technology

"pyrolysis is... complicated... by the fact... primary pyrolysis products... are... able to react among themselves... with ... from the moisture in the coal... with char or coke, or... several of these. The products... often called secondary... may differ... from the primary... Primary products can be studied... if... quench[ed]... rapidly or... [fed] directly into a suitable... instrument... [e.g.] a gas chromatograph."

"With... ... sealed within layers of inorganic ... long... geological processes can operate. Assuming typical s... [b]urial to 10 km would be equivalent to... 100-300°C. These... seem too low to drive... pyrolysis reactions... significant at... [≈]350°C. But... time is on our side... in geological time, tens of millions of years for catagenesis of humic kerogen."

"[L]arge particles may not be heated uniformly... consequently pyrolysis yields are less. Heating rate is also important. During slow heat-up as... in simple... s most coals begin to decompose [≈]350-400°C. ...[L]iquid and gaseous products ...peak ...[≈]425-475°C. This phase of pyrolysis ends ...[≈]500-550°C. ...[V]ery rapid heating [e.g.] in entrained flow gasifiers ...quickly by-passes this stage, so... evolution of liquids is nil."

"Flash pyrolysis poses three experimental difficulties..: (i) control and measurement of the temperature-time history of the coal particles (ii) suppression of secondary reactions (iii) quantitative collection of products."

"Pitch is a highly viscous residue remaining from wood pyrolysis... In the days of s, pitch was extremely valuable to seal the wood planking and for... where a tightly sticking, water-resistant material was needed."

"In fuel chemistry... we deal with several kinds of bond, and mixtures of... different compounds. At temperatures high enough to drive pyrolysis of... one kind of bond... other kinds... break... [I]mmediate products may undergo... subsequent reactions. As a result, pyrolysis... give[s] complex mixtures of products... of little utility if the intent is to produce a single product..."

"To a large extent, biomass resembles gasification, with some distinctions... The kinds... considered... include wood, wood wastes (e.g. sawdust), and s. Some... grass, such as switchgrass... grown as energy crops might also serve... [R]elative to coal, biomass usually has lower calorific value... and sulfur... higher moisture, higher... and oxygen, and produces a higher yield of volatiles on pyrolysis. ...Generally biomass chars are more reactive than coal chars, so... may[be]... less and oxygen are needed for... [its] gasification."

"Pyrolysis of biomass, heavy petroleum fractions, , , and usually produces some amount of liquid product. Pyrolysis... without an externally added... [source] is constrained... Pyrolysis produces liquids, but leaves a residue of carbonaceous char or coke. Usually... gases also form. The... proportions of solid, liquid, and gas depend on the... feedstock and... reaction conditions."

"The subject of wood distillation has... been treated in... this series. ...[W]ood is not a compound."

"[T]he survey of experimental results will be confined to flash pyrolysis at the exclusion of slow pyrolysis or ."

"Wood and biomass can be used in a variety of ways to provide energy: • by direct combustion... for... heating.., steam production and hence electricity generation. • by gasification to provide fuel gas... for heat, or in an engine or turbine for electricity generation. • by fast pyrolysis to provide a liquid fuel... for fuel oil in... static heating or electricity generation... [and] to produce... chemicals."

"[M]ain product, bio-oil... in yields up to 80%... with byproduct char and ... used within... process so no waste..."

"Because pyrolysis converts wood to highly ... charcoal... [it] is also known as . Since volatile compounds are driven off, but... residual non-volatile[s are] altered.., another name... is ."

"Condensable non-aqueous ...wood tars ...[are] produced by pyrolysis and destructive distillation. Tars can be fractionated into [1] light oils, boiling below 200°C... [2] heavy tars, boiling above that... and [3] pitch. Light tars tend to be mixtures of aldehydes, carboxylic acids, esters, and ketones. Heavy oil contains... phenol derivatives; one of its uses... a wood preservative... wood tar creosote..."

"Like their aliphatic counterparts, the smaller phenols are also water-soluble. Phenol... has... solubility...[≈]82 g/kg water. ...Phenols are produced in coal and wood pyrolysis. Any water used in such processes becomes contaminated with phenols (as well as other compounds) and requires processing before being released... into the environment."

"Groundwater could become contaminated by organic compounds during coal pyrolysis, and by various inorganic compounds liberated as the coal is consumed. Some... pose problems for environmental quality or human health."

"[L]iquids can be produced from coal by... pyrolysis... by dissolution... [i.e.] solvent extraction... or by reaction of coal with or with solvents... donating hydrogen (hydroliquification). All... constitute... coal-to-liquids (CTL) technology."

"The pyrolysis of and is often the process of choice for the production of . ...Marketing of the products of from ethane pyrolysis is greatly simplified by the low yield of by-products. ...Pyrolysis of ethane and propane produces the lowest yield of byproducts, which... minimizes the size of downstream units... as the depropanizer, debutanizer, and compressors."

"[T]he great majority of pyrolyses occur at "high" temperatures, but this only means... familiarity with compounds which cannot exist at ordinary temperatures is... extremely limited."

"Franz Fischer... performed... pyrogenic experiments in a tinned-iron tube, which would have failed in an iron tube because of deposition or other causes. ...[He] has shown that a ferrous sulfide inner lining [formed by passing through] in an iron tube also prevents carbon deposit[s] ..."

"The of mineral or organic material was one of the few preparative methods available to the alchemists and the first chemists. That materials could undergo profound changes at high temperatures became a well-recognized principle... emphasized by... landmarks as the formation of by heating ferrous sulfate (copperas) described by ... Brandt's discovery of in 1669 by destructive distillation of residues from ... isolation of benzene from oil gas by Faraday in 1825 and of pyrrole from bone oil by Runge in 1834."

"Prompted by the need of non-petroleum-based fuels, coal research has reemerged... Pyrolysis research... has gained... momentum because of its close connection to combustion, hydropyrolysis and liquification. Spectroscopic and other instrumental techniques are... producing... information about coal structure and pyrolysis mechanisms, while modeling efforts are breaking new ground in sorting out chemical and physical phenomena... [P]ostulates and assumptions of current work provide a meaningful starting point in... theoretical descriptions of greater validity and applicability."

"In s, makes up 50-80% of the weight loss, the remaining consisting of gases, water and ."

"Fast pyrolysis is a new technology that shows... potential for producing... liquid... for fuel applications or as a source for... chemicals."

"Fast pyrolysis is a high temperature process in which biomass is rapidly heated in the absence of oxygen. ...[I]t decomposes to generate mostly vapours... s and some . After cooling and condensation, a... liquid is formed which has a heating value about half... conventional . ...Fast pyrolysis ...is carefully controlled to give high yields ..."

"[E]ssential features... &bull; high heating and heat transfer rates... usually requires finely ground biomass feed &bull; carefully controlled... reaction temperature... [~]500C... vapour phase... short vapour residence typically [<]2 sec... &bull; rapid cooling of pyrolysis vapours to give... bio-oil product."

"Eventually it was understood that the residue from a fire came from... insufficient oxygen (air) to consume the wood completely. From that... came... recognition of making charcoal deliberately by heating wood in the absence of air, or burning under severely air-limited conditions. ...[I]t was [later] realized ...volatile materials "cooked" out ...during conversion... also had valuable uses."

"Production of ... with [other] chemical products... involves pyrolysis, i.e. decomposition of compounds through application of heat."

"[T]hermal decomposition of wood begins [≈]250°C. Industrial carbonization... at ≈500°C."

"Carbonization drives off moisture... with... low molecular weight organic compounds... from extractives and... pyrolysis of ... s. Condensing vapors from carbonization produces... ... a dilute solution of up to 50 small, polar (...[i.e.] water soluble) organic compounds. ...[M]ost important ...are , , and ."

"The transformation of a compound into another substance, or... substances, through... heat alone is... pyrolysis."

"[M]easurement of the coal particles' temperature is not trivial. In many cases the temperature... must be calculated from a model. The other two experimental problems, the suppression of secondary reactions and the collection of products, depend on the reactor geometry and flow pattern..."

"The organic material in oil shales requires pyrolysis to force the catagenesis of ... This can be done above ground in kilns, or underground with the shale still in place."

"Gasification of coal... [goes] back to the 1790s at least. Before World War II, the United States... had... [≈20,000] small coal gassifiers... a popular fuel gas until... the interstate natural gas pipeline network... after World War II. Many... were simple pyrolysis or steam-carbon reactions in... crude equipment having serious environmental problems."

"has not been generally used as a feedstock in simple thermal cracking... because the decomposition temperature is too high and yield of useful products too low. Nevertheless... pyrolysis of methane has been used for the production of acetylene and ... Diamonds can be formed... under suitable conditions... [E]arly stages of...decomposition are... well understood... but... details of later stages are not... clear... All oxidation reactions, including oxidative pyrolysis, have been excluded."

"Fire, as the agent for , was a favorite tool of the alchemist. Although the general prevalence... of pyrolysis has long been recognized... in the last six decades... the subject has assumed a scientific basis. Since many... data on have been incidental observations... the information is widely scattered... [T]hat ...records of many melting-point determinations are accompanied by ..."It melts with decomposition" is ...evidence ...the subject ...has ...an unorganized past."

"[A]n overall model for the simulation of pyrolysis reactors should... include the heat, momentum, s differential equations, physicochemical properties (specific heats, enthalpies, thermal conductivities, etc.) firing-box patterns, and sometimes fluid dynamic characterization (as in advanced cracking reactors)."

"Flash pyrolysis has the potential of producing maximum yields of gases and liquids from coal and organic solid wastes such as municipal refuse, tree bark, cow manure, rice hulls and grass straw using simple process equipment. The main features of the process are near ambient pressure, no requirement for added chemicals, low capital investment, high feed throughput flexibility of feedstock, variability of temperature, and minimum feed pretreatment."

"Frequently, pyrolyses are s, but... "Pyrolysis" is... broader... [and] more concise. In "decompositions", there is... formation of at least two simpler substances. In pyrolyses... not always... [R]earrangements may be caused by heat alone. ...[F]ormation of large molecules ...is often effected by heat. Both ...are pyrolytic ...but it would be awkward to classify them as decompositions."

"Some compounds decompose at the temperature of boiling water... others require red heat. ...[C]ompounds may be stable at -40° but not at 0°. All... if caused by temperature alone, are... pyrolysis."

"Occasionally... it will be helpful to note the effect of catalysts... Frequently in s, it is difficult to distinguish between the catalytic and the non-catalytic. ...Glass, or surfaces are the ones which are most used in laboratory pyrolyses. Their catalytic action is, at the best, very slight."

"In larger scale work... metallic surfaces [are usually necessary]. Wilson and Bahlke... reported that in cracking stills... -steels ("stainless" steels) [are best], or aluminum or calorized iron. Copper and some s are not satisfactory, neither... [is] ... These authors were interested in ..."

"[S]ubstances... identified among... products of wood distillation may be arranged... in a few groups of related compounds. Much of the accurate knowledge... is due to the work of Klason."

"The groups from [wood distillation] are 1. s; formic to caproic, especially . Also, furoic, angelic, s, and valerolactone. For different woods, the total acid, calculated as acetic acid, varies between 4.3 and 6.8[%]... In vacuum distillation... formic acid may be... as high as 35[%] of the acetic acid, but in ordinary distillation at atmospheric pressure, it varies from 10-20[%] of the acetic acid. Only these two acids appear to be formed in appreciable amounts. 2. Alcohols; especially and , but also isoamyl and isobutyl alcohols, and buten-3-ol-2. The content is usually... 1.3-2[%]. 3. Esters; formed by interaction of the above acids and alcohols. 4. Ketones; ... and... its homologs... [plus] small quantities of , methyl cyclopentanone, and . The acetone is not a primary [distillation] product... but is formed secondarily from the acetic acid... homologs of acetone have a similar history. 5. Aldehydes; , , methylal and dimethyl acetal, valeric aldehyde, and methyl furfural. The pentosans are... the source of the furfural and other... homologs of furan... 6. Phenols and phenol methyl ethers [only about 1 percent of the wood distilled], mostly s of di- and tris. ...These substances come largely from the . 7. [< 0.2 percent of the total] , methyl amine, and methyl pyridine... 8. , , melene, etc. 9. es; the yields of , and vary with the maximum temperature of distillation, but at 350-400° the yields from s are about 8, 4 and 1.5[%], respectively. 10. Water; the yield... varies... 22.3-27.8[%]. 11. '. ...30-45[%] ...depending on the wood, and on the maximum temperature."

"s, alkalis, and many other inorganic reagents were available... in the early nineteenth century... [T]heir use often added to... descriptive organic chemistry... without clarifying structural relationships. ...[V]igorous pyrolysis of organic compounds, involving no addition of further groups, remained a common technique until about the end of the nineteenth century. ...[M]any high-temperature reactions are fragmentations which produce simple products ...[D]irect of ...carboxylic acids and ...similar decomposition of carboxylic salts by heating with lime or are... examples."

"Mitscherlich prepared benzene as early as 1834 by vigorous distillation of and lime."

"[P]roduct distribution is the most essential information relative to the commercial utilization of pyrolysis and... sheds considerable light on reaction mechanisms."

"[P]roducts can be classified into two groups relative to the temperature dependence of the yields. , water and evolve at lower temperatures with ultimate yields that are essentially independent of temperature above 700°C. The second group... of gaseous hydrocarbons, and evolve at higher temperatures. The ultimate yield of these... continues increasing... up to 1,000°C or higher."

"We are... concerned with the evolution of tar and gases during the plastic state of coal. In this... consists of two processes in series: diffusion through the molten coal to some internal surface, that of a bubble or a pore; and transport with the bubble or through the pore to the surface of the particle. The role of preexisting pores is not well understood. ...[A] certain fraction of preexisting pores (< 60 Å) collapse during pyrolysis perhaps due to effects. Pores... 60-300 Å were preserved... but one could not distinguish preexisting pores and pores generated by the evolution of bubbles. It appears likely... the major... mass transfer occurs via bubbles while preexisting bubbles play a... minor role."

"In industrial practice... design of the pyrolysis reactor affects... composition of liquid products, because... [it] determines how long... primary products are exposed to pyrolysis temperatures..."