BE1018614A3 - FUEL COMPOSITION DERIVED FROM BIOMASS WASTE AND PROCESS FOR THEIR PRODUCTION. - Google Patents

Abstract

The present invention relates to granules allowing energy recovery from biomass sources at the end of the recovery chain, characterized by: - residual water content of less than 8% by mass; - an apparent density greater than 400 kg / m3; - a heat capacity greater than 10GJ / Tons; - a chlorine content of less than 600 ppm; - a sulfur content of less than 1500ppm; have a fluorine content of less than 100ppm. The present invention also relates to a process for the production of these granules.

Description

Fuel composition from biomass waste and process for producing same

Object of the invention

The present invention relates to the energy recovery of biomass waste from agriculture, forestry, intensive farming, sewage sludge and food industry.

The present invention also relates to solid fuel compositions from mixtures of these wastes and their manufacturing process.

Technological context

The exploitation potential of renewable energy sources is currently very underused in most parts of the world. However, it is now recognized that their exploitation contributes to the protection of the environment and sustainable development.

In particular, the use of renewable energy makes it possible to accelerate the achievement of the objectives of the Kyoto protocol.

In Directive 2001/77 / EC of 27 September 2001, the European Parliament defines more precisely the concept of renewable energy sources: these are renewable non-fossil energy sources (wind, solar, geothermal energy). , wave, tidal and hydropower, biomass, landfill gas, sewage treatment plant gas and biogas). It adds a definition of biomass: the biodegradable fraction of products, waste and residues from agriculture (including plant and animal substances), forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste. .

This same directive also provides for the possibility for member states to provide direct or indirect subsidies to electricity producers producing from renewable sources.

The transposition of this directive at national or regional level gives rise to notorious divergences. For example, legislation in the Flemish region excludes wood waste from the granting of green certificates (Decree of 5 March 2004 of the Flemish Government). This exclusion only applies to wood waste that is not contaminated by surface chemical treatments such as painted wood, or by impregnation treatments. In Wallonia, however, this matter is regulated by the decree of 12 April 2001, amended by the decree of 4 October 2007. In this decree, wood waste is considered eligible for the issue of green certificates.

In general, the combustion of waste from biomass is neutral from the point of view of the emission of greenhouse gases. In fact, CO2 produced is the result of the natural carbon cycle, unlike fossil fuels, the combustion of which re-circulates, in the form of CO2, carbon previously permanently fixed in the subsoil. The energy recovery of biomass waste makes it possible to approach the objectives of the Kyoto Protocol, aimed at reducing greenhouse gas emissions.

[0009] Directive 75/442 / EEC defines waste as any substance or object, which the holder discards or intends or is required to discard. The same directive still provides that priority should be given to reducing the production of waste at the source, but also, secondly, to promote the reuse or energy recovery of this waste.

[0010] Agriculture, and, more generally, human activities produce many biomass wastes. For example, animal manure from intensive farming, sewage sludge, filtration cakes from the sugar or brewing industry, residues from oil or fruit presses (notably grapes) ... Most of these wastes retain a significant energy potential: once dehydrated, they generally form a high calorific fuel.

The combustion of slurry waste provides further advantages over other methods of recovery of such waste, such as composting or spreading as fertilizer. For example, composting produces large quantities of other greenhouse gases, such as methane, by fermentation. The phenomena of eutrophication and contamination of groundwater are also known due to the intensive use of manure as fertilizer.

Finally, it should be noted that Directive 2000/76 / EC sets emission limits for various pollutants that can be emitted by waste incineration plants.

State of the art

The use of waste, including animal waste, as fuel has been known for a long time. An example of this is the traditional use by the Sahrawi nomads of the dung of their livestock for heating purposes.

The use of biomass waste of various origins for heating is also known for the cement kilns. The document US5392721 for example describes the use of sludge from the manufacture of paper. The document US5217624 describes, for its part, the use of purification sludge in the production of cement.

This use of waste as fuel, however, has the disadvantage of leaving ashes of uncontrolled composition in the cement, which limits the use. US5888256 discloses the use of a mixture of at least two wastes, having different ash compositions, to regulate the composition of the mixture so as to make it suitable for the production of cement.

The use of biomass waste in power generation facilities, particularly electricity / heat cogeneration facilities, is more recent. By way of example, mention may be made of document FR2854887, which describes a system and a process for thermally recycling waste, and the application of this system to the treatment of waste with a high water content. This document does not describe in any way the chemical composition of the waste, nor their calorific value. WO2007 / 005771 also describes a method for drying, pyrolysis and thermal recovery of waste from sludge of different origins.

Other documents attempt to describe modified waste compositions with a view to improving their thermal performance: for example, US5141526 proposes to replace the filter aids usually used in the food industry, generally inorganic fillers, by combustible adjuvants such as residues of corncobs. This, in order to simultaneously increase the calorific value of filter cakes, and reduce the amount of ash.

None of these documents focuses on pollutant concentrations of any potentially hazardous nature contained in this waste. It is known, however, that these wastes may contain significant amounts of such pollutants. As an example in the article "Behavior of gaseous chlorine and alkali metals during biomass thermal utilization" (Fuel 84 (2005) 841-848) compositions of waste wood and sludge purification, and the influence of these compositions on the gaseous emissions of pollutants during combustion processes.

It is further known that these wastes have a high variability in terms of composition, both in relation to time and relative to their geographical origin. The poster "Variability of the nutrient, metal and minor element composition of manure in manitoba" presented by DF Malley and PD Martin, published on the website www.pdkproj ect.corn illustrates this variability, with, for example, concentrations of certain metals varying by more than two orders of magnitude.

Goals of 11 invention

The present invention attempts to overcome the drawbacks of the state of the art and aims to provide a fuel biomass composition complying with environmental standards and having an optimum calorific value.

The present invention also describes a process for optimizing the composition of a fuel derived from mixtures of biomasses of different origins.

Summary of the invention

The present invention relates to granules for energy recovery of biomass source mixtures at the end of the recovery key, characterized by: a residual water content of less than 8% by weight; a bulk density greater than 400 kg / m3, preferably between 400 and 600 kg / m3; a heat capacity greater than IOGJ / Tonnes; a diameter greater than 10 mm, preferably greater than 12 mm, still preferably having a diameter of 15 mm plus or minus 1 mm a chlorine content of less than 600 ppm; a sulfur content of less than 1500 ppm; have a fluorine content of less than 100 ppm.

Preferably, the granules are further characterized by a chromium content of less than 70 ppm; copper less than 80 ppm; lead less than 30 ppm;

[0024] Advantageously, the granules are characterized by an arsenic content of less than 2 ppm; . Cadmium less than 1 ppm; mercury less than 0.4 ppm.

[0025] Preferably, the granules have an ash content of less than 10%.

Preferably, the granules have a PCB content of less than 0.4 ppm; hexachlorocyclohexane (lindane) less than 0.4 ppm.

in tars less than 0.5 ppm

In a preferred embodiment of the invention, the said sources of biomass are selected from the group of: slurry or intensive farm manure; winemaking must; must of vegetable oil press; composting waste; forestry waste; dry residues of biomethanation; dry residues of biomethanol production; sewage sludge; or, a mixture of these.

[0028] Preferably, said biomass sources are selected from the group of: intensive manure or manure; sewage sludge; or a mixture thereof.

According to a preferred form of the invention, said sources of biomass are selected from the group of: composting waste; forestry waste; dry residues of biomethanation; dry residues of biomethanol production; or a mixture of these,

In another preferred form of the invention, said sources are selected from the group of: winemaking wort; vegetable oil press wort, - or a mixture of these.

The present invention also relates to a method of manufacturing granules comprising the following steps: chemical analysis of different sources of biomass; calculating a combination of said sources meeting the compositional criteria of any one of claims 1 to 9, - mixing said sources according to the combination calculated in the previous step; granulation; drying to obtain a moisture content of less than 8%, said drying being carried out in a device using the heat of cogeneration during a power generation process.

Brief description of the figures

FIG. 1 represents the general concept of the method of the present invention.

Detailed description of the invention

The overall concept of the present invention is as follows: a biomass thermal power plant built according to the principle of electricity-heat coupling, recover for energy purposes waste biomass and transforms into heat and electricity, neutral in C02. The generated electricity is injected into the public network against a remuneration specific to the region in question. Moreover, the electricity thus produced makes it possible to obtain emission certificates corresponding to a production of C02-neutral electricity.

To dry the waste to be converted into fuel pellets, it uses the heat dissipated by the energy process of a biomass thermal power plant. Residual heat is still valued for industrial purposes, such as drying wood, paper, ... or for district heating purposes.

The waste can come from various sources, such as intensive livestock manure, sewage sludge, residues of oil presses, "cakes" filtering candy or breweries, chips and waste products. various woods, ...

Samples of this waste are analyzed before or after drying so as to define the following parameters: calorific value, ash content, concentration of various elements (Cl, S, F). Preferably, trace concentrations of heavy metals (Cd, Hg, Cu, Zn, Cr, As, Pb) are also determined.

This miscellaneous waste is then mixed, dried and granulated. The energy required for these drying and granulation operations will be provided according to the present invention by the combustion of biomass, as described above. The proportions of waste of different origins in the mixtures are defined according to the present invention of. in order to respect the strictest environmental and technical constraints for fuels, with the aim, for example, of maximizing the heating value of the final mixture.

Outside of the environmental constraints, other factors are to be considered. In particular, the elements Cl, S and F will be limited depending on the corrosion resistance of the hearth, these burning elements generating strong acids with water vapor.

In technologies using fluidized beds at high temperature, contaminants among the ash having a melting point below the temperature of the bed are to be limited. Indeed, these contaminants can eventually cause clogging of the bed, and a malfunction of the system. Metals and metal oxides with a low melting point should therefore be avoided. These include copper, mercury, lead, zinc and aluminum. These last two elements nevertheless pose fewer problems, as long as they remain in the oxidized state, their oxides having melting points much higher than the temperature of the usual foci.

Rather than maximizing the total heating value generated by the mixtures, it is possible to imagine other objective functions according to the goal pursued: for the production of energy as such, the total heating value will be maximized, for a reduction. the ultimate waste, we will seek a minimization of the ash rate, within the framework of a waste treatment company, we will seek to minimize the amount of waste, or, to minimize the amount of waste recoverable by other means ( wood chips).

In a particular embodiment of the invention, compositions of mixtures are calculated by maximization under the following constraints: concentrations of elements lower than the environmental and technical limits defined above; the availability of waste.

The objective function will for example be the maximization of the heating value of the mixture. Conventional commercial spreadsheets generally provide automatic tools for this type of optimization (see for example "applied management science", published by Wiley & Sons, Inc., ISBN 0471427748, Chapter 2).

If necessary, additional constraints may be added to the system: for example, in order to comply with regional regulatory constraints. Thus, the pellets for the thermal valorization of biomass in Flanders will be free of wood waste, these being excluded by the decree of the Flemish government of March 5, 2004.

The granulation will provide densification by compression so as to obtain an apparent density greater than about 400kg / m3, preferably between 400 and 600 kg / m3. Drying will be ensured until the residual moisture is reduced to less than about 8% by weight. The granules produced will preferably have dimensions greater than about 10 mm, preferably greater than 12 mm, more preferably a diameter of 15 mm +/- 1 mm. These dimensions make it possible to obtain an optimal flow of gases during combustion. This type of dimensions also allows the use of special grids in certain homes. These dimensions also allow optimal distribution in fluidized bed fires.

Description of a preferred embodiment of the invention

Different waste, delivered separately, are optionally sorted into batches and stored temporarily. They are sorted in such a way that the classes of waste, dry or wet, agricultural waste or more contaminant products are well defined, so as to allow possible prior treatment. These different batches are then, if necessary, crushed and sieved to a maximum particle size of 10 mm. During this process, any pieces of ferrous or non-ferrous metals may be removed.

This grind is then transported mechanically and stored in silos. The waste of different origins can then be mixed by gravimetric dosing of the crushes from the different silos, in proportions allowing an ideal incineration, and minimizing the impact on the environment.

The mixture is then conveyed to a drying installation in which it is dried to obtain a mixture containing less than about 10% residual moisture by weight. This drying installation is heated by means of the heat generated by the heat / electricity cogeneration plant described below.

The dry mixture is then conveyed to a storage silo before granulation. Before granulation, the mixture is conditioned according to conditions of time, humidity and defined temperature. Usually 10 to 20 minutes and 3 to 4% of steam make it possible to obtain granules of good quality. Optionally, at this stage, binders may be usefully added, so as to ensure the permanent cohesion of normally powdery materials.

The granulation is then carried out by means of a roller press feeding a die having numerous cylindrical holes having a diameter of about 15 mm, thus forming a cylinder of the dried mixture. This cylinder is cut to the required dimensions, directly at the exit of the die, thus format the granules.

The granules are then cooled and cured, avoiding their subsequent degradation. After sieving, the stable granules are stored before incineration or marketing. The granules are cooled in a countercurrent exchanger, which makes it possible to obtain good dimensional stability and additional drying.

The initial production of energy is ensured by the combustion of sawdust, bark and various wood waste, from a sawn wood production facility. This allows the energy recovery of the wood waste closer to its production, optimizing the overall energy balance of the process.

The granules of the present invention have been tested on an industrial line. This facility provides 20 MW of electrical power and thermal decoupling of up to 50 MW. The production line of the pellet processing plant processes around 150,000 t / y.

Such a combustion plant consists essentially of a feed grid, a combustion chamber located above and an integrated steam boiler. The fuel arrives in the fireplace via an automatic feeder and burns on the grill. The grid is divided into adjustable zones, independent of each other, which allows to control optimally the combustion process and thus have almost complete combustion with extremely low emissions. The ignition and the predrying of the fuel are obtained by the initial fire, the incandescence and the heat present in the hearth.

The combustion air for the grate fireplace is preheated and brought to the fireplace as primary air and, if necessary, secondary, through a fan. The wind tunnels are controlled by a speed regulator and a pressure switch. The superheated steam is removed from the steam boiler and, on the countercurrent principle, it is used in 3 stages to preheat the combustion air. The combustion air, which is admitted under the grate as primary air, is distributed in several air zones. For a very humid material, the air can be preheated to 24 0 ° C. It is thus possible to recover all biomasses, wet or dry fuel, and always adjust the combustion perfectly. This has the consequence of having optimal combustion with extremely low emissions.

More suitably, another type of hearth may be used, in which the granules are brought into an area of a fluidized bed where oxygen is present in insufficient quantity to ensure complete combustion, and where the temperature is below the optimal combustion temperature. The fluidized bed is further equipped with worm, intended to continuously remove ashes and slag after combustion. The fumes from this zone are then burned in a second zone, called post-combustion, by secondary injection of air. This zone is regulated so as to obtain an optimal combustion and a complete degradation of the organic pollutants (T> 850 ° C). Both for the transport in the feed zone, and the distribution of the granules in the fluidized bed, the apparent density and the dimensions of the granules are key parameters of the operation of this type of installation.

The flue gases are sucked from the fireplace; the furnace is constantly subjected to underpressure, generated by a suction fan, which is mounted downstream of the boiler. The pressure is controlled by a pressure switch, as part of the protection chain.

The power adjustment of the boiler installation is carried out automatically. The flow rate and the steam pressure act as control variables for the control. The fuel-02 control maintains an optimum ratio for combustion in the combustion chamber, or in the post-combustion zone.

The combustion temperature observed in the hearth is used to regulate the recirculation of the burnt gases, and, if necessary, the amount of oxygen in the primary combustion zone. This recirculation also allows a reduction of NOx.

Maintaining the depression in the home is achieved by means of the suction fan controlled frequency.

The flue gases from the combustion chamber are used in the steam boiler, which consists essentially of: an economizer, a superheater, a heated panel evaporator, tubular plates with fins, for produce superheated steam.

In nominal power, the boiler installation achieves an overall efficiency greater than 88%. The steam flow rate is regulated between 70 and 100% of the nominal power at 485 ° C, so that it is possible in this range to continuously adjust the steam flow.

The high pressure steam produced is collected in the two heating systems, conveyed to the turbine plant through a high pressure steam pipe and used there to generate current.

The high pressure steam produced in the steam boiler is supplied to the high pressure portion of the turbine via a high pressure steam line. Tapping steam is expanded to 2.9 karabsoiu and used for supplying the feedwater tank. Most of the steam continues to flow and is divided into two partial streams.

Each of these partial flows serves a heating capacitor located under the turbines. The heating capacitors are connected in series and they heat the district heating water, in two stages, from 70 to 81,5 ° C, then from 81,5 to 93 ° C. To do this, the steam is expanded to 0.59 bar absolute, resp. It is thus possible to guarantee a maximum current output with 100% heat decoupling. The efficiency is then optimized, unlike the systems of condensation withdrawal turbines.

The condensate of the turbines is then conveyed to the feedwater tank.

The generated current is directly injected into the network of the local electricity distribution company.

[0065] The district heating water is used to supply drying chambers for sawn timber, wood chip drying systems for the production of pellets and drying systems for other biomass waste used for the production of fuel. . Residual heat can still be used for domestic heating.

Example 1

The waste biomasses treated in this example are summarized in Table 1. The compositions of sewage sludge, sifted pork slurry, olive press residues and sawdust are summarized. Concentrations and calorific value are given in relation to the dry matter. The "solver" distributed with the excell ™ software was used to deduce a mixture composition that maximizes the heating value under the constraints of availability and composition summarized on the same table.

Table 2 summarizes the result obtained by the maximization, and all the constraints applied. It should be noted that the main limiting factor in this particular case is the lead concentration. Use in the production of a subsequent batch of waste with a lower lead content will eventually absorb excess unused sludge.

The mixture produced according to the calculated amounts is then dried in a forced air flow drying unit, heated by the heat produced by an electricity / heat cogeneration unit, supplied with biomass fuel derived from wood waste. . The drying is continued until a residual moisture of less than 8% is obtained.

The dried mixture is then introduced into a granulation unit producing granules of about 15 mm in diameter.

Example 2 Example 2 describes a mixture of sewage sludge from two distinct origins, and suckling sow slurry, and sifted pork manure. The compositions of these wastes are summarized in Table 3. The use of the "solver" excell ™ indicates the possibility of producing 18.2 tons of dry granules, ie 19.78 tons of pellets at 8% moisture, from mixing and drying 5 tons of sewage sludge from one source, and 20 tons of sieved slurry, 850 kg of sewage sludge from a second source, and 10 tons of suckling sow slurry. These granules have a total heating value of 327.13 GJ.

Mixing, granulation and drying are carried out in the same manner as in Example 1.

Table 1

Granules at 8% moisture: 49 Tons 1 Heating value, expressed in GJ / Ton 2 Dry matter content, expressed in percent 3 Expressed as a percentage of dry matter.

4 Concentration expressed in parts per million by weight of dry matter

Table 2 Excell ™ solver result report ______

Table 3

Granules with 8% moisture content: 19.78 5 Heating value, expressed in GJ / Ton 6 Dry matter content, expressed in percent 7 Expressed in percent relative to the dry matter.

8 Concentration expressed in parts per million by weight of dry matter

Claims (13)

1. Granules enabling the energy recovery of biomass source mixtures at the end of the recovery chain, characterized by: a residual water content of less than 8% by mass; a bulk density greater than 400 kg / m3; a heat capacity greater than IOGJ / Tonnes; a diameter greater than 10 mm; a chlorine content of less than 600 ppm; a sulfur content of less than 1500 ppm; a fluorine content of less than 100 ppm. 2. Granules according to claim 1, characterized by a chromium content of less than 70 ppm; copper less than 80 ppm; lead less than 30 ppm. 3. Granules according to any one of the preceding claims, characterized by an arsenic content of less than 2 ppm; Cadmium less than 1 ppm; mercury less than 0.4 ppm. 4. Granules according to any one of the preceding claims, characterized by an ash content of less than 10%. 5. Granules according to any one of the preceding claims, characterized by a PCB content of less than 0.4 ppm; hexachlorocyclohexane (lindane) less than 0.4 ppm. in tars less than 0.5 ppm. 6. Granules according to any one of the preceding claims, characterized in that said sources of biomass are selected from the group of: slurry or manure intensive farm; winemaking must; must of vegetable oil press; composting waste; forestry waste; dry residues of biomethanation; dry residues of biomethanol production; sewage sludge; or, a mixture of these. 7. Granules according to any one of the preceding claims characterized in that said biomass sources are selected from the group of: slurry or manure intensive farm; sewage sludge; or a mixture thereof. 8. Granules according to any one of claims 1 to 5, characterized in that said biomass sources are selected from the group of: composting waste; forestry waste; dry residues of biomethanation; dry residues of biomethanol production; or a mixture thereof. 9. Granules according to any one of claims 1 to 5 characterized in that said biomass sources are selected from the group of: winemaking wort; must of vegetable oil press; or a mixture thereof. 10. Granules according to any one of the preceding claims characterized in that the granules have a diameter greater than 12 mm. 11. Granules according to any one of the preceding claims, characterized in that the granules have a diameter of 15 mm plus or minus 1 mm. Granules according to any one of the preceding claims, characterized in that the granules have a bulk density of between 400 and 600 kg / m 3. 13. A method of manufacturing granules according to any one of the preceding claims comprising the following steps: chemical analysis of different sources of biomass; calculating a combination of said sources meeting the compositional criteria of any one of claims 1 to 9; mixing said sources according to the combination calculated in the previous step; granulation; drying to obtain a moisture content of less than 8%, said drying being carried out in a device using the heat of cogeneration during a power generation process.