CN112473390A

CN112473390A - Ultrafiltration membrane cleaning agent and cleaning method thereof

Info

Publication number: CN112473390A
Application number: CN202011506397.3A
Authority: CN
Inventors: 李廷微
Original assignee: Chongqing Titanium Industry Co Ltd
Current assignee: Chongqing Titanium Industry Co Ltd
Priority date: 2020-12-18
Filing date: 2020-12-18
Publication date: 2021-03-12

Abstract

The invention belongs to the technical field of chemical industry, and particularly relates to an ultrafiltration membrane cleaning agent and a cleaning method thereof. The invention provides an ultrafiltration membrane cleaning agent and a cleaning method thereof, aiming at effectively removing ultrafiltration membrane pollution retentate, recovering membrane flux, reducing running resistance and obviously improving cleaning effect. The cleaning agent comprises a component A and a component B; wherein, the component A is sodium hydroxide and sodium hypochlorite aqueous solution, and the component B is citric acid aqueous solution. The cleaning method comprises the steps of firstly feeding the component A into an ultrafiltration membrane, circularly washing with alkali, and then washing with water; and then the component B enters an ultrafiltration membrane, and is circularly washed by acid and then washed by water again. The invention can reduce the pressure of the running inlet end of the ultrafiltration membrane device to the maximum extent, recover the membrane flux, prolong the cleaning period and achieve good cleaning effect.

Description

Ultrafiltration membrane cleaning agent and cleaning method thereof

Technical Field

The invention belongs to the technical field of chemical industry, and particularly relates to an ultrafiltration membrane cleaning agent and a cleaning method thereof.

Background

An ultrafiltration membrane, a polymer micro-filtration membrane capable of separating polymer colloid or suspended particles with certain size from a solution. And (3) screening out solute molecules with the pore diameter smaller than the pore diameter by taking the pressure as a driving force and the pore diameter of the membrane as 1-100 nm so as to separate particles with the molecular weight larger than 500 daltons. Ultrafiltration membranes are used in the separation, concentration, purification of biological, pharmaceutical and food industries; also used for terminal treatment devices in blood treatment, wastewater treatment and ultrapure water preparation. The membrane material mainly comprises cellulose and derivatives thereof, polycarbonate, polyvinyl chloride, polyvinylidene fluoride, polysulfone, polyacrylonitrile, polyamide, polysulfone amide, sulfonated polysulfone, cross-linked polyvinyl alcohol, modified acrylic acid polymer and the like.

After the ultrafiltration membrane component operates for a period of time, colloids, suspended matters, bacteria and the like in raw water are intercepted by the surface of the membrane, and the substances can accumulate on the surface area of the membrane to cause pollution of the membrane, so that the performance of the membrane and the water permeability of the membrane are influenced. The main initial operation indexes of a single ultrafiltration device are as follows: water production flow rate 260m³H, inlet pressure is less than 0.2 MPa. After a period of operation, the ultrafiltration membrane is polluted, and the productivity is gradually reduced to 190m³And h, gradually increasing the inlet pressure to 0.28MPa, and stopping to perform off-line chemical cleaning on the membrane system when the on-line flushing cannot recover the performance and the water permeability of the membrane.

Due to the difference of materials of the ultrafiltration membranes, different system processes, different properties of treated feed liquid and different membrane components (such as a tubular component and a hollow fiber component), different pollutants trapped on the membrane surface are determined. Chemical cleaning is essentially a multiphase reaction between the precipitate and the cleaning agent, and different cleaning effects can be obtained by selecting different cleaning agents and different cleaning conditions. The universal cleaning scheme provided by a membrane manufacturer and some conventional cleaning technologies are tried, the membrane flux is improved to a certain degree, but the effect is not obvious, the service cycle is short, and the cleaning is frequent. Therefore, according to the process characteristics and water quality conditions of the existing system, different cleaning agents and cleaning conditions are urgently needed to find an optimal cleaning method.

Disclosure of Invention

The invention provides an ultrafiltration membrane cleaning agent and a cleaning method thereof, aiming at effectively removing ultrafiltration membrane pollution retentate, recovering membrane flux, reducing running resistance and obviously improving cleaning effect.

The invention aims to solve the first technical problem of providing an ultrafiltration membrane cleaning agent. Comprises a component A and a component B; the component A is an aqueous solution of sodium hydroxide and sodium hypochlorite, the pH value is 10-11, the mass concentration of the sodium hydroxide is 0.05% -0.2%, and the mass concentration of the sodium hypochlorite is 400-800 ppm; the component B is citric acid aqueous solution, the pH value is 2-3, and the mass concentration of citric acid is 0.6-2.5%.

Further, the sodium hydroxide mass concentration is 0.124%.

Further, the mass concentration of the sodium hypochlorite is 625 ppm.

Further, the citric acid mass concentration is 1.25%.

Further, the ultrafiltration membrane is made of polyvinylidene fluoride.

Furthermore, the feed liquid treated by the ultrafiltration membrane is water mainly containing microorganisms and algae. Preferably, the feed liquid is Yangtze river water.

The second technical problem to be solved by the invention is to provide a method for cleaning an ultrafiltration membrane by using the cleaning agent, which comprises the following steps: and (3) carrying out alkali washing and water washing on the ultrafiltration membrane by adopting the component A, and then carrying out acid washing and water washing by adopting the component B.

Further, the temperature in the alkaline washing is 10-30 ℃. Preferably, the temperature is 20-30 ℃.

Furthermore, in the alkaline cleaning, the cleaning pressure is 0.10-0.14 MPa.

In the alkaline washing, sodium hydroxide is supplemented to maintain the pH of the washing liquor at 10-11.

Further, the alkali washing is circulating alkali washing. The number of alkali washing times is 2-3, and each time of circulating alkali washing is 30-40 minutes.

Further, still standing and soaking steps are included after alkaline washing. And standing and soaking for 2-3 times, and each time for 30-40 minutes.

Further, the washing after the alkali washing is positive and negative washing until the pH value of the system effluent is less than 8.

Further, the temperature in the acid washing is 10-30 ℃. Preferably, the temperature is 20-30 ℃.

Furthermore, in the acid washing, the cleaning pressure is 0.10-0.14 MPa.

Furthermore, in the acid washing, citric acid is supplemented to maintain the pH of the washing liquor at 2-3.

Further, the pickling is a cyclic pickling. The acid washing times are 2-3 times, and the acid washing is circulated for 30-40 minutes each time.

Further, the pickling step also comprises a standing soaking step. And standing and soaking for 2-3 times, and each time for 30-40 minutes.

Further, the water washing after the acid washing is positive and negative washing until the pH value of the system effluent is more than 7.

Compared with the prior conventional cleaning technology, the invention has the beneficial effects that:

1. the combined cleaning medicines selected by the invention are sodium hydroxide, sodium hypochlorite and citric acid, so that bacteria, microorganisms and inorganic pollutants can be effectively removed.

2. Through circulation, soaking, recirculation, soaking of the cleaning solution, the cleaning solution can effectively diffuse and permeate into the dirt layer, multiphase reaction is better carried out, through series of hydrolysis, peptization, saponification, dissolution and integration, dirt particles generate soluble products which are dispersed into the cleaning solution, and are carried out of the surface of the membrane through water flow circulation.

3. The cleaning solution is circulated and soaked, so that the cleaning agent and the pollution particles have enough reaction time.

4. The temperature of the cleaning liquid is improved, and compared with a cleaning process without heating, the cleaning effect can be obviously improved.

Drawings

FIG. 1 is a schematic view of a cleaning system; FIG. 2 is a schematic diagram of the cleaning step.

Detailed Description

The invention aims to solve the first technical problem of providing an ultrafiltration membrane cleaning agent. The ultrafiltration membrane cleaning agent comprises a component A and a component B; wherein, the component A is sodium hydroxide and sodium hypochlorite aqueous solution, and the component B is citric acid aqueous solution.

Wherein the mass concentration of the sodium hydroxide aqueous solution is 0.05-0.2%.

Wherein the mass concentration of the sodium hypochlorite aqueous solution is 400-800 ppm.

Wherein the mass concentration of the citric acid aqueous solution is 0.6-2.5%.

Further, the sodium hydroxide mass concentration is 0.124%.

Further, the mass concentration of the sodium hypochlorite is 625 ppm.

Further, the citric acid mass concentration is 1.25%.

The second technical problem to be solved by the invention is to provide a method for cleaning an ultrafiltration membrane by using the cleaning agent. As shown in the schematic diagram of the cleaning step in fig. 2, the method comprises the following steps:

inputting a mixed cleaning liquid of sodium hydroxide and sodium hypochlorite into an ultrafiltration device by a cleaning water pump, keeping the pH value of the cleaning liquid in the ultrafiltration device at 10-11, the temperature at 10-30 ℃, and the cleaning pressure at 0.10-0.14 MPa; preferably, the temperature is 20-30 ℃; circulating the cleaning liquid in the cleaning system for 30-40 minutes, stopping a cleaning water pump, standing and soaking for 30-40 minutes for one time, and repeating the operation for 2-3 times; supplementing sodium hydroxide when the pH value is reduced in the circulation process, and keeping the pH value between 10 and 11; exhausting and emptying for 5-10 minutes after alkaline washing is finished, positively washing and back washing with water until no residual liquid medicine exists in a washing system, and detecting the pH of effluent of the system by using wide pH test paper to be less than 8.

Then inputting the citric acid solution into an ultrafiltration device, wherein the pH value is 2-3, the temperature is 10-30 ℃, and the cleaning pressure is 0.10-0.14 MPa; preferably, the temperature is 20-30 ℃; circulating the cleaning liquid in the cleaning system for 30-40 minutes, stopping a cleaning water pump, standing and soaking for 30-40 minutes for one time, and repeating the operation for 2-3 times; supplementing citric acid when the pH value rises in the circulation process, and keeping the pH value at 2-3; and (3) exhausting air for 5-10 minutes after the acid washing is finished, positively washing with water, and back washing until no residual liquid medicine exists in the system, wherein the pH of the effluent of the wide pH test paper detection system is more than 7.

In order to remarkably improve the cleaning effect, the temperature in the circulating alkali cleaning and the acid cleaning is 10-30 ℃; preferably, the temperature in the circulating alkali washing and the acid washing is 20-30 ℃.

The technical solution of the present invention is further described below by means of specific embodiments. It is to be understood that the present invention is not limited to the following examples, and that any changes and/or modifications made thereto are intended to fall within the scope of the present invention.

The cleaning system used in the following comparative examples and examples is shown in FIG. 1. The cleaned ultrafiltration membrane is used for treating Yangtze river water which is pretreated by coagulating sedimentation and filtration. The ultrafiltration membrane is made of polyvinylidene fluoride (PVDF), the membrane component is in an external pressure type, and the filtration mode is full filtration.

Comparative example 1: cleaning method recommended by membrane manufacturer

Sodium hypochlorite and sodium hydroxide mixed cleaning

(1) The alkali washing agent comprises the following components in percentage by weight: 10kg of industrial sodium hydroxide (99 wt%) and 200ppm of sodium hypochlorite (10 wt% of sodium hypochlorite (16 kg)) to prepare a mixed cleaning solution 8m³。

(2) And (4) inputting the mixed cleaning solution of sodium hypochlorite and sodium hydroxide into an ultrafiltration system by a cleaning water pump, and circulating for 30 min. The specific operation is as follows: confirming that the ultrafiltration water inlet pneumatic valve, the water inlet manual valve and the water production pneumatic valve are closed; opening the inlet and outlet valves of the cartridge filter; opening an ultrafiltration chemical cleaning water inlet manual valve, an ultrafiltration chemical cleaning water production backflow manual valve and an ultrafiltration chemical cleaning upper-row backflow manual valve, and starting a cleaning water pump; and (3) pressure control: controlling the pressure of an ultrafiltration inlet to be 0.1MPa by adjusting the opening of an upper-row reflux hand-operated valve in ultrafiltration chemical cleaning; the cleaning solution circulates between the cleaning water tank and the ultrafiltration membrane for 30 min.

(3) Soaking for 30 min. And (3) stopping the cleaning water pump, closing the ultrafiltration chemical cleaning water inlet manual valve, closing the ultrafiltration chemical cleaning water production backflow manual valve, closing the ultrafiltration chemical cleaning upper-row backflow manual valve, closing the security filter inlet and outlet valves, and soaking for 30 min.

(4) Repeating the step (2) of the medicine circulation and the step (3) of the soaking operation once.

(5) Emptying: and opening the ultrafiltration upper row pneumatic valve, opening the ultrafiltration lower row pneumatic valve, and exhausting for 5 minutes. Backwashing: and (4) turning off the lower row pneumatic valve, turning on the ultrafiltration backwashing water inlet pneumatic valve, and starting a backwashing water pump for backwashing for 5-10 minutes. Positive flushing: and (3) stopping the backwashing water pump, closing the backwashing water inlet pneumatic valve, closing the upper exhaust valve, opening the lower exhaust valve, opening the ultrafiltration water inlet manual valve and the pneumatic valve, and starting the clean water pump to flush for 5-10 minutes. And (5) detecting that the system is free of residual chlorine by using a residual chlorine detection reagent, and stopping flushing.

(6) Operation: the pressure of the ultrafiltration inlet is reduced to 0.2MPa from 0.25MPa before cleaning, and the flow of the produced water is reduced from 200m³Lifting/h to 223m³/h。

(7) The cleaning period is 45-55 days.

Comparative example 2: conventional cleaning method one

Cleaning with sodium hypochlorite and hydrochloric acid

(1) The medicament proportion is as follows: a. sodium hypochlorite 200ppm (10 wt% sodium hypochlorite 16kg), cleaning solution 8m³(ii) a b. 31 wt% industrial hydrochloric acid 8kg, preparing cleaning solution 8m³(ii) a And separately cleaning sodium hypochlorite and hydrochloric acid.

(2) Sodium hypochlorite cleaning: the steps of (2) and (3) of comparative example 1 are carried out once by the medicine circulation and the soaking operation.

(3) Washing: emptying, back flushing and forward flushing according to the step (5) of the comparative example 1 until the effluent of the system has no residual chlorine.

(4) Cleaning with hydrochloric acid: the operation of the steps (2) and (3) of the comparative example 1 is carried out once by the medicine feeding circulation and the soaking operation.

(5) Washing: emptying, back flushing and positive flushing according to the step (5) of the comparative example 1 until the effluent of the system is neutral, and detecting the pH value by using wide pH test paper to be more than or equal to 7.

(6) Data run after cleaning: the inlet pressure of the ultrafiltration is reduced from 0.26MPa to 0.21MPa, and the water production flow is reduced from 195m³Lifting to 220m³/h。

(7) The cleaning period is 45-50 days.

Example 1: cleaning method for autonomous research

(1) a, proportioning of an alkali washing agent: sodium hypochlorite 625ppm (10 wt% sodium hypochlorite 50kg), industrial sodium hydroxide (99 wt%) 10kg, mixed to prepare cleaning solution 8m³. b. Preparing an acid pickling agent: 100kg of citric acid is prepared into 8m of cleaning solution³。

(2) Alkali washing: the steps of (2) and (3) of comparative example 1 are carried out twice by the medicine circulation and the soaking operation.

(3) Washing: the operations of emptying, back washing and positive washing are carried out according to the step (5) of the comparative example 1, and the pH value of the effluent of the wide pH test paper detection system is less than 8.

(4) Pickling with citric acid: the steps of (2) and (3) of comparative example 1 are carried out twice by the medicine circulation and the soaking operation.

(5) Washing: the operations of emptying, back washing and positive washing are carried out according to the step (5) of the comparative example 1, and the pH value of the effluent of the wide pH test paper detection system is more than 7.

(6) Data run after cleaning: the pressure of the ultrafiltration inlet is reduced from 0.26MPa to 0.18MPa, and the water production flow is reduced from 193m³The per hour is lifted to 232m³/h。

(7) The cleaning period is 55-60 days.

Example 2: independent research cleaning method 2

(1) a, proportioning of an alkali washing agent: sodium hypochlorite 625ppm (10 wt% sodium hypochlorite 50kg), industrial sodium hydroxide (99 wt%) 10kg, mixed to prepare cleaning solution 8m³(ii) a b. Preparing an acid pickling agent: 100kg of citric acid is prepared into 8m of cleaning solution³。

(2) Alkali washing: adding 50% water into a cleaning water tank, opening a low-pressure steam valve, adding sodium hypochlorite and sodium hydroxide into the water tank respectively when the water temperature of the water tank is raised to 25 ℃, and adding water to prepare 8m³. And controlling the opening of the steam valve to keep the water temperature at 25-30 ℃. The steps of (2) and (3) of the comparative example 1 are carried out by the steps of medicine circulation and soaking twice.

(4) Pickling with citric acid: adding 50% water into a cleaning water tank, opening a low-pressure steam valve, adding citric acid into the water tank when the water temperature in the water tank rises to 25 ℃, and adding water to prepare 8m³. And controlling the opening of the steam valve to keep the water temperature at 25-30 ℃. The steps of (2) and (3) of comparative example 1 are carried out twice by the medicine circulation and the soaking operation.

(6) Data run after cleaning: the inlet pressure of the ultrafiltration is reduced from 0.26MPa to 0.12MPa, and the water production flow is reduced from 195m³Lifting to 257m³/h。

(7) The cleaning period is 80-85 days.

In conclusion, the invention determines the combined cleaning agent consisting of sodium hypochlorite, sodium hydroxide and citric acid by selecting the types and the proportions of the cleaning agents for many times, increases the collision frequency of cleaning agent molecules and pollution particles by increasing the temperature of the cleaning agent in a repeated circulation and soaking mode, accelerates the reaction rate, thoroughly removes pollutants in the ultrafiltration membrane, reduces the pressure of the operation inlet end of the device to the maximum extent, recovers the membrane flux and prolongs the cleaning period.

The invention is applicable to: and (3) an ultrafiltration membrane after the Yangtze river water is treated, wherein the Yangtze river water is subjected to coagulating sedimentation and filtration pretreatment. The ultrafiltration membrane is made of polyvinylidene fluoride (PVDF), the membrane component is in an external pressure type, and the filtration mode is full filtration.

Claims

1. Ultrafiltration membrane cleaning agent, is characterized in that: comprises component A and component B; Wherein, component A is sodium hydroxide and sodium hypochlorite aqueous solution, pH is 10～11, and sodium hydroxide mass concentration is 0.05%～0.2 %, the mass concentration of sodium hypochlorite is 400-800 ppm; component B is an aqueous solution of citric acid, the pH is 2-3, and the mass concentration of citric acid is 0.6%-2.5%.

2. The ultrafiltration membrane cleaning agent according to claim 1, wherein the mass concentration of the sodium hydroxide is 0.124%.

3. ultrafiltration membrane cleaning agent according to claim 1 and 2, is characterized in that: described sodium hypochlorite mass concentration is 625ppm.

4. The ultrafiltration membrane cleaning agent according to any one of claims 1 to 3, wherein the mass concentration of the citric acid is 1.25%.

5. The ultrafiltration membrane cleaning agent according to any one of claims 1 to 4, characterized in that: the material of the ultrafiltration membrane is polyvinylidene fluoride; the feed liquid processed by the ultrafiltration membrane is mainly containing microorganisms and the water quality of algae; preferably, the feed liquid is Yangtze River water.

6. The method for cleaning an ultrafiltration membrane by a cleaning agent according to any one of claims 1 to 5, characterized in that: comprising the steps of: using component A to carry out alkaline washing to the ultrafiltration membrane, then washing with water, and then using component B Pickled and washed with water.

7. cleaning agent according to claim 6 is to the method for ultrafiltration membrane cleaning, it is characterized in that: satisfy following at least one:

In the alkaline washing, the temperature is 10-30°C; preferably, the temperature is 20-30°C;

In the alkaline washing, the cleaning pressure is 0.10-0.14MPa;

In the alkaline washing, sodium hydroxide is added to maintain the pH of the washing solution at 10-11;

The alkaline washing is a cyclic alkaline washing, and after the alkaline washing, the step of standing and soaking is also included.

8 . The method for cleaning an ultrafiltration membrane with a cleaning agent according to claim 6 or 7 , wherein the water washing after the alkali washing is forward and reverse washing, and the washing is performed until the pH of the system effluent is less than 8. 9 .

9. The method for cleaning an ultrafiltration membrane by a cleaning agent according to any one of claims 6 to 8, wherein at least one of the following is satisfied:

In the acid washing, the temperature is 10-30°C; preferably, the temperature is 20-30°C;

In the pickling, the cleaning pressure is 0.10-0.14MPa;

In the acid washing, citric acid is added to maintain the pH of the washing solution at 2-3;

The pickling is a cyclic pickling, and after the pickling, the step of standing and soaking is also included.

10 . The method for cleaning an ultrafiltration membrane with a cleaning agent according to any one of claims 6 to 9 , wherein the water washing after the acid washing is forward and reverse washing, until the pH of the system effluent is greater than 7. 11 .