Method and system of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection

Abstract

The present invention discloses a method and a system of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection. The present invention applies solid, gas and liquid products of the thermochemical treatment subsystem to the biochemical treatment subsystem and applies heat produced by the biochemical treatment subsystem to the thermochemical treatment subsystem, forming multi-point and two-way interconnection between the biochemical treatment subsystem and the thermochemical treatment subsystem, thereby increasing the yield and stability of energy gas of the biochemical treatment subsystem and reducing pollution and energy consumption of the thermochemical treatment subsystem respectively. The present invention is suitable for treating biomass wastes with high and low water contents at the same time, producing soil amendment, liquid fuel and biogas, having properties of low secondary pollution and significant reduction of greenhouse gas emission and so on. The bio-stability, humus content and nitrogen content of the solid product are as high as soil amendment, making it easy to store and transport.

Claims

1. A method of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection, comprising: (1) converting dry biomass wastes into pyrolysis gas, biochar, pyrolysis oil and aqueous condensate by a pyrolyzer; (2) feeding the pyrolysis gas and the aqueous condensate into an anaerobic digester to obtain biogas and digestion residues; (3) feeding at least a portion of the biochar into the anaerobic digester wherein the portion of the biochar is discharged with the digestion residues in the anaerobic digester; (4) separating the digestion residues into slurry and fiber digestate by a solid-liquid separator; (5) composting a first portion of the fiber digestate in a composter to form a compost product; (6) employing heat generated from the pyrolysis oil and the biogas to dry a second portion of the fiber digestate, the compost product and other biomass wastes to obtain dried biomass wastes; (7) feeding the dried biomass wastes into the pyrolyzer, wherein step (4) further includes adding at least another portion of the biochar before separating the digestion residues to further increase the solid-liquid separation efficiency.

2. The method of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection of claim 1, wherein step (5) further includes adding at least another portion of the biochar into the composter to further improve performance of the composting.

3. The method of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection of claim 1, wherein, in step (2), the pyrolysis gas and the aqueous condensate are converted into the biogas by biochemical actions in the anaerobic digester and trace pollutants contained in the pyrolysis gas are removed, and the biogas contains methane.

4. The method of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection of claim 1, wherein the compost product in step (5) is used as soil amendment.

5. The method of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection of claim 4, wherein the compost product in step (5) is mixed with the biochar to be used as soil amendment.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 is a process flow chart of the present invention.

(2) Reference numbers in the drawing are as follows: 1wet biomass waste; 2dry biomass waste; 3anaerobic digestion unit; 4pyrolyzing unit; 5solidliquid separation unit; 6drying unit; 7composting unit; 8biogas utilization unit; 9biogas; 10fiber digestate; 11slurry; 12pyrolysis oil; 13biochar; 14pyrolysis gas; 15compost; 16soil amendment; 17heat; 18electricity; 19aqueous condensate; 20fuel utilization unit.

DETAILED DESCRIPTION OF THE INVENTION

(3) Hereinafter, the present invention will be described in detail with reference to the drawing and an embodiment.

(4) Embodiment

(5) The method of treating biomass wastes by biochemistry-thermochemistry multi-point interconnection employs a process shown in FIG. 1, including the following steps: (1) converting dry biomass waste 2 into pyrolysis gas 14, biochar 13, pyrolysis oil 12 and aqueous condensate 19 by the pyrolyzing unit 4; (2) feeding the pyrolysis gas 14 and the aqueous condensate 19 into a pyrolysis digestion unit 3 for treating wet biomass waste 1; (3) feeding biochar 13 into the anaerobic digestion unit 3, after which the biochar is fed into the solid-liquid separation unit 5 with the digestion residues; (4) separating the digestion residues into slurry 11 and fiber digestate 10 by the solid-liquid separation unit 5, wherein biochar 13 can be further added before the solid-liquid separation unit 5; (5) conducting post-treatment on the fiber digestate 10 in the composting unit 7 to form a compost product 15, which can be used as soil amendment 16; biochar 13 can be further added in the composting unit 7; (6) generating electricity 18 and heat 17 from the biogas 9 produced by the anaerobic digestion unit 3 through the biogas utilization unit 8, generating heat 17 from the pyrolysis oil 12 by the fuel utilization unit 20, wherein heat 17 is used for the drying operation of the drying unit 6; (7) feeding materials dried by the drying unit 6 into the pyrolyzing unit 4 again.

(6) Taking the treatment of agricultural wasteslivestock manure and crop straws as an example, livestock manure contain 0.5 t of dry organic matter, crop straws contain 0.5 t of dry organic matter, and if a single mesophilic 35 C. anaerobic digestion technology is employed, the retention time requires 40 d, the yield of methane is less than 375 m.sup.3. If the biochemistry-thermochemistry multi-point interconnection technology of the present invention is employed, livestock manure (containing 0.5 t of dry organic matter) are fed into the anaerobic digestion unit 3, while crop straws (containing 0.5 t of dry organic matter) are fed into the pyrolyzing unit 4, producing 0.15 t of pyrolysis gas 14, 0.15 t of biochar 13 and 0.2 t of pyrolysis oil 12 under the condition of 500 C. pyrolyzing temperature, wherein the pyrolysis gas contains CO.sub.2 20%, O.sub.2 1%, N.sub.2 2%, CO 30%, H.sub.2 22%, CH.sub.4 25% and some trace pollutants. After being treated by the anaerobic digestion unit 3, CO of the pyrolysis gas 14 is converted into 1.61 kmol of CH.sub.4 and H.sub.2 thereof is converted into 2.92 kmol of CH.sub.4, and together with the original 2.34 kmol of CH.sub.4 in the pyrolysis gas, there is totally 6.87 kmol of CH.sub.4 converted from the pyrolysis gas. Together with 16.74 kmol of CH.sub.4 produced from the organic matters of the livestock manure by 20 d of mesophilic 35 C. anaerobic digestion, the total yield of methane is 23.61 kmol, equivalent to 529 m.sup.3. Furthermore, the 0.2 t of pyrolysis oil 12 produced by this interconnection technology can be directly used as liquid fuel, and the 0.15 t of biochar 13 is recycled solid product which is easy to transport and store, and can be directly used as soil amendment 16 or as an additive of the anaerobic digestion unit 3, or as a conditioner of the solid-liquid separation unit 5, or as an additive of the composting unit.

(7) The interconnection technology of the present invention also has a good effect of reducing greenhouse gas emission. If the abovementioned livestock manure and crop straws both containing 0.5 t of dry organic matter are open dumped or landfilled randomly, greenhouse gas produced will be 8.4 t of CO.sub.2 equivalent. However, if a single anaerobic digestion treatment is employed, methane produced substitutes fossil fuels, and the fiber digestate are landfilled, then greenhouse gas produced is 4.255 t of CO.sub.2 equivalent. If a single anaerobic digestion treatment is employed, methane produced substitutes fossil fuels, and the fiber digestate are used as organic fertilizer instead of the chemical fertilizer to achieve organic farming, then the greenhouse gas produced is 0.1175 of CO.sub.2 equivalent. If using the interconnection technology of the present invention with a higher yield of methane, and replacing fossil fuels with pyrolysis oil and using fiber digestate containing biochar as organic fertilizer instead of chemical fertilizer to achieve organic farming, then the greenhouse gas produced is 0.998 of CO.sub.2 equivalent. The waste treatment can be converted from carbon source technology into carbon sequestration technology.

(8) The above description of embodiments is only for easy understanding and using of the present invention by one of ordinary skill in this art. Those skilled in this art can easily make various changes to these embodiments and apply the general principle described here to other embodiments without creative work. Therefore, the present invention is not limited to the above-described embodiment, and modifications and changes made without departing from the scope of the present invention by those skilled in this art according to the disclosure of the present invention would fall within the scope of the present invention.