Green sand materials are very cheap and recyclable. They could be used to produce small and middle sizes and weights castings. In addition, this material is also suitable for both small amount and large batch production. However, it is only suitable for making iron castings, not for steel castings.
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With the deepening of energy-saving and emission-reduction technologies, the potential for energy-saving and emission-reduction after iron is limited because of the heat loss after hot metal, hot metal, molten steel, continuous casting, and rolled materials. The potential for energy saving and emission reduction before the iron is huge. Before the iron base is large, in 2006 China's 400 million tons of iron production capacity, the original fuel consumption of 9 (dry basis) - 10 (wet basis) more than 100 million tons. Such a huge base, whether it is to improve the quality or reduce consumption, or reduce the water or reduce the diversion, will have great effectiveness in energy conservation and emission reduction.
Since most of the metallurgical industry in China has heavy iron and light materials, despite the fact that the three-point smelting seven-point material, the principle of fine material is understood by everyone in the industry, it is very rare to place the fine material in an important position. Iron production increased, energy consumption increased, and total costs increased. When we talk about efficiency, we talk about the factors of profit reduction. We don't say what kind of real work we do for energy conservation and consumption reduction. In fact, there was a lot of energy saving and consumption reduction work before the iron. A few examples are as follows.
Example 1: The low grade of domestic furnaces In addition to Baosteel, the status of low-grade stoves is generally present, which is one of the reasons why China's steel energy consumption is higher than in developed countries. Each industry in the industry does not guide the mining industry to go to high grades, but encourages the proliferation of low-grade ore mines. Because everybody is robbing the ore, the miner is not a fool, and there is no conscience for mixing sand in Miri. Why the demand for fine ore is so great, because of the large sintering production capacity, most of them do not use small ball sintering and fuel separation technology, only rely on the amount of fine ore, improve the grade only spend high prices with imported or increase the proportion of sintered concentrate, improve fine The reduction of the mine's specific capacity will not guarantee the use of blast furnaces. Even more short-sighted people do not use the new technology of sintering, sintering, fuel, and energy-saving technologies to sinter new grades. Some people may say that the market cannot be controlled, but there is nothing that can be done to lower the grade of the furnace through their own hands. Many units consciously or unconsciously regard the addition of waste materials to the sintering system as a resource conservation and environmental protection. However, the high energy-consuming and high-emission pollution caused by this has not been questioned. If these rubbish materials are selected using a sorting technology that is not too difficult, then adding a sintered system will not only improve the quality but also save resources. The by-products can be used for the production of masonry blocks, ceramic grains and wall and floor tiles. What will it be? effect.
Example 2: Why did you not return to the mine and why the original fuel Gaoshui New Pellet was not built in the mine? Why did you not learn Baosteel? Why did Baosteel not build the pellet plant in Shanghai and build it in Zhanjiang? One possibility was to use the land price difference between the two places. Second, it is possible to measure the water consumption of a unloading of a concentrate or a pellet with a load of 10% or more. Due to heavy iron light materials and land construction costs and other reasons, most of the manufacturers' material yards are incomplete, resulting in ineffective dumping or even negative effects. The most typical negative effect is the loss of sinters, which are hard to lose money. Insiders know that the sinters are returned to the mine one week after the open-air landing. However, the author's unit is to engage in sinter landing. When there are no pellets, they will not say anything. Is it not a lot of work for you to have a pellet to engage in slag? It may be to satisfy an expert's requirement for a sinter with a 7:3 pellet ratio. I don't know how 100% of the American pellet iron is iron-making. The technical content may be quite difficult.
I spent 2/3 of the time in the industry in 35 years working as a player. After I retired, I flipped through the previous data and found some problems. I proposed to discuss with my colleagues. Although the domestic pellets have developed rapidly in recent years, energy saving is still insufficient, which is related to the misleading of superiors. The seventh conference of the National Pellet Technology Coordination Group took the large-scale development of pelletizing equipment as the direction. The former State Metallurgical Bureau’s “10th Five-Year Plan†and “Guide to the Development of Metallurgical Science and Technology†has added one of the three pellets to improve the fineness of concentrates. . The above two items are misleading. The large-scale equipment is large with belt machines, but belt machines have large investment, low utilization of cooling heat, high equipment failure rate, hot air to reduce dust treatment to reduce wind temperature, no dust reduction pipeline wear, fan impeller impact mud balance and high temperature environment energy Is it stable and long-term operation? The belt machine has low utilization of the number of turns and the value of the input-output imbalance is of general value. The grate rotary kiln also has lower heat utilization than the belt machine. Although the investment is smaller than the belt machine, the number of turns is higher than that of the belt machine, but the problem of knot ring is difficult to avoid, and the material plate, chute, and back Hot air blowers are also high failure points. The shaft furnace investment is small, the thermal efficiency is high, the single furnace output is low, the fan is basically a cold and dustless operation, the failure is relatively low, but the life of the toothed roller and the large water beam is not too long, despite the fact that it uses the same number of turns as the general chain. The rotary kiln is almost the same as the rotary kiln, but the charge is too long in the furnace to avoid caking. Looking at several processes, it is still worthwhile for the shaft furnace. We may wish to learn from our American counterparts. One plant will have 24 shaft furnaces, and the output will not go up. There is also a benefit that belt machines and grate machines will be used in general. Manufacturers will not build a group, once the fault may affect the use of blast furnace materials, and the shaft furnace group can be avoided. The shaft furnace is also suitable for construction in small and medium-sized mines. After the mine was completed, the service life of the shaft furnace was almost the same. Equipment scrap was withdrawn, and the refurbished mines were reforested. No matter which of the above process utilization factors, the Chinese pellets have the potential to be tapped. In the 1981 translation of “Crystal Process and Equipment†published by the Metallurgical Industry Press, the “Cylinder Process and Equipment†introduced in the ring roasting method was used for a total of 22 minutes: 5 minutes of drying, 2 minutes of preheating, 5 minutes of roasting, and 3 minutes of soaking. Cool for 7 minutes. If our investors, designers, and pelletists all use 22 minutes as their goal, how high the utilization factor will be and how much energy cost will be reduced. The coefficient of utilization of the rotary kiln 11 of the new cast pipe chain rake machine and the utilization factor of the Xiangtan shaft furnace 8 should be the direction of everyone's efforts. Whether the mill is worth promoting, the mill is an electric tiger, the steel ball lining material consumption is large, -200 mesh can not increase a few percentage points, the crude material how you knead is also limited to the increase of plasticity. Not long ago, there was a piece of "influence factors of the ball burst temperature and ways to improve" in the text "Runmo lower burst temperature of 100 degrees, high-pressure roller mill and run mill to reduce the burst temperature of more than 100 degrees" argument. The reason is simple: the raw material has a low porosity and the capillary (water vapor channel) becomes smaller. Of course, it is beneficial to grind the raw material to improve the balliness of raw materials that are coarse and have a spherical shape (barium sulfate). The raw material conditions are not bad and do not require grinding. After all, they consume too much electricity. The National Pellet Technology Coordination Group meeting is held every year, but there is no consensus on the compressive strength of an important indicator of energy conservation and emission reduction. The requirement for the compressive strength of the finished ball for the Chinese translation of “Crystal Technology and Equipment†is that it has the strength to not break at least during transportation and charging of blast furnaces. The requirements for the compressive strength of finished balls in "Blast Furnace Ironmaking Production" published by Metallurgical Industry Press in 1989 are: Generally, the compressive strength of each ball greater than 100 kg can meet the requirements of blast furnace smelting. At that time, the utilization factor of the blast furnace was about 1.5, and with the height of blast furnace smelting strength and utilization factor, the excessively high cold compressive strength of the finished pellets did not make much sense because the pellets fed into the blast furnace were within a short period of time. When entering a high-temperature melt zone, what is the use of excessive compressive strength? The measures to improve the compressive strength of the finished ball (increasing the fineness of raw materials, prolonging the holding time at high temperatures, and slowing down the cooling rate) are both energy-consuming. The use of a high number of turns in the newly cast pipe-sweeping rotary kiln has a direct bearing on the compressive strength of its 1500 N/ball. In order to achieve the goal of energy-saving and emission-reduction, it is recommended that the industry provide carbon offset penalty for the waste energy behavior with the pellet strength exceeding 2000N/ball.
Based on the experience and the 22-minute concept, the author has two ideas for retrofitting the shaft furnace, which is proposed to investors, designers and peers for reference. Idea #1: Change the SP shaft furnace to a one-step carbon-based direct reduction furnace. The premise is that the raw ball is equipped with reduced coal and the outer roll is 1-2mm of baked coal. The order of renovation is (1). Add a suction crucible in the top of the furnace flue, extract the top of the exhaust gas, deacidification and pressure after cooling wash, used for tooth roller and discharge port seal. (2) Cancel the combustion chamber, and the fire crossing will help the burning of wind. Control the amount of combustion air to regulate the roasting temperature. (3) Change the combustion chamber with pressurized gas to the cooling duct, cool the sponge iron with gas, and cancel the cooling fan. (4) The waist of the shaft furnace is enlarged below the Dashuiliang beam, which resembles a trophy cup. The natural stack angle of the pellets is used to form a triangular cavity, and the open hole at the top of the cavity is used to facilitate cooling gas discharge. The discharged hot gas is washed and cooled to remove acid and return to the gas. If gasifiers are used for gas generation, gas cabinets should be used for recycling gas. (Note: The cooling gas pressure should be lower than the sealing pressure to prevent it from leaking out). The cooling gas system should have nitrogen input and discharge systems to facilitate the cooling and system replacement of sponge iron in the initial stage of the furnace opening and shutdown (5) to move the combustion chamber to the two ends of the air guide wall. Dry bed heating, until the hot sponge iron began to gas cooling, the 20% of the hot cooling gas derived from the guide wall to reach the burning nozzle to close the burner gas, only through the combustion air, also by controlling the amount of air to adjust Drying temperature. After the above several transformations can be produced, the oxidizing atmosphere above the shaft furnace fire exit, below the fire crossing is a reducing atmosphere, external rolling coal to provide the required heat for the reduction and to prevent oxygen penetration into the ball, with coal and Cooling gas involved in the reduction reaction. Due to the close contact of carbon with the mine, the reduction reaction is likely to occur under high temperature conditions. In addition, the SP shaft furnace pellets have a very long holding time in the furnace, enough for the reduction of the pellets and cooling of the sponge iron. The second idea: three shale oxidation roasting shaft furnace, the first turn, single slope drying bed turned to the roasting tank (5m × 0.6m × 2m), such as the use of two large and medium-sized special-shaped firebricks to build arched beams to ensure that the bottom along the basic Neatly arch-free arcs, without the use of large steel beams, the following arches will form the middle of the material, and the materials will be slow on both sides. The second turn, from the roasting tank to the cooling bed, the cooling bed air guiding room is in communication with the drying bed, the cooling waste heat is all used for drying, if the cooling air can not meet the drying air temperature, can be in the appropriate position of the roasting tank at both ends of the air guiding room Add burners. The third turn, from the cooling bed to the aggregate trough, pay attention to the receiving section not to close the mouth too fast, the same is to avoid the middle of the material to feed on both sides of the fast. The green balls are dried, preheated, roasted, soaked, and cooled throughout the three cycles. Since the height of the roasting tank limits the time for the high temperature of the pellets, the steel rods for the slight sticking blocks are processed, so the toothed rollers are removed. The advantages of the three-kiosks are: (1) The fabric belt does not have to be run in the hood, and (2) the drying bed has the possibility of expanding the area. (3) Shorter roasting time and energy saving. (4) The cooling wind is distributed uniformly under the bed to reduce the edge effect, and the wind utilization and cooling effects are better than the column cooling. The shortfall is also obvious. The single furnace output is low because it is exactly half of the SP shaft furnace. The SP shaft furnace is divided into two tooth rollers and a cooling bed from the dry bed ridge.
China is a big steel country and not a strong steel country. The national “Eleventh Five-Year Plan†aims to reduce energy consumption per unit of GDP by 20% on the basis of the “Tenth Five-Year Planâ€. The metallurgical industry bears the brunt of energy-saving and emission reduction.