Improving press performance step by step. Sami Remmi Vice President, Rolls & Workshop Services

Transcription

1 Improving press performance step by step Sami Remmi Vice President, Rolls & Workshop Services

2 Improving press performance step by step Case: Thai Cane Paper PM 2, Thailand On this Shared Journey Forward, the cooperation between the mill and Valmet was vital for the successful outcome The mill tackled challenges step by step in cooperation with Valmet s Laem Chabang Service center and global experts We are committed to moving our customers performance forward 2

3 Improving press performance at Thai Cane Paper PM 2 Constraints Runnability Quality Existing problems Lower paper dryness after press during lifetime Sheet drop-off from pick-up roll when using only a turbo blower Targets Maximized production rate Longer felt lifetime Improved quality Vacuum energy saving Challenges Optimize press felt design Improve press dewatering Prevent sheet drop-off 3

4 Valmet s solution step by step Case: Thai Cane Paper PM 2, Thailand 1. Focus on press felts and dewatering Valmet Press Felt SPMs were installed. The felt matches the vacuum capacity and minimizes felt marking. 2. Optimizing the vacuum system Perforated Uhle box covers were taken into use for improving the dewatering and enabling to close the extra vacuum pump. 3. Improving sheet dryness and roll performance Valmet Press Roll Cover PP was installed. Average dryness after press increased immediately. Total drive load of the second press decreased and saves money because the new cover operates without watercooling. 4. Training to ensure high performance The mill staff were trained to maintain the results. 4

5 Step 1 Valmet press felt study

6 Step 1: Valmet PresSIM2 simulation tool Dewatering calculation Roll cover and felt selection / input Press concept setting / selection 6

7 Step 1: Water speed through different felt structures Open structure = low nip dewatering Open base Slower water speed, more rewetting Mechanical pressure Hydraulic pressure Denser structure = high nip dewatering Dense base Faster water speed, less rewetting Mechanical pressure Hydraulic pressure 7

8 Step 1: Press felt trial results Felt lifetime and paper dryness after press Traditional felt design Valmet Press Felt Values Average felt lifetime [day] Average dryness after press [%] 8

9 Step 2 Vacuum optimization with perforated Valmet Uhle Box Cover

10 Step 2: Evaluation of vacuum system efficiency on board machines SEC/kWh/t Comment >80 Poor efficiency High probability of savings Savings may be possible Good level for old machines New, efficient machines With modifications to existing vacuum system, effective control system and optimization. With new turbo blower and optimization With new turbo blower, effective control system, new dewatering technology and optimization. 10

11 Step 2: Vacuum optimization with perforated Uhle box cover Principles Machines producing high BW paper/board often run based on Uhle box dewatering only The high vacuum can be compensated for with increased retention time Challenge To eliminate paper drop-off from the pick-up roll and its tendency to follow the top-ply fabric due to the poor vacuum capacity Solution Perforated Uhle box covers were taken into use improving Uhle box dewatering with less air flow and less vacuum system tuning The extra vacuum pump was closed Benefits Less friction - lower press drive load Longer felt lifetimes 11

12 Step 2: Vacuum system capacity comparison Air flow at constant vacuum level Suction couch / Pick-up Duo and Trivac boxes: back layer Transfer roll 1st Top Uhle boxes 2nd Top Uhle boxes Duovac and transfer boxes Original air flow [m3/min] New air flow [m3/min]2 12

13 Step 3 Press roll cover upgrade

14 Step 3: Nip process Typical requirement for each nip Hydraulic force Compressive force Hydraulic force Compressive force Flow-controlled nip (water flow resistance dominates) Soft roll cover More open area Coarser batt deniers Higher permeability Higher void volume Pressure-controlled nip (mechanical resistance dominates) Hard roll cover Pressing uniformity Finer batt deniers High-contact base design Mass uniformity 14

15 Step 3: Press roll cover simulation Roll cover modification Softer cover PMV 15 P&J Cover material Cover hardness Nip load (kn/m) Plain Surface topography Nip pressure, Peak [MPa] Nip pressure, Average [MPa] Nip width [mm] Indentation [mm] Press impulse [kpa s] Nip dwell time [ms] 15 October 5, 2018 Valmet Customer Days Sami Remmi PF 10 P&J 350 Blind drilled PP 12 P&J Grooved

16 Step 3: Roll upgrade with Valmet polyurethane cover Press roll drive energy savings Relative coefficient of rolling resistance Rubber cover roll Valmet polyurethane roll cover Difference of Machine speed [m/min] Power loss with cover deformation* (kw) Energy-saving technology: low coefficient of rolling resistance significantly reduces drive power needed Valmet PU cover needs no internal water cooling Savings in water circulation pump electricity and maintenance 40 kw difference energy 346 MWh/a potential savings of up to EUR 30,000 a year (based on Nordic price level for industrial electricity) 16

17 Step 3: Valmet polyurethane cover running results Comparison of average values: focus on drive load 14% reduction in total drive load of 2 nd press At transfer roll drive motor: 43 kw At 2 nd top press roll drive motor: 500 kw At 2 nd bottom roll drive motor: 500 kw 2nd speed [mpm] 2nd nip load [kn/m] 2nd total drive load [kw] Slot PUBC PUBC+PU cover PUBC= Perforated Uhle box cover 17

18 Step 4 Training and sharing results

19 Step 4: Training ensures high performance also in the future Many machines have achieved good development, but cannot sustain the results. Training can make all mill stakeholders understand how to sustain the results. During the final phase of the project, Valmet trained the mill staff to maintain the results and high performance. Valmet is our partner and gave us good services and support for this improvement. So, we would like to thank the Valmet team for providing this four-phase approach to our PM2, says Sontaya Tunsaranuwat, production Department Manager at Thai Cane Paper. 19

20 Lower steam consumption, longer felt lifetime and energy savings through press improvements = Gain 61 = Gain 35 Summary benefits Results Steam consumption decreased Allowed the mill to permanently close the vacuum pump Achieved higher dryness after the press Extended felt lifetimes with improved quality Better nip dewatering and reduced drive loads resulting in energy savings Average sheet dryness (%) Felt lifetime (days) Average vacuum energy consumption (kw/100) Average 2nd press drive load (kw/10) Average steam consumption (tonne Stram/hr) Average steam consumption decreased from 45.6 to 40.2 tonnes an hour Before After 20 Source: Article on Forward magazine 2/2018

21