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Development Trend of Cement Packaging Technology

  ABSTRACT: At present, cement packaging factories have to deal with the packaging problems of cement with various components and fineness, as well as different fluidity and aeration capacity. The demand of cement packaging system and the requirement of flexibility and simplicity of mechanical concepts are increasing day by day. Although modern packaging plants have high-performance machinery and control systems, strict and systematic planning is still needed if packaging quality and packaging capacity are to meet specific needs. This paper will discuss the most important technology and market development trends, the demand for machinery and suitable solutions for modern chemical plants.

  1 Introduction

  Cement industry consumes 60% of 23 billion valve pockets annually. Paper bags with perforated and fast exhaust are mainly used, and the consumption of two-layer paper bags is increasing year by year. Due to the size of various paper bags, the way of perforation, the number of layers of paper or whether there are polyester linings in the middle and the type of valve opening, the difference between different paper bags is very large. Similarly, the types of cement vary according to the DIN EN 197-1 standard alone (there are 27 kinds of standard cement, plus special cement that can not be estimated), and they have different product properties and bagging characteristics. In view of this background, packaging systems have to operate a wide range of cement types and packaging bags, most of which come from different manufacturers and are integrated into terminal products. In order to meet the demand of elasticity, today's packaging should also meet the three important standards of packaging capacity, weight accuracy and bag cleaning. The simplest equipment structure capable of automatic operation and maximum reliability can meet current requirements.

  2. Equipment System Scheme

  In the cement industry, more than 95 new packaging lines or modified packaging lines are now equipped with ROTO rotary packaging machines with a capacity of 1200-5500 bags per hour. Inline stationary packers are now of little practical use.

  The reason is that compared with ROTO packaging machine, it has limited packaging capacity and more complex automatic bagging. Although bagged cement accounts for less than 20% in industrialized countries, it is more than 80% in countries with poor infrastructure and low proportion of ready-mixed concrete. Packaging facilities are assembled with loading silos or placed in separate workshops. Despite the different ways of assembling sites, packaging facilities include silo unloading and vertical conveying, debris removal screens, intermediate silos, metering devices, ROTO packers with electronic weighing systems, recycling systems, handling lines for unloading and discharging facilities with weight correction systems and damaged bags, and transport facilities for packaging bags to pallets or loading facilities. The installation is almost the same. The full-automatic bag-inserting machine supplies the empty paper bags to the packing machine. In order to ensure the complete conversion of packaging bags from one to the other, the use of large bundles of packaging bags is more suitable than the package drum. Bag feeding capacity of the machine is 4000 bags. h means that the working time of a single bag is 0.9 seconds. If 17 bags of empty bags are used, a bundle of empty bags will be provided every 15 seconds. The advanced equipment system scheme also includes the empty bag unloading tray system. The core unit of the empty bag unloading tray system is an industrial robot equipped with grabs and special software. It will directly grab the empty paper bag bundles without hoops from the tray and transmit them to the automatic bagging machine. It is more automated than the empty bag roll operation and more flexible in product replacement. Cement shipping and packaging lines are often installed in remote areas along with cement production. In addition to having a high cost performance ratio, the basic development objectives are naturally reliability, durability, low maintenance requirements, even for harsh conditions and easy to operate by relatively unskilled workers. When choosing the supplier of empty paper bags, we must consider the production sequence and installation of machinery and equipment to ensure that the quality parameters required by the optimal loading process are provided. Here, there are several points to note:

  - Following the geometry of paper bags (dimension, angle, shape deviation, dimension and phase correction of valve sleeve and pinhole)

  - Avoidance of process errors (mis-cutting, folded bags, etc., hose curling and expansion due to the force of roll paper)

  - Avoiding gluing errors (excessive, excessive, defective parts, stains)

  - Sealability of paper bags (depending on the design shape of paper bags, but sometimes affected by bonding, grooving and extrusion systems)

  - Flatness of package (avoid deformation after processing; avoid drying)

  - Good exhaust performance of paper bags.

  Equipment system solutions are based on long-term shared experience between suppliers and users. The planning of equipment system should be considered comprehensively according to the following requirements:

  - Clear and orderly machine arrangement

  - Transparency of all functional subunits

  - The automatic operation of the whole system is controlled by the pre-selected program of the central processing unit.

  - With the aid of diagnostic procedures on the operating dashboard through text instructions and graphical displays, production failures under any circumstances can be detected and eliminated.

  3 charging technology

  The core unit of cement packaging line is ROTO packaging machine, which uses a rotating machine to load and weigh cement through 3-16 feeding nozzles. This idea of loading was put into the market by Haver & Boecker in 1960. Since then, the cement industry alone has purchased more than 2,500 HAVER ROTO packaging machines. The latest generation of HAVER ROTO packaging machine (Figure 4) is the packaging machine that can best integrate the demand of cement industry market. Table 1 shows the standard quota capacity of ROTO packers packed by the automatic loader according to the predetermined weight.

  3.1 Loading, Weighing and Data Technology

  Vertical feed turbine system is used for cement loading. This turbine can be equipped with wear-resistant hard metal lining. Due to the low gas flow requirement of the feed turbine, the material in the bag is highly compacted, which reduces the excessive pressure on the paper bag. Another advantage is the reduction of material reflux during loading operation. Due to the addition of a recycling guide plate, the bags are not easily contaminated by products that continue to drip out. Because the charging tube of the new generation packaging machine is equipped with an inflatable sleeve, there is no loss of the product during loading operation and bagging. Subsequently, the packing bag is smoothly pushed away from the orifice of the charging pipe, thus avoiding dust generation and no product loss from the open orifice.

  The charging operation is controlled by a more accurate HAVER MEC?-20 electronic scale system. This system has obtained PTB test certificate and international OIML certificate. MEC?-20 electronic scale system is based on microprocessor technology and realizes the combination of electronic scale system and machine control on a single system. The installed system is equipped with up to 99 types of program memory, which can be combined arbitrarily according to different bag weight, products and packaging bags provided by different suppliers. All weight parameters, rack height, unloading capacity of packing bags, automatic empty bag inserting machine and unloading procedure of empty bag unloading machine system are set by the selected type. In addition, all the parameters according to production capacity, such as the capacity of the vertical double-way grid wheel unloader before the packaging machine, the speed of the packaging machine that determines the capacity of the packaging machine, and the speed of the unloading of the packaging bag and the conveying speed of the operation line, can be optimized by buttons.

  The communication processor, also known as the server, connects the scales of the rotating parts of the packer to the non-rotating parts, such as the scales for correcting the weight. Statistics and error information are exported to higher-level network systems through servers. The statistical evaluation of data is completed by DPS V4.0 data processing system. Using some data such as line number, scale number, variety number, variety mark, actual weight, rated weight, tar weight, overweight limit, deficit weight limit, variety change, error information, status of scale and text information, the following values can be determined: average weight, standard deviation, total weight, total package number, qualified package number, loss weight package number and overweight package number, hourly packing capacity. Start and stop time for a batch of assignments. The interface of man-machine dialogue system is simple and friendly.

  This will flexibly generate and print job logs in the form of machine reports, monthly annual reports, error reports and individual weight reports. A single weight report can be used to produce weighing maps or Gauss distribution curves. Because MEC?-20 electronic scale system is equipped with trend setting mechanical equipment, HAVER weight correction system and DPS V4.0 data processing system have high accuracy of weight correction and statistical evaluation ability of single sample, so it is possible to implement ISO 9000 series standard framework not only in production quality, but also in recording documents.

  3.2 Seam Packing Technology

  Using the sewing system developed by Haver & Boecker, the valve pocket with special valve sealing device can be [6] used for ultrasonic dustless welding. This was the first time that a basic solution was provided for the complete cleaning of packaging bags. Since the first HAVER ROTOSEAL packing machine was put into operation five years ago, by May 2003, more than 430 loading tubes equipped with new stitching technology had been sold all over the world. In addition to the gypsum and mortar industries, the cement industry has installed many of these packaging machines. The user's experience is very satisfactory.

  The suture system applies high frequency vibration to the upper valve orifice to complete the suture of packaging bags. The resulting vibration results in intense (rapid) heating of the plastic in the valve, which eventually welds the two pieces of the valve opening together. After a short period of cooling, the sealing tools are re-separated to transfer the packaged bags with sealed and load-bearing valve ports to the unloading conveyor belt. The advantage of this sewing system is that each feeding nozzle is equipped with a sewing device, whose sewing time is controlled in the working cycle of the high-efficiency packaging machine.

  This suture system ensures that there is no loss of products under normal loading conditions, thus ensuring the cleanliness of packaging bags during shipment to palletizing devices and ultimately to consumers (Fig. 8). This is quite different from the traditional packaging bag valve mouth called self-sealing. Because this self-sealing is incomplete, there is a certain amount of product loss during the whole loading and unloading process from loading to palletizing. This not only pollutes the packaging bags, but also pollutes the loading equipment and its surrounding environment, and also affects the weight accuracy of the cement bags. Cement market competition is becoming more and more fierce, complete stitching, accurate weight and clean packaging bags have a stronger competitive advantage than traditional packaging bags.

  3.3 Unloading Production Line with Weight Correction System

  Perfect unloading and processing production line is composed of unloading conveyor belt, bag straight conveyor belt, bag soot blowing station, accelerating conveyor belt, HAVER weight corrector and automatic tearing and returning device for unqualified bags. Its performance can achieve reliable handling of the bag flow speed brought about by modern and efficient production.

  The above-mentioned unloading production line takes over the full package of cement bags unloaded from the ROTO packaging machine, cleans and weighs them, and sends them to consumers in this state. Material loss can be diagnosed and compensated. Any defective cement packages are automatically returned and torn to ensure that only the properly loaded cement packages arrive at the palletizing facility. The weight corrector makes the weight accuracy more accurate, so as to better complete the correction of the system output. Since the weighing function is transplanted to the periphery of the packaging machine, the operation is not sequential but parallel.

  The application of sewing system greatly simplifies the sequence of unloading production line (Fig. 10). The new valve opening stitching greatly simplifies the equipment system scheme, which is due to the fact that the natural dust removal system can be designed smaller without the need for a clean packaging bag device. Therefore, the overall height of the equipment system can be reduced and the construction cost of the building can be saved.

  3.4 Safety in Production

  This requires suppliers to provide a qualified declaration that compliance with and enforcement of safety requirements has been verified and that factory operations are authorized. Automatic packaging equipment should be designed to meet highly stringent safety standards. This includes setting up some mechanical protection in all dangerous areas, such as closed safety net, safety door, emergency stop button and pull rope, safety light barrier at the entrance and exit of safety area requiring machine operation, induction closed loop at the stop position of stacking, safety protection circuit in power outage and emergency state, safety maintenance and maintenance platform including access stairs, warning signs and phase use. Security instructions in the language of the country concerned.

  In cement factories, especially in packaging workshops, employees are exposed to technology because packaging workshops are open to the public as part of delivery facilities. We don't want people who transport cement to come into contact with equipment, but this possibility can't be completely avoided. Duty-conscientious equipment suppliers and equipment users certainly hope not to abandon the aforementioned safety-related equipment components.

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