Biomass power plant ash composition for improving soil carbon sink as well as preparation method and application of biomass power plant ash composition

Abstract

The invention discloses a biomass power plant ash composition for improving soil carbon sink as well as a preparation method and application of the biomass power plant ash composition, and belongs to the technical field of agricultural resources and environment. The composition is formed by compounding fly ash and slag according to the dry basis mass ratio of (2-3): 1, and the heavy metal content of the composition meets the agricultural safety standard. The preparation method comprises the steps of raw material pretreatment and optimized compounding. The core of the method is that the fly ash is used as a main carbon source by increasing the proportion of the fly ash, physical protection is provided by utilizing the microporous structure of the slag, and the fly ash and the slag jointly act on the soil, so that the organic carbon library of the soil is rapidly and stably increased. Experiments show that the composition provided by the invention can significantly improve the organic carbon content and the carbon library management index (CPI) of soil, effectively reduce the daily average mineralization rate of organic carbon, and realize efficient and high value-added resource utilization of biomass ash in the field of soil carbon sequestration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of agricultural resources and environment, and particularly relates to a biomass power plant ash composition for improving soil carbon sink, and a preparation method and application thereof. BACKGROUND

[0002] As solid waste, the fly ash and slag of biomass power plants are difficult to be utilized. The fly ash is rich in unburned carbon, which is a potential soil carbon sink. However, the high pH and salt content of the fly ash inhibit the microorganisms, which limits the direct agricultural use of the fly ash. The slag has a good pore structure, but its own carbon sequestration capacity is limited. The existing technology simply mixes the fly ash and the slag, and fails to precisely design and optimize the function and ratio for the specific goal of maximizing carbon sequestration.

[0003] At present, there is a lack of a special technology capable of fully utilizing the carbon source of the fly ash and stabilizing the carbon pool through the microstructure adjustment of the slag. Most methods can improve the carbon sequestration capacity, but fail to consider the long-term stability of the carbon (such as reducing the mineralization rate). Therefore, it is an urgent need to develop a special ash composition capable of significantly and stably improving the soil carbon sequestration capacity, so as to realize the high-value utilization of waste. SUMMARY

[0004] (I) Objectives

[0005] The present application aims to overcome the defects of the prior art, and provide a biomass power plant ash composition for significantly and stably improving soil carbon sink, and an application thereof in improving the organic carbon pool of degraded black calcic soil.

[0006] (II) Technical solutions

[0007] In order to achieve the above-mentioned objectives, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a biomass power plant ash composition for improving soil carbon sink, which is composed of fly ash and slag, and the dry basis mass ratio of the fly ash to the slag is (2-3):1. The biomass power plant ash can significantly increase the soil organic carbon and microbial nitrogen, but the fly ash and the slag have different effects in the soil. The fly ash inhibits the microbial mineralization by reducing the content of dissolved organic carbon, promotes the decomposition of recalcitrant organic carbon, and forms mineral-organic complex, thereby significantly improving the physical protection and chemical stability of the soil organic carbon. The low application amount of the slag activates the microbial activity, accelerates the consumption of easily oxidized organic carbon, and promotes the transformation of the organic carbon form to the stable state, thereby realizing the long-term stabilization of the carbon pool.

[0009] The physicochemical properties of the fly ash are as follows: pH 9.5-9.95, electrical conductivity 2250-2984 μS·cm -1 , specific surface area 7.50-7.85 m2 ·g -1 Organic carbon content 19.0-21.0 g·kg -1 ;

[0010] The physicochemical properties of the slag range from pH 8.94 to 9.50, electrical conductivity 380-430 μS·cm -1 Specific surface area 9.75-11.85 m 2 ·g -1 Organic carbon content 12.13-13.5 g·kg -1 ;

[0011] Furthermore, the contents of heavy metals Cd, Hg, As, Pb, Cr, Cu, Ni, Zn in the fly ash and slag meet the risk screening values specified in GB15618-2018 "Soil Environmental Quality Risk Control Standards for Agricultural Land".

[0012] Further, the dry basis mass ratio of the fly ash and slag is 2:1 or 3:1.

[0013] Further, the particle size of the fly ash and slag is less than 2 mm.

[0014] In a second aspect, the present application provides a preparation method of the biomass power plant ash composition for improving soil carbon sink, comprising the following steps:

[0015] (1) Raw material pretreatment: dry, crush and sieve the fly ash and slag respectively to obtain raw materials with a particle size of less than 2 mm;

[0016] (2) Compounding: put the pretreated fly ash and slag into a mixer according to the proportion and mix uniformly.

[0017] Further, the preparation method of the biomass power plant ash composition for improving soil carbon sink comprises the following steps:

[0018] (1) Raw material pretreatment: dry the fly ash and slag at 105±5℃ to constant weight, crush and sieve through a 2 mm standard sieve to obtain raw materials with a particle size of less than 2 mm;

[0019] (2) Optimized compounding: put the pretreated fly ash and slag into a three-dimensional mixer according to the mass ratio, mix for 20-30 minutes until uniform.

[0020] In a third aspect, the present application provides the use of the biomass power plant ash composition for improving soil carbon sink as a soil conditioner for rapidly improving the organic carbon pool of degraded black calcareous soil.

[0021] Soil application scope: pH value 7.15-8.21; organic carbon content: 8.9-10.0 g·kg-1; total nitrogen content: 1.60-1.85 g·kg-1; available phosphorus content: 25.0-35.0 g·kg-1; available potassium content: 250-260 mg·kg-1.

[0022] Further, the application comprises: applying the biomass ash composition for increasing soil carbon sink in an amount of 200-400 kg per mu to the soil plough layer 10-15 cm below the ground surface by strip application or hole application.

[0023] Further, the timing of the application is the fallow period after crop harvesting.

[0024] (Three) beneficial effects

[0025] The present scheme is designed for the "maximizing carbon sequestration" goal, which overcomes the compromise of ratio caused by pursuing multiple goals. By increasing the proportion of fly ash, the maximum carbon sequestration benefit is achieved under unit application amount, the resource orientation is clear, and the input-output ratio is high.

[0026] Through the high fly ash ratio of (2-3):1, a large amount of stable carbon source is directly input into the soil. Combined with an appropriate amount of slag, the pores of the slag are used to physically protect the carbon, and the combined action makes the soil organic carbon content and carbon pool management index (CPI) rapidly and significantly increase (see Table 3, Example 5).

[0027] The present application overcomes the defects of simply mixing ash and slag in the prior art, can accurately and efficiently simultaneously increase the soil organic carbon storage capacity, realizes the dual goals of soil health and carbon sequestration and emission reduction, and provides an innovative way for high-value resource utilization of biomass ash and slag. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] Comparative Example 1: Preparation and application of biomass ash composition (fly ash: slag = 1:1)

[0030] 1. Raw material preparation and pretreatment: Take biomass fly ash and slag meeting the safety standards of GB 15618-2018, and dry at 105℃ to constant weight. After crushing, pass through a 2mm standard sieve to obtain homogeneous raw materials with particle size less than 2mm. The detailed physical and chemical properties and heavy metal content are shown in Table 1 and Table 2.

[0031] Table 1. Basic physicochemical properties of fly ash and slag from biomass power plants

[0032]

[0033] Table 2 Heavy metal content in fly ash and slag from biomass power plants (mg·kg) -1 )

[0034] Cd Hg As Pb Cr Cu Ni Zn Fly ash 0.19 1.18 3.65 8.12 12.78 3.86 2.3 18.86 Slag 0.03 0.07 1.54 2.65 6.56 2.01 0.34 5.65 GB15618-2018 ≤0.3 ≤2.4 ≤30 ≤120 ≤200 ≤100 ≤100 ≤250

[0035] 2. Optimized compounding: Pre-treated fly ash and slag are accurately weighed at a dry basis mass ratio of 1:1 and put into a three-dimensional mixer. They are mixed at a speed of 25 rpm for 25 minutes to obtain the biomass ash and slag composition.

[0036] 3. Soil improvement application: In degraded black calcareous soil areas, after the autumn crop harvest, the composition prepared in this embodiment is applied in strips at a depth of 12-15cm below the pre-set sowing row using a fertilizer applicator at a rate of 300kg / mu.

[0037] Comparative Example 2: Preparation and Application of Biomass Ash-Slag Composition (Fly Ash: Slag = 1:2)

[0038] The only difference between this embodiment and Example 1 is the compounding ratio. Weighing and mixing are performed at a dry basis mass ratio of 1:2, and the preparation and application methods are the same as in Example 1.

[0039] Comparative Example 3: Preparation and Application of Biomass Ash-Slag Composition (Fly Ash: Slag = 1:3)

[0040] The only difference between this embodiment and Example 1 is the compounding ratio. Weighing and mixing are performed at a dry basis mass ratio of 1:3, and the preparation and application methods are the same as in Example 1.

[0041] Example 1: Preparation and application of biomass ash composition (fly ash: slag = 2:1)

[0042] The only difference between this embodiment and Example 1 is the compounding ratio. Weighing and mixing are performed at a dry basis mass ratio of 2:1, and the preparation and application methods are the same as in Example 1.

[0043] Example 2: Preparation and application of biomass ash composition (fly ash: slag = 3:1)

[0044] The only difference between this embodiment and Example 1 is the compounding ratio. Weighing and mixing were performed at a dry basis mass ratio of 3:1, and the preparation and application methods were the same as in Example 1.

[0045] Effect verification

[0046] The changes in soil organic carbon under the combined addition of fly ash and slag in the embodiments are shown in Table 3.

[0047] Table 3. Changes in soil organic carbon after the addition of a mixture of fly ash and slag.

[0048]

[0049] Conclusion: As shown in Table 3, the high fly ash ratio composition (2-3:1) provided by this invention is significantly superior to the comparative example with a low fly ash ratio in terms of increasing soil organic carbon content, increase rate, and stability (manifested as higher CPI and lower mineralization rate). Among them, Example 2 (3:1 ratio) exhibits the best comprehensive carbon sequestration performance, fully verifying the technical advancement and effectiveness of this invention in achieving the goal of "improving carbon sequestration capacity".

[0050] The physicochemical properties and heavy metal content ranges of the fly ash and slag of this invention are shown in Table 4-5.

[0051] Table 4. Range of basic physicochemical properties of fly ash and slag from biomass power plants

[0052]

[0053] Table 5. Heavy metal content range of fly ash and slag from biomass power plants (mg·kg) -1 )

[0054] Cd Hg As Pb Cr Zn Fly ash 0.14～0.19 1.18～1.24 3.51～3.65 7.70～8.12 12.78～13.54 18.86～20.20 Slag 0.01～0.03 0.05～0.07 1.23～1.54 1.26～2.65 6.07～6.56 3.79～5.65 GB15618-2018 ≤0.3 ≤2.4 ≤30 ≤120 ≤200 ≤250

[0055] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biomass power plant ash composition for enhancing soil carbon sequestration, characterized in that, Includes fly ash and slag, with the dry weight ratio of fly ash to slag being (2-3):1; The physicochemical properties of the fly ash are as follows: pH 9.5–9.95, electrical conductivity 2250–2984 μS·cm. -1 Specific surface area 7.50–7.85 m² 2 ·g -1 Organic carbon content: 19.0–21.0 g·kg -1 ; The physicochemical properties of the slag are as follows: pH 8.94–9.50, electrical conductivity 380–430 μS·cm. -1 Specific surface area 9.75–11.85 m² 2 ·g -1 Organic carbon content: 12.13–13.5 g·kg -1 ; Furthermore, the contents of heavy metals Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in the fly ash and slag all meet the risk screening values ​​specified in GB 15618-2018 "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control".

2. The biomass power plant ash composition for enhancing soil carbon sequestration according to claim 1, characterized in that, The dry weight ratio of fly ash to slag is 2:1 or 3:

1.

3. A biomass power plant ash composition for enhancing soil carbon sequestration according to any one of claims 1-3, characterized in that, The particle size of both fly ash and slag is less than 2 mm.

4. A method for preparing a biomass power plant ash composition for enhancing soil carbon sequestration as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Raw material pretreatment: Fly ash and slag are dried, crushed and screened to obtain raw materials with a particle size of less than 2 mm; (2) Mixing: The pretreated fly ash and slag are added into the mixer in proportion and mixed evenly.

5. The method for preparing a biomass ash composition according to claim 4, characterized in that, The mixer mentioned in step (2) is a three-dimensional mixer with a mixing time of 20-30 minutes.

6. The use of the biomass power plant ash composition according to any one of claims 1-3 for enhancing soil carbon sequestration as a soil conditioner for improving the carbon sequestration capacity of degraded chernozem; Soil application range: pH value 7.15~8.21; organic carbon content: 8.9~10.0 g·kg-1; total nitrogen content: 1.60~1.85 g·kg-1; available phosphorus content: 25.0~35.0 g·kg-1; available potassium content: 250~260 mg·kg-1.

7. The application of the biomass power plant ash composition for enhancing soil carbon sequestration according to claim 6 as a soil conditioner for improving the carbon sequestration capacity of degraded chernozem, characterized in that, The biomass ash composition is applied at a rate of 200-400 kg / mu to the topsoil layer 10-15 cm below the surface by strip application or hole application.

8. The application of the biomass power plant ash composition for enhancing soil carbon sequestration according to claim 6 or 7 as a soil conditioner for improving the carbon sequestration capacity of degraded chernozem, characterized in that, The application is to be performed during the fallow period after crop harvest.

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