CN104474905A - Nanofiltration membrane cleaning agent for treating polymer flooding produced wastewater and cleaning method - Google Patents

Abstract

The invention discloses a nanofiltration membrane cleaning agent and a cleaning method for treating polymer flooding oil production wastewater. The composite cleaning agent is prepared from EDTA, sodium pyrophosphate, SDS and water. The cleaning method is divided into two steps, first cleaning with the composite reagent of the present invention, and then pickling with dilute hydrochloric acid solution. The composite chemical cleaning reagent of the present invention is used to chemically clean the polluted nanofiltration membrane in the treatment of polymer flooding oil recovery wastewater. The results show that the flux recovery rate of the nanofiltration membrane after cleaning can reach more than 99%, and the recovered flux can be compared with be maintained for a long time. In addition, a variety of testing and characterization methods were further used to study the nanofiltration membrane after the cleaning process. The results showed that the composite cleaning reagent did not damage other properties of the nanofiltration membrane. After cleaning, the desalination rate, The hydrophilicity, microscopic morphology, and infrared spectrum are almost the same as those of the new membrane, which fully demonstrates that the cleaning scheme effectively realizes the "regeneration" of the contaminated nanofiltration membrane.

Description

Nanofiltration membrane cleaning agent and cleaning method for treating polymer flooding oil production wastewater

technical field

The invention belongs to the field of nanofiltration membrane treatment of polymer flooding oil recovery wastewater, and relates to a composite cleaning agent and a cleaning method used for effective and non-destructive chemical cleaning of polluted nanofiltration membranes during polymer flooding oil recovery wastewater treatment.

Background technique

The popularization and application of polymer flooding oil recovery technology in major oilfields in my country has effectively improved the oil recovery rate, but the problem of a large amount of clean water consumption and waste water production in the process has been plagued by oil production areas that are already short of water. Nanofiltration, which is between ultrafiltration and reverse osmosis, can intercept small molecular organic matter and has partial desalination capabilities. Therefore, nanofiltration membranes are used to conduct advanced treatment of ultrafiltration-treated polymer flooding oil recovery wastewater to reduce salinity and reduce the salinity. Further removal of residual organic matter in the water to ensure that the nanofiltration effluent meets the water quality requirements for polymer blending water can be reused in the polymer flooding oil recovery process, which is expected to solve the economic and environmental problems caused by clean water consumption and wastewater discharge.

However, membrane fouling is a major obstacle limiting the popularization and application of nanofiltration membranes. Although various control measures (such as pretreatment of feed liquid, optimization of operating conditions, and improvement of anti-fouling performance of membrane materials, etc.) can reduce membrane fouling, regardless of No method can completely avoid the occurrence of membrane fouling. When the membrane flux drops to a certain extent or the transmembrane pressure difference increases to a certain extent, or the effluent water quality deteriorates and cannot meet the requirements, it is necessary to carry out the polluted nanofiltration membrane. Cleaning, cleaning methods can be divided into physical cleaning and chemical cleaning. Physical cleaning is to forcibly remove pollutants from the membrane through the disturbance of physical effects such as water flow and gas. However, in the face of more stubborn pollution layers, physical cleaning usually It is difficult to obtain a satisfactory cleaning effect, and chemical cleaning is required at this time. Chemical cleaning is to destroy the structure of the polluted layer through the chemical reaction between the cleaning agent and the pollutants, reduce the binding force between the pollutants and the nanofiltration membrane, and make the pollutants migrate away from the membrane body under the action of self-diffusion and water flow disturbance, thereby restoring Membrane flux ensures the quality of effluent water and realizes the "regeneration" of polluted nanofiltration membranes.

When nanofiltration treats polymer flooding oil recovery wastewater, crude oil, polyacrylamide, natural organic matter and various salt ions in the water can cause membrane fouling. These pollutants are closely combined with the nanofiltration membrane through various physical and chemical effects. It is difficult to achieve complete recovery of membrane performance through physical cleaning, but appropriate chemical cleaning is required to achieve this goal. However, a single chemical cleaning agent often only has a good cleaning effect on a certain contaminated component, and the contaminated nanofiltration membrane in practical applications is usually compounded by a variety of different components. In order to obtain a satisfactory cleaning effect, It is necessary to use a variety of cleaning agents for multi-step cleaning, the steps are cumbersome, time-consuming and labor-intensive, and some commercially available commercial cleaning agents are not targeted to specific pollution situations. The cleaning effect of the contaminated nanofiltration membrane caused by wastewater is not good. Oxidative cleaning agents with good cleaning effect (such as sodium hypochlorite solution) will cause irreversible damage to the composite nanofiltration membrane made of polyamide, reducing the effluent quality of the nanofiltration membrane and the service life of the membrane module. Therefore, there is an urgent need for a targeted, efficient and non-destructive composite chemical cleaning reagent and cleaning method for treating contaminated nanofiltration membranes in polymer flooding oil production wastewater.

Contents of the invention

In order to solve the problems of poor cleaning performance of existing nanofiltration membrane chemical cleaning agents and damage to the membrane body, the present invention develops a technology-specific and efficient polymer flooding treatment technology for the nanofiltration treatment technology of polymer flooding oil production wastewater. Nanofiltration membrane cleaning agent and cleaning method for oil production wastewater.

The purpose of the present invention is achieved through the following technical solutions:

A nanofiltration membrane cleaning agent for treating polymer flooding oil production wastewater, which is prepared from EDTA, sodium pyrophosphate, SDS and water, and the content of each component is: 0.03~0.07wt.%EDTA, 0.15~0.25wt.%pyrophosphoric acid Sodium, 0.15~0.25wt.%SDS, the preparation method is: fully stir and dissolve 0.03~0.07%EDTA, 0.15~0.25wt.% sodium pyrophosphate and 0.15~0.25wt.%SDS, and then use NaOH to dissolve the solution The pH can be adjusted to 10.5~11.5.

When chemically cleaning the contaminated nanofiltration membrane in the treatment of polymer flooding oil production wastewater, firstly use the above-mentioned compound chemical cleaning reagent to clean for 15-30 minutes, then use the hydrochloric acid solution with pH=2 to clean for 10-20 minutes, and finally rinse the membrane module with clean water Just wash it.

The composite chemical cleaning reagent of the present invention is used to chemically clean the polluted nanofiltration membrane in the treatment of polymer flooding oil recovery wastewater. The results show that the flux recovery rate of the nanofiltration membrane after cleaning can reach more than 99%, and the recovered flux can be compared with be maintained for a long time. In addition, a variety of testing and characterization methods were further used to study the nanofiltration membrane after the cleaning process. The results showed that the composite cleaning reagent did not damage other properties of the nanofiltration membrane. After cleaning, the desalination rate, The hydrophilicity, microscopic morphology, and infrared spectrum are almost the same as those of the new membrane, which fully demonstrates that the cleaning scheme effectively realizes the "regeneration" of the contaminated nanofiltration membrane.

Description of drawings

Figure 1 shows the desalination rate of different nanofiltration membranes;

Figure 2 is an atomic force microscope image of different nanofiltration membranes;

Fig. 3 is the contact angle of different nanofiltration membranes;

Figure 4 is the infrared spectrum of different nanofiltration membranes.

Detailed ways

The technical solution of the present invention will be further described below, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered by the protection scope of the present invention middle.

Embodiment 1: This embodiment provides a nanofiltration membrane cleaning agent for treating polymer flooding oil production wastewater, which is formulated from EDTA, sodium pyrophosphate, SDS and water. The content of each component is: 0.05wt.%EDTA, 0.2wt.% sodium pyrophosphate, 0.2wt.% SDS, the preparation method is: add 0.05wt.% EDTA, 0.2wt.% sodium pyrophosphate, 0.2wt.% SDS to clean water, stir and dissolve Then adjust the pH of the solution to 11 with NaOH.

When chemically cleaning the contaminated nanofiltration membrane in the treatment of polymer flooding oil production wastewater, first use the above-mentioned compound chemical cleaning reagent to clean for 20 minutes, then use the hydrochloric acid solution with pH=2 to clean for 15 minutes, and finally rinse the membrane module with clean water. Yes, the flux recovery rate of the nanofiltration membrane after cleaning can reach more than 99%. The changes of the desalination rate, hydrophilicity, microscopic morphology and infrared spectrum of the nanofiltration membrane before and after cleaning are shown in Figure 1-4.

Figure 1 shows that the desalination rate of the polluted nanofiltration membrane has reached 91.55%, which is significantly higher than the 86.21% of the new membrane. After the membrane was cleaned by the optimized cleaning scheme, the rejection rate of sodium chloride dropped from 91.55% to 87.62%, which was very close to the 86.21% of the new membrane, which indicated that the selected chemical cleaning scheme not only effectively removed the Pollutants, and did not damage the desalination performance of the nanofiltration membrane.

Figure 2 shows that when the nanofiltration membrane is polluted, the original convex structure on the surface has been completely covered by a thick layer of viscous substance, and it is difficult to find the convex structure of the new membrane, which is exactly the reason for the decrease of membrane flux. The reason is that after cleaning with the optimized cleaning scheme, the dense pollution layer on the nanofiltration membrane has been removed, and the concave-convex structure reappears, and the morphology of the membrane surface is almost the same as that of the new membrane. From the perspective of microscopic morphology, the determined The optimized cleaning scheme can effectively remove membrane fouling substances without causing damage to the inherent structure of the membrane surface.

Figure 3 shows that the contact angle of the nanofiltration membrane after pollution increased from the initial 61.16° to 78.57°, and the appearance of the fouling layer reduced the hydrophilicity of the membrane surface, which was caused by hydrophobic crude oil pollutants. After cleaning with the optimized cleaning scheme, the nanofiltration membrane's 78.57° after pollution dropped to 59.62°, which was slightly lower than the 61.16° of the original membrane, indicating that the polluted components on the membrane had been removed, and it was restored to be more hydrophilic The surface characteristics of the film, the slightly lower contact angle than the original film may be caused by the surfactant remaining on the film during cleaning.

Figure 4 shows that the nanofiltration membrane after pollution has obvious absorption peaks at 2850cm-1, 2919 cm-1, and 3327 cm-1, respectively, and 2850cm-1 and 2919 cm-1 are the characteristic absorption peaks of crude oil pollutants, And 3327 cm-1 is the characteristic absorption peak of APAM. After cleaning with optimized cleaning scheme, these three absorption peaks disappear, and the two types of pollutants on the surface have been cleaned and removed. Compared with the original membrane, the nanofiltration membrane has a weaker absorption peak at 2926 cm-1 and 2855 cm-1 after cleaning, which may be due to the hydrophobicity of the surfactant remaining on the nanofiltration membrane during the cleaning process. The C-H asymmetry and symmetry contraction vibration absorption peaks on the end are consistent with the explanation that the contact angle of the nanofiltration membrane after cleaning is lower than that of the original membrane. The absorption peak between 3200 cm-1 and 3700 cm-1 is wider than that of the original film, which may be due to the insufficient drying of the film during the measurement and the absorption of O-H in the residual water. In addition, after cleaning The infrared spectrum of the nanofiltration membrane is almost the same as that of the original membrane, indicating that the chemical cleaning did not cause damage to the membrane.

Embodiment 2: This embodiment differs from Embodiment 1 in that the content of each component is: 0.04wt.% EDTA, 0.18wt.% sodium pyrophosphate, 0.18wt.% SDS.

Embodiment 3: This embodiment is different from Embodiment 1 in that the content of each component is: 0.06wt.% EDTA, 0.23wt.% sodium pyrophosphate, 0.23wt.% SDS.

Claims (5)

1. A nanofiltration membrane cleaning agent for processing polymer flooding oil production wastewater, characterized in that said cleaning agent is a composite cleaning agent formulated from EDTA, sodium pyrophosphate, SDS and water, and the content of each component is: 0.03~ 0.07wt.% EDTA, 0.15~0.25wt.% sodium pyrophosphate, 0.15~0.25wt.% SDS. 2. The nanofiltration membrane cleaning agent for treating polymer flooding oil production wastewater according to claim 1, characterized in that the content of each component is: 0.05wt.% EDTA, 0.2wt.% sodium pyrophosphate, 0.2wt.% SDS. 3. The nanofiltration membrane cleaning agent for treating polymer flooding oil production wastewater according to claim 1, characterized in that the content of each component is: 0.04wt.% EDTA, 0.18wt.% sodium pyrophosphate, 0.18wt.% SDS. 4. The nanofiltration membrane cleaning agent for treating polymer flooding oil production wastewater according to claim 1, characterized in that the content of each component is: 0.06wt.% EDTA, 0.23wt.% sodium pyrophosphate, 0.23wt.% SDS. 5. a method utilizing claim 1-4 arbitrary claim to process polymer flooding oil recovery waste water with nanofiltration membrane cleaning agent to clean the method of nanofiltration membrane, it is characterized in that described method step is as follows: The first step is to clean with a compound cleaning agent for 15-30 minutes; In the second step, wash with hydrochloric acid solution with pH=2 for 10-20 minutes.