There are roughly four production processes of cement wood wool board, namely, semi-dry method, hot pressing method, three-layer orientation method and flat pressing-autoclaving method. At present, the production process of cement wood wool board basically adopts semi-dry method, which is mature and reliable, but the production cycle is long, there are many auxiliary equipment, and the thickness tolerance is large, which requires sanding. However, at present, this method has relatively systematic stereotyped production equipment and reliable products, and it is a production method that is being promoted all over the world. In addition, the rapid curing of cement wood wool board by hot pressing is a hot spot at present, and many experts and scholars at home and abroad are engaged in this research, but there are still some problems in this production process, which has not been adopted by manufacturers. Here's a brief introduction: this production method is widely used in the Netherlands, Germany, France, Finland, Russia, Japan, Switzerland and other countries. Its basic meaning is that cement and wood materials are added into the mixer to ensure the water needed for cement hydration, and water is added as little as possible to make the mixture of cement wood wool board form a semi-dry state, and then the semi-dry mixture is spread on the bottom plate through the process of paving machine, and the base plate blank is stacked on the base of the model car with mold-locking mold by a laminator, with the stacking height of 2 meters, and is sent to a press for pressurization by a conveying device. Depending on the type of use of the plate, different pressures are applied to the plate in the press. General unit pressure is 2.5-3.0 MPa. The board is pressed to the required thickness on a press, locked by a locking device, and the cement and wood materials are consolidated under pressure. In order to shorten the hardening time, the locked plate should be hardened in an intensified curing kiln with a temperature of 60-80 degrees Celsius. Generally, it takes about 8 h at 540-640 degrees Celsius, then the slab is demoulded, and then it is naturally cured at 70- 1 10 degrees Celsius for 5-7 days to control the moisture content of the slab at 9% 4%.

The semi-dry production process is mature and reliable. So far, it has made a big step forward in the aspects of mechatronics of production equipment, production program control, accurate measurement and thickness control, and improvement of paving quality, etc., compared with the 1960s. It can produce plates with a thickness of 8-40 mm without carbon dioxide injection equipment. As a complete set of equipment with an annual output of 30-50 thousand cubic meters, the price is 30%-50% lower than that of the same type of hot pressing equipment.

Limitations of semi-dry process: 1 The production cycle is long, and the initial strength of demoulding can be formed. Even at 60-80℃, thermal curing takes 5-8 h, which has strict requirements on the storage period of wood materials. 2. Auxiliary production equipment is added, such as pad, corresponding pad returning device, cleaning device, conveying roller device, mold locking device, curing and hardening kiln, demoulding and stacking device. The corresponding production workshop occupies a large area and is an integral part of the semi-dry production process. The thickness deviation of semi-dry plate is large, so it needs sanding treatment.

Wood wool → mineralization and impregnation → mixing → paving and molding → preloading → pressure molding → mold locking and curing → demoulding → secondary curing → trimming → inspection.

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Cement → measurement

Figure 1. Process flow of semi-dry cement wood wool board This production method refers to that the wood materials are evenly and horizontally arranged in the core layer of cement wood wool board and vertically arranged in the surface layer, so that the dimensional stability and strength of the board are better than that of the hot-pressing semi-dry process. This directional arrangement is realized on a specific directional paving machine. But this kind of wood material should have a certain width, and flake shavings are the most suitable.

Flat pressure-high pressure sterilization method

A certain amount of siliceous raw materials were added to the composition of raw materials by flat pressing method. The best silicon content is quartz powder, but it can also be replaced by fly ash. Fly ash requires silica content less than or equal to 50% and ignition loss less than 8%. Other components of the flat-autoclaved process are basically the same as those of the semi-dry process, except that the template is not a flat plate but a special-shaped template required by the manufacturer. In the production process, the pressed and mode-locked slab should be cured in a curing kiln at 80℃ for 12- 16 h, and then demoulded and sent to an autoclave at 172- 185℃ for curing for about 20 h to form a stable tobermorite gel with small shrinkage, so as to obtain its cement wood wool board. The method refers to adding hydrated lime equivalent to about 65,438+00% of the cement mass to the mixture of cement and wood wool, heating the slab in a multi-layer hot press or a single-layer hot press, and spraying carbon dioxide equivalent to 8%-65,438+00% of the cement mass to the slab at the same time. Due to the exothermic reaction between lime and carbon dioxide in the blank, the temperature can reach 120℃, and a certain amount of carbon dioxide is produced at the same time. The hot pressing process shortens the forming time to 4-5 minutes, and the final strength can be obtained after the hot pressing plates are stacked for 2 weeks. The hot pressing method simplifies the production process, and does not need a pressure maintaining and tensioning device and a hardening and curing kiln, which greatly simplifies the number of backing plates and hot plates returning to processing devices and reduces the production site without pressure relief and demoulding facilities.