The dry production line for the red mud filter press process was opened at2020surname Nian7The actual production capacity of a single filter press is only50.36t/hThe design has not been met.55t/hThe capacity of filter press is not up to the standard, which leads to an increase in the number of operating units of the equipment, spare parts, auxiliary materials, higher energy consumption, and an increase in operating costs; the unstable operation of the red mud filter press and the low capacity constrain the progress of the dry storage of the red mud landfill, which makes the capacity problem of the filter press a bottleneck that needs to be overcome urgently in the production process.1.Process Flow IntroductionThe red mud slurry sent from the red mud slurry treatment process enters the red mud storage tank, and the red mud slurry is fed into the filter press through the feed pump. Using the pressure of the feed pump, the red mud slurry is dewatered in the filter press, and the removed water (filtrate) flows to the filtrate tank, and the filtrate is pumped back to the hot water tank located in the tank area of the evaporation tank, and heated by fresh steam to95°CAfter that, it is used as red mud washing water for red mud washing. After the completion of the filtering and dewatering process, the filter plate will be opened automatically, and the dried red mud will be unloaded into the red mud yard for dry storage through the belt conveyor.1.

2.Factors affecting the capacity of the filter press analysis of the filter press capacity is mainly determined by the filter press cycle efficiency, cake thickness, cake moisture content of three aspects. Circulation efficiency: the filter press is a batch operation equipment, to complete the unloading of a cake is to complete a cycle, the number of unloading of the cake can be completed per hour is the cycle efficiency. Production capacity=(weight of filter cake in a single cycle x cycle efficiency)–(weight of filter cake in a single cycle x recycling efficiency x water content). Through the table1The comparison shows that the filter press capacity can be increased by solving the problems of low circulation efficiency and thin cake thickness. In order to find out the reasons for the low capacity of the filter press, the factors that may lead to the substandard capacity of the filter press were analysed.

(1)Filter cloth quality poor filter press nonwoven quality requirements: air permeability2.5m 3 /m2-minFilter cloth weight750g/m2Rupture strength–radial direction320kN/mlatitudinal90kN/mThe surface of the filter cloth is smooth. Separately tested the1#, and2#Two batches of filter cloth, it can be seen that all indicators are met and are not the main factor affecting capacity.(2)Low compressed air pressure The Filter Press Operator's Manual requires that the press air pressure of the filter press be not less than0.8MPaThe pressure of the blowback air is not less than0.6MPaThe output pressure of the press air compressor and the backblow air compressor was confirmed to meet the production requirements of the filter press. Through the site to confirm that the output pressure of the press air compressor and the reverse air compressor both meet the production requirements of the filter press: the output pressure of the press air compressor is0.97MPaThe output pressure of the blowback compressor is0.75MPa, is not a major factor affecting capacity.

(3)Feed pressure setting low A filter press was selected at the site to test the relationship between the thickness change of the filter cake produced at different settings of feed pressure, from Fig.2Comparison of the table line graph can be seen, different feed pressure, the output of different thickness of the cake, feed pressure and cake thickness is positively proportional to the relationship between the main factors affecting the capacity.

(4)Low circulation efficiency "Filter Press Operation Manual" stipulates that: filter press circulation efficiency ≥2.5vice-/Hours. Randomly selected on site6One filter press test from feed–pancake unloading–The time required for the feeding process, from Table3It can be seen that the efficiency of the filter press cycle2.22vice-/hours, which falls short of design capacity and is a major factor affecting capacity.

(5)Feed solids low feed solids low, single sub-filter press to deal with the end of the bottom flow increased, but the amount of mud processing the same case increased the single sub-filter press operating time, need to reasonably control the feed solids, "Filter Press Operator's Manual" stipulates that: Filter press feed solids must be controlled at>500g/LAccording to the survey, it was found that2020surname Nian7Month-12The average feed solids of the filter presses for the month was only 0.5 per cent.452g/L, which is not up to scratch, is the main factor affecting capacity.

(6)The effect of flocculant addition after the increase in the amount of red mud, red mud in the settling tank residence time becomes shorter, the ability of red mud free settlement, compression decreases, the system needs to be added in excess of the flocculant, in order to ensure that the red mud settling, compression performance, excessive flocculant resulting in the viscosity of the red mud increased, the unloading of the cake of the filter press decreased, affecting the operating efficiency, is the main factor affecting the production capacity.

3.Measures to increase the capacity of filter presses

(1)Determine the most reasonable feed pressure to find out the relationship between feed pressure and cake thickness, cake moisture content, determine the optimal feed pressure for industrial testing, to find out the relationship between cake thickness and cake moisture content under different feed pressures to ultimately determine the most reasonable set pressure. In0.3~0.6MPaThe cake thickness and moisture content are tested at different feed pressures (each pressure is tested at a different level).3(take the average value), through the test to find out the relationship between the feed pressure and the thickness of the filter cake, water content, in order to ensure that the water content of the filter cake ≤25%conditions to achieve the thickest filter cake thickness. From the table4It can be seen that: as the set pressure is increased, the thickness of the filter cake gradually becomes thicker, but the pressure mentioned0.52barAfter that, the thickness of the filter cake is not obvious; with the set pressure to increase the water content of the filter cake shows a rising trend, but the amplitude is small, the pressure reaches0.57barAfter that, the water content of the filter cake exceeds25.0%; All things considered, the pressure is set at0.52~0.56barBetween both the water content of the cake and the ideal thickness of the cake can be obtained.

(2)Improve filter press cycle efficiency Filter presses use aPLCControl, according to the manufacturer to provide the filter press related information, the filter press operating procedures for each step of the time required for the analysis of the demonstration, to improve the efficiency of the filter press cycle, it is necessary to shorten the time of some steps, through the actual test, and ultimately determine the time to adjust the time of the steps can be feed delay, press time, blowing the filter cake, and the development of the implementation of the adjustment of the programme. The purpose of the feed delay is to ensure that the filter chamber is full of slurry to form a thick cake, if you shorten the feed delay, the thickness of the cake is not affected, you can shorten the time, through the test, the filter press feed delay is set in the240~160sBetween, the change in cake thickness is small and negligible, but decreases to160sThe large drop in cake thickness later on is evidence of the feed delay160sThis ensures that the filter press chamber is filled with slurry and a good cake thickness is obtained.160sThe later time is useless and can be removed. The length of the pressing time determines the water content of the filter cake, so the water content of the filter cake is tested on site under different pressing times, and the extra time is eliminated to choose the best pressing time. Through on-site observation, it is found that a large amount of water is discharged from the filtrate pipe at the beginning of pressing.120sThe amount of water gradually decreases thereafter.160sAfterwards almost no water is pressed out, based on this phenomenon, the selection of the160~240sTime period, per10sMeasurement of cake moisture content, per time point3The average value was taken. The test data show that the press180sAfter that, the water content of the filter cake was basically unchanged and the pressing time was set at180sThe water content of filter cake can meet the requirement of water content of filter cake. Blowing back the filter cake, the length of the blowing time determines whether the water content can be further reduced after the filter cake has been pressed, and the changes in the water content of the filter cake under different blowing times are tested on site, so as to eliminate the extra time and select the best blowing time. According to the implementation experience of shortening the pressing time and on-site observation, it is also found that more water is blown out in the early stage of blowback, and almost none in the later stage, according to this law, the best blowback time is selected.10~100sTime period, per10sMeasurement of cake moisture content, per time point3times and take the average value. The test results prove that the blowback60sAfter that, the water content of the filter cake was basically unchanged, and the time of the backblowing air was set at60sIt will be able to meet the water content requirement of the filter cake. According to the filter press programme time adjustment scheme, the operating programme and time of the filter press are optimised: the filter press feed delay time is adjusted according to160sSetting, press time by180sSetting, backblowing time is set by60sSettings. Test after adjustment10The time per cycle for each filter press was used to calculate the cycle efficiency from Table5It can be seen that10All filter presses have a cycle efficiency of2.5vice-/Hours.

(3)Improve the feed solids in principle, the higher the feed solids control of the filter press, the better, which will reduce the amount of attached liquid, reduce the feeding time, the filter press operating time will be reduced, the filter press capacity will be increased, the power consumption will also be less. But the feed solid content is too high will make the red mud is very easy to stain on the filter cloth, resulting in filter cloth cake unloading effect will be worse, the filter cloth filtration effect will be worse, the water content of the cake has increased, the filter cloth is easy to clip between the mud and lead to the filter plate splintering material, increase the failure rate of the filter press. Through continuous exploration, it is found that the feed solid content of filter press is controlled in500~550g/LBetween them, the filter press operates with high efficiency, low failure rate, and good effect of cake unloading from the filter cloth. In order to preserve the stability of the feed solids of the filter press, it is necessary to grasp the operation of the washing and settling tank: firstly, the bottom-flow pumps are backed up and overhauled in accordance with the cycle to ensure the stable operation of the equipment; secondly, the solid content of the discharged material is controlled stably through the on-line instrument and density meter, and the solid content of the discharged material is controlled in accordance with the cycle.500~550g/LEnsure that the outlet pressure of the outgoing diaphragm pump is greater than9MPa.

(4)Precise control of flocculant additive alumina production need to use flocculant to accelerate the settlement, flocculant additive, will increase the content of polymer organics in the system, in order to strengthen the production efficiency of alumina, in the red mud washing work to add flocculant beyond a certain range, plate and frame filter press filter cloth unloading the cake will gradually reduce the effect of this time the red mud cake will be in the filter cloth, so it is not difficult to see that the flocculant for the filter cloth has a certain impact on the role of flocculant, will lead to the increase in the moisture of the cake itself. Certain impact on the filter cloth will lead to an increase in the moisture of the cake itself, so in the application of flocculant need to control the amount of flocculant, flocculant dosage control also need to ensure the flexibility of the need to control, combined with the model of the filter cloth and the use of experience in selecting the dosage of flocculant, will be controlled in the range of standard ratios, to ensure the effective operation of the eventual improvement of the production capacity of alumina.

4.Conclusions By adjusting the feed pressure setting of the filter press to 0 . 5 2 ~0.56MPaThe filter press feed delay is set to160sThe press time is adjusted to180sThe blowback time is adjusted to60s; Increase feed solids control to500~550g/Lbetween; precise control of the addition of settling flocculants and other improvements.2021surname Nian1-3The capacity of the filter presses was increased to56.7t/hThe number of people who have been in the market since the beginning of the year is higher than the previous one.12.6%The filter presses are operating at a rate of73%(math.) genus2020The annual filter press operating rates were all85%In addition, the reduction in the operating rate of the filter presses has resulted in spare capacity and fewer filter presses than would otherwise have been required to meet production requirements.1The number of filter presses has been reduced, and the number of operating equipment has been reduced, saving on spare parts and material consumption, reducing energy consumption, and achieving the following results38$10,000,000/year's economic benefits.

Author:Blue Swordsman (sports) Nong Chien-Jun Tanti, come on! chum wai cheung