CN107935332B - Continuous biological dealkalization process for red mud - Google Patents
Continuous biological dealkalization process for red mud Download PDFInfo
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Abstract
The invention discloses a continuous biological dealkalization process of red mud, which comprises the steps of firstly, uniformly mixing red mud powder and nutrient solution in a proportioning tank, pumping mixed slurry into a dealkalization tank, and reducing the alkalinity of the red mud by using metabolites such as organic acid secreted by thalli and carbon dioxide generated by respiration in the dealkalization tank; the strain is maintained in logarithmic growth phase all the time in the dealkalization stage, the strain has strong acid production capacity, the dealkalized slurry is pumped into a coagulation tank, mycelium and micro red mud particles in the mixed slurry form floccules and aggregates through coagulation reaction, then the flocculated slurry enters a settling tank for solid-liquid separation, the dealkalized solution is neutral, metal elements in the dealkalized solution can be recovered, and the dealkalized red mud is neutral and can be safely stockpiled. According to the method, Aspergillus niger is used as a dealkalizing strain, thallus cells are in complete contact with red mud particles, and a continuous liquid inlet mode and a continuous liquid outlet mode are used as operation modes, so that the alkalinity in the red mud can be removed efficiently, and the method has the advantages of environmental friendliness, low energy consumption, simple process, large-scale production and the like.
Description
Technical Field
The invention relates to the field of harmless treatment of industrial solid wastes, in particular to a continuous biological dealkalization process of red mud.
Background
Red mud is solid or semi-solid powdery solid waste produced in alumina industry, which is rich in ferric ions and is red or reddish brown. About 1.5 tons of red mud are produced per 1 ton of alumina produced. By 2016, global red mud inventory exceeds 30 million tons, and is increasing at a rate of 1.2 million tons per year. The red mud stockpiling amount in China is over 4.0 million tons, and the annual output of the red mud is over 0.6 million tons. At present, the resource utilization efficiency of the red mud is very low, so that most of the discharged red mud can only be stockpiled and disposed. However, since red mud has extremely high alkalinity, once alkaline leachate of red mud flows out during stacking, serious pollution is caused to surrounding surface water, underground water or soil environment. And the alkaline dust on the surface layer of the red mud can be conveyed to peripheral farmlands through wind power, so that the alkaline pollution degree is increased. Meanwhile, the extremely high alkalinity of the red mud can seriously inhibit the resource utilization efficiency of the red mud, for example, the red mud is used as a building material additive or precious metal elements in the red mud are recycled. Therefore, the dealkalization of the red mud has important practical significance for safe stockpiling and resource utilization.
At present, the red mud dealkalization has the following methods:
1. lime dealkalization method. The method removes the alkalinity in the red mud by forming precipitates through calcium ions in the lime, hydroxyl and carbonate in the red mud, has low alkalinity removal rate, and easily releases the alkalinity again after the precipitates of calcium hydroxide, calcium carbonate and the like on the surface layer of the red mud are dissolved.
2. Carbon dioxide neutralization. The alkalinity of the red mud is reduced by forming precipitates with calcium, magnesium and the like in the red mud after the hydrolysis of the carbon dioxide, the method has the advantages of complex instruments and equipment, high energy consumption, high initial investment cost and extremely easy rebound of pH after the neutralization.
3. Acid neutralization. The alkalinity of the red mud is neutralized by inorganic acid such as sulfuric acid, hydrochloric acid and the like or organic acid such as citric acid and the like, and the method has the advantages of great acid consumption, high operating cost and easy secondary pollution.
4. Water washing neutralization method. The method dissolves alkaline substances in the red mud by the solvent water and discharges the alkaline water, thereby reducing the alkalinity of the red mud. The method has low efficiency of removing the alkalinity of the red mud, and a large amount of discharged alkaline liquid can not be directly discharged, thereby improving the subsequent treatment cost of the whole process.
5. Neutralization with seawater. The method also has the defect of low dealkalization efficiency, and is only suitable for coastal areas.
Disclosure of Invention
The invention aims to provide a continuous biological dealkalization process of red mud aiming at the defects of the prior method and technology. The process takes Aspergillus niger as a dealkalizing strain, takes the complete contact of thallus cells and red mud particles as characteristics, takes continuous liquid inlet and continuous liquid outlet as operation modes, can realize high-efficiency removal of alkalinity in red mud, and has the advantages of environmental protection, low energy consumption, simple process, large-scale production and the like.
The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. According to the continuous biological dealkalization process of the red mud provided by the invention, the process is carried out in a continuous biological dealkalization device of the red mud, and the process specifically comprises the following steps:
(1) preparing mixed slurry in a batching tank, wherein the mixed slurry consists of red mud powder and nutrient solution, the red mud powder and the nutrient solution are respectively added into the batching tank through a red mud powder feeding pipe and a nutrient solution feeding pipe, and are uniformly mixed through a stirring device; the red mud powder is prepared by grinding dry red mud and then sieving the ground dry red mud with a sieve of 10-20 meshes, wherein the mass ratio of the red mud powder to the mixed slurry is 1-15%;
(2) the biological dealkalization process of the red mud is carried out in a dealkalization tank, and the operation of the dealkalization tank is divided into a starting stage and a continuous dealkalization stage;
in the starting stage, the culture mode is batch feeding and discharging, mixed slurry in a proportioning tank enters a dealkalization tank through a flow pump, activated aspergillus niger spore suspension is inoculated in the dealkalization tank, the dealkalization tank is filled with the mixed slurry once, the red mud concentration of the mixed slurry is 1%, the culture condition is set, the culture is stopped until the pH value of the mixed slurry is reduced to 3.0 or the culture time reaches 240 hours, 85-95% of the total volume of the mixed slurry is discharged from the dealkalization tank to a coagulation tank, and the first starting period is counted; in the second starting period, the mixed slurry is fully fed into the dealkalization tank once, the red mud concentration of the mixed slurry is increased to 2%, the culture condition is the same as that of the first period, the culture is stopped until the pH value of the mixed slurry is reduced to 3.0 or the culture time reaches 240 hours, 85-95% of the total volume of the mixed slurry is discharged from the dealkalization tank to the coagulation tank, the second starting period is counted, the analogy is repeated, the red mud concentration in the mixed slurry in each next period is increased by 1% compared with that in the previous period until the red mud concentration is increased to 15%, and after the culture, the starting stage is ended; the red mud concentration in the mixed slurry in the last period of the starting stage is 15%, and after the pre-culture is finished, the mixed slurry is not discharged from the dealkalization tank any more, but is transferred to a continuous dealkalization stage;
in the continuous dealkalization stage, the system operation mode is continuous feeding and continuous discharging, the liquid inlet flow and the liquid discharge flow of the mixed slurry are adjusted by a flow pump, so that the volume of the mixed slurry in the dealkalization tank is not less than 90 percent of the total effective volume of the dealkalization tank, and the red mud concentration of the mixed slurry in the dealkalization tank is controlled to be 10 to 15 percent; the control conditions of the continuous dealkalization stage are as follows: the retention time of the mixed slurry in the dealkalization tank is that the pH value of the mixed slurry is kept between 6.5 and 7.5, and the aeration intensity is 2.8 to 3.2m3/m2h, stirring at the speed of 180-260 rpm and at the temperature of 30-36 ℃;
(3) feeding the slurry flowing out of the continuous dealkalization stage of the dealkalization tank into a coagulation tank, and enabling mycelium and micro red mud particles in the mixed slurry to form floccules and aggregates through coagulation reaction, so that solid-liquid separation in a settling tank is facilitated;
(4) enabling the slurry flowing out of the coagulation tank to enter a settling tank for solid-liquid separation, wherein the settling time is 1-3 h; supernatant on the upper part of the settling tank is dealkalized liquid of the red mud, flows out from a dealkalized liquid discharging pipe on the upper part of the settling tank, has neutral pH value, and is directly discharged or used for recovering metal ions enriched in the dealkalized liquid; the mud at the lower part of the settling tank is a mixture of somatic cells and red mud particles, flows out from a mud outlet pipe at the lower part of the settling tank, and enters a plate-and-frame filter press for further dehydration; the pressure filtrate removed in the plate-and-frame filter press flows back to the coagulation tank; the residue after dehydration is dealkalized red mud, the pH value of which is neutral, and the dealkalized red mud is safely stockpiled and disposed, or used as an additive of building materials or a raw material for recovering precious metals; or burning at high temperature of 320-350 ℃ after drying, and further removing bacterial cells in the dealkalized red mud.
The object of the present invention and the technical problems solved thereby can be further achieved by the following technical measures.
The continuous biological dealkalization process for the red mud comprises the following steps of (1): 5-15% of cane sugar, 0.01-0.02% of yeast extract, 0.01-0.02% of beef extract, 30.02-0.05% of KNO and water as a solvent;
or the nutrient solution consists of peptone, water, fruit residues and/or sugarcane residues, more than 90% of the dried and crushed fruit residues and/or sugarcane residues can pass through 18 meshes, and the adding amount of the fruit residues and/or sugarcane residues in the nutrient solution is such that the Total Organic Carbon (TOC) content in the nutrient solution is 10% -25%; the mass fraction of the peptone in the nutrient solution is 0.01-0.02%.
In the continuous biological dealkalization process for red mud, in the step (2), aspergillus niger is obtained by purchasing or self-isolated culture, and needs to be activated before inoculation, and the method comprises the following steps: inoculating Aspergillus niger spore on PDA plate, eluting mature spore with sterilized physiological salt solution to obtain spore suspension containing Aspergillus niger spore at concentration of 1 × 107～1×108Per mL; in the starting stage, the inoculation amount of the Aspergillus niger spore suspension inoculated in the dealkalization tank is 0.1-0.5% of the volume of the mixed slurry in the dealkalization tank.
In the continuous biological dealkalization process for red mud, the culture conditions in the starting stage of step (2) are as follows: the aeration intensity is 2.4-3.0 m3/m2h, stirring at 160-240 rpm at 30-36 ℃.
In the continuous biological dealkalization process of the red mud, in the starting stage of the step (2), when the red mud concentration of the mixed slurry is within 5 percent, the nutrient solution can enter the batching tank after being sterilized for 30min at the temperature of more than 120 ℃ and at the pressure of more than 102.5 kPa; when the concentration of the red mud exceeds 5 percent, the nutrient solution directly enters the batching tank without sterilization.
The continuous biological dealkalization process for the red mud comprises the following steps of (1) adding a coagulant, wherein the coagulant is polyacrylamide, the mass concentration of the coagulant is 3-5%, the coagulant adding mode is continuous feeding, the adding flow rate is 0.05-0.1% of the flow rate of slurry entering a coagulation tank, the stirring speed of a stirring device is 50-60 rpm, and the reaction time is 15-60 min.
The continuous biological dealkalization process for the red mud comprises the steps that a continuous biological dealkalization device for the red mud comprises a proportioning tank (2), a dealkalization tank (9), a coagulation tank (14) and a settling tank (15), wherein the proportioning tank (2) is connected with the dealkalization tank (9) through a pipeline, the dealkalization tank (9) is connected with the coagulation tank (14) through a pipeline, the coagulation tank (14) is connected with the settling tank (15) through a pipeline, and each pipeline is provided with a control valve (5) and a flow pump (6);
the red mud powder feeding pipe (1) and the nutrient solution feeding pipe (4) are arranged on the batching tank (2); the top of the dealkalization tank (9) is provided with an inoculation cover (18) and an exhaust hole (19) with a bacteria filter, and the bottom is provided with an aeration device; a pH monitor (7), a dissolved oxygen monitor (8) and a temperature control device (10) are arranged in the dealkalization tank (9);
a coagulant feeding pipe (13) is arranged on the coagulation tank (14), a dealkalized liquid outlet pipe (16) is arranged at the upper part of the settling tank (15), a sludge outlet pipe (17) is arranged at the bottom of the settling tank, the sludge outlet pipe (17) is connected with a plate-and-frame filter press, and a filtrate outlet of the plate-and-frame filter press is connected with an inlet of the coagulation tank (14);
and stirring devices (3) are arranged in the batching tank (2), the dealkalization tank (9) and the coagulation tank (14).
In the continuous biological dealkalization device for red mud, the material of the batching tank and the dealkalization tank are both stainless steel; the material of coagulating basin and settling cask is glass.
In the continuous biological dealkalization device for red mud, the effective volumes of the batching tank and the dealkalization tank are both 30L, the effective volume of the coagulation tank is 0.5L, and the effective volume of the settling tank is 1L.
In the continuous biological dealkalization device for red mud, the stirring device (3) is a blade-type rotating mechanical stirrer;
the aeration device comprises a microporous aeration head (11) arranged in the bottom of the dealkalization tank and an air compressor (12) arranged outside the dealkalization tank, and a bacteria filter is arranged between the microporous aeration head (11) and the air compressor (12);
the temperature control device (10) comprises a temperature control sensor and a heating rod.
By means of the technical scheme, the invention has the advantages that:
1. the invention utilizes the bacteriostatic action of the red mud on microorganisms and the growth advantage of aspergillus niger, and can maintain the high-efficiency operation of the biological dealkalization under the conditions of not constructing a strict sterile environment and not sterilizing a culture medium at high temperature and high pressure.
2. The invention adopts the operation mode of continuous feeding and continuous discharging to ensure that the dealkalization functional bacteria are always in the logarithmic phase, so the bacteria have high-efficiency metabolic acid production activity, and the defect of low metabolic efficiency of acid production in the lag phase and the death phase of the dealkalization functional bacteria in the batch operation mode can be avoided.
3. The invention can use the fruit waste as the nutrient substance of the dealkalization functional bacteria, thereby realizing the purpose of treating wastes with processes of wastes against one another.
4. The mycelia of the aspergillus niger can be in complete contact with the red mud particles, and the mechanical damage and acid dissolution of the mycelia on the red mud particles are fully exerted, so that the dealkalization efficiency of the red mud is favorably improved.
5. The invention does not need to add inorganic acid and basically has no secondary pollution. The pH value of the alkali-removed liquid is neutral and can be directly discharged. The pH value of the dealkalized red mud is neutral, and the dealkalized red mud can be safely stockpiled or directly recycled.
Drawings
FIG. 1 is a diagram of the apparatus of the present invention;
FIG. 2 is a scanning electron micrograph of the interaction of red mud with Aspergillus niger hyphae.
[ description of element symbols ]
1. A red mud powder feeding pipe; 2. A dosing tank; 3. A stirring device; 4. A nutrient solution feeding pipe;
5. a control valve; 6. A flow pump; 7. A pH monitor; 8. A dissolved oxygen monitor;
9. a dealkalization tank; 10. A temperature control device; 11. A microporous aeration head; 12. An air compressor;
13. a coagulant feeding pipe; 14. A coagulation tank; 15. A settling tank; 16. A dealkalized liquid outlet pipe;
17. a mud outlet pipe; 18. An inoculation cover; 19. air vent
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be given to the continuous dealkalized bioleaching device and method for red mud according to the present invention with reference to the accompanying drawings and preferred embodiments, and the detailed implementation modes, structures, characteristics and effects thereof are described below.
The invention is realized by the following technical scheme:
1. the preparation of the mixed slurry was carried out in the batching tank 2: the mixed slurry consists of red mud powder and nutrient solution, and the red mud powder and the nutrient solution are respectively added into the batching tank 2 through a red mud powder feeding pipe 1 and a nutrient solution feeding pipe 4 to prepare the mixed slurry. The mixing tank is provided with a stirring device 3 which can uniformly mix the red mud powder and the nutrient solution.
The red mud powder is prepared by grinding dry red mud and sieving the ground dry red mud by a sieve of 10-20 meshes. The mass ratio of the red mud powder in the mixed slurry is 1-15%.
The nutrient solution comprises the following components in percentage by mass: 5-15% of cane sugar, 0.01-0.02% of yeast extract, 0.01-0.02% of beef extract, 30.02-0.05% of KNO and water as a solvent.
Or the nutrient solution consists of peptone, water, fruit residues and/or sugarcane residues, more than 90% of the dried and crushed fruit residues and/or sugarcane residues can pass through 18 meshes, and the adding amount of the fruit residues and/or sugarcane residues in the nutrient solution is such that the Total Organic Carbon (TOC) content in the nutrient solution is 10% -25%; the mass fraction of the peptone in the nutrient solution is 0.01-0.02%.
The mixed slurry in the batching tank enters the dealkalization tank through a flow pump.
2. The biological dealkalization process of the red mud is carried out in a dealkalization tank 9. The bottom of the dealkalization tank is provided with an aeration device and a stirring device 3. The stirring device is a blade type rotating mechanical stirrer. The aeration device is an air compressor 12 and a microporous aeration head 11, and the microporous aeration head aerates at the bottom of the dealkalization tank. A bacteria filter is arranged between the air compressor and the microporous aeration head to filter the mixed bacteria in the high-pressure air entering the dealkalization tank. A pH monitor 7 and a Dissolved Oxygen (DO) monitor 8 are arranged in the dealkalization tank, and the pH and the DO can be monitored in real time. The dealkalization tank is internally provided with a temperature control device 10 which comprises a temperature sensor and a heating rod. An openable inoculation cover 18 is arranged at the top of the dealkalization tank, the inoculation cover and the dealkalization tank are well sealed, and the inoculation cover is opened only when strains are inoculated, and is closed immediately after inoculation. The top of the dealkalizing tank is provided with an air vent hole 19 with a bacteria filter, and high-pressure gas in the dealkalizing tank can enter the external space through the air vent hole during aeration to maintain the air pressure balance inside and outside the dealkalizing tank.
The operation of the dealkalization tank is divided into two stages of starting and continuous dealkalization. The starting stage has the effects of improving the adaptability of the dealkalization functional bacteria to extreme habitat of the red mud and avoiding the phenomena that the bacteria are inactivated in large quantity due to sudden contact with the high-concentration red mud and the quantity of the viable bacteria cannot be maintained in the dealkalization stage. In the dealkalization stage, the alkalinity of the red mud is reduced by metabolites such as organic acid secreted by thalli and carbon dioxide generated by respiration. The dealkalization stage adopts a continuous feeding and continuous discharging operation mode, the mode can ensure that the strains are always maintained in a logarithmic growth phase, the strains have high acid production capability, and the negative influence of a growth lag phase on the biological dealkalization efficiency is avoided.
(1) In the start-up phase, the culture mode is batch feed and batch discharge. And (3) the mixed slurry in the proportioning tank enters a dealkalization tank through a flow pump, and the activated aspergillus niger spore suspension is inoculated in the dealkalization tank, wherein the inoculation amount is 0.1-0.5% of the volume of the mixed slurry in the dealkalization tank. Aspergillus niger is commercially available or can be isolated and cultured by itself. Aspergillus niger needs to be activated before inoculation: inoculating Aspergillus niger spore on PDA plate, eluting mature spore with sterilized physiological salt solution to obtain spore suspension with Aspergillus niger spore concentration of about 1 × 107～1×108one/mL.
The dealkalization tank is filled with mixed slurry once, the red mud concentration of the mixed slurry is 1 percent, and the aeration intensity is 2.4-3.0 m3/m2h, stirring at 160-240 rpm at 30-36 ℃. And (3) stopping culturing until the pH value of the slurry is reduced to 3.0 or the culture time reaches 240 hours, and discharging 85-95% of the total volume of the slurry from the dealkalization tank to the coagulation tank to count as a first starting period. The second starting period, the mixed slurry is filled in the dealkalization tank once, the red mud concentration of the mixed slurry is increased to 2 percent, the culture condition is the same as the first period until the pH value of the slurry is reduced to 3.0 or the slurry is culturedAnd stopping culturing when the time reaches 240 hours, and discharging 85-95% of the total volume of the slurry from the dealkalization tank to the coagulation tank. By analogy, the concentration of the red mud in the mixed slurry in each next period is increased by 1% compared with that in the previous period until the concentration is increased by 15%, and the starting stage is ended after the culture.
Except for the last starting period, the dealkalized slurry discharged to the coagulation tank in each starting period reacts with a coagulant in the coagulation tank, enters a settling tank for solid-liquid separation and is discharged, namely, a complete process flow is carried out in each starting period.
When the red mud concentration of the mixed slurry is within 5 percent, the nutrient solution can enter the batching tank after being sterilized for 30min at the temperature of more than 120 ℃ and at the pressure of more than 102.5 kPa. When the concentration of the red mud exceeds 5 percent, the nutrient solution can directly enter the batching tank without sterilization. The concentration of the red mud in the mixed slurry in the last period after the pre-culture is finished is 15%, and after the culture is finished, 85-95% of the total volume of the slurry is not discharged from the dealkalization tank at one time, but the continuous dealkalization stage is carried out.
(2) In the continuous dealkalization stage, the system operation mode is continuous feeding and continuous discharging. The liquid inlet flow and the liquid discharge flow of the mixed slurry are adjusted by a flow pump, so that the volume of the mixed slurry in the dealkalization tank is not less than 90 percent of the total effective volume of the dealkalization tank. The red mud concentration of the mixed slurry in the dealkalization tank is controlled to be 10-15%. Control conditions in the dealkalization stage: the retention time of the mixed slurry in the dealkalization tank is that the pH value of the mixed slurry is kept between 6.5 and 7.5, and the aeration intensity is 2.8 to 3.2m3/m2h, stirring at the speed of 180-260 rpm and at the temperature of 30-36 ℃.
3. The slurry flowing out of the dealkalization tank enters a coagulation tank, mycelium and tiny red mud particles in the mixed slurry form flocculating constituents and aggregates through coagulation reaction, and therefore solid-liquid separation in a settling tank is facilitated. Coagulant is added through a coagulant feeding pipe at the upper part of the coagulation tank. The mixing tank is provided with a stirring device which can uniformly mix the slurry and the coagulant. The coagulant is polyacrylamide, the mass concentration of the coagulant is 3-5%, the stirring speed is 50-60 rpm, the coagulant adding mode is continuous feeding, the adding flow rate is 0.05-0.1% of the flow rate of slurry entering a coagulation tank, and the reaction time is 15-60 min.
4. And (4) allowing the slurry flowing out of the coagulation tank to enter a settling tank for solid-liquid separation, wherein the settling time is 1-3 h. The supernatant on the upper part of the settling tank is the alkali removing liquid, the alkali removing liquid flows out from an alkali removing liquid discharging pipe on the upper part of the settling tank, the pH value of the alkali removing liquid is neutral, the alkali removing liquid can be directly discharged, and metal ions such as potassium, sodium and the like enriched in the alkali removing liquid can be recovered. The mud at the lower part of the settling tank is a mixture of bacterial cells and red mud particles, and the mud flows out of a mud outlet pipe at the lower part of the settling tank and enters a plate-and-frame filter press for further dehydration. The press filtrate removed in the plate and frame filter press is refluxed to the coagulation tank. The residue after dehydration is dealkalized red mud, the pH value of which is neutral, and the dealkalized red mud can be safely stockpiled and disposed, and can also be used as an additive of building materials or a raw material for recovering precious metals. If thallus cells in the dealkalized red mud are further removed, the dealkalized red mud can be dried and then incinerated at the high temperature of 320-350 ℃.
And in the continuous dealkalization stage, the red mud concentration of the mixed slurry in the dealkalization tank is controlled to be 10-15%. The low concentration of red mud powder may cause the propagation of mixed bacteria in the nutrient solution, and the high concentration of red mud powder may inhibit the growth and metabolism activity of bacteria in the dealkalizing tank, thus reducing the dealkalizing efficiency.
Example (b):
the effective volume of the batching tank is 30L, and the material is 304 stainless steel. And grinding the dried red mud, and sieving by 10-20 meshes. The nutrient solution adopts deionized water as a solvent, and the nutrient solution comprises the following components in proportion: 10% of cane sugar, 0.02% of yeast extract, 0.02% of beef extract and KNO30.05 percent. Adding red mud powder and nutrient solution into a blending tank, uniformly mixing, wherein the initial adding amount of the red mud powder is 300g, sterilizing the nutrient solution at 121 ℃ and 103kPa, and filling the blending tank with the nutrient solution.
The effective volume of the dealkalization tank is 30L, and the material is 304 stainless steel. The batch operation mode of the start-up phase is carried out in the dealkalization tank. And (3) feeding the mixed slurry in the dosing tank into a dealkalization tank through a flow pump, opening an inoculation cover after the dealkalization tank is filled with the mixed slurry, and adding 60mL of activated Aspergillus niger spore suspension. Adjusting various operation parameters of the dealkalization tank, wherein the aeration rate is 250L/h, the stirring speed is 200rpm, and the temperature is 32 ℃. When the pH on the pH monitor was below 3.0, the reactor was stopped, 27L of the mixed slurry was discharged to the coagulation tank and the first start-up period was complete. And (3) increasing the red mud concentration of the mixed slurry in the batching tank to 2%, and filling the dealkalization tank with the mixed slurry, wherein the operation parameters of the dealkalization tank are the same as those of the first starting period. When the pH on the pH monitor was below 3.0, the reactor was stopped, 27L of the mixed slurry was discharged to the coagulation tank and the second start-up period was complete. The red mud concentration of the mixed slurry in the batching tank is increased to 3%, the dealkalization tank is filled with the mixed slurry, and the operation parameters of the dealkalization tank are the same as those of the first starting period. When the pH on the pH monitor was below 3.0, the reactor was shut down and 27L of mixed slurry was discharged and the third start-up period was complete. By analogy, the red mud concentration in the mixed slurry in each next period is improved by 1 percent compared with that in the previous period. When the concentration of red mud is 6% or above, the nutrient solution can directly enter the material mixing tank without sterilization. When the red mud concentration of the mixed slurry is increased to 15%, the mixed slurry fills up the dealkalization tank, the starting stage is ended, the system enters the dealkalization stage of continuous feeding and continuous discharging, the same amount of feeding is added while the dealkalization tank discharges, and the state that the mixed slurry is filled in the dealkalization tank is maintained. The red mud concentration of the mixed slurry in the batching tank is adjusted to 12%. The operation parameters of the dealkalization tank in the continuous dealkalization stage are as follows: the aeration rate is 280L/h, the stirring speed is 220rpm, the temperature is 32 ℃, and the retention time of the mixed slurry is 56 h. The flow pumps of the liquid inlet pipe and the liquid outlet pipe of the dealkalization tank are adjusted to ensure that the flow rate of the liquid inlet and the flow rate of the liquid outlet are controlled to be 8.9 mL/min.
And the mixed slurry flowing out of the dealkalization tank enters a coagulation tank. The effective volume of the coagulation tank is 0.5L, and the material is glass. The operational parameters of the coagulation tank are as follows: the adding speed of the polyacrylamide solution with the mass concentration of 5% is 0.3mL/h, the stirring speed is 60rpm, and the flow rate is 8.9mL/min through a flow pump.
And the slurry flowing out of the coagulation tank enters a settling tank for solid-liquid separation. The effective volume of the settling tank is 1L, and the material is glass. The flow rate was controlled by a flow pump to be 8.9 mL/min. The dealkalized red mud at the lower part of the settling tank flows out from a mud outlet pipe and enters a plate-and-frame filter press for further dehydration. The dehydrated red mud is incinerated in an incinerator at 350 ℃, and the dealkalized red mud after the thalli removal can be safely stockpiled and disposed, and also can be used as an additive of building materials or a raw material for recovering precious metal elements. The supernatant on the upper part of the settling tank is the dealkalized liquid, flows out from the dealkalized liquid outlet pipe of the settling tank and can be directly discharged.
The pH value of the dealkalized red mud treated by the system is 7.05 and the pH value of the dealkalized liquid is 6.93 through the detection of a pH determinator, so that the high-efficiency removal of the alkalinity in the red mud is realized.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and those skilled in the art can make many modifications and variations without departing from the scope of the present invention.
Claims (7)
1. A continuous biological dealkalization process of red mud is characterized by being carried out in a continuous biological dealkalization device of red mud, the continuous biological dealkalization device of red mud comprises a proportioning tank (2), a dealkalization tank (9), a coagulation tank (14) and a settling tank (15), the proportioning tank (2) is connected with the dealkalization tank (9) through a pipeline, the dealkalization tank (9) is connected with the coagulation tank (14) through a pipeline, the coagulation tank (14) is connected with the settling tank (15) through a pipeline, and each pipeline is provided with a control valve (5) and a flow pump (6); the batching tank is provided with a red mud powder feeding pipe and a nutrient solution feeding pipe; the top of the dealkalization tank (9) is provided with an inoculation cover (18) and an exhaust hole (19) with a bacteria filter, and the bottom is provided with an aeration device; a coagulant feeding pipe (13) is arranged on the coagulation tank (14), a dealkalized liquid outlet pipe (16) is arranged at the upper part of the sedimentation tank (15), and a sludge outlet pipe (17) is arranged at the bottom; stirring devices (3) are arranged in the batching tank (2), the dealkalization tank (9) and the coagulation tank (14);
the process for carrying out the continuous biological dealkalization of the red mud by adopting the device comprises the following steps:
(1) preparing mixed slurry in a batching tank, wherein the mixed slurry consists of red mud powder and nutrient solution, the red mud powder and the nutrient solution are respectively added into the batching tank through a red mud powder feeding pipe and a nutrient solution feeding pipe, and are uniformly mixed through a stirring device; the red mud powder is prepared by grinding dry red mud and then sieving the ground dry red mud with a sieve of 10-20 meshes, wherein the mass ratio of the red mud powder to the mixed slurry is 1-15%; the nutrient solution consists of peptone, water, fruit residues and/or sugarcane residues, and the adding amount of the fruit residues and/or the sugarcane residues in the nutrient solution is that the total organic carbon content in the nutrient solution is 10% -25%; the mass fraction of the peptone in the nutrient solution is 0.01-0.02%;
(2) the biological dealkalization process of the red mud is carried out in a dealkalization tank, and the operation of the dealkalization tank is divided into a starting stage and a continuous dealkalization stage;
in the starting stage, the culture mode is batch feeding and discharging, the mixed slurry in the proportioning tank enters a dealkalization tank through a flow pump, the activated aspergillus niger spore suspension is inoculated in the dealkalization tank, and the concentration of aspergillus niger spores in the aspergillus niger spore suspension is 1 multiplied by 107～1×108Per mL; in the starting stage, the inoculation amount of the Aspergillus niger spore suspension inoculated in the dealkalization tank is 0.1-0.5% of the volume of the mixed slurry in the dealkalization tank; the mixed slurry is fully fed into the dealkalization tank at one time, the red mud concentration of the mixed slurry is 1 percent, and the culture conditions are set as follows: the aeration intensity is 2.4-3.0 m3/m2h, stirring at 160-240 rpm at 30-36 ℃, culturing until the pH value of the mixed slurry is reduced to 3.0 or the culture time reaches 240 hours, stopping culturing, and discharging 85-95% of the total volume of the mixed slurry from the dealkalization tank to the coagulation tank to count as a first starting period; in the second starting period, the mixed slurry is fully fed into the dealkalization tank once, the red mud concentration of the mixed slurry is increased to 2%, the culture condition is the same as that of the first period, the culture is stopped until the pH value of the mixed slurry is reduced to 3.0 or the culture time reaches 240 hours, 85-95% of the total volume of the mixed slurry is discharged from the dealkalization tank to the coagulation tank, the second starting period is counted, the analogy is repeated, the red mud concentration in the mixed slurry in each next period is increased by 1% compared with that in the previous period until the red mud concentration is increased to 15%, and after the culture, the starting stage is ended; the red mud concentration in the mixed slurry in the last period of the starting stage is 15%, and after the pre-culture is finished, the mixed slurry is not discharged from the dealkalization tank any more, but is transferred to a continuous dealkalization stage;
in the continuous dealkalization stage, the system operation mode is continuous feeding and continuous discharging, the liquid inlet flow and the liquid discharge flow of the mixed slurry are adjusted by a flow pump, so that the volume of the mixed slurry in the dealkalization tank is not less than the total volume of the dealkalization tankThe effective volume is 90%, and the red mud concentration of the mixed slurry in the dealkalization tank is controlled to be 10-15%; the control conditions of the continuous dealkalization stage are as follows: the retention time of the mixed slurry in the dealkalization tank is that the pH value of the mixed slurry is kept between 6.5 and 7.5, and the aeration intensity is 2.8 to 3.2m3/m2h, stirring at the speed of 180-260 rpm and at the temperature of 30-36 ℃;
(3) feeding the slurry flowing out of the continuous dealkalization stage of the dealkalization tank into a coagulation tank, and enabling mycelium and micro red mud particles in the mixed slurry to form floccules and aggregates through coagulation reaction, so that solid-liquid separation in a settling tank is facilitated, adding coagulant polyacrylamide through a coagulant feeding pipe at the upper part of the coagulation tank, wherein the coagulant adding mode is continuous feeding, the adding flow rate of the coagulant adding is 0.05-0.1% of the flow rate of the slurry entering the coagulation tank, and the slurry and the coagulant are uniformly mixed through a stirring device in the coagulation tank;
(4) enabling the slurry flowing out of the coagulation tank to enter a settling tank for solid-liquid separation, wherein the settling time is 1-3 h; supernatant on the upper part of the settling tank is dealkalized liquid of the red mud, flows out from a dealkalized liquid discharging pipe on the upper part of the settling tank, has neutral pH value, and is directly discharged or used for recovering metal ions enriched in the dealkalized liquid; the mud at the lower part of the settling tank is a mixture of somatic cells and red mud particles, flows out from a mud outlet pipe at the lower part of the settling tank, and enters a plate-and-frame filter press for further dehydration; the pressure filtrate removed in the plate-and-frame filter press flows back to the coagulation tank; the residue after dehydration is dealkalized red mud, the pH value of which is neutral, and the dealkalized red mud is safely stockpiled and disposed, or used as an additive of building materials or a raw material for recovering precious metals; or burning at high temperature of 320-350 ℃ after drying, and further removing bacterial cells in the dealkalized red mud.
2. The continuous biological dealkalization process of red mud according to claim 1, characterized in that the substitution scheme of the nutrient solution composition in step (1) is according to mass concentration: 5-15% of cane sugar, 0.01-0.02% of yeast extract, 0.01-0.02% of beef extract, 30.02-0.05% of KNO and water as a solvent.
3. The continuous biological dealkalization process of red mud according to claim 1, characterized in that in the starting stage of the step (2), when the concentration of the red mud in the mixed slurry is 5% or less, the nutrient solution is sterilized for 30min at 120 ℃ or more and at 102.5kPa or more before entering the batching tank; when the concentration of the red mud exceeds 5 percent, the nutrient solution directly enters the batching tank without sterilization.
4. The continuous biological dealkalization process of red mud according to claim 1, characterized in that the mass concentration of the coagulant in the step (3) is 3-5%, the stirring speed of the stirring device is 50-60 rpm, and the reaction time is 15-60 min.
5. The continuous biological dealkalization process of red mud according to claim 1, characterized in that a pH monitor (7), a dissolved oxygen monitor (8) and a temperature control device (10) are arranged in the dealkalization tank (9); the mud outlet pipe (17) is connected with a plate-and-frame filter press, and the filtrate outlet of the plate-and-frame filter press is connected with the inlet of the coagulation tank (14).
6. The continuous biological dealkalization process of red mud of claim 1, characterized in that the material of the batching tank and the dealkalization tank is stainless steel; the material of coagulating basin and settling cask is glass.
7. The continuous biological dealkalization process of red mud of claim 1, characterized in that the aeration device comprises a micropore aeration head (11) arranged in the bottom of the dealkalization tank and an air compressor (12) arranged outside the dealkalization tank, and a bacteria filter is arranged between the micropore aeration head (11) and the air compressor (12).
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| CN101265519A (en) * | 2007-07-12 | 2008-09-17 | 中国铝业股份有限公司 | Method for reclaiming aluminum from red mud by biochemical process |
| CN103693830A (en) * | 2013-12-13 | 2014-04-02 | 吉林吉恩镍业股份有限公司 | Process for treating free alkali in red mud by microorganisms |
| CN105170307A (en) * | 2015-09-29 | 2015-12-23 | 河南理工大学 | Red-mud citric acid dealkalizing technique |
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| CN101265519A (en) * | 2007-07-12 | 2008-09-17 | 中国铝业股份有限公司 | Method for reclaiming aluminum from red mud by biochemical process |
| CN103693830A (en) * | 2013-12-13 | 2014-04-02 | 吉林吉恩镍业股份有限公司 | Process for treating free alkali in red mud by microorganisms |
| CN105170307A (en) * | 2015-09-29 | 2015-12-23 | 河南理工大学 | Red-mud citric acid dealkalizing technique |
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