Making a blast furnace but having it in a smaller size might be different from the usual way of creating a blast furnace.
The only main difference between a normal furnace and a mini furnace is that. The size of a mini furnace is significantly smaller.
The purpose of having a mini blast furnace is to melt small amounts of aluminium into ingots or sand casting to create smaller objects.
What is a Mini Blast Furnace?
Mini Blast Furnace (MBF) also known as the miniature size from a conventional normal blast furnace which is 10 times bigger than a mini blast furnace.
The reason for this type of usage is that mini furnaces only required for small operations that do not involve much.
Plus, the mini blast furnace tends to last longer than the conventional blast furnace.
The mini blast furnace is available everywhere in the world. But the most popular usage and the countries that have the majority of these mini furnaces are China, India, Brazil and Indonesia.
Most users and factories including the user that use mini furnaces for their laboratories will use these smaller furnaces to fulfil their operations.
It has made that Mini Blast Furnace as an acceptable route to create irons.
Iron Manufacturing
Although the mini furnace is just a smaller version of the normal industrial furnace. The mini blast furnace was made as a vertical shaft furnace which is different from what they are usually made.
The burden materials consisting of iron ore and charcoal used as a reducing agent.
Then, they are charged into the top of the furnace and they work on the principle of the counter current reactor.
The Mini Blast Furnace has it’s own benefits and flexibility for the productions:
Here as few features of having a mini blast furnace:
- Proven technology and equipment
- Has a simpler design and equipment that a normal conventional blast furnace
- The Flexibility with ore burdening from 100% ore lumps to any types of the blend of iron ore lumps.
- A range of reducing agents can be used including low-quality coke and charcoal
- The quality of hot metal materials produced is similar to the normal blast furnace
- The operation and maintenance are the same but the mini blast furnace is more flexible than the conventional furnace.
- An economic and reliable source of hot materials for iron foundries.
Can You Really Make Your Own Mini Furnace?
Yes. You could make your own mini metal foundry. Although you can make this yourself it’s not the best way to make if you don’t know what you are doing. It’s better to leave it to the professionals at making anything that involves danger (fire/heat).
Creating any mini furnaces that can exceed a temperature of 1000ºC, which is well above the melting point.
You must only create this project when having a piece of adequate knowledge and training with protective safety gear and in a fire-resistant area with good ventilation.
1st Step:
Using equal parts of sand and plaster, if you are planning a basic foundry/furnace. I know that it’s quite basic but it’s powerful enough to melt scrap metals.
2nd Step:
Follow these steps:
- Buy a big bag of sand
- Buy “Plaster of Paris”
- Need a 10 Quart Steel Bucket
- Table cloth to cover anything that is important
- 2.5 Quart bucket for measuring ingredients
The guide for makeshift refractory lining:
- 1 – 3/4 buckets full of plaster of paris
- 1 – 3/4 buckets of sand
- 1 – 1/4 buckets of water
3rd Step:
Once the materials are in the dry mix, you have to start the process immediately.
There are only 15 minutes in hand to complete the process. Because they will get hardened after those minutes are off.
It’s important to get the dry powder wet and work with any lumps or defects as quickly as possible.
After the mixture has been mixed for a few minutes, the mixture should be fairly runny and to confirm, all the mixture must have the same colour that compliments each other.
This is to show that it’s already mixed thoroughly. When you feel confident there’s aren’t any clumps of powder in the bucket.
The refractory mix is ready for pouring.
Transfer it to the steel bucket as slowly and carefully, to minimize the spillage.
Should be enough to full the bucket from the top.
Now that’s done, use back the plastic measuring bucket as the form of the centre of the foundry.
Fill that bucket with water to give a little bit of weight. You could also use sand or stones as well to replace the weight.
Then, push the bucket into the centre of the mixture.
The mixture will then rise upwards. Notice that it won’t spill out.
Before the mixture starts to harden, try levelling the centre by using the bucket to push up and down.
Keep the mixture still for 2 to 3 minutes. This way will give enough time to harden, so the bucket needs to stay in place.
After that. You are done!
4th Step:
Even though you’ve done the basic steps. We still need an hour to wait for it to harden up.
You can clean it first while it’s hardening.
It looks pretty neat and smooth once everything is done.
5th Step:
Now that’s left is making the crucible. Well, I prefer to have a separate crucible that is already made.
But if you feeling lucky, you can create that on your own.
You can use an empty fire extinguisher as a crucible. Make sure that it is steel.
Firstly, we need to depressurize the tank and unscrew the valve from the top.
Then cut it in half. After that, the bottom part of the fire extinguisher is the part we’ll use as a crucible.
The size of the crucible has to be a steel cup 3″ in diameter and 5″ tall.
6th Step:
In this step, you can take it further and make it more professional.
At this stage, your furnace is pretty much ready. The plaster should be hardened.
Just throw away the water that we’ve placed earlier from the bucket.
Next step, we need to pull out the bucket that we use, notice that when you pulled it out, the furnace will make up for the size and pattern from the bucket’s outer layer.
This will give a professional look to your foundry.
7th Step:
All we need now is the air supply port.
The way to do that is by using a 1-3/8″ (35mm) hole saw that is suitable for this 1″ steel tubing.
Begin making through the bucket by aligning it at the top center of the bucket.
You can cut through the metal wall, once that metal already broke.
You have to angle the hole saw at 30 degrees downwards when you’ve reached the plaster surface.
Now, you’ll have a tight, downward sloping hole, the only thing that’s left is to put the blower tube.
The usage of this is to fill in the molten metal into the foundry. It will stay in the foundry, instead of dangerously flowing out of the pipe.
As for the blower tube, you can use a steel pipe and it will need to sit on the hot coals in the foundry.
You need 1″ PVC coupling (Slip x FIPT) as well as some 1″ PVC pipe.
The threads on the half coupling screw onto the steel pipe, and slip adaptor, just need to push on the PVC tube.
Now, another thing that we need to consider is that we have to make a lid so that we can maintain the heat and trap it inside the foundry.
8th Step:
To make the lid for the foundry, you will need:
- 4″ U-bolts (make it stand upright)
- Big lid of the bucket
- 10 Cups of plaster
- 10 Cups of sand
- 7 Cups of water
After mixing those together, the plaster should be ready. Be sure that you will leave the plaster to dry and harden for at least 1 hour.
Then, you will have a lid for the foundry.
All it needs now is a vent hole to relieve the pressure. You can try drilling with a 3″ hole in the center.
You can get a nice thick lid that looks like a doughnut
This type of design is good for venting the pressure and gives you the option to melt metal efficiently.
There you have it. Your very own mini blast furnace, a metal foundry that can be made by yourself.
Also, to note that if you feel like it’s hard to make yourself, it’s way better to have a professional to create one for you or you could always save time and buy one yourself.
Besides, if you were to buy one, the quality is much better than having to create one yourself as the experience of creating one is close to none if you are not familiar with it.
A Mini Blast Furnace has a self-standing frame structure with 4 columns supporting 6 platforms and a skip-bridge standing directly on the RCC Foundation.
Profiles for Mini Blast Furnaces
| Chinese Mini Blast Furnace Profile | ||||
| No. | Parameter | Unit | Value | |
| 1 | Effective Volume | cum | 50 | 320 |
| 2 | Hearth Diameter | m | 2.25 | 4.9 |
| 3 | Belly Diameter | m | 3.05 | 5.7 |
| 4 | Throat Diameter | m | 2.0 | 3.7 |
| 5 | Height of Dead Layer | m | 0.35 | 0.6 |
| 6 | Height of Hearth | m | 1.8 | 2.7 |
| 7 | Height of Bosh | m | 2.3 | 2.9 |
| 8 | Height of Belly | m | 1 | 1 |
| 9 | Height of Shaft | m | 5.3 | 9.2 |
| 10 | Height of Throat | m | 1.27 | 1.6 |
| 11 | Effective of Height | m | 12.02 | 17.4 |
| 12 | Stack Angle | Deg | 84.27 | 83.79 |
| 13 | Bosh Angle | Deg | 81.57 | 82.15 |
| 14 | Height/Diameter ratio | 3.58 | 3.05 | |
| 15 | Number of Tuyeres | Nos. | 6.0 | 12 |
Alright, as suggested this diagram can be used as a reference if you are searching for a mini blast furnace for heat treatment applications.
There is no consistent number and metrics that you need to follow, please note these are just guidelines so that it’s suitable for your projects. Different furnaces are only suitable for different applications. Not all furnaces are the same. Best to make a custom mini furnace yourself.
