Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
  • F23C5/00—Disposition of burners with respect to the combustion chamber or to one another; Mounting of burners in combustion apparatus
  • F23C5/08—Disposition of burners
• • A—HUMAN NECESSITIES
  • A21—BAKING; EDIBLE DOUGHS
  • A21B—BAKERS' OVENS; MACHINES OR EQUIPMENT FOR BAKING
  • A21B1/00—Bakers' ovens
  • A21B1/42—Bakers' ovens characterised by the baking surfaces moving during the baking
  • A21B1/48—Bakers' ovens characterised by the baking surfaces moving during the baking with surfaces in the form of an endless band
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
  • F23D14/12—Radiant burners
  • F23D14/16—Radiant burners using permeable blocks
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23D—BURNERS
  • F23D2212/00—Burner material specifications
  • F23D2212/20—Burner material specifications metallic
  • F23D2212/201—Fibres

Definitions

• the subject of the present invention is a tunnel kiln, in particular for biscuit making, having a drive belt, and comprising burners with a direct flame gas ramp distributed over at least a part of the length of the oven from its inlet.
• This type of oven used in particular for the production of biscuits such as "crackers” has conventional gas burners producing a flame for a very intense cooking during which the heat transfer is carried out both by conduction, radiation, condensation and natural convection.
• the object of the present invention is to diversify the cooking parameters of an oven of this type in order to better control the cooking of products obtained in particular from rolled pastes or rotary pastes, such as small butters, crackers or biscuits. crackers.
• the tunnel furnace comprises in said portion of the length of the furnace which has gas ramp burners, at least one radiant burner with metal fibers disposed above the carpet.
• a radiant burner makes it possible to vary the radiative flux, which makes it possible to cook the dough pieces with long or medium infrared radiation, in combination with the other burners which do not make it possible to modulate the heat transfer by varying between the radiative mode and the convective mode.
• This type of burner also offers the possibility of making pastry products by limiting the effects of crusting on the surface.
• thin raw dough pieces that is to say of thickness between 0.2 and 1.5 mm
• crackers it is thus possible to obtain a controlled blistering of the products.
• At least some of the gas ramp burners may be disposed above the carpet. At least some gas ramp burners may be located below the carpet. At least two radiant burners may be separated by at least one gas ramp burner. According to one variant, the radiant burners are uniformly or non-uniformly distributed between 20% and 75% and in particular less than 60% or 50% of the length of the oven from its inlet.
• between 20% and 75% of its length of the furnace may comprise above the carpet only radiant burners, especially of the metal fiber type, which are evenly distributed or not.
• the furnace Downstream of said portion of the furnace length, it may comprise at least one forced convection heating zone.
• the furnace may comprise in said part of its length, at least two and at most seven zones ensuring increasing cooking temperatures.
• At least one radiant burner is advantageously of a type having a metal fiber fabric, with a radiative mode preferably extending to a power density of 500 kW / m 2 , and a convective mode beyond this power density.
• the invention also relates to a method of baking biscuits using a tunnel oven as defined above, and implementing the use of at least one said radiant burner.
• the process may be characterized in that the biscuits, in particular "crackers" are made from thin dough pieces and in that it comprises:
• At least the second step is accompanied by a fog extraction.
• the biscuits are made from thick dough pieces and it implements a cooking using radiant burners distributed over at least a part of the length of the oven.
• cooking can implement the combined action of radiant burners and gas ramp burners.
• FIG. 1 illustrates an exemplary implementation of a tunnel furnace according to the invention, having standard burners (with direct flame) and radiant burners;
• FIG. 2 shows an example of implementation of a radiant burner;
• FIGS. 3a to 3c show a rotating radiant burner variant
• FIG. 4 shows a radiant burner variant having a plurality of zones in a transverse direction of the furnace.
• Tunnel kilns used in biscuit making usually use direct-flame gas burners distributed along the furnace above the carpet (vault burners) and below the carpet (hearth burners), the burners ensuring temperature in each zone of the oven. These burners generally operate in natural convection with an air speed which is 1 m / s maximum, and an average speed of the order of 0.6 m / s.
• radiating burners with woven metal fibers makes it possible to generate a long or medium infrared radiative flux (flame of red / orange color) which makes it possible to cook thin dough pieces from inside (between 0.2 mm and 1.5 mm). mm), possibly in combination with the convective and conductive flow produced by the direct flame burners, which ensure the heating of the oven.
• a long or medium infrared radiative flux flame of red / orange color
• a device for extracting the vapors is provided for example between 30 seconds and one minute over a total cooking time of, for example, 3 minutes. seconds.
• the start of cooking (30 'to one minute) is performed with gas ramp burners to allow a first expansion of the dough and its spreading.
• the products are also subjected to the action of metal fiber radiant burners which are distributed over a length of the oven, so as to obtain a blister crackers.
• the radiative flux corresponds to 50% or more of the total flux received locally by the products.
• the radiant burners can be set for example so that everyone diffuses the same power. During this second stage, which lasts about 1 to 2 minutes, there is little or no spreading of the products.
• This radiant flux generated by the radiant burners allows a rapid increase in the temperature in the mass of the product, which leads to an increase in the kinetics of evaporation in the product.
• the formation of a boundary layer during the first part of the cooking by surface evaporation limits the exchanges between the heart of the product and the cooking chamber (the interior of the oven) from where the formation of blisters above and below the product.
• the cooking can preferably end with a forced convection cooking step (2 to 3 minutes).
• Another mode of drive drying can be implemented.
• the total cooking time is for example 3mn30 to 6mn for a cracker.
• the commissioning of the radiant burners makes it possible to increase the temperature inside the products by using them in convective rather than radiative mode and to accelerate the evacuation of the product. moisture in the product's core, which leads to improved texture by better honeycombing of the crumb.
• a radiant burner, with metallic fibers makes it possible to operate according to the power, either in radiative mode (flame of red / orange color, for example for a power density lower or equal to 500 kW / m 2 ), or in Convective mode (blue flame for power densities between 600 kW / m 2 and 1000 kW / m 2 ).
• the air speed can reach 5 m / s.
• the radiant burners alternate with the conventional direct flame burners which ensure the heating of the oven in each zone (cooking curve), the products receive convective, conductive and radiative fluxes, the radiative flux generally constituting more than 50 % of the total heat flux received by the products above the radiant burners.
• the oven has 5 zones of substantially equal length.
• the fourth and fifth zones are forced convection cooking zones (170 ° C).
• Extraction devices 11 are also provided in each of the zones. It can be seen that the radiant burners are arranged essentially at the end of the first zone, in the second zone and in the first half of the third zone.
• a radiant burner comprises a central steel tube 1 having a longitudinal slot 5 covered with a braided metallic fabric 4 welded to the central tube 1. The gas penetrating inside the tube 1 closed at its end 6 comes out through the metal fabric 4.
• Two electrodes 2 and 3 serve to initiate the combustion of the gas.
• the metal fabric 4 occupies part of the outer contour of the tube 1 and faces the carpet 10 of the furnace to produce a radiant flux.
• FIGS. 3a and 3b the braided metal fabric 4 in which combustion of the air-gas mixture occurs is carried by an annular plate 7 rotatable and whose position is fixed by locking screws 8.
• FIGS. 3c illustrate three rotational orientation positions of the radiant zone of the burner, around the slot 5 which occupies, for example, most of the perimeter of the tube 1.
• Figure 4 shows a metal fiber radiant burner with 3 zones.
• the air-gas mixture is introduced (arrow F) into a space
• the burner may have more than 3 zones, for example 5 zones.
• Screws 21, 22 and 23 having rounded heads 21 ', 22' and 23 'which are arranged in this space 20 allow or not obstruct the entrance

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Food Science & Technology (AREA)
• Gas Burners (AREA)
• Baking, Grill, Roasting (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37835071

Family Applications (1)

Country Status (4)

Families Citing this family (6)

Family Cites Families (17)

• 2006
  • 2006-07-07 FR FR0606202A patent/FR2903278B1/fr not_active Expired - Fee Related
• 2007
  • 2007-07-06 EP EP07823256A patent/EP2041489A1/fr not_active Withdrawn
  • 2007-07-06 WO PCT/FR2007/001154 patent/WO2008003869A1/fr active Application Filing
  • 2007-07-06 CN CN2007800251794A patent/CN101573559B/zh not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events