A pig manure biomass pellet fuel and its preparation method

Abstract

This invention relates to a pig manure biomass pellet fuel and its preparation method, belonging to the fields of biomass fuel technology and environmental protection technology, particularly the comprehensive treatment and resource utilization technology of livestock and poultry manure. Fresh pig manure from pig farms is separated into solid and liquid components using a spiral dry-wet separator to obtain pig manure residue. The pig manure residue is dried to reduce the moisture content to 22-30 wt%, then crushed and screened. It is then mixed with pretreated sawdust and chicken manure biochar, and further mechanically stirred for 10-15 minutes to obtain a uniform mixture with a moisture content of 22-28 wt%. The obtained mixture is extruded into pellets using a biomass pellet mill to obtain pig manure biomass pellet fuel. The pellets are naturally cooled to room temperature, and unqualified products with a length less than 4 mm are screened out. The remaining material is the qualified pig manure biomass pellet fuel product. This method not only solves the problem of ecological environmental pollution caused by pig manure but also provides ideas and directions for the comprehensive utilization of livestock and poultry manure through reduction, harmlessness, and resource recovery.

Description

Technical Field

[0001] This invention relates to a pig manure biomass pellet fuel and its preparation method, belonging to the fields of biomass fuel technology and environmental protection technology, particularly the comprehensive treatment and resource utilization technology of livestock and poultry manure. Background Technology

[0002] With the rapid development of my country's animal husbandry, especially large-scale and intensive farming, the discharge of livestock and poultry manure has been increasing and becoming more concentrated, leading to increasingly prominent ecological and environmental problems. This has seriously affected farms and their surrounding environments, making livestock and poultry manure a major source of agricultural non-point source pollution. The large surplus of livestock and poultry manure far exceeds the soil's absorption capacity, resulting in resource waste and a sharp increase in environmental pollution risks. The efficient treatment and resource utilization of livestock and poultry manure has become a key technological bottleneck restricting the sustainable development of the livestock industry.

[0003] Existing technologies for treating livestock and poultry manure include direct application as fertilizer, aerobic fermentation to produce organic fertilizer, and anaerobic fermentation to generate biogas for use as gaseous fuel. Direct application of manure to the fields is gradually being phased out due to the risk of secondary pollution to the ecological environment. Composting for organic fertilizer production has a long fermentation cycle, requires a large area, and operates in harsh environments. Using fermentation tanks to produce organic fertilizer involves significant equipment investment, high operating costs, and limited processing capacity. Anaerobic fermentation for biogas production is a lengthy process with problems such as expensive equipment, low energy efficiency, strict operating conditions, and the need for further treatment of biogas slurry and residue. Under these circumstances, how to comprehensively promote the treatment and resource utilization of livestock and poultry waste has become an urgent problem to be solved in the livestock and poultry farming industry.

[0004] Biomass fuels are widely available, renewable, and have extremely low greenhouse gas emissions throughout their life cycle. Industries using biomass energy are increasingly aware of its potential, leading to a growing demand for biomass fuels. In light of this, several technologies for preparing biomass fuels from livestock manure have emerged in recent years. For example, invention patent (CN114479974A) discloses a method for the resource utilization of solid waste from pig farming to prepare biomass pellet fuel. This method involves preliminary dehydration using an electroosmotic dehydration device for 6-12 hours, followed by further drying to a moisture content of less than 20% in the pig manure. A multi-effect antibacterial binder is added during the pelleting process to achieve both antibacterial and binding functions. Invention patent application number 201110431177.3 discloses a biomass fuel prepared from pig manure. This pellet fuel consists of pig manure, biomass powder, high-carbon ash for deodorization, quicklime, and deformed starch binder. The relatively expensive high-carbon ash is prepared from fly ash through flotation. The invention patent (CN105441155B) discloses a composite biomass fuel made from chicken manure, pig manure, yellow-brown soil, and cypress, and its preparation method. The method uses a large amount of raw materials, but chicken manure and pig manure account for less than half. The mixture of chicken manure and pig manure needs to be piled up at 30-40℃ for 20-30 days. The straw fermentation material is made by first crushing the straw and then baking it in an environment at 30-40℃ until the moisture content is 30-50%. Then, 1-3% of the straw weight of yeast is added to it, and then it is piled up and fermented for 10-20 days. Because the pellet fuel has a high moisture content, it needs to be further dried at 50-70℃ after extrusion molding. The invention patent with application number 201310324173.4 discloses a method for preparing solid briquettes using pig manure as raw material. The briquettes are composed of dried pig manure raw material, biomass and coal. The dried pig manure raw material contains 2-5% desulfurization, deodorization and mildew prevention agent. This additive is made by mixing a large amount of quicklime with two or three of the following: ferrous sulfate, magnesium carbonate and chitosan fiber, to facilitate the use and storage of pig manure briquettes.

[0005] In summary, traditional pig manure treatment and utilization technologies are limited by their long production cycles and seasonal limitations, making large-scale pig manure disposal difficult. The application of pig manure-based biogas energy is also limited in China. Existing pig manure biomass solid fuel production requires additives or fermentation to improve molding results and prevent odor and mold growth, leading to increased production costs or low efficiency, which hinders large-scale industrial production. Summary of the Invention

[0006] To address the environmental pollution caused by pig manure and the problems and shortcomings in its utilization, this invention provides a pig manure biomass pellet fuel and its preparation method. The process of this invention is simple, easy to operate, and highly efficient. By separating fresh pig manure into dry and wet components and adding self-made chicken manure biochar powder, the resulting pig manure biomass pellet fuel exhibits high mechanical strength, high forming rate, and combustion performance comparable to traditional wood-based biomass pellet fuel. It also possesses advantages such as moisture and mildew resistance and odorlessness. This method not only solves the environmental pollution problem caused by pig manure but also provides ideas and directions for the comprehensive utilization of livestock and poultry manure through reduction, harmlessness, and resource recovery.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A pig manure biomass pellet fuel, based on the dry weight of the pig manure biomass pellet fuel, is composed of 70wt%-100wt% pig manure residue, 0wt%-30wt% sawdust and 0wt%-10wt% chicken manure biochar, with the total content of sawdust and chicken manure biochar ≤30wt%.

[0009] The pig manure biomass pellet fuel is cylindrical, with a diameter of 8-10 mm and a length of 10-75 mm.

[0010] A method for preparing pig manure biomass pellet fuel includes the following steps:

[0011] (1) Fresh pig manure from pig farms is separated into solid and liquid components by a spiral dry-wet separator to obtain pig manure residue;

[0012] (2) Dry the pig manure residue to reduce the moisture content to 22-30wt%, then crush and screen it, and then mix it with pretreated wood chips and chicken manure biochar. Further mechanically stir and mix for 10-15 minutes to obtain a uniform mixture with a moisture content of 22-28wt%.

[0013] (3) The mixture obtained in step (2) is extruded and molded using a biomass pellet machine to obtain pig manure biomass pellet fuel;

[0014] (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

[0015] The moisture content of fresh pig manure in step (1) is 75-81 wt%, and the moisture content of pig manure residue after solid-liquid separation is below 58 wt%.

[0016] In step (2), the drying temperature of pig manure residue is 105-110℃. It can be used directly after simple crushing, or after further screening. The screening is performed by passing through a 10-mesh stainless steel sieve, preferably through a 20-mesh stainless steel sieve.

[0017] The wood chips in step (2) are wood chips from common trees such as white pine, fir, cypress or Masson pine after crushing, or sawdust produced during the processing of common trees. The pretreatment involves drying the wood chips to 22-28 wt% at a temperature of 105-110℃, and then crushing them through a 10-mesh stainless steel sieve.

[0018] In step (2), the chicken manure biochar is prepared by first molding and then pyrolyzing fresh chicken manure and 30wt-40wt% sawdust, with a moisture content ≤2wt%. Pretreatment involves mechanically grinding the chicken manure biochar and passing it through a 20-60 mesh stainless steel sieve to obtain chicken manure biochar powder. The chicken manure biochar in this invention is made using patent number ZL202311020383.4.

[0019] In step (3), the biomass pellet mill is either a ring type or a roller type.

[0020] Using the preparation method described above, the pig manure biomass pellet fuel obtained by this invention has a lower heating value (dry basis) of 17.1-18.5 MJ / kg, moisture content of less than 8 wt%, ash content (dry basis) of 6.6-10.9 wt%, mechanical durability (also known as mechanical strength, as received) greater than 99%, and density of 1.25-1.35 g / cm³. 3 The chlorine content (Cl, dry basis) is 0.04-0.08 wt%, the sulfur content (S, dry basis) is 0.3-0.6 wt%, and the nitrogen content (N, dry basis) is 1-1.5 wt%.

[0021] In this invention, all relevant indicators of pig manure biomass pellet fuel were obtained using the aforementioned benchmark tests.

[0022] The beneficial effects of this invention are:

[0023] (1) The fresh pig manure used was obtained through continuous dry-wet separation using a commercial spiral biomass pellet mill. Fresh pig manure does not require fermentation, greatly improving the efficiency of raw material pretreatment. Fresh pig manure contains a considerable amount of combustible materials, mainly cellulose, hemicellulose, and lignin, as well as fats, proteins, starches, and odor-causing substances such as urea, ammonia, and hydrogen sulfide dissolved in water. The fresh pig manure in the pig farm's manure collection pond was separated into solid and liquid components using a dry-wet separator, significantly removing unstable and easily moldy fats and proteins, odor-causing substances such as urea, ammonia, and hydrogen sulfide, and soluble salts. The separated manure water can be fermented in the pig farm's manure pond and used as liquid fertilizer. The separated pig manure residue is loose, with significantly reduced viscosity, and the moisture content can be reduced from 75-81 wt% in fresh pig manure to below 58 wt%. The lower the moisture content, the cleaner the fresh pig manure residue, and the less energy is consumed in subsequent drying, which is beneficial for product production.

[0024] (2) Adding self-made chicken manure biochar powder to pig manure biomass pellet fuel achieves deodorization and mold prevention effects. The pyrolyzed chicken manure biochar itself has a certain porosity, which further increases after mechanical grinding and activation, giving it the function of activated carbon to adsorb odorous gases in the pig manure pellet fuel. Secondly, biochar has stable chemical properties and good hydrophobicity, which can inhibit the pig manure pellet fuel from absorbing moisture and becoming moldy. In addition, the self-made chicken manure biochar has a higher calorific value than pig manure and sawdust, which can improve the combustion performance of pig manure pellet fuel. Simultaneously, due to the special nature of the raw material chicken manure used to prepare the biochar, the chicken manure biochar contains a certain amount of stone powder (mainly calcium carbonate) and some calcium oxide (quicklime) formed by the decomposition of stone powder during pyrolysis, which plays a role in sulfur fixation in the pig manure pellet fuel. Calcium oxide also plays a certain binding effect during the forming process of the pig manure pellet fuel under the influence of moisture and temperature.

[0025] (3) Pig manure biomass pellet fuel utilizes a biomass pellet mill for high forming efficiency and low finished product moisture content, eliminating the need for further drying and saving energy. Before entering the pellet mill, the moisture content of the pig manure mixture is controlled at 22-28 wt%. Under the pressure, shearing force, and friction of the pellet mill's grinding rollers, the particle size further decreases, increasing the contact area of ​​the powder. Residual sticky substances such as fat, protein, and starch in the pig manure residue, as well as the quicklime contained in chicken manure biochar, promote the formation of pig manure pellet fuel within the die channels. During the pelleting process, frictional heat generates heat, causing the pellet mill temperature to rise rapidly. The high-temperature moisture evaporates, softening the cellulose and lignin in the pig manure and sawdust, which is beneficial for the formation of the pig manure pellet fuel. The forming rate of pig manure biomass pellet fuel reaches over 98%, with a moisture content of less than 8 wt%, perfectly meeting the usage requirements.

[0026] (4) The preparation process of this invention is simple, low-cost and highly efficient. The obtained pig manure biomass pellet fuel has a smooth surface, dense texture, and coal-like appearance. It has high mechanical strength, is environmentally friendly and odorless, has excellent comprehensive combustion performance, is easy to store and transport, and efficiently realizes the reduction, harmlessness and resource utilization of livestock and poultry manure, providing a new way and method for biomass energy utilization.

[0027] (5) Through the preparation method of the present invention, the present invention can prepare qualified pig manure biomass pellet fuel products by using fresh pig manure residue alone without adding sawdust or chicken manure biochar. Attached Figure Description

[0028] Figure 1 This is a process flow diagram of the method for preparing pig manure biomass pellet fuel according to the present invention;

[0029] Figure 2 This is a SEM image of chicken manure biochar powder added in Example 2 of the present invention;

[0030] Figure 3 This is the finished pig manure biomass pellet fuel product prepared in Example 4 of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] like Figure 1 As shown, the pig manure biomass pellet fuel, based on the dry weight of the pig manure biomass pellet fuel, consists of 80 wt% pig manure residue, 15 wt% sawdust, and 5 wt% chicken manure biochar.

[0034] The method for preparing pig manure biomass pellet fuel includes the following steps:

[0035] (1) Fresh pig manure with a moisture content of 81 wt% was separated into solid and liquid components by a spiral dry-wet separator to obtain pig manure residue with a moisture content of 55 wt%.

[0036] (2) The pig manure residue was dried at 105℃ to reduce the moisture content to 26.08wt%, then crushed and sieved through a 10-mesh stainless steel sieve. 7kg of pig manure residue was then mixed with 1.29kg of pre-treated wood chips (wood chips from crushed white pine wood, dried at 105℃ to 24.78wt% and then sieved through a 10-mesh stainless steel sieve) and 0.33kg of chicken manure biochar (made by patent number ZL202311020383.4, with a moisture content of 2wt%, and obtained by mechanically grinding the chicken manure biochar and sieving through a 60-mesh stainless steel sieve to obtain chicken manure biochar powder). The mixture was further mechanically stirred and mixed for 15min to obtain a uniform mixture with a moisture content of 24.96wt%.

[0037] (3) The mixture obtained in step (2) is extruded and molded using a roller-type biomass pellet mill to obtain pig manure biomass pellet fuel;

[0038] (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

[0039] The pig manure biomass pellet fuel obtained in this embodiment is cylindrical, with a diameter of 8-9 mm and a length of 10-40 mm. The pig manure biomass pellet fuel is odorless, has good moisture and mildew resistance, a mechanical durability of 99.3%, and a density of 1.33 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1.

[0040] Example 2

[0041] like Figure 1As shown, the pig manure biomass pellet fuel, based on the dry weight of the pig manure biomass pellet fuel, consists of 80 wt% pig manure residue, 10 wt% sawdust, and 10 wt% chicken manure biochar.

[0042] The method for preparing pig manure biomass pellet fuel includes the following steps:

[0043] (1) Fresh pig manure with a moisture content of 79 wt% was obtained by solid-liquid separation using a spiral dry-wet separator to obtain pig manure residue with a moisture content of 58 wt%.

[0044] (2) The pig manure residue was dried at 105℃ to reduce the moisture content to 30wt%, then crushed and sieved through a 20-mesh stainless steel sieve. 7kg of pig manure residue was then mixed with 0.85kg of pretreated sawdust (fir sawdust, dried at 105℃ to 28wt% and then sieved through a 10-mesh stainless steel sieve) and 0.62kg of chicken manure biochar (made by patent number ZL202311020383.4, with a moisture content of 1.21wt%, obtained by mechanically grinding the chicken manure biochar and sieving through a 40-mesh stainless steel sieve to obtain chicken manure biochar powder). The mixture was further mechanically stirred and mixed for 15min to obtain a uniform mixture with a moisture content of 27.69wt%.

[0045] (3) The mixture obtained in step (2) is extruded and molded using a ring-mode biomass pellet mill to obtain pig manure biomass pellet fuel;

[0046] (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

[0047] The SEM (scanning electron microscope) morphology of the chicken manure biochar powder added in this embodiment is as follows: Figure 2 As shown, the well-developed pore structure inside the chicken manure biochar is clearly visible, indicating good adsorption properties.

[0048] The pig manure biomass pellet fuel obtained in this embodiment is cylindrical, with a diameter of 9-10 mm and a length of 10-50 mm. The pig manure biomass pellet fuel is odorless, has good moisture and mildew resistance, a mechanical durability of 99.1%, and a density of 1.35 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1.

[0049] Example 3

[0050] like Figure 1 As shown, the pig manure biomass pellet fuel, based on the dry weight of the pig manure biomass pellet fuel, consists of 70 wt% pig manure residue, 25 wt% sawdust, and 5 wt% chicken manure biochar.

[0051] The method for preparing pig manure biomass pellet fuel includes the following steps:

[0052] (1) Fresh pig manure with a moisture content of 77wt% was obtained by solid-liquid separation using a spiral dry-wet separator to obtain pig manure residue with a moisture content of 58wt%.

[0053] (2) The pig manure residue was dried at 110℃ to reduce the moisture content to 24.76wt%, and then crushed and used directly. 7kg of pig manure residue was then mixed with 2.47kg of pre-treated sawdust (sawdust from crushed cypress trees, dried at 105℃ to reduce the moisture content to 23.84wt%, and then passed through a 10-mesh stainless steel sieve) and 0.38kg of chicken manure biochar (made by patent number ZL202311020383.4, with a moisture content of 1wt%, and obtained by mechanically grinding the chicken manure biochar and passing it through a 20-mesh stainless steel sieve to obtain chicken manure biochar powder). The mixture was further mechanically stirred and mixed for 15min to obtain a uniform mixture with a moisture content of 23.61wt%.

[0054] (3) The mixture obtained in step (2) is extruded and molded using a ring-mode biomass pellet mill to obtain pig manure biomass pellet fuel;

[0055] (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

[0056] The pig manure biomass pellet fuel obtained in this embodiment is cylindrical, with a diameter of 9-10 mm and a length of 20-75 mm. The pig manure biomass pellet fuel is odorless, has good moisture and mildew resistance, a mechanical durability of 99.5%, and a density of 1.29 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1.

[0057] Example 4

[0058] like Figure 1 As shown, the pig manure biomass pellet fuel, based on the dry weight of the pig manure biomass pellet fuel, consists of 70 wt% pig manure residue and 30 wt% wood chips.

[0059] The method for preparing pig manure biomass pellet fuel includes the following steps:

[0060] (1) Fresh pig manure with a moisture content of 75wt% was obtained by solid-liquid separation using a spiral dry-wet separator to obtain pig manure residue with a moisture content of 52wt%.

[0061] (2) The pig manure residue was dried at 110℃ to reduce the moisture content to 22wt%, then crushed and sieved through a 20-mesh stainless steel sieve. 7kg of pig manure residue was then mixed with 3kg of pretreated sawdust (Mass pine sawdust, which was dried at 110℃ to reduce the moisture content to 22wt% and then sieved through a 10-mesh stainless steel sieve) and mechanically stirred for 10min to obtain a uniform mixture with a moisture content of 22wt%.

[0062] (3) The mixture obtained in step (2) is extruded and molded using a roller-type biomass pellet mill to obtain pig manure biomass pellet fuel;

[0063] (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

[0064] The pig manure biomass pellet fuel obtained in this embodiment is cylindrical, with a diameter of 9-10 mm and a length of 10-60 mm. The pig manure biomass pellet fuel is odorless, moisture-proof, and mildew-proof, with a mechanical durability of 99.5% and a density of 1.25 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1. A physical image of the finished pig manure biomass pellet fuel prepared in this embodiment is shown below. Figure 3 As shown, from Figure 3 As can be seen, pig manure biomass pellet fuel has a smooth surface, dense texture, and high mechanical strength.

[0065] Example 5

[0066] like Figure 1 As shown, the pig manure biomass pellet fuel, based on the dry weight of the pig manure biomass pellet fuel, consists of 98 wt% pig manure residue and 2 wt% chicken manure biochar.

[0067] The method for preparing pig manure biomass pellet fuel includes the following steps:

[0068] (1) Fresh pig manure with a moisture content of 80wt% was separated into solid and liquid components by a spiral dry-wet separator to obtain pig manure residue with a moisture content of 55wt%.

[0069] (2) The pig manure residue was dried at 108℃ to reduce the moisture content to 26wt%, then crushed and sieved through a 20-mesh stainless steel sieve. 7.21kg of pig manure residue was then mixed with 0.11kg of pretreated chicken manure biochar (made by patent number ZL202311020383.4, with a moisture content of 1wt%, and obtained by mechanically grinding the chicken manure biochar and sieving it through a 60-mesh stainless steel sieve to obtain chicken manure biochar powder) and further mechanically stirred and mixed for 10min to obtain a uniform mixture with a moisture content of 25.62wt%.

[0070] (3) The mixture obtained in step (2) is extruded and molded using a ring-mode biomass pellet mill to obtain pig manure biomass pellet fuel;

[0071] (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

[0072] The pig manure biomass pellet fuel obtained in this embodiment is cylindrical, with a diameter of 8-9 mm and a length of 10-50 mm. The pig manure biomass pellet fuel is odorless, has good moisture and mildew resistance, a mechanical durability of 99.3%, and a density of 1.32 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1.

[0073] Example 6

[0074] like Figure 1 As shown, the pig manure biomass pellet fuel, based on the dry weight of the pig manure biomass pellet fuel, consists of 100 wt% pig manure residue.

[0075] The method for preparing pig manure biomass pellet fuel includes the following steps:

[0076] (1) Fresh pig manure with a moisture content of 80wt% was obtained by solid-liquid separation using a spiral dry-wet separator to obtain pig manure residue with a moisture content of 52wt%.

[0077] (2) Dry the pig manure residue at 105℃ to reduce the moisture content to 25wt%, then crush and sieve it through a 20-mesh stainless steel sieve. Further mechanically stir and mix 8kg of pig manure residue for 10min to obtain a uniform mixture.

[0078] (3) The mixture obtained in step (2) is extruded and molded using a roller-type biomass pellet mill to obtain pig manure biomass pellet fuel;

[0079] (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

[0080] The pig manure biomass pellet fuel obtained in this embodiment is cylindrical, with a diameter of 8-9 mm and a length of 10-75 mm. The pig manure biomass pellet fuel is virtually odorless, moisture-proof and mildew-proof, has a mechanical durability of 99.1%, and a density of 1.31 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1.

[0081] Comparative Example 1

[0082] The pig manure biomass pellet fuel, based on its dry weight, consists of 80 wt% fresh pig manure residue, 15 wt% sawdust, and 5 wt% chicken manure biochar. Its composition and preparation method are the same as in Example 1, except that the moisture content of the homogeneous mixture after stirring in step (2) is 16 wt%. The prepared pig manure biomass pellet fuel is odorless, has anti-mildew properties, a mechanical durability of 78.5%, and a density of 1.16 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1.

[0083] Comparative Example 2

[0084] The pig manure biomass pellet fuel, based on its dry weight, consists of 70 wt% fresh pig manure and 30 wt% sawdust. Its composition and preparation method are the same as in Example 4, except that step (1) is omitted. Specifically, the fresh pig manure from the pig farm is not subjected to solid-liquid separation using a spiral dry-wet separator; instead, the fresh pig manure is directly dried from its original moisture content of 75 wt% to reduce the moisture content to 22 wt%. The prepared pig manure biomass pellet fuel has a distinct odor, is easily affected by moisture and deteriorates, has a mechanical durability of 95.8%, and a density of 1.35 g / cm³. 3 Other properties and molding effects of pig manure biomass pellet fuel are shown in Table 1.

[0085] Comparative Example 3

[0086] Commercially available wood-based biomass pellet fuel is cylindrical in shape, with a diameter of 9-10 mm and a length of 10-50 mm. Table 1 shows the specific properties of cylindrical wood-based biomass pellet fuel in the prior art.

[0087] Table 1. Performance of biomass pellet fuels prepared in Examples 1-6 and Comparative Examples 1-3 of this invention.

[0088]

[0089] Table 1 shows the molding rate. After the pig manure biomass pellet fuel is extruded and molded, it is screened using a stainless steel sieve with a 4mm aperture. The mass of the material on the sieve is divided by the mass fraction of the total mass of the pig manure biomass pellet fuel obtained after extrusion molding.

[0090] Based on the performance of biomass pellet fuel in Table 1 and the mechanical durability and density of pig manure biomass pellet fuel, pig manure biomass pellet fuel with added chicken manure biochar powder and sawdust has advantages such as being odorless and moisture-proof and mildew-proof. Pig manure biomass pellet fuel containing chicken manure biochar powder exhibits superior performance in these aspects. Pure pig manure biomass pellet fuel that has undergone dry-wet separation treatment is essentially odorless and also has moisture-proof and mildew-proof characteristics. Comparing Example 2 and Example 4, pig manure biomass pellet fuel without dry-wet separation has a noticeable odor, is more susceptible to moisture and deterioration, and its calorific value (i.e., calorific value), mechanical durability, and molding rate are significantly reduced, while the ash content is significantly increased. The content of elements N, S, and Cl more than doubles, especially the Cl content. Furthermore, the drying process of unseparated pig manure requires more energy and easily releases odorous gases into the air, seriously affecting the surrounding environment. This indicates that dry-wet separation and the addition of chicken manure biochar powder have a significant effect on improving the overall performance of pig manure biomass pellet fuel. The pig manure biomass pellet fuel obtained by this invention produces almost no polluting gases (including S, N or Cl gases) during combustion, and has superior environmental value.

[0091] Furthermore, comparing Comparative Example 1 and Example 2, although other properties remained largely unchanged, the mechanical durability and pellet yield of the pig manure biomass pellet fuel prepared from the mixture with a moisture content of 16% decreased sharply, reaching only 78.5% and 58.63%, respectively. Further research revealed that when the moisture content of the mixture was approximately 12%, the pellet yield of the pig manure biomass fuel was less than 1%; and when the moisture content was approximately 20%, the pellet yield was only around 90%, indicating that the moisture content of the mixture is extremely important for the pelletizing effect of pig manure biomass fuel.

[0092] As can be seen from Table 1, the calorific value of the pig manure biomass pellet fuel obtained by this invention (calorific value of Examples 1 to 6) is comparable to, or even better than, that of traditional wood-based biomass fuel (Comparative Example 3). Its ash content and elemental N, S, and Cl content are determined by the properties of livestock and poultry manure, and the sawdust used in the preparation process can be entirely derived from agricultural and forestry waste and related wood materials left over from wood processing. Therefore, the pig manure biomass pellet fuel obtained by this invention has good application prospects in the national economy and daily life.

[0093] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A pig manure biomass pellet fuel, characterized in that: Based on the dry weight of pig manure biomass pellet fuel, it consists of 70wt%-100wt% pig manure residue, 0wt%-30wt% sawdust, and 0wt%-10wt% chicken manure biochar, with the combined content of sawdust and chicken manure biochar ≤30wt%. The method for preparing pig manure biomass pellet fuel includes the following steps: (1) Fresh pig manure from pig farms is separated into solid and liquid components by a spiral dry-wet separator to obtain pig manure residue; (2) Dry the pig manure residue to reduce the moisture content to 22-30 wt%, then crush and screen it, and then mix it with pretreated wood chips and chicken manure biochar. Further mechanically stir and mix for 10-15 minutes to obtain a uniform mixture with a moisture content of 22-28 wt%. (3) The mixture obtained in step (2) is extruded and molded using a biomass pellet machine to obtain pig manure biomass pellet fuel; (4) Cool the formed pig manure biomass pellet fuel to room temperature naturally, and screen out unqualified products with a length of less than 4mm. The material left on the screen is the qualified pig manure biomass pellet fuel product.

2. The pig manure biomass pellet fuel according to claim 1, characterized in that: The pig manure biomass pellet fuel is cylindrical, with a diameter of 8-10 mm and a length of 10-75 mm.

3. The pig manure biomass pellet fuel according to claim 1, characterized in that: The moisture content of fresh pig manure in step (1) is 75-81 wt%, and the moisture content of pig manure residue after solid-liquid separation is below 58 wt%.

4. The pig manure biomass pellet fuel according to claim 1, characterized in that: In step (2), the drying temperature of pig manure residue is 105-110℃. It can be used directly after simple crushing, or it can be used after further screening of pig manure residue. The screening is performed by passing through a 10-mesh stainless steel sieve.

5. The pig manure biomass pellet fuel according to claim 1, characterized in that: In step (2), the wood chips are wood chips or sawdust from common trees such as white pine, fir, cypress or Masson pine. The pretreatment involves drying the wood to 22-28 wt% at 105-110℃ and then crushing it through a 10-mesh stainless steel sieve.

6. The pig manure biomass pellet fuel according to claim 1, characterized in that: In step (3), the biomass pellet mill is either a ring type or a roller type.

Images