Oil sludge smoldering coupled with pyrolysis oil recovery process and equipment

Abstract

The present application belongs to the technical field of oily sludge resource treatment, and discloses a process and equipment for recovering pyrolysis oil from oily sludge by smoldering coupling. The process is a coupling of smoldering and low-temperature pyrolysis, and uses the heat generated by the self-sustaining smoldering of oily sludge as the heat source for low-temperature pyrolysis of another part of the oily sludge, so as to obtain pyrolysis oil by low-temperature pyrolysis. The oily sludge used for smoldering treatment has a water content of greater than or equal to 60% and an oil content of 10% to 30%, and has a low calorific value. The oily sludge used for low-temperature pyrolysis treatment has a water content of less than or equal to 30% and an oil content of greater than or equal to 40%, and has a high calorific value. The present application improves the mechanism of the process, and combines smoldering and low-temperature pyrolysis to dispose of oily sludge, so as to convert the oily sludge into pyrolysis oil. The present application improves the disposal rate of oily sludge, reduces the energy consumption of the oily sludge pyrolysis disposal system, and realizes the harmless and resourceful disposal of oily sludge.

Description

Technical Field

[0001] This invention belongs to the field of oily sludge resource utilization technology, and more specifically, relates to an oily smoldering coupled pyrolysis oil recovery process and equipment. It utilizes the heat released by the smoldering of oily sludge and couples it with the low-temperature slow pyrolysis of oily sludge to achieve comprehensive treatment of oily sludge. It can be used for the treatment of oilfield sludge, etc. Background Technology

[0002] Oily sludge is a hazardous waste, listed in the National Hazardous Waste List (HW08). Improper disposal can cause serious environmental damage. Typical oily sludge contains 10%–70% water, 20%–80% oil, and 10%–30% solid particles by mass. The proportions and composition of these components vary greatly depending on the type of oily sludge (e.g., refining sludge has a high water content, while tank bottom sludge has a high oil content). Therefore, there is no universally applicable treatment technology. Compared to other organic wastes, oily sludge is rich in combustibles and has a higher fuel value. The solid particles in oily sludge may contain various heavy metals (such as calcium and iron). Currently, the main oily sludge treatment technologies in China include solvent extraction, incineration, biological treatment, and catalytic pyrolysis. Among these, incineration is the most widely used harmless treatment technology. It is simple, direct, significantly reduces volume, and has a fast treatment rate. However, incineration technology cannot directly process oily sludge with a moisture content higher than 50%. It requires centrifugal pretreatment to reduce the moisture content and the addition of auxiliary fuel to ensure stable incineration. Incineration technology suffers from high energy consumption and complex processes, and it cannot recover fuel oil from the oily sludge. Pyrolysis technology is a resource recovery technology that can recover pyrolysis oil from the organic matter in oily sludge through thermal decomposition (reported in literature to be around 600℃), thus achieving resource utilization of the products. This method requires a large amount of continuous external heat. The oily sludge needs to be dehydrated and dried before undergoing an endothermic pyrolysis reaction. Electric heating is generally used to power the pyrolysis technology, but the high cost limits its large-scale application.

[0003] Among the existing methods for treating oily sludge, patent CN 111425868 A describes a combined process and equipment for sludge self-sustaining smoldering and high-temperature aerobic fermentation, which utilizes a complex heat collection and transfer device for heat storage during high-temperature fermentation, but does not involve an integrated smoldering-pyrolysis furnace. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a process and equipment for recovering oily sludge through smoldering coupled with pyrolysis. By improving the process mechanism, the smoldering of oily sludge is combined with low-temperature pyrolysis, converting the oily sludge into pyrolysis oil. This increases the oily sludge treatment rate while reducing the energy consumption of the pyrolysis system, simultaneously achieving the harmless and resource-based treatment of the oily sludge. Due to the high calorific value and low ash content of oily sludge, smoldering at temperatures above 600℃ can be easily achieved, thus utilizing the heat generated by smoldering to provide a heat source for the low-temperature pyrolysis process. This invention combines the advantages of self-sustaining smoldering technology (low energy consumption, applicability to high moisture content and low calorific value, and heat generation) with the advantage of low-temperature pyrolysis technology (enabling resource utilization of oily sludge), achieving the harmless and resource-based treatment of oily sludge.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for recovering oily sludge through smoldering coupled with pyrolysis is provided. The method is characterized by coupling smoldering with low-temperature pyrolysis, utilizing the heat generated by the self-sustaining smoldering of the oily sludge via heat conduction as a heat source for the low-temperature pyrolysis of another portion of the oily sludge, thereby obtaining pyrolysis oil through low-temperature pyrolysis; wherein the temperature of the low-temperature pyrolysis is 300–500°C; and, the oily sludge treated by smoldering is designated as the first oily sludge, and the oily sludge treated by low-temperature pyrolysis... If the sludge is the second type of oily sludge, then the first type of oily sludge has a water content greater than or equal to 60 wt% and an oil content of 10 wt% to 30 wt%, and the second type of oily sludge has a water content less than or equal to 30 wt% and an oil content greater than or equal to 40 wt%. At the same time, the calorific value of the first type of oily sludge is 2 to 9 MJ / kg, and the calorific value of the second type of oily sludge is not less than 18 MJ / kg. The filling height of the mixture of the first type of oily sludge and the porous medium used for smoldering is not less than 30 cm and not more than 150 cm.

[0006] As a further preferred embodiment of the present invention, the smoldering is carried out in a smoldering chamber; the low-temperature pyrolysis is carried out in a pyrolysis chamber; the smoldering chamber and the pyrolysis chamber are separated by a thermally conductive partition; the heat generated by the self-sustaining smoldering of the oily sludge is transferred to the pyrolysis chamber through the thermally conductive partition via heat conduction;

[0007] Preferably, the smoldering chamber and the pyrolysis chamber are coaxially arranged and separated by a heat-conducting sidewall, with the smoldering chamber surrounded by the pyrolysis chamber.

[0008] As a further preferred embodiment of the present invention, the low-temperature pyrolysis is carried out with the participation of a catalyst containing calcium and / or iron.

[0009] Preferably, the catalyst containing calcium and / or iron is smoldering ash.

[0010] As a further preferred embodiment of the present invention, the smoldering is carried out by mixing porous media and first oily sludge at a mass ratio of 2:1 to 6:1 as a mixture.

[0011] Preferably, the porous medium is sand.

[0012] As a further preferred embodiment of the present invention, the smoldering specifically involves preheating the mixture after it has been piled up to a preset height, and when the mixture reaches the ignition point temperature, air is introduced to allow the first oily sludge to continuously sustain smoldering.

[0013] Preferably, the ignition point temperature is 200℃~400℃;

[0014] The preset height of the stack is not less than 30cm.

[0015] As a further preferred embodiment of the present invention, the smoldering darcy flow rate is 3 to 10 cm / s.

[0016] According to another aspect of the present invention, the present invention provides an oily sludge smoldering coupled pyrolysis oil recovery device, characterized in that it includes a smoldering chamber (5) and a pyrolysis chamber (6), wherein the smoldering chamber (5) is used for self-sustaining smoldering of a first oily sludge, and the pyrolysis chamber (6) is used for low-temperature pyrolysis of a second oily sludge; the heat generated by the self-sustaining smoldering in the smoldering chamber (5) is used as the heat source for the low-temperature pyrolysis of the pyrolysis chamber (6) through heat conduction;

[0017] The temperature of the low-temperature pyrolysis is 300-500℃; the first oily sludge has a water content higher than 60% and an oil content of 10%-30%, and the second oily sludge has a water content lower than 30% and an oil content higher than 40%.

[0018] The smoldering chamber (5) and the pyrolysis chamber (6) are coaxially arranged and separated by a heat-conducting sidewall. The smoldering chamber (5) is surrounded by the pyrolysis chamber (6).

[0019] As a further preferred embodiment of the present invention, both the smoldering chamber (5) and the pyrolysis chamber (6) are cylindrical, and the cross sections of the smoldering chamber (5) and the pyrolysis chamber (6) are concentric circles.

[0020] Preferably, the radius of the cross-sectional circle of the smoldering chamber (5) is 5 to 60 cm, and the ratio of the radius of the cross-sectional circle of the smoldering chamber (5) to the radius of the entire concentric circle is 1 / 2 to 4 / 5;

[0021] The thickness of the thermally conductive partition is 0.5 to 1 mm, and its thermal conductivity is not lower than that of stainless steel.

[0022] Preferably, the thermally conductive partition is made of copper or stainless steel;

[0023] The outer wall of the pyrolysis chamber (6) is wrapped with thermal insulation material;

[0024] Preferably, the insulation material is ceramic material or quartz wool.

[0025] As a further preferred embodiment of the present invention, the upper part of the smoldering chamber (5) is provided with a feed inlet, and the first oily sludge can be transported to the mixing chamber (2) by the raw material conveyor belt (1) and mixed with the porous medium to obtain a mixture. The mixture is then transported to the smoldering chamber (5) by the material conveyor belt (3) through the feed inlet; and a material distributor (4) is also provided directly below the feed inlet.

[0026] The upper part of the smoldering chamber (5) is also provided with a smoldering exhaust gas outlet (8), which is connected to the flue gas purification component (15).

[0027] The lower part of the smoldering chamber (5) is provided with an electric heating component (11) and a smoldering chamber air inlet (12), which are used to heat the smoldering chamber (5) to the smoldering ignition point temperature and to introduce air, respectively.

[0028] The bottom of the smoldering chamber (5) is also provided with an ash hopper (13), which is connected to the ash collection chamber (14); the ash collection chamber (14) is connected to the ash conveying assembly (7).

[0029] As a further preferred embodiment of the present invention, the upper part of the pyrolysis chamber (6) is provided with a pyrolysis gaseous product outlet, which is connected to the pyrolysis gas collection bag (20) in sequence through a water removal component (17) and a condensation component (19); wherein, the water removal component (17) is used to remove water vapor from the pyrolysis gaseous product; the condensation component (19) is used to condense the pyrolysis gaseous product, and the pyrolysis oil generated by condensation is collected through a collection bottle (18); the pyrolysis gas collection bag (20) is used to collect pyrolysis gas.

[0030] Compared with existing technologies, the technical solutions conceived in this invention, by coupling self-sustaining smoldering and slow-speed low-temperature anaerobic pyrolysis, can simultaneously treat two types of oily sludge: one with high water content and the other with high oil content. The heat generated by the self-sustaining smoldering of the oily sludge with high water content is directly used as a heat source for the low-temperature pyrolysis of the other oily sludge with high oil content through heat conduction. This achieves resource utilization of oily sludge with gradient water content and calorific value (the smoldering process targets the first type of oily sludge with a water content higher than 60%, an oil content of 10% to 30%, and a calorific value of 2 to 9 MJ / kg; the low-temperature pyrolysis process targets the second type of oily sludge with a water content lower than 30%, an oil content higher than 40%, and a calorific value not lower than 18 MJ / kg). The heat generated by smoldering is directly used to power the low-speed anaerobic pyrolysis process, achieving complementary advantages between the technologies.

[0031] Specifically, the present invention can achieve the following beneficial effects:

[0032] (1) Smoldering is suitable for treating organic solid waste with a moisture content of over 60%. It is a process in which the organic matter in the fuel is slowly burned and heat is continuously transferred after mixing with a porous medium (e.g., sand). The heat required for water evaporation and reaction is obtained entirely from the oxidation reaction of the organic matter itself, which can greatly reduce the energy consumption of pyrolysis of oily sludge. At present, because the research focus is on expanding the application scenarios of smoldering technology, there is no mature method to directly and effectively utilize the heat generated by self-sustaining smoldering. This invention divides the oily sludge into two parts, using the heat generated by the self-sustaining smoldering of the high-moisture-content oily sludge as the heat source for the pyrolysis of the other part of the low-moisture-content oily sludge. This combines self-sustaining smoldering with low-temperature anaerobic pyrolysis, thereby improving the sludge treatment rate and reducing the energy consumption of the oily sludge treatment system, achieving the harmless and resource-based treatment of oily sludge. Compared with the prior art, the treatment process of this invention is applicable to oily sludge with gradient oil content and gradient moisture content. It employs targeted treatment methods, capable of handling oily sludge from different sources and formation mechanisms. Furthermore, the size and filling height of the combustion chamber can be flexibly adjusted according to the amount of oily sludge to be treated, demonstrating strong versatility.

[0033] Taking the following embodiments as examples, the treatment rate of oily sludge is not significantly different compared to a smoldering furnace of the same size. For treating the same type and weight of oily sludge, the energy consumption of the entire treatment system decreased from 3.2 kWh to 0.9 kWh compared to electric heating. Pyrolysis oil with a calorific value close to diesel oil was successfully recovered, realizing the resource utilization of oily sludge. The ash after pyrolysis and smoldering is clean, with heavy metals not exceeding standards and free of petroleum hydrocarbons.

[0034] (2) For smoldering treatment, taking sand as a porous medium as an example, the heat storage effect of sand itself and the slow air flow rate in the sand pores result in very little heat loss. Therefore, based on this invention, after the heat generated by smoldering heats the pyrolysis chamber to the pyrolysis temperature, it will be maintained for 2-3 hours. By further optimizing and controlling the mixing ratio of the first oily sludge and sand, as well as the Darcy flow rate, it is possible to ensure that the temperature and heating rate required for slow low-temperature pyrolysis are provided, thereby achieving stable control of the pyrolysis process and ensuring the acquisition of ideal pyrolysis products. This invention utilizes the self-sustaining smoldering of oily sludge, which can serve as a heat source to maintain low-temperature pyrolysis at 300-500°C (heating rate 2-5°C / min).

[0035] (3) The filling height of the mixture used for smoldering should be no less than 30cm and no more than 150cm (the optimal filling height is 30-60cm). Because the oxidation reaction rate of smoldering is slow, the heat release is easily affected by the filling height. Excessive filling will cause moisture accumulation and downward penetration. Furthermore, due to the boundary effect, the stability of the smoldering combustion at the rear end cannot be guaranteed. Insufficient filling will result in a short smoldering reaction time, leading to insufficient heating of the pyrolysis chamber and pyrolysis failure.

[0036] (4) The intensity of the smoldering reaction is mainly controlled by the Darcy flow rate, which is preferably 3-10 cm / s, which is beneficial to the smoldering reaction and its self-sustaining propagation. In this invention, the smoldering chamber of the integrated smoldering-pyrolysis furnace is preferably located in the center of the furnace body, with the side walls surrounded by the pyrolysis chamber. At this time, the Darcy flow rate is the fastest, so the smoldering reaction is the most intense, ensuring that the oily sludge in the center and near the wall is fully treated, releasing more heat and effectively avoiding the influence of the boundary layer effect. In the integrated smoldering-pyrolysis furnace, the smoldering chamber and the pyrolysis chamber are separated by a heat-conducting baffle (the heat-conducting baffle can be made of stainless steel, for example; the higher the thermal conductivity of the heat-conducting baffle, the better. Taking stainless steel as an example, its thermal conductivity is 16.3 W / m℃, which meets the requirements). The heat generated by smoldering passes through the smoldering chamber wall through flue gas convection and sand conduction, avoiding heat loss caused by heat dissipation to the surroundings and providing sufficient heat for the pyrolysis chamber. If the pyrolysis chamber is located in the middle and surrounded by the smoldering chamber, it will lead to uneven airflow distribution, resulting in incomplete smoldering near the smoldering furnace wall, leaving behind insufficiently treated oily sludge. Furthermore, the smoldering furnace will inevitably dissipate heat to the environment, causing energy waste, which is not conducive to fully realizing the advantages of the method of the present invention.

[0037] (5) The ash contains metal oxides such as CaO and Fe2O3. The oxides of calcium and iron can promote the conversion of heavy oil in oily sludge into lighter oil during pyrolysis. Therefore, it can be further collected by an ash collection device, screened, and used as a mixture of pyrolysis oily sludge, realizing waste utilization and improving the yield of pyrolysis oil.

[0038] (6) In addition, during the design of the equipment, the gases generated by smoldering can be safely discharged after passing through the tail gas treatment system. The pyrolysis products can be collected through the condensation system to obtain pyrolysis oil that has the potential to be used directly as fuel. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a preferred process for recovering oily sludge through smoldering coupled with pyrolysis.

[0040] Figure 2 This is a schematic diagram of a preferred embodiment of the present invention: a pyrolysis oil recovery device for oily sludge with smoldering coupling.

[0041] Figure 2 The meanings of the reference numerals in the attached figures are as follows: 1 is the raw material conveyor belt, 2 is the mixing bin, 3 is the material conveyor belt, 4 is the material distributor, 5 is the smoldering chamber, 6 is the pyrolysis chamber, 7 is the ash removal device (i.e., the ash removal component), 8 is the smoldering tail gas outlet, 9 is the pyrolysis chamber insulation layer, 10 is the porous media layer, 11 is the electric heating device (i.e., the electric heating component), 12 is the smoldering chamber air inlet, 13 is the ash hopper, 14 is the ash collection chamber, 15 is the flue gas purification device (i.e., the flue gas purification component), 16 is the pyrolysis oil outlet (i.e., the pyrolysis gaseous product outlet; pyrolysis oil is obtained after condensation of the pyrolysis gaseous product), 17 is the water removal device (i.e., the water removal component), 18 is the collection bottle, 19 is the condensation device (i.e., the condensation component), and 20 is the pyrolysis gas collection bag. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0043] In summary, the combined treatment process of oily sludge smoldering coupled with pyrolysis includes two parts: self-sustaining smoldering of the oily sludge and low-temperature pyrolysis. Depending on the type of oily sludge, it is divided into two parts. The heat generated by the self-sustaining smoldering of one part of the oily sludge is used as the heat source for the low-temperature pyrolysis of the other part (that is, the heat generated by the self-sustaining smoldering process in the smoldering chamber is transferred to the pyrolysis chamber through heat conduction, which meets the temperature range and heating rate requirements for the low-temperature, slow pyrolysis of the other part of the oily sludge). For example, if there are oily sludges from different sources with different calorific values, the sludge with a high calorific value and low moisture content is selected as the pyrolysis feedstock, while the smoldering feedstock is selected as the smoldering feedstock.

[0044] Self-sustaining smoldering utilizes a continuous smoldering reaction system with a smoldering furnace as the main body to convert oily sludge into heat, gas, and ash through a self-sustaining smoldering reaction. Low-temperature pyrolysis recovers the pyrolysis oil from the oily sludge through anaerobic pyrolysis.

[0045] The present invention relates to a method for recovering oily sludge through smoldering coupled with pyrolysis, such as... Figure 1 As shown, the following steps may be included:

[0046] (1) Based on the different oil content and water content, the oily sludge is divided into two parts (for example, if oily sludge from different sources is received, oily sludge with a water content of less than 30% and an oil content of more than 40% can be selected as pyrolysis raw material, which can be recorded as oily sludge 2; oily sludge with a water content of more than 60% and an oil content of 10% to 30% can be selected as smoldering raw material, which can be recorded as oily sludge 1). Oily sludge 1 is fully mixed with sand (or other porous media known to be feasible for smoldering) in a preset mass ratio to obtain a mixture with uniform physical and chemical properties, and the mixture is sent to the predetermined smoldering position for stacking; the other part of oily sludge 2 is mixed with smoldering ash (or other catalysts containing calcium and / or iron elements can be used) and fed into the pyrolysis chamber for pyrolysis in one go.

[0047] (2) After the mixture is piled up to the preset height, it is preheated to raise its temperature. When the mixture is heated to the ignition point temperature, air is introduced to allow the sludge in the mixture to continue to self-sustain smoldering.

[0048] (3) The heat generated during the continuous self-sustaining smoldering process of the oily sludge passes through the inner wall of the smoldering chamber through heat conduction, providing energy to the pyrolysis chamber. The entire smoldering process can maintain the temperature at around 600℃, ensuring that the pyrolysis chamber remains within the temperature range required for pyrolysis.

[0049] (4) In the pyrolysis chamber, the oily sludge absorbs the heat generated by smoldering, first dehydrates and dries, and then undergoes pyrolysis (specifically, it is first rapidly heated to about 200℃ for dehydration and drying. At 200-300℃, small-molecule hydrocarbons in the oily sludge volatilize. When the temperature is raised to about 350℃, the oily sludge begins to undergo low-temperature pyrolysis). Sand is a material with a low heat transfer coefficient and high heat capacity. Therefore, as the smoldering reaction progresses from bottom to top, the pyrolysis process is also completed from bottom to top (the temperature in the pyrolysis chamber rises from 350℃ at a heating rate of 2-5K / min to about 500℃). After the smoldering process ends, low-temperature slow pyrolysis is also gradually completed. Throughout the process, due to the heat storage effect of the sand, the smoldering temperature can be maintained within a stable range, thus providing a suitable pyrolysis temperature for the low-temperature slow pyrolysis in the pyrolysis chamber. The pyrolysis temperature can also be maintained within a stable range, and the heating rate is also kept within a stable range. Due to the catalytic effect of calcium and iron metal oxides in the smoldering ash, most of the products of the cracking of heavy oil in oily sludge are light pyrolysis oil.

[0050] (5) The gases generated by smoldering are purified by the tail gas treatment system and can be safely discharged. The pyrolysis products are collected as high-calorific-value pyrolysis oil through the condensation system.

[0051] Based on this invention, an oily sludge smoldering coupled pyrolysis oil recovery device can be set up to realize the oily sludge smoldering coupled pyrolysis oil treatment process. This device may include a raw material conveyor belt 1, a mixing chamber 2, a material conveyor belt 3, an integrated smoldering-pyrolysis furnace (including a smoldering chamber 5 and a pyrolysis chamber 6), a condensation collection device 19, and a flue gas purification device 15. The raw material conveyor belt 1, mixing chamber 2, and material conveyor belt 3 are designed for the smoldering process (oily sludge can be transported via the raw material conveyor belt 1 to the mixing chamber 2 and mixed with a porous medium to obtain a mixture, which is then transported via the material conveyor belt 3 through the smoldering chamber inlet to the smoldering chamber 5), enabling continuous feeding for the smoldering process, thus ensuring continuous smoldering until low-temperature pyrolysis is completed.

[0052] The smoldering-pyrolysis integrated furnace body can be a hollow cylinder made of metal, such as... Figure 2 As shown, the smoldering chamber 5 and the pyrolysis chamber 6 are located in two chambers of the same cylindrical container (the smoldering chamber 5 is in the center, and the pyrolysis chamber 6 surrounds the smoldering chamber 5, forming a coaxial structure; the cross-sections of the smoldering chamber 5 and the pyrolysis chamber 6 are concentric circles), separated by the inner wall of the container (the space in the inner wall of the cylinder is the smoldering chamber 5; the space between the outer and inner walls of the cylinder is the pyrolysis chamber 6). A portion of the heat generated by the self-smoldering process of the oily sludge in the smoldering chamber is transferred to the pyrolysis chamber through the container wall via heat conduction.

[0053] Depending on the scale of the process, the radius of the smoldering chamber is 5 to 60 cm, and the ratio of the smoldering chamber radius to the total radius of the circle is 1 / 2 to 4 / 5.

[0054] The following are specific examples:

[0055] Implementation Case 1:

[0056] The experimental setup used in this embodiment is a 1m high hollow stainless steel cylinder. The radius of the entire cylinder is 9.4cm. The radius of the smoldering chamber is 7.5cm, and the radial width of the pyrolysis chamber is 1.5cm. The wall thickness of the smoldering chamber is 1mm, and the wall thickness of the pyrolysis chamber is 3mm. 880g of oily sludge was used as the smoldering feedstock, and 200g was used as the pyrolysis feedstock. During the smoldering process, feeding was continuous to ensure that smoldering always occurred, and the generated ash was discharged through the ash collection funnel below. The pyrolysis feedstock was added to the pyrolysis chamber all at once.

[0057] The corresponding processing method includes the following steps:

[0058] (1) A batch of refining sludge 1 and tank bottom sludge 2 from Shengli Oilfield in North China was received. The sludge 1 was found to have a moisture content of 61%, an oil content of 28%, an ash content of 11% (all by mass percentage; the same below), and a calorific value of 8.0 MJ / kg; the sludge 2 had a moisture content of 22%, an oil content of 60%, an ash content of 18%, and a calorific value of 18.9 MJ / kg. The batch of sludge was divided into two parts. Sand and sludge 1 were thoroughly mixed in a 3:1 weight ratio and the mixture was sent to a predetermined smoldering device for stacking. The other part of the oily sludge 2 was mixed with smoldering ash and placed in the pyrolysis chamber.

[0059] (2) After the mixture is piled up to a preset height of 40cm, the smoldering device is preheated. After 60 minutes, the bottom mixture is heated to 250℃ and air is introduced to make the Darcy flow rate of the air in the smoldering device 4cm / s, and the sludge in the mixture begins to smolder.

[0060] (3) The heat generated by smoldering passes through the smoldering chamber wall and reaches the pyrolysis chamber. The oily sludge begins to evaporate moisture. As the temperature gradually rises to 200℃, the moisture in the oily sludge gradually evaporates, and small molecule hydrocarbons such as methane begin to volatilize. At this time, the tail gas bag can be used to collect the vapors.

[0061] (4) As the smoldering reaction progresses upward, the temperature in the pyrolysis chamber gradually rises to 300℃. The heating rate in the pyrolysis chamber is about 5K / min, and the oily sludge begins to pyrolyze.

[0062] (5) The exhaust gas generated by smoldering was discharged after passing through a flue gas purification device, and the measured NOx and SO2 both met the emission standards. The pyrolysis products (a mixture of water and oil) generated in the pyrolysis chamber were collected, and the lower layer of water was filtered off to obtain a black, viscous recovered oil with a calorific value of 38.2 MJ / kg, slightly lower than that of diesel oil (42.6 MJ / kg). Throughout the process, oily sludge 1 and 2 were fully treated, leaving a clean mixture of ash and sand. The ash can be mixed with the oily sludge used for pyrolysis and used as a catalyst. Compared with a smoldering furnace of the same size (i.e., a smoldering furnace with a radius of 7.5 cm and a height of 1 m), the treatment rates were 0.54 kg / min / m. 2 and 0.52 kg / min / m 2 The difference is negligible. Due to the adoption of smoldering heating, compared with an electrically heated pyrolysis furnace that pyrolyzes the same weight of oily sludge 2 at the same temperature, the energy consumption is reduced from 3.2 kWh to 0.9 kWh.

[0063] Implementation Case 2:

[0064] The experimental setup used in this embodiment is a 1m high hollow stainless steel cylinder. The radius of the entire cylinder is 10.8cm, the radius of the smoldering chamber is 7.5cm, and the radius of the pyrolysis chamber is 3cm. The wall thickness of the smoldering chamber is 1mm, and the wall thickness of the pyrolysis chamber is 2mm. 1000g of oily sludge was used as the smoldering feedstock, and 210g was used as the pyrolysis feedstock. Similar to Example 1, during the smoldering process, continuous feeding was maintained to ensure that smoldering always occurred, and the generated ash was discharged through the ash collection funnel below. The pyrolysis feedstock was added to the pyrolysis chamber all at once.

[0065] The corresponding processing method includes the following steps:

[0066] (1) A batch of oil sludge 1 and tank bottom oil sludge 2 from Daqing Oilfield were received. The oil sludge 1 was found to have a water content of 63%, an oil content of 25%, an ash content of 12%, and a calorific value of 7.4 MJ / kg; the oil sludge 2 had a water content of 13%, an oil content of 76%, an ash content of 11%, and a calorific value of 19.2 MJ / kg. The batch of oil sludge was divided into two parts. Sand and oil sludge 1 were thoroughly mixed in a 3:1 weight ratio and the mixture was sent to a predetermined smoldering device for stacking. The other part of the oily sludge 2 was mixed with smoldering ash and placed in the pyrolysis chamber.

[0067] (2) After the mixture is piled up to a preset height of 34cm, the smoldering device is preheated. After 70 minutes, the bottom mixture is heated to 250°C and air is introduced to make the Darcy flow rate of the air in the smoldering device 5cm / s, and the sludge in the mixture begins to smolder.

[0068] (3) The heat generated by smoldering passes through the wall of the smoldering chamber and reaches the pyrolysis chamber, where the oily sludge begins to evaporate moisture. As the smoldering reaction progresses upward, the temperature in the pyrolysis chamber gradually rises to 300℃, and the heating rate in the pyrolysis chamber is about 4K / min, at which point the oily sludge begins to pyrolyze.

[0069] (4) The pyrolysis products (a mixture of water and oil) generated in the pyrolysis chamber were collected. The lower layer of water was filtered off, yielding a black, viscous recovered oil with a calorific value of 39.6 MJ / kg, slightly lower than that of diesel oil (42.6 MJ / kg). Throughout the process, oily sludge 1 and 2 were thoroughly treated, leaving a clean mixture of ash and sand. The ash was a brick-red powder containing ferric oxide and calcium oxide, and therefore could be mixed with the oily sludge used for pyrolysis as a catalyst. Compared to a smoldering furnace of the same size (i.e., a smoldering furnace with a radius of 7.5 cm), the treatment rates were 0.59 kg / min / m². 2 and 0.62 kg / min / m 2 Due to the adoption of smoldering heating, the energy consumption was reduced from 3.7 kWh to 0.82 kWh compared with an electrically heated pyrolysis furnace that pyrolyzes the same weight of oily sludge 2 at the same temperature.

[0070] Implementation Case 3:

[0071] The experimental setup used in this embodiment is a 1.5m high hollow stainless steel cylinder. The radius of the entire cylinder is 78cm, the radius of the smoldering chamber is 60cm, and the radial width of the pyrolysis chamber is 15cm. The wall thickness of the smoldering chamber is 1cm, and the wall thickness of the pyrolysis chamber is 2cm. In each experiment, 130kg of oily sludge was added as smoldering feedstock, and 20kg of oily sludge was added as pyrolysis feedstock. Similar to Example 1, during the smoldering process, continuous feeding was maintained to ensure that smoldering always occurred, and the generated ash was discharged through the ash collection funnel below. The pyrolysis feedstock was added to the pyrolysis chamber all at once.

[0072] (1) A batch of refining sludge 1 and tank bottom sludge 2 from an oil refinery in Dongying, Shandong Province was received. The sludge 1 was found to have a moisture content of 65%, an oil content of 21%, an ash content of 14%, and a calorific value of 6.2 MJ / kg; the sludge 2 had a moisture content of 15%, an oil content of 62%, an ash content of 23%, and a calorific value of 22.4 MJ / kg. The batch of sludge was divided into two parts. Sand and sludge 1 were thoroughly mixed in a 3:1 weight ratio and the mixture was sent to a predetermined smoldering device for stacking. The other part of the oily sludge 2 was mixed with smoldering ash and placed in a pyrolysis chamber.

[0073] (2) After the mixture is piled up to a preset height of 130cm, the smoldering device is preheated. After 80 minutes, the bottom mixture is heated to 250°C and air is introduced to make the Darcy flow rate of the air in the smoldering device 6cm / s, and the sludge in the mixture begins to smolder.

[0074] (3) The heat generated by smoldering passes through the wall of the smoldering chamber and reaches the pyrolysis chamber, where the oily sludge begins to evaporate moisture. As the smoldering reaction progresses upward, the temperature in the pyrolysis chamber gradually rises to 300℃, with a heating rate of approximately 5K / min, at which point the oily sludge begins to pyrolyze.

[0075] (4) The pyrolysis products (a mixture of water and oil) generated in the pyrolysis chamber were collected, and the lower layer of water was filtered off to obtain a black viscous recovered oil with a calorific value of 34.7 MJ / kg, which has certain potential for use as fuel.

[0076] Comparative Example 1:

[0077] This comparative example uses the same experimental setup as Example 1, a 1m high hollow stainless steel cylinder. 880g of oily sludge was used as smoldering feedstock, and 200g was used as pyrolysis feedstock. The treatment method includes the following steps:

[0078] (1) A batch of oil sludge 1 and tank bottom sludge 2 from an oil refinery in Guangdong Province was received. The oil sludge 1 was found to have a moisture content of 78%, an oil content of 10%, an ash content of 12%, and a calorific value of 1.2 MJ / kg; the oil sludge 2 had a moisture content of 25%, an oil content of 62%, an ash content of 13%, and a calorific value of 18.2 MJ / kg. The batch of oil sludge was divided into two parts. Sand and oil sludge 1 were thoroughly mixed in a 3:1 weight ratio and the mixture was sent to a predetermined smoldering device for stacking. The other part of the oily sludge 2 was mixed with smoldering ash and placed in a pyrolysis chamber.

[0079] (2) After the mixture is piled up to a preset height of 36cm, the smoldering device is preheated. After 60 minutes, the bottom mixture is heated to 250°C and air is introduced to make the Darcy flow rate of the air in the smoldering device 4.25cm / s, and the sludge in the mixture begins to smolder.

[0080] (3) The heat generated by smoldering passes through the smoldering chamber wall and reaches the pyrolysis chamber, where the oily sludge begins to evaporate moisture and pyrolyze. However, due to the low calorific value of oily sludge 1, the heat generated by smoldering is insufficient. As the smoldering reaction progresses upwards, the temperature in the pyrolysis chamber cannot be stably maintained within the range required for pyrolysis. In the end, only a small amount of yellowish-brown oily liquid was collected from the experimental products, and the experiment failed.

[0081] Comparative Example 2:

[0082] This comparative example uses the same experimental setup as Example 1, a 1m high hollow stainless steel cylinder. 900g of oily sludge was used as smoldering feedstock, and 150g of oily sludge was used as pyrolysis feedstock.

[0083] The processing method includes the following steps:

[0084] (1) A batch of refining sludge 1 and tank bottom sludge 2 from an oil refinery in Shandong Province was received. The sludge 1 was found to have a moisture content of 72%, an oil content of 18%, an ash content of 10%, and a calorific value of 3.2 MJ / kg; the sludge 2 had a moisture content of 36%, an oil content of 38%, an ash content of 26%, and a calorific value of 18.2 MJ / kg. The batch of sludge was divided into two parts. Sand and sludge 1 were thoroughly mixed in a 3:1 weight ratio and the mixture was sent to a predetermined smoldering device for stacking. The other part of the oily sludge 2 was mixed with smoldering ash and placed in a pyrolysis chamber.

[0085] (2) After the mixture is piled up to a preset height of 40cm, the smoldering device is preheated. After 90 minutes, the bottom mixture is heated to 250°C and air is introduced to make the Darcy flow rate of the air in the smoldering device 4.25cm / s, and the sludge in the mixture begins to smolder.

[0086] (3) The heat generated by smoldering passes through the smoldering chamber wall and reaches the pyrolysis chamber, where the oily sludge begins to evaporate moisture and pyrolyze. As the smoldering reaction progresses upwards, the temperature in the pyrolysis chamber gradually rises to 300℃, with a heating rate of 4K / min, and the oily sludge begins to pyrolyze. Due to the high moisture content in sludge 2, the heat provided by the smoldering of sludge 1 is only sufficient to dehydrate and dry sludge 2 in the pyrolysis chamber, resulting in incomplete pyrolysis of sludge 2. In the end, only a brown oily substance with a calorific value of 24.6 MJ / kg was recovered, and the experiment failed.

[0087] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for recovering oil from oily sludge through smoldering coupled with pyrolysis, characterized in that, This method couples smoldering with low-temperature pyrolysis. The heat generated by the self-sustaining smoldering of oily sludge is used as a heat source for the low-temperature pyrolysis of another portion of the oily sludge via heat conduction, thereby obtaining pyrolysis oil. The low-temperature pyrolysis temperature is 300-500℃. The oily sludge treated by smoldering is designated as the first oily sludge, and the oily sludge treated by low-temperature pyrolysis is designated as the second oily sludge. The first oily sludge has a moisture content greater than or equal to 60 wt% and an oil content of 10 wt%-30 wt%, while the second oily sludge has a moisture content less than or equal to 30 wt% and an oil content greater than or equal to 40 wt%. The calorific value of the first oily sludge is 2-9 MJ / kg, and the calorific value of the second oily sludge is not less than 18 MJ / kg and not more than 22.4 MJ / kg. The filling height of the mixture of the first oily sludge and sand used for smoldering is not less than 30 cm and not more than 150 cm. The smoldering is carried out in the smoldering chamber; the low-temperature pyrolysis is carried out in the pyrolysis chamber; both the smoldering chamber and the pyrolysis chamber are cylindrical, and their cross-sections are concentric circles; the smoldering chamber and the pyrolysis chamber are separated by a heat-conducting sidewall; the heat generated by the self-sustaining smoldering of the oily sludge is transferred to the pyrolysis chamber through the heat-conducting sidewall via heat conduction. The smoldering chamber and the pyrolysis chamber are coaxially arranged and separated by a heat-conducting sidewall. The smoldering chamber is surrounded by the pyrolysis chamber. The thickness of the heat-conducting sidewall is 0.5~1mm, and the thermal conductivity is not lower than that of stainless steel. The smoldering process involves mixing sand and the first oily sludge at a mass ratio of 2:1 to 6:1 as a mixture for smoldering. The smoldering darcy flow rate is 3~10cm / s.

2. The method as described in claim 1, characterized in that, The low-temperature pyrolysis is carried out with the participation of a catalyst containing calcium and / or iron.

3. The method as described in claim 2, characterized in that, The catalyst containing calcium and / or iron is smoldering ash.

4. The method as described in claim 1, characterized in that, The smoldering process specifically involves preheating the mixture after it has been piled up to a preset height, and then introducing air when the mixture reaches the ignition point temperature, so that the first oily sludge can continuously sustain smoldering. The ignition point temperature is 200℃~400℃; The preset height of the stack is not less than 30cm.

5. The method as described in claim 1, characterized in that, The cross-sectional radius of the smoldering chamber (5) is 5 to 60 cm, and the ratio of the cross-sectional radius of the smoldering chamber (5) to the radius of the entire concentric circle is 1 / 2 to 4 / 5. The material of the heat-conducting sidewall is copper or stainless steel; The outer wall of the pyrolysis chamber (6) is wrapped with thermal insulation material.

6. The method as described in claim 5, characterized in that, The insulation material is either ceramic or quartz wool.

7. The method as described in claim 1, characterized in that, The upper part of the smoldering chamber (5) is provided with a feed inlet. The first oily sludge can be transported to the mixing chamber (2) by the raw material conveyor belt (1) and mixed with sand to obtain a mixture. The mixture is then transported to the smoldering chamber (5) through the feed inlet by the material conveyor belt (3). In addition, a material distributor (4) is provided directly below the feed inlet. The upper part of the smoldering chamber (5) is also provided with a smoldering exhaust gas outlet (8), which is connected to the flue gas purification component (15). The lower part of the smoldering chamber (5) is provided with an electric heating component (11) and a smoldering chamber air inlet (12), which are used to heat the smoldering chamber (5) to the smoldering ignition point temperature and to introduce air, respectively. The bottom of the smoldering chamber (5) is also provided with an ash hopper (13), which is connected to the ash collection chamber (14); the ash collection chamber (14) is connected to the ash conveying assembly (7).

8. The method as described in claim 1, characterized in that, The upper part of the pyrolysis chamber (6) is provided with a pyrolysis gaseous product outlet, which is connected to the pyrolysis gas collection bag (20) in sequence through a water removal component (17) and a condensation component (19); wherein, the water removal component (17) is used to remove water vapor from the pyrolysis gaseous product; the condensation component (19) is used to condense the pyrolysis gaseous product, and the pyrolysis oil generated by condensation is collected through a collection bottle (18); the pyrolysis gas collection bag (20) is used to collect pyrolysis gas.

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