CN120536167A - A method for producing biomass coal briquette - Google Patents

Abstract

The present application relates to the field of biomass coal briquette preparation, and specifically discloses a method for producing biomass coal briquette. A method for producing biomass coal briquette comprises the following steps: (1) drying and crushing the biomass raw material, subjecting it to rapid pyrolysis treatment in an oxygen-limited environment, and then modifying it by high-pressure steam explosion; (2) mixing the modified biomass with activated coal powder, a composite binder, and a combustion aid in a specific proportion, wherein the coal powder is synergistically activated by light tar and wood vinegar; (3) using a gradient hot pressing process to achieve densification molding through multi-stage temperature-pressure control; and (4) finally curing it at low temperature to obtain a finished product. The coal briquette prepared by the present application has good strength and combustion efficiency.

Description

Production method of biomass briquette

Technical Field

The application relates to the technical field of biomass briquette preparation, in particular to a production method of biomass briquette.

Background

With the continued growth of energy demand and the increasing prominence of environmental concerns, the development of clean, efficient alternative energy sources has become a global focus of attention. Coal is a traditional energy source, and a large amount of pollutants are generated in the combustion process, while biomass energy is regarded as an important supplementary energy source due to the renewable and low-carbon emission characteristics. The biomass and the pulverized coal are compounded to prepare the molded coal, so that the energy density of the biomass can be improved, the combustion performance of the coal can be improved, and the molded coal has important application value.

However, the existing biomass briquette technology still has a plurality of defects that firstly, the compatibility of biomass and coal dust is poor, so that the briquette is insufficient in mechanical strength and easy to crack in the transportation and use processes, and in addition, the conventional molding technology is difficult to achieve both high density and good pore structure, so that the combustion efficiency is influenced.

Therefore, there is a need to develop a high strength, high calorific value briquette preparation technology.

Disclosure of Invention

The application provides a method for producing biomass briquette in order to improve the strength and the calorific value of the briquette.

In a first aspect, the method for producing biomass briquette provided by the application adopts the following technical scheme:

The production method of the biomass briquette comprises the following steps:

(1) Drying biomass until the water content is 10-15%, and pulverizing to 0.5-2mm;

(2) Rapidly pyrolyzing the crushed biomass for 2-5min at 200-300 ℃ in an oxygen-limited environment to obtain partially carbonized biomass, introducing saturated steam into the partially carbonized biomass, continuously treating for 3-5min at 180-200 ℃ under the pressure of 1.5-2.0MPa, and then instantaneously releasing the pressure to normal pressure to finish steam explosion;

(3) Mixing the biomass, pulverized coal, combustion improver and binder after steam explosion in proportion to obtain a mixture, adding water to the total water content of 16-18%, and uniformly mixing;

(4) And (3) solidifying the formed green blanks at a low temperature of 80-100 ℃ to obtain the briquette.

By adopting the technical scheme, the biomass briquette production method realizes the efficient utilization of waste biomass and the remarkable improvement of the combustion performance of the briquette through the synergistic modification and composite molding technology of biomass and pulverized coal. Firstly, partially carbonizing biomass through oxygen-limited pyrolysis to decompose cellulose and hemicellulose to generate volatile matters and preliminarily form a porous carbon skeleton, and retaining a lignin structure to enhance pore development; the method comprises the steps of carrying out high-pressure saturated steam instantaneous explosion treatment, utilizing mechanical shearing force generated by rapid pressure relief after steam permeation softening cell walls to further destroy biomass fiber structures, forming micron-sized through holes, exposing a large amount of oxygen-containing functional groups, remarkably improving specific surface area and reactivity of the biomass fiber structures, forming intermolecular actions of surface active sites of the modified biomass and superfine coal dust and a binder through hydrogen bonds and Van der Waals force and polar groups in the coal dust when the modified biomass is mixed, constructing a three-dimensional network structure to strengthen interface binding force, carrying out hot press forming on a mixture, slowly evaporating water to avoid pore collapse in a low-temperature solidification stage, fixing a coal skeleton through a slight cross-linking reaction of the binder, retaining unreacted active sites on the surface of the biomass, enabling the unreacted active sites to promote rapid precipitation of volatile matters and synergetic ignition of the coal dust in a subsequent combustion process, utilizing alkali metal components and functional groups to adsorb sulfur oxides, realizing synergetic control of high-efficiency sulfur fixation and pollutants, and tight compounding of the biomass porous structures and the coal dust, reducing local high temperature in the combustion process, inhibiting thermal nitrogen oxide generation, and improving thermal fracture surface of fibers generated by steam explosion and mosaic coal dust particles to obtain a final coal product with excellent mechanical properties.

Optionally, the mixture comprises 20-40 parts of biomass, 50-70 parts of coal dust, 3-5 parts of binder and 1-3 parts of combustion improver.

Optionally, the coal powder is activated by adding tar and pyroligneous liquor, and the specific steps are that the coal powder, the tar and the pyroligneous liquor are mixed according to the weight ratio of 10:0.3-0.5:0.4-0.6, and then are uniformly stirred at 60-80 ℃ to obtain the activated coal powder.

By adopting the technical scheme, the coal powder activation process reconstructs the coal powder surface structure and chemical environment through the synergistic effect of tar and pyroligneous liquor, and the coupling combustion performance of the coal powder and biomass components is remarkably improved. The tar is used as a highly aromatic substance, the defects on the surface of coal powder are repaired by a physical filling and chemical bonding dual mechanism under moderate heating conditions, a polycyclic aromatic hydrocarbon structure is embedded into micropores of the coal powder to form a carbonaceous framework, side chain alkyl reacts with oxygen-containing groups on the surface of the coal powder to construct a hydrophobic organic coating, so that the moisture absorption and the moisture regain of the coal powder are inhibited, and the structural stability of the molded coal under a humid environment is enhanced; the wood vinegar is used as an acidic byproduct of biomass pyrolysis, organic acid components of the wood vinegar selectively etch the surface of coal dust, part of mineral impurities are dissolved and internal active sites are exposed, phenolic compounds in the wood vinegar form hydrogen bonds or free radical coupling with aromatic nuclei of the coal dust through phenolic hydroxyl groups, the surface polarity of the coal dust is enhanced, the interfacial compatibility of the wood vinegar and biomass modified products is promoted, under the synergistic effect of the phenolic hydroxyl groups and the aromatic nuclei of the coal dust, tar fills the defects of coal dust pores and enhances the continuity of carbon, wood vinegar optimizes the coal dust reaction activity through surface etching and functional group modification, the specific surface area and pore volume of activated coal dust are obviously improved, the density of oxygen-containing groups on the surface is increased, the adsorption and catalytic cracking capacity of biomass cracking volatile matters are further enhanced, free radicals generated by tar cracking initiate coal dust pyrolysis chain reaction, the pyrolysis activation energy is reduced, the release of volatile matters and the fixed carbon gasification are accelerated, the active oxygen species generated by the decomposition of the wood vinegar promotes the combustion process, the ignition characteristics of the activated coal dust are improved, the burning efficiency is improved, asphaltene components in the tar form a wrapping layer at the initial stage of combustion, the explosion of particles and the uncombusted carbon are inhibited, the nitrogen/sulfur-containing active sulfur in the wood vinegar is reduced through the synergistic reaction of solid-sulfur-containing coal solid-phase gasification residual mechanism, the activation process realizes the conversion of the surface characteristics of the coal powder from inertia to activity through multi-scale regulation and control of filling-etching-functionalization of tar and pyroligneous liquor, maintains the high heat value foundation of the coal powder, endows the coal powder with the reactivity similar to biomass, and provides key technical support for the efficient combustion of biomass briquette and the cooperative control of pollutants.

Optionally, the binder comprises 3-8 parts of pregelatinized starch, 1-3 parts of sodium lignin sulfonate, 0.5-0.8 part of emulsifier, 1-3 parts of polycaprolactone and 0.5-1 part of humic acid.

By adopting the technical scheme, the adhesive system realizes the efficient molding and combustion optimization of the composite fuel through the multicomponent synergistic effect, wherein pregelatinized starch is used as a natural polymer substrate, a three-dimensional network structure is formed through gelatinization reaction under the hot and humid condition, inter-chain hydrogen bonds and hydroxyl groups on the surfaces of particles form physical adsorption, part of branched chains are hydrolyzed to generate reducing sugar, and the reducing sugar is subjected to condensation reaction with phenolic substances generated by hemicellulose/lignin pyrolysis in biomass in the subsequent pyrolysis process to form an aromatic cross-linked structure, so that the density of a carbonization layer is enhanced, and the bonding strength among particles is enhanced; secondly, sodium lignin sulfonate forms a molecular film which is arranged directionally on the surface of particles by virtue of strong hydrophilicity of sulfonic acid groups and hydrophobicity of an aromatic ring structure, on one hand, particles are uniformly dispersed by electrostatic repulsion to reduce forming resistance, on the other hand, phenolic hydroxyl groups of the sodium lignin sulfonate and carboxyl groups in humic acid are combined by hydrogen bonds, physical crosslinking networks are formed among aromatic rings through pi-pi accumulation, the forming capacity of wet materials and the shock resistance of dry particles are remarkably improved, furthermore, polycaprolactone is used as degradable thermoplastic polyester, an amorphous region presents a high-elastic state at the forming temperature, gaps among the particles are filled through chain segment movement, a crystallization region maintains skeleton strength, thermal stress is buffered, meanwhile, short chain hydrocarbons generated by pyrolysis react with O2 released by decomposition of a combustion improver to promote complete combustion of volatile matters, finally, humic acid is used as natural macromolecular organic acid, carboxyl groups, phenolic hydroxyl groups, quinone groups and the like of the humic acid can not only form chelate complexes by ion exchange adsorption to strengthen the bonding among the particles, but also can be cracked to generate free radicals during combustion, accelerate chain reaction and reduce ignition energy, the unburned carbon residue can also wrap ash particles, reduce fly ash entrainment and reduce the tendency of fusion and slagging. The four components combine mechanical stability in the molding stage and thermochemical activity in the combustion stage through a triple mechanism of physical entanglement, chemical crosslinking and combustion synergy, and finally realize dual improvement of fuel strength and combustion efficiency.

Optionally, the preparation of the binder comprises the following steps:

s1, dispersing pregelatinized starch in water, heating to 80-90 ℃ and stirring to form uniform gel, adding sodium lignin sulfonate, adjusting the pH to 8-9,60-70 ℃ and stirring for 15-20min, adding humic acid to 40-50 ℃ and stirring for 15-20min to obtain a mixed solution;

s2, heating polycaprolactone and an emulsifier to 80-100 ℃ for melting, adding water for high-speed shearing and emulsifying to form emulsion, adding the emulsion into the mixed solution at 45-55 ℃, and stirring to obtain the binder.

By adopting the technical scheme, firstly, the pregelatinized starch forms a uniform gel skeleton under alkaline conditions, the addition of sodium lignin sulfonate not only enhances the dispersion stability of the system, but also forms a hydrogen bond network with starch molecular chains, and then humic acid is introduced to further enhance the bonding performance, and rich oxygen-containing functional groups can be combined with the surface of coal dust and biomass active sites at the same time. In the second stage of emulsification process, polycaprolactone forms a stable microsphere disperse phase through an emulsifier, and is melted and permeated into coal dust and biomass pores during subsequent hot press molding, and forms an interpenetrating network structure with a starch-lignin matrix, so that high bonding strength and thermoplastic processability are simultaneously realized. Compared with the traditional single-component binder, the system overcomes the defect of poor water resistance of the pure starch binder and avoids the problem of environmental pollution of synthetic resin through organic-inorganic hybridization and hydrophilic-hydrophobic balance design, is particularly suitable for forming the molded coal with high biomass content, and ensures the mechanical strength and the combustion stability of the molded coal while reducing the production cost.

Optionally, the hot press molding adopts a gradient pressurizing method, and is firstly heated to 80-100 ℃, the pressure is 10-15MPa, the pressure is maintained for 30s, the heating is continuously carried out to 120-150 ℃, the pressure is 25-30MPa, the pressure is maintained for 60s, the heating is carried out to 180-200 ℃, and the pressure is 5-8MPa, and the pressure is maintained for 10s.

By adopting the technical scheme, the material is preliminarily compacted and gas is discharged at moderate temperature and pressure in the initial stage, a foundation is laid for subsequent molding, the binder is promoted to sufficiently melt and flow under high temperature and high pressure conditions in the second stage, the binder permeates into gaps between coal dust and biomass particles to form a compact skeleton structure, and internal stress is effectively released through moderate depressurization and high temperature setting in the final stage, so that cracking of the product is avoided.

Specifically, the initial stage is suitable in temperature and pressure to make the material particles contact and adhere to form a loose particle skeleton structure, and the pressure maintaining is carried out for 30s to ensure that the initial adhering state can be stabilized, so that the material can bear pressure better in the subsequent pressurizing process without excessive deformation or crushing, and the initial shape stability of the molded coal is ensured. Along with the promotion of the molding process, the molding process is continuously heated to 120-150 ℃, the pressure is raised to 25-30MPa, and the pressure is maintained for 60s, so that the remarkable rise of the temperature and the pressure is a key link of the compact molding of the molded coal. The high pressure further compresses the materials, eliminates gaps among the particles as much as possible, ensures that the material particles are closely arranged to form a highly compact structure, maintains the pressure for 60 seconds, ensures that the densification process can be fully carried out, ensures that the structure inside the molded coal is more uniform and stable, remarkably improves the mechanical strength of the molded coal, reduces the risks of crushing and pulverization in the processes of storage, transportation and use, and ensures the quality and combustion performance of the molded coal. Finally, the temperature is heated to 180-200 ℃, the pressure is reduced to 5-8MPa, the pressure is maintained for 10s, the chemical reaction in the material is further promoted, the bonding between the adhesive and the material particles is firmer, the pressure reduction avoids cracks or damages in the molded coal caused by over-pressurization, the reaction at high temperature can be fully completed after the short time of 10s of pressure maintaining, and the molded coal is not unnecessarily deformed or deteriorated due to long-time high-temperature and high-pressure environment. The progressive pressurizing mode not only ensures the high mechanical strength of the molded coal, but also ensures that the thermoplastic component in the binder and the biomass fiber form firm combination through the accurate control of the temperature gradient, and simultaneously maintains the porous structure of the biomass to maintain good combustion performance, thus obtaining the molded coal with high strength and good combustion efficiency.

Optionally, 0.8-1.2 parts of sodium bicarbonate is also added to the mixture.

By adopting the technical scheme, in the gradient hot press forming process, the sodium bicarbonate is heated to decompose and release carbon dioxide gas, and uniformly distributed micropore channels are formed in the molded coal, so that the specific surface area of the molded coal is effectively increased, more passages are provided for oxygen diffusion in the combustion process, and on the other hand, the micropore structures are used as heat conduction buffer layers, so that the combustion rate can be adjusted, and the molded coal fragmentation caused by local overheating is avoided. Meanwhile, sodium carbonate residues generated after the decomposition of sodium bicarbonate can fix sulfur to a certain extent, so that sulfur dioxide emission is reduced. The use of the pore-forming agent and the gradient hot-pressing process form a synergistic effect, so that the mechanical strength of the molded coal is maintained, the combustion characteristic of the molded coal is obviously improved, and the technical problems of insufficient combustion and easy slagging of the traditional molded coal are solved.

Optionally, the biomass is a mixture of straw and rice hulls, and the mixing ratio is 2:1.

By adopting the technical scheme, the straw is rich in cellulose and hemicellulose, rich active groups are generated in the pyrolysis process, the interface combination with coal dust is enhanced, and the high silicon content in the rice hulls endows the molded coal framework structure with additional supporting strength. The proportioning design not only maintains the high reactivity of the straw, but also makes up the defect of insufficient mechanical strength of the straw by utilizing the rigid structure of the rice husk. During steam explosion treatment, two different biomass fiber structures generate complementary porous characteristics, straw forms a microporous structure to promote binder permeation, rice hulls form a macroporous channel to improve oxygen diffusion, and the combustion performance of molded coal is optimized together.

In summary, the application has the following beneficial effects:

1. according to the application, through the collaborative modification process of biomass oxygen-limited pyrolysis and steam explosion, the utilization efficiency of raw materials and the product performance are obviously improved. The biomass is partially carbonized to keep volatile activity, and the micron-sized pore structure generated by steam explosion greatly increases the specific surface area, so that the interfacial binding force of the biomass and coal dust is improved by more than 50%. The oxygen-containing functional groups rich in the surface of the modified biomass form intermolecular actions with the polar groups of the pulverized coal, a stable three-dimensional network structure is constructed, and the technical problem of poor compatibility of the biomass and the pulverized coal in the traditional molded coal is solved.

2. The application forms an interpenetrating network structure through physical entanglement and chemical crosslinking by the multicomponent adhesive, thereby improving thermoplastic processability while ensuring molding strength. The gradient hot-pressing technology ensures the full penetration of the binder and the tight combination between particles through the accurate regulation and control of temperature and pressure, and effectively releases the internal stress through the final-stage depressurization and shaping, thereby greatly improving the strength of the molded coal.

Detailed Description

The present application will be described in further detail with reference to examples.

The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

The tar is biomass pyrolysis light tar, the distillation range is 180-250 ℃, the wood vinegar density is 1.05-1.15g/cm < 3 >, the organic acid content is more than or equal to 8%, and the oxygen-limited environment is that the oxygen concentration is less than or equal to 5%.

Preparation example

Preparation example 1

An activated coal dust, the preparation comprising the steps of:

80kg of coal dust is taken, 4kg of light tar and 4kg of pyroligneous liquor are added, and the mixture is stirred at the speed of 300rpm for 40 minutes at 60 ℃ to obtain activated coal dust.

Preparation example 2

An activated coal dust, the preparation comprising the steps of:

80kg of coal dust is taken, 2.4kg of light tar and 3.2kg of wood vinegar are added, and the mixture is stirred at the speed of 300rpm for 40min at 60 ℃ to obtain activated coal dust.

Preparation example 3

An activated coal dust, the preparation comprising the steps of:

80kg of coal dust is taken, 3.2kg of light tar and 4.8kg of wood vinegar are added, and the mixture is stirred at the speed of 300rpm for 40min at 60 ℃ to obtain activated coal dust.

Comparative preparation example 1

The activated pulverized coal is different from the preparation example 1 in that only wood vinegar is used for modifying the pulverized coal in the preparation example, and the preparation comprises the following steps:

80kg of coal dust is taken, 4kg of pyroligneous liquor is added, and the mixture is stirred at the speed of 300rpm for 40min at the temperature of 60 ℃ to obtain activated coal dust.

Comparative preparation example 2

The activated coal powder is different from the preparation example 1 in that only light tar is used for modifying the coal powder in the preparation example, and the preparation comprises the following steps:

80kg of coal dust is taken, 4kg of light tar is added, and the mixture is stirred at the speed of 300rpm for 40min at 60 ℃ to obtain activated coal dust.

Preparation example 4

A binder comprising 5kg pregelatinized starch, 2kg sodium lignin sulfonate, 2kg polycaprolactone, 0.65kg emulsifier, and 0.5kg humic acid, prepared comprising the steps of:

s1, dispersing 5kg of pregelatinized starch in 10kg of deionized water, heating to 85 ℃ and stirring to form uniform gel, adding 2kg of sodium lignin sulfonate, adjusting the pH to 8.5, stirring at 60 ℃ for 15min, adding 0.5kg of humic acid at 45 ℃ and stirring for 20min to obtain a mixed solution;

s2, heating 2kg of polycaprolactone and 0.65kg of Tween 80 (emulsifying agent) to 90 ℃ for melting, adding water for high-speed shearing and emulsifying to form emulsion, adding the emulsion into the mixed solution, and uniformly stirring at 50 ℃ to obtain the binder.

Preparation example 5

A binder comprising 3kg pregelatinized starch, 1kg sodium lignin sulfonate, 3kg polycaprolactone, 0.5kg emulsifier, and 1kg humic acid, prepared comprising the steps of:

S1, dispersing 3kg of pregelatinized starch in 10kg of deionized water, heating to 80-90 ℃ and stirring to form uniform gel, adding 1kg of sodium lignin sulfonate, adjusting the pH to 8,65 ℃ and stirring for 17min, adding 1kg of humic acid and stirring for 15min at 40 ℃ to obtain a mixed solution;

s2, heating 3kg of polycaprolactone and 0.5kg of Tween 80 (emulsifying agent) to 80 ℃ for melting, adding water for high-speed shearing and emulsifying to form emulsion, adding the emulsion into the mixed solution, and uniformly stirring at the temperature of 45 ℃ to obtain the binder.

Preparation example 6

A binder comprising 8kg pregelatinized starch, 3kg sodium lignin sulfonate, 1kg polycaprolactone, 1kg emulsifier, and 0.65kg humic acid, prepared comprising the steps of:

S1, dispersing 8kg of pregelatinized starch in 10kg of deionized water, heating to 90 ℃ and stirring to form uniform gel, adding 3kg of sodium lignin sulfonate, adjusting the pH to 9, stirring at 70 ℃ for 20min, adding 0.65kg of humic acid at 50 ℃ and stirring for 16min to obtain a mixed solution;

S2, heating 1kg of polycaprolactone and 1kg of Tween 80 (emulsifying agent) to 100 ℃ for melting, adding water for high-speed shearing and emulsifying to form emulsion, adding the emulsion into the mixed solution, and uniformly stirring at the temperature of 55 ℃ to obtain the binder.

Examples

Example 1

The production method of the biomass briquette comprises the following steps:

(1) Drying 30kg biomass until the water content is 12.5%, and pulverizing to 0.5-2mm;

(2) Rapidly pyrolyzing the crushed biomass at 250 ℃ for 3.5min in an oxygen-limited environment to obtain partially carbonized biomass, introducing saturated steam into the partially carbonized biomass, continuously treating the biomass at the pressure of 2.0MPa and the temperature of 190 ℃ for 4min, and then instantaneously (for <0.5 s) releasing pressure to normal pressure to finish steam explosion;

(3) Uniformly mixing the biomass after steam explosion with 60kg of ground activated coal dust, 5kg of the binder prepared in preparation example 4 and 1kg of potassium nitrate (combustion improver) to obtain a mixture, adding water to the mixture until the total water content is 16%, uniformly mixing the mixture, heating the mixture to 90 ℃ in the hot press forming process, maintaining the pressure at 12.5MPa for 30 seconds, continuously heating the mixture to 135 ℃ and the pressure at 26.5MPa for 60 seconds, heating the mixture to 190 ℃ and maintaining the pressure at 6.5MPa for 10 seconds;

(4) And (3) solidifying the formed green embryo for 2 hours at a low temperature of 90 ℃ to obtain the molded coal, wherein the biomass is a mixture of straw and rice husk, and the mixing ratio is 2:1.

Example 2

The production method of the biomass briquette comprises the following steps:

(1) Drying 40kg biomass until the water content is 10%, and pulverizing to 0.5-2mm, grinding activated coal powder prepared in preparation example 2 to 200 mesh;

(2) Rapidly pyrolyzing the crushed biomass for 2min at 300 ℃ in an oxygen-limited environment to obtain partially carbonized biomass, introducing saturated steam into the partially carbonized biomass, wherein the pressure is 1.5MPa, the temperature is 180 ℃, and after continuous treatment for 5min, instantaneously (0.5 s) releasing pressure to normal pressure to finish steam explosion;

(3) Uniformly mixing the biomass after steam explosion with 50kg of ground activated coal dust, 4kg of the binder prepared in preparation example 4 and 3kg of potassium nitrate (combustion improver) to obtain a mixture, adding water to the total water content of 18%, and uniformly mixing, wherein the mixture is heated to 80 ℃ firstly, the pressure of 15MPa and the pressure of 30s in the hot press forming process, and is continuously heated to 120 ℃ and the pressure of 30MPa, the pressure of 60s, the temperature of 180 ℃ and the pressure of 8MPa and the pressure of 10s;

(4) And solidifying the formed green embryo at a low temperature of 100 ℃ to obtain the molded coal, wherein the biomass is a mixture of straw and rice husk, and the mixing ratio is 2:1.

Example 3

The production method of the biomass briquette comprises the following steps:

(1) Drying 20kg biomass until the water content is 10%, and pulverizing to 0.5-2mm;

(2) Rapidly pyrolyzing the crushed biomass for 5min at 200 ℃ in an oxygen-limited environment to obtain partially carbonized biomass, introducing saturated steam into the partially carbonized biomass, wherein the pressure is 1.65MPa, the temperature is 200 ℃, and after continuous treatment for 5min, the pressure is released to normal pressure instantaneously (< 0.5 s), so as to finish steam explosion;

(3) Uniformly mixing the biomass after steam explosion with 70kg of ground activated coal dust, 3kg of the binder prepared in preparation example 4 and 2kg of potassium nitrate (combustion improver) to obtain a mixture, adding water to the total water content of 17%, and uniformly mixing, wherein the mixture is heated to 100 ℃ firstly, the pressure of 10MPa and the pressure of 30s in the hot press forming process, and is continuously heated to 150 ℃ and the pressure of 25MPa, the pressure of 60s, the temperature of 200 ℃ and the pressure of 5MPa and the pressure of 10s;

(4) And solidifying the formed green embryo at a low temperature of 80 ℃ to obtain the molded coal, wherein the biomass is a mixture of straw and rice husk, and the mixing ratio is 2:1.

Example 4

A biomass briquette is different from example 1 in that the binder prepared in preparation example 5 is added in this example.

Example 5

A biomass briquette is different from example 1 in that the binder prepared in preparation example 6 is added in this example.

Example 6

A biomass briquette is different from example 1 in that pregelatinized starch is used as a binder in this example.

Example 7

A biomass briquette is different from example 1 in that polycaprolactone is used as a binder in this example.

Example 8

The biomass briquette differs from example 1 in that the same amount of unactivated pulverized coal is added to replace the activated pulverized coal in this example.

Example 9

The biomass briquette is different from example 1 in that the briquette is directly heated to 190 ℃ in the hot press molding process in this example, the pressure is 6.5MPa, and the pressure is maintained for 100s.

Example 10

A biomass briquette is different from example 1 in that the briquette is directly heated to 135 ℃ and the pressure is 26.5MPa in the hot press molding process in the example, and the pressure is maintained for 100s.

Example 11

A biomass briquette is different from example 1 in that the briquette is directly heated to 90 ℃ in the hot press molding process in the example, the pressure is 12.5MPa, and the pressure is maintained for 100s.

Example 12

A biomass briquette is different from example 1 in that 0.8kg of sodium bicarbonate is also added in this example.

Example 13

A biomass briquette is different from example 1 in that 1.2kg of sodium bicarbonate is also added in this example.

Comparative example

Comparative example 1

The biomass briquette is different from example 1 in that biomass used in this comparative example is not subjected to steam explosion, and specifically includes the following steps:

(1) Drying 30kg biomass until the water content is 12.5%, and pulverizing to 0.5-2mm;

(2) Rapidly pyrolyzing the crushed biomass for 3.5min at 250 ℃ in an oxygen-limited environment to obtain partially carbonized biomass;

(3) Uniformly mixing the obtained partially carbonized biomass with 60kg of ground activated coal dust, 5kg of the binder prepared in preparation example 4 and 1kg of potassium nitrate (combustion improver) to obtain a mixture, adding water to the mixture until the total water content is 16%, uniformly mixing the mixture, heating the mixture to 90 ℃ in the hot press molding process, maintaining the pressure at 12.5MPa for 30 seconds, continuously heating the mixture to 135 ℃ and the pressure at 26.5MPa, maintaining the pressure for 60 seconds, heating the mixture to 190 ℃ and maintaining the pressure at 6.5MPa for 10 seconds;

(4) And (3) solidifying the formed green embryo for 2 hours at a low temperature of 90 ℃ to obtain the molded coal, wherein the biomass is a mixture of straw and rice husk, and the mixing ratio is 2:1.

Comparative example 2

A biomass briquette, which is different from example 1 in that biomass used in this comparative example was not subjected to rapid pyrolysis, comprising the steps of:

(1) Drying 30kg biomass until the water content is 12.5%, and pulverizing to 0.5-2mm;

(2) Introducing saturated steam into the crushed biomass, wherein the pressure is 2.0MPa, the temperature is 190 ℃, and the pressure is relieved to normal pressure immediately (< 0.5 s) after continuous treatment for 4min, so that steam explosion is completed;

(3) Uniformly mixing the biomass after steam explosion with 60kg of ground activated coal dust, 5kg of the binder prepared in preparation example 4 and 1kg of potassium nitrate (combustion improver) to obtain a mixture, adding water to the mixture until the total water content is 16%, uniformly mixing the mixture, heating the mixture to 90 ℃ in the hot press forming process, maintaining the pressure at 12.5MPa for 30 seconds, continuously heating the mixture to 135 ℃ and the pressure at 26.5MPa for 60 seconds, heating the mixture to 190 ℃ and maintaining the pressure at 6.5MPa for 10 seconds;

(4) And (3) solidifying the formed green embryo for 2 hours at a low temperature of 90 ℃ to obtain the molded coal, wherein the biomass is a mixture of straw and rice husk, and the mixing ratio is 2:1.

Comparative example 3

A biomass briquette, which is different from example 1 in that biomass used in this comparative example was not subjected to any treatment, comprising the steps of:

(1) Drying 30kg biomass until the water content is 12.5%, and pulverizing to 0.5-2mm;

(2) Uniformly mixing the biomass with 60kg of ground activated coal powder, 5kg of the binder prepared in preparation example 4 and 1kg of potassium nitrate (combustion improver) to obtain a mixture, adding water to the mixture until the total water content is 16%, uniformly mixing, heating to 90 ℃ in the hot press molding process, maintaining the pressure at 12.5MPa for 30 seconds, continuously heating to 135 ℃ at 26.5MPa, maintaining the pressure for 60 seconds, heating to 190 ℃ at 6.5MPa, and maintaining the pressure for 10 seconds;

(3) And (3) solidifying the formed green embryo for 2 hours at a low temperature of 90 ℃ to obtain the molded coal, wherein the biomass is a mixture of straw and rice husk, and the mixing ratio is 2:1.

Comparative example 4

A biomass briquette is different from example 1 in that the pulverized coal added in this comparative example was prepared in comparative preparation example 1.

Comparative example 5

A biomass briquette is different from example 1 in that the pulverized coal added in this comparative example was prepared in comparative preparation example 2.

Performance test

Test method

The intensity was measured on the molded coal prepared in examples and comparative examples according to the method shown in MT/T925-2004 method for measuring falling intensity of Industrial molded coal, and the calorific value was measured according to GB/T213-2008 method for measuring calorific value of coal.

Table 1 test results

It can be seen from the combination of examples 1-3 and comparative example 1 and Table 1 that the experimental data of examples 1-3 are better than that of comparative example 1, which shows that the steam explosion treatment can significantly destroy the fibrous structure of the biomass, increase the specific surface area and the active site, and promote the interfacial bonding force with coal dust, thereby greatly improving the strength of the molded coal, the combination of examples 1-3 and comparative example 2 and Table 1 shows that the experimental data of examples 1-3 are better than that of comparative example 2, which shows that the oxygen-limited fast pyrolysis can partially carbonize the biomass and retain the activity of volatile matters, thereby creating better pore development conditions for the subsequent steam explosion, and the combination of examples 1-3 and Table 1 shows that the use of the raw biomass without any modification treatment can significantly reduce the mechanical strength and the combustion performance of the molded coal, which shows that the dual modification process of pyrolysis and steam explosion of biomass has synergistic effect on improving the quality of the molded coal.

As can be seen from the combination of example 1 and comparative examples 4-5 and the combination of table 1, each experimental data of example 1 is better than comparative examples 4-5, which shows that the coal powder after synergistic activation by using light tar and pyroligneous liquor has a remarkable surface modification effect, wherein the tar can repair the surface defects of the coal powder and enhance hydrophobicity, the pyroligneous liquor can etch the surface and introduce active functional groups, and the synergistic effect of the tar and the pyroligneous liquor can comprehensively improve the interfacial compatibility and the reactivity of the coal powder.

As can be seen from the combination of examples 1 and examples 4 to 7 and table 1, the experimental data of examples 1 and 4 to 5 are better than those of examples 6 to 7, and the adhesive prepared by the method of the present application has good adhesion, wherein the pregelatinized starch provides basic adhesion, sodium lignin sulfonate improves dispersibility, polycaprolactone enhances thermoplasticity, humic acid enhances interfacial bonding, and each component forms a stable three-dimensional network structure through intermolecular interaction, so that the strength of the molded coal is improved.

As can be seen from the combination of example 1 and example 8 and the combination of table 1, the experimental data of example 1 is better than example 8, which shows that the activation of the pulverized coal can effectively improve the surface characteristics of the pulverized coal, and the combination strength of the pulverized coal, biomass and binder is remarkably improved by increasing the specific surface area and the density of oxygen-containing functional groups, and the reactivity in the combustion process is optimized.

As can be seen from the combination of examples 1 and examples 9 to 11 and the combination of table 1, the experimental data of example 1 are better than examples 9 to 11, which demonstrates that the gradient control of material densification can be achieved by using the staged hot press forming process, the gas is discharged through medium temperature and medium pressure and is primarily formed, the binder is fully infiltrated through high temperature and high pressure, and finally the internal stress is released through depressurization and forming, so that the molded coal product with uniform structure and no defects is obtained.

It can be seen from the combination of example 1 and comparative examples 12 to 13 and the combination of table 1 that the addition of sodium bicarbonate to the briquette can decompose to produce a microporous structure during the hot pressing process, thereby improving the oxygen diffusion condition during combustion and further improving the combustion performance of the briquette.

The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.

Claims (8)

1. The production method of the biomass briquette is characterized by comprising the following steps:

(1) Drying biomass until the water content is 10-15%, and pulverizing to 0.5-2mm;

(2) Rapidly pyrolyzing the crushed biomass for 2-5min at 200-300 ℃ in an oxygen-limited environment to obtain partially carbonized biomass, introducing saturated steam into the partially carbonized biomass, continuously treating for 3-5min at 180-200 ℃ under the pressure of 1.5-2.0MPa, and then instantaneously releasing the pressure to normal pressure to finish steam explosion;

(3) Mixing the biomass, pulverized coal, combustion improver and binder after steam explosion in proportion to obtain a mixture, adding water to the total water content of 16-18%, and uniformly mixing;

(4) And (3) solidifying the formed green blanks at a low temperature of 80-100 ℃ to obtain the briquette.

2. The method for producing biomass briquette as claimed in claim 1, wherein the mixture comprises 20-40 parts of biomass, 50-70 parts of pulverized coal, 3-5 parts of binder and 1-3 parts of combustion improver.

3. The method for producing biomass briquette according to claim 1, wherein the pulverized coal is activated by adding tar and pyroligneous liquor, and the specific steps are mixing the pulverized coal with the tar and the pyroligneous liquor in a weight ratio of 10:0.3-0.5:0.4-0.6, and stirring uniformly at 60-80 ℃ to obtain activated pulverized coal.

4. The method for producing biomass briquette as claimed in claim 1, wherein the binder comprises 3-8 parts of pregelatinized starch, 1-3 parts of sodium lignin sulfonate, 0.5-0.8 part of emulsifier, 1-3 parts of polycaprolactone and 0.5-1 part of humic acid.

5. The method for producing biomass briquette as claimed in claim 4, wherein the binder preparation comprises the following steps:

s1, dispersing pregelatinized starch in water, heating to 80-90 ℃ and stirring to form uniform gel, adding sodium lignin sulfonate, adjusting the pH to 8-9,60-70 ℃ and stirring for 15-20min, adding humic acid to 40-50 ℃ and stirring for 15-20min to obtain a mixed solution;

s2, heating polycaprolactone and an emulsifier to 80-100 ℃ for melting, adding water for high-speed shearing and emulsifying to form emulsion, adding the emulsion into the mixed solution at 45-55 ℃, and stirring to obtain the binder.

6. The method for producing biomass briquette according to claim 1, wherein the hot press molding is carried out by a gradient pressurizing method, heating to 80-100 ℃ at 10-15MPa for 30s, continuing heating to 120-150 ℃ at 25-30MPa for 60s, heating to 180-200 ℃ at 5-8MPa for 10s.

7. The method for producing biomass briquette as claimed in claim 1, wherein 0.8-1.2 parts of sodium bicarbonate is further added to the mixture.

8. The method for producing biomass briquette as claimed in claim 1, wherein the biomass is a mixture of straw and rice husk in a mixing ratio of 2:1.