Brickworks: kilns and dryers run for the worst case on gas

Kilns and dryers burn natural gas, and going electric means new plant

What happens. In most brickworks the tunnel kiln and the dryer run on natural gas. Electric firing or electric drying is discussed, but it would mean a new kiln or a rebuilt dryer, and nobody wants to sign that off without knowing how the line would then behave.

What it costs. Every tonne of fired product carries gas and carbon costs that rise with the price of both. Meanwhile, the existing plant keeps running the way it was set up years ago.

Why the usual fix fails. Waiting for the big rebuild leaves today’s savings untouched. Burner retrofits and better insulation help, but kiln and dryer are still set separately, each with its own safety margins.

How a fixed-price remote diagnosis checks it. From your kiln and dryer logs (zone temperatures, gas flows, fan speeds, push rate, dryer air) I look at where heat is spent and where kiln and dryer work against each other. The fixed-price remote diagnosis tells you how much a model that runs both together could save on the present plant, and what it would show before an electric rebuild.

Background: Economic predictive control

Nobody knows the temperature of the bricks inside the kiln car

What happens. Thermocouples in roof and walls show the gas temperature in each zone. The bricks in the middle of a dense setting lag behind, and the core of a thick block lags further. Whether a car reached its firing temperature long enough is only seen when it comes out.

What it costs. Underfired bricks in the core, overfired or discoloured ones at the edges, and rejects sorted out at the end of the line. To be safe, the curve is usually set hotter and longer than most cars need, which costs gas.

Why the usual fix fails. A trailing-thermocouple run gives a good snapshot, but only for one setting and one day. When format, setting or clay changes, the snapshot no longer holds, and the margin creeps back in.

How a fixed-price remote diagnosis checks it. From your zone temperatures, push rate, setting patterns and any trailing-thermocouple runs, I check whether the product temperature can be computed car by car. The fixed-price remote diagnosis shows how close that computed value comes to your measurements and whether you could fire to the product rather than to the roof.

Background: Computed measurements

The push rate is set for the most difficult product

What happens. The tunnel kiln pushes a car at a fixed interval. That interval was chosen for the heaviest, thickest or most sensitive product the plant makes. When easier products follow, they travel just as slowly, because nobody wants to change the push rate and the curve every time the mix changes.

What it costs. Kiln capacity you have already paid for and do not use. In busy times this means extra shifts or lost orders; in quiet times, more gas per tonne than needed.

Why the usual fix fails. Operators speed up by feel when the mix is easy, then slow down again after a batch comes out with cracks or black cores. Without a view of what is happening inside the product, every change looks like a risk.

How a fixed-price remote diagnosis checks it. From your push records, zone temperatures, product mix and reject data I check which products are limited by what: heat-up, holding time or cooling. The fixed-price remote diagnosis answers whether the push rate could follow the product within your quality limits, and what that would take in data and control.

Bricks are dried for the worst case

What happens. The dryer runs a fixed programme that is long and hot enough for the wettest, thickest product on the line. Most loads are drier or thinner and sit in warm air long after they are ready. Nobody measures the moisture inside the green bricks while they dry; the programme is the only guide.

What it costs. Gas or waste heat spent on bricks that were already dry, and dryer capacity the next load is waiting for. Drying too fast causes cracks, so operators add margin rather than take the risk.

Why the usual fix fails. Shortening the programme by hand works until a wetter clay or a new format arrives; then cracks appear and the old programme comes back. A moisture probe in a few bricks shows one spot, not the whole load.

How a fixed-price remote diagnosis checks it. From your dryer logs (air temperatures, humidity, fan speeds, weights where you have them) I estimate how moisture in the load develops and how much margin each format really needs. The fixed-price remote diagnosis tells you whether a computed moisture value can lead the dryer, and what that would take.

Kiln waste heat goes to the dryer by habit

What happens. Hot air from the kiln’s cooling zone goes to the dryer, and burners top it up. How much goes where was set years ago and is changed only when something goes wrong. When the kiln slows down or the dryer is full of a difficult product, the balance is off, and burners on both sides make up for it.

What it costs. Gas burned in the dryer while kiln heat goes up the stack, or the other way round. Cooling-zone air that is pulled too hard can also disturb the kiln.

Why the usual fix fails. Kiln and dryer usually have their own controllers and their own operators. Each side keeps its own setpoints safe, and nobody owns the link between them.

How a fixed-price remote diagnosis checks it. I compare the recovered air flows and temperatures, dryer burner gas and kiln data over several weeks, and look for the hours when heat was wasted on one side and bought on the other. The fixed-price remote diagnosis tells you whether coordinated control of the heat flows would pay and what it would need.

Background: Predictive control of process plants

Raw clay changes with the pit

What happens. The clay changes as the excavator moves through the pit: more sand, more lime, more water, different shrinkage. The mix is adjusted on experience, and dryer and kiln settings stay as they are until cracks or colour changes show up.

What it costs. Cracks in drying and firing, shifts in colour that a customer notices across a delivery, and rejects or second-grade product. Operators lose time chasing the cause.

Why the usual fix fails. Lab tests on the clay are done, but they arrive after the bricks have been made, and nobody translates them into new dryer and kiln settings. Widening every margin for the worst clay costs energy and capacity all the time.

How a fixed-price remote diagnosis checks it. Using your clay lab values, extruder data (power, water addition), dryer and kiln logs and reject records, I check whether the effect of each clay batch shows up early enough to act on. The fixed-price remote diagnosis tells you whether settings could follow the clay automatically, and which measurements that would need.

Background: Control that adapts to drift

Shuttle kilns fire fixed cycles whatever is inside

What happens. Shuttle kilns for special shapes and small series fire a stored programme. The programme was written for a full, dense load. Half loads, thinner pieces or a different setting get the same heat-up, the same soak and the same cooling.

What it costs. Gas for hours the product does not need, and kiln time that could fire the next load. When the load is denser than usual, the programme can also be too short.

Why the usual fix fails. Writing a separate programme for every load is not practical, and shortening programmes by hand is a gamble that only the most experienced people take.

How a fixed-price remote diagnosis checks it. From the kiln records (temperatures, gas, programme steps) together with load lists and quality results, I check whether the temperature of the product can be computed during the cycle and used to end each stage when the product, not the clock, is ready. The fixed-price remote diagnosis shows what this would take and how much of each cycle is margin.

Gas is bought and burned without planning production around it

What happens. Gas is bought on a contract or on the market, and the kiln and dryer burn it at whatever rate production needs. Production planning looks at orders and stock, not at the price of energy or at the plant’s own peaks.

What it costs. Energy bills that follow the market without any response from the plant, and peaks that set capacity charges. Where power is also bought at changing prices, the electrical side of the plant (fans, extruders, mills) follows the same pattern.

Why the usual fix fails. A kiln cannot be switched on and off with the price. Shifting production by hand only works for a few obvious cases, and the planner has no way to judge what a change costs in quality or throughput.

How a fixed-price remote diagnosis checks it. I go through your consumption data, contracts, production plans and the flexible parts of the line (dryer, preparation, grinding, stores between steps). The fixed-price remote diagnosis tells you which steps can move in time without harming the product, and whether planning to energy cost would pay.

Background: Economic predictive control

Kiln fans run at fixed speeds

What happens. The flue gas fan, the cooling-air fan and the recirculation fans of the tunnel kiln run at speeds or damper positions that were set at commissioning. When the push rate or the product changes, the fans stay where they are, and the dampers throttle what is not needed.

What it costs. Electrical power for air that is moved and then throttled away. Too much air through the kiln also carries heat out with it, so gas use goes up too.

Why the usual fix fails. Installing frequency converters is the first step, but if the speed is then set by hand once again, little changes. Each fan touches pressure and temperature profiles in the whole kiln, so changing one alone is risky.

How a fixed-price remote diagnosis checks it. From fan speeds, damper positions, pressures, temperatures and push rate in your logs, I check how much air the kiln really needs for each product and rate. The fixed-price remote diagnosis tells you whether coordinated air control would hold the profile with less air, and what it would take.

Fluoride and organic emissions from firing are only measured, not steered

What happens. Clay releases fluorine compounds and organic substances when it is fired. A scrubber or an afterburner deals with them, and the stack is measured. The firing curve and the clean-up are run separately: when the clay or the curve changes, the emissions change, and the operator sees it only on the stack reading.

What it costs. Lime and gas for the clean-up dosed with plenty of safety margin, and the risk of exceeding a limit when something unusual happens. Every limit breach means paperwork and questions from the authority.

Why the usual fix fails. Dosing more all the time is expensive. Adding analysers helps only if someone uses them to act before the stack value rises.

How a fixed-price remote diagnosis checks it. I look at your stack measurements, scrubber and afterburner data, firing curves and clay changes, and check whether the emissions can be computed ahead of the stack from process data. The fixed-price remote diagnosis tells you whether that would allow tighter dosing and fewer surprises, and what it would need.

Kiln cars are loaded the way they always were

What happens. Each product has a setting pattern that someone worked out years ago. When formats change, the patterns are adapted by trial. Some positions on the car, usually in the middle or near the floor, come out underfired or with a different colour, and everybody knows which ones.

What it costs. Uneven firing across the car, a share of second-grade or rejected product, and a curve that is run hotter to reach the worst spot. Less product on the car than would fit.

Why the usual fix fails. Trying new patterns in production is slow and risky, so changes are rare. Measuring every position on a car is a lot of work and is done once, not as a routine.

How a fixed-price remote diagnosis checks it. From your setting patterns, quality results by car position where you record them, and kiln data, I check how gas flow and heat reach different parts of the setting. The fixed-price remote diagnosis tells you whether a different pattern could give more even firing or a fuller car, and how to test it safely.

The kiln controller is decades old and nobody dares to change it

What happens. The kiln runs on a control system that was installed long ago. The person who programmed it has left, the documentation is incomplete, and spare parts are hard to find. Changes to the firing are made by moving setpoints, never by touching the logic.

What it costs. No improvement is possible beyond what the old logic allows. Every failure is a risk to production, and the replacement keeps being postponed.

Why the usual fix fails. A one-to-one copy onto new hardware keeps all the old limitations and the undocumented workarounds. A new system without understanding the old one leads to a long, rough commissioning.

How a fixed-price remote diagnosis checks it. I go through what you have: programme listings, drawings, operator screens, trend data and the operators’ notes. The fixed-price remote diagnosis gives you a documented picture of what the present control really does, where it holds the kiln back, and what a new control concept should contain before you ask for quotes.

The firing master retires and the know-how goes with him

What happens. One or two people know how the kiln reacts when the clay is wet, when a car is empty, when the weather turns. They change settings by feel and are called at night when things go wrong. Within a few years they retire, and nobody has learned it from them.

What it costs. The risk that firing quality drops when they leave, more rejects during the learning time, and a plant that depends on very few people.

Why the usual fix fails. Writing down rules of thumb captures only part of it, because much of the knowledge is about timing and combinations. Hiring an experienced successor is hard, since there are few such people left.

How a fixed-price remote diagnosis checks it. I look at years of trend data together with the firing master’s interventions and talk the important situations through with him. The fixed-price remote diagnosis shows how much of his knowledge can be captured in a documented model of the kiln, one that can then support the next shift or run as setpoint assistance.

Brick strength is known only days after firing

What happens. Compressive strength and other properties are tested on samples in the lab. By the time the result is there, many cars of the same product have gone through the kiln and are on the yard or already delivered.

What it costs. When a result is poor, a lot of product has to be held, re-tested or sold as second grade. To stay safe, firing is kept on the hot side, which costs gas.

Why the usual fix fails. Testing more samples makes the lab busier but not faster. The kiln and the lab are rarely looked at together, so a low value is noticed but not explained.

How a fixed-price remote diagnosis checks it. I put your lab results next to the clay data, dryer and kiln logs for the same cars, and check whether strength can be predicted from process data when the car leaves the kiln. The fixed-price remote diagnosis tells you how reliable such a prediction would be and what it would take to use it.

Background: Computed measurements

Weak house building forces kilns and dryers into part load and stop-start

What happens. When fewer houses are built, brick orders fall. Some brickworks stop production for a while and put staff on short-time work (Deutsche Handwerks Zeitung). Kilns and dryers designed for steady full load now run slower, or are held warm and restarted.

What it costs. More gas per tonne at part load, heat lost while the kiln is held, and quality problems at every restart. Refractory and kiln cars suffer from the extra temperature cycles.

Why the usual fix fails. The curves and programmes were set for full load. Running them at a slower push rate, or improvising the hold and restart, usually means wide margins and trial and error each time.

How a fixed-price remote diagnosis checks it. From your records of slow-downs, holds and restarts (temperatures, gas, push rate, rejects afterwards) I check where energy and quality are lost. The fixed-price remote diagnosis tells you whether planned part-load, hold and restart procedures from a kiln model would save gas and rejects, and what they would need.

Background: Optimal setpoint plans