JPS60103288A - Spray drier with waste-heat recovery device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a spray dryer used for drying food detergents such as powdered milk, fragrances, medicines, chemicals such as plastics, and various other powdered materials. This invention relates to a spray dryer that saves energy by recovering waste heat.

Powdered milk, powdered foods such as corn and soybeans, detergents,
Spray dryers are used to dry chemicals such as fragrances, medicines, and plastics, as well as various other types of powdered materials. For example, in the case of powdered milk, milk is sprayed into a spray dryer and dried, and in the case of soybeans and corn, it is first ground into powder, then placed in water to remove the lees, and then put into a spray dryer. It is then dried and made into a product. Therefore, the exhaust air from the spray 7 dryer used for food products contains a large amount of water.

Further, the temperature of the exhausted air is as low as about 70°C to 110°C. Since the exhaust air contains a large amount of water and has a low temperature, a large heat exchanger is required to recover the waste heat of the exhaust air. In addition, even if a large heat exchanger is used to recover waste heat, if you try to use this heat to heat the drying air, the heat dissipated from the large-diameter duct will be too much, and the equipment will be damaged. There is no real profit in investing,
It was just being dissipated.

A conventional dryer is shown in FIG. 1 and will be described in more detail.

In the figure, drying air is sucked through a suction port 1 and heated to a predetermined temperature by an air heater 2 of a steam heating type or a direct mixture of combustion gas. This heated air is
The semi-finished products that are guided through the duct 3 to the dryer 4 and supplied through the product supply port 5 are dried, and then taken out as a product from the take-out port 6. On the other hand, the air containing a large amount of moisture has fine dry powder removed by the cyclone separator 1.
Further, if necessary, fine powder is removed by a bag filter 8 and discharged through an exhaust pipe 9.

However, the amount of heat dissipated from the exhaust stack is large, and the reality is that there is an urgent need to develop techniques for effectively recovering waste heat with low equipment costs.

The present invention has been made in view of the above-mentioned circumstances, and aims to provide a spray dryer that saves energy by recovering the emitted heat and raising the temperature of drying air. That is, in the present invention, a heat exchanger for heating the suction air is provided on the suction side of the air preheater;
A heat exchanger for heat recovery is provided at the outlet of the bag or filter, and a heat medium is continuously circulated through both heat exchangers via piping, and waste heat is transferred through this heat medium. At the same time, the recovered heat is used to raise the temperature of the air on the inlet side of the air heater, thereby reducing the heat load on the air heater and drying the material to be dried.

An embodiment of the present invention will be described in detail below. In Fig. 2, 1 is an air suction port, 2 is a steam heating type or combustion gas direct mixing type air heater for raising the temperature of the drying air to a predetermined temperature, and 3 is a dryer 4 for drying air. 5 is a supply port for supplying the material to be dried;
7 is a product outlet, 7 is a cyclone separator for removing fine dry matter, 8 is a bag filter for removing fine powder, which is provided when necessary, and 9 is a diffusion tube. These are the conventional ones. It's the same.

10 is a heat exchanger for raising the temperature of suction air provided on the suction side of the air heater 2. 11 is cyclone separator 7
Alternatively, it is a heat exchanger for heat recovery provided on the outlet side of the bag filter 8, which is provided when necessary. The suction air temperature increasing heat exchanger 10 and the heat recovery heat exchanger 11 are connected by a pipe 13, and a circulation pump 12 circulates a heat medium between the exchangers. In this embodiment configured as above, its operation will be explained. First, the drying air heated to a predetermined temperature by the air heater 2 is guided into the dryer 4, dries the material to be dried supplied through the supply port 5, and is delivered as a product through the takeout port 6. It is extracted as a product. On the other hand, from the air containing a large amount of moisture, fine dried particles are removed by a cyclone separator T, fine powder is further removed by a bag filter 8 if necessary, and the air is diffused through a diffusion tube 9.

In this drying process, the air coming out of the cyclone separator T or the bag filter 8 which is further provided if necessary is moist air at 80°C to 100°C and from which dust has been removed. The temperature of this air is lowered in the heat recovery heat exchanger 11 by the circulating heat medium. Moisture (water vapor) contained in the air condenses as the temperature decreases with and the heat of condensation of the water.

The heating medium heated in this way circulates in the pipe 13 and is heated in the suction air heating heat exchanger 10 to raise the temperature of the outside air that is drawn in, and the heating medium itself cools down and heats up again. The heat is returned to the recovery heat exchanger 11 to recover the heat.

By increasing the temperature of the inlet air of the air heater 2 using waste heat, the load on the air heater 2 is reduced, and the amount of heat consumed by the air heater 2 is reduced accordingly. On the other hand, since the moisture in the air is removed by the heat recovery heat exchanger 11, the amount of water vapor (which is cooled and condensed in the atmosphere) coming out of the radiation tube 9 is reduced, thereby preventing white smoke. become. In addition, in the circulation of the heat medium, since the pipe 13 may have a small diameter, the amount of heat dissipated is small.
A heat exchanger for raising the temperature of the suction air is provided on the suction side of the air heater, and a heat exchanger for heat recovery is provided on the outlet side of the Zylon separator or a bag filter that is further provided if necessary. Connect the equipment with piping to circulate the heat medium, raise the temperature of the air on the air heater suction side, reduce the heat load on the air heater, and supply air at a predetermined temperature to the spray dryer to dry the air. By drying things, we were able to obtain a spray dryer that saves energy.

In addition, moisture in the air is removed by cooling the air at the outlet of the cyclone separator or a bag filter provided if necessary, which is extremely important in practical use, as it prevents white smoke and solves the problem of pollution at the same time. be effective.

[Brief explanation of the drawing]

The first is a schematic side view of a conventional spray dryer. FIG. 2 is a schematic side view of an embodiment of a single-blade blade. 1... Air suction port 2... Air heater 4... Dryer γ... Cyclone separator 8... Bag filter 10... Heat exchanger for raising temperature of suction air 11...
Heat recovery heat exchanger 13...Circulation circuit

Claims (1)

[Claims] An air heater (direct fire type or steam heating type) installed at the air suction port to increase the temperature of the air used to dry the material to be dried;
a heat exchanger for raising the temperature of the air drawn into the air heater, which is installed on the air intake side of the air heater, and uses waste heat to raise the temperature of the air drawn into the air heater; A spray dryer for drying the material to be dried; a cyclone separator connected to the air outlet side of the spray dryer to remove fine particles carried by the drying air; a bag filter provided when necessary; a heat recovery heat exchanger provided at the exhaust port of the bag filter to recover heat from the exhaust; the heat recovery heat exchanger and the air temperature raising heat exchanger; A spray dryer equipped with a waste heat recovery device consisting of a circulation circuit in which a heat exchange medium can be circulated between a heat exchanger and a heat exchanger connected by a pipe.