Take these measures to solve the steaming system problem

[China Packaging News] A 150t / d continuous cooking and pulping production line of a paper company in Shandong uses wheat straw as the main raw material and adopts the alkaline cooking process. The production process is composed of dry preparation, wet preparation and continuous cooking. After a series of problems in the operation of the equipment, a technical transformation was carried out, the quality was stable, and the average daily output also exceeded the original design capacity (the maximum daily output reached 180t ).

After the project has been put into operation for a period of time, the production capacity has not reached the design requirements, the equipment has many failures, frequent unexpected problems, low start-up rate, and the quality of the coarse slurry is unstable, the slurry is difficult to wash, the screening slurry volume is large, and the yield is low . In order to increase production capacity and improve quality, a comprehensive analysis of each part of the production is carried out, and the problems of segmentation search are solved one by one to achieve the optimal configuration of the entire system.

1 dry stock

( 1 ) The lawn mower ( 12t / h ) has low stand-alone efficiency and requires many personnel. With the passage of time, the Feeder is prone to fatigue, which causes the grass cutter to supply grass intermittently and unevenly, resulting in unstable load of the lawn mower and large fluctuations in the material level of the silo.

Improvements: the original four 12t / h turf cutter transformed into two 24t / h turf cutter, cut grass overall efficiency increased by 50%, to ensure the supply of raw materials even steamed. At the same time, in order to overcome the problem of uneven grass loading caused by the influence of the artificial grass loading capacity, an automatic small grass cutter was introduced to improve the efficiency of grass feeding. The 24t / h lawnmower can achieve continuous and stable operation, alleviate the phenomenon that the load on the grass is large and small, reducing equipment failures and improving the startup rate.

( 2 ) It is difficult to replace the sieve plate of the double-roll dust collector and the replacement cycle is long. If the sieve plate is not replaced in time, it will cause a poor dust removal effect or a large amount of grass chips in the dust removal foam.

Improvement measures: In order to replace the sieve plate in time when the grass quality changes and reduce downtime, the fixing method of the sieve plate of the double-roll dust collector is changed from the original bolt to the drawer type. This scheme not only reduces labor intensity, but also improves labor efficiency. The screen hole of the dust collector can be changed in time with the change of grass quality, which not only ensures the dust removal efficiency, but also reduces the loss of grass material.

( 3 ) In the actual production, there are many sliding parts of the rotating parts of the silo. Due to the poor operating environment of the equipment, it is prone to failure.

Improvement measures: In order to avoid the shutdown of the entire production line due to the failure of the silo, a belt conveyor is added on the upper part of the silo to directly connect the silo inlet to the outlet. When the material bin is faulty and needs to be shut down for maintenance, timely switch to the top conveyor to ensure continuous operation of continuous steaming. Insufficient: The buffer effect of the silo disappears, and the feeding amount of the cooking system cannot be adjusted flexibly, but it has bought time for maintenance work and ensured the start-up running time of the entire production line.

2 Wet preparation

( 1 ) The sieve holes on the sieve plate of the hydraulic grass cutter are small and dense. First, it affects the throughput of grass chips, and second, the sieve plate is easily deformed and falls off under pressure.

Improvement measures: In order to ensure the passing ability of the hydraulic lawn mower, the original hole opening method of the hydraulic lawn mower screen was transformed from the original dense small hole to the sparse large hole, which increased the grass leakage rate of the screen board and guaranteed Throughput per unit time.

( 2 ) The amount of grass supplied by the blade pump is affected by the concentration of grass in the hydraulic lawn mower, and the fluctuation varies greatly.

Improvements: In order to improve stability for grass, easing due to the influence of the concentration of water in the grass changes Toppers on the grass, the original two 450m3 / h replace the pump 600m3 / h, to ensure that the spiral ramp and back to the feed screw The feed volume of the material will pave the way for the improvement of production capacity.

( 3 ) The rotating universal joint of the oblique spiral dehydrator is seriously worn, with short running time, frequent replacement, and sometimes sudden fracture, which causes damage to the reducer casing.

Improvement measures: In view of the easy damage of the universal joint of the inclined spiral dewatering machine, the internal commutation node of the universal joint was changed from a simple sliding contact to a needle roller bearing structure during the first transformation, and the service life of the universal joint was changed from the original one. The month is extended to three months, but there is still a problem of high noise. The second technique was changed to the direct connection mode of the reducer and the spiral shaft, which greatly reduced the noise and made the operation more stable.

3 cooking

( 1 ) Abnormal phenomena such as back spraying and slipping often occur during feeding of the feeder equipment, which affects the smooth operation of the equipment and the operation safety.

Improvement measures: Analyze and determine the factors restricting production: poor dehydration of grass blades; excessive wear of spiral shaft and anti-skid strip; loose feeder belt; low pass rate of grass cutting. To solve the problems that arise: To reduce the moisture of the feeder blades, add a leaking sieve plate at the bottom of the pre-steaming screw conveyor, and the opening should be as large as possible when the strength permits; summarize the production experience and replace the screw regularly The shaft and anti-skid strip must ensure that the feeder is always in a high-efficiency and stable state; the belt of the feeder must be checked every time the machine is stopped; the inspection of incoming material acceptance rate should be strengthened, and the reserve material should be notified immediately when the grass chip acceptance rate is found to decrease Replace the grass cutting blade.

( 2 ) When the feed volume of the feeder is large, the cooking quality is unstable, the raw material is too much, and the yield is low; sometimes the local filling factor in the cooking tube is too large, the airflow is not smooth, the pressure difference is large, or the pushing torque is large, resulting in cooking Tube " channeling " .

Improvement measures: In order to save investment in new projects, three cooking tubes were used. At present, when the feeding amount of the feeder becomes larger, the phenomenon of evaporative opacity and unevenness occurs. There is more raw material, more slag is discharged in the washing and screening section, and the pulp yield decreases. In order to improve the cooking efficiency, a new cooking tube was added, and the original three tubes were changed to four tubes. After transformation, large liquid ratio cooking is used to increase the rotation speed of the cooking tube to ensure smooth flow of the gas and to prevent the occurrence of " shaft channeling " phenomenon due to excessively large filling factor . After operation, it was found that the consumption of cooking alkali decreased by 10% , the quality of cooking pulp also improved significantly, the coarse slag rate fell below 3.5% , and the pulp yield increased significantly.

( 3 ) The agitator of the unloader operates under high temperature and high pressure, and black liquid leakage often occurs. When falling into a large metal foreign body, the rotor is easy to get stuck and damage the gear of the reducer. After the decelerator is deactivated and removed, the rotor will be affected by the spraying effect of the slurry, and the stirring fin will slowly drift to the vicinity of the nozzle of the spraying and discharge, affecting the spraying.

Improvement measures: change the operation mode of the unloader, remove the original internal agitator as a whole, and transform the outlet spray line. A is the discharge valve, B is the ball valve added to the discharge line (using the quick opening and closing features), and C is the high pressure black liquor valve. Under normal conditions, the B valve is normally open and the C valve is normally closed. When the spraying is not smooth, you can open the C valve and close the B valve. After 10 to 20 seconds , open the B valve again to see the liquid level in the discharger. Whether it drops, if it drops, close the C valve and continue to turn on; if it does not drop, continue to close the B valve, and then backflush, repeated many times until it can be opened. If the valve B is turned off multiple times , it will be switched to the standby blow-off valve to ensure normal production, and then continue to backflush. After the shutdown and maintenance, the pressure of the cooking tube will be emptied and drained, and then manually cleaned.

After the renovation, not only the maintenance cost is reduced, but also a motor and its operating cost are saved. It has been proved by practice that the operating effect is good.