RU2457680C2 - Method for heating single food semi-products on conveyor inside tunnel oven - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention relates to the technology of food productions and may be used for thermal treatment of food semi-products such as beefsteaks, steaks, cutlets, meat balls, for baking bread, small loaves, biscuits, gingerbreads, for heating first and second courses in vessels, for drying rusks, grits, herbs, berries and mushrooms The semi-products heating is simultaneously performed on a belt conveyor inside the body of the tunnel oven made of 12X18H10T steel with environmental air heated inside the oven tunnel, with the conveyor belt heated inside the tunnel and with directed infrared radiation from IKZ-500 reflector infared electric lamps; the radiation penetrates through the oven tunnel walls from the outside, from below and from the sides. The lamps are placed perpendicular to the planes of the oven tunnel bottom and side surfaces with a clearance between the bulb and these surfaces amounting to 5-7 mm.

EFFECT: invention allows to simplify implementation of heating of single food semi-products moving rectilinearly.

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Description

The present invention relates to food production technology and can be used for continuous heating, or baking, or drying, or roasting, or roasting, or baking food semi-finished products, i.e. for their heat treatment. Including - until the complete preparation of the finished food product from them. The method can be used for the preparation of semi-finished products: steaks, steaks, meatballs, meatballs, for baking breads, rolls, cookies and gingerbread cookies, for heating the first and second dishes in containers, for drying crackers, cereals, herbs, berries, mushrooms, etc. P.

The method can be used for continuous heat treatment of building, engineering, instrument-making, biotechnological semi-finished products and thermoplastic materials in molds with a given accuracy.

1. The prior art

A known method of heating piece food semi-finished products on a conveyor, in which the conveyor is placed inside the lined body (inside the hearth) of the tunnel furnace, which creates a loading window for loading piece semi-finished products on the conveyor. Inside the casing (hearth), gaseous fuel is continuously burned, maintaining a predetermined high temperature inside the casing (hearth), while simultaneously removing the products of fuel combustion (through smoke tubes). In the process of heating semi-finished products, overheated steam from the steam generator is periodically fed from the top of the casing (hearth) to moisten semi-finished products that lose moisture [1, 2].

The disadvantages of this method are the complexity of the operations, huge material consumption, high energy intensity of operations, environmental pollution and fuel combustion products and its thermal pollution. Similar disadvantages have similar methods described in the sources [3-12]. Even more complicated is the method according to the application RU [13], in which, for heating, the operation of heating with electric heaters (heating elements) is additionally used (for the operation of burning fuel).

Similar methods for heating semi-finished products are known, in which the high temperature inside the body (inside the hearth) of the tunnel kiln is created and supported by electric heaters (TENs) [14-16]. These methods do not pollute the environment with fuel combustion products and exclude thermal pollution of the environment. Their disadvantages are the complexity of the operations, the huge material consumption and high energy consumption of operations due to the small outer surface of the heating elements and the long heating time of the air (due to its low thermal conductivity) inside the furnace body (hearth).

2. The closest technical solution (prototype) is a method for heating piece technical products in a tunnel kiln moving rectilinearly in a conveyor, described in [17, 18] (combined prototype).

In this method, the conveyor is made of separate interlocked bogies moving rectilinearly along the lined body (hearth) of the furnace, along the rails inside it, and air heating inside the body (hearth) is carried out by electric heaters (heating elements) or radiating tubes, which are fixedly placed in rows and above heated items and under carts.

The main objectives of the proposed invention (compared with the prototype) is to obtain the following technical results.

1) Simplification of the implementation of the method of heating food piece semi-finished products moving rectilinearly on the conveyor;

2) Reduction of material consumption of the structural elements of the method;

3) Reducing the cost of electric energy for heating;

4) A significant increase in reliability, durability and maintainability.

3. Reasons that hinder the receipt of technical results.

The most significant disadvantages of this method (prototype) are the complexity of the operations, the huge material consumption and high energy intensity of operations.

3.1. The complexity of the implementation of the method lies in the need to create a lined case (sub) of a tunnel (or any other furnace from known methods of heating piece goods) furnaces, create a conveyor moving inside this case (hearth) at high temperatures, create carts, lay rails for them, to create a foundation for rails, to provide lubrication for the wheels of bogies operating at high temperatures, as well as the need to create and maintain a steam generator and steam line for supplying steam into the body (in the sub) Chi for moisturizing, etc. The same drawback is inherent for cradle conveyors in analogues [1, 2].

3.2. The huge material consumption is due to the massiveness of the lined housing (hearth) of the furnace, conveyor elements and steam humidification elements.

3.3. The high energy intensity of operations is due to the large consumption of electric energy for heating and the drive, given the massiveness of the moving parts of the conveyor and the large energy losses due to friction in these moving parts (in links).

In fact, it is necessary to heat only semi-finished products, while in the prototype only a small part of the thermal (primary - electric) energy of electric heaters is spent on heating products.

Electric heaters pos.2 (figure 1) in the prototype [18] are placed not over products with a minimum clearance with them, but in the upper part of the internal cavity of the body (hearth). These heaters (heating elements or radiating tubes) have the property that they heat the air surrounding them, creating convection, when the air comes into contact with the heated surface of the heater, and the heated air rises. The placement of electric heaters pos.2 (in the prototype) leads to air heating by convection only under the ceiling of the body (hearth) of the furnace. These heaters (heating elements or radiating tubes) have the property that they create thermal (electromagnetic) radiation. But TENs or radiating tubes, due to the low temperature of the outer surface (700-900 ° C), generate radiation with a rather large wavelength ≈3.2 μm and a rather small specific radiation power ≈5 * 10 ⁵ W / cm ² [19, p.29, fig. 2-5]. Whereas the known sources of directional infrared radiation (infrared mirror light bulbs, with a mirror reflector inside the bulb that creates the directional radiation) of the type IKZ (infrared mirror) [20], with a nominal spiral temperature of 2350 ° K create a specific power of directed infrared radiation ≈2 * 10 ⁷ W / cm ² (19, p. 29, Fig. 2-5), i.e. ≈ 40 times more powerful at the same energy costs. Electric heaters (heating elements or radiating tubes) create uniformly dispersed thermal (partially infrared) radiation from a cylindrical surface. It partially heats the ceiling of the furnace body (hearth), partially surrounding the air and only partially the product (semi-finished product).

It is also known that the energy of directed electromagnetic radiation in the infrared spectrum is partially absorbed by the surface (heats the surface), partially reflected from the surface (scattered) and partially penetrates through the wall with the surface. It is known at the same time that chromium and iron absorb the energy of the IR spectrum best of metals, and the power of penetrating radiation decreases with increasing thickness of the irradiated wall [21].

Electric heaters pos. 3 (Fig. 1) in the prototype [18] are placed under massive trolleys and, like electric heaters 2) heat the surrounding air partially with convection and partially with radiation. Part of the radiation energy is spent on heating the air. Other parts of this energy are spent on heating the carts 4 from below and on heating a massive foundation (base) along with rails (with guides 6). Thus, only a tiny fraction of the electric power (thermal energy of electric heaters - heating elements or radiating tubes) is spent on heating the semi-finished products (products) themselves.

On the other hand, the large masses of the lined body, conveyor parts, cradles or trolleys, foundations (bases) create a greater inertia of the heating process. Heating of semi-finished products (products) can begin only after the air and carts have warmed up (cradles - in analogues). To heat up everything that is not a semi-finished product, much more energy is consumed in time than is necessary to maintain the necessary temperatures of the semi-finished products.

3.4. Low reliability, durability and maintainability are due to the fact that heating devices, moving conveyor friction elements (moving joints) and conveyor drive elements are located inside the tunnel furnace, i.e. in conditions of high temperatures and humidity. This causes accelerated wear, corrosion and the inability to replace the heaters when they fail, without stopping the entire process of the tunnel kiln.

4. Signs of the prototype, coinciding with the claimed alleged invention.

Semi-finished products are heated inside the tunnel kiln body during their movement on the conveyor inside the tunnel kiln through their interaction with the heated gas surrounding them - air. At the same time, moisturizing steam is supplied periodically or continuously into the furnace.

5. The objectives of the invention are the following technical results.

5.1. Simplification of the implementation of the method of heating food piece semi-finished products moving rectilinearly on the conveyor.

5.2. The decrease in material consumption of the structural elements of the method.

5.3. Reduced energy costs for heating.

5.4. Significant increase in reliability, durability and maintainability.

6. These technical results in the claimed method of heating food semi-finished products moving rectilinearly on the conveyor are achieved by the fact that the furnace body is made in the form of a thin-walled rectangular, in cross-section, pipe with a length greater than the diameter that is placed horizontally and motionless, and the conveyor is performed in the form of an endless, thin and heat-resistant, flat conveyor belt with a drive, a rectilinearly moving section of which, together with semi-finished products, is directed inside the pipe parallel to it with a small gap of relative relative to its inner bottom surface and with uniform gaps relative to the inner side surfaces, the semi-finished products are heated by the air surrounding them inside the pipe, the conveyor belt heated inside the pipe and directed infrared radiation penetrating through the pipe wall - while heating the pipe surface from the outside, from below and from the sides along its length, directed at it perpendicular to infrared radiation, while simultaneously measuring the temperature inside the pipe during heating and maintaining I automatically, within the specified limits, while the outer surface of the pipe from above is covered with a layer of heat-resistant thermal insulation.

7. The essence of the invention is illustrated by drawings, in which Fig. 1 shows a general technological diagram of the implementation of the proposed method, Fig. 2 shows a cross section of this diagram along the casing of a tunnel furnace, Fig. 3 shows a longitudinal section of a casing of a tunnel furnace, and Fig. 4 is a diagram of automatically maintaining a predetermined temperature inside a tunnel furnace body.

On the diagrams and in the text the following letter designations are accepted:

VPUL - the upper straight section of the conveyor belt;

B is a side part relative to the tunnel furnace body;

H is the lower part relative to the tunnel furnace body;

NIKI - directional infrared radiation;

V is the linear speed of the conveyor belt;

ARNT - a typical voltage-temperature autoregulator, for example, three-phase, thyristor, broadband, with phase limiting, containing a temperature setpoint, a set temperature indicator and an indicator of current temperature values (not shown separately in the drawings);

DT - temperature sensor, for example a thermocouple;

R _EB - the equivalent electrical resistance of the side emitters NIKI;

R _EH is the equivalent electrical resistance of the lower emitters of NIKI;

a, b, c - phases of a three-phase electric network at the power input of the ARNT;

a1, b1, c1 - phases of a three-phase electric network from a controlled power output

ARNT (in electric power circuits REB, REH);

N - common neutral (neutral wire);

PF - piece food semi-finished products;

GP - finished products from semi-finished products.

7.1. The technological scheme that implements the inventive method includes the following structural elements.

1 - a stationary horizontally mounted tunnel furnace casing (Figs. 1-3), including the upper heat-insulated part 1a of the casing 1, side heating parts (left and right) 1b of the casing 1 and the heating tray 1c of the casing 1 (Fig. 1).

Positions 2 through 2c (FIG. 1) show the kinematic transmission of a flexible, infinite, flat and thin conveyor belt, including: a flat endless conveyor belt 2 made of perforated steel tape (steel 12X18H10T) or from a mesh of the same steel. Tape 2 covers with tension the supporting cylinders 2a, the drive cylinder 2b and the tension (for example, self-loading) cylinder 2b. The drive cylinder 2b is kinematically connected to a controlled electric drive UEP (drive control unit is not shown).

On the upper straight section of the tape 2 (VPUL) in front of the entrance of the tape 2 into the housing 1 of the tunnel furnace place food semi-finished products PF (Fig.1-3). The housing 1 and the bearing housing (not shown in the drawings) of the cylinders 2a, 2b, 2c are reliably and motionlessly mounted on a fixed frame (not shown in the drawings) with supports 10 (FIG. 2) so that the axes of the cylinders 2a, 2b, 2c in the gear 2-2B are parallel and placed in the corners of the rectangle (Fig. 1).

The housing 1 consists of the following structural elements, shown schematically (figure 2, 3): 3 - thin-walled pipe of rectangular profile made of steel 12X18H10T, thickness 2-3 mm, length 2-3 m; 4 - thermal insulation of the upper part of the pipe 3 along its entire length, made, for example, of foam concrete; 5B - side emitters of NIKI, for example, electric lamps IKZ-500, with a rated power of 500 W; 6 - dielectric base (for example, a plate made of textolite) side emitters 5B NIKI. The emitters 5B motionlessly, using electric cartridges (not shown in the drawings), are attached to the base 6, perpendicular to it, for example in two rows, along the pipe 3 along its entire length. The base 6 of the emitters 5B is connected to the pipe 3 by a cylindrical hinge 7 (for example, door hinges) along its entire length. The base 6 by means of the hinge 7 is installed parallel to the lateral face of the pipe 3 so that the emitters 5B NIKI are perpendicular to this face. In this position, the base 6 is held by a gripper 8, made, for example, in the form of an elastic flat spring. When squeezing the gripper 8 up, the base 6 is moved from the vertical position 6 to the horizontal position 6a (Fig.2). The lower emitters 5H of NIKI are similar to the side emitters 5B and are connected to the same base 6. The base 6 with emitters 5H is installed horizontally in the pan 1c under the lower face of the pipe 3 in the fixed guides 9 and can be pulled out of the guides 9 or move along them under the lower face of the pipe 3 , for example, manually. The emitters 5H NIKI are perpendicular to the lower edge of the pipe 3. The gaps between the emitters 5B and the side faces of the pipe 3 are the same, minimal and, for example, 5 mm. The gaps between the emitters 5H and the lower face of the pipe 3 are the same, minimal and, for example, 5 mm. Between the rows of emitters 5H, an elastic steam pipe is freely placed (not shown in the diagrams), one end of which is hermetically connected to the nozzle 11, and the opposite end to a steam source, for example, to a steam generator (not shown in the diagrams). The pipe 11 is firmly and tightly mounted in the lower face of the pipe 3 with the possibility of supplying steam through it into the pipe 3 into its lower part (in the region of the highest temperatures).

The side emitters 5B in the side heating parts 1b, to the right and left of the pipe 3 are connected, respectively, to phases a1 and c1 (Fig. 4), electrically in parallel (R _EB ) and, similarly, to the corresponding phases a1 and c1, with a common neutral N (figure 4). Also, electrically in parallel, to the phase b1 (R _EH ) are connected the lower emitters 5H in the pallet 1B. Equivalent to the emitters 5B and 5H, an electrical load in the form of two identical resistances R _EB and a third equal to R _EB , resistance R _ЭH is connected to the controlled output of the ARNT with phases a1, b1, c1 and a common neutral N in the form of a “star”. With such an electrical connection, when R _EB and R _{EH are the} same, in the process of electrical supply of R _EB and R _EH , N electric currents do not occur in the neutral N (the "zero" wire is not loaded). The temperature sensor DT (Figs. 1-4) is fixedly mounted inside the pipe 3 of the housing 1 from above (the fastening means are not shown in the diagrams) and is electrically connected to the control input of the ARNT controller (Fig. 4). The power input of the regulator ARNT, phases a, b, c and neutral N is electrically connected to a three-phase industrial power supply network (Fig. 4). In Fig. 4, electrical wires, electrical connections, and structural blocks of the ARNT controller are not shown due to their typical nature.

The belt conveyor 2-2b (Figs. 1-3) is mounted on a fixed frame with supports 10 together with the housing 1 so that the endless belt 2 moves when the drive UEP runs parallel to the housing 1, inside the pipe 3, with a small gap of 5-7 mm relative to the inner lower surface of the pipe 3 and with the same gap, for example 5 mm, relative to the inner side surfaces of the pipe 3. When loading the section of the VPUL tape 2 semi-finished products PF this section sags down and the gap between the tape 2 and pipe 3, inside the pipe 3, decreases. Tape 2 (its BAP) inside the pipe 3 may touch the lower face of the pipe 3 and slide along this face without a gap.

Before the implementation of the proposed method, the ARNT regulator sets the desired temperature, for example 300 ° C, from the controlled output of the ARNT (phases a1, b1, c1), the electric voltage is supplied separately to the side emitters 5B (R _EB ) and to the lower emitters 5H (R _EH ). The emitters 5B and 5H create (form) directed perpendicularly to the side surfaces from below and to the lower surface of the pipe 3, NIKI, heating the pipe 3 in its lower part. Upon reaching the set temperature, a controlled UEP drive is turned on at a given speed, for example, 1 m / min, and they start loading piece PF semi-finished products to the section of the VFUL belt 2 before it enters the tunnel furnace body 1. Upon reaching the set temperature, the ARNT reduces the voltage in phases a1, b1 and c1 (figure 4) in order to avoid overheating inside the pipe 3 (figure 2).

7.2. Declared as the invention, the heating method is implemented as follows. When you turn on the drive UEP by the drive control unit UEP set the speed V of the tape 2, for example 1 m / min and, on its straight upper section VPUL, before it enters the housing 1, continuously, for example, manually, stack piece food semi-finished products PF (figure 1 , 2). The tape 2 together with the semi-finished products PF slowly moves inside and below the heated pipe 3 in the zone of its highest temperatures, the semi-finished products PF are heated to a predetermined condition and are taken out by the moving tape 2 (VFUL) from the casing 1 of the tunnel furnace in the form of finished products GP (Fig. 1), which are removed from tape 2, for example, manually. The heat treatment parameters (temperature and residence time at this temperature) of the semi-finished products are regulated, on the one hand, by the temperature set by means of the ARNT, and on the other hand, by the UEP control unit, which sets the speed of the semi-finished products PF inside pipe 3, i.e. heat treatment time. In the process of operation of the emitters NIKI 5B and 5H, i.e. during the heat treatment of semi-finished products PF inside the pipe 3, inside it, from below, through the pipe 11, steam is continuously or periodically supplied to compensate for moisture in the semi-finished products lost during their heat treatment. Thermal insulation 4, on top of the pipe 3, allows to eliminate the convection outflow of heat from the inner cavity of the pipe 3 through its wall.

7.3. Positive results

The first positive result of the present invention, namely, a significant simplification of the implementation of the method of heating food piece semi-finished products moving rectilinearly on the conveyor, is ensured by the fact that it is not necessary to create a massive lined tunnel furnace body, to create a conveyor moving inside this case at high temperatures, create trolleys, lay rails for them, create a foundation for rails, provide lubrication for conveyor parts and wheels of trolleys operating in high their temperatures.

The second positive result of the present invention, namely, a significant reduction in the material consumption of the structural elements of the method, is provided due to the absence of a massive lined body (hearth) of the furnace, conveyor elements, carts or cradles, conveyor chains, rails, etc. In the inventive method, the furnace body is a thin-walled profile (rectangular in cross-section) pipe, and the means for moving the semi-finished products during their heat treatment is a simple conveyor belt.

The third positive result of the invention, namely, the reduction in the cost of electric energy for heating, is ensured by the fact that all the energy of the NIKI 5B and 5H emitters (total electric energy) is spent only on heating food semi-finished products as follows. Each of the emitters 5B and 5H is an IKZ-500 lamp, i.e. 500 watt infrared reflector lamp. In the working position of the emitters 5B and 5H, they are perpendicular to the side and lower edges of the pipe 3 from the bottom, respectively (Fig.2). Thus, NIKI radiation from them is directed perpendicular to these faces. Part of the NIKI energy absorbed by the irradiated faces of the pipe 3 heats the outer surface of the faces, and due to heat transfer, the inner surface of the faces of the pipe 3 below, which heats the air inside the pipe 3. The part of the NIKI energy penetrating through the irradiated faces additionally heats the air inside the pipe 3, and the lower radiators 5H additionally heats the BAPP of the tape 2 inside the pipe 3 due to the small distance between the tape 2 and the inner lower surface of the pipe 3. The energy of NIKI reflected from the irradiated faces is returned inside the lamp bulb (in their specular reflector), wherein by means of their own summed with reflectors, lamps emitted NICI. As a result, the total NIKI from lamps 5B and 5H on the surface of the faces doubles (the result of the fact that the emitters 5B and 5H are perpendicular to the irradiated faces). At the same time, both the absorbed and penetrating part of the NIKI energy doubles, the intensity of heating the semi-finished products PF inside the pipe 3 increases without increasing the cost of electricity. In this regard, to maintain the same temperatures inside the pipe 3 energy is required half as much as in the known analogues and in the prototype.

The fourth positive result of the invention, namely, a significant increase in reliability, durability and maintainability, is due to the fact that all transmission elements containing bearing assemblies, electrical and electronic parts (assemblies) are outside the high-temperature internal cavity of the pipe 3. To replace the side radiators 5B, it is only necessary to bend the grip 8 and move the base 6 (Fig. 2) from a vertical position to a horizontal position - 6a. To replace the lower emitters 5H, the base 6 is advanced along the fixed guides 9.

8. Sources of information

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Claims (1)

A method of heating food piece semi-finished products on a conveyor inside a tunnel oven of rectangular cross-section, in which they are heated through their interaction with the warmed gases surrounding them and with the heat radiation of the sources of this radiation inside the tunnel of the furnace, characterized in that the walls of the tunnel are thin, heated from the outside from below and from the sides with directed infrared radiation from infrared reflector lamps IKZ-500 perpendicular to the planes of the side and lower surfaces of the tunnel, placing lamps with the azor between the bulb and these surfaces within 5-7 mm, mounting these lamps motionlessly so that the lower lamps extend out from under the bottom of the tunnel, the side lamps recline from the side walls of the tunnel, with subsequent fixation, and the semi-finished products are heated by the heat surrounding them inside tunnel air heated inside the pipe with a conveyor belt and directional infrared radiation penetrating through the pipe walls - at the same time, while the tunnel body is made of 12X18H10T steel and the outer surface of the pipe is covered with a layer of t heat-resistant thermal insulation.

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