MXPA99004713A - Method for the thermal utilization of spent grain - Google Patents

Abstract

In this method for the thermal utilization of wet spent grains (1), the wet spent grains (1) are pre-dried mechanically in a first drying stage (2). In a further drying stage (4), they are thermally dried, and finally thermally utilized by burning or gasification. In order for such a method to be economically practicable, in the further drying stage (4), the mechanically dehydrated malt spent grains (15) are heated with the aid of a flue gas stemming from the energy system of a brewery.

Description

PROCEDURE FOR THERMALLY USING SPRAYED GRAINS DESCRIPTIVE MEMORY The invention relates to a process for thermally using wet spent grains, in which the spent wet grains are previously dried mechanically in a first drying step, thermally dried in a subsequent drying step and finally used thermally for combustion or gasification, as well as an industrial plant to carry out the procedure. When beer is produced, wet spent grains with brewery feces which originate in large quantities, constitute a waste and utilization problem. About 20 kg of wet spent beans per hectoliter of beer are produced, so that large breweries have to discard, or use, hundreds of tons of spent grains per week. Due to its composition, the spent grains constitute a valuable forage. It is difficult, however, to use the spent grains as fodder in an effective manner in terms of cost. The appropriate time to sell them as fodder without problems is in winter - on the other hand, spent grains are produced in larger quantities in summer than in winter. In addition, spent grains can not be stored without drying them previously. Drying is expensive, since only indirect drying is possible due to the demands placed on the forage; which means poor thermal transmission. The proper dryers are expensive, implying high energy consumption. In addition, the sale of spent grains as fodder will become increasingly difficult in the future because of declining livestock. The conservation of spent grains by fermentation again implies the disadvantage of high costs (Brauwelt No. 39 (1991), pp. 1704 to 1707). The formation of a high quality product for soil improvement speaks in favor of the transformation into fertilizer spent grain, however the market is simply small and the production involves such high costs that will not cover the costs in any way. The spent grains are also suitable for producing biogas, however an industrial biogas plant requires high investment costs. An energetically practicable procedure for using spent grains is direct combustion. For the specialized magazine "Brauwelt" No.26 (1988), pp 1156 to 1158, "Die energetische Verwertung von Biertrebern", a procedure is known for the recovery of energy from spent grains, as described at the beginning. Industrial spent grain combustion plants are operating, however, with low effectiveness because of the necessarily intensive pre-drying (dried grains initially containing 75 to 80% by mass of water) and the relatively deficient heat value of spent grains. . The prerequisite for optimum energy utilization is the achievement of self-combustion, which will be obtained with an H20 content of approximately 55%. The invention proposes to avoid these drawbacks and difficulties and has as its object to provide a procedure of the initially defined class as well as an industrial plant to carry out said procedure, which makes possible the optimal energy use, ie more possibly profitable, of grains spent. The drying of the spent grains, in particular, must be feasible by a possibly external energy consumption to such an extent that the spent grains can be used thermally, that is to say to burn or gasify without reinforcement heating. In a method of the initially defined kind, this object is achieved in the sense that mechanically dehydrated spent grains, in a subsequent drying step, are heated with the help of a smoking gas originating in the energy system of a brewery . The smoky gas that originates in beer production is formed by the combustion of natural gas for the purpose of generating steam. In addition to combustion, it is also feasible to gasify spent grains previously dried with a fuel gas that originates as an intermediate product.

Advantageously, the gas formed during gasification is used energetically, preferably as an energy carrier, for the generation of steam within the brewery system, for example as an additional gas to natural gas, in order to make possible its energy use in the industrial plant of brewing boilers by means of combustion. Preferably, the additional drying aimed at removing the capillary water with the aid of electric fields or with the aid of high frequency fields is carried out in order to mechanically dry the spent grains in advance. The mechanical pre-drying is suitably carried out until at least one water content of 65 and, preferably, 62% by mass is reached. Suitably, solar energy can additionally be applied for the thermal drying of the previously dried spent grains mechanically. The thermal drying of the spent grains is advantageously carried out until a water content is reached which makes self-combustion possible, preferably until at least 55% by weight of water content is reached. According to the preferred embodiment, the water from the pulp presses that is formed in the prior mechanical drying is treated anaerobically the methane-containing gas that is formed is used energetically, preferably as an energy carrier for the generation of steam within the system of brewery. The waste gases that are formed in the combustion of the dried spent grains are discarded together with the waste gases formed in a steam boiler of the brewery in a cost-effective manner. According to a preferred variant, mixtures of spent grains and other organic biogenic waste substances are used thermally. An industrial plant for carrying out the process, which includes a mechanical dryer, which constitutes a first stage of drying for spent grains and a thermal dryer that constitutes a subsequent drying step for mechanically dehydrating the spent grains as well as a device for use Thermal burning or gasifying of dried spent grains is characterized in that a duct carrying smoky gas from a steam boiler of the brewery's power system feeds the thermal dryer. Preferably, the device for the thermal utilization of the spent grains includes a combustion boiler, said combustion boiler being suitably equipped with a steam generating means and said steam generating means being advantageously coupled with the brewery's energy system.

In an investment-saving manner, a flushing gas discharge duct flowing from the combustion boiler feeds a waste gas installation from an industrial beer production facility, where, appropriately, also a waste gas duct of the thermal dryer feeds the waste gas facility of the industrial beer production plant. According to another preferred embodiment, the device for thermal utilization includes a gasification air, in which, suitably, a conduit flowing from the gasification medium and carrying waste gases produced in the gasifier leads to a burner of a gasification boiler. Steam of the brewery's energy system. The mechanical dryer can be configured preferably as a press with a displacement partition or as a worm extruder. A convection dryer can be suitably used as a thermal dryer. Preferably, the thermal dryer includes a drying medium operable for solar energy. According to another advantageous embodiment, term drying, gasification and combustion can be combined in an apparatus device, in which, suitably, a conduit removes hot waste bases from the device including thermal drying, gasification and combustion is known directly to a steam chain of the brewer's energy consumer.

The thermal drying can be caused additionally with a drying medium comparable to solar energy. In the following, the invention will be explained in more detail by means of two exemplary embodiments illustrated in the drawings, in which each of FIGS. 1 and 2 represents a systematic plan of the method according to a configuration variant. First, the wet spent grains 1 are adjusted to a water content ranging from approximately 65 to 62% by mass in a first drying step 2 in a mechanical dryer 3, which, according to figure 1, It is designed as a worm press. The composition of the grades spent at such a water content is not yet possible, however, without reinforcement heating. For this reason, the subsequent drying is carried out in a further drying step 4, in which the drying of the spent dehydrated grains mechanically is carried out thermally. With this clarity, a thermal dryer 6 designed as a drum dryer is provided, according to Figure 1. The drum dryer 6 is directly heated with smoked gas fed through line 7 and having a boiler 10 installed in a 8 industrial production plant for beer. The boiler 10 is heated with natural gas, which is a list through line 9; the steam conduits are indicated with the 11. Smoke gas production can be requested directly to a waste gas blower 13 from the industrial installation of the smoking gas waste through the branch conduit 12. The smoking gas conduit 14 which part of the drum dryer 6 also feeds this industrial plant of the smoking gas waste. With the aid of such thermal drying, it is feasible to decrease the water content to less than 55% by mass in such a way that the spent grains after ignition will be burned automatically, i.e. without reinforcement heating. The combustion of the spent degrees 15 dried by several of the burners 16 is effected in a combustion boiler 17 in which a steam generating means 18 is installed. The steam generated in that steam generating means 18 is practically used for the production of beer, that is to say natural gas can be saved for the natural gas burner 19 in the boiler heated with natural gas 10. The ash is indicated with the 20. According to the modality shown in figure 2, the wet spent grains 1 they are initially subjected to mechanical drying in a first drying step 2 by means of a septum belt press 21. After this, spent dehydrated grains are mechanically supplied to a thermal dryer of the second drying stage 4, which is designed as a convection dryer 22 and in which the spent grains are dried 5 until reaching a water content below the self-combustion limit with the help of the steaming gas d from the industrial beer production plant 8, according to figure 1.

According to FIG. 2, the thermal utilization of the dry spent grains 15 is performed in a gasifier 23, which is fed with oxygen or an oxygen-containing gas such as air, through a screen plate 24. The discharge of ash is indicated with the 20. The gases (CO, H2, CO2) N2) that are formed inside the dryer 23 are easily combustible and, being combustion gases, can be used in place of a part of the natural gas used in the industrial production plant for beer; they are fed to the natural gas burner 19 through the conduit 25. The advantage of this technique in comparison with the combustion is that no additional combustion boiler of solids is needed and that the oxides of nitrogen and sulfur are avoided. they are formed during combustion. During gasification a gas will be formed consisting essentially of carbon monoxide, carbon dioxide, hydrogen and molecular nitrogen. In order to reduce or eliminate capillary water contained in spent grains, other drying processes can also be applied in addition to mechanical and thermal drying, for example drying with the aid of high-frequency fields or electromagnetic fields. Natural energy such as solar energy can also be applied to aid in thermal drying, feeding the solar energy before or after the thermal drying stage 4 - depending on the spray point of the smoking gas.

EXAMPLE In a brewery with an annual production of approximately 1.2 million hectoliters of beer, approximately 24,000 tons of spent grains 1 are produced, which have a water content of approximately 80% in more per year. The spent grains 1 obtained are previously mechanically dried until reaching a water content of approximately 62% by mass by means of a press (for example, worm 3). An amount of 24,000 tons of wet spent grains, which are mechanically dehydrated to a water content of 62% by mass, produce 11,370 tons of pulp board water per year. As a result, a waste water load of 113,700 kg of CSB results per year. The pulp board water 26 that is advantageously formed is supplied to the anaerobic water purification - which is not illustrated in detail in the figures -, where a combustible methane containing gas is recovered. From the amount of pulp press water mentioned, approximately 36,400 m3 of biogas are formed per year. By burning that gas containing 85% methane, approximately 300,000 kWh are obtained per year; this constitutes additional procedures. The water content of spent grains 5 is about 62% by mass after mechanical drying. In order to ensure self-combustion, a value of 55% by mass of water is reached.

In order to further decrease the water content, alternative methods of drying as described above can be used to reduce capillary water. This can be achieved by transporting water within an electric field (electroosmosis) or supplying energy with high frequency fields to mobilize a portion of the bound water, which can be subsequently accessible to further mechanical pressing. Depending on the effectiveness of the alternative drying methods, the thermal drying is subsequently carried out to a more or less extensive degree in order to achieve a degree of self-combustion. The spent grades 5 previously mechanically and alternately dried by means of a buffer vessel are continuously transferred to a directly heated dryer (eg drum dryer 6) and are dried by convection at least to the degree of self-combustion of about 55% by volume. % by mass of water of the hot smoky gases from 140 to 160 ° C derived from the combustion of natural gas. The dried material 15 is then supplied to a combustion tank 17 for biogenic waste and burned. The calorific smell of the spent grains is a linear portion of the water content, which is 55% by mass of water at approximately 7.68 MJ / kg. Burning a ton of spent grains, approximately 190 m3 of natural gas can be used instead. In total, 4.5 million Nm3 of natural gas per year are required from a brewery of the mentioned magnitude.

According to this, 2 million m3 of natural gas per year can be replaced by burning the spent grain, which is more than a third. High nitrogen oxide emissions were expected during the combustion of spent grains 15 due to the high nitrogen content. In tests carried out with spent grains in special combustion quantities for sawdust, however, only 10% of the possible theoretically expected values of nitrogen oxide could be determined. Through proper process control during combustion (low combustion temperatures), NOx emissions were reduced to a minimum. Another problem is constituted by the formation of sulfur dioxide during combustion. Introducing an industrial smoky gas purification plant, spent this combustion of spent grain together with smoking gases obtained in the combustion of natural gas, compliance with the limit values can be ensured with respect to the tanks for combustion of biogenic waste. Similarly, you can control the CO value for the adjustment of the landa value, thus making possible the optimization between NOx and CO values. Another approach towards NOx reduction is, for example, by spraying in NH3. The invention is not limited to the examples described above, but can be modified in several aspects. This being so, the wet spent grains can be dried in any desired number of drying steps, it being essential, however, that at least one mechanical drying step 2 and at least one thermal drying step 4 be included. In addition, configurations of pre-thermal drying, gasification and combustion apparatuses are feasible, which also satisfy the criteria set forth above. The process according to the invention can be extended to the extent that, in addition to the spent grains, other biogenic wastes, such as sewage sludge, can also be covered by the process in order to be able to increase the energy content and by consequently the formation of steam. It is made entirely from the mixture of spent grains and other biogenic wastes in the same way as explained in the description of the procedure.

Claims (15)

NOVELTY OF THE INVENTION CLAIMS

1. - A method for thermally using wet spent grains (1), in which the wet spent ones (1) are previously mechanically dried in a first drying step (2), they are thermally dried in a subsequent drying layer (4) and they are finally thermally used by combustion or gasification, further characterized in that the mechanically dehydrated spent grains (15) are heated, in the subsequent drying step (4), with the help of a smoking gas originating within the energy system of a brewery

2. A method according to claim 1, further characterized in that the smoking gas originating in the brewery is formed by the combustion of natural gas for the purpose of generating steam.

3. A method according to claim 1 or 2, further characterized in that the gas formed during the gasification of spent grains is used energetically, preferably used as an energy carrier for the generation of steam within the brewery system.

4. A method according to one or more of claims 1 to 3, further characterized in that the additional drying intended to remove the capillary water with the aid of electric fields is carried out to mechanically dry the spent grains beforehand.

5. A method according to one or more of claims 1 to 4, further characterized in that the additional drying intended to eliminate the capillary water with the help of high-frequency fields is carried out in order to mechanically dry the spent grains.

6. A method according to one or more of claims 1 to 5, further characterized in that the prior mechanical drying of the spent grains is carried out until reaching at least a water content of 65 and, preferably, until reaching less a water content of 62% by mass.

7: - A method according to one or more of claims 1 to 6, further characterized in that solar energy is additionally applied for the thermal drying of the mechanically pre-dried spent grains (5).

8. A process according to one or more of claims 1 to 7, further characterized in that, in the subsequent drying step (4), the spent grains (5) are dried until a water content is reached that makes possible the self-combustion thereof, to preferably reach at least 55% by mass of water.

9. A process according to one or more of claims 1 to 8, further characterized in that the water of the pulp press formed in the previous mechanical drying is treated anaerobically and the methane-containing gas thus formed is energetically used, preferably as an energy carrier for the generation of steam within the brewery system.

10. A method according to one or more of claims 1 to 9, further characterized in that the waste gases formed during the combustion of the spent spent grains (15) are extracted together with the waste gases that are formed. in the steam boiler of the brewery.

11. A process according to one or more of claims 1 to 10, further characterized in that mixtures of spent grains and other organic biogenic waste substances are used thermally.

12. An industrial plant for carrying out the process according to one or more of claims 1 to 11, which includes a mechanical dryer (3; 21) that constitutes a first stage of drying (2) for spent grains ( 1) and a thermal dryer (6; 22) which constitutes a further drying stage (4) for mechanically dewatering spent grains (5) as well as a device (17; 23) for the thermal utilization by combustion or gasification of spent grains. dried (15), further characterized in that a duct (7) that extracts fuming gas from a steam boiler of the brewery's energy system feeds the thermal dryer (6; 22).

13. - An industrial plant according to claim 12, further characterized in that the device for the thermal use of the spent grains includes a combustion boiler (17).

14. An industrial plant according to claim 13, further characterized in that the combustion boiler (17) is equipped with steam generating means (18).

15. An industrial plant according to claim 14, further characterized in that the steam generating means (18) is coupled with the energy system of the brewery, 16.- An industrial plant in accordance with one or more of the claims. 13 to 15, further characterized in that the flushing gas discharge duct coming from the combustion boiler (17) feeds a waste gas installation of an industrial beer production plant (8). 17.- An industrial plant in accordance with the claim 16, further characterized in that a gas and waste conduit (14) of the thermal dryer (6) feeds the waste gas installation of the industrial beer production plant (8). 18. An industrial plant according to claim 12, further characterized in that the device for thermal utilization includes a gasification means (23). 19. An industrial plant according to claim 18, further characterized in that a conduit (25) from a gasification means (23) and extracting gases produced in the gasifier leads to a burner (19) of a boiler steam from a brewery's energy system (8). 20. An industrial plant according to one or more of claims 12 to 19, further characterized in that the mechanical dryer includes a displacement septum press (21)). 21. An industrial plant according to one or more of claims 12 to 19, further characterized in that the mechanical dryer includes a worm extruder (3). 22. An industrial plant according to one or more of claims 12 to 21, further characterized in that the thermal dryer includes a convection dryer (22). 23. An industrial plant according to one or more of claims 12 to 21, further characterized in that the thermal dryer includes a drying medium operable for solar energy. 24. An industrial plant according to one or more of claims 12 to 23, further characterized by thermal drying, gasification and combustion in an apparatus device. 25. An industrial plant according to claim 24, further characterized in that a conduit that extracts hot waste gases from the device that includes thermal drying, gasification and combustion is conducted directly to the steam boiler of the energy consumer. of the brewery.