Point Of Ayr Research Articles

Creating a Wetland Using Rainwater as Mitigation for Loss of Waterfowl Habitat

ABSTRACTA major onshore hydrocarbon terminal was constructed on coastal fields at Point of Ayr on the Welsh side of the Dee Estuary which is protected under national and international environmental legislation and conventions as a wetland of major importance ‐ especially for birds. A scheme is described which was implemented to increase the carrying capacity for waterfowl in an area of farmland adjacent to the terminal. The main method for enhancing the habitat involved bringing a core area of the farm to ‘field capacity’(saturation with water) by surface wetting. Various potential water sources for the scheme were explored. The chosen system entailed the collection of rainwater runoff in a system of drains and reservoirs during the winter and the distribution of the water to bunded irrigation areas in the following autumn. The early successes of commissioning experiments are briefly described, and the key issues for further investigation are identified.

Hydrogen transfer reactions in solvent augmented coal liquefaction

Samples of Point of Ayr (POA) coal were dissolved in a solvent mixture of either tyre pyrolysis oil (TPO) and hydrogenated anthracene oil (HAO), or hydrogenated tyre pyrolysis oil (HTPO) and HAO. The addition of TPO caused an apparent reduction in percentage dissolution and introduced coking problems even at relatively moderate conditions. Analysis of the coal liquids by isotopic mass balance suggested the values of actual percentage dissolution calculated by ash balance were corrupted by coking of TPO. When a catalyst activated coal, produced by depositing iron sulphide on POA coal, was used with TPO under various hydrogen overpressures, coking was reduced, with dissolution increasing with increasing hydrogen overpressure. Samples of HTPO were produced by hydrogenating TPO in either a spinning/falling basket autoclave or a trickle bed reactor. The HTPO samples produced from the trickle bed reactor generally were not as effective in dissolving POA coal due to overproduction of saturates; however, the HTPO samples from the autoclave contained a higher proportion of > 450°C boiling point material, indicating underhydrogenation of the TPO feed. Addition of HTPO from the autoclave caused coal dissolution to increase with increasing HTPO content and no coking was observed. Measurements of H-donor contents by a chemical test procedure using sulphur as a hydrogen acceptor, suggested that the increase was probably the result of the introduction of compounds more active towards initiating cleavage of bonds between aromatic centres, rather than differences in the total H-donor contents.

Pilot-scale studies using a hydrocyclone and froth flotation for the production of beneficiated coal fractions for improved coal liquefaction

Kilogram quantities of coal fractions were produced using pilot-scale density and froth flotation methods. In the density separations a dense-liquid hydrocyclone was used with calcium nitrate solution as the dense medium. Three coals were used in the study: Point of Ayr, Blidworth and Bilsthorpe, and the coal fractions produced were liquefied in a 2 L autoclave using a hydrogenated anthracene oil solvent. For froth flotation, studies were carried out on Bilsthorpe coal using a laboratory flotation column and a Jameson cell and the final concentrates were liquefied in the 2 L autoclave. The hydrocyclone separations showed different yields of overflow and underflow for different coals and hence optimization of the separation density is required for each coal. Digestion in the 2 L autoclave of the overflow samples showed significant increases in overall conversion and oil production compared with the original feed coal. Pilot-scale tests with column flotation and a Jameson cell indicated that they were effective in producing a final concentrate with a vitrinite-rich fraction. These fractions showed increased overall conversion in the 2 L autoclave and increased oil production. For Bilsthorpe coal, the liquefaction products from the final concentrate of the flotation cell were very comparable with those from the hydrocyclone separation. The results show that beneficiation processes such as these could be applied at full scale and that, within the total coal complex, the production of the overflow fraction could be optimized and the much smaller underflow fraction then directed to gasification and combustion reactors.

96/03710 Viscosity of coal-derived liquids. 1. Application of the model to coal liquid fractions

An investigation of the reaction chemistry of catalysed coal dissolution in recycle solvent in an inert atmosphere was carried out using low-rank British bituminous coals (Point of Ayr clean and Asfordby) and a high-rank coal (Cwm) in a tubing-bomb microreactor (25 cm3 capacity) at different temperatures (300–450°C) and reaction times (15–60 min). The results revealed that the initial rupture of the coal structure is primarily a thermolytic process, largely dependent on the severity of the reaction conditions. The threshold temperature for the dissolution of Point of Ayr (PoA) coal was ∼375°C. The catalyst, Mo-based Akzo-153, did not influence the overall conversion of coal as assessed by quinoline and THF extracts. Above 400°C, however, the catalyst promoted the hydrogenation of coal radicals generated by thermal treatment to yield more low-molecular-weight products, such as oils. The high-rank Cwm coal produced only 37 wt% (daf) of THF extracts, while the PoA and Asfordby coals yielded ∼65 wt%.

96/03699 Separation of iron catalyst from coal liquefaction crude oil with high gradient magnetic separator

An investigation of the reaction chemistry of catalysed coal dissolution in recycle solvent in an inert atmosphere was carried out using low-rank British bituminous coals (Point of Ayr clean and Asfordby) and a high-rank coal (Cwm) in a tubing-bomb microreactor (25 cm3 capacity) at different temperatures (300–450°C) and reaction times (15–60 min). The results revealed that the initial rupture of the coal structure is primarily a thermolytic process, largely dependent on the severity of the reaction conditions. The threshold temperature for the dissolution of Point of Ayr (PoA) coal was ∼375°C. The catalyst, Mo-based Akzo-153, did not influence the overall conversion of coal as assessed by quinoline and THF extracts. Above 400°C, however, the catalyst promoted the hydrogenation of coal radicals generated by thermal treatment to yield more low-molecular-weight products, such as oils. The high-rank Cwm coal produced only 37 wt% (daf) of THF extracts, while the PoA and Asfordby coals yielded ∼65 wt%.

Studies of catalysed, solvent-mediated coal dissolution without H 2 overpressure

An investigation of the reaction chemistry of catalysed coal dissolution in recycle solvent in an inert atmosphere was carried out using low-rank British bituminous coals (Point of Ayr clean and Asfordby) and a high-rank coal (Cwm) in a tubing-bomb microreactor (25 cm 3 capacity) at different temperatures (300–450°C) and reaction times (15–60 min). The results revealed that the initial rupture of the coal structure is primarily a thermolytic process, largely dependent on the severity of the reaction conditions. The threshold temperature for the dissolution of Point of Ayr (PoA) coal was ∼375°C. The catalyst, Mo-based Akzo-153, did not influence the overall conversion of coal as assessed by quinoline and THF extracts. Above 400°C, however, the catalyst promoted the hydrogenation of coal radicals generated by thermal treatment to yield more low-molecular-weight products, such as oils. The high-rank Cwm coal produced only 37 wt% (daf) of THF extracts, while the PoA and Asfordby coals yielded ∼65 wt%.

Effect of changing inertinite concentration on pyrolysis yields and char reactivities of two South African coals

Pyrolysis experiments have been carried out with sets of inertinite graded samples prepared from two South African coals (Durban Navigation and Vryheid Coronation Collieries). The effects on product distributions of increasing inertinite concentration, and of different heating rates, have been determined. An atmospheric pressure wire-mesh pyrolysis reactor was used during these experiments (1 or 1000 K s -1 to 700 °C with 30 s holding at peak temperature) in order to minimize reactor related effects on the results. Tar and total volatile yields from the South African samples decreased with increasing inertinite concentration ; the decrease in yields were in line with those observed for a set of maceral concentrate samples from a UK coal (Point of Ayr) and other Northern Hemisphere coals. Total volatile yields showed no detectable deviations when plotted alongside a correlation based on data from 24 Northern Hemisphere derived coals. Relative combustion reactivities of the chars from the pyrolysis experiments have been determined using a standard TGA-based method, as a function of inertinite contents of the original samples. The lower rank DNC set showed a rapid drop in char combustion reactivity with increasing inertinite concentration. By contrast, the reactivity of the VCC samples showed no sensitivity to changes in maceral concentration. It seems tempting to ascribe this similarity between vitrinites and inertinites of the VCC samples to progressively diminishing differences between macerals of higher rank coals. Clearly, however, many more samples need to be studied before definitive conclusions can be drawn.

Two-Stage Kinetic Model of Primary Coal Liquefaction

A mathematical model enabling the calculation of reaction rate parameters for coal weight loss during liquefaction has been formulated. The model explicitly accounts for (i) product release during heatup as well as during holding at peak experimental temperature and (ii) stages of the process prior to and following the onset of extensive covalent bond scission (around 350 °C); the procedure thus allows the calculation of distinct activation energies for the two stages. In the initial phase of the calculation, both stage A processes (prior to the onset of extensive bond cleavage) and stage B processes (following the onset of extensive bond cleavage) have been modeled as single, irreversible, first-order processes. In the fully developed model, both stage A and stage B were considered to proceed by means of multiple parallel, independent, irreversible, first-order reactions with a Gaussian distribution of activation energies. Calculations were matched with liquefaction experiments in tetralin, carried out in a flowing-solvent reactor using seven Argonne PCSP coals and Point of Ayr (U.K.) coal. For stage A processes, the single-reaction model gave activation energies between 35 and 80 kJ mol-1. Energies of activation for the higher temperature range stage B processes (about 350−450 °C) were found to be significantly higher, between 124 and 238 kJ mol-1. This result confirms the validity and necessity of describing coal liquefaction in terms of a two-stage process. For stage A, the multiple parallel independent reaction model gave mean activation energies that were only slightly larger than those calculated from the single-reaction model. Activation energies for stage B processes, however, were greater, between 160 and 275 kJ mol-1, indicating that the single-reaction model significantly underestimates energies of activation for coal thermal breakdown. For individual coals, the standard deviation of the distribution of activation energies progressively decreased with increasing coal rank, apparently reflecting increasing structural uniformity and possibly also increasing degrees of cross-linking accompanying coal maturation. Activation energies reported in the literature for the liquefaction of coal, mostly based on isothermal kinetics, range from 18 to 358 kJ mol-1. Qualitative agreement has been found between values from the present work and results from a multiple, parallel independent reaction scheme fitted to data from the pyrolysis of the Argonne PCSP coals.

Effect of Changing Inertinite Concentration on Pyrolysis Yields and Char Reactivities of Two South African Coals

Pyrolysis experiments have been carried out with sets of inertinite graded samples prepared from two South African coals (Durban Navigation and Vryheid Coronation Collieries). The effects on product distributions of increasing inertinite concentration, and of different heating rates, have been determined. An atmospheric pressure wire-mesh pyrolysis reactor was used during these experiments (1 or 1000 K s -1 to 700 °C with 30 s holding at peak temperature) in order to minimize reactor related effects on the results. Tar and total volatile yields from the South African samples decreased with increasing inertinite concentration ; the decrease in yields were in line with those observed for a set of maceral concentrate samples from a UK coal (Point of Ayr) and other Northern Hemisphere coals. Total volatile yields showed no detectable deviations when plotted alongside a correlation based on data from 24 Northern Hemisphere derived coals. Relative combustion reactivities of the chars from the pyrolysis experiments have been determined using a standard TGA-based method, as a function of inertinite contents of the original samples. The lower rank DNC set showed a rapid drop in char combustion reactivity with increasing inertinite concentration. By contrast, the reactivity of the VCC samples showed no sensitivity to changes in maceral concentration. It seems tempting to ascribe this similarity between vitrinites and inertinites of the VCC samples to progressively diminishing differences between macerals of higher rank coals. Clearly, however, many more samples need to be studied before definitive conclusions can be drawn.

Liquefaction of density separated coal fractions

Density separations of a single coal, Point of Ayr, UK, have been carried out. The uncrushed coal sample was roll crushed to provide two samples at different roll separations. These samples were further screened into size fractions and selected size fractions were separated using a float-sink procedure in a heavy liquid medium. The fractions produced were analysed for maceral content, proximate analysis and liquefaction potential. The liquefactions were carried out using a tubing-bomb with a non-hydrogen-donating solvent, phenanthrene, and with a hydrogen-donating solvent, hydrogenated anthracene oil. The results show that there are significant potential benefits in carrying out coal beneficiation prior to liquefaction. The beneficiation process used does not have to be severe and density separation on particle sizes in the range 0.5–1.0 mm can be effective.

Catalytic hydroliquefaction of coal macerals: Comparison with raw coal

Catalytic hydroliquefactions (HL) of two coals (Freyming, France and Point of Ayr, United Kingdom) and their macerals were studied in a microautoclave in the presence of an H-donor solvent (tetralin). The main results of the study were related to (i) a comparison between the behaviours of such coals or macerals in the HL process; the two raw coals showed the same total conversion, and similar wt% of oil, asphaltene and preasphaltene fractions, (ii) the contribution of each maceral to the global coal liquid; the additive effect was checked, but no synergetic effect was found (using HL and the present type of liquid phase analysis) for a ‘synthetic coal’. Raw coals, vitrite and exinite had the same total conversion, whereas that for fusite was much lower, and (iii) a detailed identification of some individual compounds or of series of homologous compounds; this was made for oil fractions. 25% of these fractions were able to be investigated by GC/MS, i.e. 5–10 wt% of the initial coal. Concentrations of a large number of compounds were determined and compared from one maceral to another, and general tendencies could be deduced.

The economics of coal liquefaction. Part 1 a probabilistic approach

British Coal is developing a process for the production of transport fuels from coal and has built a pilot plant at Point of Ayr, in North Wales, to test its technical feasibility. The project is supported by the European Commission, the UK department of Energy, Ruhrkohle Oel und Gas, and Amoco. Among the project objectives is the preparation of reliable cost estimates for the production of coal-derived liquids. These provide an economic basis for further process development. This paper contains a description of the probabilistic risk assessment model, using discounted cash flow techniques, developed to assess the economic viability of commercial scale operation. An example is given that shows that a straightforward application of the current technology has a reasonable probability of being viable by the year 2015. However, this result is necessarily dependent on many assumptions, including, for example, future oil and coal prices.

Donor solvent interactions during coal liquefaction

Two UK bituminous coals (Cresswell and Point of Ayr) were liquefied using ternary solvents composed of 9,10-dihydroanthracene, 1-methylnaphthalene and a variety of aromatic and heteroatomic compounds. Coal conversion yields were measured in terms of THF- and quinoline-soluble material, following reactions in a stirred batch autoclave under standard conditions of 1 h at 400 °C, and with normalized amounts of hydroaromatic components present as solvent. Enhancement of coal conversion yields was observed for two aromatic compounds (fluorene and pyrene) and for 1- and 2-naphthol. Different mechanisms were established for the synergistic effects of fluorene and pyrene. Antisynergism was observed while using a secondary alcohol, 9-fluorenol, as a solvent component. In binary solvents composed of a hydroaromatic species and 1-methylnaphthalene, 9,10-dihydroanthracene was found to be a more efficient hydrogen donor than tetralin and the efficiency was observed to vary monotonically with the donatable hydrogen concentration of the solvent.

Gravity measurements in the north-eastern part of the Irish Sea

During the summer of 1961 124 new gravity measurements were made in the north (mainly north-east) Irish Sea with an underwater gravity meter. In north-west England, south-west Scotland, and Northern Ireland a regional rise in the Bouguer anomaly is observed on approaching the north Irish Sea; a high regional Bouguer anomaly of more than 40mgal is also characteristic of the Isle of Man. The author considers that this reflects either a crustal thinning of about 3 km or a denser crust (by about0 03g/cm 3 ) beneath the Irish Sea; denser basement rocks may in part be responsible. Over most of the sea area surveyed negative gravity anomalies of 20mgal to 40mgal amplitude are superimposed on the high regional Bouguer anomaly. Both the shape of the anomalies and their correlation with the surrounding coastal geology suggest that they are essentially caused by large sedimentary basins. The two main negative anomalies thus interpreted are ( a ) between the Point of Ayr, the Solway Firth, and Wigtown Bay (thought to be at least 2130 m [7000ft] deep), and (b) between south Cumberland and the Isle of Man (probably at least 2440m [8000ft] deep). Coastal geology suggests that Carboniferous and New Red Sandstone rocks form the major 'fill', although sediments of Old Red Sandstone or post-Triassic age cannot be ruled out. A negative anomaly of nearly 20mgal amplitude forms the south-eastern continuation into Luce Bay of the negative anomaly over the Stranraer New Red Sandstone basin. It closes to the south-east near the mouth of Luce Bay. As on land, it is interpreted as an asymmetrical basin of New Red Sandstone and earlier sedimentary infill with a steep (? faulted) northeastern margin, reaching a maximum depth of at least 1340 m (4400 ft). A single gravity traverse westwards from Peel reveals a sharp gravity drop of about 15mgal immediately off shore; this is interpreted as a sedimentary basin lying off the west coast of the Isle of Man. The Isle of Man thus appears to be an uplifted horst-like region of Lower Palaeozoic rocks with the northwestern and south-eastern coastlines controlled by the margins of steep-sided sedimentary basins of post-Lower Palaeozoic age.

III.—The Grit-rocks of the Eastern Border of North Wales

The sandstone beds which skirt the eastern border of Wales, and stretch from a little south-west of the town of Oswestry to near the Point of Ayr, on the shores of the Irish Sea, a distance of upwards of 40 miles in a direct line, have for several years past been a source of perplexity to those who have investigated their peculiarities, and who have been interested in arriving at a determination of their true age and geological horizon.