1. What is the economic evaluation of construction projects? Why do we need to conduct economic analysis on construction projects
Evaluation?
Economic evaluation of construction projects: Qualitative and quantitative analysis and evaluation of the economic benefits, financial income and expenditure status, and other aspects of the construction project.
Economic evaluation of construction projects is an organic component and main content of feasibility studies, and an important means of project decision-making.
The purpose of economic evaluation is to calculate the benefits and costs of the project based on the requirements of national economic and social development as well as industry and regional development plans, and to conduct engineering and technical research such as predicting product market demand, selecting factory sites, and selecting process technologies. Through comparison of multiple schemes, the financial feasibility and economic rationality of the proposed project are analyzed and demonstrated, and a comprehensive economic evaluation is made to provide a basis for scientific decision-making of the project. The current economic evaluation of construction projects in China is divided into two levels: financial evaluation and national economic evaluation.
What are the meanings of particle size, particle size, and particle size composition?
Particle size: The size that describes a single particle size is called particle size.
Particle size distribution: Using a certain method (such as screening) to separate a group of materials with a wide particle size range into several narrow particle size levels, all of which are called particle size distribution. Each particle size is represented by its upper limit particle size (d1) and lower limit particle size (d2), such as d,~d ₂ or d ₂~d ₁ or - d+d2. Particle size composition: The above particle sizes are arranged in different orders of coarse and fine, and the mass percentage of each particle size in the total material group is indicated. This information is called particle size composition.
What are the meanings of screening and screening efficiency? Screening: The process in which crushed materials are divided into different particle sizes through one or several layers of screen surfaces
For screening. The sieving performed in a laboratory or test site to complete particle size analysis is called experimental sieving. The screening carried out in a factory or ore dressing plant to complete production tasks is called industrial screening.
Screening efficiency: The percentage of the actual amount of product under the sieve obtained to the amount of material with a particle size smaller than the sieve opening in the screened material.
2. What are the meanings of underscreened products, overscreened products, and sieved particle size?
Sieve products: The screening process is generally continuous. After the screened raw materials are fed to the screening machinery, materials smaller than the sieve hole size pass through the sieve hole, which is called sieve products.
Sieve products: Materials larger than the sieve hole size are continuously discharged from the sieve surface, known as sieve products.
Sieve size: Under certain conditions, the minimum particle size in the product on the sieve and the maximum particle size in the product off the sieve are approximately equal to the sieve pore size on the sieve surface, which can be simply considered as the sieve size.
22. Preparation screening, auxiliary screening, pre screening, inspection screening, dehydration screening, and dehydration screening
What are the meanings of mud, medium screening, and selective screening?
Preparation screening: When screening provides selected minerals of different particle sizes for sorting operations, it is called preparation screening.
Auxiliary screening: When screening and crushing operations are carried out in conjunction, it is called auxiliary screening. Pre screening: If used to pre screen out qualified particle sizes before crushing, it is called pre screening. Check screening: If used to control the particle size of the crushed product after crushing, it is called check screening.
Dehydration screening: Screening of fragmented materials with a large amount of water (such as slurry, mud, ore slurry, etc.) as screening raw materials for the purpose of removing the liquid phase is called dehydration screening.
Desliming and media separation: In order to achieve certain process objectives, crushed materials or water mixed crushed materials are used as screening materials to remove the fine particles from them, which is called desliming screening or media separation.
Selective screening: Screening is the separation of fragmented materials according to their geometric size (particle size), but in some cases, screening can separate them by mass, such as in ore dressing or coal preparation production by grade or ash. This type of screening is called selective screening.
The screening carried out in a factory or ore dressing plant to complete production tasks is called industrial screening.
Screening efficiency: The percentage of the actual amount of product under the sieve obtained to the amount of material with a particle size smaller than the sieve opening in the screened material.
3. What are the meanings of underscreened products, overscreened products, and sieved particle size?
Sieve products: The screening process is generally continuous. After the screened raw materials are fed to the screening machinery, materials smaller than the sieve hole size pass through the sieve hole, which is called sieve products.
Sieve products: Materials larger than the sieve hole size are continuously discharged from the sieve surface, known as sieve products.
Sieve size: Under certain conditions, the minimum particle size in the product on the sieve and the maximum particle size in the product off the sieve are approximately equal to the sieve pore size on the sieve surface, which can be simply considered as the sieve size.
4. Preparation screening, auxiliary screening, pre screening, inspection screening, dehydration screening, and dehydration screening
What are the meanings of mud, medium screening, and selective screening?
Preparation screening: When screening provides selected minerals of different particle sizes for sorting operations, it is called preparation screening.
Auxiliary screening: When screening and crushing operations are carried out in conjunction, it is called auxiliary screening. Pre screening: If used to pre screen out qualified particle sizes before crushing, it is called pre screening. Check screening: If used to control the particle size of the crushed product after crushing, it is called check screening.
Dehydration screening: Screening of fragmented materials with a large amount of water (such as slurry, mud, ore slurry, etc.) as screening raw materials for the purpose of removing the liquid phase is called dehydration screening.
Desliming and media separation: In order to achieve certain process objectives, crushed materials or water mixed crushed materials are used as screening materials to remove the fine particles from them, which is called desliming screening or media separation.
Selective screening: Screening is the process of separating fragmented materials according to their geometric size (particle size), but in some cases, screening can separate them by mass, such as in ore dressing or coal preparation production by grade or ash. This type of screening is called selective screening.
