CN108424206B

CN108424206B - Method for preparing silicon-containing compound fertilizer by using fly ash acid method aluminum extraction residues, silicon-containing compound fertilizer and fly ash utilization method

Info

Publication number: CN108424206B
Application number: CN201810564662.XA
Authority: CN
Inventors: 刘汇东; 陈爱国; 王晓欢
Original assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Current assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Priority date: 2018-06-04
Filing date: 2018-06-04
Publication date: 2021-03-16
Anticipated expiration: 2038-06-04
Also published as: CN108424206A

Abstract

The invention relates to the field of utilization of fly ash acid method aluminum extraction residues and fly ash, and discloses a method for preparing a silicon-containing compound fertilizer by using fly ash acid method aluminum extraction residues, a silicon-containing compound fertilizer and a utilization method of fly ash. The method comprises the following steps: (1) mixing the residue of the acid-method aluminum extraction of the fly ash with a fertilizer source into slurry in the presence of a NaOH solution, and carrying out heating reaction, wherein the fertilizer source is a calcium source and/or a magnesium source; (2) and (2) carrying out solid-liquid separation on the reaction product obtained in the step (1), and granulating and drying the obtained filter cake to obtain a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer. The method can simplify the preparation operation, avoid the solid-liquid separation operation of sodium silicate, reduce the loss of the nutrient elements of silicon, calcium and magnesium, and obtain the compound fertilizer with low Na residue rate.

Description

Method for preparing silicon-containing compound fertilizer by using fly ash acid method aluminum extraction residues, silicon-containing compound fertilizer and fly ash utilization method

Technical Field

The invention relates to the field of utilization of aluminum residue extracted by a fly ash acid method and fly ash, in particular to a method for preparing a silicon-containing compound fertilizer by using the aluminum residue extracted by the fly ash acid method, the silicon-containing compound fertilizer and a utilization method of the fly ash.

Background

The high-alumina fly ash is a novel aluminum resource peculiar to China, and the amount of prospect resources of the high-alumina fly ash is about 100 million tons of alumina. The development and utilization of the high-alumina fly ash can greatly relieve the problem of bauxite resource shortage in China. The one-step acid dissolution method is an ideal method for extracting alumina from high-alumina fly ash, but every 100 tons of Al are produced₂O₃The method discharges about 130-150 tons of high-silicon solid waste residue, namely 'residue for extracting aluminum from fly ash', which is commonly called white mud in the industry.

At present, the utilization of the fly ash aluminum extraction residue mainly focuses on the preparation of silicon products (water glass, white carbon black, silicon micropowder and the like), the manufacture of basic building materials (cement, ceramic tiles, autoclaved bricks and the like), and the production of heat preservation materials, refractory materials and other fields. However, the application directions all have contradictions of different degrees among the economic added value, the market capacity and the consumption efficiency of the product, so that the overall utilization rate of the white mud is low. According to relevant regulations, the comprehensive utilization rate of the solid waste of a newly-built system for producing alumina by using high-alumina fly ash is required to reach more than 96%. The utilization rate of various existing white mud utilization can not reach the index, and the application and popularization of the high-alumina fly ash aluminum extraction technology are directly limited. Therefore, a high-value and high-efficiency digestion technology of the white mud needs to be developed.

In the international soil community, silicon fertilizer is listed as the fourth major element fertilizer following nitrogen, phosphorus and potassium. The national geodetic formulation has used the lack of silica as a technical standard. Silicon fertilizer has become a new fertilizer in China in the 21 st century. At present, the silicon-deficient soil in China accounts for more than 50-80% of the total cultivated land area. Taking rice as an example, the area for planting rice in China all year round reaches 3333 more than ten thousand hectares, and the silicon-deficient soil accounts for more than 50 percent. If the silicon fertilizer is completely applied, the yield of 100 ten thousand tons of paddy can be increased by 10 percent, and the popularization of the production and application of the silicon fertilizer has very obvious social and economic benefits. The silicon fertilizer industry will be in the rising stage for a long time in the future, the market space is huge, and the competitive pressure is very small. In addition, calcium and magnesium are also necessary secondary elements for plant growth and development. The soil is supplemented with Si, Ca and Mg, and the synergistic effect on the production and development of crops can be achieved.

CN1923764A discloses a citrate soluble silicon-calcium-magnesium fertilizer, wherein the raw materials and weight percentage content of the silicon-calcium-magnesium fertilizer are 60-70% of water quenched steel slag, 4-12% of light-burned magnesium, 10-20% of silicon slag, 15-20% of dilute sulphuric acid and 1-3% of brine. The preparation method comprises the steps of mixing water quenched steel slag, light-burned magnesium oxide, silicon slag and the like in proportion, adding dilute sulfuric acid, and performing acid burning for 20min at 135 ℃, thus obtaining an acidic product system under an acidic condition.

CN101591197A discloses a method for preparing a silico-calcium fertilizer by using high-alumina fly ash pre-desiliconization, which comprises the following steps of (1) adding a raw material of high-alumina fly ash into a sodium hydroxide solution for carrying out an alkali dissolution reaction; (2) filtering and separating the sodium silicate solution generated by the alkali dissolution reaction, and taking the filter cake desiliconized fly ash as an ingredient for extracting alumina; (3) adding lime milk into the sodium silicate solution after filtration and separation for precipitation reaction, and performing filtration and separation, wherein a filter cake is calcium silicate, a filtrate is a sodium hydroxide solution, and the sodium hydroxide solution is returned to the step (1) for recycling; and (4) drying and grinding the calcium silicate filter cake to obtain the calcium silicate fertilizer product. Step (2) of the process route adopted by the method relates to solid-liquid separation of sodium silicate. The sodium silicate solution (commonly called as water glass) has high viscosity, is difficult to operate during separation and has high filtration loss rate. Although heat preservation filtration (namely filtration at 90 ℃) can be adopted, the filtration pressure is increased or filtration equipment is improved, the operation difficulty or the equipment cost is increased, and the preparation cost of the silicon-containing compound fertilizer is increased.

CN107188766A discloses a method for preparing a silicon compound fertilizer by using fly ash, which comprises the following steps: (1) treating the fly ash of the power plant to 150-200 meshes by a pulverizer; (2) fully reacting the pulverized coal ash with dilute hydrochloric acid, filtering silicon-containing filter residues, and drying the silicon-containing filter residues for later use; (3) evaporating and crystallizing the filtrate in the step (2) at the temperature of 100-150 ℃ to obtain a solid mixture containing calcium chloride and magnesium chloride crystals; (4) fully reacting the dried silicon-containing filter residue obtained in the step (2) with a sodium hydroxide solution to obtain a sodium silicate-containing liquid mixture; (5) spraying the sodium silicate-containing liquid mixture obtained in the step (4) onto a material bed of a granulator for granulation to prepare a silicon compound fertilizer, wherein the materials on the material bed comprise humic acid, nitrogenous fertilizer, phosphate fertilizer, potash fertilizer, bentonite and trace element fertilizer; wherein, the weight percentages of the liquid mixture containing sodium silicate, humic acid, nitrogenous fertilizer, phosphate fertilizer, potash fertilizer, bentonite and trace element fertilizer are respectively; 5-10%, 30-35%, 20-35%, 10-25%, 0.5-1%. The preparation method of the silicon-containing compound fertilizer is essentially mechanical compound mixing of various nutrient components. In addition, the silicon source is sodium silicate solution, Na₂O/SiO₂The mass ratio is more than or equal to 1, which means that strong alkaline Na with more than one unit is introduced while one unit of available silicon is provided for soil₂And O, the fertilization result of the fertilizer has the risk of intensifying the alkalization or salinization of the soil.

It can be seen that the technical defects in the prior art in the process of preparing the silicon fertilizer and the silicon-containing compound fertilizer by using the fly ash as the raw material and adopting the NaOH alkali-soluble system are as follows: (1) the sodium element being introduced in excess, i.e.Under the condition of providing the same equivalent of effective silicon, a large amount of Na element is synchronously introduced, and the ratio of soluble sodium to effective silicon is larger than that of Na₂O/SiO₂Too high; (2) when the sodium silicate is subjected to solid-liquid separation with a solid-phase product, excessive filtration loss of Si and Na is easily caused, or indexes such as operating conditions, energy consumption cost, effective silicon content of the product and the like are easily deteriorated.

Disclosure of Invention

The invention aims to overcome the defects and provides a method for preparing a silicon-containing compound fertilizer by using fly ash acid-method aluminum extraction residues, the silicon-containing compound fertilizer and a utilization method of fly ash.

In order to achieve the above object, a first aspect of the present invention provides a method for preparing a silicon-containing compound fertilizer from fly ash acid-process aluminum extraction residues, comprising:

(1) mixing the residue of the acid-method aluminum extraction of the fly ash with a fertilizer source into slurry in the presence of a NaOH solution, and carrying out heating reaction, wherein the fertilizer source is a calcium source and/or a magnesium source;

(2) and (2) carrying out solid-liquid separation on the reaction product obtained in the step (1), and granulating and drying the obtained filter cake to obtain a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer.

Preferably, when the fertilizer source is a calcium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the aluminum extraction residue of the fly ash by the acid method, the NaOH solution and the calcium source is 1: 1.3-1.7: 0.6-0.8.

Preferably, when the fertilizer source is a calcium source and a magnesium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the NaOH solution to the calcium source to the magnesium source is 1: 1.3-1.7: 0.1-0.6: 0.4-0.04.

Preferably, when the fertilizer source is a magnesium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the aluminum residue extracted by the acid method of the fly ash, the NaOH solution and the magnesium source is 1: 1.5-1.8: 0.5-0.7.

Preferably, the heating reaction temperature is 90-160 ℃, the heating reaction pressure is normal pressure, and the heating reaction time is 1-5 h.

Preferably, the method further comprises the step of washing the filter cake with water, and then combining alkali-containing washing water obtained by washing with water and filtrate obtained by solid-liquid separation, concentrating the alkali-containing washing water and the filtrate, and returning the concentrated alkali-containing washing water and the filtrate to the NaOH solution obtained in the step (1).

Preferably, after the washing, the content of sodium oxide in the filter cake is below 8 wt%.

Preferably, the viscosity of the reaction product in step (2) is from 1 to 4mPa · s at 25 ℃.

In a second aspect, the invention provides a silicon-containing compound fertilizer prepared by the method, wherein soluble Na in the silicon-containing compound fertilizer₂The content of O is less than 6 weight percent, and the silicon-containing compound fertilizer is a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer.

In a third aspect, the present invention provides a method for utilizing fly ash, comprising: the fly ash is subjected to acid-process aluminum extraction to obtain aluminum oxide and fly ash acid-process aluminum extraction residues, and the fly ash acid-process aluminum extraction residues are prepared into a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer by the method.

Through the technical scheme, the method provided by the invention can greatly simplify the process flow, avoid the solid-liquid separation operation of sodium silicate, reduce the loss of nutrient elements and reduce the filtration loss rate of silicon elements to be lower than 1.0 weight percent. The Na residue rate of the obtained compound fertilizer is low, and the obtained compound fertilizer contains 21-38 wt% of effective silicon, 5-40 wt% of effective magnesium and 5-40 wt% of effective calcium; soluble Al harmful to agriculture₂O₃Less than 8% of soluble Na₂The O content is less than 6 percent.

The method provided by the invention recycles the alkali-containing wastewater, and can realize the minimization of water consumption and sewage discharge. The method provided by the invention has no secondary solid waste discharge.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a flow chart of a method for preparing a silicon-calcium compound fertilizer provided by the invention;

FIG. 2 is a flow chart of a method for preparing a silicon-calcium-magnesium compound fertilizer provided by the invention;

FIG. 3 is a flow chart of the method for preparing the silicon-magnesium compound fertilizer provided by the invention.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a method for preparing a silicon-containing compound fertilizer by using fly ash acid method aluminum extraction residues, which comprises the following steps:

In the invention, the residue of extracting aluminum from fly ash by acid method mainly comprises: SiO 2₂、Al₂O₃And TiO₂。SiO₂In an amount of about 70 to 80 wt.%, Al₂O₃In an amount of about 10-15% by weight and TiO₂Is present in an amount of about 3 to about 8 weight percent. Such as the acid-stripping of aluminum residues from the fly ash of Toigel₂Is about 78.7 wt%, Al₂O₃In an amount of about 13.4% by weight and TiO₂Is present in an amount of about 5.2 wt%. Further XRD analysis of the residue from acid extraction of aluminum from fly ash shows that Al is present₂O₃Substantially of mullite (3 Al)₂O₃·SiO₂) In the form of TiO₂The carrier is anatase and rutile; about 85% of the Si is present in amorphous form, the remainder being present in mullite and quartz.

According to one embodiment of the present invention, the process is shown in FIG. 1. Wherein when the fertilizer source is a calcium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the aluminum extraction residue of the fly ash by the acid method, the NaOH solution and the calcium source is 1: 1.3-1.7: 0.6-0.8.

According to another embodiment of the present invention, the process is shown in FIG. 2. Wherein when the fertilizer source is a calcium source and a magnesium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the NaOH solution to the calcium source to the magnesium source is 1: 1.3-1.7: 0.1-0.6: 0.4-0.04.

According to another embodiment of the present invention, the process is shown in FIG. 3. Wherein when the fertilizer source is a magnesium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the aluminum residue extracted by the acid method of the fly ash, the NaOH solution and the magnesium source is 1: 1.5-1.8: 0.5-0.7.

Through the three specific implementation modes, the method provided by the invention can realize that the fly ash acid method aluminum extraction residue and the fertilizer source directly react by heating in the presence of NaOH to produce the silicon-calcium compound fertilizer, the silicon-magnesium compound fertilizer or the silicon-calcium-magnesium compound fertilizer. The method can avoid the generation of sodium silicate solution intermediate products, avoid the filtration and separation operation of the sodium silicate solution which is difficult to carry out, and reduce the difficulty of the whole process flow. The method does not produce sodium silicate, does not need filtration and separation of the sodium silicate, and can reduce filtration loss.

In the present invention, the NaOH solution may have a NaOH concentration of 10 to 20 wt%.

According to the invention, the heating reaction is carried out to complete the combination of the fly ash acid method aluminum extraction residues and the silicon and calcium in the fertilizer source, or the silicon, calcium and magnesium, or the silicon and magnesium, which are subjected to chemical change to obtain the corresponding silicon-containing compound fertilizer. Preferably, the heating reaction temperature is 90-160 ℃, preferably 90-150 ℃, the heating reaction pressure is normal pressure, and the heating reaction time is 1-5h, preferably 2-5 h. In the present invention, the heating reaction is not required to be carried out under pressure, and the normal pressure may be a normal ambient pressure at which the heating reaction is carried out, and may be, for example, 0.1 to 0.2MPa in a standard state. Atmospheric pressure is gauge pressure.

According to the present invention, the NaOH solution in step (1) may be present as a catalyst, participate in the chemical reaction but is not theoretically consumed, and NaOH may be recovered by separating the reaction product obtained. Preferably, the method further comprises the step of washing the filter cake with water, and then combining alkali-containing washing water obtained by washing with water and filtrate obtained by solid-liquid separation, concentrating the alkali-containing washing water and the filtrate, and returning the concentrated alkali-containing washing water and the filtrate to the NaOH solution obtained in the step (1). Can make full use of raw materials, avoid the discharge of alkali liquor and avoid secondary pollution. The recycling efficiency (η) of NaOH can be calculated by the following method as the mass percentage of Na element used: [ (absolute mass of Na element added in step (1) -absolute mass of Na element in product)/absolute mass of Na element added in step (1) ] × 100%. The recovered NaOH solution is used in the step (1) to satisfy the feeding relation.

According to the invention, in the provided method, the NaOH solution is not tightly combined with the obtained reaction product, and the sodium element in the filter cake is easily removed through common water washing operation, so that the content of the sodium element in the filter cake can be reduced, and the negative influence of fertilization on soil can be reduced. Preferably, after the water washing, the content of sodium oxide in the filter cake is below 8 wt%.

According to the invention, the method can avoid the generation of sodium silicate, and the solid-liquid separation in the step (2) is simpler. In the present invention, the viscosity of the reaction product in the step (2) can be used to reflect the difficulty of solid-liquid separation. Preferably, the viscosity of the reaction product in step (2) is from 1 to 4 mPas, preferably from 1.2 to 3.8 mPas, at 25 ℃. The reaction product has a viscosity within this range, and can be more easily subjected to solid-liquid separation than a sodium silicate solution.

In a second aspect, the invention provides a silicon-containing compound fertilizer prepared by the method, wherein soluble Na in the silicon-containing compound fertilizer₂The O content is 6 wt% or less; the silicon-containing compound fertilizer is a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer. Soluble Na₂O is Na extractable by 0.5mol/L hydrochloric acid solution₂The percentage of the mass of O in the total mass of the silicon-containing compound fertilizer can be determined by a method for determining the silicon content in standard NY T2272-2012 'determination of the silicon-magnesium-calcium content of soil conditioner'.

According to the technical scheme, the loss of effective components in the silicon-containing compound fertilizer due to the fact that solid-liquid separation of the sodium silicate solution is required in the prior art can be reduced. The obtained silicon-containing compound fertilizer has high content of effective components. Through calculation, the content of effective silicon in the obtained silicon-containing compound fertilizer can reach 40 percent and is far more than 20 percent of the national standard.

In a third aspect, the present invention provides a method for utilizing fly ash, comprising: the fly ash is subjected to acid-process aluminum extraction to obtain aluminum oxide and fly ash acid-process aluminum extraction residues, and the fly ash acid-process aluminum extraction residues are prepared into a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer by the method. The fly ash can be more effectively utilized, and aluminum resources in the fly ash can be produced and utilized.

Wherein the fly ash can be fine ash collected from flue gas discharged from coal fired power plants after coal combustion. May be mainly composed of SiO₂、Al₂O₃And TiO₂。SiO₂Is present in an amount of about 20 to about 40 weight percent, Al₂O₃In an amount of about 45 to 60% by weight and TiO₂Is present in an amount of about 1.5 to about 4.5 wt%. For example, powder from the power plant of Shenhua inner Mongolian ChinaCoal ash of, among others, SiO₂Is about 32.43 wt%, Al₂O₃In an amount of about 50.42 wt% and TiO₂Is present in an amount of about 2.14 wt%.

The acid method for extracting aluminum in the invention can adopt a method known in the art, and is not described in detail herein.

The present invention will be described in detail below by way of examples.

The viscosities of the reaction products in the examples and comparative examples were measured by means of an NDJ-8S type viscometer. The basic principle is that the rotor can be subjected to reverse action torque of liquid in the rotation process of the liquid to be detected, and the torque is larger when the viscosity of the liquid is larger; and measuring the moment and converting to obtain the viscosity value of the liquid to be measured in unit of mPa & s.

The content of effective silicon, effective calcium, effective magnesium, soluble alumina and soluble sodium oxide in the obtained silicon-containing compound fertilizer is determined according to industry standards NY T2272-2012 'determination of content of silicon, magnesium and calcium of soil conditioner' and NY T3035-2016 'determination of content of aluminum and nickel of soil conditioner'.

The fly ash comes from Shenhua inner Mongolian China power plant, and the specific composition content is shown in Table 1.

TABLE 1

Composition of	Al₂O₃	SiO₂	P₂O₅	SO₃	K₂O	CaO	TiO₂	Fe₂O₃	MgO	Na₂O
											Content by weight%	50.42	32.43	0.19	4.0	0.37	3.03	2.14	1.71	0.18	0.03

The fly ash acid method aluminum extraction residue (white mud) comes from an alumina plant of the Niger energy Limited liability company, and the preparation method can be as follows: adding 100g of fly ash (Shenhua inner Mongolia Hua power plant) into 12mol/L hydrochloric acid solution, stirring and reacting for 30h at 100 ℃, filtering and washing to obtain an aluminum-rich solution and fly ash aluminum extraction residue by an acid method. The specific composition contents are shown in table 2.

TABLE 2

Composition of	Al₂O₃	SiO₂	P₂O₅	SO₃	K₂O	CaO	TiO₂	Fe₂O₃	ZrO₂	Na₂O
											Content by weight%	13.4	78.7	0.14	0.35	0.16	0.37	5.2	0.45	0.29	-

Example 1

The preparation of the silicon-calcium compound fertilizer is carried out according to the flow shown in figure 1.

(1) 3g of white mud is taken, added with 1.8g of CaO powder, added with 20mL of NaOH solution with the concentration of 20 weight percent and stirred evenly to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor which is preheated to 90 ℃, preserving heat for 2 hours for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.2 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 20mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 0.3% by weight.

(4) The obtained silicon-calcium compound fertilizer product is analyzed and tested, and has the effective silicon content of 27.18 percent, the effective calcium content of 37.56 percent and the soluble Na content₂The O content is 2.39 percent. Product Na₂O：SiO₂The ratio was 0.088.

The recycling efficiency eta of NaOH in the preparation process is 96.4%.

Example 2

(1) 3g of white mud is taken, added with 1.8g of CaO powder, added with 30mL of NaOH solution with the concentration of 13.3 weight percent and stirred evenly to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor which is preheated to 100 ℃, preserving heat for 3 hours for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 2.2 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 30mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 0.5% by weight.

(4) The obtained silicon-calcium compound fertilizer product is analyzed and tested, and has effective silicon content of 37.86%, effective calcium content of 35.44% and soluble Na₂The O content was 4.69%. Product Na₂O：SiO₂The ratio is 0.124.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 93.9%.

Example 3

(1) Taking 3g of white mud, adding 1.8g of CaO powder, adding 60mL of 6.65 weight percent NaOH solution, and uniformly stirring to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor preheated to 150 ℃, preserving heat for 2 hours for reaction, and keeping stirring at a stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 1.2 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 60mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 0.5% by weight.

(4) The obtained silicon-calcium compound fertilizer product is analyzed and tested, and has the effective silicon content of 34.73 percent, the effective calcium content of 36.05 percent and the soluble Na₂The O content is 4.07%. Product Na₂O：SiO₂The ratio was 0.113.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 94.6%.

Example 4

(1) Taking 6g of white mud, adding 3.2g of CaO powder, adding 15mL of NaOH solution with the concentration of 20 weight percent, and uniformly stirring to obtain reactant slurry.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.1 mPas. The total volume of the filtrate and washing water is 100mL, evaporation concentration is carried out until 15mL, and the filtrate is reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 0.5% by weight.

(4) The obtained silicon-calcium compound fertilizer product is analyzed and tested, and has the effective silicon content of 32.33 percent, the effective calcium content of 35.36 percent and the soluble Na content₂The O content is 3.76%. Product Na₂O：SiO₂The ratio is 0.106.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 95.1 percent. .

Example 5

(1) 9g of white mud is taken, 5.8g of CaO powder is added, 60mL of NaOH solution with the concentration of 20 weight percent is added, and the mixture is stirred uniformly to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor preheated to 100 ℃, preserving heat for 3.5 hours for reaction, and keeping stirring in the reaction process at a stirring speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.2 mPas. The total volume of the filtrate and washing water is 900mL, the filtrate and the washing water are evaporated and concentrated to 60mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained silicon-calcium compound fertilizer product is analyzed and tested, and has the effective silicon content of 36.0 percent, the effective calcium content of 32.7 percent and the soluble Na content₂The O content is 4.89%. Product Na₂O：SiO₂The ratio is 0.136.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 93.7%. .

Example 6

(1) Taking 400g of white mud, adding 240g of CaO powder, adding 3.0L of 17.8 weight percent NaOH solution, and uniformly stirring to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor preheated to 100 ℃, preserving heat for 3.0h for reaction, and keeping stirring in the reaction process at a stirring speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 2.8 mPas. The total amount of the filtrate and washing water is 6.0L, evaporation concentration is carried out to 3.0L, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained silicon-calcium compound fertilizer product is analyzed and tested, and the effective silicon content is 31.27 percent, the effective calcium content is 27.52 percent, and the soluble Na content₂The O content is 3.47%. Product Na₂O：SiO₂The ratio was 0.11.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 95.5 percent.

Example 7

(1) Taking 6g of white mud, adding 2.0g of CaO powder, adding 10mL of NaOH solution with the concentration of 20 weight percent, and uniformly stirring to obtain reactant slurry.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.4 mPas. The total volume of the filtrate and washing water is 50mL, the filtrate and the washing water are evaporated and concentrated to 10mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained silicon-calcium compound fertilizer product is analyzed and tested, and the effective silicon content is 13.92 percent and is lower than the standard value of 20 percent; effective calcium content 25.92%, soluble Na₂The O content is 6.89%. Product Na₂O：SiO₂The ratio was 0.49.

Example 8

(2) Transferring the obtained reactant slurry into a reactor preheated to 100 ℃, preserving heat for 15h for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.0 mPas. The total volume of the filtrate and washing water is 900mL, the filtrate and the washing water are evaporated and concentrated to 60mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained silicon-calcium compound fertilizer product shows a zeolite phase (insoluble in water or acid or alkali solution) with a stable structure through analysis and test, the effective silicon content is only 16.2 percent, the effective calcium content is 28.9 percent, and the soluble Na₂The content of O is as high as 12.55 percent. Product Na₂O：SiO₂The ratio was 0.77.

The recycling efficiency eta of NaOH in the preparation process is only 83.7 percent.

Comparative example 1

Grinding the residue of the acid-method aluminum extraction of the fly ash by a pulverizer to below 200 meshes, and then mixing the residue with 20 wt% of dilute hydrochloric acid according to the weight ratio of 1: 3(g/mL), filtering the product to obtain silicon-containing filter residue, and drying the silicon-containing filter residue for later use. And evaporating the obtained filtrate at 120 ℃ to crystallize a solid mixture containing calcium chloride and magnesium chloride crystals for later use. Reacting the silicon-containing filter residue with 25% sodium hydroxide solution at the ratio of 1:1.5(g/mL) at 80 ℃ to obtain a sodium silicate-containing liquid mixture.

50kg of weathered coal, 300kg of urea, 350kg of monoammonium phosphate, 250kg of potassium chloride, 5kg of bentonite and 10kg of trace element fertilizer (10 kg of solid mixture containing calcium chloride and magnesium chloride crystals) are put into a granulator, 50kg of sodium silicate-containing liquid mixture is sprayed onto the material bed through a liquid spray head in the granulator, the granulation is carried out until the particle size is 4mm, and the silicon-containing compound fertilizer is obtained after drying and packaging.

Analysis tests show that in the silicon-containing compound fertilizer, the effective silicon content is only 1.03 wt%, the effective calcium content is about 3 wt%, and the soluble Na content₂The O content was 0.83% by weight. Product Na₂O：SiO₂The ratio was 0.81.

Comparative example 2

(1) And adding 30mL of 20 weight percent NaOH solution into 3g of white mud, and uniformly stirring to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor preheated to 110 ℃, preserving heat for 2.5 hours for reaction, and keeping stirring in the reaction process at the stirring speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction is finished, solid-liquid separation and filter cake washing are carried out, and the viscosity of a reaction product is 16 mPas. The filter cake contains sodium metasilicate, is viscous and pasty, is difficult to filter and dry, and the filtration loss (entering the filter cake) rate of Si element is more than 10 percent by weight.

(4) Adding 1.8g of CaO powder into the obtained filtrate (the main component of sodium metasilicate), stirring uniformly, transferring into a reactor which is preheated to 90 ℃, preserving heat for 20min for reaction, keeping stirring in the reaction process, and stirring at the speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(5) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 2.2 mPas. The filtrate and washing water amounted to 50mL, and were evaporated to 20mL, which was used for the next batch to prepare reactant slurry.

(6) Drying the filter cake to obtain the silicon-calcium compound fertilizer, and analyzing and testing that the effective silicon content is only 18.75 percent and is lower than the standard value of 20 percent; effective calcium content of 39.18%, soluble Na₂The O content is 4.65%. Product Na₂O：SiO₂The ratio was 0.25.

The energy consumption of the preparation process is that the recycling efficiency eta of the NaOH is less than 85 percent.

Example 9

The preparation of the silicon-calcium-magnesium compound fertilizer is carried out according to the flow shown in figure 2.

(1) 3g of white mud was added with 0.9g of CaO powder and 0.64g of MgO powder, and 60mL of 6.67 wt% NaOH solution was added thereto and stirred uniformly to obtain a reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor which is preheated to 90 ℃, preserving heat for 3 hours for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 2.4 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 60mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium-magnesium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained Si-Ca-Mg compound fertilizer product is analyzed and tested, and has the effective silicon content of 28.38 percent, the effective calcium content of 22.72 percent, the effective magnesium content of 17.19 percent and the soluble Na content₂The O content is 4.64%. Product Na₂O： SiO₂The ratio is 0.16.

The recycling efficiency eta of NaOH in the preparation process is 96.1%.

Example 10

(1) 3g of white mud is taken, added with 1.6g of CaO powder and 0.14g of MgO powder, and added with 20mL of NaOH solution with the concentration of 20 weight percent, and stirred evenly to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor which is preheated to 100 ℃, preserving heat for 2 hours for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.8 mPas. The filtering is easy, the total amount of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 20mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium-magnesium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained silicon-calcium-magnesium compound fertilizer product is analyzed and tested to obtain effective silicon36.20 percent of the total calcium, 28.64 percent of the effective calcium, 5.44 percent of the effective magnesium and soluble Na₂The O content is 4.60%. Product Na₂O：SiO₂The ratio is 0.127.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 92.5 percent.

Example 11

(1) Taking 3g of white mud, adding 0.3g of CaO powder and 1.07g of MgO powder, adding 30mL of NaOH solution with the concentration of 13.3 weight percent, and uniformly stirring to obtain reactant slurry.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.0 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 30mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-calcium-magnesium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The analysis and test of the obtained silicon-calcium-magnesium compound fertilizer product show that the effective silicon content is 26.55 percent, the effective calcium content is 5.35 percent, the effective magnesium content is 19.10 percent, and the soluble Na content₂The O content is 3.25%.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 90.8%.

Comparative example 3

(2) Transferring the obtained reactant slurry into a reactor preheated to 140 ℃, preserving heat for 1.5h for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(4) Adding 0.9g of CaO powder and 0.64g of MgO powder into the obtained filtrate (the main component of sodium metasilicate), stirring uniformly, transferring into a reactor which is preheated to 60 ℃, preserving heat for 1h for reaction, keeping stirring in the reaction process, and stirring at the speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(6) Drying the filter cake to obtain the silicon-calcium-magnesium compound fertilizer, and analyzing and testing that the effective silicon content is 16.30 percent and is lower than the standard value of 20 percent; 22.50% of available calcium, 17.30% of available magnesium and soluble Na₂The O content is 4.08%. Product Na₂O：SiO₂The ratio was 0.25.

Example 12

The silicon-magnesium compound fertilizer preparation is carried out according to the flow shown in figure 3.

(1) Adding 1.29g of MgO powder into 3g of white mud, adding 30mL of NaOH solution with the concentration of 20 weight percent, and uniformly stirring to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor preheated to 120 ℃, preserving heat for 3 hours for reaction, and keeping stirring in the reaction process at a stirring speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.4 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 30mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-magnesium compound fertilizer product. The filtration loss (entering filtrate and washing water) rate of Si element is less than 1.0 percent

(4) The obtained Si-Mg compound fertilizer has 21.94% effective Si content and effective Mg content39.34% of soluble Na₂The O content is 2.64 percent.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 92.3 percent.

Example 13

(1) Adding 1.29g of MgO powder into 3g of white mud, adding 60mL of 20 weight percent NaOH solution, and uniformly stirring to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor preheated to 140 ℃, preserving heat for 2 hours for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.1 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 60mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-magnesium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained Si-Mg compound fertilizer has the effective Si content of 23.88%, effective Mg content of 31.99% and soluble Na content₂The O content was 4.73%.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 92.0 percent.

Example 14

(1) Adding 3g of white mud into 1.29g of MgO powder, adding 20mL of 20 weight percent NaOH solution, and uniformly stirring to obtain reactant slurry.

(2) Transferring the obtained reactant slurry into a reactor preheated to 160 ℃, preserving heat for 5 hours for reaction, and keeping stirring in the reaction process at a stirring speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 3.0 mPas. The total volume of the filtrate and washing water is 100mL, the filtrate and the washing water are evaporated and concentrated to 20mL, and the filtrate and the washing water are reserved for preparing reactant slurry in the next batch; and drying the filter cake to obtain the silicon-magnesium compound fertilizer product. The filtration loss (into the filtrate and the washing water) of the Si element was less than 1.0% by weight.

(4) The obtained Si-Mg compound fertilizer has effective Si content of 30.50%, effective Mg content of 31.98%, and soluble Na content₂The O content is 8.12%.

The energy consumption of the preparation process is that the recycling efficiency eta of NaOH is 90.6%.

Comparative example 4

(2) Transferring the obtained reactant slurry into a reactor preheated to 120 ℃, preserving heat for 2 hours for reaction, and keeping stirring at the stirring speed of 80rpm in the reaction process; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(3) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 15.5 mPas. The filter cake contains sodium metasilicate, is viscous and pasty, is difficult to filter and dry, and the filtration loss (entering the filter cake) rate of Si element is more than 10 percent by weight.

(4) Adding 1.29g of MgO powder into the obtained filtrate (the main component of sodium metasilicate), stirring uniformly, transferring into a reactor which is preheated to 20 ℃, preserving heat for 1.5h for reaction, keeping stirring in the reaction process, and stirring at the speed of 80 rpm; the reaction container is a non-pressure container in a closed form to prevent the rapid loss of water; the reaction pressure is close to normal pressure.

(5) After the reaction, solid-liquid separation and filter cake washing are carried out, and the viscosity of the reaction product is 2.2 mPas. The filtrate and washing water amounted to 100mL, and were evaporated to 20mL, which was used for the next batch to prepare reactant slurry.

(6) Drying the filter cake to obtain the silicon-magnesium compound fertilizer, wherein the effective silicon content is only 11.94 percent and is lower than the standard value of 20 percent through analysis and test; effective magnesium content 49.34%, soluble Na₂The O content is 2.64 percent.

As can be seen from the results of the above examples and comparative examples, the method provided by the present invention can effectively increase the amount of soil nutrient elements remaining in the prepared silicon-containing compound fertilizer, the effective silicon content in the compound fertilizer can be 21-38 wt%, the effective magnesium content can be 5-40%, andthe content of the effective calcium can be 5-40%; at the same time, soluble Al which is harmful to agriculture₂O₃Less than 8% of soluble Na₂The O content is less than 6 percent.

By implementing the method provided by the invention, a reaction product with low viscosity can be obtained, and the generation of a sodium silicate solution which is difficult to separate solid from liquid is avoided. Moreover, the heating reaction involved in the steps of the method can be carried out at a lower reaction temperature (90-160 ℃), a shorter reaction time (2-5h) and normal pressure. The utilization efficiency of the white mud is 100%, the used NaOH solution can be recycled, the loss is low, and the discharge of alkali-containing wastewater can be reduced.

The amount of CaO and NaOH solutions added in example 7 is outside the range defined by the present invention, resulting in the standard that the effective silicon content in the obtained silicon-calcium compound fertilizer is less than 20 wt%. In example 8, the heating reaction time is out of the range defined by the invention, so that the content of effective silicon in the obtained silicon-calcium compound fertilizer is lower than the standard, the residual quantity of sodium element is too high, and the recovery rate of NaOH is low.

Comparative example 1 is a prior art process and the resulting compound fertilizer has a low content of available silicon. Comparative examples 2 to 4 adopt the method of the prior art, sodium silicate is produced in the preparation process, the viscosity of the reaction product is large, the loss of silicon element in the filtration process is large, and the content of effective silicon in the silicon calcium, silicon calcium magnesium or silicon magnesium compound fertilizer is low.

In addition, the method provided by the invention has the advantages of extremely simple process, small equipment investment, wide product application range, large market space and small competitive pressure, and can generate good environmental and economic benefits.

Claims

1. A method for preparing a silicon-containing compound fertilizer by using fly ash acid method aluminum extraction residues comprises the following steps:

(2) carrying out solid-liquid separation on the reaction product obtained in the step (1), and granulating and drying the obtained filter cake to obtain a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer;

wherein, theWhen the fertilizer source is a calcium source, the fly ash acid method is used for extracting aluminum residues by using SiO₂The weight ratio of the aluminum extraction residue of the fly ash by the acid method, the NaOH solution and the calcium source is 1: 1.3-1.7: 0.6-0.8;

wherein when the fertilizer source is a calcium source and a magnesium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the NaOH solution to the calcium source to the magnesium source is 1: 1.3-1.7: 0.1-0.6: 0.4-0.04;

wherein when the fertilizer source is a magnesium source, the fly ash acid method aluminum extraction residue is SiO₂The weight ratio of the aluminum residue extracted by the acid method of the fly ash, the NaOH solution and the magnesium source is 1: 1.5-1.8: 0.5-0.7;

wherein the heating reaction temperature is 90-160 ℃, the heating reaction pressure is normal pressure, and the heating reaction time is 1-5 h.

2. The method according to claim 1, further comprising washing the filter cake with water, combining the alkali-containing washing water obtained by washing with water and the filtrate obtained by solid-liquid separation, concentrating the combined water, and adding the concentrated solution back to the NaOH solution obtained in step (1).

3. The method of claim 1, wherein after the water washing, the sodium oxide content of the filter cake is 8 wt% or less.

4. The process according to claim 1, wherein the viscosity of the reaction product in step (2) at 25 ℃ is 1-4 mPa-s.

5. A silicon-containing compound fertilizer prepared by the method of any one of claims 1 to 4, wherein soluble Na in the silicon-containing compound fertilizer₂The O content is 6 wt% or less; the silicon-containing compound fertilizer is a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer.

6. A utilization method of fly ash comprises the following steps: carrying out acid method aluminum extraction on fly ash to obtain aluminum oxide and fly ash acid method aluminum extraction residues, and preparing the fly ash acid method aluminum extraction residues by the method of any one of claims 1-4 to obtain a silicon-calcium compound fertilizer, a silicon-magnesium compound fertilizer or a silicon-calcium-magnesium compound fertilizer.