DE2931854A1 - Energy recovery from thickening processes - by compressing vapours and condensing them through isobaric cooling - Google Patents

Abstract

Energy is recovered from thickening processes of liqs. in the food industry when the process is carried out at atmospheric pressure by the application of heat. Vapours which have been released by the thickening process are first compressed adiabatically, followed by isobaric cooling to achieve condensn. Heat recovered is re-utilised for the thickening process. Used in dairies and for mash or wort boiling in breweries. This greatly reduces the power requirement and eliminates the emission of smells during mash or wort boiling.

Description

Method and device for energy recovery

in thickening processes taking place under atmospheric pressure and with the addition of heat of liquids in the food industry The invention relates to a method and a device for energy recovery at under atmospheric pressure and heat supply thickening processes taking place in the food industry, insbeßondo, re in the beer production.

In brewery operations there is generally an excess of heat in one Temperature level below 1000C available. This primarily depends on the various Waste heat sources from the brewery together. As solc'.e are present - the Pre-cooling section of the plate apparatus for wort cooling - the vapor condenser system when cooking mash and wort - the post-evaporation plumes in the condensate management for steam-supplied companies - an economizer for directly heated breweries.

All of these waste heat sources have so far been used exclusively for hot water generation used.

The supply of warm brewing water of around So0C is almost done today exclusively through the recovered warm water from the pre-cooling department of the Plate apparatus for wort cooling. It fits both in terms of quantity and temperature very well together and is 1.1 hl hot water at 80 ° C per hl wort. The need for warm water in the rest of the company (barrel cleaning systems, sanitary facilities, Sterilization water etc.), on the other hand, fluctuates within wide limits, but is within the range Most of all establishments sell about 0.5 hl / hl beer. Alone, through a vapor condenser system However, around 0.8 hl of hot water can be recovered per hl of beer sold will, so that just by this one waste heat source there is already an excess. This fact becomes problematic because according to the valid Federal Immission Control Act the evaporated steam must be destroyed during the mash and wort boiling, because they are connected with an odor emission and that on the other hand also that Discharge of hot water with a temperature of over 350C in accordance with waste water legislation is not allowed.

The evaporated steam could also be used for the stove Absorption refrigeration systems are used. However, the effort involved is very high large, so that economic efficiency cannot be calculated.

The use of a heat pump system has so far been ruled out because that was required Temperature level is in the order of 1400C and so far not a suitable one Refrigerant is available.

The object of the invention is therefore to find another way of how the steam evaporated during the mash and / or wort boiling can be used; to feed the energy content of the steam back into the brewing process.

This object is achieved in that the mash and / or wort boiling evaporated plumes first compacted as adiabatically as possible and then by isobaric Cooling are condensed, with the heat released during the condensation again is used for mash and / or wort boiling.

This method has the advantage that a considerable reduction in the Primary energy requirement in the mash and / or wort boiling is achieved and that further the odor emissions that have so far occurred during the mash and / or wort boiling completely is prevented.

The work necessary for compaction is preferably carried out by means of a Combustion engine applied, the waste heat used for hot water preparation which leads to a further reduction in the primary energy requirement.

For the same purpose one can also use the one contained in the condensate warmth use for water heating. Instead of an internal combustion engine, it can be used For reasons of lower energy consumption, an electric motor can be used when the The need for hot water is low and therefore the waste heat from an internal combustion engine cannot be used.

In terms of an optimal use of the steam in the steam It is also beneficial if the condensate contains the compressed steam steam is mixed in, so that it changes from the overheated state to saturated steam temperature be cooled down. However, it is more efficient in terms of efficiency if the steam plumes condensate is added during compression.

The device for carrying out the method according to the invention is characterized in that a screw compressor is used to compress the evaporated steam is provided, which is followed by a known external boiler in which the heating of the wort and / or mash by means of the released heat of condensation he follows.

With this device, difficulties that occur are avoided if the steam is mixed too much with air or with foreign matter is contaminated, because on the one hand the external boiler allows the wort to be boiled with the hood door closed, so that only small amounts of air in the steam swather from the start are present and on the other hand, the screw compression is capable of low levels of contamination to cope with the steam that comes from the hops. The outside cooker has also the advantage that it can be easily cleaned if necessary.

A diesel engine is preferably used to drive the screw compressor provided because its efficiency is very high and thus the gas engine and the Gas turbine is far superior.

Both the condensate contained in the condensate can be used for hot water preparation Heat as well as the waste heat from the diesel engine can be used. It is therefore preferable A heat exchanger is connected downstream of the external boiler, in which heat is extracted from the condensate and is fed to the process water. In addition or as an alternative, there is the diesel engine coupled with a heat exchanger, in which the waste heat from the diesel engine is used for water heating. When using both systems for hot water preparation is then expediently the first-mentioned heat exchanger with the second-mentioned Heat exchangers connected in series, so that the process water with that in the condensate The heat contained is preheated and with the waste heat from the diesel engine to the final temperature is brought.

The screw compressor can also be driven by means of an electric motor take place.

The external boiler is preferably preceded by a steam cooler, the Condensate from the external boiler for injection into the compressed steam plumes is feedable.

As an alternative to the steam cooler, the screw compressor can do this be designed that him condensate from the external boiler for injection into the Steam can be supplied during compression.

The application of the method and the device according to the invention its implementation is not limited to beer production, but can generally take place in all thickening processes in the food industry. In addition to beer production, a preferred field of application is also the dairy industry.

One embodiment of the invention is for beer production shown in the form of a flow sheet in Fig. 1 of the accompanying drawings and is described in more detail below. Fig. 2 shows a diagram for screw compressors, that is used in the calculation example given below.

Wort W is in the direction of the arrow from a wort kettle 1 to an external boiler 2 out and passed back from there to the wort copper 1 after they have the Has flowed through the external boiler 2. At the beginning the wort is in the external boiler 2 by means of live steam F supplied from a steam boiler, not shown, at boiling temperature heated. As soon as there is sufficient vapor BD in the wort kettle 1, will this steam in a screw compressor 3 is approximately adiabatically compressed and over a steam cooler 4 is supplied to the external boiler 2, where it emits heat the wort W condenses. The wort W is now heated in the external boiler 2 completely through the supply of condensation heat and no longer by means of live steam FD.

The screw compressor 3 is driven by a diesel engine 5, its waste heat from cooling water and flue gas RG in a heat exchanger 6 for heating is used by process water BW.

The condensate K produced in the external boiler 2 becomes a heat exchanger 7 and / or a condensate collector 8.

In the heat exchanger 7, heat contained in the condensate is used for preheating of the process water BW is used, which is then fed to the heat exchanger 6, to be heated to the final temperature there. From the condensate collector 8 is if necessary, condensate is fed to the steam cooler, in which it is then compressed into the Steam is injected to cool it down to saturation temperature. The condensate collector 8 and the heat exchanger 7 supplied Quantities of condensate are regulated by a quantity regulator 9. That from the heat exchanger 7 escaping condensate is directed into the sewer. The one entering the steam cooler The amount of condensate is regulated by means of a temperature-regulated valve 10.

As an alternative to the steam cooler, the screw compressor can also be used be designed so that it condensate from the condensate collector 8 for injection can be supplied in the vapor plumes during compression, as indicated by the dash-dotted line Line from the condensate collector 8 to the compressor 3 is indicated.

Furthermore, the condensate can also be used to generate live steam (double dashed line), if for any reason the external boiler 2 live steam FD must also be supplied.

An example calculation follows: 1. Hourly Heat expended when boiling the wort (heat of condensation) ii% cast wort quantity 100 hl / brew heat of evaporation at 1 013 mbar: 2 255.5 kJ / kg Density of the water at 1000C: 0.958 kg / l heating surface efficiency 0.87 to 0.93 (per depending on the quality of the insulation) The hourly heat expended when boiling the wort (heat of condensation) can be calculated on the basis of these values to 11 hl / h.100 l / hl.2 255.5 kJ / kg 0.958 kg / l 0.87 (0.93) = 2 732 (2 556) Mj / h corresponding to 758.9 (709.9) kW 2nd hourly Fuel consumption when boiling wort on the steam boiler Boiler efficiency 82% density of the extra light heating oil = 0.83 kg / l lower calorific value of the extra light heating oil 42.7 MJ / kg The hourly fuel consumption is calculated as 2 732 (2,556) bU / h = 94.00 (87.95 <1/100 hl.

42.7 MJ / kg. 0.83 kg / l. 0.82 3. Power requirement for vapor compression The power requirement on the shaft of the screw compressor is different depending on the Heating steam pressures calculated. Although already cookers with a heating steam pressure of 2.5 bar are in use and with an external heating surface a pressure of 2 bar is sufficient is, however, for the sake of completeness, heating steam pressures of up to 4 bar are also used included in the calculation. The basis of the calculation is that shown in FIG Diagram for screw compressors showing a realistic overall efficiency of 65% (m quality grade x mechanical efficiency) is taken into account.

In this diagram, the coefficient of performance of the heat pump is WP SkJ / kJg plotted as a function of various pressure differences (as temperature difference). The performance figure for the various heating steam pressures can be found as follows: Heating steam pressure (bar) 2.0 2.5 3.0 3.5 4.0 associated saturated steam temperature cc 120.23 127.43 133.54 138.88 143.63 Capacity factor of the heat pump (kJ / kJ) 11.6 9.1 7.5 6.45 5.75 After the heat of condensation on the heating surface is known to be 709.9 to 758.9 kW the power requirement of the vapor compression can be calculated as follows: heating steam pressure (bar) 2.0 2.5 3.0 Required drive power kWeff 61.2-65.4 78.0-83.4 97.7-101.2 Continuation: Heating steam pressure (bar) 3.5 4.0 required drive power kWeff 110.1-117.7 123.5-132.0 4. Calculation of the heating steam pressure in the equilibrium state Since the evaporated Steaming during wort boiling with the amount of condensation heat on the heating floor indirectly are related, arises at a very specific, to be determined heating steam pressure a state of equilibrium which the supplied indexed Compressor output is just sufficient to cover the heat losses. It becomes of it assumed that 11 hl evaporate every hour, so that the heat of evaporation of 2 255.5 kJ / kg (at 1 013 mbar) and the density of the water of 0.958 kg / l (at 1000C) the hourly heat of vaporization is calculated as follows: 11 hl / h. 100 l / hl. 2 255.5 kJ / kg 0.958 kg / l = 2,376,846 kJ / h = 660.23 kW.

The mechanical efficiency of the screw may be taken into account of the partial load behavior can be assumed to be 90%. This is how the indexed Compressor output and the condensation output (actual value and setpoint) for heating steam pressure (bar) 2.0 2.5 3.0 Heat of evaporation kW 660.2 660.2 660.2 indicated compressor output k. 55.1- 58.9 70.2- 75.1 85.2- 91.1 Heat of condensation kw (actual) 715.3-719.1 730.4-735.3 745.4-? 51.3 Heat of condensation kW (target) 709.9-758.9 709.9-758.9 709.9-758.9 Continuation: Heating steam pressure (bar) 3.5 4 Heat of evaporation kW 660.2 660.2 indicated compressor output kW. 99.1-105.9 111.2-118.8 Heat of condensation kW (actual) 759.3-766.1 771.4-779.0 Heat of condensation kW (target) 709.9-758.9 709.9-758.9 This table shows that there is a state of equilibrium between condensation capacity, evaporation capacity and indicated compressor capacity sets at a heating steam pressure between 2 and 3 bar.

In this pressure range, the heat pump's heat balance is met. However, since a heating surface efficiency of only 87% (lower limit value) is practical only occurs with an uninsulated heating surface, the heating steam pressure will in practice set between 2.0 and 2.5 bar.

5. Fuel consumption for the diesel to drive the propeller The efficiency of the diesel used to drive the screw is given as 39%. Considering the partial load behavior should be used in the following calculation by one Efficiency of an average of 35% can be assumed.

Heating steam pressure (bar) 2.0 2.5 3.0 Fuel consumption in kW 174.9-186.9 229.9-238.3 270.6-289.1 Fuel consumption in SJ / h 629.6-672.8 802.4-857.9 974.2-1040.8 Fuel consumption in kg / h 14.74-15.76 18.79-20.09 22.81-24.37 fuel consumption in l / h 17.8 -19.0 22.6-24.2 27.5-29.4 fuel consumption without vapor compression in Medium (l / h) 90.0 90.0 90.0 Savings in% 79% -80% 73% -75% 67% -69% 6. Economy of the vapor compression system Since the hot steam pressure inevitably lies between 2.0 and 2.5 bar and this steam pressure with external cookers is safe for the technologically The required evaporation capacity is sufficient by means of such a vapor compression system at the Wort boiling savings between 73% and 80% achieved.

In addition, it must be taken into account that through such a system at the same time a 100 $ fulfillment of the Federal Immission Control Act becomes possible and neither vapor plumes nor odorous substances are released into the environment.

7. Waste heat recovery With the vaporized steam during the mashing and wort boiling is done with the help of so-called pan vapor condenser systems in the Brewery sometimes met the need for hot process water. This need fluctuates in the majority of all breweries between 0.3 and 0.5 hl / hl of beer.

Now both the waste heat from the diesel engine and that in the Boiling condensate running in the sewer is used to prepare warm process water.

The heat exchanger 7 allows the condensate to be subcooled to 60.degree (hK = 20.91 kJ / kg).

50% of the diesel agbase can be used for hot water preparation. The following table provides information about the use of waste heat.

Heating steam pressure (bar) 2.0 2.5 3.0 accumulating boiling condensate with heating surface efficiency v. 90% kg / h 1 200 1 212 1 222 Heat content of the condensate kJ / kg 504.52 535.2 561.2 Heat content of the water at 60 "C kJ / kg 250.91 250.91 250.91 usable amount of heat kJ / kg 253.61 284.29 310.29 Usable amount of heat MJ / h 304 345 379 Diesel exhaust gases 50% MJ / h 315-336 401-429 487-520 heat recovery in hot water total tiJ / h 619-640 746-774 866-899 For generating 1 hl of hot water at 800C from cold water at 700C 29.269 PE are required. The boiling time of a brew takes 90 minutes and the slack of the cast wort (AW) for the sales beer (VB) is 10%.

The following amount of hot water can therefore be generated from the waste heat: Heating steam pressure (bar) 2.0 2.5 Hot water generation hl / h 21.15-21.87 25.49-26.44 hot water generation hl / brew 31.7 -32.8 38.2 -39.7 hot water generation hl / hl AW 0.32- 0.33 0.38- 0.40 hot water generation hl / hl VB 0.36- 0.37 0.42- 0.44 Continuation: Heating steam pressure (bar) 3.0 Hot water gener. hl / h 29.59-30.72 hot water generation hl / brew 44.4 -46.1 hot water generation hl / hl AW 0.44- 0.46 hot water generation hl / hl VB 0.49- 0.51 As can be seen from the table, the hot water requirement of the brewery can be covered in (almost) all cases 100 zig be, so that through the use of a diesel-driven vapor compression system in the wort boiling process, the primary energy requirement can be reduced by around 73 to 80%. The use of such a system therefore results in an ideal NiArm balance reach. An even more favorable coupling of the heat is hardly conceivable.

Claims (14)

Claims 1. A method for energy recovery at under atmospheric pressure thickening processes of liquids taking place in the food industry, it is not stated that vapor evaporated during the thickening process initially compressed as adiabptively as possible and then condensed by isobaric cooling are, with the heat released during the condensation reused for the thickening process will. 2. The method according to claim 1, g e k e n n z e i c hn e t by his Application in the dairy. 3. The method of claim 1, g e k e n n z e i c hn e t by his Use for mixing and / or wort boiling in beer breweries. 4. The method according to any one of claims 1 to 3, d ad u r c h g e k It is noted that the work required for compression by means of an internal combustion engine is applied, the waste heat of which is used to generate hot water. 5. Method according to one of claims 1 to 3, d ad u r c h g e k e n n z e i c h n e t that the work required for compression by means of an electric motor is applied. 6. The method according to any one of claims 1 to 5, d ad u r c h g e k It is noted that the heat contained in the condensate is used to generate hot water is used. 7. The method according to any one of the preceding claims, d a d u r c it is not noted that condensate is mixed with the steam, in order to keep or cool them approximately to saturated steam temperature. 8. Device for performing the method according to the claims 1 to 7, d a d u r c h e k e n n i c h n e t that for the compression of the evaporated A screw compressor (3) is provided, which has a known external boiler (2) is connected downstream, in which the heating of the liquid (W) by means of released Heat of condensation occurs. 9. Apparatus according to claim 8, d a d u r c h g ek e n n z e i c h n e t that the external boiler (2) is followed by a heat exchanger (7) in which Heat is extracted from the condensate (K) and fed to the process water (BW). 10. Apparatus according to claim 8 or 9, d a d u r c h g e k e n n it is clear that the screw compressor (3) can be driven by a diesel engine (5) is, which is coupled to a heat exchanger (6) in which the waste heat from the diesel engine (5) is used for water heating. 11. The device according to claim 8 or 9, d a d u r c h g e k e n n z e i c h n e t that the screw compressor (3) can be driven by an electric motor is. 12. The apparatus of claim 10, d a d u r c h g ek e n n z e i c h n e t that the first-mentioned heat exchanger (7) with the second-mentioned heat exchanger (6) is connected in series. 13. Device according to one of claims 8 to 12, d a d u r c h g It is not noted that the external boiler (2) is preceded by a steam cooler (4) is, the condensate (K) from the external boiler (2) for injection into the compressed Steam can be supplied. 14. Device according to one of claims 8 to 12, d a d u r c h ge no indication that the screw compressor (3) condensate (K) from the external boiler (2) can be supplied for injection into the vapor plumes during compression.