Industry
Technical analysis of chemical process with ultrapure water
Raw water pretreatment is good or bad will directly affect the reverse osmosis system of water production, water quality of water changes such as transformation of groundwater and surface water will directly affect the stand or fall of pretreatment, will also lead to water quality changes on reverse osmosis system. A not fussy for water, stable water quality of pretreatment system also becomes one of the target of modern high-end water users. Chemical water treatment system as an example for analysis, discusses some existing and new thought of to solve the problem.
Reverse osmosis technology was introduced into China in the 1970s, after decades of development are widely used in various industries and fields, many factories enterprises such as: power plant chemical water treatment, chemical process with high pure water, and so on are high pure water, the electronics industry with the continuous development of water treatment technology and benefit a lot. Reverse osmosis water treatment technology is to use membrane separation, belong to the physical method, with the pressure as a driving force, do not need to acid, alkali regeneration, no pollution, low energy consumption, equipment cover an area of an area small, can run automatically, operation and maintenance workload small, compared to the previous mode of water treatment has the incomparable advantage. But higher requirements on the pretreatment system, reverse osmosis system generally reverse osmosis water quality requirements: 1.0 NTU turbidity (< 0.3 NTU), 15 min best SDI < 5.0 (< 3.0);The free gas content < 0.1 PPM. The design of water treatment system is designed for the raw water quality, in principle, a water source water quality corresponding to a kind of water treatment design patterns. If the water quality changes, and the corresponding pretreatment model to corresponding changes, such as adjusting the flocculant and the addition amount of scale inhibitors.
Water treatment system is to produce water quality is not stable, often appear conductivity = 1.0 us/cm, at the same time made occasional bacteria in water. First-grade product rate of this kind of situation lead to PTFE resin, PTFE first-grade product rate of vinyl chloride products from the original 50% to 30%, or less, to cause serious economic enterprises the loss Water treatment system of water quality is not stable cause analysis is as follows: (1) the raw water quality is not stable chemical water treatment system of water for municipal tap water, In general more stable water quality, fluctuation is not big, but because of the water resources deficiency, so water companies often have change, sometimes is the surface water of the Yellow River, sometimes is exploitation of groundwater, thus indirectly caused chemical water treatment system to the uncertainty of water.
Compared to water and underground water has the following features: Yellow River is the surface water, oxygen consumption, high turbidity, high suspended solids content, organic matter, microorganism content. But total hardness is low, low ion content, total alkalinity, free CO, soluble SiO2, meta silicate are below the underground water, compared with in addition to the turbidity, bacteria, organic matter content in other performance are better than that of groundwater.
For the raw water quality instability and poor pretreatment effect analysis of the technical improvement measures, tap water, raw water quality being unstable residual chlorine content of uncertainty (high and low), the water particles, colloid, bacteria, microbes such as suspended solids, and other changes along with the switch of Yellow River and groundwater. Although the tap water meet GB5749-2005 "water quality standard of drinking water, however, residual air oxidation of reverse osmosis membrane, its content is uncertain, is unable to determine the amount of reducing agent to add; At the same time scale inhibitor and flocculant by the end of total soluble solids (TDS) and the content of suspended solids and can not be sure, this will lead to reverse osmosis membrane oxidation, fouling, pollution, scale, desalination rate can drop directly. Desalination rate decline will make subsequent ion exchanger failure ahead of time, International effect is Yang bed, Yin bed once every 4 to 7 days activation, mixed bed every 2~ 5 months activation time, increase the workload of workers, directly at the same time because of the emissions of acid and alkali, also increased the blow down cost, polluting the environment. Pretreatment of manual operation, the filter backwashing is wash effect is not good, cause the security filter element changed frequently, and excessive use of flocculants will be more heavy filter using effect is poor. Figure 2 for the more advanced technology. Raw water to the original water tank, the water pump - self-cleaning filter - super encounter a high-pressure pump a security filter, reverse osmosis devices, ion exchange pure water system.
By the analysis of the causes of this process is as follows:
Although there are fluctuations, water quality raw water for tap water, however, has been treated with municipal tap water company, not the drinking water quality indicators and the country is so different, its bacteria, suspended solids, colloid, etc can all be self-cleaning filter by 100 goals and ultrafiltration (note: ultrafiltration aperture for nanoscale, intercept molecular weight of 50000 daltons). Removal of ultrafiltration for cross-flow filtration, can get rid of all the bacteria, suspended solids, colloid, etc., to ensure that the reverse osmosis water quality stability, the fouling effects of reverse osmosis. This set of full automatic control for the process, after setting the differential, self-cleaning filter, ultrafiltration and reverse osmosis system linkage rev. Stop, without real time supervision, at the same time don't need to add the flocculant, just before the security filter adding scale inhibitors. The security filter cartridge replacement frequency will be greatly reduced.(2) in view of the imperfection of the post-processing technology reform measures are analyzed In view of the pure water tank and after-treatment system of bacteria pollution, take the following measures:
A Pure water and air in contact with all piping and valves closed, leave A (vent pipe, on the vent pipe with air breathing apparatus, can prevent the dust in the air, bacteria and microbes into pure water, high pure water of aseptic.
B In the pure water tank and micro-porous filter mounted between the ultraviolet sterilization device, online to kill bacteria and microbe, at the same time, the micro-porous filter cartridge from the original 1 μm to 0.1PM, improving the capacity of micro-porous filter filtration, because 1 um filter will not be able to filter out bacteria and microbes, and 0.1 um filter can remove bacteria, viruses and other organisms.
