Qiqihar Railway Vehicle (Group) Co., Ltd. is a large-scale enterprise in China's truck and vehicle industry. The cast steel branch is responsible for the company's heavy production tasks. However, for a long time, the heating equipment of the branch factory is backward, and the following problems are common in the cast steel heat treatment furnace: the combustion device is backward, the combustion effect is poor, and the single consumption of the furnace is high; the temperature difference in the furnace is large, and the workpiece heating waste rate is high.
In 1998, (Group) Company entrusted the Industrial Furnace Research Institute of the Fifth Design and Research Institute of Machinery Industry to design and renovate a 18.7m2 gas trolley type heat treatment furnace of the foundry branch. The newly built furnace has been selected and integrated in four aspects from the selection of furnace material, the configuration of the combustion device, the selection of air heat exchanger, the setting of electric control and temperature control, and effectively improved the furnace. The thermal efficiency reduces the fuel consumption, ensures the temperature uniformity in the furnace, improves the output and quality of the workpiece, and improves the service life of the furnace. The overall operation of the furnace refers to the management of equipment.
The target has reached the domestic advanced level. The following is a brief introduction to the transformation of the furnace.
1 furnace lining material The original trolley type heat treatment furnace is a refractory brick structure, the two sides and the back furnace wall are heavy clay bricks, and the top of the furnace is a clay vault structure. The sides of the furnace wall are reinforced side pillars, and more beam steel frames are reinforced. Thermal deformation, the top of the furnace is vulnerable, the furnace wall is damaged, and the furnace life is short. At the same time, due to the large heat storage and heat loss of the brick structure, the furnace heating rate is slow and the fuel consumption is large.
The design and transformation of the background car heat treatment furnace is the full fiber roof and furnace wall structure. The advantages are as follows: the refractory fiber has good heat insulation performance, small heat storage loss, shortens heating time, increases heating rate, and saves fuel.
The refractory fiber is a light refractory material with a small specific gravity and light weight. After being installed on the top of the furnace, the side thrust is much smaller than the original structure. Therefore, the steel structure of the furnace body becomes a light steel structure, which not only saves steel but also facilitates construction.
Due to the good thermal insulation performance of the refractory fiber, the thermal deformation of the furnace body is small, so the furnace body is less damaged and the service life of the furnace is improved.
2 The trolley-type heat treatment furnace after the design and modification of the combustion device uses a high-speed temperature-regulating burner. The burner is an energy-efficient device widely used in China, and is composed of a gas nozzle, an air distributor, a combustion cylinder, a combustion chamber casing, an igniter and a flame monitor. The high-speed temperature-regulating burner itself has a small closed combustion chamber, the fuel is substantially completely burned in the combustion chamber, and the high-temperature airflow after combustion is ejected into the furnace at a high speed of 80-100 m/s. Its characteristics are: the high-speed airflow from the burner strengthens the convective heat transfer in the furnace, shortens the heating time and improves the productivity of the furnace.
The high-speed airflow has greater kinetic energy, and the high-speed burners arranged on the upper and lower sides are more conducive to furnace gas circulation, which is beneficial to the furnace temperature uniformity < *5*C, which improves the heating quality.
The burner is equipped with three times of air distribution, uniform mixing and complete combustion, which improves fuel utilization and saves fuel.
The burner can be equipped with automatic ignition and flame monitoring to match the furnace control system for automatic operation.
3 Air Heat Exchanger The air heat exchanger is a waste heat utilization device that uses the flue gas discharged from the kiln to preheat the combustion air. The newly designed trolley heat treatment furnace uses a slot metal heat exchanger. Its characteristics are: the main material is made of stainless steel, the service life is long; the loss of smoke and air side resistance is small; the application of air heat exchanger in the trolley type heat treatment furnace brings many benefits to the furnace itself: 70% of the exhaust fumes The waste heat is utilized; the theoretical combustion temperature of the furnace fuel is increased; the fuel is saved because the hot air is brought into physical heat.
Hot air enters the furnace, promotes fuel mixing, improves combustion and improves heating quality.
4 automatic control system in the upper and lower rows of 5 burners arranged. Each burner is equipped with an automatic ignition small burner, a flame monitor and a cold air protection device. The burner is matched with a high-pressure igniter, a burner controller and a special valve to form a PLC pulse combustion system.
Each of the burners is composed of two zones, and the two burners near the furnace door are each a zone, which is divided into six zones and controlled by multiple points to achieve the heat treatment process requirements.
4.2 Furnace temperature control Each zone adopts Ou Lu 818P intelligent temperature controller for temperature control. Each instrument can be set with multiple process curves. The setup is simple and easy to operate. The heating rate and temperature can be modified online. The control cabinet is equipped with fault alarm. Turn off the fire alarm and other functions.
4.3 Detection and electronically controlled air temperature galvanic detection and digital display; flue gas temperature galvanic detection and digital display; use of angular travel electric actuator to adjust wind pressure and air volume; in addition to mechanical transmission, mainly for furnace door lifting and lowering Chain control is carried out for vehicle walking, fan opening and closing, pressure switch, flame detection and alarm.
5 Economic benefits Due to the long life of the furnace, the overhaul cycle is extended. From the original two years to a major revision to the current five-year major overhaul. This year alone, the cost of overhaul is 120,000 yuan.
The fuel consumption of the furnace decreased, the product quality improved, and the average energy consumption per ton of steel castings was 15.57m3 lower than the original. The annual cost savings totaled more than RMB 240,000.
Design and renovate the background car type heat treatment furnace. In the past few years, the burner, butterfly valve and ignition device have been continuously improved, the production is stable, the performance is superior, and the economic benefit is remarkable.
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