CN111269729A - Method and system for preparing biochar by co-pyrolysis of sludge and waste tires - Google Patents

Abstract

The invention discloses a method for preparing biochar by co-pyrolysis of sludge and waste tires, which comprises the following steps: (1) drying the dewatered sludge; (2) crushing the dried sludge and the waste tires respectively; (3) uniformly mixing the crushed sludge and the crushed solid particles of the waste tire according to a certain proportion, adding a zinc chloride solution, soaking for 20-30h at room temperature, and drying; (4) carrying out pyrolysis and carbonization on the dried material; (5) washing the pyrolyzed solid product by using dilute hydrochloric acid and deionized water in sequence, and drying to obtain biochar; the invention also provides a system for preparing biochar by co-pyrolysis of sludge and waste tires. The invention fully realizes the resource utilization and the energy efficient utilization of the waste tires, and avoids the resource waste caused by the accumulation of the waste tires and the environmental pollution caused by simple burning.

Description

A method and system for preparing biochar by co-pyrolysis of sludge and waste tires

technical field

The invention relates to a method and a system for preparing biochar by co-pyrolysis of sludge and waste tires, belonging to the field of comprehensive utilization of municipal waste and sludge resources.

Background technique

With the rapid development of my country's social economy and urbanization, the scale of urban sewage treatment plants has continued to expand, and the amount of sludge produced has also increased significantly. The characteristics of urban sludge in my country are high water content, low calorific value of sludge components, and easy generation of a large amount of odor and other harmful pollutants during the treatment process.

Traditional sludge treatment methods mainly include marine disposal, landfill, compost and incineration:

1) Marine disposal method: The sludge is directly thrown into the sea, endangering the marine ecosystem and causing the deterioration of the marine environment;

2) Landfill method: Sludge landfill occupies a large amount of land, which reduces the usable land in the suburbs of the city, and even leads to permanent disposal. Moreover, the sludge has high moisture content and high viscosity, which not only makes landfill operation difficult, but also makes landfill prone to occur. Deformation and landslides become "swampy land", causing potential safety hazards. In addition, the sludge is rich in harmful microorganisms such as pathogens and viruses, and is highly polluting, which will affect the ecological "food chain" and endanger the safety of residents;

3) Composting method: adding a certain proportion of leavening agents and conditioners such as straw, straw, sawdust or household waste to the sludge, and using the microorganisms of the sludge to ferment and convert them into humus-like plants as crop fertilizers, but after composting The product pathogens may still survive, the composting efficiency and nutrients are low, the heavy metals and toxic organics cannot be controlled, and the application effect is not good;

4) Incineration method: The sludge is incinerated and burned in an incinerator, so that all the organic matter is carbonized, and various pathogens are killed. The final product is inorganic ash with a solid content of more than 99%, but sludge exists in the combustion process. The disadvantages of low calorific value, high fuel consumption, heavy pollution, complex operation and management, large investment and high operating cost make the incineration method unable to be applied on a large scale.

Therefore, traditional sludge treatment methods can no longer meet the needs of social development, and it is imperative to develop new treatment technologies.

Biochar has a very unique pore structure and surface functional groups, has acid resistance, alkali resistance, heat resistance and other properties, good chemical stability, strong adsorption capacity, and convenient regeneration. With the development of society and the improvement of people's living standards, the demand for biochar is showing an upward trend year by year. However, the high cost of raw materials and high energy consumption for preparing biochar seriously restrict its further development and application. The sludge has high hydrocarbon content and many organic matter components. As a raw material for preparing carbon adsorption materials, biochar with good performance can be prepared by carbonization treatment at a certain temperature. The advantages of this method are: (1) preparing sludge biochar instead of commercial biochar can save wood, coal and other raw material resources and reduce the production cost of biochar; (2) preparing sludge into biochar with good adsorption performance, It provides a new way for the efficient resource utilization of sludge from urban sewage plants.

Some researchers have carried out related explorations for sludge treatment and production of biochar adsorption materials. CN103396815A discloses a method for preparing carbon material from sludge. After the sludge is hydrothermally dehydrated, it is used for anaerobic fermentation to generate biogas or biochar; the method needs to consume external energy and increases the cost of sludge treatment . CN102337142A discloses a method for preparing sludge charcoal by utilizing a heat-conducting oil furnace heat-conducting hollow blade vaporization reactor and a hollow blade carbonization reactor, and the produced sludge charcoal is returned to the boiler for combustion to supply heat to the vaporization reactor and the carbonization reactor; CN102358861A provides a method for deodorizing and sterilizing sludge and biomass fuel by lime method and then mixing with pulverized coal to prepare carbon-containing fuel for combustion; these two methods are limited to the reduction treatment of sludge, and use low value. CN102071033A discloses a sludge thermochemical charcoal disposal method. The sludge is heated to 170°C to 250°C, and carbon monoxide, carbon dioxide and other gases are continuously injected under the condition of fully enclosed heat preservation, so that the organic matter, protein, fiber, etc. Under the combined action of mechanical force and temperature, bacterial micelles are concentrated into thermoforming rods (or balls) with a moisture content of ≤9%, which are used for fuel combustion; High standard. The above patents mainly obtain sludge charcoal adsorption materials with good performance by adjusting the carbonization temperature, atmosphere and activator, etc., but they fail to solve the problems of high energy consumption and high raw material cost in the production process.

According to the research of scholars at home and abroad, waste tires are a kind of solid waste with high calorific value and high carbon content. The combustible gas obtained from tire pyrolysis is mainly composed of hydrogen and methane, which can be used as fuel, and can also be burned in situ to meet the needs of the thermal decomposition process, so that the heat required by the entire process system can be self-supplied, saving energy and environmental protection. According to previous research, adding appropriate amount of waste tire particles during sludge pyrolysis can help to form biochar products with high yield, large specific surface area and good porosity, and the prepared biochar can stabilize heavy metal elements in In the crystal structure formed by the pyrolysis process, the precipitation during use is prevented, the immobilization effect is good, and the transformation of sludge into a biochar product that is safe and harmless to the environment is realized.

SUMMARY OF THE INVENTION

In view of the above problems in the prior art, the present invention provides a method for preparing biochar by co-pyrolysis of sludge and waste tires, and the prepared pyrolysis biochar has high adsorption performance.

The invention also provides a system for preparing biochar by co-pyrolysis of sludge and waste tires.

In order to achieve the above object, a method for preparing biochar by co-pyrolysis of sludge and waste tires adopted in the present invention comprises the following steps:

(1) drying the dewatered sludge;

(2) Crushing the dried sludge and waste tires respectively;

(3) After the crushed sludge and the crushed waste tire solid particles are mixed uniformly according to a certain proportion, zinc chloride solution is added, soaked at room temperature for 20-30 hours, and dried;

(4) After drying, the material is pyrolyzed and carbonized;

(5) After pyrolysis, the solid product is washed with dilute hydrochloric acid and deionized water in turn, and dried to obtain biochar.

Preferably, the sludge in the step (1) is the sludge with a water content <95% after mechanical dehydration in the sewage plant;

Among them, the sludge drying method is direct drying or indirect drying, and the moisture content of the sludge after drying is less than 30%.

Preferably, in the step (2), the particle sizes of the crushed sludge and waste tire particles are both <30mm.

Preferably, in the step (3), the mass of the solid particles of the waste tires accounts for 5%-15% of the total mass of the sludge and the solid particles of the waste tires.

Preferably, the concentration of the zinc chloride solution in the step (3) is 2.5 mol/L.

Preferably, in the step (4), the pyrolysis and carbonization temperature of the mixture of sludge and waste tires is 700°C, the heating rate is 10°C/min, and the pyrolysis and carbonization time is 120min.

In addition, the present invention also provides a system for preparing biochar by co-pyrolysis of sludge and waste tires, including a waste tire preparation unit, a sludge preparation unit and a mixing unit;

The waste tire preparation unit includes a shredding device, a first crushing device, a first buffer silo and a first quantitative feeding device, and the sludge preparation unit includes a front drying device, a second crushing device, and a second buffer material. a bin and a second dosing device, the mixing unit includes a mixing device, a dosing activation device, a middle drying device, a carbonization device, a washing device and a post-drying device;

The waste tire preparation unit, the sludge preparation unit and the mixing unit are respectively connected with each other through conveying devices.

Preferably, after the pyrolysis gas generated by the carbonization device is processed by the gas treatment device, it is used to burn and heat the carbonization device, and the flue gas generated by the combustion enters the drying device;

The carbonization device is a moving bed type or rotary kiln type carbonization furnace, and the gas treatment device is a dry or wet gas purification device with deacidification function.

Preferably, the pre-drying device is a rotary drying device, the middle-drying device is a fluidized drying device, and the post-drying device is a disc-type drying device.

Preferably, the shredding device is a tire shredder; the first shredding device is a shearing shredder, and the second shredding device is a roller shredder;

The first quantitative feeding device and the second quantitative feeding device are screw feeders or star feeders;

The mixing device is one of a coulter-type mixer, a rake-type mixer, a drum-type mixer or a stirring-type mixer; the conveying device is a belt conveyor or a scraper conveyor.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention fully realizes the efficient utilization of waste tires as resources and energy, and avoids the waste of resources caused by the accumulation of waste tires and the environmental pollution caused by simple incineration.

(2) The present invention takes full advantage of the high calorific value of waste tires, and uses the pyrolysis gas generated in the carbonization process to be burned as an external heat source for carbonization. Drying and dehydration completely solves the problem of energy self-sufficiency in the whole process, fully embodies the concept of cleaner production and circular economy, and has significant benefits in energy saving and cost reduction.

(3) In the present invention, the sludge and waste tires containing a large amount of organic matter are mixed and pyrolyzed to prepare biochar, and the activated pore-forming method combined with ZnCl ₂ solution soaking makes the pyrolysis process easier to carry out, which is different from direct incineration, pyrolysis and adding Compared with the methods of pyrolysis of crops such as corn stalks, the invention helps to form biochar products with high yield, large specific surface area and good porosity, and the prepared biochar can stabilize heavy metal elements in the pyrolysis process. In the formed crystal structure, precipitation during use is prevented, the immobilization effect is good, and the transformation of excess sludge into biochar products that are safe and harmless to the environment is realized.

(4) The present invention utilizes waste tires and sludge to mix and pyrolyze to prepare carbon adsorption materials, introduces municipal waste into the field of carbon material preparation, turns waste into treasure, the process is simple and practical, and greatly reduces the cost of preparing carbon adsorption materials from sludge. The market competitiveness is improved, and the application prospect is broad.

Description of drawings

Fig. 1 is the SEM image of the biochar obtained in Example 1 of the present invention;

Fig. 2 is the process unit flow chart of the present invention;

In the figure: 1. Shredding device, 2. First crushing device, 3. First buffer silo, 4. First quantitative feeding device, 5. Front drying device, 6. Second crushing device, 7. First Two buffer silo, 8, second dosing device, 9, mixing device, 10, dosing activation device, 11, middle drying device, 12, carbonization device, 13, washing device, 14, post drying device, 15, Gas processing device, 16. Conveying device.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below. However, it should be understood that the specific embodiments described herein are only used to explain the present invention, and not to limit the scope of the present invention.

A method for preparing biochar by co-pyrolysis of sludge and waste tires, comprising the following steps:

(1) drying the dewatered sludge;

(2) Crushing the dried sludge and waste tires respectively;

(3) After the crushed sludge and the crushed waste tire solid particles are mixed uniformly according to a certain proportion, zinc chloride solution is added, soaked at room temperature for 20-30 hours, and dried;

(4) After drying, the material is pyrolyzed and carbonized;

(5) After pyrolysis, the solid product is washed with dilute hydrochloric acid and deionized water in turn, and dried to obtain biochar.

Preferably, the sludge in the step (1) is the sludge with a water content <95% after mechanical dehydration in the sewage plant;

Among them, the sludge drying method is direct drying or indirect drying, and the moisture content of the sludge after drying is less than 30%.

Preferably, in the step (2), the particle sizes of the crushed sludge and waste tire particles are both <30mm.

Preferably, in the step (3), the mass of the solid particles of the waste tires accounts for 5%-15% of the total mass of the sludge and the solid particles of the waste tires.

Preferably, the concentration of the zinc chloride solution in the step (3) is 2.5 mol/L.

Preferably, in the step (4), the pyrolysis and carbonization temperature of the mixture of sludge and waste tires is 700°C, the heating rate is 10°C/min, and the pyrolysis and carbonization time is 120min.

In addition, the present invention also provides a system for preparing biochar by co-pyrolysis of sludge and waste tires, including a waste tire preparation unit, a sludge preparation unit and a mixing unit;

The waste tire preparation unit includes a shredding device 1, a first crushing device 2, a first buffer silo 3 and a first quantitative feeding device 4, and the sludge preparation unit includes a front drying device 5, a second crushing device 6. The second buffer silo 7, the second dosing device 8, the mixing unit includes a mixing device 9, a dosing activation device 10, a middle drying device 11, a carbonization device 12, a washing device 13 and a post-drying device 14 ;

The waste tire preparation unit, the sludge preparation unit and the mixing unit are connected with each other through the conveying device 16 respectively.

Preferably, after the pyrolysis gas generated by the carbonization device 12 is processed by the gas treatment device 15, it is used to burn and heat the carbonization device 12, and the flue gas generated by the combustion enters each drying device;

The carbonization device 12 is a moving bed type or rotary kiln type carbonization furnace, and the gas treatment device 15 is a dry or wet gas purification device with deacidification function.

Preferably, the pre-drying device 5 is a rotary drying device, the middle drying device 11 is a fluidized drying device, and the post-drying device 14 is a disc-type drying device.

Preferably, the shredding device 1 is a tire shredder; the first shredding device 2 is a shearing shredder, and the second shredding device 6 is a roller crusher;

The first quantitative feeding device 4 and the second quantitative feeding device 8 are screw feeders or star feeders;

The mixing device 9 is one of a coulter-type mixer, a rake-type mixer, a drum-type mixer or a stirring-type mixer; the conveying device 16 is a belt conveyor or a scraper conveyor .

Example 1

A method for preparing biochar by co-pyrolysis of sludge and waste tires, comprising the following steps:

(1) Take the sludge with a moisture content of <95% after mechanical dehydration and drying in the sewage treatment plant, use direct drying and control the moisture content of the sludge after drying to <30%;

(2) the sludge after drying in step (1) and the waste tires taken from the recycling station are respectively crushed to particle size<30mm;

(3) Weigh 0.1kg of the crushed sludge and 0.9kg of the crushed waste tire solid particles, after mixing evenly, add a zinc chloride solution with a concentration of 2.5mol/L, so that the zinc chloride solution is immersed in the sludge and waste. Tire solid particles, soaked at room temperature for 24 hours, and dried;

(4) the material after drying in step (3) is pyrolyzed and carbonized for 120min at 700°C (controlling the heating rate to be 10°C/min);

(5) The pyrolysis carbonization product is washed with conventional dilute hydrochloric acid and deionized water in turn, and dried to obtain biochar.

The yield of the obtained biochar was determined by the laboratory to be 64.77%.

In terms of adsorption performance: the specific surface area of the biochar is 806.15m2/g, and the iodine adsorption value is 619.69mg/g;

The immobilization ratio of heavy metals is: Cu, 91.10%; Ni, 88.64%; Cr, 68.07%; Cd, 77.20%; Zn, 89.69%; Pb, 84.12%.

In addition, Figure 1 provides an SEM image of the biochar prepared in this example, and it can be seen from the figure that the morphology of the biochar has an obvious pore structure.

Compared with the biochar prepared only with sludge (yield 45.70%; specific surface area 632.54m2/g, iodine adsorption value 506.27mg/g; heavy metal immobilization ratio: Cu, 85.22%; Ni, 83.27%; Cr, 60.81 %; Cd, 71.45%; Zn, 87.36%; Pb, 76.20%), the performance of the biochar of the present invention has been significantly improved in all aspects.

The element ratio analysis of the biochar prepared in this example and the biochar prepared only with sludge is shown in Table 1.

Table 1 Elemental ratio analysis of biochar samples

Analysis of Table 1 shows that compared with the biochar prepared by using only sludge, the H/C value of the biochar prepared in this example decreased by 34.04%, indicating that the aromatization degree of the biochar prepared in this example was enhanced, and the waste tire catalyzed The pyrolysis of sludge was reduced; the O/C value decreased by 12.80%, indicating that the hydrophilicity of the biochar prepared in this example decreased; the (O+N)/C value decreased by 11.90%, indicating that the biochar prepared in this example decreased. The polarity decreased; the C/N value increased by 11.27%. Therefore, the surface functional groups of the biochar prepared in this example were reduced, the properties were more stable, and it was not easy to be decomposed by mineralization.

Example 2

As shown in Figure 2, a system for preparing biochar by co-pyrolysis of sludge and waste tires includes a waste tire preparation unit, a sludge preparation unit and a mixing unit;

The waste tire preparation unit includes a shredding device 1, a first crushing device 2, a first buffer silo 3 and a first quantitative feeding device 4, and the shredding device 1, the first crushing device 2, the first buffer material The bin 3 and the first quantitative feeding device 4 are sequentially connected through the conveying device 16;

The sludge preparation unit includes a front drying device 5, a second crushing device 6, a second buffer silo 7, a second quantitative feeding device 8, and a front drying device 5, a second crushing device 6, and a second buffer silo. 7 and the second quantitative feeding device 8 are sequentially connected through the conveying device 16;

The mixing unit includes a mixing device 9, a dosing activation device 10, a middle drying device 11, a carbonization device 12, a washing device 13 and a post-drying device 14, and the mixing device 9, the dosing activation device 10, the middle drying device 11, The carbonization device 12, the washing device 13 and the post-drying device 14 are sequentially connected through the conveying device 16;

And the first quantitative feeding device 4 and the mixing device 9 and the second quantitative feeding device 8 and the mixing device 9 are connected by the conveying device 16, which realizes the waste tire preparation unit, the sludge preparation unit and the mixing unit. connect.

In addition, after the pyrolysis gas produced by the carbonization device 12 is processed by the gas treatment device 15, it is used to burn and heat the carbonization device 12;

The equipment and devices in the system of the present invention are described as follows, and each of the following devices can be directly purchased in the market:

The shredding device 1 is an ordinary tire shredder; the first shredding device 2 is a tire shearing shredder;

The first buffer silo 3 is a common silo, the upper part is cylindrical and the lower part is cone-shaped, or the upper part is square and the lower part is pyramid-shaped;

The first quantitative feeding device 4 is a screw feeder or a star feeder; the front drying device 5 is a rotary drying device;

The second crushing device 6 is a roller crusher;

The second buffer silo 7 is a common silo, the upper part is cylindrical and the lower part is cone-shaped, or the upper part is square and the lower part is pyramid-shaped;

The second quantitative feeding device 8 is a screw feeder or a star feeder;

The mixing device 9 is any of a coulter-type mixer, a rake-type mixer, a drum-type mixer or a stirring-type mixer;

The dosing activation device 10 is a combination of a material storage tank and an automatic dosing mixer;

The middle drying device 11 is fluidized drying equipment;

The carbonization device 12 is an ordinary biomass carbonization furnace, which can be a moving bed type or rotary kiln type carbonization furnace;

The washing device 13 is an integrated device for pickling and water washing; the post-drying device 14 is a disc-type drying device;

The gas treatment device 15 is a dry or wet gas purification device with deacidification function;

The conveying device 16 is a belt conveyor or a scraper conveyor.

In the invention, the crushed waste tires and the dried sludge are uniformly mixed in a certain proportion, the mixed materials are activated by zinc chloride and then carbonized to prepare carbon adsorption materials, and the pyrolysis gas generated in the carbonization process is burned as carbonization. The flue gas generated by combustion is used for drying and dehydration of sludge, activated mixed material and washed biochar, which solves the problem of energy self-sufficiency in the process of sludge pyrolysis to prepare carbon adsorption materials.

The invention introduces municipal waste into the technical field of sludge preparation of carbon materials, utilizes waste tires to improve the performance indicators of sludge pyrolysis carbon, and at the same time takes advantage of the high calorific value of waste tires, on the one hand, completely solves the energy involved in material drying and carbonization processes. On the other hand, it avoids the waste of resources caused by the accumulation of waste tires and the environmental pollution caused by simple incineration, realizes the high value-added utilization of waste tires, fully reflects the concept of clean production and circular economy, and has significant energy saving and environmental protection benefits . The method is simple and practical in process, greatly reduces the cost of preparing carbon adsorption materials from sludge, improves market competitiveness, and has broad application prospects.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. A method for preparing biochar by co-pyrolysis of sludge and waste tires is characterized by comprising the following steps:

(1) drying the dewatered sludge;

(2) crushing the dried sludge and the waste tires respectively;

(3) uniformly mixing the crushed sludge and the crushed solid particles of the waste tire according to a certain proportion, adding a zinc chloride solution, soaking for 20-30h at room temperature, and drying;

(4) carrying out pyrolysis and carbonization on the dried material;

(5) and washing the pyrolyzed solid product by using dilute hydrochloric acid and deionized water in sequence, and drying to obtain the biochar.

2. The method for preparing biochar by co-pyrolysis of sludge and waste tires according to claim 1, wherein the sludge in the step (1) is sludge with the water content of less than 95% after mechanical dehydration in a sewage plant;

wherein, the sludge drying method is direct drying or indirect drying, and the water content of the dried sludge is less than 30 percent.

3. The method for preparing biochar by co-pyrolysis of sludge and waste tires according to claim 1, wherein in the step (2), the granularity of the crushed sludge and the crushed waste tire particles is less than 30 mm.

4. The method for preparing biochar by co-pyrolysis of sludge and waste tires according to claim 1, characterized in that in the step (3), the mass of the waste tire solid particles accounts for 5% -15% of the total mass of the sludge and the waste tire solid particles.

5. The method for preparing biochar by co-pyrolysis of sludge and waste tires according to claim 1 or 4, characterized in that the concentration of the zinc chloride solution in the step (3) is 2.5 mol/L.

6. The method for preparing biochar by co-pyrolysis of sludge and waste tires according to claim 1, wherein the mixture of sludge and waste tires in the step (4) has a pyrolysis carbonization temperature of 700 ℃, a temperature rise rate of 10 ℃/min and a pyrolysis carbonization time of 120 min.

7. A system for preparing biochar by co-pyrolysis of sludge and waste tires is characterized by comprising a waste tire material preparation unit, a sludge material preparation unit and a material mixing unit;

the waste tire material preparation unit comprises a shredding device (1), a first crushing device (2), a first buffer bin (3) and a first quantitative feeding device (4), the sludge material preparation unit comprises a front drying device (5), a second crushing device (6), a second buffer bin (7) and a second quantitative feeding device (8), and the material mixing unit comprises a mixing device (9), a medicine adding activation device (10), a middle drying device (11), a carbonization device (12), a washing device (13) and a rear drying device (14);

the waste tire material preparing unit, the sludge material preparing unit and the material mixing unit are connected with each other through a conveying device (16).

8. The system for preparing biochar by utilizing co-pyrolysis of sludge and waste tires as claimed in claim 7, wherein the pyrolysis gas generated by the carbonizing device (12) is treated by a gas treatment device (15) and is used for burning and heating the carbonizing device (12), and the flue gas generated by burning enters a drying device;

the carbonization device (12) is a moving bed type or rotary kiln type carbonization furnace, and the gas treatment device (15) is dry or wet gas purification equipment with a deacidification function.

9. The system for preparing biochar by co-pyrolysis of sludge and waste tires as claimed in claim 7 or 8, characterized in that the front drying device (5) is a rotary drying device, the middle drying device (11) is a fluidized drying device, and the rear drying device (14) is a disc type drying device.

10. The system for preparing biochar by co-pyrolysis of sludge and waste tires according to claim 7 or 8, characterized in that the shredding device (1) is a tire shredder; the first crushing device (2) is a shear type crusher, and the second crushing device (6) is a roller type crusher;

the first quantitative feeding device (4) and the second quantitative feeding device (8) are screw feeders or star feeders;

the mixing device (9) is one of a coulter type mixer, a rake type mixer, a rotary drum type mixer or a stirring type mixer; the conveying device (16) is a belt conveyor or a scraper conveyor.

Images