HELLO CHINA

INDUSTRY CLUSTER · New materials

Xinjiang Yiwu oil-rich coal pyrolysis

The hard part of oil-rich coal pyrolysis is not heating coal but controlling dust, residence time and secondary oil-gas reactions inside a narrow thermal window. Feed size, furnace sealing, tar dust, raw-gas use and semicoke quality interact, while each Yiwu project must be understood at its own construction or commissioning stage.

Formation and regional foundations

Yiwu’s coal resources and existing conversion plants first provided feed, gas and utility interfaces, followed by staged-use projects using low-temperature pyrolysis and tar upgrading. Mine output, power projects and other coal-chemical plants are adjacent conditions, not substitutes for actual furnace operation, product quality or environmental and safety performance.

Coal heats without oxygen, volatiles leave as oil and gas, and a solid semicoke remains. The sequence looks simple but every stage is vulnerable to entrained dust and thermal drift. If tar condenses again in piping or raw gas lacks a continuous user, downstream constraints set the rhythm of the entire plant.

Core geography: A coal-conversion area in Yiwu, Hami, centred on oil-rich low-rank coal sorting, low-temperature pyrolysis, oil-dust separation, gas purification, tar upgrading and semicoke use

Five operating states after coal leaves storage

Separate paths for solids, tar and gas in Yiwu plants

Sorted coal enters enclosed pyrolysis before oil-gas and solids split. Gas users, tar upgrading and semicoke destinations are prerequisites for continuous operation; instability at any outlet pushes back into furnace conditions.

  • Coal sorting and drying — Size, moisture and oil yield determine feed uniformity.
  • Enclosed low-temperature pyrolysis — Temperature, residence, differential pressure and sealing form oil-gas and semicoke.
  • Oil-dust separation and condensation — Hot particles are removed before tar fractions condense by temperature zone.
  • Raw-gas cleaning and use — Dust removal, desulphurisation and continuous users determine gas export.
  • Semicoke, tar and water systems — Product quality, moisture and wastewater treatment jointly constrain plant load.

01 · Fines first change how the furnace breathes

Uneven size disturbs pressure drop, heat transfer and oil-dust separation together.

Oil-rich coal is crushed and sized before pyrolysis. Coal continues degrading in transport and transfer, so furnace size can differ from mine screening. Oversize pieces heat slowly, while fines readily leave the furnace with oil-gas. A larger fine fraction changes bed permeability and pressure drop, then raises tar ash and exchanger fouling downstream. The first operating variable in Yiwu is therefore coal size, moisture and feed uniformity rather than product-tank level.

Sending every fine particle into one furnace to maximise feed utilisation can convert screening loss into system instability. A separate use or agglomeration route for screened fines keeps utilisation pressure off the main furnace. Bed, moving-bed and other pyrolysis designs have their own size windows, and fines recycling is constrained by sealing, dust removal and semicoke requirements. Feed fit should include the destination of screened coal and dust-capture capability, not only the percentage entering the furnace.

Before a new coal enters the plant, measure full size distribution, surface and inherent moisture, then observe tar yield and degradation by fraction. Feeder fluctuation can create local voids and short-circuit gas paths through the bed. The operating plan should state the fines limit, recycle location and response to excursions. During feeding, align feed-rate fluctuation with furnace pressure drop, tar dust and semicoke size on one timeline to identify whether a disturbance began in feed or separation.

  • Manage dust at coal sizing rather than after tar reaches storage.

02 · Oxygen-free operation does not mean risk-free operation

Small leaks, local overheating and combustible-gas accumulation can reinforce one another.

Pyrolysis relies on low-oxygen or oxygen-free conditions so volatiles evolve rather than burn, making furnace sealing and slight negative pressure essential. Seal wear often appears first as oxygen and draft change rather than a visible leak. Air ingress can create local oxidation in hot oil-gas zones, while gas leakage presents toxicity and explosion hazards. The furnace has gradients across height, centre and wall that determine conversion and coking locations.

A stable average temperature can hide local overheating or blockage, and one pressure reading cannot show gas distribution through the bed. A temperature point far from the reaction zone shows only a delayed wall response. Fine deposition, feed channelling and seal wear gradually change resistance until oil-gas outlet or semicoke discharge becomes visibly abnormal. Safety interlocks should address these developing conditions rather than wait for one temperature to cross a shutdown limit.

Before startup, prove nitrogen purging, combustible-gas detection, furnace differential pressure and fail positions of critical valves, including response to power or instrument-air loss. Post-shutdown inerting and residual-gas handling also belong to the pyrolysis safety cycle. During operation, compare trends across temperature zones, pressure points and discharge temperature rather than watching one alarm. If oxygen rises, reduce load under procedure and locate leakage instead of masking a damaged seal with more suction.

  • Protect containment through pressure, oxygen and temperature gradients.

03 · Tar must leave the gas phase in the right temperature zone

Cooling too early blocks lines; cooling too late loses fractions.

Oil-gas leaving the furnace contains coal dust, steam and organics over a wide boiling range. Insulation integrity in hot dust removal determines whether tar binds the filter medium. Hot-side equipment must remove particles without condensing tar too early, while later condensers recover fractions by temperature zone. A cold spot on the pipe lets viscous tar bind dust into hard deposits and raises pressure drop over time.

High tar dust does not necessarily mean one cyclone or filter failed. Deposit growth rate predicts the next cleaning window better than one pressure-drop value. Excess feed fines, higher furnace gas velocity or disturbed char discharge can be responsible. Adding filtration at storage can hide the upstream cause and create more difficult filter residue. Diagnosis should trace feed, furnace, hot dust removal, condensation and line temperature to find where particles and tar first lose control.

A performance test can record coal fines, hot-side collection efficiency, each condensation temperature, tar ash and line pressure drop together. Tar and dust can harden in valve dead legs and cause incomplete travel or internal leakage. Sampling points should distinguish a furnace-outlet issue from one created after condensation. Cleaning interval and deposit composition are useful too; abundant unreacted coal in deposits points back to feed and furnace flow rather than heat tracing alone.

  • Design dust removal, condensation and storage temperature as one sequence.

04 · Tar upgrading begins with water and solids

Impurities consume hydrogen, block beds and poison catalysts.

Pyrolysis tar commonly contains water, fine solids, heavy fractions and sulphur- or nitrogen-bearing compounds, and its viscosity rises as storage temperature falls. Uneven tank heating creates vertical viscosity differences that distort sampling and pumping. Before hydrogenation or other upgrading, water and particles must be controlled to protect pumping, heat transfer, bed pressure and catalyst life. Tar from different furnace conditions may vary enough that volume alone should not govern tank blending.

Lowering condensation temperature to raise tar yield can bring more water and lights into the product. Mass difference across filtration can show how much tar leaves with filter residue. Aggressive filtration for lower solids increases media load and tar loss. An upgrader values a stable inlet more than one best result. Product coordination among Yiwu projects depends on compatible tar specifications, segregated storage and continuous supply rhythm.

Before tar transfer, define sampling temperature, homogenisation, water, ash, viscosity and key elements, stating whether the sample represents one tank or a blend. Upgrader catalyst pressure trend often reveals solids carryover earlier than product colour. A trial supply can use segregated tanks to observe settling and temperature effects before filtration and blend ratios are set. If downstream bed pressure rises, trace the tank lot and furnace conditions rather than assign all blame to the hydrogenation catalyst.

  • Organise dewatering, filtration and blending around downstream inlet limits.

05 · Raw gas needs a continuous and compatible user

Production does not guarantee stable export.

Pyrolysis raw gas contains hydrogen, methane, carbon monoxide and varying tar mist, dust and sulphur compounds, with composition changing by coal and temperature. Similar gas calorific value can conceal different hydrogen, carbon monoxide and methane effects downstream. Fuel and chemical-feed uses demand different cleaning, pressure and calorific value. Guanghui disclosures show a downstream chemical interface, but each receiving unit retains its own operating window.

Without adequate buffering, a downstream turndown quickly raises upstream pressure and forces the pyrolysis furnace to cut feed or flare. Usable gas-holder buffer is bounded by minimum pressure and safe high level, not gross volume. Furnace variation can also disturb synthesis or combustion through gas composition. Matching projects by annual gas volume misses minute- and hour-scale dynamics; continuous coordination needs storage, compression, bypasses and dispatch rules together.

Before linked commissioning, map minimum, normal and maximum flow for each source and user, with acceptable calorific value, sulphur and tar-mist limits. A flare is not a normal user; continuous disposal loses product value and emission margin. Simulate downstream trips to prove gas-holder margin, vent or flare capacity and furnace turndown rate. Check analyser location and lag so control does not adjust the present blend using obsolete composition.

  • Balance composition, pressure, cleaning and downstream load dynamically.

06 · Semicoke is not automatically a qualified coproduct

Volatiles, strength and size determine its destination.

Semicoke retains ash, fixed carbon and some volatiles, while reactivity and strength depend on feed and thermal history. Hot particles carried through semicoke cooling can keep raising pile temperature after storage. Hot discharge needs controlled cooling because premature air contact can oxidise or self-heat. Sizing produces products and fines for different fuel, reductant or material uses; all solids should not be collapsed into one specification.

Higher pyrolysis temperature may reduce semicoke volatiles while changing tar yield and gas composition; longer residence also reduces furnace throughput. Fines and lump semicoke have different bulk density and need separate bin and vehicle calculations. Semicoke quality cannot be optimised alone because oil-gas value helps set the operating point. If a user accepts only a narrow size, fines without a stable destination can fill storage and constrain the main unit.

When setting semicoke use, sample hot discharge, cooled material and sized products separately for moisture, volatiles, ash, strength and size. End-use reactivity can change pyrolysis severity and feed back into oil and gas yield. Storage should monitor temperature and carbon-monoxide trends, with isolation and handling rules for abnormal piles. A requested change in size or reactivity needs assessment of tar, gas and furnace-load effects rather than a standalone discharge adjustment.

  • Match cooling, sizing and storage to end use and self-heating risk.

07 · The water system can cap operating load

Phenolic, ammonia and oily water do not disappear through dilution.

Coal moisture, reaction water and condensation or scrubbing create complex streams containing oil, phenols, ammonia and dissolved organics. Separating concentrated phenolic-ammonia water from dilute washdown reduces treatment volume. Concentration and biodegradability differ by source; early mixing increases variation for oil removal, dephenolisation, ammonia stripping and biological treatment. In arid Yiwu, reuse conserves make-up water while gradually concentrating salts.

Water use is often higher during commissioning, and flushing or upset discharge creates peaks that annual design averages do not capture. A reuse system with an unclosed salt balance eventually needs a defined salt purge. If wastewater treatment becomes the bottleneck, a mechanically available furnace cannot increase load. Excess reuse can also cause corrosion or scaling in exchangers and cooling water, so both water volume and quality need control.

Integrated commissioning should measure each condensate, scrubber water, washdown and accidental drain for flow and key pollutants, proving equalisation and emergency capacity under peaks. Oil layers and suspended solids in accidental drainage also consume effective equalisation volume. Reuse water needs oil, salt and hardness limits by service. A coal or condensation change should trigger a water-load estimate before end-of-pipe exceedance forces a furnace-temperature reduction.

  • Organise segregation, reuse and treatment around peak loads.

08 · A commissioning curve is not annual output

Project progress and stable operation require separate evidence.

Yiwu disclosures cover existing enterprises, new projects and units at commissioning milestones. A sustained run should include normal disturbances and product changes rather than avoid every unstable period. A single-machine test proves equipment can run; first feed and product show initial process continuity. Sustained operation and performance testing are needed to establish agreed load, energy use and quality. Combining them all as “in production” overstates current availability.

The bottleneck in a large pyrolysis project often lies outside the furnace: tar storage, gas users, wastewater treatment, semicoke bins or instrument reliability can interrupt a run. Performance-test sampling must cover furnace variation; one best sample is not representative. Briefly reaching design flow does not prove these systems stable. Maturity is better judged by sustained mass balance, recovery after disturbance and repeated compliance with downstream product inlets.

When engaging a Yiwu project, identify whether it is under construction, purging, feed commissioning, performance testing or stable operation, with conditions for the latest sustained run. Integrated availability must include utility, storage and downstream outages, not only furnace uptime. Capacity figures should be labelled design, commissioning peak or actual average. A proposed coal, tar or gas movement also requires the relevant storage and downstream unit to be open; a main-unit milestone is not integrated availability.

  • Use sustained duration, balance and performance tests to establish maturity.

Sources and reading notes

Pyrolysis, gasification, direct liquefaction and ordinary coal washing are different processes. Plant status is separated into construction, mechanical completion, feed commissioning, performance testing and stable operation; product figures need feed properties, furnace type, sampling point and load at the time.

  • Yiwu oil-rich coal pyrolysis enters the 2025 national distinctive cluster list under its formal name.
  • Hami public information identifies Guanghui, Huineng and Jiangna within the cluster setting.
  • Huineng disclosures identify unit configuration and commissioning timing rather than full-year output.
  • Yiwu science projects address low-temperature pyrolysis, safety control and gas purification.

Related companies

These companies have a locally relevant industry role supported by public information. Order is not a ranking, inclusion does not imply authorization, partnership or endorsement, and Hello China does not participate in or guarantee transactions.

A company may request a free correction or removal through the formal channel if its record is inaccurate or it does not wish to be shown. Do not send business licences, authorization letters or other sensitive files through insecure channels.

Sources

Use the original publishers to check dates, scope and definitions; public material is not a transaction guarantee.