boost the efficiency of your gas-fired aluminum ...
The increasing demand for aluminum castings makes people pay attention to the efficiency of aluminum casting plants.
Hidden errors and losses in small production operations (
Because they don\'t mean a lot of money)
Now, as the order quantity and scale increase, the order is exponentially enlarged.
At the heart of these gas inefficiencies --
The user is melting the cost. Gas-
Firing reverts are designed to quickly melt a large amount of metal, but not the most energy efficient way. The gas-
The combustion reverb furnace consists of three parts: a fireplace at one end;
A chimney or chimney at the other end;
And the bed between the two that are heated in ingot or scrap.
In practice, the flame in the fireplace heats the ingot or scrap and then is reflected down or \"reflected\" by the refractory to the melting below to maintain the melting temperature.
The simplicity of this furnace is an obstacle that the foundry must cross because the design reduces energy efficiency.
Compared to other furnaces, the large open chamber of the reflection furnace requires a lot of energy to heat the refractory, Chamber space, and then the neatness of the \"reverb\" ingot/scrap and melting.
To improve efficiency, manufacturers have developed a variety of aluminum melting configurations to optimize the main benefits of gasesfired reverb.
Three examples of reverb furnace design are: Wet Bath-
Design of this furnace]
Diagram omitted in figure 1]
Work by filling all the metal directly into the back of the melting thing in the furnace, which helps to melt by importing heat into the cold loading.
For a large fee, the pre-heating furnace is provided.
A popular waste charging method is to transfer the waste material through the opening of the side wall of the furnace.
In addition, most wet baths recover charging from one end and have a leaching well when pouring at the other end. Dry Hearth -
Melting method of this furnace]
Diagram omitted in figure 2]
It is to charge all cold metal directly to the dry refractory bottom, thus avoiding the possibility of moisture entering the molten bath through the charging material.
The dry furnace is manufactured as a medium-sized unit (Melt 1000)
For melting, steel and large units (
More than 15,000)
Melt only once. Stack/Tower -
Stack/Tower furnace similar to Chongtian furnace 【
Diagram omitted in figure 3]
Charge all cold metal using a conveyor belt (ingot or scrap)
In the exhaust cylinder
In this pile, before the charge material is deposited on the dry furnace bed, warm up and soften using the heated combustion product and direct flame.
Since the heated combustion gas is used to warm up the loading, the furnace quickly melts and is considered to be the most effective in the three groups.
Since the new furnace is not suitable for all operations or budgets, this article focuses on the composition of the gasfired reverb -
Burner, Combustion Control, refractory, again
Cycle, melting, charging method, lid, transmission mode and maintenance-
And how to adjust them to improve energy efficiency.
Hiccups in gas
The position and quantity of the burner is very important.
The furnaces designed for end or side combustion have two burners, they are arranged into a \"W\" type combustion, forcing the combustion product to leave the burner before returning through the bathtub to the outlet through the flue [
Diagram omitted in figure 4].
These two burners
Regeneration or heatair -
Can be used for considerable fuel savings (as much as 50%)
Depending on the metal temperature requirements.
Typically, the extra cost of these burners makes them only suitable for stoves that run 10,000 lbs/hour.
Reply with roof
Installation burner (
One or more according to melting requirements)
Lower roof design to save energy compared to end or side wallsInstall the burner.
The Bath of the furnace covers more evenly the direct heat dissipation and radiation of these burners. The hot-
However, the air option is available due to the location of the burner and the recovery option is not.
Built-in for stacked furnaces-
It is available in heat exchangers that use combustion products to gradually warm up as charged materials enter the chimney.
Another option is an external heat exchanger or heat exchanger, which can save a lot of fuel, but may deteriorate due to normal melting requirements.
Combustion Control most reverts have basic ratio control, including automatic air control valves that work with at least four to one adjusting burner.
If the furnace operates at full load to achieve maximum melting capacity, the presence of ingredient control is minimal.
An improved air
The gas control system will be fuel-
Control of Air ratio (micro-ratio valve)
Keep an accurate proportion and save fuel.
Automatic air door for flue]
Diagram omitted in figure 5]
It is a good function of wet bath reverb, but it is not practical for dry furnace or heap furnace.
The air door works with the air valve to open and close as needed.
A popular type is a dual damper system with a damper (the low-fire damper)
Always open when larger or higher
Automatic Control of fire valves.
Other types of shock absorbers include air-jet (
Claimed 15% fuel savings)
Or in the church, both can save fuel.
Large melting units may benefit from a complete combustion control system including PLC
Based on the controller, transmitter, oxygen sensor, air and fuel actuator driver and pressure control.
The first step in the design of a refractive reflective refractory is to contact the material of molten aluminum.
Before the next section of the refractory, it must have a high thermal conductivity and thickness to provide a frozen plane.
As far as the temperature of the shell is concerned, it must remain \"cooled\" at 200F \"(93C)or less.
Reducing the temperature of the housing will save energy, but it also means sacrificing the safe freezing flat area and/or increasing the overall refractory thickness to an impractical level.
The better goal of energy saving is the upper wall and roof of the reverb.
Refractory materials with low thermal conductivity can be used to reduce heat loss, but attention should still be paid to the strength of refractory materials.
The upper wall, which is completely composed of ceramic fibers, is installed to greatly reduce the heat loss, but the inherent splash of aluminum, insufficient resistance to oxide accumulation and insufficient total strength make the fiber less ideal, despite the savings
Ceramic Fiber is a feasible lining for charging doors, which can achieve reasonable fuel savings.
Can reduce the heat loss through the door by 50-
90% depends on the composition of existing refractory materials.
Many users of reflection furnaces with a capacity of more than 50,000 have been installed or are considering an increase
Circulating molten metal device [
Diagram omitted in figure 6].
These devices are available in electronics and motors-
Drive the design to increase energy savings by increasing the melting rate and productivity while increasing the uniformity of the metal.
When the same benefits are required, it is recommended to use a circulation device to melt the powder such as debris and turning.
Manufacturer of Re-
Cycle Units save up to 20% of fuel.
The use of a suitable melting technology is another energy-saving method.
Removing the oxide from the metal increases the fluidity, thus filling the mold more effectively and reducing the scrap.
The flux application should not be smaller than the recommended volume and should not be longer than the required time.
If possible, the flux injection used should distribute the flux evenly and contribute to the heat circulation inside the metal.
Charging method for solid melting (Ingot and scrap)
It can be done in an outdoor well, in a furnace, or in a combination of both.
In a dry furnace, all metal is deposited on the bottom of the furnace and directly hit by a flame on the bottom of the Furnace (
Not a means of saving energy).
For maximum fuel efficiency, the dry furnace melt will be in bulk-
Charge, if possible, the ingot will be charged through the scrap.
If the combustion product and heat transfer can be used through the bath, the wet bath furnace is the most effective.
The design of the furnace shall pass the combustion product through the main trough, through the pre-heating furnace cylinder or the waste loading area.
The heap/Tower melter charges all ingots and waste materials through the heap or flue, making full use of direct flames and combustion products.
When the chimney is continuously charged, the furnace runs with the highest efficiency.
If all melting is performed at the metal supplier\'s factory and the user receives only hot metal, considerable fuel savings can also be achieved.
As long as it is possible and/or actual, use a highly insulated furnace cover on the open well. At 1300F (704C)
The radiation heat loss generated by reverb is 12,000 btu/square foot.
Since the stove has to provide another 12,000 btu/square feet to cover the heat loss, the total fuel saved is estimated to be 24,000 btu/square feet.
Transfer means that the most common way to transfer the molten metal from the center melting device to other holding furnaces is through the transfer package from the furnace faucet
Out of the hole or pump.
However, this is an energy efficiency nightmare because when the molten metal is tapped or pumped, and during transportation from the melting device to the holding station, the molten metal loses its temperature.
To compensate for the loss, the temperature in the melting device increases or the time of the melting device in the holding furnace increases.
Therefore, users are faced with the hazards of high fuel cost, increased metal loss, further maintenance, shorter furnace age, high maintenance cost of ladle package and transportation of molten metal.
Some of these problems can be used by high
Quality insulation materials, including electric heating barrels or covered barrels.
When using a single alloy in a factory or in a melting pool, the transfer problem can be eliminated by using the covered molten metal launder system, which connects the melting device to the holding furnace.
Whether it\'s gas-
Power for launch or more energy-
Heating system, the launder system saves fuel by maintaining metal temperature by transportation, in addition to providing safer and more dangerous working conditions, reducing waste and Labor content.
The Launder system is an option for any existing facility in which the new plant and furnace run straight.
Maintaining natural gas is the last but easiest way to reduce energy costs
Transmitting reverb is maintenance.
Minimum daily cleaning of furnace walls and molten metal surfaces should be carried out without exception, as excessive oxide scum and sludge can lead to increased fuel costs.
Basic plant rules for reverb maintenance include: * removal of any oxide build-
Climb up from the fireside wall at least once a day;
* Melting and slag removal of the furnace body every day;
* Check the thermocouple protection tube, remove parts-
Replace and replace broken pipes every day;
* Check the temperature controller for correct calibration at least twice a year;
* Repair door seals if necessary;
* Check whether the combustion equipment is operating properly and be repaired annually by a qualified furnace or combustion service engineer.
In addition to focusing on the specific components mentioned above, there are other opportunities to use gas to save energyfired reverb.
They include: * continuous charging in a wet bath furnace instead of batch charging;
* Fully operated stove
Rated capacity if there is no automatic flue air door.
With a stack/Tower melting device, it is also important to keep the stack full of metal;
* Keep the furnace door closed except when necessary;
* Keep the metal bath temperature as low as possible.
There are many energy-saving options available to users of reflection furnaces.
While some may be too expensive or impractical, the foundry always has good furnace and burner maintenance habits to choose from, it saves energy and cash by keeping the stove working at full capacity for as long as possible.
This article is adapted from an article published in Die Casting Engineer in November/December 1997.
Related articles: Measuring furnace efficiency and melting loss the cost of melting 1 pound of aluminum is often overlooked in the operating costs of the foundry.
Although the foundry workers must use melting equipment in their Foundry
Equipment that may be very old and inefficient
They can still have significant control over the cost of melting.
Table 1 lists the approximate efficiency and melting loss of various aluminum furnaces.
It is based on published literature and actual melting tests by various furnace manufacturers.
The btu per pound and efficiency range are deliberately wide as this is the area in which the foundry can have a great impact by increasing the melting control and properly maintaining the melting equipment.
Gas reversions in this table include wet bath reverts and dry furnace reverts, so the efficiency range listed is very wide.
A single casting melting controller can place the foundry at the top or bottom efficiency of a specific furnace type.
In addition, the rated power of the electric furnace is kWh per pound.
This has been converted to btu per pound for ease of comparison.
Table 2 examines another melting cost that is often overlooked
Due to the oxidation of molten aluminum through contact with the atmosphere and furnace combustion gas, the cost of metal loss.
This table shows the huge impact of reducing the loss of melting on the overall cost.
This table assumes that the daily production output of the foundry requires 7143 lbs of molten aluminum.
The loss of metal at melting is 2%, and the foundry must melt 7289 of metal to meet this daily production demand (
Add an extra 146 to compensate for the loss). At $0.
The aluminum ingot is 90/lb, and 2% of the loss of melting is $34,060 per year in the lost metal.
Add this cost to the cost of melting an additional 146 pounds of metal per day, and the cost will increase more each year.
With better furnace control, improved burner efficiency and ingredient control, a simple reduction of melting loss can bring considerable profit gains to the foundry. -