Synthesis gas generation by chemical-looping reforming in a continuously operating laboratory reactor

Chemical-looping reforming is a technology that can be used for partial oxidation and steam reforming of hydrocarbon fuels. This paper describes continuous chemical-looping reforming of natural gas in a laboratory reactor consisting of two interconnected fluidized beds. Particles composed of 60 wt% NiO and 40 wt% MgAl₂O₄ are used as bed material, oxygen carrier and reformer catalyst. There is a continuous circulation of particles between the reactors. In the fuel reactor, the particles are reduced by the fuel, which in turn is partially oxidized to H₂, CO, CO₂ and H₂O. In the air reactor the reduced oxygen carrier is reoxidized with air. Complete conversion of natural gas was achieved and the selectivity towards H₂ and CO was high. In total, 41 h of reforming were recorded. Formation of solid carbon was noticed for some cases. Adding 25 vol% steam to the natural gas reduced or eliminated the carbon formation.     

Hydrogen formation from a real biogas using electrochemical cell with gadolinium-doped ceria porous electrolyte

The electrochemical cell consisting of a gadolinium-doped ceria (GDC, Ce_0.9Gd_0.1O_1.95) porous electrolyte, Ni–GDC cathode and Ru–GDC anode was applied for the dry-reforming (CH₄+CO₂→2H₂+2CO) of a real biogas (CH₄ 60.0%, CO₂ 37.5%, N₂ 2.5%) produced from waste sweet potato. The composition of the supplied gas was adjusted to CH₄/CO₂=1/1 volume ratio. The supplied gas changed continuously into a H₂–CO mixed fuel with H₂/CO=1/0.949–1/1.312 vol ratios at 800 °C for 24 h under the applied voltage of 1–2 V. The yield of the mixed fuel was higher than 80%. This dry-reforming reaction was thermodynamically controlled at 800 °C. The application of external voltage assisted the reduction of NiO and the elimination of solid carbon deposited slightly in the cathode. The decrease of heating temperature to 700 °C reduced gradually the fraction of the H₂–CO fuel (61.3–18.6%) within 24 h. Because the Gibbs free energy change was calculated to be negative values at 700–600 °C, the above result at 700–600 °C originated from the gradual deposition of carbon over Ni catalyst through the competitive parallel reactions (CH₄→C+2H₂, 2CO→C+CO₂). The application of external voltage decreased the formation temperature of carbon by the disproportionation of CO gas. At 600 °C, the H₂–CO fuel based on the Faraday's law was produced continuously by the electrochemical reforming of the biogas.     

Effect of three processes on CO2 and O2 simultaneously reforming of coke oven gas to syngas

CO₂ and O₂ simultaneously reforming of coke oven gas (COG) in three processes including non-catalytic process (NCP), catalytic process (CP), and two-stage process (TSP) was investigated under two important operating conditions, CO₂/CH₄ and O₂/CH₄, over Ni-based catalyst in a fixed bed reactor. It was found that the technical indexes depend strongly on CO₂/CH₄ and O₂/CH₄ in different processes. CO₂ can adjust H₂/CO ratio in a wider range (0.52–3.83) in the presence of O₂. The conversions of CH₄ increase in overall COG reforming processes by adding O₂. Also, a little O₂ promotes CO₂ conversions in NCP and restrains CO₂ conversions in CP and TSP. The addition of O₂ can also adjust H₂/CO ratio of syngas, which is actually at the cost of H₂ consumption by oxidation rather than reverse water gas shift (RWGS) reaction. In addition, H₂ combustion in the first-stage of TSP provides heat to drive the endothermic CH₄ reforming reactions and RWGS reaction in the second-stage of TSP to achieve higher CH₄ and CO₂ conversions. Therefore, TSP precedes significantly NCP and CP in the reforming of COG. When H₂/CO ratio is 2.10, the conversions of CH₄ and CO₂ are 98.96 and 62.32% respectively; and, oxygen consumption is 0.13 m³ per COG m³ at gas hour space velocity 9256 h⁻¹ in TSP.     

Development of electrochemical cell with layered composite of the Gd-doped ceria/electronic conductor system for generation of H2–CO fuel through oxidation–reduction of CH4–CO2 mixed gases

This paper shows the recent results on the development of layered composite promoting two types of electrochemical reactions (oxidation and reduction) in one cell. This cell consisted of porous Ni–Gd-doped (GDC) ceria cathode/thin porous GDC electrolyte (50 μm)/porous SrRuO₃–GDC anode. The external electric current was flowed in this cell at the electric field strength of 1.25 and 6.25 V/cm. The mixed gases of CH₄ (30–70%) and CO₂ (70–30%) were fed at the rate of 50 ml/min to the cell heated at 400–800 °C under the electric field. In the cathode, CO₂ was reduced to CO (CO₂ + 2e^? → CO + O^2?) and the formed CO and O^2? ions were transported to the anode through the pores and surface and interior of grains of GDC film. On the other hand, CH₄ was oxidized in the anode to form CO and H₂ through the reaction with diffusing O^2? ions (CH₄ + O^2? → CO + 2H₂ + 2e^?). As a result, H₂–CO mixed fuel was produced from the CH₄–CO₂ mixed gases (CH₄ + CO₂ → 2H₂ + 2CO). This electrochemical reaction proceeded completely at 800 °C and no blockage of gases was measured for long time (>10 h). Only H₂–CO fuel was generated in the wide gas compositions of starting CH₄–CO₂ gases.     

Optimising H2 production from model biogas via combined steam reforming and CO shift reactions

H₂ production was studied through steam reforming of a clean model biogas in a fluidized-bed reactor followed by two stages of CO shift reactions (fixed-bed reactors). The steam reforming of biogas was performed over 11.5 wt.% Ni/Al₂O₃ and a molar CH₄/CO₂ ratio of 1.5 was employed as clean model biogas. Excess steam resulted in strong inhibition of carbon formation and an almost complete CH₄ (>98%) conversion was achieved.To optimise H₂ production, CO shift reactions were carried out at high (523–723 K) and low temperatures (423–523 K) using commercial catalysts, based on Cu/Fe/Cr and Cu/Zn, respectively. Increasing steam concentrations led to a lean CO, high H₂ product. The final product compositions following low temperature CO shift reaction (steam to dry gas ratio of 1.5 at 483 K) yielded H₂ at 68% and a CO concentration of 0.2% (equivalent to CO conversion of >99%).     

Evaluation of different oxygen carriers for biomass tar reforming (II): Carbon deposition in experiments with methane and other gases

This work is a continuation of a previous paper by the authors [1] which analyzed the suitability of the Chemical Looping technology in biomass tar reforming. Four different oxygen carriers were tested with toluene as tar model compound: 60% NiO/MgAl₂O₄ (Ni60), 40% NiO/NiAl₂O₄ (Ni40), 40% Mn₃O₄/Mg-ZrO₂ (Mn40) and FeTiO₃ (Fe) and their tendency to carbon deposition was analyzed in the temperature range 873-1073 K. In the present paper, the reactivity of these carriers to other compounds in the gasification gas is studied, also with special emphasis on the tendency to carbon deposition. Experiments were carried out in a TGA apparatus and a fixed bed reactor. Ni-based carriers showed a tendency to form carbon in the reaction with CH₄, especially Ni60. The addition of water in H₂O/CH₄ molar ratios of 0.4-2.3 could decrease the carbon deposited, but not in the case of Ni60. Mn-based sample reacted with CH₄ almost completely and with low tendency to carbon deposition, while the Fe-based sample showed low reactivity. Ni40 showed more reactivity to CO than Mn40, although in both cases carbon was deposited, especially at 873 K. When H₂ was present, it reacted rapidly with both carriers, decreasing the amount of carbon deposited. The presence of CO₂ could also decrease the carbon deposited on Ni40 at 1073 K. According to both these and the previous results [1], it can be concluded that Mn40 is the most adequate for minimization of carbon deposition in Chemical Looping Reforming (CLR).     

Reactivity of a NiO/Al2O3 oxygen carrier prepared by impregnation for chemical-looping combustion

The reactivity of a Ni-based oxygen carrier prepared by hot incipient wetness impregnation (HIWI) on α-Al₂O₃ with a NiO content of 18 wt% was studied in this work. Pulse experiments with the reduction period divided into 4-s pulses were performed in a fluidized bed reactor at 1223 K using CH₄ as fuel. The number of pulses was between 2 and 12. Information about the gaseous product distribution and secondary reactions during the reduction was obtained. In addition to the direct reaction of the combustible gas with the oxygen carrier, CH₄ steam reforming also had a significant role in the process, forming H₂ and CO. This reaction was catalyzed by metallic Ni in the oxygen carrier and H₂ and CO acted as intermediate products of the combustion. No evidence of carbon deposition was found in any case. Redox cycles were also carried out in a thermogravimetric analyzer (TGA) with H₂ as fuel. Both tests showed that there was a relation between the solid conversion reached during the reduction and the relative amount of NiO and NiAl₂O₄ in the oxygen carrier. When solid conversion increased, the NiO content also increased, and consequently NiAl₂O₄ decreased. Approximately 20% of the reduced nickel was oxidized to NiAl₂O₄, regardless ΔX_s. NiAl₂O₄ was also an active compound for the combustion reaction, but with lower reactivity than NiO. Further, the consequences of these results with respect to the design of a CLC system were investigated. When formation of NiAl₂O₄ occurred, the average reactivity in the fuel reactor decreased. Therefore, the presence of both NiO and NiAl₂O₄ phases must be considered for the design of a CLC facility.     

Nickel aluminate spinel formation during sintering of simulated Ni-laden sludge and kaolinite

Incorporating Ni-laden waste sludge into kaolinite-based construction ceramic materials appears promising based on the identified nickel bearing phases, evaluated incorporation efficiency and nickel leachability of the products. Nickel aluminate spinel (NiAl₂O₄) results from sintering kaolinite and nickel oxide between 990 and 1480 °C, with more than 90% incorporation efficiency achieved at 1250 °C and 3 h sintering. At lower temperature (990 °C), NiAl₂O₄ formed from the reaction between nickel oxide and the defect spinel generated from the kaolinite–mullite reaction series. In addition to sintering temperature and time, four raw material mixing procedures were employed, and the ball-milled slurry samples had the highest nickel incorporation efficiency. Prolonged leach testing of NiO, NiAl₂O₄ and the product from sintered kaolinite + NiO mixtures was carried out using the TCLP extraction fluid #1 (pH 4.9) to evaluate the product stability, and the results revealed the superiority of spinel products over NiO in stabilizing nickel.     

Transient response of catalyst bed temperature in the pulsed reaction of partial oxidation of methane to synthesis gas over supported group VIII metal catalysts

Mechanisms of partial oxidation of methane to synthesis gas were studied using a pulsed reaction technique and temperature jump measurement. Catalyst bed temperatures were directly measured by introducing 1 and 3 ml pulses of a mixture of CH₄ and O₂ (2/1). With Ir, Pt and Ni/TiO₂ catalysts, a sudden temperature increase at the front edge of the catalyst bed was observed upon introduction of the pulse. The synthesis gas production basically proceeded via two-step paths consisting of highly exothermic complete methane oxidation to give H₂O and CO₂, followed by the endothermic reforming of methane with H₂O and CO₂. In contrast, with the Rh and Pd/TiO₂ catalysts, the temperature at the front edge of the catalyst bed decreased upon introduction of the CH₄/O₂ (2/1) pulse and a small increase in the temperature at the rear end was observed. Initially, the endothermic decomposition of CH₄ to H₂ and deposited carbon or CH_x probably took place at the front edge of the catalyst bed, after which the deposited carbon or generated CH_x species would be oxidized into CO_x. When the Ru/TiO₂ catalyst was used, a temperature increase at the front edge of the catalyst bed was observed upon introduction of the 3 ml pulse of CH₄/O₂. In contrast, the temperature drop at the front edge of the catalyst bed was observed for a 1 ml pulse of CH₄/O₂. These results seemed to exhibit two possibilities for a synthesis gas formation route over the Ru/TiO₂ catalyst. The reaction pathway of the partial oxidation of methane with group VIII metal-loaded catalysts depended strongly upon the metal species and reaction conditions.     

Effect of alkali doping on catalytic properties of alumina-supported nickel oxide in the selective oxidehydrogenation of cyclohexane

The influence of alkali metal (Na, K, Cs) doping on the surface and catalytic properties of γ-Al₂O₃ supported nickel oxide in the selective oxidehydrogenation of cyclohexane was investigated. Among the organic products quantified were cyclohexene, 1,3-cyclohexadiene, benzene, and CO, CO₂, and H₂O as inorganic products, respectively. Cyclohexene selectivities of up to 75% were achieved. Doping of the catalyst with alkali was found to have no promoting effect. Selectivity to cyclohexene increased in the following order: NiO/Cs-Al₂O₃ < NiO/K-Al₂O₃ < NiO/Na-Al₂O₃ < NiO/Al₂O₃.     

Using continuous and pulse experiments to compare two promising nickel-based oxygen carriers for use in chemical-looping technologies

Chemical-looping technologies have obtained widespread recognition as power or hydrogen production units with inherent carbon capture in a future scenario where CO₂ capture and storage (CCS) is reality. In this paper three different techniques are described; chemical-looping combustion and two categories of chemical-looping reforming. The three techniques are all based on oxygen carriers that are circulating between an air- and a fuel reactor, providing the fuel with undiluted oxygen. Two different oxygen carriers; NiO/NiAl₂O₄ (40/60 wt/wt) and NiO/MgAl₂O₄ (60/40 wt/wt) are compared. Both continuous and pulse experiments were performed in a batch laboratory fluidized bed working at 950 °C using methane as fuel. It was found that pulse experiments offer advantages in comparison to continuous experiments, particularly when evaluating suitable particles for autothermal chemical-looping reforming. Firstly, smaller conversion ranges can be investigated in more detail, and secondly, the onset and extent of carbon formation can be determined more accurately. Of the two oxygen carriers, NiO/MgAl₂O₄ offers several advantages at elevated temperatures, i.e. higher methane conversion, higher selectivity to reforming and lesser tendency for carbon formation.     

Characterization of single crystalline a-TiO2 films on MgAl2O4(100) substrates by MOCVD

Anatase phase TiO₂ (a-TiO₂) films have been deposited on MgAl₂O₄(100) substrates at the substrate temperatures of 500–650 °C by the metal organic chemical vapor deposition (MOCVD) method using tetrakis-dimethylamino titanium (TDMAT) as the organometallic (OM) source. The structural analyses indicated that the TiO₂ film prepared at 600 °C had the best single crystalline quality with no twins. The out-of-plane and in-plane epitaxial relationships of the film were a-TiO₂(001)||MgAl₂O₄(100) and TiO₂[100]||MgAl₂O₄[100], respectively. A uniform and compact surface with stoichiometric composition was also obtained for the 600 °C-deposited sample. The average transmittance of all the TiO₂ films in the visible range exceeded 91% and the optical band gap of the films varied from 3.31 to 3.41 eV.     

Comparison of lithium nickel cobalt oxides synthesized from NiO,Co3O4, and LiOH·H2O or Li2CO3 by solid-state reaction method

LiNi_1?yCo_yO₂ (y = 0.1, 0.3 and 0.5) cathode materials were synthesized by the solid-state reaction method at different temperatures from LiOH·H₂O, NiO and Co₃O₄ and from Li₂CO₃, NiO and Co₃O₄ as the starting materials. The physical and electrochemical properties of the synthesized samples were then compared. Among LiNi_1?yCo_yO₂ (y = 0.1, 0.3 and 0.5) synthesized for 40 h from LiOH·H₂O, NiO and Co₃O₄, and from Li₂CO₃, NiO and Co₃O₄, LiNi_0.5Co_0.5O₂ synthesized from Li₂CO₃, NiO and Co₃O₄ at 800 °C has relatively large first discharge capacity and relatively good cycling performance. This sample is considered the best one with relatively good electrochemical properties.     

Investigation of NiO-based mixed oxides in a 300-W chemical-looping combustor

Chemical-looping combustion, CLC, is a novel combustion concept with inherent separation of CO₂. This study evaluates the performance of spray-dried nickel-based oxygen-carrier particles prepared from commercially available materials. The possibility to optimize the methane conversion while retaining the oxygen transport capacity by mixing different NiO-based oxygen carriers was evaluated, and the results showed that such optimization was indeed possible. Experiments were carried out in a batch reactor as well as in a continuous 300-W unit. Experiments in the batch reactor evaluated the performance of two different spray-dried particles, individually and mixed, at two different temperatures, 850 °C and 950 °C. The reference particle, referred to as N-VITO in this study, contained only NiO and NiAl₂O₄ while the other spray-dried particle was similar to the reference but contained a small amount of MgO as additive in the starting material. It was found that the reference particle had good oxygen-transport characteristics, but that methane conversion left room for improvement. The particle with MgO addition, on the other hand, showed excellent methane conversion, but poor oxygen transport capability, especially at the lower temperature. The 50/50_mass-mixture of the two particles resulted in a potent oxygen-carrier batch with the desired qualities. Three experimental series were conducted in the 300-W CLC-unit: (i) using only the reference particle, (ii) using a mixture of the reference particle and the particle with MgO-addition, and (iii) using the previous mixed oxide system together with a small quantity of a high-surface impregnated oxygen-carrier based on NiO and Al₂O₃. The methane conversion to CO₂ was found to depend not only on the solids flux in the reactor system, but also on the temperature in the fuel reactor. Results showed that the operation was more stable and that it was possible to obtain better fuel conversion when the mixtures of two or three different oxygen-carrier particles were used. With these mixtures, the methane fraction could be brought down to <0.1% while still maintaining a low CO fraction.     

Catalytic CO2 reforming of methane over Ir/Ce0.9Gd0.1O2−x

CO₂ reforming of methane over Ir loaded Ce_0.9Gd_0.1O_2−x (Ir/CGO) has been studied between 600 and 800 °C and for CH₄/CO₂ ratios between 2 and 0.66 in order to evaluate its potential use as an anode material for direct conversion of biogas at moderate temperatures in solid oxide fuel cells. The catalyst exhibited a superior catalytic activity compared to the support alone and other Ir based catalysts. High CH₄/CO₂ ratios and temperatures were required to obtain the maximum H₂/CO ratio, which could never exceed unity. Long-term experiments were carried out, showing the excellent stability of the catalyst with time on stream. Carbon formation was totally inhibited (in most experimental conditions) or very limited in the most severe conditions of the study (800 °C, CH₄/CO₂ = 2). This carbon was found to be highly reactive towards O₂ upon TPO experiments.     

Removal of hydrogen sulfide from a steam-hydrogasifier product gas by zinc oxide sorbent: Effect of non-steam gas components

Removal of H₂S from a steam-hydrogasifier product gas was studied at 636 K and 1 atm using a commercially available zinc oxide sorbent in a packed-bed reactor. A mixture gas containing 22% CH₄, 18.7% H₂, 8.8% CO and 5.5% CO₂ (non-steam components subtotaling to 55%) balanced with steam was used to simulate the steam-hydrogasifier product gas. Sorbent particles of 150–250 μm size were used to eliminate the effect of intraparticle mass transfer limitation. Experiments were conducted to monitor H₂S breakthrough of reactor effluent stream for operation parameters such as space velocity and inlet H₂S concentration. With space velocity varied from 6000 to 8000 to 12,000 h^?1 for inlet H₂S concentration in the range of 100–800 ppmv, sulfur capture capacity of the sorbent (S_cap) for 2 ppmv H₂S breakthrough did not change notably, indicating that, for each inlet H₂S concentration tested, sorbent utilization for sulfur removal was not affected by the space velocity. Meanwhile, for each space velocity tested, S_cap increased monotonically as the inlet H₂S concentration increased from 100 to 500 to 800 ppmv, which is opposite to the result observed for the mixture gas devoid of CH₄, H₂, CO and CO₂. As the overall content of these non-steam components of the simulation gas was halved for each inlet H₂S concentration tested at 8000 h^?1 space velocity, S_cap for non-steam gas components of 27.5% content corresponded approximately to the median value of those for the non-steam gas components of 55% and 0% content, suggestive of linear dependency of S_cap upon the content of the non-steam components for the inlet H₂S concentration tested.     

Effect of support on reactivity and selectivity of Ni-based oxygen carriers for chemical-looping combustion

Different Ni-based oxygen carriers were prepared by dry impregnation using γ-Al₂O₃ as support. The reactivity, selectivity during methane combustion, attrition rate and agglomeration behavior of the oxygen carriers were measured and analyzed in a thermogravimetric analyzer and in a batch fluidized bed during multi-cycle reduction-oxidation tests.Ni-based oxygen carriers prepared on γ-Al₂O₃ showed low reactivity and low methane combustion selectivity to CO₂ and H₂O, because most of the impregnated NiO reacted to NiAl₂O₄. To avoid or to minimize the interaction of NiO with alumina some modifications of the support via thermal treatment or chemical deactivation with Mg or Ca oxides were analyzed. Thermal treatment of γ-Al₂O₃ at 1150 °C produced the phase transformation to α-Al₂O₃. Ni-based oxygen carriers prepared on α-Al₂O₃, MgAl₂O₄, or CaAl₂O₄ as support showed very high reactivity and high methane combustion selectivity to CO₂ and H₂O because the interaction between the NiO and the support was decreased. In addition, these oxygen carriers had very low attrition rates and did not show any agglomeration problems during operation in fluidized beds, and so, they seem to be suitable for the chemical-looping combustion process.     

Role of support in CO2 reforming of CH4 over a Ni/γ-Al2O3 catalyst

A catalyst of 10% Ni/γ-Al₂O₃ for CO₂/CH₄ reforming was prepared and characterized by TPR, TPD, XPS, XRD and activity measurements. XPS and TPR showed that Ni mainly exists in the form of NiAl₂O₄ in the calcined catalyst and is hard to reduce below 650°C, indicating a strong interaction between metal and support. Reduction of the calcined catalyst results in fine particles of Ni⁰, with an average diameter of about 20 nm as determined by XRD. The uptake of H on the reduced catalyst measured by H₂-TPD is 4.2–4.6 mole per mole of Ni species and does not depend on the reduction degree of Ni species. This provides a convincing piece of evidence for the occurrence of hydrogen spillover in the reduced catalyst. Only reduced catalysts present good activity, but the degree of nickel reduction has almost no effect on the reforming activity. This seems to suggest that Ni⁰ is vital for the reforming activity, but γ-Al₂O₃ is also involved in CO₂/CH₄ reforming and contributes even more. Based on the mechanism proposed by Bradford et al. and on our observations, a mechanistic model has been proposed to elucidate the role of γ-Al₂O₃ in CO₂/CH₄ reforming.     

Modification of alumina support with TiO2-P25 in CO2 reforming of CH4

Catalyst activity and stability for CO₂ reforming of CH₄ depends specifically upon the support and the active metal. A side reaction of dry reforming of methane is the decomposition to carbon that covers the Ni particles causing catalyst deactivation. Hence, an appropriate combination of Ni with support is needed to allow for long term stable operation. In this paper, CO₂ reforming of CH₄ is studied by investigating the effect of addition of TiO₂-P25 separately to γ-Al₂O₃ and α-Al₂O₃ supports used for nickel based catalyst. The reforming reactions are performed using (CO₂:CH₄) feed ratio of 1:1 and reaction temperature range of 500–800 °C. Both fresh and used catalysts are characterized by SEM and TGA techniques. It is found when α-Al₂O₃ support is modified with 20 wt% TiO₂-P25, the catalyst activity and stability is enhanced. The conversion rates of CH₄ and CO₂ without and with 20 wt% TiO₂-P25, respectively, are changed from 72.3% to 76.7% and 73.3% to 81.2%, respectively, and, most importantly, carbon formation is reduced from 28.1 to 12.8, respectively. However, when γ-Al₂O₃ support is modified with TiO₂-P25, the catalyst activity is enhanced with simultaneous increase in carbon formation.     

The use of petroleum coke as fuel in chemical-looping combustion

Chemical-looping combustion is a novel technique used for CO₂ separation that previously has been demonstrated for gaseous fuel. This work demonstrates the feasibility of using solid fuel (petroleum coke) in chemical-looping combustion (CLC). Here, the reaction between the oxygen carrier and solid fuel occurs via the gasification intermediates, primarily CO and H₂. A laboratory fluidized-bed reactor system for solid fuel, simulating a CLC-system by exposing oxygen-carrying particles to alternating reducing and oxidizing conditions, has been developed. In each reducing period, 0.2 g of petroleum coke was added to 20 g of oxygen carrier composed of 60% active material of Fe₂O₃ and 40% inert MgAl₂O₄. The effect of steam and SO₂ concentration in the fluidizing gas was investigated as well as effect of temperature. The rate of reaction was found to be highly dependent on the steam and SO₂ concentration as well as the temperature. Also shown was that the presence of a metal oxide enhances the gasification of petroleum coke. A preliminary estimation of the oxygen carrier inventory needed in a real CLC system showed that it would be below 2000 kg/MW_th.