Analysis of sewage treatment technology in pulse circulating fluidized bed
1 Preface
Fluidized bed is a kind of reactor which uses the concept of fluidization to carry on the mass transfer and heat transfer operation. It is different with the traditional fixed bed reactor, the bed body has solid particles suspended in a liquid (gas) in the body and strenuous exercise, thus greatly strengthen the diffusion process of the material, improve the reaction speed, liquid volume of the reactant can make unit volume can be increased by 2 ~ 10 times of treatment, which makes the fluidization can be widely in the industrial application.
Study of biological fluidized bed sewage treatment technology applied to wastewater treatment began in the United States in 1970s. The research and application of the fluidized bed in China began at the end of 70s. The initial research focused on exploring the operation mode, carrier characteristics, filling method, biological membrane control and update, in order to understand the law of purification and solve practical problems, and on this basis, the design parameters are recommended. Into 80, 90s, the domestic and foreign have been built many types of small and medium sized fluidized bed device, and in some industrial wastewater and domestic sewage into the use of. Through a variety of domestic and foreign reports, due to the water distribution and biological carrier to the limitations of existing biological fluidized bed treatment scale is mostly in the hundreds of tons / day, basically is still in the research stage, has not been able to achieve industrialization of large area promotion, really play a huge advantage in the field of biological fluidized bed sewage purification.
In recent years, the chemical industry has made rapid development. Polyurethane material with light weight, high porosity, good flexibility, corrosion resistance and other special biological carrier required. And the production is more and more big, the price is also getting lower and lower, which also provides a strong support for the development of fluidized bed technology filler.
A patented technology that is completed by the use of decades of work experience and years of research and development in the central, central, Wan generation engineering and technology in the process of pulse circulating fluidized bed. The dual advantages of double fluidized bed system concentrated together biological activated sludge and biofilm, do the system highly stable and reliable, the pollutant removal rate increased several times than the general process. Completed a major revolution in biological wastewater treatment.
2 principles
The unit is the actual pulsed fluidized bed reaction principle application of anaerobic hydrolysis acidification reaction, in pulsed fluidized bed reaction unit for efficient biological affinity with a certain amount of filler, the pulse water distribution function impulse water distributor, the filler to achieve "fluidization floating settlement" in the reactor.
The pulse fluidized bed (hydrolytic acidification) was not only a biological degradation function, but also had a hydrolysis acidification effect. The effect of biodegradation of ideal mainly depends on the biological sludge concentration and water distribution effect, must ensure that the hydrolysis acidification pool has a certain amount of filler and biological sludge, and the pool water are fully mixed and the high affinity filler in a fluidized state, the pollutants in water by sludge adsorption and decomposition. If the filler and the sludge is not up to a certain concentration, the slurry mixing effect is poor, the anaerobic part of the treatment effect will be very poor. Therefore, whether the water distribution uniformity and anaerobic sludge concentration will determine the efficiency of hydrolysis acidification.
Automatic pulsed water distributing device according to the requirement of the pulsed fluidized bed flow state and the various water distributor characteristics developed, is a more efficient water distribution system, ideal for reliable operation. The water distributor has the following advantages: simple structure, no need of complex equipment, the whole process of water suction cloth by water automatically, convenient maintenance and management; second, low energy consumption, high efficiency, and improve the water does not need other power; the uniform water distribution, water stirring effect is good; and long service life etc..
Pulse water distribution, ensure the sludge concentration and filler and water mixing effect, control of flammable, malodorous gases generated at the same time, because of the sewage and flora formation flow state, greatly improving the processing efficiency, reduces the cost of investment.
The circulating fluidized bed unit is the actual application of aerobic microorganism oxidation reaction principle, the high affinity filler added in a circulating fluidized bed, the microporous aeration technology in air, hydraulic shock and stirring, achieve good fluidization. The water outlet end of the circulating fluidized bed is to be returned to the water inlet end of the circulating fluidized bed through the water pushing device, and the whole process of the circulating fluidized bed is completed.
In the circulating fluidized bed, the variable microporous floating aeration device is used, and the high efficiency of the tubular variable microporous aeration pipe is adopted to improve the utilization rate of oxygen. During maintenance, only the aerator branch and the supporting tube to lift, aerator group needs repair from the water up to repair, replacement, without draining the pool of sewage, to achieve on-line maintenance.
The pulse in circulating fluidized bed is porous filler as biological carrier, through the stirring effect of aeration of the carrier in the flow state, the biofilm carrier surface and internal growth, adsorption, oxidation and decomposition of organic matter in wastewater. This kind of high efficiency biological affinity filler is a new type of biological material which has been developed in the near future. It is one of the key technologies of pulse circulating fluidized bed. It is composed of a variety of metal oxide polyurethane and a certain proportion of the ratio of processing and. The porosity of the filler is 90% ~ 95%, and the density is slightly larger than that of water. The filler has good elasticity, in the hydraulic and air mixing, under the impact of filler shape will change a little, the shape changes to ensure a good condition for the formation of material exchange between the filler inside and outside, breathing "role in this process is also known as high affinity packing". A variety of metal oxides contained in the filler promoted the biochemical reaction of microorganisms. In the experiment and engineering practice, the shape and size of the highly efficient biological affinity filler in the reactor are clearly defined.
High efficiency biological affinity filler in the case of the growth of microbial attachment, will spontaneously form a "floating - settlement" of the cycle process. Filler is added to the initial stage of the biochemical reaction pool, and a small amount of microorganism is attached to the filler, and the filler is suspended in the reaction pool. With the gradual increase of microorganisms on the filler, the proportion of the whole filler increased, and at this time the filler was deposited at the bottom of the reaction tank. Sediment on the bottom of the filler material due to the material transport weakened and produce anaerobic reaction, produce a small amount of gas, and gradually restored to the suspended state, repeating the "floating" cycle process. The advantages of pulse - circulating fluidized bed technology are:
(1) due to the use of pulsed water distribution technology and the construction of a unique organic polymer anaerobic filler, can maintain and significantly improve the sludge amount and sludge activity of the anaerobic system, to ensure the stable operation of the system.
(2) to achieve a rapid and uniform mixing of fresh sewage and biological carrier, greatly improving the speed of the reaction. In the pulsed fluidized bed, the removal rate of 2kg/m3/d can reach CODCr ~ 5kg/m3/d.
(3) circulating fluidized bed system composed of high variable microporous aeration system and the unique structure of aerobic organic polymer filler, the removal rate of CODCr can reach 3kg/m3/d ~ 8kg/m3/d, is the general biological reactor can not be compared.
(4) organic polymer filler affinity biological agent and reinforcing agent, with a large surface area, can reach 2000m2/m3 ~ 3500m2/m3, in the reaction system become a good living biological carrier, and has the advantages of good hydraulics performance and long service life etc..
(5) the high efficiency biological carrier filling material has the characteristics of self - breathing function, self - localization tendency and the absorption function of gas in the process of fluidization. This system makes the aeration gas greatly extend the residence time in the water, the dissolved oxygen rate increased by 30% to 60% than the general aerobic biochemical system, greatly reduces the energy consumption of biochemical systems.
(6) water, mud, filler three-phase separating system has the advantages of novel design, unique shape, high efficiency, simple operation, is an important equipment of double fluidized bed.
(7) due to the unique dual fluidized bed biochemical system, make the system effective removal of nitrogen in wastewater, the removal rate is up to 70% ~ 80%.
(8) automatic control system of double fluidized bed can realize automatic control of dissolved oxygen and water quality of influent quantity and system, make the system become intelligent system with high efficiency and high automation.
(9) in the fluidized bed adding efficient biological affinity packing, increased biomass and biochemical system, the formation of filler reside in microorganisms and activated sludge microorganisms in two biological phase, two biological phase complementary functions, improve the biochemical treatment system the removal rate and increase the operation stability of the system.
(10) the high efficiency biological affinity filler in the pulse circulating fluidized bed, the system has strong ability to resist shock load, and there is no active sludge expansion phenomenon.
(11) in this process, the use of highly efficient biological affinity filler does not need support, and the packing is simple.
(12) compared with the traditional combination or other forms, the high efficiency biological affinity filler has the advantages of low cost, convenient use and high volume load, and has obvious advantages in the transformation of the old project.
3 application
Pulse circulating fluidized bed technology is applied in engineering practice. Foshan City, a textile printing and dyeing Co., Ltd. 15000m3/d printing and dyeing wastewater treatment project has successfully applied the technology. The project in February 2005 a comprehensive debugging qualified, the effluent CODCr is 50mg/L ~ 60mg/L, better than the national and local emission standards of sewage, the project cost less than the conventional process is relatively low, the operation cost is very low, only 0.4 yuan /m3 to 0.5 yuan /m3.
The pulsed circulating fluidized bed has successfully solved the problem of biological carrier and water distribution, which has opened up a road for large-scale industrial application in the field of environmental biological purification. Pulse - circulating fluidized bed is a product of application and development of environmental biotechnology, it conforms to the development trend of environmental biotechnology, that is as far as possible to improve the concentration of microorganisms in the reactor volume, increase the organisms and pollutants in the reaction system with maximum limit, the highest level of play microbial activity, reduce the investment and operation cost effectively.
Pulse circulating fluidized bed in the traditional activated sludge process and contact oxidation process to find a good fit between the points, both of the two kinds of technology, and has a stable system, treatment effect
