23rd World Gas Conference, Amsterdam 2006

DEVELOPMENT OF NEW TECHNOLOGY FOR SYNTHETIC FUELS PRODUCTION FROM NATURAL GAS

D.A. Miroshnichenko

Russia

ABSTRACT In the recent years the subject of vitality of commercial technologies development and

implementation for synthetic liquid fuels (GTL) production became one of the majors in the world oil and gas business. GAZPROM earnestly pursues to develop own technology for GTL. The interest of principal Russian gas company to the said program is well justified. GTL production will enable GAZPROM to significantly diversify activities and approach the world fuel markets with commercially valuable products as well as settle the task of developing remote fields. Perspectives of promoting natural gas conversion to GTL is also determined by the possibility of yield beside fuels also wide spectrum of products allowing to flexibly react to any changes on the market.

In order to create the Russian prospective GTL technology was elaborated the work program comprising construction of testing and pilot units at VNIIGAZ testing facilities and pilot-industrial unit at one of GAZPROM sites. This program was approved by GAZPROM Board in January 2003. Its fulfillment and coordination was mandated to VNIIGAZ.

All the existing and newly developed GTL production schemes are multi-stage, including the stage of syngas (carbon monoxide and hydrogen mixture) production, stage of HC mixture synthesis (synthetic fuel) or demethyl ether (DME) and the stage of catalytic enriching of synthetic oil with production of highly commercial products.

One of the major factors of GTL production efficiency is selecting the way of producing syngas, which could not only provide for minimal specific flow of natural gas for end product yield but also maximally reduce the technological production wastes.

Comparative analysis of different methods of syngas production fulfilled by VNIIGAZ indicated that in terms of energy consumption with average natural gas flow (1-3 bn cu m per annum) high efficiency has demonstrated natural gas conversion technology under Tandem scheme. Besides this method of conversion upon some complimentary improvements enables to produce syngas with ratio of H2/CO close to 2, which is optimal for Fischer-Tropsche process at cobalt catalyst.

F-T synthesis represents the second stage in the process of conversion natural gas to GTL: syngas obtained at the first stage is converted into HC mixture mainly paraffins and olefins of normal structure. Majority of western companies developing F-T synthesis technology recommend using three-phase so called slurry-reactors. While developing our own technology we look to various designs of fixed-bed reactors. In particular to organize F-T synthesis VNIIGAZ developed radial type reactor having advantage over tubular reactor in preventing overheating of the catalyst and hydraulic pressure reduction. One more reason for sticking to this design is rather a vast operation practice in Russia. Beside new technical solutions in technological schemes and reactor designs under way are activities for elaborating new highly efficient catalytic systems for F-T synthesis.

The third stage, i.e. HC mixture processing to the end product is similar to oil processing and as a rule includes various combinations of hydrocracking, isomerization and fractionating technologically well developed in Russia.

For transit to designing the pilot-industrial unit is worked out F-T synthesis and testing of various catalysts of this process at the level of rather simple testing units. And as output data are obtained necessary dependencies to elaborate thermo-dynamical and kinetic process models. At the same time we work on creating the pilot unit. This unit is designated for working at all the three stages of technological scheme for F-T GTL process.

The obtained results and level of development give grounds to assume that on their base will be developed commercially efficient technology for GTL corresponding to the world class flow parameters.

TABLE OF CONTENTS

Abstract

Body of Paper

The formed factors and tendencies in the world energy-fuel complex pose the task of developing this direction which would provide for production of additional amount of high quality environmentally pure motor fuels using as initial feed the currently flared natural and associated gases from different size remote fields. Simultaneously it would solve the problem of energy carriers profitable transmission to the consumers and will enhance reduction of greenhouse gases emission into atmosphere.

Accordingly during the recent decade underway has been continuous discussion and search

for options of natural and associated gas use from remote fields, alternative to pipeline transmission. Main alternatives are:

- gas liquefaction on production site and transmission to consumer by tankers-gas carriers; - methanol production from gas on site; - associated gas re-injection into reservoir; - liquid hydrocarbons production from gas (motor fuels, oils, paraffins etc. ) and DME. The projects of natural gas liquefaction (LNG) are already implemented on a wide scale.

These projects are rather capital - intensive and are justified only in case of major gas fields designated for the 20-30 years development and located either in the coastal areas or on the shelf.

Organization of methanol production from natural gas will not solve the reviewed problem, as

the world market of methanol is not huge (2,5×107÷3×107 ton/year) and demand well satisfied. Associated gas reinjection into the formation implies rather significant investments and

operational costs, it represents only the temporal flaring of gas and will not address the task of using the gas of remote fields and leaves it unsolved for the coming years.

One of the prospective directions of natural and associated gas from remote field use is gas

conversion into the synthetic liquid fuels which can be used both on site or transported to other regions including for export.

Technical possibility of converting natural gas into liquid hydrocarbons and some separate

elements of GTL technology have been well known within the last 75 years, however commercial implementation GTL plants constructions projects became feasible only by the end of XX century due to some recent achievements in the chemistry of technological processes, catalysis and design-technical solutions which allowed to reduce capital expenditures approximately two times. Such achievements include:

- increase of single capacity of air separation units up to 2500 ton per day; - increase of singular capacity of syngas producing units (Н2+СО) 3-4 times; - improvement of reactor design for multi-phase syngas conversion process - creating new catalysts on cobalt base to increase activity and selectivity. New stage in development of technology and GTL projects was also promoted by economic

stimuli of the last decades, related to growth of oil prices, discovery and development of new remote oil and gas fields, trends to prohibition of the HC gases and their combustion products emission into the atmosphere in the framework of measures preventing global warming.

Within the last several years JSC «GAZPROM» has been securing much attention to the

problem of technology elaboration for GTL production from natural gas. The interest of major Russian gas company to this subject is well justified. GTL production technology implementation will enable OAO “GAZPROM” to significantly diversify its activities and enter the world fuel markets with highly commercial product and also solve the problem of remote fields development and fields with depleting gas production. Prospective potential of natural gas conversion to GTL is also defined by the possibility to produce besides fuels the wide range of products allowing to flexibly pursue the change on the world market.

The fulfilled by VNIIGAZ analysis demonstrates that in Russia there doesn’t exist any large-

scale ready-to-implement commercial GTL technology. Nevertheless while establishing the industrial production, development and delivery of significant part of equipment can be provided by domestic design and machine building enterprises. If we consider the structure of GTL plant expenditures (fig.

1), we can see that the domestic plants are unable to supply main technological equipment for Fischer-Tropsche synthesis, corresponding in price terms to only 15% from the total volume of necessary capital investments.

Fig. 1 – Structure of capital expenditures of GTL plant

Besides, scientific-research organizations of Russia possess significant scientific base in the

reviewed area. To transform these achievements into the real commercially efficient industrial technology was worked out the work program on elaborating the domestic GTL production technology envisaging construction of stand and pilot units at the pilot-experimental base of VNIIGAZ, and pilot-industrial unit at one of the sites of GAZPROM. This program is approved by the Management Board of GAZPROM in January 2003. Its fulfillment and coordination was mandated to VNIIGAZ.

All the existing and newly developed processes of GTL production are multi-stage (fig 2) and

include the stage of syngas production (mixture of carbon monoxide and hydrogen), stage of synthesis of HC mixture (synthetic oil) or de-methyl ether (DME) and stage of catalytic enriching of synthetic fuel with production of highly commercial product, and prior to all environmentally clean diesel fuel.

Fig. 2 – Block-scheme of synthetic liquid fuels production

One of the major factors of production efficiency is syngas production method selection

capable not only to provide for minimal natural gas flow rate for production of designated product but also reduce to minimum the production technological wastes.

To produce syngas practically all the western companies suggest to apply auto-thermal

technologies. In these schemes in this or that way is combined methane oxidation by water vapor and oxygen. Comparative analysis of various methods of syngas production fulfilled by VNIIGAZ showed that in terms of energy-material expenditures and with loading on natural gas from 5×104 m3/hour - high efficiency is demonstrated by natural gas conversion technology under Tandem scheme (fig.3). Besides this method of conversion with necessary improvements, in particular carbon dioxide recirculation to the stream, provides for the possibility to produce syngas with ratio Н2/СО close to 2, which serves optimal for F-T process on cobalt catalyst.

Fig. 3 – Scheme of natural gas conversion underTandem scheme

F-T synthesis represents the second stage in the process of natural gas conversion to GTL:

syngas obtained on the first stage is converted to HC mixture, mainly normal structure paraffins and olefins. While applying the ferric catalysts as a rule occurs formation beside HC of paraffin row also big amount of olefins, and significant amount of alcohols, aromatic HC, small concentrations of acids and ketones. Due to this reason in the developed technology will be applied catalysts on the basis of cobalt. However due to high activity of cobalt catalysts, at their use in the similar volume reactor much more heat is generated than in case of ferric catalysts use, therefore important problem becomes heat by-pass from reaction zone.

To substantiate technical solutions for F-T synthesis technological diagram, we fulfilled patent

search for conversion reactor design of syngas to liquid hydrocarbons. Majority of companies-developers of F-T synthesis technology recommend the use of three-phase so called slurry-reactors.

Exception is made by "Shell", which in its new projects suggests the use of tube reactors with

fixed bed. Disadvantage of such reactors is high hydraulic resistance of the catalyst poured into the pipes as well as heat by-pass from reaction zone.

As the practice of designing and operation of slurry-reactors for GTL production in Russia

does not exist, we mainly follow in our works various designs of reactors with fixed bed. In particular for F-T- synthesis we together with NIPHI named after L.Ya Karpov Institute elaborated radial type reactor, which unlike tube reactor, enables to prevent overheat of the catalyst and reduce hydraulic

resistance. One more reason to select this design was rather vast experience in developing and operating of the similar reactors in Russia.

The third stage i.e. processing of HC into end product is similar to oil processing and as a rule

includes various combinations of hydrocracking, isomerization and fractionation processes which technological approaches are well developed in domestic industry.

Fig. 2 shows as separate block the DME production. The works on technology for DME

production acquired extreme actuality, as in 2002 Government of Moscow signed the program of converting the municipal diesel transport to DME. At the first stage Moscow will be provided with new fuel base on reconstruction of the idle facilities for methanol production. Then is planned construction of a unit designated solely for DME production, with productivity up to 5×105 ton/year. Now exist two approaches to DME production. First – use of bi-functional catalyst on which occur simultaneous formation of methanol and its dehydration. The second – use of two successive reactors: the first reactor of methanol synthesis and the second reactor of methanol dehydration with DME production.

To transfer to designing the pilot and then experimental-industrial unit, in the first place is

necessary to elaborate the stages of F-T and DME synthesis at the level of rather simple stand units. And thus will be obtained necessary data for creating the thermal-dynamic and kinetic models of the processes, which will allow to transit then to development of the overall GTL production scheme- from natural gas preparation to obtaining commercial product. The important task, which can also be fulfilled on the stand units, is selection of the efficient catalysts and execution of their resource testing.

At the stand units will be carried out investigations for the following tasks: - experimental verification of the mathematical model of the F-T synthesis process; - investigation of the process kinetics; - investigation and optimization of thermodynamical parameters of the process in order to

issue recommendations on technological modes; - comparison between efficiency of domestic and foreign catalysts for GTL production. Joint team of ООО «VNIIGAZ» and FGUP NIPHI named after L.Ya. Karpov together with the

specialized enterprises worked out the main technical requirements, fulfilled technical projects, developed working documentation, carried out manufacturing the equipment and installation of technological blocks of stand units.

At present under construction are three units for study of F-T process and two units to study

the process of DME production. Operation of the stand units will be done under the flowing mode where implemented are the main technological parameters of GTL production process. These units will allow to carry out investigations at pressures up to 107 Pa and temperatures up to 400 0

С. For the stand operation is planned to use the ready gas mixture, which composition corresponds to synthesis-gas necessary for F-T and DME processes. For F-T synthesis will be used reactors of radial type, and for synthesis of DME – two-berth reactors where on the first berth is located catalyst of methanol synthesis and on the second – catalyst of methanol dehydration. It should be noted that reactors design allows, if need be, to carry out changes in the type of reactor accessories for investigation of other technological modes and catalysts. The scheme of stand units is shown on fig.4.

Fig. 4 – Scheme of stand unit for development of technology for GTL production (1, 7 – receivers; 2, 8 – electric heaters; 3 – reactor of F-T synthesis; 4, 10 – refrigerators-condensers;

5, 11 – separators; 6, 12 – vessels; 9– reactor of DME synthesis)

At present we work on creating the pilot unit. This unit is designated for elaborating the whole

three stages of technological scheme of GTL production under F-T process. The pilot unit operation will be done under the circular scheme. The pilot unit comprises the block of syngas production, block of F-T synthesis and block of short-cycle adsorption to separate carbon oxide (fig 5).

Fig. 5 – Block-scheme of pilot unit for GTL production

It was found out that for production of syngas within the pilot unit at the loading on natural gas

about 10 m3, most feasible is the use of steam conversion in reactor with electric heating. It is induced by the following factors:

- process of conversion under Tandem scheme for the unit of small productivity is not economically viable due to high specific heat losses and necessity of including into the technological process the block of oxygen production;

- the process under Tandem scheme is elaborated on the industrial scale at JSC «Grodno Azot» (Belarus Republic) and does not demand additional verification and testing at the level of pilot unit;

- the scheme of steam conversion with inclusion into the technological stream of natural gas of carbon dioxide can provide the syngas break-down similar to that obtained under Tandem scheme. To elaborate the stage of F-T synthesis aimed at reducing the cost of the pilot unit is planned

use of equipment and partially management systems of investigation stands of GTL production. On the base of created site in 2006-2007 is planned to fulfill complex of scientific-investigation

works, which will allow to obtain necessary initial data to substantiate investments and designing the first experimental-industrial unit in Gazprom.