Notes

What affect the molding result of biomass pellets?<br>
Biomass energy has many application settings, such as biogas, alcohol, and also biomass molding fuel. Biomass molding gas is one of the most practical and also cost-effective mode. Biomass molding gas has biomass pellets and biomass briquettes 2 forms. Biomass pellets progressively replace briquettes owing to tiny size, high thickness, and easy use.



Biomass briquettes and also biomass pellets

Biomass pellets are made from timber pellet machine. It utilizes high pressure from roller and die to mold biomass products into high-density solid pellets. The molding effect is affected by the basic material top quality, molding procedure, and also equipment performance. To improve the molding impacts of biomass pellets, you ought to learn about the list below elements.



Resources quality

Raw material make-up

The raw materials for making wood pellets are made up of different contents. They have different responses in high warmth and also high pressure. Some materials like proteins as well as lignin will soften and have gluing result. Some components like cellulose and not natural fragments are difficult to break down or split. They impede the molding of wood pellets, yet they takes up one of the most part of biomass products




The make-up of raw materials has the largest impact on the pellet durability. The complying with chart shows the Pellet Top quality Coefficient (PQF) of numerous usual basic materials



The larger the PQF, the tighter the timber pellets are bound. Some products like bentonite, lignin have high PQF. They can function as binders. Some products like acid oil has low PQF, the bits inside can not bind with each other effectively. Loose biomass pellets has less sturdiness. Only when the total PQF of all materials amount to more than 4.7, the timber pellets can take shape successfully.



The excellence of resources.

Resources with smaller sized granularity have larger surface, so they are simple to bind. And the created pellets are more compact and smooth, difficult to break. The smaller the granulates, the higher the timber pellet toughness. Yet too little granulates needs high energy consumption for grating. It is not recommend to seek too small granulates.



The granulates ought to be consistent in size. Also huge granulates are difficult to bind with others, and the surface tend to be harsh. Large particles generally trigger glowing crack, where the timber pellets are simple to damage. Too big granulates are difficult to get into the die openings. They will certainly intensify the abrasion of pellet mill die and roller, decrease the timber pellet manufacturing, and also lower the molding price.



Consequently, the granularity of raw materials must be 1/2 -2/ 3 of the wood pellet size. You can adopt a screener with the pore diameter less than 10mm in pulverizing procedure, to make sure that the raw materials can fulfill the criterion for pelletizing and blending, and also lower the power consumption as well as tools abrasion.



The dampness of resources.

The moisture in the biomass products have lubrication function. They can decrease the rubbing in between the granulates, and also improve their bonding. The moisture can additionally soften the materials to ensure that they are much easier to deform as well as mold.



Biomass materials differs in wetness material, generally between 8% -15%. The wetness is influenced by temperature level. For those products with over-high dampness, we need to dry them before making pellets.



Molding procedure

The molding temperature level

The biomass molding is to make the natural parts of biomass soften, bond as well as transformed under heat as well as pressure.



Generally, the raw materials soften at the temperature of 70 ℃ ～ 80 ℃, bond at the temperature level of 160 ℃, melt at the temperature of 240 ℃. With the increase temperature, the raw materials become a lot more soften, the liquidity enhances, the resistance in between basic materials decrease, so they are much easier to mold and mildew. As determined, the molding stress in high temperature is half of that in high temperature.



Heat is not constantly excellent. Over- useful site will certainly cause carbonization of the biomass products. Such carbonization is neither uniform neither controllable, which will certainly impede molding as well as affect the timber pellet top quality.



The thickness of product layer

In pellet makers, there is a clearance between the roller and also die, where the biomass products form a layer. The clearance can be readjusted from 0.1 mm to 0.3 mm. To produce small-size wood pellets, the clearance is tiny, as well as the other way around.



The density of product layer likewise influence the power usage of the pellet maker. When the product layer is thick, the extrusion stress will boost. With excessive raw materials entering the die openings, they will be as well limited to discharge, and also even cause damages to the devices. When the product layer is as well slim, the extrusion stress is small, the raw materials squeezed right into the die holes want, so the timber pellet production is low.



The picture below shows the impact of basic materials on the extrusion pressure. B describes appropriate density, A refers to the layer is too thick, C describes the layer is as well slim. In the A standing, the extrusion force increase a great deal owing to the lengthy pressing location. In manual pellet maker , the extrusion force is also tiny. So an ideal density is a property of high-efficient production.



Tools efficiency

Extrusion speed

Extrusion rate determines the moment that raw materials are in the die openings, so as to influence the molding quality. When the raw products leave in the die holes for short time, the device power consumption is reduced, yet the wood pellets may hang. When the raw materials leave in the die openings for long, the timber pellets will have higher density and top quality, the system power intake likewise increase.



If the raw materials leave in the die holes for as well long, the friction will certainly be too high, the pellets will certainly be too thick, the pellet equipment will be hot and even quit.



The extrusion rate of a pellet equipment is affected by the roller size and revolving speed. A correct extrusion speed make certain the tools work continually with low power intake.



Extrusion toughness

The pressing stress on the raw products figures out the density of timber pellets. High pressure extrusion and friction will soften and also flaw the raw materials and bind them with each other.



If the extrusion strength is insufficient, the raw products can not be formed effectively. If the extrusion stamina is too high, it will worsen the abrasion of dies and include in cost.



The parameters of die hole

The specifications of die openings are restricted by basic material granularity, extrusion rate, squeezing out toughness. Oppositely, the criteria of die holes influence the molding of timber pellets.



Pellet mill die openings have certain compression proportion. High compression proportion enhance the extrusion strength, lower the extrusion speed. They are suitable for the products with reduced sticky force.



The hole access shape influence the speed of resources getting into the die holes, as well as influence the thickness of raw materials.



The specification of die holes should be changed according to different materials, to ensure that you can obtain top quality wood pellets with reduced unit power consumption.

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