JPS643317B2 - - Google Patents

Description

[Detailed description of the invention] The present invention provides dielectric heating using microwave irradiation,
The present invention relates to a microwave melting furnace for melting materials to be melted, such as incineration ash of sewage sludge.

2. Description of the Related Art Conventionally, a microwave melting furnace is known in which a dielectric material to be melted placed in a metal retort is directly irradiated with microwaves from above to heat and melt the material.

However, in such conventional microwave melting furnaces, ionized gas jumps out from the surface of the melt heated by microwave irradiation, which causes an electrical discharge phenomenon in the furnace, causing a large amount of microwave energy to be emitted. In addition to causing losses, the power must be turned off to prevent discharge, which leads to problems in that smooth operation is impaired.

The present invention was made by focusing on the above-mentioned problems of conventional microwave melting furnaces.The retort for melting the material to be melted is made of a heat-resistant dielectric material, and the temperature is raised by irradiating the retort with microwaves. The object of the present invention is to solve the above-mentioned problems by indirectly heating the material to be melted using radiant heat or the like, and by preventing microwaves from passing through the ion gas atmosphere in the furnace.

Embodiments of the invention will be described below with reference to the figures. The melting furnace main body 1 includes a feeder 2 capable of continuously supplying the material to be melted M on the upper side thereof, and an exhaust port 3 on the other side thereof. A blower pipe 4 is led to the upper part of the main body 1 and blows air into the furnace. The retort 5 at the bottom of the main body 1 is made of a heat-resistant dielectric material such as SiC sintered body,
A sprue 5a for discharging the molten metal m is provided on the upper side. The retort 5 is surrounded on the outside by a metal outer frame 7 with a heat-resistant and low microwave loss heat insulating material 6 (for example, a heat insulating material made of a spiral body containing alumina, silica, etc.) interposed therebetween. The end of a microwave waveguide 8 connected to a microwave power source (not shown) is connected to the side opening 7a of the outer frame 7, and the microwave W is irradiated toward the retort 5 inside.

A waveguide 9 is also connected to the upper part of the melting furnace main body 1,
Microwaves w and air will continue to be introduced into the furnace. This microwave w can be directly irradiated onto the dielectric object M to be melted inside the retort 5 .

Next, the effect will be explained. From the feeder 2, a material to be melted M, such as incinerated ash of sewage sludge, is continuously supplied into the retort 5. By irradiating the microwave W, the temperature of the retort 5 made of a dielectric material increases rapidly. Radiant heat from the high temperature retort 5,
The material to be melted M in the retort 5 is heated and melted by the conduction heat, and is sequentially discharged from the sprue 5a. Air is blown into the furnace from an upper blast pipe 4, and gas generated in the furnace due to heating is exhausted from an exhaust port 3. Moreover, the microwave w is guided into the waveguide 9 only for a certain period of time at the start of operation, when the material to be melted M is in an unmelted state. That is, dielectric heating is performed by irradiating the microwave directly from the waveguide 9 to the material to be melted M only during a certain period of time when the material to be melted M has poor thermal conductivity. In an unmolten state, no ionized gas is generated in the furnace and no discharge phenomenon occurs, which is effective.

The invention is not limited to the illustrated embodiment. For example, the surface of the retort can be coated with a heat-resistant metal to prevent chemical reactions between the molten metal and the surface of the retort. The processing format can be taken as follows.

As explained above, in the present invention, the retort 5 is made of a heat-resistant dielectric material, dielectrically heated by irradiating the retort 5 with microwaves W from the side, and the object to be melted M inside the retort 5 is heated by radiation heat and conduction heat. In addition to heating and melting, the upper open part of the retort 5 is also temporarily irradiated with microwaves, which eliminates electrical discharge inside the furnace and enables efficient and smooth melting. have an effect.

[Brief explanation of drawings]

The drawings are schematic cross-sectional views showing one embodiment of the present invention. 1... Melting furnace, 2... Feeder, 3... Exhaust port, 4... Air pipe, 5... Retort, 5a... Sprue, 6... Insulating material, 7... Outer frame, 8... Wave guide tube,
9... waveguide, M... object to be melted, m... molten metal,
W, w...Microwave.

Claims (1)

[Scope of Claims] 1. A retort made of a heat-resistant dielectric material and having an open top and a sprue on the side, and an outer frame made of a heat-resistant metal that covers the outside of the retort with a heat insulating material having low microwave loss. , a feeder capable of feeding a material to be melted into the retort; a microwave waveguide connected to a side surface of the retort so as to be able to irradiate microwaves from a side opening of the outer frame; and an upper opening of the retort. 1. A microwave melting furnace characterized by comprising: a microwave waveguide connected to the retort from above so as to be able to directly irradiate microwaves to the object to be melted in the retort.