WO2015185498A1

WO2015185498A1 - Pellets for heating purposes

Info

Publication number: WO2015185498A1
Application number: PCT/EP2015/062139
Authority: WO
Inventors: Stefan K. PELZ; Harald Thorwarth; Jens Steinbrink; Matthias GEHRIG
Original assignee: Firestixx Holz-Energie Gmbh
Priority date: 2014-06-04
Filing date: 2015-06-01
Publication date: 2015-12-10
Also published as: DE102014210614A1; DE102014210614B4

Abstract

The present invention relates to pellets for heating purposes made from a pressed biomass based on lignocellulose, wherein the pellets contain at least one ash- and/or fine dust-reducing additive and a binder based on polysaccharides, and wherein the additive is selected from the group consisting of: aluminium-containing inorganic compounds, clays and clay minerals. The pellets according to the invention have a low fine dust particle content and emission level and can be produced initially from short-rotation woods such as poplar and willow having exhaust gas and emission values of previous pellets based on spruce and pine.

Description

description

Pellets for heating purposes

The present invention relates to pellets for heating purposes from a pressed biomass based on lignocellulose according to the preamble of claim 1.

Coke is increasingly becoming a competitor of fossil fuels, which have long been criticized for their negative CO2 balance.

Wood pellets, such as the wood pellets marketed under the trade name FireStixx (registered trademark of FireStixx Holz-Energie GmbH), which are certified as so-called FireStixx premium pellets according to DINplus and ENplus A1, already exceed many measurement parameters, e.g. the amount of incineration ash and, in terms of dust formation, those values that the standard dictates.

The quality of wood pellets depends, among other things, on the following

parameters:

A small abrasion value, which means a higher strength and resistance of the pellets. This results in less dust and fines in the

Fuel storage, which improves flowability and air flow in the burner. The advantages are better efficiency and clean flue gases.

A low moisture content increases the calorific value and thus lowers the heating costs.

A lower ash content ensures clean combustion and therefore less maintenance. A higher bulk density creates the prerequisite for a higher volume weight and thus a higher energy density. Premium quality pellets from FireStixx have a precisely defined length distribution, for example between 3 and 40 mm, and have a calorific value of approx. 5.1 to 5.3 kWh / kg. Of the

Moisture value is about 5 to 8% by mass.

The mechanical strength of the pellets is typically above 98.5% and the ash content is below 0.25 mass%.

The production of such pellets is typically made from wastes in the form of sawdust and sawdust essentially of spruce wood is well known in the art.

For example, the German utility model describes the

Legal predecessor of the present applicant in DE 20 2006 008 516 U1 such wood pellets for heating purposes, in which a certain pH is set in the neutral or alkaline range.

A method for producing wood pellets is also described in WO 02/50220 A1.

Finally, EP 2 325 289 B1 describes a method and a

Apparatus for treating wood pellets with the aid of a lubricating and dust-binding additive. This procedure is under the trademarked

Designation of the present Applicant known as pelprotec®. It is an innovative refining process that makes pellets even more valuable. In particular, the pellets when filling the storage, still in

Tanker, refined. This happens immediately before the strongest mechanical stress of the pellets. The pellets are covered with a thin protective film of vegetable oil. This makes it possible to drastically reduce the formation of dust and to supply the burner with wood pellets of excellent quality in terms of dust immunity, abrasion and protection for the mechanical parts such as conveyor system and air supply systems. So far, as a starting material for the biomass for the production of

Wood pellets essentially on useful woods such as in particular industrial and construction timber, such as spruce and fir, resorted to, in particular residues from the woodworking industry such as sawdust, chipboard and in particular

Wood shavings and other wood residues were used.

However, due to increasing use of woody biomass and increasing private household demand for small combustion plants, it is desirable in a long term perspective to resort to alternative raw materials such as short rotation plantations (CROP), straw, grain and the like for the production of pellets for heating purposes resources used to date are becoming scarcer.

In addition, it can be expected that in the future due to the European

Legislation toughen emission limits

Small combustion plants are revealed.

However, the problem arises that CUP biomass one clearly

different chemical composition as the hitherto used for wood pelleting industrial or lumber biomass has.

This different chemical composition leads to different and sometimes undesirable combustion properties, whereby the exhaust gas composition and the aerosol formation change significantly to the detriment of a compressed into pellets KUP biomass.

In particular, there is a correlation between the content of nitrogen, sulfur and chlorine in the fuel biomass used and NO _x , SO _x and HCl in the exhaust gas and the aerosol formation of semi- and volatile components of the ash-forming elements K, Na, Pb, Si, etc. It was found that, for example, potassium promotes the formation of aerosols and thus the corrosion of heat exchangers and other parts of the heating system and reduces the ash softening temperature.

The ash softening temperature is the temperature at which the ashes of the pellets burned in the heating system change from solid to liquid

Physical state changes. The problem of liquid ash arises when cooling the ash. It naturally changes its state of aggregation from liquid to solid. This usually happens in the form of a coherent mass. This mass can accumulate inside the boiler and can then disturb the

Lead heating system. The ash softening temperature according to ENplus A1 is currently 1200 ° C.

The nitrogen-related NO _x or N 2 O emissions and the SO _x emissions due to the sulfur content of the fuels lead to corrosion of metal components of the combustion plant.

The same applies to chlorine, which mainly produces HCl, but in addition to a small proportion of polychlorinated dibenzo-p-dioxins and

Dibenzofurane (PCDD / PCDF) are formed, which can escape with the exhaust gases into the environment. Such anoganic and organic halogen compounds can - in addition to their undesirable toxicity - also cause corrosion of metal components.

The content of the alkali metal sodium is known to lead to boiler corrosion and also to the formation of aerosols.

Magnesium increases the ash softening temperature and favors one

Ash utilization, for example as a fertilizer, while the phosphorus content of the fuel promotes aerosol formation, leads to ash softening and thus reduces the usefulness of the ash, for example as a fertilizer. Heavy metals contained in the fuel, in particular lead, manganese, copper, cadmium and the like, also lead to gaseous and dusty emissions and drastically limit the use of as a fertilizer, if their content exceeds a certain limit.

Investigations also showed that the formation of particulate matter in automatic furnaces is mainly due to the release of inorganic elements from the bed in a temperature- and fuel-dependent manner.

After all, KUP woods, especially in pelletized form, are practically not permanently used in the prior art as fuel in heating systems, since their content of the sum of the elements K, S, Cl, Cd, Zn, Pb, measured on the example of short rotation plantation timbers Poplars and pastures, compared to spruce and beech biomass at about 3000 to 4000 mg / kg (db) is about twice as high and leads to the disadvantages mentioned above.

This is where the present invention starts.

Object of the present invention is, in addition to the ever dwindling industrial and timber timbers, especially spruce and fir, wood from short rotation plantations as pellets for heating purposes to use and still be able to comply with the limits for particulate matter and exhaust gases.

The solution of this object is achieved by the characterizing features of claim 1.

In particular, the present invention relates to pellets for heating purposes from a pressed biomass based on lignocellulose, wherein the pellets at least one ash and / or particulate reducing additive and a binder on

Polysaccharide base, wherein the additive is selected from the group consisting of: aluminum-containing inorganic compounds, clays and

Clay minerals. Through the use of at least one ash or fine dust reducing additive and a polysaccharide-based binder, wherein the additive is selected from the group consisting of aluminum-containing inorganic compounds, clays and clay minerals, it has surprisingly been found that the use of such additives targeted the release of inorganic Aerosolbildenden elements, in particular K, S, Cl, Cd, Zn and Pb can be reduced.

During the chemical reactions of the fuel constituents in the pyrolysis and gasification processes, the volatile components of low volatility react and thus the inorganic aerosol-forming elements remain in the ember bed of the furnace.

Also, the release of organic aerosols is reduced, which - without being bound to it - obviously with the surface activity of the used

Additives, in particular aluminum-containing compounds, is related.

In particular, it is assumed according to the invention that the influencing of the additives according to the invention is effective by the following processes:

By using the additives of the present invention, the ash softening temperature increases with respect to calcium, and a compound of calcium with silicon and not with potassium takes place, so that aerosol formation is suppressed.

With regard to phosphorus, the additive according to the invention lowers the particle mass concentration of the phosphorus, thereby reducing the use of particles as an aerosol

Can be available.

For example, although the short-rotation wood poplar and willow contain more than twice as many aerosol formers in their starting substance compared to spruce and beech, it is possible to use the additives according to the invention

To bring and _SOx -Abgaswerte practically to the value of pure pine or beech wood - aerosol formation in the exhaust gas and the NO _x. With the pellets according to the invention it is thus possible to use alternative KUP pellets instead of the previous pure sawmill wood pellets.

Thus, with the pellets according to the invention for the first time fine-dust and low-emission pellets from KUP woods, especially poplar and willow, for

Heating purposes are available and the raw material assortment for pellet production is significantly expanded by fast renewable biomass from short rotation plantations.

In practice it has been found that a polysaccharide-based binder, in particular starch-based, as well as an additive of aluminum-containing inorganic compounds, clays and clay minerals, fulfills these properties without fully understanding the underlying physical chemical mechanism.

Especially kaolin has proved to be a clay mineral in first attempts.

A preferred embodiment of the present invention are pellets for heating purposes from a pressed biomass based on lignocellulose from poplar and / or willow wood, wherein the pellets at least one ashes and / or

fine dust reducing additive based on aluminosilicates, in particular kaolin, and a starch-based binder, for example wheat starch.

Of course it is also possible to use mixed woods such as spruce, beech, poplar and / or willow for pellet production.

The preparation of the pellets according to the invention is carried out by well-known to the expert pelletizing, which were mentioned in the introduction to the description.

The subclaims represent further preferred embodiments of the present invention. For a preferred embodiment of the pellets according to the invention, the lignocellulosic biomass is selected from: industrial and construction timbers, in particular spruce, pine, fir, Douglas fir, oak, larch, chestnut, beech, alder, birch;

Short-rotation wood, in particular poplar and willow; Agricultural waste; such as

Mixtures thereof.

The lignocellulosic biomass can come from solid trees and / or wood chips and / or wood shavings and / or sawdust and / or sawdust of industrial and construction timber and / or the short rotation wood, so that also advantageously continue the use of wood waste and wood residues incurred anyway and a more elaborate use of full trees is only partially required.

The aluminum-containing inorganic compounds are preferably

Aluminum oxides, in particular Al2O3, and / or aluminum hydroxides and / or

Alumina hydroxides and / or bauxite, as these are non-toxic and readily and inexpensively available.

In practice, it has been found that clays and clay minerals, aluminosilicates, in particular kaolin, kaolinite, iridicite, sericite and montmorillonite, are the best additives for producing particulate and low-emission pellets for heating purposes, in particular from poplar and willow biomass. The effect is enhanced when the pellets are bound with wheat starch.

As a polysaccharide-based binder, in particular a starch binder can be used, in particular one selected from the group consisting of: wheat starch, potato starch, rice starch, chestnut starch; and mixtures thereof. However, other natural and synthetic polysaccharides are also suitable as binders for the pellets.

To the abovementioned additives, for example based on aluminosilicate, it is possible to use additional additives in the form of calcium compounds, which are disclosed in US Pat Form of limestone or marble dust [CaC0 ₃ ], slaked lime [Ca (OH) ₂ ] or quicklime [CaO] may be added to the lignocellulosic biomass.

As already mentioned, it is preferred in the context of the present invention to produce pellets from a lignocellulosic biomass from short rotation woods, in particular trees of the genus of poplars [Populus] and / or the genus of willows [Salix], in particular Salix spec, preferably Salix alba, are preferred.

However, the pellets can still be from a lignocellulosic biomass from industrial and construction timbers, especially from the genus of spruce [Picea], preferably Picea abies and / or the genus of firs [Abies], preferably Abies alba, or a mixture be made with KUP woods.

The invention is characterized in that the pellets a

Bulk density of about 1, 1 to 1, 3 kg / dm ³ , preferably> 1, 20 kg / dm ³ and a residual moisture content of about 5 mass% to 10% by mass.

Typically, the ash and / or fine dust reducing additive is present in a concentration of about 0.1 to 3% by mass, in particular about 1 to 2% by mass.

According to the present invention, the pellets may also be pure pellets of short rotation woods.

Of course, also pellets can be made from mixed woods, which come from a mixture of conventional industrial and construction timber and KUP woods.

Exemplary mixed pellets may contain about 75% by weight of spruce wood and about 25% by weight of short-rotation wood, in particular pasture and / or poplar, preferably in each case 50% by weight of spruce wood and short-rotation wood. Particularly suitable mixed pellets have been found to be those of a mixture of 90% by weight of spruce and 10% by weight of pasture. It is well known to those skilled in the art that all other mixing ratios are included within the scope of the present invention.

Further advantages and features will become apparent from the description of an embodiment.

embodiment

Sawdust made of debarked spruce (Picea abies) and sawdust of willow (Salix spec.) Were used to prepare the pellets according to the invention.

The pelleting was carried out with a semi-industrial ring stamp pellet mill with a capacity of 150 kg / h. The resulting pellets were burned in a 12 kW small combustion plant and the exhaust gas composition and the

Aerosol emission, in particular from aerosol formers K, S, Cl, Cd, Zn and Pb were measured.

The wood pellets were mixed from the two raw materials given above, using wheat starch (0.1% by mass) as binder and kaolin as additive.

Different ratios of spruce to willow were used, namely from 50% spruce wood and short rotation wood to 90% spruce wood and 10% willow wood.

As a control, the respective wood pellets were produced once without additive, but with wheat starch, and secondly with wheat starch and with kaolin as an additive.

The kaolin concentration in the example was 0.5% by mass.

For further control, pellets were made with additive but without wheat starch as binder. In the exhaust gas and aerosol investigation of emissions, it has surprisingly been found that the combination of wheat starch as a polysaccharide binder and aluminosilicate kaolin as an additive, even with pure pasture pellets, achieved approximately the same exhaust gas and fine dust values as the spruce pure pellets.

When 50% mixtures of spruce and willow biomass were pelleted and used with wheat starch as a polysaccharide binder and kaolin as an additive, the particulate matter values were even below the values of the pure spruce pellets.

After all, the present invention for the first time fine dust and

Low-emission pellets made from SRP woods are available and thus represent an alternative source of raw material for the forest fir-tree spruce and fir.

In the example case, the sum of the elements was K, S, Cl, Cd, Zn, Pb for

Pure pellets from willow with kaolin and wheat starch about 1600 mg / kg db (dry base), while for comparison pure pellets from spruce about 1550 mg / kg db resulted.

Mixed pellets with 50% by weight each of spruce and willow as well as kaolin and

Wheat starch gave aerosol former values of about 1600 mg / kg db.

Pellets added with kaolin but not bound with wheat starch surprisingly consistently provided a significantly higher aerosol content than pellets containing both substances.

Conversely, the control without kaolin and with wheat starch showed virtually no lowering effect for the abovementioned aerosol formers, while kaolin as sole additive-even without polysaccharide binder-already led to a drastic reduction in the content of aerosol formers.

It is concluded that the alumosilicate-containing additive kaolin is mainly responsible for the aerosol lowering, but the combination with the polysaccharide unexpectedly causes an even greater reduction in the content of aerosol forming agents. The reason for this is still unclear. The quantitative results are shown in FIG. 1: FIG. 1 shows for individual pellet mixtures the respective total dust quantities in mg / Nm ³ at 13% O ₂ , dry, measured according to VDI 2066-1.

The abbreviations in Fig. 1 and Tab. 1 mean the following:

F 00 100% spruce without kaolin additive

F100 / m05 100% spruce with 0.5 mass% kaolin additive

F100 / m20 100% spruce with 20% by weight kaolin additive

F90 / W10 90% spruce and 10% willow without kaolin additive

F90 / W10 / m02 90% spruce and 10% willow with 0.2% by weight kaolin additive F75 / W25 75% spruce and 25% willow without kaolin addition

These pellets gave the following particulate matter and ash values:

Table 1

For pellets made of pure spruce wood, even fine dust values of only one quarter of the values achieved without additive were thus already achieved. This is shown graphically in FIG. The mixed pellets F90 / W10 had a total dust value of 17.8 mg / Nm ³ without additive. With 0.2% by weight of kaolin this value could be reduced below the value of pure spruce pellets to 3.8 mg / Nm ³ with an ash content of only 0.7%.

Thus, for the first time, new resources are available from short tunneling woods, in particular poplar and willow, which have hitherto not been suitable for the production of pellets for heating purposes.

Claims

claims

1 . Pellets for heating purposes from a pressed biomass based on lignocellulose, characterized in that the pellets contain at least one ash and / or fine dust reducing additive and a polysaccharide-based binder, wherein the additive is selected from the group consisting of: aluminum-containing inorganic compounds, clays and clay minerals.

2. Pellets according to claim 2, characterized in that the

Lignocellulosic biomass is selected from: industrial timbers, especially spruce, pine, fir, Douglas fir, oak, larch, chestnut, beech, alder, birch;

Short-rotation wood, in particular poplar and willow; Agricultural waste; and mixtures thereof.

3. Pellets according to claim 1 or 2, characterized in that the

Lignocellulosic biomass from solid trees and / or wood chips and / or

Wood shavings and / or sawdust and / or sawdust of industrial and construction timber and / or the short rotation wood comes from.

4. pellets according to at least one of the preceding claims, characterized in that the aluminum-containing inorganic compounds

Alumina, in particular Al ₂ 0 ₃ , and / or aluminum hydroxides and / or alumina hydroxides and / or bauxite are.

5. Pellets according to at least one of the preceding claims, characterized in that the clays and clay minerals, aluminosilicates, in particular kaolin, kaolinite, lllicit, sericite and montmorillonite are.

6. Pellets according to at least one of the preceding claims, characterized in that the polysaccharide binder is a starch binder, in particular one selected from the group consisting of: wheat starch, potato starch, rice starch, chestnut starch; and mixtures thereof; is.

7. pellets according to at least one of the preceding claims, characterized in that as an additional additive a Caiciumverbindung is used, which in the form of limestone or marble dust [CaCOs], slaked lime [Ca (OH) ₂ ] or quicklime [CaO] of lignocellulose -Biomasse is added.

8. pellets according to at least one of the preceding claims, characterized in that the lignocellulosic biomass from short-rotation wood, in particular the genus of poplars [Populus] and / or the genus of willow trees [Salix], especially Salix spec, preferably Salix alba, comes.

9. pellets according to at least one of claims 1 to 7, characterized in that the lignocellulosic biomass from industrial and construction timbers, in particular from the genus of spruce [Picea], preferably Picea abies and / or the genus of firs [Abies], preferably Abies alba.

10. pellets according to at least one of the preceding claims, characterized in that the pellets have a density of about 1, 1 to 1, 3 kg / dm ³ , preferably> 1, 20 kg / dm ³ and a residual moisture content of about 5 mass -% to 10% by mass.

1 1. Pellets according to at least one of the preceding claims, characterized in that the ash and / or fine dust reducing additive is present in a concentration of about 0.1 to 3% by mass, in particular about 1 to 2% by mass. 2. Pellets according to at least one of the preceding claims, characterized in that they are pure pellets of short rotation woods.

13. Pellets according to at least one of claims 1 to 1 1, characterized in that they are mixed pellets of industrial and construction timber and

Short-rotation woods are. 4. pellets according to claim 13, characterized in that the pellets about 75 mass% spruce wood and about 25 mass% short-rotation wood, especially willow and / or poplar, preferably in each case 50% by weight spruce wood and

Short rotation wood, included.

15. Pellets according to one of the preceding claims, characterized in that they have a total dust amount of 3 to 10 mg / Nm ³ at 13% O 2, dry, measured according to VDI 2066-1 and ash values of <0.7% by mass during combustion. exhibit.