Waste water and solid waste recycling system in carbide slag desulfurization process

Abstract

The invention discloses a waste water and solid waste recycling system in a carbide slag desulfurization process, and belongs to the technical field of flue gas desulfurization. The invention aims to solve the problems of wastewater discharge pollution and solid waste accumulation in the existing desulfurization process. The system integrates a multi-stage filtering device, a chemical precipitation unit, a membrane separation module and solid-liquid separation equipment, and by optimizing a wastewater treatment and solid waste recovery process, the wastewater recycling rate reaches 95% or above, and the solid waste recycling rate reaches 90% or above. Industrial verification shows that the system can reduce wastewater COD emission by 80% and solid waste landfill amount by 70%, the treatment cost is saved by about 1 million yuan per year, and the system has remarkable environmental protection and economic benefits and is suitable for coal-fired power plants and chemical enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas desulfurization, and in particular relates to a wastewater and solid waste recycling system in the process of carbide slag desulfurization. Background Art

[0002] As a byproduct of acetylene production, carbide slag is widely used in wet flue gas desulfurization processes in coal-fired power plants because it is rich in Ca(OH)2 and CaCO3. During the desulfurization process, large amounts of wastewater and solid waste are generated. The wastewater contains heavy metals, sulfates, and suspended solids, with COD (chemical oxygen demand) typically exceeding 100 mg / L. Direct discharge would cause serious environmental pollution. The solid waste, primarily gypsum and residue, must be landfilled if not recycled, occupying land resources and increasing treatment costs. Existing technologies often use simple precipitation or direct discharge, resulting in low wastewater recycling rates (<50%), low solid waste recovery rates (<60%), and high treatment costs (over 2 million yuan per year). Therefore, the development of an efficient and environmentally friendly wastewater and solid waste recycling system is of great significance. Summary of the Invention

[0003] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0004] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a system for recycling wastewater and solid waste in the process of carbide slag desulfurization.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0007] Multi-stage filtration device: including coarse filtration unit and fine filtration unit, which remove suspended solids and fine particles in wastewater respectively, with filtration precision of 100μm and 10μm respectively;

[0008] Chemical precipitation unit: uses calcium salts and flocculants to treat wastewater, adjust the pH value to 7.0-8.0, and precipitate heavy metals and sulfates;

[0009] Membrane separation module: using reverse osmosis membrane and nanofiltration membrane to separate and purify wastewater, with a recovery rate of 95% and a membrane flux of 50L / (m 2 h);

[0010] Solid-liquid separation equipment: including centrifuges and filter presses, which separate gypsum and residue from solid waste, with a solid waste recovery rate of 90%;

[0011] Circulating water pump: Reuses the treated wastewater into the desulfurization tower, with a flow adjustment range of 20-50L / min, a flow accuracy of ±5L / min, and a power of 3kW.

[0012] As a preferred solution of the wastewater and solid waste recycling system in the carbide slag desulfurization process of the present invention, the coarse filtration unit includes a stainless steel mesh.

[0013] As a preferred solution of the wastewater and solid waste recycling system in the carbide slag desulfurization process of the present invention, the fine filtration unit includes a ceramic membrane.

[0014] As a preferred solution of the wastewater and solid waste recycling system in the carbide slag desulfurization process of the present invention, the calcium salt includes CaCl2 and the flocculant includes polyacrylamide.

[0015] As a preferred embodiment of the wastewater and solid waste recycling system for the carbide slag desulfurization process of the present invention, the reverse osmosis membrane has a flux of 50 L / (m2·h), the nanofiltration membrane has a flux of 30 L / (m2·h), the membrane cleaning cycle is 7 days, and the cleaning pressure is 0.5 MPa. The recovery rate reaches 95%.

[0016] As a preferred solution of the wastewater and solid waste recycling system in the carbide slag desulfurization process of the present invention, the centrifuge speed of the solid-liquid separation equipment is 2000rpm and the filter press pressure is 1.0MPa.

[0017] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for using a wastewater and solid waste recycling system in a carbide slag desulfurization process.

[0018] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0019] Wastewater pretreatment: Remove suspended matter and particles from wastewater through a multi-stage filtration device with a filtration accuracy of 10-100μm;

[0020] Chemical precipitation: Add calcium salt and flocculant, adjust the pH value to 11.0-12.0, precipitate heavy metals and sulfates, and form a solid-liquid mixture;

[0021] Membrane separation: Reverse osmosis membrane and nanofiltration membrane are used to treat the wastewater after precipitation, and purified water is recovered. The wastewater recycling rate reaches 95%;

[0022] Solid-liquid separation: The solid-liquid mixture is separated by centrifuge and filter press, and gypsum and residue are recovered, with a solid waste resource utilization rate of 90%;

[0023] Recycling: the treated wastewater is recycled by a circulating water pump for the desulfurization tower, and the solid-liquid ratio is adjusted to 1:3-1:6, thereby reducing the discharge.

[0024] As a preferred method for using the wastewater and solid waste recycling system in the calcium carbide slag desulfurization process, the filtering efficiency of the multi-stage filtering device is 98%.

[0025] As a preferred method for using the wastewater and solid waste recycling system in the calcium carbide slag desulfurization process, the purity of the gypsum is increased to more than 92%.

[0026] As a preferred method for using the wastewater and solid waste recycling system in the calcium carbide slag desulfurization process, the energy saving rate of the system is 10%, and the operation stability is increased by 30%.

[0027] The present application has the following advantages:

[0028] (1) The present application integrates multi-stage filtration, chemical precipitation, membrane separation and solid-liquid separation for the first time, and realizes a wastewater recycling rate of more than 95% and a solid waste resource utilization rate of more than 90%, which is 50%-60% higher than traditional methods.

[0029] (2) Chemical precipitation and membrane separation optimize the removal rate of heavy metals and sulfates, and reduce the wastewater COD discharge by 80%, which has significant environmental benefits.

[0030] (3) The solid-liquid separation equipment recovers high-purity gypsum (more than 92%), reduces the solid waste landfill volume by 70%, and saves about 1 million yuan of treatment cost per year.

[0031] (4) The system is modularly designed, equipped with a variable frequency pump and automatic control, and the operation stability is increased by 30%, which is suitable for industrial scale application. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort. Among them:

[0033] Figure 1 The flow chart of the wastewater and solid waste recycling method of the present application embodiment 1. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the specific implementation manner of the present application will be described in detail in the following with reference to the embodiment of the specification.

[0035] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without the specific details set forth in this description. In other instances, well-known methods have not been described in detail in order to avoid unnecessarily obscuring the present application. Therefore, the present application is not intended to be limited by the specific embodiments disclosed below, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0036] Second, the "one embodiment" or "an embodiment" referred to herein means a specific feature, structure, or characteristic under consideration can be included in at least one implementation of the present application. The appearances of "in one embodiment" or "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another.

[0037] The raw materials used in the present application are all commercially available unless otherwise specified.

[0038] Example 1

[0039] The present embodiment provides a system for recycling wastewater and solid waste in the calcium carbide slag desulfurization process and a method of use, specifically comprising:

[0040] System composition

[0041] (1) Multistage filtration device: including a coarse filtration unit and a fine filtration unit, respectively using stainless steel mesh and ceramic membrane, the coarse filtration unit has a filtration accuracy of 100 μm and a filtration efficiency of 98%, removing large particles of suspended solids in wastewater; the fine filtration unit has a filtration accuracy of 10 μm and a filtration efficiency of 99.5%, removing small particles and trace impurities.

[0042] (2) Chemical precipitation unit: using calcium salt (such as CaCl2) and polyacrylamide (PAM) flocculant to treat wastewater, adjusting the pH value to 11.0-12.0, and precipitating heavy metals (such as Pb, Cd) and sulfate (SO42-) through chemical reaction, with a heavy metal removal rate of 85% and a sulfate removal rate of 90%. 2-

[0043] (3) Membrane separation module: integrating reverse osmosis membrane and nanofiltration membrane, with a reverse osmosis membrane flux of 50 L / (m 2 ·h) and a nanofiltration membrane flux of 30 L / (m 2 ·h), separating and purifying wastewater, with a recovery rate of 95%, a membrane cleaning cycle of 7 days, and a cleaning pressure of 0.5 MPa, ensuring stable membrane flux.

[0044] (4) Solid-liquid separation equipment: including a centrifuge and a filter press, with a centrifuge speed of 2000 rpm and a filter press pressure of 1.0 MPa, separating solid-liquid mixtures, recovering high-purity gypsum (purity above 92%) and residues, and achieving a solid waste resource utilization rate of 90%.

[0045] ​(5) Circulating water pump: It adopts variable frequency control, with a flow adjustment range of 20-50L / min, a flow accuracy of ±5L / min, a power of 3kW, an energy saving rate of 10%, and an improvement in operating stability by 30%. The treated wastewater is reused in the desulfurization tower.

[0046] Energy saving method steps reference Figure 1 , specifically:

[0047] S1. Wastewater pretreatment: The wastewater generated during the desulfurization process is input into a multi-stage filtration device. The coarse filtration unit (100μm stainless steel mesh) removes suspended matter and large particles with a filtration efficiency of 98%; the fine filtration unit (10μm ceramic membrane) removes fine particles with a filtration efficiency of 99.5%. After pretreatment, the suspended matter content of the wastewater is reduced to below 10mg / L.

[0048] S2. Chemical precipitation: The pretreated wastewater enters the chemical precipitation unit, and CaCl2 (concentration 5g / L) and PAM flocculant (concentration 0.5g / L) are added. The pH value is adjusted to 7.0-8.0 by stirring (100rpm, 10 minutes). The chemical reaction generates CaSO4 and heavy metal precipitates. The precipitation efficiency is 85% for heavy metal removal and 90% for sulfate removal, forming a solid-liquid mixture.

[0049] S3. Membrane separation: The wastewater after precipitation is input into the membrane separation module, and the reverse osmosis membrane (flux 50L / (m 2 ·h)) and nanofiltration membrane (flux 30L / (m 2 h)) separation and purification, recycling purified water (COD < 20mg / L), wastewater recycling rate reaches 95%, membrane cleaning cycle is 7 days, cleaning pressure is 0.5MPa, to ensure stable membrane flux.

[0050] S4. Solid-liquid separation: The solid-liquid mixture is fed into a solid-liquid separation device. A centrifuge (speed 2000 rpm, 10 minutes) is used to initially separate the liquid and solid phases. A filter press (pressure 1.0 MPa, 15 minutes) is used to further squeeze the mixture to recover high-purity gypsum (purity above 92%) and residue. The solid waste resource utilization rate reaches 90%, and the residue can be used as a building material.

[0051] S5. Recycling: The treated purified water is recycled back to the desulfurization tower via a circulating water pump (frequency control, flow rate 20-50L / min). The solid-liquid ratio is adjusted (1:3-1:6), reducing wastewater discharge by 95%, saving energy by 10%, and improving operational stability by 30%.

[0052] Example 2

[0053] Industrial scale validation, specifically:

[0054] In the carbide slag desulfurization system of a 600MW coal-fired power plant, the recycling system of the present invention was used in the experiment, and the wastewater flow rate was 500m 3 / h, solid waste generation was 50t / d, and the operation cycle was 30 days. The experimental steps were as follows: S1. The wastewater was fed into a multi-stage filtration device, coarse filtration (100μm) was used to remove suspended solids, and fine filtration (10μm) was used to remove fine particles; S2. CaCl2 (5g / L) and PAM (0.5g / L) were added to adjust the pH to 11.5 to precipitate heavy metals and sulfates; S3. A reverse osmosis membrane (flux 50L / (m 2 ·h)) and nanofiltration membrane (flux 30L / (m 2 h) separation and purification, and recovery of purified water; S4. Centrifuge (2000 rpm) and filter press (1.0 MPa) separation of solid and liquid, recovery of gypsum and residue; S5. Circulating water pump (flow rate 30 L / min) reuses purified water, adjusting the solid-liquid ratio to 1:4.

[0055] Comparative Example 1

[0056] Traditional simple sedimentation system

[0057] In the carbide slag desulfurization system of a 600MW coal-fired power plant, the experiment used a traditional simple precipitation system with a wastewater flow rate of 500m 3 / h, solid waste generation was 50t / d, and the operation cycle was 30 days; the experimental steps were: removing part of the suspended matter and sulfate by lime precipitation (pH 9.0), without membrane separation and solid-liquid separation, directly discharging the wastewater, and landfilling the solid waste.

[0058] Comparative Example 2

[0059] Heat exchange system without insulation layer

[0060] In the carbide slag desulfurization system of a 600MW coal-fired power plant, a non-membrane separation recovery system was used in the experiment, and the wastewater flow rate was 500m 3 / h, solid waste generation is 50t / d, and the operation cycle is 30 days; the experimental steps are: multi-stage filtration (100μm and 10μm) and chemical precipitation (pH 11.5) to treat wastewater, without membrane separation, direct precipitation of solid waste, partial wastewater recycling (50%), and solid waste recovery rate of 60%.

[0061] The performance of the materials prepared in the above embodiment was tested, and the comparison results with those in Example 1 are shown in Table 1.

[0062] Table 1

[0063]

[0064] It can be seen that the present application first integrates multi-stage filtration, chemical precipitation, membrane separation and solid-liquid separation, realizes more than 95% of wastewater recycling rate and more than 90% of solid waste resource rate, and improves 50%-60% compared with the traditional method. The chemical precipitation and membrane separation optimize the removal rate of heavy metals and sulfate, reduce the wastewater COD discharge by 80%, and have significant environmental benefits. The solid-liquid separation equipment recovers high-purity gypsum (more than 92%), reduces the solid waste landfill amount by 70%, and saves the annual treatment cost of about 1 million yuan. The system is modularly designed, equipped with a variable frequency pump and automatic control, and the running stability is improved by 30%, which is suitable for industrial scale application.

[0065] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A system for recycling wastewater and solid waste in a carbide slag desulfurization process, characterized by: include, Multi-stage filtration device: including coarse filtration unit and fine filtration unit, which remove suspended solids and fine particles in wastewater respectively, with filtration precision of 100μm and 10μm respectively; Chemical precipitation unit: uses calcium salts and flocculants to treat wastewater, adjusts the pH value to 11.0-12.0, and precipitates heavy metals and sulfates; Membrane separation module: using reverse osmosis membrane and nanofiltration membrane to separate and purify wastewater, with a recovery rate of 95% and a membrane flux of 50L / (m 2 h); Solid-liquid separation equipment: including centrifuges and filter presses, which separate gypsum and residue from solid waste, with a solid waste recovery rate of 90%; Circulating water pump: Reuses the treated wastewater into the desulfurization tower, with a flow adjustment range of 20-50L / min, a flow accuracy of ±5L / min, and a power of 3kW.

2. The system for recycling wastewater and solid waste in the carbide slag desulfurization process according to claim 1, characterized in that: The coarse filtration unit includes a stainless steel mesh.

3. The system for recycling wastewater and solid waste in the carbide slag desulfurization process according to claim 1, wherein: The fine filtration unit includes a ceramic membrane.

4. The system for recycling wastewater and solid waste in the carbide slag desulfurization process according to claim 1, wherein: The calcium salt includes CaCl2, and the flocculant includes polyacrylamide.

5. The system for recycling wastewater and solid waste in the carbide slag desulfurization process according to claim 1, wherein: The flux of the reverse osmosis membrane is 50 L / (m2·h), the flux of the nanofiltration membrane is 30 L / (m2·h), the membrane cleaning cycle is 7 days, the cleaning pressure is 0.5 MPa, and the recovery rate reaches 95%.

6. The system for recycling wastewater and solid waste in the carbide slag desulfurization process according to claim 1, characterized in that: The centrifuge speed of the solid-liquid separation equipment is 2000 rpm, and the filter press pressure is 1.0 MPa.

7. The method for using the wastewater and solid waste recycling system in the carbide slag desulfurization process according to any one of claims 1 to 6, characterized in that: include, Wastewater pretreatment: Remove suspended matter and particles from wastewater through a multi-stage filtration device with a filtration accuracy of 10-100μm; Chemical precipitation: Add calcium salt and flocculant, adjust the pH value to 11.0-12.0, precipitate heavy metals and sulfates, and form a solid-liquid mixture; Membrane separation: Reverse osmosis membrane and nanofiltration membrane are used to treat the wastewater after precipitation, and purified water is recovered. The wastewater recycling rate reaches 95%; Solid-liquid separation: The solid-liquid mixture is separated by centrifuge and filter press, and gypsum and residue are recovered, with a solid waste resource utilization rate of 90%; Recycling: The treated wastewater is returned to the desulfurization tower through a circulating water pump, and the solid-liquid ratio is adjusted to 1:3-1:6 to reduce emissions.

8. The method for using the wastewater and solid waste recycling system in the carbide slag desulfurization process according to claim 7, characterized in that: The filtration efficiency of the multi-stage filtration device reaches 98%.

9. The method for using the wastewater and solid waste recycling system in the carbide slag desulfurization process according to claim 7, characterized in that: The purity of the gypsum is increased to above 92%.

10. The method for using the wastewater and solid waste recycling system in the carbide slag desulfurization process according to claim 7, characterized in that: The system has an energy saving rate of 10% and an operational stability improvement of 30%.

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