CN116064181A

CN116064181A - Sludge biomass composite particle fuel and preparation method and application thereof

Info

Publication number: CN116064181A
Application number: CN202211672811.7A
Authority: CN
Inventors: 侯浩波; 游以文; 张鹏举; 曾天宇; 陈金定; 黄一洪; 纪建业; 何彩霞; 蔡建亮
Original assignee: Institute Of Resources And Environmental Technology Wuhan University Zhaoqing
Current assignee: Institute Of Resources And Environmental Technology Wuhan University Zhaoqing
Priority date: 2022-12-26
Filing date: 2022-12-26
Publication date: 2023-05-05

Abstract

The invention discloses a sludge biomass composite particle fuel and a preparation method and application thereof. The granular fuel comprises sludge and plant residues; the plant residues consist of wood residues and straw residues, and the mass ratio of the sludge to the wood residues to the straw residues is 4-5: 1 to 1.5:3 to 4. The granular fuel is creatively proportioned according to the content of each element in the raw materials based on the synergistic effect of each component, and the obtained granular fuel has high heat value, low volatile and ash residues; the content of aluminosilicate in the ash is controlled, and the obtained ash has good gelling activity and excellent heavy metal fixing effect. The pellet fuel is prepared by mechanically activating raw materials, mixing, and performing twice mould pressing, and has the advantages of simple preparation and excellent water resistance and mechanical properties. Based on the excellent performance of the granular fuel, the granular fuel can be used for boiler heating, ash residues after the granular fuel is combusted can be used for preparing filter material ceramsite of a water treatment reactor, and comprehensive utilization of solid waste materials is realized.

Description

Sludge biomass composite particle fuel and preparation method and application thereof

Technical Field

The invention relates to a composite particle fuel, in particular to a sludge biomass composite particle fuel and a preparation method and application thereof, and belongs to the technical field of solid waste recycling technology.

Background

Municipal sludge is a byproduct of sewage treatment, and generally refers to precipitates, particles and floaters composed of various microorganisms and organic and inorganic particles generated when domestic sewage and industrial wastewater are treated. It is mainly composed of primary sludge, secondary sludge and chemical sludge, and the urban sewage discharge amount in 2021 is up to 800 hundred million tons, calculated by 70% urban sewage treatment rate and 80% sludge water content, and the sludge yield has broken through 5000 ten thousand tons. In the face of the huge output and complex-component sludge, how to safely and properly treat and dispose the sludge really realizes the reduction, harmless and recycling of the sludge becomes a great difficult problem to be solved in the environmental field.

The sludge combustion can not only furthest realize sludge reduction and completely kill toxic and harmful substances, but also recover energy in the sludge, and is the most effective and thorough final sludge treatment method. The main advantages of sludge combustion compared with other methods are: (1) reducing the volume of sludge. The ash produced after the sludge incineration has stable property and small volume, and realizes the volume reduction rate of about 95%; (2) innocuous. The high-temperature incineration can kill pathogens and destroy the structure of toxic organic molecules, so that the sludge is thoroughly harmless; (3) Most of heavy metals are deposited in the ash, the heavy metals in the ash are more stable than the original sludge, and meanwhile, the ash can be used as an adsorbent and a raw material of a brick plant; (4) The heat value of the dry sludge is almost equal to that of lignite, and the heat recovery and utilization of the dry sludge can be realized by incineration. Therefore, the proportion of the sludge incineration disposal is higher and higher in recent years at home and abroad, and the incineration technology is rapidly popularized and applied. The national environmental protection department issued 'guide (trial) of the best feasible technology for pollution control of sludge treatment and disposal in urban sewage treatment plants' prescribes that sludge incineration is one of the best feasible technologies for sludge disposal. However, the municipal sludge has higher water content and lower heat value after dehydration treatment, and if the municipal sludge is directly burnt, the problems of low heat efficiency, low heat value, unstable combustion and the like exist, so that the requirements of heat supply and power generation of an industrial boiler are hardly met. Thus, a sludge complex fuel combustion technology has been developed. The technology of the sludge composite fuel is to mix the sludge and the heat value

The high fuel, such as coal dust, organic garbage and the like, is prepared into the mixed fuel, and is then sent into the burning equipment of a chain furnace, a coal dust boiler, a circulating fluidized bed boiler and the like for burning.

However, the traditional sludge composite fuel technology cannot achieve effective balance of high heat value, low volatile matters and secondary utilization of ash, and in order to promote combustion to be more sufficient, the addition amount of the high heat value fuel is excessive, and the carbon content in the selected high heat value fuel is too high, so that the content of silicon-aluminum oxide in the obtained ash is too low, and the ash is difficult to use for building material production; in addition, the high-calorific-value fuel also contains a large amount of nitrogen and sulfur substances, so that the volatile matters contain a large amount of nitrogen and sulfur compounds, secondary pollution to air can be caused, and the fixation of heavy metals in the composite fuel cannot be controlled, thereby causing larger environmental problems.

Therefore, research on sludge-biomass composite fuels is beginning to be widely focused and a practical treatment scheme is needed in order to realize sludge reduction, recycling and energy application.

Disclosure of Invention

Aiming at the problems existing in the prior art, the first aim of the invention is to provide a sludge biomass composite granular fuel, which is creatively proportioned according to the content of each element in raw materials based on the synergistic effect of each component, greatly reduces the generation of volatile matters and ash slag on the premise of ensuring that the granular fuel has high heat value, and strictly controls the content of gelling components such as silicon aluminum and the like in the ash slag; furthermore, the obtained ash has good gelling activity, has excellent fixing effect on heavy metals in the granular fuel, and avoids secondary pollution of the environment caused by heavy metal particles entering the environment along with volatile matters.

The second aim of the invention is to provide a preparation method of the sludge biomass composite particle fuel, which is based on an integrated forming process, the particle raw materials are fully mixed after being energized by a high-energy ball milling surface, and the internal stress of the material is eliminated by adopting two-stage mould pressing, so that the particle fuel is ensured to have excellent water resistance and mechanical property, and is convenient for subsequent use.

A third object of the invention is to provide the use of a sludge biomass composite pellet fuel for boiler heating; the ash residue after the granular fuel is combusted is used for preparing the water treatment reactor filter material ceramsite. Based on the raw material proportion of the granular fuel provided by the invention, the granular fuel has excellent heat value, and nitrogen and sulfur substances in volatile matters meet emission standards, and through tests, the heat value of the granular fuel provided by the invention is 11000-12000kJ/kg, the content of silicon oxide in ash is 55% -60%, the emission amount of nitrogen oxide is 170-200mg/m < 3 >, and the emission amount of sulfur oxide is 60-70mg/m < 3 >. The pollutant emission concentration meets the domestic garbage incineration pollution control standard (GB 18085-2014).

In order to achieve the technical purpose, the invention provides a sludge biomass composite particle fuel, which is characterized in that: including sludge and plant residues; the sludge is at least one of river bottom sludge, municipal sludge and industrial sludge; the plant residues consist of wood residues and straw residues, and the mass ratio of the sludge to the wood residues to the straw residues is 4-5: 1 to 1.5:3 to 4.

The composite granular fuel provided by the invention is prepared from solid waste materials without adding additional components and auxiliary agents, creatively mixes according to the content of each element in the raw materials, effectively solves the problems of low fixed carbon content, difficult ignition and the like in sludge, pertinently selects plant residues, ensures that the obtained ash slag can effectively fix heavy metals in the fuel, also contains higher silica components and has certain gelatinization activity, and realizes the recycling and energy utilization of the sludge and the plant residues.

As a preferable scheme, the wood residue is at least one of wood chips, wood shavings and wood residues, and the straw residue is at least one of husks, rice stalks and corncobs. Further preferably, the wood residues are wood chips, and the straw residues are rice hulls.

As a preferable scheme, the main inorganic component of the sludge is SiO ₂ 、Al ₂ O ₃ And Fe (Fe) ₂ O ₃ 。

As a preferable scheme, the rice hulls are derived from waste rice hulls in rural areas of far urban areas in Wuhan City, and the main inorganic component of the rice hulls is SiO ₂ And Al ₂ O ₃ 。

As a preferable scheme, the wood chipsWaste wood dust from forest farms in the far urban areas of the Wuhan city, wherein the main inorganic component of the wood dust is SiO ₂ 、Al ₂ O ₃ And CaO.

The mixing of rice husk and wood dust can improve the ignition temperature of sludge, stabilize combustion characteristics such as combustion performance, combustion rate, burnout temperature and the like, reduce the generation of toxic smoke, promote the complete reaction of combustible matters and organic pollutants, and supplement the silica content in ash.

As a preferable scheme, the sludge biomass composite particle fuel comprises the following components in percentage by mass: 40-45% of sludge, 10-15% of wood chips and 30-40% of rice hulls. The addition of each component of the raw material of the granular fuel is strictly carried out according to the requirements, if the content of the sludge is too high, the granular fuel is difficult to ignite, the combustible substances in the sludge can not be completely combusted, and coking and adhering to a combustion chamber are generated; if the rice hull content is too high, the flue gas amount is too large, and the discharged nitrogen and sulfur substances are too much, so that secondary pollution is caused to the environment; if the wood chip content is too high, the density of the obtained composite particles is too low, the mechanical property is reduced, the total amount of ash is increased, the silica content in the ash is reduced, and the gelation activity of the ash is reduced.

As a preferable scheme, the molding density of the granular fuel is 1.40-1.50 g/cm ³ The relaxation density is 1.30-1.40 g/cm ³ 。

The invention also provides a preparation method of the sludge biomass composite particle fuel, which comprises the steps of respectively crushing and sieving fuel raw materials including sludge, wood residues and plant residues, uniformly mixing, and sequentially carrying out primary mould pressing, secondary mould pressing, demoulding and standing.

The preparation method provided by the invention is based on an integrated forming process, the particle raw materials are fully mixed after being energized by the high-energy ball milling surface, and the internal stress of the material is eliminated by adopting two-stage mould pressing, so that the particle fuel is ensured to have excellent water resistance and mechanical property, and is convenient for subsequent use.

As a preferable scheme, the crushing process is high-energy ball milling and crushing, and the high-energy ball milling conditions are as follows: the rotating speed is 2500-3000 r/min, and the time is 10-15 min. The high-energy ball milling process is strictly carried out according to the requirements, and if the rotating speed is too low or the time is too short, the surface energization of the raw materials cannot be realized, the adhesive force of the raw materials is reduced, and the molding is not facilitated; if the time is too long, the raw material is partially carbonized, and the molding of the raw material is not facilitated.

As a preferable embodiment, the particle size of the fuel raw material is 150 to 250 μm; the water content of the granular fuel is 10-20%. The water content of the granular fuel is one of key factors of forming, the high water content in the sludge can improve the pores of the synthetic fuel after mixing and drying, promote air to go deep into the fuel, further enable combustion to be complete, and the sludge can also provide water required by the technological process in the gasification process; however, if the water content in the sludge is too high, the water content of the granular fuel can be greatly increased, the mechanical property and water permeability resistance of the fuel are reduced, and the storage and transportation of raw materials are not facilitated.

As a preferred solution, the one-stage molding is a manual pre-pressing, provided that: the pressure is 0.1-0.2 MPa, and the time is 5-10 s; the two-stage compression molding is molding compression molding, and the conditions are as follows: the pressure is 11.5MPa to 13.4MPa, and the time is 1.0 to 1.5min. The two-stage molding adopted by the invention can effectively ensure the mechanical strength of the material, the one-stage manual pre-pressing can promote the compaction of the raw material, the initial molding, the two-stage molding can ensure the adhesion of the water in the raw material, the gelling substances in the sludge, the semi-fibers and other gelling substances in the plant residues, and the rebound of the fuel is reduced, so that the fuel molding can be realized without auxiliary agents.

The invention also provides application of the sludge biomass composite pellet fuel, wherein the pellet fuel is used for heating a boiler; the ash residue after the granular fuel is combusted is used for preparing ceramsite. .

Based on the raw material proportion of the granular fuel provided by the invention, the granular fuel has excellent heat value, and nitrogen and sulfur substances in volatile matters meet emission standards, and through tests, the heat value of the granular fuel provided by the invention is 11000-12000kJ/kg, the content of silicon oxide in ash is 55% -60%, the emission amount of nitrogen oxide is 170-200mg/m < 3 >, and the emission amount of sulfur oxide is 60-70mg/m < 3 >. The pollutant emission concentration meets the domestic garbage incineration pollution control standard (GB 18085-2014).

As a preferable scheme, the ceramsite preparation process comprises the following steps: ash, sludge and clay are mixed according to the mass ratio of 6-7: 2-3: 1-2, fully mixing and then obtaining raw material balls through a granulator; and drying, preheating and roasting raw material balls in sequence, and then cooling along with a furnace to obtain the material balls.

Further, the invention also provides a detailed preparation process of the ceramsite:

the preparation raw materials of the ceramsite comprise: ash, domestic sludge and clay formed after the combustion of the sludge-biomass fuel are adopted, part of the sludge is doped to serve as an air generating agent and a binder for firing the ceramsite, and part of the clay is doped to improve the strength and the cohesiveness of the ceramsite. The mixing mass ratio of the ceramsite raw materials is ash: sludge: clay= (6-7): (2-3): (1-2). The ceramsite is prepared according to the following steps:

(1) Mixing

Drying the sludge in the sun, mixing and burning ash, drying clay in a baking oven at 105 ℃ until the weight is constant, crushing, sieving, and mixing and burning ash according to the mass ratio: sludge: clay= (6-7): (2-3): (1-2) mixing them;

(2) Ball forming

Weighing three raw materials according to a proportion, putting the three raw materials into a stirrer, adding a proper amount of water, stirring uniformly, and when the appearance is sticky and has certain viscosity, preparing the mixture into raw material balls in a granulator, wherein the particle size of the raw material balls is 7-9 mm;

(3) Pretreatment of

Placing the raw material balls in an oven, drying for 20-45 minutes at the temperature of 90-110 ℃, and removing part of water in the raw material balls to prevent cracking of the raw material balls in the roasting process;

(4) Preheating and roasting

And (3) placing the preheated raw material balls into a porcelain boat, moving into a muffle furnace (KSY-12D-16, wuhan), heating to the designed roasting temperature, and roasting at a constant temperature. The firing mechanism is as follows: the initial preheating temperature is 550 ℃, the preheating is carried out for 15min, and then the temperature is continuously increased to 1050-1150 ℃ from the preheating temperature, and the heating rate is 25 ℃/min. Roasting for 15min at 1050-1150 ℃;

(5) Cooling

And taking out the sintered ceramsite from the furnace after the hearth is naturally cooled, thus obtaining the ceramic.

The ceramsite prepared by the ash after the granular fuel is combusted, based on the content of special aluminosilicate in the ash, has the advantages of large specific surface area, rich multi-stage pore canal structure and the like after secondary proportioning with sludge, can have good adsorption effect on pollutants in water, and realizes the full-flow resource utilization of the granular fuel.

Compared with the prior art, the technical scheme of the invention has the following beneficial technical effects:

1) The composite particle fuel provided by the invention creatively carries out proportioning according to the content of each element in raw materials based on the synergistic effect of each component, effectively solves the problems of low fixed carbon content, difficult ignition and the like in sludge, pertinently selects plant residues, ensures that the obtained ash can effectively fix heavy metals in the fuel, can also contain higher silica components, has certain gelatinization activity, and realizes the recycling and energy utilization of the sludge and the plant residues.

2) According to the technical scheme provided by the invention, based on an integrated forming process, the particle raw materials are fully mixed after being energized on the surface of the high-energy ball mill, and the internal stress of the material is eliminated by adopting two-stage mould pressing, so that the particle fuel is ensured to have excellent water resistance and mechanical property, and is convenient for subsequent use.

3) According to the technical scheme provided by the invention, based on the raw material proportion of the granular fuel provided by the invention, the granular fuel has excellent heat value, and nitrogen and sulfur substances in volatile matters meet emission standards, and through tests, the heat value of the granular fuel provided by the invention is 11000-12000kJ/kg, the content of silicon oxide in ash is 55% -60%, the emission amount of nitrogen oxide is 170-200mg/m < 3 >, and the emission amount of sulfur oxide is 60-70mg/m < 3 >. The pollutant emission concentration meets the domestic garbage incineration pollution control standard (GB 18085-2014).

4) The composite particle fuel provided by the invention is made of solid waste materials, and the sludge is not required to be placed in a digestion tank for anaerobic digestion treatment, the coal is not required to be mixed, and external additives such as wall breaking agents, combustion improvers and the like are not required to be added; the raw materials are wide in source, low in treatment cost, simple in operation condition, high in fuel heat value and stable in combustion, and can simultaneously realize the resource utilization of municipal sludge and agricultural and forestry waste, and the prepared composite fuel can be used in garbage power plants, coal-fired power plants and other scenes to replace traditional fuel, so that the purpose of treating waste by waste is realized.

Drawings

FIG. 1 is a graph of TG curves of the combustion of single-component municipal sludge, wood chips, rice hulls, and three different-component municipal sludge-wood chip-rice hull composite fuels N50D45M5, N50D35M15, and N50D5M45 of example 5;

FIG. 2 is a DTG curve of the combustion of single component municipal sludge, wood chips, rice hulls, and three different component municipal sludge-wood chip-rice hull composite fuels N50D45M5, N50D35M15, and N50D5M45 of example 5;

FIG. 3 is a graph showing the detection of the combustion products of the single-component municipal sludge, wood chips, rice hulls, and three different-component municipal sludge-wood chip-rice hull composite fuels N50D45M5, N50D35M15, and N50D5M45 of example 5;

wherein FIG. 3 (a) is CO ₂ Detection Curve, FIG. 3 (b) NO ₂ Detection Curve, FIG. 3 (c) SO ₂ A detection curve, fig. 3 (d) NO detection curve;

in FIGS. 1 to 3, N50D45M5 represents 50% of sludge, 45% of wood chips and 5% of rice hulls; N50D35M15 represents 50% of sludge, 35% of wood chips and 15% of rice hulls; N50D5M45 is expressed as 50% of sludge, 5% of wood chips and 45% of rice hulls;

FIG. 4 is a solid view showing the appearance of the ceramic granules prepared in example 6;

FIG. 5 is a scanning electron microscope image of the ceramsite prepared in example 6.

Detailed Description

The invention will be further described with reference to the following specific examples, but the scope of the invention is not limited thereto.

The municipal sludge in the embodiment of the invention is sourced from a municipal sewage treatment plant in Wuhan city, and the sludge is pretreated according to the following steps to reduce the water content to 15-25%. Drying the sludge at 115-125 ℃ for 1.5-2.0 h, grinding the sludge for 10-15 min at 2500-3000 r/min by using a ball mill (XQM-4L), and sieving the sludge by a 60-mesh square-hole sieve with the aperture of 0.25 mm;

the rice hulls are derived from rural abandoned rice hulls in the far urban areas of Wuhan, and are pretreated according to the following steps. Grinding for 10-15 min at 2500-3000 r/min by using a ball mill (XQM-4L), sieving by a 60-mesh square-hole sieve with the aperture of 0.25mm, and drying for 2-3 h in a drying oven with the temperature of 100-110 ℃;

the wood chips are derived from waste wood chips in forest lands in far urban areas of the Wuhan city, and are pretreated in the following manner. Grinding for 10-15 min at 2500-3000 r/min by a ball mill (XQM-4L), sieving by a 60-mesh square-hole sieve with the aperture of 0.25mm, and drying for 2-3 h in an oven with the temperature of 100-110 ℃.

According to the industrial analysis method of solid biomass fuel (GB/T28731-2010) and the industrial analysis method of coal (GB/T212-2008), urban rice hulls, wood chips and sludge are respectively subjected to industrial analysis. Elemental analysis of the feedstock the main elemental content of carbon, hydrogen, oxygen, nitrogen, sulfur, etc. in the sample was automatically determined using a CHNS/O elemental analyzer (Vario EL cube, elementar, germany). The low-position heating value of the raw materials is measured by a high-precision dual-purpose full-automatic calorimeter (SDC 5015, changsha Sande) according to an oxygen bomb combustion method (GB/T213-2008). The experimental results of industrial, elemental analysis and dry basis calorific value of the three raw materials are shown in table 3.1.

Raw material industry, elemental analysis, and calorific value

Wherein A is _ad Ash content (%): v (V) _ad Volatile content (%): FC (fiber channel) _ad Represents the fixed carbon content (%): LHV (liquid suction volume) _ad Indicating calorific value (kJ/kg)

The urban sludge, rice hulls and wood chips are mixed according to the following weight parts, N50D15M35 (urban sludge: wood chips: rice hulls=50%: 15%: 35%), N50D25M25 (urban sludge: wood chips: rice hulls=50%: 25%: 25%), N50D35M15 (urban sludge: wood chips: rice hulls=50%: 35%: 15%), the molding pressures are respectively 50kN, 70kN and 100kN, and the average water contents of the raw materials after mixing are respectively 5%, 10% and 20%.

Compound fuel molding experiment influence factor and level gauge

Pouring the mixed raw materials into a detachable column-shaped die with the dimension of phi 40 multiplied by 45mm for manual pre-pressing so as to discharge air in the mixed materials. The mould with the mixture is placed on a force application platform of a press, the mixture particles at the initial stage of pressurization slowly abut against each other so as to discharge air, the forming pressure is adjusted to a set level, and finally the composite fuel is compressed. After molding, the mold was placed on a small-sized stripper and the composite fuel was extruded from the top of the mold by bottom pressure. After the composite fuel is demoulded, part of elastic energy can be released by the mixture particles, so that the fuel is rebounded, and is loosened to a certain extent in the axial direction and the radial direction, and when the composite fuel is placed for about 3 days, the volume is not changed any more and is kept constant.

Example 1

And (3) air-drying the formed composite fuel at room temperature for 10min, measuring the mass, the diameter and the height of the formed composite fuel, and calculating the forming density of the fuel according to a formula. After the composite fuel is placed for 3d at room temperature, the related parameters are measured again according to the method, and finally the relaxation density of the fuel can be obtained according to the formula.

Wherein ρ represents the density of the composite fuel in g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the m represents the mass of the composite fuel, and the unit g; v represents the volume of the composite fuel in cm ³ The method comprises the steps of carrying out a first treatment on the surface of the l represents the length of the composite fuel in cm; d represents the diameter of the composite fuel, cm.

The results of the molding density and relaxation density under the conditions of different raw material ratios, molding pressures and average water contents of the raw materials are shown in the following table.

Composite fuel L ₉ (3 ⁴ ) Density results of orthogonal experimental modeling

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Composite fuel L ₉ (3 ⁴ ) Results of orthogonal experimental relaxation Density

Among the influencing factors of the relaxation density of the composite fuel, the influencing degree is water content, forming pressure and raw material proportion from large to small. The water content is the most main influencing factor influencing the relaxation density of the sludge-biomass composite fuel, and the higher the water content is, the larger the rebound quantity of compressed rice hulls and wood chips is after the fuel is formed and placed, so that the structure of the fuel is loosened, and the relaxation density of the composite fuel is reduced.

The effect of each factor on the forming density shows the same law as the relaxation density. In order to meet the requirements of transportation and storage of composite fuel, the molding density and relaxation density of the composite fuel are more than 1g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the As can be seen from orthogonal experiments, the molding density and the relaxation density of the sludge-biomass composite fuel are all more than 1g/cm almost in various proportions ³ Can meet the transportation and storage requirements.

The test results show that: the raw material ratio is N50D35M15, the molding pressure is 100kN, and when the average water content is 10%, the composite fuel is optimal in terms of molding density and relaxation density.

Example 2

Aiming at the composite fuel prepared under the conditions of different raw material proportions, molding pressure and average water content of raw materials, the radial compressive strength of the composite fuel is detected, and the specific method is as follows: the composite fuel is placed on a universal material testing machine (WE-300S, shaoxing Kent) platform, the testing machine applies pressure to the composite fuel at a constant displacement of 15mm/min, the test is stopped when the composite fuel is crushed, and the testing machine automatically records the pressure value when the composite fuel is crushed.

The compressive strength test results of the composite fuel under the conditions of different raw material ratios, molding pressures and average water content of the raw materials are shown in the following table.

Composite fuel L ₉ (3 ⁴ ) Compressive Strength results of orthogonal experiments

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The influence degree of each factor on the compressive strength of the composite fuel is sequentially from large to small, namely the water content, the molding pressure and the raw material ratio. The compressive strength values of the 9 groups of samples are compared, and the compressive strength of three groups of composite fuels with the water content of 10 percent is found to be higher than 315N, wherein the maximum value is 375.43N, which is obviously higher than that of other groups, and the compression strength of the three groups of composite fuels is found to be higher than that of the other groups from K of the column with the water content _ij The value can also obtain the rule, the water content has the greatest influence on the compressive strength of the fuel, and too high or too low water content has great fluctuation on the compressive strength of the composite fuel, because when the water content of the raw materials is too low, the raw material particles are prevented from sliding, the fluidity is reduced, the contact area between the particles is reduced, the raw material particles are not tightly adhered, when the water content of the raw materials is too high, the lubrication effect of the water in the raw materials is too large, the water is extruded during pressurization, and the method is also disadvantageousAnd bonding and molding among the particles. The higher the rice hull content and the lower the wood chip content, the higher the compressive strength of the composite fuel. The cellulose and hemicellulose content in rice hulls is higher and the lignin content is lower than in wood chips, hemicellulose is a viscoelastic substance that can act as a viscosity between amorphous lignin and crystalline cellulose. In addition, the abundant proteins and polysaccharides in municipal sludge can form a firm reinforcement cage with hemicellulose and cellulose, which may be the reason for the increased rice hull content and the increased compressive strength. The greater the molding pressure, the greater the adhesion between the raw material particles, the denser the molding, the higher the compressive strength, and the stronger the ability of the fuel to resist extrusion impact during transportation and stacking.

As shown by the extremely poor compression strength results, the optimal technological parameter is A3B3C2, and the optimal technological parameter is exactly on the ninth group of composite fuel, namely, the compression strength of the composite fuel is maximum when the raw material proportion is N50D35M15, the forming pressure is 100kN, and the average water content of the raw material is 10%. As seen from the results of the variances of the compressive strengths, the F values of the water content and the molding pressure are 46.12 and 28.61 respectively, which are larger than the critical value 19, so that the influence is remarkable, and the F value of the raw material ratio is only 7.56, which is smaller than the critical value, so that the influence is not remarkable. The F values of the three factors are water content, forming pressure and raw material proportion from large to small in sequence, so that the influence degree of the water content on compressive strength is the greatest, the influence of the forming pressure is secondary, and the influence of the raw material proportion is the least.

Example 3

The drop strength of the composite fuel is detected according to the composite fuel prepared under the conditions of different raw material proportions, molding pressure and average water content of the raw materials, and the experimental method is referred to the methods for measuring the drop strength of industrial coal (MT/T925-2005) and the methods for measuring the drop strength of coal (GB/T15459-1995). m is m ₀ The composite fuel sample with the mass is freely dropped onto the cement floor at the height of 2m, the fuel sample with the mass larger than 13mm in the dropped sample is collected and freely dropped again, the experiment is repeated for 3 times, and finally the sample with the mass m larger than 13mm after being weighed and crushed is obtained _i The drop strength is calculated according to the formula.

The results of the drop strength of the composite fuel produced under the conditions of different raw material ratios, molding pressures and average water contents of the raw materials are shown in the following table.

Composite fuel L ₉ (3 ⁴ ) Drop strength results from orthogonal experiments

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It can be seen that the primary and secondary relation of the influence of each factor on the falling strength of the composite fuel is that the water content is greater than the forming pressure and greater than the raw material ratio, so that the water content is a main influence factor on the falling strength of the composite fuel. As can be seen from the result of the extremely poor analysis, the horizontal combination of the factors of the optimal drop strength is A3B3C2, namely the ratio of the urban sludge to the rice hulls to the wood chips is N50D35M15, the molding pressure is 100kN, and the drop strength of the composite fuel is optimal when the average water content is 10 percent, and is consistent with the optimal compression strength combination and the optimal relaxation density combination.

The drop strength value is in direct proportion to the molding pressure, and the higher the molding pressure is, the more tightly the raw material particles are bonded, and the higher the drop strength of the fuel is. Too high or too low a water content may cause a large fluctuation in the falling strength of the sample, which may be that when the water content is too low, the raw material particles are hindered from sliding, the fluidity is reduced, the contact area between the particles becomes small, the raw material particles are not tightly bonded, when the water content of the raw material is too high, the lubrication effect of the water in the raw material is too large, and the water is extruded during pressurization, which is also unfavorable for the bonding formation between the particles. The higher the rice hull content and the lower the wood chip content, the higher the compressive strength of the sludge composite fuel. Rice hulls have a higher cellulose and hemicellulose content and a lower lignin content than wood chips, and hemicellulose is a viscoelastic material that is capable of achieving a viscous effect between amorphous lignin and crystalline cellulose. Meanwhile, abundant proteins and polysaccharides in the municipal sludge can form a firm reinforcement cage with hemicellulose and cellulose, which may be the reason for the increased rice hull content and the enhanced falling strength.

Example 4

Aiming at the composite fuel prepared under the conditions of different raw material proportions, molding pressure and average water content of raw materials, a water permeation resistance experiment is carried out, and the specific method is as follows: immersing the composite fuel sample in water, keeping the water temperature at about 20 ℃, covering the upper part of the container by a glass plate to prevent the fuel from floating on the water surface, and recording the time when the composite fuel is completely loosened. Five experiments were repeated for each sample and the results averaged.

The results of the permeation resistance test of the composite fuel prepared under the conditions of different raw material ratios, molding pressures and average water content of the raw materials are shown in the following table.

Composite fuel L ₉ (3 ⁴ ) Results of orthogonal experiments on permeation resistance

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It can be seen that the influence degree of the water impermeability of the composite fuel is sequentially from large to small, namely the water content, the forming pressure and the raw material ratio. The greater the forming pressure, the better the water penetration resistance of the sample. This is probably because, after the pressure is increased, the large particles in the raw material are broken into fine particles, the particles are embedded into each other, the gaps become smaller, and the adhesion is more dense, so that the water permeation resistance of the fuel is enhanced. The proper water content can lead the sample to have optimal water seepage resistance performance, and too high and too low water content can lead the water seepage resistance to be reduced. This may be that when the water content is too low, the raw material particles are prevented from sliding, the fluidity is reduced, the contact area between the particles becomes small, the raw material particles are not tightly bonded, so that the water permeation resistance of the fuel is deteriorated.

As shown by the extremely poor water impermeability results, the optimal process parameter is A3B3C2, namely, when the raw material ratio is N50D35M15, the molding pressure is 100kN, and the average water content of the raw materials is 10%, the water impermeability of the composite fuel is optimal. As shown by the variance results of the water impermeability, the F values of the water content and the forming pressure are 31.69 and 25.80 respectively and are larger than the critical value 19, so that the influence is remarkable, the F value of the raw material proportion is only 11.10 and smaller than the critical value, and the influence is not remarkable. The F values of the three factors are water content, forming pressure and raw material proportion from large to small in sequence, so that the influence degree of the water content on the fuel impermeability is maximum, the influence of the forming pressure is secondary, and the influence of the raw material proportion is minimum.

Example 5

Mixing municipal sludge, rice hulls and wood chips according to the following weight portions, wherein N50D45M5 (municipal sludge: wood chips: rice hulls=50%: 45%: 5%), N50D35M15 (municipal sludge: wood chips: rice hulls=50%: 35%: 15%), and N50D5M45 (municipal sludge: wood chips: rice hulls=50%: 5%: 45%), wherein the water content of the mixed raw materials is controlled within a range of 15-20%, placing the mixture into a detachable column-type die with the size of phi 40 x 45mm, and performing compression molding within a pressure range of 95-105 kN by using a NYL-300 type press to obtain 3 groups of sludge-biomass composite fuels with different raw material components.

The single-component urban sludge, rice hulls, wood chips and 3 groups of sludge-biomass composite fuel with different raw material components are crushed and sieved into powder with the particle size of 1mm by adopting a ball mill for combustion experiments. Thermogravimetric-mass spectrometry analysis was performed on the 6 samples.

The experimental instrument is a German STA 449 thermogravimetric-mass spectrometer; the experimental atmosphere is a mixed gas consisting of 20% of high-purity oxygen and 80% of high-purity nitrogen, and the flow is 70ml/min; the fuel quantity is about 10mg, and the fuel is heated to 1000 ℃ by adopting combustion rates of 5 ℃/min, 10 ℃/min, 15 ℃/min and 20 ℃/min respectively; and detected a molecular weight of 30 (N)O)、44(CO ₂ )、46(NO ₂ ) And 64 (SO) ₂ ) Is a combustion product of (a) a combustion product of (b).

When the combustion rate is 15 ℃/min, TG and DTG curves of the combustion of the municipal sludge, rice hulls, wood chips and sludge-biomass composite fuel are shown in the accompanying figures 1 and 2. It can be seen that the weight loss range and weight loss difference between the single component fuel and the composite fuel is large between 200-350 ℃. Wherein the weight loss range of the sludge is 200-352.5 ℃, the weight loss range of the rice hulls is 200-337.4 ℃, the weight loss range of the wood chips is 200-369.7 ℃, and the weight loss ranges of the three groups of composite fuels (N50D 45M5, N50D35M15 and N50D45M 5) are all about 200-350 ℃. As can be seen from FIG. 3, CO from the combustion of municipal sludge and a complex fuel ₂ And NO ₂ CO generated mainly in the region and generated by rice husk and wood dust ₂ And NO ₂ Has two obvious peaks, one peak is in the range of the temperature range, and six fuels are combusted to generate SO ₂ All are generated in this temperature range, and therefore, it can be judged that the volatile combustion process of six kinds of fuels mainly occurs in this temperature range.

The combustion of the sludge-biomass composite fuel is mainly divided into two combustion processes, and the combustion is mainly carried out on volatile matters in the fuel at lower temperature to generate CO ₂ 、NO ₂ 、SO ₂ The constant carbon in the fuel is mainly burnt at higher temperature to generate CO ₂ 、NO ₂ . The rice husk and the wood dust are doped, so that the defects of low volatile content and low fixed carbon content of the sludge fuel can be overcome, and the combustion reaction intensity and heat release quantity of the sludge fuel are increased.

The heat value of the sludge-biomass fuel with three groups of different raw material ratios and the emission concentration of NOX and SO2 formed after combustion are respectively detected, and the results are as follows:

in this embodiment, the chemical composition of the mixed combustion ash formed by burning three groups of sludge-biomass fuels with different raw material ratios is also analyzed, and the chemical composition of the single-component raw materials is compared, and the results are shown as follows:

chemical composition of the mixed combustion ash and weight percent

In this embodiment, the total amount and leaching concentration of the heavy metals in the mixed ash formed by burning the sludge-biomass composite fuel with three different raw material ratios are also detected, and compared with the raw sludge, the results are shown as follows:

total heavy metal content in the mixed combustion ash, mg/kg

Concentration of heavy metal leached in the mixed combustion ash, mg/L

The result shows that the total amount of heavy metals in the ash is obviously higher than that in the sludge after incineration, and the heavy metals in the sludge are enriched, and the leaching test result shows that the leaching rate of the heavy metals after entering the ash is extremely low, so that the comprehensive sewage discharge standard is reached, and the heavy metals in the sludge can be better solidified and stabilized, and the harm to the environment is reduced.

Example 6:

the ash residue obtained in the embodiment 5 is fully combusted after the conforming particle combustion, and the ash residue is used as a raw material, and the mixed combustion ash, sludge and clay are used for preparing the ceramsite according to the following steps:

(1) Mixing

Drying the sludge in the sun, mixing and burning ash, drying clay in a baking oven at 105 ℃ until the weight is constant, crushing, sieving, and mixing and burning ash according to the mass ratio: sludge: clay = 7:2:1;

(2) Ball forming

Weighing three raw materials according to a proportion, putting the three raw materials into a stirrer, adding a proper amount of water, stirring uniformly, and when the appearance is sticky and the hand feeling has certain viscosity, turning the mixture into balls (raw material balls) in the palm, wherein the particle size of the raw material balls is controlled to be about 8 mm;

(3) Pretreatment of

Placing the raw material balls in an oven, drying for 30 minutes at 105 ℃, removing part of water in the raw material balls, and preventing the balls from cracking in the roasting process;

(4) Preheating and roasting

(5) Cooling

And taking out the sintered ceramsite from the furnace after the hearth is naturally cooled.

The specific surface area, compressive strength, water absorption, apparent density and other performances of the ceramsite product are tested, and the test results are as follows:

firing process and ceramsite product performance

As can be seen from the table, the three groups of ceramsite have larger performance difference, the water absorption rate and specific surface area of the ceramsite gradually decrease with the increase of the roasting temperature, and the compressive strength and apparent density of the particle gradually increase. The apparent density of the three groups of ceramsite is 1.29-1.34g/cm < 3 >, the apparent density and the bulk density of the ceramsite are in a general direct proportion relationship, and the bulk density of the three groups of ceramsite is 665.81-794.84kg/m < 3 >, thus the ceramsite belongs to the 700-800 grade artificial lightweight aggregate of lightweight aggregate and experimental method (GB/T17431.1-1998). The T1 ceramsite compression strength is 5.16MPa, the converted cylinder pressure strength is 3.87MPa, the requirements of 700-grade artificial lightweight aggregate qualified products in lightweight aggregate and experimental methods thereof (GB/T17431.1-1998) are met, and the cylinder pressure strength of T2 and T3 ceramsite also meets the requirements of qualified products. On the premise that all three groups of ceramsite meet the requirement of light weight and have certain compressive strength, the specific surface area and the water absorption are used as main control indexes, and the specific surface areas of the T1 and T2 ceramsite are more than 0.5m2/g, so that the industrial standard of the artificial ceramsite for water treatment is met.

Comparative analysis is carried out on the leaching toxicity of heavy metals in sludge and ceramsite, and the result is as follows:

ceramsite and sludge heavy metal TCLP (total chemical mechanical polishing) experimental leaching amount, mg/L

The leaching concentration of the four target heavy metals in the T1 haydite does not exceed the legal threshold of the first-level standard of the comprehensive sewage discharge standard and the III standard of the underground water. The heavy metal leaching concentration of the mixed-burned ash ceramsite is obviously lower than that of the heavy metal in ash slag after high-temperature roasting, because most of the heavy metal in the mixed-burned ash can be fixed in formed silicate, glass and the like through high-temperature roasting after roasting, so that a stable solid solution is formed. The mobility of the fixed heavy metals in the high temperature fired crystalline phase and amorphous glass body is reduced. Therefore, the method has less harm to the environment caused by heavy metal leaching of the mixed-burned ash sintered ceramsite, and the mixed-burned ash sintered ceramsite is used as a water treatment filter material, so that the safety meets the requirements.

Claims

1. The utility model provides a mud living beings composite pellet fuel which characterized in that: including sludge and plant residues; the sludge is at least one of river bottom sludge, municipal sludge and industrial sludge; the plant residues consist of wood residues and straw residues, and the mass ratio of the sludge to the wood residues to the straw residues is 4-5: 1 to 1.5:3 to 4.

2. The sludge biomass composite pellet fuel as claimed in claim 1, wherein: the wood residues are at least one of wood chips, wood shavings and wood residues, and the straw residues are at least one of fruit shells, rice husks, rice stalks and corncobs.

3. The sludge biomass composite pellet fuel as claimed in claim 2, wherein: comprises the following components in percentage by mass: 40-45% of sludge, 10-15% of wood chips and 30-40% of rice hulls.

4. The sludge biomass composite pellet fuel as claimed in claim 1, wherein: the molding density of the granular fuel is 1.40-1.50 g/cm ³ The relaxation density is 1.30-1.40 g/cm ³ 。

5. The method for preparing the sludge biomass composite particle fuel as claimed in claims 1 to 4, which is characterized in that: respectively crushing and sieving fuel raw materials including sludge, woody residues and plant residues, uniformly mixing, and sequentially carrying out primary mould pressing, secondary mould pressing, demoulding and standing to obtain the fuel.

6. The method for preparing the sludge biomass composite particle fuel according to claim 5, which is characterized in that: the crushing process is high-energy ball milling and crushing, and the high-energy ball milling conditions are as follows: the rotating speed is 2500-3000 r/min, and the time is 10-15 min.

7. The method for preparing the sludge biomass composite particle fuel according to claim 5, which is characterized in that: the particle size of the fuel raw material is 150-250 mu m; the water content of the granular fuel is 10-20%.

8. The method for preparing the sludge biomass composite particle fuel according to claim 5, which is characterized in that: the one-section mould pressing is manual pre-pressing, and the conditions are as follows: the pressure is 0.1-0.2 MPa, and the time is 5-10 s; the two-stage compression molding is molding compression molding, and the conditions are as follows: the pressure is 11.5MPa to 13.4MPa, and the time is 1.0 to 1.5min.

9. The use of a sludge biomass composite pellet fuel as claimed in claims 1-4, characterized in that: the granular fuel is used for heating a boiler; the ash residue after the granular fuel is combusted is used for preparing the water treatment reactor filter material ceramsite.

10. The use of a sludge biomass composite pellet fuel as claimed in claim 9, wherein: the preparation process of the ceramsite comprises the following steps: ash, sludge and clay are mixed according to the mass ratio of 6-7: 2-3: 1-2, fully mixing and then obtaining raw material balls through a granulator; and drying, preheating and roasting raw material balls in sequence, and then cooling along with a furnace to obtain the material balls.