2022-04-09
Heating equipment has great energy-saving potential. The basic requirements for energy-saving equipment are large furnace, effective utilization area rate, uniform temperature area, high loading capacity, good heating device, cheap energy, good heat transfer effect, good thermal insulation capacity, less heat loss, high thermal efficiency, etc. According to this requirement, the introduction, transformation, spontaneous development and rational use of equipment can effectively carry out energy-saving production.
(1) Rational selection of energy
① The electricity is clean and easy to control, such as resistance furnace, which is an indirect heating workpiece with low thermal efficiency. The thermal efficiency is improved by strengthening radiation, reducing heat storage in furnace lining and heat dissipation on furnace wall; Pulse ion nitriding furnace uses electric energy to ionize low vacuum gas into ions. Under the action of electric field, it impacts the workpiece at high speed. While heating the workpiece, it penetrates nitrogen into the workpiece. This heat treatment method has high thermal efficiency; Medium frequency induction heating: the crankshaft in alternating electromagnetic field generates alternating current, i.e. eddy current, which instantly heats the crankshaft surface to high temperature. It belongs to direct heating and has high thermal efficiency, up to 55% ~ 90%. Induction quenching belongs to local treatment, which saves nearly 80% ~ 90% energy compared with overall quenching.
② The fuel is cheap. It is best to use natural gas or coal gas, which is a gas with high calorific value. It can form a flame on the jet burner and directly heat the workpiece by means of thermal shock, thermal radiation and thermal convection. It has high heat exchange coefficient and heating speed, so the thermal efficiency is high. Bright annealing line for horizontal looper (LPG heated) uses natural gas as heating energy to treat workpieces.
(2) Reduce heat loss and improve thermal efficiency
① In order to reduce the heat storage of the furnace lining, the composite furnace lining is adopted, the furnace wall is made of ceramic fiber, and the surface of the inner wall is coated with infrared reflective coating; Considering the high strength requirements, the furnace bottom adopts clay brick + light refractory brick structure; The furnace door is pasted with ceramic fiber on the inner wall.
② In order to improve the sealing performance of the furnace, the furnace body shall be less perforated as far as possible to avoid heat loss.
③ Reduce the weight of the material tray and material frame, as long as it can bear the maximum furnace loading allowed by the equipment, so as to avoid consuming more energy to heat the material tray and material frame.
(3) Fuel furnace -Development and application of high efficiency burner
The excellent burner shall be able to automatically adjust the ratio of gas to air, and the combustion flame can realize strong radiation and convection in the furnace. Bright annealing line for horizontal looper (LPG heated) uses SIC100HB burner, which is relatively crossed with the opposite side and placed evenly. The walls on both sides of the furnace are close to the bottom. After ignition, the temperature rises rapidly, which is conducive to promoting the recycling of hot gas flow and significantly saving energy.
(4) Make full use of afterheat and waste heat
① As shown in the figure, gas soft nitriding, heating to 590 ℃ and high temperature insulation for 3h, cooling down to 540 ℃ with the furnace after power failure, and using the afterheat in the furnace to continue nitriding the medium can obtain very good results, provided that the equipment has good sealing performance. For example, the Pit Nitriding Furnace and Nitriding furnace of STRONG TECHNOLOGY of our company can treat the same products, and each crankshaft product before and after improvement can save 20 degrees of electricity.
Figure 1. Process before improvement of gas soft nitriding
Figure 2 improved process of gas soft nitriding
② Bright annealing line for horizontal looper (LPG heated) uses natural gas as fuel for heating. Its chimney not only removes waste gas, but also takes away 20% ~ 50% of the heat in the furnace. Then, in the design and installation of the equipment, the reuse of waste heat is fully considered. The combustion supporting air pipe is set close to the chimney to preheat the combustion supporting air. The air just entering the furnace can reach 100 ~ 200 ℃, which can reduce the heat loss.
(5) Reasonable selection of furnace type
When the batch and process of heat treatment products are determined, the selection of furnace type has become the key to realize process, energy saving and cost reduction. Continuous furnace consumes less energy than periodic furnace, and the thermal efficiency of various furnaces ranges from high to low: Bell-type furnace, Pit Type furnace, conveyor belt furnace, borel furnace or table furnace. When the batch is large, the continuous furnace should be selected; When there are more varieties and fewer quantities, the periodic furnace will be used intensively.
(6) Popularize the heat treatment of ammonia atmosphere furnace (Ammonia Cracker)
Amino atmosphere is used for tempering heat treatment with special requirements of customers, which can achieve the effect of less and no oxidation decarburization and bright and no rust on the surface of the workpiece; For chemical heat treatment, it can reduce internal oxidation, prevent corrosion and improve the quality of chemical heat treatment. The gas source of amino atmosphere is rich and the cost is low. It has good safety, strong adaptability and less pollution. Water and carbon dioxide generated after waste gas combustion are released into the air. Liquefied ammonia is generally used as a protective atmosphere and a medium resource for chemical heat treatment.
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