Industrial, elemental and calorific value analysis methods for oil sludge

(1) Industrial analysis of oil sludge

The industrial analysis method of oil sludge adopts the industrial analysis method of GB/T 212-2008 coal. Since the water content has been obtained by distillation, the ash content, volatile matter content and fixed carbon content of the sample are determined only by this method.
Ash calculation formula for oil sludge:
Aad = (m2-m0)/m1 x 100%……………………………….. ……………..Formula (2-4)
Where: Aad… mass fraction of air-dried ash, the value is expressed in %;
Mo…the mass of the constant weight ash dish, in g;
M1 … sample quality, the unit is g;
M2… The quality of the ash dish and the sample after burning, in g.

Volatile formula of oil sludge:
Vad = (m1+-m0-m2)/m1 x 100% – w1……………………………. …….Formula(2-5)
Where: Vad… volatile matter of oil sludge, the value is expressed in %;
Mo…the mass of the constant weight (including the lid) in g;
M1 … sample quality, the unit is g;
M2…heated crucible (including lid) and sample mass in g;
W1… moisture content of oil sludge, the value is expressed in %.

Fixed carbon calculation formula for oil sludge:
FCad = 100 – w1 – Aad – Vad ………………………………….. ………………Form (2-6)
Where: FCad… fixed carbon of oil sludge, the value is expressed in %;
W1 ……. moisture content of oil sludge, the value is expressed in %;
Aad …, the ash content of oil sludge, the value is expressed in %;
Vad… Volatile matter of oil sludge, the value is expressed in %.

(2) Analysis of oil sludge elements
The organic element analysis of oil sludge is tested and analyzed by organic element test analyzer.
Analysis of C, H, N, S elements.

(3) Analysis of calorific value of oil sludge
In this analysis, the calorific value of GB213-2008 coal was used to determine the calorific value of oil sludge.
The experimental instrument adopts a fully automatic calorimeter. The specific measurement steps are as follows:
Mixing uniformly mixed oil sludge from 0.9000g to 1.1000g (accurate to 0.0002g) and placing it in constant mass.
In the combustion vessel, two ends of a known mass of the ignition wire are respectively attached to the electrode column, and a cotton wire of a known heat value is attached to the wire. The other end of the cotton thread is in contact with the sludge sample, and 10 ml of deionized water is injected into the oxygen bomb, and the oxygen bomb cover is tightened; then the oxygen bomb is slowly filled with oxygen by an automatic oxygenator to a pressure of about 3.0 MPa for 10 s. Put the oxygen bomb into the instrument, input the relevant parameters on the computer screen, click the measurement button, the system will automatically run and automatically analyze the data. After the test, record the high heat on the screen, and each sample will be made into multiple parallel samples. When the difference between the two measurements does not exceed 200 J, the average value is recorded as the calorific value of the sample.

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Cement kiln co-processing hazardous waste in the engineering design needs attention

As a new type of hazardous waste disposal technology, cement kiln co-disposal of hazardous waste has many advantages such as high disposal rate, high disposal volume, environmental protection emission standards, various types of disposal, low project investment, short construction period and low disposal cost. Gradually gain wide recognition.

In recent years, especially in 2017 and 2018, the cement kiln co-processing hazardous waste project has been blown out in all parts of the country. The major environmental protection enterprises across the country have been involved in the cement kiln co-processing hazardous waste industry. Then, what links should be paid attention to in the engineering design of the cement kiln co-processing hazardous waste project, and what are the key points?

First, the process, the master plan is the key to the success or failure of the project:

1. The cement kiln co-disposal of hazardous waste projects should consider the process layout without affecting the normal production and maintenance of the cement production line. In particular, consider the space for the normal maintenance of the cement production line, the main transportation channels and other factors.

2. Make full use of the original public facilities produced by cement to reduce unnecessary investment. Mainly consider the sharing problems of transportation roads, water supply and drainage systems, power control systems, fire protection systems, laboratories, and dormitories.

3, make full use of the original topography of the cement plant, consider the process layout should be adapted to local conditions, such as the height difference of the terrain, reduce the height of the material and so on.

4. Minimize the process route, reduce energy consumption, and make it simple and reasonable. When conditions permit, try to arrange the hazardous waste disposal lines as much as possible to facilitate future operation and management.

Second, construction, structure professional:

1. Due to the complex types and types of hazardous wastes to be disposed of, the division of fire protection grades of plant and storage and the confirmation of fire resistance rating should be given high priority to ensure safety compliance and not over-design.
2. The anti-seepage practices of buildings and equipment foundations strictly follow the design specifications and give each concrete node map on the construction drawing to facilitate quality control during construction.

3, the practice of the factory and the storage floor must strictly implement the design specifications, the choice of materials must meet the anti-corrosion requirements and meet the wear-resistant requirements.

4. The energy-saving design of the workshop and storage warehouse is in line with the national and local requirements.

5. The anti-floating design of deep foundation pits should be taken seriously.

Third, electrical instrumentation:

1. The cement kiln coordinated disposal of hazardous waste projects requires dual power supply.

2. The selection of the toxic and harmful gas detectors in the workshop and storage, the installation location, and the setting of the fan for automatic smoke evacuation should meet the process requirements.

3. Fire protection system and supporting facilities, fire pool, fire control room and other settings need to be considered comprehensively.

4. Control points, monitoring signals, fire alarms, etc. need to be introduced into the central control room of the cement plant for centralized control, which is convenient for combining cement production with hazardous waste disposal.

Fourth, water supply and drainage, HVAC professional: handling the smell determines the pros and cons of the project.

1. Smell and dust treatment: choose a reasonable number of ventilation. The plant is closed, maintaining micro-negative pressure, and the internal circulation and deodorization, air curtain, etc. should be considered comprehensively.

2. The odor mainly uses the pipeline of the factory or storage to guide the odor to the high temperature section of the cement chiller.

3. Consider the combination of the initial rainwater harvesting system and the sewage collection system.

4. The heating and ventilation of the workshop and storage should be considered comprehensively to achieve the best results.

With the continuous deepening of the research on the construction of cement kiln co-processing hazardous waste projects, relevant policies, norms and standards are continuously introduced, and the design and construction of cement kiln co-processing hazardous waste projects will become more and more standardized and more professional.

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Regulations for homogenization, storage and kiln production in cement plant design

The degree of homogenization of raw materials and raw materials in cement plants is an important factor in determining the quality of the final product. In order to make full use of low-grade limestone, expand the raw material resources and improve the quality of clinker, modern cement factories attach great importance to the pre-homogenization of raw materials and the homogenization of raw materials. In the vertical kiln cement plant, because the vertical kiln calcination is not uniform, it is necessary to reduce the fluctuation of raw material composition and improve the uniformity of raw materials into the kiln. This is an important condition for the high quality and high yield of the shaft kiln.

The homogenization of raw materials is completed in the production process from mining, transportation, crushing and storage, grinding, and raw material agitation. Each production process has a certain degree of homogenization, and finally reaches the raw material composition of the kiln. The required control criteria, in which limestone pre-homogenization and homogenization of the milled raw meal are the two most important homogenization processes to complete this homogenization process.

1. The design of the raw material homogenization library should meet the following requirements:

(1) The homogenization method should adopt continuous homogenization;

(2) The standard deviation of the calcium oxide content of the raw material into the kiln shall be less than 0.25%.

(3) The raw material moisture should be controlled below 0.5%, and the maximum should not exceed 1.0%;

(4) Dust collection equipment should be installed at the top of the raw material homogenization and the bottom of the reservoir.

2. The design of continuous raw material homogenization library should meet the following requirements:

(1) Each process production line should be equipped with one or two continuous homogenization banks;

(2) Raw materials should be evenly dispersed in the storage, and the storage of the top material distributor should be selected according to the diameter of the reservoir;

(3) When designing the inflation system, the resistance should be reduced. The arrangement of the inflatable box should reduce the dead zone in the warehouse, and the gas permeable layer material with good air permeability, uniform air distribution and wear resistance should be selected; the gas box and piping system should be well sealed;

(4) The bottom of the library should be supplied with a Roots blower, and should be reserved. The amount of inflation should be determined according to the form of the bottom of the reservoir and the area of ​​the same inflation. The inflation pressure should be 40 kPa – 70 kPa;

(5) The bottom of the library should be used for unloading, and each warehouse should have more than one discharge port, and the unloading device equipped with sub-moving inspection gates, quick-opening valves and flow control valves should be selected;

(6) It is advisable to set up a warehouse roof in a cold or rainy area;

(7) A patrol inspection channel should be set between the top of the library and the preheater tower. The raw material for delivery should be set back to the transport circuit of the warehouse.

3. The design of raw material into the kiln system should meet the following requirements:

(1) The material level of the feeding bin should be stable, and the load cell should be used to measure and control the material level in the bin, and the corresponding material level adjusting circuit should be set;

(2) The feeding equipment should be able to adjust the feeding amount conveniently and accurately; the measurement accuracy level should not be lower than 1.0, and should meet the requirements of measurement and calibration;

(3) A dust collecting device shall be installed at the transfer point of the conveying equipment of the kiln system.

In order to ensure normal production and improve the operation rate of equipment and systems, operators must grasp the performance and operation essentials of each equipment on the basis of the above requirements, so as to solve the problems at any time in actual operation.

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Method for determining moisture content, oil content and slag content of oil sludge

(1) Method for determining moisture content of oil sludge

At present, the laboratory determines that the water content of the oil sludge is mostly by the drying method. At 105 ° C, the water escapes in the form of water vapor, and the moisture content of the sample is obtained by the mass change of the sample before and after drying. However, this method is not suitable for the determination of the moisture content of oil sludge, because some of the low-boiling oil will also escape together during the drying process, resulting in uncertain measurement errors; therefore, the water content of crude oil can be compared with GB8929-2006. Method Distillation is used to determine the moisture content of oil sludge.

The specific measurement method is as follows; weigh the appropriate amount of oil sludge sample into the flask, add enough xylene (in accordance with GB3407 superior grade) solvent to the flask, in order to prevent bumping, add 3-5 glass beads, according to the experimental device Connect the device to the condensate tube and heat it back. The initial stage is followed by slow heating. After the boiling speed is stabilized, the heating rate is adjusted so that the distillate is dropped into the receiver at a rate of 2-5 drops per second, and the distillation is continued until no part of the instrument is visible except the receiver. Water is visible, and the volume of water in the receiver does not change within 5 minutes. The distillation is stopped. After cooling to room temperature, the volume of water in the receiver is recorded as V2; only the above-mentioned same volume of xylene reagent is repeated. The volume of water in the receiver is recorded as V1. Three parallel samples were made for each set of experiments to avoid operational errors affecting the accuracy of the experiment.

(2) Method for determining oil content and slag content of oil sludge

Determination of oil content and slag content of oil sludge is designed according to the method for determining mineral oil in the sludge test method of CJ/T221-2005 municipal sewage treatment plant. The method adopts a Soxhlet extractor to extract the oil phase in the oil sludge, and then the remaining residue is dried and weighed to obtain the slag-containing rate of the oil sludge, and then the oil content of the oil sludge is obtained by the reduction method. rate.

The specific measurement method is as follows: Weigh an appropriate amount of oil sludge sample, put it into the filter paper bag of mass MO in advance and soak it with carbon tetrachloride, wrap it in the extraction cylinder of Soxhlet extractor, and put it into the flask. Add enough carbon tetrachloride solvent, connect the device according to the experimental device diagram, start heating after the water is condensed, and heat it in a water bath. After the first reflux, the reflux time is controlled at 20-25 minutes. After the carbon tetrachloride in the extraction cylinder is clarified and colorless, and the total extraction time is not less than 6 hours, the extraction is completed. After cooling to room temperature, the device is disassembled, and the filter paper package of the sample wrapped in the extraction cylinder is taken out and placed. The oven was cooled to a constant weight in an oven at a temperature of 120 ° C, and placed in a desiccator to cool to room temperature, and the mass of the filter paper package was found to be m 2 . Three parallel samples were made for each set of experiments to avoid operational errors affecting the accuracy of the experiment.

 

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Analysis physical and chemical properties of oil sludge

Oil sludge has been included in the HW08 waste mineral oil in the Hazardous Waste List. The composition of oil sludge is very complex, and it contains a large amount of aged crude oil, solid suspended solids, salts, bacteria, corrosion products and the like. The slag-containing rate and oil-bearing rate of oil sludges from different sources and different types are very different, and the physical and chemical properties are also very different. The physical and chemical properties of oil-soil mixing are important reference for the treatment process. It is necessary to analyze different types of oil sludge. It is very important to study the physical and chemical properties of different types of oil sludge.

In order to more comprehensively characterize the physical and chemical properties of various types of oil sludge, special research and analysis are carried out for four different types of oil sludge. The four types of oil-bearing sludge are: oilfield floor sludge, petrochemical plant tank bottom sludge, petrochemical refinery water treatment station sludge and oil field production of mixed sludge. The following figure is a real shot of the above four oil sludge samples.

From the appearance, the four oil sludges are dark brown and viscous solid, with typical pungent oil odor. The oil floor mud is a fluffy porous structure, and large particles of mud and sand are visible. The sludge is more fluid than the other three types of sludge. The four types of sludge are emulsified structures in which water, oil and slag are intertwined. The bottom of the tank and the oil sludge are placed for a long time, and the surface is oozing.

The main instruments and related specifications used in the pyrolysis treatment of oil sludge are shown in the table below.

Instrument Model / Specification
Muffle furnace KSL-1200X-J
Organic element analyzer VARIO EL cube
Automatic calorimeter DY-ZDHW-6
Inductively coupled plasma mass spectrometer 7700 Series
Gas Chromatograph Agilent 7890A
X-ray fluorescence spectrometer LAB CENTRE XRF-1800
X-ray diffractometer D8FOCUS
Thermogravimetric differential thermal analyzer STA7300
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Introduction of oil sludge treatment technology

Oil sludge can be classified into two categories according to the treatment technology characteristics: The first type is oil sludge treatment technology based on harmless treatment, including oil sludge filling method, oil sludge solidification method, and oil sludge. Biological treatment method, oil sludge control and re-injection method; the second category is oil-based sludge treatment technology based on resource treatment, including oil sludge extraction method, oil sludge incineration method, oil sludge oxidation Hot washing method, oil sludge pyrolysis method, etc.

A comparison of various oil processing techniques is shown in the table below:

Processing technology Advantages Disadvantages
 

Oil sludge harmless treatment technology

 Oil sludge landfill disposal technology The treatment process is simple and rapid, the operation cost is low, and the operation and management are simple; Occupy land resources, easily cause secondary pollution, and cannot recover oil resources;
Oil sludge solidification treatment technology Mature technology, simple operation and good processing effect; A large amount of high-energy curing agent is required, and the characteristics of the treatment sludge are high;
Oil sludge biological treatment technology Simple operation, energy saving, almost no need to add chemical reagents, and little pollution to the environment; Long treatment period, unable to recover oil resources, unsuitable for handling high oil content sludge;
Oil sludge profile control technology Improved the effect of water injection development and improved oil recovery rate; High requirements on sludge characteristics, mainly limited to the treatment of oil field sludge;
Oil sludge resource treatment technology Oil sludge solvent extraction technology The process is simple, the energy consumption is small, and most of the oil phase in the sludge can be recovered; The loss of extractant greatly increases the cost and pollutes the environment;
Oil sludge incineration treatment technology The realization of the maximum reduction of sludge, the treatment of sludge is more thorough, applicable to all kinds of sludge； The investment is large, the operation is complicated, and the incineration process is prone to secondary pollution caused by dioxin, toxic and harmful fumes, dust, etc.;
Oil sludge chemical hot washing technology Simple operation, low energy consumption, and recovery of most of the oil resources; Incomplete treatment, secondary pollution caused by treated wastewater;
Oil sludge pyrolysis treatment technology Handle thoroughly, recover the oil resources, obtain flammable gas at the same time, and have almost no secondary pollution; The investment is complicated, the processing cost is high, the energy consumption is large, and the residual oil cannot be used;

 

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Brief introduction of oil sludge treatment technology

People’s awareness of environmental protection and strict environmental standards have made it necessary to detoxify, reduce, and recycle oil sludge containing petroleum resources. At present, the oil sludge treatment technologies mainly include: oil sludge solvent extraction technology, oil sludge incineration treatment technology, oil sludge chemical hot washing technology, oil sludge thermal treatment technology, etc., in order to achieve oil-free sludge harmful, reduced, and resourced.

First. Oil sludge solvent extraction technology
Oil sludge solvent extraction technology is a physical and chemical separation technology, the core of which is the selection of organic extractant. The principle of solvent extraction technology for oil sludge is: “similar compatibility” of the solvent, mainly extracting the oil phase components in the sludge, and then distilling and fractionating the extracted solvent to realize the oil and the extraction solvent. Separation, the solvent is repeatedly used to recover oil resources. The extraction solvent currently used is mainly two kinds of organic solvent and supercritical solvent. The key of solvent extraction technology of oil sludge is the selection of extractant. To separate the oil phase in the sludge, the selected extractant must have good oil phase. Solubility, and the nature of the extractant and the oil phase should be different in the boiling range, thus ensuring the recycling of the extractant.

The solvent extraction technology of oil sludge has the advantages that the extractant can be reused, the process is simple, and most of the oil phase in the sludge can be recovered. However, most of the extractants are volatile and toxic, resulting in a large loss in the treatment process. Cost, and it will pollute the environment. At present, the research on solvent extraction technology of oil sludge mainly focuses on the development of cost-effective extractant and multi-stage treatment technology combined with other treatment processes.

Second, oil sludge incineration treatment technology
The oil sludge incineration treatment technology refers to the transportation of the oil sludge after dewatering and drying into a high-temperature combustion furnace, and the organic components are subjected to combustion reaction under oxygen-rich conditions to realize the harmlessness of the oil-containing sludge. The process of reducing the processing. The oil sludge incineration treatment technology can quickly and thoroughly treat the oil sludge harmlessly, so that the sludge volume is greatly reduced and the technical process is relatively mature, so it is considered to be one of the most practical technologies. The oil sludge incineration treatment technology is the main way for many developed countries to deal with oil sludge. The heat generated by incineration is used to generate electricity or heat, and the burned residue is used as building materials. In China, many refineries and oil fields have also put into operation a number of incineration stations for the treatment of oil sludge. For example, Yanshan Petrochemical Plant and Shengli Oilfield have built incineration stations.

Although the oil sludge incineration treatment technology can minimize the sludge and treat the sludge more thoroughly, the sludge incineration technology also has many shortcomings. The main disadvantage is that the incineration equipment occupies a large area, the investment is large, the operation is complicated, and the incineration the flue gas generated in the process contains dioxins, a large amount of SO2, NOx and other gases as well as a large amount of dust, which may cause secondary pollution if not handled properly.

Third, oil sludge chemical hot wash technology
The chemical hot-washing technology of oil sludge has two kinds of treatment processes: low-temperature hot washing and high-temperature hot-washing according to the temperature. Generally, the processing temperature below 100 °C is called low-temperature hot washing, and the processing higher than 100 °C is called Hot wash at high temperature. The chemical hot-washing technology of oil sludge is mainly to add a certain amount of chemical reagents (alkali and a small amount of surface activator) to the oil sludge for repeated washing at a certain temperature, and then to realize oil and slag by means of a device such as swirling or air floating. Separation, adding a demulsifier to the oil-water phase, destroying the oil-water emulsion which is stable and recovering the oil resources therein. Compared with high-temperature hot-washing, low-temperature hot-washing has the advantages of less energy consumption and lower processing cost, but the waxy and asphaltene gums in the oil-containing sludge are not completely removed, resulting in the oil sludge after treatment being insufficient. Emission Standards. The chemical hot-washing technology of oil sludge is currently used for floor sludge with a large slag rate, and most of them are treated with hot alkaline water to treat such sludge.

Forth. Oil sludge thermal treatment technology
The oil sludge pyrolysis treatment technology was first applied to the dry distillation of coal. It was introduced in the 1990s for the recycling of solid waste. In recent years, the pyrolysis treatment technology of oil sludge has developed rapidly, and it is considered to be the most advantageous technology for resource treatment of oil sludge. The oil sludge pyrolysis treatment technology is to heat the sludge to a certain temperature in an environment of isolating oxygen, and to carry out complicated chemical reactions, including thermal cracking reaction and thermal condensation reaction, among various hydrocarbons, waxes and colloidal asphaltenes. In order to realize the harmless, reduced and resource-based treatment technology of oil sludge.

The processing conditions of the oil sludge pyrolysis treatment technology are generally atmospheric pressure, so the requirements on the equipment are not high, and no high-pressure material is required, which greatly reduces the investment cost; and the equipment is relatively simple, and the processed pyrolysis product has a high The use of value reduces operating costs. The toxic and harmful gases generated during the pyrolysis treatment of oil sludge are less, and the residue after treatment can achieve oil content ≤3‰. Although the oil sludge pyrolysis treatment technology has many advantages, there are still many problems. The gas generated during the pyrolysis process often has a foul odor. If it is not handled properly, it will cause secondary pollution. The recovered oil contains more impurities, and the raw materials are different. Residues that can cause high levels of heavy oil to become unusable are still classified as hazardous.

The oil sludge pyrolysis gasification unit independently researched and developed by our institute has the advantages of precise automation control, safe and reliable system operation, high dry distillation efficiency, etc., through the resource treatment of oil sludge, gas-liquid solid three-phase separation, extraction of oil sludge oil products to achieve a win-win situation for resource recovery and environmental protection. The sludge decontamination gasification unit will become a general trend of sludge treatment for the harmless, resource treatment and utilization of oil sludge.

 

 

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Principle of pyrolysis of oil sludge

Pyrolysis of oil sludge is also called thermal cracking of oil sludge. It is to decompose organic matter in an oxygen-free state to: 1 solid residue mainly composed of coke and carbon black; 2 in liquid form at normal temperature of fuel oil; 3 chemical decomposition process of flammable gas mainly composed of H2, CO, CH4 and some low molecular hydrocarbons. The compounds in the oil sludge are mainly hydrocarbons, including alkanes, alkenes, naphthenes, aromatic hydrocarbons, colloids, asphaltenes and the like. In the state of anoxic or anaerobic conditions, the compounds in the oil sludge undergo a series of complex chemical processes such as dehydrogenation and chain scission under high temperature heating conditions. These processes are mainly divided into two categories: one is endothermic pyrolysis. The reaction process, the second is the exothermic condensation reaction process.

At present, the mechanism of pyrolysis of a relatively recognized hydrocarbon compound such as oil sludge is a radical chain reaction mechanism. The free radical reaction of hydrocarbon pyrolysis such as oil sludge is divided into three stages: chain initiation, chain growth and chain termination.

(1) Pyrolysis stage of oil sludge
The pyrolysis chain initiation stage of the oil sludge is mainly the generation of hydrocarbon radicals such as oil sludge, and the hydrocarbon molecules are decomposed into radicals due to the breakage of the C-C bond, and the sites where the different hydrocarbons break are different. The main part of the break of the C-C bond of the alkane occurs in the middle of the carbon chain. The position at which the olefin breaks is mainly at the C=C double bond, and the position at which the alkyl aromatic hydrocarbon breaks is mainly at the β position of the aromatic ring.

(2) Oil sludge slowing chain growth stage
The growth stage of the pyrolysis chain of the oil sludge is mainly the conversion of the free radicals of hydrocarbons such as oil sludge, and one free radical is converted into another free radical. It is the repeated transfer of free radicals that causes the reaction to proceed continuously. The specific reaction process is as follows:

a) Free radical hydrogen scavenging in the pyrolysis stage of oil sludge
The free radical hydrogen abstraction reaction of the oil sludge pyrolysis stage is as follows:

H + RH = H2 + R  ………………………………..Stage （1-1）

R + RH = RH + R ………………………………..Stage （1-2）

The C-H bond energy on the primary, secondary, and tertiary carbon atoms is different, resulting in a different degree of difficulty in capturing hydrogen on the carbon atom. Studies have shown that the order of difficulty in capturing hydrogen at different positions on the carbon atoms of hydrocarbon molecules in oil sludge (from easy to difficult) is: tertiary carbon > secondary carbon > primary carbon, and the reaction rate of free radicals is also the same as above.

b) Free radical decomposition in the pyrolysis stage of oil sludge
In the pyrolysis stage of oil sludge, the free radical itself will decompose and decompose to form two parts: the olefin molecule and another free radical, so that the free radicals are continuously transmitted. It is known from the β-fracture rule that the main site of this special reaction of free radicals is mostly on the β-site carbon of unpaired electrons.

c) Free radical addition in the pyrolysis stage of oil sludge
Compared with the free radical decomposition reaction, the addition reaction of free radicals in the pyrolysis stage of oil sludge can be considered as the reverse reaction. An olefin molecule can be combined with a free radical to form a new radical with a relatively high carbon number.

d) Free radical shift in the pyrolysis stage of oil sludge
The displacement of free radicals in the pyrolysis stage of oily sludge is mainly caused by the internal transfer of hydrogen inside the free radicals, which causes the free radicals to shift. This situation mostly occurs on the alkyl radicals with carbon number >6.

(3) Chain termination stage of oil sludge pyrolysis stage
In the pyrolysis stage of oil sludge, a binding reaction can also occur between the free radical and the free radical. When the free radicals are combined to form a stable hydrocarbon fraction, the chain reaction is terminated.

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Factors affecting pyrolysis of oil sludge

The change in pyrolysis parameters has a significant effect on the pyrolysis reaction of oil sludge. According to the research and analysis, the parameters that have a great influence on the pyrolysis process of oil sludge are pyrolysis temperature and pyrolysis time, while other parameters such as heating rate, residence time of pyrolysis gas, type of sludge, particle size, heat The type of solution furnace and whether there are other additives will also have a certain impact on the pyrolysis reaction of oil sludge.

(1) Effect of pyrolysis temperature on pyrolysis characteristics of oil sludge

The pyrolysis reaction temperature is the most critical parameter in the pyrolysis process of oil sludge. The pyrolysis experiment of oil sludge is carried out under different pyrolysis conditions to investigate the effects of different factors on the pyrolysis of oil sludge. The results show that : Thermal cracking temperature > Other factors. From the kinetic point of view, the temperature mainly affects the activation energy of the reaction, and then changes the chemical reaction rate. From the thermodynamic point of view, the temperature affects the change of the Gibbs free energy in the reaction process, which in turn affects the direction of the reaction, and finally determines the product. Composition the pyrolysis temperature of oil sludge will affect the yield and oil and gas quality of the three-phase product produced by pyrolysis of oil sludge. In order to cause thermal cracking and thermal condensation reaction of hydrocarbon organic matter and non-hydrocarbon organic matter in oil sludge, it must be provided sufficient energy, when the pyrolysis temperature is too low, the organic matter in the oil sludge will not get enough energy to generate sufficient thermal cracking reaction, which will cause the pyrolysis residue to reach the discharge standard; when the pyrolysis temperature is too high, not only will it Increasing the energy consumption and the oil resources generated by the cracking will also cause a secondary cracking reaction and increase the gas production.

(2) Effect of heating rate on pyrolysis characteristics of oil sludge

By selecting petroleum refinery oil to explore the effects of different heating rates on pyrolysis experiments, studies have shown that as the heating rate increases, more liquid components undergo secondary cracking at higher heating rates, resulting in the liquid phase yield is lower and the gas production is significantly increased. The effect of pyrolysis rate on pyrolysis characteristics was investigated under high temperature conditions. The experimental results show that the pyrolysis rate has little effect on pyrolysis, and the effect becomes smaller as the temperature increases, but it has a great influence on the gas production. Through the study of different heating methods, it was found that the liquid phase yield under rapid heating was lower than that in the slow heating mode, and it was found that the difference in heating mode had an effect on the gas phase, but there was almost no solid phase yield. The effect is mainly due to the secondary cracking of hydrocarbons. Most scholars believe that when pyrolysis is carried out at a relatively slow pyrolysis rate, the residence time of the pyrolysis oil in a relatively hot pyrolysis temperature environment becomes longer, so that the thermal pyrolysis oil undergoes secondary thermal cracking to form small molecules. The gaseous product results in a decrease in the yield of the oil sludge pyrolysis oil phase product.

(3) Effect of pyrolysis time on pyrolysis characteristics of oil sludge

The pyrolysis reaction time generally refers to the residence time of the pyrolysis reaction of the oil sludge in the reaction equipment under high temperature conditions, and the length of the reaction is affected by a series of parameters such as the characteristics of the sludge itself, the particle size of the material, and the reaction temperature. Insufficient reaction time may result in the residue still not meeting the discharge standard after treatment, and the reaction time is too long, which will increase the energy consumption and increase the treatment cost. The pyrolysis reaction time of oil sludge was determined as 30min, 40min, 50min, 60min, 70min, 80min respectively. The experimental results showed that the conversion rate increased with time before 60min, and the conversion rate remained stable after 60min. The waste plastic was selected as the research material of pyrolysis, and the influence of pyrolysis reaction time on the yield of pyrolysis oil produced by oil sludge was investigated. The reaction time was set from 0 to 120 min. The experimental results showed that the pyrolysis reaction time of oil sludge was 30 min. The pyrolysis reaction has almost been completed. The influence of the pyrolysis reaction time of the oil sludge on the thermal cracking reaction depends mainly on whether the pyrolysis reaction of the material is completed. As the reaction time of the material is prolonged, the yield of the liquid phase product is gradually increased, but when the reaction time exceeds a certain value, the reaction is almost completed, and the yield is no longer increased.

The gas phase generated by pyrolysis in a high temperature atmosphere may affect the progress of the secondary cracking reaction due to the difference in residence time, thereby affecting the liquid and gas production rate. The oil sludge was selected for research. It was found that the residence time of the pyrolysis gas affected the yield of the liquid phase product. The yield was the highest at 525 ° C and 1.5 s, which was 30% of the total weight. The difference in carrier gas permeation rate during the pyrolysis reaction of oil sludge will affect the gas residence time and thus the yield of the gas phase product.

(4) Effect of different types of oil sludge on pyrolysis characteristics

The pyrolysis characteristics of different types of oil sludge vary greatly. The oil sludge from different oil fields is selected as the research object. The research shows that the gas-liquid fraction yield of oil sludge is related to the volatility in sludge, and it is highly volatile. The pyrolysis of the oil sludge is obvious, while the oil content of the low-volume oil sludge is lower, and the residue content is higher. This is because the pyrolysis process of the oil sludge is the volatile component. The process of thermal volatilization and thermal conversion. The higher the volatile content, the higher the gas-liquid yield; the lower the volatile content, the higher the solid phase yield. Pyrolysis experiments were carried out on different types of oil sludges. Under the same pyrolysis conditions, the pyrolysis products of the two types of oil sludges were different, and the liquid phase yield of the oil sludge with high ash content was higher than that of volatiles. Liquid phase yield of oil sludge. According to the above research, the yield of the three-phase product is closely related to the original oil sludge itself. Different types of oil sludge, in which the three-phase components and the content of ash and volatile matter are different, these will affect the pyrolysis reaction of oil sludge and the product.

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Summary of sludge treatment methods

Various sludges have their own characteristics, and many technologies are applicable to these sludges. The technologies used are different depending on the treatment requirements. The sludge treatment generally includes landfill, fertilizer, power generation, heating, etc. method. So let’s talk about the specifics of the sludge treatment methods, and what are the different treatment methods.

Sanitary landfill

The disposal method is simple, easy, and low in cost, and the sludge does not need to be highly dehydrated and has strong adaptability. However, there are also some problems in sludge landfill, especially the formation of landfill leachate and gas. Leachate is a heavily polluted liquid that can contaminate the groundwater environment if sited or improperly operated. The gas produced by landfills is mainly methane, which can cause explosions and combustion if appropriate measures are not taken.

Land use

Direct use of sludge land is considered to be the most promising disposal method due to the advantages of low investment, low energy consumption, low operating cost and organic component conversion into soil improver. Scientific and rational land use can be reduced. The negative effects of sludge. The use of forest land and municipal greening has become an effective way of sludge land use because it is not easy to cause pollution of the food chain. The use and use of sludge for the repair and reconstruction of heavily disturbed land (such as mine land, forest harvesting sites, landfills, and severely damaged areas) reduces the potential threat of sludge to human life. Both the sludge was disposed and the ecological environment was restored.

Incineration

The application of wet sludge to direct incineration is more common. It is not only difficult to directly incinerate without drying the sludge, but it is also extremely uneconomical in terms of energy consumption. The sludge treatment method with incineration as the core is one of the most thorough sludge treatment methods. It can completely carbonize organic matter and kill pathogens, which can minimize the sludge volume. However, the disadvantage is that the treatment facility has large investment and treatment. High cost, high equipment maintenance costs, and the production of strong carcinogen dioxin.

Sludge drying

Sludge drying is a treatment method that uses artificial heat source to deep dewater sludge with industrial equipment. Although the direct result of sludge drying is the decrease of sludge moisture content (dehydration), its application purpose and effect are compared with mechanical dewatering. There are big differences.

Sludge mechanical dewatering (including sludge concentration), the purpose of its application is to reduce the volume of sludge treatment (sludge concentration and mechanical dewatering can usually reduce the sludge volume by about 4 times), but the dewatered sludge cake In addition to the water content and related physical properties, such as the difference between fluidity and undisturbed sludge, its chemical and biological properties are not changed by dehydration.

Sludge drying requires an artificial heat source due to the requirement of increasing the evaporation strength of water. The operating temperature (for sludge particles) is usually greater than 100 ° C. The effect of drying on sludge is not only deep dehydration but also heat treatment effect. In addition, the sludge drying treatment product can control the water content below 20%, that is, the level of inhibiting the microbial activity in the sludge, so the sludge drying treatment can simultaneously change the physical, chemical and biological characteristics of the sludge.

New technology

With the strengthening of environmental protection and people’s further understanding of the limitations of existing sludge treatment and disposal technologies, countries all over the world are investing heavily in research and development of new technologies to find a more economical and rational sludge treatment program.

Free processing

The technology innovation uses a sludge washing process to first wash out the organic matter in the sludge, separate the inorganic material sludge soil, and then concentrate the organic sludge for high temperature anaerobic digestion. The precipitated sludge is washed and washed out of the semi-solid inorganic sludge soil in the sludge, reducing the biological treatment amount by half, saving engineering investment and treatment cost; treating the organic sludge separately, removing the precipitation of the inorganic sludge soil in the reactor, Reduce equipment wear and maintenance of the reactor; the precipitated sludge is washed and washed out of the sludge, which is easy to precipitate heavy metal and inorganic sludge soil, which improves the quality of the organic fertilizer; the washed sludge soil can also produce pavement color Brick, permeable brick. Other innovative processes: ultra-high temperature anaerobic digestion, multi-stage anaerobic digestion, biogas residue floating, etc., sludge biological treatment speed increased several times and biogas production increased by more than 20%.

Precipitated sludge biological treatment system, engineering design innovation uses buried, compact, multi-stage digestion reactor design, several independent anaerobic digestion reactors, you and I have you integrated, saving building materials, using The concrete structure is inexpensive to manufacture. The existing anaerobic digestion reactors at home and abroad generally adopt the above-ground structure, and the above ground structure can make the equipment convenient for maintenance and facilitate the biogas residue discharge to prevent the precipitation of the biogas residue. The biological treatment system engineering design has well solved the maintenance of supporting equipment and the deposition of biogas residue. The system is equipped with few equipments, only a few pumps are needed, that is, the pump is broken and replaced with one for less than 20 minutes to ensure that the equipment maintenance does not stop; The precipitated sludge is washed to remove the inorganic sludge soil which is easy to precipitate, and the organic sludge floats and floats and does not precipitate. The buried anaerobic digestion reactor not only has low investment, does not occupy land, but also can prevent earthquakes, lightning strikes and long service life, and reduce heat loss of the digestive system.

Sludge fermented organic fertilizer

There are three traditional sludge treatment methods: incineration, landfill and resource utilization. Many countries use incineration technology, but the investment is huge, which is easy to cause air pollution; landfill is used in China, but it needs to occupy a large amount of land, and it will cause secondary pollution of the environment. Domestic and other large and medium-sized cities in China have few land regeneration resources. This method has been adopted for a long time. Chen Liqiao said that the prospect of treating sludge with microorganisms is broad. Through the on-site test and practical application of the sewage treatment plant, the economic benefit of about 150 yuan can be obtained for each ton of sludge treated. In addition, the use of microbial aerobic fermentation can also eliminate the foul odor of the sludge, effectively control the secondary pollution of the sludge, and the environmental benefits are also significant.

The sludge is fermented into organic fertilizer. If some cow dung is added, it will be fermented into high-quality organic fertilizer. The specific operation method is as follows:

1. Add bacteria. 1 kg of gold baby fertilizer starter can ferment about 4 tons of sludge + cow dung. It is necessary to add 30-50% of cow dung, or straw powder, mushroom residue, peanut shell powder, or rice husk, sawdust and other organic materials in order to adjust the air permeability. If rice husk and sawdust are added, the fermentation time should be prolonged because of the high cellulose lignin. Strain dilution: add 5-10 kg of rice bran (or bran, corn flour and other substitutes) per kg of starter, mix well and then evenly sprinkle into the material pile, the effect will be better.

2. Build a pile. After the preparation, the bacteria should be built and the pile height and volume should not be too short and too small. Requirements: stack height 1.5-2 meters, width 2 meters, length 2-4 meters

3. Mix well and ventilate. Jinbao fertilizer fermenting agent needs good (consumption) oxygen fermentation, so it should increase the oxygen supply measures, so that mixing, digging, and ventilation are appropriate. Otherwise, it will lead to anaerobic fermentation and produce odor, which will affect the effect.

4. Moisture. The moisture content of the fermentation material should be controlled at 60-65%. Moisture judgment: hold a hand tightly on the material, see the watermark but not dripping, and it is appropriate to land. Low water fermentation, slow water and poor ventilation, can also lead to “septic bacteria” work and produce odor.

5. Temperature. The starting temperature should be better than 15 °C (the four seasons can be operated, not affected by the season, and the winter should be fermented indoors or in the greenhouse), and the fermentation temperature should be controlled below 70-75 °C.

6. Complete. On the 2-3rd day, the temperature should be over 65 °C. It should be overturned. Generally, the fermentation can be completed within one week. The material is dark brown and the temperature begins to drop to normal temperature, indicating that the fermentation is completed. If there are too many excipients such as sawdust, sawdust and rice husk, the fermentation time should be prolonged until fully decomposed. Fermented organic fertilizer, good fertilizer effect, safe and convenient to use, anti-disease and long-term, can also fertilize soil and so on.

Lime dosing technology

The dehydrated sludge enters the hopper, and lime and amino citric acid are added to the hopper. The amount of lime is 10% to 15% of the amount of wet mud, and the amount of amino citric acid is about 1% of the amount of lime. Since aminoguanic acid generates ammonia during the reaction, the sterilization effect of the entire process is enhanced and the reaction temperature is lowered. After the sludge, quicklime and amino citric acid are stirred in the hopper, they are pushed into the inlet of the plunger pump by the double screw feeder, sent to the reactor through the plunger pump, and stay at 70 ° C for 30 min, and the output product can be Meet the US EPA PART503 CLASS A standard. The reacted sludge is pumped to the silo, and the gas generated in the sealed container is discharged by the washing tower.

The characteristics of the process:

pH>12, long duration, complete sterilization; high pH makes most metal ions precipitate, which reduces its solubility and activity; the solid content of sludge can be increased to 30%; the odor in sludge is removed, the system Fully sealed, no environmental pollution; fully automatic system, easy operation and maintenance: adding a small amount of amino acid, reducing the amount of lime and reaction time, reducing operating costs.

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