A lot of conifer cones open as they dry. While they will do this eventually at room temperature, it's a lot faster if heat them up to about 50 C (130 F) for a few hours.

I'm looking at batch processin cones.

This is in essence a glorified food dehydrator.

Thoughts so far:

1. Build it with a circulating fan and an exhaust fan. Circulating fan runs all tie time.
2. Exhaust fan runs when the humidity rises to a certain amount above ambient.
3. Heating element when temperature drops below some profile set point.
4. Build the exhaust with some form of damper.
5. Screen all the openings to keep bugs, birds, rodents out.
6. First approximation will use an upright freezer for a cabinet. Easy to pick up at local landfill. Most will have freon drained. Cut holes with hole saw.
7. From tests they will open stacked 3 cones deep. In doing this, they will double in diameter. Trays can be made from cut down bread racks. So stacking cones 1 inch deep will dry to a stack of cones 3-4 inches deep. This varies by species.
8. The ideal drying profile initially uses low heat, and frequent air changes. This both puts less stress on the seeds, and minimizes power used. As the easy surface moisture is depleated, it takes longer to trigger an air exchange (humidity dependent. As the cones get drier, they need higher heat. This suggests an ardino or a raspberry pi as a controller.
9. At present we want to process about 50 liters (12 gallons) of cones at a time. From tests they will open stacked 3 deep. Trays can be made from cut down bread racks. A freezer with a 18" x 24" interior foot print, and 5 feet internal height can hold 15 trays at 4 inches each. Note that some provision must be left for air circulation. At this point I'm leaning to a plenum made from perforated tool board -- 1/4" hardboard with spaced holes. So we lose the bottom rack and the back inch. May need to drill out some of th e holes to be larger. The goal is to have a loop with slow flow through the stacked trays and fast flow through the plenum. Overall has to be fast enough thaqt there is not much temperature drop over the path through the stack.

Unknowns at th is time:

1. How much water do we need to evaporate from a batch? We can test this with a batch of sacrificial cones with before and after weighing.
2. HOw long does it take to dry a cone enough to open it sufficiently to get all the seeds out. This will be species and possibly colleciton lot dependent. We are working on tumblers with mesh windows to shake the seeds out of the cones. We can try to take a batch, tumble them for a while, put them back in the dryer for X hours, then tumble more. Test both lots for viability to verify that longer heating hasn't killed too many seeds.

 

This project is a first, much different from a boot dryer project.
I am guessing that speed and production yield are the variables to be optimized.
Since drying is partly dependent on humidity, it makes the most sense to continuing air replacement.
My guess is that uniform drying will be the most desired result. Thus both temperature and humidity should be uniform within the enclosure. And certainly providing heat recovery from the vented air to the replacement air will save energy and cost.
A thermostat controlled electric heater will be the simplest part, and probably a small computer style fan will provide adequate air flow. Unfortunately I have no ideas as to how hot will be optimum, although I GUESS about 140 degrees F.

 

A couple ofd things:

Laminar Flow
Blast chillers, commercial rack ovens, and other thing that need to make quick, uniform changes in temperature for items on racks depend on laminar flow of the air adding or removing heat over the product.

This is accomplished by using long opening formed by slats along two opposing walls of the box. Air is forced into one said and exhausted out the other.

The source side slats are adjustable to balance the air across the span. By limiting the turbulence, the efficiency annd uniformity are greatly increased because pockets of standing air are eliminated—or at least substantially reeduced.

PID Control
A PID (Proportional-Intregral-Derivative) controller, targeting a particular ambient humidity and a maximum temperature would make the system dynamically optimal, adjusting to the changing conditions as the cones dry—as well as compensating for ambient conditions or vexatious in the moisture content of the cones.

PID controllers. when properly tuned, constantly approach the setpoint without overshoot or rapid cycling.

 

This project is a first, much different from a boot dryer project.
I am guessing that speed and production yield are the variables to be optimized.
Since drying is partly dependent on humidity, it makes the most sense to continuing air replacement.
My guess is that uniform drying will be the most desired result. Thus both temperature and humidity should be uniform within the enclosure. And certainly providing heat recovery from the vented air to the replacement air will save energy and cost.
A thermostat controlled electric heater will be the simplest part, and probably a small computer style fan will provide adequate air flow. Unfortunately I have no ideas as to how hot will be optimum, although I GUESS about 140 degrees F.

Criteria:
1. Seed viability.
2. Drying should be fairly slow to mimic natural conditions. Commercially they use high heat, but lose about 10% viability of seed. My intent is to try 40 C (110 F) to 60 C (160 F) So having a temperature controlled relay to operate the heater is fine.
3. 125 mm (5") computer fans move air at about 600 cfm. A 20 cuft freezer then would have an air move every 2 seconds, if it wasn't impeded. That's not going to happen. Amazon has such fans, that are basically 110v to variable voltage DC, and so have variable speed. They run about 30 bucks each.
4. One of my concerns is fire safety. Putting a heat source in an insulated box, with fan powered air exhange, and a bunch of flamable stuff inside. What could go wrong. I'm sufficiently wary of this, that initial trials will be outside. This suggests that I need to be paranoid about safety, and make it as close to fail safe as possible.

4a. Run the power into the box near the top. Have a small box with a temperature fused link. Fire safety companies have these I think. So if I decide that the max temp is never above 180F, then I get that temperature link It melts and the power to everything goes off.

4b. The exhaust port has two dampers. In normal operation a very light weigh damper can be opened by air pressure of the fan. This can be as siimple as a piece of cardboard. There is also a heavy damper, say a double thickness square of drywall, that is normally kept up by an electromagnet. When the power is off it slams closed.

4c. I'd like to do with with an ardino or R-Pi and hook up multiple sensors to it -- e.g. bottom, middle and top of the box. This also allows time dependent temp humidity profiles. One of the things that should be possible is for the SBC to cut the power to the whole unit. That is, if it detects a failure condition, it cuts everything off.

4d. I'd like the unit to wirelessly log to a server on another computer. I have reasonable wifi coverage at the usage site. I'd like to be able to program run cycles from this other computer or through an embedded web server on the SBC, so that I don't need to take the SBC in and reflash it everytime.

5: I still don't know what to use for a heater. Need something that:

5a: I can bypass the built in thermostat. Most heaters will not go above about 35-40C (about 100F) ambient)
5b: Do not get locally hot enough to melt the plastic lining of the box. (This actually needs to be one of my first tests: Can I get the interior temp of the box up to 200F without the plastic lining warping.)
5c: Relatively low wattage. Many heaters are 1500 W My temp controlled relay is rated at 1200 W. I think I would be fine with 500W
5d: Low profile. to stay out of the way.
5e: Screened. I have mental images of a shelf failing and dumping a load of cones on the heater. The heater has to proof against this.

Oil convection are good for local temp, but they are big, and cannot be put on their side. Radiant heat, via a heat bulb or element get very hot locally.

A metal box containing a heating element could work. One of the safety thermistors is attached to the top of the box so that if it gets hotter than X, the event is logged, and the system shuts down.

Hmm. Toaster on it's side, with fan blowing through it. Ok. This also adds a criteria to the fan list: Need to be able to measure fan RPM. Fan rpm < X AND Temp above minimal operating temp => log and shutdown. Be nice to have an external LED that showed that the fan was turning.

 

It can improve the efficiency to include a heat exchange section so that some heat from the hot humid discharge air.

 

[QUOTE="Ya’akov, post: 1947365, member: 600651"

Cool! Recommended starting point for PID controllers?

not sure if full laminar flow is needed or possible. Typically cones woukd be stacked 3-4 deep.
There are two stsges. One is that the cones need to dry to a certain moisture level. For this, just maintaining humidity below 40% at room temperature is syffucient. May take several weeks.

some cones are sealed with pitch. They need to be exposed to 60 C for a few hours or up to 300 C for 15 seconds. These are fire succession trees. Jack lidgepole pines and black spruce are among these.

the nature if cones suggests that laminar flow through a bed of irregular objects isn’t goung to work is unless the air velocity is very slow, or they are spaced on racks individually

Commercialy they are often processed in a trombel. A rotating tube with a slope so that cones added at one end gradually move to the other. But this is much larger infrastructure than I need for pricessing batches of 1 pail in size.

 

[QUOTE="Ya’akov, post: 1947365, member: 600651"

Cool! Recommended starting point for PID controllers?

not sure if full laminar flow is needed or possible. Typically cones woukd be stacked 3-4 deep.
There are two stsges. One is that the cones need to dry to a certain moisture level. For this, just maintaining humidity below 40% at room temperature is syffucient. May take several weeks.

some cones are sealed with pitch. They need to be exposed to 60 C for a few hours or up to 300 C for 15 seconds. These are fire succession trees. Jack lidgepole pines and black spruce are among these.

the nature if cones suggests that laminar flow through a bed of irregular objects isn’t goung to work is unless the air velocity is very slow, or they are spaced on racks individually

Commercialy they are often processed in a trombel. A rotating tube with a slope so that cones added at one end gradually move to the other. But this is much larger infrastructure than I need for pricessing batches of 1 pail in size.

The challenge you will have is getting consistent results because the position in the pile will determine how dry the cone is after N minutes of drying. Forcing the air through the stack (as oppose to just trying to move the around, is one possibility. In any case I would abandon fans and focus on centrifugal blowers which can create pressure—while fans cannot.

It strikes me that perhaps there is some potential in the idea of adapting a tumble dryer. Greatly slowing down the drum, obviously, for one thing.

For PID controllers, this document is pretty good. It has some math, but it can be glossed over if that‘s not your thing. On the other hand, it’s worth the slog even if all you get from it is the idea of how the terms relate (e.g.: A is (inveresly) proportional to B; or a rises geometrically with B—&c.).

And this page has basic information on implementing PID in the Arduino environment.

 

How close does the temperature control really need to be for this application?? I am thinking that a simple ON/OFF controller with very low hysteresis and quite rapid response time will be adequate, if the temperature sensor is a thermistor directly in the air stream. Certainly there would be a small constant oscillation about the set point, but the temperature would stay within a narrow range.

 

How close does the temperature control really need to be for this application?? I am thinking that a simple ON/OFF controller with very low hysteresis and quite rapid response time will be adequate, if the temperature sensor is a thermistor directly in the air stream. Certainly there would be a small constant oscillation about the set point, but the temperature would stay within a narrow range.

My expectation is that controlling for humidity is the thing to do. I am imagining something akin to CV/CC charging, CT/CH. So it would start of with constant max temperature then as the humidity drops to some level, it switches from CT to CH—to maximize speed while avoiding ”burning”.

 

With the mention of a "food grade conveyer" I am wondering if this is collecting the seeds for planting, or collecting them for FOOD??? I had not considered the food possibility.
And as for controlling the humidity, I had guessed that closely controlling the temperature would be enough. I am learning here.

 

With the mention of a "food grade conveyer" I am wondering if this is collecting the seeds for planting, or collecting them for FOOD??? I had not considered the food possibility.
And as for controlling the humidity, I had guessed that closely controlling the temperature would be enough. I am learning here.

The reason I am considering the idea of a humidity driven solution is that he moisture level of the cones will vary, and so there can be not fixed solution for the right temperature. I am also concerned that as the humidity drops, the heat should also be reduced to avoid over-cooking, so to speak.

This may not be necessary, but for consistent drying to a desired moisture level, it seems it would be. Also, since the goal is to open the cones, it would be very nice to be able to sense that and terminate the process based in it.

 

OK, and now it seems that there is a whole lot more involved than just some electrical controls. This ia a whole system integration project with the controls being the easy part. A fair amountof heat transfer planning and air flow work is needed. And while a vision system with a bit of smarts can certainly do that, integrating it into a system will be an interesting challenge.

 

OK, this is an area outside of my experience. Controls and instrumentation I can help with, though. I understand electrical enclosure heat and cooling considerations, and even about electrical systems for farms.Not much about pine cone processing.

 

The Allen Bradley Control Logic PLC interfaces the motor panel having ethernet. any PLC would work but this was recommended.
Because of fire safety at this scale a well contained automatic pellet stove wood suffice as a heat source.
In a bio-massive operation the cone waste contribution is too small for management to concider at this time.
However ash in general plays a role in germination in some pine, cautioned not to repeat crown fire species.

The vertical height and catalytic reburn plays a role in exchanger efficiency in small scale warmed air taken from the top of the enclosure is fed to the middle back of the dryer. The stove is already designed the enclosure but the dryer and heat source work together. The heat source door should remain closed. The Lumptahs should warm their hands on the dryer located midheight back exaust. Expect lots of changes. This allows for things that move.
if two frigerators are strapped together one will remain fixed and whatever ducts are decided on you won't paint yourself in a corner because
the ducts have a gasket. If the front simply used a door then great, but there is your cold spot. Did'nt Charles circuits work on a much more important mission.

 

It may not provide sufficient heat but have you considered the heating cable that is used to defrost ice from roofs? Mains powered, temp is self regulating, insulated, flexible enough to route along shelves etc.

 

Lots to consider:

* Can't control just with humidity. As cones get closer to dry,, the humidity will drop. I don't want the temperature to arbitrarily increase. A system that tracks both humidity (to know when to do an air exchange) and temperature (To know when to ad more heat. With time I'll figuire it out, but at present I expect that an initial fairly high air temp will work, as the cones will be cooled be evaporation. Need to measure a few spots to veryify this. But I think in general I want ot keep the tempuratrue at X until the humidity drops below Y, then shut down.

* Cone stacking: The position in the pile will affect drying rate. In general I have used 2.5 inches or an average of 2-3 cones deep whichever is larger. Deeper can result in the bottom layer not opening due to the weight of the ones above.

* Downside of trombels is both the noise, and the expense. I will be using modified driers to shake the seeds out of hte cones, once the cones are open. But slow drying is easy to do in a warm room and LOTS of bread racks.

* Temperature control doesn't have to be very precies. If T hunted 5-10 F it would be fine. My expectation is that it will vary far more than that when the air change fan comes on.

Remember that my quantities are small. I'm doing a few barrels of cones a year.

Sparky1: I think you linked in the wrong video.

I'm intrigued by the idea of a pellet stove. I don't think a pellet stove would run slow enough for this small a volume. Good idea for a room sized one.

 

It would take diligent effort to find prospects for project with scale. Shows need for EE forestry equipment design,
such as cone processing. High tech joining low tech it's always same story, funding availability. Work safe.

Tree Planting | Wisconsin DNR
Wisconsin DNR Forest Genetics Program Strategic Plan 2019-2029

 

The best way to harvest cones is to sit still and watch squirrel.

A bit mroe background: I'm trying to get into a positon where I can sell packets of seed on places like Amazon and Etsy. A given cone depending on species and growth conditions has 50 to 100 seeds. So a cone represents 2-4 seed packets.

The stand up freezer represents stage 2 of my project. It by itself may be enough to keep up. Stage 3 is likely to be styrofoam sized boxes with independent units. By that time I may have as a refinement, incorporating a weigh scale as an additional input.

A cubic foot of cones is about 15 lbs. As they open they become 2 to 2.5 cubic feet. Once they are open the seeds of most species will fall out with a shake or tap. So a few minutes in a trommel, or being shaken in a screen bottom box, where the mesh allows seeds thorough is enough.

Cones can be dried until most are mostly open, shaken, and the cones returned to the drier. In this way it's easy to find out how much drying to get to the point of diminishing return.

The empty cones have some value to the crafts trade, and can be painted, stained, etc and used as christmas tree ornaments.

Further processing: Seed needs to be dewinged. This is usyually done by a short soak in warm water. This will also separate out empty hulls -- they float. Seeds need to be dried to 6-8% moisture. Some of htat is air drying, but air drying stops at 12-15% dpeending on humidity. Final drying is with a jar and silica gel, with periodic reweighing to see when the seeds are at their final moisture level. In glass jars, the seeds will keep 5-20 eyars at -18C.

Still working on making the packeting process automated. Will need to actually buy a machine or so for this.

 

The best way to harvest cones is to sit still and watch squirrels I have about 30 mountain pine (P. uncinata) that are finally of cone bearing size. Too me 2-3 hours to pick half a cuft of cones (about 15 liters) I have a stand of 25-30 foot Scots pine, of a cultivar called "Lake Superior Blue" An hour and a half got me about 10 liters of cones. Then, as I was looking at tree number 2, it didn't have any cones on it. Looking at the ground, I saw piles of cones. In the next 30 minutes, I had another 50 liters. I leave peanuts or sunflower seeds in exchange. (Cones run about 10% seed. Sunflowers about 30% seed. So 20 liters of cones is replaced with 6 liters of sunflower seeds. I want that squirrel to come back next year.)


A bit mroe background: I'm trying to get into a positon where I can sell packets of seed on places like Amazon and Etsy. A given cone depending on species and growth conditions has 50 to 100 seeds. So a cone represents 2-4 seed packets.

Current experments, have wall brackets that can hold a bread tray. The tray is lined with window screen. A 1500 W electric oil convection heater is put under it, and piece of carpet and a thermometer on top. Temp for single layer stabilize around 30C. Not in a hurry. So 2-3 days is fine.

Later I will try with stacks of bread trays. Not sure if the convection will be enough. Certainly thye bottom tray will dry faster. May need to put a barrier cloth in the bottom tray,. leave it empty. This is wehre I need a Raspberry Pi with a zillion multiplexed temperature and humitity sensors.

The stand up freezer represents stage 2 of my project. It by itself may be enough to keep up. Stage 3 is likely to be styrofoam sized boxes with independent controllers. Put each of them on a dolly. By that time I may have as a refinement, incorporating a weigh scale as an additional input.

A cubic foot of cones is about 15 lbs. As they open they become 2 to 2.5 cubic feet. Once they are open the seeds of most species will fall out with a shake or tap. So a few minutes in a trommel, or being shaken in a screen bottom box, where the mesh allows seeds thorough is enough.

Cones can be dried until most are mostly open, shaken, and the cones returned to the drier. In this way it's easy to find out how much drying to get to the point of diminishing return.

The empty cones have some value to the crafts trade, and can be painted, stained, etc and used as christmas tree ornaments.

Further processing: Seed needs to be dewinged. This is usyually done by a short soak in warm water. This will also separate out empty hulls -- they float. Seeds need to be dried to 6-8% moisture. Some of htat is air drying, but air drying stops at 12-15% dpeending on humidity. Final drying is with a jar and silica gel, with periodic reweighing to see when the seeds are at their final moisture level. In glass jars, the seeds will keep 5-20 eyars at -18C.

Still working on making the packeting process automated. Will need to actually buy a machine or so for this.

Thanks for the two links. I'm groveling thr0ugh them now for people to contact.

 

Those building and installing alternative heating will tell you that building code and fire safety standards
for insurance are hassle but are doable, a small garage heater that an inspector will allow.
A propane heater can be regulated much like a propane generator set.
Charles Wenzel oven control circuit is for warming small components.
See the circuit using OP7 located after figure 3, circuit is also used on the barometer.
having a number of pcboards with 10k thermistor sensors control fans pushing air where ever needed.
The heater symbol can be replaced with a subcircuit. Once the propane heater is started the circuit
controls the flow of gas up or down, a drip oil furnace does have an airtight variant but is not as safe.
The sensors in the dryer allow the ramp up and settle to a stable temperature. The necessary BTU could be
approximated from the heater's rated output and fuel consumption. A presentable study will show feasibility.
Patent of design and process improvement starts with reliable numbers and equipment.

Oven Controllers