Introduction

Coal preparation is more used at present, the cement industry vertical slow pulverized coal, raw coal into the grinding feed and measurement plays an important role in the process of pulverized coal preparation, if the equipment is wrong or failure rate is too high, easily happened in the production run coal or broken coal, which can lead to stop number increase in the mill, which severely restricts the system production and operation stability.

01 Existing Problems

A company / 4000 d NSP cement clinker production line of form a complete set of pulverized coal preparation system USES a specification for double roller HRM2200M vertical mill, the production capacity of 40 or higher in the late wear th, raw coal into grinding feed using sealed constant feeder specifications for MDGV100-350/80 – WX, front-rear center distance of 3500 mm, the bandwidth of 1000 mm, 50 mm or less conveying material particle size, the dynamic measurement error of plus or minus 1%. The sealing type quantitative feeding machine has good dustproof and noise isolation effect. It is through the operation of the belt scale to carry on the quantitative transmission of materials, when the original coal bunker material into the belt scale, under the measurement of the load sensor, through the frequency converter to adjust the motor speed control belt scale running speed, so as to control the volume of material on the belt scale, to achieve continuous and uniform feeding.

In order to prevent the coal accumulation material damage to the belt scale, in the original design, the inner side and the bottom of the conveyor belt scale are equipped with a belt scale cleaning device, its role is to remove the material adhering to the inner and outer surface of the belt scale, improve the weighing accuracy and the safety and stability of the belt scale operation, the internal structure is shown in Figure 1. Belt scale inside cleaner scraping sheet material is high polymer polyethylene board, inside the cleaner also plays a tensioning role on belt scale. Chain scraper type cleaning mechanism is located in the body bottom plate below the metering conveyor belt scale, cleaning scraper is installed on the chain, through the way of gear transmission by the chain drive scraper forward to realize the material cleaning, so that it is transported into the mill, keep the bottom of the body without material accumulation, to ensure the safe and stable operation of belt scale. The chain scraper type cleaning mechanism can be manually controlled on the spot, or automatically timed or continuously cleaned when the coal feeder is running.

Figure 1 Internal structure diagram of sealed feeder

1-Raw coal into grinding; 2-Observation window;

3-feeder housing; 4-Top access door; 5- Rod valve;

6-original coal bunker; 7- Expansion joint; 8- Horizontal roller;

9 – Belt scale; 10 a maintenance door; 11-Scraping system;

12-Chain and scraper; 13-Scraper movement direction;

14- Raw coal blanking slit; 15- Inner scraper; 16- Speed sensor.

Sealed constant feeder operation process, there are many factors can lead to a conveyor belt scale of running deviation, such as the uneven grinding raw coal particle is larger, coal, water content, such as the original coal bunker under unstable, belt scale will have a lot of raw coal leakage into the scrape bin at the bottom of coal feeder, affected by the chain scraper sweeper transmission capacity, a foreign body when there is too much product coal or difficult to clean, easy to cut the belt, scraping chain feeder load is bigger, damage to the motor reducer leakage often occurs. For this reason, by adding interlocking control, the chain detection device will send out the fault signal of broken chain when there are more materials in the scraping bin or the chain load is large. Through the DCS interlocking system, the belt scale will jump to stop, so as to prevent the foreign body from scratching the belt scale. Then, through manual intervention, the normal boot will be started after cleaning. Although these measures reduce the damage to the equipment to a certain extent, they seriously affect the continuity and stability of the system production.

02 Renovation scheme and effects

In order to reduce the failure of the scraping system to stop, to achieve continuous and stable operation, at the same time, the deposit of coal spilled and leaked to the bottom of the feeder is conveyed into the mill in time, the chain scraper cleaner is transformed into the blanking slit, in order to realize the leakage of coal into the blanking slit directly, to avoid the damage of the deposit of coal to the belt balance. After measuring the height of the feeder platform and the feeding platform of the mill on site, a slanting chute was made by using wear-resistant steel plate instead of the scraper, and the slanting chute was connected with the grinding chute to ensure that the coal leaking from the belt scale could enter the mill. The inclined slit is provided with an access door for timely cleaning of the blocking material. Taking into account the slope of the chute, in order to ensure that the chute is smooth, a vibration motor is installed on the chute, which is controlled by the central control.

Enclosed scraper constant feeder system after modification for oblique valve, basically solved the leakage of coal to the effects of belt scale operation, the overall equipment operation, good for near stop times is greatly reduced, can guarantee the continuous and stable production system, and at the same time, the coal mill system when yields by about 2 t/d, reduce the operation time, greatly reduces the equipment loss, save production cost and equipment maintenance cost about $98000.

Table 1 Statistical table of annual running time of coal mill system before and after modification

03 Conclusions

In the process of the new era, high quality development is a new requirement for the cement industry, energy saving, environmental protection and high efficiency should be the development goals pursued by cement enterprises. Current peak production, industry self-discipline production, heavy pollution influence factors such as weather, cement production line in operation rate reduced year by year, in order to win the market, the cement enterprises in the production of effective period can take various measures to improve equipment availability, by promoting technical innovation and technical reform of the existing equipment and transformation, improve the production efficiency, reduce product consumption to improve the market competitiveness of enterprises.

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