AU2021100066A4

AU2021100066A4 - Method of increasing the thickness of the outer enamel layer of ceramsite with sludge slurry

Info

Publication number: AU2021100066A4
Application number: AU2021100066A
Authority: AU
Inventors: Feiyuan Fang; Rundong LI; Yanlong Li; Weiyun WANG; Tianhua Yang
Original assignee: Shenyang Aerospace University
Current assignee: Shenyang Aerospace University
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2021-04-22
Anticipated expiration: 2029-01-07

Abstract

The present disclosure belongs to the field of paint and pertains to a method of increasing the thickness of the outer enamel layer of ceramsite with sludge slurry. The method includes the following steps: Three materials of sludge, fly ash and coal gangue are respectively ground mechanically for 1-2 hours, and sieved over a 100-mesh screen; They are mixed uniformly following certain weight parts for 20-30 minutes, and dried in a blast air oven at 90-105°C until the mass is constant; A tablet press is used for pressure shaping at a shaping pressure greater than 3 MPa to get cylindrical complex green bodies of raw materials; The sieved sludge materials are mixed with water at a certain proportion to produce sludge slurry; The green bodies are wetted in the sludge slurry transiently and bound with the sludge slurry evenly, ready for sintering; They are sintered at 1000°C-1250°C with an air velocity of 50-100 ml/min; and upon the completion of sintering, they are cooled to room temperature to get the shaped ceramsite. Ceramsite binding with sludge can effectively increase the thickness of the outer enamel layer of ceramsite products, and the outer enamel layer of sintered ceramsite products is smooth and flat.

Description

METHOD OF INCREASING THE THICKNESS OF THE OUTER ENAMEL LAYER OF CERAMSITE WITH SLUDGE SLURRY TECHNICAL FIELD

The present disclosure belongs to the field of paint, and pertains to a method of increasing

the thickness of the outer enamel layer of ceramsite with sludge slurry.

BACKGROUD

Nowadays, China's urban sewage treatment capacity has been increasing year by year. As a

byproduct of sewage treatment, the production of sewage sludge also increases gradually, with

D the main hazards of large amount, large volume, high moisture content, high heavy metals

content and odor. Sludge contains various heavy metals and other bio-toxic substances which

may cause secondary pollution. If not treatment effectively, the heavy metals in sludge tend to

return to the ecological environment and accumulate in organisms, finally increasing the risk of

cancers to human. The existing sludge treatment methods mainly include landfill, compost,

natural drying, incineration and so on. Currently, the most effective harmless treatment method is

"drying and incineration". On the other hand, a large amount of concrete is used in the

construction of cities, and there are a lot of natural sand and stone as aggregate in concrete.

Concrete has consumed huge amounts of natural resources for a long time. The annual concrete

consumption in China is about 1 billion m3 . At present, there are many artificial ceramsite

. materials widely used in China, such as clay ceramsite, fly ash ceramsite, etc. These ceramsite

have different engineering characteristics and uses. Ceramsite has low density, high strength,

good fire resistance and low weight, thus having an economic benefit of replacing traditional

natural building materials for further development. The utilization of sludge together with other

industrial wastes for the preparation of ceramsite not only solves the pollution of sludge, but also

allows the recycling of industrial wastes to produce economical value, being a very effective and

promising method for collaborative resourcing of wastes.

It is an object of the present invention to address the foregoing problems or at least to

provide the public with a useful choice.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed

with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing

description which is given by way of example only. DISCLOSURE OF INVENTION The present disclosure aims to utilize the three wastes of sludge, fly ash and coal gangue in

a collaborative resourcing way and to provide an artificial lightweight aggregate building

J material with excellent performances.

The present disclosure provides a sludge mixed ceramsite, wherein the ceramsite includes

sludge, fly ash and coal gangue in the following parts by weight: 60-80 parts of sludge, 10-20

parts of fly ash, and 10-20 parts of coal gangue.

Further, the chemical compositions of the three raw materials are respectively:

Sludge ash after incineration: A1 2 0 3 27.3%, SiO 2 34.6%, P 2 05 15.9%, Fe203 6.4%, CaO

6.2%, and others 7.8%;

Fly ash: A1 2 0 3 18.3%, SiO 2 43.4%, CaO 24.3%, and others 10.1%;

Coal gangue: A1 2 0 3 38.3%, SiO 2 59.5%, Fe203 0.6%, CaO 0.2%, and others 1.4%.

According to another aspect of the present disclosure, it provides a method of increasing

o the thickness of the outer enamel layer of ceramsite with sludge slurry, the specific steps of

which are as below:

(1) Drying: Mechanically dehydrated sludge, coal gangue and fly ash are dried in a blast

air oven with the temperature maintaining at 100-105°C for a period of 48-72 hours respectively,

until the mass is constant;

(2) Crushing: the three materials in step (1) are respectively ground mechanically for 1-2

hours, and sieved over a 100-mesh screen;

(3) Mixing: the sieved fine materials from step (2) are mixed uniformly following the

above weight parts with stirring for 1-2 hours, are dried in a blast air oven with the temperature

maintaining at 100-105°C for a period of 12-24 hours, until the mass is constant;

o (4) Shaping: the dried fine materials from step (3) are pressed into shape in a tablet press at a shaping pressure greater than 3 MPa, to get complexes of raw materials;

(5) Slurry preparation: the sieved sludge powder is mixed with water at a solid-to-liquid

ratio in a range of 1:1-1:3, to produce sludge slurry;

(6) Slurry wrapping: the complex green bodies of raw materials obtained from step (4) are

bound with the sludge slurry produced in step (5) evenly, so that the surfaces of the complex

green bodies are wetted with the sludge slurry fully and then ready for sintering;

(7) Sintering: the complexes of raw materials from step (6) are sintered, during which air is

charged at a velocity of 50-100 ml/min and the temperature and the heating rate are changed so

that the complexes of raw materials expand at high temperature; and upon the completion of

J sintering, they are cooled to room temperature to get the shaped ceramsite.

Further, the sintering temperature is 1000-1200°C, and air atmosphere is charged into the

furnace. After sintering, expansive porous structures are obtained. The outer surface of the

product has a tight and smooth structure and is dark brown, and there are many air holes inside

the product.

According to a first aspect there is provided a method of increasing the thickness of the

outer enamel layer of ceramsite with sludge slurry, wherein, the ceramsite includes sludge, fly

ash and coal gangue in the following parts by weight: 60-80 parts of sludge, 10-20 parts of fly

ash, and 10-20 parts of coal gangue.

Preferably, the chemical compositions of the three raw materials are respectively:

o - Sludge after incineration lost: A1 2 0 3 27.3%, Si02 34.6%, P 2 05 15.9%, Fe203 6.4%, CaO 6.2%, and others 7.8%;

- Fly ash: A1 2 0 3 18.3%, Si02 43.4%, CaO 24.3%, and others 10.1%;

- Coal gangue: A12 0 3 38.3%, Si02 59.5%, Fe203 0.6%, CaO 0.2%, and others 1.4%.

Preferably, the method includes the following steps:

until the mass is constant;

hours, and sieved over a 100-mesh screen;

o (3) Mixing: the sieved fine materials from step (2) are mixed uniformly following the above weight parts with stirring for 1-2 hours, are dried in a blast air oven with the temperature maintaining at 100-105°C for a period of 12-24 hours, until the mass is constant;

(4) Shaping: the dried fine materials from step (3) are pressed into shape in a tablet press at

a shaping pressure greater than 3 MPa, to get complexes of raw materials;

ratio in a range of 1:1-1:3, to produce sludge slurry;

9 (7) Sintering: the complexes of raw materials from step (6) are sintered, during which air is

sintering, they are cooled to room temperature to get the shaped ceramsite.

Preferably, the sintering temperature in step (7) is 1000-1200°C, air atmosphere is charged

into the furnace for sintering to get expansive porous structures, the outer surface of the product

has a tight and smooth structure and is dark brown, and there are many air holes inside the

product.

The present disclosure has the following beneficial effects:

The outer enamel layer of ceramsite obtained through the solution of the present disclosure

o is smooth, flat and thick. Through the method of the present disclosure, the sintering temperature

of enamel layer on the ceramsite surface is decreased, meanwhile the thickness of enamel layer

is increased, and the resulting shaped ceramsite will have higher compressive strength, lower

water absorptivity, lower specific surface area and good environmental characteristics. Specific

component proportion, heating rate, sintering temperature, as well as the utilization of sludge as

the foaming agent and the expanding agent, all help to promote the expansion of raw materials at

high temperature and improve the quality of products. The present disclosure utilizes one

municipal waste and two industrial wastes to collaboratively prepare artificial ceramsite. The

resulting ceramsite has good performances, which is superior to simple sludge fly ash ceramsite

and has a broad application prospect. The method of the present disclosure turns sludge and other

o wastes into wealth and recycles resources, which is an environmentally friendly and economically meaningful method.

BEST MODES FOR CARRYING OUT THE INVENTION

In order to make the objective, the technical solution and advantages of the present

disclosure more clearly, the present disclosure will be further illustrated in more detail

accompanying with the following embodiments. It should be understood that specific

embodiments described herein are only used to interpret the present disclosure, but not intend to

limit it.

Embodiment 1

A method of increasing the thickness of the outer enamel layer of ceramsite with sludge

J slurry, the specific steps of which were as below:

(1) Drying: Dehydrated sludge, coal gangue and fly ash were dried in a blast air oven with

the temperature maintaining at 105°C for a period of 48 hours respectively, until the mass of

materials was constant;

(2) Crushing: the three materials in step (1) were respectively ground mechanically for 2

hours and sieved over a 100-mesh screen, getting fine materials with particle sizes < 0.154 mm;

(3) Mixing: the sieved fine materials from step (2) were mixed with stirring for 1-2 hours

following the weight parts as below: 70 parts of sludge, 15 parts of fly ash and 15 parts of coal

gangue. The content of each chemical component in the mixed material was: A1 2 0 3 27.6%, Si0 2

39.66%, Fe203 4.57%, P2 0 5 11.13%, CaO 8%, and others 9.04%;

o (4) Shaping: the dried fine materials from step (3) were pressed into shape in a type HY-12

infrared tablet press at a shaping pressure of 6 MPa, to get cylindrical complexes of raw

materials with diameters of 10 mm and heights of 5 mm;

(5) Slurry preparation: the sieved sludge powder was mixed with water at a mass ratio of

1:2, to produce sludge slurry;

(6) Slurry wrapping: the complex green bodies of raw materials obtained from step (4)

were bound with the sludge slurry produced in step (5) evenly, so that the surfaces of the

complex green bodies were wetted with the sludge slurry fully and then ready for sintering;

(7) Sintering: the complexes of raw materials from step (6) were sintered, for which the

complexes of raw materials were preheated and sintered in a single zone atmosphere tube

o furnace that was connected to an air flow meter through an air compressor, and the air atmosphere was charged into the furnace at a velocity of 100 ml/min. During preheating period, the complexes of raw materials were heated to 500°C at a heating rate of 5°C/min, and then sintered by heating, during which they were heated to 800°C at a heating rate of10°C/min, then heated to 1000°C at a heating rate of 5°C/min, then heated to 1235°C at a heating rate of

3°C/min, and kept for 35 min. Upon the completion of sintering, they were cooled to 100°C at a

rate of 10°C/min, taken out with a high temperature clamp and cooled naturally to room

temperature to get the ceramsite 1.

It was determined that the ceramsite 1 has a compressive strength of 5.37 MPa, a water

absorptivity of 0.8%, and a specific surface area of 1.92 g/cm 3. They all met the national

J standard GB/T17431.1-2010 of density grade of 876 kg/m3 and were superior to the standard of

"Grade One Product". The ceramsite 1 was ground, and extracted by mixing with an extractant

(glacial acetic acid solution), and shaken by a flip oscillator for a period of 48 hours with the

temperature maintaining at 26-28°C. The extracted supernatant was tested for the concentration

of heavy metals. The leaching concentration of each heavy metal in the ceramsite 1 was

determined: Cr 0.050 mg/L, Ni 0.161 mg/L, Cu 6.928 mg/L, Zn 1.739 mg/L, all meeting the

national standards.

Embodiment 2

slurry, the specific steps of which were as below:

o (1) Drying: Dehydrated sludge, coal gangue and fly ash were dried in a blast air oven with

the temperature maintaining at 100-105°C for a period of 48 hours respectively, until the mass of

materials was constant;

(2) Crushing: the three materials in step (1) were respectively ground mechanically for 1-2

(3) Mixing: the sieved fine materials from step (2) were mixed with stirring for 1 hour

following the weight parts as below: 80 parts of sludge, 10 parts of fly ash and 10 parts of coal

gangue. The content of each chemical component in the mixed material was: A1 2 0 3 27.5%, SiO 2

37.97%, Fe203 5.18%, P2 0 5 12.72%, CaO 7.41%, and others 10.33%;

(4) Shaping: the dried fine materials from step (3) were pressed into shape in a type HY-12

o infrared tablet press at a shaping pressure of 6 MPa, to get cylindrical complexes of raw materials with diameters of 10 mm and heights of 5 mm;

1:1.5, to produce sludge slurry;

(7) Sintering: the complexes of raw materials were preheated and sintered in a single zone

atmosphere tube furnace that was connected to an air flow meter through an air compressor, and

the air atmosphere was charged into the furnace at a velocity of 100 ml/min. During preheating

J period, the complexes of raw materials were heated to 500°C at a heating rate of 5°C/min, and

then sintered by heating, during which they were heated to 800°C at a heating rate of10°C/min,

then heated to 1000°C at a heating rate of 5°C/min, then heated to 1235°C at a heating rate of

temperature to get the ceramsite 2.

It was determined that the ceramsite 2 has a compressive strength of 6.22 MPa, a water

absorptivity of 0.71%, and a specific surface area of 1.83 g/cm3 . They all met the national

standard GB/T17431.1-2010 of density grade of 876 kg/m3 and were superior to the standard of

"Grade One Product". The ceramsite 2 was ground, and extracted by mixing with an extractant

of heavy metals. The leaching concentration of each heavy metal in the ceramsite 2 was

determined: Cr 0.039 mg/L, Ni 0.168 mg/L, Cu 0.027 mg/L, Zn 0.110 mg/L, all meeting the

national standards.

It can be seen from the above embodiments that various performances of the sintered products were superior to those of simple sludge, fly ash or coal gangue ceramsite, and the

ceramsite sintered after binding and wrapping processes may produce more outer enamel layer

compared to ordinary ceramsite; moreover, the enamel layer of the ceramsite was more smooth,

flat, full and thick, which may provide higher compressive strength and lower water absorptivity.

o Wherein, the compressive strength was enhanced by 37.03-88.71% relatively; the water absorptivity was reduced by 11.57-19.38% relatively; and the leaching concentration of each heavy metal also decreased, meanwhile the average temperature of sintering and shaping was reduced by 100-200°C, which greatly reduced the production cost. The reasons lie in that fly ash and coal gangue contain a high proportion of SiO 2 , and coal gangue contains a high content of

A120 3 , molten matrix is easily formed on the surface of complex green bodies at high

temperature, which increases the viscosity of the surface and it is more prone to form full and

porous ceramsite structures. On the other hand, a high content of aluminosilicate mineral can

effectively inhibit the migration and leaching of heavy metals and reduce the damages to the

environment.

J The above disclosed preferred embodiments of the present disclosure are only used to

assist in elaborating the present disclosure. The preferred embodiments do not describe all the

details in detail, and not limit the present disclosure to the specific implementation ways

described herein. Obviously, many modifications and variations can be made according to the

context of the description. These embodiments are chosen and described concretely in the

description of the present disclosure to better illustrate the principle and actual application of the

present disclosure, so that those of skills in the art can understand and utilize the present

disclosure better. The present disclosure is only limited by the claims as well as the full scope

and equivalents thereof.

EDITORIAL NOTE

2021100066

THERE ARE TWO PAGES OF CLAIMS ONLY

Claims

Claims WHAT IS CLAIMED IS:

1. A method of increasing the thickness of the outer enamel layer of ceramsite with sludge

slurry, wherein, the ceramsite includes three raw materials, the three raw materials

including sludge, fly ash and coal gangue in the following parts by weight: 60-80 parts of

sludge, 10-20 parts of fly ash, and 10-20 parts of coal gangue.

2. The method as claimed in claim 1, wherein, the chemical compositions of the three raw

materials are respectively:

- Sludge ash after incineration: A1 2 0 3 27.3%, SiO 2 34.6%, P 2 05 15.9%, Fe203 6.4%,

CaO 6.2%, and others 7.8%;

- fly ash: A1 2 0 3 18.3%, SiO 2 43.4%, CaO 24.3%, and others 10.1%;

- coal gangue: A1 2 0 3 38.3%, SiO 2 59.5%, Fe203 0.6%, CaO 0.2%, and others 1.4%.

3. The method as claimed in claim 1 or claim 2, including the following steps:

air oven with the temperature maintaining at 100-105°C for a period of 48-72 hours

respectively, until the mass is constant;

hours, and sieved over a 100-mesh screen;

above weight parts with stirring for 1-2 hours, are dried in a blast air oven with the

temperature maintaining at 100-105°C for a period of 12-24 hours, until the mass is

constant;

a shaping pressure greater than 3 MPa, to get complexes of raw materials;

ratio in a range of 1:1-1:3, to produce sludge slurry;

bound with the sludge slurry produced in step (5) evenly, so that the surfaces of the

complex green bodies are wetted with the sludge slurry fully and then ready for

sintering;

charged at a velocity of 50-100 ml/min and the temperature and the heating rate are

changed so that the complexes of raw materials expand at high temperature; and upon

the completion of sintering, they are cooled to room temperature to get the shaped

ceramsite.

4. The method as claimed in claim 3, wherein, the sintering temperature in step (7) is

1000-1200°C, air atmosphere is charged into the furnace for sintering to get expansive

porous structures, the outer surface of the product has a tight and smooth structure and is

dark brown, and there are many air holes inside the product.