Practical research on optimizing inventory and reducing cost of blast furnace

　　Abstract: the first phase project of Rizhao Co., Ltd. of Shandong Iron and Steel Group has a designed sinter capacity of 11.172 million tons. The iron containing raw materials for sintering are 100% imported ores every year, of which the number of Changxie ores accounts for about 60%. The quality of Changxie ore is more stable and the quantity is more guaranteed. In terms of stabilizing the quality of sintering mix, the use of Changxie ore proportioning is much better than that of trade ore. However, using Changxie mine also has disadvantages, such as the annual consumption must be large and guaranteed, and the whole ship loading and unloading will lead to a sharp increase in inventory, poor flexibility of changing materials, etc. Therefore, an appropriate proportion of Changxie ore and trade ore can not only ensure the quality of sintering mixture, but also effectively reduce the total inventory of stockyard, save money and stabilize production. This paper mainly studies the optimization of mineral material inventory structure, and makes full use of the respective characteristics of Changxie mine and trade mine, so as to achieve the purpose of reducing mineral material inventory and cost, ensuring the reasonable and stable production of inventory structure, and ensuring the quality of sintered minerals.

　　Key words: ore blending team, long association ore, trade ore, inventory structure, ore blending structure

　　1. Foreword

　　Rizhao Co., Ltd. of Shandong Iron and Steel Group currently has two 500m2 sintering machines and a 1.5 million ton grate rotary kiln, which have been successfully put into production. According to the statistics of last year's average output, under normal production conditions, hundreds of thousands of tons of iron containing raw materials are stored in the stockyard at a time, hundreds of thousands of tons of iron containing raw materials are stored in the comprehensive stockyard, hundreds of thousands of tons of iron containing raw materials are stored in port and in transit, and the total stock of the total stock is about 1.5 million tons (including the stock of lump ore for blast furnace). At present, the monthly consumption of iron containing raw materials for sintering is about 700000 tons, and the monthly consumption of iron containing raw materials for pelletizing is more than 100000 tons. The stockyard of Rizhao company of Shandong Iron and Steel Co., Ltd. is very close to Lanshan Port and Rizhao Port Wharf, especially Lanshan Port Wharf. If the pipe belt conveyor is normally transported, it can arrive at the factory as soon as more than ten minutes. The unique geographical location has created good conditions for us to reduce raw material inventory and improve the utilization rate of capital turnover. The main purpose of this paper is to give full play to the existing process equipment, human resources and geographical advantages, further optimize and reduce the total inventory of mineral materials, and improve the utilization rate of capital turnover.

　　2. Specific measures to optimize inventory

　　2.1 establish ore blending team

　　From the marketing department, production department, finance department, ironmaking department, international trade and other units, select some backbone personnel who are familiar with the business to form a batching team. According to the production and quality requirements of the final product, including chemical composition control, output control, and comprehensive consideration of physical performance quality and ore cost and other factors, formulate the sintering and pellet proportioning structure plan from the source, carry out raw material procurement according to this, and regularly hold relevant meetings to promote and implement the actual proportioning structure of sintering pellets.

　　2.2 stable raw material proportioning structure

　　Shandong Iron and Steel Group Rizhao Co., Ltd. has two 5100m3 blast furnaces, with a daily output of more than 20000 tons of molten iron. According to the current burden structure, the daily demand for qualified sinter is more than 20000 tons and pellet is about 5000 tons. In order to ensure the stable and smooth operation of the blast furnace, the quality of sintered minerals must meet the requirements, and the stable sintering mix proportioning structure is the basic condition for the stable quality of sintered minerals. The raw material structure of the sintering mix is stable, the moisture content, particle size and chemical composition of the mix are relatively stable, and the sintering production process parameters are relatively stable, so the quality of the sintering mineral is also stable. In addition, the structure of sintering raw materials has been stabilized, and the daily and monthly consumption of various ferrous raw materials for sintering has remained relatively stable, so that we can calculate the specific cutting time of various mineral materials in time according to the existing inventory. As long as the next batch of materials can arrive at the stockyard in advance before the specific cutting time node, we can meet the production demand, which also creates conditions for us to provide a more accurate material consumption plan.

　　2.3 stable or solidified raw material varieties

　　The same or similar types of raw materials are conducive to the fixed location management of the primary stockyard and improve the stacking capacity and stacking efficiency. The same variety of iron ore powder from different ships can be mixed because of their close physical and chemical properties. At the same time, the long-term use of raw materials with the same properties is also conducive to the stability and improvement of the quality of sintered minerals.

　　2.4 stabilize the production order of the comprehensive stockyard

　　At present, our comprehensive stockyard has two blending sites, each with a stacking capacity of about 250000 tons. During normal production, one is used for batching and the other for production. The production pace is stable, and the stockpile is replaced every 10 days on average, and the stockpile is closed about 1 day in advance before the pile change. That is, the batching time of each pile is about 9 days, and the production time is about 10 days. Since the ore blending structure has been predicted in advance according to the batching plan, and the actual demand for various raw materials for each pile is very clear, we can analyze and predict in advance the possible material shortage and disconnection accidents in the production process of unloading or even unloading mixing materials, and prevent them in advance to avoid the production accident of shutdown due to material interruption.

　　2.5 optimize the loading volume of Changxie mine

　　According to the different proportion of each mineral aggregate in the mixed material, combined with the normal loading volume of the mining company where the mineral aggregate is located, the actual loading volume of each mineral aggregate is optimized. For example, Australian crude series iron ore powder No. 1 Australian mine, mining companies can load 110000 tons of small boats, or 170000 tons or 200000 tons of large ships. If our current actual consumption of No. 1 Australian mine is 100000 tons / month, it usually takes 12 to 15 days from loading port to unloading port. If we only consider the stability of materials, we can ship 110000 ton small ships every month, 170000 ton large ships every five months, and 200000 ton large ships every two months. The above three methods seem to have no problems in terms of production stability, but from the perspective of reasonable inventory, the first method is significantly better than the latter two methods. In addition, the smaller the shipment volume, the better. We also have to comprehensively consider the shipment period of different mines, the procurement period and the risk of delay due to storms during maritime transportation. If our current actual consumption of Brazilian mine 1 is also 100000 tons / month, the loading volume of Brazilian mine 1 to Brazilian mine 1 is generally 140000 tons, 170000 tons, 220000 tons and 300000 tons, and the loading port to unloading port of Brazilian mine 1 generally ranges from 43 to 50 days. Considering the unique sintering performance of No. 1 Brazilian ore, it is not easy to replace it with other materials, and it is not convenient to buy it at any time, we will generally consider purchasing a 170000 ton ship, and when it is used continuously, we will appropriately make the inventory a little more surplus to ensure that there is no risk of material breakage. In this way, factors such as the usage of each mineral material, the port trade mineral volume, and the transportation connection risk are comprehensively considered, and the shipping volume of each mineral material is comprehensively determined, which can not only ensure the stable and smooth production, but also reduce the total inventory and improve the utilization rate of funds.

　　2.6 optimize inventory through reallocation

　　Our usage of each raw material varies according to the change of ore blending structure. For some single materials with relatively small proportion, for example, the monthly sales volume is maintained at about 40000 tons. When purchasing Changxie mine, even if we choose the minimum shipment of 100000 tons each time, the production can be maintained for two and a half months (75 days) after feeding. According to our production experience, the inventory condition of each material to ensure stable production is generally 30 to 40 days. In order to improve the utilization rate of funds, in this case, we can consider exporting the material consumption for 20-30 days through internal adjustment (sharing a ship mine with Laigang) or external secondment, so as to recover funds and reduce inventory.

　　There is another case. For example, we know through calculation that the on-site inventory of an Australian mine can only be used for 5 days, and the next captain will assist the mine. It is estimated that the mineral powder will not arrive in Hong Kong until a week later due to maritime transportation delays and other reasons. At this time, we can also consider purchasing the consumption of about 10 days from the port through the normal market trade of Shangang international trade, so as to ensure the stable production and normal continuity of the mineral powder.

　　2.7 adjust the inventory appropriately according to the fluctuation of iron ore price

　　Optimizing inventory does not always reduce inventory. When the iron ore price is at a low point, the procurement cost is greatly reduced. At this time, the inventory procurement volume can be appropriately increased according to the location of goods in the plant and the amount of working capital, so as to obtain the price difference benefit of iron ore price increase in the future.

　　3. Conclusion

　　Through the practice of sintering proportioning structure and the exploration of iron ore market, we have summarized the following conclusions in optimizing inventory:

　　(1) Optimizing inventory should be carried out on the premise of ensuring the quality of sintered minerals. The premise of stable quality of sintered minerals is that the proportioning structure of sintering mixture is relatively stable and the type of iron ore powder used for sintering is relatively stable.

　　(2) Optimizing inventory can be carried out in parallel by adjusting the shipment volume of Changxie mine and appropriate procurement, internal coordination or external secondment of trade mines, but the premise is to ensure the safety inventory of various mineral materials for 20 to 40 days, and ensure that there is no shortage of materials and materials in the mixing production line.

　　(3) Optimizing inventory should fully combine the geographical advantages of the unit. Mineral materials that are easy to purchase and transport can appropriately reduce the on-site inventory; Mineral materials with high grade, high proportion and less trade volume cannot be blindly reduced in inventory.

　　(4) Optimizing the inventory does not mean that it will never rise. In the trough of the iron ore market, the price of iron ore is relatively low. At this time, the stock in the factory can be appropriately increased according to the actual situation, so as to obtain the benefit of iron ore price difference while reducing the purchase cost.