CN101306812B

CN101306812B - Process for preparing active carbon by co-decomposition of city sludge and agricultural wastes

Info

Publication number: CN101306812B
Application number: CN2008101233836A
Authority: CN
Inventors: 张双全
Original assignee: China University of Mining and Technology CUMT
Current assignee: China University of Mining and Technology CUMT
Priority date: 2008-05-26
Filing date: 2008-05-26
Publication date: 2011-05-11
Anticipated expiration: 2028-05-26
Also published as: CN101306812A

Abstract

A process for preparing activated carbon by co-pyrolysis of municipal sludge and agricultural waste comprises the steps of mixing the agricultural waste and the municipal sludge in a certain proportion to obtain a mixture; heating the mixture at a certain temperature under the condition of air isolation, keeping the temperature for a period of time, collecting a solid product, and cooling; and pulverizing the solid product to obtain the activated carbon product. In order to obtain an activated carbon with higher absorptive capacity, a certain amount of nitrate can be added into the mixture. Because the agricultural waste can make up the low heat value shortcoming of the sludge, while the municipal sludge can solve the problems with the agricultural waste that the pyrolysis solid product is easy to flow away and difficult to store, the inventive process can not only solve the high energy consumption and high cost problems of the prior sludge incineration, pyrolysis and other heat treatment methods, but also can be used for environmental treatment to save energy and reduce emission.

Description

Municipal sludge and agricultural wastes process for preparing active carbon by co-decomposition

Technical field

The present invention relates to a kind of Preparation of Activated Carbon, especially for municipal sludge and agricultural wastes copyrolysis preparing active carbon.

Background technology

Municipal sludge is the sedimentable matter that produces in the municipal sewage treatment process.Establish to 661 in China in 2006 and to build together into 791 of sewage works in the city, city, about 1,730,000 tons of mud annual production (dry weight), and annual speed with about 10% is increasing.It is generally acknowledged that sludge quantity accounts for 0.5%～0.7% (volume) of sewage quantity usually, perhaps is about 1%～2% (quality) of sewage load.If the sewage disposal degree of depth strengthens, sludge quantity also can increase by 0.5～1 times sometimes.

Municipal sludge is municipal sewage plant's sludge discharged, also can be the organic mud that contains that discharges during industrial sewage is handled.Contain various trace elements and organic matters such as solid particulates such as silt particle, fiber, plant and animal residues, microorganism and agglomerative floss thereof and more nitrogen, phosphorus in the municipal sludge, also containing a large amount of pathogenic agent, parasite (ovum) and a certain amount of heavy metal and multiple toxic organics, is all difficult problems of ten minutes headache of present countries in the world.

Agricultural wastes are meant vegetalitas waste materials such as waste in depleted stalk in agricultural-food production, the course of processing, husk, shell, waste residue and the wood working process such as wood chip.Since the reform and opening-up, because farmers' income improves constantly, peasant's mode of life has the trend of urbanization.The agricultural crop straw that past uses as fuel wood in the rural area, present most of Rural areas is abandoned by the peasant, even is seen as burden.Therefore, every harvesting season is for following the line of least resistance, the peasant usually gets the agricultural crop straw on-site incineration over, has not only wasted resource, has also caused serious atmospheric pollution simultaneously, the usually normal operation of the vehicles around the influence, near the particularly safe landing of aircraft the influence.

Sludge treatment is disposed and to be mainly contained with the traditional way that utilizes that to abandon sea, landfill, burn and do fertilizer etc. several.Because it is big that mud is abandoned sea disposal environmental stress, is under an embargo in most of country.Actually, the disposal options that generally adopts at present is landfill and as fertilizer sources use on agricultural.The sanitary landfill of mud starts from the sixties in last century, up to the present, has developed into the Sludge Disposal Techniques of a comparative maturity, and its advantage is that investment is less, capacity big, instant effect.Yet also there are many problems in the municipal sludge sanitary landfill.The various hazardous and noxious substances that contain in the mud also will take a large amount of soils simultaneously through etch and the seepage meeting polluted underground water and the atmosphere of rainwater, and in addition, trucking costs is high at a distance also is an important factor of the sanitary landfill of restriction mud.Environmental pollution can not be finally avoided in the sanitary landfill of mud, and has just delayed generation time.More than all unfavorable factors limited the development of the sanitary landfill of mud, will can not become the developing direction of sludge ultimate disposal.

With regard to environmentAL safety, sludge incineration is best treatment process relatively.The burning of mud once had been subjected to people's welcome very much, needed to handle etc. again and had limited its use yet sludge incineration is big with one-time investment again, facility investment is high, running expense is high, can produce highly toxic substance such as Dioxins, burn ash.Because incinerator equipment complexity, construction and transport expense are used far above general method for sludge treatment, burning cost is 2～4 times of other technologies (ton dewatered sludge comprehensive treating process cost is about 700～1000 yuan), is difficult to economically support, and therefore can't be applied actually.With regard to present situation, recycling sludge is the megatrend of development.

Summary of the invention

The objective of the invention is to overcome the deficiency in the prior art, provide a kind of investment little, expense is low, municipal sludge of turning waste into wealth and agricultural wastes process for preparing active carbon by co-decomposition.

Municipal sludge of the present invention and agricultural wastes process for preparing active carbon by co-decomposition:

A. agricultural wastes and municipal sludge are mixed by a certain percentage;

B. with said mixture secluding air heating at a certain temperature, and constant temperature takes out solid product and cools off after for some time;

C. solid product is pulverized, promptly obtained activated carbon product.

Add nitrate in the mixture of described agricultural wastes and municipal sludge, it is 0% or 1%～10% that the addition of nitrate accounts for municipal sludge, agricultural wastes and nitrate three mixture butt weight percent; It is 10%～70% that described agricultural wastes account for mixture butt weight percent; It is 30%～90% that described municipal sludge accounts for mixture butt weight percent; The temperature of described secluding air heating is 350～550 ℃; Described constant temperature for some time is 10～20min.

Beneficial effect: with municipal sludge and agricultural wastes copyrolysis, the difficulty and the problem that run into separately in the time of can solving the independent pyrolysis processing of these two kinds of materials of municipal sludge and farm crop agricultural wastes.Because the characteristics of agricultural wastes are organic content height, the calorific value height of pyrolysis product, but solid product density low, easily waft, be difficult to storing; And the moisture height of municipal sludge, calorific value are low, need extraneous supplementing energy during pyrolysis, cause high energy consumption, and solid product density is big, and viscosity is difficult to greatly carry simultaneously.These two kinds of materials by suitable mixed, then can be learnt from other's strong points to offset one's weaknesses, can make the solution of problem become easy.Particularly bring new chance and potentiality for the recycling treatment of mud and the application of product.Agricultural wastes can remedy the low defective of sludge calorific value, and mud can remedy the problem that agricultural wastes pyrolysis solid product easily wafts and is difficult to store and transport, and the pyrolysis solid product then can be used for environmental improvement, achieves many things at one stroke.Except that above-mentioned advantage, also have following benefit:

Innoxious and resource utilization: two kinds of materials of mud and agricultural wastes all can thoroughly transform, innoxious and resource utilization, compare with existing disposal options, disadvantageous effect to environment almost can be reduced to zero, solid product can transform into the low cost of market in urgent need, high efficiency low-cost sorbent, and awkward degradation of sewage is handled with some waste gas such as fume desulfuring and denitrifying processing scheme feasible, that have obvious economic advantages is provided;

Heat self balance: in mud, add agricultural wastes, can significantly improve the physicochemical property of mud, as viscosity, dry heat transfer, mass transfer process and kinetics, the heat transfer in the pyrolysis, mass transfer process and kinetics; Improve its composition,, improve organic content and calorific value, help realizing the self-equilibrating of pyrolytic process heat as remarkable reduction moisture content;

Energy-saving and emission-reduction: pyrolyzing sludge institute energy requirement is resolved, and can not cause energy consumption and CO because of extra use fossil oil additional heat ₂The increase of discharging meets the policy of national energy-saving and emission-reduction;

Economic advantages are obvious: because methods of disposal such as existing mud landfill, burning need a large amount of fiscal subsidy, cost of disposal is up to 500～1000 yuan/t dewatered sludge, major cause is to take valuable land resources, equipment working cost height, need the additive decrementation energy etc., and the present invention is converted into sorbing material with mud and agricultural wastes combination treatment, can be used for the improvement of waste water and gas, it is worth and is higher than the value of using as the energy far away, and can fundamentally solve the expensive problem of thermal treatment methods such as existing sludge incineration, pyrolysis;

Save the soil, do not have environmental risk: owing to do not adopt the treatment process of landfill, can save a large amount of soils, eliminate the pathogenic risk of landfill and the agricultural secondary pollution that brings and potential simultaneously, social benefit could be estimated!

Accelerate drying sludge speed: after adding the agricultural wastes of pulverizing in the mud, destroyed the bonding state of mud, increased the surface-area of particle or agglomerate, heat transfer when helping drying and mass transfer can be accelerated dry and pyrolytic speed, cut down the consumption of energy.

Embodiment

Embodiment one, be 60% pulverizing straw with the butt weight percent and be that 40% municipal sludge mixes the butt weight percent; Secluding air is heated to 350 ℃, takes out solid product and cooling behind the constant temperature 10min, then solid product is pulverized, and promptly obtaining iodine number is the 404mg/g activated carbon product.

Embodiment two, be 38.5% pulverizing straw with the butt weight percent and be that 58% municipal sludge and weight percent are that 3.5% nitrate mixes the butt weight percent; Secluding air is heated to 400 ℃, takes out solid product and cooling behind the constant temperature 10min, then solid product is pulverized, and promptly obtaining iodine number is the 506mg/g activated carbon product.

Embodiment three, be that 28.50% pulverizing straw, butt weight percent are that 68% municipal sludge and weight percent are that 3.5% nitrate mixes with the butt weight percent; Secluding air is heated to 450 ℃, takes out solid product and cooling behind the constant temperature 10min, then solid product is pulverized, and promptly obtaining iodine number is the 425mg/g activated carbon product.

Embodiment four, be that 57% pulverizing straw, butt weight percent are that 38% municipal sludge and weight percent are that 5% nitrate mixes with the butt weight percent; Secluding air is heated to 500 ℃, takes out solid product and cooling behind the constant temperature 20min, then solid product is pulverized, and promptly obtaining iodine number is the 417mg/g activated carbon product.

Embodiment five, be that 57% pulverizing straw, butt weight percent are that 36.5% municipal sludge and weight percent are that 6.5% nitrate mixes with the butt weight percent; Secluding air is heated to 500 ℃, takes out solid product and cooling behind the constant temperature 20min, then solid product is pulverized, and promptly obtaining iodine number is the 439mg/g activated carbon product.

Embodiment six, be that 35.5% pulverizing wheat straw, butt weight percent are that 55% municipal sludge and weight percent are that 9.5% nitrate mixes with the butt weight percent; Secluding air is heated to 500 ℃, takes out solid product and cooling behind the constant temperature 20min, then solid product is pulverized, and promptly obtaining iodine number is the 420mg/g activated carbon product.

Claims

1. municipal sludge and agricultural wastes process for preparing active carbon by co-decomposition, be included in the mixture of agricultural wastes and municipal sludge and add nitrate, it is 0% or 1～10% that the addition of nitrate accounts for municipal sludge, agricultural wastes and nitrate three mixture butt weight percent, it is characterized in that:

A. be that 10%～70% agricultural wastes, butt weight percent are that 30%～90% municipal sludge and butt weight percent are that 0% or 1～10% nitrate mixes with the butt weight percent;

B. said mixture secluding air under 350～500 ℃ of temperature is heated, and take out solid product and cooling after constant temperature 10～20min time;

C. solid product is pulverized, promptly obtained activated carbon product.