CN117107055A - Treatment method of coking wastewater sludge - Google Patents

Abstract

The invention relates to a method for treating coking wastewater sludge, which includes: 1) mixing coke powder, iron ore powder, coking wastewater sludge, tar residue, and solvent, extruding them into agglomerates, cold-consolidating the agglomerates, and drying them Until the moisture content does not exceed 2%; place the dried briquettes under oxygen-free or inert gas protection conditions for roasting pretreatment at 500-800°C for 0.5-5 hours. Lay charcoal under the dried briquettes. After roasting, carbonization is obtained. Agglomerate; continue to raise the temperature to 1350~1550℃, add _H2 or CO for direct reduction for 0.2~3h, and then generate direct reduced iron and slag. The direct reduced iron drips directly in liquid state; then add _N2 or Ar, and the slag is cooled. It is an amorphous powder. After complete cooling, cyclone centrifugal separation is used to separate the slag powder and coke. The invention uses coking wastewater sludge to prepare direct reduced iron, realizes the recovery and reuse of valuable elements in the sludge, reduces the emission of polycyclic aromatic hydrocarbons and benzene pollutants, realizes the recycling of tail gas and heat, and realizes green and low-carbon production. .

Description

A method for treating coking wastewater sludge

Technical field

The invention belongs to the technical field of coking coal blending and relates to a method for treating coking wastewater sludge.

Background technique

A large amount of carbon-containing solid waste will be produced during the coking production process, and approximately 0.2% of biochemical sludge will be produced in the coking wastewater treatment unit. For coking wastewater sludge, due to its complex composition, including inorganic substances, toxic and harmful substances (such as microorganisms, organic substances) and sludge, it is a semi-dry solid waste with complex rheology. For this coking wastewater sludge, physical chemistry is generally used. Method, the plate and frame are simply dehydrated under pressure and then placed in the coal pile yard for stacking as a coal blending additive or sent to the solid waste landfill for landfill; for tar residue, there are three types of sources. One is from the mechanized tar ammonia water clarification tank. Due to the relative The density is relatively high, and the coal tar residue settles at the bottom of the clarification tank and is continuously discharged in a semi-solid state through a scraper. It is the main source of coal tar residue in the coking plant. The second is the tar after natural sedimentation. In order to remove the finer particles The fine residue is further separated using a super centrifuge and separated into a semi-liquid coal tar residue with a high slag content; the rest is clear tank coal tar residue after natural settlement of the tar storage tank, with a consistency between mechanized Between the clarifier tar residue and the super centrifuge tar residue, the generally adopted method is to directly mix the tar residue from these three sources with the briquettes as a coal blending binder or burn them as fuel.

It has been tested that the average moisture content of coking wastewater sludge is 76.6%, and the average sludge ash content is as high as 34.7%. The Fe ₂ O ₃ content in the sludge ash is relatively high, with an average of 75.21%. This is mainly due to coagulation and precipitation in the later stage of the biological denitrification process. Generally, flocculants such as polymeric ferric sulfate need to be added, or ferrous sulfate is added when the Fenton process is used for deep treatment. Because coking wastewater sludge contains a large amount of inorganic components (such as sulfates, aluminum-containing polymers, etc.), uneven blending into coking coal will have a significant impact on the quality of the coke; the viscosity and composition of the tar residue The volatility will cause the oil residue to stick to the belt conveyor and the belt roller, resulting in uneven coal blending process. The volatility of the tar residue component makes it difficult to accurately batch the ingredients, resulting in unstable coke quality and unstable coke quality. The heat load on the coke oven increases. Because there are a large amount of polycyclic aromatic hydrocarbons (such as polycyclic aromatic hydrocarbons and benzene) in coking wastewater sludge and tar residue, when used as fuel or coal blending additives, a large amount of toxic and harmful gases will be produced during incomplete combustion, resulting in an increase in atmospheric emissions from coking plants. Difficulty and cost of processing.

To this end, it is necessary to formulate an environmentally friendly, resource-efficient recycling treatment technology based on the characteristics of coking wastewater sludge to realize the recycling of valuable elements while reducing pollutant emissions.

Contents of the invention

The object of the present invention is to provide a method for treating coking wastewater sludge, using coking wastewater sludge and tar residue to prepare direct reduced iron, realizing the recovery and reuse of valuable elements in the sludge and tar residue, and reducing polycyclic aromatic hydrocarbons, The emission of benzene pollutants is achieved, exhaust gas and heat are recycled, and green and low-carbon production applications are realized.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A method for treating coking wastewater sludge, including the following steps:

1) Mix coke powder, iron ore powder, coking wastewater sludge, tar residue, and solvent in proportion, and use a 1000-2000N press to extrudate the block into a flat mass with a particle size of 10mm-20mm, in which the coking wastewater The sludge should be dried until the moisture content does not exceed 5%; the sludge should be cold-solidified at room temperature and dried at low temperature until the moisture content does not exceed 2%.

Coke powder includes dry quenched coke primary dust removal coke powder, secondary dust removal coke powder, and screened coke powder, in which the fixed carbon content is ≥78%, the coke powder particle size is ≤1mm, the ash content is ≤15%, and the moisture is ≤1.0%; coking wastewater Mud comes from coking product recycling wastewater or water quenching coke tank wastewater, with fixed carbon content ≥ 25%, and Fe ₂ O ₃ content in ash not less than 30%; the solvent includes one of CaO, CaCO ₃ and Ca(OH) ₂ or more.

The raw material ratio in step 1) is calculated in parts by weight: 30 to 60 parts of coke powder, 20 to 40 parts of iron ore powder, 5 to 35 parts of coking wastewater sludge, 3 to 10 parts of tar residue, and 3 to 15 parts of solvent. share.

The cold consolidation temperature does not exceed 30℃, and the drying temperature does not exceed 60℃.

2) Place the dried briquettes in step 1) under oxygen-free or inert gas protection conditions for low-temperature roasting pretreatment at 500 to 800°C for 0.5 to 5 hours. Place coke dices under the dried briquettes. The coke is laid in layers and placed in a high-temperature furnace. After heating, the briquettes are dried to obtain retort briquettes. The material volume density of the retort briquettes is 1.5-3.5g/cm ³ , the compressive strength is ≥40kg, and the iron grade reaches more than 60%. During the low-temperature reduction roasting process, due to the moisture and volatilization in the coking wastewater sludge, a large number of pore structures will be distributed in the retort briquettes, with a porosity of 10 to 50%.

The particle size of the diced coke laid under the drying briquettes is ≥10mm. The diced coke can be reused after the reaction. The compressive strength of the diced coke is ≥25kg. The diced coke can ensure the reducing atmosphere during the reaction process, filter the slag powder, and prevent the slag powder from flowing directly. Reduced iron dripping.

3) Continue to raise the temperature to 1350~1550℃, introduce reducing gas for direct reduction for 0.2~3 hours, and then generate direct reduced iron and slag; the tail gas is discharged from the top of the furnace, and the introduced reducing gas will pass through a large number of pore structures distributed in the retort briquettes And a rapid reduction reaction occurs with it.

The reducing gas is H ₂ or CO or a mixed gas of H ₂ and CO.

4) Afterwards, N ₂ or Ar is introduced, and the direct reduced iron drops directly in liquid form. The slag is instantly cooled into amorphous powder. After complete cooling, cyclone centrifugal separation is used to separate the slag powder and coke.

The metallization rate of direct reduced iron is ≥90%.

Slag powder includes iron ore powder, slag phase minerals after direct reduction of iron from wastewater sludge, and coke ash.

The tail gas generated during the reaction process is subjected to dust removal and activated carbon adsorption. The high-temperature reduction gas after CO ₂ removal can be reused in step 3) to reduce heat loss. Activated carbon adsorbs and removes polycyclic aromatic hydrocarbons and benzene in the exhaust gas, and the temperature of the reused high-temperature gas is not lower than 200°C.

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

Use coking wastewater sludge and tar residue to prepare direct reduced iron, realize the recovery and reuse of valuable metal elements in the sludge or tar residue, reduce the emission of polycyclic aromatic hydrocarbons and benzene pollutants, recycle tail gas and heat, and achieve greening , low-carbon production applications. Among them, the addition of coke powder can increase the fixed carbon content in the briquettes after carbonization, which is beneficial to high-temperature direct reduction. Since both coke powder and tar residue are coal chemical products, they have a certain affinity, but coke powder has almost no cohesiveness. The powder plays a skeleton role in consolidating the agglomerates with iron ore powder, coking wastewater sludge, tar residue and solvent as the main raw materials. The tar residue has strong viscosity and can act as a binder in the cold consolidation of the above raw materials, improving the Extrusion rate into lumps. Cold-solidified agglomerates can improve the wettability of liquid tar residues among various materials and reduce cracks caused by water volatilization. During the roasting process of cold-solidified agglomerates, due to the volatilization of organic matter in tar residues and sludge, the dry distillation agglomerates The block is porous, which effectively improves the air permeability of the block during the direct reduction process and opens up the reducing gas to enter the internal channels of the retort block. On the one hand, the coke laid under the briquettes can ensure a reducing atmosphere. On the other hand, due to the different viscosity of liquid iron and blast furnace slag, the liquid iron is more likely to pass through the coke layer and then drip, while the liquid blast furnace slag is more likely to drip due to its viscosity. Relatively large, the coke layer becomes the separation layer between liquid blast furnace slag and direct reduced iron. After heating is stopped and cooling protective gas is introduced, the blast furnace slag turns into amorphous powder, achieving solid-liquid separation.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the specific implementation modes of the present invention will be further described below in conjunction with the examples. The following examples are used to specifically illustrate the content of the present invention. These embodiments are only general representations of the content of the present invention. Description does not limit the content of the invention.

Example 1:

A method for treating coking wastewater sludge is to mix 30 parts of coke powder, 40 parts of iron ore powder, 20 parts of coking wastewater sludge, 5 parts of tar residue and 5 parts of solvent. Among them, the coke powder is mainly CDQ primary dust removal coke powder, with a fixed carbon content of 78%, an ash content of 15%, and a moisture content of 1.0%. The coke powder is all pre-ground to less than 1 mm. The carbon-containing sludge mainly comes from coking product recycling wastewater. Sludge, fixed carbon content is 25%, Fe ₂ O ₃ content in ash is 10%, coking wastewater sludge should be dried until the moisture content does not exceed 5%, and the solvent is CaO.

After mixing the above materials, use a 1000N press to extrude them into flat briquettes with a particle size of 15mm; cold-consolidate the formed flat briquettes into briquettes. The consolidated briquettes have a compressive strength of 500N and are dried at low temperature. The moisture content of the cold-consolidated mass is 2%, and the cold-consolidation temperature is 25°C to prevent cracks due to excessive temperature;

Under the cold-solidified briquettes, coke dices with a particle size of 10 mm and a compressive strength of 25 kg were laid. The dried briquettes and coke dices were layered in a high-temperature furnace and roasted at 800°C for 2 hours under Ar inert gas. Dry the briquettes to obtain retort briquettes. The material volume density of the retort briquettes is 3.5g/cm ³ , the compressive strength is 40kg, and the iron grade reaches 62%. During the low-temperature reduction roasting process, due to the moisture in the coking wastewater sludge And volatilization analysis will make the retort briquettes have a large number of pore structures, and the porosity reaches 35%. The coke can ensure the reducing atmosphere during the reaction process, filter the slag powder, and prevent the slag powder from dripping along with the direct reduced iron.

Continue to raise the temperature to 1400°C, and the solvent CaO promotes the generation of the liquid phase in the retort briquettes. Direct reduction is carried out under CO atmosphere for 0.2 h. The direct reduced iron with a metallization rate of 95% drips from the coke layer and then stops heating. , Ar inert gas is introduced, the blast furnace slag is transformed into microcrystalline powder due to rapid cooling after Ar is introduced, and then the coke and powdered slag are discharged, and a cyclone centrifuge is used to separate the coke from the powdery slag and coke ash. The compressive strength is greater than 25kg and can be reused for the next preparation of direct reduced iron. The tail gas is discharged from the top of the furnace, and the introduced reducing gas will pass through a large number of pore structures distributed in the retort briquettes and undergo a rapid reduction reaction with the valuable Fe in the briquettes. The tail gas generated during the reaction process is treated with dust removal and activated carbon adsorption. The high-temperature gas after _CO2 removal is reused for high-temperature direct reduction of iron to reduce heat loss. Activated carbon adsorbs and removes polycyclic aromatic hydrocarbons and benzene in the exhaust gas, and the temperature of the reused high-temperature gas reaches 200°C.

Example 2:

A method for treating coking wastewater sludge, including 40 parts of coke powder, 30 parts of iron ore powder, 30 parts of coking wastewater sludge, 10 parts of tar residue and 10 parts of solvent. Among them, the coke powder is mainly screened coke dusted coke powder, with a fixed carbon content of 78%, an ash content of 13.5%, and a moisture content of 0.5%. The coke powder is all pre-ground to less than 0.5mm, and the carbon-containing sludge mainly comes from water-quenched coke. The fixed carbon content of pond wastewater sludge is 35%, and the Fe ₂ O ₃ content in ash is 5%. The coking wastewater sludge should be dried until the moisture content does not exceed 3%, and the solvent is CaCO ₃ .

After mixing the above materials, use a 2000N press to extrude them into flat pellets with a particle size of 20mm;

Cold-consolidate the formed flat agglomerates into agglomerates. The compressive strength of the consolidated agglomerates is 800N. Dry at low temperature. The moisture content of the cold-consolidated agglomerates is 1%. The cold-consolidation temperature is 50°C to prevent excessive temperature. High occurrence of cracks;

Under the cold-solidified briquettes, coke dices with a particle size of 15 mm and a compressive strength of 30 kg were laid. The dried briquettes and coke dices were layered in a high-temperature furnace and roasted at 500°C for 5 hours under Ar inert gas. After heating, Dry the briquettes to obtain retort briquettes. The material volume density of the retort briquettes is 1.5g/cm ³ , the compressive strength is 50kg, and the iron grade reaches 61%. During the low-temperature reduction roasting process, due to the moisture in the coking wastewater sludge And volatilization analysis will make the retort briquettes have a large number of pore structures, and the porosity reaches 50%. The coke can ensure the reducing atmosphere during the reaction process, filter the slag powder, and prevent the slag powder from dripping along with the direct reduced iron.

Continue to raise the temperature to 1350°C. The solvent CaCO ₃ promotes the formation of the liquid phase in the retort briquettes. Direct reduction is carried out under CO atmosphere for 3 hours. The direct reduced iron with a metallization rate of 90% drips from the coke layer and then stops heating. , N ₂ inert gas is introduced, and the blast furnace slag is transformed into microcrystalline powder due to rapid cooling after N ₂ is introduced, and then the diced coke and powdered slag are discharged, and a cyclone centrifuge is used to separate the diced coke, powdery slag, and coke ash. Coke diced with a compressive strength greater than 30kg can be reused for the next preparation of direct reduced iron. The tail gas is discharged from the top of the furnace, and the introduced reducing gas will pass through a large number of pore structures distributed in the retort briquettes and undergo a rapid reduction reaction with the valuable Fe in the briquettes. The tail gas generated during the reaction process is treated with dust removal and activated carbon adsorption. The high-temperature gas after _CO2 removal is reused for high-temperature direct reduction of iron to reduce heat loss. Activated carbon adsorbs and removes polycyclic aromatic hydrocarbons and benzene in the exhaust gas, and the temperature of the reused high-temperature gas reaches 250°C.

Example 3:

A method for treating coking wastewater sludge, which includes 50 parts of coke powder, 35 parts of iron ore powder, 25 parts of coking wastewater sludge, 3 parts of tar residue, and 12 parts of solvent. Among them, the coke powder is mainly dry-quenched coke secondary dust removal coke powder, with a fixed carbon content of 80%, an ash content of 14.5%, and a moisture content of 1%. The coke powder is all pre-ground to less than 200 mesh, and the carbon-containing sludge mainly comes from water quenching. The coking tank wastewater sludge has a fixed carbon content of 30% and an ash Fe ₂ O ₃ content of 15%. The coking wastewater sludge should be dried until the moisture content does not exceed 5%, and the solvent is Ca(OH) ₂ .

After mixing the above materials, use a 1500N press to extrude them into flat pellets with a particle size of 10mm;

Cold-consolidate the formed flat agglomerates into agglomerates. The compressive strength of the consolidated agglomerates is 1000N. Dry at low temperature. The moisture content of the cold-consolidated agglomerates is 1.5%. The cold-consolidation temperature is 35°C to prevent excessive temperature. High occurrence of cracks;

Under the cold-solidified briquettes, coke dices with a particle size of 20mm and a compressive strength of 30kg were laid. The dried briquettes and coke dices were layered in a high-temperature furnace, roasted at 800°C for 0.5h under Ar inert gas, and heated. The briquettes are then dried to obtain retort briquettes. The material volume density of the retort briquettes is 2.5g/cm ³ , the compressive strength is 50kg, and the iron grade reaches 63%. During the low-temperature reduction roasting process, due to the water in the coking wastewater sludge The components and volatilization are analyzed, which will make the retort briquettes have a large number of pore structures, and the porosity reaches 10%. The coke can ensure the reducing atmosphere during the reaction process, filter the slag powder, and prevent the slag powder from dripping along with the direct reduced iron.

Continuing to raise the temperature to 1550°C, the solvent CaCO ₃ promotes the generation of the liquid phase in the retort briquettes, and direct reduction is carried out under CO atmosphere for 0.2 h. The direct reduced iron with a metallization rate of 96% drips from the coke layer and then stops. Heating, N ₂ inert gas is introduced, the blast furnace slag is quenched after N ₂ is introduced, and is transformed into microcrystalline powder, and then the diced coke and powdered slag are discharged, and a cyclone centrifuge is used to separate the diced coke, powdery slag, and coke ash. , the compressive strength of coke butin is greater than 35kg and can be reused for the next preparation of direct reduced iron. The tail gas is discharged from the top of the furnace, and the introduced reducing gas will pass through a large number of pore structures distributed in the retort briquettes and undergo a rapid reduction reaction with the valuable Fe in the briquettes. The tail gas generated during the reaction process is treated with dust removal and activated carbon adsorption. The high-temperature gas after _CO2 removal is reused for high-temperature direct reduction of iron to reduce heat loss. Activated carbon adsorbs and removes polycyclic aromatic hydrocarbons and benzene in the exhaust gas, and the temperature of the reused high-temperature gas reaches 200°C.

In summary, the experiments show that when the temperature is raised to 1350°C, the direct reduced iron can be separated from the briquettes and dripped through the coke layer. The gas is cooled to achieve amorphous powdering of the liquid slag and the separation of slag and iron. The smelting temperature is much lower than that of traditional blast furnace smelting. Iron temperature is low. In addition, increasing the direct reduction temperature can increase the metallization rate of direct reduced iron. This solution not only realizes the recycling of metallic iron in wastewater sludge, but also recovers inorganic substances in sludge and tar residue. The hazardous waste of tar residue is treated harmlessly, increases the added value of coke powder utilization, and realizes the recovery of organic waste and inorganic waste. Comprehensive utilization of waste.

Claims (9)

1. The method for treating the coking wastewater sludge is characterized by comprising the following steps of:

1) Uniformly mixing coke powder, iron ore powder, coking wastewater sludge, tar slag and solvent, extruding into a block, cold solidifying the block at room temperature, and drying until the water content is not more than 2%, wherein the compression strength of the cold solidified block is not less than 500N;

2) Roasting the dried briquette obtained in the step 1) at 500-800 ℃ under the protection of oxygen-free or inert gas for 0.5-5 hours, paving a diced coke under the dried briquette, and roasting to obtain a dry distillation briquette;

3) Continuously heating to 1350-1550 ℃, introducing reducing gas to directly reduce for 0.2-3 h, and further generating direct reduced iron and slag, wherein the direct reduced iron is in a liquid state and directly drops;

4) Then stopping heating and introducing N ₂ Or Ar, slag meets normal temperature N ₂ Or Ar is cooled to be amorphous powder, and after the Ar is completely cooled, cyclone centrifugal separation is adopted to separate slag powder from the coke breeze.

2. The method for treating coking wastewater sludge according to claim 1, wherein the coke powder comprises dry quenching primary dust-removing coke powder, secondary dust-removing coke powder and screening and transporting coke powder, wherein the fixed carbon content is more than or equal to 78%, the coke powder granularity is less than or equal to 1mm, the ash content is less than or equal to 15%, and the water content is less than or equal to 1.0%; the coking wastewater sludge is from coking product recovery wastewater or water quenching Jiao Jiaochi wastewater, the fixed carbon content is more than or equal to 25%, and Fe in ash is contained in the coking product recovery wastewater or water quenching Jiao Jiaochi wastewater ₂ O ₃ The content is not less than 5%; the solvent comprises CaO, caCO ₃ 、Ca(OH) ₂ One or more of the following.

3. The method for treating coking wastewater sludge according to claim 1, wherein the raw material ratio in the step 1) is as follows in parts by weight: 30-60 parts of coke powder, 20-40 parts of iron ore powder, 5-35 parts of coking wastewater sludge, 3-10 parts of tar residues and 3-15 parts of solvent.

4. The method for treating coking wastewater sludge according to claim 1, wherein the cold setting temperature in the step 1) is not more than 30 ℃ and the drying temperature is not more than 60 ℃.

5. The method for treating coking wastewater sludge according to claim 1, wherein the agglomerate in the step 1) is a flat agglomerate having a particle diameter of 10mm to 20mm, and wherein the water content of the coking wastewater sludge is not more than 5%.

6. The method for treating coking wastewater sludge according to claim 1, wherein the granularity of the coke oven-dried powder paved below the drying agglomerate in the step 2) is more than or equal to 10mm, and the compressive strength of the coke oven-dried powder is more than or equal to 25kg; the bulk density of the dry distilled lump is 1.5-3.5 g/cm ³ The compressive strength is more than or equal to 40kg, the iron grade is more than 60%, and the porosity is 10% -50%.

7. The method for treating coking wastewater sludge according to claim 1, wherein the metallization rate of the direct reduced iron in the step 4) is not less than 90%.

8. The method for treating coking wastewater sludge according to claim 1, wherein the tail gas generated in the reaction process is treated by dust removal and activated carbon adsorption, and CO ₂ The removed reducing gas can be repeatedly used in the step 3), and the temperature of the repeatedly used high-temperature gas is not lower than 200 ℃.

9. The method for treating coking wastewater sludge according to claim 8, wherein said reducing gas is H ₂ Or CO or H ₂ And CO mixed gas.