A downdraft biomass gasification experimental method and experimental device

Abstract

A downdraft biomass gasification experimental method and a special experimental device thereof are disclosed. The ash layer, reduction layer, oxidation layer and drying layer in a reaction state in a gasifier are physically partitioned by setting a material carrying grate, the reduction layer and the oxidation layer are separated by a lifting device, the gas between the oxidation layer and the reduction layer is sampled for gas composition analysis, nitrogen is filled in the gasifier to rapidly extinguish the flame, and the material composition analysis is performed on the biomass materials in the reduction layer and the oxidation layer. The method stratifies the gas generated in the gasifier, especially the oxidation-reduction layer of tar, through human intervention, and then directly obtains the original gas at the source of the gas, so as to analyze the gas composition and calorific value based on the original gas. The analysis by this method can simulate the working conditions under the natural state, obtain accurate data, and provide a basis for the subsequent research and solution of tar and calorific value loss.

Description

Technical Field

[0001] The invention relates to a downdraft biomass gasification experimental method and an experimental device, belonging to the field of biomass fuel experiments. Background Art

[0002] Biomass is a renewable energy source that can develop in harmony with the environment and has great development potential. Biomass gasification is an effective way to utilize biomass energy in a clean and efficient manner. Biomass gasification is the reaction of solid biomass with a gasifying agent (such as air) under high temperature conditions to obtain small molecular combustible gas, which mainly includes four reaction processes: drying, pyrolysis, oxidation and reduction.

[0003] The downdraft gasification biomass device is a downdraft gasification equipment that has been widely used in rural centralized gas supply and small-scale biomass power generation. The structural principle is shown in the figure. During the reaction process, the materials in the furnace are divided into a drying layer, a pyrolysis oxidation layer, a reduction layer, and an ash layer from top to bottom.

[0004] The biomass raw materials and the gasification agent (air) enter the gasification equipment and are first dried under the action of heat to separate the moisture contained in the biomass. This area is the drying zone.

[0005] Then, when the temperature exceeds about 150°C, pyrolysis reaction begins. In this process, the chains of high molecular hydrocarbons that make up the biomass are broken, and the volatiles in the biomass are separated, leaving charcoal to form a bed for further reactions. During the pyrolysis process, the volatiles come into contact with the co-added combustion aid (air, etc.) and undergo an oxidation reaction. The combustion produces a flame that surrounds the fixed carbon and ash particles. Some of the hot carbon will also burn in this area. The combustion process will produce a large amount of CO2 and release heat, supplying sufficient energy for the pyrolysis and reduction reactions. Since the pyrolysis and oxidation layers intersect with each other and the boundary is not obvious, these two layers are often combined into a pyrolysis oxidation layer, and the temperature range of this layer is 150°C-1100°C. The main chemical reactions in this area are:

[0006] CH a O b N c →C+H2O+CO+CO2+tar

[0007] C+O2=CO2

[0008] 2C+O2=2CO

[0009] The reduction layer is located below the oxidation layer. The water vapor and carbon dioxide generated in the oxidation layer react with the carbon in this layer to generate combustible gases such as hydrogen, carbon monoxide and methane, and a small amount of high molecular weight tar. The temperature range of the reduction zone is 1100℃-600℃. The main chemical reactions in this area are:

[0010] C+CO2=2CO

[0011] C+H2O=CO+H2

[0012] CO+H2O=CO2+H2

[0013] C+2H2=CH4

[0014] The bottom layer of the equipment is the ash layer. The main residues in this stage are ash and carbon residue. The gasification reaction is basically finished here. The inert zone has a coarse filtering effect. The biomass gas produced by gasification is directly sent to the purification system after being filtered through this layer. The temperature range of this interval is 600℃-500℃.

[0015] Downdraft gasification equipment is a straight-cylinder structure with an open furnace top. Air and biomass raw materials enter from the top and can be evenly distributed in the furnace. This type of furnace has unique advantages in simulation, amplification, manufacturing and operation, so it has been widely used. However, due to the low calorific value of the combustible gas it produces and the high tar content, it is easy to clog pipelines and equipment, affecting the commercial application of gasification technology. The key to solving the problem lies in mastering the laws of a series of complex chemical reactions and physical processes inside the pyrolysis oxidation layer and reduction layer, obtaining the chemical reactions and reactant components inside the two layers, revealing the nature of the gasification reaction and the reaction mechanism of tar, so as to improve the structure of the gasifier, optimize the gasification process, reduce the tar content, and improve the gasification efficiency. All of these are inseparable from the research and development of experimental methods and experimental equipment for the pyrolysis oxidation layer and reduction layer.

[0016] There are methods for testing the calorific value and gas composition of biomass fuels in the prior art, such as Chinese patent CN108504391 A, but this test method has important defects. The reason is that: this technical solution collects the gas generated by the biomass fuel through simple gas collection and then analyzes it, but does not take into account the changes in gas composition caused by the complex working conditions in the gasifier, especially does not take into account the filtration generated when the gas flows between the biomass fuels, so that most of the gas components are diluted or filtered, making the experimental data inaccurate, and unable to obtain the original gas from the source of gas generation, which leads to the inability to lay a foundation for solving the tar and calorific value loss problems based on effective data. Summary of the invention

[0017] In order to solve the defects of the prior art, the present invention provides a downdraft biomass gasification experimental method and experimental device. This method stratifies the gas produced in the gasifier, especially the redox layer of tar, through human intervention, and then obtains the original gas directly at the source of the gas, so as to analyze the gas composition and calorific value based on the original gas. The analysis by this method can simulate the working conditions under the natural state and obtain accurate data, which provides a basis for the subsequent research and solution of tar and calorific value loss.

[0018] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a downdraft biomass gasification experimental method, by setting a material carrying grate, the ash layer, reduction layer, oxidation layer and drying layer in the reaction state in the gasifier are physically divided, the reduction layer and the oxidation layer are separated by a lifting device, the gas between the oxidation layer and the reduction layer is sampled for gas composition analysis, nitrogen is filled in the gasifier to rapidly extinguish the flame, and the material composition analysis of the biomass material in the reduction layer and the oxidation layer is performed.

[0019] A downdraft biomass gasification experimental method, using the following steps:

[0020] A gasifier has multiple independently liftable stacked material carrying grates, on which biomass materials are placed, and the upper material carrying grates squeeze the materials on the lower material carrying grates to make the materials compact;

[0021] B. Ignite the biomass material on the bottom material carrying grate, observe through the observation window, and after the bottom material is stably burned, start the induced draft fan, and the flame burns upward layer by layer, so that the biomass material on the multi-layer material carrying grate forms an ash layer, a reduction layer, an oxidation layer and a drying layer from bottom to top;

[0022] C. During the reaction process, the gaps between the layers are adjusted in time to ensure that the entire furnace space is in a tight state. After the reaction is stable, the material carrying grate carrying the ash layer and the reduction layer is lowered or the material carrying grate carrying the oxidation layer and the drying layer is raised to separate the material carrying grate carrying the reduction layer from the material carrying grate carrying the oxidation layer;

[0023] D. Extend the gas collection device into the gap between the oxidation layer and the reduction layer in the furnace to analyze the gas composition between the reduction layer and the oxidation layer;

[0024] E. Fill the gasifier with nitrogen to extinguish the flame in the gasifier rapidly, move the multi-layer material carrying grate upward, take out the material carrying grate carrying the reduction layer and the material carrying grate carrying the oxidation layer, and perform material composition analysis on the biomass material in the reduction layer and the oxidation layer.

[0025] Preferably, there are at least four groups of material-carrying grates, preferably ten groups of material-carrying grates, to facilitate the stratification of the biomass material through full combustion.

[0026] Preferably, the probe is inserted between the reduction layer and the oxidation layer to analyze the gas composition.

[0027] Preferably, the gasifier is provided with gas sampling holes to draw out the gas between the reduction layer and the oxidation layer to analyze the gas composition, and there are at least two gas sampling holes regularly arranged on the wall of the gasifier.

[0028] In order to realize the above-mentioned experimental method, the present invention also provides a special experimental device for the downdraft biomass gasification experimental method, including a gasifier, characterized in that a plurality of stacked material carrying grates are arranged in the gasifier, and the material carrying grates are installed in the gasifier through a lifting device. The material carrying grates can be independently lifted and lowered in the gasifier through the lifting device, and the material carrying grates are used to carry biomass materials; the gasifier is also connected to a nitrogen source.

[0029] Preferably, at least two groups of slide seats are regularly arranged at the side ends of the material carrying grate, a slide rail is provided in the gasifier, and the material carrying grate is slidably installed in the gasifier via the slide seats and the slide rail.

[0030] Preferably, there are at least four groups of material-carrying grates, preferably ten groups of material-carrying grates, to facilitate the stratification of the biomass material through full combustion.

[0031] Preferably, the lifting device includes a threaded column, on which a threaded seat and a connecting seat opposite to the threaded seat are installed, the threaded seat and the connecting seat are connected by a telescopic connecting piece, and the connecting seat is fixedly connected to the material carrying grate. In the lifting state, the threaded seat moves toward the threaded column through the telescopic connecting piece and cooperates with the thread on the threaded column, and the material carrying grate is driven upward or downward by the rotation of the threaded column.

[0032] Preferably, the telescopic connecting member is a cylinder or a telescopic spring, and the end of the threaded column is connected to a driving motor.

[0033] Preferably, the lifting devices are in two groups, which are regularly arranged at the side ends of the material carrying grate.

[0034] Preferably, a see-through area is provided on one of the furnace walls of the gasifier; this technical solution is helpful for researchers to observe the combustion state.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: by setting a material carrying grate, the material is artificially stratified. Since the material carrying grate has a number of through holes, the upper and lower layers of the material can continue to burn, thereby simulating a natural combustion state. Under the combustion state, the material on the carrying grate in the gasifier forms an ash layer, a reduction layer, an oxidation layer and a drying layer in a natural state. Since tar and combustible gas are mainly generated in the oxidation layer and the reduction layer, the original gas and the biomass in the intermediate state of the reaction are collected from between the oxidation-reduction layers as samples for analysis, which is of great significance for understanding the oxidation-reduction process and taking effective measures to improve the calorific value of the gas and reduce the tar component. Therefore, the present invention arranges a material carrying grate that can move up and down, and creates conditions for the collection and analysis of the original gas by separating the reduction layer and the oxidation layer, so that the original gas is collected and subsequently analyzed. The analysis range includes but is not limited to carbon monoxide, carbon dioxide, tar, hydrogen, hydrocarbons, water, water vapor, pressure, temperature, etc. Through research, it is found that the interference with the calorific value and gas is also affected by the state of the material. Therefore, the material carrying grate in the present invention creates favorable conditions for removing the materials in the oxidation layer and the reduction layer, facilitates the removal of the materials for subsequent analysis, and thus creates conditions for solving the problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] To further illustrate the present invention, the following drawings and specific implementation methods are listed. Those skilled in the art should be aware that the following implementation methods do not limit the technical solutions provided by the present invention.

[0037] Figure 1 This is a schematic diagram of the structure of the device provided by the present invention.

[0038] Figure 2 This is a schematic diagram of the longitudinal section structure of the device provided by the present invention.

[0039] Figure 3 This is a schematic diagram of the transverse cross-sectional structure of the device provided by the present invention.

[0040] Figure 4 This is a schematic diagram of the cross-sectional structure of the gasifier provided by the present invention.

[0041] Figure 5 This is a schematic diagram of the material carrying grate structure of the device provided by the present invention.

[0042] Figure 6 This is a schematic diagram of the connection structure between the threaded seat and the connecting seat of the device provided by the present invention.

[0043] Figure 7 This is a schematic diagram of the local structure of the threaded column of the gasifier provided by the device of the present invention.

[0044] Figure 8 This is a schematic diagram of the structure described in the background technology. DETAILED DESCRIPTION

[0045] like Figure 1-7 As shown, a downdraft biomass gasification experimental method is provided, by setting a material carrying grate (2, 3, 4, 5), the ash layer 21, the reduction layer 31, the oxidation layer 41 and the drying layer 51 in the reaction state in the gasifier 1 are physically divided, the reduction layer 31 and the oxidation layer 41 are separated by a lifting device, the gas between the oxidation layer 41 and the reduction layer 31 is sampled for gas composition analysis, nitrogen is filled in the gasifier 1 to rapidly extinguish the flame, and the material composition analysis of the biomass material in the reduction layer 31 and the oxidation layer 41 is performed.

[0046] A downdraft biomass gasification experimental method, using the following steps:

[0047] A gasifier 1 has a plurality of independently liftable and stacked material carrying grates (2, 3, 4, 5), on which biomass materials are placed, and an upper material carrying grate squeezes the materials on a lower material carrying grate, so that the materials are in a compact state;

[0048] B. Ignite the biomass material 51 on the bottom material carrying grate 5, observe through the observation window (i.e., the transparent area 8), and after the bottom material is stably burned, start the induced draft fan, and the flame burns upward layer by layer, so that the biomass material on the multi-layer material carrying grate (2, 3, 4, 5) forms an ash layer 21, a reduction layer 31, an oxidation layer 41 and a drying layer 51 respectively;

[0049] C. During the reaction process, the gaps between the layers are adjusted in time to ensure that the entire furnace space is in a tight state. After the reaction is stable, the material carrying grates (2, 3) carrying the ash layer 21 and the reduction layer 31 are lowered or the material carrying grates (4, 5) carrying the oxidation layer 41 and the drying layer 51 are raised to separate the material carrying grate 3 carrying the reduction layer 31 from the material carrying grate 4 carrying the oxidation layer 41;

[0050] D. Extend the gas collection device into the gap between the oxidation layer and the reduction layer in the furnace to analyze the gas composition between the reduction layer 31 and the oxidation layer 41;

[0051] E. Nitrogen is filled into the gasifier 1 to rapidly extinguish the flame in the gasifier 1, and the multi-layer material carrying grates (2, 3, 4, 5) are moved upward, and the material carrying grate 3 carrying the reduction layer 31 and the material carrying grate 4 carrying the oxidation layer 41 are taken out, and the material composition analysis of the biomass material in the reduction layer 31 and the oxidation layer 41 is performed.

[0052] Preferably, there are at least four groups of material carrying grates, preferably ten groups of material carrying grates, to facilitate stratification of biomass materials through complete combustion. In this embodiment, for ease of understanding, four groups of material carrying grates (2, 3, 4, 5) are used, corresponding to the ash layer 21, the reduction layer 31, the oxidation layer 41 and the drying layer 51, respectively.

[0053] Preferably, a probe (not shown) is inserted between the reduction layer 31 and the oxidation layer 41 to analyze the gas composition.

[0054] Preferably, the gasifier 1 is provided with gas sampling holes (not shown) to draw out the gas between the reduction layer 31 and the oxidation layer 41 to analyze the gas composition. There are at least two gas sampling holes regularly arranged on the wall of the gasifier 1.

[0055] In order to realize the above experimental method, the present invention also provides a special experimental device for a downdraft biomass gasification experimental method, comprising a gasifier 1, wherein a plurality of stacked material carrying grates (2, 3, 4, 5) are arranged in the gasifier 1, wherein the material carrying grates (2, 3, 4, 5) are installed in the gasifier 1 through a lifting device, wherein the material carrying grates (2, 3, 4, 5) can independently perform lifting and lowering movements in the gasifier 1 through the lifting device, and wherein the material carrying grates (2, 3, 4, 5) are used for carrying biomass materials; and the gasifier 1 is also connected to a nitrogen source (not shown).

[0056] Preferably, there are at least four groups of material-carrying grates (2, 3, 4, 5), preferably ten groups of material-carrying grates, so as to facilitate the stratification of the biomass material through full combustion.

[0057] Preferably, at least two groups of slide seats 6 are regularly arranged at the side ends of the material carrying grates (2, 3, 4, 5), a slide rail 61 is provided in the gasifier 1, and the material carrying grates (2, 3, 4, 5) are slidably installed in the gasifier 1 through the slide seats 6 and the slide rails 61.

[0058] Preferably, the lifting device includes a threaded column 7, on which a threaded seat 71 and a connecting seat 72 oppositely connected to the threaded seat 71 are installed, the threaded seat 71 and the connecting seat 72 are connected via a telescopic connecting piece 73, and the connecting seat 72 is fixedly connected to the material carrying grate (2, 3, 4, 5). In the lifting state, the threaded seat 71 moves toward the threaded column 7 via the telescopic connecting piece 73 and cooperates with the thread on the threaded column 7, and the material carrying grate (2, 3, 4, 5) is driven upward or downward by the rotation of the threaded column 7.

[0059] Preferably, the telescopic connection member 73 is a cylinder or a telescopic spring, and the end of the threaded column 7 is connected to a driving motor 74 .

[0060] Preferably, the lifting devices are in two groups, which are regularly arranged at the side ends of the material carrying grates (2, 3, 4, 5).

[0061] Preferably, a see-through area 8 is provided on one of the furnace walls of the gasification furnace 1 .

[0062] In addition, in this embodiment, no material is shown in the ash layer 21, the reduction layer 31, the oxidation layer 41 and the drying layer 51, but those skilled in the art should know that the ash layer 21, the reduction layer 31, the oxidation layer 41 and the drying layer 51 refer to the corresponding material layers.

[0063] Obviously, the above-mentioned embodiments are merely exemplary embodiments of the present invention, and those skilled in the art should be aware that other embodiments may be extended based on the above-mentioned embodiments, so any improvements based on the principles or structures provided by the present invention belong to the protection scope of the present invention.

Claims

1. A downdraft biomass gasification experimental method, characterized in that By setting a material carrying grate, the ash layer, reduction layer, oxidation layer and drying layer in the gasifier in the reaction state are physically divided, the reduction layer and the oxidation layer are separated by a lifting device, the gas between the oxidation layer and the reduction layer is sampled for gas composition analysis, nitrogen is filled in the gasifier to extinguish the flame rapidly, and the material composition analysis of the biomass material in the reduction layer and the oxidation layer is performed. The following steps are adopted: A gasifier has multiple independently liftable stacked material carrying grates, on which biomass materials are placed, and the upper material carrying grates squeeze the materials on the lower material carrying grates to make the materials compact; B. Ignite the biomass material on the bottom material carrying grate, observe through the observation window, and after the bottom material is stably burned, start the induced draft fan, and the flame burns upward layer by layer, so that the biomass material on the multi-layer material carrying grate forms an ash layer, a reduction layer, an oxidation layer and a drying layer from bottom to top; C. During the reaction process, the gaps between the layers are adjusted in time to ensure that the entire furnace space is in a tight state. After the reaction is stable, the material carrying grate carrying the ash layer and the reduction layer is lowered or the material carrying grate carrying the oxidation layer and the drying layer is raised to separate the material carrying grate carrying the reduction layer from the material carrying grate carrying the oxidation layer; D. Extend the gas collection device into the gap between the oxidation layer and the reduction layer in the furnace to analyze the gas composition between the reduction layer and the oxidation layer; E. Fill the gasifier with nitrogen to extinguish the flame in the gasifier rapidly, move the multi-layer material carrying grate upward, take out the material carrying grate carrying the reduction layer and the material carrying grate carrying the oxidation layer, and perform material composition analysis on the biomass material in the reduction layer and the oxidation layer.

2. A downdraft biomass gasification experimental method according to claim 1, characterized in that The probe is inserted between the reduction layer and the oxidation layer to analyze the gas composition.

3. A downdraft biomass gasification experimental method according to claim 1, characterized in that The gasifier is provided with gas sampling holes to draw out the gas between the reduction layer and the oxidation layer to analyze the gas composition. There are at least two gas sampling holes regularly arranged on the wall of the gasifier.

4. A special experimental device for downdraft biomass gasification experimental method, comprising a gasifier, characterized in that A plurality of stacked material carrying grates are arranged in the gasifier, and the material carrying grates are installed in the gasifier through a lifting device. The material carrying grates can independently perform lifting and lowering movements in the gasifier through the lifting device, and the material carrying grates are used to carry biomass materials; the gasifier is also connected to a nitrogen source.

5. A special experimental device for downdraft biomass gasification experimental method according to claim 4, characterized in that At least two groups of slide seats are regularly arranged at the side ends of the material carrying grate, and a slide rail is arranged in the gasifier. The material carrying grate is slidably installed in the gasifier through the slide seat and the slide rail.

6. A special experimental device for downdraft biomass gasification experimental method according to claim 4, characterized in that The lifting device includes a threaded column, on which a threaded seat and a connecting seat opposite to the threaded seat are installed. The threaded seat and the connecting seat are connected by a telescopic connecting piece. The connecting seat is fixedly connected to the material carrying grate. In the lifting state, the threaded seat moves toward the threaded column through the telescopic connecting piece and cooperates with the thread on the threaded column. The material carrying grate is driven upward or downward by the rotation of the threaded column.

7. A special experimental device for downdraft biomass gasification experimental method according to claim 6, characterized in that The telescopic connecting piece is a cylinder or a telescopic spring, and the end of the threaded column is connected to a driving motor.

8. The special experimental device for downdraft biomass gasification experimental method according to claim 6, characterized in that The lifting devices are divided into two groups and are regularly arranged at the side ends of the material carrying grate.

9. A special experimental device for downdraft biomass gasification experimental method according to claim 4, characterized in that A see-through area is arranged on one of the furnace walls of the gasifier.

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