JP2779808B2 - Fluidized bed dryer for food - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a fluidized-bed dryer using superheated steam,
In particular, a metal filter is attached to the upper part of the drying chamber to enable drying of the powdery food.

(Prior Art) Fluidized bed dryers are often used to dry powders. In the fluidized bed drying apparatus, a ventilation plate is provided on the bottom of the drying chamber, and a hot air supply duct is further connected to the ventilation plate to blow up hot air from the ventilation plate to the drying chamber to form a fluidized bed in the drying chamber. It is suitable for drying the granules efficiently and continuously.

By the way, in general, a fluidized bed drying apparatus is provided with a bag filter formed using a woven cloth, felt, or the like at the upper part of a drying chamber, and collects light-weight particles rising toward an exhaust duct. However, when the powder is a food in the form of powder, clogging is liable to occur since the crosslinking phenomenon easily occurs in the filter bag. In particular, the drying of food uses superheated steam for sterilization, so the tendency is remarkable.In addition, it is extremely difficult for these filter bags to remove clogged powder particles by backwashing, and furthermore, felt bags made of felt are used. Filter bags cannot be washed with water and cannot be reused once they become clogged.

For this reason, conventionally, bag filters are not attached to fluidized bed dryers for foods, and instead, cyclone dust collectors or multi-cyclone dust collectors are connected to the exhaust path, and the powder particles discharged outside the machine together with exhaust gas Measures were taken to capture

(Problems of the prior art) However, cyclone dust collectors and multi-cyclone dust collectors cannot collect fine powder of several microns or less, so a high-performance dust collector such as a scrubber must be provided at a later stage. I didn't get it.

As a result, there has been a problem that equipment costs are increased and maintenance is troublesome.

(Object of the Invention) It is an object of the present invention to attach a metal filter which is hardly clogged even when superheated steam is used as hot air for drying and can be backwashed.

(Summary of the Invention) In the present invention, a metal filter is formed by stacking several wire nets each having a wire of several tens to several hundreds of micrometers in plain weave or tatami weave, and used as a metal filter for collecting fine powder. Therefore, it is attached to a predetermined position of a fluidized-bed dryer.

(Examples) Hereinafter, the present invention will be specifically described based on illustrated examples.

The figure schematically shows a fluidized bed drying apparatus for food according to the present invention. In the figure, reference numeral 1 denotes a dryer main body, 2 denotes a material to be dried to be supplied constant, and 3 denotes a superheated steam supply.

The dryer main body 1 is the same as the dryer main body of a general fluidized bed drying apparatus except that a collecting device formed using a metal filter is attached to a filter chamber. That is, the dryer main body 1 includes a fluidized-bed chamber 4 and a filter chamber 5, and the fluidized-bed chamber 4 is formed at one end with an inlet 6 for a material to be dried.
A drying material fixed supply device 2 is connected to the drying device so that powdered food to be dried, such as shavings and rabbit flowers, is quantitatively charged into the fluidized bed chamber 4, and the other end of the drying product is taken out. A mouth 7 is formed from which the dried powdered food is taken out. A ventilation 8 is formed on the bottom surface, and a hot air supply duct 9 is formed below the ventilation 8. A superheated steam supply device 3 is connected to the ventilation duct 8. Superheated steam is blown up. An exhaust port 10 is formed at the upper end of the filter chamber 5 to discharge drying exhaust gas (superheated steam) from the exhaust port 10 and a collection device 11 formed using a metal filter is attached to the inside of the chamber. The powdered food that rises and floats on the surface is filtered and collected.

More specifically, the material-to-be-dried 2 is composed of a constant-rate feeder 12, a feed conveyor 13, a hopper 14, and the like, and intermittently or continuously feeds the food to be dried in accordance with the processing speed in the dryer body 1. The hopper 13 is supplied to the hopper 13, and the hopper 13 is supplied to the dryer body 1.

The superheated steam supply device 3 includes a demister 15, a heater 16, and a blower 17.
The demister 15 includes a steam generator 18 such as a boiler.
Is connected, and the steam supplied from the steam generator 18 is heated to a desired temperature and sent to the hot air supply duct 9.

In addition to the use of superheated steam, this apparatus is not only heat-insulated, but also the exhaust gas discharged from the dryer body 1 is returned to the demister 15 for circulating use. Rotary valves 20 and 21 are attached to the material inlet 6 and dried product outlet 7 to prevent the invasion of outside air, and to maintain the inside of the system at a low air concentration of 3% V / V or less to enhance the sterilization effect. It has become.

Reference numeral 22 denotes a preheating tube, which is a rotary valve 2 before feeding the first food to be dried when the drying operation is started.
0, to heat the others to remove condensation from this part.

By the way, a metal filter is formed by laminating several to several tens of wire meshes in which a wire of several tens to several hundreds of micrometers is plain-woven or tatami-woven, welds the fulcrums of the wire mesh and the contact points of each layer to form a sheet. It was done.

(Operation) To perform the drying operation, first, heated steam is blown from the hot air supply duct 9 toward the dryer main body 1 to preheat the inner wall of the dryer main body 1, the ventilation plate 8, the metal filter 11, and the like, and further, the rotary The valve 20 and the like are preheated to remove condensation adhering thereto, and thereafter, the rotary valve 20 is opened and the food to be dried is put into the fluidized bed chamber 4.

When the metal filter 11 is clogged due to the progress of the work and the air permeability decreases, the work is interrupted and the backwash is performed. In this case, it is appropriate to use the superheated steam in the system as the backwash gas. That is, in this case, not only the operation is simple, but also since the outside air does not enter the system, the drying operation with a low air concentration can be continued, and the sterilizing effect can be maintained.

(Effects) As described in detail above, the present invention relates to a fluidized bed drying apparatus for food using superheated steam, in which several wire meshes plain or woven using a metal wire having a wire diameter of several tens to several hundred micrometers are used. A metal filter formed by laminating dozens of sheets is attached to the filter chamber 5, and since the metal filter is heat-resistant and organic solvent-resistant, a high-temperature drying gas can be used, so that a sterilizing effect is obtained. Suitable for required food drying.

In particular, this metal filter is less likely to cause clogging, and the clogging can be easily removed by backwashing, so that superheated steam can be used as a drying gas, and this superheated steam can be used as a backwashing gas. Can also be used, so that it can be dried at a low air concentration and the sterilization effect can be enhanced. In this respect, it is also suitable for drying powdered foods.

Further, since the present method is a closed system, the exhaust gas is circulated and reused again as a blowing gas, but since the exhaust gas has been purified by passing through a metal filter in the machine,
There is no clogging of the heater due to the blown gas, and it can withstand long-term operation.

However, 2 kg / cm ² of saturated steam was passed through a heater 16 heated to 120 to 150 ° C. to become superheated steam, which was then dried.
After purging the air in the apparatus by blowing air into the fluidized bed chamber 4, the rabbit flowers previously granulated to 1 to 4 mmφ by the granulator were allowed to flow for 20 minutes.
It is dried from 80% to 5%, and E. coli is 200,000 / g to 100 /
g.

[Brief description of the drawings]

The figure is a flow sheet diagram showing an example of the fluidized bed drying apparatus for food according to the present invention. 1: Dryer main unit, 2: Fixed volume supply device 3: Superheated steam supply device, 4: Fluidized bed room 5: Filter room, 6: Inlet 7: Outlet, 8: Vent plate 9: Hot air supply duct, 10: Exhaust port 11: metal filter, 12: fixed-quantity feeder 13: feed conveyor, 14: hopper 15: demister, 16: heater 17: blower, 18: steam generator 22: preheating tube

Claims (1)

(57) [Claims] In a fluidized bed drying apparatus provided with a bag filter in a filter chamber, the bag filter is formed by laminating several to several tens of wire meshes in which a metal wire having a wire diameter of several tens to several hundreds of micrometers is plain or woven. It is formed using a metal filter formed by welding each fulcrum of the wire mesh and the contact point of each layer into a sheet shape. The fluidized bed drying device is connected with a superheated steam supply device to a hot air supply duct and dried. A fluidized bed drying apparatus for food, wherein superheated steam is used as a heat medium.