ABB Lummus Global Technical Information Package for Shell

Technical Information Package for Shell Thermal Conversion Technologies Proposal No. 3-3676 ABB Lummus Global ABB Lummus Global B.V. TECHNICAL INFORMATION PACKAGE -- 30927,0 DMS 1 0 SSVB - TECHNICAL INFORMATION PACKAGE INDEX 30927LDR-0 Index 1. INTRODUCTION 1.1 VISBREAKER HISTORY AND DEVELOPMENTS 1.2 CHEMISTRY OF VISBREAKING 1.3 CONVERSION AND VISCOSITY REDUCTION 1.4 PRODUCT PROPERTIES AND USE 2. TECHNOLOGY OVERVIEW 2.1 INTRODUCTION 2.2 SHELL SOAKER VISBREAKING TECHNOLOGY 2.3 VACUUM FLASHER TECHNOLOGY 2.4 SHELL DEEP THERMAL CONVERSION TECHNOLOGY 2.5 SHELL THERMAL GASOIL PROCESS 2.6 UPGRADING POSSIBILITIES FOR THE VISBREAKER UNITS 2.7 PLANT AVAILABILITY 3. COMPETITIVE ADVANTAGES 3.1 COMPARISON SHELL SOAKER VISBREAKER VS. COIL VISBREAKER TECHNOLOGY 3.2 LICENSING FROM ABB LUMMUS GLOBAL 4. EXPERIENCE SUMMARY 4.1 LICENSE SUMMARY LGV SFOR 03-2000-01.001 (1996-06-20) DMS, propla0.dot , 1 30927LDR-0 /N24P0845.001 30927,0 Page 1 of 1 ABB Lummus Global B.V. TECHNICAL INFORMATION PACKAGE -- 30928,0 DMS 1 0 SSVB - TECHNICAL INFORMATION PACKAGE 1. INTRODUCTION 30928LDR-0 1. Introduction 1.1 VISBREAKER HISTORY AND DEVELOPMENTS Thermal cracking units built before 1930 were plagued with coking and mechanical problems. In these units, cracking was initiated in a heater and completed in a soaking drum. Runs were short, largely because the important parameters of cracking were not well under- stood. Because of the problems with coke formation in the soaking drum, visbreakers after 1933 were the coil cracking type. The soaking drum was eliminated and the heater outlet temperature increased, so that all cracking could take place in the heater. Improved heaters and cheap fuel largely contributed to this change. Therefore, it was natural to build this same type of visbreaker when visbreakers became popular in Europe after 1960. One advantage was that the higher outlet temperature permit- ted deep flashing of visbreaker effluent without the application of high vacuum, so that in addition to middle distillate a heavy gas oil could be produced. This could be cracked to yield additional middle distillates. The depth of flashing was, however, not very impressive; and whenever larger quantities of thermal cracker feedstock were required, a vacuum flasher for the residue was necessary. Most of the visbreakers built between 1960 and 1975 were combined with heavy distillate thermal cracking units. These combination units were particularly useful in reducing the heavy-fuel-oil pour point when waxy feedstocks were processed, such as those originating from Libyan crude oils. The thermal cracking residues from these feedstocks have pour points which can be 15 to 20°C lower than those of the corresponding heavy gas oil feedstocks. At about the same time that ABB Lummus Global started to design and construct several visbreaking units for Shell, a separate program was launched by Shell International to convert some old thermal cracking units into soaker-type visbreakers. The first of these units was started up in 1962 in Curaçao. It was soon followed by other units. The main objective was to achieve a maximum visbreaking capacity for a given heater size. It soon appeared that the soaking units had a number of additional advantages. Since the oil crisis in 1973, these advantages became so pronounced that Shell started to convert its existing visbreaking-thermal cracking units into soaker-type visbreakers. Vacuum flashers were added to increase the production of thermal cracker feedstock. All new visbreakers built by Shell are of the soaker type. Refining developments have also played a role in the expansion of visbreaking. In the refin- ery configuration which has developed over the last 10 years the catalytic cracker has played a predominant role in meeting gasoline requirements. This and cat cracker demands on vacuum gas oil, combined with the reduced demand for heavy fuel oil, has led to the present upsurge in the construction of visbreakers for heavy vacuum residues. LGV SFOR 03-2000-01.001 (1996-06-20) DMS, propla0.dot , 1 30928LDR-0 /N24P0845.002 30928,0 Page 1 of 9 ABB Lummus Global B.V. TECHNICAL INFORMATION PACKAGE -- 1. Introduction In addition, visbreakers have been built or planned for long residue feedstock for the simpler hydroskimming refineries. These units can be built as single stage visbreakers with soakers or as combination units with an additional thermal cracker heater for heavy gas oil. Alter- nately, the heavy gas oil can be used as feedstock for the catalytic cracking unit. 1.2 CHEMISTRY OF VISBREAKING A residual oil can be described as a colloidal system in which the dispersed phase consists of micelle containing asphaltenes and high molecular weight aromatic malthenes. The continuous phase contains the balance of the malthenes. Asphaltenes are, in general, very complex high-molecular-weight hydrocarbons containing very little hydrogen. They also contain sulfur, nitrogen, and oxygen, and have a strong aromatic character and aliphatic side chains. They are very soluble in carbon tetrachloride, carbon disulfide, and aromatic hydrocarbons, but not in light, paraffinic hydrocarbons. Malthe- nes are soluble in all kinds of hydrocarbons and in carbon disulfide. The micelle consists of a core of asphaltenes to which high-molecular-weight aromatic hydrocarbons from the malthene fraction are absorbed. To these high-molecular-weight aromatic hydrocarbons, other hydrocarbons with a some- what higher hydrogen content are absorbed, until the micelle at their periphery contain hydrocarbons with a hydrogen content about equal to that of the continuous malthene phase. In a stable oil, the system of absorbed malthenes is such that all absorption forces are satu- rated. The micelle is then in physical equilibrium with the surrounding oil phase. In other words, the asphaltenes are peptized. The absorption equilibrium can be disturbed in several ways, for instance, by adding hydrocarbons with a high hydrogen content (aliphatic hydrocarbons) and by increasing the temperature. Part of the absorbed compounds then dissolve in the continuous malthene phase, whereby the asphaltene cores precipitate. During the visbreaking process, the continuous oil phase is cracked to smaller molecules. Also, new asphaltenes are formed from malthenes, and the malthene phase composition changes in character. Eventually the equilibrium between asphaltenes and malthenes is disturbed to such an extent that part of the asphaltenes flocculate. At that point, the cracked fuel oil becomes unstable. The cracking reactivity of the various hydrocarbons differs for the various classes of hydrocarbons, and decreases in the following order: LGV SFOR 03-2000-01.001 (1996-06-20) DMS, propla0.dot , 1 30928LDR-0 /N24P0845.002 30928,0 Page 2 of 9 ABB Lummus Global B.V. TECHNICAL INFORMATION PACKAGE -- 1. Introduction n Normal paraffins n Iso-paraffins n Cycloparaffins n Aromatics n Naphthenes n Polynuclear aromatics. Paraffins are mostly cracked to smaller paraffins and olefins. Practically no carbon and hydrogen are formed, so that no coke formation takes place in the primary cracking reaction. An olefin is cracked to form either two smaller olefins or olefin plus diolefin. The diolefins usually have short chains, and the amount formed is less at lower cracking temperatures. Naphthenes and aromatics with long side chains are mainly cracked so that the side chains are shortened to methyl or ethyl groups. Cracking of naphthene rings usually does not start at temperatures below 490°C. Apart from cracking reactions, several other reactions take place, particularly when aromatics and polynuclear aromatics are present. For instance, inter and intramolecular condensation can take place as shown in Figure 1. Figure 1 LGV SFOR 03-2000-01.001 (1996-06-20) DMS, propla0.dot , 1 30928LDR-0 /N24P0845.002 30928,0 Page 3 of 9 ABB Lummus Global B.V. TECHNICAL INFORMATION PACKAGE -- 1. Introduction The condensation reactions are largely responsible for the formation of asphaltenes which, at increasing conversion eventually leads asphaltenes to precipitate and, therefore, produces unstable fuel oil. The concept of stability and how it is affected by visbreaking is illustrated by Figure 2. In this diagram, the corners represent three components of a residue: asphaltenes, paraffins, and aromatics. An area of immiscibility exists between the asphaltenes and paraffins, as already implied by the definition of asphaltenes, namely the material precipitated from an oil product by the addition of heptane or pentane. Figure 2 Suppose a residue has a composition represented by point A, which is in the stable region. During the visbreaking process, asphaltenes are formed at the expense of aromatics, so that the composition moves into direction B. At too high a conversion, the composition can move into the unstable region. In practice, a safe margin should always be kept to account for disturbances in the colloidal structure because of prolonged storage at elevated temperature, oxidation by air and other factors. LGV SFOR 03-2000-01.001 (1996-06-20) DMS, propla0.dot , 1 30928LDR-0 /N24P0845.002 30928,0 Page 4 of 9 ABB Lummus Global B.V. TECHNICAL INFORMATION PACKAGE -- 1. Introduction Also, adding cutterstock to obtain a specified viscosity may have a negative effect on the stability, depending on the nature of the cutterstock. Possible effects of cutterstock addition are shown in Figure 2. The stability can either be improved or impaired as movement occurs away from or towards the region of immiscibility. Figure 2 only gives a qualitative insight into the stability phenomena because aromaticity is not the only yardstick for the suitability of cutterstock. A more quantitative insight can only be obtained by long term practical experience and laboratory testing. 1.3 CONVERSION AND VISCOSITY REDUCTION The effect of visbreaking operation can be expressed in terms of the conversion or yield of light products. Alternately, it can be expressed as the reduction in viscosity of the product.

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