Structure Internal Force Analysis Of The Circular Coal Yard

With the development of domestic and international economic and the enhancement of the awareness of environmental protection and environmental requirements of governments, thermal power plant coal handling system applying this new design concept-closed circular coal yard more and more. It has a lot of advantage-especially when applied in coastal power plant, such as smaller occupancy of area, larger amount of coal storage, higher degree of automation, easier of coal blending, safer and more reliable operation, less pollution to the environment, smaller coal loss and better landscape compared with the traditional way of coal storage of bucket wheel machine in open air and dry coal shed. Since high cost of the closed circular coal yard is the main factor that restricts the promotion of this structure, it becomes the main research direction to save the cost of construction and reduce the cost. The arrangement of process and the selection of equipment and structure should be mainly considered to solve the problem fundamentally. The selection of structure requires reasonable optimization of the internal force analysis. Only applying the most economical and reasonable structure can contribute more to the promotion and application of the closed circular coal yard in the thermal power plant today.The optimized monolithic coal bulkhead structure is mainly constituted by the coal bulkhead, the ring beam on top and bottom, and it’s different from the coal yard of large diameter with counterfort columns style. To make full use of the coal pressure assumed by circumferential reinforcing steel bar in warehouse wall, the horizontal thrust and temperature stress generated by the upper roof truss structure, no vertical temperature seam is set along the ring of silo wall. In this way we can reduce the cross section area of the silo wall effectively, save footprint and reduce cost. It has the advantages such as good integrity, convenient construction, lower project cost and so on, but the force condition is complicated.To analysis mechanical characteristics of the structure, the article take the China Power’s Investment in Dalian ganjingzi Thermal Power Plant (2×300MW) for example. Dalian ganjingzi Thermal Power Plant has a circular coal yard, whose diameter is100m.The coal bulkhead is17m high, the lower part of the silo wall is1000mm thick, the upper part of the silo wall is700mm thick, the inside of the silo wall is made of concrete block to insulate heat. The thickness of the silo wall changes according to the linear rule from top to bottom, the inside is vertical while the outside is inclined. The biggest pile of the coal is31.88m high, pile over the coal bulkhead is16m high, it’s38degrees between the coal pile edge line and the horizontal line. We analysis with the MIDAS finite element software in natural foundations case, and obtained different internal force distribution of the wall of coal storage yard, the top ring beam and the bottom ring beam in conditions of the full warehouse coal, half warehouse coal, temperature ranges with season and temperature ranges inside and outside the warehouse. In this way we got the mechanical characteristics of coal storage yard and thus got the most adverse combinations of condition load. This follows what we got by analysising with MIDAS finite element software.We conclude from the stress cloud and the deformation of full warehouse coal and half warehouse coal:the maximum stress occurs at the bottom of the warehouse wall. The top ring beam and bottom ring beam have a great hoop effect on the warehouse wall. The max deformation occurs at the upper part in the middle of the warehouse wall and the stress decreases from the bottom to the top. There is a stress mutation in the hole corner when it’s a300degrees coal pile. We suspect that the warehouse wall is weaken and there’s a stress concentration in the hole corner. We can reinforce the hole corner with ribs to resist stress mutation. It makes no difference to the hole corner when the coal is piled at240and120degrees horizontally. By analysising the stress cloud of240and120degrees coal pile, we found that warehouse wall with no coal pile area constrains coal pile area obviously, the constrains shows structure features of tension force of the ring reinforcement in concrete warehouse wall and the warehouse wall itself.We can conclude from the stress cloud and the deformation of temperature in conditions of full warehouse coal and half warehouse coal, that the stress cloud of the warehouse wall continuous with no obvious stress mutation. The maximun stress inside the warehouse wall occurs at the bottom, and stress in the inner surface of the warehouse wall decreases from bottom to top; The maximun stress outside the warehouse wall occurs in the middle, and stress in the outside surface of the warehouse wall increases from bottom to the middle part, then starts decreasing after the middle peak. The top ring beam and bottom ring beam have a great hoop effect on the warehouse wall. The max deformation occurs at the upper part in the middle of the warehouse wall and the stress decreases from the bottom to the top.We can conclude from the stress cloud and the deformation of temperature in conditions of temperature ranges with season, that the stress cloud of the warehouse wall continuous with no obvious stress mutation. The maximun stress occurs at the bottom. The bottom ring beam has a great hoop effect on the warehouse wall. The max deformation occurs at the upper part in the middle of the warehouse wall and the stress decreases from the bottom to the top.Due to the unique geological conditions of the project, the basis of the bottom ring beam constraints the coal bulkhead, the bottom ring beam and the rock around are casted integrally to make sure the wall and the foundation formed integrally, it makes full use of the rock and bottom ring beam build-in effect on the concrete coal bulkhead, and can reduce cross section area of coal bulkhead foundation (bottom ring beam),thus lower the cost.