Research and feasibility of sludge ceramsite technology

Sludge ceramsite is an artificial lightweight coarse aggregate. Due to its light weight, high strength and thermal insulation properties, it is a new type of building material with development potential. The modified sludge can be made into ceramsite as a building material. The preparation of sludge ceramsite is the use of clay and slag as auxiliary materials, sludge as the main raw material, and the filter material with certain hardness and adsorption capacity formed by roasting and forming into balls, which can be applied to sewage treatment. Sludge ceramsite has also been successfully developed using sludge, clay and a certain amount of fuel. Sludge ceramsite is an important member of lightweight aggregates and is currently the most widely used form. Sludge ceramsite firing is generally carried out by rotary kiln incineration process, matching raw material preparation, sludge dewatering, drying, grinding, kiln ball formation, kiln ball formation, firing thermal engineering, screening grading, raw material testing Control, finished product inspection and its appropriate firing technology, equipment support, automatic control.

The technology of making ceramsite from sludge in the 1980s has matured abroad. At present, there are mature processes in China. However, the technical process needs to establish an independent incinerator in the construction, the investment operation cost is large, the organic components of the sludge cannot be completely decomposed and utilized, and even some of the finished ceramics have insufficient swelling property. It can be used for reference to foreign crafts, fine-tuning the process, and testing the physical properties and leaching solution of the sludge ceramsite after the finished product to reach the standard of ceramics as building materials.

There are three kinds of substances in the process of forming ceramics. One type of materials are: SiO2, Al2O3 and Fe2O3, which account for a large proportion of sludge raw materials. In addition, the flux oxides that act as fluxing are: Na2O, K2O. , FeO, MgO, the third is a gas-generating substance, which generates gas when the material reaches a high temperature, such as water vapor, carbon dioxide, oxygen, carbon monoxide, hydrogen, etc., when the sludge is calcined, gas is generated, and the corresponding process flow is combined with the auxiliary agent. It is technically feasible to inflate the ball to achieve the ceramsite requirements, but it is necessary to find the best sintering plan for the sludge making and control the process parameters.

/by

Brief introduction of sludge anaerobic digestion technology and analysis of its advantages and disadvantages

Anaerobic digestion of sludge refers to the process of decomposing biodegradable organic matter in sludge into carbon dioxide, methane and water by facultative bacteria and anaerobic bacteria under anaerobic conditions to stabilize the sludge. It is one of the commonly used means of sludge reduction and stabilization. Anaerobic digestion of sludge has the advantages of reducing sludge volume, stabilizing sludge properties, and generating methane gas.

Traditional sludge anaerobic digestion has the disadvantages of slow reaction, low degradation rate of organic matter and low methane production, which limits the advantages of sludge anaerobic digestion technology. According to Bryant’s three-stage theory, sludge hydrolysis is the rate-limiting step in sludge anaerobic digestion. Therefore, since the 1970s, various sludge anaerobic digestion enhancement technologies including high temperature thermal hydrolysis, ultrasonic pretreatment, alkaline hydrolysis pretreatment and ozone pretreatment have been studied. The cell wall of the sludge transfers the intracellular organic matter from the solid phase to the liquid phase, promotes sludge hydrolysis, and improves the anaerobic digestion effect of the sludge.

As the amount of sludge in various countries continues to increase and the demand for energy and the quality of treated sludge continue to increase, some of the original sludge anaerobic digestion facilities are facing expansion and transformation. Sludge pretreatment technology can improve the anaerobic digestion effect of sludge, improve sludge dewatering effect and increase biogas production. It can replace the benefit of digestive tank expansion to a certain extent, so it has been widely used in research and application. Among them, the high-temperature thermal hydrolysis technology of sludge is relatively mature. At present, this technology has developed various processes such as Cambi thermal hydrolysis, Biothelysis thermal hydrolysis and Monsal enzymatic hydrolysis, which have been popularized and applied in Europe in recent years, Norway, the United Kingdom and Australia has successfully applied cases.

In view of the limitation of low solid content of traditional sludge anaerobic digestion, research on high-solid sludge anaerobic digestion technology has also become a hot spot. The advantage of high-solids sludge anaerobic digestion is that the biogas production efficiency is higher than the traditional anaerobic digestion, because the solid content of the sludge is greatly increased, and the amount of organic matter in the sludge anaerobic digestion tank can be contacted and digested. As a result, the gas production efficiency and processing load are also increased. At present, a variety of high-solid sludge anaerobic digestion technologies have been developed in foreign countries, and have been applied in practical projects. For example, the Finnish HLAD process controls the sludge solid content into the pre-reaction tank by 10% to 15%. Gas production efficiency is 30% higher than traditional sludge anaerobic digestion.

Advantages of sludge anaerobic digestion technology:

  • The sludge anaerobic digestion process can kill some pathogenic bacteria and parasite eggs, so that the sludge is stabilized and not rancid.
  • The anaerobic digestion process of the sludge produces biogas, which can effectively recover the sludge biomass energy.
  • Sludge anaerobic digestion can degrade 35%~50% volatile solids in sludge, reduce the dry solids of sludge, and help reduce the cost of subsequent sludge treatment and disposal. At the same time, sludge anaerobic digestion helps to improve sludge dewatering performance, and the sludge volume can be further reduced after dewatering.

Disadvantages of sludge anaerobic digestion technology:

  • Maintaining the temperature required for anaerobic digestion of sludge requires a significant amount of heat.
  • Sludge anaerobic digestion process has a long residence time, usually reaching 20~30d, resulting in a large volume of sludge anaerobic digestion tank and complicated operation and management.
  • Methanogenic bacteria require high environmental conditions, and must be cultured in the start-up phase, with initial initial debugging time.
  • The sludge moisture content after sludge anaerobic digestion is still high, and must be followed up. Commonly used methods are heat drying and deep dewatering.

 

/by

New dry process cement production line process

The new dry-process cement production line technology was developed in the 1950s. So far, in Japan, Germany and other developed countries, the production rate of new dry-process cement clinker with suspension preheating and pre-decomposition as the core accounted for 95%. A suspension preheating and precalcining kiln was commissioned in 1976. The advantages of this technology: rapid heat transfer, high thermal efficiency, large volume per unit volume of wet cement, and low heat consumption. Development stage: The first stage, from the 1950s to the early 1970s, was the birth and development stage of suspension preheating technology. The second stage, in the early 1970s, was the birth and development stage of pre-decomposition technology.

Process steps of the new dry process cement production line: crushing and pre-homogenization → raw material preparation → raw material homogenization → preheating decomposition → cement clinker burning → cement grinding → cement packaging.

First, Cement production of raw fuel and ingredients

The main raw materials for the production of Portland cement are lime raw materials and clay raw materials. Sometimes, according to fuel quality and cement varieties, correcting raw materials are added to supplement the deficiency of certain components, and industrial waste residue can also be used as raw materials or mixed materials of cement. in production.

1. Limestone raw materials

The calcareous raw material refers to limestone, marl, chalk and shells containing calcium carbonate as a main component. Limestone is the main raw material for cement production. Each production – ton of clinker requires about 1.3 tons of limestone, and more than 80% of the raw meal is limestone.

2. Clay raw materials

Clay raw materials mainly provide a small amount of cement clinker. Natural clay materials include loess, clay, shale, siltstone and river mud. Among them, loess and clay are used the most. In addition, there are industrial wastes such as fly ash and coal gangue. Clay is a finely dispersed sedimentary rock composed of different minerals such as kaolin, montmorillonite, hydromica and other hydrated aluminosilicates.

3. Correcting raw materials

When the raw material composition of the calcareous raw material and the clay raw material can not meet the requirements of the batching scheme (some content is insufficient, some and the content is insufficient), the corresponding calibration raw materials must be added according to the missing components: (1) siliceous The calibration raw material contains more than 80%; (2) the aluminum-corrected raw material contains more than 30%; and (3) the iron-corrected raw material contains more than 50%.

Second, the mineral composition of Portland cement clinker

The mineral of the Portland cement clinker is mainly composed of tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite.

Third, the process

1. Fragmentation and pre-homogenization

(1) In the process of crushing cement production, most of the raw materials are crushed, such as limestone, clay, iron ore and coal. Limestone is the raw material for producing the largest amount of cement. After mining, the particle size is larger and the hardness is higher. Therefore, limestone is the raw material for producing the largest amount of cement. After mining, the particle size is larger and the hardness is higher. Therefore, the limestone is crushed in the cement plant. The fragmentation plays a more important role. The crushing process is economical and convenient than the grinding process. It is very important to use crushing equipment and grinding equipment reasonably. Before the material enters the grinding equipment, the bulk material is broken into small and uniform particle size as much as possible to reduce the load of the grinding equipment and increase the output of the corrosion machine. After the material is crushed, the separation of materials of different particle sizes during transportation and storage can be reduced, and the raw materials with uniform composition can be obtained, and the accuracy of the ingredients can be improved.

(2) Raw material pre-homogenization pre-homogenization technology is to use the scientific stacking and reclaiming technology to realize the initial homogenization of raw materials in the process of depositing and taking raw materials, so that the raw material storage yard has the functions of storage and homogenization. The basic principle of raw material pre-homogenization is that when the materials are stacked, the incoming raw materials are continuously stacked in a certain manner into as many parallel layers, upper and lower overlaps and the same thickness. When taking the material, in the direction perpendicular to the layer of the material, all the layers are cut as much as possible, and cut in order, until the end is taken, that is, “tiling straight”.

Significance:

A. Homogenize raw material components, reduce quality fluctuations, facilitate the production of higher quality clinker, and stabilize the production of the firing system.

B. Expand the utilization of mine resources, improve mining efficiency, maximize the coverage of the mine and the interlayer, and produce no or less waste rock during the mining process.

C. It is possible to relax the quality and control requirements of mining and reduce the mining cost of the mine.

D. It has strong adaptability to sticky materials.

E. Provide long-term stable raw materials for the factory. It is also possible to mix the raw materials of different components in the yard to make it a pre-mixing yard, creating conditions for stable production and improved equipment operation rate.

F. High degree of automation.

2. Raw material preparation

In the cement production process, at least 3 tons of materials (including various raw materials, fuels, clinker, mixture, gypsum) should be ground for every ton of Portland cement produced. According to statistics, the dry cement production line needs to be consumed. The power accounts for more than 60% of the power of the whole plant, of which raw material grinding accounts for more than 30%, coal grinding accounts for about 3%, and cement grinding accounts for about 40%. Therefore, rational selection of grinding equipment and process, optimization of process parameters, correct operation, and control of operating systems are of great significance for ensuring product quality and reducing energy consumption.

Working principle:

The electric motor drives the grinding disc to rotate through the speed reducing device, and the material is dropped into the center of the grinding disc through the wind-feeding device through the wind-locking feeding device, and is crushed by the grinding roller under the action of the centrifugal force, and the crushed material is rubbed from the grinding disc. The edge overflows and is dried by the hot air flow from the nozzle at a high speed. According to the different air flow speed, part of the material is taken by the air flow to the high-efficiency classifier, and the coarse powder is separated and returned to the grinding disc for re-grinding; The powder is ground with the airflow and collected in the system dust collecting device, which is the product. The coarse-grained material that has not been taken up by the hot air is fed to the classifier by the bucket elevator that is externally circulated after overflowing the grinding disc, and the coarse particles fall back to the grinding disc and are again squeezed and ground.

3. Raw material homogenization

In the process of new dry process cement production, the stable raw material composition is the premise of stable clinker burning thermal system, and the raw material homogenization system plays the role of stabilizing the raw material composition.

Homogenization principle: air agitation and gravity are used to produce a “funnel effect”, so that when the raw meal powder is discharged downward, the multi-layered material surface is cut as much as possible and thoroughly mixed. Different fluidizing air is used to cause different sizes of fluidization expansion in the parallel material surface of the reservoir. Some areas are unloaded and some areas are fluidized, so that the inner surface of the reservoir is inclined and radially mixed and homogenized.

4. Preheat decomposition

The preheating and partial decomposition of the raw material are completed by the preheater, instead of the partial function of the rotary kiln, the length of the return kiln is shortened, and the gas heat exchange process in the kiln is carried out in a stacked state, and moved to the preheater. The suspension is carried out in a state of being suspended, so that the raw material can be thoroughly mixed with the hot gas discharged from the kiln, the contact area of ​​the gas material is increased, the heat transfer speed is fast, and the heat exchange efficiency is high, thereby improving the production efficiency of the kiln system and reducing the heat of clinker burning. The purpose of consumption.

Working principle:

The main function of the preheater is to make full use of the residual heat of the exhaust gas discharged from the rotary kiln and the decomposition furnace to heat the raw material, so that the raw material is preheated and some carbonate is decomposed. In order to maximize the heat exchange efficiency between the gas and solid, to achieve high quality, high yield and low consumption of the entire calcination system, it is necessary to have three functions of uniform gas-solid dispersion, rapid heat transfer and high-efficiency separation.

(1) Material dispersion

80% of the heat transfer takes place in the inlet pipe. The raw material fed into the preheater pipe, under the impact of the high-speed updraft, the material turns and moves with the airflow while being dispersed.

(2) Gas-solid separation

When the airflow carries the powder into the cyclone, it is forced to rotate in the annular space between the cyclone cylinder and the inner cylinder (exhaust pipe), and rotates side-down, from the cylinder to the cone The body can extend to the end of the cone and then rotate upwards upwards and exit by the exhaust pipe.

(3) Pre-decomposition

The emergence of pre-decomposition technology is a technological leap in the cement calcination process. It is a decomposing furnace added between the preheater and the rotary kiln, and a flue gas is used to raise the flue by the kiln tail, and a fuel injection device is provided to make the exothermic process of burning the fuel and the endothermic carbonate decomposition process. The furnace is rapidly carried out in a suspended state or a fluidized state, so that the decomposition rate of the raw material into the kiln is increased to 90% or more. The carbonate decomposition task originally carried out in the rotary kiln is moved to the decomposition furnace; most of the fuel is added from the decomposition furnace, and a small part is added by the kiln head, which reduces the heat load of the calcination zone in the kiln and extends the lining. The material life is conducive to the large-scale production. Because the fuel and the raw material are uniformly mixed, the fuel combustion heat is transferred to the material in time, and the combustion, heat exchange and carbonate decomposition processes are optimized. Therefore, it has a series of excellent performances and features such as high quality, high efficiency and low consumption.

4. Burning of cement clinker

After the raw material is preheated and pre-decomposed in the cyclone preheater, the next step is to enter the rotary kiln for clinker firing. In the rotary kiln, the carbonate is further rapidly decomposed and a series of solid phase reactions occur to form minerals in the cement clinker. As the temperature of the material rises, the minerals become liquid, and the dissolved in the liquid phase reacts to form a large amount (clinker). After the clinker is fired, the temperature begins to decrease. Finally, the cement clinker cooling machine cools the high temperature clinker discharged from the rotary kiln to the temperature that can be withstood by the downstream conveying, storage and cement grinding, and recovers the sensible heat of the high temperature clinker to improve the thermal efficiency and clinker quality of the system.

5. Cement grinding

Cement grinding is the last step in cement manufacturing and the most energy-intensive process. Its main function is to grind cement clinker (and gelling agent, performance adjusting material, etc.) to a suitable particle size (expressed by fineness, specific surface area, etc.) to form a certain particle gradation and increase its hydration area. Accelerate the hydration speed to meet the requirements of cement slurry condensation and hardening.

6. Cement packaging

The cement is shipped in both bagged and bulk shipping modes.

/by

Analysis of related technologies and advantages and disadvantages of sludge treatment and disposal

At present, the treatment and disposal technology of sludge mainly refers to the processing of concentration, regulation, dehydration, stabilization, drying or incineration of sludge to achieve sludge reduction, stabilization and harmlessness. At present, the commonly used sludge treatment and disposal technologies include anaerobic digestion technology, aerobic fermentation technology, deep dehydration technology, thermal drying technology, lime stabilization technology and incineration technology.

1. Anaerobic digestion technology

Anaerobic digestion of sludge refers to the process of decomposing biodegradable organic matter in sludge into carbon dioxide, methane and water by facultative bacteria and anaerobic bacteria under anaerobic conditions to stabilize the sludge. It is one of the commonly used means of sludge reduction and stabilization. Anaerobic digestion of sludge has the advantages of reducing sludge volume, stabilizing sludge properties, and generating methane gas.

Traditional sludge anaerobic digestion has the disadvantages of slow reaction, low degradation rate of organic matter and low methane production, which limits the advantages of anaerobic digestion technology. According to Bryant’s three-stage theory, hydrolysis is the rate-limiting step in sludge anaerobic digestion. Therefore, since the 1970s, various sludge anaerobic digestion enhancement technologies including high temperature thermal hydrolysis, ultrasonic pretreatment, alkaline hydrolysis pretreatment and ozone pretreatment have been studied. The cell wall of the sludge transfers the intracellular organic matter from the solid phase to the liquid phase, promotes sludge hydrolysis, and improves the anaerobic digestion effect of the sludge.

As the amount of sludge in various countries continues to increase and the demand for energy and the quality of treated sludge continue to increase, some of the original sludge anaerobic digestion facilities are facing expansion and transformation. Sludge pretreatment technology can improve the anaerobic digestion effect of sludge, improve sludge dewatering effect and increase biogas production. It can replace the benefit of digestive tank expansion to a certain extent, so it has been widely used in research and application. Among them, high temperature thermal hydrolysis technology is relatively mature. At present, this technology has developed various processes such as Cambi thermal hydrolysis, Biothelysis thermal hydrolysis and Monsal enzymatic hydrolysis. It has been promoted and applied in Europe in recent years, Norway, Britain and Australia. There are cases of successful application.

In view of the limitation of low solid content of traditional sludge anaerobic digestion, research on high-solid sludge anaerobic digestion technology has also become a hot spot. The advantage of high-solids sludge anaerobic digestion is that the biogas production efficiency is higher than the traditional anaerobic digestion, because the solid content of the mud is greatly increased, and the amount of organic matter that can be contacted and digested by the unit microbial biomass in the anaerobic digester is greatly improved. Its gas production efficiency and processing load also increase. At present, a variety of high-solid sludge anaerobic digestion technologies have been developed in foreign countries, and have been applied in practical projects. For example, the Finnish HLAD process controls the sludge solid content into the pre-reaction tank by 10% to 15%. Gas production efficiency is 30% higher than traditional sludge anaerobic digestion.

Technical advantages:

The anaerobic digestion process can kill some pathogenic bacteria and parasite eggs, so that the sludge is stabilized and not rancid.

The anaerobic digestion process produces biogas, which enables efficient recovery of sludge biomass energy.

Anaerobic digestion can degrade 35%~50% volatile solids in sludge, reduce the dry solids of sludge, and help reduce the cost of subsequent sludge treatment and disposal. At the same time, anaerobic digestion helps to improve sludge dewatering performance, and the sludge volume can be further reduced after dewatering.

Technical disadvantages:

Maintaining the temperature required for anaerobic digestion requires a significant amount of heat.

The sludge anaerobic digestion process has a long residence time, usually reaching 20~30d, resulting in a large volume of anaerobic digestion tank and complicated operation and management.

Methanogenic bacteria require high environmental conditions, and must be cultured in the start-up phase, with initial initial debugging time.

After anaerobic digestion, the moisture content of the sludge is still high, and must be followed up. Commonly used methods are heat drying and deep dewatering.

2. Aerobic fermentation technology

Aerobic fermentation is a process in which, under aerobic conditions, microorganisms oxidize a portion of the absorbed organic matter into a simple inorganic substance through absorption, oxidation, decomposition, etc., while releasing the energy required for microbial growth activities; and another part of the organic matter. It is then synthesized into a new cytoplasm, allowing microorganisms to grow and multiply, producing more organisms. High-temperature aerobic fermentation of sludge continuously decomposes organic matter, so that the temperature of the heap is continuously increased, and the pathogenic bacteria and parasitic eggs can be killed and rendered harmless. The high-temperature aerobic fermentation of sludge is called compost and can be used as a soil improver and organic fertilizer. High-temperature aerobic fermentation of sludge should pay attention to the problem of heavy metal pollution of sludge. During the treatment, due to the action of aerobic bacteria, it is easy to produce malignant odor. Therefore, odor pollution should be prevented. The moisture content of sludge after treatment can generally be less than 40%.

At present, the main process forms of sludge composting are divided into static and dynamic, and can be divided into strip type and warehouse type according to the material stacking form. Other reactors in the form of reactors are generally used in small projects.

There are five main aspects that restrict the industrial application of sludge composting technology: floor space, secondary pollution caused by odor discharge, dry material feeding and safe storage and transportation, final sludge disposal and operator health and safety. problem. Compared with the static composting process, the dynamic composting process has made certain breakthroughs in these five aspects. On the basis of mechanical turning technology and forced venting static composting technology, China has developed a complete set of CTB automatic control biological composting technology with independent intellectual property rights. This technology composts short time, small floor space, no odor, waste water, etc. Environmental pollution problems, technical integrity and support. The newly developed sludge aerobic composting process (SACT) is based on the theory of horizontal open fermentation tanks, which is improved and innovated through the construction of structures, improvement of mechanical turning equipment, and adoption of automatic entry and exit systems. The theory of automated composting system further reduces investment and operating costs in engineering applications and achieves good engineering results.

Technical advantages:

The aerobic fermentation process can kill pathogenic bacteria and weed seeds in the sludge and achieve harmlessness.

The aerobic fermentation process can degrade most of the organic matter in the sludge and reduce the moisture content of the sludge to 40%, which is reduced.

The fertilizer produced after aerobic fermentation can be applied to the land to achieve resource utilization.

No external heating source is required and the operating cost is relatively low.

Technical disadvantages:

The sludge mud is unstable, and heavy metals are difficult to stabilize. The surface is narrow and can only be used as a landscaping fertilizer.

Large footprint.

A large amount of odor is generated during the composting process, which pollutes the surrounding environment.

3. Deep dewatering technology

In recent years, sludge dewatering technology has been greatly developed, and technological breakthroughs have focused on the development of conditioning agents before sludge dewatering and the improvement of dewatering machinery and equipment. At present, using sludge chemical conditioning + mechanical dewatering technology, sludge conditioning agent is added to the wet sludge raw mud to destroy the microbial structure of the sludge floc and dissolve, and the physical combined water is separated. The moisture of the organism of the microorganism is separated, and finally the majority of the bound water in the sludge is converted into free water, and the free state water is separated by a mechanical dehydration device. The technology has been applied in large scale in sludge treatment of tannery sewage treatment plant. The moisture content of sludge after treatment can be less than 50%. In order to meet the requirements of sludge subsequent treatment and disposal, it is necessary to further reduce the moisture content of conventional mechanical dewatered sludge. .

The quenching and tempering treatment of sludge is the key link and core technology for deep dewatering of sludge. It can be said that sludge conditioning technology determines the success or failure of sludge deep dewatering project. There are many methods for quenching and tempering domestic sludge. It is common to add dehydrating agent, flocculant or coagulant to the sludge to change the existence and structure of water molecules (mainly interstitial water and capillary water) in the sludge. Conducive to the separation of water and mud under certain conditions. Commonly used conditioning agents are ferric chloride (or ferric sulfate, polymeric ferric sulfate) plus quicklime.

The sludge deep dewatering equipment is mainly a high pressure diaphragm plate frame filter press. By applying pressure from the outside of the sludge, the moisture in the quenched and tempered sludge is leached and separated to obtain a mud cake having a high solid content. There are many domestic equipment manufacturers, and the brand awareness is higher. The equipment performance is better in Shandong Jingjin and Hangzhou Xingyuan. The equipment manufacturing process and quality have been improved.

Technical advantages: good reduction effect, low energy consumption, small floor space, short construction period and short processing time.

Technical disadvantages: Ferric chloride is highly corrosive, and quicklime is easy to scale. As a result, the high-pressure diaphragm frame filter press has high operation and maintenance costs, stable and insufficient sterilization, slightly odor, and the organic matter content in the sludge is not reduced.

4. Sludge thermal drying technology

The thermal drying of sludge refers to the process of removing moisture from the sludge through the heat transfer between the sludge and the heat medium. The sludge thermal drying system mainly includes the storage and transportation system, the drying system, the exhaust gas purification and treatment system, the electrical self-control instrument system and its auxiliary system.

According to the degree of drying of the sludge, it is divided into two types: full drying and semi-drying. “Full drying” refers to the type of higher solid content, such as the solid content of sludge after drying is more than 85%; Semi-drying mainly refers to the type of sludge with a solid content of about 45 to 60% after drying. In the form of sludge drying, the sludge is divided into direct drying and indirect drying. Direct drying is to directly contact the sludge with a hot drying medium (such as flue gas) to transfer heat in a convective manner. And take away the evaporated water, also known as the heat convection drying system; indirect drying is the use of conduction means by the heat medium (such as steam) through the metal wall to transfer heat to the sludge, the evaporated water through the carrier gas (such as air Take away and wash the condensation, also known as the heat transfer drying system.

At present, the drying machines used for sludge drying mainly include: convection heat transfer fluidized bed dryer, drum dryer, belt dryer, conduction heating rotary disc dryer, paddle Dryer, turbofilm drying machine combined with convection and conduction heating.

The sludge is significantly reduced in volume and the volume can be reduced by about 4 times.

After the drying treatment, a stable product can be formed, and the sludge property is greatly improved.

The dried product is odorless and free of pathogens, reducing the negative effects associated with sludge and making the treated product more acceptable.

The dried product is used for a variety of purposes, such as fertilizers, soil amendments, alternative energy sources, and the like.

Technical disadvantages:

Large investment, high energy consumption and high operating costs.

Drying at high temperatures is prone to odor.

The dust control in the drying process is strict and there are safety hazards.

5. Lime stabilization technology

By adding a certain proportion of quicklime to the dewatered sludge and uniformly blending, the quicklime reacts with the moisture in the dewatered sludge to form calcium hydroxide and calcium carbonate and release heat. Lime stabilization technology can effectively deodorize, sterilize, inhibit corrosion, dehydration, and passivate heavy metal ions.

The typical process is as follows: sludge with a water content of 80% is sent from the screw conveyor to the silo for temporary storage, and the sludge and quicklime are respectively sent to the material reaction system according to the ratio of mass ratio of 4:1 by the metering and conveying device. In the material reaction system, the sludge and quicklime react and react, so that the temperature in the system is rapidly increased to 100 degrees, and the water in the sludge is evaporated in a large amount to complete the drying and dehydration process of the sludge. The dried sludge is transported to an outdoor stacking shed by a double screw mixer for storage and storage. In order to prevent secondary pollution in the sludge drying process, the treatment of the discharged lime dust and malodorous gas can be realized by adding dust removal and deodorization equipment.

In practical applications, in addition to adding lime, other excipients are often added to enhance the effect. Some of these excipients contain N, increase the production of NH3 gas, strengthen sterilization and facilitate land use; some are strong acid iron and aluminum salts. The reaction temperature is increased and the ratio of solid inorganic components is more suitable for building materials utilization; generally it is acidic, in addition to increasing the exotherm, the pH can be moderately adjusted, and the common effect is to reduce the amount of lime added and save costs.

Technical advantages:

The investment is small, the running cost is low, the floor space is small, and the operation and management are simple.

It can effectively eliminate bacteria and there is no risk of bacterial regeneration.

The dried product is rich in a large amount of calcium hydroxide, silicon oxide, calcium carbonate and the like, and can be used as a base material for building materials, a road infrastructure auxiliary material, a cushion soil for a landfill, and a backfill for road construction.

The lime stabilized sludge has a high pH value and can be used as a desulfurizing agent for incineration equipment.

Especially suitable for emergency or phased disposal.

Technical disadvantages:

Due to the large amount of lime added, the degree of reduction is not high compared to other processes.

It is strongly alkaline, with low land use value and narrow surface.

The drug use fee is high.

6. Sludge incineration technology

Sludge incineration refers to the conversion of organic matter in sludge to CO2, H2O, N2, etc. under a certain temperature and sufficient aerobic conditions. The heat released during the reaction is used to maintain the temperature conditions of the reaction. Sludge incineration is the most thorough sludge treatment method. It removes all organic matter, kills all pathogens, and minimizes sludge volume.

Sludge incineration generally adopts fluidized bed process and is divided into fixed (bubble) fluidized bed incinerator, circulating fluidized bed incinerator and rotary fluidized bed incinerator. The flue gas from sludge incineration should be treated and meet the relevant regulations of the Domestic Waste Incineration Pollution Control Standard. The ash from sludge incineration and the fly ash collected by dust removal equipment should be collected, stored and transported separately. The state encourages the comprehensive utilization of slag that meets the requirements: fly ash needs to be properly disposed of after identification. The sludge incineration process is widely used in large and medium-sized cities with more developed economies. Generally, the combined use of dry incineration is used to improve the thermal energy utilization efficiency of the sludge.

Technical advantages:

The sludge is treated by incineration to maximize the reduction, stabilization and harmlessness.

The ash after incineration can be directly or treated with a heavy metal chelating agent to enter the landfill depending on the heavy metal content, and can also be used as building materials or paving.

Technical disadvantages:

The investment is large and the equipment maintenance cost is high.

The sludge itself has a low calorific value and needs to be mixed with domestic garbage and coal, and the running cost is high.

Exhaust gas emissions are large, and it is easy to cause secondary pollution.

7. Comprehensive evaluation

The goal of sludge treatment is to reduce, stabilize, and detoxify. To be used as a resource is a yearning, and there is a long way to go with reality. It is generally “incapable” and cannot be a goal that must be achieved. Each treatment method has different advantages.

The degree of reduction, heat drying and incineration are the highest. Lime stabilization and aerobic fermentation (composting) are at a considerable level, generally up to 35% (aerobic fermentation has a large variation of 15~40 due to different ratios of different processes, different strains and straw-based excipients). %). It is worse than deep dehydration (42%) after chemical conditioning, but the moisture content of the product is lower (because the amount of solids injected is larger), the digestion + semi-drying is 50%, and the drying incineration is 95%, but the economic input is Much bigger.

The degree of stabilization, heat drying and incineration are the most thorough. Lime stability, aerobic fermentation, anaerobic digestion can also achieve a good degree of stability, there is still a gap in deep dehydration.

The degree of harmlessness, heat drying and incineration kill the pathogens most thoroughly. The aerobic fermentation and lime stabilizing ability are second, and the anaerobic digestion and deep dehydration ability are slightly insufficient.

In terms of land occupation, lime stabilization and deep dewatering technology have a short processing time and occupy the least amount of land. Aerobic fermentation and anaerobic digestion generally take a long time and occupy a large area of ​​land.

In terms of economy, lime stabilized construction investment and operating costs are the lowest, anaerobic digestion, aerobic fermentation, deep dewatering, thermal drying and incineration technology investment and operating costs are higher.

There is no best in the choice of sludge treatment technology, only the most suitable. According to different regions and different sludge types, considering the climate, regional characteristics, construction conditions, etc., it is an ideal choice to combine various processes to achieve the best results.

/by

Overview and classification of oil tank bottom sludge

During long-term use of oil tanks, colloids, asphaltenes, high-melting waxes and entrained impurities (such as sand, heavy metal salts, mud, etc.) in crude oil and oil will slowly settle with water. Accumulated in the bottom of the tank to form a thick layer of black gelatinous material called tank bottom sludge. The production and accumulation of oil sludge not only affects the quality of oil, but also affects the use of oil storage equipment. If the oil bottom sludge is not removed in time, it will not only accelerate the corrosion of the tank bottom, but also reduce the service life of the tank, and will have a certain impact on the quality and effective volume of the tank.

oil tank bottom sludge

Because it contains substances such as phenols and benzenes, the bottom of the tank is odorous and toxic, and the composition is very complicated. Direct discharge is prohibited. The amount is generally as high as 1% to 2% of the tank capacity. Under normal circumstances, the composition of tank bottom sludge is roughly divided into water, emulsified oil or adsorbed oil, solid foreign matter, inorganic salt, etc., generally has high water content, large oil content and contains other harmful substances. The biggest characteristic distinguishing it from other oil sludges is that the hydrocarbon content is extremely high.

The bottom of the oil tank is divided into three layers according to the depth of the mud of different mud ages, namely the initial oil sludge, the upper oil sludge and the bottom oil sludge.

The initial oil sludge is a deposit produced by a new oil reservoir during the settling period and belongs to an unstable silt layer. The layer continues to exchange material with the crude oil layer while new deposits are continuously covering the surface. At the same time, with the change of the operating state of the tank, during the lifting process, most of the paraffin crystals are repeatedly dissolved and recrystallized, and most of them become heavy paraffin with high density, high melting point and coarse granularity. During the constant temperature of the oil tank, heavy paraffin, asphalt micelles, mechanical impurities and water masses in the initial sludge gradually settle to the upper sludge.

The upper layer of oil sludge is the main oil sludge formation layer. Under the repeated influence of the temperature change of the storage tank, the asphalt micelles will continuously gather and fuse into a honeycomb superglue. At the same time, the large amount of liquid hydrocarbons adhering to the outer surface of the micelle, as well as the coarse-grained sediment, water mass, heavy paraffin and mechanical impurities in the gap of the micelle, have been permanently consolidated and become permanent. Oil sludge and layered on top of the oil bottom sludge.

The oil bottom layer of sludge is a stable accumulation layer, which is formed by continuous layering of permanent oil sludge. As the oil storage and time goes by, the mud layer is increasingly solid and thick.

It can be seen that after the initial exchange of materials between the oil sludge layers, most of the micelles slowly descend to the upper layer of oil sludge. Then, the upper layer of the micelles is continuously fused into super micelles, which are then denatured into permanent oil sludge, which is superimposed on the upper part of the oil bottom sludge. As time went by, it continued to reciprocate, eventually forming a large amount of oil tank bottom sludge.

/by

Status of urban sewage sludge and industrial sludge treatment

In recent years, China’s urbanization has developed at a rapid pace, and the urban population has increased year by year. The resulting urban sewage discharge has been increasing year by year, resulting in an increase in the output of urban sewage sludge. China is an industrial power and is now promoting energy conservation and environmental protection. Under the background, the various drawbacks of the traditional industrial model are becoming more and more obvious. The treatment of industrial wastewater has been paid more and more attention. How to treat industrial sludge with environmental protection and high efficiency is also a difficult problem in China.

classification of oil sludge

Under current technologies and conditions, urban sewage sludge and industrial sludge treatment methods are:
(1) Ocean dumping method
The ocean dumping method is to put the sludge into the sea, and the treatment cost is low, but it will cause a certain degree of damage to the marine ecology. Therefore, this method is gradually prohibited by legislation;

(2) Sludge landfill method
Sludge landfill method is currently the main sludge disposal method in China. The landfill method is to select a suitable location on the periphery of the city to directly deposit the sludge into the landfill. This method is low in cost, but it will lead to unstable soil in the area while occupying a large area of ​​land. The loss of heavy metals will cause the drawbacks of the re-contamination landfill law of the soil and water bodies to become increasingly apparent;

(3) Sludge composting
Sludge composting agricultural use is also called land use method. This method can effectively utilize plant nutrient elements such as N, P, K in sludge, and is a method for recycling sludge. Developed countries in Europe and the United States prefer this method because they produce less industrial sludge and mainly treat domestic sludge. China’s industrial sludge accounts for a large proportion. The industrial sludge contains high heavy metals, which are absorbed by plants and eventually enriched into the human body through the food chain, endangering human health. Other metal salts in the sludge may also destroy the farmland soil, so this method should be used to determine the composition of the sludge;

(4) Sludge building materials utilization method
The sludge building materials utilization method is because the sludge has a high ash content, and its ash can be used as a raw material for bricks, cement, etc., and has considerable mature utilization technology in Europe, America, and Japan, and has already been applied to a large scale.

(5) Sludge incineration method
Sludge incineration is a method of incinerating dried sludge. This method can quickly process sludge and recover heat from the sludge. The incineration treatment can remove pathogenic bacteria, microorganisms and toxic compounds (phenol, etc.) in the sludge. The incinerated ash has the characteristics of small volume and stable nature, so the incineration method can reduce the sludge.

(6) Sludge pyrolysis method
Sludge pyrolysis method refers to the use of high volatile matter in sludge, which is volatilized and analyzed by heating. The precipitated product can be used as fuel to replenish the heat required for pyrolysis. Due to the complex composition of the sludge and the high moisture content, safe, continuous and efficient sludge pyrolysis has become a major highlight of sludge treatment. The use of resources for the solid waste after pyrolysis can also be realized, for example, as a raw material for construction.

 

/by

Cause analysis and countermeasures for damage of refractory lining of cement rotary kiln

The damage of the refractory lining of the rotary kiln often affects the continuity of production. It is one of the common equipment accidents. The causes of the defects include design structure, refractory quality, masonry quality and operation and maintenance. A comprehensive analysis of various lining damage accidents is conducive to identifying some common causes, and taking pre-control measures to minimize the occurrence of accidents.

First, the role of rotary kiln refractory lining

Prevent high-temperature flame or airflow from directly damaging the kiln body, protect the kiln cylinder; prevent harmful substances (CO, SO2) from eroding the kiln; prevent material and airflow from eroding the kiln; reduce the temperature of the kiln and prevent the kiln from being Oxidative erosion; has the function of heat storage and heat preservation; can improve the performance of hanging kiln skin.

Second, the form of refractory lining damage

1. Common damage forms

The combined effects of mechanical stress, material friction, thermal stress, airflow and chemical erosion of the rotary kiln refractory lining under long-term rotation often lead to the following problems: First, the lifting block is subjected to the mechanical rotation gravity eccentricity effect for a long time. The high temperature effect and the impact friction of the stone cause the prefabricated block to be twisted, the refractory material is detached, the thickness is reduced, and the refractory brick filled between the lifting blocks is deformed and fallen off; the second is the melting loss of the high temperature calcined sintered layer; the third is the large temperature difference in the kiln body. The air flow causes the dust to be sintered at a high temperature to bond to the surface of the refractory material. When the kiln body rotates, the separation of the gravity causes the refractory material to partially peel off, the brick lining is thinned, the temperature of the kiln body is increased, and the steel structure changes to varying degrees, and the kiln is lowered. The life of the body.

2. Probability of various damages

After a large number of experimental studies on the refractory materials after use, and the statistics of the main causes of the main causes of damage are: mechanical stress accounted for 37%, due to deformation of the cylinder and thermal expansion of the brick; chemical erosion accounted for 36%, due to Caused by the erosion of clinker silicate and alkali salt; thermal stress accounted for 27% due to overheating and thermal shock.

With the different types of kiln, operation and kiln lining in the kiln, the above three factors play different roles, mainly depending on the deformation state of the flame, kiln material and kiln cylinder during operation. The lining is subjected to a variety of different stresses.

Third, the cause analysis of fire damage and countermeasures

1. Mechanical stress damage

(1) Thermal expansion squeezing refractory bricks

When the temperature of the kiln rises to a certain extent, the thermal expansion will generate pressure in the axial direction of the kiln, causing the adjacent refractory bricks to squeeze each other. When the pressure is greater than the strength of the refractory brick, the refractory brick surface will be peeled off. The following measures should be taken: dry refractory bricks, reasonable sideboards, 2mm fire mud joints for wet refractory bricks; suitable brick retaining rings.

(2) Iron plate stress damage

At the hot end of the refractory brick, the magnesium oxide in the veneer iron plate and the magnesia brick reacts at a high temperature to form a magnesium iron compound, which increases the volume and extrudes the refractory brick, causing horizontal fracture. In response to this situation, the refractory brick veneer should be replaced or replaced with fire mud.

(3) Large-area skewed dislocation of refractory brick

Because the masonry is too loose, the kiln is frequently opened and closed, resulting in deformation of the kiln cylinder, so that the kiln cylinder body and the cold surface of the lining brick move relatively, causing the lining brick to be twisted and misaligned and the brick surface to burst and fall off. The following measures should be taken: when building, the large surface of the refractory brick is hammered with a wooden hammer, the locking brick should be locked, and the wedge iron is added twice; the stable thermal system is maintained; the deformed part of the kiln cylinder is flattened with high temperature cement.

(4) Elliptical stress extrusion

Due to the increase of the horn clearance of the rotary kiln wheel, the cylinder body has a large ellipticity, which causes the refractory brick to be squeezed. The ellipticity of the cylinder should be checked regularly. If the ellipse value exceeds 1/10 of the diameter of the kiln, the pad should be replaced or the horn should be added to adjust the wheel gap.

(5) Locking iron stress extrusion

When the brick is locked, the iron in the lock is too tight, which will result in the formation of a brick groove at the lock. The following measures shall be taken: at the same lock, the number of irons in the lock shall not exceed 3; the spacing of the iron at the lock shall be as dispersed as possible; the outer and outer joints shall be loose when the brick is locked; the iron at the lock shall be kept away from the thin lock brick as far as possible.

(6) brick ring extrusion refractory brick

The retaining bricks (shaped bricks) at the brick blocking ring are subject to crushing and cracking, and in this case, the single-track brick ring should be changed into a double-stop brick ring, and the bricks should be built on the brick blocking ring to avoid processing the shaped bricks. .

2. Thermal damage

(1) Overheating

Local overheating of the kiln temperature causes the refractory brick to melt and form a pit. In order to avoid this, the burner should be properly adjusted and a reasonable refractory material should be selected at different locations.

(2) Thermal shock phenomenon

The thermal stress caused by sudden changes in temperature causes spalling and cracking of the brick surface, mainly due to the frequent opening and closing of extremely cold and extremely hot. Stable production operations should be established and a reasonable heating and cooling kiln system should be established.

3. Chemical erosion damage

(1) Alkali erosion

The gas phase alkali salt compound penetrates into the voids of the brick body to condense and solidify, and forms a horizontal permeation layer of the alkali salt in the brick body, and the alkali salt content in the kiln should be reduced in the production.

(2) Hydration

MgO reacts with water to form Mg(OH)2, which increases in volume and destroys the overall structure of the refractory brick. Since refractory bricks containing MgO and CaO have hydration reactions, it is necessary to ensure that moisture, water and rain are avoided during storage, transportation and masonry of refractory bricks.

It can be seen from the damage mechanism of the above refractory bricks that the standardization of refractory construction can effectively extend the service life of refractory materials, and professional and dedicated masonry personnel are important factors to ensure the quality of refractory construction.

Fourth, the quality requirements of refractory masonry

1. Pre-laying control

Refractory materials should be carefully handled during handling, and the breakage rate of refractory bricks should be controlled within 3%. The line shall be ready for laying. The vertical reference line of the kiln shall be placed in a “ten” shape and symmetry along the circumference. Each line shall be parallel to the axis of the kiln; each line of the hoop reference line shall be placed at 2 m, and each line shall be parallel and Vertical to the kiln axis. Ensure that the kiln plate is clean and remove the corroded iron. It is strictly forbidden to use the refractory brick with the edge loss and corner loss exceeding the control range.

2. Masonry process control

During the construction process, the refractory material is protected from moisture, and the processed bricks are processed by a brick cutter. After cutting, the length of the brick must exceed 50% of the length of the original brick, and the thickness must reach 70% of the original thickness. The masonry is carried out by the ring-laying method, and the bricks are closely attached to the kiln body, and it is necessary to ensure that the four corners of the brick are in contact with the kiln body. The following common problems should be avoided in masonry: upside down, lottery, mixing, misalignment, tilting, uneven crevices, climbing, detachment, heavy seams, through seams, open mouth, void, crevices, serpentine bends, Masonry bulge, missing corners.

Wood hammers or rubber hammers should be used for refractory brick masonry. It is strictly forbidden to use hammers. The refractory mud is prepared by using clean water, accurately weighed, evenly adjusted, and used with the adjustment. The prepared mud should not be used any more. The mud that has been initially set up must not be used any more, and the different quality mud should be cleaned in time. clean.

3. Brick ring lock control

Only use the original bricks to lock the bricks, and do not use the processing bricks. If several bricks are used to lock the seams, the jointed bricks shall not be used in conjunction with each other. The standard type shall be used in conjunction with each other; no more than two types of lock seam bricks per type of refractory brick. In the lock seam belt, ensure that the horizontal seam of the brick is parallel to the kiln shaft. The thickness of the metal plate of the lock seam is not more than 2 mm. Only one piece of lock seam steel plate can be used in each joint. If several steel plates are required, they should be evenly distributed in the whole lock brick zone. The number of blocks of each ring lock seam steel plate should not exceed 4.

Fifth, the principle of selection of refractory materials

When selecting refractory materials, the following requirements should be met:

(1) High temperature resistance. It can operate in high temperature environment for a long time.

(2) High strength and good wear resistance. The refractory material in the rotary kiln must have a certain mechanical strength to withstand the stress caused by the expansion stress at high temperature and the deformation of the rotary kiln shell. At the same time, due to the wear of the refractory material by the charge and the flue gas, the refractory material needs to have good wear resistance.

(3) It has good chemical stability. To resist the erosion of chemicals in the smoke.

(4) Good thermal stability. It can withstand the alternating stress in the incineration state. When the conditions of shutdown, start-up, and rotating operation are unstable, the temperature change in the kiln is relatively large, and there is no possibility of cracking or peeling.

(5) Thermal expansion stability. The refractory material may expand larger than the rotary kiln shell and may fall off easily.

(6) The porosity is low. If the porosity is high, the fumes will penetrate the refractory material and erode the refractory material.

In summary, the configuration of the refractory bricks in the rotary kiln, the quality of the refractory bricks, the storage of the refractory bricks, the refractory brick masonry, the rotary kiln drying kiln, and the improper handling of all aspects of the production can affect the service life of the rotary kiln. A series of measures to maintain the refractory bricks helps to achieve the best results with the most economical kiln lining.

/by

Analysis of industry, element and calorific value of oil sludge

Oil sludge industry and calorific value analysis

Oil sludge type

 Industry Heat Value

Vad

 Aad FCad

MJ/kg

Refinery water treatment station sludge

 23.44% 11.72% 2.28%

10.55

Oil field sludge

 23.68% 38.65% 2.06%

7.97

Petrochemical plant tank bottom sludge

 51.96% 10.42% 3.31%

25.55
Liaohe mixed sludge 66.61% 3.77% 4.49%

31.48

It can be seen from the oil sludge industry and calorific value analysis in the above table that different types of oil sludge have different volatiles due to different composition and oil content, but the volatiles are relatively high. Liaohe mixed sludge is up to 66. More than %, the volatile matter is mainly the thermal decomposition products of hydrocarbon organic matter and non-hydrocarbon organic matter in oil sludge, the content of which mainly affects the distribution of pyrolysis products, and the oil sludge with high volatile matter content after pyrolysis The oil sludge with high rate and low volatile content has low gas-liquid yield after pyrolysis; the ash is mainly inorganic residue after incineration, which is derived from the slag phase in the oil sludge, mainly affecting the content of residue after heat treatment. The floor sludge is generally muddy soil contaminated by crude oil, so the ash content is relatively high: the calorific value of the oil sludge is related to its own oil content and oil quality. The above calorific value is the calorific value of the wet base sludge, except for the Liaohe mixed sludge heat. In addition to the larger value, the other three types of oil sludges have lower calorific value than the standard coal calorific value (29.3 MJ/kg) because of the relatively low water content. To be three types of oil sludge drying process accordingly.

Elemental analysis of oil sludge

Oil sludge type

 N C H S

H/C

Refinery water treatment station sludge

 1.44% 16.21% 2.68% 1.09%

1.98%

Oil field sludge

 1.53% 18.28% 2.89% 0.46%

1.89%

Petrochemical plant tank bottom sludge

 2.83% 40.71% 5.37% 1.02%

1.58%
Liaohe mixed sludge 3.66% 54.15% 7.40% 0.38%

1.64%

The element content in the analysis of oil sludge is the content of wet base sludge. The main components of organic elements are C, H, N, S, O. These elements are derived from the oil phase components in the sludge and the non-hydrocarbons in the slag phase. Organic matter, as can be seen from the above table, the content of elements in different types of sludge differs greatly, among which the content of C is the highest. The content of S and N mainly affects the choice of treatment methods. The sludge with high S and N content is not suitable for direct incineration: The H/C atomic ratio is an important parameter reflecting the chemical composition of the oil. The smaller the H/C atomic ratio, the more cyclic structures in the oil phase, and the more the chain structure, the more sludge and sludge in the water treatment station. The H/C atomic ratio is comparable to that of crude oil, while the H/C atomic ratio of the bottom sludge and the mixed sludge is relatively low, and the annular phase structure of the oil phase component is relatively large, which is equivalent to the atmospheric vacuum residue.

/by

Three-phase analysis of water, oil and slag of oil sludge

Oil sludge type

 Moisture content Oil content Slag content

Refinery water treatment station sludge

 62.56% 21.47%

15.97%

Oil field sludge

 35.62% 20.79%

43.59%

Petrochemical plant tank bottom sludge

 34.31% 54.42%

11.27%
Liaohe mixed sludge 25.13% 70.69%

4.18%

It can be seen from the content of the three-phase components of the oil sludge in the above table that the content of the three-phase components of different types of oil sludge varies greatly. The oil sludge of the refinery water treatment station is produced during the process of oil sewage treatment. Generally, it only performs simple dehydration treatment, so its water content is the highest. The oil content of the four oil sludges is above 20%, especially in the Liaohe River. The sludge has the highest oil content, up to 70.69%. This type of sludge has high recycling value. The oil field is the soil contaminated by oil, so the slag rate is the highest, and the difference is caused by the pollution degree. The slag-containing rate of the bottom sludge is related to the cleaning period of the oil storage tank. The cleaning period of the petrochemical plant is about 3 years, so the slag content of the bottom sludge produced by the tank is relatively high.

In summary, different types of oil sludge should be treated and recycled according to their own characteristics.

/by

Analytical method for heavy metal content of oil sludge

(1) Method for determining heavy metal content of oil sludge

The content of heavy metals in oil sludge was determined by inductively coupled plasma mass spectrometry after atmospheric pressure digestion; the digestion procedure of sludge was referred to CJ/221-2005 municipal sewage treatment plant sludge test method.

(2) Analysis method of oil phase components of oil sludge
The oil phase components of the oil sludge were analyzed by total hydrocarbon gas chromatography. The analysis was carried out with reference to SY/T 5779-2008 petroleum and sedimentary organic hydrocarbon gas and chromatographic method. The instrument was tested by Agilent 7890A gas chromatograph. It is a high purity nitrogen gas (99.999%), an inlet temperature of 300 ° C, and a detector FID temperature of 300 ° C. The carrier gas flow rate was constant flow 1 ml/min, split injection, and the split ratio was 20:1. Column: HP-1 elastic quartz capillary column (60m x 0.25mm x 0.25um); Guiwen: initial temperature 40 ° C, hold for 10min, 4 ° C warm to 70 ° C, then increase the temperature to 300 ° C at 8 ° C / min, Keep it for 40 minutes.
The oil phase components used in the analysis were extracted by Soxhlet extraction, and the extraction reagent was CH2Cl2. The extraction temperature was 40 ° C and the extraction time was 72 h. The oil phase used for the analysis obtained after extracting the extractant by steaming off the obtained liquid by a rotary evaporator.

(3) Analysis method of slag phase composition of oil sludge
The composition analysis of the oil sludge slag phase was analyzed by X-ray diffractometer and X-ray fluorescence spectrometer. The test instrument was analyzed for solid products using a D8FOCUS XRD diffractometer from AXS, Germany, and a LAB CENTRE XRF-1800 XPF spectrometer from SHADIZU, Japan. The test sample is prepared as follows: the slag phase component obtained after the oil sludge is extracted is subjected to dry grinding and the test sample is prepared by a 325 mesh (44 um) sample.

(4) Thermogravimetric analysis method for oil sludge
The thermogravimetric analysis of the oil sludge was carried out by the STA7300 type thermogravimetric differential thermal analyzer manufactured by HITACHI Co., Ltd., and the TG and DTG curves obtained by the experiment were analyzed. The experimental carrier gas was high purity nitrogen (99.999%), the flow rate was 100 ml/min, the heating rate was 10 ° C / min, and the temperature was raised from room temperature to 1000 ° C.

/by