Process for treating cellulose acetate mother liquor wastewater

Abstract

The application discloses a cellulose acetate mother liquor wastewater treatment process. The cellulose acetate mother liquor wastewater treatment process specifically comprises the following steps: S1, filtration: filtering waste liquid at the bottom of a reactor kettle with a PH value of 2-3 by using a silicon carbide ceramic microfiltration membrane to obtain clarified liquid; S2, nanofiltration: performing nanofiltration on the clarified liquid obtained in the step S1 by using an acid-resistant nanofiltration membrane to obtain reverse osmosis concentrated water and product water respectively; S3, evaporation recovery: performing evaporation crystallization on the reverse osmosis concentrated water obtained in the step S2 by using an evaporator to obtain magnesium sulfate solid; and S4, biochemical treatment: performing biochemical treatment on the product water obtained in the step S2. In the cellulose acetate mother liquor wastewater treatment process, the waste liquid at the bottom of the reactor kettle is directly filtered in a strong acid condition, so that cellulose acetate is prevented from seeping out, the use of alkaline reagents such as ammonia water is reduced, the cost is lowered, and pollution caused by the use of alkaline reagents is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental protection, in particular to a cellulose acetate mother liquor wastewater treatment process. BACKGROUND

[0002] In the tobacco industry, cellulose acetate filter is a widely accepted mechanical filter for both low tar and high tar cigarettes. Cellulose acetate is non-toxic, odorless, oil-resistant, impact-resistant, non-static, and has small suction resistance, good elasticity and adsorption, and can selectively adsorb harmful components in smoke while retaining a certain amount of nicotine without losing the taste of tobacco. In the production process of cellulose acetate, a large amount of acetic acid, sulfuric acid and magnesium sulfate is used in the reaction kettle, resulting in strong acidity of the reaction kettle bottom waste liquid, high COD and high salt content. The COD or salt content alone cannot meet the discharge requirements, and the high salt content affects the biochemical treatment. SUMMARY

[0003] The purpose of the present application is to provide a cellulose acetate mother liquor wastewater treatment process to solve the above technical problems.

[0004] To achieve the above purpose, the present application provides the following technical scheme:

[0005] The cellulose acetate mother liquor wastewater treatment process disclosed in the present application is characterized by the following specific steps:

[0006] S1, filtering: filtering the reaction kettle bottom waste liquid with a pH of 2-3 using a silicon carbide ceramic microfiltration membrane to obtain a clear liquid;

[0007] S2, nanofiltration: nanofiltrating the clear liquid obtained in step S1 using an acid-resistant nanofiltration membrane to obtain reverse osmosis concentrated water and product water, wherein the concentration of magnesium sulfate in the reverse osmosis concentrated water is greater than 10%;

[0008] S3, evaporation recovery: evaporating and crystallizing the reverse osmosis concentrated water obtained in step S2 using an evaporator to obtain magnesium sulfate solids;

[0009] S4, biochemical treatment: biochemically treating and discharging the product water obtained in step S2;

[0010] The order of steps S3 and S4 can be interchanged or performed simultaneously.

[0011] Further, in the above cellulose acetate mother liquor wastewater treatment process, the pore size of the silicon carbide ceramic microfiltration membrane is 0.04-0.5 μm, the pressure of the filtration is 0-0.12 MPa, and the membrane pressure difference of the silicon carbide ceramic microfiltration membrane is less than 0.2 MPa.

[0012] Further, in the cellulose acetate mother liquor wastewater treatment process, the step S1 further comprises:

[0013] Step S11, backwashing: backwashing the silicon carbide ceramic microfiltration membrane with water to obtain backwashing waste liquid;

[0014] Step S12, pressure filtration: pressure filtration of the backwashing waste liquid to obtain permeate and waste residue.

[0015] Further, in the cellulose acetate mother liquor wastewater treatment process, the frequency of the backwashing in the step S11 is 10-100 min / time, and the time of each backwashing is 5-60.

[0016] Further, in the cellulose acetate mother liquor wastewater treatment process, the permeate obtained in the step S12 is refluxed to the reactor bottom waste liquid.

[0017] Further, in the cellulose acetate mother liquor wastewater treatment process, the evaporator is connected with a condensing device and a condensate water recovery device.

[0018] Further, in the cellulose acetate mother liquor wastewater treatment process, the biochemical treatment of the step S4 is one or more of anaerobic treatment, hydrolysis acidification treatment, anoxic treatment and aerobic treatment.

[0019] Compared with the prior art, the cellulose acetate mother liquor wastewater treatment process has the advantages that the reactor bottom waste liquid is directly filtered in a strong acid condition to avoid cellulose acetate exudation, reduce the use of alkaline reagents such as ammonia water, reduce costs, and avoid pollution caused by the use of alkaline reagents. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0021] Figure 1 The cellulose acetate mother liquor wastewater treatment process route chart in the specific embodiment of the present application is shown. DETAILED DESCRIPTION

[0022] The present application is further illustrated by the following examples: According to the following examples, the present application can be better understood. However, those skilled in the art will readily understand that the specific material ratio, process conditions and results described in the examples are only used to illustrate the present application, and should not and will not limit the present application described in detail in the claims.

[0023] Embodiment

[0024] In combination Figure 1 As shown in the figure, the acetate fiber production reactor bottom waste liquid with COD greater than 2000 ppm, salt content greater than 10000 ppm, and pH value of 2 is collected in the wastewater pool for harmless recovery treatment, including the following steps:

[0025] S1, filtration: using silicon carbide ceramic microfiltration membrane to directly filter the reactor bottom waste liquid without adjusting the pH value, avoiding acetate fiber seepage which causes the inability to use silicon carbide ceramic microfiltration membrane for filtration. After filtration, clear liquid is obtained. Every 10-100 min, the silicon carbide ceramic microfiltration membrane is back-flushed with water for 5-60 s, and back-flushed waste liquid is obtained. The back-flushed waste liquid is pressure-filtered to obtain permeate and waste residue. The permeate enters the silicon carbide ceramic microfiltration membrane again with the reactor bottom waste liquid, and the waste residue is treated as solid waste. The pore size of the silicon carbide ceramic microfiltration membrane is 0.04-0.5 μm, the inlet water pressure of the reactor bottom waste liquid is controlled below 0.12 MPa, and the membrane pressure difference of the silicon carbide ceramic microfiltration membrane is controlled below 0.2 MPa.

[0026] S2, nanofiltration: using acid-resistant nanofiltration membrane to nanofiltrate the clear liquid obtained in step S1 to obtain reverse osmosis concentrated water and product water, respectively. The concentration of magnesium sulfate in the reverse osmosis concentrated water is greater than 10%.

[0027] S3, evaporation recovery: using an evaporator to evaporate and crystallize the reverse osmosis concentrated water obtained in step S2 to obtain magnesium sulfate solids. The evaporator is connected with a condensing device and a condensate recovery device, and the condensate is collected and reused.

[0028] S4, biochemical treatment: using one or more of anaerobic treatment, hydrolysis acidification treatment, anoxic treatment, and aerobic treatment to treat the product water obtained in step S2.

[0029] The order of steps S3 and S4 can be interchanged or performed simultaneously.

[0030] Take 4 portions of the wastewater sample after biochemical treatment, and test the chemical oxygen demand, ammonia nitrogen content, total phosphorus content, and dissolved solids according to the dichromate method (H828-2017), Nash reagent spectrophotometry (HJ 535-2009), ammonium molybdate spectrophotometry (GB / T 11893-1989), and urban wastewater quality standard test method (CJ / T 51-2018), respectively. The test results are: chemical oxygen demand 14 mg / L, ammonia nitrogen content 0.40 mg / L, total phosphorus content 0.13 mg / L, and dissolved solids 191 mg / L, which meets the requirements of agricultural irrigation water and can be directly discharged or used for agricultural irrigation.

[0031] In summary, in the cellulose acetate mother liquor wastewater treatment process, the waste liquid at the bottom of the reaction kettle is directly filtered in a strong acid condition, thereby avoiding cellulose acetate seepage, reducing the use of ammonia and other alkaline reagents, reducing costs, and also avoiding pollution caused by the use of alkaline reagents.

[0032] It should also be noted that, in order to avoid obscuring the present application with unnecessary details, only structures and / or processing steps closely related to the solution according to the present application are shown in the drawings, while other details that are less relevant to the present application are omitted.

[0033] Finally, it should be noted that the terms "comprises", "comprising", or any other variants thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or apparatus that comprises a list of elements does not only include those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Claims

1. A process for the treatment of cellulose acetate mother liquor wastewater, characterized in that, The specific steps are as follows: S1, filtering: filtering the reactor bottom waste liquid with a PH value of 2-3 by using a silicon carbide ceramic microfiltration membrane, to obtain a clear liquid, without adjusting the PH value to avoid acetate fiber seepage; S2, nanofiltration: nanofiltration of the clear liquid obtained in step S1 by using an acid-resistant nanofiltration membrane, to obtain reverse osmosis concentrated water and product water, wherein the concentration of magnesium sulfate in the reverse osmosis concentrated water is greater than 10%; S3, evaporation recovery: evaporation crystallization of the reverse osmosis concentrated water obtained in step S2 by using an evaporator, to obtain magnesium sulfate solids; S4, biochemical treatment: biochemical treatment of the product water obtained in step S2 and discharge; The order of steps S3 and S4 can be interchanged or performed simultaneously.

2. The cellulose acetate mother liquor wastewater treatment process of claim 1, wherein: The pore size of the silicon carbide ceramic microfiltration membrane is 0.04-0.5 μm, the pressure of the filtration is 0-0.12 MPa, and the membrane pressure difference of the silicon carbide ceramic microfiltration membrane is less than 0.2 MPa.

3. The cellulose acetate mother liquor wastewater treatment process of claim 1, wherein: Step S1 further comprises: Step S11, backflushing: backflushing the silicon carbide ceramic microfiltration membrane with water to obtain backflushing waste liquid; Step S12, pressure filtration: pressure filtration of the backflushing waste liquid to obtain permeate and waste residue.

4. The cellulose acetate mother liquor wastewater treatment process of claim 3, wherein: The frequency of backflushing in step S11 is 10-100 min / time, and the time of each backflushing is 5-60 s.

5. The cellulose acetate mother liquor wastewater treatment process of claim 3, wherein: The permeate obtained in step S12 is returned to the reactor bottom waste liquid.

6. The cellulose acetate mother liquor wastewater treatment process of claim 1, wherein: The evaporator is connected with a condensing device and a condensate recovery device.

7. The cellulose acetate mother liquor wastewater treatment process of claim 1, wherein: The biochemical treatment in step S4 is one or more of anaerobic treatment, hydrolysis acidification treatment, anoxic treatment, and aerobic treatment.

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