With this year’s UKGrain event coming up on 5 November, Mick Roberts looked at why, when it comes to grain-drying, the heat is certainly on
This past season’s extraordinary weather will have stretched many grain drying and storage systems to the limit. Depending on the past level of investment, this will have either exposed cracks or ripped existing flaws wide open.
Possibly the most pressing concern for farms with near-ambient on-floor stores is how to manage and dry grain that is sitting obstinately at moisture contents of 17-18%. Andrew Kneeshaw of the Farm Energy Centre explains research shows that this kind of drying system is predicted to “fail” in two years out of 20.
The first and most obvious step is to keep up vigilant monitoring of the crops in store and deal immediately with any problems such as heating and capping as soon as they arise.
“I’m afraid that this year urgent and drastic action is required that could even mean moving the whole heap, by emptying and refilling the store. This is because the dry grain will be at the bottom with the wetter material at the top,” he adds.
Race against time
Grain drying is always a race against time, and this year the climate has ignored the rules. “If you are looking at a shed full of wet grain in October the faster you attack the problem the better, and possibly the cheaper, the remedy. I have heard of horrendous costs – up to £30/t – being quoted for contract drying,” says Mr Kneeshaw.
Even if the contract drier is charging £10/t for a typical 1000t store, it’s still much cheaper to dry it in position, says Mr Kneeshaw. “If the store has a 100kW fan and 200kW heater it will cost about £20/hour to run. So for the same amount as it would cost to contract dry that grain you could operate the fan and heater flat-out for 500 hours – that’s running them day and night for 20 days. But the grain will be dried in less time than that, even in late October,” he explains.
The key to drying in the autumn is using heat because as temperatures fall the moisture-carrying capacity of the air also reduces. Heating the air will not only lower its relative humidity, but also increase its ability to hold water.
“If the store’s heater is capable of only reducing the relative humidity of the air by 25% that’s not going to be enough at this time of year. Adding another heater capable of reducing it a further 25% will make the significant difference required,” he says.
“In the summer a ‘bit’ of heat will suffice to reduce the warmer air from say 80% humidity to 55%. But in the winter with cold air at 95% you are only going to get it down to 70% – and drying will not progress at this RH,” says Mr Kneeshaw.
The answer is to hire or buy a further heater, capable of reducing the relative humidity by another 25% and run this in parallel with the existing heater. This will supply the bulk of the heat, while the original heat source can be varied according to what is required using its controller.
“Trying to dry grain in October without extra heating is just not going to work. Similarly it’s too late to try and ‘chase it’ down in incremental steps, waiting for ‘good’ days and saving money but shutting the system down when it is particularly damp. A concerted effort and investment is needed now, before it is too late,” advises Mr Kneeshaw.
“It’s also important to keep this system going until the grain is dry. Shutting it on and off will increase the risk of creating condensation.”
After securing this year’s grain in store, it’s time to plan a storage strategy for next season. This will include identifying this season’s inadequacies and possibly investing in extra capacity and modifications.
That means checking the fan speed and whether its capacity matches the current grain depth.
Some stores are now holding 20% more than their design capacity and this means the fan not only has to dry more grain, but the depth also creates a higher back pressure. Simply cleaning ducts and grilles as well as sealing leaks will improve performance significantly.
- The UKGrain event, at the George Stephenson Exhibition Hall, Newark Showground, Nottinghamshire, on Wednesday 5 November (9am-5pm), provides an ideal opportunity to investigate cost-effective ways of improving grain drying and storage facilities and hearing the experts’ views on where the volatile cereals market is heading. Cost is £10 on the gate or you can download tickets at half price on www.farm-smart.co.uk. For more details ring 08454 900 142