WO2012095226A1 - Method and apparatus for dehydration treatment, and treatment before dehydration of a sludge substance - Google Patents

Method and apparatus for dehydration treatment, and treatment before dehydration of a sludge substance Download PDF

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Publication number
WO2012095226A1
WO2012095226A1 PCT/EP2011/072265 EP2011072265W WO2012095226A1 WO 2012095226 A1 WO2012095226 A1 WO 2012095226A1 EP 2011072265 W EP2011072265 W EP 2011072265W WO 2012095226 A1 WO2012095226 A1 WO 2012095226A1
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WO
WIPO (PCT)
Prior art keywords
electrolyte
conductivity
sludge
sludge substance
added
Prior art date
Application number
PCT/EP2011/072265
Other languages
French (fr)
Inventor
He Qing ZHANG
Chun Jiang MENG
Sunand SREERAMACHANDRAN
Jing Wei ZHANG
Original Assignee
Siemens Aktiengesellschaft
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Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO2012095226A1 publication Critical patent/WO2012095226A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/006—Electrochemical treatment, e.g. electro-oxidation or electro-osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
    • C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/15—Treatment of sludge; Devices therefor by de-watering, drying or thickening by treatment with electric, magnetic or electromagnetic fields; by treatment with ultrasonic waves
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/003—Downstream control, i.e. outlet monitoring, e.g. to check the treating agents, such as halogens or ozone, leaving the process
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/05—Conductivity or salinity
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage

Definitions

  • the present invention relates to the technology for the treatment and disposal of sludge substances and, in particu ⁇ lar, to a dehydration method and a treatment method before dehydration, of a sludge substance, and an apparatus there ⁇ fore .
  • Dehydration is a critical process during the treatment and disposal of a sludge substance. Since the sludge sub ⁇ stances have properties of high water contents and being dif ⁇ ficult to be dewatered, the water contents have significant effects on the total costs of the treatment and disposal of the sludge. However, most of the water in sludge substances, in addition to small doses of free water and capillary water, is present between sludge floes and within sludge cells, re ⁇ ferred to as bound water, and such bound water is difficult to remove by mechanical dewatering means.
  • tradi ⁇ tional mechanical dewatering means such as belt filter presses, plate and frame filter presses and centrifugal dehy- drators, etc.
  • they can only remove most of the free water and capillary water, and can at best reduce the water content of a sludge substance to about 80%.
  • mud cakes of a water content of 80% are difficult to transport, tend to cause pollution along the way, have high costs in the subse ⁇ quent treatment and disposal, and have quite large negative effects on all terminal disposal technologies such as the subsequent compost, landfill, incineration, etc.
  • Particu ⁇ larly, regulations in China provide that sludge should have a water content below 60% before entering a garbage sanitary landfill site.
  • the electric dehydration is a deep dehydration technology which is highly efficient, energy-saving, green and easy to operate, and which has attracted more and more attention re ⁇ cently.
  • the electric dehydration technology can reduce the water content of a sludge substance to below 60%.
  • a general process for electric dehydration can be described as the following three steps of:
  • step 2) delivering the mud cake obtained in step 1) or a sludge substance having a relatively high water content to be treated to between the cathode and anode, and simultaneously applying a certain mechanical pressure thereto;
  • the above electric dehydration process needs to consume a large quantity of electric energy.
  • the elec ⁇ tric energy consumption has become the most important compo ⁇ nent of the costs during the whole electric dehydration treatment of the sludge substance. Therefore, the question of how to reduce the electric energy consumption during the electric dehydration of sludge is the key point for reducing costs in the electric dehydration treatment of a sludge sub- stance.
  • embodiments of the present invention provide a dehydration method and a treatment method before dehydration, of a sludge substance, and an apparatus therefor, to reduce the electric energy consumption in the electric dehydration treatment while significantly increasing the dehydration efficiency, so as to reduce the costs of the electric dehydration treatment of a sludge substance.
  • a method for treating a sludge substance before dehydra ⁇ tion thereof as described in the embodiments of the present invention comprises adding an electrolyte into the sludge substance to be treated before carrying out an electric dehy- dration to said sludge to be treated.
  • Said method for dehydration treatment of a sludge sub ⁇ stance in the embodiments of the present invention comprises the step of adding an electrolyte into the sludge substance to be treated; and carrying out an electric dehydration treatment on the sludge substance added with the electrolyte.
  • the step of adding an electrolyte into the sludge sub ⁇ stance to be treated comprises: setting an expected conduc ⁇ tivity of the sludge substance; determining the dose of the electrolyte to be added according to the original conductiv- ity of the sludge substance to be treated and the expected conductivity; and adding the electrolyte in the determined dose into the sludge substance to be treated.
  • the step of determining the dose of the electrolyte to be added according to the original conductiv- ity of the sludge substance to be treated and the expected conductivity comprises: carrying out a plurality of tests of adding a solid electrolyte into samples of the sludge sub ⁇ stance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the doses of the solid electrolyte added; and determining the do ⁇ se of the solid electrolyte to be added according to the to ⁇ tal quantity/ flow rate of the sludge substance to be trea- ted, the original conductivity, the expected conductivity, and the relationship between the changes in the conductivity of the sludge substance and the doses of the solid electro ⁇ lyte added.
  • the step of determining the dose of the electrolyte to be added according to the original conductivity of the sludge substance to be treated and the expected conductivity com ⁇ prises carrying out a plurality of tests of adding an elec ⁇ trolyte solution into samples of the sludge substance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the concentra ⁇ tions of the electrolyte solution to be added; determining the concentration of the electrolyte to be added according to the total quantity/ flow rate of the sludge substance to be treated, the original conductivity, the expected conductiv- ity, and the relationship between the changes in the conduc ⁇ tivity of the sludge substance and the concentrations of the electrolyte solution to be added; and determining the dose of the electrolyte to be added according to the concentration of the electrolyte solution to be added and the total quantity or flow rate of the sludge substance to be treated.
  • the step of determining the dose of the electrolyte to be added according to the original conductivity of the sludge substance to be treated and the expected conductivity com ⁇ prises: determining the concentration of the electrolyte so- lution to be added according to the equation a 2 - S 2 - S 1 ⁇ wherein represents the concentration of the electrolyte solution to be added; 1 represents the original conductivity of the sludge substance; represents the empirical coeffi- cient for the original conductivity; 2 represents the ex- pected conductivity of the sludge substance; and repre ⁇ sents the empirical coefficient for the expected conductiv ⁇ ity; and determining the dose of the electrolyte to be added according to the concentration of the electrolyte solution to be added and the total quantity or flow rate of the sludge substance to be treated.
  • the step of adding an electrolyte into the sludge substance to be treated comprises the steps of: A. setting an expected conductivity and a dose of an electrolyte to be added each time; B. adding the electrolyte in said dose of the electrolyte to be added each time into said sludge substance to be treated, and stirring them uniformly; and measuring the conductivity of the sludge substance after add ⁇ ing the electrolyte and comparing the result with said ex ⁇ pected conductivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity, then step B is executed again.
  • An apparatus for treating a sludge substance before dehy ⁇ dration thereof as described in the embodiments of the pre ⁇ sent invention comprises a pre-treatment module, which is used for adding an electrolyte into the sludge substance to be treated before carrying out an electric dehydration to the sludge substance to be treated.
  • An apparatus for dehydration of a sludge substance as de ⁇ scribed in the embodiments of the present invention com ⁇ prises: a pre-treatment module 100 which is used for adding an electrolyte into the sludge substance to be treated; and an electric dehydration device 200 which is used for carrying out an electric dehydration treatment on the sludge substance added with the electrolyte.
  • Said pre-treatment module 100 comprises: a conductivity determining unit 101 which is used for determining an ex- pected conductivity; an electrolyte dose determining unit
  • an electrolyte adding unit 103 which is used for adding the electrolyte in the dose so determined into the sludge substance to be treated.
  • the electrolyte dose determining unit 102 comprises: a setting subunit, which is used for setting the relationship between the changes in the conductivity of said sludge substance and the doses of the electrolyte or electro ⁇ lyte solution to be added; and an electrolyte dose calculat ⁇ ing subunit, which is used for determining the dose of the electrolyte to be added according to the total quantity/ flow rate of the sludge substance to be treated, the original con ⁇ ductivity, the expected conductivity, and the relationship set between the changes in the conductivity of the sludge substance and the doses of the electrolyte to be added.
  • a conductivity determining unit 101 which is used for determining an expected conductivity
  • an electrolyte dose determining unit 102' which is used for setting the dose of the electrolyte to be added each time
  • an electrolyte adding unit 103' which is used for adding the electrolyte in the dose of the electrolyte to be added each time into said sludge substance to be treated
  • a stirring unit 104 which is used for stirring the sludge substance to be treated after adding the electrolyte uniformly
  • a conductivity measur- ing unit 105 which is used for measuring the conductivity of the sludge substance after stirring and comparing the result with said expected conductivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity, then the electrolyte adding unit 103' is instructed to add the electrolyte again in said dose of the electrolyte to be added each time into said sludge substance to be treated.
  • the method and apparatus for dehydration treatment as de ⁇ scribed in the embodiments of the present invention increase the conductivity of a sludge substance to be treated by add ⁇ ing an electrolyte in advance into the sludge substance to be treated, and thus can significantly reduce the electric en ⁇ ergy consumption in the subsequent electric dehydration treatment, and at the same time increase the efficiency in the sludge treatment, which in turn can reduce the treatment costs during the whole dehydration of the sludge substance.
  • FIG. 1 is a flow diagram of a method for dehydration treatment of a sludge substance as described in an embodiment of the present invention
  • Fig. 2 is a schematic diagram showing the inner structure of an apparatus for dehydration treatment of a sludge sub ⁇ stance as described in an embodiment of the present inven ⁇ tion;
  • Fig. 3 is a schematic diagram of the inner structure of a pre-treatment module
  • Fig. 4 is a schematic diagram of the inner structure of another pre-treatment module.
  • Fig. 5 shows the relationship between the unit electric energy consumption and the solid content of the treated slud ⁇ ge by using an existing electric dehydration method and a me- thod for dehydration treatment according to the present invention, respectively.
  • a method for dehydration of a sludge substance provided in an embodiment of the present invention mainly comprises:
  • step 1 adding an electrolyte into the sludge substance to be treated;
  • step 2 carrying out an electric dehydration treatment on the sludge substance added with the electrolyte.
  • the electric dehydration mechanism includes two synchronous processes: an electrophoresis process of so ⁇ lid particles in an aqueous phase, and an electric osmosis process of water molecules between the solid particles
  • the inventor has found after research that the dehydration efficiency can be improved by increasing the conductivity of a sludge substance. Therefore, by adding an electrolyte in or ⁇ der to increase the conductivity of a sludge substance, the method provided in the embodiments of the present invention efficiently improve the dehydration efficiency of a subse ⁇ quent electric dehydration unit while significantly reducing the electric energy consumption in the electric dehydration treatment, and in turn significantly reducing the costs in the electric dehydration treatment of the sludge substance.
  • the electro ⁇ lyte as mentioned in step 1 above may be, for example, an io- nic salt substance that is water soluble.
  • it can be sodium salts such as sodium chloride (NaCl), sodium sul ⁇ fate (Na 2 SC>4) , etc., or potassium salts such as potassium chloride (KC1), potassium sulfate (K 2 SO 4 ) , etc., or else mag ⁇ nesium salts such as magnesium chloride (MgCl 2 ) , etc.
  • said electrolytes are prefera ⁇ bly electrolytes free of heavy metal or toxic and harmful ions, to avoid producing harmful effects to the subsequent treatment and disposal of sludge. Furthermore, other electro- lytes which are advantageous to the environment protection and subsequent treatment and disposal of sludge can also be selected according to practical needs.
  • an expected conductivity can be set in advance, then the dose of the electrolyte to be added is determined according to the original conductivity of said sludge sub ⁇ stance to be treated and said expected conductivity, and fi ⁇ nally the electrolyte is added in the determined dose into said sludge substance to be treated.
  • said electrolyte can be a solid electrolyte, or it can also be an electrolyte solution.
  • the concentration of the electrolyte solution to be added is first determined accord ⁇ ing to the original conductivity and the expected conductiv- ity of the sludge substance to be treated; and then the dose of the electrolyte to be added is determined according to the concentration of the electrolyte solution to be added and the total quantity (mass or volume) /flow rate of the sludge sub ⁇ stance to be treated.
  • a plurality of tests of adding an electrolyte solution can be first car ⁇ ried out on samples of the sludge substance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the concentrations of the electrolyte solution to be added; then an expected conductiv ⁇ ity of the sludge substance is determined; then the concen ⁇ tration of the electrolyte to be added is determined accord ⁇ ing to the expected conductivity and the relationship between the changes in the conductivity of the sludge substance and the concentrations of the electrolyte solution to be added; and finally, the dose of the electrolyte to be added is de ⁇ termined according to the concentration of the electrolyte solution to be added and the total quantity or flow rate of the sludge substance to be treated.
  • the concentration of the electrolyte solution to be added is determined directly according to the following equation (1) . It is proven by experiments that by using this alternative solution, there may be a certain deviation between the resulting conductivity of the sludge substance added with an electrolyte and the expected conductivity, but this deviation is acceptable in practical applications and easy to calcu ⁇ late. The final conductivity after adding an electrolyte is based on the actually measured value.
  • a represents the empirical coefficient between the concentration of the electrolyte solution to be added and the conductivity of the solution, particularly as a function of the valency of the electrolyte to be added, as shown in table 1;
  • S represents the conductivity in microsie- mens/cm (us/cm) ;
  • AC represents the concentration of the electrolyte solution to be added, in milligram/liter (mg/L) .
  • Si represents the original conductivity of the sludge substance
  • ⁇ represents an empirical coefficient un ⁇ der the original conductivity
  • S ⁇ represents the expected conductivity of the sludge substance;
  • a ⁇ represents an empirical coefficient under the expected conductivity.
  • the electro ⁇ lyte can be added in the dose so determined into the sludge substance to be treated. Further, the sludge substance added with the electrolyte can be stirred uniformly. The conductivity of the sludge substance after adding the electrolyte can be further measured, to determine whether the conductivity of the sludge substance after adding the electrolyte reaches the expected conductivity. If not, then the electrolyte can be added again into the sludge substance by the method as de ⁇ scribed above.
  • the relationship obtained by the experiments between the changes in the conductivity of the sludge substance and the doses of the electrolyte added can be corrected according to the measured conductivity of the sludge substance after adding the electrolyte and the dose of the electrolyte added.
  • a method for adding an electrolyte in portions which particularly comprises:
  • step 11 setting an expected conductivity and a dose of an electrolyte added each time; wherein the dose of an elec ⁇ trolyte added each time can be set according to the relation ⁇ ship obtained by the experiments between the changes in the conductivity of the sludge substance and the doses of the electrolyte added, or determined according to an empirical value; the dose of the electrolyte to be added each time can be identical for each time, and also can be gradually in ⁇ creased or decreased; and in order to reach the expected con- ductivity better and more efficiently, the dose of the elec ⁇ trolyte to be added each time can be adjusted during the ad ⁇ dition;
  • step 12 adding the electrolyte in the set dose of the electrolyte to be added each time into said sludge substance to be treated, and stirring them uniformly;
  • step 13 measuring the conductivity of the sludge sub ⁇ stance after adding the electrolyte.
  • step 14 comparing the conductivity of the sludge sub ⁇ stance after adding the electrolyte with said expected con- ductivity, and returning to step 12 if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity.
  • step 14 can further comprise stopping the operation, i.e., not returning to step 12, until the con- ductivity of the sludge substance after adding the electro ⁇ lyte is larger than or equal to the expected conductivity.
  • step 14 can comprise stopping the operation until the difference between the conductivity in the sludge substance after adding the electrolyte and the expected con- ductivity is equal to or smaller than a threshold value.
  • the electrolyte added can be a solid electrolyte, or can be an electrolyte solution.
  • step 2 of the embodi ⁇ ment of the present invention can use any existing electric dehydration treatment technology.
  • the key point of the present inven ⁇ tion is adding a process for treating a sludge substance be ⁇ fore dehydration thereof as shown in step 1 before dehydrat- ing the sludge substance to be treated, i.e., adding an elec ⁇ trolyte into the sludge substance to be treated before dehy ⁇ drating the sludge substance to be treated, and providing a particular adding method.
  • the above treatment process before dehy- dration of a sludge substance can also be applied before other dehydration treatments of a sludge substance, to reduce the costs in the dehydration treatment of the sludge sub ⁇ stance .
  • embodiments of the present invention also provide an apparatus for treating a sludge substance before dehydration thereof.
  • An apparatus for treat ⁇ ing a sludge substance before dehydration thereof provided in the embodiments of the present invention comprises a pre ⁇ treatment module which is used for adding an electrolyte into the sludge substance to be treated before carrying out an electric dehydration to the sludge substance to be treated.
  • the treatment module as mentioned in the embodiments of the present invention can be disposed just before the dehydration apparatus for a sludge substance, and can even be disposed within the transportation pipes of the sludge substance.
  • said pre-treatment module can also constitute a dehydration apparatus for a sludge substance together with any existing electric dehydration device.
  • the pre-treatment module will not produce any harmful effect on subsequent electric dehydration equipment.
  • the apparatus for dehydration of a sludge substance has an inner structure as shown in Fig. 2, which mainly comprises: a pre-treatment module 100 which is used for adding an electrolyte into the sludge substance to be treated; and an electric dehydration device 200 which is used for carrying out an electric dehydration treatment on the sludge substance added with the electrolyte .
  • Said pre-treatment module 100 has an inner structure as shown in Fig. 3, which can particularly comprises:
  • a conductivity determining unit 101 which is used for de ⁇ termining an expected conductivity; in particular the determining unit can be set and adjusted by a user, embodied as a human machine interface or embodied as a storage device, for example ;
  • an electrolyte dose determining unit 102 which is used for determining the dose of the electrolyte to be added ac ⁇ cording to the original conductivity of said sludge substance to be treated and said expected conductivity;
  • an electrolyte adding unit 103 which is used for adding the electrolyte in the dose determined into the sludge sub ⁇ stance to be treated.
  • the pre-treatment module can also comprise a stirring unit, which is used for stirring the sludge sub ⁇ stance added with the electrolyte uniformly.
  • the pre-treatment module can also comprise a conductivity measuring unit which is used for measuring the conductivity of the sludge substance and comparing the result with the expected conductivity, and if the expected conduc ⁇ tivity is not reached, then the electrolyte dose determining unit can be informed to determine the dose of the electrolyte to be added.
  • the sludge substance hence can be added again with the electrolyte until reaching the expected conductiv ⁇ ity.
  • the electrolyte dose determining unit 102 can particularly comprise: a setting subunit, which is used for setting the relationship between the changes in the conductivity of said sludge substance and the doses of the elec ⁇ trolyte or electrolyte solution to be added; and an electro- lyte dose calculating subunit, which is used for determining the dose of the electrolyte to be added according to the to ⁇ tal quantity/ flow rate of the sludge substance to be treated, the original conductivity, the expected conductivity, and the relationship set between the changes in the conductivity of the sludge substance and the doses of the electrolyte added.
  • Said pre-treatment module 100 may otherwise have an inner structure as shown in Fig. 4, which particularly comprises: a conductivity determining unit 101 which is used for de- termining an expected conductivity; reference can be made to the embodiment as shown in Fig. 3 for the particular implementation thereof;
  • an electrolyte dose determining unit 102' which is used for setting the dose of the electrolyte added each time; the dose of the electrolyte to be added each time can be set and adjusted by the user himself or can be adjusted by the device itself, and the dose of the electrolyte to be added each time can be identical for each time, or can be gradually increased or decreased;
  • an electrolyte adding unit 103' which is used for adding the electrolyte in the dose of the electrolyte to be added each time into said sludge substance to be treated;
  • a stirring unit 104 which is used for stirring the sludge substance to be treated after adding the electrolyte uni- formly;
  • a conductivity measuring unit 105 which is used for meas ⁇ uring the conductivity of the sludge substance after stirring and comparing the result with said expected conductivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity, then the electrolyte adding unit 103' is instructed to add the electrolyte again in said dose of the electrolyte to be added each time into said sludge substance to be treated.
  • the conductivity measuring unit 105 can, for example, stop the addition, that is to say, it will not instruct the electrolyte adding unit 103' to add the electrolyte again.
  • the apparatus for dehydration of a sludge sub ⁇ stance increases the conductivity of the sludge substance to be treated to an expected value by using the pre-treatment module 100 to add an electrolyte into the sludge substance to be treated, so that the dehydration effi ⁇ ciency of a subsequent electric dehydration unit can be effi ⁇ ciently improved and at the same time significantly reduce the electric energy consumption during the electric dehydra ⁇ tion treatment, which in turn can significantly reduce the costs of the electric dehydration treatment of the sludge substance .
  • the sludge substance in the embodiments of the present invention may be sludge, for exam ⁇ ple, municipal sludge and industrial sludge, and may also be substances similar to sludge, such as organic mud slurry, etc .
  • the unit electric energy consumption and the solid content of the sludge after the dehydration treat- ment were also measured at different electric dehydration voltages after increasing the conductivity of the sludge sub ⁇ stance to a fixed value.
  • the unit electric energy consumption and the solid content of the sludge after the dehydration treatment for original sludge without addi- tion of an electrolyte at different electric dehydration voltages were measured.
  • an existing elec ⁇ tric dehydration technology was employed for the dehydration treatment.
  • the experimental results are shown in Fig. 5.
  • the round dots represent the unit electric energy consumption vs.
  • the square dots represent the unit electric energy consumption vs. solid content in the sludge after the dehy ⁇ dration treatment at different electric dehydration voltages (20 V, 40 V, 60 V and 80 V) when the conductivity of the sludge substance is increased to 4575 ⁇ / ⁇ ; and the rhombic dots represent the unit electric energy consumption vs.

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Abstract

Disclosed in the present invention is a method for treating a sludge substance before dehydration thereof, which method comprises adding an electrolyte into the sludge substance to be treated before carrying out an electric dehydration thereon. Further disclosed in the present invention is a method for the dehydration treatment of a sludge substance, which method comprises adding an electrolyte into the sludge substance to be treated; and carrying out an electric dehydration treatment on the sludge substance added with the electrolyte. Correspondingly, further disclosed in the present invention is an apparatus for treating a sludge substance before dehydration thereof and a dehydration apparatus for the sludge substance. By adding an electrolyte in advance into a sludge substance to be treated to increase the conductivity thereof, the present invention can efficiently improve the dehydration efficiency of a subsequent electric dehydration unit, and at the same time significantly reduce the electric energy consumption during the electric dehydration treatment, which in turn can significantly reduce the costs of the electric dehydration treatment of the sludge substance.

Description

Description
Method and apparatus for dehydration treatment, and treatment before dehydration of a sludge substance
Technical Field
The present invention relates to the technology for the treatment and disposal of sludge substances and, in particu¬ lar, to a dehydration method and a treatment method before dehydration, of a sludge substance, and an apparatus there¬ fore .
Background Art
Dehydration is a critical process during the treatment and disposal of a sludge substance. Since the sludge sub¬ stances have properties of high water contents and being dif¬ ficult to be dewatered, the water contents have significant effects on the total costs of the treatment and disposal of the sludge. However, most of the water in sludge substances, in addition to small doses of free water and capillary water, is present between sludge floes and within sludge cells, re¬ ferred to as bound water, and such bound water is difficult to remove by mechanical dewatering means. As to the tradi¬ tional mechanical dewatering means, such as belt filter presses, plate and frame filter presses and centrifugal dehy- drators, etc., they can only remove most of the free water and capillary water, and can at best reduce the water content of a sludge substance to about 80%. However, mud cakes of a water content of 80% are difficult to transport, tend to cause pollution along the way, have high costs in the subse¬ quent treatment and disposal, and have quite large negative effects on all terminal disposal technologies such as the subsequent compost, landfill, incineration, etc. Particu¬ larly, regulations in China provide that sludge should have a water content below 60% before entering a garbage sanitary landfill site. In December 2010, the Ministry of Environmental Protection issued a "notice on enhancing the pollution prevention and control in municipal wastewater treatment plants", which specifically provides that the wastewater treatment plants which transport sludge out of the plants for the purpose of storage (i.e. disposal without treatment) have to have the sludge dewatered to a water content below 50%.
It can be seen that with the continuous improvement in the treatment and disposal of sludge, deep dewatering of a sludge substance has become a problem to be solved urgently.
The electric dehydration is a deep dehydration technology which is highly efficient, energy-saving, green and easy to operate, and which has attracted more and more attention re¬ cently. Generally, the electric dehydration technology can reduce the water content of a sludge substance to below 60%. A general process for electric dehydration can be described as the following three steps of:
1) adding a flocculant in a sludge substance having a relatively high water content (for example, 98%) to be trea¬ ted to carry out a flocculation reaction, and then mechanically dehydrating the same by means of a belt filter press, etc., to obtain a mud cake having a water content of about 80%;
2) delivering the mud cake obtained in step 1) or a sludge substance having a relatively high water content to be treated to between the cathode and anode, and simultaneously applying a certain mechanical pressure thereto; and
3) applying a certain voltage between the two electrodes to make the sludge particle substances in the sludge migrate towards the anode and the water in the sludge migrate towards the cathode under the action of the electric field, in order to separate out part of the bound water in the sludge, to fi- nish the electric dehydration treatment.
It can be seen from the above process that the free water in a sludge substance can be removed by means of mechanical dewatering while a part of the bound water can be removed by the action of an electric field.
However, the above electric dehydration process needs to consume a large quantity of electric energy. Hence, the elec¬ tric energy consumption has become the most important compo¬ nent of the costs during the whole electric dehydration treatment of the sludge substance. Therefore, the question of how to reduce the electric energy consumption during the electric dehydration of sludge is the key point for reducing costs in the electric dehydration treatment of a sludge sub- stance.
Contents of the invention
In order to reduce the costs of the electric dehydration treatment of a sludge substance, embodiments of the present invention provide a dehydration method and a treatment method before dehydration, of a sludge substance, and an apparatus therefor, to reduce the electric energy consumption in the electric dehydration treatment while significantly increasing the dehydration efficiency, so as to reduce the costs of the electric dehydration treatment of a sludge substance.
A method for treating a sludge substance before dehydra¬ tion thereof as described in the embodiments of the present invention comprises adding an electrolyte into the sludge substance to be treated before carrying out an electric dehy- dration to said sludge to be treated.
Said method for dehydration treatment of a sludge sub¬ stance in the embodiments of the present invention comprises the step of adding an electrolyte into the sludge substance to be treated; and carrying out an electric dehydration treatment on the sludge substance added with the electrolyte.
The step of adding an electrolyte into the sludge sub¬ stance to be treated comprises: setting an expected conduc¬ tivity of the sludge substance; determining the dose of the electrolyte to be added according to the original conductiv- ity of the sludge substance to be treated and the expected conductivity; and adding the electrolyte in the determined dose into the sludge substance to be treated.
In this case, the step of determining the dose of the electrolyte to be added according to the original conductiv- ity of the sludge substance to be treated and the expected conductivity comprises: carrying out a plurality of tests of adding a solid electrolyte into samples of the sludge sub¬ stance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the doses of the solid electrolyte added; and determining the do¬ se of the solid electrolyte to be added according to the to¬ tal quantity/ flow rate of the sludge substance to be trea- ted, the original conductivity, the expected conductivity, and the relationship between the changes in the conductivity of the sludge substance and the doses of the solid electro¬ lyte added.
The step of determining the dose of the electrolyte to be added according to the original conductivity of the sludge substance to be treated and the expected conductivity com¬ prises: carrying out a plurality of tests of adding an elec¬ trolyte solution into samples of the sludge substance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the concentra¬ tions of the electrolyte solution to be added; determining the concentration of the electrolyte to be added according to the total quantity/ flow rate of the sludge substance to be treated, the original conductivity, the expected conductiv- ity, and the relationship between the changes in the conduc¬ tivity of the sludge substance and the concentrations of the electrolyte solution to be added; and determining the dose of the electrolyte to be added according to the concentration of the electrolyte solution to be added and the total quantity or flow rate of the sludge substance to be treated.
The step of determining the dose of the electrolyte to be added according to the original conductivity of the sludge substance to be treated and the expected conductivity com¬ prises: determining the concentration of the electrolyte so- lution to be added according to the equation = a2- S2 - S1 ^ wherein represents the concentration of the electrolyte solution to be added; 1 represents the original conductivity of the sludge substance; represents the empirical coeffi- cient for the original conductivity; 2 represents the ex- pected conductivity of the sludge substance; and repre¬ sents the empirical coefficient for the expected conductiv¬ ity; and determining the dose of the electrolyte to be added according to the concentration of the electrolyte solution to be added and the total quantity or flow rate of the sludge substance to be treated.
Alternatively, the step of adding an electrolyte into the sludge substance to be treated comprises the steps of: A. setting an expected conductivity and a dose of an electrolyte to be added each time; B. adding the electrolyte in said dose of the electrolyte to be added each time into said sludge substance to be treated, and stirring them uniformly; and measuring the conductivity of the sludge substance after add¬ ing the electrolyte and comparing the result with said ex¬ pected conductivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity, then step B is executed again.
An apparatus for treating a sludge substance before dehy¬ dration thereof as described in the embodiments of the pre¬ sent invention comprises a pre-treatment module, which is used for adding an electrolyte into the sludge substance to be treated before carrying out an electric dehydration to the sludge substance to be treated.
An apparatus for dehydration of a sludge substance as de¬ scribed in the embodiments of the present invention com¬ prises: a pre-treatment module 100 which is used for adding an electrolyte into the sludge substance to be treated; and an electric dehydration device 200 which is used for carrying out an electric dehydration treatment on the sludge substance added with the electrolyte.
Said pre-treatment module 100 comprises: a conductivity determining unit 101 which is used for determining an ex- pected conductivity; an electrolyte dose determining unit
102, which is used for determining the dose of the electro¬ lyte to be added according to the original conductivity of said sludge substance to be treated and said expected conduc¬ tivity; and an electrolyte adding unit 103, which is used for adding the electrolyte in the dose so determined into the sludge substance to be treated.
In this case, the electrolyte dose determining unit 102 comprises: a setting subunit, which is used for setting the relationship between the changes in the conductivity of said sludge substance and the doses of the electrolyte or electro¬ lyte solution to be added; and an electrolyte dose calculat¬ ing subunit, which is used for determining the dose of the electrolyte to be added according to the total quantity/ flow rate of the sludge substance to be treated, the original con¬ ductivity, the expected conductivity, and the relationship set between the changes in the conductivity of the sludge substance and the doses of the electrolyte to be added.
Alternatively, the above described pre-treatment module
10 comprises: a conductivity determining unit 101 which is used for determining an expected conductivity; an electrolyte dose determining unit 102', which is used for setting the dose of the electrolyte to be added each time; an electrolyte adding unit 103' , which is used for adding the electrolyte in the dose of the electrolyte to be added each time into said sludge substance to be treated; a stirring unit 104, which is used for stirring the sludge substance to be treated after adding the electrolyte uniformly; and a conductivity measur- ing unit 105, which is used for measuring the conductivity of the sludge substance after stirring and comparing the result with said expected conductivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity, then the electrolyte adding unit 103' is instructed to add the electrolyte again in said dose of the electrolyte to be added each time into said sludge substance to be treated.
The method and apparatus for dehydration treatment as de¬ scribed in the embodiments of the present invention increase the conductivity of a sludge substance to be treated by add¬ ing an electrolyte in advance into the sludge substance to be treated, and thus can significantly reduce the electric en¬ ergy consumption in the subsequent electric dehydration treatment, and at the same time increase the efficiency in the sludge treatment, which in turn can reduce the treatment costs during the whole dehydration of the sludge substance.
Brief description of the drawings Fig. 1 is a flow diagram of a method for dehydration treatment of a sludge substance as described in an embodiment of the present invention;
Fig. 2 is a schematic diagram showing the inner structure of an apparatus for dehydration treatment of a sludge sub¬ stance as described in an embodiment of the present inven¬ tion;
Fig. 3 is a schematic diagram of the inner structure of a pre-treatment module;
Fig. 4 is a schematic diagram of the inner structure of another pre-treatment module; and
Fig. 5 shows the relationship between the unit electric energy consumption and the solid content of the treated slud¬ ge by using an existing electric dehydration method and a me- thod for dehydration treatment according to the present invention, respectively.
Exemplary embodiments
As shown in Fig. 1, a method for dehydration of a sludge substance provided in an embodiment of the present invention mainly comprises:
step 1, adding an electrolyte into the sludge substance to be treated; and
step 2, carrying out an electric dehydration treatment on the sludge substance added with the electrolyte.
Given that the electric dehydration mechanism includes two synchronous processes: an electrophoresis process of so¬ lid particles in an aqueous phase, and an electric osmosis process of water molecules between the solid particles, the inventor has found after research that the dehydration efficiency can be improved by increasing the conductivity of a sludge substance. Therefore, by adding an electrolyte in or¬ der to increase the conductivity of a sludge substance, the method provided in the embodiments of the present invention efficiently improve the dehydration efficiency of a subse¬ quent electric dehydration unit while significantly reducing the electric energy consumption in the electric dehydration treatment, and in turn significantly reducing the costs in the electric dehydration treatment of the sludge substance.
In one embodiment of the present invention, the electro¬ lyte as mentioned in step 1 above may be, for example, an io- nic salt substance that is water soluble. For example, it can be sodium salts such as sodium chloride (NaCl), sodium sul¬ fate (Na2SC>4) , etc., or potassium salts such as potassium chloride (KC1), potassium sulfate (K2SO4) , etc., or else mag¬ nesium salts such as magnesium chloride (MgCl2) , etc. Fur- ther, in order to be in conformity with standards relevant to sludge emission and disposal, said electrolytes are prefera¬ bly electrolytes free of heavy metal or toxic and harmful ions, to avoid producing harmful effects to the subsequent treatment and disposal of sludge. Furthermore, other electro- lytes which are advantageous to the environment protection and subsequent treatment and disposal of sludge can also be selected according to practical needs.
In order to add an electrolyte into a sludge substance to be treated, an expected conductivity can be set in advance, then the dose of the electrolyte to be added is determined according to the original conductivity of said sludge sub¬ stance to be treated and said expected conductivity, and fi¬ nally the electrolyte is added in the determined dose into said sludge substance to be treated.
Since different sludge substances have different proper¬ ties, the relationships between the conductivity and the so¬ lid content (water content) after hydration and the electric energy consumption in the electric dehydration for different sludge substances are also different. Hence, in practical ap- plications, firstly, a plurality of tests of adding an elec¬ trolyte can be carried out on samples of a sludge substance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the doses of the electrolyte to be added; secondly, an expected conductiv- ity of the sludge substance is set, and as described above, a maximum conductivity would be generally recommended by a me¬ chanical device for electric dehydration, and the expected conductivity should be lower than the maximum conductivity; then, the dose of the electrolyte to be added is determined according to the total quantity (mass or volume) /flow rate of the sludge substance to be treated, the expected conductiv¬ ity, and the relationship between the changes in the conduc- tivity of the sludge substance and the doses of the electro¬ lyte to be added; and finally, the relationship between the dose of the electrolyte to be added and the dehydration effi¬ ciency of the sludge and the electric energy consumption in the electric dehydration is determined by experiments.
In the present invention, said electrolyte can be a solid electrolyte, or it can also be an electrolyte solution.
When adding an electrolyte into a sludge substance to be treated, after determining the expected conductivity of the sludge substance, it is necessary firstly to carry out a plu- rality of tests of adding a solid electrolyte to samples of said sludge substance to be treated, to obtain the relation¬ ship between the changes in the conductivity of the sludge substance and the doses of the solid electrolyte added; and determine the dose of the solid electrolyte to be added ac- cording to the total quantity (mass or volume) /flow rate of said sludge substance to be treated, the original conductiv¬ ity, the expected conductivity, and the relationship between the changes in the conductivity of the sludge substance and the doses of the solid electrolyte added.
When adding an electrolyte solution into a sludge sub¬ stance to be treated, after determining the expected conduc¬ tivity of the sludge substance, the concentration of the electrolyte solution to be added is first determined accord¬ ing to the original conductivity and the expected conductiv- ity of the sludge substance to be treated; and then the dose of the electrolyte to be added is determined according to the concentration of the electrolyte solution to be added and the total quantity (mass or volume) /flow rate of the sludge sub¬ stance to be treated. In practical applications, a plurality of tests of adding an electrolyte solution can be first car¬ ried out on samples of the sludge substance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the concentrations of the electrolyte solution to be added; then an expected conductiv¬ ity of the sludge substance is determined; then the concen¬ tration of the electrolyte to be added is determined accord¬ ing to the expected conductivity and the relationship between the changes in the conductivity of the sludge substance and the concentrations of the electrolyte solution to be added; and finally, the dose of the electrolyte to be added is de¬ termined according to the concentration of the electrolyte solution to be added and the total quantity or flow rate of the sludge substance to be treated. Or alternatively, after determining an expected conductivity of the sludge substance, the concentration of the electrolyte solution to be added is determined directly according to the following equation (1) . It is proven by experiments that by using this alternative solution, there may be a certain deviation between the resulting conductivity of the sludge substance added with an electrolyte and the expected conductivity, but this deviation is acceptable in practical applications and easy to calcu¬ late. The final conductivity after adding an electrolyte is based on the actually measured value.
In this equation, a represents the empirical coefficient between the concentration of the electrolyte solution to be added and the conductivity of the solution, particularly as a function of the valency of the electrolyte to be added, as shown in table 1; S represents the conductivity in microsie- mens/cm (us/cm) ; and AC represents the concentration of the electrolyte solution to be added, in milligram/liter (mg/L) . Particularly, Si represents the original conductivity of the sludge substance, ± represents an empirical coefficient un¬ der the original conductivity, S∑ represents the expected conductivity of the sludge substance; and a∑ represents an empirical coefficient under the expected conductivity.
Figure imgf000012_0001
1.0 0.29 0.25 0.23 0.42
t.J 0.» 0.27 0.23 0.44
2.0 0.30 0.2» 0.24 0.45
2.0 -5.0 0.30-0.32 0.2* -0.31 0.25 -0.27 0.45-0.8
5.0-10 0.31-0.34 0.31 -0.34 0.0-0.30 Q.4S-0.5I
1*-» 0.34-0.3S 0.34-0. «2 0.30-0.37 05! -OS*
SO- WO 011-0.40 0.42 -0.47 0.37-0.41 0 S* -0.61
100-500 0.40-0.4» 0.47 -0.58 -0.43-0.51 0.61 -0,70
W - 1000 0.45-0.47 O.J«-0.63 0.51 -0.56 0.70-0.74
I 000-1 MO 047-0.49 0.03-0.6? 0.56-0.5» 0.74-0.76
1500 - 2000 0.4 -a 50 0.67-0.70 0.59-0.61 §,«-«,is
3000 - 3000 0.50-0.51 0.70-0.73 0.61 -0.65 0.71-0.11
O.Jt -0.53 0.73-0.7» 0.65-0.70 on -a »
5000-10000 0.53-056 0.79-0. «6 0.70-0. IS 0.14-0. »9
Table 1
After determining the dose of the electrolyte to be added (a solid electrolyte or electrolyte solution) , the electro¬ lyte can be added in the dose so determined into the sludge substance to be treated. Further, the sludge substance added with the electrolyte can be stirred uniformly. The conductivity of the sludge substance after adding the electrolyte can be further measured, to determine whether the conductivity of the sludge substance after adding the electrolyte reaches the expected conductivity. If not, then the electrolyte can be added again into the sludge substance by the method as de¬ scribed above. In addition, the relationship obtained by the experiments between the changes in the conductivity of the sludge substance and the doses of the electrolyte added can be corrected according to the measured conductivity of the sludge substance after adding the electrolyte and the dose of the electrolyte added.
Furthermore, in addition to the above method for adding an electrolyte in one portion into the sludge substance to be treated, a method for adding an electrolyte in portions can be employed, which particularly comprises:
step 11, setting an expected conductivity and a dose of an electrolyte added each time; wherein the dose of an elec¬ trolyte added each time can be set according to the relation¬ ship obtained by the experiments between the changes in the conductivity of the sludge substance and the doses of the electrolyte added, or determined according to an empirical value; the dose of the electrolyte to be added each time can be identical for each time, and also can be gradually in¬ creased or decreased; and in order to reach the expected con- ductivity better and more efficiently, the dose of the elec¬ trolyte to be added each time can be adjusted during the ad¬ dition;
step 12, adding the electrolyte in the set dose of the electrolyte to be added each time into said sludge substance to be treated, and stirring them uniformly;
step 13, measuring the conductivity of the sludge sub¬ stance after adding the electrolyte; and
step 14, comparing the conductivity of the sludge sub¬ stance after adding the electrolyte with said expected con- ductivity, and returning to step 12 if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity.
In this embodiment, step 14 can further comprise stopping the operation, i.e., not returning to step 12, until the con- ductivity of the sludge substance after adding the electro¬ lyte is larger than or equal to the expected conductivity. Alternatively, step 14 can comprise stopping the operation until the difference between the conductivity in the sludge substance after adding the electrolyte and the expected con- ductivity is equal to or smaller than a threshold value.
It is to be stated that in the method described above, the electrolyte added can be a solid electrolyte, or can be an electrolyte solution.
It is to be stated that the operation of adding an elec- trolyte into a sludge substance to be treated as described above will not produce any harmful effect to the subsequent electric dehydration treatment and therefore, the method for dehydration treatment as described in step 2 of the embodi¬ ment of the present invention can use any existing electric dehydration treatment technology.
From another aspect, the key point of the present inven¬ tion is adding a process for treating a sludge substance be¬ fore dehydration thereof as shown in step 1 before dehydrat- ing the sludge substance to be treated, i.e., adding an elec¬ trolyte into the sludge substance to be treated before dehy¬ drating the sludge substance to be treated, and providing a particular adding method. By this pretreatment process of adding an electrolyte in advance into a sludge substance to be treated, the conductivity of the sludge substance to be treated is increased to such an expected value, that the de¬ hydration efficiency of a subsequent electric dehydration unit can be efficiently improved and at the same time sig- nificantly reduce the electric energy consumption during the electric dehydration treatment, which in turn can significantly reduce the costs of the electric dehydration treat¬ ment of the sludge substance. In addition to the electric de¬ hydration treatment, the above treatment process before dehy- dration of a sludge substance can also be applied before other dehydration treatments of a sludge substance, to reduce the costs in the dehydration treatment of the sludge sub¬ stance .
Corresponding to the above methods for dehydration treat- ment of a sludge substance and for treating a sludge sub¬ stance before dehydration thereof, embodiments of the present invention also provide an apparatus for treating a sludge substance before dehydration thereof. An apparatus for treat¬ ing a sludge substance before dehydration thereof provided in the embodiments of the present invention comprises a pre¬ treatment module which is used for adding an electrolyte into the sludge substance to be treated before carrying out an electric dehydration to the sludge substance to be treated.
It is to be stated that the treatment module as mentioned in the embodiments of the present invention can be disposed just before the dehydration apparatus for a sludge substance, and can even be disposed within the transportation pipes of the sludge substance.
Further, said pre-treatment module can also constitute a dehydration apparatus for a sludge substance together with any existing electric dehydration device. The pre-treatment module will not produce any harmful effect on subsequent electric dehydration equipment. At this time, the apparatus for dehydration of a sludge substance has an inner structure as shown in Fig. 2, which mainly comprises: a pre-treatment module 100 which is used for adding an electrolyte into the sludge substance to be treated; and an electric dehydration device 200 which is used for carrying out an electric dehydration treatment on the sludge substance added with the electrolyte .
Said pre-treatment module 100 has an inner structure as shown in Fig. 3, which can particularly comprises:
a conductivity determining unit 101 which is used for de¬ termining an expected conductivity; in particular the determining unit can be set and adjusted by a user, embodied as a human machine interface or embodied as a storage device, for example ;
an electrolyte dose determining unit 102, which is used for determining the dose of the electrolyte to be added ac¬ cording to the original conductivity of said sludge substance to be treated and said expected conductivity; and
an electrolyte adding unit 103, which is used for adding the electrolyte in the dose determined into the sludge sub¬ stance to be treated.
Furthermore, the pre-treatment module can also comprise a stirring unit, which is used for stirring the sludge sub¬ stance added with the electrolyte uniformly.
Furthermore, the pre-treatment module can also comprise a conductivity measuring unit which is used for measuring the conductivity of the sludge substance and comparing the result with the expected conductivity, and if the expected conduc¬ tivity is not reached, then the electrolyte dose determining unit can be informed to determine the dose of the electrolyte to be added. The sludge substance hence can be added again with the electrolyte until reaching the expected conductiv¬ ity.
In this case, the electrolyte dose determining unit 102 can particularly comprise: a setting subunit, which is used for setting the relationship between the changes in the conductivity of said sludge substance and the doses of the elec¬ trolyte or electrolyte solution to be added; and an electro- lyte dose calculating subunit, which is used for determining the dose of the electrolyte to be added according to the to¬ tal quantity/ flow rate of the sludge substance to be treated, the original conductivity, the expected conductivity, and the relationship set between the changes in the conductivity of the sludge substance and the doses of the electrolyte added.
Said pre-treatment module 100 may otherwise have an inner structure as shown in Fig. 4, which particularly comprises: a conductivity determining unit 101 which is used for de- termining an expected conductivity; reference can be made to the embodiment as shown in Fig. 3 for the particular implementation thereof;
an electrolyte dose determining unit 102', which is used for setting the dose of the electrolyte added each time; the dose of the electrolyte to be added each time can be set and adjusted by the user himself or can be adjusted by the device itself, and the dose of the electrolyte to be added each time can be identical for each time, or can be gradually increased or decreased;
an electrolyte adding unit 103' , which is used for adding the electrolyte in the dose of the electrolyte to be added each time into said sludge substance to be treated;
a stirring unit 104, which is used for stirring the sludge substance to be treated after adding the electrolyte uni- formly; and
a conductivity measuring unit 105 which is used for meas¬ uring the conductivity of the sludge substance after stirring and comparing the result with said expected conductivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity, then the electrolyte adding unit 103' is instructed to add the electrolyte again in said dose of the electrolyte to be added each time into said sludge substance to be treated.
In this embodiment, when the difference between the con- ductivity of the sludge substance after adding the electro¬ lyte and the expected conductivity is smaller than or equal to a threshold value, the conductivity measuring unit 105 can, for example, stop the addition, that is to say, it will not instruct the electrolyte adding unit 103' to add the electrolyte again.
Likewise, the apparatus for dehydration of a sludge sub¬ stance as described above increases the conductivity of the sludge substance to be treated to an expected value by using the pre-treatment module 100 to add an electrolyte into the sludge substance to be treated, so that the dehydration effi¬ ciency of a subsequent electric dehydration unit can be effi¬ ciently improved and at the same time significantly reduce the electric energy consumption during the electric dehydra¬ tion treatment, which in turn can significantly reduce the costs of the electric dehydration treatment of the sludge substance .
It is to be emphasized that the sludge substance in the embodiments of the present invention may be sludge, for exam¬ ple, municipal sludge and industrial sludge, and may also be substances similar to sludge, such as organic mud slurry, etc .
The beneficial effects which can be brought by the me- thod and apparatus for dehydration treatment of a sludge sub¬ stance as described in the embodiments of the present inven¬ tion are described below in detail by particular experimental results. During the present experiment, the unit electric en¬ ergy consumption (the unit is kilowatt hour/ton of dry sludge (kwh/tonDS)) and the solid content of the sludge after the dehydration treatment were first measured by changing the conductivity of the sludge substance at a given electric de¬ hydration voltage. The unit electric energy consumption and the solid content of the sludge after the dehydration treat- ment were also measured at different electric dehydration voltages after increasing the conductivity of the sludge sub¬ stance to a fixed value. For comparison, the unit electric energy consumption and the solid content of the sludge after the dehydration treatment for original sludge without addi- tion of an electrolyte at different electric dehydration voltages were measured. In this experiment, an existing elec¬ tric dehydration technology was employed for the dehydration treatment. The experimental results are shown in Fig. 5. In figure 5, the round dots represent the unit electric energy consumption vs. solid content in the sludge after the dehy¬ dration treatment for the original without addition of an electrolyte at different electric dehydration voltages (the conductivity of the original sludge was about 1200-1500 με/αη) ; the square dots represent the unit electric energy consumption vs. solid content in the sludge after the dehy¬ dration treatment at different electric dehydration voltages (20 V, 40 V, 60 V and 80 V) when the conductivity of the sludge substance is increased to 4575 με/αη; and the rhombic dots represent the unit electric energy consumption vs. solid content in the sludge after the dehydration treatment at an electric dehydration voltage of 60 V when the conductivity of the sludge substance is 1585 με/αη (the original sludge) , 2920 με/αη, and 4885 με/αη, respectively. It can be seen by comparing the locations of the round and square dots at the same solid content in the sludge after the electric dehydra¬ tion treatment that all the square dots are on the left of the round dots, indicating that when increasing the conduc- tivity of the sludge substance from 1200-1500 με/αη to 4575 με/αη, the unit electric energy consumption required for ob¬ taining the same solid content in the sludge will be greatly reduced, which proves that by increasing the conductivity of the sludge substance, one can reduce the electric energy con- sumption during the electric dehydration while improving the dehydration efficiency of the electric dehydration, and in turn reducing the treatment costs during the whole dehydra¬ tion process. Furthermore, it can be seen by comparing the locations of the round and rhombic dots at the same solid content in the sludge that all the rhombic dots are on the left of the round dots (expect the rhombic dots corresponding to the original sludge) , and the rhombic dots are further from the round dots when the conductivity is higher, indicat¬ ing likewise that when increasing the conductivity of the sludge substance from 1200-1500 με/αη to 2920 με/αη and 4885 με/αη, respectively, the unit electric energy consumption re¬ quired for obtaining the same solid content in the sludge is also greatly reduced, and the unit electric energy consump- tion required for obtaining the same solid content in the sludge is less when the conductivity of the sludge substance is higher, which also proves that by increasing the conduc¬ tivity of the sludge substance, it can reduce the electric energy consumption during the electric dehydration while improving the dehydration efficiency of the electric dehydra¬ tion, and in turn reducing the treatment costs during the whole dehydration process.

Claims

Claims
1. A method for treating a sludge substance before dehy¬ dration thereof, characterized in that it comprises adding an electrolyte into a sludge substance to be treated before car¬ rying out an electric dehydration thereon.
2. A method for dehydration treatment of a sludge sub¬ stance, characterized in that it comprises:
adding an electrolyte into a sludge substance to be trea¬ ted ( 1 ) ; and
carrying out an electric dehydration treatment on the sludge substance added with the electrolyte (2) .
3. The method as claimed in claim 1 or 2, characterized in that said electrolyte is an ionic salt substance that is water soluble.
4. The method as claimed in claim 3, characterized in that said salt substance is a sodium salt, a potassium salt or a magnesium salt.
5. The method as claimed in claim 1 or 2, characterized in that said adding the electrolyte into the sludge substance to be treated (1) comprises:
setting an expected conductivity;
determining the dose of the electrolyte to be added ac¬ cording to the original conductivity of said sludge substance to be treated and said expected conductivity; and
adding the electrolyte in the dose determined into said sludge substance to be treated.
6. The method as claimed in claim 5, characterized in that said determining the dose of the electrolyte to be added according to the original conductivity of said sludge sub¬ stance to be treated and said expected conductivity com¬ prises : carrying out a plurality of tests of adding a solid elec¬ trolyte into samples of said sludge substance to be treated, so as to obtain the relationship between the changes in the conductivity of the sludge substance and the doses of the solid electrolyte added; and
determining the dose of the solid electrolyte to be added according to the total quantity of said sludge substance to be treated, the original conductivity, the expected conduc¬ tivity, and the relationship between the changes in the con- ductivity of the sludge substance and the doses of the solid electrolyte added; or determining the dose of the solid elec¬ trolyte to be added according to the flow rate of said sludge substance to be treated, the original conductivity, the ex¬ pected conductivity, and the relationship between the changes in the conductivity of the sludge substance and the doses of the solid electrolyte added.
7. The method as claimed in claim 5, characterized in that determining the dose of the electrolyte to be added ac- cording to the original conductivity of said sludge substance to be treated and said expected conductivity comprises:
carrying out a plurality of tests of adding an electro¬ lyte solution into samples of said sludge substance to be treated, to obtain the relationship between the changes in the conductivity of the sludge substance and the concentra¬ tions of the electrolyte solution to be added;
determining the concentration of the electrolyte solution to be added according to the total quantity of said sludge substance to be treated, the original conductivity, the ex- pected conductivity, and the relationship between the changes in the conductivity of the sludge substance and the concen¬ trations of the electrolyte solution to be added; or deter¬ mining the concentration of the electrolyte solution to be added according to the flow rate of said sludge substance to be treated, the original conductivity, the expected conduc¬ tivity, and the relationship between the changes in the con¬ ductivity of the sludge substance and the concentrations of the electrolyte solution to be added; and determining the dose of the electrolyte to be added ac¬ cording to the concentration of the electrolyte solution to be added and the total quantity or flow rate of said sludge substance to be treated.
8. The method as claimed in claim 5, characterized in that said determining the dose of the electrolyte to be added according to the original conductivity of said sludge sub¬ stance to be treated and said expected conductivity com- prises:
determining the concentration of the electrolyte solution to be added according to the equation ~ i ' 2 a\ ' i r wherein AC represents the concentration of the electrolyte solution to be added; 1 represents the original conductivity of the sludge substance; represents the empirical coefficient for the original conductivity; 2 represents the expected conduc¬ tivity of the sludge substance; and represents the em¬ pirical coefficient for the expected conductivity, and
determining the dose of the electrolyte to be added ac- cording to the concentration of the electrolyte solution to be added and the total quantity or flow rate of said sludge substance to be treated.
9. The method as claimed in claim 1 or 2, characterized in that said adding an electrolyte into the sludge substance to be treated (1) comprises:
A. setting an expected conductivity and the dose of an electrolyte to be added each time;
B. adding the electrolyte in said dose of the electro- lyte to be added each time into said sludge substance to be treated, and mixing them uniformly; and
C. measuring the conductivity of the sludge substance after adding the electrolyte and comparing the result with said expected conductivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conductivity, then step B is executed again un¬ til the conductivity of the sludge substance after adding the electrolyte is larger than or equal to said expected conduc¬ tivity.
10. An apparatus for treating a sludge substance before dehydration thereof, comprising a pre-treatment module (100), which is used for adding an electrolyte into the sludge sub¬ stance to be treated before carrying out an electric dehydra¬ tion thereon.
11. An apparatus for dehydration of a sludge substance, comprising :
a pre-treatment module (100), which is used for adding an electrolyte into the sludge substance to be treated; and
an electric dehydration device (200), which is used for carrying out an electric dehydration treatment on the sludge substance added with the electrolyte.
12. The apparatus as claimed in claim 10 or 11, charac¬ terized in that said pre-treatment module (100) comprises: a conductivity determining unit (101) which is used for determining an expected conductivity;
an electrolyte dose determining unit (102), which is used for determining the dose of the electrolyte to be added ac¬ cording to the original conductivity of said sludge substance to be treated and said expected conductivity; and
an electrolyte adding unit (103), which is used for add¬ ing the electrolyte in the dose determined into the sludge substance to be treated.
13. The apparatus as claimed in claim 12, characterized in that said electrolyte dose determining unit (102) com¬ prises :
a setting subunit, which is used for setting the rela¬ tionship between the changes in the conductivity of said sludge substance and the doses of the electrolyte or electro¬ lyte solution to be added; and
an electrolyte dose calculating subunit, which is used for determining the dose of the electrolyte to be added ac- cording to the total quantity of said sludge substance to be treated, the original conductivity, the expected conductiv¬ ity, and the relationship set between the changes in the con¬ ductivity of the sludge substance and the doses of the elec- trolyte added; or determining the dose of the electrolyte to be added according to the flow rate of said sludge substance to be treated, the original conductivity, the expected con¬ ductivity, and the relationship set between the changes in the conductivity of the sludge substance and the doses of the electrolyte added.
14. The apparatus as claimed in claim 10 or 11, charac¬ terized in that said pre-treatment module (100) comprises: a conductivity determining unit (101) which is used for determining an expected conductivity;
an electrolyte dose determining unit (102'), which is used for setting the dose of the electrolyte added each time; an electrolyte adding unit (103'), which is used for add¬ ing the electrolyte in said set dose of the electrolyte to be added each time into said sludge substance to be treated; a stirring unit (104), which is used for uniformly stirring the sludge substance to be treated after adding the electrolyte therein; and
a conductivity measuring unit (105), which is used for measuring the conductivity of the sludge substance after stirring and comparing the result with said expected conduc¬ tivity, and if the conductivity of the sludge substance after adding the electrolyte is smaller than said expected conduc¬ tivity, then said electrolyte adding unit (103') is in- structed to add the electrolyte again in said dose of the electrolyte to be added each time into said sludge substance to be treated.
PCT/EP2011/072265 2011-01-11 2011-12-09 Method and apparatus for dehydration treatment, and treatment before dehydration of a sludge substance WO2012095226A1 (en)

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CN109336352A (en) * 2018-11-05 2019-02-15 李舒馨 A kind of method for sludge treatment
CN111253031A (en) * 2020-03-19 2020-06-09 西安理工大学 Method for strengthening sludge stabilization through electrochemical chlorination

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Publication number Priority date Publication date Assignee Title
CN109336352A (en) * 2018-11-05 2019-02-15 李舒馨 A kind of method for sludge treatment
CN111253031A (en) * 2020-03-19 2020-06-09 西安理工大学 Method for strengthening sludge stabilization through electrochemical chlorination

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