Homeowners who heat their homes with solid fuel boilers and stoves are well aware of how difficult and inconvenient it is to burn small fractions of coal, and especially coal dust. Some of this fuel is poured into the ash compartment and is disposed of, while another blocks the air flow from the grate and therefore burns poorly.
The solution to the problem is to compact this small thing into briquettes that give good burning and generate a lot of heat. Industrial briquetting of coal has been used for a long time, but the pressing technology can be implemented at home. How to do this - we study in this material.
Production of coal briquettes in the factory
Fine coal fractions and dust are notable for their low density and low specific calorific value. But you can buy them cheaply, and then turn them into high-quality fuel by compaction in a limited volume. Simply put, to produce pressed coal briquettes, whose density and calorific value are much higher.
To make such briquettes from fine coal with your own hands, you need to figure out how and with what machines they are stamped at the factory. Equipment for the production of heating briquettes is a technological line consisting of the following plants:
- crusher;
- drying chamber;
- briquetting press.
Note. Units of equipment are listed in the same order in which they stand according to technology. The supply of raw materials and its movement between units is carried out by means of belt or screw conveyors.
The process of pressing coal fuel is as follows:
- In a crusher, small coal is crushed to particles of the same size, depending on the characteristics of the press equipment. The maximum allowable size of the fraction is 6 mm.
- In the dryer, the moisture content of the feed is reduced to 15% (maximum).
- The last stage is pressing performed under pressure from 20 to 120 MPa, depending on the technology used.
Sometimes, for the strength of the final product, organic or mineral binders are added to the raw materials, and before the mixture is densified, it is heated to a temperature of 250-350 ° С. There are 2 ways to press coal briquettes for heating:
- on stamp (roll) presses;
- through extrusion machines.
The stamp press squeezes the heated coal mixture in special forms, developing a force of 100-120 MPa, after which the briquetted coal goes through the cooling and filling process. The output is products in the form of "tablets", "pads", cylinders and bricks with holes.
This method of production of coal briquettes is used for the manufacture of fuel in large quantities and entails considerable financial and energy costs.
Extrusion fabrication consists in forcing raw materials through a screw press through a die with calibrated holes. At the exit we have a coal briquette of cylindrical shape in the form of a “sausage”. This is a cheaper but less productive technology for coal briquetting.
The fuel composition is affected by the composition of the initial raw material - brown or hard coal, the presence of binders and other factors. But usually the calorific value of a factory briquette is at least 7 kW / kg with a moisture content of 8% and a maximum ash content of 8.5%.
How can I make briquettes from coal with my own hands?
At home, it is impossible to implement industrial technology. The reasons are the high price of equipment for the production of coal briquettes, high energy costs and the need to coordinate their actions with local authorities.But the owner of a private house does not even need to deploy a grandiose scale production to ensure heating of the home. It is enough to make 3-4 tons of coal briquettes, which are enough for the whole winter.
Pressed charcoal in briquettes can be obtained in two ways:
- weld a briquette forming machine from metal rolling and extrude products manually;
- to assemble a screw press with your own hands to briquette the coal fines by extrusion.
In either case, it will not be possible to achieve characteristics close to those of factory-made fuel. But you can successfully heat the house by burning home-made briquettes instead of coal dust, which is much more convenient and practical.
Manual pressing
For manual extrusion, a machine for making bricks at home, well known to many craftsmen, is suitable. Its frame is welded from profile pipes and corners 40x40 mm, a receiving hopper is installed on top. A manual mechanism for pressing products in a rectangular shape is attached to the frame. A drawing of a homemade press for manual briquetting of coal is shown in the figure:
The rectangular shape used to make bricks can be replaced with a cylindrical one, and plugged tubes can be placed inside so that there are through holes in the products. They are needed for the best burning of a coal briquette made by yourself.
The technology of manual briquetting of coal looks like this:
- Raw materials should be tried to grind. The smaller the fraction, the stronger and better the homemade briquette will be.
- Pour a little water and mix so that the mixture is molded by hand. Some home craftsmen add clay as a binder, but this will lead to an increase in the ash content of the fuel.
- Pour the mixture into the hopper, and from there fill the form. Squeeze out the briquette by pressing the lever.
- The lever during the reverse stroke pushes the product out. After it should be removed and placed on a sunny platform for drying. Press details are shown in the video:
Extruder Briquetting
This more productive method will require financial costs for the assembly of a screw press, consisting of the following elements:
- a case made of thick-walled steel pipe grooved from the inside to fit the size of a screw, or made of a solid metal bar on a lathe;
- Carbon steel screw of increased hardness;
- a matrix with one or more holes is made from the same steel;
- an electric motor with a power of at least 4 kW;
- Belt drive on multi-belt pulleys (at least 3 belts);
- receiving hopper.
Note. Instead of a belt drive, a gearbox can be used, but then the drive will be rigidly connected to the shaft. In the event of any accident, the gearbox or auger may fail.
The most difficult to make the body, matrix and screw. For this, it is better to turn to a familiar turner, at the same time he will carve out multi-ribbed pulleys of the right size to you. Please note: the pulley diameters should be selected so that the screw speed does not exceed 200 rpm. The powerful engine of the machine must be grounded and connected to the home electrical system through circuit breakers.
The briquetting technology on the extruder is quite simple and is implemented in several stages:
- If possible, grind the raw materials and mix with water to a thick consistency.
- Turn on the extruder motor and shovel load a portion of the coal mixture into the hopper.
- Break the “sausages” emerging from the holes of the matrix according to the desired length and lay them on the drying rack.
The benefits of coal briquettes - conclusions
If we argue theoretically and take into account the assurances of coal briquette producers, then by calorific value they should defeat all other types of solid fuel. Indeed, only pure anthracite is able to isolate when burning 7.7-8 kW per 1 kg.Firewood, pellets and wood briquettes in terms of specific heat of combustion are far behind, since they emit no more than 5 kW / kg.
But judging by the feedback from users of solid fuel boilers at thematic forums, the demand for briquetted coals is inferior to any kind of wood due to such reasons:
- badly flare up and give off little heat;
- form a large amount of ash, or even pebbles, repeating the shape of briquettes;
- crumble into dust even during transportation;
- emit too unpleasant odors before and during combustion.
If we analyze all the reviews about coal briquettes, it turns out that 70% of them are negative. This is primarily due to the fact that fuel producers are trying to make a profit using waste materials - sludge, burden and other indecent varieties of hard and brown coals. A briquette pressed from anthracite residues is not common.
This suggests the conclusion: if you want to get good fuel, then use the appropriate raw materials for briquetting yourself. When at your disposal there is only dust and fines of low-calorie varieties of coal, then pressing them is not always advisable. On the other hand, such briquettes can be burned together with firewood, reducing the cost of their acquisition.