Hello, my partner! Let's explore the mining machine together!

[email protected]

troubleshoot humidity problems with rotary louvers dryer ebooks

troubleshooting rotary vane vacuum pump

troubleshooting rotary vane vacuum pump

The installed rotor of a rotary vane vacuum pump is tangent to the stator fixed surface inside the pump eccentric, two or more rotary vanes slide in the rotor slot and contact with the inner wall of the stator, which makes the pump chamber divided into several variable volumes.

A rotary vane vacuum pump can remove the dry gas from the sealed container. It can remove a certain amount of condensable gas if it has gas ballast device. However, it is not appropriate to remove some gases that are highly oxygenated, corrosive to metals, react chemically to pump oil, and contain particulate dust.

It means the highest oil temperature measured near a low level exhaust valve exceed the specified value of the operating instruction. The pump oil viscosity sharply drops because temperature of the pump elevated, which makes the saturated vapor pressure on the pump oil and the limit pressure in the pump increase and the pumping efficiency decrease.

Oil leakage occurs to the sealing surface of shaft seal, oil box and pump parts, oil drain plug, oil label, oil hole plug, through hole connection between the stator components and bearing and gas ballast valve, which is caused by aging of sealing parts, improper installation, damage and failure, uneven surface, impurities, rough and loose casting. If stopping pump return oil, the oil will enter the gas ballast valve. Close the gas ballast valve, otherwise oil leaks. When making the rubber mat, it should be sure to use oil resistant rubber, and be shaped according to the original design. If the sealing surface is too big, it will cause oil leakage.

Water leakage occurs to some places, including pipe head, water jacket sealing surface, the drain hole screw plug and drain valve, etc. Water jacket drilling, casting defects, freezing crack, may lead to water leakage as well.

Continuous working for a long period of time will lead to excessive maximum power, mainly reflected in the inlet and exhaust pressure are too high, temperature of the pump is too high, and the clearance of rotary vanes is too small, high voltage and pump liquid back into the pump. Excessive maximum power will lead to the motor damage. Continuous operation near the maximum power should be avoided as far as possible. If there are some sediments, it should be regularly cleaned.

It can be caused by external leakage, internal leakage, oil hole blockage, poor pump oil quality or pollution deterioration, water vapor and other condensable substances, instrument distortion and pump operation is not normal.

If external leakage is too much, white steam can be seen at the exhaust vent. There are a lot of bubbles in the oil mark and low level exhaust valve. The exhaust pressure is felt when a hand is put on the exhaust vent, the power will increase as well. At this moment, first check whether the gas ballast valve has been closed. In case of external leakage, check the pump port, pipe, valve and container one by one. In addition, seal failure of the outer shaft no oil in the oil cup, oil hole leakage can cause external leakage as well. Internal leakage can cause by the movement gap between the pump, exhaust valve plane, exhaust valve sealing surface, internal shaft seals, pump cover plates, air intake pipe, sealing parts of the valve will cause to wear, corrosion, and bite, which makes the operation gap increase. When the fuel tank is well sealed, if the hand feels sucked on the vent, the exhaust valve may fail.

If pump oil is clean and long storage unused, the gas ballast valve can be open to purify the water vapor in the pump. If pump oil is yellow, white or have been emulsified, fully open the air ballast, adjust air quantity and purify operation. When necessary can put the right amount of gas into the pump mouth operation, which can speed up the purification process. If the pump oil is mixed with other volatile gas or liquid, it is necessary to change oil timely and clean the oil tank. Some vacuum pumps, the pump fluid will be deposited in the interstage airway. In order to achieve a good oil exchanges effect, try to discharge the sedimentary pump fluid.

Ultimate pressure is measured by compression mercury vacuum gauge, when it is measured with a calibrated thermocouple gauge, the measured value increases. It is recommended to reserve a parallel calibration regulator for comparison in case of suspected regulatory pollution distortion. Ultimate pressure increasing will make the extraction efficiency decrease in high vacuum period as well as ultimate fully pressure increase. The above can be used to judge, check and deal with failures of reduced pumping efficiency and increased ultimate fully pressure.

There are many reasons for vacuum pumps making noise, such as the structure design of vacuum pump, the motor and pump bearing making noise, rotary vanes not smooth, large intake volume, loose parts in the vacuum pump and unequal installation making vibration.

There are many factors that influence the oil spouts of vacuum pump, which are the size, position and sealing condition of the oil box return hole as well as the design and installation of the oil baffle plate. The Mist eliminator, oil baffle cap and oil and gas separator of exhaust port and the height of the oil level and the size of the oil intake influences the oil spouts of vacuum pump as well.

edv-4000 rotary desiccant dehumidifier | eva-dry

edv-4000 rotary desiccant dehumidifier | eva-dry

The EDV-4000 is the first home/office dehumidifier to use innovative rotary desiccant technology to provide high volume dehumidification without requiring a compressor. The unit is safer than compressor-based systems and designed for low maintenance operation, with a high capacity water catch basin that requires only periodic emptying. Also includes a built-in ionizer and bacteria-killing filter to improve air quality, if needed.

I have been using my EDV-4000 for 2-3 years (cant remember the date of purchase), but she has worked beautifully whenever I need it on my boat in SWFL. I was initially concerned when the unit stopped producing a drainage, but the RH was staying extremely low, around 32-35% RH, inside my boat. I set the unit on a ledge above my galley and ran the drain hose to the sink for ease of maintenance. I particularly like using the Turbo Dry Mode to take the chill out of the air on these 40-50 chilly mornings in December and January. !

Versatile Unit. Shipped quickly and nicely packaged. Unboxed, plugged in and it went right to work. Quality plastics and fit and finish thru-out. Excellent printed User Guide! Control panel is easy to use and has a lot of options given your use. Noise levels on low are suitable for any location, on high the unit would be not welcome in a living space. The unit has lots of LEDs, so use in a bedroom would be difficult for most, given the light produced. The drain hose is a bit vexing, but Eva-dry does sell a proper hose (would be nice if they put a link right on the product page!). The unit does remove a lot of moisture in the basement of my home, which is around 55 degrees. The older compressor model I had struggled in the cooler air and was a lot noisier; the Eva-dry works better, is quieter, lighter and has a smaller footprint. All wins. One concern is I dont see any certifications from UL or ETL etc. on this Chinese made machine. While this seems a well made unit, Id feel better if the unit had a certification.

I have owned this dehumidifier for years now and I am writing a review about it as I am shopping for additional Units for a Florida Trailer that is not able to stay dry and has developed a mold smell in the back room and the living room. I have always used my device in a area that was made into a beautiful viewing area that was created from a porch so it has always been a problem. I am able to actually have my bedroom in there with my dehumidifier so I am positive that I HAVE to purchase the same type of Dehumidifier for the new problems. Yes, there are some less expensive options that are out there but its not a good idea to buy a product, save a few bucks, when I know that a slightly more expensive version will do the job and give me years of of exceptional service! This is a good product and I am sure that you will be happy with your purchase.!

I bought this dehumidifier about 3 years ago and it is absolutely the greatest! It is quiet and efficient. I use it in my partially finished basement which is also my art and music studio. The ionized air smells so fresh which is really important for a basement. I have to empty the bucket out every day during the summer when it gets humid (I live in Alabama) but since I am down there everyday anyway, its just part of my routine. I most definitely 100% recommend this product it is worth every penny. Thank you, Inventors, for bringing us such an awesome product!!

I purchased the EDV-4000 in September 2018 for a basement studio apartment that is almost exactly the square footage recommended for this unit. The humidity is very high and Ive battled with mold and mildew issues. Ive been using the EDV-4000 a little over 4 months and it has performed wonderfully well! Its relatively quiet and the design is great its compact and lightweight compared to other dehumidifiers on the market a good quality product. Its easy to empty, easy to clean (although it hasnt really needed much cleaning), and does a great job keeping my apartment humidity down. Since Ive been running it, the mold issues have gone away. I would definitely recommend it!

Bought two as needed them for each side of my basement. These are efficient and so quiet vs compressor dehumdifier!! I bought longer drain hose to reach drain on other side of basement. I wish the electric chord was longer for far side cellar so I could move it around more but working without reposition unlike the compressor dehumidifier. Lastly, I wish I had read your instructions on attaching drain hose as I had difficulty not taking off those bucket lids. Great product, Will run both year around in northeast, loving electric savings too!!

Although I initially liked the EDV4000 very much and eventually (and very recently) ordered three of these expensive dehumidifiers for all of my bedrooms, even retiring Ivation IVADM45 (I also purchased recently). However, I am increasingly becoming disenchanted with them. All three of them have developed a noisy rattling sound that will awaken even a sound sleeper. One of them I have had to discontinue using because of the increasingly annoying sound. Because all three have the same deficit, I am reasonably sure it is a design flaw and seemingly has to do with the rotating desiccant wheel. I have not opened any of them to truly identify the offending part or parts. I am accordingly asking AMAZON to contact the manufacturer on my behalf to see if there might be a simple fix that I can perform myself. I want to keep them and use them; but I am afraid I made an expensive mistake.

Ive lived in the SouthEast for the past 20 years and have used indoor dehumidifiers since then. The variously branded big-box store dehumidifiers in the $100 to $150 range all worked about the same. Removed humidity and lasted about 2 years at best. I finally splurged on a top DeLonghi unit with the built-in pump and was amazed. Four (4) years and still going strong, keep the humidity below 50% in the summer! Well, looking for the next best thing I purchased this not-inexpensive EDV-4000. Why yes, it is quieter and smaller, but thats about it. Revised rating. The stink with the original unit dissipated after about 2 years of use. Since the unit is much quieter than a compressor-based unit, I ordered another. Eva-dry has been working on the problem! The new unit has no odor and works well. It still doesnt remove the volume of water, per day, that the better compressor-based units do, I now recommend this unit.

Was apprehensive trying this new technology, but year two, no problems yet. I was replacing our de-humidifier every year. They are all junk. Freezing up ect. This one uses ceramic heating plates, and during the humid time of the year it eally strips the moisture out of the air. I leave it on Auto mode. Not sure if the ionization function is actually doing anything. But overall I would buy another. One negative is it does not include a drain tube. Very difficult to size, 12mm inner diameter- ended up stretching a surgical hose over the drain port, including having to make the access hole bigger on the side to get my fingers in. Emptying the small tank everyday does get old. I hope Eva-Dry designers take note: include a drain hose please! And make it easier to connect! Thanks.

Weve had the Eva-Dry EDV-4000 for about four months now and have it plugged into a Dayton 1UHG2 dehumidifier controller (sold here on Amazon). I *highly* recommend you purchase this controller with this unit. It has a more sensitive built-in hygrometer, and it can measure the ambient room humidity from a location separate from your dehumidifier. Even if you purchase a different dehumidifier than the Eva-Dry, I suggest you purchase this controller. We have ours connected to a utility-room plug located about four feet off the concrete floor, so its measuring the humidity in a more central location, rather than close to the floor. The Dayton controller also keeps your dehumidifier from cycling on and off. The Eva-Dry will do this to sniff the air and determine whether it needs to dehumidify. I would expect that this reduction in operating time will extend the life of the unit, since its not cycling on as often.

The Eva-Dry saves its settings when powered down, so it operates well with the Dayton controller. If you purchase a different dehumidifier than the Eva-Dry and plan to use the Dayton controller, be sure to purchase a dehumidifier that saves its settings when powered down.

So far, were very pleased with the Eva-Dry dehumidifier. Its much smaller and lighter than we expected, which is a good thing. Its very attractive and appears to be of excellent quality. The control panel is flat with detent push buttons that control the various features. LEDs display settings, and an autorotating baffle can be used to direct the flow of air up and down. It can also be placed in a stationary setting, if you need airflow focused in a specific direction.

We installed it next to our sump pump, so I needed to install a drain hose in the back of the unit. This hose it not included with the dehumidifier. I found this part of the installation to be a real pain! Another review here stated that they called Eva-Dry and Eva-Dry stated to use a specific size I wont repeat here because it doesnt work. I purchased that size and the hose simply doesnt fit. I returned it and then went to two different big-box stores and brought the dehumidifier with me, trying to match a hose. Neither store had a hose that fit. I asked for help, and the person was unable to find anything in the massive store that would work. As I was about to leave, he came running up. Wait! Wait!

What he found was right next to the stores dehumidifier section. Clipped to the edge of the shelving, right next to where the dehumidifiers were located, were bags labeled, Dehumidifier Hose. These fit perfectly! I was soooooo happy to locate this! I can only think that the hose is a standard size for dehumidifier drains? I dont know All I know is it works.

The message here is, if you buy this unit, go to your local big-box store (I went to the one that starts with an L) and look for dehumidifier hoses next to the dehumidifier section. Assuming they have similar stock located in the same area, you should be good to go!

The first thing I noticed was the strange smell others reported here. Its a chemical smell, presumably from the desiccant used during the dehumidification process. Its a little off-putting, but I didnt have a major problem with it. Being in the lower level of our home, I was able to ignore it. If youll be placing the unit in a bedroom or a common living location, you should consider how youre going to deal with this smell once you receive the unit. I found the smell went away after a few days. It could take upwards of a week, depending how often your dehumidifier cycles on when you first get it. We only noticed the smell when the dehumidifier was actually operating. When its off, theres no smell.

We find the sound level to be very acceptable. Ive been around dehumidifiers in the past that have a different quality of sound when the unit cycles on. These units have a combination of sounds. The fan and compressor each combine to form two layers of sounds that mesh together into one overall noise. This isnt the case with the Eva-Dry. The Eva-Dry has only one white-noise hush that may be about the same decibel level as some compressor-type dehumidifiers, but I find the Eva-Dry to be much more tolerant simply because of the quality of the sound.

As an example, our Eva-Dry is in the lower level of our home. We have a futon bed down there, which I used recently when we had guests at the house. Sleeping down there, the Eva-Dry was probably twenty of so feet from where I was sleeping. The unit cycled on and off periodically through the night, but I slept right through it quite comfortably. The reason is it has a white-noise hush. I sleep well with this quality of sound. A regular dehumidifier has a white-noise sound from its fan, but it also has a rattling sound from the compressor. Its a different quality of sound that would probably wake me up if I were trying to sleep around it.

As for dehumidification, I can only base this on the digital display on the Dayton controller. The Dayton not only reports a drop in humidification levels, but it also gives evidence of this by cycling off the dehumidifier at periodic intervals. Our lower level is only about 500 square feet. The Eva-Dry dehumidifier does a fine job keeping things dry down there.

Were very happy with the EDV-4000. Im very pleased that I learned about a desiccant dehumidifier. Im very dubious over the quality of standard dehumidifiers these days. They seem built to fail in two to five years. This didnt seem to be true when I was younger in the 1970s. We had a dehumidifier that operated fine for close to twenty years. Ive had a number of friends who seem to go through them in only a few years. I dont want to have that experience. Ive rolled the dice and am taking a gamble with the Eva-Dry in the hopes that it is more reliable and lasts for many years to come.

I promise I will update this review and report ANY issues I have with the Eva-Dry EDV-4000. Im very active on Amazon and pay close attention to the reviews I write. Ive been writing them since 1997. If you dont see any additional comments in this review, that means our dehumidifier is doing well and running fine.

I love my EDV 4000 by Eva dry. Im using it in my office/music studio, and after using a disastrous frigidaire FAD 70 pint dehumidifier, I couldnt be happier. My frigidaire was noisy, rattled, and guess what! It had an automatic shut-off when the bucket got full. Automatic shut-off? Hell! it shut off alright, went to work one morning and when I came back home my studio with my piano and $30000.00 church organ was completely flooded, and the damn thing was still running. Ive had several different dehumidifiers over the years and that frigidaire was the pits! I have this unit on awall mounted controler, so that I can have more precise control than the controls on the unit, I like my humidity especially in my studio at 42 to no more than 45%, and my EDV4000 does this superbly.It does have a small water bucket, but mine is emptying into a condensate pump which takes it outside of the room. The fan isnt that loud really, and in all honesty, its the compressors that make the shakes rattles, and junky sounds that you get from some dehumidifiers, especially those Wretched frigidaires! Good God! I truthfully think you will be quite happy with this machine, especially if used in a bedroom, office, or even your living room. As a piano technician, I _know what humidity can do especially in pianos, and thats why im really picky about a dehumidifier. I hope this has helped you, and one last thing, if you do buy this unit, invest in some kine of drain hose, you can get one for this machine for about $7.00and with such a small tank, about 2 leaders, believe me! its worth the investment. Thanks for reading, take care of yourself, and have an awesome spring and summer. See ya next time with another review.

how to prevent dryer system fires and explosions | 2015-02-13 | process heating

how to prevent dryer system fires and explosions | 2015-02-13 | process heating

Uncontrolled and unplanned fires and explosions in the plant are obviously undesirable. The most important reason to take measures to reduce and, hopefully, eliminate fires and explosions in a dryer system is personnel safety. At the end of the day, you want all employees to leave the plant in the same condition as they entered. While a slow fire may give personnel time to react, an explosion could kill or severely injure someone who happens to be in the wrong spot at the wrong time.

The longevity of your equipment is another reason to reduce fires and explosions. All equipment is designed to operate under set conditions. The high heat produced by a fire can easily degrade the structure of your equipment, making it more prone to failure. Similarly, explosions can catastrophically damage equipment, ductwork, supporting structures, piping systems and other key elements.

As we now live in a litigious society, any adverse situation in a plant setting can result in legal accusations. It is important to note that any fire or explosion in the system that injures personnel or damages equipment could cost your company serious money in a lawsuit.

For any or all of these reasons, unplanned and uncontrolled fires or explosions will significantly affect the bottom line on your plants ledger. But large costs aside, at the very least, unplanned and uncontrolled fires and explosions can cause downtime, potentially cost maintenance dollars and likely damage a portion of the product. For most plants running on tight margins, any of these losses can be problematic. For some, such a loss closes the plant permanently.

In order to have a fire or explosion, three elements oxygen, a fuel source and an ignition source must be present at the same time in the same location. Remove any one of them and you cannot have a fire or explosion.

Most of the conditions described below that could lead to fires and explosions affect direct-fired, rotary drum dryers, but many apply to almost any type of dryer system. (Make sure to see the April 2015 issue of Process Heating, where Part 2 of this series will discuss the specific measures to take to prevent fires and explosions.)

It is in the very nature of a dryer system to have two of the three elements required for a fire to occur. The product being dried is the fuel, and the heat present for drying serves as the ignition. Therefore, when a fire starts in an industrial dryer, the most common reason for it to occur is high oxygen content. A fire can be started with the right mix of fuel, oxygen and ignition. For this reason, your dryer system will be at risk for a fire or an explosion when free oxygen is introduced.

Oxygen can enter your system in many ways. For instance, air leaks allow oxygen into the system. Explosion doors or manway covers may not seal properly. Also, it is not uncommon to have cracks in equipment or ductwork. However, the number one cause of air leaks in a rotary drum dryer system is poor drum sealing surfaces with incorrectly designed drum seals. The seal rings can get divots or become out-of-round. If your drum flexes while rotating and resembles a water balloon rolling down the sidewalk always wider than tall, on a slightly less visible scale the seals will never match up to round inlet and outlet rings. This mismatch will create gaps that the seals cannot cover. Thick rubber seals, hardened with age, are not flexible enough. Metal leaf seals may work for a short period of time, but their effectiveness is drastically reduced through the wear of metal-to-metal contact.

Neglected airlock maintenance can lead to poor airlock conditions that also contribute to higher oxygen content. Gaps between the rotors and housing allow air and combustible dry dust back into the system. If the system infeed or outfeed is a trough auger or drag chain, it is nearly impossible to seal those against air being drawn into the system.

The second condition that can lead to fires and explosions or worsen the situation, should one occur is dirty ductwork. For instance, the black tar buildup that tends to accumulate in the ductwork of dryer systems used for distillers dried grains with solubles (DDGS) and likely others is condensable volatile organic compounds (VOCs). VOCs can be created when a product is thermally damaged by excessive and radiant heat.

To help prevent buildup, industry experts recommend keeping ductwork at temperatures above 220F (104C) for DDGS dryers and most wood product dryers. As the temperature in the ductwork falls below this threshold, water and VOC vapors will condense on the sides of the ductwork. Keep in mind that dryer systems for other products may produce different VOCs that have condensate temperatures above or below those for DDGS and wood products. To determine whether your system is susceptible to VOC buildup within the ductwork, consult with your dryer manufacturer.

Buildup inside of the ductwork is flammable and could have a lower autoignition temperature than the material you are drying. A fire could even start when you are operating within specifications if your oxygen (O2) content is high. If a fire starts elsewhere and spreads to tar-encrusted ductwork, the ductwork or more could be destroyed.

Thermal damage also leads to the creation of fine particulate (<30 microns). Separation devices, including outlet hoppers and cyclones, are not efficient enough in removing these finer particles. The unseparated particles remain in the gas stream, if exhaust gas recycle (flue gas recycle) is being utilized, and get burned or partially burned, increasing the VOC load and buildup on ductwork.

Lastly, operations and control systems can create conditions that cause fires and explosions. Poor shutdown and startup sequences, the way in which upset conditions are handled, variations in infeed moisture content and operator error all can result in a fire event. The majority of fires and explosions occur during startup or shutdown of a dryer system. The system is full of oxygen (atmospheric air) during startup. It is not until the system is up and running that this oxygen has been safely burned by the system. Until then, it is available to interact with fuel that may be present, just waiting for a spark to ignite.

During rapid shutdowns such as those experienced with the use of an emergency-stop switch or caused by an upset condition, gas temperatures and volumes drop immediately. This creates negative pressure voids that pull fresh air into the system. If a high temperature alarm triggers burner shutdown, that action immediately creates an inrush of oxygen-rich air to make up the void created by the burner. This oxygen will only aid any fire that might have created the high temperature event in the first place. Therefore, proper programming capable of handling upset conditions without introducing conditions that intensify the problem is required.

Inconsistent product infeed moisture conditions and mass flows can throw a dryers control system into a cat-and-dog chase where no one wins. All refractory, metal and the high volume of gases hold a great amount of inertia a thermal flywheel, so to speak that must be overcome should an adjustment in running rates be needed. When an infeed product is wetter than what was previously introduced, the burner is required to spike its output to compensate for the lower drum temperatures that are caused by the introduction of that wetter material. When the normal moisture-content product returns, there is still energy left over by the thermal flywheel from the spike. As a result, there will not be enough moisture to remove the extra energy. This creates an overtemperature situation and overdried product because the incoming drier product does not have the moisture required to remove the extra energy. This causes the burner output to drop off, which could result in a void where oxygen can be introduced. This oscillation of burner output will continue for hours until the system reaches steady state, all the while creating elevated risks of fire and explosions.

Sometimes, an error is a matter of a lack of operator training. Should an upset condition occur and the operator does not know how to alleviate the potential risks by putting the dryer system into manual to stop or minimize the swings of the control system, the dryer system will be at risk for a fire or explosion.

In the words of a trusty bear, only you can prevent unwanted fires and explosions. Fortunately, each potentially hazardous condition has a simple solution. Reduce the risk of unwanted fires and explosions by:

As discussed, direct-fired rotary dryer systems have fuel, ignition, oxygen and the potential for pressure to build up. Therefore, fires and explosions are a real risk. There is no manner of preparation a plant can do to fully eliminate the risk of unwanted fires and explosions. Therefore, your system should be equipped with pressure-relief panels or doors properly located to relieve the pressure without endangering plant personnel. Pressure-relief panels and doors will go a long way toward protecting the equipment and personnel in an adverse situation.

Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the Process Heating audience. All Sponsored Content is supplied by the advertising company. Interested in participating in our Sponsored Content section? Contact your local rep.

Vacuum Heat Treatment is a comprehensive introduction and technical resource for vacuum processes and equipment, focusing on subjects that engineers, heat treaters, quality assurance personnel and metallurgists need to know.

Check out the June 2021 edition of Process Heating, featuring temperature uniformity optimization in process ovens and dryers, retrofitting a convection oven with gas catalytic infrared heaters, an equipment overview on convection and conduction heaters and much more!

improving dryer moisture control | 2015-11-16 | process heating

improving dryer moisture control | 2015-11-16 | process heating

FIGURE 2. The in-dryer moisture-content sensor addresses each of the common problems with moisture-content control in dryers. The model relates moisture content to a temperature drop (T) process variable that is easily measured, and the sensor can be installed inside the dryer.

Industrial dryers no matter how effective they are in drying solid materials are incapable of maintaining product target moisture content (MC) at the lowest level practicable when evaporative-load changes to the dryer occur. Why? One big reason is that most dryers are controlled using moisture-content data obtained too late to be effectively used in a control system. Long dead times (time to detect an evaporative-load disturbance entering the dryer) produce proportionally wider moisture-content variations.

What does this mean for most dryer operators? Lack of effective moisture-content control forces operators to run at lower target moisture-content levels to avoid producing wet product. This is a costly practice that results in less production, higher energy costs and poorer product quality.

After viewing many drying operations over nearly 30 years, my experience has shown there are three common problems with currently used (PID-based) systems for moisture sensing and control. These problems prevent recovery of the above-mentioned productivity losses. They are:

Long dead time is one of the three major problems that prevent effective moisture-content control. This is not a new problem. It has existed since the beginning of feedback-type control. There is a dead-time barrier at the dryer exit that prevents significant improvement in currently used moisture-content sensing and control systems.

The only way this barrier can be breached is to move the moisture-content sensor closer to the feed point inside the dryer. Unfortunately, most inline moisture-content sensors are incapable of operating in the harsh environment of a dryer.

Inline Moisture-Content and Laboratory-Samples Methods. Both the inline moisture-content meter method and the laboratory-samples method are located remotely from the product infeed and, therefore, produce long dead times.

Figure 1 depicts a dryer with two methods for supplying moisture-content data for control. It takes 20 minutes for an evaporative-load disturbance entering the dryer to be detected by an inline moisture-content meter and control action to commence. The laboratory sample requires 30 minutes for detection. Because dead time and moisture-content variation are directly proportional, control of this dryer is essentially no control due to the long dead times. This, however, is the case for a large proportion of dryers operating today. This causes wide moisture-content distributions that are costly in terms of production, thermal energy and quality.

A feedforward signal for the evaporative load often is suggested for use in reducing dead time. However, this fix has limited success in dryer moisture-content control systems due to the difficulty of measuring the wet-feed moisture content. Other methods suggested are complex and often too much for the average plant control personnel to maintain in many plants.

Exhaust Temperature Control Method. The third method is using the exhaust temperature as a measure of moisture content. Exhaust temperature control sometimes is used for moisture control in rotary and flash dryers. It offers an inline moisture-content sensor with a lower dead time; however, this improvement can be negated by the tenuous moisture-content vs. exhaust temperature relationship.

Using the exhaust temperature for moisture control is effective only as long as there are no evaporative-load disturbances. As soon as an evaporative-load change enters the dryer, the exhaust temperature control method requires a new setpoint. But, there is no precise, mathematical method available for calculating a new setpoint. In most installations using this method, the operator has placed the controller in manual mode. It is continually searching, but seldom finding, the proper setpoint that maintains the target moisture.

The lack of a simple, effective evaporative-load sensor also affects dryer moisture-level control. As previously discussed, the devices currently used to determine the evaporative load have not been effective due to problems with sensing the moisture content of wet feed. One way to resolve this is to find an evaporative-load sensor that is simple, effective and can be installed inside the dryer closer to the feed point.

The model relates the moisture-content level of the product when exiting a dryer to two variables: the temperature drop (T) of the hot air after contact with the product, and the evaporative load or dryer speed (S). The calculation of constants (K1 and K2) and exponents (p and q) are not required for the system to work properly.

The in-dryer moisture-content sensor addresses each of the common problems with moisture-content control in dryers. The model relates moisture content to a temperature drop (T) process variable that is easily measured. The sensor can be installed inside the dryer (figure 2). The sensor nearly eliminates the dead-time delay for dryers. It consists of two ordinary temperature sensors and software. It can be applied to direct, indirect and batch dryers. Figure 3 illustrates some of the applications for direct dryers using hot air or superheated steam as the drying medium.

The evaporative-load moisture-content soft sensor eliminates the need for moisture-content and mass-flow meters on the feed prior to entering the dryer. It has been mathematically shown that the evaporative load may be sensed in terms of the (T) process variable simply by substituting it for moisture content in the in-dryer moisture-content sensor and software. The sensor solution uses a mathematical method for calculating the (T) setpoint needed to maintain the target moisture content following evaporative-load changes to the dryer.

The in-dryer moisture-content sensing and control system has been shown to deliver results. In testing, the target moisture content is maintained with at least 30 percent less moisture-content variation than that achieved using alternative dryer moisture-content control systems. When two dryers are operated in series and each independently controlled with an in-dryer moisture-content sensing and control system, the possible percent reduction in standard deviation of the final product is 51 percent. Actual reductions in standard deviation have ranged from 45 to 47 percent in company testing.

Sponsored Content is a special paid section where industry companies provide high quality, objective, non-commercial content around topics of interest to the Process Heating audience. All Sponsored Content is supplied by the advertising company. Interested in participating in our Sponsored Content section? Contact your local rep.

Vacuum Heat Treatment is a comprehensive introduction and technical resource for vacuum processes and equipment, focusing on subjects that engineers, heat treaters, quality assurance personnel and metallurgists need to know.

Check out the June 2021 edition of Process Heating, featuring temperature uniformity optimization in process ovens and dryers, retrofitting a convection oven with gas catalytic infrared heaters, an equipment overview on convection and conduction heaters and much more!

Related News
  1. cement pulveriser machine
  2. cement mixer for sale gumtree glasgow
  3. definition of mini cement plant in india
  4. silie cement for sale
  5. crusher concrete demolition
  6. rotary drier werribee
  7. cement plant duct auto design
  8. rotary kiln for lime plants
  9. concrete crusher new mexico for rent
  10. rotary dryer kya h in hindi
  11. grinding angle in roller mill
  12. efficient agitation tank gravity separation cheap
  13. limeston grinding roller mill nepal
  14. mining crusher crawler
  15. sand washer 27
  16. jaw crusher stone crusher rock crusher jaw crusher supplier
  17. stone crusher project cost
  18. smooth double roll crusher for aggregate fertilizer
  19. gelatin powder making machine price in pakistan
  20. vertical roller mill in thailand