LSS series Multi StageHigh Consistency Pressurized Screen - LSS

I. Overview

Being a new generation of LSS Series Upwash Pressurized Screen, LDS Series Multilevel Upwash Pressurized Screen contains three patented technologies, which can realize 2 to 4-level screening of stock with the same device. This greatly simplifies pulping flow and reduces chests, pumps and piping. While it reduces investment, it significantly decreases electricity consumption.

II. Working Principle

The stock goes through the bottom of LDS Series Multilevel Upwash Pressurized Screen and enters the first screening section. The heavy impurities which can damage the device enter the deslagging mouth at the bottom. The accepted stock enters next step after going through the first strainer drum (Level 1 screening section). The tailing discharged by the first strainer drum gets into the mixing and dilution area of Level 1 stock, which is between the first and second strainer drums. In this area, the dilution water from the outside of device and the tailing get fully mixed. Then they enter the second strainer drum (i.e. Level 2 screening section). The accepted stock passing the second strainer drum can go to next step directly or the first screening section for screening after mixing with the virgin pulp directly. The second-section tailing failed in passing the second strainer drum can be discharged directly or gets into the mixing and dilution section of Level 2 stock, which is between the second and third strainer drums. In this area, the dilution water from the outside of device gets fully mixed with the second-section tailing. Then they enter the third strainer drum (i.e. Level 3 screening section). The accepted stock which passes the third strainer drum returns to Level 2 screening section under the draining effect of dilution water which enters the mixing and dilution area of Level 1 stock. Depending on its utilization value, the tailing failed in passing the third strainer drum can be discharged directly or gets into the mixing and dilution area of Level 3 stock, which is between the third and fourth strainer drums. In this area, the dilution water from the outside of device and the tailing get fully mixed. Then they enter the fourth strainer drum (i.e. Level 4 screening section). The accepted stock which passes the fourth strainer drum returns to Level 3 screening section under the draining effect of dilution water which enter the mixing and dilution area of Level 2 stock. Because it has become useless, the tailing failed in passing the fourth strainer drum can be discharged out of the device directly through the deslagging piping.

III. Main Technical Parameters

The main technical parameters of LDS Series Multilevel Upwash Pressurized Screen depend on the types of stocks and technological requirements of pulping. The strainer drums are in two basic forms: hole screen and slotted screen whose minimum size reaches 0.08mm. The maximum capacity of single machine can reach 500T/D and the maximum screening area of Level 1 strainer drum of single machine can reach 8M². The power consumption varies with the types of strainer drums, screening levels, sizes of screening holes (slots), types of stocks and concentration of feeding pulp.

Pressure requirement for the pulp feeding LDS Series Multilevel Upwash Pressurized Screen: ≥0.1Mpa.

Pressure requirement for the dilution water: pressure of feeding pulp +≥0.05Mpa.

Concentration of Feeding Pulp: 0.1-3% (slotted screen) and 0.1-6% (hole screen).

IV. Structure and Features

The device is consisted of motor transmission system, rotor, strainer drums in the screening sections of Level 1 to multilevel, dilution and mixing areas of Level 1 to multilevel, one to two pipes for return flow pulp, one to three water inlets for dilution water, feeding pulp, heavy slag deslagging mouth, tailing deslagging mouth, etc. It can realize multilevel screening for paper pulp, particularly for the pulp regenerated from waste paper, resulting in very little fiber content in tailing pulp

LDS Series Multilevel Upwash Pressurized Screen has three national patented technologies on its rotor and housing, which enable very low power consumption and prevent impurities from tangling the rotor.

V. Operation Instruction

1. Trial Run

(1). Before the first operation, the pipeline shall be thoroughly cleaned. Then open the upper cover of multilevel pressurized screen, eliminate the impurities entering it and close the upper cover. Manually rotate the pulley of multilevel pressurized screen for several turns to ensure there is no any abnormal phenomenon.

(2). Open the valves for feeding, discharging, return flow, deslagging and dilution water pipes. Put in rinsing or the white water for paper machines. After the air is removed, close the deslagging valve. Open the sealing water and ensure its pressure is 0.1-0.2MPa higher than that of feeding pulp.

(3). Inch the motor to rotate the multilevel pressurized screen for a short while and start it up entirely only when no abnormal phenomenon is found and correct rotating direction is confirmed.

(4). Switch on the feed pump of multilevel pressurized screen.

(5). Adjust the flow of internal circulating pulp.

(6). Adjust the flow of dilution water.

(7). Adjust the valve of deslagging mouth to an appropriate position.

2. Normal Operation

(1) During normal operation, except for the valve of dilution water pipe of main feeding pulp pipe, the valves for the other dilution water pipes shall be opened. If the pressures in the pulp pipes at the various levels become bigger or the pressures in the discharging pulp pipes at various levels become smaller, it demonstrates that the screening plates are blocked. At this time, switch off the feed pump and the valve of discharging pulp pipe. After a few seconds, start up the feed pump and observe whether there is any change in the pressures of feeding and discharging pulp pipes. If the abnormal situation still exists, stop the machine for cleaning.

(2) If the deslagging pipe is blocked, open the valve of dilution water pipe of main feeding pulp pipe until deslagging gets normal.

3. Shutdown Operation:

(1). Dilute the stock in the multilevel pressurized screen with rinsing or white water;

(2). Turn off the feed pump;

(3). Continue to add water into the multilevel pressurized screen until water flows out from the deslagging mouth;

(4). Shut down the motor of multilevel pressurized screen.