Salt mining

    First, the type of salt mining ship and its choice

According to the working principle of the mining mechanism, the salt mining ship has the types of suction type, chain bucket type, shoveling type and grab type (Fig. 1). The salt lake solid deposit is covered by surface brine, or its crystal is filled with brine, which generally meets the requirements of mining process water. Therefore, the suction-type salt mining ship is often used to realize the mining and transportation of salt ore with water as the medium. According to the soft and hard layer of the mine, the suction type salt mining vessel uses different types of pine ore devices, such as reamer type, spiral ore type, chain gear type, wheel bucket type and hydraulic impulse type.

Figure 1 Schematic diagram of salt mining vessels of different mining agencies

A-sucking type; b-chain bucket type; c-shovel type; d-grab type

The work migration mode of salt mining vessels is pile type (step type) and anchor type (traction type). In recent years, salt mining vessels combined with floating and crawler walking have been developed in the mining of salt lakes.

When there is no pressurized water under the bottom of the ore layer, or if there is confined water but the water-repellent layer is thick, the deposit will not be damaged by the confined water top when mining, and the pile-type migration salt mining vessel can be selected; when the lower part of the ore layer is under pressure If the water is not allowed to be damaged by the bottom of the mine, an anchor-type migration or a crawler-type salt mining ship is used.

The suction-type salt mining ship is the most promising mining equipment for mining water-filled salt lake deposits. China, the Soviet Union, Israel, Jordan and other countries have accumulated valuable experience in mining salt lake solid deposits with salt mining vessels.

    Second, the mining process

(1) Process methods and their applicable conditions

There are four process options to choose from depending on the type of transportation equipment and the matching relationship with the salt mining vessel:

1. Mining salt mining - automobile transportation and mining technology;

2, extractive salt mining ship - the railway transport mining process;

3. Mining salt mining - pipeline transportation and mining technology;

4. Salt mining ship mining-barge transportation mining technology.

The automobile or railway transportation mining process is suitable for the dry salt lake, the surface of the mine is free of brine, flat and can carry transport vehicles. For example, the tea card salt lake uses the cutter suction type salt mining ship and the narrow rail railway transportation to cooperate with the mining of rock salt. Since the mining is continuous operation and the transportation is intermittent equipment, a dewatering loading vessel is installed next to the salt mining vessel, and the bucket elevator is used to load the mining vehicle.

The hydraulic pipeline or barge transport mining process is not limited by the presence or absence of brine and carrying capacity on the surface. The pipe can be laid on the surface of the ore and can also float on the surface of the water. Barge transportation is more adaptable. Salt mining vessels are available for excavation channels in the lake area. The development process itself is also a mining process. The Jordan Dead Sea Potash Project and the Chaerhan Salt Lake Potassium Salt Project in China, and the Yantian Carnallite Mine Mining are all combined with the mining process of salt mining vessels and pipeline transportation.

(2) Ship mining technology

When there is water on the surface of the ore and the water depth can meet the requirements of the hull draft, the salt mining vessel starts mining directly from the side of the mining area. In the dry salt lake, the ship's nest must be excavated on the side of the mining area, and the hull must be introduced into it, and moved while mining, until it is dug to the designed mining depth and put into normal production.

There are two methods for mining salt trees by mining salt and straight mining methods. The former is suitable for mining soft thin ore layers, straight forward, and full thickness at one time. The horizontal digging method is suitable for mining medium and thick ore bodies. It is divided into many strips along the length of the mining area, and the pile or main (tail) anchor is used as the swing center to realize the working migration of the hull.

The working method of the cross-cutting method has two types: the middle cut-in split double layer and the side cut-in split single layer. As shown in Fig. 2, it is a middle cut-in and two-layer mining operation mode. When the thickness of the ore layer is large and the reamer swings a few round trips to the bottom plate, in order to reduce the mining loss and ultra-deep mining, the thickness of the lowermost layer should be reduced, so that the bottom residual pillar is as small as possible.

Figure 2 Middle cut into two-layer mining track map

1- salt mining ship; 2- reaper position when dropping left steel pile; 3-water level surface; 4- reaping movement trajectory;

5- one round swing swing thickness; 6-layer thickness

As shown in Fig. 3, it is a side-cutting and single-layer mining operation mode. Its advantages are easy to operate and not easy to mess. The main disadvantage is the repeated excavation at the beginning and end.

Figure 3 Edge cut into single layer mining track map

1-position position of the reamer when the main pile is below; 2- center line of the mining belt; 3-water level surface;

4-layer thickness; 5-lower pile position

    Third, the main technical parameters

(1) The moving step of the pile-type migration salt mining ship

The pile type migration salt mining ship is a step forward movement, as shown in Fig. 4, and the moving step distance s is obtained by the formula (1).

Figure 4 shows the movement step

(1)

In the formula:

S-moving step, m.

The optimum value of the moving step is related to the mechanical properties of the ore layer and the structure of the reamer. If the reamer is at an angle of 45° to the horizontal and the length and diameter of the reamer are equal, then

(2)

The s value thus obtained is applicable to the mining of soft and dense deposits. However, the residual pillar with a height of h cannot be extracted and becomes a recovery loss.

(2) The main scale of the reamer

The main dimensions of the reamer are the diameter and length. The length L can be represented by the diameter d, L = ξd. Generally open reamer ξ≈ 1.0 ~ 1.3; closed reamer ξ≈ 0.7 ~ 1.0. The diameter of the reamer is determined by equation (3):

(3)

In the formula:

D-reamer diameter, m;

Q-knife cutting ability m ³ /h;

Θ-reaping swing gauge and traverse cable angle, θ=30～40°;

Η-efficiency;

v _m - reamer traverse speed, m / h;

K ₁ - the influence coefficient of the forward step, K ₁ = 0.3 to 1.0;

K ₂ - coefficient, taking K ₂ = 0.4 to 1.0.