In recent years, cement kiln cooperative disposal of solid waste technology turbulent worship, numerous ancient cement manufacturing enterprises involved in solid waste disposal.For the example of cement kiln collaborative disposal of solid waste pollution prevention, the state has set the relevant scale and policy:HJ662-2013 "cement kiln synergy dispose solid waste situation guard technology paradigm", GB30485-2013 "cement kiln synergy dispose solid waste tainted master scale", "cement industry polluted prevention and control technology policy" (guard department announced no. 31, 2013), the cement industry clean manufacturing evaluation target system (to carry out the transformation committee announced in 2014, no. 3), GB30760-2014 "cement kiln synergy dispose of solid waste technology paradigm", "cement kiln collaborative action prevention and control of solid waste tainted technology policy of environmental protection issued (this year).New technologies driven by policy include: pollution emission reduction technology in the manufacturing process of cement kilns for collaborative disposal of solid wastes;Improve the efficient operation technology of cement kiln for cooperative disposal of solid waste, such as offline incineration system for large amount of solid waste;Efficient pre-disposal techniques for collaborative disposal of solid waste, such as the preparation of high quality waste derived fuel (RDF).Cooperative disposal of waste products in cement kiln is one of the best disposal techniques of waste products.The production probability and amount of dioxins in different processes are different, so are the water content of waste products entering the furnace, the calorific value of incinerated gas (or pyrolysis gas), the starting method of combustion, the temperature of heat carrier entering the furnace, the slag cooling method and the thermal exercise compliance.The advantages and disadvantages of various processes are proved to be beneficial to the improvement of the cooperative disposal of living wastes in cement kilns.
1 reverse kiln incineration system
1.1 fundamentals
The reverse kiln incinerator, also known as the reverse kiln, evolved from the cement reverse kiln.The main body is a torsional degree cylindrical shell made of steel plate lined with refractory materials.Tube axis and water level protection.There is a certain degree of skew, solid and semi-solid waste from the high end (head) through the feed machine into the kiln, followed by the cylinder body torsional slowly to the tail.Kiln body torsion makes the material in the process of burning and burning atmosphere abundant war, the realization of drying up, burning, burning, all the process of the cylinder body, into the burning room and fuel slag characteristics, by the aircraft ash and slag emissions.According to the difference between the activity bias of furnace gas and solid, or the position of heat source (incinerator) in the reverse kiln, the reverse kiln can be divided into upstream and downstream modes, and the progress of the reverse kiln tends to be retained.Flue gas flow similar, also known as counterflow.The plan of reversing kiln is suitable for feeding and pre-disposal, which can increase the time of flue gas, and is widely used in hazardous waste incineration system.Counter-current reversing kiln is more suitable for dangerous wastes (such as sludge) with high moisture content or low calorific value.
1.2 model process
The reverse kiln incinerator has a wide range of material suitability and can dispose of hazardous solid, liquid and solid wastes simultaneously.The reversing kiln is one of the empty cylinders, with a light thin askew lining and firebrick, usually very long.Through all kinds of dangerous waste in the process of the disposition and compatibility captive experience difference method in burning system, in itself and inversion of gravity kiln in reverse, turn stretched out under the propulsion of furnace and combustion atmosphere abundant battle, dry (water evaporation), gasification and burning process, after very preheater of residual slag, slag discharge in succession after water seal machine.
2 links of architectural interpretation
2.1 vertical incinerator
Vertical incinerator is a suitable type of waste incinerator based on the ancient type.Vertical incinerator with simple layout, convenient operation, moderate weight of the characteristics of the cement kiln collaborative disposal of living waste technology was used.Its operation method of accepting upper feed, lower discharge, upper air outlet and lower (or waist) oxygen supply is one of the very basic ancient calciner types.The critical outcome of vertical incinerators is incineration or incineration.Organic ash after incineration or incineration of living waste simply comes into the cement kiln system along with the incineration gas. The volume of inorganic slag is less than 5% of the volume of the original waste.The solid objects in the inorganic slag are metal, ceramic, brick and tile, glass, etc., and the metal objects are sorted.Sorting the surplus inorganic slag as cement material application;High temperature flue gas, dust and incineration gas with calorific value are sent to the pre-section furnace of cement kiln for heating and degradation of dioxins.
2.2 reverse pyrolysis furnace
The reverse pyrolysis furnace is an ATP furnace and a waste pyrolysis furnace on the bottom of the Garrett furnace based on the general technology of the reverse pyrolysis furnace.Different from the conventional reversing kiln used for calcining, the pyrolysis furnace is used to transfer heat from the solid heat carrier heated to a higher temperature (around 650℃) to the waste products at the feed end of the pyrolysis furnace, so that the waste products can reach the pyrolysis temperature (400~450℃) without or without oxygen, and produce the pyrolysis gas and slag with little dioxins content.After the slag is continuously heated to a higher temperature (650~750℃) at the kiln head (discharge end), the partial high-temperature fine slag is sent to the feed end of the kiln head again for pyrolysis with waste inclusion.Partial pyrolysis gas is used as fuel to heat the pyrolysis furnace.The excess pyrolysis gas is sent to the pre-section release furnace of cement kiln as fuel and degraded in the pre-section release furnace.After the pyrolysis gas at the heating end of the pyrolysis furnace is incinerated, the high-temperature flue gas with less oxygen content (over 800℃) will pass the heat to the waste products in the activity process from the kiln head to the kiln tail, which will also reach the pyrolysis results.The way of waste pyrolysis is based on the above mentioned solid heat carrier method and high temperature smoke fighting method.In all pyrolysis processes, waste products have little chance of fighting with oxygen, so the amount of dioxins produced is also low.
2.3 the dryer
The heat source of the waste dryer comes from the partial or all high temperature exhaust gas of the grate cooler (about 250℃).Regardless of the grate dryer or the reverse dryer, the waste balance temperature in the dryer is around 150℃.The drying gas is used in the grate cooler as a cooling gas, which can be used reasonably.
3. Process description and exploration
3.1 furnace type and dioxins production
The difference between pyrolysis furnace and vertical incinerator is pyrolysis and incineration.Although the ultimate inorganic slag foundation is similar, the mechanism of pyrolysis and incineration is different in quality.The former is the heating process of organic matter in the absence of oxygen or hypoxia to crack the high molecular hydrocarbon chain into low-molecular hydrocarbon dominated gas, medium molecular fuel and carbon black inclusions, while the latter is the oxidative heat release feedback of hydrocarbon in the premise of oxygen or oxygen enrichment to produce CO2 and H2O.Large quantities of dioxins and furans are easily produced by incineration, and dioxins are one of the most toxic organics in the world.Oxidation feedback from incineration and chlorine in plastic products are the premise of dioxins production. Although large partial dioxins can be released at a high temperature above 800℃, the hot active atoms of heavy metals in incineration become catalysts for the recovery of dioxins. Dioxins are produced again at a temperature of 300~500℃.Waste pyrolysis is the process of pyrolysis of waste products under the condition of no oxygen or hypoxia.Waste pyrolysis not only eliminated the premise of oxidation feedback production, but also reduced the production of dioxins precursor and suppressed the occurrence of dioxins from the bottom.Because the heavy metals in the waste products do not have the premise of high-temperature oxidation, it is not easy to produce catalysts that stimulate the production of dioxins, so it can be said that the production of dioxins can be eliminated from the spring.
3.2 with oxygen
The waste products of the collaborative disposal process of vertical incinerator were not dried and dehydrated before incineration, and the water content was around 20% (higher water content in summer), and even the waste products were mixed with appropriate amount of coal to be incinerated.The CO2 production of waste products is high without pre-drying.At the same time, due to the high water content of waste products, the calorific value of incinerated gas is low, and the calorific value of incinerated gas is lower than 3500kJ/Nm3, which has an inevitable impact on the consolidation of the section release furnace.
Conclusion: in recent years, with the country's dangerous waste of the prison intensified.Large inverting kiln incineration technology will be more widely used in disposal of hazardous wastes.
——Author：ebico