PERP Program New Report Alert

Transcription

1 PERP Program New Report Alert March 2005 Nexant s ChemSystems Process Evaluation/Research Planning program has published a new report, (03/04-4). Background is the lowest molecular weight primary alcohol and has a wide range of applications. The use of methanol can be divided into two categories: chemical related and fuel related applications. Figure 1 illustrates the uses and applications that constitute the drivers of methanol demand. In 2003, about 72 percent of the global consumption went into the production of formaldehyde, acetic acid, and MTBE. Technology Commercially-viable catalysts that can selectively activate methane to methanol, with an acceptable methane conversion and a reasonably high methanol selectivity, have yet to be established. In lieu of this ideal route, today's practical methanol production technology still employs the less efficient two-step process by first generating synthesis gas (carbon monoxide and hydrogen) from natural gas (methane) or other hydrocarbon feedstocks, such as naphtha, heavy oils, and coal. The synthesis gas generated in the first step is then converted to methanol in the second step. Natural gas based synthesis gas can be produced via partial oxidation (Reaction 1 below) and/or steam reforming (Reaction 2 below) of methane as follows: CH 4 + ½ O 2 CO + 2H 2 CH 4 + H 2 O CO + 3H 2 (1) (2) Q404_ CDX Currently, the synthesis gas generation technologies are basically grouped in accordance with Reactions (1) and (2) above as follows: Non-catalytic partial oxidation Catalytic partial oxidation reforming Combined reforming

2 - 2 - Figure 1 Demand Drivers METHANOL CH3 OH -H 2 FORMALDEHYDE HCHO Urea Phenol Melamine Resins Resins Resins Poly w/eg Polyacetal (High Growth) p-xylene DIMETHYL TEREPHTHALATE C6H4(COOCH 3)2 Poly w/eg Polyester Resins (esp. PET) CO ACETIC ACID CH3COOH O 2 C = 2 Vinyl Acetate (VAM) EVA PVAC Adhesives, Specialties Latex Paints PVOH ic = 4 METHYL t-butyl ETHER (CH3)3COCH3 Gasoline Additive (2-Methylbutene ex FCC) t-amyl METHYL ETHER (CH3)2C(OCH 3)CH2CH3 Gasoline Additive Methacrylamide sulfate or METHYL METHACRYLATE methacrylic acid CH2C(CH3)COOCH 3 Poly MMA (PMMA) + MBS Resins Cast, Extruded Sheet Molding/Powder Resins Protective Coatings GASOLINE/FUEL Used As SOLVENTS Used As Cellulosics, Resins, Dyes Q404_ PPT OTHER USES Used As Chemical Synthesis - Methyl Amine - Methyl Chloride Dehydrator Synthetic Proteins The steam reforming reaction is a highly endothermic reaction. It takes place inside the catalyst filled tubes of a reformer furnace. The endothermic heat is supplied externally by firing additional amounts of natural gas. Simultaneous to the steam reforming reaction, the water/gas shift reaction also takes place: CO + H 2 O CO 2 + H 2 (3) Q404_ CDX The steam reformer requires a high steam to carbon ratio to prevent carbon from being deposited on the catalyst, thereby reducing its activity. High steam-to-carbon ratios imply high consumption of energy in the process of vaporizing the required steam, and also increased hydrogen production due to the water/gas shift reaction.

3 - 3 - Alternatively, synthesis gas can be produced via catalytic or non-catalytic partial oxidation of methane (POX), an exothermic reaction that does not require additional heat. However, there is an implicit energy input in the form of power in the generation of pure oxygen from atmospheric air in an air separation unit (ASU). The conversion of synthesis gas to methanol is a strongly exothermic process. The methanol synthesis reactions can be represented as follows: CO + 2H 2 CO 2 + 3H 2 CH 3 OH CH 3 OH + H 2 O (4) (5) Q404_ CDX The goal is to achieve a relatively high carbon efficiency and thereby minimize the amount of synthesis gas to be processed and, thus, the natural gas or other feedstock consumption. The carbon efficiency of the synthesis process increases as: The synthesis pressure increases (typically bar for a world-scale plant) The inerts decrease (resulting in a smaller purge) The molar ratio of carbon monoxide to carbon dioxide increases The conversion rate per pass decreases While it is desirable to employ high synthesis pressure in order to achieve high carbon efficiency, the requirements for increased compression duty and increased wall thickness of the equipment and piping due to the increased pressure need to be taken into account. Equally, while low conversion rate per pass will favor high carbon efficiency, it will result in an increased recycle rate and, thus, in a higher compression duty and investment. The ideal synthesis gas composition for practical use would have a molar ratio of just over two when calculated according to the following formula: H 2 -CO 2 Ratio = CO + CO 2 Addition of CO 2 is one option for adjusting this ratio; other methods relate to the process design configuration, particularly around the reformer. There are several variants of methanol technology available or under development. The main options with respect to reformer configuration are described below and shown in much simplified block diagram form in Figure 2.

4 - 4 - Figure 2 Selected Options CONVENTIONAL Fuel Purification Converter Distillation CO 2 COMBINED REFORMER (CR) Fuel Oxygen Purification Primary Autothermal Converter Distillation SINGLE AUTOTHERMAL REFORMER Oxygen Purification Autothermal Converter Distillation GAS HEATED REFORMER Oxygen Purification Gas Heated Autothermal Converter Distillation Key Main Process Flow Optional Q404_ PPT

5 - 5 - At the front end, all processes contain a gas purification section to remove impurities, primarily sulfur, which could poison the catalysts. Similarly, all processes include a distillation section two or three stage at the back end to remove impurities from the crude methanol produced in the synthesis section. The conventional process employs a steam reformer with catalyst packed in tubes (SMR or Methane ) that are heated externally by burners using natural gas or other streams with high calorific value. The feedstock to the reformer is a mixture of desulfurized natural gas and steam (typically up to 3:1 steam to carbon ratio). Excess hydrogen is produced unless CO 2 can be added. The synthesis gas is compressed and passes to the converter, where methanol is produced. If a quench-type converter is used, part of the synthesis gas is injected at various positions to moderate the temperature. The unconverted syngas is recirculated to the converter by a compressor. The level of once-through conversion in the converter affects the size of the recycle and total flow to the converter. In the combined reformer or two-step reforming process, the tubular reformer is combined in series with a secondary reformer to which oxygen is added. Part of the natural gas feedstock may be diverted to the secondary, or autothermal, reformer. Energy is provided by the heat of reaction of the partial oxidation process, considerably offloading the primary reformer. Synthesis gas from an oxygen-blown reformer is deficient in hydrogen compared to the ideal molar ratio, so the two reformers together can produce the ideal ratio. Compared to the conventional process, the combined reformer process requires additional capital in terms of an Air Separation Unit (ASU) and the secondary reformer, plus associated items. However, capital cost advantages are gained from a smaller primary reformer, smaller equipment in the syngas system, and a smaller syngas compressor. Some licensors offer a system with a single stage autothermal reformer based on oxygen addition. The syngas is deficient in hydrogen compared to the ideal molar ratio. This can be remedied if hydrogen is available, such as from an existing conventional reformer system. The advantages cited for a single autothermal reformer include reduced capital cost because the system is simpler than a combined reformer system. In addition, the reactor may be operated at high pressures, removing load from the main syngas compressor. The steam to carbon ratio can be lower than with the conventional SMR. The advantages and disadvantages of the combined reformer system, apart from the ability to balance the syngas composition, apply to the single autothermal reactor. The gas heated reformer system dispenses with a fired primary reformer. Instead, the hot gases from the secondary oxygen-blown secondary reformer are used to provide indirect heat to an unfired

6 - 6 - primary reformer. The advantages are claimed to include the benefits of combined reforming, plus improved thermal efficiency resulting from direct use of hot gases rather than by conversion to steam. The synthesis reactor, or converter, may be of several forms. One of the differentiating factors is the method of moderating the reaction. One technique is the injection of shots of syngas at various positions, the quench system. In another type of converter steam is raised, often from a shell and tube configuration, and is usually used as process steam for the reformer. Two stage converter systems are available, and are particularly useful in reducing equipment sizes at very large capacities. Another differentiating factor is axial versus radial flow through the catalyst bed(s). All designs address the provision of process steam for reforming, recovery of heat from reforming, and drives for the equipment such as syngas main and loop compressors. The configuration differs between technologies, with some processes producing significant quantities of export steam. There has been much discussion of large-scale methanol processes of 5,000 tons per day or more. Such a capacity represents around six percent of the current global demand for methanol, and so clearly the market ability to absorb such capacities is limited. Most licensors are offering methanol plant capacities at this scale, but so far only two projects have passed financial closure and neither has yet completed construction: The world s first methanol plant with this capacity (5,000 MTPD) is the Methanex/BP joint venture ( Atlas ) in Trinidad which employs Lurgi technology and is to be commissioned in The world s second large-scale methanol plant (5,400 MTPD) will be the Holdings plant, also in Trinidad, which will employ the technology of JM Catalysts/Davy Process Technology and is due to start up in Although touted as a 5,400 MTPD plant, the plant is in fact a 5,000 MTPD facility with a side-stream unit to collect purge gas from other nearby plants and produce 400 MTPD of additional methanol. The plant includes CO 2 addition from nearby ammonia facilities to balance the syngas ratio. Economics An economic comparison of 5,000 metric ton per day methanol plants for the U.S. Gulf Coast and second quarter 2004 is provided covering these processes: Methane Reforming and Synthesis Combined Reforming and Synthesis Foster Wheeler Starchem Process JM Synetix Leading Concept Process

7 - 7 - Production cost varies by 9-11 percent among these processes. An economic comparison is also provided for a Middle East location for the same processes on the same capacity and time bases. Here, cash cost varies about 15 percent, while cost plus return varies about 10 percent. Commercial The report discusses both chemical and fuel applications for methanol, the latter including bans and restrictions on methyl tertiary butyl ether, derived from methanol, as a gasoline component. World methanol demand, segmented by eight regions, is presented for the period A global capacity listing is provided, along with the global supply/demand balance, both for the period. Regional details are given for North America, South America, Western Europe, Middle East and Asia Pacific. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Copyright by Nexant, Inc All Rights Reserved. Nexant, Inc. ( is a leading management consultancy to the global energy, chemical, and related industries. For over 38 years, Nexant/ChemSystems has helped clients increase business value through assistance in all aspects of business strategy, including business intelligence, project feasibility and implementation, operational improvement, portfolio planning, and growth through M&A activities. Nexant s chemicals and petroleum group has its main offices in White Plains (New York) and London (UK), and satellite offices worldwide. These reports are for the exclusive use of the purchasing company or its subsidiaries, from Nexant, Inc., 44 South Broadway, 5 th Floor, White Plains, New York U.S.A. For further information about these reports contact Dr. Jeffrey S. Plotkin, Vice President and Global Director, PERP Program, phone: ; fax: ; jplotkin@nexant.com; or Heidi Junker Coleman, phone: , address: hcoleman@nexant.com, Website: