PolyMet stock skyrockets on court decision over water permit

The allegations came from the Fond du Lac Band of Lake Superior Chippewa, WaterLegacy, Minnesota Center for Environmental Advocacy, Center for Biological Diversity and Friends of the Boundary Waters Wilderness.

They argued that the state agency “engaged in an unprecedented and deceptive campaign to keep U.S. Environmental Protection Agency’s (EPA) written comments on the draft PolyMet permit hidden from the public and the courts.”

“At no time did the MPCA try to discourage or prevent the EPA from submitting written comments on either the pre-proposed permit or the final permit,” judge John Guthmann wrote.

The district court’s conclusion will be incorporated into a broader challenge to the permit currently pending before the court of appeals.

In that case, environmental groups and the Fond du Lac Band have challenged the MPCA’s decision to issue the permit and its denial of a contested-case hearing.

“We are pleased with the district court’s ruling and look forward to defending the challenge to the water permit currently pending in the court of appeals,” said Jon Cherry, PolyMet chairman, president and CEO.

“We remain confident the water quality permit meets all applicable standards and will ultimately be upheld by the courts.”

The $1 billion NorthMet project has been met with criticism and resistance from environmental groups who are concerned about its potential impact on nearby water sources.

If permitted, the proposed mine on the Iron Range would become Minnesota’s first copper-nickel operation with an estimated 290 million tonnes of proven and probable reserves grading 0.29% copper and 0.08% nickel.

 

AG/SAG Mill Liners Manufacturer

Semi-autogenous grinding mill liner also called SAG mill liner, Autogenous grinding mill liner also called AG mill liner. Since the 2014 year, H&G Machinery has had become one of the largest AG/SAG mill liner manufacturers from China. No matter which material you want, manganese steel or Ni-hard steel or Cr-Mo steel or alloy steel; No matter which type of your mill liners need. wave shape or raised edge shape or stepped shape; H&G Machinery is your first choice.

 

Which Choose H&G Machinery’s AG/SAG Mill Liners?

• Rich experience. H&G Machinery supplies more than 10,000 tons of various kinds of mill liners.
• Various material.  We offer different materials to suit different work conditions. Such as manganese steel, Ni-hard steel, Cr-Mo steel, and other alloy steels.
• Complete QC system. H&G Machinery supply a complete quality control system and records. You can check all the documents and records when you visit us or we send them to you.
• OEM service.  H&G Machinery can manufacture your liners by your design or our engineer design.

AG SAG Mill Liner Function

Semi-autogenous grinding and autogenous grinding is a powder mill with a large cylinder diameter and a slow rotation. The material is fed into the mill through the hollow journal at the feeding end. Under the interaction of the materials, the material crushed to a certain fineness passes through the discharge The hollow journal at the end is discharged out of the machine. The liner is an important part of the grinding machine.

1. The lifting liner lifts the material to a certain height, the impact of the free fall, and the friction effect between the friction between the materials, so that the materials are crushed and finely ground.
2. The shape of the end cover lining board is relatively special. The bulk materials are added through the feeding port. The small pieces of material fall uniformly on the bottom center of the cylinder along the surface of the wave lining and then diffuse to both sides, while the large pieces of material have greater kinetic energy. : The projectile point always tends to the far side, but part of it will inevitably collide with the two sides of the wave lining. Due to the counterattack effect of the wave lining, it can prevent the material from being “segregated” in the axial large and small pieces, so that the large pieces of material can be evenly distributed. The coarse material returned from the discharge end along the lower side, like the newly added material block, evenly falls on the center of the bottom of the cylinder and then diffuses to both sides. The large and fine-grained materials move in the opposite direction along the axial direction at the bottom of the simplified Chinese, so they have a grinding effect.
3. Both the lifting T-shaped lining plate and the wave plate have the function of wedging the block. With the rotation of the mill, the position of the block increases, and the compressive force quickly disappears and becomes a tension when the “arched” bridge moves upward and collapses so that the instantaneous stress generated by the continuous reciprocating motion will cause the block The monomers are separated, resulting in grinding.

AG/SAG Mill Liner Material Selection

Different crushed material, different working conditions need different material liners to suit. In order to meet the requirements for customer AG or SAG mill liners, the materials of large mill liners are mainly high manganese steel, high alloy white cast iron, high carbon chromium-molybdenum steel, medium carbon chromium-molybdenum steel, etc. The matrix structure includes austenite, martensite, bainite, and pearlite.

H&G Machinery supplies the following material to cast your AG or SAG mill liners:

 

High Manganese Steel

High manganese steel is a traditional material for abrasion resistance and mill lining. It is widely used in various wear conditions because of its remarkable work hardening effect. The reason why the high manganese steel lining plate has a long service life is that the large ball mill has a slow speed and a large impact force between the grinding ball and the ore. The work hardening effect of the high manganese steel is significant, and the relative between the ore and the lining plate The speed is small. However, high manganese steel also has a fatal weakness, that is, in the case of large impact, due to its low yield strength, it is easy to rheology, resulting in large deformation of the liner, difficult to disassemble the liner, and the bolt will be broken in severe cases.

 

Alloy white cast iron

The representative material of alloy white cast iron is high chromium cast iron, and the Cr content is usually greater than 12%. Because it contains isolated rod-like high-hardness M7C3 type carbides, it shows higher hardness and better impact toughness (compared to white cast iron), and it has been widely regarded as a new generation of wear-resistant materials, and It has been applied to the liner of ball mill. However, the impact toughness of high-chromium cast iron is still relatively low (usually 5~7 J/cm2), so high-chromium cast iron is only suitable for the mining of small-size liners and large-size liners in cement mills Wet small-diameter mills (diameters below 2.5 m) are not suitable for large-diameter mills with large impact strength, especially large SAG mill.

 

Alloy Steel

Alloy steel as a wear-resistant material has also achieved good results in practical applications. The main reason is that the carbon content of alloy steel and the types and contents of alloy elements can be varied within a large range. With different heat treatment processes, The structure and properties of alloy steel can be adjusted within a relatively large range to obtain better comprehensive mechanical properties and meet the requirements of different working conditions. Research and practice  have shown that alloy steel is suitable as a mill liner for large self-grinding machines and semi-self-grinding machines, as shown in the table:

Relative Life Of Alloy Liner Used In AG Mill
Alloy Steel Species	Ball Media	Diameter 11.0m AG Mill Shell liner	Diameter 8.2m AG Mill Shell liner	Diameter 9.8m AG Mill Shell liner	Diameter 9.8m AG Mill End liner	Diameter 14.4m AG Mill End liner
Austenitic 12%Mn steel	0.64	/	/	/	/	/
Pearlite 0.8%C Cr-Mo alloy	0.7	/	0.46	0.48	/	0.54
Martensite 0.4%C Cr-Mo alloy	0.77	0.63	0.67	/	0.73	0.81
Martensite 1.0%C Cr-Mo alloy	0.85	/	/	/	/	0.94
Martensite 2%Cr-4%Ni iron alloy	0.83	0.67	/	/	/	/
Martensite 8%Cr-4%Ni iron alloy	/	0.79	/	/	/	/
Chromium-molybdenum cast iron	1.0	1.0	1.0	1.0	1.0	1.0

It can be seen that the martensitic Cr-Mo alloy steel lining plate has a good use effect in the self-grinding machine, followed by the pearlite Cr-Mo alloy steel lining plate. Pearlite Cr-Mo alloy steel lining has been widely used in semi-automatic mills. Although its wear resistance is slightly worse than martensitic Cr-Mo alloy steel, its impact toughness is higher than martensitic Cr -Mo alloy steel, so it is suitable for large semi-self-milling machine with relatively large impact.

AG/SAG Mill Liners Shapes

The shape of the AG/SAG mill liners include:

• Flat liner. For fine grinding silo, the rising height of the grinding body depends on the static friction coefficient between the lining plates.
• Bead liner. Used in the first bin, it can make the grinding body rise higher and have larger impact energy.
• Convex ribbed liner. Similar to bead liner.
• Wave liner. Suitable for baseball grinding.
• Ladder liner. It is suitable for crushing silo and it is widely used.
• Hemispherical liner. Suitable for crushing silo.

AG/SAG Mill Liners Installation

Preparation Work

1. Prepare all need to replace mill liners.
2. Check the shape and size of all liner plates, remove hair wings, casting slag, etc.;
3. Be prepared to replace the required bolts, nuts and washers and other accessories;
4. Check carefully whether lifting appliances, appliances and rigging are safe and reliable.
5. Prepare 36V safety power supply for construction lighting in the tube;
6. Before the mill is stopped, there must be enough minerals in the barrel suitable for the entry and exit of the liner before stopping.
7. All construction personnel must wear labor protection supplies including hard hats, masks, and non-slip shoes before entering the site.

 

Installation Steps

1. Remove the feed trolley and lift the receiving hopper;
2. Remove the fixing bolts of the liner piece by piece to protect and clean up all screw holes. Do not dismantle more than 3 sets of liners at one time;
3. Lift out the removed AG mill liners one by one by using the driving, and then hang the lining board to be replaced into the tube;
4. Under the direction of the hoisting commander, use the vehicle to wear the wire rope through the bolt holes of the cylinder, pull the lining board to the required installation position, and then use the crowbar to straighten the screw and nut. Fill the two screw holes of the lining board alternately with hemp rings (not less than 5 in each group), install the leak stop rubber ring and flat washer and tighten the nut;
5. When installing the mill liner, the deposits and debris at the installation location should be cleaned up;
6. If it is found that the discharge trough of the grid plate installation site is seriously worn, the discharge trough must be replaced before the grid plate is replaced;
7. Install the recovery feed trolley and mine funnel.

 

Safety measures and technical requirements

1. Before lifting operations, all appliances must be carefully checked in strict accordance with relevant regulations. The strapping must be firm when lifting items, and pedestrians should be reminded to avoid. The command must appoint a special person to be responsible;
2. The construction personnel must strictly abide by the safety technical operation regulations, eliminate illegal commands and illegal operations, wear various labor protection supplies, and prohibit drinking and drinking;
3. The mill liners should be fixed firmly without looseness. All bolts must be tightened in place. There shall be no slurry leakage in the gaps around the screw after driving;
4. Take good protection around the site to prevent falling. High-altitude operations should fasten seat belts in accordance with relevant regulations, to prevent simultaneous up and down operations;
5. When the cylinder needs to be driven according to the replacement of the lining plate, first of all, it is necessary to confirm whether there are people in the cylinder and the surroundings before the cylinder can be driven. The hollow shaft lubricating oil pump must be started before cranking;
6. When working in the mill, you must first cut off the power of the relevant equipment and hang the warning sign. The lighting in the tube must ensure good cable insulation and use safe voltage;
7. Construction equipment such as slings, rigging, and crowbars will be discontinued once they are found to be damaged or defective.