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Preventive Maintenance
In Milling
Back up power for boiler feed pump when turbine tripped
In Milling
uliang v
Honorary
Honorary
May 21, 2022
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Fat pit size for POM
In General Discussion
uliang v
Honorary
Honorary
Apr 16, 2022
The oil in your Pond#2 could be free oil or cellular oil. Free oil can be recovered at the Fat Pit by static separation with sufficient retention time. Cellular oil cannot be separated by static separation or mechanical separation (sludge centrifuge, decanters, etc). You can read more about this at http://poeb.mpob.gov.my/nature-of-oil-in-sludge-discharge/. Oil accumulation in Cooling Ponds after sometime is unavoidable. The challenge for millers is to eliminate the loss of free oil from the mill. C.S.Tan is spot on with the recommendation of having two Fat Pits. One for the heavy phase (final discharge) from the Sludge Separators and Decanters and the other for the streams of liquid with free oil, like the Sterilizer Condensate, flushing from the Sand Cyclones, overflows from Crude Oil Tanks, etc. It make no sense to mix the waste sludge strams from the Sludge Separator and Decanters, which usually has less than 1% oil on sample, with the free oil from the other streams, and then try to recover the oil from the mixture in the Fat Pit. The primary purpose of Fat Pit for the heavy phase sludge from the centrifuges and decanters is to ensure the centrifuges and decanters are not bypass during operation. Presence of free oil in this pit will indicate problems with the machines or operator apathy. I have come across operators running centrifuges minus the nozzles. The Fat Pit for the other streams is the one from which the mill can easily recovery free oil. Excessive oil in this pit, will alert the mill supervisory staff of operational issues like repeated overflows from tanks, sterilization cycles or FFB quality issues all leading to higher oil losses. I also concur with C.S.Tan, the monitoring of oil losses should be on Oil/DM or OIl/NOS instead of oil on sample. Excessive dilution will show lower oil loss on sample but the net oil loss will be higher.
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Superheater operating at 70% Loading
In Milling
uliang v
Honorary
Honorary
Feb 17, 2022
Mr CS Tan has excellently outlined what one should be looking out for in the operation of the Superheater in Boilers to prevent overheating and distortion of superheater tubes. I will add to that by sharing an experience of a friend who was operating a mill in Johore several years ago. The mill had bought, installed and commissioned a boiler equipped with superheaters.. After less than 2 years in operation, the superheater tubes failed. The boiler manufacturer attributed the failure of the superheater to wrong operating procedure, namely: 1. Superheater drain valves not opened during steam built-up during boiler start up operation. 2. Again superhaeater drain valves not opened after boiler shutdown. The boiler manufacturer decided to install an automatic drain valve for the superheater tube bank to prevent steam starvation during start up and shutdown. Again, after less than 2 years of replacing the damage superheater tubes and installing automatic drain valves, the superheater tubes failed again. The problem was finally resolved by reducing the number of tubes in the superheater tube bank. This effectively increased the flow of steam in the remaining tubes of the superheater and prevented overheating of the tubes. Lessons for Mill Engineers: 1. Inspect your superheater tubes for signs of overheating (distortion) during inspection. 2. Check your superheated steam temperature and the degree of superheat. 3. Do not run your boiler at very low throughput for long period. 4. If you need to invest in a bigger boiler for future requirement, inform your boiler supplier so that the superheater can be sized for your current capacity requirement instead of the rated capacity of the boiler. 5. Refer to the SOPs by Mr. CS Tan.
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Superheater operating at 70% Loading
In Milling
uliang v
Honorary
Honorary
Feb 17, 2022
@Wanna be Fish A superheater is basically an add-om to a boiler. Boiler without superheater will generate dry and saturated (DNS) steam. Boilers will superheaters will generate superheated steam. What is DNS Steam? https://www.corrosionpedia.com/definition/1005/saturated-steam When heat is applied to water, its temperature continues to rise until it reaches its boiling point at that pressure. As further heat is added, the water vaporizes and converts to steam. The steam that exists at the same temperature as the water from which it is formed is known as saturated steam. In other words, saturated steam exists at approximately 100°C (212°F) at atmospheric pressure. At higher boiler pressures, the DNS steam temperature will be higher e.g. for a boiler operating at 30 barg the DNS will be 233.84'C. One of the main characteristics of saturated steam is that it is dry; i.e., it does not contain any water droplets. Another critical property of saturated steam is that it is invisible to the human eye. Saturated steam can be observed near the nozzles of some steam vents because as the saturated steam travels further away from the nozzle and into the atmosphere, its temperature drops and condenses to form visible clouds of white vapor (droplets of water), also called wet steam. What is Superheated Steam? https://www.corrosionpedia.com/definition/1050/superheated-steam When saturated steam produced in a boiler is exposed to a surface with a higher temperature, its temperature will increase above the boiling temperature. The steam is then described as superheated by the number of degrees through which it has been heated above saturation temperature. The saturated steam drawn from a boiler is passed through a detached heating device which transfers extra heat to the steam by contact or by radiation. The properties of superheated steam are close to a perfect gas rather than a vapor. Since superheated steam has no direct relationship between temperature and pressure, at a particular pressure it may be possible for superheated steam to exist at a wide range of temperatures. Superheated steam’s greatest value lies in its tremendous internal energy that can be used for kinetic reaction through mechanical expansion against turbine blades and reciprocating pistons, producing rotary motion of a shaft. In the context of a palm oil mill, boilers without superheaters are usually coupled to Single Stage Turbines. For Multi-Stage Turbines, superheated steam is recommended. Besides giving higher power, superheated steam will reduce the wetness of the steam in the later stages of the turbine. Wet steam will cause erosion and corrosion of the turbine blades. Advantages of Superheated Steam 1. The steam turbine efficiency increased by approxiamtely 29% of each percent of moisture removed and superheating reduces the percentage cut off in steam turbine, therefore steam consumption per unit power output is reduced. 2. The superheated steam increases the overall cycle efficiency as well as avoids to much condensation in the last stages of the turbine which reduces blade erosion and corrosion. 3. Superheated steam has a higher heat content and hence higher power for the same quantity of steam generated. Any brand of boiler can be supplied with Superheaters. The degrees of superheat should be determined as per the requirement of your Steam Turbine.
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POM DOWNSTREAM ACTIVITIES
In General Discussion
uliang v
Honorary
Honorary
Jan 24, 2022
I share the concerns raised by Chia Sheak Chong on the safety issues related to the downstream activities e.g. Solvent Extraction Plant and Biogas Capture. The operation and maintenance of these processes may be unfamiliar to the technical and operational staff of a standard palm oil mill. I hope Mr.Yong KC, Mr.Lee YC and Mr.Chang CS can enlighten us on the following questions: Do the technical and operation staff of a normal palm oil mill have the required skilled and technical know how to operate the plant and equipment in the downstream activities? If no or insufficient, then what are the skills that have to be acquired? What changes are necessary in the organization structure (besides the number of staff and employee head count which is obvious) in a normal palm oil mill to operate and maintain the downstream activities? Do you have to depend a lot on the technology provider for the operation and maintenance of the plant and equipment of the downstream activities? I note that most of the mills that have successfully benefited from the downstream activities are mills in excess of 60-100 tons FFB per hour and with throughput of about 400,000 - 500,000 tons FFB per year. Can smaller mills go into downstream activities? What would be the optimal capacity of mills (tons FFB per hour and tons FFB per year) for the following downstream activities: a. Biogas capture b. Solvent Plant Extraction c. Empty Bunch Fibre processing d. Decanter Solids drying e. Composting of solid wastes and bio-solids. Appreciate your sharing.
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Running Mill with Power from Diesel Generating Set only
In Milling
uliang v
Honorary
Honorary
Jan 21, 2022
To run the mill at your rated capacity (or usual capacity) without running the turbine and with 100% process steam from the bypass line from the main steam header to the BPR, you will need to operate the boiler at your usual working pressure. If you run the boiler at, say 100 psig, you can throttle the steam pressure down to 45 psig but the flow rate of the steam will be very much lower. This is due to the difference in specific volume of steam at 100 psi (0.273 m3/kg) and 300 psi (01.100 m3/kg). Hence for the same pipe size, higher boiler operating pressure will deliver more steam to the BPR. The next bottleneck to getting enough quantity of steam for the milling processes is the sizes and length of the Main Steam pipe and the Bypass pipe. A 6 inches diameter steam pipe can deliver up to 16,193 kg per hour of steam at 10 barg. The same pipe can deliver about 30,250 kg per hour of steam @ 20 barg. In both cases, steam velocity taken at 40 m per sec, assuming saturated steam quality. For superheated steam, the velocity can be higher, up to 70 m per sec. It should be noted that high steam velocity in pipes will produce noise and erosion of the pipe wall. Say your normal milling capacity is 45 tons FFB per hour. For this you will need about 22.5 tons of steam @ 45 psig per hour. If you run the boiler at 10 barg, assuming 6 inches diameter steam pipe, you will only get about 16 tons of steam per hour. However if you run the boiler at 20 barg, you will get about 30 tons of steam per hour. Of course the final flow rate will depend on the length of main steam pipe, the number of bends and the pressure drop (caused by the velocity of steam). In most mill, the Bypass Steam Line from the Main Steam pipe to the BPR is only designed for make-up steam, not full flow of the required process steam. The PRV and the Bypass line at the PRV are usually smaller in diameter and may further restrict the flow of steam. So you will need to adjust the boiler operating pressure to get the optimal steam flow from your system. It should be noted that the steam in the BPR will be superheated after the reduction in pressure from the Main Steam pipe into the BPR. It may not be ideal for sterilization, but this is a compromise you will have to make to get the mill running until your turbine is repaired. Hope this will give you some idea to get the mill running as close to your rated capacity.
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Running Mill with Power from Diesel Generating Set only
In Milling
OER & Total Oil Loss
In Milling
uliang v
Honorary
Honorary
Jan 04, 2022
1. The recommendation to adopt the concept of Total Oil = OER + Oil Losses makes sense for a mill processing FFB from known sources. When the year of planting, planting material and composition of FFB delivered to the mill are known, the various ratios for the calculation of the absolute total Oil Losses can be fairly determined. This is not practical for private mills that process FFB from smallholders and dealers. 2. The math is straight forward but, as acknowledged by the authors, determining the Oil Losses in the mill requires great effort and suitable sampling and testing equipment. Most mills are not equipped with proper material handling facilities to collect and weigh the various components of the FFB during the milling process. Using constants instead actual measurements compromises the accuracy of the Total Oil Losses determined. Which bring us to the next question. 3. What is the purpose of determining the Total Oil Losses? It is for finger-pointing during periods of low OER or for generally low OER? This may be a good management metric for agency mills (mill operating as part of the estate arrangement) to determine the reasons (or assign blame) for low OER. In my opinion, any attempt to determine Total Oil Losses (as percentage to FFB) would be is a precious waste of time and resources for private millers. 4. Private millers are better off with monitoring and controlling the performance of the various processes and plant & equipment based on the samples collected at predetermined intervals. Mills should try to ensure all processes and plant & equipment operate within industry-set control limits. For this, mill should give more attention to the collection, testing, storage and analyzing of data from the various sample points in the mill. The use of PC to store, retrieve and analyze data is highly recommended. Mill should consider the use of Statistical Process Control Charts to monitor and control the processes in the mill.. See my Case Study 'Get more information from your Mill Laboratory Data' for some ideas on this. To minimize oil losses, mill should endeavour to ensure mill operation is stable with minimal fluctuation in pressure, temperature, flow rates and electrical loads. Refer to my Case Studies 'Power, Steam and Fuel Balance & Steam Management in POM' and 'A Better Way to Sterilize FFB' on how to achieve stable milling operation.
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OER & Total Oil Loss
In Milling
uliang v
Honorary
Honorary
Dec 30, 2021
Can you be more specific?
0
POME
In General Discussion

uliang v

Writer
Honorary
Moderator
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