GB2384161A

GB2384161A - Conditioning powders

Info

Publication number: GB2384161A
Application number: GB0129014A
Authority: GB
Inventors: John Lee; Paul Richard Mayer
Original assignee: POWDER CONDITIONING Ltd
Current assignee: POWDER CONDITIONING Ltd
Priority date: 2001-12-04
Filing date: 2001-12-04
Publication date: 2003-07-23
Also published as: GB0129014D0; AU2002347341A1; WO2003048664A1

Abstract

The powder, particularly flour, is fed batchwise into a conditioning column (2) defining an internal conditioning space, and having a base construction (1) with a conical gas-permeable membrane in between. Gas, pre-conditioned as to temperature and moisture, is blown up through the membrane to fluidize the powder above. The gas flow is distributed so that powder lying over higher-flow regions spills over on to lower-flow regions, creating a circulation of powder in the column and efficient conditioning. Powder can be discharged through a central port at the column base, controllable by an automated discharge valve (3).

Description

METHODS AND APPARATUS FOR CONDITIONING POWDERS

This invention relates to methods and apparatus for conditioning powders in the context of industrial processes.

While not limited in this respect, we envisage particular applicability of the present concepts for the conditioning of

flour. Powders used in industrial processes raise special issues of storage, handling and transport. Particular issues associated with the particulate nature of the material include temperature control; - moisture absorption; aggregation; settlement) separation of mixed components or different particle sizes; - chemical degradation and others. Difficulties in any one or more of these respects can raise serious problems in downstream processing of a material, in terms of the processing as such and/or in terms of the quality of the resulting product.

An example of a powder material presenting processing problems is flour, used in the baking of dough/pastry products e.g. bread loaves. For a given dough/pastry preparation, there is usually an optimum temperature for the flour e.g.

18C when charged to a dough mixture. Above the optimum temperature, yeast in the dough is prematurely activated and moisture is driven off from the dough mix. This tends to make the finished loaf underweight, so the charging temperature is important. However flour is typically delivered from the mill retaining, to varying degrees, heat from the milling process.

It is transferred from bulk storage to a batch weigh hopper (positioned above a dough mixer), usually by pneumatic transfer. The transfer temperature depends on ambient conditions and may be as high as 35C ; in any event it is hard to control. As a result the ideal charging temperature (18C ) cannot be achieved reliably.

It would be desirable to have a means for processing powder, for example flour, that enables all or some of these difficulties to be addressed. A preferred aim is to be able to deliver flour to a mixing process at a predetermined charging temperature.

What we propose is to charge the powder into a conditioning chamber having a gas-permeable base and subjecting the charge of powder to an up- flow of gas through the base. The gas flow rate differs in different regions over the base, causing powder in one or more higher-flow regions to rise and spill over to one or more lower-flow regions, bringing about progressive mixing and agitation of the powder

in a ventilated state, and preferably in a fluidised state.

This characteristic movement of the powder in the chamber lends itself to conditioning the powder rapidly in various ways, because the entire batch of powder can progressively and rapidly be exposed to predetermined conditions. The conditions can be determined by controlling the nature and state of the gas which is blown, and/or the conditions in the chamber. Thus, gas may be blown into the chamber at a regulated temperature and/or moisture content. The chamber wall may be temperature-controlled, e.g. by means of a heating or cooling jacket. The chemical nature of the gas may be selected according to the powder being processed. For flour, air is preferred.

The powder material is usually charged to the conditioning chamber batchwise.

The mode of discharge of the conditioned powder material from the chamber is not strictly limited, but we particularly prefer to discharge the material through a discharge port having a discharge valve whose valve element seats against a valve seat of the port from the interior of the chamber.

Preferably the valve element and/or the discharge port includes one or more regions subject to a clearing flow of gas. Such a flow can serve to keep the sealing surfaces of the valve element and seat clear of powder as they meet,

and/or facilitate the flow of powder out through the port.

Such a flow may be provided by surfaces at or adjacent the port and/or valve element having one or more gas flow openings in communication with a pressurised gas supply conduit.

The discharge port is preferably through the centre of the chamber base.

Another aspect of the invention is apparatus for conditioning powder, e.g. flour conditioning apparatus, comprising a conditioning chamber e.g. in the form of an upright column; a gas-permeable base of said column, e.g. a mesh, sinter or porous plate, with gas permeation holes small enough for the base to retain the powder to be processed; a gas distribution system for introducing a flow of pressurized gas into the chamber interior through the gas-

permeable base, the gas distribution system including means for providing a higher gas flow pressure at one or more higher-flow regions of the gaspermeable base than at one or more other lower-flow regions thereof.

In a preferred embodiment the gas distribution system includes means such as dividing walls or discrete sub-chambers for enabling flows of gas at different pressures to different respective regions of the gas-permeable base. For example a distribution chamber mounted beneath the base of the

conditioning chamber may be divided into sub-chambers. The sub-chambers may have discrete gas supplies for full control.

Or, pressure differential between chambers may be created by restricted flow communications between sub-chambers.

The gas-permeable base may be held in place between peripheral walls of the conditioning chamber and gas distribution chamber.

The conditioning chamber may be provided with any one or more of temperature control means, e.g. a heating/cooling jacket, sensing means for measuring conditions (e.g. temperature pressure) inside the chamber or at its wall and weighing means for weighing the charge in the chamber.

A discharge port may be provided through the base of the chamber as discussed previously. Because a discharge channel of the port may extend down through a gas distribution chamber as described above, the gas distribution system may easily communicate with this channel via one or more ports, jets or permeable walls to provide a clearing gas flow as mentioned previously. The valve element of a discharge valve may have a convex leading surface shaped to seat against an annular valve seat of the discharge port. A drive for the valve element may have a drive member extending to an opposite extreme, e.g. the top, of the conditioning chamber where is it operatively connected to a drive. The valve element may have one or more internal gas flow channels leading to its surface, to clear

powder from the surface in use as mentioned previously. A gas supply for this purpose may be fed along a drive member on which the valve element is mounted.

Preferably the chamber base inclines down towards the discharge port, to assist discharge of material. It may have a conical form, for example.

The apparatus may be programmed so that operation of the discharge valve can be made dependent on the readings of one or more sensors as mentioned above.

A further aspect of the invention is a method of making a flour-based product in which flour is fed from storage to a mixing stage by way of a method or apparatus as specified herein. A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: FIGURE 1 shows a side view of the Flour Conditioning Tower (FCT) FIGURE 2 shows a sectional side view of the Gas Distribution Reservoir (GDR) FIGURE 3 shows a sectional side view of the Flour Conditioning Column (FCC) FIGURE 4 shows a side view of the Pearl Drop Valve (PDV).

FIGURE 5 shows a sectional view of the Pearl Drop Valve (PDV).

FIGURE 6 shows a view of the Flour Conditioning Tower Figure 1 on loadcells.

Figure 1 shows the principle sub-assemblies that make up the Flour Conditioning Tower and comprises a Gas Distribution Reservoir 1, Flour Conditioning Column 2 and Pearl Drop Valve Figure 2 shows a more detailed view of the Gas Distribution Reservoir that comprises the following components: upper flange 4, reservoir outer wall 5, reservoir base 6, central column 7 and internal divider plates 8. When these five components are joined together they form a number of gas tight chambers embodied within the Gas Distribution Reservoir Figure 2. The primary membrane 9, is secured to flange 4, by a locating and locking mechanism 14, and then tensioned against the central column 5, by the removable valve seat 10, which incorporates the secondary membrane 13. The removable valve seat 10, is then secured into position by a locking mechanism Final tensioning of the primary membrane 9, is achieved by securing the primary membrane 9, between the clamping spines 12, and the internal divider plates 8.

Figure 3 shows a more detailed view of the Flour Conditioning Column that comprises the following components: a lower flange 15, inner column wall 16, fixed/removable column top 17, intermediate jacket wall 18, outer insulation wall 19 and multiple sensor pods 20. When these six components are joined together they form the top section of the Flour Conditioning Tower Figure 3 which is attached to the Gas Distribution Reservoir Figure 2 as set out in Figure 1.

Figure 4 shows a view of the Pearl Drop Valve that comprises the following components: inter-changeable valve head 21, housing 22, main shaft 23, shaft housing 24 and linear actuator 25. When these five components are joined together they form the Pearl Drop Valve (PDY) assembly.

Figure 5 shows a more detail view of the Pearl Drop Valve gas purge fluidising system that comprises the following components: interchangeable valve head 21, housing 22, main shaft 23, shaft housing 24 and linear actuator 25. When these five components are joined together they form the Pearl Drop Valve (PDV) assembly.

Figure 6 shows a view of the Flour Conditioning Column Figure 1 supported on load-cells 26.

The configuration of the Gas Distribution Reservoir Figure 2, the state of the pre-conditioned gas and the pressure/transfer velocity of the gas from the Gas Distribution Reservoir Figure 2, into the Flour Conditioning Column Figure 3 are particular embodiments of the invention that ensure the flour is homogeneously conditioned before being discharged from the Flour Conditioning Column Figure 3, for onward processing.

Homogeneous and successful conditioning of a flour is a factor of the flours bulk density and specific-gravity as these will determine the pressure and transfer velocity of the preconditioned gas from the Gas Distribution Reservoir Figure 2, into the column of flour contained within the Flour Conditioning Column Figure 3.

As shown in Figure 2, a particularly preferred embodiment of the invention the Gas Distribution Reservoir Figure 3, is subdivided to form a number of individual gas tight chambers that can range in number between 2 and 72. Each chamber within the Gas Distribution Reservoir Figure 2, can be independently controlled to receive and transfer into the Flour Conditioning Column Figure 3, preconditioned gas.

In a particularly preferred embodiment of the invention the assembly angle of the primary membrane 9, which is an

embodiment of the Gas Distribution Reservoir Figure 2, can be varied dependent upon the flour characteristics and the process parameters and is an aid to conditioning and discharging the flour from the Flour Conditioning Tower Figure By varying the pressure and transfer velocity of the preconditioned gas from within the Gas Distribution Reservoir Figure 2, into the column of flour contained within the Flour Conditioning Column Figure 3, the flour is encouraged to migrate vertically upwards and downwards.

A particularly preferred embodiment of the invention relates to each of the chambers contained within the Gas Distribution Reservoir Figure 2. By varying the.pressure and transfer velocity of the preconditioned gas from each chamber of the Gas Distribution Reservoir Figure 2, flour above each chamber is forced to migrate upwards and downwards on a pressure wave within the Flour Conditioning Column Figure 3, at different velocities. Flour situated above a chamber that has been set with a higher pressure and transfer velocity will rise at a faster rate than flour that is situated above a chamber that has been set with a lower pressure and transfer velocity as this flour will rise

at a slower rate. This disproportionate rate of movement of the flour within the Flour Conditioning Column Figure 3, will cause the flour that is rising at a faster rate to shear off the flour column by virtue of the flours angle of repose and into the column of flour that is moving at a slower rate.

As more material migrates from the high pressure flour column onto the low pressure flour column a back pressure is created that will cause the flour at the base of the low pressure column to migrate across the Flour Conditioning Column Figure 3, and into the path of a flour column containing a differential pressure and transfer velocity.

As a result of the differential movement of the flour and the process variable that may be different for each grade of flour a migratory path for the flour is created within the Flour Conditioning Column Figure 3, that will ensure a homogenous conditioning of the flour is achieved.

In one particular embodiment of the invention the environment of the Flour Conditioning Column Figure 3, can be either directly or indirectly conditioned other than by receiving preconditioned gas directly from the Gas Distribution Reservoir Figure 2. This manner of conditioning the Flour Conditioning Column Figure 3, other from the Gas Distribution

Reservoir Figure 2, is known as the Secondary Conditioning Stage (SCS).

The Flour Conditioning Column Figure 3, can be jacketed externally and insulated to accept hot, cold or chilled water, steam or any other cooling or temperature raising media.

Alternatively an electrical heat trace system can be applied to the external surface of the Flour Conditioning Column Figure 3, as a means of controlling the vessels internal environment. Within certain industrial processes it may be necessary or preferred to provide a direct Secondary Conditioning Stage into the flour column within the Flour Conditioning Column Figure 3, either separately from or simultaneously with the Primary Conditioning Stage. Where this form of conditioning is preferred this can be achieved through strategically placed injectors, lances or spray balls.

Within certain industrial processes it may be desirable or necessary to add various forms of essences or flavourings to the flour during the final conditioning stage of the flour to ensure optimum dispersion. Where this form of secondary conditioning is preferred this can be achieved through strategically placed injectors, lances or spray balls.

As a process vessel the Flour Conditioning Tower Figure 1, is continually monitored throughout all it elements with sensors that will typically monitor both the Gas Distribution Reservoir Figure 2, and the Flour Conditioning Column Figure 3, for gas pressure, gas flow, gas temperature and gas moisture. Data for each of these elements is collected and compared automatically against the process set points for the flour and where the processing elements need to be varied this is carried out automatically within an intellectually secure program that is embedded within a Programmable Logic Controller (PLC).

In a particularly preferred embodiment of the invention the Flour Conditioning Tower Figure 1,.incorporates a discharge devise known as a Pearl Drop Valve (PDV) Figure 4, that is vertically supported from and centrally positioned within the Flour Conditioning Column Figure 3.

The Pearl Drop Valve Figure 4, acts to shut off the flow of flour from the Flour Conditioning Column Figure 3. As the valve head 21, travels vertically downwards it centrally docks self and seals against the removable valve seat 10.

In a particularly preferred embodiment of the invention the interchangeable valve head 21, is positively guided and docked into position by an integral design feature that is embedded within either the clamping spines 12, or the inter-

changeable valve head 21. The choice of embodiment in respect of the docking protocol will be dependent upon the characteristics of the flour and the process parameters.

In a particularly preferred embodiment of the invention the interchangeable valve head 21, can be pressurised to emit gas jets through strategically placed ports so that as the inter-

changeable valve head 21, approaches it docking and sealing position the sealing face of the removable valve seat 10, is cleared of any residual flour by the jets of pressurized gas.

As the inter-changeable valve head 21, is raised vertically upwards flour is encouraged to discharge from the Flour Conditioning Column Figure 3, via the Pearl Drop Valve Figure 4, at a flow rate that is dictated by process conditions.

One particularly preferred aspect of the invention is that of raising vertically the Pearl Drop Valve Figure 4, by means of a linear actuator that incorporates a form of proportional control so that flour flowing from the Flour Conditioning Column Figure 3, is discharged at a metered flow rate.

In a particularly preferred embodiment of the invention the flour can be fluidised at five separate stations situated within the Flour Conditioning Tower Figure 1, to assist in discharging the flour and these are explained as follows: The Gas Distribution Reservoir Figure 2, contains four of the fluidising stations with the main fluidising station being the primary membrane 9, where depending on the characteristics of the flour the whole of the primary membrane 9, is exposed to a constant or variable pressure and velocity of preconditioned gas. By passing the preconditioned gas through the primary membrane 9, flour that is at the base of the flour column and close to the primary membrane 9, changes state and takes on a fluidised conditions that allows it to flow freely and discharge its self from the Flour Conditioning Tower Figure 1.

The second fluidising station is located between the central column 7, and the removable valve seat 10. Preconditioned gas can be passed through the secondary membrane 13, either directly from the Gas Distribution Reservoir Figure 2, or indirectly piped in from an independent gas source.

One particularly preferred aspect of the invention is that the pressure and velocity of the independent gas source can be varied to that of the main gas source held within the Gas Distribution Reservoir Figure 2. This variation in pressure and velocity is a further endearment to promoting an efficient flour flow from the Flour Conditioning Tower Figure 1.

The third fluidising station is maintained as an integral design feature within the removable valve seat 10, and can comprises multiple rows of through holes on the sealing face of the removable valve seat 10. Dependant upon the flours characteristics and process parameters preconditioned gas can be passed through the primary membrane 9, either directly from the Gas Distribution Reservoir Figure 2, or indirectly piped in from an independent gas source.

The forth fluidising station is maintained as an integral design feature within the clamping spines 12, and can

comprises multiple rows of through holes on the flanks of the clamping spines 12. Dependant upon the flours characteristics and process parameters preconditioned gas can be passed through the primary membrane 9, either directly from the Gas Distribution Reservoir Figure 2, or indirectly piped in from an independent gas source.

One particularly preferred aspect of the invention is that the pressure and velocity of the independent gas source can be varied to that of the main gas source held within the Gas Distribution Reservoir Figure 2, This variation in pressure and velocity is a further endearment to promoting an efficient flour flow from the Flour Conditioning Tower Figure The fifth fluidising station is maintained as an integral design feature within the Pearl Drop Valve Figure 5, and can comprises multiple rows of through holes on the surface of the inter-changeable valve head 21, through which an independent and preconditioned gas source is passed.

One particularly preferred aspect of the invention is that the pressure and velocity of the independent gas source can be varied to that of the main gas source held within the Gas Distribution Reservoir Figure 2. This variation in pressure

and velocity is a further endearment to promoting an efficient flour flow from the Flour Conditioning Tower Figure 1.

In one particularly preferred aspect of the invention the Flour Conditioning Tower Figure 1, can be incorporated into a weighing system. Figure 6, shows one such example where the Flour Conditioning Tower Figure 1, is supported on load-cells 26, where the function of the load- cells 26, is to record by weight the flour entering the Flour Conditioning Tower Figure 1. When a predetermined set point is breached within the load-

cell weighing system flour is prevented from entering the Flour Conditioning Column Figure 1.

In a particularly preferred embodiment of the invention, the operation of the Pearl Drop Valve Figure 4, can be proportionately controlled so as to modulate its movement vertically up and down relative to a discharge flow rate or dosing rate of flour from the Flour Conditioning Tower Figure Data from the load-cell system that is continuously monitoring the weight loss of flour from the Flour Conditioning Tower Figure 1, is collected and compared automatically within an intellectually secure program that is embedded within a Programmable Logic Controller (PLC).

Where the discharge flow rate or dosing rate of flour from the Flour Conditioning Tower Figure 1, moves away from the process set point the Pearl Drop Valve Figure 4, is signalled to proportionately modulated up or down to increase or decrease the flow rate or dosing rate of the flour being discharged from the Flour Conditioning Tower Figure 1.

The method of the invention provides a homogeneously conditioned batch of flour that can be held at a predetermined set point condition as dictated by the process parameters that can be when required totally, partially or consistently discharged from the Flour Conditioning Tower Figure 1.

The invention is not limited to the embodiments hereinbefore described that may be varied in detail.

Claims

1. A powder conditioning method in which powder is charged into a conditioning chamber (2) having a gas 5 permeable base (9) and subjected to up-flow of gas through the permeable base (9), causing powder in regions of the chamber where the up-flow of gas has a higher rate to rise and spill over onto regions where the up-flow of gas has a relatively lower rate, bring about progressive 10 mixing and agitation of the powder.

2. Method according to claim l in which the up-flow of gas fluidizes the powder.

15

3. Method according to claim l or 2 in which the blown gas is preconditioned as to temperature and/or moisture content.

4. Method according to any one of the preceding claims 20 in which gas is blown through the base of the conditioning chamber from plural segregated supply chambers at different supply rates.

5. Method according to any one of the preceding claims 25 in which the conditions inside the conditioning chamber are monitored, and ongoing conditions applied to the chamber, including any one or more of input gas moisture, input gas temperature, input gas rate, heat or cooling applied to column wall or column interior, is controlled 30 or varied in dependence on the monitored values.

6. Method according to any one of the preceding claims including discharging the powder from the conditioning chamber through a port in the base of the chamber.

7. Method according to claim 6 in which the port is central in the base and the base slopes down towards the port. 5

8. Method according to any one of the preceding claims in which the powder is a food ingredient.

9. Method according to any one of the preceding claims in which the powder is flour.

10. Food production method, for example for flour-based products, in which a food ingredient powder such as flour is conditioned by a method according to claim 8 or 9 before subsequent processing such as mixing and baking.

11. Apparatus for conditioning powder comprising a conditioning chamber (2), a gas-permeable base (9) for said chamber, and a gas distributing system for introducing a flow of 20 pressurized gas into the chamber interior through the gas-permeable base (9), the gas distribution system being adapted to providing a higher gas flow pressure at one or more higher-flow regions of the gas-permeable base than at one or more other, lower-flow regions thereof.

12. Apparatus according to claim 11 in which the gas distribution system includes a sub-divided chamber beneath the gas-permeable base of the column.

30

13. Apparatus according to claim 11 or 12 in which the conditioning chamber has a discharge port through its base.

14. Apparatus according to claim 13 in which the base of 35 the chamber slopes down towards the discharge port.

15. Apparatus according to claim 13 or 14 in which the discharge port is in the centre of the base.

16. Apparatus according to any one of claims 11 to 15, S comprising one or more sensors for detecting conditions inside the conditioning chamber.

17. Apparatus according to claim 16 in which said sensors include temperature sensors and/or moisture 10 sensors.

18. Apparatus according to any one of claims 11 to 17 including temperature adjustment means for controlling the temperature in the conditioning chamber, e.g. in 15 dependence on conditions detected therein.

19. Apparatus according to any one of claims 11 to 18 in which a discharge valve of the apparatus is operable to discharge conditioned powder from the conditioning space 20 at a variable controlled rate.