Method for synchronously promoting dissolution of oil-containing iron sludge and rapid separation of iron in dissolved solution

Abstract

The invention discloses a method for synchronously promoting dissolution of oil-containing iron sludge and rapid separation of iron in a dissolved solution, which comprises the following steps: preparing a solvent, dissolving the oil-containing iron sludge, oxidizing and precipitating iron, recovering grease, regenerating and recycling the solvent and the like, and synchronously realizing the dissolution of the oil-containing iron sludge and the oxidizing and precipitating of dissolved iron. According to the method, iron in a water phase can be efficiently removed, other metal elements are efficiently enriched and retained, and meanwhile, a grease layer and a catalytic regeneration solvent are synchronously and accurately recycled. The method has the advantages of high oil-containing iron sludge dissolving speed, good solvent regeneration effect, high purity of recycled iron powder, low operation cost and the like.

Description

Technical Field

[0001] The present invention relates to a resource utilization method, belonging to the field of environmental protection technology, and is mainly used for treating oil-containing iron sludge. Other elements in the iron sludge include one or more of manganese, copper, aluminum, precious metals, and rare earth metals. Background Art

[0002] Oil-containing iron sludge mainly comes from the metal processing industry. Its composition is complex, mainly including metallic iron, iron-containing oxides, lubricating oil, emulsifying liquid, etc. used in processing, and other doping elements and their oxidation components in iron-containing components. Such oil-containing iron sludge is mainly used as solid waste. After being recycled by a solid waste company, it is safely solidified and landfilled. In recent years, some reports have involved the resource utilization of oil-containing iron sludge, mainly aiming to remove organic substances and impurities such as iron and recover high-value doping elements.

[0003] High-temperature treatment is one of the effective methods for removing impurities from iron-containing oil sludge. After drying the iron-containing oil sludge at 100°C, it is further heated to 700 - 1000°C for calcination. In this process, the organic components in the iron-containing oil sludge are burned to gas by high temperature, while the internal metals are rapidly oxidized by heat and fragmented into corresponding oxide powders. In this process, iron is directly oxidized to Fe2O3, and the doping elements are also converted into corresponding oxides. The organic components in the oil sludge burn, generating thick smoke. At the same time, high-temperature equipment is expensive, and the supporting equipment cannot be miniaturized and precisionized. Compared with the high-temperature treatment method, organic solvent cleaning mainly aims to remove oil. Acetone, absolute ethanol, diethylene glycol methyl ether, etc. are used to clean the oil-containing iron sludge to remove the organic components in the oil-containing iron sludge. Some reports point out that adding additives or surfactants such as acetic acid, sodium carbonate, strong alkali, phosphate, TX-10, etc. can improve the removal effect of the organic components in the oil-containing iron sludge. This operation can be carried out at room temperature, and the equipment can be scaled up and miniaturized.

[0004] After the organic components in the iron-containing oil sludge are removed by the above methods, the acid dissolution method is usually used to remove iron and recover the doping elements therein. The removal of iron in the acid solution includes the following methods. (1) Aeration with air is used to oxidize ferrous iron to ferric iron, and the pH value is gradually adjusted to promote the hydrolysis of ferric iron to generate iron-containing precipitates; (2) Adding oxidants such as hydrogen peroxide and sodium hypochlorite to rapidly oxidize ferrous iron to ferric iron. This method is often used in combination with (1) to further oxidize ferrous iron and promote the hydrolysis of ferric iron to reduce the residual iron concentration in the aqueous phase; (3) Using pure oxygen or ozone to catalytically oxidize divalent iron to ferric iron, but iron precipitates are easily attached to the surface of the catalyst, resulting in catalyst failure; (4) Adding nitrite to rapidly oxidize ferrous iron to ferric iron in the acid solution. The gas released in the reaction is collected, and then catalytically oxidized with pure oxygen and reused for aerating the acid solution; this method has a fast oxidation rate of ferrous iron, but nitrite remains in the acid solution, which is not convenient for subsequent acid solution treatment. Summary of the Invention

[0005] The object of the present invention is to propose a method for dissolving iron-containing oily sludge - removing iron by iron oxidation - recovering grease - recycling and regenerating solvent, which can dissolve iron-containing oily sludge and remove iron in the solution simultaneously, and efficiently regenerate the solvent and accurately recover the grease layer generated by the dissolution of the oily sludge.

[0006] 1. Range of oil-containing iron sludge

[0007] The oil-containing iron sludge is generated in the metal processing process. Its components include cutting oil, lubricating oil, etc. The metal parts are iron and its oxides, and the admixtures in the metal parts are one or more of manganese, copper, aluminum, precious metals, and rare earth metals.

[0008] 2. Preparation of solvent

[0009] The solvent contains 4 components, namely chloroform, 2,3-dimethyl-2,3-dinitrobutane, nitroethylbenzene, and nitroquinoline, and their volume ratio is 7.2:1.5:2.3:1. The ratio of the solvent volume to the iron content in the oily sludge to be treated is between 8.5 - 11.5L:1kg.

[0010] 3. Dissolution of iron-containing oily sludge

[0011] The solvent, oily sludge, and inorganic acid are added to the dissolution tank in sequence. The inorganic acid is 20% hydrochloric acid or sulfuric acid, and its volume is 10% - 40% of the organic solvent. Start stirring at a speed of 50 - 120rpm for 3 - 5h; at the same time, turn on the condensation device to reflux the solvent, and control the reaction temperature at 60°C. After the reaction is completed, let it stand for 0.5 - 1h, and the liquid layers. The top layer is suspended carbon-based insoluble matter, the upper layer is a transparent aqueous solution, the middle layer is a turbid layer, the lower layer is an emulsified organic phase, and the bottom layer is a reddish-brown insoluble matter. The total iron concentration in the upper transparent aqueous solution is less than 30mg / L, and the content of impurity metal elements in the bottom reddish-brown insoluble matter is less than 1.8%.

[0012] 4. Recovery of grease

[0013] The grease recovery device consists of the following: Sensors A and B are placed at the upper and lower ends of the dissolution tank respectively. The sensors are connected to the controller, and the controller is respectively connected to the motor and the pump; one end of the pump is connected to the collection pipe, and the other end is connected to the delivery pipe; the delivery pipe is connected to the separation membrane box; the left side of the separation membrane box is connected to the grease bucket, the bottom is connected to the liquid storage bucket, the bottom of the liquid storage bucket is connected to the delivery pipe, the delivery pipe is connected to the pump, and the pump is connected to the dissolution tank.

[0014] During operation, sensors A and B output signals to the controller. After comparison and calculation, the controller determines the position of the middle brown turbid layer, outputs signals to the motor, and when the motor moves to control the displacement of the pump and the collection pipe to the brown turbid layer, the pump is started to recover the mixed liquid of the turbid layer through the collection pipe. During the collection of the turbid layer, as the solution of the turbid layer is discharged, the liquid level drops; correspondingly, the sensors continue to transmit signals to the controller to adjust the displacement of the motor to control the pump and the collection pipe. The brown turbid liquid transported by the pump, after passing through the separation membrane, the grease layer flows into the grease bucket, and the solvent and water permeate through the separation membrane and enter the liquid storage bucket. The operation time is set to 3 minutes, then the controller is stopped, and the motor and the pump stop automatically; then the pump at the bottom of the liquid storage bucket is started to pump the liquid in the liquid storage bucket into the dissolution tank.

[0015] Sensors A and B are Coriolis flow sensors of the same specification, measuring the mass flow rate of the fluid at the contact ports of A and B, marked as m A and m B , with the unit of kg / h; at sensors A and B, piezoelectric sensors are embedded, marked as a and b, and the electrical signals output are marked as I a and I b , with the unit of mV; the installation distance between sensors A and B is H, and the position of the middle layer from the installation position of sensor A is marked as h, then the height of h is calculated according to the following formula:

[0016]

[0017] In the above formula, k is the proportional adjustment constant, which is determined by the following experimental method: Inject tap water into the dissolution tank, control the water level line at H - h = 1m, start the sensors, record the corresponding data, and input it into the above formula to calculate the value of k.

[0018] 5. Solvent regeneration

[0019] An external cooling circulating water system is installed in the dissolution tank, which is lifted by a heat pump and transported to the solvent regeneration tank to complete the following operations:

[0020] (1) Start the heat pump device to maintain the reaction temperature at 80 - 90°C, start the condensation system, and evaporate and recover chloroform;

[0021] (2) Start the bottom aeration device, introduce air into the remaining solution, and the aeration volume is 1L / m 3 ·min;

[0022] (3) Start the ultraviolet light device to activate the Cu / MnFeO4 catalyst;

[0023] (4) Start the heat pump device to maintain the reaction temperature at 80 - 90°C, and react for 24 - 48h;

[0024] (5) Turn off the ultraviolet light system and the aeration system, and continue to keep the temperature constant for 3 - 5h;

[0025] (6) Collect the evaporation liquid and the remaining solvent separately. After the remaining solvent is remixed with chloroform, it is recycled for sludge dissolution and iron oxidation.

[0026] After being treated by the above method, the iron recovery rate in the iron-containing sludge is higher than 99%; after the generated iron-containing precipitate is dried, the iron content is higher than 65%, and the retention rate of other metals in the aqueous phase is higher than 98%.

[0027] The present invention proposes a new method of organic solvent / acids dissolution - iron removal by oxidation - grease recovery, which has the following advantages compared with the above method:

[0028] (1) Realize the simultaneous dissolution of iron-containing sludge and the removal of ferrous ions in the acid solution;

[0029] (2) The organic solvent can be regenerated and used for oil cleaning in iron-containing sludge and ferrous oxidation;

[0030] (3) Can accurately recover the grease layer at the organic / aqueous phase interface;

[0031] (4) Avoid the additional use of heating or high-temperature devices. Examples

[0032] Disposal of iron, manganese and copper-containing sludge in Example 1

[0033] (1) Sludge dissolution

[0034] An iron-containing sludge contains 47.5% Fe, 16.5% Mn, 14.7% Cu and 8.3% fatty oil. Weigh 10 kg of sludge and put it into the dissolution tank, then add 90 L of a mixed solvent containing chloroform, 2,3-dimethyl-2,3-dinitrobutane, nitroethylbenzene and nitroquinoline (volume ratio 7.2:1.5:2.3:1), and finally add 25 L of 20% hydrochloric acid. Turn on the condensation device at the top of the dissolution tank; start the stirrer and stir at 70 rpm for 3 h; start the circulating cooling system of the reaction tank and control the reaction temperature at 60 °C. After the reaction ends, let it stand for 1 h.

[0035] (2) Iron separation

[0036] For the generated solution, there are aggregated carbon particles at the top, a transparent solution in the upper part, a turbid grease layer in the middle, an emulsified yellow organic phase in the lower part, and a reddish-brown precipitate at the bottom. The total Fe concentration in the upper transparent solution is 18 mg / L, and the Mn and Cu concentrations are 52.4 g / L and 45.9 g / L. After the reddish-brown precipitate at the bottom is collected and dried at 105 °C for 5 h, the component analysis results show that Fe, Mn and Cu are 65.2%, 0.8% and 0.9% respectively.

[0037] (3) Grease recovery

[0038] (3-1) Dissolution Tank Parameter Tuning

[0039] Before step (1), tap water is injected into the dissolution tank. When the water depth from the lower sensor is 1 m, the marked displacement is 1 m. The sensor is started to record data, and the solved k value is 1.734×10 -4 . Open the vent valve to empty the tap water in the dissolution tank.

[0040] (3-2) Grease Layer Recovery Control

[0041] Start sensors A / B and the controller to determine the position of the middle brown turbid layer; the output signal controls the movement of the motor, and the movement of the motor causes the pump and the collection pipe to displace to the brown turbid layer; the pump is started, and the mixed liquid of the turbid layer is recovered through the collection pipe; as the liquid level drops, the pump and the collection pipe are also controlled to displace accordingly; after the pump operates for 3 minutes, the sensors, the controller, the motor, etc. stop operating.

[0042] (3-3) Grease Separation

[0043] The brown turbid liquid collected in step (3-2) is directly treated with a separation membrane. The aqueous phase and the organic phase pass through the membrane and enter the storage bucket, and the grease enters the grease bucket flowing into the bottom of the membrane. Start the pump of the storage bucket and pump this part of the liquid into the dissolution tank.

[0044] (4) Solvent Regeneration

[0045] Introduce the cooling circulating water in step (1). After recovering the heat energy through a heat pump, it is transported to the solvent regeneration tank to complete the following operations:

[0046] (4-1) Maintain the reaction temperature at 80 - 90 °C, and start the condensation recovery system at the top of the regeneration tank and operate for 1 h to recover clean chloroform;

[0047] (4-2) Then start the bottom aeration device and introduce air into the remaining solution, with the aeration rate of 1 L / m 3 ·min;

[0048] (4-3) Start the ultraviolet light device to activate the Cu / MnFeO4 catalyst and react for 24 h;

[0049] (4-4) Turn off the ultraviolet light system and the aeration system, and continue to maintain the constant temperature for 3 h;

[0050] (4-5) The remaining solvent is remixed with chloroform and reused for sludge dissolution.

[0051] Example 2 Disposal of Iron-Containing Praseodymium-Cobalt Sludge

[0052] A cutting-generated iron, praseodymium, and cobalt-containing sludge contains 57.6% Fe, 22.8% Pr, 5.6% Co, and 11.5% oil. Using the dissolution tank in the aforementioned Example (1), the sludge is recycled, and the main steps are as follows:

[0053] (1) Sludge dissolution

[0054] Weigh 10 kg of sludge and put it into the dissolution tank. Then add 54 L of chloroform and then 25 L of 20% hydrochloric acid. Turn on the condensing device at the top of the dissolution tank; start the stirrer and stir at 70 rpm for 3 h; start the circulating cooling system of the reaction tank and control the reaction temperature at 60°C. After the reaction ends, let it stand for 1 h. The upper part is a dark green solution, the middle part is a turbid grease layer, the lower layer is an organic phase, and there is a small amount of gray insoluble matter at the bottom.

[0055] (2) Grease recovery

[0056] Start sensors A / B and the controller, brake the motor, and displace the pump and the collection pipe in the dissolution tank along the fixed rod to the brown turbid layer; start the pump in the tank and recover the mixed liquid of the turbid layer through the collection pipe; as the liquid level drops, the pump and the collection pipe in the tank also move; after the pump runs for 3 minutes, stop it together with the sensors, controller, motor, etc. The collected mixed liquid of the turbid layer directly enters the separation membrane, and the grease flows along the membrane surface into the grease bucket at the bottom, and the aqueous phase and the organic phase pass through the membrane and enter the liquid storage bucket. Start the pump of the liquid storage bucket and pump this part of the liquid into the dissolution tank.

[0057] (3) Separation of iron in the upper solution

[0058] Transfer the dark green solution in the upper part of the dissolution tank to the aeration reaction tank. Then add 36 L of a mixed solvent of 2,3-dimethyl-2,3-dinitrobutane, nitroethylbenzene, and nitroquinoline (volume ratio 1.5:2.3:1); turn on the stirrer at a speed of 60 rpm; after 30 min, start the pH control device to adjust the pH value, gradually to 1.5, and finally stabilize at 2.5; stop stirring and let it stand for 30 min. The upper part is a transparent aqueous phase, the middle part is an oily organic component, and a reddish-brown precipitate is produced at the bottom. The iron concentration in the supernatant is 27 mg / L, and the concentrations of Pr and Co are 86.1 and 21.1 g / L respectively. The precipitate is collected and dried at 105°C for 5 h, and the Fe content is 66.1%, and the contents of Pr and Co are 0.3% and 0.4% respectively.

[0059] (4) Solvent regeneration

[0060] Transfer the lower organic solvent in step (1) to the solvent regeneration tank. Then introduce the cooling circulating water in step (1) to heat the solvent regeneration tank. Start the condensation collection system at the top of the regeneration tank to collect the organic solvent; stop running after reacting for 30 min, and there is yellow base oil remaining at the bottom of the regeneration tank.

[0061] (5) Regeneration of the organic phase in step (3)

[0062] Collect the organic phase in step (3) and put it into the regeneration tank. Then introduce the cooling circulating water in step (1) and start the heat pump to maintain the temperature in the regeneration tank at 80 - 90 °C; start the bottom aeration device to introduce air into the organic solution, and the aeration volume is 1 L / m 3 ·min; start the ultraviolet light device to activate the Cu / MnFeO4 catalyst and react for 24 h; turn off the ultraviolet light system and the aeration system, and continue to keep the temperature constant for 3 h; the regenerated organic phase is repeatedly used for separating iron in the solution in step (3).

Claims

1. A method for simultaneously promoting the dissolution of oil-containing iron mud and the rapid separation of iron in the dissolving solution, comprising the steps of solvent preparation, oil-containing iron mud dissolution and iron oxidation precipitation, oil recovery, solvent regeneration and recycling, wherein: The solvent contains four components, namely chloroform, 2,3-dimethyl-2,3-dinitrobutane, nitroethylbenzene and nitroquinoline, with a volume ratio of 7.2:1.5:2.3:1, and the ratio of the solvent volume to the iron content in the oil sludge to be treated is between 8.5-11.5L:1kg.

2. The method of claim 1, wherein: The steps of dissolving oily iron sludge and iron oxide precipitation include the following processes: Add sludge and solvent to the dissolution tank, and then add inorganic acid (20% sulfuric acid or hydrochloric acid aqueous solution); the volume of the inorganic acid is 10% to 40% of the organic solvent, stirring at a speed of 50-120rpm for 3-5h; at the same time, turn on the condensing device to reflux the solvent, and control the reaction temperature to 60°C. After the reaction is completed, let it stand for 0.5-1h, and the liquid will be separated into layers, wherein the top is suspended carbon-based insoluble matter, the upper layer is a transparent aqueous solution, the middle is a turbid layer, the lower layer is an emulsified organic phase, and the bottom is a reddish-brown insoluble matter. The total iron concentration in the upper transparent aqueous solution is less than 30mg / L, and the impurity metal element content in the reddish-brown insoluble matter at the bottom is less than 3.8%.

3. The method of claim 1, wherein: The grease recovery step includes the following processes: Sensors A and B are placed at the upper and lower ends of the dissolving tank respectively. The sensors are connected to the controller, which is connected to the motor and the pump respectively. One end of the pump is connected to the collection pipe, and the other end is connected to the delivery pipe. The delivery pipe is connected to the separation membrane box. The left side of the separation membrane box is connected to the grease barrel, and the bottom is connected to the liquid storage barrel. The bottom of the liquid storage barrel is connected to the delivery pipe, which is connected to the pump, and the pump is connected to the dissolving tank. During operation, sensors A and B output signals to the controller. After comparison operations, the controller determines the position of the middle brown turbid layer and outputs a signal to the motor. After the motor moves to control the displacement of the pump and the collecting tube to the brown turbid layer, the pump is started to recover the mixed liquid of the turbid layer through the collecting tube. During the collection of the turbid layer, as the solution of the turbid layer is discharged, the liquid level drops. Accordingly, the sensor continues to send signals to the controller to adjust the displacement of the motor to control the pump and the collecting tube. The brown turbid liquid transported by the pump passes through the separation membrane, and the grease layer flows into the grease barrel, and the solvent and water pass through the separation membrane into the liquid storage barrel. The running time is set to 3 minutes, and then the controller is stopped, and the motor and pump stop automatically. Then the pump at the bottom of the liquid storage barrel is started to pump the liquid in the liquid storage barrel into the dissolution tank.

4. The method of claim 3, wherein: The method for determining the position of the middle layer in the controller is as follows: Sensors A and B are Coriolis flow sensors of the same specification, measuring the mass flow of the fluid at the contact ports A and B, marked as m A and m B , the unit is kg / h; at sensors A and B, piezoelectric sensors are embedded, marked as a and b, and the output electrical signal is marked as I a and I b , the unit is mV; the installation distance between sensors A and B is H, and the distance between the middle layer and the installation position of sensor A is marked as h. The height of h is calculated according to the following formula: In the above formula, k is the proportional adjustment constant, which is determined by the following experimental method: inject tap water into the dissolution tank, control the water level line to Hh=1m, start the sensor, record the corresponding data, and input it into the above formula to calculate the k value.

5. The method of claim 1, wherein: The solvent regeneration and recycling steps include the following processes: The dissolving tank is equipped with an external cooling circulating water system, which is lifted by a heat pump and transported to the solvent regeneration tank to complete the following operations: (1) Start the heat pump device to maintain the reaction temperature at 80-90°C, start the condensation system, and evaporate and recover chloroform; (2) Start the bottom aeration device to introduce air into the remaining solution at an aeration rate of 1L / m 3 ·min; (3) Start the ultraviolet light device to excite the Cu / MnFeO4 catalyst; (4) Start the heat pump device to maintain the reaction temperature at 80-90°C and react for 24-48 hours; (5) Turn off the ultraviolet light system and aeration system and continue to maintain the constant temperature for 3-5 hours; (6) Collect the evaporated liquid and the remaining solvent separately. The remaining solvent is mixed with chloroform again and reused in step [2] of sludge dissolution and iron oxidation.

Images