CN101041136A - Modification dolomite and the preparing method and the application - Google Patents

Abstract

The invention discloses a modified dolomite and its preparation method and application, which is characterized in that the weight composition includes: MgO 1-10wt%, NiO 10-30wt%, dolomite 60-89wt%, the modified dolomite The preparation method is that magnesium nitrate is added to dolomite in the form of solution through co-precipitation, dried and shaped, and then calcined at 900°C. The modified dolomite can be used as a catalyst for biomass gasification. Compared with the dolomite, the modified dolomite of the present invention greatly improves the strength of the dolomite and the catalytic cracking ability of the tar oil. Thereby reducing the cost of the biomass catalytic gasification process, improving the economy of the process, and promoting the development of the biomass catalytic gasification technology.

Description

A kind of modified dolomite and its preparation method and application

technical field

The invention relates to a modified dolomite and a preparation method thereof, in particular to a modified dolomite using magnesium nitrate as a reinforcing agent to improve the strength of the dolomite and a method for preparing the modified dolomite.

Background technique

With the improvement of human living standards, people rely more and more on energy. However, due to the non-renewability of fossil fuels and their limited reserves, fossil energy has been increasingly exhausted, and the environmental crisis has become increasingly obvious. Today, seeking and developing new energy sources, especially renewable energy sources with little environmental pollution, has attracted global attention.

Biomass usually refers to terrestrial plants (wood, fuelwood, straw, etc.) and aquatic plants. It is a stable renewable energy resource with abundant sources. my country is a large agricultural country, and a large amount of biomass waste is produced every year. The output of crop straw in my country alone is about 700 million tons per year, and the amount of resources that can be used as energy is 280-350 million tons; the annual reasonable exploitation of fuelwood is about 158 million tons, and there are also a large number of aquatic plants. However, these resources have not been fully utilized so far, and they often pollute the environment due to incineration, which has become a national problem. Biomass is an environment-friendly resource, and the research, development and utilization of biomass energy have attracted widespread attention at home and abroad. Using biomass as a raw material to produce synthetic gas and hydrogen-rich gas through gasification to provide raw materials or energy is one of the methods for effectively utilizing biomass energy.

In the process of biomass gasification, tar is an inevitable by-product. Tar not only reduces the gasification efficiency but also easily blocks the gas pipeline, which makes the operation of gasification equipment difficult, especially for high-end applications such as fuel cell power generation and liquid fuel synthesis. field, the problem is more prominent.

Guan Hu et al reported a biomass gasification method using dolomite as a catalyst in Steam gasification of apricot stones with olivine and dolomite as downstream catalysts, although this method can significantly reduce the tar content in biomass gas, and dolomite is cheap However, due to the poor strength and fragility of dolomite, the service life is short and the pulverized powder is easy to cause blockage of the subsequent pipeline.

Therefore, seeking a modified dolomite and its preparation method can reflect the advantages of dolomite, which can not only promote the development of biomass catalytic gasification technology, but also help to improve the economy of biomass gasification process.

Contents of the invention

The technical problem to be solved in the present invention is to disclose a modified dolomite and its preparation method and application, so as to overcome the above-mentioned defects in the prior art and solve the problem that the dolomite is easy to powder in the biomass gasification process.

Design of the present invention:

Dolomite is cheap and easy to obtain, and has the advantage of high catalytic cracking efficiency of tar oil. However, dolomite has poor strength and is brittle, resulting in short service life and the pulverized powder is easy to cause blockage of subsequent pipelines. The inventors have found that the strength of dolomite can be increased by adding magnesium nitrate to dolomite to modify the dolomite. At the same time, due to the large molecule of tar, it is difficult to enter the micropores inside the catalyst, and it is easy to coke on the surface of the catalyst. Mesopores are added inside the modified dolomite, which increases the specific surface area of the catalyst and makes the tar with large molecules enter the mesoporous catalysis first. The cracked particles become small molecules and then enter the micropores, reducing the surface area carbon of dolomite and improving its catalytic cracking ability of tar oil.

Modified dolomite of the present invention, weight composition comprises:

MgO 1～10wt%, NiO 10～30wt%, dolomite 60～89wt%;

Preferably: MgO 1wt%, NiO 18wt%, dolomite 81wt%;

Method of the present invention comprises the steps:

(1) Calcining natural dolomite at 800-1000°C in air atmosphere for 8-12 hours, cooling, crushing into 100-120 mesh powder, adding water 3-5 times the weight of dolomite powder, and preparing dolomite suspension liquid;

(2) Add the dolomite suspension into the mixture of nickel nitrate aqueous solution and magnesium nitrate aqueous solution, stir for 1 to 2 hours, co-precipitate, stand still for 10 to 60 minutes, collect the precipitate, and put it at 100 to 130°C Baking for 10-12 hours, forming the dried precipitate into particles, and then calcining in an air atmosphere at 800-1000°C for 8-12 hours to obtain nickel/modified dolomite;

The concentration of nickel nitrate aqueous solution and magnesium nitrate aqueous solution is 0.5～2M;

The consumption of nickel nitrate aqueous solution is 4～30% of said precipitate by the weight of nickel oxide, and the consumption of nickel nitrate aqueous solution is 1～10% of said precipitate by the weight of magnesium oxide;

Preferably, in step (1), the 200-300 mesh active carbon of raw material dolomite powder weight 0.5～2%, mixes with said dolomite powder, then prepares the suspension of dolomite and active carbon, obtains nickel/medium Pore-modified dolomite catalysts.

The modified dolomite of the present invention can be used as a catalyst for biomass gasification.

The invention greatly improves the strength of the dolomite and its catalytic cracking ability of tar by adding magnesium nitrate to the dolomite to modify the dolomite and adding mesopores inside the modified dolomite. Thereby reducing the cost of the biomass catalytic gasification process, improving the economy of the process, and promoting the development of the biomass catalytic gasification technology.

Description of drawings

Figure 1 is a flow chart of a biomass gasification device.

Detailed ways

Below by embodiment the present invention will be further described, but do not affect protection scope of the present invention:

Example 1

(1) Calcining natural dolomite at 1000° C. for 12 hours in an air atmosphere, cooling, pulverizing into 120 mesh powder, adding water 5 times the weight of dolomite powder, and preparing dolomite suspension;

(2) Add 500g of dolomite suspension to the mixture of nickel nitrate aqueous solution and magnesium nitrate aqueous solution, stir for 2 hours, co-precipitate, stand still for 60 minutes, collect the precipitate, bake at 110°C for 12 hours, and dry the dried The precipitate is formed into particles by a molding machine, and then calcined for 12 hours at 1000°C in an air atmosphere to obtain nickel/modified dolomite;

The concentration of nickel nitrate aqueous solution and magnesium nitrate aqueous solution is 1M;

The consumption of nickel nitrate aqueous solution is 30% of said precipitate calcined by the weight of nickel oxide, and the consumption of magnesium nitrate aqueous solution is 10% of said precipitate calcined by the weight of magnesium oxide.

The weight composition of the nickel/modified dolomite that obtains is:

MgO 10wt%, NiO 30wt%, Dolomite 60wt%

Example 2

(1) Calcining natural dolomite at 800° C. for 8 hours in an air atmosphere, cooling, pulverizing into 100-mesh powder, adding water 3 times the weight of dolomite powder, and preparing dolomite suspension;

(2) Add 500g of dolomite suspension to the mixture of nickel nitrate aqueous solution and magnesium nitrate aqueous solution, stir for 1 hour, co-precipitate, stand still for 10 minutes, collect the precipitate, bake at 120°C for 10 hours, and dry the dried The precipitate is shaped into particles by a molding machine, and then calcined at 800°C for 8 hours in an air atmosphere to obtain nickel/modified dolomite;

The concentration of nickel nitrate aqueous solution and magnesium nitrate aqueous solution is 1M;

The consumption of nickel nitrate aqueous solution is 10% of said precipitate calcined by the weight of nickel oxide, and the consumption of magnesium nitrate aqueous solution is 1% of said precipitate calcined by the weight of magnesium oxide.

The weight composition of the nickel/modified dolomite that obtains is:

MgO 1wt%, NiO 10wt%, Dolomite 89wt%

Example 3

In step (1), with the 250 order active carbon of raw material dolomite powder weight 0.5%, mix with said dolomite powder, then prepare the suspension of dolomite and active carbon, adopt the same method of embodiment 1, obtain nickel/ Mesoporous modified dolomite catalyst.

Example 4

This experimental method has been described in detail in the Chinese patent previously applied for by the inventor, the publication number being CN1919722A, as follows:

The experimental device flow chart is as accompanying drawing 1, and the nickel/modified dolomite catalyst prepared by the method of embodiment 1 is put in the normal pressure fixed-bed catalytic reactor 3, and the height of catalyst is 30mm.

The raw material used for the reaction is: sawdust with a particle size of 40-60 mesh.

The sawdust enters the fluidized bed gasifier 1 and undergoes gasification reaction with the water vapor entering the fluidized bed gasifier 1. The gasification reaction temperature is 750°C, and the gasification reaction pressure (gauge pressure) is 30mmH ₂ O. The amount of wood chips added is 2.0kg/h; the mass ratio of water vapor to wood chips (S/B) is 1.5;

The residence time of water vapor in the fluidized bed is 3.0 seconds, and the residence time of wood chips in the fluidized bed reactor 1 is 6.0 seconds;

The vaporized gas discharged from the top of the fluidized bed reactor 1 enters the normal pressure fixed bed catalytic reactor 2 filled with catalyst, and the vaporized gas reacts with the incoming water vapor to obtain hydrogen, carbon monoxide, methane, carbon dioxide and trace amounts of Unsaturated hydrocarbon gas mixture, wherein the main components are hydrogen and carbon monoxide, the catalytic reaction temperature is 800°C, the catalytic pressure is 30mmH ₂ O (gauge pressure), and the residence time of the gas in the catalyst bed is 1.0 second;

The volume ratio of water vapor/gasification gas is 1.6;

The gas coming out of the catalytic reactor 2 is cooled to 400°C, and enters the medium shift reactor 3 and the low shift reactor 4, the reaction temperature of the medium temperature shift is 350°C, and the reaction temperature of the low temperature shift is 300°C, and the carbon monoxide component is shifted into hydrogen, and then collect hydrogen, wherein the hydrogen content (volume percentage) reaches 38.46%. After the catalyst operated continuously for 30 hours, the hydrogen content (volume percentage) only decreased by 2.6% between 30 hours and 35 hours.

Example 5

Except the nickel/mesoporous modified dolomite catalyst prepared by the method of Example 3, other process conditions were the same as in Example 4, and the hydrogen content (volume percentage) in the gas after the reaction reached 40.6%. After the catalyst was continuously operated for 30 hours, the hydrogen content (volume percentage) only decreased by 0.2% between 30 hours and 35 hours.

Claims (5)

1. a modification dolomite is characterized in that, weight is formed and comprised:

MgO 1～10wt%, NiO 10～30wt%, dolomite 60～89wt%.

2. modification dolomite according to claim 1 is characterized in that, preferred weight consists of: MgO 1wt%, NiO 18wt%, dolomite 81wt%.

3. prepare the method for claim 1 or 2 described modification dolomites, it is characterized in that, comprise the steps:

(1) natural dolomite is calcined 8～12h under 800～1000 ℃ in air atmosphere, cooling is ground into 100～120 order powder, adds the water of 3～5 times of dolomite powder weight, is mixed with the suspension of dolomite;

(2) with the suspension adding nickel nitrate aqueous solution of said dolomite and the mixture of magnesium nitrate aqueous solution, stirred 1～2 hour minute, co-precipitation, static 10～60 minutes, the collecting precipitation thing dried by the fire 10～12 hours down at 100～130 ℃, and the sediment of drying is shaped to particle, under 800～1000 ℃ of air atmospheres, calcined 8～12 hours then, promptly obtain nickel/modification dolomite;

The concentration of nickel nitrate aqueous solution and magnesium nitrate aqueous solution is 0.5～2M;

The consumption of nickel nitrate aqueous solution is counted said sedimentary 4～30% with the weight of nickel oxide, the consumption of magnesium nitrate aqueous solution counts said sedimentary 1～10% with magnesian weight.

4. method according to claim 3 is characterized in that, in step (1), 200-300 order active carbon with raw material dolomite powder weight 0.5～2%, mix with said dolomite powder, prepare the suspension of dolomite and active carbon then, obtain nickel/mesoporous modification dolomite catalyst.

5. the application of modification dolomite according to claim 1 and 2 is characterized in that, as catalyst for biomass gasification.

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