CN116410015B - A method for firing ceramsite from high-salinity and high-organic-matter marine sludge - Google Patents

Abstract

The invention discloses a method for firing ceramsite by using sea-related sludge with high salt content and high organic matter, and belongs to the technical field of ceramics. The method comprises the following steps: adjusting the pH value of sea-related sludge to be acidic, adding hydrogen peroxide and Fe ²⁺, adjusting the pH value to 6-8 by alkali after the reaction is completed, dehydrating, adding fly ash and slag, uniformly mixing, grinding, granulating, drying to obtain a ceramic green body, and pre-sintering and sintering the ceramic green body to obtain ceramic. The ceramsite prepared by the method has high strength and low water absorption, and can meet the requirements of being used as a building engineering material.

Description

A method for firing ceramsite from high-salinity and high-organic-matter marine sludge

Technical Field

The invention relates to the technical field of ceramics, and in particular to a method for firing ceramsite from high-salt and high-organic-matter marine sludge.

Background technique

As a unique product of coastal development, oil extraction and other offshore operations, marine silt not only poses the risk of blocking waterways and endangering navigation safety, but the accumulation of marine silt will cause eutrophication of seawater, endangering coastal aquaculture bases. In severe cases, it will cause siltation or even abandonment of marine aquaculture farms, greatly affecting the economic development of coastal areas.

Every year, relevant departments in coastal areas spend a lot of manpower and material resources on dredging and clearing silt from ports and waterways. However, the cleared marine silt has high salt and organic matter content, which leads to many limitations in its application. How to utilize high-salt and high-organic marine silt as a resource is a technical problem that needs to be urgently solved in this field.

Summary of the invention

The purpose of the present invention is to provide a method for firing ceramsite from high-salinity and high-organic marine sludge. First, organic matter in the high-salinity and high-organic marine sludge is removed by Fenton oxidation, and then the salt in the high-salinity and high-organic marine sludge is removed by dehydration, and finally high-strength ceramsite is made by combining with other materials.

To achieve the above object, the present invention provides the following technical solutions:

One of the technical solutions of the present invention is to provide a method for firing ceramsite from high-salinity and high-organic-matter marine sludge, comprising the following steps:

The pH value of the marine sludge is adjusted to acidic, hydrogen peroxide and Fe ²⁺ are added, and after the reaction is completed, the pH value is adjusted to 6-8 with alkali, dehydrated, fly ash and slag are added, mixed evenly and ground, and then granulated and dried to obtain ceramsite green body, which is first pre-sintered and then sintered to obtain ceramsite.

The sea-related silt selected in the present invention can be used as a binder when preparing ceramsite, which can improve the viscosity and plasticity of the ceramsite, making it easy to shape and avoiding breakage caused by particle movement during the sintering process.

Preferably, the pH value of the marine sludge is adjusted to be acidic by using hydrochloric acid to adjust the pH value of the marine sludge to 3-5.

Fenton's reagent generally degrades organic matter under acidic conditions. Under neutral or alkaline conditions, it is difficult for Fe2 ⁺ to catalyze the oxidation _{of H2O2 to} produce hydroxyl radicals. Alkaline conditions will cause Fe2 ⁺ to form a precipitate and lose its catalytic ability. If the H ⁺ concentration is too high, it will be difficult for Fe3 ⁺ to be reduced to Fe2 ⁺ , hindering the catalytic reaction. When the pH value is 3-5, the entire reaction system can proceed rapidly and the degradation rate of organic matter is fast.

Preferably, the mass ratio of the hydrogen peroxide to the marine silt is (1-1.5):10; the molar ratio of the Fe ²⁺ to the hydrogen peroxide is 1:(4-8).

Preferably, the reaction time is 10 to 15 minutes.

Preferably, the dehydration is to remove 50-60% of the water in the marine sludge whose pH value is adjusted to 6-8.

Since the salt in the high-salt, high-organic-matter marine silt is mainly soluble salt, the salt in the marine silt can be removed simultaneously during the water removal process, thus avoiding the defects of increased sintering temperature and increased energy consumption caused by excessively high salt content in the marine silt when preparing expanded clay.

Preferably, the mass ratio of the fly ash, the slag and the marine sludge is (22-35):(13-33):(45-52).

Preferably, the drying temperature is 100-150° C. and the drying time is 4-6 hours.

Preferably, the pre-sintering temperature is 480-550° C. and the time is 10-15 minutes.

The present invention adds a pre-sintering step. Firstly, the ferrous hydroxide formed previously can be decomposed into ferric oxide. The generated ferric oxide can be used as a solvent to reduce the sintering temperature. Meanwhile, the ferric oxide can make the ceramsite produce more liquid phases and more complex crystal phases at about 1000 DEG C, so that the sintered surface structure is more compact and the strength of the ceramsite is effectively improved. Secondly, the ceramsite green body can be pre-expanded through the medium-temperature pre-sintering step to prevent the ceramsite green body from expanding too fast due to direct high temperature, generating cracks and affecting the strength of the ceramsite.

Preferably, the sintering temperature is 950-1050° C. and the sintering time is 15-20 min.

Compared with the existing scheme of using sea sludge to burn ceramsite in the art, the sintering temperature of the present invention is greatly reduced (the existing technology is generally around 1200°C), effectively reducing the energy consumption of resource utilization of sea sludge.

The second technical solution of the present invention is to provide ceramsite prepared by the method for firing ceramsite from the above-mentioned high-salt content, high-organic matter marine sludge.

The ceramsite fired by the invention has high strength and can meet the requirements of construction engineering.

The beneficial technical effects of the present invention are as follows:

The invention provides a technical solution for firing ceramsite by taking high-salinity and high-organic-matter marine sludge as raw material.

Firstly, organic matter in high-salinity and high-organic-matter marine sludge is removed by Fenton oxidation. During oxidation, the pH value of the marine sludge is adjusted to acidic to increase the removal rate and speed of organic matter.

Then, the pH value is adjusted to 6-8 using alkali. This step can convert Fe2 ⁺ in the Fenton reagent into ferrous hydroxide precipitate. The formed precipitate can be converted into solvent iron oxide through a subsequent pre-sintering process.

The salt in the high-salinity and high-organic-matter marine sludge is further removed by dehydration. Since the salt in the marine sludge is soluble salt, the salt is taken away in the process of removing water.

The dehydrated marine sludge is compounded with fly ash (the residual carbon in the fly ash can be used as fuel to provide heat energy, saving the energy consumed by sintering) and slag, and then ground and granulated to obtain ceramsite green body;

The obtained ceramsite green body is then made into high-strength ceramsite through a series of drying and sintering processes.

The method for resource utilization of high-salinity and high-organic-matter marine sludge provided by the present invention can effectively solve the disposal problem of marine sludge. At the same time, the ceramsite prepared with it as raw material has high strength and low energy consumption in the preparation process, and has great promotion value.

Detailed ways

Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the invention.

The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

The marine sludge used in the embodiments of the present invention is sourced from the Bohai Sea (with a water content of 85%). The contents of the components in the dry matter of the marine sludge (the dry matter is the remaining material after drying at 105° C. to a constant weight) are shown in Table 1.

Table 1 Content of each component in the dry matter of marine silt

The contents of the various components in the fly ash used in the examples of the present invention are shown in Table 2.

Table 2 Content of each component in fly ash

The slag used in the embodiments of the present invention is blast furnace slag (particle size ≤ 25 mm), and the content of each component is shown in Table 3.

Table 3 Content of each component in blast furnace slag

Example 1

In this embodiment, the mass proportions of fly ash, blast furnace slag and marine sludge are 30 parts, 20 parts and 50 parts respectively.

The steps for preparing ceramsite are as follows:

(1) Add the marine sludge into a stirrer, adjust the pH value of the marine sludge to 3.5 with a 2 mol/L hydrochloric acid solution, add 18 parts of 30% hydrogen peroxide by mass, and then add ferrous sulfate heptahydrate corresponding to 1/4 molar amount of H ₂ O ₂ , stir evenly, and react for 10 minutes;

(2) After the reaction is completed, the pH value of the reaction system is adjusted to 6.5 using a 2 mol/L NaOH solution, and the reaction system is transferred to a diaphragm plate and frame filter press for filtration until the water content of the marine sludge is 60%;

(3) Add fly ash and blast furnace slag, mix well and then crush with double rollers (the distance between the two rollers is adjusted to 4 mm);

(4) adding the crushed slurry into a granulator for granulation (the particle size is 10 to 20 mm), and baking at 105° C. for 6 h after granulation to obtain ceramsite green body;

(5) The ceramsite green body is placed in a rotary kiln, pre-sintered at 500°C for 15 minutes, then heated to 1000°C and sintered for 15 minutes to obtain ceramsite.

Example 2

In this embodiment, the mass proportions of fly ash, blast furnace slag and marine sludge are 25 parts, 30 parts and 45 parts respectively.

The steps for preparing ceramsite are as follows:

(1) Add the marine sludge into a stirrer, adjust the pH value of the marine sludge to 5 with a 2 mol/L hydrochloric acid solution, add 17 parts of 30% hydrogen peroxide, and then add ferrous sulfate heptahydrate corresponding to 1/4 molar amount of H ₂ O ₂ , stir evenly, and react for 13 minutes;

(2) After the reaction is completed, the pH value of the reaction system is adjusted to 6.5 using a 2 mol/L NaOH solution, and the reaction system is transferred to a diaphragm plate and frame filter press for filtration until the water content of the marine sludge is 60%;

(3) Add fly ash and blast furnace slag, mix well and then crush with double rollers (the distance between the two rollers is adjusted to 4 mm);

(4) adding the crushed slurry into a granulator for granulation (the particle size is 10 to 20 mm), and baking at 130° C. for 5 h after granulation to obtain ceramsite green body;

(5) The ceramsite green body is placed in a rotary kiln, pre-sintered at 520°C for 13 min, then heated to 1000°C and sintered for 15 min to obtain ceramsite.

Example 3

In this embodiment, the mass proportions of fly ash, blast furnace slag and marine sludge are 35 parts, 13 parts and 52 parts respectively.

The steps for preparing ceramsite are as follows:

(1) Add the marine sludge into a stirrer, adjust the pH value of the marine sludge to 4 with a 2 mol/L hydrochloric acid solution, add 22 parts of 30% hydrogen peroxide, and then add ferrous sulfate heptahydrate corresponding to 1/6 molar amount of H ₂ O ₂ , stir evenly, and react for 10 minutes;

(2) After the reaction is completed, the pH value of the reaction system is adjusted to 7 using a 2 mol/L NaOH solution, and the reaction system is transferred to a diaphragm plate-and-frame filter press for filtration until the water content of the marine sludge is 50%;

(3) Add fly ash and blast furnace slag, mix well and then crush with double rollers (the distance between the two rollers is adjusted to 4 mm);

(4) adding the crushed slurry into a granulator for granulation (the particle size is 10 to 20 mm), and baking at 150° C. for 4 h after granulation to obtain ceramsite green body;

(5) The ceramsite green body is placed in a rotary kiln, pre-sintered at 480°C for 15 min, then heated to 950°C and sintered for 20 min to obtain ceramsite.

Example 4

In this embodiment, the mass proportions of fly ash, blast furnace slag and marine sludge are 22 parts, 33 parts and 45 parts respectively.

The steps for preparing ceramsite are as follows:

(1) Add the marine sludge into a stirrer, adjust the pH value of the marine sludge to 3 with a 2 mol/L hydrochloric acid solution, add 14 parts of 30% hydrogen peroxide by mass, and then add ferrous sulfate heptahydrate corresponding to 1/8 mole of H ₂ O ₂ , stir evenly, and react for 15 minutes;

(2) After the reaction is completed, the pH value of the reaction system is adjusted to 8 using a 2 mol/L NaOH solution, and the reaction system is transferred to a diaphragm plate-and-frame filter press for filtration until the water content of the marine sludge is 50%;

(3) Add fly ash and blast furnace slag, mix well and then crush with double rollers (the distance between the two rollers is adjusted to 4 mm);

(4) adding the crushed slurry into a granulator for granulation (the particle size is 10 to 20 mm), and baking at 105° C. for 6 h after granulation to obtain ceramsite green body;

(5) The ceramsite green body is placed in a rotary kiln, pre-sintered at 550°C for 10 min, then heated to 1050°C and sintered for 15 min to obtain ceramsite.

Comparative Example 1

Compared with Example 1, the difference is that the pre-sintering step is omitted, the sintering time is extended by 10 minutes, and the other operations are the same as Example 1.

Comparative Example 2

In this comparative example, the mass proportions of fly ash, blast furnace slag and marine sludge are 30 parts, 20 parts and 50 parts respectively (the same as in Example 1).

The steps for preparing ceramsite are as follows:

(1) Add the marine sludge into a stirrer, adjust the pH value of the marine sludge to 3.5 with a 2 mol/L hydrochloric acid solution, add 18 parts of 30% hydrogen peroxide by mass, and then add ferrous sulfate heptahydrate corresponding to 1/4 molar amount of H ₂ O ₂ , stir evenly, and react for 10 minutes;

(2) After the reaction is completed, the sludge is transferred to a membrane plate-frame filter press for filtration until the water content of the marine sludge is 60% (the difference from Example 1 is that the step of adjusting the pH value with alkali is omitted);

(3) Add fly ash and blast furnace slag, mix well and then crush with double rollers (the distance between the two rollers is adjusted to 4 mm);

(4) adding the crushed slurry into a granulator for granulation (the particle size is 10 to 20 mm), and baking at 105° C. for 6 h after granulation to obtain ceramsite green body;

(5) The ceramsite green body is placed in a rotary kiln, pre-sintered at 500°C for 15 minutes, then heated to 1000°C and sintered for 15 minutes to obtain ceramsite.

Comparative Example 3

In this comparative example, the mass proportions of fly ash, blast furnace slag and marine sludge are 30 parts, 20 parts and 50 parts respectively (the same as in Example 1).

The steps for preparing ceramsite are as follows:

(1) placing the marine sludge in a diaphragm plate-and-frame filter press for filtration until the water content of the marine sludge is 60% (the difference from Example 1 is that the steps of Fenton oxidation and adding alkali to adjust the pH value are omitted);

(2) Add fly ash and blast furnace slag, mix well and then crush with double rollers (the distance between the two rollers is adjusted to 4 mm);

(3) adding the crushed slurry into a granulator for granulation (the particle size is 10 to 20 mm), and baking at 105° C. for 6 h after granulation to obtain ceramsite green body;

(4) The ceramsite green body is placed in a rotary kiln, pre-sintered at 500°C for 15 minutes, then heated to 1000°C and sintered for 15 minutes to obtain ceramsite.

The technical indicators of the ceramsite prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were measured respectively, and the measurement results are shown in Table 4.

According to GB/T 2842-1981 "Test methods for lightweight aggregates", the cylinder compressive strength of each group of samples was tested;

The loose bulk density is obtained by dividing the total mass of the uncompacted granular material in a natural bulk state by the total volume of the bulk material;

The water absorption rate was determined by soaking each group of ceramsite in water for 1 hour, taking it out and drying the surface water with a towel, weighing it (m ₁ ), and then drying it at 105°C to constant weight (m ₂ ). Water absorption rate (%) = (m ₁ -m ₂ )/m ₂ × 100%.

Table 4 Technical indicators of ceramsite obtained in each embodiment and comparative example

As can be seen from Table 4, the ceramsite prepared in Examples 1 to 4 of the present invention has high strength and low water absorption; in the case of omitting pre-sintering (Comparative Example 1), the cylinder compressive strength of the ceramsite is reduced, and the water absorption rate and loose bulk density are improved. The reason may be that in the case of omitting pre-sintering, the expansion rate of the sintering process is too fast, resulting in an increase in volume and a small amount of cracks, which affects the cylinder compressive strength of the ceramsite; in the case of omitting alkali to adjust the pH value (Comparative Example 2), the cylinder compressive strength of the ceramsite is reduced, and the loose bulk density and water absorption rate are slightly improved. The reason may be that when the pH value is not adjusted to near neutral, the iron salt is also reduced accordingly during the dehydration process, and the iron oxide content is reduced during the later sintering process, which affects the density of the ceramsite and causes the cylinder compressive strength to decrease; in the case of omitting Fenton oxidation (Comparative Example 3), the cylinder compressive strength of the ceramsite is significantly reduced, and the water absorption rate and loose bulk density are significantly improved. The reason may be that in the case of not removing organic matter, the organic matter of the ceramsite is decomposed in large quantities during the firing process, resulting in excessive thermal expansion of the ceramsite, which directly affects the cylinder compressive strength and water absorption rate of the ceramsite.

The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims (2)

1. A method for sintering ceramsite from high-salinity, high-organic-matter marine sludge, characterized in that it comprises the following steps: The pH value of the marine sludge is adjusted to acidic, hydrogen peroxide and Fe ²⁺ are added, and after the reaction is completed, the pH value is adjusted to 6-8 with alkali, dehydrated, fly ash and slag are added, mixed evenly, ground, granulated, and dried to obtain ceramsite green body, and the ceramsite green body is pre-sintered and then sintered to obtain ceramsite; The pH value of the marine sludge is adjusted to be acidic by using hydrochloric acid to adjust the pH value of the marine sludge to 3 to 5; The mass ratio of the hydrogen peroxide to the marine sludge is (1-1.5):10; the molar ratio of Fe2 ⁺ to the hydrogen peroxide is 1:(4-8); The reaction time is 10 to 15 minutes; The dehydration is to remove 50-60% of the water in the marine sludge with a pH value adjusted to 6-8; The mass ratio of the fly ash, the slag and the marine sludge is (22-35):(13-33):(45-52); The drying temperature is 100-150°C and the drying time is 4-6 hours; The pre-sintering temperature is 480-550°C and the time is 10-15 minutes; The sintering temperature is 950-1050° C. and the sintering time is 15-20 minutes. 2. A ceramsite prepared according to the method for sintering ceramsite from high-salinity, high-organic-matter marine sludge as described in claim 1.