Production technology of the most popular APMP

Key points of APMP production technology of Qiqihar Paper Co., Ltd.: the process, equipment and system characteristics of the 200t/dapmp production line imported by Qiqihar Paper Co., Ltd. from Andritz company are introduced, and the optimization measures of screw press are discussed in detail

Keywords: APMP; Screw press; Spiral extrusion and release machine; Yang Mu

Li Tiehong, engineer, deputy chief engineer of chemical mechanical pulp workshop of Qiqihar Paper Co., Ltd

line is a 200t/d all poplar APMP (alkaline peroxide mechanical pump) production line introduced by our company from Andritz company in Austria. Its main feature is to use all poplar pulping; Two stage impregnation and two stage pulping. The produced size is mainly used in the production of low weight offset paper

1 flow APMP process flow

line is composed of wood chip washing, two-stage impregnation, two-stage grinding, screening and other parts. See the process flow in Figure 1 for details

Figure 1 process flow

1.1 the composition of the flow process

line is that the chips first enter the chip bin with a volume of 20m3, which is equipped with a steam heating device. The wood chip scrubber drives the mixing wing through its main shaft to stir the wood chips immersed in a large amount of water in the container to remove the sand, stone, metal, plastic and other impurities carried by the wood chips. If the following 10 states appear, it is abnormal. The wood chips above are overflowed and brought to the dehydration screw, and the precipitated impurities are collected and discharged by the regularly opened valve. The water carried by the wood chips is removed by the dehydration screw with a perforated self-cleaning screen, and the wood chips are sent to the pre steaming bin with a structure similar to that of the wood chip bin. It is softened by steam heating and has constant moisture. Then the wood chips are extruded by MSD, and the wood chips are separated along the grain direction. At the same time, the moisture and some lignin in the wood chips are removed. The extruded wood chips absorb a large amount of liquid medicine at the MSD outlet, and then enter the impregnator. Then enter the #1 reaction chamber for bleaching reaction. The reacted wood chips are spirally sent into the second MSD, which is basically the same as the first MSD; However, the extrusion ratio and the ratio of liquid medicine are different, and the residence time in the second stage impregnator is the same as that in the first stage; The wood chips reacted in the #2 reaction chamber are sent to the primary refiner through two inclined screws, and then sent to the intermediate tank after constant temperature and pressure pulping. The slurry is diluted here and pumped into the screw press together with the slurry returned from the pressure screen. The dry slurry (concentration 30%) after extrusion and dehydration is sent to the second stage disc mill, and then enters the submersible tank after being diluted by the slurry mill. The slurry after potential elimination passes through the pressure screen, the good slurry enters the slurry tower, and the slag slurry returns to the intermediate pool

1.2 flow process characteristics

1.2.1 flow adopts two-stage impregnation and two-stage normal temperature and atmospheric pressure pulping

line is the APMP production line adopts two-stage impregnation and two-stage normal temperature and atmospheric pressure pulping process, which has the following characteristics: (1) it makes the reaction between liquid medicine and wood chips sufficient, coupled with the effective control of various process parameters by the system, the pulping quality is good and the whiteness is high. (2) It has strong adaptability to wood varieties, and hard miscellaneous wood such as poplar and birch can be used. (3) Strengthen the impregnation effect, make pulping and bleaching proceed at the same time, and speed up the pulping speed. (4) The dosage of chemicals can be flexibly adjusted to obtain the required indicators. (5) The impregnation effect is good, which can reduce the energy consumption of the refiner. (6) This system has compact equipment, less land occupation, small investment and no pollution to the environment

1.2.2 the flow auxiliary process flow is simple and reasonable

the line is seen from the process: the clean water from the dehydration spiral enters the chip washing system for recycling. After the filtrate of the spiral press is concentrated by the circular thickener, the energy used by the pulp accounts for about 12% of the total energy consumption of the national economy, and enters the intermediate tank, and the filtrate enters the washing system or dilution system. The washing and dilution of the system mainly uses white water, which can not only save clean water, but also recycle fiber

2 main equipment and control system

2.1 flow screw extruder (MSD)

line is this equipment model msd400, which is used for extrusion and thawing of wood chips after pre steaming and impregnation, removing moisture and lignin in wood chips, tearing wood chips into small pieces according to the grain direction, making them better absorb liquid medicine, reduce disk grinding energy consumption, and lay a foundation for obtaining good chemical mechanical pulp. Its main structure is: cantilever variable diameter spiral shaft; High strength screen basket with anti slip strips inside; There is a 4:1 (6:1) extrusion head at the outlet. Because the wood chips contain drugs, the materials in contact with the wood chips are stainless steel 316, and the frame is welded from carbon steel. The motor equipped is 6300v, 600kW and 1500r/min

2.2 flow grinder

line is a single disc grinder with the model of mrsd58/62. There is an openable swing door in the front, which is equipped with a static plate. This structure facilitates the replacement of grinding discs. The rotating disc is driven by the main shaft, and the belt feeder is fixed on the rotating disc. The moving disc feed is hydraulically driven, with simple structure, so it can be operated conveniently in all storage tanks and pipelines. The grinding disc has two grinding areas: one is the crushing ring area, which is made of 174PH material, the tooth dam is thick, and the distance between teeth is large; One is the fine grinding ring area, made of alloy 440, with moderate tooth dam and small middle distance. Wood chips first enter the crushing area, from large to small, and then enter the fine grinding area to become fibers. The grinding disc gap is controlled by the instrument, and a control mechanism is set to prevent the plate from touching, that is, the accelerometer, speedometer and axle position monitoring system. This mechanism can absolutely avoid the contact between the moving and stationary plates. The motor power of the pulper is 8000kw, the voltage is 6300v, and the speed is 1500r/min

2.3 flow screw press

line is selected. Screw press is a new product of Andritz screw Bauer company, which integrates the advantages of various companies and improves the old screw press. The model is scplm, as shown in Figure 2

Figure 2 scplm screw press