Which pellets are better 6 or 8 mm. How to determine quality pellets, which ones are better? Visual assessment of pellet quality

Last update: 31-10-2015

The use of wood pellets as fuel obliges the owner of the boiler to know the parameters by which they should be selected. Understand the indicators that are indicated in the certificates of product quality.

If, when buying pellets, you ask questions about what is indicated in the certificate, then the likelihood of purchasing low-quality fuel will increase significantly.

To understand the methods for determining the quality of pellets and their physical indicators, let's get acquainted with the main indicators.

Of course, the simplest method for determining the quality is to burn a test amount of fuel. Under the same conditions, it is possible to obtain average values ​​from a number of studies, but this is by no means always possible. Therefore, it is necessary to navigate by indirect signs.

Burning pellets, like any other fuel, has its own time, which is directly related to its quality. Therefore, when buying a new batch of fuel, you need to know the approximate combustion time.

How to evaluate the quality of pellets visually

1. Pellets good quality with a shiny surface. They are dense, do not have longitudinal or transverse cracks. This is an indicator of the quality of production - maintaining the desired temperature during granulation, when lignin binds pellets well.
2. If you try the granules for a break, then they should not crumble or break. Pellets that crumble or break will also behave during transport and loading. In the mass of such fuel, the passage of air, which ensures proper combustion, will be uneven. Part of the pellets will not burn completely and will clog the ash pan. This parameter is called abrasiveness by specialists and is determined by a lignotester. The sample is pressed with a weight of 0.1 t for 1 min, and then blown with air. The more crumbs, the lower the quality. The amount of crumbs determines the dustiness of the fuel.

Granules have two standard sizes 6 and 8 mm, but according to observations, larger granules are less likely to crumble, more resistant to transportation and loading.

Visual quality analysis by color is ineffective. The color determines the raw material used and the granulation temperature. The same can be said for smell.

Dissolving pellets in water can only indicate the use in the manufacturing process of chemical components for high-quality gluing of granules.

Laboratory indicators of pellet quality

The most accurate indicators of pellets can only be determined by laboratory analysis with special professional equipment. Based on the results of the study, a certificate for products is issued, in which there are basic indicators. These indicators are summarized in a table depending on chemical and physical parameters.

Parameter		Parameter dependency
Chemical characteristics
Humidity			Determines storage conditions, indicates calorific value loss and spontaneous combustion
Calorific value			Possibility of application in this installation with the greatest efficiency
Chlorine			Durability of chimneys
Nitrogen			NO2 emission rate, HCN
Sulfur			Emission of sulfur oxides
Potassium			Slag formation, ash melting point reduction
Magnesium, Cadmium, Lead			Increasing the melting point of ash
Heavy metals			Environmental safety, ash disposal
Ash content			Chimney cleaning costs, increased ash disposal costs
Microbiology			Impact on human health
physical characteristics
Density, dimensions			Increased transport and storage costs
Dust volumes			Losses in transit
Abrasiveness			Loss in use

Pellet standardization

Standardization of pellet production in the Russian Federation is not currently being carried out. Manufacturers often justify their specifications both on the quality of production and on the quality of the resulting product, but Western manufacturers serve as a guideline, where the market has long been formed and pellets are very popular.

On the market of pellet boilers there is a large number of manufacturers. Each manufacturer dictates its own conditions for fuel in its recommendations. Guarantee conditions are directly dependent on the fulfillment of these conditions, which forces pellet manufacturers to develop such standardization in which the fuel will be in demand among consumers.

The pellet fuel market has not yet been fully formed; not all indicators for products have become common in determining quality. This work depends largely on the consumer, who can give his comments or suggestions.

At the moment, there are a large number of offers on the market for the sale of pellets from different manufacturers. But, not all manufacturers can produce quality products. To do this, before buying, be sure to check the product.

Burning part of the fuel in your boiler - The best way check the quality of the pellets, but in this case it is possible to check the quality of only a certain batch, and this is possible only after its purchase.

It is also possible to evaluate the quality visually. Eco granules with a smooth, shiny surface without any cracks are a clear sign of a quality product. During its production were observed temperature conditions and when granulated, lignin (a binder found in wood) was able to “stick” the fuel well.

With a special apparatus - a lignotester, you can check the granules for abrasiveness and find out their abrasion coefficient. Initially, the sample receives a load of 100 kg for 60 seconds, and then it is blown with air under pressure. After the procedure, the particles are studied, and the more particles are smaller than the standard size, the worse the quality of the granules.

Also, the harder the fuel, the better, because soft granules will simply crumble into pieces during transportation or loading into the furnace, which will affect the efficiency of the boiler.

It is impossible to determine the quality by the diameter of the pellets, although they come in both 6 and 8 millimeters in diameter. It is enough to read the characteristics when buying equipment, they indicate what diameter of fuel should be used in such boilers.

Larger diameter pellets should not be used in boilers designed for 6mm pellets, this only increases the load on the equipment, which can cause its emergency failure.

By color, it is possible to determine what the pellets were made from, for example, white-yellow granules are obtained from furniture production waste, and brown streaks on fuel indicate that the material was used together with tree bark.

By smell, it is possible to determine whether the pellets are fresh or have been stored for a long time in the storage area. A freshly produced product either does not smell at all, or smells like the wood from which they were made. Stale granules stored not in vacuum bags absorb moisture and smell from environment.

You can check if chemicals were used in production with a simple test. It is enough to lower the pellet into water and, if there are no chemical impurities in it, after a while it will turn into wet wood pulp.

If you lower the pellet into a glass of water and rotate it, you can approximately determine the amount of sand, earth and other heavy particles. A large number of them suggests that after burning such fuel, much more slag will remain than when using high-quality pellets.

Large manufacturers have regular suppliers, which can guarantee constant product quality, while small productions most likely they do not have them, which may affect the quality of fuel from batch to batch.

Pellets are more expensive than natural gas, but their use is not limited by the availability main gas pipeline. Compared to wood and charcoal, wood pellets have more low price, and after burning them, there is practically no ash left.

Checking the quality of pellets

According to calculations, 5-6 tons of pellets are required for heating a private house during one season. It is more expedient to buy the entire volume of fuel at once than to carry it in small batches. It is important to immediately check the pellets, because only high-quality pellets will not lose their properties during long-term storage, they will not damage the boiler and will provide a sufficient amount of heat.

Before buying pellets, you can independently evaluate the quality of the pellets.

• Color- varies from light yellow to almost black. It is generally accepted that light granules are of higher quality. But this is not always true, because the granules can "burn" during drying. Nevertheless, the type of raw material can be determined by the color of the pellets - light pellets are made from waste furniture production and hardwoods, dark inclusions may indicate that bark has been added to sawdust and shavings.
• Smell– high-quality pellets do not smell at all or have a slight woody aroma. The presence of a musty odor indicates a long-term storage of granules in conditions of high humidity.
• The presence of chemical impurities- is detected by dissolving pellets in water. The granules retain their shape thanks to a natural binder - lignin, which is destroyed by liquid. If, when immersed in water, the pellets do not break down into sawdust, then some kind of chemical was used as a binder.
• Presence of sand- this indicator is accurately determined only after the pellets are burned in the boiler and is characterized by the amount of waste (ash and slag). The ash content of high-quality pellets is no more than 3% by weight of the fuel. If after burning pellets more waste is obtained, then the pellets were made from low-quality raw materials (with the addition of bark or picked up from the ground). Such pellets reduce the efficiency of boilers, clog pellet burners with slag and can lead to breakdown of heating equipment.
• Dimensions– the diameter of the wood pellets is 6–10 mm and is not an indicator of the quality of the pellets. Boiler manufacturers indicate the size of the pellets that are best suited for a particular unit, which should be followed when buying fuel.

In order for the heating season to pass without problems, purchase pellets from trusted manufacturers. Woodworking Plant CJSC produces pellets from its own woodworking waste using modern high-tech equipment and guarantees the high quality of its products. There are many benefits to working with us.

traditional firewood, fuel briquettes, coal - all this has its advantages and disadvantages. The choice is dictated by the availability and individual performance characteristics of each type of fuel, as well as technical specifications equipment.

In this article we will talk about an alternative source of thermal energy - pellets for space heating.

Comparative characteristics

Below are the main characteristics of known types of fuel.

1. Firewood. The most common and efficient type of fuel. For high-quality heating of premises in firewood there should be no more than 25% humidity. If this indicator is higher, the firewood may not flare up or will smoke heavily. Their main and, perhaps, the only drawback is the need to constantly monitor the amount of fuel in the burner. By the way, unlike pellets, the supply of which is fully automated, it is enough to pour a portion of fuel into the furnace once, and this will be enough for several days of boiler operation.

   Firewood is a relatively cheap material if you harvest it yourself. Ordering dry wood, chopped into neat segments, will cost 2-3 times more. Conifers (spruce, pine) are among the most expensive, but burn out faster than others. Oak, hornbeam, maple, ash are premium options. An intermediate position in terms of price and properties is occupied by birch, alder, and aspen.

2. Coal. This type of fuel has excellent performance in terms of burning time and the amount of thermal energy released. However, the disadvantages are no less significant. In particular, after the combustion of coal, a large amount of slag remains inside the boiler, so it will have to be cleaned regularly. The second negative is the unpleasant smell that spreads throughout the room.
3. Fuel briquettes. They are nothing more than waste from the woodworking industry compressed into small blocks. Like fuel pellets, briquettes are environmentally friendly, leaving a minimum of waste. For some, the decisive factor may be that they do not require additional boiler equipment.

   It is not recommended to use cheap briquettes made from waste fiberboard, chipboard or MDF boards - they contain a lot harmful substances, in particular, furniture glue. It is easy to distinguish such fuel by its white color and fine-grained structure.

4. Pellets. They are produced in the same way as briquettes, only compressed into small granules. They require additional equipment of heating equipment with a special pellet burner. This will entail additional expenses, but will fully pay off in efficiency and cost-effectiveness.

The choice of the type of solid fuel for the boiler is limited only by the budget and your own ideas about efficiency.

Note that the Kupper boilers operate on all types of fuel, so here the user is not limited in his choice by anything other than the budget and his own ideas about the efficiency of a particular variety.

Please note that the boiler equipment manufactured by Teplodar is characterized by the maximum configuration among other analogues on the market. The basic package includes accessories for cleaning the boiler, a heating element block, a thermometer and a stainless steel rotary valve.

Pellets for boilers: advantages and disadvantages

The main advantages of fuel pellets include:

• efficient heat generation at more than a small consumption (1 ton of pellets gives as much heat energy as 1.5 tons of firewood or 500 m 3 of gas);
• minimum waste (ash is 1% of the initial volume of fuel);
• the rarity of cleaning the boiler (no more than 1-2 times a month);
• uniform combustion and temperature constancy;
• lack of spark;
• ease of transportation (pellets are delivered in packages);
• absence of unpleasant odors;
• environmental friendliness (only 0.03% sulfur is produced during combustion);
• ash can be used as fertilizer;
• acceptable cost of fuel;
• permits are not required to equip the boiler with a pellet burner.

Solid fuel has such an indicator as calorific value - the amount of energy obtained by burning 1 kg of material. For pellets, it is 4500-5300 kcal / kg, which is comparable to the calorific value of black coal and dry firewood.

This fuel has only one drawback: before using pellets, you will have to buy a special burner.

The use of pressed pellets sometimes requires the purchase of a new boiler, although more often you can get by with retrofitting an existing one. Pellet boilers are special devices that work only on this fuel. The devices organize a full-fledged heating circuit inside the house, and also provide the owners with hot water.

Before using pellet fuel, you will have to buy a special burner.

Selection rules

Alas, not every manufacturer delivers good quality products to the consumer. Next - about the types of fuel and how to determine the quality of the pellets in appearance.

Pellets consist of sawdust, shavings, may include straw, peat, seed shells.

Fuel standardization is poorly developed in the Russian Federation, so low-quality products are, unfortunately, quite common.

Typically, fuel is supplied in bags (packages) from 5 to 25 kg. Well, if there is an opportunity to look inside and assess the condition of the granules. Some recommendations for fuel selection:

• the less dust, fine fraction, broken granules, the better;
• the color of quality pellets is brown or slightly lighter;
• the dark color of the fuel is a sign of a high concentration of bark, which makes combustion difficult;
• the lighter the granules, the more chemical impurities they contain.

The main criterion for classifying fuel by quality is moisture content. There are three classes:

• the first (minimum humidity, heat transfer up to 95%, high cost);
• the second (an intermediate option in terms of price and quality);
• the third (fuel is noticeably moist, smokes a lot, leaves a lot of ash, is cheap).

In terms of cost, pellets of classes I and III differ by 20-30%.

Usually pellets are supplied in bags (packages) from 5 to 25 kg. Well, if there is an opportunity to look inside and assess the condition of the granules.

Terms of storage and use

When buying a large batch of pellets, you need to take care of the place of their storage. When stored indoors, they must not be placed near open sources of fire. It is also necessary to protect the material from the worst enemy - dampness.

How to store pellets if there is no space in the house? Closed bags / packages can be folded outside under a canopy. However, this option is undesirable - when it rains, the risk of wetting the package and irreversible damage to the fuel increases.

A few words about how to properly heat a solid fuel boiler with pellets. This requires a burner, which can be bought separately and installed on the boiler in just half an hour. The operation of such a tandem is extremely simple - the user will need to fill the hopper with fresh pellets from time to time and clean out the ash. The temperature balance is controlled by the control panel.

Fuel pellets - economical, affordable, efficient solid fuel. And, although the cost of a special pellet burner is quite high, within no more than 1 year, investments in equipment are fully paid off.

Lack of information gives rise to myths and legends. Below we have tried to summarize some of our knowledge on this topic and tell you how you can determine the quality of the pellets. Which, by the way, is one of the main questions asked when buying pellets, so we answer it many times a day.

In short, the most important thing is that the best pellet quality TEST is to burn a test bag from the manufacturer in your boiler (of course, provided that all further pellets come from the same manufacturer and were produced at about the same time).

WHAT ARE PELLETS

Pellets are an alternative fuel for heating suburban real estate. Cheap (2 times cheaper than diesel fuel, but still more expensive than gas), convenient, environmentally friendly. Like any fuel, pellets have their own requirements for storage and transportation, but we note right away that these requirements are softer than the requirements for liquid or gaseous fuels. You can sprinkle pellets on the site without consequences, they will not smell or stain the environment.

However, miracles should not be expected: pellets are not a universal fuel that can be stored in any conditions, burn forever and be of any quality.

VISUAL ASSESSMENT OF PELLET QUALITY

High-quality pellets, as a rule, have a smooth shiny surface without longitudinal cracks. The presence of a smooth and shiny surface indicates, first of all, that the granulation process was carried out at the right temperature, as a result of which the lignin contained in the tree, which is a natural binder, "glued" the pellets properly.

You can try scrap pellets. In general, the harder the pellets, the better, since soft pellets crumble when unloading / transferring to the hopper and feeding to the burner zone. This parameter is called abrasiveness and is measured by a device called Lingotester, in short, the technology is as follows: a weight of 100 kg is applied to the samples for one minute, and then blown with air under pressure. The quality of the pellets is determined by the number of particles less than a certain size specified by the standard - the more particles (respectively, the pellets crumble), the lower the quality of the pellets. By the way, when considering the amount of dust and small particles in a pellet package, it is worth taking into account how many times these pellets were reloaded, since with each unloading and loading, the number of small particles and, as a result, dust increases. As a rule, pellets in bags have a lower amount of dust compared to pellets shipped in bulk.

PELLET DIAMETER

Sometimes you have to hear that 6 mm are the right pellets, but 8 mm is no longer there. This statement is due to the fact that 8 mm pellets are made on equipment converted from domestic granulators that were previously used in agriculture for the manufacture of compound feed, and accordingly, it cannot be of high quality, and 6 mm is mainly produced on imported equipment. However, like 6 mm pellets, 8 mm pellets come in completely different qualities.

On the other hand, pellet fireplaces, for example, due to the design of the feed system, work better on 6 mm pellets. The equipment manufacturer usually indicates the type and diameter of the pellets used. It is not recommended to use pellets of other sizes, because, firstly, the boiler automation is configured for the optimal supply of air and pellets of this particular diameter, and secondly, the use of pellets of a larger size than recommended leads to increased loads on the boiler mechanics, which can lead to premature exit him out of order.

From own experience we can see that the smaller the diameter of the pellets, the faster they crumble.

COLOR

Usually, white-yellow pellets are made from furniture production waste, pellets with brown inclusions are made from raw materials with the addition of bark. However, the color of the pellets is not a quality criterion. By the color of the pellets, you can determine what raw materials were used, how the pelletizing took place and how the pellets were stored. But the color will say little about the quality of the pellets themselves.

SMELL

As a rule, pellets smell like the wood from which they were made or do not smell at all. On the other hand, pellets, during long-term storage, absorb moisture from the surrounding air and, accordingly, odors.

PELLET DISSOLUTION

If you lower the pellets into a glass of water, then after a while the pellets will turn into a wet mass. If this does not happen, then apparently some external chemical substance was used as a binder. When rotating the glass, you can determine the amount of heavy particles, a large number of which indicates the presence of sand, or the use of wood waste with dust from grinders. Let us immediately state that this method detection of sand in pellets is inferior in accuracy to the method of burning pellets in a boiler.

However, we repeat once again, the color and smell are indicators of what kind of wood, how the pellets were produced and how they were stored, however, they say little about whether there are non-metallic impurities (sand) in the pellets, namely, it is the main “enemy” of pellet boilers .

When determining the quality of pellets, it is not superfluous to pay attention to the production itself. First, as a rule, in large industries, raw materials come from one source, which in some way guarantees the stability of production. In small pellet plants, as a rule, there is no source of raw materials (otherwise it would be a large production) and raw materials are collected at nearby sawmills, etc.

As a rule, the larger the production volume at the enterprise, the more stable the quality of the pellets. With small volumes, as a rule, different raw materials are used, and the equipment is often not rebuilt for one or another raw material, which ultimately can lead to a decrease in the quality of the pellets.

By the way, for example, the Austrian standard describes not only the quality of the pellets themselves, but also the production and transportation of pellets.

WHAT CANNOT BE AN EVALUATION CRITERION

Pellets always sink in water, both good and bad, since the density of pellets is greater than 1 (one).

The smell of pellets is not an evaluation criterion, with the exception of foreign odors indicating the use of chemicals. binders or improper storage.

A smooth edge at the break of the pellet also says little.

LABORATORY ASSESSMENT OF PELLET QUALITY

A more detailed and reliable assessment can be made in a specialized laboratory, but it should be borne in mind that this is a voluntary matter and, as a rule, the manufacturer receives a certificate at the beginning of production, which does not always guarantee that subsequent batches will be of the same quality. Typically, the results of laboratory tests indicate the following parameters.

Parameter	Effect (What does it affect)
CHEMICAL CHARACTERISTICS
Humidity	Storage conditions, calorific value, losses, spontaneous combustion
Calorific value	Pellet use, fuel efficiency
Chlorine	HCL, chimney corrosion
Nitrogen	Emissions of NO x HCN and H 2 O
Sulfur	SO x
Potassium	Reducing the melting point of ash, the formation of slag
Magnesium, Cadmium, Lead	Increasing the melting point of ash
Heavy metals	Environmental pollution, the possibility of using ash
Ash content	Possibility and cost of ash disposal
Microbiology	health risk
PHYSICAL CHARACTERISTICS
Density, dimensions	Transport costs, storage costs
Dust volumes	Losses in transit
Abrasiveness	Loss in use

Today in our country there are no standards for pellets, so most manufacturers are guided by Western standards, which, by the way, differ from country to country or invent their own specifications. As far as we know, a single European standard is under development. In addition, existing Western standards sometimes include not only the standard for the pellets themselves, but also standards for their production, storage and transportation.

Certificates for pellets in our country are issued by various organizations. If a manufacturer sells pellets abroad (where 95% of the production goes today), then it would be more logical to obtain a certificate from international accredited laboratories Incolab and SGS. However, for internal purposes, you can make a certificate in domestic research institutes. The difference in price is more than significant. As a rule, in domestic laboratories all analyzes are done according to GOST, and in Incolab and SGS according to ISO, ASTM, SS, etc. on imported equipment.

Thus, it is possible to ask the manufacturer for a certificate for the produced pellets, however, it should be borne in mind that this certificate may not correspond to the final product.

ASH, SLAG AND TU

With the onset of the next heating season, the quality of pellets once again becomes relevant. Let's also talk about ash and slag.

First, let's first define the concepts. Let's start with ASH.

Ash is a mineral by-product obtained by burning wood. According to information from various scientific sources, minerals make up no more than 1% of the mass of stem wood and no more than 3% of the mass of the bark. The increased content of mineral impurities in the bark is due to the fact that the surface of the bark during growth is blown by atmospheric air and absorbs the mineral aerosols contained in it.

Thus, even in the unrealistic case of making pellets from a mixture of sawdust that exists only in theory, containing 50% sawdust from stem wood and 50% sawdust from bark, the total ash content of the resulting pellets will not exceed 2.5%. (By the way, in reality, pellets from such a mixture will not work due to the lack of lignin in the bark, and usually the bark does not exceed 10% -15% of the total mass of pellets. Such pellets can be distinguished by the presence of brown inclusions, although the color may we can also talk about the wrong setting of the pellet press (pellets overheat) As a result, no more than 2% of the mass of fuel.

It can also be noted that part of the ash is blown into the chimney by fans that pump oxygen (primary and secondary air) to burn the pellets. The chimney from this may eventually reduce its diameter somewhat, therefore, by the way, pipes for pellet boilers and fireplaces must be cleaned more often than for similar gas or diesel heat generators. It is worth noting that the most advanced boilers are equipped with "draft" sensors and automatically regulate the air supply (including reporting possible problems).

Let's sum up the intermediate result - when burning 1 ton of unrealistic pellets made half of the bark, we should not get more than 25 kg of ash, some of which will safely fly into the chimney. From experience we can say that much less ash is formed from good pellets. Now the question is - where do the notorious 7% come from, for example, in such specifications? And why do pellet burners crash?

The answer is the following: there is such a thing - SLAG. These are mineral inclusions (in other words: sand and earth) that got into the pellets at the stage of their manufacture, storage or transportation. So they then give the% ash content that is missing to the ash content declared by the above manufacturer. In the laboratory, they usually do not separate the concepts of "ash" and "slag" and simply write "ash content". So anything above 2-3% is slag. Here's what it looks like.

Where does the sand in the pellets come from - as a rule, sand gets stuck in the bark of a tree when it is transported by dragging along the ground at a logging site. Sometimes a pellet manufacturer takes logging and woodworking waste directly from the ground, inadvertently scooping up the ground as well. Some responsible manufacturers install mineral impurity traps, but, as a rule, most do not "bother", although, as time shows, in vain, granulator matrices fail faster.

Slag is also unpleasant because, unlike ash flying into the chimney, it accumulates in the pellet burner and, as a rule, leads to its emergency shutdown.

CONCLUSION

Above we have tried to describe possible ways checking the quality of pellets at home and in the laboratory. In our opinion, we repeat one more time, the best test is the burning of pellets in the boiler and the examination of the results. This is what we are focusing on.

Of course, since the market for pellets is still being formed and the above stated by us does not claim to be absolute accuracy, we will be grateful for comments and corrections and suggestions on the topic of this article.

CONCLUSIONS:

1. Don't be afraid of ash, be afraid of slag.
2. Look for reliable fuel suppliers.
3. Don't trust certificates.