When PTG Treatments opened its new £500,000 fire-retardant (FR) treatment plant at Tilbury, it was the culmination of months of planning.

In particular, careful consideration was given to the choice of kilns for the new facility, which is one of only a handful of such plants in the UK, and is designed to treat solid timber and plywood with Osmose‘s FR solution, Firepro.

“We’ve always been good at treating wood and consider ourselves experts in the area,” said PTG managing director Neil Ryan. “However, the FR treatment of wood also involves an element of drying, which is something we’d never done before.”

It was a whole new arena for PTG, and it quickly became clear it needed expert help to find the right answer to meet the company’s specialist drying needs. After careful consideration, it chose Kiln Services, which was then given a broad brief to develop PTG’s kilning solution.

“We wanted to dry not only timber but also plywood, which is completely different to what most kilns are used for,” said Mr Ryan.

“Most kilns are used to take water out of wood that has been in the tree: what we wanted it to do was take water out of wood and plywood that we’d actually put in there.”

The two timber drying kilns at Tilbury each have a batch load capacity for 2,400 sheets of plywood. After treating with Firepro, each batch load takes approximately 18 hours to dry.


As the kilns were to be used primarily for drying sheet material, special consideration had to be given to the stacking arrangement to ensure that the plywood sheets remained flat and free from degrade and that there was an even gap between each layer of boards to allow for optimum air circulation.

“Together, we had to design a system to support the sheets of plywood across the whole depth, and are now using a unique system of mesh and sticks to keep the plywood completely flat during the kilning process,” explained Mr Ryan.

With this in mind, special consideration was given to the design of the kilns in order to provide very high air velocity, to make allowance for the large open areas between the board layers, and ensure that fast drying times were achieved.

Each of the kilns has a state-of-the-art MP4032 central control system that has drying programs for special materials, such as plywood boards, and some 250 species of timber.

The control system is designed to be simple to use and allows the kiln operator to monitor and control both kilns from one central location. Data printouts are provided in tabular or graph form, showing all phases of the drying runs in progress and previously completed drying runs.

The first treated material came off the line at the start of October. Mr Ryan has been pleased with initial levels of interest.

“We are already up to where we should have been, given that the plant was originally due to be up and running in July,” he said. “We are getting the volumes through the plant and through the kilns as well.

“One of the reasons we decided to go for Tilbury, despite it being a fairly expensive location, was because it is a big plywood importing centre in the UK,” he said.

“To have a treatment centre on the doorstep of a major plywood import location makes good sense.”

Spare capacity

And, with the boiler plant installed providing enough heat for the two timber drying kilns and the fire-retardant treatment plant, there is also spare capacity to run an additional two kilns. In effect, Kiln Services has provided a completely integrated process – and one that helps reduce energy costs.

Mr Ryan is convinced that, between them, PTG and Kiln Services have the science right: now it is working on the ‘art’ of the process, modifying existing kilning schedules to optimise them in terms of time and energy costs – without causing degrade to the final product.