How to Select Appropriate Equipment and Flow Design for A 5000 T/d Limestone Aggregate Production Line

A gravel aggregate production line mainly consists of coarse crushing and mud removing system, fine crushing system, screening system, sand making system(optional), storing, delivering and transporting system, dust removing and washing system, laboratories and electromechanical maintenance. This article is going to introduce technical points of the cement plant’s use of its own limestone mine to build an aggregate production line whose production capacity is 5 thousand tons.

The previous limestone crushing production line

The previous limestone crushing system of the cement plant includes a heavy plate feeder, a roll crusher and a hammer crusher, whose overall crushing capacity is 900-1100 t/h.

The main points of building a gravel aggregate production line

I. The proposal of crushing equipment

• A jaw crusher and an impact crusher
• A jaw crusher, a cone crusher and a shaping machine
• A hammer crusher and an impact crusher

The hammer crusher, used for the limestone crushing production line, has been designed and put in use. However, it also needs to update it and add the aggregate production line into a crushing system with two production lines. Therefore, the gravel aggregate production line adopts the third proposal, that is, a hammer crusher and an impact crusher.

The gap between the grates of the heavy hammer crusher is widened to ensure the particle size remain no higher than 90mm, which not only satisfies the requirements for high content of powder and of fine aggregate in the raw material in the cement clinker production line, but also enables excellent aggregate shapes and continuous grading after the impact crusher crushes relative large limestone. This act helps manufacturers get high-quality sand and gravel aggregate, and also reduces power consumption of raw material grinding in the cement production line.

In general, the5000 t/d clinker production line consumes about 6600 tons of limestone. In light of the capacity of the limestone crushing system, the machine runs for 14 hours in two shifts every day. After 310 days, the aggregate production line whose capacity is 2,000,000 tons per year can be perfectly achieved.

II. The main equipment and process flow

See table 1 for the data of the third proposal used in the sandstone aggregate production line matched with the construction of self-owned limestone mine.

Table 1 The Data of The Proposal of The Hammer Crusher and The Impact Crusher

Workshop	Capacity	quantity	installed capacity/KW
Coarse Crushing and Mud Removing System	Heavy Plate feeder：800-1200 t/h	1	75
	Roll feeder：800-1200t/h	1	45
	Single-stage Hammer crusher：900t/h	1	900
Fine Crushing System	Impact crusher：800-900t/h	1	900
Primary Screening	Double-layer vibrating screen：1000t/h	1	2x37
Secondary Screening	Double-layer vibrating screen：900t/h	1	2x37
Tertial Screening	Single-layer vibrating screen：200t/h	2	45
Powder Separating	V-shaped separator ：250t/h	1

III. The process flow of sand and gravel aggregate production line

Coarse Crushing and Desilting System

It adopts the same equipment as the previous limestone crushing production line.

A workshop for primary screening

The workshop for the primary screening is located in the aggregate manufacturing factory. The material crushed by the hammer crusher is sent to this workshop via the belt conveyor. It is equipped with a double-layer vibrating screen whose capacity is 1000 t/h, with an upper sieving mesh whose side length is 42mm and a lower mesh of 22mmm.

• The materials whose size is more than 40mm are sent to the aggregate fine crushing system;
• Those whose size is 20-40mm are directly transported to the aggregate warehouse or to the pre-homogenized limestone yard of the cement production line.
• Those in a size of less than 2mm are sent into the pre-homogenized limestone yard via the belt conveyor.

The fine crushing system

An impact crusher is used in the artificial aggregate crushing workshop in the factory. Those material in the size of more than 40mm from the screening workshop are crushed in the impact crusher whose feeding size is no more than 100mm and discharging size no more than 40mm.the hammer crusher can crush about 800 tons of stone per hour and 90% of the crushed product is in the size of no more than 31.5mm. After that, the crushed materials are sent to the secondary screening workshop by the belt conveyor or to the pre-homogenized limestone yard of cement production line through the belt conveyor after the artificial aggregate production line is temporarily stopped.

A workshop for secondary screening

This workshop is situated in the aggregate production plant.The material crushed by the impact crusher is sent to this workshop through the belt conveyor. A double-layer vibrating screen is installed in the workshop, with an upper screen mesh of square hole 32mm×32mm, a lower screen mesh of 16mm×16mm and the processing capacity of 900 t/h.

• The limestone whose size is more than 31.5mm is transported to the aggregate fine crushing system;
• The limestone in a size of 15-31.5mm is directly sent to the warehouse for aggregate product;
• The limestone whose size is less than 15mm is transported to the tertial screening workshop by the belt conveyor.

A workshop for tertial screening

This workshop is situated in the aggregate production plant. The material is transported from the secondary screening workshop to the tertial one by the belt conveyor. There are two single-layer screen meshes installed in the workshop with the capacity of about 200 t/h and a long hole whose size is 3.6mm×120mm.

• The limestone whose size is 5-15mm is directly sent into the aggregate product warehouse;
• The limestone whose size is less than 5mm is transported into the V-shaped classifier by the belt conveyor. After sorting, the aggregate is sent into the warehouse and the powder into the powder warehouse.

The storage,delievery and transportation of finished products

The list of finished products warehouse is exhibited in table 2.

Size	Specification	Storage/t	Number
20-40mm	12m*30m	3000	1
15-31.5mm	12m*30m	3000	1
5-15mm	12m*30m	3000	1
0-5mm	12m*30m	3000	1

Each warehouse is equipped with a car bulk whose capacity is 300 t/h. In addition, a dehumidifier is installed at the warehouse for finished products in a size of 0-5mm to reduce dust and to ensure high-quality artificial sand and. The warehouse of 5-15mm is equipped with belt conveyors which can directly send the aggregate of 5-15mm to the pre-homogenized limestone yard of the cement production line.

IV. The proportion of finished products and the production capacity

Adopt the proposal of a heavy hammer crusher plus an impact crusher in the sandstone aggregate production line of the own limestone mine; the percentage of products and the production capacity except sand making are shown in table 3.

Product	used for cement (＜50mm)	Stone Powder	0-5mm	5-15mm	15-31.5mm	20-40mm
Percentage/%	45.8	4.2	12.5	8.25	21	8.25
Capacity(t/h)	550	50	150	100	250	100

Nowadays some large cement manufacturing enterprises have adopted this process flow described above to produce premier-quality aggregate from their own limestone mines. However, given the manufacturing equipment varies with the mineral components and structure of processing rocks, finished products will also vary in particle sizes, shapes and the content of stone powder. Not to mention limestone in different mines has different physical features and diagenesis conditions. Hence not all factories are suitable for this process flow.