Shell Middle Distillate Synthesis Process Research Articles

Potential of interactions between fuels and future powertrains

A large part of the world’s natural gas reserves is located in areas where domestic demand is small. These remote gas fields can be developed by converting the natural gas to synthetic diesel fuel via the Shell Middle Distillate Synthesis (SMDS) process, a modern version of the Fischer-Tropsch process. This process produces high quality, environmentally friendly diesel fuel. Simultaneous exhaust emission reductions of 50 % for particulates and 20 % for NOx have been found in Volkswagen Bora diesel vehicles with SMDS fuel compared to standard diesel. Due to the flexibility of the SMDS process, fuels can be tailored to meet the specific needs of future engine technologies like the Combined Combustion System, a homogeneous combustion technology developed by Volkswagen.

99/02461 The Shell middle distillate synthesis process: commercial plant experience and outlook into the future

99/02461 The Shell middle distillate synthesis process: commercial plant experience and outlook into the future

Carbon: Hydrogen carrier or disappearing skeleton?

The use of liquid hydrocarbons as energy carriers implies the use of carbon as a carrier for hydrogen to facilitate hydrogen transport and storage. The current trend for liquid energy carriers used in the transport sector is to maximize the load of hydrogen on the carbon carrier. The recently developed Shell Middle Distillate Hydrogenation process for the manufacture of high quality diesel from aromatic refinery streams fits this picture. In the future, the hydrogen required to raise the product's sol H C ratio will be increasingly produced via gasification of large amounts of heavy residues. In the light of the strong preference towards using liquid fuels in the transport sector, the Shell Middle Distillate Synthesis process to convert natural gas into diesel of very high quality is discussed. Finally, a few comments on the use of hydrogen without a carbon carrier are made. Long lead times and the likelihood of producing the “first” hydrogen from fossil fuel are highlighted.

Production costs of liquid fuels by indirect coal liquefaction

Since the oil crisis of 1973 considerable interest has been shown in the production of liquid fuels from alternative sources. In particular, processes utilizing coal as the feedstock have received considerable interest. These processes can be divided into indirect, direct liquefaction and pyrolysis. This paper describes the modelling of indirect coal liquefaction processes in order to perform a technical and economic assessment of the production of liquid fuels from coal and lignite, using a variety of gasification and synthesis gas conversion technologies. The technologies are modelled on a ‘step model’ basis where a step is defined as a combination of individual unit operations which together perform a significant function on the process streams, such as a methanol synthesis step or gasification and physical gas cleaning step. Sample results of the modelling, covering a wide range of gasifiers, liquid synthesis processes and products are presented in this paper. There are a large number of combinations of feeds (3), gasifiers (10), products (6), other technical parameters (up to 20) and economic or financial parameters (17), as well as sensitivity studies, giving a total number of possible results in excess of 50 000. The main results show that methanol is the most attractive fuel relative to current market prices, followed by fuel alcohol, diesel from the Shell Middle Distillate Synthesis process, diesel from the Mobil Methanol Olefins Gasoline Diesel (MOGD) process, gasoline from the same process and finally gasoline from Mobil Methanol to Gasoline (MTG) process. There was a variation in production costs of up to 100% for most products depending on type of gasifier chosen and type of feedstock.

Production costs of liquid fuels from biomass

There has been considerable interest in producing fuels from biomass and wastes since the oil crises of the last two decades which has been reinforced by subsequent environmental concerns and recent political events in the Middle East. This project was undertaken to provide a consistent and thorough review of the full range of processes for producing liquid fuels from biomass to compare both alternative technologies and processes within those technologies in order to identify the most promising opportunities that deserve closer attention. Thermochemical conversion of wood, straw and refuse includes both indirect liquefaction through gasification, and direct liquefaction through pyrolysis and liquefaction in pressurized solvents. Biochemical conversion is based on a different set of feedstocks that includes wood as well as wheat and sugar beet. Both acid and enzyme hydrolysis are included as options, followed by fermentation. The liquid products considered include gasoline and diesel hydrocarbons that in some cases would require minor refining to convert them into marketable products, and conventional alcohol fuels of methanol and ethanol which have established opportunities for utilization, and fuel alcohol which is as yet unproven in the market place. Results are given both as absolute fuel costs and as a comparison of estimated cost to market price. The results from these two interpretations are quite different. In terms of absolute fuel costs, thermochemical conversion offers the lowest cost products, with the least complex processes generally having an advantage. Exceptions are the unproven direct liquefaction route through zeolites which may be very optimistic, and the Shell middle distillate synthesis process. Biochemical routes are the least attractive. The most attractive processes from comparing production costs to product values are generally the alcohol fuels which enjoy a higher market value. This final analysis should be viewed cautiously since product values are very uncertain and can change significantly over short periods of time, and feedstock prices are also subject to substantial variation with time and location, and this is often the major cost item in the production costs. There is still considerable analysis to be carried out on results from the model, including production cost analyses and sensitivity studies, as well as continued development to improve accuracy and extend the range of technologies considered.

Economics of liquid fuels production by coal gasification

Since the oil crisis of 1973 considerable interest has been shown in the production of liquid fuels from alternative sources. In particular, processes utilizing coal as the feedstock have received considerable interest. These processes can be divided into indirect liquefaction, direct liquefaction and pyrolysis. This paper describes the modelling of indirect coal liquefaction processes in order to perform a consistent technical and economic assessment of the production of liquid fuels from coal and lignite, using a variety of gasification and synthesis gas conversion technologies. The technologies are modelled on a ‘step model’ basis where a step is defined as a combination of individual unit operations which together perform a significant function on the process streams, such as a methanol synthesis step or gasification and a physical gas cleaning step. Sample results of the modelling are presented to illustrate the scope of the work. These cover a representative range of gasifiers, liquid synthesis processes and products from the large number of combinations of feeds (3 alternatives), gasifiers (10 alternatives), products (6 alternatives), other technical parameters (up to 20 variables) and economic or financial parameters (17 variables), as well as possible sensitivity studies. The results have been validated by major European companies in absolute as well as comparative terms. The main results show that methanol is the most attractive fuel relative to current market prices, followed by fuel alcohol (a mixture of alcohols produced by modified Fischer-Tropsch synthesis), diesel from the Shell middle distillate synthesis process, diesel from the Mobil methanol to olefins gasoline diesel process, gasoline from the same process and finally gasoline from the Mobil methanol to gasoline process. Some products are currently economic based on typical world coal prices. There was a variation in production costs of up to 100% for most products depending on the type of gasifier chosen and specific feedstock.

Conversion of natural gas to transportation fuels via the shell middle distillate synthesis process (SMDS)

For several decades Shell's research has been involved in syngas chemistry, with special focus on routes to convert natural gas into easily transportable liquid hydrocarbons. This effort has resulted in the development of the SMDS process, for which the first commercial plant is being constructed in Sarawak, Malaysia. The heart of SMDS is an enhanced Fischer-Tropsch synthesis. Fundamentals of the Fischer-Tropsch synthesis are reviewed. The relation between catalyst characteristics and choice of the synthesis reactor is discussed. In the case of fluid-bed technology, the type of reactor places a clear limitation on product carbon numbers. For fixed and ebulliating beds diffusion limitations within the catalyst particles are quantified, while extra-particle mass-transfer limitations can be observed in slurry reactors. Cracking of Fischer-Tropsch waxes follows the synthesis step in the SMDS process. The control of the chain-length distribution in the selective hydrocracking step is elaborated. It is this combination of synthesis and hydrocracking that forms the basis of the SMDS process. The concept of the process is explained with emphasis on process integration, product quality and environmental aspects.

The shell middle distillate synthesis process (SMDS)

Since the early 1970s Shell's research has been involved in syngas chemistry with special focus on routes to convert (remote) natural gas into easily transportable liquid hydrocarbons. This has resulted in the development of the SMDS process. The world's first commercial SMDS plant is being constructed on a site adjoining the Bintulu LNG plant in Sarawak, Malaysia, and will come on stream in the last quarter of 1992. The heart of SMDS is an enhanced Fischer-Tropsch process. However, direct FT synthesis does not allow the selective production of materials of narrow carbon number range. To overcome this limitation the flexible two-stage concept of SMDS has been developed, which combines the chain-length-independent FT chain-growth reaction with a chain-length-dependent cracking process. Naphtha, kerosene and gas oil yield ratios can be varied from 15∶25∶60 to 25∶50∶25. Both the kerosene and gas oil show excellent combustion properties: the smoke point of the kerosene can be over 45 mm and the gas oil has a cetane number in excess of 70. Further attention is paid to the production of the synthesis gas because of its impact on overall process efficiency, to the selection of multitubular FT reactors, and to the environmental merits of the SMDS process and its clean, aromatics-free products.