Granite is a common hard rock. Taking granite as an example, this paper introduces seven aspects of the production line planning, process design, equipment configuration, and environmental protection of granite sand making plant with an annual output of 3 million tons. For other hard rocks that are harder to break, such as basalt, diabase, andesite, etc. , also can be used for reference.
Raw material
Suitable raw materials for processing manufactured sand are mainly granite, limestone and other mountain-type raw materials, mainly pebbles and other river-type raw material. There are a variety of industrial waste slag-based tailings-type raw materials. In line with the principle of comprehensive utilization of resources and local policy, the selection of raw materials for sand production varies from place to place.
In this case, granite is used as raw material for processing machine sand. The requirements for selecting a mine are shallow overburden, good quality, large mineral reserves and convenient transportation.
Scale
New mines have a capital construction period of one year or so, in general. The blasting mining area is not large in the first two years of mining. And the stone materials that can be mined out are limited. After two years, as the mining area becomes larger, the mining scale also becomes larger. Therefore, in the two years before mining, control the annual production of sand 1 million ton, annual production of crushed stone 1 million ton. 2 years later adjusted to the annual production of sand 2 million ton, annual production of crushed stone 1 million ton.
Classification
Products are mainly located in construction stone and construction sand.
The Standard of building stone mainly has 0 ~ 5 mm, 5 ~ 10 mm, 10 ~ 31.5 mm, 31.5 ~ 60 mm.
The specifications of architectural sand mainly include class I and Class II sand of 0ー4.5 mm.
According to the market demand, the raw stone with particle size less than 800 mm and the stone powder with particle size less than 0.075 mm also can be provided.
Method
At present, the sand making process is mainly composed of the dry and wet mode of production. And there is also a “wet first, then semi-dry” semi-dry process. Combined with the local environmental requirements, the project selection of dry production process.
Granite sand making plant layout
According to the characteristics of granite, the technological process is designed as four-stage crushing. Primary crushing, medium crushing, fine crushing and sand-making. In order to meet the demand of aggregate for concrete of various gradation ratio, the primary crushing is open-circuit production with declining facilities reserved, and the medium crushing, fine crushing and sand-making are combined with the corresponding screening workshop to form a closed-circuit production process.
(1) Mining and road open up
Combined with the actual situation of the mine, the way of mine open up chooses internal highway development and automobile transportation. The total length of the highway trunk line is about 1800m, the ore is transported to the unloading platform of crushing workshop.
(2) Primary crushing
Less than 800mm of raw materials by car transport into the unloading pit, with a vibrating screen device feeder transport. Materials that smaller than 150mm don’t need to be broken which directly fall on the belt into the primary yard. The material that larger than 150mm is crushed by jaw crusher (150mm discharge opening), and the crushed material enters the primary storage yard.
(3) Medium-break system and sieving
The medium-break system is relatively flexible. It can be separated from the primary crushing system by the intermediate material bank and run independently. Also can be directly connected with the primary broken system by the belt.
The system consists of one coarse cavity cone crusher machine and one fine cavity cone crusher in series. In fact, it should be called 2-break and 3-crushing. It can increase the output and reduce the power consumption when the material goes through the heavy-duty screen pre-screening before the second breaking. The medium break system and vibrating screen system have a dedusting device.
The materials less than 31.5 mm will be directly screened out into the conical discharge belt. Larger than 31.5 mm are put into a coarse cavity cone crusher, and after the screening, the materials larger than 31.5 mm are put into a fine cavity cone crusher for further crushing. After being crushed by two cone crushers, the mixed materials were screened by two three-layer circular vibrating screens. The materials with size less than 31.5 mm were screened by three sizes: 0 ~ 5 mm, 5 ~ 13 mm and 13 ~ 31.5 mm.
(4) Rubble storage
After the cone crusher equipment crushing and screening, 3 kinds of materials were transported to 3 round storages which 2500t through the belt.
(5) Crushed stone
The crushed stone is discharged from the bottom of the storage through the ARC valve into the belt and transported to detritus release depots.
(6) Screening of artificial sand and separation of stone powder
According to the arrangement of 4 sets of sand crusher. The main raw material for sand-making is 0 ~ 13 mm material from the front cone crusher breaking. And considers the sand-making effect should add a part of 13 ~ 31.5 mm material. The content of stone powder in the sand is about 5 %.
As a result of dry production, in order to reduce the distribution and transport links in the dust, sand need to spray water treatment in the loading process. The sand making plant, the vibrating screen system and the sorting system have dust removal devices.
The raw materials for sand making are mainly the mixture of 0 ~ 5 mm, 5 ~ 13 mm and part of 13 ~ 31.5 mm. After entering the sand making machine to be broken, the materials larger than 5 mm are transported through the belt into the three-layer vibrating sand screen machine. And returned to the sand making machine to continue to be broken (they can also be sold as fine stones). The remaining materials are divided into 3 ~ 5 mm and less than 3 mm materials. Materials less than 3mm are fed into the separator by belt conveyor to separate the stone powder and sand. The sand is mixed with the pre-screened 3 ~ 5 mm materials to produce the finished sand.
(7) Sand storage
The finished sand is transported to 2 finished product storages by belt conveyor. The stone powder is transported to one powder storages which can storages 2500t by elevator. Finished sand from the bottom of the sand storage through the ARC valve discharge into the belt conveying to 2300 ton sand release warehouse. After water spray treatment, release factory, stone powder through the cement bulk equipment release factory.
(8) Electrical control
The total installed capacity of the plant equipment is 6500kw, 0.4 kv equipment. Equipment is 3 types of electrical load, the rest do not set up security power.
One 10 KV substation is installed in the plant. 10 / 0.4 kv and 2000 KVA transformers are installed in the complex building that providing low-voltage power for medium crushing, sand-making, storage, distribution and water pump house, office building, etc. The primary crushing workshop is installed with 10 / 0.4 kv 630kVA transformer.
(9) Industrial television surveillance and automatic control
Remote video monitoring and automatic centralized control of the production line can effectively ensure a continuous production line. And reduce the number of operators, achieve energy-saving, cost-saving purposes, is the commonly used control method.
Main sand plant equipment
1. vibrating feeder
2. jaw crusher
3. heavy-duty vibrating screen
4. cone crusher
5. circular vibrating screen
6. Sand making machine
7. belt conveyor
Environmental issues
Due to the special requirements of environmental protection for the project. The use of dry process method of production has solved the problem of sewage treatment. But dry process production is easy to produce dust, solving the dust problem is the key.
1. Adding a high-pressure spraying system at the jaw crusher unloading pit and vibrating feeder to reduce dust;
(2) All equipment is operated in the closed factory building. The Belt Conveyor is equipped with dust-proof cover and dust-removing device at all dust-raising points, which can effectively solve dust and noise problems.
(3) Round storehouse is selected for material storage, and dust remover is arranged on the top of the storehouse, so the dust treatment is better.
(4) Spraying 5% water on the finished products (mainly sand) can effectively solve the dust problem during transportation and shipment
(5) the whole plant shall be set up according to the “provincial green mines” , with reasonable planning and large-scale planting of trees and lawns.
The granite sand making plant embodies the concept of “reliable, advanced, energy-saving and environmental protection”. The front and back systems of the production line link up smoothly, the general layout is reasonable and has good flexibility. The different specifications of crushed stone products can be separated. The dust and noise control very good. We hope to have a certain reference value to the colleague and the sand making enterprise.