CN117964058A - Electrolysis system and method for recycling phosphorus from sludge digestion liquid - Google Patents
Electrolysis system and method for recycling phosphorus from sludge digestion liquid Download PDFInfo
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- CN117964058A CN117964058A CN202410315619.5A CN202410315619A CN117964058A CN 117964058 A CN117964058 A CN 117964058A CN 202410315619 A CN202410315619 A CN 202410315619A CN 117964058 A CN117964058 A CN 117964058A
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- 239000010802 sludge Substances 0.000 title claims abstract description 152
- 239000007788 liquid Substances 0.000 title claims abstract description 95
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 title claims abstract description 82
- 238000005868 electrolysis reaction Methods 0.000 title claims abstract description 80
- 229910052698 phosphorus Inorganic materials 0.000 title claims abstract description 80
- 239000011574 phosphorus Substances 0.000 title claims abstract description 80
- 230000029087 digestion Effects 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000004064 recycling Methods 0.000 title description 7
- 238000002156 mixing Methods 0.000 claims abstract description 42
- 230000018044 dehydration Effects 0.000 claims abstract description 30
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 30
- 238000011084 recovery Methods 0.000 claims abstract description 28
- 238000006243 chemical reaction Methods 0.000 claims abstract description 20
- 239000003513 alkali Substances 0.000 claims abstract description 11
- 239000011575 calcium Substances 0.000 claims abstract description 11
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims abstract description 10
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 10
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052742 iron Inorganic materials 0.000 claims abstract description 10
- -1 iron ions Chemical class 0.000 claims abstract description 10
- 239000011777 magnesium Substances 0.000 claims abstract description 10
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 10
- 239000002699 waste material Substances 0.000 claims abstract description 10
- 239000002253 acid Substances 0.000 claims abstract description 9
- 238000012545 processing Methods 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 102
- 230000001079 digestive effect Effects 0.000 claims description 28
- 235000011389 fruit/vegetable juice Nutrition 0.000 claims description 28
- 230000020477 pH reduction Effects 0.000 claims description 15
- 230000002378 acidificating effect Effects 0.000 claims description 14
- 238000000926 separation method Methods 0.000 claims description 12
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 11
- 239000010936 titanium Substances 0.000 claims description 11
- 229910052719 titanium Inorganic materials 0.000 claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000011065 in-situ storage Methods 0.000 claims description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 6
- 229910001220 stainless steel Inorganic materials 0.000 claims description 5
- 239000010935 stainless steel Substances 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 3
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 229910044991 metal oxide Inorganic materials 0.000 claims description 3
- 150000004706 metal oxides Chemical class 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- 239000013043 chemical agent Substances 0.000 abstract description 5
- 239000003014 ion exchange membrane Substances 0.000 abstract description 5
- 230000000694 effects Effects 0.000 description 15
- 238000002386 leaching Methods 0.000 description 13
- 239000002585 base Substances 0.000 description 5
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- 238000000605 extraction Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
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- 230000035484 reaction time Effects 0.000 description 2
- 239000010865 sewage Substances 0.000 description 2
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- 230000001360 synchronised effect Effects 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 239000008346 aqueous phase Substances 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000006385 ozonation reaction Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
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- Treatment Of Sludge (AREA)
- Water Treatment By Electricity Or Magnetism (AREA)
Abstract
The invention relates to an electrolysis system and a method for recovering phosphorus from sludge digestion liquid, comprising the following steps: electrochemical electrolysis unit, mud centrifugal dehydration unit and mixed processing unit. According to the invention, in the electrolysis process, the sludge digestion liquid is continuously introduced from the bottom near the anode of the electrolysis unit, and the electrolyzed acid liquid and the sludge digestion liquid are continuously extracted from the top end of the anode filter cylinder and mixed in a cross flow manner, and the reaction waste liquid is continuously introduced from the bottom near the cathode of the electrolysis unit and overflows out of the alkali liquid, so that phosphorus, ammonium, magnesium, calcium and iron ions separated out from the acidified sludge digestion liquid near the anode of the electrolysis unit are mixed with the overflowed alkali liquid near the cathode of the electrolysis unit in the mixing treatment unit, and the phosphorus recovery in the sludge digestion liquid is realized without adding chemical agents and ion exchange membranes.
Description
Technical Field
The invention relates to the technical field of sludge treatment of sewage plants, in particular to an electrolysis system and method for recycling phosphorus from sludge digestion liquid.
Background
Phosphorus (P) is a limited, non-renewable resource, an essential, non-replaceable element for all biological growth, mainly extracted from phosphorus-containing minerals (mainly phosphorus ores) located in a small number of countries. Currently, more than 90% of mineral phosphorus is used as fertilizer to increase plant yield. As the global population continues to grow and the demand for food continues to increase, the demand for phosphorus in the food production industry is expected to continue to grow. And unlike other elements such as carbon (C) or nitrogen (N), phosphorus is a non-renewable mineral resource. A large number of studies have demonstrated that, at current production rates, most of the phosphorus reserves will be depleted within 100 years.
At present, about 90% of the phosphorus entering municipal sewage plants (WWTP) is removed and incorporated into wastewater sludge, while sludge digestate is a slurry produced by anaerobic digestion of wastewater sludge, and is typically rich in inorganic orthophosphates in both aqueous and solid phases, and also in a large amount of ammonium, calcium, magnesium and iron ions, which is a promising source of phosphorus recovery. Current techniques for leaching phosphorus from sludge digestate are mainly strong acid and strong base, complexing agents, ozonation, ultrasound, and heat treatment. Although the methods have the characteristics, the methods have certain limitations, have the problems of large equipment investment, high energy consumption, high operation cost, secondary pollution to the environment and the like in different degrees, only leach phosphorus from the sludge digestion liquid, only transfer and separate pollutants in the sludge digestion liquid, and not recycle the pollutants, and further need to carry out subsequent treatment, so that the treatment cost of the sludge digestion liquid is increased, and the method is limited in the process of putting into practical application.
Compared with the phosphorus leaching process, the sludge digestive juice acidification treatment phosphorus leaching process by electrochemical in-situ acid production has the advantages of no secondary pollution, small equipment occupation area, good phosphorus leaching effect and the like, and is gradually and widely paid attention to both home and abroad.
Problems with this process include: (1) Only the anode acid-producing and acidification sludge digestion liquid is used for leaching phosphorus, the cathode alkali-producing reaction is not synchronously utilized, the synchronous recovery of the sludge digestion liquid acid-leaching phosphorus and phosphorus can not be realized, and additional chemical agents are needed to be added for recovering the phosphorus; (2) The reaction area cannot be divided into an anode area and a cathode area, and acid and alkali generated by the anode and the cathode are mixed, so that the acidification of sludge digestive juice cannot be satisfied, the leaching effect of phosphorus, ammonium, calcium, magnesium and iron ions is poor, and the subsequent phosphorus recovery efficiency is reduced; (3) If the reaction zone is divided into a cathode zone and an anode zone by using an ion exchange membrane, although the problem of neutralization of acid and alkali of the cathode and the anode can be solved, membrane pollution can be caused in the process of electrolyzing wastewater, so that the treatment cost of leaching and recycling phosphorus is higher; (4) The sludge digestive juice simply flows through the anode side, and the sludge digestive juice cannot fully contact with the acidic water body generated by the anode due to the obstruction of the air film on the surface of the anode, so that the phosphorus leaching capability and the sludge reduction effect are poor.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides an electrolysis system and a method for recycling phosphorus from sludge digestion liquid.
The invention provides an electrolysis system for recovering phosphorus from sludge digestion liquid, which comprises:
Electrochemical electrolysis unit: the acid water body generated by continuously hydrolyzing water through the anode (1-1) is used for acidizing the sludge digestive juice; the alkaline water body generated by continuously decomposing water through the cathode (1-2) is used for recycling the phosphorus which is separated out by acidification in the sludge digestion liquid;
a sludge centrifugal dehydration unit: performing mud-water separation on the acidified sludge digestion liquid;
And a mixing processing unit: the method is used for mixing and reacting the solution after the acidification of the sludge digestion solution is centrifuged and alkaline water overflowed near the cathode (1-2) of the electrochemical electrolysis unit (1).
Further, the electrochemical electrolysis unit comprises an anode and a cathode; the anode is a screen strong filter cylinder electrode, the inside of the anode is a cavity, the wall of the anode is of a porous structure, the two ends of the cylinder are respectively provided with a water inlet and a water outlet, and the cathode is an annular electrode net.
Further, the electrochemical electrolysis unit also comprises a water inlet for introducing sludge digestive juice into the anode side of the electrochemical electrolysis unit, a water inlet for introducing water after reaction into the cathode side of the electrochemical electrolysis unit, an anode water outlet of the electrochemical electrolysis unit and a cathode overflow port of the electrochemical electrolysis unit.
Further, the anode is made of a platinum filter element, a titanium dioxide filter element or a carbon filter element;
The cathode is made of stainless steel, graphite, titanium or titanium-based metal oxide;
further, the distance between the anode and the cathode of the filter element is 1-10cm.
Further, the filter element anode is connected with the power supply anode, the cathode is connected with the power supply cathode, and the current density used for reaction is between 5 and 25mA/cm 2.
The working steps of the electrolytic system of the invention are as follows:
the sludge centrifugal dehydration unit (2) is used for separating mud from water, the sludge digestion liquid which is acidified near the anode of the electrolysis unit is conveyed to the sludge centrifugal dehydration unit (2) through the first water inlet (2-1), the centrifugal liquid after centrifugation is conveyed into the mixing treatment unit (3) through the third water outlet (2-3), and meanwhile, the produced sludge is conveyed and conveyed outwards through the sludge outlet (2-2);
The mixing treatment unit (3) receives the centrifugal liquid outlet water from the sludge centrifugal dehydration unit (2) and the alkali liquor near the cathode (1-2) overflowed from the second water outlet (1-6) and conveyed through the third water inlet (3-2) through the second water inlet (3-1), and the mixed liquid is conveyed to the reaction waste liquid inlet (1-4) through the fourth water outlet (3-3) through standing precipitation and finally enters near the cathode (1-2).
The invention also provides an electrolytic method for recovering phosphorus from sludge digestion liquid, comprising the following steps:
A. The step of electrochemical anodic acidification of sludge digestion liquid and electrochemical cathodic alkali production:
The sludge digestive juice enters the vicinity of an anode (1-1) of an electrochemical electrolysis unit (1), is mixed and acidified with an acidic water body generated by the anode (1-1), and the acidified sludge digestive juice is conveyed to a sludge centrifugal dehydration unit (2); electrolyzed water near a cathode (1-2) of an electrochemical electrolysis unit (1) generates alkaline water body, and the alkaline water body is overflowed and conveyed to a mixing treatment unit (3);
B. and (3) solid-liquid separation of the sludge centrifugal dehydration unit:
sludge digestion liquid acidized from an anode (1-1) of an electrochemical electrolysis unit (1) is subjected to mud-water separation in a sludge centrifugal dehydration unit (2), and the centrifugal liquid is conveyed to a mixing treatment unit (3); the dehydrated sludge is transported outwards through a sludge outlet (2-2);
C. mixing:
The centrifugal liquid is conveyed from the sludge centrifugal dehydration unit (2) and the alkaline water overflowed near the cathode (1-2) of the electrochemical electrolysis unit (1) are mixed and reacted in the mixing treatment unit, so that phosphorus recovery is completed.
On the basis of the scheme, the current density in the steps of electrochemical leaching of phosphorus and phosphorus recovery is between 5 and 25mA/cm 2; the speed of the cross flow of the sludge digestive juice and the acidic water body at the anode side of the electrochemical electrolysis unit is 10-50ml/min.
In the electrolysis process, the sludge digestion liquid is continuously introduced from the bottom of the tank near the anode of the electrochemical electrolysis unit and the reaction waste liquid is continuously introduced from the bottom of the tank near the cathode of the electrolysis unit, and the purpose of acid-base separation can be achieved without an internal ion exchange membrane by continuously extracting the mixed liquid of the acid liquid near the anode and the sludge digestion liquid from the top end of the anode filter cylinder, so that the acid-base mixing generated by the electrode is slowed down, the alkaline environment near the cathode of the electrolysis unit is maintained, and the subsequent phosphorus recovery efficiency is improved. The chemical (ionic) equations for the cathodic and anodic reactions are:
H2O+e−→H2↑+OH-
O2+H2O+e−→4OH−
Acidizing the sludge digestion liquid by using an acidic water body extracted near the anode of the electrochemical treatment unit, and leaching rich phosphorus, ammonium, calcium, magnesium and iron ions contained in the sludge digestion liquid. The acidified sludge digestion liquid cannot recover phosphorus by mixing mud and water, and the acidified sludge digestion liquid containing rich phosphorus, ammonium, calcium, magnesium and iron ions needs to be further treated.
Specifically, sludge digestion liquid which is acidified from the vicinity of the anode of the electrochemical electrolysis unit is introduced into the sludge centrifugal dehydration unit, sludge-water separation is carried out, and centrifugal liquid is introduced into the mixing treatment unit.
Specifically, the mixed treatment unit is filled with a separating liquid containing rich phosphorus, ammonium, calcium, magnesium and iron ions and an alkaline water body overflowed near the cathode of the electrochemical electrolysis unit to be mixed with each other, and phosphorus is recovered in an alkaline atmosphere; the chemical (ionic) equation for the reaction is:
PO4 3−+Ca2++OH−→Ca5(PO4)3(OH)↓
PO4 3−+ Mg2++NH4 ++H2O→MgNH4PO4·6H2O↓
PO4 3−+Fe3++OH-→FePO4↓+H2O
by combining the technical scheme, the invention has the advantages and positive effects that:
(1) In the electrolysis process of the patent, sludge digestion liquid is continuously introduced from the bottom near the anode of the electrochemical electrolysis unit, reaction waste liquid is introduced from the bottom near the cathode of the electrochemical electrolysis unit, acidic liquid and sludge digestion liquid are continuously extracted from the vicinity of the anode of the electrochemical electrolysis unit to carry out mixed liquid in a cross flow mode, centrifugal liquid is obtained through the sludge centrifugal dehydration unit and is mixed with alkaline liquid overflowed from the vicinity of the cathode of the electrochemical electrolysis unit, and synchronous phosphorus leaching and phosphorus recovery are realized without adding additional chemical agents.
(2) By continuously extracting the acidified sludge digestion liquid from the vicinity of the anode of the electrolysis unit, the purpose of acid-base separation can be achieved without an internal ion exchange membrane, acid-base mixing generated by the electrode is slowed down, the acidic environment in the vicinity of the anode of the electrochemical electrolysis unit and the alkaline environment in the vicinity of the cathode of the electrochemical electrolysis unit are maintained, the acidification of the sludge digestion liquid is facilitated, the leaching of phosphorus, ammonium, calcium, magnesium and iron ions is improved, and the subsequent phosphorus recovery efficiency is enhanced.
(3) This patent is comparing in other electrolysis systems that contain ion exchange membrane, and the body system does not produce the membrane pollution, need not extra chemical agent and washs the membrane, when having eliminated secondary pollution, the economic input of very big reduction.
(4) The cross-flow water inlet is adopted near the anode of the electrochemical electrolysis unit, so that the obstruction of a liquid film on the surface of the anode is eliminated, the mixing effect of the sludge digestive juice and the acidic water body is improved, the precipitation of rich phosphorus, ammonium, calcium, magnesium and iron ions in the sludge digestive juice is enhanced, and no additional chemical agent is needed to recover the phosphorus from the sludge digestive juice.
(5) The system is environment-friendly, energy-saving and environment-friendly, and the alkaline water body of the reaction waste liquid after phosphorus recovery flows back to the vicinity of the cathode of the electrochemical electrolysis unit, so that the alkaline water body is continuously generated, secondary pollution is not generated due to cyclic utilization, the cost is greatly reduced, and the full utilization of resources is realized.
Drawings
FIG. 1 is a schematic diagram of an electrolytic system and method for recovering phosphorus from a sludge digestion solution in accordance with the present invention;
FIG. 2 is the effect of using the system of the present invention on the recovery of phosphorus from sludge digestion liquor and the effect of current density in application example 1;
FIG. 3 is a graph showing the effect of different current densities on pH near the anode in application example 1 on the effect of pH near the anode on phosphorus release of sludge digestive juice;
FIG. 4 is the effect of acidified sludge digestate of different current densities on sludge reduction in application example 1;
FIG. 5 shows the effect of cross-flow rate on phosphorus recovery from sludge digestion solution using the system of the present invention in application example 2.
In the accompanying drawings:
The electrochemical electrolysis unit 1, the anode 1-1, the cathode 1-2, the sludge digestion liquid water inlet 1-3, the reaction waste liquid water inlet 1-4, the first water outlet 1-5 and the second water outlet 1-6;
the sludge centrifugal dehydration unit 2, the first water inlet 2-1, the sludge outlet 2-2 and the third water outlet 2-3;
the mixing treatment unit 3, the second water inlet 3-1, the third water inlet 3-2 and the fourth water outlet 3-3.
Detailed Description
In order to further describe the technical means and effects adopted by the present invention for achieving the intended purpose, the following detailed description will refer to the specific implementation, structure, characteristics and effects according to the present invention with reference to the accompanying drawings and preferred embodiments.
Example 1
As shown in fig. 1 and 2, an electrolysis system and method for recovering phosphorus from a sludge digestion solution, comprising:
electrochemical electrolysis unit 1: the method is used for in-situ generation of acidic water near the anode (1-1) to acidify the sludge digestion liquid to release phosphorus, ammonium, calcium, magnesium and iron ions, and in-situ generation of alkaline water near the cathode (1-2) to be used for subsequent phosphorus recovery;
A sludge centrifugal dehydration unit 2: the method is used for separating sludge from water of the acidified sludge digestion liquid conveyed near the anode (1-1) of the electrochemical electrolysis unit (1);
mixing processing unit 3: is used for mixing and reacting the centrifugate conveyed from the sludge centrifugal dehydration unit (2) and alkaline water overflowed near the cathode (1-2) of the electrochemical electrolysis unit (1) to recycle phosphorus.
Specifically, the electrochemical electrolysis unit (1) comprises an anode (1-1) and an annular net-shaped cathode (1-2); the anode (1-1) is a screen cylindrical electrode, a sludge digestion liquid water inlet (1-3) and a first water outlet (1-5) are arranged at the bottom near the anode, a reaction waste liquid water inlet (1-4) and a second water outlet (1-6) are arranged at the bottom near the cathode, and the cathode is an annular mesh electrode.
As a preferable scheme, the acidic water body and the sludge digestion liquid near the anode (1-1) are mixed in a cross flow mode, and after the sludge digestion liquid is acidified, the mixture is extracted from the filter cylinder through the first water outlet (1-5), and the cross flow velocity is 30ml/min. The alkaline water body near the cathode (1-2) overflows to the mixing treatment unit (3);
as a preferable scheme, the anode (1-1) is made of a platinum filter element, a titanium dioxide filter element or a carbon filter element;
as a preferable scheme, the cathode (1-2) is made of stainless steel, graphite, titanium or titanium-based metal oxide;
The electrochemical electrolysis unit (1) is cylindrical, the anode (1-1) and the annular net-shaped cathode (1-2) are arranged in the electrochemical electrolysis unit (1), and the anode (1-1) is arranged in the cathode (1-2);
The anode (1-1) is connected with the positive electrode of the power supply, the cathode (1-2) is connected with the negative electrode of the power supply, and the current density used for the reaction is between 5 and 25mA/cm 2.
The sludge centrifugal dehydration unit (2) comprises a first water inlet (2-1) for conveying acidified sludge digestion liquid, a second water outlet (2-3) for conveying centrifugal liquid and a sludge discharge outlet (2-2) for conveying dehydrated sludge.
The mixing treatment unit (3) comprises a second water inlet (3-1) for receiving centrifugal liquid, a third water inlet (3-2) for receiving alkaline water overflowed near the cathode (1-2) of the electrochemical electrolysis unit (1), and a fourth water outlet (3-3) for recycling reaction waste liquid.
Example 2
An electrolysis system and method for recovering phosphorus from a sludge digestion liquor uses the recovery system of example 1.
Specifically, the recovery method comprises the following steps:
A. A step of electrochemical anodic acidification of sludge digestion liquid and electrochemical cathodic alkali production;
The sludge digestive juice enters the vicinity of an anode (1-1) of an electrochemical electrolysis unit (1), is mixed and acidified with an acidic water body generated by the anode (1-1), and the acidified sludge digestive juice is conveyed to a sludge centrifugal dehydration unit (2); electrolyzed water near a cathode (1-2) of an electrochemical electrolysis unit (1) generates alkaline water body, and the alkaline water body is overflowed and conveyed to a mixing treatment unit (3);
B. a step of solid-liquid separation of the sludge centrifugal dehydration unit;
Sludge digestion liquid acidized from an anode (1-1) of an electrochemical electrolysis unit (1) is subjected to sludge-water separation in a sludge centrifugal dehydration unit (2), the centrifugal liquid is conveyed to a mixing treatment unit (3), and dehydrated sludge is conveyed outwards through a sludge discharge port (2-2);
C. mixing;
The centrifugal liquid conveyed from the sludge centrifugal dehydration unit (2) and the alkaline water overflowed near the cathode (1-2) of the electrochemical electrolysis unit (1) are mixed and reacted in the mixing treatment unit (3) to complete phosphorus recovery
And extracting the sludge digestion liquid after cross-flow mixing acidification from the vicinity of the anode of the electrochemical electrolysis unit (1), carrying out sludge-water separation by the sludge centrifugal dehydration unit (2), transporting the separated sludge outwards, and conveying the centrifugal liquid to the mixing treatment unit (3) to be mixed and reacted with alkaline water overflowed from the vicinity of the cathode (1-2) to complete phosphorus recovery.
As a preferred solution, the acidified sludge digestion solution mixed by cross flow is extracted from the inside of the anode (1-1) through the first water outlet (1-5); the speed of the cross-flow mixing and extracting the acidified sludge digestion liquid is 10-50ml/min. In the extraction process, acidic water generated by electrolysis of the anode (1-1) continuously passes through holes in the wall of the anode (1-1) from the outside of the anode (1-1) to be mixed with sludge digestive juice entering the anode in a cross-flow manner, so that the sludge digestive juice is fully acidified.
The degree of releasing phosphorus by sludge acidification is adjusted by different flow rates of cross-flow extraction.
The current density in the steps of electrochemically anodically acidifying the sludge digestion solution and electrochemically cathodically producing alkali is maintained at 20mA/cm -2.
Use example 1
The material of the cathode (1-2) in the electrolysis unit is stainless steel, the material of the anode (1-1) is a titanium filter core electrode (the titanium filter core electrode is cylindrical, the inside is a cavity, the wall is a porous structure, the filtering precision is 0.45-50 mu m, the porosity is 35-45%), the current density is 5, 10, 15, 20, 25mA/cm 2, and the electrode spacing is 5 cm.
The sludge digestive juice entering from the sludge digestive juice water inlet (1-3) has a solid concentration of 10g/L, a phosphorus concentration of 20mg/g in the solid, a total phosphorus concentration of the sludge digestive juice of 250mg/L, a water inflow of 20ml/min, an anode cross-flow extraction water flow of 30ml/min, and a water outflow of 10ml/min at the alkaline water body second water outlet (1-6).
The mixing treatment unit (3) is used for mixing and reacting the centrifugate from the sludge centrifugal dehydration unit (2) with alkaline water overflowed from the vicinity of the cathode, and measuring the phosphorus recovery effect under different current densities at the same reaction time of 3 hours. As shown in fig. 2.
The sludge digestion solution with the initial pH=7-8 enters the anode (1-1) of the electrochemical treatment unit (1) to be subjected to cross-flow mixing acidification treatment, and samples are taken every 30min for testing, and the pH generated in the vicinity of the anode (1-1) within the same reaction time of 3h and the influence on the degree of phosphorus release from the sludge digestion solution are measured, as shown in fig. 3.
The sludge centrifugal dehydration unit (2) is used for separating sludge from water of the acidified digestion liquid, the dehydrated sludge is transported outwards, the centrifugal liquid is conveyed to the mixing treatment unit (3), and the influence on sludge reduction after acidification of the sludge digestion liquid under different current densities is measured, as shown in fig. 4.
Use example 2:
The material of the cathode (1-2) in the electrolysis unit is stainless steel, the material of the anode (1-1) is a titanium filter core electrode (the titanium filter core electrode is cylindrical, the inside is a cavity, the wall is of a porous structure, the filtering precision is 0.45-50 mu m, the porosity is 35-45%), the current density is 20mA/cm 2, and the electrode spacing is 5 cm.
The sludge digestive juice entering from the sludge digestive juice water inlet (1-3) has the solid concentration of 10g/L, the phosphorus concentration in the solid of 20mg/g, the total phosphorus concentration of the sludge digestive juice of 250mg/L, the water inflow of 20ml/min, the anode cross-flow extraction water flow of 10ml/min, 20ml/min, 30 ml/min, 40 ml/min and 50ml/min, and the water outflow of the alkaline water body second water outlet (1-6) is 10ml/min.
The sludge centrifugal dehydration unit (2) is used for separating the acidified digestive juice from the sludge, the dehydrated sludge is transported outwards, and the centrifugal liquid is conveyed to the mixing treatment unit (3).
The mixing treatment unit (3) is used for mixing and reacting the centrifugate from the sludge centrifugal dehydration unit (2) and the alkaline water overflowed from the vicinity of the cathode, and measuring the phosphorus recovery effect under different cross flow speeds, as shown in fig. 5.
Through the cross-flow mixing mode, the problems of obstruction of a liquid film on the surface of the anode (1-1) and uneven mixing of the anode acidic water body and the sludge digestive juice are solved, the release of phosphorus in the sludge digestive juice is improved, and the recovery effect of the phosphorus is enhanced.
The present invention is not limited to the above embodiments, but is capable of modification and variation in detail, and other modifications and variations can be made by those skilled in the art without departing from the scope of the present invention.
Claims (7)
1. An electrolysis system for recovering phosphorus from a sludge digestion solution, comprising:
Electrochemical electrolysis unit (1): the method is used for in-situ acidification of sludge digestion liquid and in-situ alkali production liquid, acidic water is continuously extracted from the vicinity of an anode (1-1) of an electrochemical electrolysis unit (1) during electrolysis, and phosphorus, ammonium, calcium, magnesium and iron ions in the sludge digestion liquid are released by cross-flow mixing of the sludge digestion liquid input from the bottom of the anode of the electrochemical electrolysis unit, reaction waste liquid is conveyed from the bottom of a cathode (1-2) of the electrochemical electrolysis unit (1), and alkaline water overflows after in-situ alkaline water is produced from the vicinity of the cathode (1-2) for phosphorus recovery;
sludge centrifugal dehydration unit (2): the method is used for separating mud from water of the digested sludge liquid after acidification near the anode (1-1) of the electrochemical electrolysis unit (1);
Mixing processing unit (3): the device is used for mixing and reacting the centrifugal liquid conveyed from the sludge centrifugal dehydration unit (2) and alkaline water overflowed near the cathode (1-2) to realize phosphorus recovery.
2. An electrolysis system for recovery of phosphorus from a sludge digestion solution as claimed in claim 1,
The electrochemical electrolysis unit (1) comprises an anode (1-1) and a cathode (1-2);
The anode (1-1) is a screen barrel-shaped electrode, a sludge digestion liquid water inlet (1-3) and a first water outlet (1-5) are arranged at the bottom near the anode (1-1), the cathode (1-2) is an annular net-shaped electrode, a reaction waste liquid water inlet (1-4) and a second water outlet (1-6) are arranged at the bottom near the cathode (1-2).
3. An electrolysis system for recovery of phosphorus from a sludge digestion solution as claimed in claim 2, wherein,
The anode (1-1) is a filter element electrode, a cavity is formed in the anode, a porous structure is arranged on the wall, and the anode is made of a platinum filter element, a titanium sub-oxide filter element or a carbon filter element;
The cathode (1-2) is a porous net barrel electrode, and is made of stainless steel, graphite, titanium or titanium-based metal oxide.
4. An electrolysis system for recovering phosphorus from a sludge digestion solution according to claim 2, characterized in that the electrochemical electrolysis unit (1) is cylindrical, the anode (1-1) is sleeved in the cathode (1-2), and the distance between the cathode (1-2) and the anode (1-1) is 1-10cm.
5. An electrolysis system for recovery of phosphorus from sludge digestion liquor according to claim 2, characterized in that the anode (1-1) is connected to the positive power supply and the cathode (1-2) is connected to the negative power supply, the current density used for the reaction being between 5-25mA/cm 2.
6. An electrolysis system for recovery of phosphorus from sludge digestion liquor according to claim 2, characterized in that the acid liquor extracted near the anode (1-1) is cross-flowed with the sludge digestion liquor introduced from the bottom, and the flow rate used for the reaction is 10-50 ml/min.
7. An electrolysis process for recovery of phosphorus from sludge digestate using the system of any of the preceding claims, characterized by the specific steps of:
A. The step of electrochemical anodic acidification of sludge digestion liquid and electrochemical cathodic alkali production:
The sludge digestive juice enters the vicinity of an anode (1-1) of an electrochemical electrolysis unit (1), is mixed and acidified with an acidic water body generated by the anode (1-1), and the acidified sludge digestive juice is conveyed to a sludge centrifugal dehydration unit (2); electrolyzed water near a cathode (1-2) of an electrochemical electrolysis unit (1) generates alkaline water body, and the alkaline water body is overflowed and conveyed to a mixing treatment unit (3);
B. a step of solid-liquid separation of the sludge centrifugal dehydration unit;
The sludge digestion liquid acidized from the anode (1-1) of the electrochemical electrolysis unit (1) is subjected to solid-liquid separation in the sludge centrifugal dehydration unit (2), and the separated liquid is conveyed to the mixing treatment unit (3); the dehydrated sludge is transported outwards through a sludge outlet (2-2);
C. mixing;
The separation liquid conveyed from the sludge centrifugal dehydration unit (2) and the alkaline water overflowed near the cathode (1-2) of the electrochemical electrolysis unit (1) are mixed and reacted in the mixing treatment unit (3) to complete phosphorus recovery.
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| CN115537816B (en) * | 2022-10-08 | 2024-06-07 | 青岛理工大学 | Rotational flow electrolysis system and method for regenerating acidic copper chloride etchant and recycling copper |
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