Extraction of Wheat Straw Pulping Black Liquor

I. The current practical technologies for the treatment of straw pulp pollution mainly fall into the following three categories:

(1) Sulfate/alkali wheat straw soda liquor alkali recovery technology: alkali recovery rate of 60%, reduce pollution load 60% -70%, supporting biochemical or physical treatment after removal of COD can be 90%;

 (2) semi-chemical pulp, lime straw waste liquor made by two stages of anaerobic digestion can remove COD 70%, and can recover biogas;

 (3) The comprehensive utilization of straw pulp waste liquid, recovery of lignin and other resources, can remove COD 60%, with simple biochemical and physical treatment, COD removal rate of 80%. 

Second, the status of black liquor extraction equipment in wheat straw mills

1. Drum type vacuum washer

The equipment uses multiple countercurrent dilution, concentration, and supplemented by the principle of displacement washing, generally consisting of 3-4 units in series, reliable operation, simple operation, is a relatively better equipment for straw pulp alkali recovery extraction section.

 2, stainless steel spiral mesh belt washing machine

不锈钢 The stainless steel spiral net washing machine included in the 1994 Young Industrial Science and Technology Development Project was jointly designed, developed and tested successfully by China Paper Development Baoding Design Corporation, Zhucheng Papermaking Machinery Factory and Anqiu City Paper Mill.

不锈钢 Stainless steel spiral mesh belt washing machine adopts stainless steel spiral mesh belt (opening rate: 45°%) as support and power transmission. The above covered polyester online flanging 45 angle, the overall structure of the box, stainless steel mesh on both sides of the edge Sealed and sealed by the screen plate, under the net by the case roller support, under the steel belt by the high-pressure centrifugal fan suction, roll assisted liquid removal. The steel belt filter operates in the box, which overcomes the problem of running liquid and running slurry, improves the black liquor recovery rate, and the steel belt and the filter mesh are connected at one end, and the replacement is convenient. At the same time can be arranged on the first floor. 

The equipment sizing is easy, wide adaptability, solve the black back black phenomenon; easy operation, stable operation, layout for the plane network type; compact structure, small footprint, civil construction and investment province, low operating costs, for our country wheat straw ink Liquid extraction provides a more advanced device. 

3, vacuum roller type net washing machine

The vacuum roll-type net washing machine developed by Jining Light Industry Machinery Plant of Shandong Province is a kind of full-displacement washing machine. It has now been put into trial operation at Tai'an Paper Mill in Shandong Province. The principle is similar to horizontal belt type vacuum pulp washer and DD pulp washer, and has the advantages of vacuum drum type pulp washer and horizontal belt type vacuum washer, which can meet the needs of black liquor extraction of straw pulp.

真空 Vacuum roller type net-gripper washer consists of five vacuum rollers and two filter screens. It has one forming section and four countercurrent replacement sections. The mass transfer speed is fast and the replacement effect is good. The immersion type displacement washer is used to make the slurry. Both the washing liquid and the washing liquid are placed in the tank body, which effectively prevents the problems of running, running, dripping and leaking; the sliding friction surface is small, the transmission power is reduced, the energy saving effect is remarkable, and the service life is long; the structure is simple, the operation is convenient, the area is small, and the manufacturing cost is low low. But still need to pass the test of actual production and operation. 

Third, to improve the black liquor extraction performance

It is no longer a simple research topic to improve the black liquor extraction performance of straw pulp, but it is a systematic project for equipment development, factory trial, process control, performance testing, and process design. It should be extracted from raw materials, steamed, washed, and removed silicon. Various aspects are optimized to improve the performance of straw pulp filtration and concentrate on a production line to effectively improve the extraction performance of black liquor. If wet and dry preparation is used, the removal of silt and grass clippings in wheat straw will help prevent fouling of the filter mesh; rapid steam cooking, cold spray and other improved cooking processes will retain certain steamed residual alkali, which can make the crude slurry slightly incoherent. Better water drainage is maintained at high hardness. The effects of immersion washing, spray washing, and diffusion washing on the extraction of pulp black liquor were studied and applied to the grass pulp mill. 

Although, the new tapered valve vacuum drum washer, stainless steel spiral mesh washer, and vacuum roller net washer have been put into trial operation at the factory, it may become an advanced straw black liquor extraction equipment, Good market prospects. However, in order to thoroughly solve the problem of extraction of black liquor from straw pulp, it is necessary to improve and improve the above equipment and develop pulp washers that are suitable for the characteristics of straw pulp.

 The country provides corresponding loan taxation concessions, and invests a lot of manpower and material resources, introduces advanced foreign technology equipment, and fully guarantees the extraction capacity in design, with a production capacity of 1t pulp/d equipped with 1m2 extraction equipment as a benchmark and guarantees With an extraction rate of 85% and a concentration of 6°Be' (60°C), the extraction rate is improved to 90% and the concentration is 8°Be' (80°C), so that alkali wheat straw black liquor extraction and even alkali recovery will be achieved. Breakthrough progress.