WO2012160332A1 - Système hydrothermique et procede pour éliminer l'humidité d'un charbon - Google Patents

Système hydrothermique et procede pour éliminer l'humidité d'un charbon Download PDF

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Publication number
WO2012160332A1
WO2012160332A1 PCT/GB2012/000460 GB2012000460W WO2012160332A1 WO 2012160332 A1 WO2012160332 A1 WO 2012160332A1 GB 2012000460 W GB2012000460 W GB 2012000460W WO 2012160332 A1 WO2012160332 A1 WO 2012160332A1
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WO
WIPO (PCT)
Prior art keywords
autoclave
dewatering system
pressure
heater
hydrothermal dewatering
Prior art date
Application number
PCT/GB2012/000460
Other languages
English (en)
Inventor
Patrick Foss-Smith
Original Assignee
Coomtech Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Coomtech Ltd. filed Critical Coomtech Ltd.
Priority to AU2012260681A priority Critical patent/AU2012260681B2/en
Publication of WO2012160332A1 publication Critical patent/WO2012160332A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10F—DRYING OR WORKING-UP OF PEAT
    • C10F5/00—Drying or de-watering peat
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
    • C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
    • C10B57/08—Non-mechanical pretreatment of the charge, e.g. desulfurization
    • C10B57/10—Drying
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L9/00—Treating solid fuels to improve their combustion
    • C10L9/08—Treating solid fuels to improve their combustion by heat treatments, e.g. calcining
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L9/00—Treating solid fuels to improve their combustion
    • C10L9/08—Treating solid fuels to improve their combustion by heat treatments, e.g. calcining
    • C10L9/086—Hydrothermal carbonization
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/04—Heating arrangements using electric heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/04—Heating arrangements using electric heating
    • F26B23/06—Heating arrangements using electric heating resistance heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B25/00—Details of general application not covered by group F26B21/00 or F26B23/00
    • F26B25/001—Handling, e.g. loading or unloading arrangements
    • F26B25/002—Handling, e.g. loading or unloading arrangements for bulk goods
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B3/00—Drying solid materials or objects by processes involving the application of heat
    • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
    • F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
    • F26B3/353—Resistance heating, e.g. using the materials or objects to be dried as an electrical resistance
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B7/00—Drying solid materials or objects by processes using a combination of processes not covered by a single one of groups F26B3/00 and F26B5/00
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B17/00—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement
    • F26B17/10—Machines or apparatus for drying materials in loose, plastic, or fluidised form, e.g. granules, staple fibres, with progressive movement with movement performed by fluid currents, e.g. issuing from a nozzle, e.g. pneumatic, flash, vortex or entrainment dryers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying good
    • F26B2200/18—Sludges, e.g. sewage, waste, industrial processes, cooling towers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/001—Heating arrangements using waste heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/12—Drying solid materials or objects by processes not involving the application of heat by suction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Definitions

  • the present invention concerns a system (method and apparatus) for removing moisture, in particular 'inherent moisture', from coal or other solid fuels.
  • the system particularly suits dewatering of brown coal but may also suit other solid fuels and especially those that suffer from a significant inherent moisture content.
  • the moisture content of coal can be categorised as existing in five basic forms, including: i) interior adsorption; ii) surface adsorption; iii) capillary; iv) inter-particle moisture; and v) adhesion moisture.
  • the interior adsorption moisture otherwise known as inherent moisture, is water that is contained in micro-pores and micro-capillaries within each coal particle.
  • the inherent moisture of coal is water that was deposited during the coal's formation.
  • Surface adsorption moisture of coal is water that forms a layer of water molecules adjacent to coal molecules but on the coal particle surface only.
  • Capillary and inter-particle moisture is water contained in capillaries and small crevices found between two or more particles.
  • Adhesion moisture is water that forms a layer or film around the surface of individual or agglomerated particles.
  • moisture forms For the purposes of drying, the most relevant distinction between moisture forms is that between surface moisture and inherent moisture.
  • Surface moisture can be relatively easily removed by the application of mechanical pressure reducing the coal moisture content from as high as, say, 60% down to more moderate levels of the order of 30%.
  • the remaining inherent moisture is, however, much more difficult to remove as it is tightly bound to the internal surfaces of the micro-pores and micro-capillaries.
  • Non-thermal methods of drying include reductions in fuel consumption and may include reductions in atmospheric emissions of Sulphur Dioxide, Carbon Dioxide, Chlorine, Mercury and other harmful pollutants.
  • Hydrothermal dewatering, or 'Hot. Water Drying' is a known non-evaporative system for drying high moisture content coals such as lignite/ brown coal and, in particular, removing inherent moisture without needing to apply high levels of heat to do so.
  • the hydrothermal dewatering method at its heart involves a decarboxylation process under pressure that generates C0 2 which expands and displaces moisture from the micro-pores of the coal.
  • a ground, low-rank coal such as lignite is treated at coal-specific temperatures beginning at as low as about 240°C, at the corresponding saturated steam pressure, for several minutes to bring about the decarboxylation reaction.
  • devolatilised tars/oils being hydrophobic, remain on the coal surface in the pressurised aqueous environment. It is thought that these tars/oils produce a uniform coating that seals the micro-pores and limits moisture re-absbrption, a major advantage of the process. Because the coating retains most of the low rank coal volatile matter, high energy recovery and excellent combustion performance can be obtained. It is probable also that alkali cations, a major source of boiler fouling associated with the carboxyl groups, are released in the aqueous phase in the process which can then be removed during the final mechanical dewatering step.
  • Sudden particle shrinkage causes fracturing, destroys moisture reaction sites, and liberates the ash- creating mineral matter. It is possible that this effect may also liberate pyritic sulphur and, if so, the reduction in total sulphur may be a significant additional benefit. It is also possible that the process can extensively decrease the oxygen content by decomposing carboxyl groups, thereby upgrading the low rank coal by increasing its calorific value. This benefit cannot be accrued using conventional evaporative drying.
  • This method of hydrothermal dewatering may also be applied to materials other than coal including biomass, sewage sludge and municipal solid wastes.
  • hydrothermal dewatering systems are in principle energetically efficient since they require relatively low levels of heat input, in their current form as practised they are rather limited in applicability.
  • the existing commercial systems generally induce the critical decarboxylation reaction in one of two main ways, both of which are commercially marginal.
  • the first approach is primarily carried out as a batch treatment process using autoclaves in sequentially operated process lines and has a seriously limited throughput. Aspects of this approach are subject of a number of published patent applications and patents, including US patents US 7198655 (Evergreen Energy Inc.) and US 6497737 (K-Fuel Inc.).
  • the second approach is a continuous flow process that is reliant on intense hydrostatic pressures created in very deep mineshafts. In this latter case the geographical location of the treatment is generally restricted to the immediate locale of deep mines.
  • the second approach is also subject of a number of published patent applications including US-A- 2004144019 (Exergen Pty Ltd).
  • the present invention seeks, inter alia, to address these major limitations of the existing hydrothermal dewatering systems to enable an efficient and cost-efficient continuous flow process for primary coal drying and which is not fundamentally location dependent but which can be implemented at a wide range of different sites.
  • a hydrothermal dewatering system for removing moisture from coal or other carbonaceous solid fuel materials, the system having an autoclave to heat the materials to an elevated temperature and under pressure, characterised in that the autoclave is a continuous flow autoclave.
  • the continuous flow autoclave particularly preferably comprises: i) a positive displacement pumping system to drive the materials in a slurry in a continuous flow through the autoclave; ii) a heater to heat the flowing materials in the autoclave rapidly and substantially uniformly to the required temperature for decarboxylation; and iii) pressure let down valve means at the outflow of the autoclave to reduce the pressure of the outflowing slurry rapidly and in a controlled manner.
  • the heater is an ohmic heater.
  • the output slurry from the pressure let down valve means may be passed to a fluid separator to separate solid from liquid without further heating/ drying and is then stored, suitably after, compressing into a densified form (eg briquettes, pellets or laminates) if to be handled subsequently in conventional manner. If the output slurry is, however, needed in granular form (eg. such as to be subjected to drying to- remove surface water by a novel system as set forth in the present applicant's parallel UK patent application of today's date) then the output slurry is best left uncompressed. 000460
  • the pressure let down valve means is particularly preferably multi-staged, suitably of two or more sequential pressure let down valves, whereby the pressure of the slurry is reduced towards ambient in stages.
  • the pressure let down valve means throttle the working fluid (moving slurry) and convert the pressure vector of the fluid to a velocity vector.
  • Using pressure let down valves and dropping the pressure from, say, 200 bar to 1 bar in one step results in an extremely high discharge velocity from the autoclave of over 30m/s generally resulting in very high erosion.
  • the use of multistage let-down valves attenuates the velocity of the fluid gradually and greatly reduces erosion damage to the system.
  • the pressure let-down valve means suitably has a variable inlet and outlet port geometry and which preferably is continuously variable by the user.
  • the pressure let-down valve means incorporates ceramic elements to reduce erosion by the slurry.
  • the pressure let-down valve means are configured for easy disassembly for clearing, inspection and maintenance.
  • the pressure letdown valve means suitably has a wide operating pressure range of from 50 to 200bar and most usefully of the order of 150bar.
  • the system further comprises a tank of fluid into which the outflow may pass, preferably via a submerged outlet, whereby the fluid in the tank absorbs kinetic energy from the outflow.
  • the tank suitably holds water and thus functions as a water brake.
  • a process for carrying out hydrothermal dewatering of coal or other carbonaceous solid fuel materials at elevated pressure and temperature the process being characterised by application of pressure to the materials from positive displacement pumps and heating the flowing materials by ohmic heating to raise the temperature of the coal / water slurry quickly and uniformly, the process being a continuous flow process.
  • the pressurised, heated slurry passing from the ohmic heating suitably passes through a linear heat exchanger to be cooled before being depressurised in a controlled and sustainable manner by being throttled through a let-down valve to atmospheric pressure.
  • Figure 1 is a schematic diagram of a first preferred embodiment of the system
  • Figure 2 is a longitudinal sectional diagram of the autoclave/ thermal reactor and heat exchange sections . of a variant of the preferred embodiment of the system;
  • Figure 3a is a longitudinal sectional diagram of an ohmic heaters formed as a short tube/ pipe length with an annular electrode and passageways for injecting an annular water sheath;
  • Figure 3b is a transverse section of the flow through the pipe taken along the line IIMII in Figure 3a and showing the annular film/ sheath of water and electrolyte.
  • FIG. 1 this shows the general scheme of the process.
  • a stockpile 1 of untreated wet coal is readied for processing.
  • the coal is fed into a coal crusher 3 to reduce the coal to particles of around 15mm largest dimension. Both larger and smaller particles can be accommodated according to the specification of the coal and the desired output specification of the whole system.
  • the crushed coal is screened through a sizing screen 4 to remove oversize coal particles which are returned to the crusher for re-processing to achieve the proper particle size.
  • Screened coal is continuously loaded into a blender 5 together with a regulated water supply.
  • the water and coal is continuously and gently mixed to produce water-coal slurry. Mixing is also continued to ensure that the coal does not precipitate out of suspension.
  • the resulting blended coal and water is continuously drawn from the blender 5 and screened 6 for oversize agglomerated or clumped particles and tramp metal is removed using magnets.
  • the slurry is next processed through a continuous flow autoclave 19 comprised of a positive displacement pump 7, a first heat exchanger 8, an Ohmic heater 9, a second heat exchanger 11 and a pressure let-down array 12.
  • the autoclave is provided to raise the temperature of the slurry at high pressure. Water is maintained in the liquid phase. The temperature and pressure are raised sufficiently for the decarboxylation reaction to take place.
  • the residence time for the reaction to take place is variable from a few seconds to several minutes. The residence time is dictated by the length of the autoclave and, in particular, the distance between the ohmic heater 9 and the pressure let-down array 12.
  • the positive displacement pump 7 of the autoclave 19 is provided to raise the pressure of the slurry passing through the autoclave 19 to a maximum pressure of the order of 200 bar. Most positive displacement pumps able to reach this pressure are unable to do so in the presence of a significant proportion of suspended solids. However, we have found that concrete placing pumps capable of handling 30mm aggregate and achieving in excess of 250 bar continuously; and Oil and Gas exploration pumps used for the bulk transfer of abrasive drill chippings are capable of handling a wide range of particle sizes to a pressure in excess of 300 bar and are adaptable to use for the system of the present invention.
  • the pump 17 has one or more pulsation dampers to produce an even flow at the pump discharge.
  • the system therefore uses a method of heating which quickly and evenly raises the temperature across the pipe.
  • the ohmic heater 9 has high electrical to heat energy conversion efficiency and the heating is uniform throughout the slurry cross section, heating both water and coal particles simultaneously.
  • the ohmic heating subsystem suitably has a wide operating temperature range of from 100°C to 500°C with a temperature of approximately 450°C being used for brown coal (lignite).
  • the ohmic heater 9 (also known as a conduction heater) of the autoclave 19 serves as a continuous flow process heater and utilises the heating effect of either low voltage / high current Direct Current or Alternating Current 10 to produce a high current density within the slurry passing through the heater.
  • Ohmic heaters are sometimes used in the food processing industry where liquid, semi liquid or paste foods require rapid cooking followed by rapid cooling. The technique involves passing current through the target material to produce a uniform and rapid heating effect.
  • the ohmic heater 9 is suitably arranged within the process line whereby the process pipe includes two replaceable electrically conducting bands, for instance copper, secured to the inside diameter of the process pipe.
  • the bands are insulated from each other and also from the process pipe.
  • the slurry passing through the pipe forms a conductor between the two bands allowing current to pass. In this way the slurry between the two bands is uniformly heated across the entire cross section of the material.
  • the feasibility of the application of ohmic heating to hydrothermal dewatering of coal is dependent on the conductivity of the coal / water slurry and in this case the overall conductivity of the slurry is increased by the presence of coal having a relatively low electrical resistance.
  • the coal appears to form preferential electrical paths with significant conduction, and therefore heating, taking place throughout the coal particle.
  • the autoclave 19 needs to quickly raise the temperature of coal particles to initiate the carboxylation reaction.
  • the temperature of carboxylation cannot be achieved unless the transport medium, water, is maintained in the liquid phase.
  • the target temperature for carboxylation to occur will vary according to coal type.
  • the water is prevented from turning into steam by raising the pressure first by the positive displacement pump 7 before heating by the ohmic heater 9 for quick and uniform heating.
  • the pressure required to maintain water in the liquid phase is directly related to its temperature which can be found in standard reference Steam Tables.
  • the pressurisation of water containing a high proportion of mineral solids is complicated by the difficulty of achieving zero unintentional leakage of the slurry through valves and seals. This is further complicated by erosion and abrasion.
  • the autoclave 19 is configured to be sufficiently long to allow the required carboxylation reaction to develop fully.
  • a pair of linear heat exchangers 8 and 11 are provided at each end of the autoclave 19 to recover heat energy from the slurry/ process material as a closed-loop, feed-and-return, liquid filled energy recovery system with the two exchangers 8 and 11 being within a circulation loop 20.
  • At the inlet end of the autoclave 19 is the first heat exchanger 8 and at the outlet end is the second heat exchanger 11. Heat from the hot slurry exiting the ohmic heater 9 is given up to second heat exchanger 11 and the closed loop circulation system 20 transfers the recovered heat to the slurry entering the ohmic heater 9 through the first heat exchanger 8.
  • the slurry is pre-heated when it enters the heater and cooled when it exits the autoclave.
  • Energy recovery is important to the commercial viability of the system as a cost control measure. However, a little heat retained in the slurry may provide evaporative drying at the final discharge of the system.
  • the slurry is cool but still at high pressure.
  • the slurry is de-pressurised using a pressure let-down valve array 12 which, by means of a variable geometry throttle, reduces the pressure to atmospheric pressure.
  • the pressure let-down valve array 12 is, in the preferred embodiment, arranged as several let-down valve units in series, to throttle down the fluid, reducing its pressure in stages.
  • the array 12 functions by converting the pressure component of the fluid into a velocity component whereby the fluid exits the array as a high velocity jet.
  • the jet is received into a water brake in the form of an agitated slurry tank 13 containing the process slurry.
  • the pressurisation subsystem enables continuous flow operation with a variable throughput.
  • the slurry throughput rate may range from 5 to 100 tonnes per hour (tph) per pump and heater, with a high throughput of around 90 tph being preferred.
  • the system is designed to have very high resistance to erosion and abrasion to suit this including the use of ceramic components and surfaces in the most vulnerable parts and use of pressure let-down arrays and water brakes.
  • the system is able to handle variable slurry consistency ranging from, say, 1 % to 80% coal fines in the water (w/w), while an optimal consistency of slurry would be of the order of 60%.
  • the particle size range may be 1mm to 25mm with a wide particle size distribution while an optimal size may be of the order of 7.5mm.
  • the operating pressure for decarboxylation in the autoclave may range from 50 to 200bar while an optimal pressure would be of the order of 150bar.
  • the system can provide on-demand heating requiring no warm-up cycle.
  • the system can be stopped and started for day work (ie non-shift) operations.
  • the high degree of heat recovery of the system reduces heating costs. Since, following decarboxylation, the slurry requires cooling, the system recovers heat energy there, recycling heat from the processed slurry to pre-heat the slurry before it enters the ohmic heater.
  • the cooling stage can be engineered to maximise the heat recovery by extending the heat-exchanger to a sufficient length.
  • the system of the present invention can be located in a wide variety of industrial locations since it does not rely on gravity / hydrostatic pressure and thus not need to be limited to the locale of mines or cliffs.
  • the apparatus provides a continuous flow process with a high throughput capability and is energy efficient with good potential for energy recuperation.
  • the system advantageously uses primarily off-the-shelf existing commercially available mechanical components with proven in-service reliability and longevity and the bespoke fabrications can be entirely limited to non-moving parts.
  • the system is controllable with each process variable being user adjustable.
  • the produced coal is hydrophobic and resistant to re-absorption of moisture and the chemical fuel content of the coal is not diminished during the process but certain deleterious contaminants are mobilised and removed during the process.
  • the treated coal can, furthermore, be safely transported and stockpiled without significant tendency towards spontaneous combustion.
  • it may, for example, be applied to a coal / water / biomass slurry to produce a hybrid solid fuel for briquetting or blending.
  • the system might also have applicability to other fields such as high volume / high pressure commercial cooking or pasteurisation.
  • a closed loop heat exchange fluid circuit 20 is used for heat recovery to receive and transfer the heat from the outflow from the ohmic heater 9 to the inflow to the ohmic heater 9
  • the heat exchange is more direct.
  • the outflow from the ohmic heater 9 is turned to be passed back alongside the inflow to the ohmic heater 9 whereby direct heat exchange from the outflow to the inflow may take place.
  • the heater outflow is passed over the exterior of the heater inflow via an heater outflow pipe 21 that in a heat exchange length 21a thereof encases a heat exchange length 22a of the inflow pipe 22 in a substantially concentric manner.
  • the outer pipe's wall will suitably be a thick walled steel cylinder. Because it does not need to have the full pressure bearing abilities and to reduce cost and optimise heat transfer, the heat exchange length 22a of the inflow pipe 22 is suitably substantially thinner walled than the heat exchange length 21a of the heater outflow pipe 21 that ⁇ encases it. it may be 50 % thinner and even down to a level of the order of 10% the thickness of the heat exchange length 21a of the heater outflow pipe 21 that encases it.
  • the heat exchanger and indeed the whole of the thermal reactor/ autoclave 19 including the inflow pipe 22 ohmic heater 9 outflow pipe 21 is suitably thermally insulated by a surrounding vacuum tube or lagging 23 to minimise heat losses to the environment
  • conventional pipe insulation lagging materials may be used to depths of 20 to 30cm or more.
  • the ohmic heater 9 comprises one or more ohmic heater rings.
  • the ohmic heater 9 rings are suitably electrically connected together groups of three in star or delta arrangements to be powered from a common power source, such as, for example, a 400V AC three-phase supply. There may be several groups of rings to elevate the temperature of the particulate materials sufficiently for the reaction.
  • Each heater ring preferably has an internal diameter of 30cm or so substantially conforming to the internal diameter of the autoclave's pipe-work.
  • the overall residence time/ reaction time for the materials in the thermal reactor / autoclave 19 will for many target particulate materials be from 3 to 20 minutes (10 minutes being typical) as the material flows slowly from the first of the ohmic heaters 9 through to the last of the ohmic heaters 9 and beyond to eventually give up its heat at the heat exchanger section.
  • the flow rate may be as low as of the order of 0.1 to 0.2 m/s to reduce the level of dynamic abrasion and the length of the thermal reactor / autoclave 9 may be of the order of 40 to 50m.
  • the configuration of the heat exchange section may be reversed wherein the heater 9 outflow pipe 21 is inserted to run internally through the heater 9 inflow pipe 22, so that the heater 9 inflow pipe encases the thermal exchange length of the heater 9 outflow pipe.
  • the wall of the pipe that is innermost in the exchanger is suitably reduced in thickness compared to the outer pipe.
  • the interior wall surfaces of the pipes through which the particulates flow are suitably lined with a wear-resistant lining.
  • Example wear-resistant lining materials may, for example, comprise glass or ceramic and the lining is especially suitably used at bends, elbows and Tee-pieces and co-axial pipe centralisers where the frictional forces and potential for wear will be at its greatest.
  • the autoclave is preferably modular in construction, with a series of pipe lengths, preferably circular cylindrical, that are assembled together. This facilitates maintenance of the system to remedy / prevent wear problems as well as making the system versatile to suit a wide range of sites/ installations and for different grades of materials to be treated.
  • the one or more ohmic heaters 9 are suitably each formed as a short tube/ pipe length to be readily integrated into the pipe-work of the autoclave assembled sandwiched between lengths of the pipe-work.
  • the ohmic heaters 9 may comprise a pair of proximal and distal annular tube sections 9a, 9b between which is sandwiched an annular electrode 9c - which suitably is of copper or other metal/ highly electro-conductive material. Where it faces into the bore of the pipe the electrode preferably is protected by a wear resistant layer or coating.
  • the system suitably is adapted as shown in Figures 3A and 3B to have a film of water W formed on the interior wall surfaces of the autoclave's pipes through which the particulates flow.
  • the film of water W may be introduced at the ohmic heaters 9 and preferably upstream of them.
  • the water W suitably carries one or more electrolytes for electrical conductivity to facilitate the ohmic heating of the particulates and the film is suitably bled into the pipe/ distributed to be substantially annular in form, as seen in Figure 3B, substantially fully covering the pipe internal cylindrical surface for the length of the pipe-work through which the water flows.
  • the system as illustrated in Figure 2 has a number of further adaptations to reduce wear including provision of gravel boxes 24 at the bends of the pipe-work to minimise wear at those bends.
  • Each gravel box 24 is a wear- reducing shunt on the outside radius of a bend of the pipe forming a dead spot within which a substantially stationary mass of the particulates can accumulate and that can serve as a wear-resistant interface/ buffer absorbing the frictional forces at the outside of the bend as the flow of particulates is turned at the bend.
  • the gravel boxes 24 may conveniently comprise/ further serve as rodding eyes, through which a high pressure jetting lance/ cleaning rod may be inserted for cleaning maintenance of the pipe-work.

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  • Solid Fuels And Fuel-Associated Substances (AREA)

Abstract

La présente invention concerne un système de déshydratation hydrothermique destiné à éliminer l'humidité d'un charbon ou d'autres matières combustibles solides carbonées. Le système comprend un autoclave à flux continu servant à chauffer les matières à une température élevée et sous pression. L'autoclave comprend avantageusement: i) un système de pompage à déplacement positif qui envoie en flux continu les matières sous forme de boues à travers l'autoclave; ii) un dispositif de chauffage ohmique pour chauffer les matières en écoulement dans l'autoclave de manière rapide et uniforme à la température requise; et iii) des soupapes de baisse de pression ménagées à la sortie de l'autoclave pour réduire de manière rapide et contrôlée la pression des boues sortantes. Le système, qui peut s'installer sur un grand nombre de sites industriels, offre un débit très élevé tout en étant cependant très économe en énergie.
PCT/GB2012/000460 2011-05-24 2012-05-24 Système hydrothermique et procede pour éliminer l'humidité d'un charbon WO2012160332A1 (fr)

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GB1108727.7A GB2499970C (en) 2011-05-24 2011-05-24 System for removing moisture from coal

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US20140325867A1 (en) * 2011-05-24 2014-11-06 Coomtech Ltd System for removing surface moisture from coal
CN107191650A (zh) * 2017-04-17 2017-09-22 成都特普瑞斯节能环保科技有限公司 一种真空保温阀的异形接头管结构
WO2017178626A1 (fr) * 2016-04-15 2017-10-19 Industrial Chemicals Group Limited Procédé de production d'un produit combustible
CN109373739A (zh) * 2016-09-28 2019-02-22 青岛科技大学 一种干燥速度智能控制的干燥系统
CN115305127A (zh) * 2022-09-14 2022-11-08 中国科学院青岛生物能源与过程研究所 一种固体燃料多效一体耦合提质方法及系统

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CN114413574B (zh) * 2022-01-20 2023-07-14 子长县泳泉煤业有限公司 一种水洗煤炭的脱水装置

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140325867A1 (en) * 2011-05-24 2014-11-06 Coomtech Ltd System for removing surface moisture from coal
US9309477B2 (en) * 2011-05-24 2016-04-12 Coomtech Ltd. System for removing surface moisture from coal
WO2017178626A1 (fr) * 2016-04-15 2017-10-19 Industrial Chemicals Group Limited Procédé de production d'un produit combustible
CN109373739A (zh) * 2016-09-28 2019-02-22 青岛科技大学 一种干燥速度智能控制的干燥系统
CN107191650A (zh) * 2017-04-17 2017-09-22 成都特普瑞斯节能环保科技有限公司 一种真空保温阀的异形接头管结构
CN115305127A (zh) * 2022-09-14 2022-11-08 中国科学院青岛生物能源与过程研究所 一种固体燃料多效一体耦合提质方法及系统
CN115305127B (zh) * 2022-09-14 2024-04-05 中国科学院青岛生物能源与过程研究所 一种固体燃料多效一体耦合提质方法及系统

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GB2499970A (en) 2013-09-11
GB201108727D0 (en) 2011-07-06
GB2499970C (en) 2015-01-21
AU2012260681A1 (en) 2013-02-21
AU2012260681B2 (en) 2017-04-27
GB2499970B (en) 2014-08-13

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