EP3333244A1 - System for supplying powder from granules, method and facility for the gasification of a feedstock of carbon material in a fluidized bed reactor (fbr) using such a system - Google Patents

Abstract

The invention relates to a system (1) for feeding powder, comprising: - A conveyor device (2) with metering, suitable for conveying one or more materials in the form of granules, at a given average flow rate; - a grinder (5) adapted to grind the dosed granules, into a powder; - A gravity injection device (3) of the powder, in the form of a truncated cone, arranged below the mill. It also relates to an associated continuous gasification and continuous installation process.

Description

Technical area

The present invention generally relates to a powder supply system for a part of a downstream installation, such as a reactor in a thermochemical conversion plant.

In particular, it relates to supplies of cohesive powders, such as wood powders, that is to say that they have a natural tendency to spontaneously form arches and vaults.

The invention relates more particularly to an application of food, pressurized containers or not, in powders of carbonaceous material charge, such as biomass, coal or any other type of powders such as a crushed waste ... The Containers to be fed can advantageously be gasification reactors, or other thermochemical conversion systems. In this application, the mass flow rates of solid can be very variable, from a few kilograms up to several tons per hour in industrial conditions.

The invention aims to improve such powder supply systems.

More particularly, the invention finds its application in a process for gasification of biomass and, more generally, carbonaceous material feedstock, in a flow-type gasification reactor driven, to produce fuels or fuels.

Although described with reference to biomass, for conversion into a fuel or a fuel, in particular a liquid fuel, or another synthetic product, the invention can be used for the conversion of other charges of carbonaceous material (coal, pet coke, organic waste ...) or solid recovered fuels (CSR).

State of the art

The term carbonaceous filler means any combustible material consisting of carbon-containing compounds.

It can therefore be biomass, ie any inhomogeneous material of plant origin containing carbon, such as lignocellulosic biomass, forest or agricultural residues (straw), or household waste. All these loads can be dry or wet.

It can also be a fossil fuel, such as coal.

It can also be combustible waste of industrial origin containing carbon, such as plastics. It can thus be solid recovery fuels (CSR), as defined in the EN 15359 standard, ie solid fuels prepared from non-hazardous waste for energy recovery in incineration or co-generation plants. incineration.

It can also be a combination of these different loads.

Current processes under study or at the industrial pilot scale, for thermochemically converting biomass or other charges into liquid or gaseous fuel by chemical synthesis, necessarily include a step of gasification of the carbonaceous feedstock for obtain a synthesis gas containing carbon monoxide (CO) and hydrogen (H2).

The actual gasification step is carried out continuously from the carbonaceous filler of different types and sizes, usually stored at atmospheric pressure.

The gasification of biomass and coal has been known for a long time. In general, it can be defined as a thermochemical transformation of biomass or coal by the action of heat in the presence of gassing agents. It is sought to generate, after the gasification, a gas mixture said synthesis gas which comprises carbon monoxide and hydrogen (CO + H2) among others.

Thus, the gasification processes of the lignocellulosic biomass make it possible to generate a synthesis gas which makes it possible to produce downstream either liquid fuels or other organic products. This gasification takes place in the presence typically of water vapor at 1300-1600 ° C for driven flow reactors (RFE). Conventionally, these processes convert carbon from biomass with a gas at the outlet of the gasifier with an average composition of 20-25% CO, 8-12% CH ₄ , 18-22% CO ₂ and about 38-42% in H ₂ and organic compounds C ₂ to C ₁₆ plus inorganic compounds.

There are various operational or research stage gasification processes that can be grouped as follows: fixed-bed, counter-current, fixed-bed co-current, fluidized-bed gasification and finally, flow-through gasification. .

In a driven flow reactor (RFE), the combustion reaction takes the form of a flame, which implies a very specific mode of injection of biomass.

Thus, it must be introduced into the reactor in the form of atomized powder, suspended in a carrier gas or carrier gas.

The primary reason for pulverizing the biomass material is the need for sufficiently rapid gasification of the particles that make it up. Indeed, for the powder has time to be completely gasified during its fall in the reactor it must be sufficiently fine.

The atomized jet is then brought into contact with the oxidizing agent, a mixture of oxygen and water vapor. In order to obtain good combustion, the mixture with the oxidant must be done quickly and in the most homogeneous manner possible. However, the combustion of a part of the material is one option among others to bring the necessary heat to the gasification process. One can very well have a burner supplied with oxygen and / or methane if one does not wish to burn the material to gasify.

The biomass powder feed of a driven flow gasification reactor and, more generally, a powder feed of various and varied containers, must be made with a conveying device with powder dosing, that is to say which makes it possible to convey and control the quantity of powder, and downstream with a device for the injection of powders into a container, continuously or discontinuously.

Among the conveyor devices with widespread metering, there may be mentioned devices with storage hopper connected downstream worm, rotary locks or pressurizing airlock, commonly called "lock hoppers" in English.

For example, the patent application WO2012 / 152742A1 discloses a rotary lock for metering a powder which feeds directly from the lock a kneader.

The patent US9227790B2 relates to a gasification plant for biomass or coal in which the powder is conveyed by a helical worm conveyor.

There are also pressurization airlock, whose more or less important volume defines the fineness of the dosage. An advantage of locks and airlock chambers is that they also have a sealing effect vis-à-vis possible pressure fluctuations upstream and downstream.

The main disadvantage of using a hopper for storing a cohesive powder is that its flow is done by forming a kind of chimney, or even arches that will limit the flow of powder out of the hopper, even prevent it.

The major disadvantage of metering screws, locks and lock-hoppers is the highly discontinuous nature of the powder flow generated. In addition, the compaction of the powder in a worm can lead to blocking of the latter.

In order to overcome these disadvantages, several solutions exist.

First of all, it is known to use vibratory systems to ensure the flow of the powder within the storage hopper.

Furthermore, it is usual to replace a worm by a pneumatic conveyor, which is expensive and does not guarantee the absence of compaction of the conveyed powder.

Another solution usually consists in arranging a large number of metering devices, either in fluidic series with a volume, therefore a decreasing flow rate, for example rotating locks with an increasing number of buckets of decreasing size going towards the point. injection, or in parallel, with an alternating dosage of several devices. In addition to the investment and management constraints of alternate operation, this solution has the disadvantage of generating a significant footprint. On the other hand, for cohesive powders, problems of plugging by compaction of the powder in the cups occur frequently.

In the field of conveying and gasification of coal powder, the solution consists in controlling the solid flow rate by an additional flow of gas: see publications [1], [2]. A conveying with gas, also referred to as "aerated injection", has the advantage of not generating additional space. On the other hand, it generates highly diluted phase flow, which may not be compatible with many downstream processes.

This is particularly problematic in a thermochemical conversion plant in which the gas does not participate in the reaction and thereby decreases the efficiency. This can be particularly penalizing at high pressure, because of the density increased gas, which increases the ratios between gas mass flow and solid mass flow. For example, using a conveying gas by diluting the powder particles in a biomass gasification plant would require using a portion of the energy of the gasification reaction to heat the initially cold gas, which would have the effect of undesirable to decrease the overall yield of the reaction.

With regard to the injection devices, mention may be made of the old literature and provided on the discharge silos. These "funnel" type elements in the form of a truncated cone make it possible to inject a granular material into a smaller container. On the other hand, these funnels, usually called injection cones, do not have the function of dosing the granular material and provide just a discharge by gravity. Thus, in these known injection devices, the value of the flow rate is not adjustable.

The major disadvantage of the injection cones is that the powder can cause clogging within them, due to the irregular arrival of powder in the form of packets and not constant flow, these packages can also have a certain cohesion due to compaction in the upstream conveying device, such as a worm. One solution is to add a vibratory system to the injection cone, which as for the injection hopper is expensive and does not guarantee the absence of clogging.

Various gas-free injection devices can also be found, described in detail in the publication [2]. Thus, as for conveyors with dosing, these injection devices find an application in the diluted phase with a solid volume fraction reached which is a few%.

Another disadvantage of this type of aerated injection is that the dosing and powder injection functions are not separated since it is the two-phase mixture and therefore the gas flow rate that largely determines the solid flow rate.

Finally, for very cohesive powders and / or not easily fluidizable, this type of injection is complex to achieve and very dependent on the nature of the powders, as explained by the publication [2].

If in the prior art, there are dense phase powder supply systems that combine a conveying device with powder metering and an injection device, the disadvantages specific to each device remain.

Thus, all state-of-the-art solutions increase the cost and complexity of a powder supply system and do not guarantee systematically its smooth operation according to the flowability properties of the variable powder depending on the type of material (x) forming the powder.

There is therefore a general need to improve the powder supply systems of downstream industrial equipment, in particular to avoid the problems of chimney flow with arches, compaction of the powder which can lead to capping all or part of the systems with a fine, precise and stable dosing, without compromising the cost of systems realization.

There is a particular need to improve the powder supply systems of a feedstock of carbonaceous material, preferably lignocellulosic biomass, of a continuous plant with a driven flow type gasification reactor, with a view to to produce fuels or fuels, in particular to ensure reliable operation and increase the profitability of the overall installation.

The object of the invention is to at least partially meet this (these) need (s).

Presentation of the invention

• un dispositif de convoyage avec dosage, adapté pour convoyer un ou des matériaux sous la forme de granulés, selon un débit moyen donné;
• un broyeur adapté pour broyer les granulés dosés, en une poudre ;
• un dispositif d'injection par gravité de la poudre, sous la forme d'un tronc de cône, agencé en dessous du broyeur.

To do this, the subject of the invention is a powder supply system, comprising:

• a metered conveying device adapted to convey one or more materials in the form of granules, at a given average flow rate;
• a mill adapted to grind the dosed granules into a powder;
• a device for gravity injection of the powder, in the form of a truncated cone, arranged below the mill.

According to an advantageous variant embodiment, the metering conveying device comprises a hopper for storing the granules and an endless screw whose inlet is connected to the outlet of the hopper.

The mill is preferably a roller mill.

The choice of a roller mill is particularly judicious.

On the one hand it is simple to design and implement in a continuous manufacturing facility, especially in an existing installation.

In addition, when the carbonaceous feedstock is solid recovery fuels which contain a high content of plastics, it is not possible to achieve the melting of the granules formed in a roller mill, which may not to be the case in other mill technologies, such as in a knife mill in which the viscous heating of the material can be important.

1. a/ convoyage avec dosage de granulés de charge de matière carbonée, selon un débit moyen donné;
2. b/ broyage de granulés, de sorte à obtenir une poudre;
3. c/ injection par gravité de la poudre dans un réacteur de gazéification de type à flux entrainé (RFE), de préférence à des températures comprises entre 1300 et 1600°C.

The invention also relates, in another aspect, to a process for gasification of a carbonaceous material charge into a synthesis gas for producing a fuel or a fuel, in particular a liquid fuel, or another product. synthesis, comprising the following steps:

1. a / conveying with dosage of granules of carbonaceous material charge, according to a given average flow rate;
2. b / grinding granules, so as to obtain a powder;
3. c / gravity injection of the powder into a forced flow type gasification reactor (RFE), preferably at temperatures between 1300 and 1600 ° C.

The size of the powder particles resulting from step b / grinding is preferably between 100 μm and 1 mm.

The granules can be biofuel granules or solid recovery fuel granules (SRF).

• un broyeur, agencé en dessous du dispositif de convoyage avec dosage du système d'alimentation décrit précédemment;
• un dispositif d'injection par gravité de la poudre, sous la forme d'un tronc de cône, agencé en dessous du broyeur ;
• un réacteur de gazéification de type à flux entraîné (RFE), agencé en dessous du dispositif d'injection.

Finally, the subject of the invention is a carbonaceous material charge gasification installation intended to continuously implement the process described above, comprising:

• a mill, arranged below the conveyor device with dosing of the feed system described above;
• a device for gravity injection of the powder, in the form of a truncated cone, arranged below the mill;
• a flow-type gasification reactor (RFE) arranged below the injection device.

Thus, the invention essentially consists in carrying out the conveying and the dosing of the carbonaceous feedstock in the form of granules and then in carrying out their grinding so as to obtain a powder having the desired particle size properties before it enters the injection cone.

The granules may advantageously be in the form of small cylinders of the type of biocombustible wood pellets marketed for home heating or of any other shape and / or size allowing their satisfactory flow both in a hopper and in a conventional conveying device, such as a worm.

The granules can be manufactured as usually by compaction of a powder whose particle size is that desired for proper operation of the driven flow reactor.

The mill according to the invention makes it possible to grind or in other words to crumble the granules to give again the initial particle size, typically between 100 microns and 1 mm, of the powder which constitutes them. Very advantageously, the crumbling of the granules represents a low energetic cost compared to the initial grinding of the material before granulation to obtain the powder at the desired particle size for the gasification reactor or the like.

At the outlet of the mill, the powder obtained is not compacted and its flow can be done in a regular and aerated manner, and thus allow a good flow within the injection cone and hence in any downstream reactor or equipment putting into operation. an industrial process.

The inventors have been against the reflexes of a person skilled in the art who has so far always considered the problem of conveying and injecting the charge in the form of powder, without ever thinking of conveying and dose the load in another less restrictive form.

• suppression des problèmes de blocage, arches, bouchon et autres que l'on rencontre dans les systèmes d'alimentation en poudre selon l'état de l'art;
• obtention d'un débit matière plus régulier que dans les systèmes d'alimentation en poudre selon l'état de l'art. Un broyeur à rouleaux peut contribuer également à obtenir un débit plus constant de biomasse en entrée de réacteur de gazéification;
• moindre dépendance à la coulabilité de la poudre de matière d'alimentation puisque seuls les granulés sont à calibrer en fonction du type de trémie de stockage et de dispositif de convoyage, tel qu'une vis sans fin, pour obtenir un bon écoulement en vue d'une injection dans un réacteur aval ou dans tout équipement industriel aval mettant en oeuvre un procédé ;
• moindre surcoût comparativement aux systèmes d'alimentation en poudre selon l'état de l'art dans lesquels le convoyage et dosage des poudres nécessite l'ajout de systèmes coûteux et complexes (systèmes vibratoires, de fluidisation...) ;
• pour un procédé industriel aval de conversion thermochimique, en particulier pour la gazéification, possibilité d'utiliser une plus grande variété de matière carbonée du fait que la fabrication des granulés avec les dimensions requises par le système est simple.

The invention which has just been described has numerous advantages among which we can mention:

• removal of blockage problems, arches, plugs and others found in powder supply systems according to the state of the art;
• obtaining a flow rate more regular than in powder supply systems according to the state of the art. A roller mill may also contribute to a more constant flow of biomass at the inlet of the gasification reactor;
• less dependence on the flowability of the feed material powder since only the granules are to be calibrated according to the type of storage hopper and conveying device, such as a worm, to obtain a good flow for an injection in a downstream reactor or in any downstream industrial equipment implementing a method;
• lower overhead compared to powder supply systems according to the state of the art in which the conveying and dosage of powders requires the addition of expensive and complex systems (vibratory systems, fluidization ...);
• for a downstream industrial process of thermochemical conversion, in particular for gasification, possibility of using a wider variety of carbonaceous material because the manufacture of granules with the dimensions required by the system is simple.

detailed description

• la figure 1 est une vue schématique d'une partie d'une installation de conversion thermochimique en continu d'une charge de matière carbonée selon l'état de l'art mettant en oeuvre un système d'alimentation en poudre de la charge, avant son injection dans un réacteur de gazéification de type à flux entraîné;
• la figure 2 est une vue schématique d'une partie d'une installation de conversion thermochimique en continu d'une charge de matière carbonée selon l'invention mettant en oeuvre un système d'alimentation en poudre de la charge avec stockage et convoyage de la charge sous forme de granulés suivi d'un broyage avant l'injection de la poudre résultante dans un réacteur de gazéification de type à flux entraîné.

Other advantages and features of the invention will emerge more clearly from a reading of the detailed description of the invention, given by way of illustration and without limitation with reference to the following figures among which:

• the figure 1 is a schematic view of a portion of a continuous thermochemical conversion plant of a carbonaceous material feedstock according to the state of the art using a powder feed system of the feed, before its injection into a flow-type gasification reactor;
• the figure 2 is a schematic view of a portion of a continuous thermochemical conversion plant of a carbonaceous material feedstock according to the invention using a powder feed system of the feed with storage and conveying of the feedstock in the form of of granules followed by grinding prior to injection of the resulting powder into a flow-type gasification reactor.

In the description which follows the terms "input", "output" "upstream", "downstream", are used by reference with the direction of transfer of the carbonaceous material charge in the gasification plant according to the invention.

For the sake of clarity, the same references designating the same elements of an installation according to the state of the art and of an installation according to the invention are used for Figures 1 and 2 .

It is specified that if, figure 1 , the storage hopper is shown above the gasification reactor with a worm horizontally, this is a schematic representation and in practice, the hopper rests on the ground next to the reactor and the worm is arranged obliquely and conveys the carbonaceous feed powder from bottom to top.

As illustrated in figure 1 , a continuous installation according to the state of the art implements the process of a gasification of a carbonaceous charge by supplying the charge under a powder by a system 1 adapted, in a reactor 4 of type to driven flow.

Thus, the gasification reactor 4 entrained flow (EFR or RFE, English acronym for "entrained flow reactor") preferably operating at temperatures typically between 1300 to 1600 ° C and a pressure between 30 and 50 bars is fed with continuous by the load by a conveying device with dosage 2.

More specifically, the carbonaceous material feed is prepared by grinding to be put into the form of a powder P which is stored in a suitable storage hopper 20.

The continuous feed with metering is carried out by means of at least one worm 21, for example as described in the patent application. WO 2005/092749 .

Below the end of the worm 21 is arranged an injection cone 3 which makes it possible to inject the carbonaceous feed powder directly into the reactor 4 situated below said cone 3.

In this type of installation 1 according to the state of the art, it has been observed upstream of the gasification reactor 4, several problems related to the use of the powder to feed the reactor.

First of all, the powder can flow by forming a chimney in the storage hopper 20, possibly with the formation of arches which will limit the flow of powder out of the hopper 20 or even prevent it.

In addition, the powder may tend to compact in the worm 21, which can lead to the blocking of the latter.

Finally, the irregular arrival of the powder in the form of packets and not constant flow in the injection cone 3 can lead to clogging, the packets may also have some cohesion due to compaction in the worm 21 .

Instead of implanting replacement and / or additional devices, such as vibratory devices, pneumatic conveyors or powder fluidization gas injection devices, the inventors have thought of conveying and dosing the carbonaceous feed no longer under powder form but in the form of granules and then grinding them to obtain the powder upstream of the injection into the gasification reactor 4.

Thus, according to the invention, as illustrated in figure 2 a grinding reactor 5 is added between the free end of the worm 21 and the injection cone 3 in powder form.

Thus, the carbonaceous material charge is stored in the form of granules G, which are conveyed as such by the worm before being discharged by gravity into the mill 5.

The powder P which results from the grinding within the mill 5 then also feeds by gravity the injection cone 3 which itself feeds the reactor (RFE) 4 with the powder P.

The mill 5 is preferably a roller mill, that is to say which uses at least two rollers with rotating axes which rotate in opposite directions relative to each other and between which the granules G fall to be crushed or crumbled and thus produce the powder P to the desired particle size.

For a lignocellulosic biomass gasification application or for solid recovery fuels (CSR), the granules G are produced and the mill 5 is dimensioned so that the particles of the powder P obtained by grinding the granules have a dimension between 100 microns and 1mm.

Although described with reference only to biomass, the conversion plant into a fuel or a fuel, in particular a liquid fuel, or another synthetic product, the invention may be used for the conversion of other feeds of carbonaceous material. (coal, pet coke, organic waste ...) or solid recovered fuels (CSR).

Other variants and improvements may be provided without departing from the scope of the invention.

The invention is not limited to the examples which have just been described; it is possible in particular to combine with one another characteristics of the illustrated examples within non-illustrated variants.

References Cited

• [1]: " Pneumatic convection of solids ", KLINGZING, GE, RIZK, F., MARCUS, R. & LEUNG, LS, third edition, 2010 .
• [2]: " Pneumatic conveying design guide ", MILLS, D, Elsevier, 2006 .

Claims (7)

Powder feeding system (1), comprising: - A conveyor device (2) with metering, suitable for conveying one or more materials in the form of granules, at a given average flow rate; - a grinder (5) adapted to grind the dosed granules, into a powder; - A gravity injection device (3) of the powder, in the form of a truncated cone, arranged below the mill. System (1) for feeding according to claim 1, the metering conveying device comprising a storage hopper (20) granules and a worm (21), whose input is connected to the outlet of the hopper. Feeding system (1) according to claim 1 or 2, the mill (5) being a roller mill. A method of gasifying a carbonaceous material feedstock to a synthesis gas for producing a fuel or a fuel, such as a liquid fuel, or other synthetic product, comprising the steps of: a / conveying with dosage of granules of carbonaceous material charge, according to a given average flow rate; b / grinding granules, so as to obtain a powder; c / gravity injection of the powder into a forced flow type gasification reactor (RFE), preferably at temperatures between 1300 and 1600 ° C. Gasification process according to claim 4, the size of the powder particles from step b / grinding being between 100μm and 1mm. Gasification process according to claim 4 or 5, the granules being biofuel granules or solid recovery fuel granules (CSR). Carbonaceous material charge gasification plant for continuous operation of the process according to one of claims 4 to 6, comprising: - a mill (5), arranged below the conveying device (2) with metering of the feed system (1) according to any one of claims 1 to 3; - A gravity injection device (3) of the powder, in the form of a truncated cone, arranged below the mill; - A gasification reactor (4) of the driven flow type (RFE), arranged below the injection device.

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