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author：Mr.Qin 2020-01-03
At present, the strategies typically used to treat and dispose of hazardous wastes consist of ocean disposal, incineration, chemical and biochemical treatment, solidification treatment, etc.In latest years, the software of incineration technological know-how is more and more extensive, it is a kind of incinerator to region the unsafe waste, make its flamable element oxidation decomposition processing method.In the incineration technology, due to the characteristics of correct working continuity, lengthy carrier life, secure operation, mature science and so on, rotary kiln incineration technological know-how suggests a robust advantage.However, due to the fast development of rotary kiln incineration technology in latest years, and the improvement of relevant technical key factors is lagging behind, so the emission of flue gasoline is no longer up to wellknown and other problems.
1 technology and manipulate of pollutants in flue gas
1.1 technology and manipulate of acid gas
Acid fuel pollution are frequently composed of nitrogen oxides, chlorides and sulfur oxides. During the combustion process, compounds such as Cl and S contained in stable waste ordinarily produce HCI and SO2.The acid gases such as HCI and SO2 in the flue gas have been controlled by using wet, semi-dry and dry cleansing methods.
The formation mechanism of NOx usually comes from three aspects: the formation of NOx by way of combustion of auxiliary fuel, the oxidation of nitrogen in the air at excessive temperature to produce NO, and the formation of NOx by way of nitrogen-containing components in waste at some point of combustion.The foremost strategies to manipulate NOx are:
(1) selective non-catalytic reduction (SNCR)
Ammonia or urea is injected into the incinerator, and eventually CO2, water and nitrogen are formed after the reduction reaction. Nitrogen oxides in the flue gas are reduced.
(2) selective catalytic reduction (SCR)
The SCR gadget is particularly effective.The NO in the smoke.Reacting with decreasing dealers such as ammonia and water, NOx in the flue gasoline is converted into water and nitrogen under the action of the catalyst.
(3) combustion control method
Maintain suitable furnace temperature and stability, temperature type NO.The condition of technology is temperature >1400V, so to manage its generation, the furnace temperature can be controlled (to limit nearby high temperature era in the furnace) via realistic air grant (reducing oxygen attention in the combustion field).
1.2 technology and control of dust and heavy metallic pollutants
Inert inorganic materials, such as condensable gasoline pollutants and ash, are the predominant elements of dirt in incineration flue gas.Heavy metal pollution include arsenic, chromium, lead and other elemental oxides and chlorides.After incineration at excessive temperature, heavy metals in the waste material, phase of the volatilization into the flue gas, part of the residue in the ash.
At present, the elimination of heavy metals in the incineration tail fuel cure gadget adopts the technique of activated carbon adsorption, and ultimately it is collected through the bag filter for safe landfill.After the bag filter, a small amount of volatile heavy steel mercury with low boiling point nevertheless exists as gas, but because of its water-soluble property, it is in the end removed by way of washing liquid in the acid absorption tower.
1.3 technology and manage of dioxins
Dioxins are the general names of PCDFs and PCDDs.The formation mechanism of dioxins in the main includes: (1) direct release mechanism;(2) high temperature gas reaction mechanism;(3) precursor synthesis mechanism;(4) DE novo synthesis reaction mechanism.
2. Flue gas purification technology of hazardous waste incineration in chemical industry
2.1 technological process
The standard flue gasoline purification technological know-how and procedure are flue gasoline quenching + dry deacidification + activated carbon adsorption + bag dirt removal + wet deacidification.
The flue gasoline purification science and procedure adopted in this undertaking is the flue fuel excessive temperature denitration + flue gasoline quenching + dry deacidification + activated carbon powder injection + bagging dirt elimination + two-stage moist deacidification + electrostatic deatomizer + activated carbon adsorption bed.
2.2 optimization of flue gasoline purification process
2.2.1 manipulate N0.Technical optimization
(1) temperature manipulate of rotary kiln
Empirical information show that the production of NOx at 1000oC is 1/10 of that at 1300V.In order to manage the technology of NOx, it is vital to maintain the appropriate furnace temperature and combustion stability.In the rotary kiln, the mission set up an infrared thermometer to robotically manipulate the furnace temperature via far off monitoring.The challenge additionally USES a aggregate burner to hold stable combustion in the furnace, and optimizes the structure of the rotary kiln's head tuyars, efficiently decreasing emissions of pollution such as nitrogen oxides.
(2) optimize the association of secondary air
The oxygen content is controlled at 6% ~ 10% in the rotary kiln via two instances of combustion, so that the substances can be burned in a single combustion in a susceptible discount environment to promote the conversion of nitrogen compounds to N2, and fully incinerated in the secondary combustion chamber to absolutely burn out the detrimental substances.
In order to efficaciously minimize the generation of NO, it is imperative to prepare the secondary air inlet reasonably.In this project, a secondary air distributor is arranged in the straight section of the contraction orifice of the secondary combustion chamber. The smoke disturbance will increase the applied venturi effect, and the air nozzles are evenly disbursed on the same section. After tangential flow into the secondary combustion chamber, an imaginary circle will be shaped in the center.
Under the disturbance of secondary wind, the incineration flue fuel spirals up, increasing the tour of flue gasoline flow, extending the dwelling time of flue gas in the secondary combustion chamber, and the house time of flue fuel is larger than 2.0s.
The hazardous supplies in the flue gas decompose completely.
(3) optimization of nitrogen elimination system
The denitrification response system is located in the first return experience of the waste warmness boiler.NO was controlled by SNCR (non-catalytic method).And the key of SNCR technological know-how is the determination of temperature window.
In the vicinity of the nozzle, the assignment sets the thermocouple, window temperature 930C works best, set to 900 ~ 1000"C.And I'm going to do NO.Export analysis system is set in the boiler, the real-time monitoring NOx concentration, transmitted to the PLC, NOx attention indicators were amassed in accordance to the awareness values, PLC to regulate the injection extent of urea solution, output float manipulate signal, will ultimately be quantitative injection incinerator in urea answer by spraying system, the boiler thermal decomposition of nitrogen in urea solution, and below the most appropriate temperature and boiler NOx discount reaction, reduction of water and nitrogen, eventually removal of nitrogen oxide in flue gas.
The reducing agent of this task is urea solution.The device the usage of synthetic feeding combined reductant, by the scene of the soft water piping will be wished for configuration gentle water to urea solution with cans, mixture of 40% urea solution, followed via centrifugal pumps, the solution to storage tanks, thru on line dilution metering allocation module, 40% of the urea answer diluted into 5% of the urea solution, by way of distributing the metering device to jet atomization spray system.The storage tank of this undertaking is geared up with an electric powered heating device, and steam tracing in the pipeline is provided to avoid recrystallization of urea solution.At the equal time, in order to stop overtemperature and blockage of the nozzle, the spray gun is geared up with compressed air to protect the air. It is additionally arranged symmetrically in layers, with 12 interfaces reserved. In order to make certain the denitration effect, the spray gun's injection position can be adjusted in accordance to the working conditions.Under the idea of modular design, almost all the equipment of SNCR gadget in this mission is installed on the modules that have been tested by way of the factory in advance. The flow manage machine adopted is advanced. After analyzing the facts collected in the field, the glide control signal is output to recognize the automatic whole-process control.
2.2.2 optimization of acidic gasoline elimination process
In order to improve the deacidification effect, the flue gasoline purification method of this assignment is upgraded from the normal dry + moist deacidification manner to dry + double wet deacidification process.
(1) dry deacidification
In order to attain deacidification, the purification absorbent Ca(OH)2 powder used to be introduced to the deacidification tower.HF, HCI, SO, and S0: in the flue gasoline react with Ca(OH)2 in the deacidification tower to produce CaF2, CaCl2, CaSO3, CaSO4, etc.At the identical time, there is C02 in the flue gas, Ca(OH)2 consumes some to generate CaCO2, and the fly ash generated with the aid of the incineration and these particles together enter the bag filter, which is filtered out by the filter bag in the bag filter.
The flue gas is washed by using double-wet method, and there is a pre-cooler (the pre-cooling tank feeds water from the washing tank, and the washing water is commonly despatched to the pre-cooling tank thru the washing drainage pump.Some of the precoolers are reused and the rest are discharged to the sewage station, which now not solely reduces the excessive awareness of salt water, however additionally reduces the alkali consumption of scrubbers.The automated switching machine is set on the precooling water grant line, which can be routinely changed to the standby precooling water line thru the pneumatic ball valve, and the precooling water pump is routinely commenced to make sure the steady operation of precooling water.C, then enter the washing tower, which selects the sieve plate tower, and the acid gas (HF, HCI, SO2) in the flue fuel in the tower is neutralized and absorbed by using NaOH.Lye maintained within a positive pH value by a washing cycle pump.The corrugated plate mist eliminator is set at the outlet of the scrubber tower. The droplets entrainedin the tower are separated by way of the mist eliminator. The 3 ~ 5um droplets can be efficaciously removed.The mist eliminator has a flushing nozzle that can be intermittently sprayed with high-pressure cleaning water to smooth the mist eliminator, designed to remove salts that may additionally precipitate on it.
2.2.3 optimization of dioxin manage technology
(1) optimization of electrostatic defogging process
After wet washing, the moisture content in the flue gas is extraordinarily high. If it is discharged immediately through the chimney, white plume will be generated. Therefore, in previous projects, the flue gasoline heater was once set in the scrubber tower to heat the temperature of the flue fuel to greater than 110oC and then discharged.The venture used to be modified to an electrostatic demister to separate and eliminate aerosols, droplets and water mist from the flue gas.The above issues were solved, and the ultrafine particles in the flue gasoline had been in addition removed, which had been adsorbed on the surface of fly ash.
(2) optimization of activated carbon adsorption process
Through the study, it was observed that the primary structure of dioxins is particulate matter, so the emission of dirt wishes to be strictly controlled, the most high-quality way to take away erying ying is activated carbon injection adsorption + bag dirt removal, however additionally to reduce the concentration of heavy steel mercury emissions.
Considering the splendid volatility of material components, this task will be activated carbon adsorption mattress (adopted warehouse design, a complete of three can meet the necessities of warehouse composition.Adsorption layer set stress and temperature measurement points, according to the use of activated carbon, warehouse resistance replacement.At the same time, the by-pass is set up, and the adsorption system is adjusted in accordance to the wishes of use.) the rear cease of the electrostatic precipitator is delivered to once more purify pollution such as dioxins and heavy metals in the flue gas, so as to ensure the emission of flue gas up to the standard.
3 conclusion
Rotary kiln incineration flue fuel purification device of the present manner where there is a lot of improvement, such as washing water aerosol kingdom of the second properly English category material, activated carbon adsorption reason secondary pollution, NH SNCR system, escape, and so on, via all the design of the system control, combined with the task funding and different factors, according to specific materials and state of affairs in the challenge application, modified method plan content, with this technological know-how will be increasingly more perfect, to recognize harmless, discount of chemical hazardous waste disposal.