## 3 Methodology
### Discussion
As shown in Table 7, the construction of coal storage and distribution bases reduces the inventory costs in the radiating coal consumption places by concentrating inventories in the coal consumption places in coal storage and distribution bases and then transporting them to the coal consumption places in small batches through small running trains according to the consumption rate in the coal consumption places so as to reduce the inventory costs in the coal consumption places. Due to the scale effect, although the transport distance and the cost of transport to the coal storage and distribution base increase, the inventory cost saved by storing at the coal storage and distribution base exceeds the increased transport cost, the total cost being reduced by 5.9% and the inventory cost by 5.2%. As shown in Figures 7 and 8, when coal storage and distribution bases are not considered, the coal-consuming places hold higher inventories of between 1000 tons and 6000 tons to prevent shortages which could affect production. When considering coal storage and distribution bases, when a coal storage and distribution base and a coal consumption place are relatively close, the time for transporting coal is more flexible using roads and a coal consumption place can hold a lower inventory of 1000 tons to 3000 tons and transfer the inventory to the coal storage and distribution base. For coal consumption places to hold smaller inventories, in real-life production, there needs to be a high degree of information transfer, production, transportation, and sales integration to overcome information barriers  
Comparison of whether or not to refine time comparisons  
There are many problems in the existing coal transport system, such as when a coal source produces a sufficient amount of coal that is directly transported by rail without lean management, resulting in the accumulation of inventory in the coal consumption place, so this paper refines the study of the coal transfer program. The research period for the transport link is 15 min, and the rate of coal consumption by a power plant and a coal chemical plant within the enterprise is stable and continuous. The study period for the coal consumption link is 1 h, which can not only meet the coal demand of the coal consumption place on time but also achieve a balance between transport cost and inventory cost. At present, most of the studies on coal transfer schemes containing time factors are planned according to days and cycles; the consideration of storage, transport, and demand links with time factors is rougher, with an insufficient degree of refined management; and inventories of coal consumption places are expressed through demand intervals. This paper will compare these two optimization methods. If the coal transfer scheme is not refined, the demand for a coal consumption place is treated as a daily demand interval, and a two-day demand for coal consumption place is combined, as shown in Table 8.  
The demand of each coal consumption place is expressed in intervals, and the coal arrival time is restricted to a desired time window, with no penalty for coal shipped within the time window, an early-arrival penalty for coal arriving earlier than the interval, and a late-arrival penalty for coal arriving later than the interval. The supply capacity of each coal source is combined with each coal consumer to obtain the alternative set of supply-demand matchings, the path with the minimum cost for each OD pair in a day is obtained, and whether or not \(k\) batches of coal are shipped at the minimum total cost is determined, as shown in Table 9.