CN101503643B

CN101503643B - Solid fuel for sludge anhydration

Info

Publication number: CN101503643B
Application number: CN2009100472374A
Authority: CN
Inventors: 赵由才; 刘大江; 林敏�; 宋玉
Original assignee: SHANGHAI TONGJI HIGH-TECH DEVELOPMENT Co Ltd
Current assignee: SHANGHAI TONGJI ENVIRONMENT ENGINEERING TECHNOLOGY Co Ltd
Priority date: 2009-03-09
Filing date: 2009-03-09
Publication date: 2012-12-12
Anticipated expiration: 2029-03-09
Also published as: CN101503643A

Abstract

The invention discloses a dried sludge solid fuel, which relates to a formula of a solid fuel prepared by drying sludge. The dried sludge solid fuel is prepared by mixing and press forming or powdering the sludge and an additive, wherein according to the weight of the sludge, the additive comprises the following components by weight percentage: 5 to 10 percent of wooden meal, 0 to 20 percent of coal powder, 5 to 15 percent of screen residues of aged refuse, and 1 to 5 percent of dewatering agent; the sludge is dewatered sludge with an initial moisture content of 80 percent and a dry base heat value of 7,000 to 18,000 kJ/kg from a sewage plant; the dewatering agent comprises calcium oxide, magnesium oxide, magnesium chloride and aluminum chloride in a mass portion ratio of 1:5.5-10:1:2.5-3; and the screen residues of aged refuse are screen residues mainly comprising plastic, fibers and paper which are landfilled for 8 to 10 years, initially ground and passed through a screen with an aperture of 60 millimeters. By changing the conventional method for preparing a fuel by using sludge as an additive, the method can fully realize the stabilization and recycling of the sludge and fulfill the aim of treatment of wastes with processes of wastes against one another. The product of the method completely meets the requirement on stable burning for power generation and has better economic and social benefits.

Description

Sludge drying solid fuel

Technical Field

A sludge drying solid fuel relates to a formula of a solid fuel prepared by sludge drying. Belongs to the technical field of solid waste recycling.

Background

With the increasingly perfect sewage treatment facilities, how to rapidly realize the recycling and harmless treatment of sludge becomes the development direction of sludge treatment. At present, sludge treatment modes mainly comprise sludge solidification and landfill, sludge composting and sludge incineration, wherein the sludge incineration is increasingly valued by people as the most rapid sludge recycling and harmless treatment means.

The sludge is the residual microorganism residue in the sewage treatment process, contains a large amount of organic matters and certain fiber lignin, has a certain heat value, can be treated by adopting an incineration mode, but has a low heat value due to too high water content. When the lower calorific value is less than 6000kJ/kg, the fuel cannot be stably incinerated and used as energy. According to statistics, although the dry basis heat value range of the sludge is 7468 kJ/kg-17923 kJ/kg, the water content of the dewatered sludge of the actual sewage treatment plant is 75% -85%, the water is converted into steam in the sludge incineration process, and partial energy is taken away in the form of gasification latent heat. Therefore, sludge incineration often requires the addition of auxiliary fuels. The high incineration cost becomes a bottleneck limiting the development of the sludge incineration technology.

A sludge drying and incinerating treatment method (publication No. CN 1931753) comprises 5 steps of dewatering, granulating, mixing with dry sludge fine powder, drying, heating and incinerating. The heat released by the condensation of the steam generated in the sludge drying process is used for carrying out temperature-rising pretreatment on the sludge particles through the heat exchanger, so that the heat utilization efficiency is improved; after being heated and heated, odor and other harmful gases generated in the drying process are used as secondary air or tertiary air to be sent into the sludge incinerator for incineration treatment, so that the pollution to the environment and the harm to the health of a human body can be effectively avoided. The method achieves the purpose of sludge drying incineration by changing the structure of the sludge incinerator, but the furnace type modification cost is higher, the related drying method has more complicated steps, and the accurate temperature control of each step has certain difficulty in practical application and is not suitable for large-scale treatment of sludge.

A process for preparing sludge-type briquette includes such steps as proportionally mixing powdered coal, sludge, wooden chips or powder and desulfurizing and deodouring agent, stirring while wetting, and die pressing. The added sludge component replaces clay to be used as a briquette binder, and meanwhile, the heat productivity of the briquette can be improved, the coal consumption is saved, and the generation amount of ash after the briquette is burnt out is reduced. However, the method still uses coal as a main raw material, and the addition amount of the sludge is small (20-35%), so that the method is not ideal as a sludge recycling method.

A sludge fuel rod and its preparation method (publication No. CN 1810940A) are prepared from dewatered sludge, combustion improver, adhesive and desulfurizing agent through proportional mixing, granulating, baking and shaping. Wherein the combustion improver adopts fly ash, plant straws, grains or coal, the addition amount is 20-50%, the binder adopts glass cement, clay or cement, the addition amount is 3-5%, and the desulfurizer adopts CaO, furnace slag, coal cinder or fly ash, and the like, and the addition amount is 5-10%. The dry basis heat value of the dewatered sludge adopted by the method is 16270kJ/kg, the water content of the prepared fuel rod is 40.9 percent, and the low-level heat value reaches 11454 kJ/kg. The fuel rod produced by the method has high heat value, but needs to be added with a binder in the production process, needs to consume energy in the drying process, and has large addition amount of combustion improver components and high cost.

Disclosure of Invention

The invention aims to disclose a formula which has low cost, can quickly reduce the water content of sludge after being fully mixed, improves the heat value to reach the heat value of solid fuel prepared by drying the sludge, meets the requirements of thermal power generation, and can replace part of medium-low-grade coal powder.

In order to achieve the purpose, the invention changes the traditional thought of taking sludge as an additive, and takes the sludge as a main solid fuel, reduces the addition amount of a dehydrating agent and a heat value improving substance as much as possible, forms a solid fuel which is pressed, molded or powdered, has heat productivity meeting the requirements of thermal power generation, and can replace part of middle-low-grade coal powder. Researches show that the water content of the sludge can be reduced from about 80% to below 20% in 5-10 days by mixing different additives and the sludge in a proper proportion, and the low calorific value is increased from 0kJ/kg to 8000 kJ/kg.

The invention is composed of sludge and additives, the additives are composed of mineralized refuse oversize, sawdust, dehydrating agent and coal powder, the amount of each component of the additives is measured by the weight of the sludge, and the components are fully mixed and pressed to form or prepare powder.

Wherein,

the addition amount of the wood dust is 5 to 10 weight percent of the weight of the sludge

The addition amount of the coal dust is 0 to 20 weight percent of the weight of the sludge (the addition amount is determined according to the dry basis heat value of the sludge and the heat value required by the solid fuel)

The addition amount of the oversize material of the mineralized refuse is 5 to 15 weight percent of the weight of the sludge

The addition amount of the dehydrating agent is 1 to 5 weight percent of the weight of the sludge

The sludge is the dewatered sludge of the sewage plant which has the initial water content of about 80 percent and the dry basis heat value of 7000 kJ/kg-18000 kJ/kg and is generated by the sewage plant;

the dehydrating agent is calcium oxide, magnesium chloride and aluminum chloride; the mass ratio of calcium oxide to magnesium chloride to aluminum chloride is 1: 5.5-10: 1: 2.5-3.

The oversize material of the mineralized refuse is converted into an oversize material which has soil fragrance after being buried for 8-10 years, is primarily crushed and then is sieved by a 60mm aperture, and the main component of the oversize material is plastic, fiber and paper.

The invention has the following advantages:

1. the method takes the dewatered sludge from sewage plants with wide sources as the main raw material, the sludge is naturally dried for 5-10 days, the water content of the sludge is reduced from about 80% to below 20%, the low calorific value is increased from about 0kJ/kg to more than 8000kJ/kg, and substances such as mineralized refuse oversize products and the like are added, so that the comprehensive treatment targets of treating wastes with wastes and recycling resources are realized.

2. The invention takes calcium oxide, magnesium chloride, aluminum chloride and the like which do not contain any harmful components and have wide sources and low cost as dehydrating agents, can quickly reduce the moisture content of the sludge in a short time, has important effects on deodorization and moisture content reduction of the sludge, has high heat value of solid fuel, completely meets the requirement of stable incineration power generation, and can be used as a raw material for incineration power generation.

3. The invention effectively combines the treatment of mineralized refuse and sludge, realizes the aim of treating waste by waste, has lower cost and can replace part of medium-low-grade coal powder, and the calorific value meets the requirement of thermal power generation.

4. The drying in the manufacturing process of the solid fuel does not need energy consumption, the time is short, the production cost can be effectively reduced, and the engineering and industrialization are facilitated.

5. The ash after combustion can be used as backfill soil, a general roadbed filling material and the like, and the resource recycling is realized.

Detailed Description

Example 1

The invention is composed of sludge and additives, and the additive is prepared by fully mixing the components in weight of the sludge.

Wherein,

the amount of wood chips added is 5% by weight of the sludge

The addition amount of the coal dust is 20 weight percent of the weight of the sludge

The addition amount of the oversize material of the mineralized refuse is 10 weight percent of the weight of the sludge

The addition amount of the dehydrating agent is 5 weight percent of the weight of the sludge

The main components of the dehydrating agent are calcium oxide, magnesium chloride and aluminum chloride, and the mass ratio of the calcium oxide to the magnesium chloride to the aluminum chloride is 1: 10: 1: 3.

50kg of sludge with dry basis heat value of 7109kJ/kg is taken, additives (2.5 kg of wood chips, 10kg of coal powder, 5kg of mineralized refuse oversize products and 2.5kg of dehydrating agents) are added according to the proportion and are uniformly mixed, and then the mixture is pressed into a honeycomb shape under 50 MPa. Under the condition of average temperature of 12 ℃, after natural air drying for 5 days, the water content is reduced from 75.0 percent to 23.3 percent, and the low calorific value is increased from 0kJ/kg to 13469 kJ/kg; after natural air drying for 10 days, the water content is reduced to 11.6%, the low-grade heat value is increased to 15910kJ/kg, and the requirements of combustion power generation are completely met. The dry basis ash yield was 32.8%.

Example 2

The additive consists of sludge and additives, and the amount of each component of the additives is measured by the weight of the sludge.

The amount of wood chips added is 10% by weight of the sludge

The addition amount of the dehydrating agent is 2 weight percent of the weight of the sludge

Wherein the main components of the dehydrating agent are calcium oxide, magnesium chloride, aluminum chloride and the like, and the mass ratio of the calcium oxide to the magnesium chloride to the aluminum chloride is 2: 11: 2: 5.

Taking 50kg of sludge with the dry basis heat value of 12582kJ/kg, adding various additives (5 kg of wood chips, 5kg of mineralized refuse oversize and 1kg of dehydrating agent) according to a proportion, stacking and air-drying after uniformly mixing, wherein the thickness of a pile is 0.1 m. Naturally drying for 5 days at the average temperature of 10 ℃, reducing the water content of the sludge from 81.1% to 30.3%, and increasing the low calorific value from 0kJ/kg to 8098 kJ/kg; after natural air drying for 10 days, the water content is reduced to 21.2 percent, the low-grade heat value is improved to 9484kJ/kg, and the requirement of combustion power generation is met. The dry basis ash yield was 38.2%.

Claims

1. A sludge drying solid fuel is characterized in that: the additive is prepared by weighing the components of the additive according to the weight of the sludge, fully mixing, pressing and molding or preparing into powder;

wherein,

the addition amount of the wood chips is 5 weight percent of the weight of the sludge;

the adding amount of the coal dust is 20 weight percent of the weight of the sludge;

the addition amount of the oversize product of the mineralized refuse is 10 weight percent of the weight of the sludge; the mineralized refuse oversize is converted into oversize with earth fragrance after being buried for 8-10 years, and the main components of the oversize are plastics, fibers and paper after being primarily crushed and sieved by a 60mm aperture;

the addition amount of the dehydrating agent is 5 weight percent of the weight of the sludge;

the water content of the sludge is 75.0 percent, and the dry basis heat value is 7109 kJ/kg;

the dehydrating agent is calcium oxide, magnesium chloride and aluminum chloride, and the mass ratio of the calcium oxide to the magnesium chloride to the aluminum chloride is 1: 10: 1: 3.

2. A sludge drying solid fuel is characterized in that: the additive is prepared by weighing the components of the additive according to the weight of the sludge, fully mixing, pressing and molding or preparing into powder;

wherein,

the addition amount of the wood chips is 10 weight percent of the weight of the sludge;

the addition amount of the dehydrating agent is 2 weight percent of the weight of the sludge;

the water content of the sludge is 81.1 percent, and the dry basis heat value is 12582 kJ/kg;

the dehydrating agent is calcium oxide, magnesium chloride and aluminum chloride, and the mass ratio of the calcium oxide to the magnesium chloride to the aluminum chloride is 2: 11: 2: 5.