Technical Field

Aspects of the present invention relate to a method for gasification of a solid fuel in a fluidized bed gasifier, wherein the fluidized bed gasifier comprises a vessel having a turbulent fluidized bed region. Aspects of the present invention also relate to an apparatus for gasification of a solid fuel, wherein the apparatus comprises a fluidized bed gasifier having a vessel with a turbulent fluidized bed region, a cyclone in fluid communication with the turbulent fluidized bed region and a return leg conduit fluidly connected to the cyclone. The return leg conduit is also fluidly connected to the turbulent fluidized bed region.

Background

In general, a fluidized bed gasifier performs gasification of a solid fuel, for example biomass, and produces or generates a product gas, which may be provided to a combustor of a power generation plant, for example a combustor of a gas turbine power generation plant, possibly via a product gas treatment arrangement of said plant. The product gas may also be called fuel gas. In general, the combustor produces a flue gas which is provided to a gas turbine of said plant. The gas turbine may in turn be mechanically coupled to an electric generator, which generates electric power. Since solid fuel particles may leave the fluidized bed gasifier together with the product gas, a cyclone is provided downstream of the fluidized bed gasifier. The purpose of the cyclone is to capture the solid fuel particles from the gas stream leaving the fluidized bed gasifier. The cyclone may be coupled to a return leg conduit. The purpose of the return leg conduit is to return the solid fuel particles to the fluidized bed gasifier.

Summary

The inventors of the present invention have identified that the process of gasification of the solid fuel in the fluidized bed gasifier is not efficient enough and can be further improved.

An object of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

According to a first aspect of the invention, the above-mentioned and further objects are attained with a method for gasification of a solid fuel in a fluidized bed gasifier, wherein the fluidized bed gasifier comprises a vessel having a first end section and a second end section, wherein the vessel has a longitudinal extension between the first end section of the vessel and the second end section of the vessel, wherein the second end section is located at a level above the first end section, wherein the vessel contains a turbulent fluidized bed in a turbulent fluidized bed region, the turbulent fluidized bed comprising solid fuel particles of the solid fuel to which a gasification medium is added, wherein a cyclone is in fluid communication with the turbulent fluidized bed region for receiving a gas-solid mixture of a product gas and solid fuel particles from the turbulent fluidized bed, and wherein a return leg conduit, which has a first end section and a second end section, is fluidly connected to the cyclone via its first end section and fluidly connected to the turbulent fluidized bed region via its second end section, wherein the return leg conduit has a longitudinal extension between its first end section and second end section, wherein the first end section of the return leg conduit is located at a level above the second end section of the return leg conduit, wherein the method comprises: introducing first solid material particles and second solid material particles into the turbulent fluidized bed, wherein the particle weight of each of the first solid material particles is greater than the particle weight of each of the second solid material particles; maintaining at least most of the first solid material particles in the turbulent fluidized bed; receiving at least most of the second solid material particles included in the gas-solid mixture in the cyclone; in the return leg conduit, collecting at least most of the solid fuel particles separated from the gas-solid mixture in the cyclone and collecting at least most of the second solid material particles separated from the gas-solid mixture in the cyclone; and feeding at least most of the second solid material particles from the return leg conduit and at least most of the solid fuel particles from the return leg conduit into the turbulent fluidized bed of the vessel. In general, solid fuel particles which have escaped the vessel should be prevented from travelling further downstream in the gas turbine power generation plant.

An advantage of the method according to the first aspect is that the first solid material particles assist in mixing the solid fuel in the turbulent fluidized bed in the vessel in an efficient manner, whereby the gasification of the solid fuel in the fluidized bed gasifier is improved. By way of the method according to the first aspect, a particle bed including both solid fuel particles, which have escaped from the vessel, and second solid material particles, which have left the vessel, is formed in the return leg conduit.

In general, each of the second solid material particles is heavier than each of the solid fuel particles. An advantage of the method according to the first aspect is that the density of the particle bed in the return leg conduit is increased by way of the second solid material particles, and thus the feeding of solid fuel particles into the turbulent fluidized bed of the vessel, and even into the bottom of the turbulent fluidized bed, is made more efficient by means of the second solid material particles.

An advantage of the method according to the first aspect is that the return of the solid fuel particles captured in the cyclone to the fluidized bed gasifier is improved and made more efficient. An advantage of the method according to the first aspect is that an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region is provided. An advantage of the method according to the first aspect is that the process of gasification of the solid fuel in the fluidized bed gasifier is improved. An advantage of the method according to the first aspect is that the fluidized bed gasifier and/or the vessel of the fluidized bed gasifier can be made more compact or smaller in size in relation to conventional solutions. For example, the height of the fluidized bed gasifier and/or of the vessel of the fluidized bed gasifier can be radically reduced and thus take up less space. An advantage of the method according to the first aspect is that the feeding of solid fuel to the vessel of the fluidized bed gasifier is improved. For example, the diameter of a feeder, for example a feeding screw, does not have to be reduced to compensate for a lower height of the vessel of the fluidized bed gasifier as a result of the method according to the first aspect.

According to an advantageous embodiment of the method according to the first aspect, the height of the turbulent fluidized bed in the turbulent fluidized bed region is between 1 and 10 metres. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is improved. However, the turbulent fluidized bed region may have a different height.

According to a further advantageous embodiment of the method according to the first aspect, the particle weight of each of the first solid material particles is at least four times greater than the particle weight of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved and made more efficient. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to another advantageous embodiment of the method according to the first aspect, the particle weight of each of the first solid material particles is at least eight times greater than the particle weight of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved and made more efficient. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to yet another advantageous embodiment of the method according to the first aspect, the particle size of each of the first solid material particles is larger than the particle size of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved and made more efficient. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved. According to still another advantageous embodiment of the method according to the first aspect, the particle size of each of the first solid material particles is at least 1.5 times larger than the particle size of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to an advantageous embodiment of the method according to the first aspect, the particle size of each of the first solid material particles is at least three times larger than the particle size of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to a further advantageous embodiment of the method according to the first aspect, the particle size of each of the first solid material particles is between 150 pm and 300 pm, and the particle size of each of the second solid material particles is between 50 pm and 100 pm. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved and made more efficient. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to another advantageous embodiment of the method according to the first aspect, the particle size of each of the first solid material particles is between 300 pm and 700 pm, and the particle size of each of the second solid material particles is between 50 miti and 250 pm. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved and made more efficient. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to still another advantageous embodiment of the method according to the first aspect, the particle size of each of the first solid material particles is between 400 pm and 1000 pm, and the particle size of each of the second solid material particles is between 50 pm and 250 pm. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved and made more efficient. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to yet another advantageous embodiment of the method according to the first aspect, the density of each of the first solid material particles is equal to the density of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved. According to another advantageous embodiment of the method according to the first aspect, the density of each of the first solid material particles is larger than the density of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved. According to yet another advantageous embodiment of the method according to the first aspect, the density of each of the first solid material particles is at least 1.2 times larger than the density of each of the second solid material particles. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved. According to still another advantageous embodiment of the method according to the first aspect, the cross-sectional area of the turbulent fluidized bed region of the vessel is between 0.05 and 7 m ² . An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to an advantageous embodiment of the method according to the first aspect, the vessel, the cyclone and the return leg conduit are pressurized, and wherein the pressure of the turbulent fluidized bed in the vessel is at least 10 bar. An advantage of this embodiment is that the gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to a further advantageous embodiment of the method according to the first aspect, the vessel, the cyclone and the return leg conduit are pressurized, and wherein the pressure of turbulent fluidized bed in the vessel is at least 20 bar. An advantage of this embodiment is that the gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to another advantageous embodiment of the method according to the first aspect, the method is characterized by feeding at least most of the second solid material particles from the return leg conduit and at least most of the solid fuel particles from the return leg conduit into the turbulent fluidized bed of the vessel at least by means of gravity. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to yet another advantageous embodiment of the method according to the first aspect, the turbulent fluidized bed has a top portion and a bottom portion, the top portion being at a level above the bottom portion, wherein the method is characterized by feeding at least most of the second solid material particles from the return leg conduit and at least most of the solid fuel particles from the return leg conduit into the bottom portion of the turbulent fluidized bed. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to still another advantageous embodiment of the method according to the first aspect, the vessel of the fluidized bed gasifier, the cyclone and the return leg conduit together form an internal system, wherein an external system is fluidly connected to the internal system, and wherein the introduction of the first solid material particles and the second solid material particles into the turbulent fluidized bed is performed by introducing the first solid material particles and the second solid material particles from the external system into the turbulent fluidized bed located in the turbulent fluidized bed region of the internal system. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved. According to an advantageous embodiment of the method according to the first aspect, the vessel of the fluidized bed gasifier, the cyclone and the return leg conduit together form an internal system, wherein an external system is fluidly connected to the internal system, wherein the method is characterized by producing the second solid material particles outside the internal system. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to a further advantageous embodiment of the method according to the first aspect, the vessel comprises a first inlet located in the turbulent fluidized bed region and a second inlet located in the turbulent fluidized bed region, wherein the second end section of the return leg conduit is fluidly connected to the second inlet, wherein the introduction of the first solid material particles and the second solid material particles into the turbulent fluidized bed is performed by introducing the first solid material particles into the turbulent fluidized bed via the first inlet and by introducing the second solid material particles from the return leg conduit into the turbulent fluidized bed via the second inlet. An advantage of this embodiment is that the return of the solid fuel particles, which are captured in the cyclone, to the fluidized bed gasifier is further improved, which involves an improved mixing of the turbulent fluidized bed in the turbulent fluidized bed region. An advantage of this embodiment is that the process of gasification of the solid fuel in the fluidized bed gasifier is further improved.

According to a second aspect of the invention, the above-mentioned and further objects are attained with an apparatus for gasification of a solid fuel, wherein the apparatus comprises a fluidized bed gasifier in which the gasification of the solid fuel is performed, wherein the fluidized bed gasifier comprises a vessel, wherein the vessel has a first end section and a second end section, wherein the vessel has a longitudinal extension between the first end section and the second end section, wherein the second end section of the vessel is configured to be located at a level above the first end section of the vessel when the apparatus is installed, wherein the vessel has a turbulent fluidized bed region and is configured to contain a turbulent fluidized bed in the turbulent fluidized bed region, the turbulent fluidized bed comprising solid fuel particles of the solid fuel to which a gasification medium is added, a cyclone in fluid communication with the turbulent fluidized bed region and configured to receive a gas-solid mixture of a product gas and solid fuel particles from the turbulent fluidized bed of the vessel, and a return leg conduit having a first end section and a second end section, wherein the return leg conduit has a longitudinal extension between its first end section and second end section, wherein the first end section of the return leg conduit is configured to be located at a level above the second end section of the return leg conduit when the apparatus is installed, wherein the return leg conduit is fluidly connected to the cyclone via the first end section of the return leg conduit, wherein the return leg conduit is fluidly connected to the turbulent fluidized bed region via the second end section of the return leg conduit, wherein the apparatus is configured to: introduce first solid material particles and second solid material particles into the turbulent fluidized bed, wherein the particle weight of each of the first solid material particles is greater than the particle weight of each of the second solid material particles, maintain at least most of the first solid material particles in the turbulent fluidized bed, receive at least most of the second solid material particles included in the gas-solid mixture in the cyclone, in the return leg conduit, collect at least most of the solid fuel particles separated from the gas-solid mixture in the cyclone and collect at least most of the second solid material particles separated from the gas-solid mixture in the cyclone, and feed at least most of the second solid material particles from the return leg conduit and at least most of the solid fuel particles from the return leg conduit into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

Positive technical effects of the apparatus according to the second aspect, and its embodiments, correspond to the technical effects mentioned in connection with the method according to the first aspect, and its embodiments. According to an advantageous embodiment of the apparatus according to the second aspect, the height of the turbulent fluidized bed region is between 1 and 10 metres when the apparatus is installed. According to a further advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle weight of each of the first solid material particles being at least four times greater than the particle weight of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle weight of each of the first solid material particles being at least eight times greater than the particle weight of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to still another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle size of each of the first solid material particles being larger than the particle size of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to yet another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle size of each of first solid material particles being at least 1.5 times larger than the particle size of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to an advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle size of each of first solid material particles being at least three times larger than the particle size of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to a further advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle size of each of the first solid material particles being between 150 pm and 300 pm, and the particle size of each of the second solid material particles being between 50 pm and 100 pm, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle size of each of the first solid material particles being between 300 pm and 700 pm, and the particle size of each of the second solid material particles being between 50 pm and 250 pm, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel. According to still another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the particle size of each of the first solid material particles being between 400 pm and 1000 pm, and the particle size of each of the second solid material particles being between 50 pm and 250 pm, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to yet another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the density of each of the first solid material particles being equal to the density of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel. According to another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the density of each of the first solid material particles being larger than the density of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel.

According to yet another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to introduce the first solid material particles and the second solid material particles, the density of each of first solid material particles being at least 1.2 times larger than the density of each of the second solid material particles, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel. According to still another advantageous embodiment of the apparatus according to the second aspect, the cross-sectional area of the turbulent fluidized bed region of the vessel is between 0.05 and 7 m ² .

According to an advantageous embodiment of the apparatus according to the second aspect, the vessel, the cyclone and the return leg conduit are configured to be pressurized, wherein the apparatus is configured such that the pressure of the turbulent fluidized bed in the vessel is at least 10 bar when the apparatus is operated. According to a further advantageous embodiment of the apparatus according to the second aspect, the vessel, the cyclone and the return leg conduit are configured to be pressurized, wherein the apparatus is configured such that the pressure of the turbulent fluidized bed in the vessel is at least 20 bar when the apparatus is operated.

According to another advantageous embodiment of the apparatus according to the second aspect, the apparatus is configured to feed at least most of the second solid material particles from the return leg conduit and at least most of the solid fuel particles from the return leg conduit into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel at least by means of gravity when the apparatus is installed.

According to still another advantageous embodiment of the apparatus according to the second aspect, the turbulent fluidized bed region has a first part and a second part, wherein when the apparatus is installed the second part is located at a level above the first part, wherein the vessel comprises a first inlet located in the turbulent fluidized bed region and a second inlet located in the first part of turbulent fluidized bed region, wherein the second end section of the return leg conduit is fluidly connected to the second inlet, wherein the apparatus is configured to introduce the first solid material particles into the turbulent fluidized bed via the first inlet, and wherein the apparatus is configured to feed at least most of the second solid material particles from the return leg conduit and at least most of the solid fuel particles from the return leg conduit into the turbulent fluidized bed located in the turbulent fluidized bed region via the second inlet.

According to yet another advantageous embodiment of the apparatus according to the second aspect, the vessel comprises a first inlet located in the turbulent fluidized bed region and a second inlet located in the turbulent fluidized bed region, wherein the second end section of the return leg conduit is fluidly connected to the second inlet, wherein the apparatus is configured to introduce the first solid material particles into the turbulent fluidized bed via the first inlet, and wherein the apparatus is configured to introduce the second material particles into the turbulent fluidized bed via the second inlet.

According to an advantageous embodiment of the apparatus according to the second aspect, the apparatus comprises an internal system, the internal system comprising the vessel of the fluidized bed gasifier, the cyclone and the return leg conduit, wherein the apparatus comprises an external system fluidly connected to the internal system, and wherein the apparatus is configured to introduce the first solid material particles and the second solid material particles from the external system into the turbulent fluidized bed located in the turbulent fluidized bed region of the internal system. According to a further advantageous embodiment of the apparatus according to the second aspect, the apparatus comprises an internal system, the internal system comprising the vessel of the fluidized bed gasifier, the cyclone and the return leg conduit, wherein the apparatus comprises an external system fluidly connected to the internal system, and wherein the apparatus is configured to produce the second solid material particles in the external system and outside the internal system.

The above-mentioned features and embodiments of the method and the apparatus, respectively, may be combined in various possible ways providing further advantageous embodiments.

Further advantageous embodiments and advantages of the embodiments emerge from the dependent claims and the detailed description of embodiments.

Brief Description of the Drawings

The present invention will now be described, for exemplary purposes, in more detail by way of embodiments and with reference to the enclosed drawings, in which:

Fig. 1 is a schematic side view of an embodiment of the apparatus according to the second aspect; and

Fig. 2 is a schematic flow chart illustrating aspects of an embodiment of the method according to the first aspect.

Detailed Description

With reference to Fig. 1 , an embodiment of the apparatus 102 for gasification of a solid fuel according to the second aspect is schematically illustrated. The apparatus 102 may be included in a gas turbine power generation plant. The solid fuel may be a solid carbon fuel, for example biomass, wastes, coal etc. The apparatus 102 includes a fluidized bed gasifier 104 in which the gasification of the solid fuel is performed. The fluidized bed gasifier 104 may be included in a gas turbine power generation plant. The fluidized bed gasifier 104 may be called a reactor. The fluidized bed gasifier 104 includes a vessel 106. The vessel 106 may have a tubular shape and the vessel 106 may be made of a suitable metal material, or any other suitable material. The vessel 106 may comprise one or more refractory and/or insulation layers, which for example may be located inside of a tubular metal wall of the vessel 106. The vessel 106 has a first end section 108 and a second end section 110. The vessel 106 has a longitudinal extension between the first end section 108 and the second end section 110. The longitudinal extension extends in a longitudinal direction 112. The second end section 110 of the vessel 106 is configured to be located at a level above the first end section 108 of the vessel 106 when the apparatus 102 has been installed. Each end section 108, 110 may be called an end portion. The longitudinal extension of the vessel 106 may extend in a vertical direction 112 when the fluidized bed gasifier 104 has been installed. However, not the entire vessel 104 needs to extend in a vertical direction 112 when the fluidized bed gasifier 104 is or has been installed.

The vessel 106 has a turbulent fluidized bed region 114 and is configured to contain a turbulent fluidized bed 116 in the turbulent fluidized bed region 114. The turbulent fluidized bed 116 comprises a solid fuel and solid fuel particles to which a gasification medium, for example including one or more of: H2O, air, O2, N2 and steam, is added. The solid fuel particles may be solid carbon fuel particles. The turbulent fluidized bed 116 may be, or may be called, a bubbling fluidized bed. The turbulent fluidized bed 116 may be, or may be called, a turbulent and bubbling fluidized bed. The height h of the turbulent fluidized bed region 114 may be between 1 and 10 metres, for example between 2 and 10 metres, when the apparatus 102 has been installed. However, other heights are possible. The cross-sectional area of the turbulent fluidized bed region 114 of the vessel 106 may for example be between 0.05 and 7 m ² , such as between 0.2 and 7 m ² for some embodiments. However, other cross-sectional areas are possible.

The apparatus 102 includes a cyclone 118, which is in fluid communication with the turbulent fluidized bed region 114 and thus in fluid communication with the vessel 106. The cyclone 118 is configured to receive a gas-solid mixture of a product gas and solid fuel particles from the turbulent fluidized bed 116 of the vessel 106. The cyclone 118 may be called a separator. The product gas may be called fuel gas. Fluid communication between two entities in the context of this disclosure means that a fluid can travel between the two entities. The cyclone 118 is configured to separate solid fuel particles from the gas-solid mixture to prevent the solid fuel particles, which have escaped from the vessel 106, from travelling further downstream in the gas turbine power generation plant. Further, the cyclone 118 is configured to separate second solid material particles 128 from the gas-solid mixture in the cyclone 118. The cyclone 118 may be configured to separate at least most of the solid fuel particles from the gas-solid mixture and separate at least most of the second solid material particles 128 from the gas-solid mixture in the cyclone 118.

The apparatus 102 includes a return leg conduit 120, or return leg pipe, which has a first end section 122 and a second end section 124. Each end section 122, 124 may be called an end portion. The return leg conduit 120 may have a tubular shape and may be made of a suitable metal material, or any other suitable material. The return leg conduit 120 has a longitudinal extension between its first end section 122 and second end section 124. The first end section 122 of the return leg conduit 120 is configured to be located at a level above the second end section 124 of the return leg conduit 120 when the apparatus 102 has been installed. The return leg conduit 120 is fluidly connected to the cyclone 118 via the first end section 122 of the return leg conduit 120. The return leg conduit 120 is fluidly connected to the turbulent fluidized bed region 114 via the second end section 124 of the return leg conduit 120. The term “fluidly connected” in the context of this disclosure means that there is a fluid communication between the two entities which are connected. The longitudinal extension of the return leg conduit 120 may extend in a vertical direction 112 when the fluidized bed gasifier 104 and the apparatus 102 have been installed. However, not the entire longitudinal extension of the return leg conduit 120 needs to extend in a vertical direction 112 when the fluidized bed gasifier 104 is installed

In the shown embodiment, the vessel 106, the cyclone 118 and the return leg conduit 120 are configured to be pressurized. In the shown embodiment, the apparatus 102 is configured such that the pressure of the turbulent fluidized bed 116 in the vessel 106 is at least 10 bar, for example at least 20 bar, when the apparatus 102 is operated.

The apparatus 102 is configured to introduce first solid material particles 126 and second solid material particles 128 into the turbulent fluidized bed 116. The particle weight of each of the first solid material particles 126 is greater than the particle weight of each of the second solid material particles 128. Thus, each of the first solid material particles 126 is heavier than each of the second solid material particles 128. The particle weights of the first solid material particles 126 do not have to be the same, but can differ from one another. The particle weights of the second solid material particles 128 do not have to be the same, but can differ from one another. In Fig. 1 , only a few first solid material particles 126 and second solid material particles 128 are illustrated for illustrative purposes. However, it is to be understood that many more first solid material particles 126 and second solid material particles 128 are present in the embodiments of the invention.

The material of the first solid material particles 126 does not have to be the same as the material of the second solid material particles 128. However, the material of the first solid material particles 126 may be the same as the material of the second solid material particles 128. All of the first solid material particles 126 may be or may not be made from the same material. Thus, the first solid material particles 126 may include particles made from different materials. All of the second solid material particles 128 may be or may not be made from the same material. Thus, the second solid material particles 128 may include particles made from different materials. The material of the first solid material particles 126 may, for example, comprise one or more from the group of: silica sand, domolite, olivine and magnesite. The material of the second solid material particles 128 may, for example, comprise one or more from the group of: silica sand, domolite, olivine and magnesite.

The apparatus 102 is configured to maintain at least most of the first solid material particles 126 in the turbulent fluidized bed 116. This is inter alia attained because the particle weight of each of the first solid material particles 126 is greater than the particle weight of each of the second solid material particles 128. To keep the first solid material particles 126 in the turbulent fluidized bed 116, and also to provide an efficient process of gasification of the solid fuel in the fluidized bed gasifier 104, one or more process variables may be adjusted during or before operation of the apparatus 102. The process variable may be any one of: the pressure of the vessel 104, the rate of introduction of the gasification medium into the fluidized bed region 114 of the vessel 106, the selection of the gasification medium introduced into the fluidized bed region 114 of the vessel 106, and the rate of introduction of new solid fuel into the vessel 106 etc.

The apparatus 102 is configured to receive at least most of the second solid material particles 128 included in the gas-solid mixture in the cyclone 118. The second solid material particles 128, which are lighter than the first solid material particles 126, are added to and follow the gas-solid mixture to the cyclone 118.

The apparatus 102 is configured to, in the return leg conduit 120, collect at least most of the solid fuel particles separated from the gas-solid mixture in the cyclone 118 and collect at least most of the second solid material particles 128 separated from the gas-solid mixture in the cyclone 118. The solid fuel particles collected from the cyclone 118 may be char particles. The apparatus 102 is configured to feed, or reintroduce, at least most of the second solid material particles 128 from the return leg conduit 120 into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the vessel 106. The apparatus 102 is configured to feed at least most of the solid fuel particles from the return leg conduit 120 into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the vessel 106. Thus, the apparatus 102 is configured to feed the second solid material particles 128 together with the solid fuel particles from the return leg conduit 120 into the turbulent fluidized bed 116.

“At least most of the first solid material particles” may correspond to “substantially all first solid material particles” or at least 90-95 % of the first solid material particles. “At least most of the first solid material particles” may correspond to the “first solid material particles. “At least most of the second solid material particles” may correspond to “substantially all second solid material particles” or at least 90-95 % of the second solid material particles. “At least most of the second solid material particles” may correspond to the “second solid material particles. “At least most of the solid fuel particles” may correspond to “substantially all solid fuel particles or at least 90-95 % of the solid fuel particles. “At least most of the solid fuel particles” may correspond to the “solid fuel particles”. However, other levels than 90-95 % as mentioned above are possible. The first solid material particles 126 assist in mixing the solid fuel in the turbulent fluidized bed 116 in the vessel 106 in an efficient manner, whereby the gasification of the solid fuel in the fluidized bed gasifier 104 is improved. In general, solid fuel particles which have escaped from the vessel 106 should be prevented from travelling further downstream in the gas turbine power generation plant. The purpose of the cyclone 118 is to capture the solid fuel particles which have escaped from the vessel 106. Thus, the cyclone 118 is configured to capture the solid fuel particles which have escaped from the vessel 106. A particle bed 129, which includes both solid fuel particles, which have escaped from the vessel 106, and the second solid material particles 128, which have left the vessel 106, is formed in the return leg conduit 120. Because of the second solid material particles 128 present in the particle bed 129 in the return leg conduit 120, the density of the particle bed 129 in the return leg conduit 120 is increased in relation to prior art return leg conduits, because in general, each of the second solid material particles 128 is heavier than each of the solid fuel particles. Therefore, the feeding of solid fuel particles into the turbulent fluidized bed 116 of the vessel 106, even into the bottom of the turbulent fluidized bed 116, is improved by means of the second solid material particles 128 in the embodiments of the present invention. Thus, the return of the solid fuel particles, which have escaped from the vessel 106 and have been captured in the cyclone 118, to the fluidized bed gasifier 104 is improved.

The apparatus 102 may be configured to introduce the first solid material particles 126 and the second solid material particles 128, the particle weight of each of the first solid material particles 126 being at least four times greater, or even at least eight times greater, than the particle weight of each of the second solid material particles 128, into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the vessel 106. The apparatus 102 may be configured to introduce the first solid material particles 126 and the second solid material particles 128, the particle size of each of the first solid material particles 126 being larger, for example at least 1.5 times larger, or even at least three times larger, than the particle size of each of the second solid material particles 128, into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the vessel 106. The apparatus 102 may be configured to introduce the first solid material particles 126 and the second solid material particles 128, the particle size of each of the first solid material particles 126 being between 150 pm and 300 pm while the particle size of each of the second solid material particles 128 being between 50 pm and 100 pm, into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the vessel 106. For example, in some embodiments, the particle size of each of the first solid material particles may be between 300 pm and 700 pm while the particle size of each of the second solid material particles may be between 50 pm and 250 pm. In some embodiments, the particle size of each of the first solid material particles may be between 400 pm and 1000 pm while the particle size of each of the second solid material particles being between 50 pm and 250 pm.

In some embodiments, the apparatus 102 may be configured to introduce the first solid material particles 126 and the second solid material particles 128, the density of each of the first solid material particles 126 being larger, for example at least 1.2 times larger, than the density of each of the second solid material particles 128, into the turbulent fluidized bed located in the turbulent fluidized bed region of the vessel. In alternative embodiments, the density of each of the first solid material particles 126 may be equal to the density of each of the second solid material particles 128.

In the embodiments where the density of each of the first solid material particles 126 is equal to the density of each of the second solid material particles 128, it is to be understood that the density of each of the first solid material particles 126 is substantially equal to the density of each of the second solid material particles 128, i.e. there may still be a small but neglectable difference between the density of each of the first solid material particles 126 and the density of each of the second solid material particles 128.

In the shown embodiment, the apparatus 102 is configured to feed at least most of the second solid material particles 128 from the return leg conduit 120 and at least most of the solid fuel particles from the return leg conduit 120 into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the vessel 106 at least by means of gravity when the apparatus 102 has been installed. In addition, in some embodiments, the pressure within the vessel 106, the cyclone 118 and the return leg conduit 120, or the pressure difference therebetween, may assist in feeding at least most of the second solid material particles 128 from the return leg conduit 120 and at least most of the solid fuel particles from the return leg conduit 120 into the turbulent fluidized bed 116.

The turbulent fluidized bed region 114 has a first part 130 and a second part 132. When the apparatus 102 has been installed, the second part 132 is located at a level above the first part 130. In the shown embodiment, the vessel 106 has a first inlet 134 located in the turbulent fluidized bed region 114, for example adjacent to the first end section 108 of the vessel 106. In the shown embodiment, the vessel 106 has a second inlet 136 located in the first part 130 of turbulent fluidized bed region 114 and, for example, located adjacent to the first end section 108 of the vessel 106. The second end section 124 of the return leg conduit 120 is fluidly connected to the second inlet 136. The apparatus 102 may be configured to introduce the first solid material particles 126 into the turbulent fluidized bed 116 via the first inlet 134 and optionally introduce the second solid material particles 128 into the turbulent fluidized bed 116 via the first inlet 134. The apparatus 102 may be configured to feed at least most of the second solid material particles 128 from the return leg conduit 120 and at least most of the solid fuel particles from the return leg conduit 120 into the turbulent fluidized bed 116, which is located in the turbulent fluidized bed region 114, via the second inlet 136. As an alternative, or in addition thereto, the second inlet 136 may instead be located anywhere else in the turbulent fluidized bed region 114. As an alternative, the apparatus 102 may be configured to introduce the second material particles 128 into the turbulent fluidized bed 116 via that second inlet 136.

The vessel 106 may comprise a third inlet 142 in the fluidized bed region 116, for the inlet of the solid fuel to the fluidized bed region 116 of the vessel 106. The vessel 106 may comprise a fourth inlet 144 in the fluidized bed region 116, for the inlet of the gasification medium, for example including one or more of: H2O, air, O2, N2 and steam (water vapour), as mentioned above.

The apparatus 102 may be defined to include an internal system 138 which includes the vessel 106 of the fluidized bed gasifier 104, the cyclone 118 and the return leg conduit 120. The apparatus 102 may have an external system 140 fluidly connected to the internal system 138. Then, the apparatus 102 is configured to introduce the first solid material particles 126 and the second solid material particles 128 from the external system 140 into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the internal system 138. The apparatus 102 may be configured to produce the second solid material particles 128, and optionally also the first solid material particles 126, in the external system 140 and outside the internal system 138. Thus, the second solid material particles 128, and optionally also the first solid material particles 126, are generated externally to the internal system 138 before being introduced into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114.

With reference to Fig. 2, aspects of an embodiment of the method for the gasification, or a method for a process of gasification, of a solid fuel in a fluidized bed gasifier 104 according to the first aspect is schematically illustrated. The illustrated method includes the steps of: introducing 201 solid fuel and/or solid fuel particles to the fluidized bed region 114 of the vessel 106; introducing 202 the gasification medium into the fluidized bed region 114 of the vessel 106; introducing 203 first solid material particles 126 and second solid material particles 128 into the turbulent fluidized bed 116, wherein the particle weight of each of the first solid material particles 126 is greater than the particle weight of each of the second solid material particles 128; maintaining 204 at least most of the first solid material particles 126 in the turbulent fluidized bed 116; receiving 205 at least most of the second solid material particles 128 included in the gas-solid mixture in the cyclone 118; separating 206 at least most of the solid fuel particles from the gas-solid mixture and separating 206 at least most of the second solid material particles 128 from the gas-solid mixture in the cyclone 118. in the return leg conduit, collecting 207 at least most of the solid fuel particles separated from the gas-solid mixture in the cyclone 118 and collecting 207 at least most of the second solid material particles 128 separated from the gas-solid mixture in the cyclone 118, wherein the solid fuel particles collected from the cyclone 118 may be char particles; and feeding 208 at least most of the second solid material particles 128 from the return leg conduit 120 together with at least most of the solid fuel particles from the return leg conduit 120 into the turbulent fluidized bed 116 of the vessel 106.

The first and second solid material particles 126, 128 included in the embodiments of the method according to the first aspect may be similar or equal to the first and second solid material particles 126, 128 disclosed above in connection with the embodiments of the apparatus 102 according to the second aspect.

The step of feeding 208 may include the feeding 208 of at least most of the second solid material particles 128 from the return leg conduit 120 together with at least most of the solid fuel particles from the return leg conduit 120 into the turbulent fluidized bed 116 of the vessel 106 at least by means of gravity.

The turbulent fluidized bed 116 may have a top portion 146 and a bottom portion 148, the top portion 146 being at a level above the bottom portion 148. The step of feeding 208 may include the feeding 208 of at least most of the second solid material particles 128 from the return leg conduit 120 and at least most of the solid fuel particles from the return leg conduit 120 into the bottom portion 148 of the turbulent fluidized bed 116 of the vessel 106.

The step of introduction 203 of the first solid material particles 126 and the second solid material particles 128 into the turbulent fluidized bed 116 may be performed by introducing 203 the first solid material particles 126 and the second solid material particles 128 from the external system 140 into the turbulent fluidized bed 116 located in the turbulent fluidized bed region 114 of the internal system 138. The method may include the step of producing 203a the second solid material particles 128, and optionally producing the first solid material particles 126, outside the internal system 138. The introduction 203 of the first solid material particles 126 and the second solid material particles 128 into the turbulent fluidized bed 116 may be performed by introducing 203 the first solid material particles 126 into the turbulent fluidized bed 116 via the first inlet 134 and by introducing 203 the second solid material particles 128 from the return leg conduit 120 into the turbulent fluidized bed 116 via the second inlet 136.

The method may be defined or seen as a cycle or a continuous process, where the steps may be repeated a plurality of times. The step of “feeding” 208 mentioned in the passages above relates to the reintroduction of the second solid material particles 128 together with solid fuel particles into the turbulent fluidized bed 116 of the vessel 106 and is separate from the step of introduction 203 of the second solid material particles 128. Unless disclosed otherwise, it should be noted that the method steps illustrated in Fig. 2 and described herein do not necessarily have to be executed in the order illustrated in Fig 2. The steps may essentially be executed in any suitable and possible order. Further, one or more steps may be excluded or added without departing from the scope of the appended claims.

The features of the different embodiments of the apparatus and the method disclosed above may be combined in various possible ways providing further advantageous embodiments. The invention shall not be considered limited to the embodiments illustrated, but can be modified and altered in many ways by one skilled in the art, without departing from the scope of the appended claims.