CN102757807B - Method for increasing tar yield in hydropyrolysis of coal by using ferric ammonium salt - Google Patents

Abstract

The invention relates to the technical field of hydropyrolysis of coal, in particular to a method for increasing tar yield in hydropyrolysis of coal by using a ferric ammonium salt. The method is carried out according to the following steps of: (1) adding a catalyst by an immersion method: uniformly mixing coal, a ferric ammonium salt catalyst (in term of ferrum) and distilled water according to a mass ratio of 100:1:150-100:7:300; keeping a mixture at a constant temperature of 30-80 DEG C for 8-16 h; and mechanically stirring the mixture at a stirring speed of 100-300 r/min during keeping the mixture at the constant temperature; the method for increasing the tar yield in the hydropyrolysis of the coal by using the ferric ammonium salt, provided by the invention, has the advantage of simple and easy process; the cheap ferric ammonium salt catalyst is adopted as the catalyst in the hydropyrolysis of the coal; and as the ferric ammonium salt is adopted as the catalyst in the hydropyrolysis of the coal in the process, the tar yield of the method can be greatly increased when compared with the hydropyrolysis of the coal, in which the catalyst is not added.

Description

Method for improving tar yield in coal hydropyrolysis with iron ammonium salt

technical field

The invention relates to the technical field of coal hydropyrolysis, and relates to a method for improving the yield of tar in coal hydropyrolysis with iron ammonium salt.

Background technique

Coal pyrolysis process is a method of extracting hydrogen-rich components in coal through pyrolysis under relatively mild conditions to make chemical raw materials or high-quality liquids, so as to improve coal utilization efficiency. However, the amount of tar produced by traditional coal pyrolysis is small, and the content of heavy components in the tar is high. In order to improve the yield and quality of tar, a third route between gasification and liquefaction—coal hydropyrolysis was proposed. The principle of this process is to saturate the free radicals produced by coal pyrolysis by adding hydrogen, avoiding the secondary reaction of mutual polymerization between free radicals, and combining free radicals with hydrogen to form light tar. Catalytic hydropyrolysis of coal is a method to increase the conversion rate of coal pyrolysis and the yield of tar under the action of a catalyst. Metals that can be used as catalysts include Fe, Ni, Co, SnCl ₂ , ZnCl ₂ , MoS ₂ , etc. Among them, MoS ₂ catalyst has the best catalytic effect.

On page 255 of the Fuel journal in volume 70 in 1991, Li Baoqing et al. used (NH ₄ ) ₂ MoS ₄ as a precursor to support MoS ₂ in situ as a catalyst, and heated it at a temperature of 5K/min at a pressure of 3Mpa. At 650 °C, under the condition of loading 0.5% Mo, the tar yield of coal hydropyrolysis increased by 35 percentage points, which was 3.3 times that of non-catalytic hydropyrolysis under the same conditions. But (NH ₄ ) ₂ MoS ₄ is expensive, and the current average price in the market is about 200 yuan/gram. Under the current international oil price, it has no industrial application value.

On page 119 of the journal Fuel Process.Technol. Volume 62 in 2000, Miura believed that in order to increase the tar yield in the coal pyrolysis process, there should be enough methyl and hydrogen free radicals before the mutual polymerization of the pyrolytic free radicals. , proposed coal-methanol mixture (CMM) pyrolysis. Methanol can swell coal at room temperature, hoping to achieve the efficient transfer of methyl and hydrogen radicals in coal particles to achieve the purpose of stabilizing free radicals; the experimental results show that the tar yield reaches 23% when CMM is rapidly pyrolyzed at 750 °C, It is 1.6 times of the rapid pyrolysis of raw coal. However, although the heating rate is greater than 1000K/s, this condition is quite harsh, the energy consumption is large, the equipment requirements are high, and it is difficult to realize industrialization.

In page 1583 of Fuel Journal, Vol. 63, 1984, Kandiyoti et al. supported ZnCl ₂ on a coal sample, and carried out pyrolysis reaction under an inert atmosphere. It was found that in the slow pyrolysis process, the yield of semi-coke was higher, but the yield of tar decreased; on the contrary, in the process of fast pyrolysis, the yield of tar was greatly increased. Although the heating rate is greater than 1000K/s, this condition is quite harsh, the energy consumption is large, the equipment requirements are high, and it is difficult to realize industrialization.

The Chinese patent literature with publication number CN1224043A discloses a method for increasing oil and reducing water during coal pyrolysis and coking. Under coke oven gas atmosphere, Yanzhou bituminous coal with 5% polyethylene was subjected to pyrolysis test, and the results were found to be Under the coke oven gas atmosphere with a total pressure of 5MPa and a flow rate of 1L/min, the tar yield under the condition of heating to 650°C at a heating rate of 10°C/min and constant temperature for 10 minutes is the same as that under the _H2 atmosphere 1.2 times (Chinese invention patent ZL 98104732.7). Higher pressure is used in this method, and the increase of pressure means the increase of equipment investment cost.

The Chinese patent literature with publication number CN1664069A disclosed that Hu Haoquan and others conducted a coal pyrolysis test on a reactor with a coal seam in the upper layer and a catalyst layer in the lower layer and found that when the reaction gas was 400ml/min CH ₄ and 100ml/min O ₂ , When the pyrolysis temperature is 700°C and the pressure is 2MPa, the tar yield of Yanzhou coal is 1.7 times that of the tar yield under the same conditions under the _H2 atmosphere (Chinese invention patent ZL200510045853.8). The improvement of the equipment means the increase of equipment investment cost. At the same time, the coupling technology with more complicated process is used, which increases the unstable factors of equipment operation, which is not conducive to the realization of industrialization.

To sum up, as far as the pyrolysis process aimed at increasing the tar yield is concerned, the existing process is relatively complicated and the reaction conditions are harsh. Although it can greatly increase the tar yield, it is more difficult for industrial applications.

Contents of the invention

The present invention provides a method for improving the tar yield in coal hydropyrolysis with iron ammonium salt, which overcomes the deficiencies of the above-mentioned prior art, and can effectively solve the problems of expensive catalyst, relatively complicated existing process and harsh reaction conditions. problem, its tar yield can be greatly improved.

One of technical scheme of the present invention is realized by following measure: a kind of iron ammonium salt improves the method for tar yield in coal hydropyrolysis, and this method is carried out according to the following steps:

In the first step, the impregnation method is used to add the catalyst:

(1) Coal, iron ammonium salt catalyst (calculated as iron) and distilled water are mixed evenly at a mass ratio of 100:1:150 to 100:7:300, and kept at a temperature of 30°C to 80°C for 8 hours to 16h, with mechanical stirring at constant temperature, the stirring rate is 100 r/min to 300 r/min;

(2) Vacuum drying is carried out after impregnation, and the coal sample is obtained after vacuum drying. The temperature of vacuum drying is 60°C to 120°C, the degree of vacuum is 0.02MPa to 0.08MPa, and the drying time is 12h to 36h;

(3) Transfer the coal sample obtained after drying to a desiccator for storage;

The second step, coal hydropyrolysis reaction:

(1) Take the coal sample stored in the first step (3), put it into the fixed bed reactor, feed hydrogen with a purity volume percentage greater than 99% into the fixed bed reactor, and adjust the flow rate of hydrogen to 100mL/min After reaching 500mL/min, flush the fixed-bed reaction system with hydrogen at this flow rate for 5 minutes. Under normal pressure, increase the temperature at a rate of 5°C/min to 30°C/min to 400°C to 700°C and then keep the temperature for 30 minutes. After the constant temperature is completed, the heating furnace of the fixed-bed reactor is opened to allow the fixed-bed reactor to cool down to room temperature naturally;

(2) The pyrolysis product produced by the reaction in the fixed bed reactor in the second step (1) is condensed by a cold trap at -14°C to -17°C to obtain a liquid product;

 The third step, separation of tar and water and yield calculation:

Tar was separated from the liquid product obtained in the second step (2) by ASTM D95-05 ^el (2005).

Below is the further optimization or/and improvement to above-mentioned technical scheme of the invention:

The above-mentioned iron ammonium salt catalyst may be any one of commercially available (NH ₄ ) ₂ Fe(SO ₄ ) ₂ ·6H ₂ O and NH ₄ Fe(SO ₄ ) ₂ ·12H ₂ O.

The coal mentioned above can be any one of Tiechanggou coal and Nantaizi coal.

The process of the present invention is simple and easy. By using cheap iron ammonium salt as a catalyst in coal hydropyrolysis, the process uses iron ammonium salt as a catalyst to carry out coal hydropyrolysis, which is different from coal hydrothermal pyrolysis without catalyst. Compared with the solution, the tar yield can be greatly improved.

Detailed ways

The present invention will be further described below in conjunction with embodiment:

Embodiment 1, the method that this iron ammonium salt improves the tar yield in coal hydropyrolysis, carries out according to the following steps:

In the first step, the impregnation method is used to add the catalyst:

(1) Tiechanggou coal, iron ammonium salt (calculated as iron) and distilled water are mixed evenly at a mass ratio of 100:1:150 to 100:7:300, and kept at a constant temperature at a temperature of 30°C to 80°C 8h to 16h, with mechanical stirring at constant temperature, the stirring rate is 100 r/min to 300 r/min; the iron ammonium salt catalyst is (NH ₄ ) ₂ Fe(SO ₄ ) ₂ ·6H ₂ O;

(2) Vacuum drying is carried out after impregnation, and the coal sample is obtained after vacuum drying. The temperature of vacuum drying is 60°C to 120°C, the degree of vacuum is 0.02MPa to 0.08MPa, and the drying time is 12h to 36h;

(3) Transfer the coal sample obtained after drying to a desiccator for storage;

The second step, coal hydropyrolysis reaction:

(1) Take the coal sample stored in the first step (3), put it into the fixed bed reactor, feed hydrogen with a purity volume percentage greater than 99% into the fixed bed reactor, and adjust the flow rate of hydrogen to 100mL/min After reaching 500mL/min, flush the fixed-bed reaction system with hydrogen at this flow rate for 5 minutes. Under normal pressure, increase the temperature at a rate of 5°C/min to 30°C/min to 400°C to 700°C and then keep the temperature for 30 minutes. After the constant temperature is completed, the heating furnace of the fixed-bed reactor is opened to allow the fixed-bed reactor to cool down to room temperature naturally;

(2) The pyrolysis product produced by the reaction in the fixed bed reactor in the second step (1) is condensed by a cold trap at -14°C to -17°C to obtain a liquid product;

 The third step, separation of tar and water and yield calculation:

Use ASTM D95-05 ^el (2005) method to separate tar from the liquid product obtained in the second step (2); the basis for calculating the yield of tar is dry ash-free base abbreviated as daf; the yield of tar obtained is 14.8wt %daf to 21.2 wt% daf with an average tar yield of 16.5 wt% daf.

Example 2, the difference from Example 1 is that the iron ammonium salt catalyst uses NH ₄ Fe(SO ₄ ) ₂ 12H ₂ O, and the tar yield obtained is 14.8wt%daf to 17.4wt%daf, and the tar yield The average value of 16.2wt%daf.

Example 3, the difference from Example 1 is that the coal is Nantaizi coal, the tar yield is 15.6wt%daf to 21.2wt%daf, and the average tar yield is 18.2wt%daf.

Example 4 differs from Example 2 in that the coal is Nantaizi coal, and the tar yield is 15.3wt%daf to 18.6wt%daf, and the average tar yield is 16.7wt%daf.

Embodiment 5, the method that this iron ammonium salt improves the tar yield in coal hydropyrolysis, carries out according to the following steps:

In the first step, the impregnation method is used to add the catalyst:

(1) (NH ₄ ) ₂ Fe(SO ₄ ) ₂ 6H ₂ O was used as the catalyst for iron ammonium salt. Iron meter) and distilled water were mixed uniformly in a beaker according to the mass ratio of 100:5:200, placed in a constant temperature water bath at 40°C for 12 hours, mechanically stirred while maintaining the temperature, and the stirring rate was 200 r/min;

(2) After impregnation, move it to an evaporating dish, put it in a vacuum drying oven to dry for 24 hours, and obtain a coal sample after vacuum drying. The temperature of vacuum drying is 105°C, and the vacuum degree is 0.08MPa;

(3) Transfer the coal sample obtained after drying to a desiccator for storage;

The second step, coal hydropyrolysis reaction:

(1) Take the coal sample stored in the first step (3), put it into the fixed bed reactor, pass hydrogen gas with a purity volume percentage greater than 99% into the fixed bed reactor, and adjust the flow rate of hydrogen to 400mL/min Finally, flush the fixed-bed reaction system with the hydrogen gas under the flow rate for 5 minutes. Open the fixed bed reactor to cool down to room temperature naturally;

(2) The pyrolysis product produced by the reaction in the fixed bed reactor is condensed by a cold trap at -16°C to obtain a liquid product;

The third step, separation of tar and water and yield calculation:

The tar and water in the liquid product were separated by ASTM D95-05 ^el (2005), and the tar yield was 17.9wt%daf.

Embodiment 6, this iron ammonium salt improves the method for the tar yield in coal hydropyrolysis, carries out according to the following steps:

In the first step, the impregnation method is used to add the catalyst:

(1) NH ₄ Fe(SO ₄ ) ₂ ·12H ₂ O was used as the catalyst for iron ammonium salt. The selected coal was Tiechanggou coal, 10g of coal was used for the experiment, Tiechanggou coal, iron ammonium salt catalyst (calculated as iron) Mix with distilled water in a beaker according to the mass ratio of 100:5:200, put it in a constant temperature water bath at 40°C for 12 hours, and mechanically stir at the same time, the stirring rate is 200 r/min;

(2) After impregnation, move it to an evaporating dish, put it in a vacuum drying oven to dry for 24 hours, and obtain a coal sample after vacuum drying. The temperature of vacuum drying is 105°C, and the vacuum degree is 0.08MPa;

(3) Transfer the coal sample obtained after drying to a desiccator for storage;

The second step, coal hydropyrolysis reaction:

(1) Take the coal sample stored in the first step (3), put it into the fixed bed reactor, pass hydrogen gas with a purity volume percentage greater than 99% into the fixed bed reactor, and adjust the flow rate of hydrogen to 400mL/min Finally, flush the fixed-bed reaction system with the hydrogen gas under the flow rate for 5 minutes. Open the fixed bed reactor to cool down to room temperature naturally;

(2) The pyrolysis product produced by the reaction in the fixed bed reactor is condensed by a cold trap at -16°C to obtain a liquid product;

The third step, separation of tar and water and yield calculation:

The tar and water in the liquid product were separated by ASTM D95-05 ^el (2005), and the tar yield was 17.4wt%daf.

Embodiment 7, the method that this iron ammonium salt improves the tar yield in coal hydropyrolysis, carries out according to the following steps:

In the first step, the impregnation method is used to add the catalyst:

(1) (NH ₄ ) ₂ Fe(SO ₄ ) ₂ ·6H ₂ O was used as the catalyst of iron ammonium salt. ) and distilled water were mixed evenly in a beaker according to the mass ratio of 100:3:200, placed in a constant temperature water bath at 40°C for 12 hours, mechanically stirred while maintaining the temperature, and the stirring rate was 200 r/min;

(2) After impregnation, move it to an evaporating dish, put it in a vacuum drying oven to dry for 24 hours, and obtain a coal sample after vacuum drying. The temperature of vacuum drying is 105°C, and the vacuum degree is 0.08MPa;

(3) Transfer the coal sample obtained after drying to a desiccator for storage;

The second step, coal hydropyrolysis reaction:

(1) Take the coal sample stored in the first step (3), put it into the fixed bed reactor, pass hydrogen gas with a purity volume percentage greater than 99% into the fixed bed reactor, and adjust the flow rate of hydrogen to 90mL/min Finally, flush the fixed-bed reaction system with the hydrogen gas under the flow rate for 5 minutes. Open the fixed bed reactor to cool down to room temperature naturally;

(2) The pyrolysis product produced by the reaction in the fixed bed reactor is condensed by a cold trap at -16°C to obtain a liquid product;

The third step, separation of tar and water and yield calculation:

The tar and water in the liquid product were separated by ASTM D95-05 ^el (2005) method, and the yield of tar obtained was 21.2wt%daf.

The coal kind used in the present invention is any one in Tiechanggou coal or Nantaizi coal, just for the convenience of drawing materials, but not limited to Tiechanggou coal or Nantaizi coal.

The Tiechanggou coal in the present invention is the coal type of Tiechanggou Coal Mine of Shenhua Xinjiang Energy Co., Ltd.

The Zhongnantaizi coal of the present invention is the coal type of the Nantaizi Coal Mine of the Fourth Agricultural Division Revitalization General Factory.

The industrial analysis and elemental analysis of China Iron Factory Coal and Nantaizi Coal in the present invention are shown in Table 1.

When there is no catalyst, the coal used is Tiechanggou coal, the coal used in the experiment is 10g, the pyrolysis conditions are temperature 600°C, constant temperature 30min, pressure is normal pressure, hydrogen flow rate 400ml/min, open the heating furnace and allow it to cool naturally to room temperature ; The pyrolysis product from the fixed bed reactor is condensed by a cold trap at -16°C to condense the liquid product, and the solid semi-coke and liquid product are obtained by subtracting the mass difference between the reaction tube and the cold trap before and after the reaction; ASTM D95-05 ^el (2005) method separates tar and water in the liquid product; The tar yield that obtains is 14.2wt%daf; The tar yield of comparative example 1 to embodiment 7 can find out, after using iron ammonium salt catalyst, tar yield It has been greatly improved, and the average market price of ferric ammonium salt is about 8 yuan/kg, which saves costs compared with the use of expensive catalysts.

When there is no catalyst, the coal used is Nantaizi coal, and the coal used in the experiment is 2g. The pyrolysis conditions are temperature 650°C, constant temperature 30min, pressure is normal pressure, hydrogen flow rate 90ml/min, and the heating furnace is opened to allow it to cool naturally to room temperature; The pyrolysis product from the fixed-bed reactor is condensed by a cold trap at -16°C, and the solid semi-coke and liquid product are obtained by subtracting the mass difference between the reaction tube and the cold trap before and after the reaction; ASTM D95-05 ^el ( 2005) method to separate tar and water in the liquid product; the tar yield obtained is 14.8wt%daf; the tar yield of comparative example 1 to embodiment 7 can be found out, after using the iron ammonium salt catalyst, the tar yield obtains It has been greatly improved, and the average market price of ferric ammonium salt is about 8 yuan/kg, which saves costs compared with the use of expensive catalysts.

Claims (3)

1. a kind of iron ammonium salt improves the method for tar yield in coal hydropyrolysis, it is characterized in that the method is carried out according to the following steps: In the first step, the impregnation method is used to add the catalyst: (1) Coal, ferric ammonium salt catalyst measured by iron and distilled water are mixed evenly at a mass ratio of 100:1:150 to 100:7:300, and kept at a constant temperature for 8h to 16h at a temperature of 30°C to 80°C , with mechanical stirring at constant temperature, the stirring rate is 100 r/min to 300 r/min; (2) Vacuum drying is carried out after impregnation, and the coal sample is obtained after vacuum drying. The temperature of vacuum drying is 60°C to 120°C, the degree of vacuum is 0.02MPa to 0.08MPa, and the drying time is 12h to 36h; (3) Transfer the coal sample obtained after drying to a desiccator for storage; The second step, coal hydropyrolysis reaction: (1) Take the coal sample stored in the first step (3), put it into the fixed bed reactor, feed hydrogen with a purity volume percentage greater than 99% into the fixed bed reactor, and adjust the flow rate of hydrogen to 100mL/min After reaching 500mL/min, flush the fixed-bed reaction system with hydrogen at this flow rate for 5 minutes. Under normal pressure, increase the temperature at a rate of 5°C/min to 30°C/min to 400°C to 700°C and then keep the temperature for 30 minutes. After the constant temperature is completed, the heating furnace of the fixed-bed reactor is opened to allow the fixed-bed reactor to cool down to room temperature naturally; (2) The pyrolysis product produced by the reaction in the fixed bed reactor in the second step (1) is condensed by a cold trap at -14°C to -17°C to obtain a liquid product; The third step, separation of tar and water and yield calculation: Tar was separated from the liquid product obtained in the second step (2) by ASTM D95-05 ^el method. 2. The method for improving the tar yield in coal hydropyrolysis by iron ammonium salt according to claim 1, characterized in that the iron ammonium salt catalyst is commercially available (NH ₄ ) ₂ Fe(SO ₄ ) ₂ 6H ₂ Any one of O and NH ₄ Fe(SO ₄ ) ₂ ·12H ₂ O. 3. according to claim 1 and 2 described iron ammonium salts improve the method for tar yield in coal hydropyrolysis, it is characterized in that coal adopts any one in Tiechanggou coal and Nantaizi coal.