Process research and design of waste gas treatment of polyester chemical fiber textile wastewater
The waste water of polyester chemical fiber enterprises mainly comes from all kinds of waste water produced in the process of polyester chemical fiber production and process cleaning waste water. All kinds of wastewater produced in the production process of enterprises often contain strong alkali, strong acid, alcohol, pectin, cellulose, hemicellulose, esters, dioxane, 2-Md and other compounds, as well as volatile organic pollutants.
Conventional hydrolysis acidification contact oxidation, Fenton Catalytic oxidation, membrane bioreactor (MBR) and other treatment processes can not achieve satisfactory results.
In view of the complex water quality, high content of refractory organic compounds and poor biodegradability of wastewater produced by such enterprises, a large number of volatile organic pollutants, such as acrolein and acrolein alcohol, which are toxic to microorganisms, are also produced along with the production of wastewater. These two kinds of organic pollutants have strong irritation to human eyes, such as tear, eyes and respiratory tract, The liquid acrolein is also corrosive.
Ozone catalytic oxidation MBR immobilized biological aerated filter (g-baf) – bioaugmentation carbon filtration combined process integrates immobilized biological filter, bioaugmentation, catalytic oxidation and membrane technology, and has been successfully applied to the actual project.
Through this project, the recycling mode of polyester chemical fiber wastewater harmless resource is realized, which not only has an important impact on the water saving, emission reduction and sustainable development of enterprises, but also hopes to provide reference for the research and development and application of wastewater treatment technology of similar enterprises.
The main sources of wastewater from polyester chemical fiber enterprises are production wastewater from process workshop, domestic wastewater and washing wastewater from workshop and process tank. The daily discharge of wastewater is about 48T.
Considering the amount of unforeseen waste water that may be generated, a wastewater treatment system with a treatment capacity of 60t / D is designed, in which the industrial wastewater is 24t / d.
The designed influent pH is 6-9, cod is 2.5-3.5g/l, BOD5 ≤ 300mg / L, and the mass concentrations of SS, NH3-N and animal and vegetable oil are 200-300, ≤ 30 and 1.2mg/l respectively. The treated effluent is required to meet the urban greening water standard of GB / T18920-2002.
The waste gas comes from the production wastewater process and wastewater treatment system. The mass flow rates of ethylene glycol, H2O, acetaldehyde, methanol and air in the waste gas are 0.01, 0.29, 0.76, 0.21 and 12.70 kg / h respectively, with a total of 13.97 kg / h.
The exhaust emission is required to meet the Tianjin local standard DB12 / 524-2014, that is, the mass concentration of VOCs at the outlet is less than or equal to 50mg / m ³， The mass flow at 20m altitude is less than 4.5kg/h.
According to the wastewater synthesis process, the waste water and waste gas of the enterprise were qualitatively analyzed by GC-MS. the components in the waste water include glycol, acetaldehyde, acrolein, acrylic acid, ethylene terephthalate, dioxane, 2-Md, acrolein and acrolein. The waste gas includes glycol, acetaldehyde, acrolein, acrylic acid, air and other gases.
Polyester chemical fiber wastewater is a kind of refractory industrial wastewater with high content of organic matter, biological toxicity, poor biodegradability, complex composition and biological toxicity.
The wastewater treatment station of the plant covers an area of 200m ²， The comprehensive equipment room is a workshop in the plant area. The comprehensive equipment room is equipped with membrane outlet pump, power distribution control room, Membrane Backwash dosing tank, ozone generator, laboratory, etc. The tank is of carbon steel structure, and the waste water tank body is of carbon steel, with two-layer antirust primer inside and outside and two-layer finish outside.
- The domestic wastewater in the plant area enters the collecting well after passing through the wedge wire screen grid. The function of the wedge wire screen grid is to remove large impurities, fibrous substances and hair from the sewage and prevent the blockage of the lifting pump. The wastewater from the collecting well is lifted by the lifting pump and then enters the regulating tank. The industrial wastewater in the plant area directly enters into the industrial wastewater collection tank. The industrial wastewater from the overflow port at the upper end of the tank is left in the regulating tank.
- The water from the regulating tank enters the hydrolytic acidification tank through the lifting pump, and the hydrolytic acidification tank improves the biodegradability of wastewater. The effluent goes into the g-bafmbr reaction tank. At the same time, the bioaugmentation microbial agent is stirred evenly through the stirring tank to activate the biological activity and then added into the g-baf to improve the biodegradation efficiency and degrade most of the pollutants in the water. The effluent is filtered by the carbon filter tower and then returned to the clean water tank for greening in the plant area.
- The whole treatment system is airtight. The collected system tail gas and industrial waste gas are sucked into the spray tower through the suction fan. After the gas is passed into the washing tower, it is washed with water to dissolve the water-soluble gases such as acrylic acid and propylene alcohol in water.
- The waste water containing waste gas flows back to the industrial sewage collection tank. Ozone and wastewater from industrial wastewater collection tank enter the ozonation tower for full contact and reaction. Through ozone catalytic oxidation, the toxicity of wastewater can be removed and its biodegradability can be improved.
- The tail gas is washed by the spray tower and adsorbed by the activated carbon adsorption tower before reaching the emission standard at 20m altitude.
Main structures and equipment
- Wedge wire screen grating and collecting well.
The mechanical grille is set in front of the collecting well, and the size between the gratings is 1.20m × 0.5m × 1.2m。 The size of collecting well is 4.0m × 2.0m × 5.0m, underground structure. Two submersible sewage pumps (one for standby and one for use) are set. The pump parameters are volume flow 3M ³/ h. The head is 10m and the power is 0.55kw.
- Industrial wastewater collection tank.
The effective size of the tank is 2.5m × 2.0m × 3.5m, internal anti-corrosion, effective volume of 15m ³。 The residence time of sewage is 15h. The tank body is made of carbon steel. The industrial wastewater from the overflow port at the upper end of the tank is left in the regulating tank. All tanks are closed, and industrial exhaust gas and tank exhaust gas flow back to the industrial sewage collection tank after washing through the spray tower.
- Regulating tank.
The industrial wastewater and domestic wastewater are fully mixed in the regulating tank, and the regulating tank is set. The size of regulating tank is 2.5m × 3.0m × 3.5m, effective volume 22.5m ³， Internal corrosion protection. The tank body is made of carbon steel.
The perforated aeration pipe is installed in the tank, and the air is introduced for mixing, so that the wastewater can be mixed evenly, and the deposition of suspended solids in the water and the stench of sewage can be prevented. There are two submersible sewage pumps in the tank (one for standby and one for use, with a volume flow of 3M) ³/ h. 37KW), and equipped with liquid level floating ball to automatically control the start and stop of the pump.
- Ozone catalytic oxidation tower.
The ozone output of ozonator is 1kg / h, including ozonator, dryer, filter and ozonation tower. The size of ozonation tower is Φ Quasi 0.9m × 2.9 m, lined with 3 mm thick acid resistant and carbon steel, external second coat antirust primer and second coat finish. The ozone gas enters the ozonation tower through the microporous aeration plate at the bottom of the reactor.
The inner part of the oxidation tower contains support frame, filter cap, packing net, cushion and so on, and supports catalyst. The catalyst is a columnar activated carbon containing multiple transition metal elements. Set pH to 6.8. The volume flow of cooling water is 3-4m ³/ h.
- Hydrolysis acidification tank.
The well mixed wastewater is pumped into the hydrolytic acidification tank by submersible sewage pump. The tank body is made of carbon steel, and the effective volume of the hydrolytic acidification tank is 36m ³， The pool size is 4.8m × 2.5m × 3.5m, anti-corrosion inside the box. The residence time of sewage is 14.4h. The elastic packing is installed inside, and the spacing of packing pieces is 200 mm.
Elastic filler 12m ³， Provide attachment points for anaerobic microorganisms. The perforated aeration pipe is laid at the bottom of the tank, and the compressed air is introduced to play the role of stirring, so that the waste water is mixed evenly. There is an overflow port inside, and the wastewater directly overflows into g-baf through overflow. The mass concentration of do is not higher than 0.4mg/l.
Through the overflow port, the wastewater in the hydrolysis acidification tank is overflowed into the good cultivation tank. The size is 7.2m × 2.5m × 3.5m, anti-corrosion inside the box, effective volume of 54m ³， The HRT is 14.4h. The tank body is made of carbon steel. The pool is equipped with polyurethane composite filler, which is 30m long ³， One set of packing frame is welded by channel steel and thread steel. Microporous aeration system is laid at the bottom of the tank, and compressed air is introduced for aeration to increase the concentration of aerobic microorganisms in wastewater. There is an overflow port inside, and the wastewater flows into the MBR tank through the overflow.
- MBR biochemical pool.
The pool size is 14.5m × 2.5m × The effective volume of the box is 108.75m ³。 The HRT was 43.5h. The tank body is a carbon steel box with MBR. The effluent of biochemical tank is separated by membrane. PVDF curtain membrane was used, 14 pieces of membrane, and the membrane area was 18m ²/ The film. Aeration system is set in the reactor, the volume ratio of air to water is 20:1, and the compressed air enters from the bottom of the tank through pipeline. A reflux device is set to reflux regularly to maintain the sludge concentration in the biochemical tank. The membrane outlet pump is one for standby and one for use, with the volume flow rate of 3.5m ³/ h. The head is 12m and the power is 0.37kw.
- The tank size is Φ Quasi 2.4m × 3.0m, equipped with mixing and aeration device. The wastewater from the regulating tank was pumped into the device and stirred for 24h. The purpose is to fully mix the dried bacteria preparation with the wastewater in the tank and activate the biological activity. Then, the bacteria preparation aqueous solution is pumped into g-baf by submersible sewage pump. 0.5kg bacteria preparation was added to 1t wastewater.
- Spray tower. The size of spray tower is Φ Quasi 0.8m × 2.2M, lined with 3 mm thick acid and alkali resistant glass fiber reinforced plastic, external second coat of antirust primer and second coat. It is divided into tower body, tray and packing. The diameter of industrial waste gas collection pipe is dn80mm, and the pressure drop is calculated as pure air 10Pa / 100M. The volume flow of fan is 400-500m ³/ h. The power is 0.75KW.
- Activated carbon adsorption tower. The size of adsorption tower is Φ Quasi 1.8m × 8 m, lined with 3 mm thick acid and alkali resistant glass fiber reinforced plastics, external second degree antirust primer, second degree finish coat, the treated waste gas will be absorbed by activated carbon, and then discharged at 20 m altitude.
- Carbon filter. The size of adsorption tower is Φ Quasi 0.6m × 2.5m, lined with 3mm thick acid and alkali resistant glass fiber reinforced plastics, external second coat of antirust primer and second coat of finish. The treated wastewater is sent to the clean water tank through the carbon filter.