Biomass fluidized bed gasification bed material and preparation method thereof

Abstract

The invention belongs to the technical field of fluidized bed material preparation, and particularly relates to a biomass fluidized bed gasification bed material and a preparation method thereof. The preparation method comprises the following steps: firstly, carrying out alkali activation treatment on coal gangue, then granulating with bauxite, and sintering. The fluidized bed material prepared by the method can bear higher temperature, melting and slagging in the fluidization process are avoided, and the service life is prolonged; k active sites are provided through alkali activation, alkali (soil) metal can be absorbed in the gasification process, the reaction is catalyzed, the gasification efficiency is improved, and high-temperature wall surface corrosion and heated surface ash slagging are relieved; meanwhile, high-value utilization of the coal gangue is achieved, and the environmental problem caused by coal gangue stockpiling is relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of fluidized bed material preparation, and in particular relates to a biomass fluidized bed gasification bed material and a preparation method thereof. Background Art

[0002] The massive consumption of traditional fossil fuels has caused serious environmental pollution and resource shortages, prompting people to develop new renewable clean energy to replace traditional fossil energy. As the world's fourth largest resource after coal, oil and natural gas, biomass has the properties of green, low-carbon, clean and environmentally friendly, and has great development potential in the energy field. The annual output of biomass resources is huge. If it is not properly handled, it will cause serious waste of resources and environmental pollution. In the process of gasification / combustion, biomass will have serious problems such as low fuel utilization efficiency due to low density and calorific value, high-temperature wall corrosion caused by rich chlorine and alkali, and ash slagging on the heated surface. It has high requirements for equipment and operation, high investment costs, and the supply of raw materials is limited by geographical and sustainability.

[0003] Fluidized bed bed materials refer to solid particulate materials used in fluidized bed reactors. Bed materials can effectively transfer heat, maintain temperature uniformity in the fluidized bed, and improve the stability and efficiency of the reaction; they can promote the mass transfer process between gas and solid and enhance reactivity. Common fluidized bed bed materials include quartz sand, alumina bed materials and catalyst bed materials. Among them, sand (silica sand) has stable chemical properties, but has a large density, which increases energy consumption during the fluidization process; it has a large wear on the fluidized bed equipment, which will increase the maintenance cost of the equipment, and has no catalytic effect on the gasification process. Slagging is serious when the temperature is high. Alumina bed materials can withstand high temperatures and are therefore suitable for high-temperature reactions, but their cost is high and their economic applicability is not strong. Catalyst bed materials can be designed according to the needs of the reaction, which helps to improve the gasification reaction rate and selectivity, but the catalyst is easily deactivated during the reaction, increasing the operating cost and operational complexity. Therefore, designing a catalytic and low-cost bed material suitable for biomass fluidized bed gasification can help solve the above problems.

[0004] At present, there have been many studies on catalyst bed materials suitable for biomass gasification process.

[0005] CN105219477A discloses a fluidized bed material with a surface-loaded rare earth oxide catalyst prepared by using high-temperature hot steel slag as a raw material. The bed material is prepared by mixing hot steel slag with a quenching and tempering auxiliary material at high temperature to obtain a liquid low-viscosity silicate melt; the fluidized bed material with a surface-loaded rare earth oxide catalyst is obtained by high-temperature granulation and dusting treatment. The bed material can reduce the ignition point of coal in a coal-fired fluidized bed, accelerate the combustion speed, and inhibit fuel-type NO x Generation of.

[0006] CN114703001A discloses an additive for synergistically inhibiting slagging and corrosion of CFB boilers. The additive combines Al 2 O 3 After ultrasonication, drying and grinding, sulfuric acid was used to load SO 4 2- , using Ca(NO 3 ) 2 Load Ca 2+ After drying, calcining and grinding, an additive for synergistically inhibiting slagging and corrosion of CFB boilers was obtained. The additive was mixed into quartz sand in a certain proportion to participate in gasification. The results showed that the additive can synergistically adsorb and solidify K and Cl released by biomass combustion, and can effectively inhibit the slagging and corrosion problems caused by K and Cl in biomass fluidized bed boilers.

[0007] However, the catalytic bed material / bed material additive prepared by the above method has a high preparation cost, is easily deactivated during the reaction, and does not take into account the sphericity and fluidization effect, and further improvement is needed.

[0008] Therefore, it is very necessary to develop a bed material with stable catalytic effect and low price suitable for biomass fluidized bed gasification. Summary of the invention

[0009] In view of this, the purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a biomass fluidized bed gasification bed material and a preparation method thereof. The present invention starts with improving the gasification efficiency of biomass, treats the coal gangue through alkali activation, and then granulates and sintering it with bauxite. The fluidized bed material prepared by this method can withstand higher temperatures, avoid melting and slagging during the gasification process, and increase the service life of the furnace material; alkali activation provides K active sites, which can absorb alkaline (earth) metals during the gasification process, catalyze the reaction, improve the gasification efficiency, and alleviate the wall corrosion caused by high-temperature flue gas and the accumulation of ash and slagging in the furnace; at the same time, it realizes the high-value utilization of coal gangue and alleviates the environmental problems caused by coal gangue storage.

[0010] To achieve the above object, the technical solution of the present invention is as follows:

[0011] A method for preparing biomass fluidized bed gasification bed material comprises the following steps: using alkali activated coal gangue and bauxite as mixed raw materials, adding water or a binder, granulating, drying, sintering and screening to obtain biomass fluidized bed gasification bed material.

[0012] Furthermore, in terms of weight, the alkali-activated coal gangue is 10 to 50 parts, and the bauxite is 50 to 100 parts.

[0013] Furthermore, the mass fraction of the water or binder in the mixed raw material is 2-25wt%. In the granulation process of the present invention, the amount of water added needs to be strictly controlled to ensure the sphericity and size of the proppant, and the water content in the reaction mixture after adding water in the granulation process can be controlled to achieve the best technical effect.

[0014] Furthermore, the binder is polyvinyl alcohol.

[0015] Furthermore, the preparation method of the alkali-activated coal gangue is: mixing the coal gangue with an alkali solution, performing an alkali activation treatment, and obtaining the alkali-activated coal gangue.

[0016] Furthermore, the ratio of the volume of the alkaline solution to the mass of the coal gangue is 3 to 15 L / g, preferably 5 to 10 L / g.

[0017] Furthermore, the temperature of the alkali activation treatment is 60-120°C and the time is 0.5-6 hours. The temperature and time of the alkali treatment should not be too low, otherwise the activation degree of the coal gangue is insufficient to reach the activation reaction activity; the temperature and time of the alkali treatment should not be too high, otherwise sodium silicate slag will be produced, affecting the overall performance of the bed material.

[0018] Furthermore, the coal gangue has an aluminum oxide content of ≤30% and >10wt%, a calcium oxide content of <10wt%, and a silicon oxide content of >40wt%.

[0019] Furthermore, the alkaline solution includes NaOH solution and / or KOH solution, and the concentration is 0.05-0.4 mol / L. If the concentration of the alkaline solution of the present invention is too low, the active sites generated by the reaction are low, the content of K element adsorbed during the gasification process is low, and it cannot play the role of adsorbing alkaline (earth) metals, and cannot play a good bonding effect during the granulation process, resulting in low sphericity of the particles; if the concentration is too high, a large amount of alkali metals will remain, which will reduce the melting point of the bed material, cause slagging in the furnace, and affect the overall performance.

[0020] Furthermore, the aluminum oxide content in the bauxite is >70wt%.

[0021] Furthermore, the granulation conditions are as follows: the time is 1-30 min; the equipment is an inclined intensive mixer or a disc granulator, preferably an inclined intensive mixer, the barrel speed of the inclined intensive mixer is 20-80 r / min, and the rotor speed is 500-4000 r / min; the mixing of water and the mixed raw materials is step-by-step mixing or all-at-once mixing, preferably step-by-step mixing, and the step-by-step mixing includes first mixing water accounting for 5 to 15 wt% of the mass fraction of the mixed raw materials with all the mixed raw materials for 0.5 to 20 min, and then adding the remaining water to continue mixing.

[0022] Furthermore, the sintering conditions are: a heating rate of 5 to 20° C. / min, a temperature of 500 to 1600° C., and a holding time of 0.5 to 10 h.

[0023] Furthermore, the screening is through a 10-50 mesh sieve. In the present invention, the bed material should have a sphericity of >0.7, and the bed material of the 10-50 mesh part is screened. If the particle size is too small, it will cause difficulties in the transportation and feeding process. If the sphericity is too low / the particle size is too large, it will reduce the fluidization effect and lead to poor results.

[0024] A biomass fluidized bed gasification bed material is obtained by adopting the above-mentioned preparation method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the present invention, the gangue undergoes a chemical reaction during the alkali activation process, wherein low melting point substances such as calcium oxide and magnesium oxide are dissolved by the alkali solution, and the Na / K ions in the alkali solution remain in the system, which can play a role of fluxing at high temperature, increase the mass transfer rate, and improve the sintering performance of the gangue. The retained Na / K ions can promote the formation of aluminosilicate minerals in the gangue, and can be used as catalytically active alkaline (earth) metals (AAEMs) to catalyze the biomass gasification reaction process and improve the combustion process of the biomass. The amorphous silica present in the gangue will react with Na / K to form a colloidal substance during the alkali activation process, which is conducive to balling during the granulation process. Due to the silica active sites provided by the alkali treatment, alkaline oxides can be absorbed during the gasification process, alleviating high-temperature wall corrosion and ash slagging on the heated surface.

[0027] The invention prepares mullite-based bed material by adjusting the proportion of alkali-activated coal gangue and bauxite. The prepared fluidized bed material can withstand a higher temperature, avoid melting and slagging during the gasification process, and improve the service life of the furnace material.

[0028] In summary, the present invention not only improves the sintering performance of coal gangue by alkali activation, but also improves its catalytic activity in biomass gasification reaction. This not only provides a new way for the comprehensive utilization of coal gangue, but also opens up new prospects for the efficient utilization of biomass energy. DETAILED DESCRIPTION

[0029] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0030] The coal gangue in the following embodiments is coal gangue produced by a thermal power plant in Shandong, wherein the content of aluminum oxide is 16.78 wt %, the content of silicon dioxide is 55.21 wt %, and the content of calcium oxide is 1.37 wt %.

[0031] Example 1

[0032] A method for preparing a biomass fluidized bed gasification bed material comprises the following steps:

[0033] (1) according to the ratio of the volume of NaOH solution to the mass of coal gangue being 10 L / g, coal gangue is mixed with a NaOH solution having a concentration of 0.5 mol / L, and an activation reaction is carried out in a closed reactor at a reaction temperature of 95° C. for a reaction time of 2 h, with sufficient stirring. After the reaction is completed, the slurry is filtered, washed, and dried to obtain alkali-activated coal gangue;

[0034] (2) 30 parts of alkali-activated coal gangue are taken and passed through a standard sieve of 100-300 meshes, and then 70 parts of bauxite (alumina content of 76.32 wt%) passed through a standard sieve of 100-300 meshes are added, and then polyvinyl alcohol accounting for 16 wt% of the mass fraction of the alkali-activated coal gangue and bauxite is added, and the mixture is poured into an inclined strong mixer, and the barrel is adjusted to rotate forward at a speed of 50 r / min, and the rotor is adjusted to rotate forward at a speed of 4000 r / min, and the mixture is mixed for 1 min, and then water accounting for 5 wt% of the mass fraction of the alkali-activated coal gangue and bauxite is added, and the barrel is adjusted to rotate forward at a speed of 50 r / min, and the rotor is adjusted to rotate forward at a speed of 2000 r / min, and the mixture is mixed for 3 min, and then the mixture is discharged and dried to obtain a green bed material;

[0035] (3) The ceramic green body is placed in an electric heating furnace for firing at a temperature of 900°C, a heating rate of 10°C / min, and kept warm for 3 hours. After cooling in the furnace, it is sieved through a 20-40 mesh sieve to obtain a biomass fluidized bed gasification bed material.

[0036] Example 2

[0037] This embodiment provides a method for preparing a biomass fluidized bed gasification bed material. The preparation method is the same as that of Embodiment 1 except that the 6 wt % of polyvinyl alcohol in step (2) is replaced by 15 wt % of water.

[0038] The gasification parameters, slagging, and recovery of the biomass fluidized bed gasification bed materials prepared in Examples 1 and 2, quartz sand bed materials, and kaolinite bed materials were used for eucalyptus bark fluidized bed gasification. The results are shown in Table 1. The bed materials prepared by the present invention have higher gasification efficiency and bed material recovery rate than quartz sand and kaolinite, and have a stable catalytic effect in the biomass gasification process. However, quartz sand will produce obvious slagging during the gasification process of eucalyptus bark.

[0039] Table 1 Gasification parameters, density and slagging of eucalyptus bark formed under different bed materials

[0040]

[0041] The biomass fluidized bed gasification bed materials, quartz sand bed materials, kaolinite bed materials and straw biomass ash prepared in Example 1 and Example 2 were mixed in a mass ratio of 1:1 and then the melting characteristics were tested. The results are shown in Table 2. The bed materials of the present invention can withstand higher temperatures.

[0042] Table 2 Melting characteristics of biomass ash and bed material mixed in a ratio of 1:1

[0043]

[0044] The above description is only for better explaining the embodiments of the present invention, and is not intended to limit the present invention. Any modification or equivalent substitution that does not depart from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing a biomass fluidized bed gasification bed material, characterized in that: The method comprises the following steps: using alkali activated coal gangue and bauxite as mixed raw materials, adding water or a binder, granulating, drying, sintering and screening to obtain biomass fluidized bed gasification bed material.

2. The method for preparing a biomass fluidized bed gasification bed material according to claim 1, characterized in that: In terms of weight, the alkali-activated coal gangue is 10 to 50 parts, and the bauxite is 50 to 100 parts.

3. The method for preparing a biomass fluidized bed gasification bed material according to claim 1, characterized in that: The mass fraction of the water or the binder in the mixed raw materials is 2-25wt%; the binder is polyvinyl alcohol.

4. The method for preparing a biomass fluidized bed gasification bed material according to claim 1, characterized in that: The preparation method of alkali-activated coal gangue is as follows: coal gangue is mixed with an alkali solution, and alkali-activated treatment is performed to obtain alkali-activated coal gangue; wherein the ratio of the volume of the alkali solution to the mass of the coal gangue is 3 to 15 L / g; the temperature of the alkali activation treatment is 60 to 120° C., and the time is 0.5 to 6 hours.

5. The method for preparing a biomass fluidized bed gasification bed material according to claim 4, characterized in that: The coal gangue has an aluminum oxide content of ≤30% and >10wt%, a calcium oxide content of <10wt%, and a silicon oxide content of >40wt%.

6. The method for preparing a biomass fluidized bed gasification bed material according to claim 4, characterized in that: The alkaline solution includes NaOH solution and / or KOH solution with a concentration of 0.05-0.4 mol / L.

7. The method for preparing a biomass fluidized bed gasification bed material according to claim 1, characterized in that: The content of aluminum oxide in the bauxite is greater than 70 wt%.

8. The method for preparing a biomass fluidized bed gasification bed material according to claim 1, characterized in that: The granulation conditions are as follows: the time is 1-30 minutes, the equipment is an inclined strong mixer or a disc granulator, and the mixing of water and the mixed raw materials is step-by-step mixing or all-in-one mixing.

9. The method for preparing a biomass fluidized bed gasification bed material according to claim 1, characterized in that: The sintering conditions are: a heating rate of 5 to 20° C. / min, a temperature of 500 to 1600° C., and a heat preservation time of 0.5 to 10 h; and the sieving is through a 10-50 mesh sieve.

10. A biomass fluidized bed gasification bed material, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 9.

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