A method for preparing biomass fuel based on pulping black liquor and papermaking sludge and its application

Abstract

The present invention belongs to the technical field of biomass fuel, and specifically relates to a method for preparing biomass fuel based on pulping black liquor and papermaking sludge and its application. The preparation method comprises the following steps: (1) adding a mixed bacterial agent to pulping black liquor, mixing evenly, aerobically fermenting, obtaining pulping black liquor fermentation product, concentrating the pulping black liquor fermentation product, and obtaining pulping black liquor material; (2) adding composite bacillus to papermaking sludge, mixing evenly, and fermenting in a fermentation tank to obtain papermaking sludge fermentation product; concentrating the papermaking sludge fermentation product, and then pulverizing to obtain papermaking sludge material; (3) mixing the pulping black liquor material and the papermaking sludge material evenly to obtain a mixed material, granulating, and obtaining a biomass fuel based on pulping black liquor and papermaking sludge. The biomass fuel prepared by the present invention completely uses papermaking waste, does not need to add other fuel components, and has excellent physical and chemical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass fuels, and in particular relates to a method for preparing biomass fuel based on pulping black liquor and papermaking sludge and application thereof. Background Art

[0002] Pulping night and papermaking sludge are two important by-products in the papermaking industry, which come from the pulping and papermaking processes respectively. Pulping night mainly comes from the alkaline or kraft pulping process. Wood cellulose is separated for papermaking, while the remaining lignin and hemicellulose are dissolved in the cooking liquid to form a black liquid, namely pulping night. The direct discharge of untreated pulping night will cause serious pollution to water bodies, leading to problems such as water quality deterioration and ecosystem damage. Papermaking sludge is a solid waste generated in the papermaking process, mainly from sediments and filtrates in the sewage treatment system and waste residues generated during pulping and washing. If untreated papermaking sludge is directly discharged or landfilled, it may cause pollution to soil, water bodies and air, especially the heavy metals and harmful chemicals therein.

[0003] Pulping black liquor and papermaking sludge are directly discharged into the sewage treatment system, but since pulping black liquor contains a large amount of solids, it will cause an increase in the amount of sludge produced in the sewage system, increasing the water treatment load; in addition, since pulping black liquor contains a large amount of water pollutants, especially the COD content is very high, if it is directly discharged into the sewage system, it will greatly increase the amount of reagents added, thereby greatly increasing the treatment cost. At present, in order to treat this type of wastewater, many papermaking companies usually use alkali recovery equipment with high investment costs and low returns to separate calcium salts and sodium salts. This method also has high investment costs and low returns.

[0004] As global energy demand continues to rise, the desire for renewable energy and environmental protection is also growing. As a sustainable form of energy, biomass fuel shows great development potential and market prospects. Pulping black liquor itself contains lignin and carbon, etc., and has a good combustion value; paper sludge mainly comes from fibers and ash and other substances lost with white water during the pulping and papermaking process, and also has a high calorific value. However, in the existing technology, paper sludge is usually processed and prepared together with other fuel components, but this requires purchasing raw materials from outside, which will further increase the processing cost of papermaking enterprises.

[0005] Therefore, there is an urgent need for a method for preparing biomass fuel based on pulping black liquor and papermaking sludge and its application. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing biomass fuel based on pulping black liquor and papermaking sludge and its application.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing biomass fuel based on pulping black liquor and papermaking sludge comprises the following steps:

[0009] (1) adding a mixed bacterial agent to pulping black liquor, mixing evenly, aerobically fermenting at 30-35° C. for 5-7 days to obtain a pulping black liquor fermentation product, and concentrating the pulping black liquor fermentation product to obtain a pulping black liquor material;

[0010] (2) adding composite Bacillus to papermaking sludge, mixing evenly, and placing in a fermentation tank for static fermentation, wherein the temperature rises naturally during the static fermentation process, and the fermentation is carried out for 6-8 days to obtain a papermaking sludge fermentation product; concentrating the papermaking sludge fermentation product, and then pulverizing it to obtain a papermaking sludge material;

[0011] (3) The pulping black liquor material and the papermaking sludge material are mixed evenly to obtain a mixed material, and the mixed material is granulated to obtain a biomass fuel based on the pulping black liquor and the papermaking sludge.

[0012] The present invention can reduce the pollution of particulate pollutants to the environment during combustion by fermenting pulping black liquor and papermaking sludge, and significantly reduce the emission of smoke and pollutant concentration. During the fermentation process, microorganisms decompose complex organic matter and convert it into more flammable compounds, thereby improving the overall combustibility of the fuel and generating less incomplete combustion residues during combustion. At the same time, the fermentation process can adjust the sulfur content in the raw materials and reduce the generation of sulfur dioxide gas during combustion.

[0013] Furthermore, the mixed bacterial agent in step (1) comprises white rot fungi, Pseudomonas aeruginosa and Bacillus thuringiensis in a weight ratio of 1: (1.2-1.4): (0.5-0.7).

[0014] During the aerobic fermentation process in step (1), ventilation is performed for 10 minutes every 4 hours, with a ventilation volume (v / v) of 1:1, and stirring is performed for 10 minutes every 7 hours at a rotation speed of 100 rpm.

[0015] Furthermore, the dosage of the mixed bacterial agent is 1-1.3 kg of the mixed bacterial agent per ton of pulping black liquor.

[0016] Furthermore, in step (2), the composite Bacillus comprises Bacillus cereus, Bacillus subtilis and Brevibacillus laterosporus in a weight ratio of (0.4-0.7):(1.4-1.7):1.

[0017] Furthermore, the addition amount of the composite Bacillus is 0.6-0.8 kg of the composite Bacillus per ton of papermaking sludge.

[0018] The present invention can change the carbon chain length of organic matter in pulping black liquor and papermaking sludge by fermenting pulping black liquor and papermaking sludge, thereby improving the combustion thermal efficiency of biomass fuel and enabling it to be fully burned.

[0019] Furthermore, in the step (1), the pulping black liquor fermentation product is passed through an MVR (mechanical vapor recompression) section to be concentrated to a water content of 50-55 wt%.

[0020] Furthermore, in the step (2), the fermented papermaking sludge is physically squeezed and concentrated to a water content of 48-52 wt%, and then pulverized so that more than 99% of the mass passes through an 80-mesh sieve.

[0021] Furthermore, in the step (3), the weight ratio of the pulping black liquor fermentation material to the papermaking sludge fermentation material is 1:(3-5).

[0022] Furthermore, in step (3), the weight ratio of the pulping black liquor fermentation material to the papermaking sludge fermentation material is 1:5.

[0023] In the present invention, the weight ratio of pulping black liquor fermentation material to papermaking sludge fermentation material is 1:5, the biomass fuel has good molding effect, the particle molding effect is good, it is not only convenient to manage and transport, but also can improve the density and strength of the particles, making the biomass particles more stable and durable.

[0024] Furthermore, the granulation method in step (3) comprises the following steps: drying the mixture by hot air drying to reduce the water content to below 10wt%, crushing the dried mixture to a particle size of 2-10mm, feeding it into a pelletizing machine, pressing it into granules by high temperature and high pressure, and cooling it.

[0025] The conditions of high temperature and high pressure are: temperature of 400℃-600℃; pressure parameter of 1.0MPa-6.0MPa.

[0026] The second aspect of the present invention also provides the use of the biomass fuel preparation method based on pulping black liquor and papermaking sludge in treating papermaking waste.

[0027] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0028] 1. The present invention develops an innovative technology to mix pulping black liquor and papermaking sludge to extract pellets to prepare biomass fuel. This method can not only realize the resource utilization of waste, but also promote the sustainable utilization of energy, which is in line with the concept of environmental protection and resource recycling. Through this conversion, not only can the negative impact of industrial wastewater on the environment be reduced, but also economic benefits can be brought to enterprises, realizing the resource utilization of waste and sustainable utilization of energy.

[0029] 2. The raw materials of the biomass fuel prepared by the present invention are completely papermaking waste, and the two industrial wastes, pulping black liquor and papermaking sludge, are utilized as resources, which reduces the discharge of waste and conforms to the concept of circular economy and green development. Papermaking sludge contains a large amount of organic matter and minerals, which can be used as a binder for biomass particles to increase the density and strength of the particles, making the biomass particles more stable and durable. Papermaking sludge contains a certain amount of ash, which can form a stable molten layer during the combustion process, which helps the combustion stability and combustion efficiency of biomass particles.

[0030] 3. The biomass fuel prepared by the present invention completely uses papermaking waste, and no other fuel components need to be added. The entire biomass fuel preparation process can be simplified. This not only reduces the process steps, but also may reduce operational complexity and maintenance costs. By using only the waste generated by the paper mill itself, the maximum utilization of the waste is achieved, and the waste of resources or unnecessary cost expenditure caused by mixing other materials is avoided. This approach helps to reduce waste emissions and further reduce the impact on the environment. Since there is no need to purchase additional fuel components, companies can save this part of the expenses. In addition, if biomass fuel is overproduced, it can also be considered to sell it to increase additional sources of income. At the same time, it also helps to enhance the image and competitiveness of the company in the market, which is in line with the current society's expectations for sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the biomass fuel prepared in Example 1.

[0032] Figure 2 Schematic diagram of the biomass fuel prepared in Example 2.

[0033] Figure 3 Schematic diagram of the biomass fuel prepared in Example 3. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The raw materials used in the following examples are:

[0036] Pulping black liquor is a waste liquid containing various organic and inorganic substances produced when cellulose is separated from wood during the bleaching chemical-mechanical pulping process of Dongguan Jianhui Paper Co., Ltd. It is a by-product of the cooking stage in the pulping process and is produced in chemical pulping (kraft process).

[0037] Papermaking sludge: Dongguan Jianhui Paper Co., Ltd. uses various waste paper raw materials in the waste paper pulping process to produce coated white board paper and kraft paper. During the pulping and papermaking process, the ash and fine fiber components that cannot be retained on the paper sheets are discharged from the system. This part of the ash and fine components that cannot be reused in the discharge system become sludge, which is directly pulled into the power station boiler for mixing and burning in the original way.

[0038] The strains used in the present invention are all commercially available products:

[0039] White rot fungi, product number: SHMCCD82075, Shanghai Baocang Microorganism Co., Ltd.

[0040] Pseudomonas aeruginosa, product number: SHMCCD10840, Shanghai Baocang Microbiology Co., Ltd.

[0041] Bacillus thuringiensis, product number: SHMCCD10504, Shanghai Baocang Microbiology Co., Ltd.

[0042] Bacillus cereus, product number: CICC21290, China Industrial Microbiology Culture Collection Management Center.

[0043] Bacillus subtilis, product number: SHMCCD10486, Shanghai Baocang Microbiology Co., Ltd.

[0044] Brevibacillus laterosporus, product number: SHMCCD10876, Shanghai Baocang Microbiology Co., Ltd.

[0045] Example 1

[0046] This embodiment provides a method for preparing biomass fuel based on pulping black liquor and papermaking sludge, comprising the following steps:

[0047] (1) Adding a mixed bacterial agent to the pulping black liquor, mixing evenly, and aerobically fermenting at 32° C. for 6 days, aerating for 10 minutes every 4 hours during the aerobic fermentation, with an aeration volume (v / v) of 1:1, stirring for 10 minutes every 7 hours, and rotating at 100 rpm to obtain a pulping black liquor fermentation product, and concentrating the pulping black liquor fermentation product to a water content of 53 wt% through an MVR (mechanical vapor recompression) section to obtain a pulping black liquor material; the mixed bacterial agent comprises white rot fungi, Pseudomonas aeruginosa, and Bacillus thuringiensis in a weight ratio of 1:1.3:0.6. The dosage of the mixed bacterial agent is 1.2 kg of the mixed bacterial agent per ton of pulping black liquor.

[0048] (2) adding composite Bacillus to papermaking sludge, mixing evenly, and placing in a fermentation tank for static fermentation, during which the temperature rises naturally, and fermenting for 7 days to obtain papermaking sludge fermentation product; physically extruding the papermaking sludge fermentation product, concentrating it to a water content of 50wt%, and then pulverizing it so that the mass passing through an 80-mesh sieve accounts for more than 99%, thereby obtaining papermaking sludge material; the composite Bacillus includes Bacillus cereus, Bacillus subtilis and Bacillus laterosporus in a weight ratio of 0.6:1.5:1; the addition amount of the composite Bacillus is 0.7 kg of composite Bacillus per ton of papermaking sludge.

[0049] (3) Mix the pulping black liquor material and the papermaking sludge material in a weight ratio of 1:5 to obtain a mixed material, granulate the mixed material, dry the mixed material by hot air drying to reduce the water content to less than 10wt%, crush the dried mixed material to a particle size of 2-10mm, send it to a briquette press, and press it into granules by high temperature and high pressure. The conditions of high temperature and high pressure are: temperature of 500°C; pressure parameter of 3.0MP, and cooling. Biomass fuel based on pulping black liquor and papermaking sludge is obtained.

[0050] Example 2

[0051] The difference between this embodiment and embodiment 1 is that the pulping black liquor material and the papermaking sludge material are mixed evenly in a weight ratio of 1:4 to obtain a mixed material.

[0052] Example 3

[0053] The difference between this embodiment and embodiment 1 is that the pulping black liquor material and the papermaking sludge material are mixed evenly in a weight ratio of 1:3 to obtain a mixed material.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that the pulping black liquor is not fermented.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that the mixed bacterial agent in step (1) is replaced by white rot fungi.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that the mixed bacterial agent in step (1) comprises white rot fungi, Pseudomonas aeruginosa and Bacillus thuringiensis in a weight ratio of 1:1:1.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that the papermaking sludge is not fermented.

[0062] Comparative Example 5

[0063] The difference between this comparative example and Example 1 is that the composite Bacillus in step (2) is replaced by Bacillus subtilis.

[0064] Comparative Example 6

[0065] The difference between this comparative example and Example 1 is that the composite Bacillus in step (2) includes Bacillus cereus, Bacillus subtilis and Brevibacillus laterosporus in a weight ratio of 1:1:1.

[0066] Performance Testing

[0067] 1. The physical and chemical properties of the biomass fuels prepared in Examples 1-3 were analyzed according to the national standard method. The results are shown in Tables 1 and Figure 1-3 . "Indonesian coal (low calorie)" Indonesian coal Nar3800K.

[0068] GB474-2008 Coal sample preparation method.

[0069] GB475-2008 Manual sampling method for commercial coal.

[0070] GBT212-2008 Industrial analysis methods for coal.

[0071] GBT214-2007 Determination method for total sulfur in coal.

[0072] GBT211-2017 Method for determination of total moisture in coal.

[0073] Table 1 Analysis results of physical and chemical properties of biomass fuels in Examples 1-3

[0074]

[0075]

[0076] It can be seen from Table 1 that the biomass fuels prepared in Examples 1-3 of the present invention have excellent physical and chemical properties. Figure 1 It can be seen that in Example 1, the weight ratio of pulping black liquor fermentation material to papermaking sludge fermentation material is 1:5, and the biomass fuel has a good molding effect and a good particle molding effect. Figure 2 and 3 It can be seen that the weight ratio of pulping black liquor fermentation material and papermaking sludge fermentation material in Example 2 and Example 3 is changed, and the molding effect of biomass fuel is worse than that in Example 1.

[0077] 2. Referring to the calorific value determination method of coal in GBT213-2008, the lower heating value of the biomass fuels of Examples 1-3 and Comparative Examples 1-6 was determined. The results are shown in Table 2.

[0078] Table 2 Analysis results of low calorific value

[0079] Lower calorific value Cal / g Indonesian coal 3857.2 Example 1 3421.1 Example 2 3411.6 Example 3 3195.5 Comparative Example 1 2804.8 Comparative Example 2 2969.3 Comparative Example 3 3094.7 Comparative Example 4 2703.2 Comparative Example 5 2887.4 Comparative Example 6 2954.0

[0080] The lower calorific value refers to the heat released when the water vapor in the combustion product of a unit mass of fuel exists in a gaseous state under constant volume conditions when the fuel is completely burned. It does not include the latent heat of vaporization released when the water vapor in the flue gas condenses into water. It is closer to the actual calorific value of industrial boiler combustion, because the flue gas temperature in industrial boilers is usually higher than the condensation temperature of water vapor, and the water vapor is discharged in a gaseous form, and its latent heat of vaporization is not utilized. It is often used in industrial calculations and practical applications because it more directly reflects the energy output of the fuel in actual use.

[0081] It can be seen from Table 2 that the low calorific value of the biomass fuel prepared by the present invention is higher than that of Indonesian coal. Comparative Example 1 shows that the low calorific value decreases when the pulping black liquor is not fermented, and Comparative Example 2 shows that the low calorific value decreases when a single bacteria is used for fermentation, and Comparative Example 3 shows that the low calorific value is also lower than that of Example 1 when different proportions of bacteria are used for fermentation, indicating that the three bacteria of the present invention can play a synergistic role in a specific proportion to improve the low calorific value.

[0082] It can be seen from Comparative Example 3 that the low calorific value decreases when papermaking sludge is not fermented. It can be seen from Comparative Example 2 that the low calorific value decreases when a single bacteria is used for fermentation. It can be seen from Comparative Example 3 that the low calorific value is also lower than that of Example 1 when different proportions of bacteria are used for fermentation, indicating that the three bacteria of the present invention can play a synergistic role in a specific proportion to improve the low calorific value of biomass fuel.

[0083] 3. The smoke emission and smoke pollutant emission concentration of the biomass fuels of Examples 1-3 and Comparative Examples 1-6 were tested with reference to GB / T5468-1991 "Boiler Smoke Test Method" and GB / T13271-2014 "Boiler Air Pollutant Emission Standard", and the diameter of the circular pipe was 180 mm. The results are shown in Table 3.

[0084] Table 3 Smoke emission test results

[0085]

[0086]

[0087] It can be seen from Table 3 that by fermenting pulping black liquor and papermaking sludge, the pollution of particulate pollutants to the environment during combustion can be reduced, and the emission of smoke and pollutant concentration can be significantly reduced.

[0088] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing biomass fuel based on pulping black liquor and papermaking sludge, characterized in that: The following steps are involved: (1) adding a mixed bacterial agent to pulping black liquor, mixing evenly, aerobically fermenting at 30-35° C. for 5-7 days to obtain a pulping black liquor fermentation product, and concentrating the pulping black liquor fermentation product to obtain a pulping black liquor material; (2) adding composite Bacillus to papermaking sludge, mixing evenly, and placing in a fermentation tank for static fermentation, wherein the temperature rises naturally during the static fermentation process, and the fermentation is carried out for 6-8 days to obtain a papermaking sludge fermentation product; concentrating the papermaking sludge fermentation product, and then pulverizing it to obtain a papermaking sludge material; (3) The pulping black liquor material and the papermaking sludge material are mixed evenly to obtain a mixed material, and the mixed material is granulated to obtain a biomass fuel based on the pulping black liquor and the papermaking sludge.

2. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 1, characterized in that: The mixed bacterial agent in step (1) comprises white rot fungi, Pseudomonas aeruginosa and Bacillus thuringiensis in a weight ratio of 1: (1.2-1.4): (0.5-0.7).

3. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 2, characterized in that: The dosage of the mixed bacterial agent is 1-1.3 kg of the mixed bacterial agent added to every ton of pulping black liquor.

4. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 1, characterized in that: The composite Bacillus in step (2) includes Bacillus cereus, Bacillus subtilis and Brevibacillus laterosporus in a weight ratio of (0.4-0.7):(1.4-1.7):

1.

5. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 4, characterized in that: The addition amount of the composite Bacillus is 0.6-0.8 kg of composite Bacillus per ton of papermaking sludge.

6. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 1, characterized in that: In the step (3), the weight ratio of the pulping black liquor fermentation material to the papermaking sludge fermentation material is 1:(3-5).

7. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 6, characterized in that: In the step (3), the weight ratio of the pulping black liquor fermentation material to the papermaking sludge fermentation material is 1:

5.

8. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 1, characterized in that: The granulation method in step (3) comprises the following steps: drying the mixture by hot air drying to reduce the water content to below 10wt%, crushing the dried mixture to a particle size of 2-10mm, feeding it into a pelletizing machine, pressing it into granules by high temperature and high pressure, and cooling it.

9. The method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to claim 8, characterized in that: The conditions of high temperature and high pressure are: temperature of 400℃-600℃; pressure parameter of 1.0MPa-6.0MPa.

10. Use of the method for preparing biomass fuel based on pulping black liquor and papermaking sludge according to any one of claims 1 to 9 in treating papermaking waste.

Images