane plates, it is possible to swell the membranes, and mechanically compress the solids accumulated in the chamber (filter cake) . This swelling is achieved by means of a fluid that circulates behind the membranes and which can also transfer heat to the membranes and from these to the cake, favoring the vacuum drying that will come later.

A filter of this kind is described in the document U.S. Pat. No. 5,558,773, or a version with modified plates in the U.S. Pat. No. 6,180,002 and the US 2006/0032805.

The particular filter used here is based on filter presses with the latest technology but subjected to several changes to allow BSG dehydration. It consists of a membrane filter press and associated vacuum circuit that reduces the pressure inside the filtration chambers and thus promotes the water vaporization below 100 ⁰ C while holding a driving force for the extraction of moisture. Modifications were made to allow the dehydration of BSG as it proceeds from the beer production process, including:

1) The use of a progressive cavity pump. 2) Implementation of a modified proportional, integral and derivative control chain (PIDM) . This control chain was specifically developed to enable the effective control of the pressure generated by the progressive cavity pump, inside the filter. Without such effective control it would not be possible to use the progressive cavity pump coupled to the filter press . The control chain comprises a pressure sensor, two independent proportional-integral- derivative (PID) controllers, a temporizer and a frequency variator, the latter being the actuator that determines the rotational speed of the progressive pump motor and therefore limits the pressure inside the filter. This chain is distinguished from a usual closed loop control chain by using two PID controllers with independent parameterization. The need for two independent PID controllers arises from the fact that during the filtration operation there are two distinct sequential stages which can be designated by cake formation and cake consolidation and each of these stages requires a controller (PID) with specific parameterization. The choice of the controller actuating in a given moment of the process is made via a timer properly parameterized.

3) Monitoring the evolution of the cake moisture through a humidity sensor installed in the vacuum line. 4) Filtration plates to optimize the duration and the final result of the dehydration cycle, as shown in Figure 1.

Only one application of this technology to brewer's spent grain is known until the present time. This application was developed by the same research group that is now submitting this patent

(El-Shafey, E.I., Gameiro, M., Correia, P., de Carvalho, J.,

2004. Dewatering of brewer's spent grain using a membrane filter press: a pilot plant study. Separation Science and Technology) .

However, the published paper enclosed a more primitive version of the presented technology. Polypropylene membrane plates were used in the filter and a diaphragm pump for feeding brewer' s spent grain to the filter. This implementation required a dilution of the brewer' s spent grain to more than 97% of moisture content. This led to high water consumption, to the need of both stirred dilution tanks and larger filtrate collection tanks. The high dilution of the produced filtrate invalidated its use as a source of polyphenols for several industrial processes. On an industrial scale (400 ton / week of brewer's spent grain with 73% -75% of moisture content), water quantity requirements and tanks volumes would prevent any application of this process. Moreover, the brewer's spent grain used in the published paper was supplied by another brewery which used a different milling process. Thus, the particles of brewer's spent grain obtained had a much coarser granulometry. This issue is highly relevant. Larger particles increase the cake porosity and thereby facilitate moisture removal, especially during the step of vacuum drying. This made the process faster and more linear. In the present invention, the set of equipment presented in Figures 1 and 2 was used. A caption and brief explanation of the content of the figures is presented below. Figure 1 shows an integrated unit of filtration, compression and vacuum, using an electrical resistance as the heat source for the compression fluid.

Figure 1 caption:

1 - Brewer's spent grain (as produced in the process of brewing) feed line to the system that includes a feed hopper, a crusher and a progressive cavity pump.

2 - Hopper with crusher. This equipment was connected to the progressive cavity pump and allowed the homogenization of the brewer' s spent grain previous to its processing by the invention. 3 - Progressive cavity pump. This pump can feed brewer's spent grain (as produced in the process of brewing) to the filter. The filter presses are typically used for dewatering liquid like slurries. In opposition, brewer's spent grain resembles more like a wet solid. The pressure supplied by the pump is controlled by the control chain described above. Thus the choice of this type of pump and associated control system is an innovation which results from another innovation, which is the possibility of processing brewer' s spent grain as produced in the process of brewing.

4 - Brewer's spent grain feed piping to the filter. Along the piping, several isolating valves and pressure and temperature sensors monitor and control the process. One of the pressure sensors in the feed piping is part of the control chain that allows for the effective control of the pressure inside the filter.

5 - Set of filter plates which constitute the membrane plates filter press.

6 - Hydraulic cylinder for closing the filter, to a maximum pressure of 700 bar.

7 - Vacuum line connected to the output filtrate piping. During the vacuum drying step, the valve at the end of the filter output piping is closed to prevent the contact with the atmosphere. The valve in the vacuum line is opened. This allows the attainment of reduced pressure inside the filtration chambers (50 mbar) when the vacuum pump is connected. Thus the filter cake moisture can evaporate at a lower temperature (about 4O ⁰ C) . In this vacuum line a humidity sensor is installed for monitoring the progress of the filter cake vacuum drying. 8 - Exit piping for the liquid resulting from the filtration and compression steps.

9 - Lower distributor of the compression and heating cycle, which allows the supply of the hot compression fluid to the filter plates. 10 - Centrifugal pump for feeding the compression fluid to the filter plates.

11 - Heater for compression water. Item 11 relates only to figure 1. In Figure 2, it is replaced by items 18 and 19. Figure 1 shows a unit characterized by the use of water heated by an electrical resistance for the heating and compression of the cakes . Figure 2 presents the case for the use of process hot water or low pressure steam produced in a boiler for the same purpose . 12 - Upper distributor of the compression and heating cycle. A valve to produce suitable pressure loss, and thereby increase the pressure inside the compression plates, is embodied in it.

13 - Vacuum line condenser. This equipment allows the condensation of the moisture removed during the vacuum drying step. This issue is essential for the proper functioning of the vacuum pump and for the monitoring of the vacuum stage by controlling the condensates' volume according to the duration of the cycle .

14 - Condensate tank. Tank attached to the condenser that allows the collection of water removed from the filter cakes. This tank allows monitoring the condensates volume.

15 - Vacuum pump. The pump used is an oil ring vacuum pump. However, other types of pumps can be used, such as aqueous liquid ring pumps. These pumps allow pressure reduction in the filtration chambers (space between two consecutive filter plates) to values of around 50 mbar. Thus in these conditions the water boiling temperature drops to about 40°C.

16 - Vacuum line gases collection and venting system.

17 - Filter cakes removal and collection system. Figure 2 is identical to Figure 1 except differences in the compression fluid heating system, represented in the figure under items 18 and 19. Figure 2 caption:

18 - Boiler for low pressure steam production to be used in the compression circuit .

19 - Plate heat exchanger for heating the thermal compression fluid. This heat exchanger allows both the transfer of heat from the low pressure steam produced in the boiler to the heating fluid that circulates through the plates and the use of hot water as an energy source for the heat transfer fluid.

Brewer' s spent grain dewatering process With the available equipment two processes are considered in the present invention.

Process 1 (preferred embodiment of the invention)

In this innovative process, which will be described below, brewer' s spent grain with a moisture content between 72% and 85%, preferably higher than 75% and at a temperature between

20°C-70°C, preferably about 40-60 ⁰ C, is fed (1) to the hopper

(2) (with crusher) and pumped to the filter (5) by the progressive cavity pump (3) . The solids deposit in the filtration chambers originating what is known as the filter cake. The filter cloths, preferably from polypropylene fabric, mono-mono filament, with the air porosity of 500 L/dm2.min, cover the plates, coating the membranes and allowing the passage of fluid as the solids are retained at their surface. The fluid, with a low solid content, a high polyphenol content and consequently high antioxidant power, is collected through small holes on the edge of the membranes and directed by consecutive channels in the 4 corners of each plate to an external piping system and collected in (8) .

The progressive cavity pump (3) feeds the filter (5) , keeping a constant value of the filtration pressure of 3-6 bar preferably 4 bar, until the flow rate of fluid collected in (8) is very low. At this time completion of the filtration step is achieved. The filtration step lasts about 10 minutes. After turning the feed pump (3) off, the isolating valve of the feed channel (4) is closed. The second step of the mechanical dehydration starts: cake compression. A thermal fluid, preferably water (up to 120°C) or low pressure steam circulates through the lower distributor (9) , passes through the inner part of the plates (5) and exits through the top, where the upper distributor (12) and their piping lead it back to the heat source (11 and 18) , preferably a heat exchanger (19) or a steam production boiler (18) . A valve at the outlet of the upper distributor (12) creates a pressure drop, increasing the pressure upstream in the circuit, causing membranes' dilatation and consequent cake compression. At the same time, heat is transferred from the thermal fluid to the solids. This compression step takes place at a pressure of 4-8 bar. The compression pressure must be at least 1 bar higher than the filtration pressure, preferably 3 bar, i.e., at a 4 bar filtration pressure, the compression must take place at 7 bar. The compression fluid is again collected in (8) and added to the filtrate. When the compression fluid flow rate decreases significantly, the compression is completed. The pressure inside the membranes is reduced to 2-3 bar in order to ensure good contact between the heated membranes and the cake surface without compressing it too much. The central filter channel - "core-blow"- is then unblocked. The filtrate exits are closed, the center channel purge valve is opened and compressed air is injected in the chambers through one of the corner channels that communicate with the filtration chambers through the filtrate collecting eyelets . The pressure increases within the chambers due to the compressed air injection and causes the expulsion of the wettest and less consolidated brewer' s spent grain accumulated in the central channel. Depending on the degree of consolidation of the brewer's spent grain accumulated in the central channel, the required pressure of the compressed air can be between 1 and 3 bar. The duration of this step is usually about 1 minute. At the end of this step, the central channel purge valve is closed.

The next step, which is optional, is cake blowing. The plate sets that allow for on-line blowing have the filtrate collection eyelets asymmetrically placed in each consecutive plate. Thus on one side of the cake surface the filtrate collection is achieved in the top and bottom right corners and on the other side in the top and bottom left corners. Therefore, by closing the valves of the upper right and lower left filtrate collecting channels, air can be injected under pressure through the upper-left channel, across the cake and exits the system through the bottom right channel . This step lasts for about 5 minutes and allows the removal of some moisture from both the piping and the cake. It also increases cake porosity. After the blowing step completion, air injection valves are closed and the vacuum drying stage starts. The four filtrate output channels are opened; the exit (8) is closed. The collection of air / steam / water starts to be carried out by the vacuum circuit (7). Heating is kept between 60-120 ⁰ C, preferably between 80 ⁰ C and 90 ⁰ C when polypropylene membrane plates are used. If higher temperatures are required (up to 12O ⁰ C) Ethylene Propylene Diene Monomer (EPDM) membranes and low pressure steam may be used. The condenser (13) cooling fluid is circulated and the vacuum pump, preferably an oil ring vacuum pump (15) is turned on. A reduced pressure of around 15 to 100 mbar (absolute) , preferably between 15-50 mbar is applied inside the filtration chambers through the filtrate exits while maintaining the membranes compression pressure at 2-3 bar. With this arrangement, it is possible to vaporize water at temperatures of around 40 ⁰ C.

Through the condensed liquid accumulation in the transparent tank (14) and the humidity sensor installed in the vacuum line the progress of the drying operation and the rate of moisture removal from the cakes may be monitored. The drying operation is prolonged until the cake reaches the desired moisture values, usually around 15%.

After completion of the dehydration process, the vacuum pump (15) is stopped and the system is vented (8) to restore pressure in the pipes. The compression circuit upper distributor valve is opened, reducing the compression pressure to zero. The thermal fluid circulation is stopped. The filter is opened and the dry cakes are discharged.

This procedure, as well as all operations on the valves, can be carried out either manually or automatically through electronic valves and belt systems for the automatic filter opening. The supervision of an operator would only be required during the cake discharge step.

The membrane plates used in the proposed process have the main body made of polypropylene. The membranes, which can be detachable or welded to the plate, can be made of polypropylene or EPDM according to the required working temperatures.

The thickness of the cakes produced should not exceed 2.0 cm, being preferably 1.5 cm. Two membrane plate combinations were developed to be used with BSG: i) In a first combination, all membrane plates are recessed

(concave) , or alternatively all membrane plates are flat with interspersed frames. However, recessed membrane plates have advantages due to the fact that they are easier to handle and provide a better seal for creating vacuum in the filtration chambers . ii) In the second combination, the recessed membrane plates alternate with recessed rigid plates. These rigid recessed plates have several extraction holes evenly distributed on the surface area of the plate (figure 3) . This combination allows the use of higher compression pressures and necessarily involves the use of higher temperatures for the thermal fluid in order to compensate the fact that the heating is carried out only on one side of the cake. Since the rigid plates have a greater number of extraction points spread over the entire surface of the cake, a more effective drying is achieved.

Figure 3 Caption:

20 - Channels for the collection of filtrate.

21 - Central feed channel of BSG.

22 - Extraction points of water and steam, evenly distributed on the surface of the plate . The choice of the plates and filter medium depends on the available energy source in each brewery, as well as on the manufacturing process, which may produce BSG with different particle sizes.

Process 2 (alternative process) The alternative process for using the filter press with membrane plates for the dehydration of BSG is to use the filter press only for mechanical dewatering. The mechanical dewatering is carried out through filtration and compression, as previously described in case 1, but with the possibility of operating at higher pressures (up to 50-70 bar) . This procedure requires the strengthening of the structure of the filter and the use of suitable filter plates.

In this process, the possibility of using the mash filters, which exist in the breweries, is considered. As previously stated, the BSG results from low pressure filtration of must (lautering) , resulting in a filtrate (which will lead to beer) and a solid that accumulates in the filter chambers (the BSG) . If the filtration cycle is extended by increasing the pressure on the cake up to 50-70 bar, using for example, membrane plates that operate on compressed air, a large amount of exudate, rich in polyphenols, is extracted. However, this extract cannot be mixed with the filtrate obtained in the low pressure filtration stage, since that would be detrimental to the taste of the beer. This process would save time of filtration and would have a low investment cost for the filtration equipment.

The filter for mash separation could also be used for process 1. However, that would not be advantageous since in that case the modifications and upgrades required by the filter equipment (strengthening of the structure, new membrane plates, installing a vacuum line, installing a pressurized thermal fluid line, etc) would be as expensive as the acquisition of the complete set of equipment described in process 1. Furthermore, the process of beer manufacturing would be impaired.

The BSG resulting from this mechanical dewatering, with moisture contents ranging from 40% to 60%, depending on the time of the filtration cycle and the range of pressures used, may then be thermally dried in conventional thermal dryers. This alternative process reduces the humidity of BSG, without spending any thermal energy and the BSG obtained has a moisture content that allows its preservation for a few days, and thus, has added value in the market. However, the process is not self- sufficient, since it failed to stabilize the BSG for a long period, and thermal drying is still required.

Example 1

A cycle of dehydration of the BSG was carried out, as it proceeds from the beer manufacturing process (75% humidity and

50° C of temperature), using the following experimental conditions:

- 4 filtering plates as previously described in combination i) , that is, recessed plates with EPDM membranes that allow the formation of 3 cakes with 15 mm of thickness .

- Filtration at 4 bar for 10 minutes, using a progressive cavity pump. The pressure was monitored and controlled by a control chain which comprises a pressure sensor present in the feed channel, two independent proportional integral and derivative controllers (PID) , a timer and a frequency variator, that determines the rotational speed of the progressive pump motor and therefore controls and keeps the pressure constant inside the filter. Filtration takes place until the filter becomes full and the flow of exudate is less than 25 mL/min which corresponds to a reduction in the BSG humidity from 75% to 55-60%. - Compression of the filter cakes through the membranes of the plates actuated by water at a temperature of 90 ⁰ C at a pressure of 7 bar and 10 minutes. The moisture of the cake is reduced to 50%.

- Implementation of the "core-blow" and the cake blow at a pressure of 2 bars for 1 and 3 minutes respectively.

- Vacuum drying through the action of an oil ring vacuum pump, which allows the attainment of an absolute pressure inside the filter of 50 mbar. This phase, which lasts for 4 hours, yields a dry final cake with only 15% of moisture. During this stage, the steam from the filter cake is condensed and collected in a vessel, where it can be monitored and measured. If the drying procedure is conducted at lower vacuum pressure, the final moisture content of 15% is achieved faster. In conclusion, by using vacuum pressure ranging from 10 to 100 mbar, for 3 to 5 hours, it is possible to obtain filter cakes with 15% of humidity.

Example 2

A cycle of dehydration of the BSG was carried out, as it proceeds from the brewing process (75% humidity and 50° C of temperature), using the following experimental conditions:

- 5 filtering plates as previously described in combination ii) , that is, 2 recessed rigid plates with various extraction points and 3 recessed plates with EPDM membranes) allowing the formation of 4 cakes with 15 mm of thickness. - Compression of the cakes through the membranes of the plates actuated by water at 105 ° C at a pressure of 7 bar for 10 minutes. The moisture of the cake is reduced to 45-50%. - Implementation of the "core-blow" and the cake blow at a pressure of 2 bars for 1 and 3 minutes respectively.

- Vacuum drying through the action of an oil ring vacuum pump, which allows the attainment of an absolute pressure inside the filter of 50 mbar. After 3.5 hours of vacuum drying, the final cake moisture is reduced to 13%. During this phase, the steam from the filter cake is condensed and collected in a vessel, where it can be monitored and measured. The final result depends on the duration of this step and on the vacuum pressure inside the filtration chambers.

Brewer's spent grain

This innovative and alternative process described herein produces a stabilized and dried BSG (15% humidity) that maintains all its nutritional characteristics. This process is technically and economically feasible, with a production cost of 50 €/ton of dry BSG, which is considered very competitive as raw material for animal feed. The BSG resulting from this process can be used either in feed for ruminants and non-ruminants, as well as for human consumption, and as a stable raw material for other industries . Studies conducted with BSG obtained from the unit described in this invention suggest that a diet with BSG is beneficial to the animals. For example, it was found that the inclusion of BSG in the diet of young animals being weaned prevent them from suffering from diarrhea. The BSG can also be used by the bakery industry or for biotechnological processes. In the countries of Central Europe, the brewers use the BSG after drying and grinding, to mix with conventional flour and produce healthier bread. Despite the high nutritional value of BSG, this by-product after being dried can be burnt in the furnace of a steam generator or thermoelectric generator in order to produce power and energy for self- consumption at the brewery.

Due to the fact that the dried BSG produced as described herein is chemically and microbiologically stable, it can be stored for a long period of time (several years) before being marketed or used in is multiple applications and therefore there is a clear economic recovery from this process .

Exudates The exudate collected in the steps of filtering and compression is a fluid rich in polyphenols, which, depending on the pressures used and the type of grain used in the manufacture of beer, may have a polyphenol content of between 20 and 300 ppm.

This by-product, obtained in this invention, from the process of dehydration of BSG, may be applicable to the pharmaceutical and cosmetic industries, since polyphenols are well-known antioxidants .

Date: April 5 ^th , 2010