Method for preparing water gas based on gasification fine slag

Abstract

The invention relates to the technical field of water gas preparation processes, and particularly discloses a method for preparing water gas based on gasified fine slag, which comprises the following steps: 1) preparing gasified fine slag with water content of 30-40% and dry basis fixed carbon of 55-65%; 2) uniformly mixing the prepared gasified fine slag and a binder according to a mass ratio of 8: 2, and adding the mixture into granulation equipment for extrusion forming; 3) adding the gasified fine slag subjected to extrusion forming as a raw material and pure oxygen and water vapor as gasifying agents into a fixed bed pure oxygen continuous gasification furnace, keeping the gasification temperature at 1100-1200 DEG C, and discharging water gas generated by reaction from the fixed bed pure oxygen continuous gasification furnace; and 4) cooling and washing the water gas discharged from the fixed bed pure oxygen continuous gasification furnace. The gasification fine slag serving as solid waste can be reused as a raw material for producing water gas at low cost, the carbon conversion rate and utilization rate are increased, carbon emission is reduced, waste is turned into wealth, and the method conforms to the development direction of the coal chemical industry, has good market prospects and is suitable for wide popularization and application.

Description

Technical Field

[0001] The present invention relates to the technical field of water gas preparation technology, and in particular to a method for preparing water gas based on gasified fine slag. Background Art

[0002] The energy utilization mode of direct coal combustion has problems such as low utilization efficiency, single method and serious pollution. The modern coal chemical industry based on clean coal technology has broad development prospects. Coal gasification is the foundation and core of coal chemical industry. It has high comprehensive efficiency and can reduce NO X It can reduce the emission of various pollutants such as SO2 and is easy to control, and is one of the priority directions of clean coal technology.

[0003] Gasification fines are a solid waste inevitably generated during the coal gasification process. They possess low volatile matter, high dry fixed carbon, small particle size, high ignition point, and low reactivity. However, due to their small particle size, they readily flow out of the gasifier with the gas, making them unsuitable for use as a gasification feedstock in conventional gasifiers. Their well-developed internal porosity and high concentration of bound water further complicate their use. Furthermore, the ash melting point of gasification fines is only around 900°C, while the gasifier temperature must be no less than 1100°C. Consequently, gasification fines easily melt and adhere to the inner walls of the gasifier, potentially clogging pipes. These factors render gasification fines unsuitable for use as a gasification feedstock for water gas production, despite their high dry fixed carbon content.

[0004] The existing Chinese patent with publication number CN111363592A discloses a two-stage entrained flow system using gasification carbon residue for gasification. It uses an entrained flow system to react gasified slag with water vapor and air / enriched oxygen as reaction materials to produce water gas at a high temperature of 1400°C. Although water gas has been successfully produced using gasified slag as a raw material, many problems still exist. First, the initial form of the gasified slag is a gasified slag filter cake with a high moisture content, which requires additional energy to dry, increasing the cost of gasification. Second, an entrained flow gasifier must be used, which has very high production and maintenance costs. Third, the gasified slag still has the problem of melting and clogging.

[0005] Therefore, the current cost of using gasification fine slag as raw material for coal gasification is extremely high, which is unaffordable for general enterprises and difficult to promote and apply. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing water gas at low cost using gasified fine slag as raw material.

[0007] In order to achieve the above object, the present invention is implemented by the following technical solution: a method for preparing water gas based on gasified fine slag, comprising the following steps:

[0008] (1) preparing gasification fine slag with a moisture content of 30% to 40% and a dry basis fixed carbon content of 55% to 65%;

[0009] (2) The prepared gasified fine slag and the binder are mixed uniformly in a mass ratio of 8:2, and then added to a granulation device for extrusion molding;

[0010] (3) The extruded gasified fine slag is added as raw material to a fixed-bed pure oxygen continuous gasification furnace, pure oxygen and water vapor are introduced as gasifying agents into the fixed-bed pure oxygen continuous gasification furnace, and the gasification temperature is maintained at 1100°C to 1200°C. The water gas generated by the reaction is discharged from the fixed-bed pure oxygen continuous gasification furnace;

[0011] (4) The water gas discharged from the fixed-bed pure oxygen continuous gasification furnace is cooled and washed to obtain the product.

[0012] This technical solution mixes gasified slag with a high dry fixed carbon content with a binder, extrudes it through a granulation device, and then adds it as a raw material to a fixed-bed pure oxygen continuous gasifier. It reacts with a mixture of water vapor and pure oxygen to produce water gas. After cooling, washing, and separation, pure water gas is produced. The extruded slag, mixed with the binder, no longer forms a powder and does not flow out with the airflow. Furthermore, the ash melting point of the formed slag is increased (approximately 1300°C), while the reaction temperature is 1100°C to 1200°C. Therefore, the slag does not melt and adhere to the inner walls of the gasifier, and the reaction temperature can be controlled by controlling the amount of water vapor. Furthermore, since a fixed-bed pure oxygen continuous gasifier is used as the reaction equipment, the slag does not need to have a strictly low moisture content as a raw material. Simply squeezing and dehydrating the slag is sufficient to meet the reaction requirements, significantly reducing the cost of using the slag as a raw material for water gas production.

[0013] In order to better implement the method of the present invention, further, the binder used in step (2) is a lignin sulfonate binder of product model sls-1-Z.

[0014] In order to better implement the method of the present invention, further, in the step (2), the gasified fine slag is mixed with the binder and then extruded into a rod shape using a granulating device at 120° C. and 100 MPa.

[0015] In order to better implement the method of the present invention, further, in step (3), the fixed-bed pure oxygen continuous gasification furnace also has a waste heat recovery system, which recovers the waste heat generated by the fixed-bed pure oxygen continuous gasification furnace and can use the recovered waste heat to dry the gasified fine slag extruded into a rod shape.

[0016] In order to better implement the method of the present invention, further, in the step (4), the mixed gas discharged from the fixed-bed pure oxygen continuous gasification furnace is cooled and washed in a cooling and washing tower to remove ash in the water gas and obtain pure water gas.

[0017] In order to better implement the method of the present invention, further, in step (3), the purity of the pure oxygen in the gasifying agent is 99.6%.

[0018] In order to better implement the method of the present invention, further, in step (1), the specific process of preparing the gasified fine slag with a moisture content of 30% to 40% and a dry basis fixed carbon content of 55% to 65% is as follows:

[0019] (1.1) Adding a flocculant to a slurry of gasified fine slag having a fixed carbon content of 55% to 65% on a dry basis, and then performing preliminary filter pressing and dehydration on the slurry of gasified fine slag using at least one of a vacuum filter, a membrane plate and frame filter press, and a horizontal spiral centrifuge to obtain a solid or semi-solid gasified fine slag filter cake having a moisture content of 48% to 67%;

[0020] (1.2) Using a super press, the gasification fine slag filter cake with a moisture content of 48% to 67% is squeezed and dehydrated to obtain gasification fine slag with a moisture content of 30% to 40%.

[0021] In order to better implement the method of the present invention, further, the super press in the step (1.2) includes a frame, a conveying device and a pressing device, a collecting trough is provided in the frame, the conveying device is provided on the frame and located above the collecting trough, the two ends of the conveying device are respectively connected to the two ends of the frame, and the two ends of the conveying device extend out of the two ends of the frame respectively, the pressing device is provided above the conveying device, and the pressing device is used to press and dehydrate the gasified fine slag filter cake conveyed on the conveying device.

[0022] In order to better implement the method of the present invention, further, the main operating parameters of the super press in step (1.2) include:

[0023] Amount of gasification fine slag filter cake processed by a single machine: 10m 3 / h;

[0024] Design pressure: 80kg / cm 2 ;

[0025] Working pressure acting on gasification fine slag filter cake: 50~60kg / cm 2 ;

[0026] Pressing time: 180s;

[0027] Power: 125kw.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) The present invention prevents the gasified fine slag from flowing out of the gasifier due to its small particle size by mixing and extruding the gasified fine slag with a binder. The ash melting point of the prepared rod-shaped material can be increased to 1300°C, so that the materials in the gasifier can react at a higher temperature. The gasified fine slag will not melt in the gasifier, so that the gasified fine slag can be used as a raw material for preparing water gas.

[0030] (2) The present invention uses a fixed-bed pure oxygen continuous gasification furnace as the equipment for producing water gas. It does not strictly require ultra-low moisture content of gasified fine slag as the raw material. The gasified fine slag filter cake can be squeezed and dehydrated by a super-strong press, and then mixed with a binder to form a rod-shaped material. The rod-shaped material is directly added to the fixed-bed pure oxygen continuous gasification furnace as the raw material for producing water gas, which greatly reduces the cost of using the gasified fine slag as the raw material.

[0031] (3) Compared with the fluidized bed continuous gasification furnace, the fixed bed pure oxygen continuous gasification furnace used in the present invention has a simpler structure and lower production and maintenance costs. The rod-shaped material produced by gasification fine slag has better air permeability and a more complete reaction, so that the gasification fine slag, which is used as waste, can be used as a raw material for preparing water gas at a lower cost, thereby improving the carbon conversion rate and utilization rate, reducing carbon emissions, having good market prospects, and being suitable for wide promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0033] Figure 1 is a block diagram of the process equipment of the present invention;

[0034] Figure 2 This is a diagram of the pure gasified fine slag and the extrusion molding sample with the addition of a binder in the present invention;

[0035] Figure 3 Graphs showing the states of the gasified fine slag mixed with a binder and extruded and the powdered gasified fine slag at different temperatures in the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, process conditions and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the following embodiments. However, the embodiments of the present invention are not limited thereto. Without departing from the above-mentioned technical ideas of the present invention, various replacements and changes are made according to common technical knowledge and customary means in this field, which should be included in the scope of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Example 1:

[0038] This embodiment provides a method for preparing water gas based on gasified fine slag, and its specific production process and equipment are as follows: Figure 1 As shown, the specific process is as follows:

[0039] Step S1: Selecting gasified fine slag produced by a shell gasifier, the gasified fine slag typically having a dry basis fixed carbon content of 55% or more, adding a flocculant to the slurry of the gasified fine slag, and then performing preliminary filter pressing and dehydration on the slurry through a vacuum filter to obtain a solid or semi-solid gasified fine slag filter cake having a moisture content of 48% to 67%. The solid or semi-solid gasified fine slag filter cake having a moisture content of 48% to 67% is conveyed to a storage bin via a conveyor belt for storage;

[0040] Step S2: The solid or semi-solid gasified fine slag filter cake with a moisture content of 48% to 67% in the storage bin is conveyed to a super press via a screw conveyor, and the super press is used to squeeze and dehydrate the gasified fine slag with a moisture content of 30% to 40%, also known as gasified fine slag dried slag. The pressed liquid from the super press enters a water treatment system for recovery and treatment;

[0041] Step S3: adding the obtained gasified fine slag with a moisture content of 30% to 40% and a binder in a mass ratio of 8:2 to a mixer for mixing, and then adding the mixture to a granulation device for extrusion molding;

[0042] Step S4: The extruded gasified fine slag is added as a raw material to a fixed-bed pure oxygen continuous gasifier, and pure oxygen with a purity of 99.6% and 500°C water vapor are mixed into a mixed gas at 270°C through a gas mixer. The mixed gas is then introduced into the fixed-bed pure oxygen continuous gasifier as a gasifying agent, so that the gasified fine slag, oxygen, and water vapor react in the fixed-bed pure oxygen continuous gasifier at a temperature of 1100°C to 1200°C to generate water gas. The reaction temperature in the fixed-bed pure oxygen continuous gasifier can be controlled by controlling the water vapor content in the gasifying agent (fixed-bed pure oxygen continuous gasifier). If the temperature in the fixed-bed pure oxygen continuous gasification furnace is too high, the water vapor content in the gasifying agent is increased; if the temperature in the fixed-bed pure oxygen continuous gasification furnace is too low, the water vapor content in the gasifying agent is reduced). Although a higher temperature is conducive to the reaction, a high temperature will melt the gasified fine slag. Therefore, it is necessary to control the reaction temperature so that, although it cannot reach the optimal reaction temperature, it can maintain a continuous and stable reaction. The fixed-bed pure oxygen continuous gasification furnace is also connected to an automatic ash discharge device to discharge the ash in the furnace. The fixed-bed pure oxygen continuous gasification furnace is a mature product produced by Jiangxi Changyu Industrial Co., Ltd. and belongs to the existing technology, so it will not be described in detail here.

[0043] Step S5: The water gas generated by the reaction is discharged from the fixed-bed pure oxygen continuous gasification furnace, washed and cooled in a cooling and washing tower to remove ash and residue, thereby obtaining pure water gas.

[0044] The raw materials in this embodiment, namely, gasified fine slag and dried slag, have industrial analysis data as shown in Table 1:

[0045] Table 1 Industrial analysis data of gasification fine slag and drying slag

[0046] Moisture internal water ash content Volatile matter Dry basis fixed carbon Received base high calorific value Received base lower calorific value 34.3％ 0.36％ 35.05％ 1.43％ 63.16％ 20621J / g 12557J / g

[0047] The industrial analysis data of the water gas finally produced in this embodiment are shown in Table 2:

[0048] Table 2 Water gas composition analysis data

[0049] Element <![CDATA[CO2]]> CO <![CDATA[H2]]> <![CDATA[N2]]> <![CDATA[O2]]> <![CDATA[CH4]]> <![CDATA[CO+H2]]> content(%) 16.9 37.5 42.8 0.5 0.1 2.2 80.3

[0050] According to the contents of Table 1 and Table 2, it can be seen that the process method provided in this embodiment can successfully prepare pure water gas from gasified fine slag and dried slag.

[0051] Example 2:

[0052] Based on the above embodiment, this embodiment further adds a dryer and a waste heat recovery system. The waste heat recovery system recovers the waste heat of the fixed-bed pure oxygen continuous gasification furnace during the reaction process and uses this waste heat as a drying heat source for the dryer. The extruded gasification fine slag is first dried in the dryer to further reduce the moisture content before being added as raw material to the fixed-bed pure oxygen continuous gasification furnace to react with the mixed gas of oxygen and water vapor, which can further improve the reaction efficiency and water gas production.

[0053] Example 3:

[0054] Based on the above embodiment, this embodiment further defines the structure of the super press, which includes a frame, a conveying device and a pressing device. A collecting trough is provided in the frame, and the conveying device is provided on the frame and located above the collecting trough. The two ends of the conveying device are respectively connected to the two ends of the frame, and the two ends of the conveying device extend out of the two ends of the frame respectively. The pressing device is provided above the conveying device, and the pressing device is used to press and dehydrate the gasified fine slag filter cake transported on the conveying device. The specific structure of the super press has been applied for an invention patent with the application number 202010587504.3, and has been disclosed. It belongs to the prior art and will not be elaborated here.

[0055] The main working parameters of the super press include:

[0056] Amount of gasification fine slag filter cake processed by a single machine: 10m 3 / h;

[0057] Design pressure: 80kg / cm 2 ;

[0058] Working pressure acting on gasification fine slag filter cake: 50~60kg / cm 2 ;

[0059] Pressing time: 180s;

[0060] Power: 125kw.

[0061] Example 4:

[0062] This example further defines the binder used, which is lignin sulfonate, and designs the following experiment:

[0063] Three types of lignin sulfonates produced by Wugang Chengxinyuan Technology Co., Ltd. were selected, and the selected product models were sls-1-Z, sls-1-C, and sls-1-G. The gasified fine slag and dried slag were mixed with the three lignin sulfonate binders sls-1-Z, sls-1-C, and sls-1-G respectively in a mass ratio of 8:2, and then added to the granulation equipment and extruded under the conditions of 120℃ and 100Mpa to form samples, such as Figure 2 As shown, it is then tested and the results are shown in Table 3:

[0064] Table 3 Parameters of samples after extrusion molding

[0065] <![CDATA[Forming density (g / cm 3 )]]> <![CDATA[Compressive strength (N / cm 2 )]]> Pure gasification fine slag drying slag / / <![CDATA[20W t %sls-1-C]]> 1.19864±0.02785 / <![CDATA[20W t %sls-1-G]]> 1.21363±0.01395 0.026 <![CDATA[20W t %sls-1-Z]]> 1.35493±0.05445 0.099±0.02571

[0066] The test results show that the pure gasified fine slag and dried slag samples cannot be shaped and have no compressive strength, while the samples with added binders can all be shaped. The compressive strength of the sls-1-C sample is lower than the limit value, and the sls-1-Z sample has the best physical properties.

[0067] Therefore, the preferred binder is lignin sulfonate binder with the binder type sls-1-Z.

[0068] Example 5:

[0069] In this embodiment, based on the above embodiment, in order to verify whether the ash melting point of the gasified fine slag after adding a binder is significantly improved, the following experiment is conducted:

[0070] The gasified fine slag and dried slag were mixed with the lignin sulfonate binder sls-1-Z in a mass ratio of 8:2, and then added into the granulation equipment and extruded into rods under the conditions of 120℃ and 100Mpa as the experimental group. At the same time, the gasified fine slag and dried slag were used as the control group. The morphologies of the two at different temperatures were observed.

[0071] The experimental results are as follows Figure 3 As shown in the figure, the deformation temperature (DT), softening temperature (ST), hemisphere temperature (HT), and flow temperature (FT) of the experimental group are significantly higher than those of the control group. It can be seen that the melting point of the gasified fine slag ash with the addition of binder is significantly improved, and the morphology is stable at a temperature not higher than 1300℃.

[0072] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for preparing water gas based on gasification of fine slag, characterized in that: The following steps are involved: (1) preparing gasification fine slag with a moisture content of 30% to 40% and a dry basis fixed carbon content of 55% to 65%; (2) The prepared gasified fine slag and the binder are mixed evenly in a mass ratio of 8:2, and then added to a granulation device for extrusion molding; (3) The extruded gasification fine slag is added as raw material to a fixed bed pure oxygen continuous gasification furnace, pure oxygen and water vapor are introduced as gasifying agents into the fixed bed pure oxygen continuous gasification furnace, the gasification temperature is maintained at 1100°C to 1200°C, and the water gas generated by the reaction is discharged from the fixed bed pure oxygen continuous gasification furnace; (4) The obtained product is obtained by cooling and washing the water gas discharged from the fixed bed pure oxygen continuous gasification furnace.

2. The method for preparing water gas based on gasification of fine slag according to claim 1, characterized in that: The binder used in step (2) is a lignin sulfonate binder with product model sls-1-Z.

3. A method for preparing water gas based on gasification of fine slag according to claim 1 or 2, characterized in that: In the step (2), the gasified fine slag is mixed with a binder and then extruded into a rod shape using a granulating device at 120° C. and 100 MPa.

4. A method for preparing water gas based on gasification of fine slag according to claim 1 or 2, characterized in that: In the step (3), the fixed bed pure oxygen continuous gasification furnace further comprises a waste heat recovery system, which recovers waste heat generated by the fixed bed pure oxygen continuous gasification furnace and can utilize the recovered waste heat to dry the gasified fine slag extruded into a rod shape.

5. A method for preparing water gas based on gasification of fine slag according to claim 1 or 2, characterized in that: In the step (3), the purity of pure oxygen in the gasifying agent is 99.6%.

6. A method for preparing water gas based on gasification of fine slag according to claim 1 or 2, characterized in that: In the step (4), the mixed gas discharged from the fixed bed pure oxygen continuous gasification furnace is cooled and washed in a cooling and washing tower to remove ash in the water gas and obtain pure water gas.

7. A method for preparing water gas based on gasification of fine slag according to claim 1 or 2, characterized in that: In step (1), the specific process of preparing gasified fine slag with a moisture content of 30% to 40% and a dry basis fixed carbon content of 55% to 65% is as follows: (1.1) Adding a flocculant to the slurry of gasified fine slag with a dry fixed carbon content of 55% to 65%, and then performing preliminary pressure filtration and dehydration on the slurry of gasified fine slag by at least one of a vacuum filter, a membrane plate and frame filter press, and a horizontal spiral centrifuge to obtain a solid or semi-solid gasified fine slag filter cake with a moisture content of 48% to 67%; (1.2) The gasification fine slag filter cake with a moisture content of 48% to 67% is squeezed and dehydrated using a super press to obtain gasification fine slag with a moisture content of 30% to 40%.

8. The method for preparing water gas based on gasification of fine slag according to claim 7, characterized in that: The super press in the step (1.2) comprises a frame, a conveying device and a pressing device, wherein a collecting trough is arranged in the frame, the conveying device is arranged on the frame and located above the collecting trough, two ends of the conveying device are respectively connected to two ends of the frame, and the two ends of the conveying device extend out of two ends of the frame respectively, and the pressing device is arranged above the conveying device, and the pressing device is used to press and dehydrate the gasified fine slag filter cake conveyed by the conveying device.

9. The method for preparing water gas based on gasification of fine slag according to claim 8, characterized in that: The main operating parameters of the super press in step (1.2) include: Amount of gasification fine slag filter cake processed by a single machine: 10m 3 / h; Design pressure: 80kg / cm 2 ; Working pressure acting on gasification fine slag filter cake: 50~60 kg / cm 2 ; Pressing time: 180s; Power: 125kw.

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