Energy saving and clean production technology of aluminum profile processing industry
Although China's aluminum production for five consecutive years has been ranked first in the world, but compared to the aluminum industry production technology with the United States, Japan, Germany, Italy and other countries there are still large gaps, the major task of energy saving and emission reduction. Mainly in the following aspects:
(1) energy consumption and pollutant emission in aluminum industry;
The average production of 1 tons of aluminum consumption of industrial water is about 16 - 18 tons; surface treatment contains a variety of metal impurity ions generated in the wastewater; high energy consumption; produce a lot of waste, only an annual output of 2400 tons of aluminum anodizing production line, annual production of about 150 thousand tons of sludge, waste slag 2000 tons, a large quantity of. The composition of wastewater and sludge is very complicated. Most factories now use landfill to treat these sludge. This not only takes up limited land resources, but also wastes resources and pollutes the environment.
(2) the cause of high energy consumption and high pollution in aluminum industry
The smelting and recycling of aluminum melting furnace in the furnace at present, accounted for 5%, oil accounted for 91%, accounted for 4% of the gas furnace, resulting in remelting production 1 tons extrusion ingot consumption is 55.17% higher than the developed countries, while the actual ingot (rolling ingot and extrusion ingot) the average melting energy consumption is much higher than industrial developed countries. In addition, the overall energy consumption of aluminum smelting furnace is still in the middle and low levels.
The casting, rolling and extrusion: lack of high-grade products; small machine, extrusion equipment is relatively backward, low efficiency; equipment automation degree is low, unable to realize the fast isothermal extrusion, precision mold production profile; poor quality.
Surface treatment: surface treatment is the high power consumption, high consumption of water and high pollution in the process of aluminum processing.
Energy saving and emission reduction become the aluminum processing enterprises urgently need to solve the problem, this article from the aluminum melting furnace, holding furnace, extrusion rod furnace, oxidation treatment of sludge deep processing and utilization of some new methods and strategies, so that the aluminum processing enterprises to achieve the purpose of energy-saving emission reduction and clean production.
Energy saving, emission reduction and clean production technology of 2 aluminium melting furnace
2.1 working process of aluminium melting furnace
The smelting process of aluminium smelting furnace can be divided into 4 stages, that is, charging the charge to soften, staying, softening, staying until the furnace is flat, melting the furnace to the whole melting point (that is, producing oxidized dross) and heating up the aluminum liquid. The heating of aluminum material is accomplished by convection heat transfer of burner flame, radiant heat of flame and furnace wall, and conduction heat transfer between aluminum material.
Throughout the process, the ratio between the three is constantly changing. Solid aluminum density small, high heat conduction. With the melting process, the charge enters the critical state of semi liquid and semi solid, and its thermal conductivity decreases, and the thermodynamic properties undergo a fundamental change. The heat transfer capacity of liquid aluminum is only 40% of that of solid aluminum, and the conduction heat transfer from the upper part of the bath to the bottom is very slow. Porous scum floating on a metal mirror forms an insulating barrier of heat transfer. At the same time, the oxide film on the weld pool surface has been turned on, losing the protective effect and increasing the tendency of oxidation and suction. The flame for aluminum melting furnace, melting in aluminum, furnace temperature control in 1200 degrees, the temperature of flue gas is released as the temperature of the furnace, flue gas heat stove heat load of 50 accounted for about 70%, taking into account the other 10% of the heat loss, effective heat utilization is only 30 - 40%, if not make full use of the waste heat, will cause great waste, so that the heat efficiency of furnace is very low.
To sum up, it is an effective way to increase the furnace heat efficiency and to ensure the least direct fuel consumption in the smelting process by choosing the effective way to strengthen the heating and recycling the waste heat of the flue gas to preheat the combustion air.
2.2 using high temperature air combustion technology
High temperature air combustion has changed the traditional combustion mode, fuel furnace with flue gas recirculation or direct injection combustion mode, mainly through the combustion air of the ceramic honeycomb is preheated to above 1000 DEG C, the speed is sprayed into the furnace proper, suction, stirring and mixing furnace combustion products in high speed airflow volume, in the air of 21% oxygen diluted at low oxygen concentrations (minimum 5% - 6.5%) fluid combustion in high temperature air combustion can be realized under the condition of low air ratio combustion, reduce the loss of aluminum oxide.
Regenerative combustion system includes a burner, a regenerator of a reversing device, a control system and a pipeline system.
When the furnace gas temperature is 1000 - 1200 DEG C, the combustion air temperature can be preheated to 800 - 1000 DEG C, and the fuel consumption can be saved by about 50% compared with the aluminum smelting furnace using the wall type air heat exchanger.
The gas mixture at the burner outlet is ejected at about 60m/s, the flame length is about 2.5 - 3M, and the flame diameter is about 0.5 - 0.7m. The burners in the furnace are reversed and the high temperature area is exchanged frequently to ensure uniform temperature in the furnace without forming a low temperature zone.
2.3 high speed burner technology
For an old stove in use, it is difficult for an enterprise to spend 300 thousand yuan on a new regenerative burner.
Using high speed burner nozzle, spray gas at a high speed of more than 100m/s to the furnace, combustion air at a speed of 90m/s in the combustion of aluminum, the heap of impact, strong acceleration of melting, in order to prevent the removal of fire, the gas nozzle placed a burning torch.
Our days in the digestive absorption of the United States based high speed burner products, developed the excellent performance of high-speed burner, flue gas flow rate can reach 180m/s, load regulation rate reached 1:20, the excess air coefficient can be adjusted between 0.65 and 10.8.