JPS60244442A - Reconditioning method of molding sand by fluidized roasting furnace - Google Patents

Abstract

PURPOSE:To obtain roasted sand having high quality by replenishing oxygen to the down flow bed of the molding sand below the blow-off position of fluidizing air so that the molding sand descends in an oxygen-rich condition and that the unburned part of the molding sand is burned away. CONSTITUTION:The fluidizing air blown from a nozzle 108 flows partly toward an air take-out port 112 when the port 112 is opened by operating a flow rate regulating valve 113. The flow of the air is then formed in the down flow bed of the molding sand from the nozzle 108 to the port 112, by which oxygen is replenished into the down flow layer of the molding sand. The molding sand a'' is therefore dropped in the oxygen-rich state below the nozzle 108 and the unburned part thereof is burned away during this time. The sand a'' descends in the form of layers in the part below the successively completed without receiving the agitating effect as in the fluidized bed 111. The remaining unburned part is thus considerably decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for recycling foundry sand in which foundry sand containing a combustible binder is roasted in a fluidized roasting furnace, and in particular This invention relates to an improvement in a method for regenerating foundry sand using a fluidized torrefaction furnace that naturally roasts foundry sand using the heat energy of combustion of materials.

As a method for regenerating foundry sand using this type of fluidized roasting furnace, the present inventor has proposed a method for recycling foundry sand that has been roasted in a fluidized bed directly below the fluidized bed, as previously disclosed in Japanese Patent Application No. 58-90519. The fluidized air is allowed to flow down into the heating section, and the fluidized air is heated to around the roasting temperature by heat exchange in this heating section, and then the heated fluidized air is blown out into the fluidized bed to naturally roast the foundry sand. I suggested that they be allowed to do so.

That is, according to this method, as shown in the IT diagram, first, the foundry sand a is charged from the hopper 5 to a predetermined level and then stopped, and the blower 9 starts blowing air to pour the foundry sand a.
After forming a fluidized bed 11 at the lower part of the roasting section 3 above the fluidized air nozzle 8, the burner 6 is ignited to form a fluidized bed 11.
The molding sand a'' forming the molding sand a- is heated and roasted, and after waiting for this fluidized bed 11 to rise to the roasting temperature, the take-out 7 is opened, and at the same time, the injection of the molding sand a- is restarted. The fluidized air passing through the heat exchanger 10, which is a pipe connecting the fluidized air nozzle 8 and the blower 9, is mixed with the foundry sand a"° flowing down in the upper fluidized air heating section 4, which has been roasted by the fluidized air M!Ill. Heat is exchanged and heated. By repeating this, when the fluidized air is heated to around the roasting temperature by heat exchange in the fluidized air heating section 4, the temperature of the fluidized bed 11 remains at a predetermined level even if the burner 6 is completely stopped. The roasting temperature is maintained, and the foundry sand a can then be roasted naturally without using the burner 6.

In this way, according to the method disclosed in Japanese Patent Application No. 58-90519, it is possible to directly recover the thermal energy of torrefaction of foundry sand and to greatly improve the thermal efficiency of the fluidized torrefaction furnace. After transitioning to the natural roasting state, there is no fuel consumption by the burner, and the amount of fuel consumed for roasting and regenerating the foundry sand can be significantly reduced. Therefore, it is possible to regenerate foundry sand at a low cost commensurate with profitability even in medium and small-scale foundries, and can greatly contribute to resource and energy conservation.

Although the method disclosed in Japanese Patent Application No. 58-90515 is extremely excellent as described above, there still remains room for improvement as described below.

That is, in the fluidized bed 11, the foundry sand a' is stirred by the moving air blown out from the nozzle 8, so that the foundry sand a' has different residence times, that is, the roasted foundry sand a' and the unroasted foundry sand. This results in a mixture of a° and a°. This phenomenon is particularly remarkable when the foundry sand a is continuously introduced into the fluidized bed 11. Therefore, the foundry sand a'' that is flowed down from the fluidized bed 11 to the fluidized air heating section 4 is not necessarily roasted, but also includes unroasted sand, and the bed is made up of a mixture of these sands. It is forced to move downward.

By the way, considering the pressure distribution inside the furnace, the pressure inside the furnace is maximum at the fluidized air blowing position, that is, at the nozzle 8 position, and the pressure gradually decreases as it moves above this nozzle 8 position, that is, as it approaches the surface of the fluidized bed 11. .

This tendency for the pressure to decrease is the same below the nozzle 8 position, and the pressure gradually decreases toward the take-out lower position, dropping to atmospheric pressure at the take-out lower position.

1. Therefore, in the lower layer of the foundry sand flow below the nozzle 8 position, the pressure is reduced as described above, and the foundry sand a'' is less agitated by the flowing air and moves in layers, so there is less ventilation resistance. Due to its large size, the amount of air flowing through it is extremely small.

Therefore, the foundry sand a'l is allowed to flow down from the nozzle 8 position to the take-out lower part in a state where there is very little air, that is, in a so-called oxygen-deficient state. is difficult to burn, and there is a risk that it will be discharged as is from the outlet.

The present invention has been improved in order to eliminate the above-mentioned inconveniences in the method of naturally roasting foundry sand, and minimizes the amount of unburned parts remaining in the foundry sand discharged from the outlet. The method of the present invention that solves this problem provides a method for regenerating foundry sand using a fluidized roasting furnace that can obtain a roasted part of higher quality. This is to supply oxygen to the lower layer of the foundry sand flow.

The method of the present invention will be specifically explained below with reference to FIG.

FIG. 2 shows an example of a fluidized roasting furnace for carrying out the method of the present invention. First, the configuration of this fluidized roasting furnace will be explained.

That is, in the fluidized roasting furnace 101, the preheating section 1 is opened from above.
02, a roasting section 103 and a fluidized air heating section 104 are sequentially formed, and an input hopper 1 is placed above the preheating section 102.
05 is provided on the furnace wall of the roasting section 103, and a /Hena i06 directed toward the inside of the furnace is provided, and a takeout 0107 is provided on the bottom of the lower furnace of the fluidized air heating ffB104. Furthermore, the area between the roasting section 103 and the fluidized air heating section 104 below it is partially partitioned by a fluidized air nozzle 108. No means exist. and,
Flowing air nozzle 108 and blower 109 outside the lower part of the furnace body
The part of the piping connecting between the two is formed in a meandering shape in order to make the contact area with the molding sand in the heating part 104 as uniform as possible. It is configured as a heat exchanger 1.10. Further, an air outlet 112 is provided at one or more locations on the furnace wall below the nozzle lO8 position.

This air outlet 112 is open to the atmosphere outside the furnace via a flow rate adjustment valve 113, or is connected to a dust collector.

Therefore, when carrying out the method of the present invention using the fluidized roasting furnace 101 having such a configuration, first the molding sand a is introduced from the omper 105 to a predetermined level and then stopped, and the blower 109 starts blowing air. After forming a fluidized bed 111 of the foundry sand a' at the lower part of the roasting m103 on the nozzle 108, the burner 106 is ignited to heat and roast the foundry sand a' forming the fluidized bed 111. , this fluidized bed l
11 rises to the roasting temperature, and then open the outlet 10.
7, and at the same time start adding foundry sand a.

Here, the foundry sand a is charged into the preheating section 102, dried and preheated by exhaust gas, and then descends in the roasting section 103 to reach the fluidized bed 111. a" is roasted by the burner 106 and heated to the highest temperature in the furnace. Next, the thus roasted foundry sand a" is heated to the fluidized air heating section 10 with almost no temperature drop.
During this time, the sensible heat is exchanged with the flowing air passing through the heat exchanger 110, and is eventually discharged from the outlet 107.

As this process is repeated, the fluidized air heating section 10
4 increases, and at the same time the temperature of the flowing air undergoing heat exchange also gradually increases. Therefore, as the temperature of the fluidized air increases, the temperature of the fluidized bed 111 from which the fluidized air is blown also tends to increase. Eventually, even when the burner 106 is completely stopped, the roasting temperature is maintained, the state shifts to a natural roasting state, and after that the foundry sand a'
is naturally roasted without using the burner 106.

During this time, the flow rate adjustment valve 113 is operated to open the air outlet 112. Air outlet 11
2 is opened, a part of the flowing air blown out from the nozzle 108 flows in the direction of the air outlet 112, and the nozzle 1
An air flow is formed in the lower layer of the foundry sand flow from 08 to the air outlet 112, and oxygen is supplied to the lower layer of the foundry sand flow.

Therefore, the foundry sand a'' is forced to flow down the nozzle 108 in an oxygen-enriched state, and the foundry sand a
During this period, the unburned portion of "A" is burned and removed. Furthermore, in the area below the nozzle 108, the foundry sand "A" descends in layers and is less likely to be subjected to the stirring action as in the fluidized bed 111. During the descending process, the roasting of the unroasted foundry sand a'' is completed one by one, and the amount of unburnt parts remaining becomes extremely small.The amount of air discharged from the air outlet 112 is adjusted by adjusting the flow rate. It is assumed that the valve 113 is used for appropriate adjustment, and the adjustment is also performed at appropriate times as necessary.

As detailed above, according to the present invention, since oxygen is supplied to the lower layer of the casting sand flow below the blowout position of the fluidized air, specifically, the fluidized air actively forms an air flow in the lower layer of the foundry sand flow. Therefore, even if foundry sand is mixed with unburned sand and flows down to the fluidized air heating section, the foundry sand will descend in an oxygen-enriched state, and during that time, the unburned foundry sand will The part will be burnt off and a higher quality roasted part can thus be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view showing a fluidized roasting furnace used in a conventional method, and FIG. 2 is a schematic vertical sectional view showing an example of a fluidized roasting furnace for carrying out the method of the present invention. 101... Fluidized roasting furnace 102... Preheating section 103... Roasting section 104... Fluidized air heating section 106... Burner 108... Fluidized air nozzle 109... Blower 110... Heat exchanger lit...Fluidized bed 112...Air outlet 113...Flow rate adjustment valves a, a', a''...Casting sand Patent applicant Nippon Steel Pipe Fitting Co., Ltd. Representative Patent attorney Takashi Suzue - Figure 1 Figure 2

Claims (1)

[Claims] The foundry sand roasted in the fluidized bed is passed through the fluidized air heating section directly below the fluidized bed, and the fluidized air is heated to around the roasting temperature by heat exchange in this heating section. In the method for regenerating foundry sand using a fluidized torrefaction furnace, in which foundry sand is naturally roasted by being blown out into the fluidized bed, oxygen is supplied to a lower layer of the foundry sand flow below the blowing position of the fluidized air. A method for regenerating foundry sand using a fluidized torrefaction furnace.