Excess Steam Research Articles

Steam gasification for waste valorization with energy recovery

Steam gasification seems a promising technology of waste transformation since the steam is the only oxidizing reagent in the process and gaseous carrier of volatiles. Gasses are equilibrated at high temperature for conversion to the H2-rich syngas. After this step, the excess of steam condenses during cooling, together with non-converted tars, oils and fine particles. Condensing steam efficiently absorbs hydrogen bromide and hydrogen chloride. The use of steam eliminates carbonaceous residue from the solid mineral/metal product, which is convenient for further processing (for example extraction of metals). The syngas and the solid residue are generally the only products of gasification, because aqueous condensate may be returned to the process together with non-volatile hydrocarbons and sediments. The process was illustrated by laboratory scale gasification experiments with a) carton packaging, b) abrasive disc, c) pork bones, d) Cu multiwire cable e) PC/AT card and f) inverter (PCB board). The mineral/metal products of gasification may be considered as a raw materials for further processing, including typical routes of metals recovery. There is no direct emission to the atmosphere from the process. However, providing the energy from the syngas back to the reactor as well as the energy balance of steam condensation and recirculation of condensate to the reactor need careful analysis.

A hybrid energy storage concept for future application in industrial processes

The efficiency of many industrial processes, applying steam as heat transfer medium, can be increased by integrating Ruths steam accumulator. This component makes it possible to store surplus steam for consumption at later time, whereby high loading and unloading rates can be realized with this storage type. For improving this storage type in terms of storage capacity and application range a hybrid storage approach is presented. The concept combines a Ruths steam storage with phase change material and electrical heating elements. For a first analysis of the interaction between the Ruths steam accumulator and the phase change material, which surrounds the steam storage vessel, a dynamic model was created. Also, an example which consist of a charging, storing, and discharging phase is presented. The simulation results show a positive impact in terms of storage capacity. Therefore, the hybrid storage concept is a promising approach for integration in industrial processes.

Utilization of excess steam through dry steam cycle at Kamojang geothermal power plant

We present the investigation of the electricity generation by utilizing the working fluid from the excess steam at Kamojang geothermal power plant which currently discharged to the atmosphere despite its thermal energy potential due to the vapor-domination of the steam. To produce accurate results, a model validated with real data of Kamojang plant will be employed in this study. Constraint of the model calculation is set based on the regime of allowable condenser pressure and cooling water temperature. Optimization of the system is carried out by investigating the most excellent gas removal system (GRS) of the non-condensable gasses (NCGs) based on real data operation. The GRS configurations will be developed from one-stage and two-stage of both liquid ring vacuum pump (LRVP) and steam ejector, and the hybrid system. We found that a one-stage LRVP is the best GRS among others, while it can produce an electric power of 15.94 MW from the 28.45 kg/s of working fluid. Considering the zero cost of the discharged excess steam, the installation of the plant will support the plant capacity and the surrounding area.

Balancing the energy demand by a resource circulation project in Daejeon, Korea

Demand for sustainable renewable energy is on an increase worldwide, whereas the supply is limited. This paper analyses the feasibility of generating electricity and supplying the surplus steam to Daeduk Industrial Complex, by incinerating the combustible municipal waste generated in Daejeon Metropolitan City. The economic feasibility of surplus biogas generated from the anaerobic digestion of food waste and food waste leachate has been analysed. This study estimated resource circulation facility to supply 23,200 m3/day of biogas generated to Daejeon Combined Heat and Power plant. By 2023, it is expected to supply 25.7 tons of steam per hour all year round. The additional steam demand in Daeduk Industrial Complex is estimated as 101,537 tons/year. Surplus biogas will be supplied through an additional 960-m new installation. The cost of biogas is estimated at 30% of the unit biogas production cost. Daejeon Combined Heat and Power plant expects to make 60% additional profit, and Daeduk Industrial Complex and the communities nearby expect to achieve 10% cost savings. It also reduces the dependence of energy on fossil fuels, contributes to national environmental energy policy in reduction in greenhouse gases, creates competitiveness in local business and reduces corporate tax and generates revenue.

Thermodynamic and economic optimization of multi-effect desalination unit integrated with utility steam network

The integration of a multi-effect desalination (MED) unit with utility steam network system has been evaluated in this study. The generated steam from utility system has been used as a motive steam of MED unit. The opportunity to use excess steam of each steam levels of steam network of utility system has been investigated. The prices of steam for each one of the steam levels are calculated. The MED unit is designed for integration with each steam level. Thermodynamic and economic analyses demonstrate that utilizing steam from MP steam level has the highest rate of desalinated water production and using steam from LP steam level has the best exergy efficiency and period of return. Therefore steam has been extracted from LP steam level. Parametric study and sensitivity have been performed to characterize the effect of each one of the variables on the MED unit. Then, thermodynamic optimization for maximizing produced desalinated water and economic optimization for minimizing the period of return are performed. Thermodynamic optimization results in freshwater production rate increase from 10.431 to 20.149kg/s. In the end, two-objective optimization results have been presented.

Increasing the Effectiveness and the Ecologic Efficiency of the Heat Recovery System of a Condensation Type by Injecting Moisture into the Boiler Furnace

To increase the effectiveness and ecological indices of the system used for the deep recovery of the heat of exhaust gases of the boiler unit with a low steam capacity we proposed to inject moisture into the boiler furnace. This technology is relatively inexpensive, because the pipelines of a large diameter are not required. This technology can be highly efficient for the systems of a condensation type, because the heat loss with exhaust gasses is not increased in them. Due to an increase in the amount of heat released during the condensation of excess water steam added by gasses escaping from the boiler the efficiency factor of the system or the flow rate of heated up water and condensate can also be increased. This fact is proved by the computational investigation carried out to estimate the effect of this technology on engineering and economical performances and also on heat-engineering and structural characteristics of the heat recovery system and its elements using the computer program. The injection of 10 % of the moisture into the fuel burning zone results in the increase of the efficiency factor of the system by 1.1 % and the flow rate of the water heated for the hot water supply system is increased by 0.0679 kg/s (244 kg/h) and the condensate flow rate is increased by 0,00405 kg/s (14,6 kg/h). The temperature of heated water is increased by 1.9 °С. The estimation of the influence of the injected moisture on the level of a decrease in the emission of nitrogen oxides into the environment done using the well –known methods showed that the proposed technology is also rather efficient from the standpoint of improved ecological indices, in particular the nitrogen oxide concentration in fuel burning products has decreased by 25% with the injection of 10% of the moisture into the combustion zone.

Enhanced catalytic performance of Ni/α-Al2O3 catalyst modified with CaZrO3 nanoparticles in steam-methane reforming

Ni/α-Al2O3 catalysts containing CaZrO3 nanoparticles as a promoter were prepared by sequential impregnation for H2 production from steam-methane reforming. The effects of different loadings of CaZrO3 nanoparticles from 0 to 15 wt% on the catalytic performance of Ni/α-Al2O3 catalysts in steam-methane reforming were studied. The Ni/α-Al2O3 catalysts containing 15 wt% CaZrO3 nanoparticles provided the highest H2 yield due to facilitative steps of enormous steam adsorption-dissociation at the sites of oxygen vacancies on the surface of CaZrO3 nanoparticles. The existence of facilitative steps created additional H+ and OH− enhancing both H2 yield and the gasification of deposited carbon, respectively. The tests of steam-methane reforming at low S/C ratio of 1/3 for 97 h revealed that the catalytic performance of CaZrO3-modified Ni/α-Al2O3 catalysts was higher than that of the unmodified Ni/α-Al2O3 catalyst. Interestingly, at high S/C ratio of 3 excessive steam adsorption at the oxygen vacancies on CaZrO3 nanoparticles resulted in highly competitive adsorption between steam and methane decreasing CH4 dissociation. The results suggested that in the steam-methane reforming, optimum S/C ratios for the CaZrO3-modified Ni/α-Al2O3 catalysts were relatively lower than those for the unmodified Ni/α-Al2O3 catalyst due to excellent steam adsorption-dissociation capability for CaZrO3 nanoparticles.

Dry steam cycle application for excess steam utilization: Kamojang geothermal power plant case study

Abstract This study investigated the utilization of available excess steam by the Kamojang geothermal power plant, which, owing to the vapor-domination of the steam, utilizes a dry steam cycle. A model of the system was validated against actual Kamojang Unit-2 data and found to produce accurate results within a low discrepancy level (

Targeting for Energy Efficiency and Improved Energy Collaboration Between Different Companies Using Total Site Analysis (TSA)

A chemical cluster located in Stenungsund on the West Coast of Sweden is analyzed to determine the total site level energy efficiency opportunities using the Total Site Analysis (TSA) method. The cluster consists of 5 chemical companies, i.e., AGA Gas AB producing industrial gases, Akzo Nobel Sverige AB producing amines and surfactants, Borealis AB producing ethylene, and PE, INEOS Sverige AB producing PVC and Perstorp Oxo AB producing speciality chemicals. The heart of the cluster is a steam cracker plant run by Borealis, which delivers partly feedstock and fuel to the other plants. The overall heating and cooling demands of the site are ∼ 442 and 953 Mw, respectively. TSA is used to stepwise design a site-wide utility system which improves energy efficiency. Utility savings of ≤ 122 Mw can be achieved, plus a steam excess of 7 Mw. Qualitative evaluation of the suggested measures shows that 60 Mw of the savings potential can be expected to be achieved with moderate changes to the process utility system. This is an abstract of a paper presented at the 19th International Congress of Chemical and Process Engineering and 7th European Congress of Chemical Engineering (Prague, Czech Republic 8/28/2010-9/1/2010).

Energy Analysis for Conversion of a Kraft Pulp Mill into a Dissolving Pulp Mill

Currently, kraft pulp mills in Europe and North America are facing several challenges and have been forced to think along new products and new business areas. One opportunity is the conversion of chemical pulp mills into dissolving pulp mills by extracting hemicellulose prior to digesting via pre-hydrolysis. From the extracted wood chips, the more valuable dissolving pulp can be produced whereas the hydrolysate can be upgraded to high-value products. In this paper, pinch analysis is used to evaluate the consequences in the energy balance and utility system of a kraft mill converted into dissolving pulp production as well as to identify the potential for heat integration within the host mill itself, between the host mill and the pre-hydrolysis unit and with a hemicellulose upgrading process. The results show that proper heat integration within the host mill itself, and between the host mill and the pre-hydrolysis unit gives significant amounts of surplus steam which could be exported to a hemicelluloses upgrading process, used for power generation or to facilitate lignin extraction.

Bagasse-based co-generation at Hippo Valley Estates sugar factory in Zimbabwe

The paper reports on the assessment of the use of bagasse for cogeneration purposes at Hippo Valley Estates (HVE), a sugar manufacturing company in Zimbabwe. Much emphasis was on an assessment of the quantity of energy that was lost due to inefficient combustion of bagasse and the use of steam that was generated. The study investigated the quantity of sugar cane processed and the possible corresponding steam produced; the sugarcane processed was found to be approximately 2.33 million tons per annum and the steam produced was 193.1 tons per hour. The steam was used in the process department as well as to drive mills. The excess steam generated was found to be 81.03 tons per hour. Economic analysis on the use of excess steam to produce extra power for sale to the utility company was also undertaken. It was established that the power plant for the company could generate an annual surplus of US2.8Million as revenue, and the payback period was found to be 3.3 years. The sensitivity analysis of the project indicated that the electricity prices as well as the energy produced were the most sensitive areas in the project. The other inputs such as operations and maintenance costs, interest, capital investment and number of years were not as sensitive as the price and the energy.

Characteristics of microalgae gasification through chemical looping in the presence of steam

As a novel gasification technology, chemical looping gasification (CLG) was considered as a promising technology in solid fuel gasification. In this work, CLG was applied into microalgae, and the characteristics of syngas production and oxygen carrier in the presence of steam were obtained through experiments in a fixed bed reactor. The results showed that the partial oxidation of oxygen carrier improved the gasification efficiency from 61.65% to 81.64%, with the combustible gas yield of 1.05 Nm3/kg, and this promotion effect mainly occurred at char gasification stage. Also, an optimal Fe2O3/C molar ratio of 0.25 was determined for the maximum gasification efficiency. 800 °C was needed for the gasification efficiency over 70%, but excess temperature caused the formation of dense layer on oxygen carrier particle surface. Steam as gasification agent promoted syngas production, but excess steam decreased the gasification efficiency. Steam also enhanced the hydrogen production by the conversion of Fe/FeO into Fe3O4, avoiding the intensive reduction of oxygen carrier. The Fe2O3 oxygen carrier maintained a good reactivity in 10th cycle while used for microalgae CLG. The results indicated that CLG provided a potential route for producing combustible gas from microalgae.

Modeling of a Novel Catalytic Supercritical Water Gasification Power Plant Combined with Reversible Solid Oxide Cell

Using catalytic supercritical water gasification (CSCWG) in generating energy from wet biomass (e.g sewage sludge, moisture content > 80%wt) is efficient and environmental friendly. However, one of the main challenges in using CSCWG is the low syngas heating value. Syngas for power and synthetic fuel production requires high-purity and high heating value. In this work, a novel system is proposed which increases the CSCWG syngas heating value and produce electricity using reversible solid oxide cell (ReSOC). Further, CSCWG-SOFC power plant is a thermally efficient system, SOFC releases heat, and CSCWG needs heat and both processes work at similar temperature. Eventually the plant can be used for syngas production, working in electrolyser mode powered by excess renewable electrical energy. This is expected to increase the financial returns on the investment.The CSCWG-ReSOC presented in this work operates in two modes: CSCWG-solid oxide fuel cell (SOFC) for power production or CSCWG-solid oxide electrolyser cell (SOFC) for hydrogen and methane production. CSCWG-SOEC mode: electricity output from wind or solar energy, powers the electrolyser, the heat required for high temperature electrolysis come from by feeding the electrolyser with steam rich CSCWG gas. As methanation is an exothermic reaction, heat could potentially be added by promoting spontaneous methanation in the electrolyser. Combustion of small amounts of syngas can also provide a part of heat required for electrolysis and gasification processes. CSCWG-SOFC mode: heat required for endothermic reactions of supercritical water gasification is supplied by exothermal oxidation of fuel in the SOFC.CSCWG (operating conditions 500 °C, 250 bar) convers almost 100% organic matter into gas phase. Ash contained in the biomass is recovered in a salt separation system and ZnO layer removes remaining sulfur compounds before reach the gasifier Boukis et. al 2017. The gas at equilibrium contains CH4, H2, CO2 and around 80% H2O at high pressure and temperature. Before the gas is fed to the SOFC, the excess steam is removed and pressure and temperature are changed to SOFC operating conditions. Besides, the SOFC can also be feed with fuel produced in the CSCWG-SOEC mode.In contrast, methanation is sustained at high pressure. Subsequently steam rich gas at high pressure and temperature represents preheated electrolyser input. The pressure of the gas is adjusted at around 680°C and 20 bar. Then the high pressure SOEC at endothermal conditions generates additional hydrogen and methane which can be converted into synthetic fuel, or stored in tanks and converted into electricity by solid oxide fuel cells. After designing and modelling the process in Aspen PlusTM, it is seen with the preliminary results that the CSCWG syngas LHV increases significantly. The energy efficiency of the CSCWG--SOEC is in the order of 60-70%. The effects of CSCWG and ReSOC pressure and temperature on the amount of hydrogen and methane production are analysed. Details of the hydrogen and methane yields, SOFC power production, stack efficiencies etc will be described in the complete paper.The thermodynamic analysis of CSCWG for syngas production combined with ReSOC operation shows to be attractive for fuel and power production at reduced cost. Such a system might become even more attractive when is combined with an auxiliary methanation unit or if the system is applied to sanitation purposes, i.e., where the wet biomass is human waste.

Performance comparison of methanol steam reforming integrated to Pd-Ag membrane: Membrane reformer vs. membrane separator

Abstract Integration of methanol steam reforming with hydrogen selective dense Pd-Ag membranes makes membrane reformers compact and efficient for ‘on-board’ hydrogen generation. However, hydrogen permeation through standalone dense Pd-Ag membranes is largely reported to be limited by gas mixtures such as CO, CO 2 and steam. These gas mixtures are also basic constituents of methanol reformate with approximately 60% hydrogen by mole. Therefore, it is mostly assumed that such gas inhibition behavior would significantly affect membrane reformer performance. Apparently, this assumption is not valid until a comparison is made under similar experimental conditions for the same membrane. Using 100 µm thick self-supported dense Pd-Ag membrane, the current work compares the performance of membrane reformer with membrane separator under similar operating conditions. By definition, membrane separator is principally a purifier which is used to separate hydrogen from various components such as CO 2 , H 2 O, CH 4 and CO. On the other hand, membrane reformer is a system which generates hydrogen from a reaction such as steam reforming and simultaneously separates it using membranes, integrated in the same physical device. In this study, membrane reformer performance was optimized with effect of steam/methanol ratio, temperature and pressure. Under optimal conditions, synthetic gases of similar composition as of produced reformate were used to evaluate membrane separator performance. No significant inhibition was observed due to CO, CO 2 and steam at optimal temperature 673 K and pressure 3 bar. Presence of excess steam however dilutes the hydrogen partial pressure in reformate which reduced hydrogen flux. Comparison of membrane reformer vs. membrane separator further showed equivalent flux as well as high hydrogen purity indicating a good feasibility of these systems to be tested further for pilot scale studies.

Experimental investigation of high temperature air and steam biomass gasification in a fixed-bed downdraft gasifier

ABSTRACTIn order to enhance the quality of producer gas obtained from the biomass gasification process without the use of oxygen, high temperature air-steam gasification may be an advantageous technology. A highly preheated agent (air and steam) can provide additional energy into the process that improves thermal decomposition of the gasified biomass feedstock, and promotes endothermic reactions. In this investigation, the high temperature air-stream gasification process was performed on a fixed-bed downdraft biomass gasifier. The results showed that increasing the gasifying agent preheat temperature led to increased concentrations of H2 and CO and decreased contaminated tar in the producer gas. Increasing the equivalence ratio resulted in decreased H2 and CO concentrations and also reduced tar content. The introduction of steam increased gas quality, but excessive steam degraded gas quality. The increased higher heating value of the gasified gas varied between 4.15 and 6.21 MJ/Nm3.

6-3.余剰蒸気からのエネルギ回収量を増加させるための蒸気過熱器の開発((1)省エネルギー型機器,Session 6 省エネルギー)

6-3.余剰蒸気からのエネルギ回収量を増加させるための蒸気過熱器の開発((1)省エネルギー型機器,Session 6 省エネルギー)

Performance and costs of CCS in the pulp and paper industry part 1: Performance of amine-based post-combustion CO2 capture

The performance of an amine-based post-combustion CO2 capture and storage (CCS) process in an existing Kraft pulp mill and an existing pulp and board mill was assessed. The pulp and paper industry is an energy-intensive industry, with significant amounts of CO2 emitted onsite. The majority of this CO2 originates from the combustion of biomass, which renders it carbon neutral if the biomass used by the industry is grown and harvested in a sustainable manner. If the CO2 emissions from the pulp and paper industry were to be captured and permanently stored, then this could make the industry a potential carbon sink. In this evaluation, different configurations of capturing CO2 from the flue gases of the recovery boiler, the multi-fuel boiler and the lime kiln were assessed. For a stand-alone Kraft pulp mill, the excess steam available is sufficient to cover the demand from the CO2 capture plant. For an integrated pulp and board mill, there is less excess steam available for the CO2 capture plant and an auxiliary boiler may be required. The retrofit of a post-combustion CO2 capture plant into an existing pulp mill increases the steam demand by 1–8GJ/air dried tonne (adt) pulp, depending on the volume of the flue gas treated. This translates to a reduction in the amount of electricity exported to the grid by 0.1–1.0MWh/adt pulp for a stand-alone Kraft pulp mill, and by 0.1–0.5MWh/adt pulp for an integrated pulp and board mill. The total potential for negative CO2 emissions amounts to just under 2.0 Mt CO2/a both for the market pulp mill and for the integrated pulp and board mill.

Chemical equilibrium analysis of hydrogen production from shale gas using sorption enhanced chemical looping steam reforming

Detailed chemical equilibrium analysis based on minimisation of Gibbs Energy is conducted to illustrate the benefits of integrating sorption enhancement (SE) and chemical looping (CL) together with the conventional catalytic steam reforming (C-SR) process for hydrogen production from a typical shale gas feedstock. CaO(S) was chosen as the CO2 sorbent and Ni/NiO is the oxygen transfer material (OTM) doubling as steam reforming catalyst. Up to 49% and 52% rise in H2 yield and purity respectively were achieved with SE-CLSR with a lower enthalpy change compared to C-SR at S:C 3 and 800K. A minimum energy of 159kJ was required to produce 1mol of H2 at S:C 3 and 800K in C-SR process, this significantly dropped to 34kJ/mol of produced H2 in the CaO(S)/NiO system at same operating condition without regeneration of the sorbent, when the energy of regenerating the sorbent at 1170K was included, the enthalpy rose to 92kJ/mol H2, i.e., significantly lower than the Ca-free system. The presence of inert bed materials in the reactor bed such as catalyst support or degraded CO2 sorbent introduced a very substantial heating burden to bring these materials from reforming temperature to sorbent regeneration temperature or to Ni oxidation temperature. The choice of S:C ratio in conditions of excess steam represents a compromise between the higher H2 yield and purity and lower risk of coking, balanced by the increased enthalpy cost of raising excess steam.

Preparation and application of nickel based carbon fibers for the steam reforming of methane

The steam and KOH activation methods were used to activate lignin based carbon fibers. The original and activated carbon fibers were applied to prepare three kinds of nickel based catalysts. The characterization results illustrated that the KOH activated carbon fibers (KACF) possessed the best surface structural parameters. The tests for catalytic performance showed that the catalyst supported on the KACF was the greatest in the steam reforming of methane. Based on that, the catalysts with different metal content were prepared to obtain an optimal content, which possessed the greatest catalytic activity. The catalyst of 5% metal content supported on the KACF was proved to have the highest methane conversion rate and syngas selectivity. And the optimal catalyst was applied for the steam reforming of methane. The CH4 conversion ratio could reach more than 90%. The influence of catalyst dosage, reaction temperature and the molar ratio of H2O/CH4 was investigated. The results indicated that the ratio of hydrogen to carbon monoxide could be adjusted by the temperature and the ratio of H2O/CH4. Higher temperatures could increase the ratio of H2/CO, while the excess steam decreased it. Besides, the carbon deposition experiment of methane decomposition with the catalysts of 5% Ni/SKACF and 5% Ni/γ-Al2O3 proved that the catalyst prepared by carbon fiber support has great properties for carbon deposition resistance.

Techno-economic analysis of ECF bleaching and TCF bleaching for a bleached eucalyptus kraft pulp mill

An early stage techno-economic analysis was performed to compare a traditional elemental chlorine free (ECF) sequence (O O D0 [EOP] D1 P) with the proposed totally chlorine free (TCF) sequence (O O A [ZEO]1 [ZEO]2 P)] for a bleached eucalyptus kraft pulp mill. Similar operating costs (ECF = US$465/a.d. metric ton; TCF = US$468/a.d. metric ton) and similar internal rate of return (ECF = 16.5%; TCF = 16.4%) were obtained. Although the TCF case has lower revenue with surplus steam, savings with chemicals (e.g., sodium chlorate and methanol) pays for the higher consumption of electricity. Probabilistic analyses were also performed to evaluate the financial risks associated with the variability of chemical costs and electricity price. Probabilistic analyses have shown that the price volatility of sodium hydroxide and sodium chlorate have a significant impact on the probability distribution of internal rate of return (IRR). Despite its promising potential, the new TCF sequence has only been tested in laboratory scale and further scaleup has to be performed to validate the technology. However, the techno-economic economic analysis shows that the proposed TCF technology has promising potential for future industrial application.