Siemens PLC and Fully Automatic De-Ashing: A Hardcore Breakdown of the "Autonomous" Control Center in Industrial Solid Waste Incinerators
In modern hazardous and industrial solid waste disposal sites, the old scene of a worker holding an iron hook, frequently checking the fire, and adjusting dampers based on experience is rarely seen in the control room.
Replacing it is a color touch screen embedded in a control cabinet, with a Siemens SIMATIC S7 series PLC silently calculating behind it. Acting as the brain of the industrial solid waste incinerator, it integrates temperature collection, air-fuel ratio adjustment, de-ashing timing, and alarm interlocks into a fully automatic logic system.
A truly mature industrial solid waste incinerator is no longer a piece of equipment that relies on human "babysitting." It is an "autonomous" system capable of self-judgment, self-correction, and self-cleaning, ensuring the incineration process continuously meets the strict 3T+E (Temperature, Time, Turbulence, Excess Air) requirements without human intervention.
Why Industrial Solid Waste Incinerators Cannot Run in "Manual Mode"
The composition of industrial solid waste (including hazardous waste) fluctuates wildly. You might feed high-heating-value waste solvents in the morning and high-salt, low-heating-value filter cakes in the afternoon. The heating value entering the furnace can violently jump between 800 and 25,000 kJ/kg. Relying on manual operation introduces at least three hidden dangers:
Temperature Loss of Control: Operator response is delayed. If the primary chamber drops below 600℃, it results in black smoke and incomplete combustion; if the secondary chamber briefly exceeds 1200℃, it accelerates refractory erosion or even damages the furnace body.
Improper Air Distribution: If primary/secondary air is not adjusted according to the combustion stage, it causes localized hypoxia (generating CO and carbon black) or excess cold air, which drags down the furnace temperature and increases the load on the induced draft (ID) fan.
Delayed De-Ashing: Failing to notice a rise in baghouse differential pressure in time leads to clogged filter bags, skyrocketing system resistance, insufficient draft, and positive pressure smoking from the furnace.
Therefore, a compliant industrial solid waste incinerator must be equipped with PLC-based Automatic Combustion Control (ACC) and Sequential Control (SEQ) to manage critical parameters in a closed loop.
Decoding the Siemens PLC Architecture: The "Nerve Center"
BNTET industrial solid waste incinerators typically utilize the Siemens S7-1200 (for small/medium furnaces) or S7-1500 (for large continuous furnaces) as the master station, paired with ET 200SP/ET 200M remote I/O stations to collect field signals:
Analog Input (AI): Primary/secondary chamber K-type or S-type thermocouples (dual-point verification), flue gas oxygen content (zirconia probe), baghouse differential pressure transmitters, gas/oil pressure transmitters, circulating water temperature, etc.
Digital Input (DI): Burner operation/fault feedback, ID fan operation feedback, emergency stop buttons, limit switches (furnace doors, slag doors), high/low liquid level switches.
Analog Output (AO): Controls the opening of primary air motorized regulating valves, total secondary air flow, burner modulation signals (0~10 V / 4~20 mA), and SNCR reducing agent metering pump frequency.
Digital Output (DO): Burner start/stop, ID/combustion fan start/stop, pneumatic valve switches (feed double-layer gates, quench water valves, activated carbon feeders), and sound/light alarms.
The Siemens TIA Portal programming environment implements nested PID loops, ladder logic, and sequential control (Graph), empowering the incinerator with core automatic functions:
Dual-Zone PID Control: Uses primary chamber temperature as the controlled variable to adjust primary air dampers and feed speed; uses secondary chamber temperature to adjust the burner air-fuel ratio and ID fan frequency, maintaining the secondary chamber at ≥850℃ (≥1100℃ for hazardous waste) with fluctuations ≤±30℃.
Oxygen Correction: Fine-tunes the total excess air coefficient based on the secondary chamber O₂ content (set at 6%~10%), ensuring complete oxidation while preventing excess cold air from lowering the temperature.
Furnace Negative Pressure Control: A micro-differential pressure transmitter detects the pressure difference between the furnace and secondary chamber (usually -20 to -50 Pa) and outputs a signal to the ID fan inverter, ensuring no smoke or fire blowback when the feed door opens.
Fail-Safe Interlocks: Low gas pressure/leakage, ID fan stall, secondary chamber timeout <750℃, or emergency stop trigger—activating any of these immediately cuts off the burner's gas/oil solenoid valve and triggers an alarm, forcing the incinerator into a safe state.
Fully Automatic De-Ashing and Cleaning Sequences: Making the Incinerator "Clean Itself"
High-ash hazardous waste (e.g., dye residue, Chinese medicine residue ash, salt filter cake ash) deposits ash on heating surfaces, flues, and bag surfaces. The BNTET control system executes fully automatic cleaning based on the following logic:
Baghouse Pulse Jet: Real-time monitoring of differential pressure (ΔP). When ΔP hits the upper limit (e.g., 1200 Pa), it automatically starts the pulse valve group to inject 0.4~0.6 MPa compressed air in sequence; it stops when ΔP falls to the lower limit (e.g., 800 Pa). Timer-based pulsing (e.g., every 30 mins) can also be set as a supplement.
Flue Rapping/Air Cannons: At prone-to-coking areas like the secondary chamber outlet, quench tower, and vertical flues, pneumatic rappers or air cannons are triggered at set intervals (adjustable 15~60 mins) to shake off attached ash into the hopper.
Slag Extractor Interlock: Burned-out ash at the end of the grate is continuously discharged via a water-sealed or dry slag extractor. The control cabinet displays a "Slag Extractor Stall" alarm to prompt inspection for jammed foreign objects.
Fly Ash Stabilization Linkage: When fly ash in the hopper reaches the level switch, the system prompts or auto-starts the stabilization/chelation feeding program, preventing illegal open-air storage of unstabilized fly ash.
This process requires no manual button-pushing. Operators only need to monitor the differential pressure trend and "Estimated Time to Next Cleaning" on the touch screen, drastically lowering the reliance on stoker qualifications and experience.
HMI and Data Traceability: The Incinerator's "Black Box"
The 10-15 inch color touch screen of a BNTET industrial solid waste incinerator usually includes the following screens:
Overview Diagram: Displays primary/secondary chamber temps, O₂, ΔP, burner status, ID fan frequency, and feed/slag operation status.
Trend Curves: Can simultaneously pull up the last 24h of secondary chamber temp, O₂, CO, and ΔP curves, making it easy to trace combustion quality.
Alarm Summary: Lists unacknowledged/acknowledged alarms in chronological order; clicking jumps to the relevant screen.
Parameter Settings: Password-protected engineer-level page to modify PID parameters, cleaning ΔP limits, timer cycles, etc.
Operation Record Storage: Critical data is archived every 1 or 5 minutes to an SD card or upper computer (WinCC/Kingview optional), meeting environmental department review requirements (usually kept for ≥1 year).
These functions give the incinerator "self-explanatory" capabilities. When regulators ask, "Did the secondary chamber meet standards last night?" you can instantly export the temperature-time curve as the answer.
BNTET Industrial Solid Waste Incinerators: Making "Autonomous Driving" the Standard
BNTET provides more than just burners and furnace bodies; we view the automatic control system as a core competitive advantage:
Siemens Core Hardware: PLC, I/O modules, and touch screens are all original Siemens or equivalent reliable brands, resisting industrial interference and adapting to field voltage fluctuations and inverter harmonics.
On-Site ACC Algorithm Tuning: During hot commissioning, engineers tune PID parameters based on the actual heating value fluctuation range of the waste, ensuring the primary chamber doesn't smolder and the secondary chamber stays hot.
Complete Safety Interlocks: Gas dual-solenoid valves with leak detectors (EuroSit or equivalent), UV flame detectors, and air pressure switch interlocks comply with strict burner safety standards.
Training and Documentation: We provide PLC I/O lists, wiring diagrams, SOPs, and alarm handling manuals, conducting on-site training for client operators/mechanics until they can independently start, stop, and monitor the system.
Half the value of a modern industrial solid waste incinerator lies in its refractory lining and secondary chamber design; the other half lies in its automatic control and fully automatic de-ashing system, centered around the Siemens PLC. Reject the outdated model of maintaining operations based on a master stoker's "feel." Let the equipment sense the temperature itself, adjust the air distribution itself, clean the ash itself, and trigger alarms itself.
With an engineering-verified smart control center, the BNTET industrial solid waste incinerator helps your solid waste disposal line run stably, audit clearly, and free up human labor.
