CA2296302A1 - A mobile modular production system including a drying tunnel - Google Patents

Abstract

A portable modular production system (1) comprising a modular production line (12) and a modular support building (3, 4, 9, 10, 11), a production line (12) in particular a portable production line (12) arranged in a series of isolatable cells (30) arranged in the form of a drying tunnel and a process for dehydrating a product, in particular a biological product.

Description

A MOBILE MODULAR PRODUCTION SYSTEM i<VCLUDiTIG A DRYING TUNNEL
The invention relates to a production or manufacturing system, and in particular to a drying system. The invention also relates to a production line, in particular a production line of the drying tunnel type and to a process for dehydrating a product in particular a biological product.
The construction and assembly of manufacturing/production facilities is a time consuming, labour intensive and expensive operation. Accordingly, it is not usually feasible to construct ~ such facilities on a temporary basis e.g. where production/manufacturing facilities are only required on a seasonal basis or are simply ancillary to another temporary operation. Accordingly, due to the absence or lack of economically feasible portable and/or modular manufacturing/production facilities natural and agricultural resources and the like remain unexploited or poorly exploited.
Various attempts have been made to develop portable manufacturing/production facilities. U.S. Patent Specification No. 5,526,583 describes a portable drying kiln for drying timber.

2 0 However, the kiln of U.S. Patent Specification No. 5,526,583 does not result in an efficient production/manufacturing system as timber to be dried within the kiln is simply loaded into the kiln and .retained in the kiln until the drying is complete. The kiln of U.S. Patent Specification No. 5,526,583 does not facilitate movement of timber through the kiln akin to a normal production or manufacturing line having a continuous throughout.
U.S. Patent Specification No. 4,104,850 describes a storage container which is portable and locatable in a field or the like for storing grain during harvesting of the grain prior to delivery. A bin, which is not a permanent stored structure, is described which is adapted to receive grain on a temporary basis before delivery of the grain by trucks or the like from the bin to a desired location. Accordingly, U.S. Patent Specification No.
4,104,850 in essence contemplates a temporary storage bin and does not envisage the location of a temporary or portable production or manufacturing facility adj scent to the grain to be harvested.
Many processes exist for drying products such as foods, fruits, vegetables and other biological materials. Such processes include freeze drying, osmotic drying and heat drying.
Heat drying relies on a combination of heat and mass transfer while, in general, efficient dehydration systems are obtained by suitably adjusting vapour pressure and temperature gradients between an external drying fluid, typically, air and the interior part of a product to be dehydrated.
PCT Patent Application No. PCT/IE 96/00037, the contents of which is incorporated herein by reference discloses a particularly efficient drying process and dried product obtained by the process. In said process, close control of temperature and relative humidity of a drying medium to maintain optimal conditions for the mass transfer of moisture from the products being dried is achieved.
2 0 However, despite the many available drying processes, a disadvantage of such processes and their corresponding apparatus is that the biological products to be dehydrated e.g. fruits and the like must frequently be conveyed from remote locations to a factory. For example, fruits may have to be transported long 2 5 distances and in some cases imported from overseas to a factory when local supplies are out of season. In addition, transport of fruits, etc. over comparatively short distances can cause deterioration in the fruit before dehydration sometimes giving rise to substandard dried product.

3 0 Many rich sources of fruits etc. can also be in locations lacking sufficient infrastructure to reliably and efficiently convey crops to a factory for processing giving rise to wastage and perishing of valuable food resource.
An object of the invention is to overcome the problems of the prior art.
A further object of the invention is to provide a mobile production system.
A still further object of the invention is to provide a dehydration system that minimises transportation of biological product to be dehydrated following harvesting.
According to the invention, there is provided a portable modular production system comprising a modular production line and a modular support building.
Preferably, the system further comprises a modular power source.
More preferably, the production line is housed in a transportable container. Suitably, the transportable container is road transportable. Advantageously, the transportable container is rail transportable.
Preferably, the support buildings are pneumatically supported buildings.
2 0 Preferably, the system further comprises canopy or tentlike ancillary buildings. Suitably, the pneumatic and canopy or tentlike buildings are mountable on concrete. Preferably, service conveying conduits are detachably insertable in the concrete.
Preferably, the modular power source is mounted in a transportable container. Suitably, the transportable container is road transportable. Preferably, the transportable container is rail transportable.

WO 99/04209 PCT/fE98/00059 Advantageously, the power source comprises a combined heat and power unit. Preferably, the combined heat and power unit is diesel fuelled.
In a particularly preferred embodiment of the invention, the production system comprises a drying tunnel. Suitably, the production line comprises a series of communicable and isolatable drying cells disposed in a transportable container.
Preferably, at least one of the drying cells comprises a heat exchanger.
The invention also extends to a production system in which each cell is defined by a first housing spaced apart from a second housing, the first and second housings being located either side of a central passage disposed parallel to the central longitudinal axis of the transportable container.
Preferably, each cell is provided with internal drying medium circulating means for circulating drying medium within the cell.
Preferably, the internal circulating means comprises a fan located in the cell.
In a preferred embodiment of the invention each cell is provided 2 0 with drying medium communicating means for facilitating movement of drying medium between the cells. Preferably, the drying medium communicating means comprises a hole communicable between the cells. Suitably, the hole comprises control means for controlling movement of drying medium.
2 5 Advantageously, the drying tunnel is provided with external drying medium circulating means for drawing drying medium through the drying tunnel. Suitably, the external drying medium circulating means comprises an exit duct in the drying tunnel for extracting drying medium from the tunnel.

The invention also extends to a production line comprising an . elongate chamber for receiving product having a central longitudinal axis and first and second end walls, a ceiling, a floor, first and second side walls, and a door at the first end 5 wall into the chamber for receiving product and a processing region being defined within the chamber adapted to receive the product for processing.
Suitably the processing region is arranged in a series of intercommunicable cells.
1 0 Preferably each cell is defined by a first housing spaced-apart from a second housing, the first and second housings being located either side of a central passage disposed parallel to the central longitudinal axis.
More preferably at least one cell is provided with drying medium circulating means for circulating drying medium within the cell.
Suitably the production line is provided with control means for controlling the circulating means. Preferably the circulating means comprise a fan.
Suitably, each cell is provided with drying medium communicating 2 0 means for facilitating movement of drying medium between the cells. Preferably, the drying medium co~nunicating means comprises a hole communicable between the cells. Advantageously, the hole comprises control means for controlling movement of drying medium.
2 5 Advantageously, the control means comprises a fan located in the first cell of the processing region.
In a preferred embodiment of the invention, at least one cell is provided with a heating element. Preferably, the heating element comprises a heat exchanger.

Advantageously, the second end wall comprises a door to facilitate exit of product from the chamber.
In a preferred embodiment of the invention, the production line is portable and preferably, the production line comprises a transportable container. Suitably, the transportable container is road or rail transportable.
Advantageously, each cell is isolatable from each adjacent cell.
Preferably, each cell is isolatable from an adjacent cell by a product conveying means moveable through the central passage between the first and second end walls.
Suitably, the conveying means comprises a trolley and preferably the trolley is engageable with the housings to isolate the cells.
Preferably, the housing comprises sealing means for sealing the trolley between the first and second housings to isolate the cell.
In a preferred embodiment of the invention, the floor is sloped to facilitate flow of liquid on the floor towards the first or second end walls. Preferably, the floor is sloped towards the first end wall of the chamber.
The invention also extends to a process for dehydrating a 2 0 biological product comprising urging the product through a processing region of an elongate chamber having first and second end walls, from the first end wall to the second end wall, introducing drying medium into the chamber at the second end wall, circulating the drying medium through the processing region with drying medium circulating means, monitoring the drying medium circulating means and exhausting the drying medium from the chamber at the first end wall.
Preferably, movement of the drying medium between the second and first end walls is effected through a series of isolatable cells defined within the chamber between the first and second end wails for receiving the product.
Advantageously, the process further comprises the step of heating the drying medium. Suitably, the process further comprises monitoring the humidity of the drying medium in the chamber and controlling the flow rate of the drying medium between the first and second end walls. Advantageously, the drying medium comprises air.
The invention also extends to the use of a transportable container 1 0 in the construction of a production line and preferably in a production line which comprises a drying tunnel.
The invention also extends to the use of a pneumatically supported building in the construction of a production system.
The production system of the invention has many outstanding advantages. The portability and mobility of the production system facilitates quick erection and fit out of the production system in a desired location. The use of pneumatic ancillary structures in the production system facilitates a high degree of hygiene which can be maintained at low cost. Moreover due to the absence of 2 0 internal supporting frames and other structures in the pneumatic structures a totally unobstructed interior space is provided within the pneumatic structures of the production systems. The pneumatic structures employed for the ancillary structures in the production system of the invention are also collapsible to a 2 5 highly portable pack size of low volume.
. Similarly, the use of tent-like structures in the production system of the invention facilitates the rapid assembly and . disassembly of temporary building structures as required.
Moreover, the tent-like structures are also easily and quickly 30 collapsible to render the tent-like structures easily transportable.

The use of portable power units such as combined heat and power units obviates the necessity of local electricity and/or other power supplies. Accordingly, the production system of the invention may be constructed in remote locations unserviced by power supplies and the like. The combined heat and power units may be transported in road or rail transportable containers in a ready to use form without requiring construction or assembly in situ.
Similarly, the use of a production line housed within a road or rail transportable container facilitates rapid commissioning of the production system of the invention e.g. where it is desired to rapidly process crops and the like whilst the crop is at its peak for harvesting purposes.
The production system of the invention is also environmentally friendly as the production system or facility may be rapidly assembled or constructed and subsequently disassembled for subsequent use without causing permanent damage to the environment.
Accordingly, the drying system of the invention may have 2 0 application in other technologies such as food processing operations generally, manufacturing and high valued protected cropping enclosures.
The invention will now be described by way of example with reference to the accompanying drawings in which:
2 5 Fig. 1 is a perspective view from above of a production system of the drying or dehydrating system type in accordance with the invention;
Fig. 2 is a flow diagram of the drying system of Fig. 1;
Fig. 3 is an end elevation of the transport container housed drying tunnel shown in the system of Fig. 1;
Fig. 4 is a partially cut away side elevation of the drying tunnel of Fig. 3 with the direction of movement of product to be dehydrated in the tunnel being indicated by the arrows;
Fig. 5 is an upper front perspective view from the wet end of a portion of the drying tunnel with the transport container walls removed for clarity and with the longitudinal direction of movement of the drying medium between the cells being indicated by arrows;
Fig. 6 is a perspective view from above of an individual drying cell of the drying tunnel of Figs. 2 to 5 with the circular or helical direction of movement of the drying medium within the drying cell being indicated by arrows in broken lines and the direction of movement of drying medium between cells and along the drying medium conduit being indicated by solid arrows;
Fig. 7 is a perspective view from above of the first drying cell of the drying tunnel with the drying trolley removed for clarity;
Fig. 8 is a perspective view from above of an individual drying trolley for use in the drying tunnel according to the invention;
Fig. 9 is a perspective view from above of an individual 2 5 drying tray for use in the drying trolley of Fig. 8;
Fig. 10 is an end elevation of the first or wet end of the drying tunnel in accordance with the invention;
Fig. 11 is a downward view along the line XI-XI of Fig. 10 showing the ram extending outwards from the entry door of the drying tunnel;
Fig. 12 is a cut away view along the line XII-XII of Fig.

10, and 5 Fig. 13 is an end elevation of the exit end of the drying tunnel in accordance with the invention.
Figs. 1 and 2 show perspective views from above and a flow diagram respectively of a production system 1 in accordance with the invention. In the present embodiment, the production system 1 is 10 a drying or dehydration system 1. However, it will be appreciated by those skilled in the art that the production system of the invention can be employed in many manufacturing and production applications where modularity and/or portability is required.
As shown in the drawings, the drying system 1 is provided with a central fixed administration building 2. The central fixed building 2 is an optional component of the drying system 1 of the invention in that the drying system 1 is adapted to carry out a dehydration process in the absence of the central fixed building 2 which is simply present where a more or quasi-permanent structure 2 0 is required of the drying system 1.
The drying system 1 shown in Figs. 1 and 2 is a double drying system in that identical system components are disposed symmetrically either side of the central fixed building 2. The drying system 1 is therefore made up of two sorting/cleaning 2 5 canopies 3,4 supported on sorting/cleaning canopies frames 5,6 which are in turn disposed over concrete floors 7,8 respectively.
The sorting/cleaning canopies 3,4 can be of conventional construction and are collapsible for transport to another site of the drying system 1 of the invention.
30 The sorting/cleaning canopies 3,4 are positioned immediately adjacent or before respective pneumatically supported processing buildings 9,10. The pneumatic processing buildings 9,10 are of a fabric construction and are supported in an upright position by pressurised air.
The pneumatic processing buildings 9,10 are in turn connected by a pneumatic connector tunnel 11 to the central fixed building 2.
In addition, the pneumatic processing buildings 9,10 each communicate with two elongate drying tunnels 12. The drying tunnels 12 are of elongate transport container construction which shall be explained more fully below. The drying tunnels 12 in turn communicate at their free end with two detraying/packing pneumatic buildings 14,15 disposed either side of the central fixed building 2. A pneumatic connector tunnel 13 is disposed between each drying tunnel 12 and its respective detraying/packing pneumatic building 14,15.
The detraying/packing pneumatic buildings 14,15 in turn are communicable with pneumatic exit tunnels 17,18 at their ends remote from the drying tunnel 12 through which dried produce exits the system 1.
2 0 It should be noted that the central fixed building 2 is also in communication with the detraying/packing pneumatic buildings by a pneumatic building exit tunnel 19.
The system 1 shown in Fig. 1 is provided with heat and power by combined heating and power (CHP) units 20 disposed between the 2 5 detraying/packing pneumatic buildings 14,15 and in communication with the central fixed building 2.
As shown in Fig. 2, harvested material to be dehydrated or a feedstock source 21 is conveyed to the location of the system 1 and is sorted and cleaned beneath the sorting/cleaning canopies 30 3,4. The sorted and cleaned product to be dehydrated such as fruit is then conveyed into the pneumatic processing buildings 9,10 where the feedstock is prepared for the dehydration process.
The feedstock is then conveyed from the pneumatic processing buildings 9,10 into the dehydration tunnel 12.
A preferred method of dehydration is that disclosed in our co-pending PCT Patent Application No. PCTIIE 96/00037 the contents of which are incorporated herein by reference. However, other conventional dehydration methods can be employed in the system 1 according to the invention.
Moreover, as indicated above, the production system 1 of the invention can be employed for manufacturing and production systems apart from dehydration where modularity and portability is required.
The dehydrated product exits from the drying tunnel 12 into the detraying/packing pneumatic buildings 14,15 where the dehydrated product is removed from drying trays etc. and conveyed through the pneumatic exit tunnel 17,18 onto vehicles etc. for transportation to a marketplace or the like.
CHP units 2 0 The heat and power necessary to carry out a dehydration process in the system 1 of the invention and to provide the pressurised air necessary to support the pneumatic buildings 9,10,14 and 15 and their corresponding pneumatic tunnel 11,13,17,18 and 19 in the upright position is provided by the CHP units 20.
More particularly, the CHP unit 20 provides the necessary power to support services to the system 1 e.g. the necessary power to support the pneumatic buildings and the necessary heating to carry out dehydration. The CHP unit communicates with the system 1 through ducts/pipelines etc. (not shown) disposed beneath the floors of the system 1.

The ducts/pipelines etc. are preferably themselves removable to facilitate transport of same to another location following relocation of the factory.
The buildings of the system 1 are arranged so that the energy requirements are balanced with the output of the CHP unit 20. For example, where diesel is utilised as a fuel for the CHP unit 20, the thermal/electrical output of the CHP unit 20 is compatible with the thermal/electrical requirements of the system 1.
The CHP unit 20, like the drying tunnels I2, is a stand-alone unit in the form of a transport container that can be conveyed to remote locations. However, other power source units may be suitable in place of a diesel powered CHP unit. However, all power units should be in the form of a transport container or at least easily transportable. As indicated above, for ease of transport, the CHP unit 20 is also typically in the form of a forty foot (approximately 12 metres) transport container which is transportable by road, rail or sea.
The forty foot container can also house a boiler to supplement the thermal output of the power unit if necessary.
2 0 A suitable diesel powered CHP unit 20 for use in the drying system 1 in accordance with the present invention has the following typical specification:
CHP set reference SDM 185 Engine Cummins 2 5 (Trade Mark) Running speed 1500 rpm Ratings* Flywheel output max 254 kW
Prime 231 kW

Continuous 200 kW
Alternator Newage (Trade Mark) HC14C
Alternator ratings At Class H Temp. rise 200 kW
At Class F Temp. rise 176 kW
Alternator efficiency 92.5%
Continuous electrical output 185 kW
Fuel Consumption 38 1/hour Secondary cooling water flow rate assumed 250 1/min Secondary cooling water inlet temp. assumed 70°C
Output temperature with full exhaust heat recovery 85°C
Output temperature without full exhaust heat recovery 79°C
* Rating is at 110 m altitude, a temperature of 25°C, relative humidity 30% with fuel to BS 2869 Class A2.
An advantage of the CHP unit 20 is that fuel utilization of more 2 0 than 90% can be achieved thereby maximising efficiency of the drying system 1. Moreover, as indicated previously, balancing of the electrical and thermal loads in accordance with the natural output ratios of the CHP unit 20 can further maximise efficiency of the drying system 1 of the invention.
Balancing is enhanced as much as possible through the use of switchable loads i.e. loads which can be served either by electrical or thermal energy. For example, air being taken into the dehydration tunnel I2 from the detraying/packing pneumatic buildings 14,15 is preheated to maximise balancing.
As indicated above the preferred fuel for use with the CHP unit 20 is diesel although natural gas or liquid petroleum gas may also be used. An advantage of a diesel fuel is the higher energy concentration associated with diesel. Further advantages of diesel are the wide availability of the fuel, the elimination of 5 mains gas supply requirements and pressurised fuel storage vessel requirements. Diesel is also less flammable than many fuels and accordingly has significant safety advantages.
A diesel powered CHP unit 20 also enjoys advantages as compared with conventional power supply sources such as electricity 10 supplied from mains supply and heat supplied by combustion.
It will be appreciated that mains electricity supplies, where available, can be used with the manufacturing system 1 in accordance with the invention. Moreover, if a mains electricity supply is not available, a generator can be used. However, 15 generators result in decreased efficiency e.g. wastage of more than 55% of the calorific value of the fuel used to produce electricity is known.
Pneumatic structures The general method of constructing the pneumatic buildings or 2 0 structures 9,10,11,13,17,18 and 19 is known. The pneumatic buildings are also known as presso-static buildings. Examples of suitable pneumatic structures are available from Plasteco Milano S.P.A., Italy. The pneumatic structures are formed from a single or double envelope of polyester fabric coated with polyvinyl 2 5 chloride (PVC) on both sides. Various components of the polyester fabric PVC coated material are joined together by high frequency welding or by fasteners. The pneumatic structures are generally mounted on a concrete base or floor to which the pneumatic structure is fixed. The pipelines/conduits etc. referred to above 3 0 are housed beneath the floor. Typically, the pneumatic structure is fixed at its base to a metallic pipe adjacent the concrete floor to distribute stresses on the pneumatic structure uniformly at the base. A centrifugal fan, located externally of the pneumatic structure, is used to blow air into the pneumatic structure through a ventilation sleeve to support the pneumatic structure.
Inflation can be achieved rapidly. Following inflation, the fan, utilising minimum power input, maintains a constant overpressure in the pneumatic structure typically varying from 20 to 30mm of water (1/500 to 1/300 atmosphere).
In order to avoid any unwanted decreases in pressure, the pneumatic structures 9,10,14 and 15 communicate with the non-pneumatic structures through the pneumatic tunnels 11,13,17,18 and 19 at air-tight doors disposed in the tunnels. Connection of pneumatic structures to non-pneumatic structures is typically achieved by wrap-around connections connected between the pneumatic and non-pneumatic structures by crimped sleeves or belts.
The pneumatic structures can be easily deflated or collapsed and folded into comparatively small sizes to be conveyed to another location in which it is desired to locate the production system 1 of the invention.
2 0 In the double envelope configuration, a lighter fabric is welded inside the primary polyester fabric PUC coated fabric. Air is blown through a flexible pipe into the space defined between the inner and outer fabric which serves as an insulating element in the envelope.
The buildings of the system 1 are arranged so that maximum benefit is obtained from the output of the CHP unit 20.
The pneumatic structures 9,10,11,13,14,15,17,18,19 can be rapidly assembled and disassembled for portability. In addition, the material and shape of the pneumatic structures facilitates easy cleaning of curved surfaces.

In addition, due to the absence of support structures such as trusses etc. the pneumatic structures can be rearranged as required with minimal effort.
Due to the nature of the pneumatic structures, and the positive pressure within the structures as compared with the exterior, small leakages or punctures etc. in the structure do not distort the pneumatic structure. Moreover, due to the constant throughput of air from the pneumatic blowers, the air can be filtered continuously to arrive at a near sterile air environment within the pneumatic structures which is clearly beneficial in food processing applications.
The floor of the pneumatic structures is typically formed from a concrete slab, the perimeter of which is used to anchor the pneumatic structure. In situations which may require a higher level of interior hygiene, a floor covering manufactured from a food grade material such as Tedlar (Trade Mark) may be used.
In many dehydration or drying processes, severe condensation occurs on the internal walls of the factory which can give rise to the formation of water droplets which can contaminate food 2 0 products being processed. However, in the present system, due to the double membrane structure and the low thermal capacity of the structural membranes, condensation can be easily controlled or eliminated by minor alterations in the temperature or humidity of the air employed to inflate the pneumatic structure.
The air blower used to inflate the pneumatic structures can be provided with control means and recirculation means to function as a climate control system to control ambient conditions within the pneumatic structures.
As indicated above, details on the construction, assembly and maintenance of such pneumatic structure can be obtained in the publications of Plasteco Milano S.P.A., Italy the contents of which are incorporated herein by reference.
Production/Manufacturing Tunnel Figs. 3 to 13 show enlarged drawings of a particularly preferred form of a manufacturing/production tunnel 12 in accordance with the invention. In the present embodiment, the production/manufacturing tunnel 12 is described as a heat/vapour drying tunnel 12 for use in the production system 1 according to the invention when employed as a drying system, as previously described.
The drying tunnel 12, like the CHP unit 20 hereinbefore described, is constructed in the form of an elongate transport container 22 having a central longitudinal axis, typically, of the type formed from a forty foot (approximately 12 meters) steel container. The container 22 is attachable to a vehicle (not shown) to be conveyed to the desired location for the system 1 of the invention.
Externally, the container 22, is of substantially standard steel transport container construction and is made up of a bottom wall or floor 23, two side walls 24,25 upstanding from the bottom wall 23 and a top wall or ceiling 26. The container 22 is further 2 0 provided with an external rear end wall 72 provided with a sealable door 27 and a front or "wet" end wall 71 provided with a sealable door 70.
The doors 27,70 are similar in construction and are made up of hydraulically controlled sub-doors 73,74. The hydraulically controlled sub-doors 73,74 are openable and closeable by respective hydraulic rams 75,76 mounted between the sub-doors 74,74 of each door 27,70 and their respective rear end wall 72 and front end wall 71.
The doors 27,70 are mounted in front and rear openings 78,77 respectively defined in the respective front and rear walls 71,72.

Pneumatically controllable or inflatable seals 79 are located between the doors 27,70 and their respective openings 78,77 so that the openings 77,78 may be sealed when closed.
The bottom wall 23, the side walls 24,25, the top wall 26 and the rear end wall 72 and the front end wall 71 define an internal chamber 69. The side walls 24,25 extend downwards either side of the bottom wall 23 to define supporting side wall extensions 29 while the bottom wall 23 is also provided with two elongate support beams 28 disposed parallel to the side wall extensions 29.
Internally, the container 22 is sub-divided into a series of drying cells 30 supported within frame-like support cages 48. In use, the drying cells 30 can be isolated from each other to form distinct drying units within the container 22 but are communicable with each other via a central longitudinal passage 35 disposed parallel to and along the central longitudinal axis of the container 22 between the bottom wall 23 and the top wall 26. The bottom wall 23 in the passage 35 is sloped so that fluid from the product being dehydrated can flow from the container 22 for collection. As shown in the drawings, each cell 30 is made up of 2 0 a pair of housings 16 disposed either side of the central longitudinal passage 35 namely a first housing 16 adjacent the side wall 24 and a second almost identical opposing housing 16 adjacent the side wall 25, the housings 16 being disposed either side of the central passage 35.
The housings 16 are made up of a curved or arcuate back wall 53 and two side walls 54,55 upstanding from the curved back wall 53 so that the housing 16 is substantially "bath-tub" shaped.
Each pair of housings 16 is separated by the central passage 35 and the housing 16 adjacent the side wall 24 extends between the bottom wall 23 and the top wall 26 of the container 22 while the cell back wall 53 of each housing 16 together with the side wails 54,55 define an open mouth 63 disposed inwards towards the central passage 35.
The open mouth 63 can be covered with an air permeable filter if desired to cause the circulating air to be scrubbed during dehydration.
5 The housing 16 disposed adjacent the side wall 25 is a cut-away form of the housing 16 adjacent the cell wall 24. More particularly, a lower portion of the cell back wall 53 and side wall 54,55 are cut away so that the housing 16 does not extend fully between the top wall 26 and the bottom wall 23. Moreover, 10 the housing 16 is mounted on a horizontal shelf 33 such that the housing defines a cell top portion 31 disposed over the shelf 33.
The shelf 33 defines an opening 51 (see also Fig. 6) which communicates between the cell top portion 31 and a fan housing portion 32 beneath the shelf 33.
15 An elongate horizontal platform 34 extends between the cells 30 along the longitudinal axis of the container 22 between the rear end wall 27 and the front wall of the container 22 in the passage 35. The platform 34 is provided with parallel rails 36 on its top surface on which a trolley can be conveyed as shall be explained 2 0 more fully below.
The pair of parallel rails 36 project from the front end wall 71 at 80 below the front door 70 to receive product into the drying tunnel through the front door 70 as shall be explained more fully below.
Due to the arcuate nature of the cell housing back walls 53, a first upper dead space 37 is defined between the cell back wall 53 of the housing 16 and the upright wall 24. A lower dead space 38 is defined between the back wall 53 and the upright side wall 24 while a second upper dead space 39 is defined between the cell top portion 31 and the side wall 25.

The dead spaces 37, 38 and 39 extend the length of the container 22 so that pipelines and services may be conveyed through the dead spaces 37,38 and 39. More particularly, fluid conveying pipelines or loop 40 can pass through the lower dead space 38 to co~unicate S with heat exchangers 49 as shall be explained more fully below while a drying medium conduit 41 for conveying drying medium from an external blower or the like through an air intake port 81 defined in the rear end wall 72 to the drying cells 30 and the chamber 69 and in turn to an air outlet port 82 defined in the front end wall 71 is mounted in the second upper dead space 39 between the top cell portion 31, the top wall 26 of the container 22 and the side wall 25 of the container 22.
Drying medium conveyed within the drying medium conduit 41 can enter into every fourth cell 30 through an internal air inlet port 47 disposed between the conduit 41 and the cell back wall 53 as shown in Fig. 5. If desired, every cell 30 could be provided with an air inlet port 47 to admit drying medium to the cells 30.
The central longitudinal passage 35 defined between the platform 34 and the top wall 26 is adapted to receive a trolley 42. The 2 0 trolley 42 is rollable on the rails 36 along the length of the platform 34 so that the trolley 42 can move from cell to cell 30 along the length of the container 22 as shall be described more fully below.
As shown particularly in Figs. 5, 6 and 7 each cell 30 is supported within its respective support cage 48 mounted within the container 22. The cell 30 is provided with a heat exchanger 49 disposed horizontally within the housing 16 of the cell 30 between the platform 34 in the corresponding segment of the passage 35 and the cell back wall 53 of the cell 30. The heat exchangers 49 are each connected to the pipelines 40 which convey hot and cold fluid to the heat exchangers 49 within each cell 30 as required. A
series of substantially horizontally disposed baffles 45 are mounted between side walls 54,55 of the cell 30 immediately below the heat exchanger 49. The baffles 45 serve to direct drying medium through the heat exchanger 49 as shall be explained more fully below. The side wall 54 of the cell 30 is further provided with pipeline inlets 56 through which the pipeline 40 bearing heating fluid extends into the cell 30 to communicate with the heat exchanger 49.
The side wall 54 is also provided with drying medium communicating outiets/inlets 46 disposed in the region of the cell 30 above the heat exchanger 49. The outlet/inlets 46 are disposed in each of the side walls 54,55 so that drying medium can pass through and between the cells 30 and parallel to the longitudinal axis of the container 22.
The movement of drying medium through the communicating outlets/inlets 46 facilitates intercellular drying medium flux between the cells 30. Moreover, the communicating outlets/inlets 46 are adjustable by means of a rotary cover plate (not shown) which can be controlled to effect the drying medium inter cellular air flux between the cells 30. Such control ensures that the drying process used in the drying system of the invention can be 2 0 regulated over the full length of a drying cycle for a product to be dehydrated.
Each cell 30 is provided with a temperature sensor 83 to detect the temperature of fluid, typically water, entering the heat exchanger 49. The temperature sensor is mounted adjacent the heat 2 5 exchanger 49 on the fluid conveying pipelines 40.
Each cell 30 is also provided with a drying medium temperature first probe 84 for detecting the temperature of the drying medium prior to contacting product and a drying medium temperature and humidity second probe 85 for detecting temperature and humidity of 3 0 the drying medium following contact with product.
The temperature sensor 83, the drying medium temperature first probe 84 and the drying medium temperature second probe 85 are in communication with and transmit data to a process control unit which controls operation of the drying tunnel 12 as is explained more fully below.
The drying medium temperature first probe 84 therefore detects the temperature of drying medium following contact of the drying medium with the heat exchanger while the drying medium temperature and humidity second probe 85 detects the temperature and humidity of the drying medium following contact with the product. The drying medium temperature first probe 84 and the drying medium temperature and humidity second probe 85 are centrally located above the platform 34 within the first and second housings 16 of the cell 30 to detect as close to an average reading of temperature and humidity as possible.
In an alternative embodiment of the invention, it is not necessary to provide a temperature sensor 83, a drying medium temperature first probe 84 and a drying medium temperature and humidity second probe 85 in each cell 30 of the drying tunnel 12. For example, alternate cells 30 could be provided with the sensor and probes 2 0 83,84,85 in addition to the first cell 30 and the last cell 30 of the drying tunnel 12.
As shown in Fig. 7, an exit duct 67 is provided in the side wall of the cell top portion 31 of the first cell 30 of the series of cells 30 in the drying tunnel. The exit duct 67 is further 2 5 provided with an extraction fan 68 which in use maintains the net longitudinal flow of drying medium progressing from the dry end of the tunnel 12 at the end wall 72 towards the wet end 71 contrary to the direction of movement of the trolley 42.
Accordingly, overall drying medium movement is helical in nature, 30 typically with an imagined parcel of drying medium executing several dozen circular traverses in a cell 30 before moving to its more humid adjacent neighbouring cell 30. The precise ratio of the main circular flows to the "bias" longitudinal flow is determined by the modulation index best suited to the product being dehydrated. Details of modulation indices are to be found in PCT Patent Application No. PCT/IE 96/00037, the contents of which, as previously indicated, is incorporated herein by reference.
Movement of drying medium within the drying tunnel 12 of the invention and more particularly between the cells 30 occurs in a direction opposite to the direction of movement of material to be 1 0 dehydrated within the drying tunnel 12. For example, as shown in Figs. 5 and 6, drying medium is urged through the cells 30 of the drying tunnel 12 along a longitudinal axis disposed parallel to the central longitudinal axis of the drying tunnel 12 while, as described above, movement of drying medium within an individual cell 30 is effected in a substantially helical direction substantially perpendicular to the longitudinal direction of flow of the drying medium between cells 30 while the trolley 42 bearing material to be dehydrated within the drying tunnel 12 is urged through the drying tunnel 12 along the length of the platform 34 2 0 in a direction opposite to the longitudinal direction of movement of drying medium shown in Figs. 5 and 6 i.e. from the front end wall 71 to the rear end wall 72. Movement of the trolley 42 in a direction opposite to the longitudinal direction of movement of the drying medium optimises the dehydration perimeter and moisture 2 5 extraction from the product to be dehydrated.
An axial fan 50 is disposed within the fan portion 32 of the cell 30 adjacent the side wall 25. More particularly, the fan 50 is disposed in the opening fan air inlet 51. Air can be directed by the fan 50 from the inlet 51 to a fan air outlet 52 which 30 communicates between the fan portion 32 and the passage portion 35 disposed beneath the platform 34. A centrifugal fan can be used in place of the axial fan 50 if desired.
Figs. 8 and 9 show enlarged views of the trolley 42 and a tray 59 adapted to be mounted in the trolley 42. As shown in the drawings, the trolley 42 is provided with a planar quadrilateral base 43 having trolley wheels 44 disposed at each corner of the quadrilateral. The planar quadrilateral base 43 is provided with 5 a downwardly depending skirt 65 which extends downwards from the edges of the quadrilateral base 43. The downwardly depending skirt 65 extends almost to the platform engaging bottom of the trolley wheels 44. In addition, the trolley 42 is provided with a bottom blanking plate (not shown) beneath the planar quadrilateral 10 base 43 which enhances the sealing nature of the trolley 42.
The trolley 42 enjoys a sealing relationship with flexible seals 66 disposed on the portion of the frame 48 defining the passage 35 of the tunnel 12.
Accordingly, the trolley 42 co-operates with the seals 66 to 15 provide a near hermetic isolation of each cell 30 from adjacent cells 30 as the trolley 42 is passed through the tunnel 12. More particularly, the trolley 42 is provided with two upstanding side walls 58 disposed either side of the base 43. A series of support bars 64 are disposed between the side walls 58. The support bars 20 64 are adapted to receive and support trays 59 between the side walls 58 in conventional fashion.
The side walls 58 therefore are co-planar with the side walls 54,55 of the housing when the trolley 42 is positioned within a cell 30 to isolate the cell 30 to create a controllable 2 5 environment for the dehydration of product carried by the trolley 42. The trolley wheels are guided along the platform 34 by the rails 36.
The tray 59 is made up of a substantially rectangular tray frame 60 having a mesh 61 disposed across the frame 60. The frame is further provided with a central reinforcing support member 62 across the centre of the frame 60 to prevent deformation of the mesh 61.

In use, the side walls 58 serve to form a sealing relationship with the seals 66 of the passage 35, and with the housings 16 so that each cell is hermetically isolated from adjacent cells by the trolleys 42.
A trolley 42 is urged through the tunnel 12 by the next subsequent trolley being placed in the tunnel 12.
As shown in Figs. 10,11 and I2, a mechanical hydraulic or pneumatic ram 86 extends outwards from the front end wall 71 parallel to the central longitudinal axis of the drying tunnel 12 to urge trolleys 42 through the door 70. The ram 86 is mounted below the door 70 and is positioned between the rail extensions 80 to urge trolleys 42 mounted on the rail extensions 80 through the open door 70 which is subsequently sealed by inflating the seals 79. Extension of the ram 86 causes the trolley 42 to be urged forward through the front door 27.
Product to be dehydrated is placed on a tray 59 on a trolley 42.
Clearly, multiple trays 59 can be placed on the trolley 42 as shown in the drawings. A trolley 42 is loaded into the tunnel 12 by opening the sealable front door 70 at the wet end or front end 2 0 wall 71 of the tunnel 12. The trolley 42 is urged along the rails 36 by the ram 80 and is moved in step wise fashion from cell to cell 30 at intervals of about 15 to 60 minutes depending on product, thickness of pieces etc. As previously described, drying medium is urged through the drying medium conduit 41 from the inlet 81 in a longitudinal direction indicated by the arrow in Fig. 6 contrary to the direction of movement of the trolley 42.
The drying medium can enter a cell 30 through an inlet port 47 in communication between the drying medium conduit 41 and the cell 30. Drying medium is circulated within the cell 30 by the fan 50 as previously described while movement of the drying medium between cells 30 is effected through the drying medium communicating outlets/inlets 46 along a longitudinal axis disposed parallel to the central longitudinal axis of the drying tunnel 12 while the trolley 42 is urged through the tunnel 12 in a direction opposite to the longitudinal direction of movement of the drying medium.
Tn each cell 30, major drying medium (typically air) movement is in a roughly circular pattern in a vertical plane as shown by the arrows in Fig. 6. The air volume is completely recirculated within the cell 30. Every fourth drying cell 30, provided with a drying medium inlet port 47, receives a measured flow of dry, heated ambient air through the air inlet port 47. The drying medium is drawn through the cells 30 of the tunnel 12 by the fan 68 located in the exit duct 67 to exit from the tunnel at the exit duct 67. This net influx of drying medium moves in gradual progression towards the exit duct 67 in the wet end 71 via the inter cellular communicating holes 46. The longitudinal air flux is thus in a direction opposite to that of product movement on the trollies 42.
The operation and use of the production system 1, the production line 1 and production process of the invention as described in relation to Figs. 1 to 13 will now be described by way of example 2 0 only having regard to the drawings and the following non-limiting examples:
ale 1:
g~y~na of strawberries in sliced form Fresh strawberries were brought to the production system 1 and 2 5 were first put through intake processing steps familiar to those skilled in the art namely, weighing, washing, visual inspection and assorting to remove any imperfect fruits in the support buildings 3, 4, 9, 10, 11. The washed and sorted fruits were then subjected to a series of steps to transform the fruits to the 3 0 shape desired. Any remaining detritus on the fruit was removed and the whole fruits were sliced into slices having a thickness of approximately lOmm.

Slices were then placed in a single layer on the mesh 61 of the trays 59. The fully loaded trays 59 were then placed into the trolleys 42. The trolleys 42 were transported throughout the production system 1 of the invention (prior to loading into the drying tunnel 12) on wheeled dollies to prevent contact of the trolley wheels 42 with the floors of the production system 1.
Air was used as a drying medium.
Fully loaded trolleys 42 were then loaded into the first drying cell 30 of the drying tunnel 12 by rolling manually from the dollies onto the rail extensions 80 and urged by the ram 86 through the door 70 onto the rails proper 36 disposed on the platform 34 in the tunnel 12. The platform 34 and the rails 36 are adapted to convey the trolleys 42 through the drying tunnel 12 as previously described.
More particularly, the presence of the trolley 42 at the first drying cell 30 is detected by a sensor in communication with the process control unit. Upon instruction from the process control unit, a series of coordinated operations was initiated. Firstly, the door seals 79 were deflated at the door 70 of the wet end 71 2 0 of the drying tunnel chamber 69 and the door 70 (and if necessary also the exit door 27) was/were opened. Generally (except where the trolley 42 was the first trolley 42 to be inserted in the drying tunnel 12), each trolley 42 abutted a preceding trolley 42 in the passage 35 of the drying tunnel 12 to urge the preceding 2 5 trolley 42 from the first drying cell 30 into the second drying cell 30. Similarly, where multiple trolleys 42 are already loaded in the tunnel 12 insertion of a trolley 42 caused progression or movement of each preceding trolley 42 by one cell 30 in a domino-type movement through the multicellular drying tunnel 12.
30 Accordingly, each trolley 42 to be loaded moved a train of trolleys 42 within the drying tunnel 12 forward by the length of one cell 30 in the drying tunnel 12.

Each trolley 42 was urged into the drying tunnel 12 by extending the ram 86. The ram 86 was then retracted while the train of trolleys 42 was prevented from rolling rearwards on the platform 34 by a stopper. Following loading of each trolley 42, the doors 27,70 were then closed and sealed by inflating the seals 79.
The loaded trolley 42 and the strawberry slices were then heated to a temperature of approximately 55°C and a relative humidity of between approximately 65% and approximately 70% in the first drying cell 30 of the drying tunnel 12. The trolley 42 was held within the first cell 30 of the drying tunnel 12 for a period of between approximately 50 minutes and 60 minutes. The temperature and humidity of the air circulating within the drying cell 30 was measured before and following passage of the air over the strawberry slices by the sensor and probes 83,84,85 described above and the readings of the sensor and probes 83,84,85 relayed to the process control unit and any necessary adjustments made to fluid and drying medium flow rates to adjust the humidity and temperature within the individual cells 30 as required.
Heat was supplied to the cell 30 (and indeed to every subsequent 2 0 cell 30) by the heat exchangers 49 located within the cells 30.
In the present example, the first cell 30 of the drying tunnel 12 was provided with two heat exchangers 49 mounted within the cell 30. The first of the two heat exchangers 49 was supplied with heat from the circulating hot water loop 40, the hot water within the loop 40 having a temperature in the range of approximately 70°C to 75°C. The second heat exchanger 49 within the first cell of the drying tunnel 12 was a supplementary finned tube heat exchanger 49 heated by electric power. The use of an electrically powered heat exchanger 49 facilitated a rapid response and, in the 30 case of the first cell 30 of the drying tunnel 12, additional heating capacity.
The last cell 30 of the drying tunnel 12, or indeed any other cell of the drying tunnel 12, could also be provided with a second heat exchanger 49 as required.
In the course of the passage of each trolley 42 along its journey through the passage 35 of the drying tunnel 12, the trolley 42 resided an equal amount of time in each of the twelve cells 30 of 5 the drying tunnel 12. Moreover, in the course of the journey, the ambient temperature within the drying tunnel 12 was raised to a maximum of approximately 60°C and furthermore, increased towards the exit door 27 of the drying tunnel 12 to approximately 50°C.
The humidity through the cells 30 of the drying tunnel 12 followed 10 a characteristic profile determined by the product which decreased towards the exit door 27 to a relative humidity in the range of approximately 5% to 8%.
Details of suitable parameters for varying fruits are to be found in PCT Patent Application No. PCT/IE 96/00037 referred to above.
15 Heat delivery within the cells 30 of the drying tunnel 12 was regulated by the temperature sensor 83, and probe 84,85 the processing unit and electrically actuated valves in the circulating hot water loop 40 to regulate the feed of hot water in the hot water loop 40 at each heat exchanger 49. Relative 2 0 humidity within the cells 30 was controlled by regulation of the speed of the fan 68 in the exit duct 67 which extracted air at the wet end 71 of the drying tunnel 12.
Air was forced over the product bearing trolleys 42 within each cell 30 by the fan 50 located within each cell 30. The air speed 2 5 over the strawberry slices was maintained in the range of 2 meters to 2.5 meters per second while the curved back wall 53 of each cell 30 ensured uniform air flow over the strawberry slices.
Overall coordination of the handling operations as well as automatic regulation of the parameters within the drying tunnel 12 30 was accomplished with a programable logic controller of the process control unit which was in cor~rnunication with the probes _ and sensors 83,84,85 control valves and fans 50,67 etc. In the present example an Allen Bradley S.L.C. 500 series controllers was used.
Following a complete journey of the trolley 42 along the passage 35 through the cells 30 of the drying tunnel 12, the resultant product emerged from the drying tunnel 12 with a residual moisture content of between 3% and 5%. The dehydrated slices of strawberry were very crisp while the colour of the strawberry slices was an intense red colour characteristic of the fresh fruit.
The strawberry slices were removed from the trolleys 42 by sliding out the trays 59 individually from the trolleys 42 and freeing the dehydrated slices from the mesh 60 by gentle tapping. The loose dry dehydrated strawberry slices were then visually inspected and any non-conforming pieces removed. The product was then loaded into pouches or other containers made of high barrier material while air was removed and a dry inert gas injected into each container followed by sealing of the container.
All post-dehydration operations were conducted in an 2 0 atmospherically controlled room to achieve low humidity thereby preventing moisture regain by the dehydrated product.
In the present example, the heat exchangers 49 were finned-tube or fin-block type heat exchangers generally fabricated from galvanised steel bearing plates having copper tubes to carry the heating fluid and aluminium fins mechanically bonded to the tubes in order to improve the heat contact with the air stream. The heat exchangers 49 were dipped into a bath of coating material and oven baked to provide a hard, chemically inert and easily cleanable surface. Examples of suitable heat exchangers are the heat exchangers fabricated by Thermal Heated Exchangers Limited which provide maximum heat transfer of approximately 45kw when fed with water at 80°C at a rate of approximately 0.6 litres per second with an air side pressure drop of 10 to l5Pa.
Exa le 2 Parsley leaf drying Fresh parsley was received and cleaned as in Example 1. The parsley was then brought into the production system 1 and stem materials removed.
The leaf material of the parsley was then chopped into pieces of the desired size by mechanical chopping machines.
The prepared product was then loaded into mesh sachets adapted to 1 0 lie flat on the trays 59 which were loaded into the trolleys as before.
The mesh sachets were required in order to reduce the loss of product to air flow in the drying tunnel 12 due to the low weight of the parsley.
The loaded trolleys 42 were positioned as earlier described at the first cell 30. At the predetermined time, the trolleys 42 were loaded in (and in a steady state, another trolley 42 is pushed out from the dry end of the drying tunnel 12). Typically, in the case of leaf parsley, the loading frequency was once every 10 to 15 2 0 minutes.
During dehydration, the temperature and humidity of each cell 30 of the drying tunnel I2 were maintained at values predetermined as optimal for the particular cut of parsley being handled and the particular requirements of the purchasers.
Typically, the temperature was limited to a maximum in the range of 50°C to 55°C throughout the drying tunnel 12, decreasing to 45°C to 50°C near the exit end. Humidity normally peaked in the range of 55% to 60% and decreased to very low values (approximately 5%) near the discharge end.
Post dehydration handling of the parsley was similar to the handling of the strawberry slices of Example 1 with the exception that the vacuum step in the packing operation was curtailed or omitted due to the presence of small and light particles of parsley.
The resulting dehydrated parsley product had an intense green colour characteristic of fresh parsley and a fresh parsley taste and smell with easy recovery of the fresh product appearance upon dehydration.

Claims (40)

CLAIMS:

1. A production line (12) comprising an elongate chamber (69) for receiving product having a central longitudinal axis and first and second end walls (71,72), a ceiling (26), a floor (23), first and second side walls (24,25), and a door (70) at the first end wall (71) into the chamber (69) for receiving product and a processing region being defined within the chamber (69) adapted to receive the product for processing characterised in that the processing region is arranged in a series of inter-communicable cells (30) and each cell (30) is defined by a first housing (16) spaced-apart from a second housing (16), the first and second housings (16) being located either side of a central passage (35) disposed parallel to the central longitudinal axis.

2. A production line (12) as claimed in Claim 1 characterised in that the production line (12) further comprises a drying medium supply system (41) having a drying medium intake port (81) located at the second end wall (72) of the chamber (69) and a drying medium outlet port (82) located at the front end wall (71) of the chamber (69) and means (41,47,45,46,50,51,52) for effecting movement of drying medium between the intake port (81) and the outlet port (82).

3. A production line (12) as claimed in Claim 1 or Claim 2 characterised in that at least one cell (30) is provided with drying medium circulating means (50) for circulating drying medium within the cell (30).

4. A production line (12) as claimed in Claim 3 characterised in that the production line (12) is provided with control means for controlling the circulating means (50).

5. A production line (12) as claimed in Claim 3 or Claim 4 characterised in that the circulating means comprises a fan (50).

6. A production line (12) as claimed in any of Claims 1 to 5 characterised in that each cell (30) is provided with drying medium communicating means (46,67,68) for facilitating movement of drying medium between the cells (30).

7. A production line (12) as claimed in Claim 5 characterised in that the drying medium communicating means (46) comprises a hole (46) communicable between the cells (30).

8. A production line (12) as claimed in Claim 7 characterised in that the hole (46) comprises control means for controlling movement of drying medium.

9. A production line as claimed in Claim 8 characterised in that the control means comprises a fan (68) located in the first cell (30) of the processing region.

10. A production line (12) as claimed in any of Claims 1 to 9 characterised in that at least one cell (30) is provided with a heating element (49).

11. A production line (12) as claimed in Claim 10 characterised in that the heating element (49) comprises a heat exchanger (49).

12. A production line (12) as claimed in any of Claims 1 to 11 characterised in that the second end wall (72) comprises a door (27) to facilitate exit of product from the chamber (69).

13. A production line (12) as claimed in any of Claims 1 to 12 characterised in that the production line (12) is portable.

14. A production line (12) as claimed in Claim 13 characterised in that the production line (12) comprises a transportable container (22).

15. A production line as claimed in Claim 14 characterised in that the transportable container (22) is road or rail transportable.

16. A production line (12) as claimed in any of Claims 1 to 15 characterised in that each cell (30) is isolatable from each adjacent cell (30).

17. A production line (12) as claimed in Claim 16 characterised in that each cell (30) is isolatable from an adjacent cell (30) by a product conveying means (42) moveable through the central passage (35) between the first and second end walls (71,72).

18. A production line (12) as claimed in Claim 17 characterised in that the conveying means (42) comprises a trolley (42).

19. A production line (12) as claimed in Claim 18 characterised in that the trolley (42) is engageable with the housings (16) to isolate the cell (30).

20. A production line (12) as claimed in Claim 19 characterised in that the housing (16) comprises sealing means (66) for sealing the trolley (42) between the first and second housings (16) to isolate the cell (30).

21. A production line (12) as claimed in any of Claims 1 to 20 characterised in that the floor (23) is sloped to facilitate flow of liquid on the floor (23) towards the first or second end walls (71,72).

22. A production line (12) as claimed in Claim 21 characterised in that the floor (23) is sloped towards the first end wall (71) of the chamber (69).

23. A production line as claimed in any of Claims 1 to 22 characterised in that the production line (12) is provided with external drying medium circulating means (67,68) for drawing drying medium through the production line (12).

24. A production line as claimed in Claim 23 characterised in that the external drying medium circulating means (67,68) comprises an exit duct (67) in the production line (12) for extracting drying medium from the production line (12).

25. A portable modular production system (1) comprising a modular production line (12) as claimed in any of Claims 1 to 24 and a modular support building (3,4,9,10,11).

26. A production system as claimed in Claim 25 characterised in that the system (1) further comprises a modular power source (20).

27. A production system (1) as claimed in Claim 25 or Claim 26 characterised in that the support buildings (3,4,9,10,11) are pneumatically supported buildings (3,4,9,10,11).

28. A production system as claimed in any of Claims 25 to 27 characterised in that the system (1) further comprises canopy or tentlike ancillary buildings (3,4,9,10,11).

29. A production system as claimed in Claim 28 characterised in that the pneumatic and canopy or tentlike buildings (3,4,9,10,11) are mountable on concrete (7,8).

30. A production system as claimed in Claim 29 characterised in that service conveying conduits are detachably insertable in the concrete.

31. A production system as claimed in any of Claims 26 to 30 characterised in that the modular power source (20) is mounted in a transportable container (22).

32. A production system as claimed in Claim 31 characterised in that the transportable container (22) is road transportable.

33. A production system as claimed in Claim 31 characterised in that the transportable container (22) is rail transportable.

34. A production system as claimed in any of Claims 26 to 33 characterised in that the power source (20) comprises a combined heat and power unit.

35. A production system as claimed in Claim 34 characterised in that the combined heat and power unit (20) is diesel fuelled.

36. A production system as claimed in any of Claims 25 to 35 characterised in that the production line comprises a drying tunnel (12).

37. A process for dehydrating a biological product in a production line of Claim 1 comprising urging the product through the processing region from the first end wall (71) to the second end wall (72), introducing drying medium into the chamber (69) at the second end wall (72), circulating the drying medium through the processing region (30) with the drying medium circulating means (45,50,51,52,63), monitoring the drying medium circulating means (45,50,51,52,63) and exhausting the drying medium from the chamber (69) at the first end wall (71) movement of the drying medium between the second and first end walls (71,72) being effected along the central passage (35) through the series of isolatable cells (30) defined within the chamber (69) between the first and second end walls (71,72) for receiving the product.

38. A process as claimed in Claim 37 characterised in that the process further comprises the step of heating the drying medium.

39. A process as claimed in Claim 37 or Claim 38 characterised in that the process further comprises monitoring the humidity of the drying medium in the chamber (69) and controlling the flow rate of the drying medium between the first and second end walls (71,72).

40. A process as claimed in any of Claims 37 to 39 characterised in that the drying medium comprises air.