阅读说明：本技术 一种生物煤的制备方法 (Preparation method of biological coal ) 是由 江鸿 江顺风 陈雅丽 于 2019-10-21 设计创作，主要内容包括：本发明提供了一种生物煤的制备方法,包括以下步骤：A)利用生物质废弃物制备生物油；B)将所述生物油进行常压蒸馏,所述常压蒸馏的温度为200～240℃时保温后冷却,得到生物煤。本申请通过常压蒸馏的方法加速生物油的热聚合,使生物油快速结焦,而结焦的残留物经过自然冷却,即得到高热值的固体燃料-生物煤,从而实现生物油的提质增值。(The invention provides a preparation method of biological coal, which comprises the following steps: A) preparing bio-oil by using biomass waste; B) and carrying out normal pressure distillation on the bio-oil, and cooling after heat preservation when the temperature of the normal pressure distillation is 200-240 ℃ to obtain the bio-coal. According to the method, the thermal polymerization of the bio-oil is accelerated by a normal pressure distillation method, so that the bio-oil is rapidly coked, and the coked residues are naturally cooled to obtain the solid fuel with high heat value, namely the bio-coal, so that the quality improvement and the value increase of the bio-oil are realized.)

1. A preparation method of biological coal comprises the following steps:

A) preparing bio-oil by using biomass waste;

B) and carrying out normal pressure distillation on the bio-oil, and cooling after heat preservation when the temperature of the normal pressure distillation is 200-240 ℃ to obtain the bio-coal.

2. The preparation method according to claim 1, wherein step a) is specifically:

and carrying out fast pyrolysis on the biomass waste at the temperature of 400-600 ℃, and condensing to obtain the bio-oil.

3. The method of claim 2, wherein the fast pyrolysis further comprises, prior to the fast pyrolysis:

crushing the biomass waste, screening and drying; the particle size of the screening is 60-100 meshes.

4. The method of claim 1, further comprising, after the cooling:

and crushing the cooled residue, sieving with a sieve of 80-100 meshes, and drying in vacuum.

5. The preparation method according to claim 4, wherein the temperature of the vacuum drying is 80-100 ℃ and the time is 12-24 h.

6. The preparation method according to claim 1, wherein the heat preservation time is 10-30 min.

7. The method according to claim 1, wherein the bio-coal has a carbon content of 67 to 70 wt%, a hydrogen content of 5.5 to 6.5 wt%, and an oxygen content of 22 to 27 wt%; the mass energy density is 25-29 MJ/kg.

8. The preparation method according to any one of claims 1 to 7, wherein the biomass waste is selected from rice straw, wheat straw, bagasse or soybean straw.

Technical Field

The invention relates to the technical field of agricultural and forestry waste recycling, in particular to a preparation method of biological coal.

Background

With the development of human civilization, fossil energy is continuously being developed. Excessive use of fossil fuels not only causes energy depletion, but also causes serious climate change and environmental pollution problems. Biofuel is considered as a substitute for fossil energy as a new energy source from a wide range of sources. The united states independent and safe law predicts that 160 billion gallons of cellulosic biofuels will be produced globally in 2022. However, most of the raw materials of biofuels are grains at present, and the large-scale production of biofuels inevitably affects the global grain supply. Therefore, the method for converting the lignocellulose biomass into the renewable bio-oil by using the fast pyrolysis method has wider application prospect than the grain-derived biofuel. Bio-oil is a mixture of water, hydrocarbons and oxygen-containing compounds, which has the disadvantages of high corrosiveness, low calorific value and chemical instability, and thus, it is required to process bio-oil to obtain a liquid fuel of higher quality. Although the processing of bio-oil has been greatly advanced and a series of techniques have been verified in the pilot plant stage, the defects of thermal polymerization and catalyst deactivation of bio-oil itself still prevent its large-scale application.

Atmospheric distillation is a simple and economical separation technique for mixtures and has been widely used industrially for over a century. However, due to the thermal polymerization properties of bio-oil, only a small fraction can be recovered, and thus, such a mature separation technique has not been used for bio-oil separation. In addition, due to the poor thermal stability of bio-oil, coke is formed after heating, which makes distillation of bio-oil more difficult. Although molecular distillation has been used for bio-oil separation, the recovery of carbon content in the light fraction is low, accounting for only 17% of the carbon content in bio-oil. To date, the development of biomass pyrolysis to produce renewable fuels has been limited by the lack of efficient separation methods.

Disclosure of Invention

The invention aims to provide a preparation method of biological coal, and the biological coal with high calorific value is prepared by using agricultural and forestry wastes.

In view of the above, the present application provides a method for preparing bio-coal, comprising the following steps:

A) preparing bio-oil by using biomass waste;

B) and carrying out normal pressure distillation on the bio-oil, and cooling after heat preservation when the temperature of the normal pressure distillation is 200-240 ℃ to obtain the bio-coal.

Preferably, step a) is specifically:

and carrying out fast pyrolysis on the biomass waste at the temperature of 400-600 ℃, and condensing to obtain the bio-oil.

Preferably, the fast pyrolysis further comprises, before:

crushing the biomass waste, screening and drying; the particle size of the screening is 60-100 meshes.

Preferably, the cooling further comprises:

and crushing the cooled residue, sieving with a sieve of 80-100 meshes, and drying in vacuum.

Preferably, the temperature of the vacuum drying is 80-100 ℃, and the time is 12-24 h.

Preferably, the heat preservation time is 10-30 min.

Preferably, the carbon content of the biological coal is 67-70 wt%, the hydrogen content is 5.5-6.5 wt%, and the oxygen content is 22-27 wt%; the mass energy density is 25-29 MJ/kg.

Preferably, the biomass waste is selected from rice straw, wheat straw, bagasse or soybean straw.

The application provides a preparation method of biological coal, which comprises the steps of firstly preparing biological oil by using biomass waste, and then distilling the biological oil by adopting a normal-pressure distillation mode to obtain the biological coal. According to the method, the thermal polymerization of the bio-oil is accelerated by a normal pressure distillation method, so that the bio-oil is rapidly coked, and the coked residues are naturally cooled to obtain the solid fuel with high heat value, namely the bio-coal, so that the quality improvement and the value increase of the bio-oil are realized.

Drawings

FIG. 1 is a synthetic route and a characteristic analysis diagram of biological coal;

FIG. 2 is a graph showing the variation of components in the production process of sawdust bio-coal.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

During pyrolysis, the major components in biomass (lignin, cellulose and hemicellulose) are rapidly thermochemically decomposed in a few seconds to form small molecule compounds, of which about 50% of the volatiles can condense to form bio-oil; the carbon content of the bio-oil is 30-50%, the high heat value of the bio-oil is about 15MJ/kg, and the bio-oil contains about 30% of water besides organic compounds, so that the high heat value of the bio-oil can be obviously reduced. Thus, by removing water, the high heating value of the residue is increased, rather than a lower high heating value light fraction being obtained. In the present invention, a new bio-oil treatment strategy is proposed to accelerate the thermal polymerization of bio-oil by atmospheric distillation to obtain solid fuel, and distillation residue of the thermal polymerization has a very high calorific value, which is defined as bio-coal. Thus, the present application provides a method for preparing bio-coal, comprising the steps of:

A) preparing bio-oil by using biomass waste;

B) and carrying out normal pressure distillation on the bio-oil, and cooling after heat preservation when the temperature of the normal pressure distillation is 200-240 ℃ to obtain the bio-coal.

In the process of preparing the bio-coal, the bio-oil is prepared by using the biomass waste, the bio-oil is prepared by fast pyrolyzing the biomass waste at the temperature of 400-600 ℃, and the bio-oil is obtained after fast pyrolyzing and condensing. In order to improve the yield of the bio-oil, the biomass waste is firstly crushed and then screened before the fast pyrolysis, and then dried; the particle size of the screening is 60-100 meshes. The drying temperature is 80-120 ℃. More specifically, placing biomass waste particles in a sample inlet pipe, introducing nitrogen into a reactor, and keeping for 20-30 min to remove residual air in the reactor; and when the temperature reaches 400-500 ℃, quickly feeding the biomass waste into the reactor, carrying out nitrogen flow on volatile matters generated by pyrolysis out of the reactor, and condensing the volatile matters with the glacial ethanol to obtain the bio-oil.

And after obtaining the bio-oil, carrying out atmospheric distillation on the bio-oil, wherein the atmospheric distillation temperature is 200-240 ℃ and the atmospheric distillation time is 10-30 min in the process. More specifically, the bio-oil is placed in an oil bath and slowly heated to 200-240 ℃ under magnetic stirring; in the intermittent distillation process, volatile components in the biological oil are gradually reduced, residues are continuously condensed along with the increase of the distillation temperature, the viscosity is increased, and the heating and the natural cooling are stopped after the distillation temperature reaches the highest temperature and is kept for 10-30 min. The residue obtained by atmospheric distillation gradually becomes black solid at room temperature, and the black solid is proved by analysis and characterization to be similar to commercial coal in the prior art in mass energy density and can be used as a substitute product of the commercial coal, so that the black solid obtained by the method can be used as the later biological coal. Atmospheric distillation temperatures can affect the composition of the bio-coal.

In order to improve the application of the biological coal, the black solid is crushed, sieved by a sieve with 80-100 meshes, and dried in vacuum, and the moisture in the black solid is removed, so that the biological coal is obtained. The temperature of the vacuum drying is 80-100 ℃, and the time is 12-24 hours.

Through analysis and characterization, the carbon content of the biological coal prepared by the method is 67-70 wt%, the hydrogen content is 5.5-6.5 wt%, and the oxygen content is 22-27 wt%; the mass energy density is 25-29 MJ/kg. The mass energy density is an important index for measuring the quality of the solid fuel, the mass energy density of the biological coal prepared by the application is not different from that of the commercial coal, and the biological coal provided by the application can be used as a substitute of the commercial coal.

The method for preparing the bio-coal is applicable to all biomass wastes, can be selected from rice straws, wheat straws, bagasse or soybean straws, and the source of the bio-coal is not particularly limited in the application.

The application accelerates the thermal polymerization of bio-oil by atmospheric distillation to obtain solid fuel, and distillation residues of the thermal polymer are called as bio-coal in the application and have high heat value; meanwhile, the biological coal can be rapidly prepared in a large scale and can replace part of commercial coal, and the problem of global warming can be relieved by utilizing biomass in a carbon balance manner; in addition, the biological coal can be used as a carbon storage warehouse instead of being used, can be stored for a long time and is convenient to transport.

For further understanding of the present invention, the following examples are given to illustrate the preparation of the bio-coal according to the present invention, and the scope of the present invention is not limited by the following examples.