CN1579614A - Method for preparing active carbon base material SO2 adsorbent - Google Patents

Abstract

The invention discloses a method for preparing activated carbon-based material _SO2 adsorbent, which is characterized in that carbon-containing materials such as lignite semi-coke or anthracite, bituminous coal semi-coke are firstly modified by pressurized hydrothermochemistry, and then by 30-65% HNO ₃ or HF, H ₂ SO ₄ oxidation treatment, and finally activation under N ₂ atmosphere. The present invention is characterized by wide sources of carbon-based materials such as semi-coke and low price, and the prepared adsorbent can be regenerated and recycled repeatedly, and can finally be used for waste water treatment or boiler fuel without secondary pollution. It can be widely used in the desulfurization and purification of flue gas from coal-fired power plants, coal-fired boilers and coal-fired kilns in environmental protection industries.

Description

A kind of method for preparing active carbon-based material SO2 adsorbent

technical field

The present invention relates to a kind of preparation method of gas purification and desulfurization agent in coal-fired power plant, coal-fired boiler and coal-fired kiln and other flue gas desulfurization purification environmental protection industry, more specifically a kind of activated carbon-based material _SO2 adsorbent preparation method.

Background technique

Coal accounts for 69% of my country's energy consumption structure. The massive combustion of coal has caused soot-type pollution to the national atmosphere. Especially since the 1980s, with the rapid development of China's economy, coal consumption has increased day by day, and SO ₂ emissions have continued to increase, resulting in serious air pollution. According to statistics, China's SO ₂ emission _was 15.3 million tons in 1985, increased to 23.7 million tons in 1995, and 25.9 million tons in 2000. Due to the massive discharge of SO ₂ , the ecological environment is destroyed, and the phenomenon of acid rain is serious. At present, the area of acid rain in my country has accounted for 40% of the country's land area, and the average acidity of precipitation across the country has increased by 2-8 times. It is rare in the world that the pH value of precipitation is lower than 4. The economic loss caused by acid rain deposition to agriculture, forestry and materials is as high as more than 100 billion yuan per year (the World Bank estimates it as 500 billion yuan). So, to prevent further aggravation of _SO2 atmospheric pollution. Based on national conditions, the development of flue gas desulfurization technologies suitable for different scales has become the main task at present and for a long time in the future.

According to China's sustainable development strategy and "China's 21st Century Agenda", at the beginning of this century, the total emission of SO ₂ in the country shall not exceed 23.7 million tons in 1995. However, as far as the current flue gas desulfurization technology is concerned, its investment and operating costs are high and difficult to promote. As a result, although the environmental protection department will increase the fines for SO ₂ emissions year by year, it cannot fundamentally provide relevant technologies to solve it. At present, there are about a dozen flue gas desulfurization technologies that have been industrialized and are being studied at home and abroad. These methods can be divided into dry methods and wet methods in terms of technology, and can be divided into abandonment methods and recovery methods in terms of recycling of desulfurizers . Among them, the main methods that have been industrialized or pilot-tested are: 1) ammonium sulfite method; 2) citrate method; 3) activated carbon wet desulfurization; 4) wet desulfurization to produce phosphorus and ammonium compound fertilizer; 5) electron beam desulfurization ; 6) Lime-gypsum desulfurization, etc. The above methods either have large investment and high operating costs, or the waste desulfurizer cannot be used after desulfurization, causing secondary pollution. For large-capacity boilers in power plants, the stacking of waste slag is restricted by freight costs or limited by site stacking, all of which affect desulfurization. A key factor in the commercialization of technology. Therefore, these technologies are currently difficult to promote and use on a large scale in our country. Among them, the flue gas desulfurization technology lime-gypsum method, which has been commercially applied on a large scale in the world, has a high degree of technological maturity. There are also power plants in my country that have introduced it. However, due to high cost, large investment, and by-product gypsum, there is no comprehensive utilization and no success. At present, most researchers believe that the modified active semi-coke has the most development prospect.

Research on the removal of SO ₂ from flue gas by activated carbon-based materials such as activated semi-coke has been very active at home and abroad. Li Wenhua from the Beijing Coal Chemical Research Institute of the Domestic Coal Research Institute, Liu Changjian from the Chemical Metallurgy Institute of the Chinese Academy of Sciences, and Japan’s Hitachi Manufacturing Co., Ltd. Kenichi Gomi, Takeyong Komuro, etc. have done a lot of research work and achieved some results, but they all use traditional activated carbon production methods (high temperature water or oxygen activation) to modify semi-coke, resulting in limited modification of chemical properties. At the same time, the carbon loss is large (up to 40%) and the cost is high.

Contents of the invention

Aiming at the shortcomings of the preparation of the above-mentioned activated carbon-based materials, the object of the present invention is to provide a method for preparing an efficient, inexpensive and reusable activated carbon-based material _SO2 adsorbent.

A method for preparing activated carbon-based material _SO2 adsorbent, characterized in that carbonaceous materials such as lignite semi-coke or anthracite, bituminous coal semi-coke are first modified by pressurized hydrothermochemistry, and then passed through 30-65% _HNO3 or HF, H ₂ SO ₄ oxidation treatment, and finally activation under N ₂ atmosphere; this method can also impregnate CuSO ₄ with equal volume after acid oxidation treatment, and then activate under N ₂ atmosphere. The carbon-containing materials such as lignite semi-coke or anthracite and bituminous coal semi-coke have a bulk density of 0.5-0.7g/ml, a specific surface area of ^10-200m2 /g, a carbon content of 70-85%, and a hydrogen content of 0.5 -2.5%, oxygen content 10-30%, nitrogen content 0.3-1.2%, moisture content 2-9%, ash content 3-15%, volatile matter content 6-18%.

The preparation process is as follows: the semi-coke that meets the above physical and chemical conditions is screened to obtain 4-10 mesh particles, the semi-coke particles and water are mixed at a volume ratio of 1:0.6-1.2, and then put into a high-pressure reactor. React at 6-43atm for 1-8h, take it out after natural cooling, then dry the semi-coke at 100-120°C for 2h, then use 30-65% HNO ₃ or HF, H ₂ SO in a reflux device at 45-90°C ₄ Oxidation treatment for 1-8 hours, washed with water to neutrality and then dried at 110°C for 2 hours, then impregnated with CuSO ₄ in an equal volume so that the amount of CuO accounts for 0.5-10% of the total weight of the semi-coke, and left for 24 hours, then emptied at 500-700°C It can be obtained by roasting in 50-5000h ^-1 N ₂ atmosphere for 1-8h activation.

The activity and sulfur capacity tests of the adsorbent were carried out in a fixed-bed glass reactor with an inner diameter of 20 mm, a desulfurizer of 4-8 mesh, a filling volume of 25 ml, and a reactor bed height of 100 mm to remove SO ₂ The temperature is 60-160°C, the space velocity is 550-1500h ^-1 , the particle/pipe diameter ratio is 0.1-0.13, and the flue gas composition is SO ₂ 1500-2200ppm, O ₂ 5%, H ₂ O 0-8%, and the rest Balanced by _N2 . The sulfur capacity is the cumulative sulfur capacity calculated when the desulfurization rate is equal to 90%.

The present invention is characterized by wide sources of carbon-based materials such as semi-coke and low price, and the prepared adsorbent can be regenerated and recycled repeatedly, and can finally be used for waste water treatment or boiler fuel without secondary pollution. It can be widely used in the desulfurization and purification of flue gas from coal-fired power plants, coal-fired boilers and coal-fired kilns in environmental protection industries. As we all know, the last century was the century of "silicon materials", and this century is likely to be the century of "carbon materials". Therefore, the present invention has broad application prospects.

Detailed ways

The present invention will be described in detail below by way of examples.

Example 1:

Mix the 4-10 mesh particles obtained after semi-coke sieving with water at a volume ratio of 1:0.83, then put them into a high-pressure reactor, and react at a temperature of 150-270°C and a pressure of 8, 10, 12, 14 and 43 atm respectively 4h, take it out after natural cooling, and then measure its specific surface area, pore volume and desulfurization activity. The results are shown in Table 1.

Table 1. Specific surface area _and

The change of pore volume and its influence on breakthrough time and sulfur capacity

Sample Raw Semi-coke 8atm 10atm 12atm 14atm 43atm

Specific surface area m ² /g 49.19 1115.84 610.35 414.74 510.63 482.64

Pore volume ml/g 0.0351 0.4593 0.3412 0.1310 0.2470 0.3214

Penetration time h 1.5 3.8 3.9 4.2 5.2 5.5

Sulfur capacity gSO ₂ /100gC 0.68 2.68 2.75 3.10 3.33 3.47

Experimental conditions: temperature: 85°C; space velocity: 900-1000h ^-1 ; SO ₂ concentration: 1700-2100ppm;

O ₂ : ~5%; H ₂ O (g): 6-10%.

Example 2:

The modified semi-coke obtained according to the preparation method described in Example 1 was oxidized with 45% HNO ₃ for 2 hours, washed with water until neutral, and then dried at 110°C for 2 hours, and then at 700°C with a space velocity of 2000h ^-1 N ₂ It is obtained by calcination treatment in the atmosphere for 2h activation. Then its desulfurization activity was measured. The results are shown in Table 2.

Table 2. Breakthrough time of semi-coke after pressurized hydrothermochemical modification, _HNO3 modification and 700 °C _N2 activation

and sulfur capacity changes

Sample Raw Semi-coke 8atm 10atm 12atm 14atm 43atm

Penetration time h 1.5 11.5 14 15 15.5 15.9

Sulfur capacity gSO ₂ /100gC 0.68 8.27 9.37 12.76 12.50 12.84

Experimental conditions: temperature: 85°C; space velocity: 900-1000h ^-1 ; SO ₂ concentration: 1700-2100ppm

O ₂ : ~5%; H ₂ O(g): 6-10%

It can be seen that after the pressurized hydrothermochemically modified semi-coke is modified by HNO ₃ and activated by 700°C N ₂ , the sulfur capacity can be increased by 11-18 times, and the breakthrough time is extended by nearly 14 hours.

Example 3:

According to the preparation method described in Example 2, the activated carbon-based material _SO2 adsorbent (this adsorbent is prepared under 12 atm) is used for desulfurization/regeneration experiment with two towers connected in series, and the results are shown in Table 3.

Table 3. Relationship between regeneration times and breakthrough time and sulfur capacity of activated carbon-based material _SO2 flue gas adsorbent

Sample once once twice twice three times four times five times

Penetration time 35 23 21 20 21

Sulfur capacity gSO ₂ /100gC 24.30 18.48 14.03 14.31 14.27

Regeneration conditions: Soak with equal volume of distilled water at 85°C and wash repeatedly until the pH value is close to 7.

It can be seen that after five desulfurization regenerations, the desulfurization activity has not decreased significantly. It shows that the carbon-based material SO ₂ adsorbent has great desulfurization potential.

Example 4:

The bulk density is 0.5-0.7g/ml, the specific surface area is 10-200m ² /g, the carbon content is 70-85%, the hydrogen content is 0.5-2.5%, the oxygen content is 10-30%, and the nitrogen content is 0.3-1.2 %, the moisture content is 2-9%, the ash content is 3-15%, and the volatile content is 6-18%. Mix it with water at a volume ratio of 1:0.83, put it into a high-pressure reactor, react at 270°C and 43atm for 8 hours, take it out after natural cooling, then dry the semi-coke at 100°C for 2 hours, and then use 45% Oxidation treatment with HNO ₃ for 4 hours, washing with water to neutrality, drying at 110°C for 2 hours, then impregnating CuSO ₄ with an equal volume so that the amount of CuO accounted for 2.0% of the total weight of the modified semi-coke, and standing for 24 hours, followed by 100 hours at a space velocity of 700°C ^-1 N ₂ atmosphere roasting treatment 0.5h activated and made. The inner diameter of the reactor is 20mm, the desulfurizer is 4-8 mesh, the desulfurizer filling volume is 25ml, the weight is 12-15g, the reactor bed height is 100mm, the _SO2 removal temperature is 60-160℃, and the space velocity is _{Activated carbon} ^- _{based _} The material _SO2 adsorbent has a breakthrough time of 17 hours and a breakthrough sulfur capacity of 9.5%.

Embodiment 5 (industrial side stream embodiment):

According to the method in the above-mentioned Example 1, expand the equipment and output, and use it for a side-flow test of a gangue power plant flue gas desulfurization plant. The reactor diameter is 70 mm, the filling volume is 1 liter, the weight is 581 grams, and the desulfurization temperature is 60-160 ° C. , the space velocity is 550-1500h ^-1 , the flue gas composition is SO ₂ 500-2600ppm, O ₂ 9.5-14.8%, CO 75-435ppm, and the rest is CO ₂ and N ₂ conditions, to obtain activated semi-coke-based material SO ₂ The breakthrough time of the adsorbent is 36 hours, and the breakthrough sulfur capacity is 21.0%. The desulfurization effect is higher than that of the laboratory, because the test parameters of the industrial side flow test device are more ideal than those of the laboratory.

Claims (4)

1. A method for preparing active carbon-based material SO2 adsorbent, characterized in that lignite semi-coke or anthracite, bituminous coal semi-coke are first modified by pressurized hydrothermochemistry, then by 30-65% HNO ₃ or HF, H ₂ SO ₄ oxidation treatment, and finally activation under N ₂ atmosphere. 2. The method for preparing the adsorbent according to claim 1, characterized in that the lignite semi-coke or anthracite and bituminous coal semi-coke have a bulk density of 0.5-0.7g/ml and a specific surface area of ^10-200m2 /g , carbon content is 70-85%, hydrogen content is 0.5-2.5%, oxygen content is 10-30%, nitrogen content is 0.3-1.2%, moisture content is 2-9%, ash content is 3-15%, volatile Min content is 6-18%. 3. The preparation method of the adsorbent according to claim 1, characterized in that after acid oxidation treatment, CuSO ₄ is impregnated in equal volume, and then activated under N ₂ atmosphere. 4. The preparation method of the adsorbent according to claim 1 or 3, characterized in that the semi-coke is sieved to obtain 4-10 mesh particles, and the semi-coke particles and water are mixed in a volume ratio of 1:0.6-1.2 Put into a high-pressure reactor, react at 150-270°C, 6-43atm for 1-8h, take it out after natural cooling, then dry the semi-coke at 100-120°C for 2h, then use 30- 65% HNO ₃ or HF, H ₂ SO ₄ oxidation treatment for 1-8 hours, washed with water to neutral and then dried at 110°C for 2 hours, then impregnated with CuSO ₄ in equal volume, so that the amount of CuO accounts for 0.5-10% of the total weight of semi-coke, And put it aside for 24 hours, and then activate it by firing in an atmosphere of 500-700°C with a space velocity of 50-5000h ^-1 N ₂ for 1-8h.