|1.||A process for the continuous or batch "cooking" of ground or crushed cereals or slurries for the production of grain spirits or extracts, characterised in that heat energy is recycled by permitting the dissipation thereof to take place by the formation of fl steam and subsequently, recovering and using the latent heat and a portion of the sensible heat of this flash steam at or below atmospheric pressure to heat the incom slurry in stages, to approach the flash steam saturation temperature, prior to entry to the existing cooker.|
|2.||A process as claimed in claim 1, characterised in that enzymic material is added before the staged preheat by flash steam to accelerate the hydrolysis of the starc reduce the viscosity of the intermediate product and mak it possible to carry out the final cooking reaction at a lower temperature.|
In a known process for the purpose stated prepared batches or cereal .are cooked or heated under pressure to reach fixed temperatures in closed vessels by direct injection of steam for specified times to solubilise the 0 starches or produce soluble extracts. On completion of this cooking stage, the vessel is emptied and the excess heat content above the atmospheric saturation temperature flashes off as steam or water vapour at low pressure. Alternatively a continuous flow of prepared ground cereal slurry is 5 pumped at a known rate through a known swept volume of plant in the form of a continuous tube or in series flow through a number of column type vessels. In the latter process steam at a pressure of approximately 9 - 13 atmospheres is directly blown into the slurry and the Q temperature of the mixture is raised to the required level (say 150°C) for the required time to produce the required solubility. As in the batch cooking process, the next stage of the process is to cool the cooked product initially to •100 C and finally to the reaction temperature for conversion = to sugars by an enzymic reaction. Again, this cooling process requires the rejection or dissipation to the atmosphere, of at least 80% of the heat energy added to cook the slurry. These cooking processes require high energy inputs and produce high energy losses. 0 DISCLOSURE OF INVENTION
The primary objects of the invention are to reduce ' the energy input requirements and the energy losses.
In the attainment of these objects the present invention provides for' the recycling of heat energy hitherto dissipated 5 to the atmosphere, and for lowering of the gross energy.
requirements by improving the method of adding the enzymi materials and so lowering the final cooking temperature.
In accordance with the present invention, the. recycl of heat energy is achieved by permitting the dissipation of heat energy to take place by the formation of flash steam and, subsequently, recovering and using the latent heat and a portion of the sensible heat of this flash steam at or below atmospheric pressure to heat the incomi slurry in stages, to approach the flash steam saturation temperature, prior to entry to the existing cooker. In this way, the use of live steam generated at the works steam boiler plant is replaced by flash steam and the net energy input of the process is reduced.
Selected enzymic material is preferably added before the staged preheating by flash steam to accelerate the hydrolysis of the starch, reduce the viscosity of the intermediate product and make it possible to carry out the final cooking reaction at a lower temperature.
BRIEF DESCRIPTION OF DRAWINGS Reference is now made to the accompanying drawings, wherein Fig.l illustrates diagrammatically plant used in a known process for thecontinuouscooking of prepared ground cereal slurry for the production of grain spirits, and Fig. 2 shows the flow diagram of a continuous flow cereal, cooking plant in accordance with the present invention.
DESCRIPTION OF PLANT USED IN KNOWN PROCESS
Referring firstly to Fig. 1 water and ground maize are fed through respective supply lines 10 and 11 into a -wetting out tank 12 equipped with a stirrer 13. The resulting slurry is at 60°C and leaves the tank 12 through the bottom thereof along a pipe 14 and reaches the supply side of cooker supply pumps 15 wherefrom it is pumped through a pipe 16 to a bank 17 of όooker tubes. The level of the slurry in the tank 12 is controlled by level
controller 18 via line 19 linking a pneumatic control valve 20. The line 14 is fitted with a manually-controlled isolating valve 21. At the suction side of each pump 15 is a manually-controlled isolating valve 22 and at the discharge side of each pump 15 is a manually-controlled isolating . valve 23 directly downstream of which is a non-return valve 24. Prior to linking with the bank 17 of cooker tubes, the line 16 is fitted with a manually-controlled isolating valve 25 downstream of which is a non-return valve 26, and, immediately upstream of the bank 17 of cooker tubes, steam at a pressure of 9 - 13 atmospheres and supplied from a boiler is blown through a line 27 directly into the slurry in the line 16. A non-return valve 28 is fitted into the line 27 prior to linking with the line 16 and upstream of the valve 28 in the line 27 is a pneumatic control valve 29 where a line 30 from a temperature controller 31 links with the line. 7, the temperature controller 31 controlling the temperature of the steam- slurry mixture at input to the bank 17 of cooker tubes. On passage through the bank 17 of cooker tubes, the temperature of the steam- slurry mixture is raised to the required level (say 150°C) for the required time to produce the required solubility. The next stage in the process is to cool the cooked product initially to 100°C and finally to the reaction temperature for conversion to sugars by an enzymic reaction. To this end the cooked product leaving the bank 17 of cooker tubes passes through a line 32 into a first stage cooler 33. A pneumatic control valve 34 is fitted into the line 32 where a line 35 from a pressure controller 36 links with the line 32 upstream of the cooler 33, the pressure controller 36 controlling the pressure of the cooked product immediately prior to leaving the bank 17 of cooker tubes. Heat energy released from the cooked product in the first stage cooler 33 is vented to atmosphere. The heat energy rejected or dissipated
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to atmosphere in this way, represents at least 55% of th heat energy added to cook the slurry.
The cooked product passes through the bottom of the first stage cooler 33 by way of a pipe 39 to a second stage cooler 40, entering the latter substantially midwa of the height thereof. The level of the cooked product in the first stage cooler 33 is controlled by a level controller 41, a line 42 from which is linked by way of a pneumatic control valve 43 with the line 39. Vapour rising from the cooked product in the second stage coole 40 flows through a line 44 to a condenser 45 whence the foul condensate is discharged to drain through a line 46. A pressure controller 47 for control of the pressu in the second stage cooler 40 is linked through a line 4 with the line 44 by way of a pneumatic control valve 49. The product discharged from the second stage cooler 40 through the bottom thereof flows through a pipe 50 to wort pumps (not shown) and then to convertor tubes (not shown) to which are separately supplied malt and an enzy The malt is supplied from a malt slurry tank 51 through a discharge line 52 therefrom, through malt pumps 53 and 54, and a line 55 to the convertor tubes, a flow meter 56 intercepting the line 55. The enzyme is supplied fro an enzyme tank 57 through a discharge line 58 therefrom, through enzyme pumps 59 and 60, and a line 61 to the convertor tubes, a flow meter 62 intercepting the line 6
BEST MODE OF CARRYING OUT THE INVENTION
Referring now to Fig. 2, wherein like parts already identified in Fig. 1 have been allotted the same referenc numerals to avoid duplication of description, in t he flow diagram of a continuous flow cereal cooking plant in accordance with the invention, the ground cereal slurried in hot water proportionately dosed witft a suitable enzyme selected according to the end product of the plant (e.g.
- 5 - grain whisky or neutral spirit for other uses) is pumped by first stage slurry heater pumps 65 to a first stage heater 66, where it is instantly heated by recycled low- pressure steam (flash steam), supplied through line 67, to the appropriate temperature to optimise the relationship between reaction rate and lifespan for the enzyme in use.
The output from the first stage slurry heater 66 drops to a holding tank 68. This tank 68 is sized to supply the reaction time necessary to permit part of the thinning reaction of the enzyme to take place as a r as is possible in a single continuously mixed reaction vessel.
The partially thinned product is then pumped, by second stage slurry heater pumps 69, in 'slug' flow through a bank 70 of pre-cooker tubes to ensure that all of the product has a minimum of the required reaction time and temperature to ensure a satisfactory enzyme reaction.
The product from the bank 70 of pre-cooker tubes is discharged through the nozzle of the second stage slurry heater 71 where it is instantly heated to a level close to its atmospheric boiling point by the remaining recycled low pressure vapour (flash steam) supplied through line 72.
Discharge from the second stage slurry heater 71 is direct to a small head tank 73, connected to the main cooker supply pumps 74 through line 75.
The necessary heat to complete the liquefaction and extraction process of the starch and heat the remaining insoluble slurry is then supplied by the direct injection of steam from the works boiler plant through the line 27. The slurry output from the bank 17 of main cooker tubes at a ' controlled pressure related to the final processing or cooking temperature, passes through the pressure reducing or let down valve .34 to the first stage cooler 33 which operates at a normal condition of 1-2 p.s.i.g. 216°F. The slurry heaters used employ the principle of the jet pump.
The slurry in each case is pumped at pressure through
- δ - a nozzle and the depression in pressure, created by the liquid jet velocity, is used to induce the flow of low pressure vapour into the vena contracta so formed. By this method, the recovered flash steam can be induced int the slurry at pressures close to or slightly below atmospheric and totally condensed.
Initial start-up of the plant would be by means of ■ a low pressure make-up steam supply from the works boiler plant throught a line 76. This supply would only be use during start-up or in an emergency and would be shut-down as soon as the normal flow of low pressure flash vapour became available from the first stage cooler.
Emergency control features to shut down the supply of cereal in the event of failure of the enzyme supply are incorporated into the control system as shown in Fig. 2.
In addition to the normal pressure and temperature contro functions, interlocking on the outlet temperature for the 1st slurry heater would be incorporated to ensure that th outlet temperature appropriate to the enzyme in use was automatically preset.
Equally,there is an inbuilt control function which assures that changeover, for example, to grain spirit for whisky production, can be accomplished without the presen of any enzymes foreign to the natural malt enzymes used for that purpose.
MODIFICATIONS OR DEVELOPMENTS OF THE INVENTION (i) The variation of the particular enzyme used and the effect this in turn would have on the operating temperatures of the first stage slurr heater.
(ii) The use of indirect heat exchanger systems in place of the two stage slurry heating system (iii) The use of the 2nd stage cooler condenser as source of preheat for the water used for slurry of cereals.
ADVANTAGES OF THE INVENTION (i) Energy cost savings due to the recycling of and use of flash steam from the process at low pressure in place of steam supplied from conventional Boiler Plant. These savings are in order of 33% of present fuel costs for cooking (ii) Energy cost savings due to the improvements in addition of enzymic materials and the consequent reduction in processing temperatures this improvement _ provides. The savings are in the order of 31% of the present fuel costs for cooking and are dependent on the initial cooking temperature. Processing temperatures are reduced due to the improvemenets in the methods of enzyme addition. (iii) The drop in processing temperature permits a further saving in energy costs in the order of 31% of the present fuel costs. Overall energy cost savings in the order of 64% are thus obtained, dependent in the final cooking temperature. (iv) Possible process cost savings e to reduction in overall use of enzymic materials.
INDUSTRIAL APPLICABILITY A process according to the invention for the continuous or batch "cooking" of ground or crushed cereals or slurries is epecially applicable in distilleries. The process is, however, generally applicable to the conversion in insoluble starches to soluble starches and the conversion of these soluble starches to sugars.
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