Carbide Slag Recycling Solution
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Carbide Slag Recycling Solution
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Solved Problem

Project background and Solution

In addition to calcium hydroxide as the main component, calcium carbide slurry contains a variety of solid impurities such as ferrosilicon particles, coke particles, electrode residual rods, and micro calcium carbide particles that are not completely hydrolyzed.

The chemical analysis of ferrosilicon particle slag in calcium carbide slag contains Si25-30%, iron content above 70%, specific gravity greater than 6.5g/cm3, and density difference from calcium carbide slag average  volume is 1.8-2.2g/cm3, which is low qualit  ferrosilicon . The separation of this part of ferrosilicon and calcium carbide slurry can be realized by TPC-800 continuous automatic swirling centrifuge concentrator , and the recovery effect is highly perfect.

0.9-2MM                                                       0.9mm below                                                        2-5mm                                                                      5mm above

 

Project Background   

In order to improve the comprehensive utilization of the secondary resources of calcium carbide slag,  turn waste into treasure as well as  to improve the working conditions,  in purpose on strengthening afety management and reducing the wear and cost of the follow-up section, the following  requirements are proposed by the contactor:

  1. A. High-efficiency recovery technology is used to enrich and utilize the bottom-flow slag ferro-iron particles,to design an automatic sorting program to replace the labor-intensive manual flushing and recycling method so as to reduce labor intensity and effectively prevent potential safety hazards;
  2. B.Using high-efficiency recovery technology-centrifugal  gravity processing technology to enrich  the overflow fine-grained ferrosilicon so as to reduce the wear casued by  high-hardness impurities in the calcium carbide slag on the filter cloth and pipe valve system;
  3. C.The jigging screening recovery system is used to separate the carbon particles in the calcium carbide slurry to recover the high-quality clean fuel and reducing agent to realize the comprehensive utilization on the resource; in the technology of replacing the limestone with calcium carbide and producing cement clinker, in the calcium carbide slag the ferrosilicon particles have a direct impact on the output of the cement raw mill and the loss of the grinding body. The reduction of the ferrosilicon content can achieve better economic benefits and save a lot of energy and resources for the society;
  4.     

 

n order to understand the source of valuable components in the calcium carbide slag, the fluctuation stability of the by-products is to be recycled, the project team specially investigated  an upstream calcium carbide production enterprise located in Dahuangshan Industrial Park, Changji City. ,China

Mainly understand as follow:

1) source of raw materials;

2) Inspection of raw materials into the factory;

3) calcium carbide production process;

4) Product quality control.

The main raw materials for the production of calcium carbide in Zhongtai Mining and Metallurgical Company are limestone and coke, which are basically supplied by the surrounding supporting enterprises. In order to save the cost of raw materials, the company also has purchased some low-cost granitic charcoal as a substitute for metallurgical coke and added ingredients into the furnace.

The clients requires the laboratory to control  the effective calcium oxide CaO over 80% in the limestone and the factory-fired lime, the acid content is less than 1.8%; the third oxide is <1.6% with P<0.025%; The monitoring data displayed in the control room is up to standard. We randomly sampled the quicklime calcined from the beam shaft furnace by the mining and metallurgical company, and obtained the chemical composition as follows:

Table Date 1

Element C O Si P S Na Mg Al K Ca Fe Sr
contain/% 2.2 39 0.94 0.005 0.03 0.014 0.39 0.2 0.02 56.07 0.3 0.37

The detection and control of coke into the plant requires a fixed carbon rate at +84%, ash <15%, volatile matter <1.5% andmoisture <3%. Among them, the ash component of the main reducing agent coke required to be controlled is more than 5% higher than that of high-quality metallurgical coke, which means that the amount of silica and iron oxide caused by coke impure in the production of calcium carbide exceeds 1% and 0.5% respectively.

As a product of cheap weak coal or brown coal, it is sold at a lower price than coke. As a carbonaceous reduction, it does not affect the chemical reduction reaction, but its ash content is higher than that of coke, and the main impurity SiO2 is brought into the ore furnace. Fe2O3 is significantly larger than the full use of high quality metallurgical coke.

From the examination on the calcium carbide production process plant., we believe that its production process equipment and production process control are standardized and reliable. The by-product of ferrosilicon is mainly  produced due to the  insufficient purity of raw materials such as limestone, coke and blue carbon. It contains excessive impurities of silica and ferric oxide. The impurities are synchronously reduced in the calcium carbide ore furnace. The yield of by-product ferrosilicon is basically stable between 2% and 3%

Magnetic Separation test of Ferrosilicon Particles

  1. Magnetic separation test of large particles

The 200mT weak magnet seperator is used for magnetic separation in the lab, and the recovery rate on  ferrosilicon particles is about 20%.  When test with magnetic  of 1T magnetism  strength, about 95% of large-sized ferrosilicon can be adsorbed (including by passing materials).

  1. Magnetic separation test of small particles

The adsorption recovery rate of ferrosilicon in fine particle slag by weak magnetic strength at 20mT is 15%; the weak magnetic field has poor adsorption on fine ferrosilicon in fine slag below 0.3mm, and the recovery on such particles at 0.15mm is also not good, therefore  it is not recommended to use magnetic separation to recover fine-grained ferrosilicon in carbide slag.

Gravity Speration test on  Ferrosilicon particles

  1. Course Particle Gravity Test

The ferrosilicon particles with  diameter +2mm are easily screened,  after sieving, the content of ferrosilicon above sieve is higher than 90%. Particle slag larger than 2 mm can be separated by jigg mahcine. Tests have shown that carbon particles of 2mm above can be s recovered by 90%.

     2. Gravitytest of small particles

Part of the calcium carbide slurry with a particle size of less than 2 mm can be recovered by a TPC-800 vertical continuous centrifugal  cencentrator under the condition of a water backflush of 5 L/min.

Recovery Data

For Such particle at size below 2mm, the recycling rate on ferro-silicon with different feeding is as follow:

Table 2:

Sample(g) Heavy sand ferro-silicon ( g) Recycling Rate
100 22.9 87.7
125 29.8 91.4
150 35.9 91.5
175 41.7 91.2
200 49.4 94.6

For such particle at 1mm below, the production and recycling rate by concentrator as below:

Table 3:

production(rate) quality Recycling rate %
10.0 40.0 51.2
7.9 39.0 35.4
5.6 46.5 31.0
5.1 43.3 26.0
4.8 45.9 25.3
4.2 49.7 24.7

Conclusion: in a given feeding condition, the conpresensive recovery on silicon metal  is 65%  with quality rate at 40% if use TPC 800 centrifugal concentrator

 

Economical Return Analyzis:

A.Water Consumption

Table Data 4

S.N SYSTEM/EQUIPMENT QTY M 3/h 3

M /d

REMARK
1 COURSE PARTICLE RECYCLING SYSTEM COURSE SLAG VIBRATING SCREEN 1 2.0 8.0 RUNING 4 HOURS
2 COURSE SLAG JIG 2 2.0×2 16.0 RUNING 4 HOURS
3 FINE PARTICLE RECYCLING SYSTEM FINE PARTICLE SLAG VIBRATING SCREEN 1 3.0 72.0 RUNING 24 HOURS
4 CONTRIFUGAL CONCENTRATOR 1 10.0 240.0 RUNING 24 HOURS
5 FINE SLIM SHAKING TABLE 4 1.5×4 144.0 RUNING 24 HOURS
Remark: Major water source is recycling water except the concentrate 480.0 34USD / DAY
Yearly Water cost: 34USD*330(DAY)=11220USD

 

B: )ELECTRICAL CONSUMPTION (DAILY)

Table Data 5

S.N SYSTEM/EQUIPMENT QTY POWER(Kw) TOTAL REMARK
1  

COURSE PARTICLE RECYCLING SYSTEM

Vibrating Feeder 1 1.0×4 4.0
2 Course Particle Screen 1 3.0×4 12.0
3  

Coarse Jig

2 5.0×4 20.0
4 FINE PARTICLE RECYCLING SYSTEM Fine particle Slurry Pump 1 3.0×24 72.0
5 Sedimentation tank slurry pump

 

2 3×24 72.0  

one standby

 

6  

Fine particle Slurry Pump

1 1.5×24 36.0
7 Centrifugal Concentrator 1 15.0×24 360.0
8 Fine slim shaking table 4 6×24 144.0 4
Total power consumption 720.0 55USD/DAY
Total Annual Power cost:55USD*330 =18150USD/YEAR

 

C: WORKFORCE COST

Table Data 6

S.N SYSTEM/EQUIPMENT QTY MONTHLY SALARY YEAR SALARY
1 COURSE PARTICLE RECYCLING SYSTEM 1 448USD 5376USD
2 Fine particle recovery system 1 448USD 5376USD
 TOTAL WORKFORCE COST IN A YEAR : 10752USD

D:BENIFIT ANALYSIS

Table data 7:

PRODUCT DAILY RECYCLING YEARLY RECYCLING Market PRICE
Ferro-silicon particles 10 Ton 3300Ton 134.33USD/TON
Carbon Particles 2.5 Ton 825Ton 65.67USD/TON

 

  1.  GENRAL BENIFIT ANALYSIS

Table Data 8

Item Overall Economical Benefit Remark
Overall Benefit (3300*134.33USD)+(825*65.67USD)=495237USD These figures are based on the normal running cost in one year of the whole plant
Overall Cost 465,97.00USD
Net Benefit 447,761.00USD

 

Total Net Benifit on year is 540,000.00USD  based on the normal operation of Centrifugal Concentrator

 

 

 

Flow Chart

Process Solution

The coarse particle slag  is lifted by bucket elevator  and loaded into the silo, and are evenly fed into the vibrating screen under the control of the feeder screen. The sieved material is sorted into a coarse-grained jig, and the sieved material is sorted into a fine-grained jig to produce ferrosilicon concentrate and fine carbon.

The materials treated by the fine-grained ferrosilicon/carbon particle recovery system are the fine slag generated during manual flushing of the bottom slag and the calcium carbide slag in the overflow. After the homogenization, sedimentation and screening process, the sieved material is fed into the fine-grain jig. The sieved material is fed into a cyclone centrifuge and enriched by high-speed centrifugation to achieve a recovery rate of 50-65%. The heavy sand generated by the swirling centrifuge is pumped to the shaker distributor, evenly distributed to the shaker, and the fine-grain ferrosilicon concentrate, fine-grained  carbon residue and tailings are sorted, and the tailings flow into the slag ditch.

PS:Ti’s have Customizable process
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