When choosing the general contract of a coal preparation plant, there are several key problems that should be carefully considered. These problems relate to the technical, scheduling, financial, and legal aspects of the project. They include:

1. Technical design and capacity: The design and capacity of the coal preparation plant should be specified in the contract. It is important to ensure that the plant will meet the desired production capacity, quality standards, and environmental regulations. The detailed technical specifications, equipment selection, and engineering design should be clearly defined.

2. Project schedule and milestones: The contract should clearly outline the project schedule and milestones. It should specify the start and end dates of the project, as well as the completion dates of different stages or components. This is important to ensure that the project is completed within the desired timeframe.

3. Performance guarantees: The contract should include performance guarantees for the coal preparation plant. These guarantees should specify the expected performance of the plant in terms of coal quality, recovery rates, and efficiency. In case of performance failure, there should be adequate penalties or compensation mechanisms in place.

4. Cost and payment terms: The contract should clearly outline the cost and payment terms. This should include the total project cost, payment schedule, and any provisions for cost escalation or changes in the scope of work. It is important to ensure that the financial aspects of the project are well-defined and manageable.

5. Safety and environmental considerations: The contract should include provisions for safety and environmental protection. It should specify the safety standards that need to be followed during the construction and operation of the plant. Additionally, it should also address the environmental impact of the plant and include measures to mitigate any potential adverse effects.

6. Quality control and supervision: The contract should emphasize the need for strict quality control and supervision during the construction and operation of the coal preparation plant. This should include regular inspections, testing, and monitoring to ensure that the plant meets the required standards and specifications.

7. Intellectual property rights: The contract should address the issue of intellectual property rights. It should specify the ownership and usage rights of any intellectual property, such as patented technologies or proprietary processes, used in the plant. This is important to protect the interests of both the contractor and the owner of the coal preparation plant.

8. Dispute resolution mechanisms: The contract should include dispute resolution mechanisms to address any potential conflicts between the parties involved. This could include provisions for negotiation, mediation, arbitration, or litigation. Having clear and effective dispute resolution mechanisms in place can help avoid unnecessary delays and costs.

9. Contract termination and force majeure: The contract should include provisions for contract termination and force majeure events. It should clearly define the conditions under which the contract can be terminated, as well as the consequences of such termination. Additionally, it should address the impact of force majeure events, such as natural disasters or political unrest, on the project.

10. Compliance with local regulations: The contract should ensure that the coal preparation plant complies with all relevant local laws and regulations. This includes environmental regulations, labor laws, health and safety standards, and any other legal requirements. Failure to comply with local regulations can lead to fines, penalties, or even the shutdown of the plant.

In summary, when choosing the general contract of a coal preparation plant, it is essential to pay attention to the technical, scheduling, financial, and legal aspects of the project. Addressing these key problems in the contract can help ensure the successful implementation and operation of the plant.