Vacuum pulp washing machine is one common pulp washing equipment, suitable for various pulp materials such as wood pulp and straw pulp. It is the key technical equipment for solving wastewater pollution and implementing alkali recovery projects in the paper industry.
Main process parameters of vacuum washer:
Pulp concentration: wood pulp 0.8-1.5%, straw pulp 1.0-3.5%, pulp concentration 10-15%. Vacuum washer mainly relies on water legs to generate vacuum, sometimes supplemented by vacuum pump.
Working principle of vacuum washer:
It mainly consists of drum, tank, flat distribution valve, washing device, pulp stripping device, screen washing device, transmission device, and screw conveyor. It can be used as single unit or in series as a group. The entire drum surface of the washing machine drum is divided into several compartments, each of which is connected to the corresponding compartment on the valve seat end face through filtrate flow channel. The valve core divides the entire end face into vacuum zone, pulp stripping zone, and exhaust zone. The drum rotates inside the tank containing the pulp. With each revolution, each discharge port passes through the vacuum filtration zone, pulp stripping zone, and exhaust zone. Due to the vacuum suction effect, the liquid in the pulp is extracted from the filtrate channel and distribution valve, and the pulp is adsorbed on the outer surface of the drum and peeled off by scraper, achieving the process of pulp filtration, pulp stripping, and exhaust.
The drum body of the vacuum washer is divided into several small chambers that are not connected to each other. When the chambers rotate clockwise and enter the paper material, they are connected to the natural filtration zone that is the same as the atmosphere. At this time, the static pressure of the pulp allows some of the filtrate to enter the chamber and form a pulp layer on the mesh surface. The chamber continues to rotate and penetrates below the liquid surface, while also communicating with the vacuum filtration zone. Under high pressure difference, it is forcibly sucked and filtered to increase the thickness of the pulp layer. After the liquid surface is turned out, it continues to dry the pulp layer on the mesh surface, completing the dilution and dehydration process. The chamber continues to rotate and communicates with the vacuum suction filtration zone to suck the washing liquid on the surface of the pulp layer into the drum, completing the displacement washing operation. The chamber continues to rotate and communicates with the stripping zone, making the vacuum degree in the chamber disappear Pulp.
The flow rate and resistance of the filtrate have a significant impact on production capacity and efficiency. To obtain the necessary vacuum degree, the water leg tube needs to meet the following requirements:
① The washing machine needs to be installed at a high position, generally at an elevation of about 12m, so that the effective length of the water leg pipe is above 9m;
② The filtrate should have sufficient flow velocity inside the tube, and when the flow in the tube reaches a certain speed, it can suck in the gas and quickly extract it in the form of a gas-liquid mixture. The recommended flow rate of the filtrate in the water leg tube is 1-3m/s, which can be lower for straw pulp and higher for wood pulp and bleached pulp;
③ The water leg pipe should be installed vertically as much as possible, avoiding the use of horizontal sections and reducing the number of bends to minimize resistance.
