DK172334B1 - Process and aggregate for use in the manufacture and combustion of a combustible mixture product - Google Patents

Abstract

In a method for the production and combustion of a combustible composite product being converted from a combustible organic material in a plant comprising an infeed zone (I), a reaction zone (II) and a combustion zone (III), said plant being capable e.g. of being connected to a conventional boiler plant, the main novel features are a) that the combustible organic material is advanced continuously through the infeed zone (I) and fed into the reaction zone (II), in which, in a reaction chamber (4) adapted for the purpose, it is converted while using a gaseous reaction medium being supplied via through openings (8) in a controlled condition with regard to quantity, speed and temperature, so as to cause the formation of a combustible composite product comprising gas, especially pyrolysis gas, tar and powder-like charcoal and having an internal temperature above the ignition temperature, but without molten slag being formed, and b) that the combustible composite product formed is made to enter the combustion zone (III), in which the air for combustion is preferably supplied in a manner to prevent or minimize the formation of nitrogen oxides, in order to avoid high combustion temperatures. <IMAGE>

Description

DK 172334 B1

The present invention relates to a method and assembly for use in the manufacture and combustion of a combustible blend product which is converted from combustible organic material.

5 Combustion of combustible organic material, e.g.

biomass including straw, hay, grass and wood are usually done by combustion systems such as systems with combustion grids, fluid-bed systems or cyclone firing systems. In special cases, specially adapted systems such as 10 powder firing systems or firing systems are used to burn whole straw bales.

The use of plants with combustion grids is limited by the fact that it is difficult to adapt the size of the grate to the necessary boiler technology because of the excessive system performance.

15 Just as it is difficult to control an even fuel layer and good air distribution, which is a necessary prerequisite for achieving good combustion. Systems with combustion grids are therefore usually limited to systems with a maximum fired power of approx. 200 MW.

20 fluid-bed systems can be used for low reactivity fuels ie. types which are slow combustion and also for higher firing effects, but for high reactivity fuels ie. fast burning such as straw and other annual crops, it is necessary to use an additional fuel such as. coal to stabilize the combustion process with.

Cyclone firing systems are used where, with small physical dimensions, a high turnover rate is desired. The disadvantage here is that cyclone firing gives high combustion temperatures and 30 for most organic material types, this means that the slag is taken out liquid. This encapsulates the fertilizer value of the slag and can therefore no longer be utilized. This means that the slag product goes to landfill, which is undesirable partly because the landfill gives increased costs 35 partly as mentioned because the fertilizer value is lost.

Powder firing is especially known as a combustion method DK 172334 B1 2 for large coal-fired power plant boilers, since coal can be ground into powder without major problems besides dust nuisance. For organic material types, problems arise, since the grinding of biomass crops is difficult to do and only 5 when using large amounts of energy because these crops contain tough or long-fiber material. In addition, the water content of this type of crop is usually high and therefore prior drying is necessary before grinding.

10 Combustion plants for the combustion of whole straw bales are known in several variants. Some plants burn the whole straw bales at one time, while other plants burn the straw bales from one end, as the straw bales advance as the combustion takes place. With these types of systems, problems can arise in maintaining a continuous and uniform combustion process, as it is difficult to ensure uniform and homogeneous straw bales in terms of the calorific value.

Common to the incinerators mentioned is that all 20 use cold combustion air or combustion air preheated to a maximum of 350 ° C. For the mechanical plants, this is due to the necessity of cooling the system structures, while for the fluid bed systems it is primarily a matter of keeping the combustion temperature down to prevent the melting of sand and ash with low melting points.

The use of each of these known combustion systems is thus associated with both advantages and disadvantages depending on the combustible organic material used, but common to these systems is that they are only difficult to use for combustion of large quantities of organic material.

EP-A2-0,239,281 discloses a waste incineration plant for the complete incineration of waste, which consists of combustible and non-combustible materials which can occur in varying proportions. It is intended to produce a gas which can be used in a subsequent gas turbine, and a gasification process with the addition of air and water vapor is used to ensure a complete conversion of the carbonaceous waste material to a "clean" gas.

WO-88/09364-A1 discloses the corresponding production of 5 generator gas in a pyrolysis combustion of a straw chip fraction based on raw straw. Here, too, a complete conversion to a "clean" gas is intended to operate a generator.

US-A-4,517,906 discloses a two-stage combustion process for the efficient combustion of combustible material. In a first 10 steps, the combustible material is converted by gas to steam and vapor products, which, as in the above-mentioned writings, is intended to be as pure a gas phase as possible. This pure gas phase is then completely burned in another step.

The burning of such "clean" gas phases gives a very concentrated "cold" and not particularly heat-radiant flame, which is not suitable for traditional boiler systems.

It is an object of this invention to provide a method and aggregate for use in continuous production and combustion of large quantities of combustible organic materials, where even very high conversion rates with difficult materials are obtained, e.g. a high water content and suitable for use in connection with a traditional boiler system.

This object is achieved according to the invention by a method of the kind mentioned in the preamble of claim 1 and characterized by the measures specified in the characterizing part of claim 1.

Also, this object is achieved with an assembly of the kind mentioned in claim 5 and characterized by the measures specified in the characterizing part of claim 5.

The invention thus makes it possible to convert a combustible organic material into a combustible blend product of gas, tar and powdery coal having a very high combustion value and a very high reactivity and burning 35 with a powerful radiant flame and thus suitable for combustion. in connection with a traditional boiler system.

DK 172334 B1 4

The invention will now be described in more detail in the following and with reference to the accompanying drawing, which schematically shows an embodiment of an assembly which can be used in connection with the method.

5 The unit for converting and combustion of the combustible organic material comprises various zones located one after the other in the direction of feed of the material and in essence these are a feed zone (I), a reaction zone (II) and a combustion zone (III). Thus, the combustion device may e.g. is connected to a traditional boiler system, replacing or supplementing the traditional heating equipment.

The feed zone (I) comprises a feed system (1) for use in continuous feed of the combustible organic material to the reaction zone (II). The native system itself may e.g. consist of one or more augers, or hydraulic systems with reversing pistons. The material is thus conveyed by the feed system (1) via a feed channel (2) which may have different cross-sectional shapes. In the feed channel (2) is provided an adjustable restraint (3), which allows an adequate compacting and partial retention of the introduced material, and thus a backpressure can be established and maintained which creates a tightness in the material and which prevents gas and combustion products 25 to penetrate the feed system (1).

The reaction zone (II) may be constructed with a reaction chamber (4) consisting of an inner part with passage openings (8), which are preferably constructed as small air nozzles, ie. with a small cross section. The passage openings (8) are e.g. via an air distribution sheath (9) connected to supply ducts (7), and thus the gaseous reaction medium enters the reaction chamber (4) via the supply ducts (7), the air distribution sheath (9) and the passage openings (8). The reaction medium can be supplied by commonly known air supply devices and therefore no details are given here. In addition, the reaction chamber DK 172334 B1 5 (4) consists of an outer part, e.g. may contain an insulating layer (6). The reaction chamber (4) may have any conceivable cross-sectional shape, e.g. square or oval but it is preferred that the reaction chamber (4) is a generally cylindrical device having a length-to-diameter ratio of at least 1 and preferably at least 3-4 to provide space for an optimal number of passage openings (8) for the gaseous reaction medium. .

In this connection, it should be mentioned that the gaseous reaction medium used e.g. may comprise atmospheric air, oxygen, flue gases and mixtures thereof and that it must be preheated to a temperature of more than 500 ° C and preferably between 650-900 ° C. And at the same time to obtain as reactive a blend product as possible, the gaseous reaction medium contains oxygen in an amount corresponding to a maximum of 25% of the stoichiometric amount used in the case of complete burnout and preferably in an amount of between 15-25%.

The gaseous reaction medium should preferably be supplied to the interior of the reaction chamber through as many openings as possible, in order to obtain as uniform an air distribution and as uniform a heat distribution as possible. Thus, it is the combination of a small amount of oxygen, a high velocity and a high temperature for the reaction medium as well as a relatively large length and small diameter of the reaction chamber, which allows large quantities of combustible organic material to be reacted. At the same time, the small amount of oxygen contained in the reaction medium means that the reaction temperature can be controlled so that molten slag is not formed, which allows the use of the slag as a fertilizer.

The converted combustible mixture product contains approx. 50% gas and tar and approx. 50% powdery coal as it leaves the reaction zone (II) and enters the combustion zone (III). The actual conversion occurs without the use of mechanical means. It has an internal temperature which is above the ignition temperature but without forming molten slag, and the formed combustible mixture product is introduced into the combustion zone where, to avoid high combustion temperatures and to prevent or minimize the formation of nitrogen filters ( N0X) adds the combustion air in a controlled manner.

The combustion zone (III) is provided with an air processor (5) through which the necessary combustion air can be added. The air processor (5) must be of a type capable of incrementally adding the combustion air in order to prevent or minimize the formation of nitrogen oxides.

In this embodiment of the combustion zone (III), it forms a final part of the reaction zone (II), but it could as well lie independently of the reaction zone 15 (II).

Claims (6)

A process for the preparation and combustion of a combustible blend product which is converted from a combustible organic material, preferably biomass, into an aggregate comprising a feed zone, a reaction zone and a combustion zone, and e.g. can be connected to a conventional boiler system where the combustible organic material is continuously fed through the feed zone (I) and fed into the reaction zone (II), where it is converted into a reaction chamber (4) adapted thereto using a gaseous reaction medium such as atmospheric air, oxygen, flue gases and mixtures thereof supplied via through-openings (8) in a controlled state in terms of quantity, velocity and temperature, characterized in that a) first a combustible mixture product is formed containing approx. 50% gas, especially pyrolysis gas, and tar and approx. 50% powdery coal, and the conversion occurs without the use of mechanical means, wherein the product has an internal temperature which is above the ignition temperature, but without the formation of molten slag, and b) that the combustible blend product formed is a a state in which the powdery coal is carried by the gas and then introduced into the combustion zone (III), in order to avoid high combustion temperatures, the combustion air is added stepwise and in such a way as to prevent or minimize the formation of nitrogen oxides. Process according to claim 1, characterized in that the gaseous reaction media used contains oxygen in an amount corresponding to a maximum of 25% of the stoichiometric amount used in connection with a complete burnout and preferably in an amount of between 15-25%. DK 172334 B1 8 Process according to claims 1-2, characterized in that the gaseous reaction medium used is preheated to a temperature of more than 500 ° C and preferably between 650-900 ° C. 5 Method according to claims 1-3, characterized in that the gaseous reaction medium used is supplied to the interior of the reaction chamber (4) through a large number of openings (8), in order to obtain as smooth an air distribution as possible. 10 An assembly for use in the method according to any one of claims 1-4, which can be connected to a conventional boiler system, and wherein the different zones are located immediately in succession in the direction of feed of the material, and in which a feeding zone (I) is provided. system (1) for use in continuous feeding of the material to the reaction zone (II) via an also provided feed channel (2), in which is located an adjustable stop (3), by which a compacting of the material can be achieved and thus a maintenance of a backpressure which creates a tightness in the material and which prevents gas and combustion products from returning to the feed system (1) and that in the reaction zone (II) a reaction chamber (4) comprising an outer part and an inner part is provided. with through-openings 25 (8), characterized in that a) the through-openings (8) are connected via an air distribution jacket (9) to supply ducts (7) for the tapered rea b) the combustion zone (III) is provided with an air processor (5) through which the necessary combustion air can be added preferably to prevent 35 or minimize the formation of nitrogen oxides. DK 172334 B1 9 An assembly according to claim 5, characterized in that the reaction chamber (4) is a substantially cylindrical device having a length-to-diameter ratio of at least 1 and preferably at least 3-4 to provide space for an optimal number of passage openings (8). for the gaseous reaction medium.