Method for determining minimum gradient required by self-flow conveying of ore pulp pipeline

Abstract

The invention relates to the field of mineral separation, in particular to a method for determining the minimum gradient needed by ore pulp pipeline self-flow conveying. Determining the fullness degree h / d of the self-flowing pipe and the cross section area coefficient KA of the self-flowing pipe; determining a hydraulic radius coefficient KR and a fall coefficient C; the minimum gradient I = K * Vkp2 / C2 / R is needed for ore pulp pipeline self-flow conveying, the unit of I is%, and K is a coefficient and generally ranges from 1.05 to 1.10. After the critical flow velocity of the mineral pulp is solved, the sectional area required by the mineral pulp pipeline during self-flow conveying can be solved by combining the quantity of minerals required to be conveyed, and meanwhile, the area coefficient is solved, so that the required diameter of the conveying pipe can be solved, and then the hydraulic radius and the coefficient of the selected pipeline under the working condition are calculated; and finally, the minimum slope needing to be laid can be determined.

Description

Technical Field

[0001] The invention relates to the field of ore dressing, and in particular to the field of ore slurry pipeline gravity transportation. Background Art

[0002] The mineral processing production line of an enterprise requires a lot of slurry self-flowing pipelines, and the design of the pipeline slope is crucial. There is a big difference between the self-flowing transportation of slurry pipelines and the self-flowing transportation of water pipelines. For self-flowing transportation of water pipelines, as long as there is a slight slope in the pipeline, there is no problem for water to flow in the pipeline, but slurry is different. Slurries of different properties need to be transported in the pipeline by gravity, and the minimum slope required for pipeline laying is different. It is more complicated to determine the slope of the slurry pipeline to meet the gravity transportation. If the slope of the slurry pipeline is not determined reasonably, it will lead to three problems. First, if the slope is small, the solid particles in the slurry will deposit and block the pipeline, and the requirements of gravity transportation cannot be achieved; second, if the slope is too large, the slurry outlet flow rate will be too large, which will not only increase the height difference of the plant and increase the construction investment cost, but also cause the slurry to splash at the outlet of the conveying pipe, which is not conducive to the operation control and environmental sanitation of the production site; third, for the sake of insurance, the designers avoided cumbersome calculations and designed the pipeline gravity transportation that could be designed as power transportation, which increased production consumption.

[0003] The critical velocity of slurry is the primary factor that must be considered in slurry transportation. Only when the slurry velocity is greater than or equal to the critical velocity, the mineral particles in the transportation process will not settle and clog the pipeline. The critical velocity is closely related to the specific gravity of solid particles in the slurry, the particle size and the slurry concentration, but in the relevant data (such as the mineral processing design manual), there is no clear calculation formula that combines these three factors. There are only non-continuous experimental data for medium specific gravity (2.70t / m3), which requires repeated reference and calculation, which is very cumbersome, labor-intensive and prone to errors. Many engineering and technical personnel are not willing to do such tedious work, and often determine the critical velocity based on experience, taking the principle of preferring large to small. This will inevitably lead to poor design accuracy and increase the investment in design and construction costs. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide an accurate, simple and convenient method for determining the minimum slope required for gravity transportation of slurry pipelines, so as to avoid the need to constantly and repeatedly consult data when designing gravity transportation, and to continuously perform manual experience-based value selection of various parameters, which leads to a large workload for designers, easy errors, and an increase in construction investment and production costs.

[0005] The technical solution adopted by the present invention is: a method for determining the minimum slope required for gravity transportation of slurry pipelines, which is carried out according to the following steps:

[0006] Step 1: Determine the critical slurry velocity Vkp , when d cp <0.074mm, V kp ={1+0.2×(C w -20) / 20+0.2×((d cp -0.074) / 0.074+5.419)}×(ρ / 1.7-1 / 1.7) 1 / 2 ; When 0.074mm≤d cp When ≤1.5mm, V kp =(1+0.2×(C w -20) / 20+0.2×5.419)×(ρ / 1.7-1 / 1.7) 1 / 2 When d cp >1.5mm, V kp ={1+0.2×(C w -20) / 20+0.2×[5.419+(d cp -1.5) / 1.5)]}×(ρ / 1.7-1 / 1.7) 1 / 2 ; Among them, V kp The unit is m / s, d cp is the average particle size of the slurry, in mm, C w is the slurry weight concentration (or slurry mass concentration), ρ is the slurry specific gravity, the unit is t / m3, ρ = 100 / (38.5-0.2654×β), β is the ore grade;

[0007] Step 2: Determine the filling degree h / d and cross-sectional area coefficient K of the gravity pipe A , h / d=-0.005×C w +0.65, K A =-0.8525×(h / d) 3 +1.2675×(h / d) 2 +0.3839×(h / d)-0.009, where C w is the slurry weight concentration;

[0008] Step 3: Determine the hydraulic radius coefficient K R and Xie Cai coefficient C, K R =-0.4979×

[0009] (h / d) 2 +0.7894h / d-0.0166, C=1.2266n －0.955 R －99.573n×n+13.37n－0.0017 , R = K R ×d, where R is the hydraulic radius in meters, n is the roughness coefficient of the gravity pipe, and d is the effective inner diameter of the gravity pipe in meters;

[0010] Step 4: Gravity transportation of slurry pipeline requires a minimum slope of I = K × V kp 2 / C 2 / R, where I is in %, and K is a coefficient, which is generally between 1.05 and 1.10.

[0011] The cross section of the gravity pipe is a circle, that is, the slurry pipe is a round pipe.

[0012] The beneficial effects of the present invention are as follows: the present invention is applicable to the design of the minimum slope of gravity-flow transportation of slurry pipelines, and is convenient for determining the minimum slope of slurry pipelines for gravity-flow transportation of slurries of different properties in a newly built beneficiation plant. At the same time, it can also verify whether the slurry transportation between processes in the original beneficiation plant is suitable for gravity-flow transportation, so as to reduce the power transmission link and reduce production costs. In particular, when a new beneficiation plant is newly built, gravity-flow is used to transport slurry between processes. There are many processes, different slurry amounts, and different slurry properties. The requirements for the diameter of the gravity-flow pipe and the minimum laying slope are different. Manual calculations one by one are cumbersome and prone to errors. The present invention innovatively solves the difficult problem of accurately determining the diameter of the slurry gravity-flow transportation pipeline and the minimum laying slope when designing a beneficiation plant, and provides engineering and technical designers with a convenient calculation program for obtaining gravity-flow transportation of slurry pipelines.

[0013] The present invention analyzes the influence of different mineral grades (affecting specific gravity), particle size and pulp concentration on the critical velocity, and creates a formula for calculating the critical velocity of mineral slurry based on the approximate empirical value of the critical velocity of mineral slurry with a specific gravity of 2.70t / m3 in Table 8.9-26 of the Mineral Processing Design Manual. After the critical velocity of the mineral slurry is obtained, the cross-sectional area required for gravity transportation of the mineral slurry pipeline can be calculated in combination with the amount of mineral to be transported, and the area coefficient can be calculated at the same time, so that the required conveying pipe diameter can be obtained, and then the hydraulic radius and the Xiecai coefficient of the selected pipeline under the working conditions can be calculated, and finally the minimum slope required for laying can be determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram of the modification of the gravity flow pipe in Example 1 of the present invention;

[0015] Among them, 1. High-frequency fine screen, 2. Concentration magnetic separation feed pipe, 3. Concentration magnetic separator. DETAILED DESCRIPTION

[0016] Example 1

[0017] The mineral processing (iron ore) production process of a certain limited company has a process where the ore pulp on the screen needs to be concentrated and magnetically separated before being ground. The design unit adopted a conservative design, that is, the ore pulp on the screen first flows by gravity to the slurry pump pool, and then is powered by the slurry pump to the thickening magnetic separator. The 321 series and 111 series of this process are equipped with slurry pumps with installed powers of 90kWh and 55kWh respectively, with an annual production cost of more than 830,000 yuan.

[0018] The weight concentration percentage of the slurry on the test sieve is C w % = 48%, the amount of mineral solids to be transported (designed mineral flow rate) is 75t / h, the ore grade β is 58%, and the average particle size of the slurry is d cp The median particle size of the slurry (d50, mm) is 1, and the roughness coefficient n of the selected gravity pipe is 0.013. The specific gravity of the slurry is 100 / (38.5-0.2654×β)≈1.91t / m 3 ;

[0019] 0.074mm≤d cp ≤1.5mm,

[0020] Slurry critical velocity V kp =(1+0.2×(C w -20) / 20+0.2×5.419)×(ρ / 1.7-1 / 1.7) 1 / 2 ≈3.31m / s;

[0021] Gravity pipe filling degree h / d=-0.005×C w +0.65=0.41; h is the slurry height in the gravity pipe, and d is the effective inner diameter of the gravity pipe.

[0022] Cross-sectional area coefficient K of gravity pipe A =-0.8525×(h / d) 3 +1.2675×(h / d) 2 +0.3839×

[0023] (h / d)-0.009≈0.303;

[0024] Hydraulic radius coefficient K R =-0.4979×(h / d) 2 +0.7894h / d-0.0166≈0.223;

[0025] The effective inner diameter of the gravity pipe is d = 200 mm = 0.2 m (optional);

[0026] Hydraulic radius R = K R ×d=≈0.0447m;

[0027] Xie Cai coefficient C = 1.2266n －0.955 R －99.573n×n+13.37n－0.0017 =47.89

[0028] The minimum slope required for gravity flow of slurry pipeline is I=K×V kp 2 / C 2 / R≈11.73%.

[0029] The calculation results show that to achieve pipeline gravity transportation, the pipeline laying slope only needs to meet 11.73%. The height difference between the high-frequency fine screen outlet and the concentrated magnetic separator feed port is 1138mm, the horizontal distance of transportation is 8850mm, and the slope is 12.86%, which is greater than the minimum slope of 11.73% required for laying. Pipeline gravity transportation can be fully implemented. Based on this, on-site transformation was carried out to eliminate the slurry pump power transmission link.

[0030] The success of the above embodiments shows that the present invention can be used to easily calculate the possibility of existing mineral processing slurry to achieve pipeline gravity transportation in combination with operating conditions, so that engineering and technical personnel do not have to adopt conservative power transmission due to repeated calculations. It provides an extremely convenient method for engineering design and transformation of existing processes, which is beneficial for enterprises to reduce investment expenses and production costs.

[0031] Example 2

[0032] The mineral processing (iron ore) production process of a certain limited company requires a grinding process after the ore pulp on the screen is concentrated and magnetically separated. The design unit adopted a conservative design, that is, the ore pulp on the screen first flows by gravity to the slurry pump pool, and then the slurry pump is used to transport it to the concentrating magnetic separator.

[0033] The weight concentration percentage of the slurry on the test sieve is C w % = 55%, the amount of mineral solids to be transported (designed mineral flow rate) is 800t / h, the ore grade β is 34%, and the average particle size of the slurry is d cp The median particle size of the slurry (d50, mm) is 2, and the roughness coefficient n of the selected gravity pipe is 0.013. The specific gravity of the slurry is 100 / (38.5-0.2654×β)≈2.22t / m 3 ;

[0034] d cp >1.5mm

[0035] Critical slurry velocity

[0036] V kp ={1+0.2×(C w -20) / 20+0.2×[5.419+(d cp -1.5) / 1.5)]}×(ρ / 1.7-1 / 1.7) 1 / 2 ≈2.97m / s;

[0037] Gravity pipe filling degree h / d=-0.005×C w +0.65=0.38;

[0038] Cross-sectional area coefficient K of gravity pipeA =-0.8525×(h / d) 3 +1.2675×(h / d) 2 +0.3839×

[0039] (h / d)-0.009≈0.268;

[0040] Hydraulic radius coefficient K R =-0.4979×(h / d) 2 +0.7894h / d-0.0166≈0.21;

[0041] The effective inner diameter of the gravity pipe is d = 600 mm = 0.6 m (optional);

[0042] Hydraulic radius R = K R ×d=≈0.1256m;

[0043] Xie Cai coefficient C = 1.2266n －0.955 R －99.573n×n+13.37n－0.0017 =56.23

[0044] The minimum slope required for gravity flow of slurry pipeline is I=K×V kp 2 / C 2 / R≈2.43%.

[0045] The calculation results show that to achieve pipeline gravity transportation, the pipeline laying slope must meet 2.43%, the height difference between the high-frequency fine screen outlet and the concentrated magnetic separator feed port is 1138mm, the horizontal distance of transportation is 8850mm, and the slope is 12.86%, which is greater than the minimum slope of 2.43% required for laying, and pipeline gravity transportation can be fully implemented. Based on this, on-site transformation was carried out to eliminate the slurry pump power transmission link.

Claims

1. A method for determining the minimum slope required for gravity transportation of slurry pipelines, characterized in that: Follow the steps below Step 1: Determine the critical slurry velocity V kp , when d cp <0.074mm, V kp ={1+0.2×(C w -20) / 20+0.2×((d cp -0.074) / 0.074+5.419)}×(ρ / 1.7-1 / 1.7) 1 / 2 ; When 0.074mm≤d cp When ≤1.5mm, V kp =(1+0.2×(C w -20) / 20+0.2×5.419)×(ρ / 1.7-1 / 1.7) 1 / 2 When d cp >1.5mm, V kp ={1+0.2×(C w -20) / 20+0.2×[5.419+(d cp -1.5) / 1.5)]}×(ρ / 1.7-1 / 1.7) 1 / 2 ; Among them, V kp The unit is m / s, d cp is the average particle size of the slurry, in mm, C w is the slurry weight concentration, ρ is the slurry specific gravity, the unit is t / m3, ρ = 100 / (38.5-0.2654×β), β is the ore grade of the slurry; Step 2: Determine the filling degree h / d and cross-sectional area coefficient K of the gravity pipe A , h / d=-0.005×C w +0.65, K A =-0.8525×(h / d) 3 +1.2675×(h / d) 2 +0.3839×(h / d)-0.009, where C w is the slurry weight concentration; Step 3: Determine the hydraulic radius coefficient K R and Xie Cai coefficient C, K R =-0.4979× (h / d) 2 +0.7894h / d-0.0166, C=1.2266n －0.955 R －99.573n×n+13.37n－0.0017 , R = K R ×d, where R is the hydraulic radius in meters, n is the roughness coefficient of the gravity pipe, and d is the effective inner diameter of the gravity pipe in meters; Step 4: Gravity transportation of slurry pipeline requires a minimum slope of I = K × V kp 2 / C 2 / R, where I is in %, and K is a coefficient, which is generally between 1.05 and 1.

10.

2. The method for determining the minimum slope required for gravity transportation of slurry pipeline according to claim 1, characterized in that: The cross section of the gravity pipe is a circle, that is, the slurry pipe is a round pipe.

Images