Analysis of two‐stage waste heat recovery based on natural gas‐fired boiler

Author(s):  
Xinying Cui ◽  
Haiyan Zhang ◽  
Jiangfeng Guo ◽  
Xiulan Huai ◽  
Min Xu
Author(s):  
Guillermo Valencia ◽  
Armando Fontalvo ◽  
Yulineth Cardenas ◽  
Jorge Duarte ◽  
Cesar Isaza

One way to increase overall natural gas engine efficiency is to transform exhaust waste heat into useful energy by means of a bottoming cycle. Organic Rankine cycle (ORC) is a promising technology to convert medium and low grade waste heat into mechanical power and electricity. This paper presents an energy and exergy analysis of three ORC-Waste heat recovery configurations by using an intermediate thermal oil circuit: Simple ORC (SORC), ORC with Recuperator (RORC) and ORC with Double Pressure (DORC), and Cyclohexane, Toluene and Acetone have been proposed as working fluids. An energy and exergy thermodynamic model is proposed to evaluate each configuration performance, while available exhaust thermal energy variation under different engine loads was determined through an experimentally validated mathematical model. Additionally, the effect of evaportating pressure on net power output , absolute thermal efficiency increase, absolute specific fuel consumption decrease, overall energy conversion efficiency, and component exergy destruction is also investigated. Results evidence an improvement in operational performance for heat recovery through RORC with Toluene at an evaporation pressure of 3.4 MPa, achieving 146.25 kW of net power output, 11.58% of overall conversion efficiency, 28.4% of ORC thermal efficiency, and an specific fuel consumption reduction of 7.67% at a 1482 rpm engine speed, a 120.2 L/min natural gas Flow, 1.784 lambda, and 1758.77 kW mechanical engine power.


Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2378 ◽  
Author(s):  
Guillermo Valencia ◽  
Armando Fontalvo ◽  
Yulineth Cárdenas ◽  
Jorge Duarte ◽  
Cesar Isaza

Waste heat recovery (WHR) from exhaust gases in natural gas engines improves the overall conversion efficiency. The organic Rankine cycle (ORC) has emerged as a promising technology to convert medium and low-grade waste heat into mechanical power and electricity. This paper presents the energy and exergy analyses of three ORC–WHR configurations that use a coupling thermal oil circuit. A simple ORC (SORC), an ORC with a recuperator (RORC), and an ORC with double-pressure (DORC) configuration are considered; cyclohexane, toluene, and acetone are simulated as ORC working fluids. Energy and exergy thermodynamic balances are employed to evaluate each configuration performance, while the available exhaust thermal energy variation under different engine loads is determined through an experimentally validated mathematical model. In addition, the effect of evaporating pressure on the net power output, thermal efficiency increase, specific fuel consumption, overall energy conversion efficiency, and exergy destruction is also investigated. The comparative analysis of natural gas engine performance indicators integrated with ORC configurations present evidence that RORC with toluene improves the operational performance by achieving a net power output of 146.25 kW, an overall conversion efficiency of 11.58%, an ORC thermal efficiency of 28.4%, and a specific fuel consumption reduction of 7.67% at a 1482 rpm engine speed, a 120.2 L/min natural gas flow, 1.784 lambda, and 1758.77 kW of mechanical engine power.


2019 ◽  
Vol 7 (11) ◽  
pp. 397 ◽  
Author(s):  
Marco Altosole ◽  
Ugo Campora ◽  
Silvia Donnarumma ◽  
Raphael Zaccone

Waste Heat Recovery (WHR) marine systems represent a valid solution for the ship energy efficiency improvement, especially in Liquefied Natural Gas (LNG) propulsion applications. Compared to traditional diesel fuel oil, a better thermal power can be recovered from the exhaust gas produced by a LNG-fueled engine. Therefore, steam surplus production may be used to feed a turbogenerator in order to increase the ship electric energy availability without additional fuel consumption. However, a correct design procedure of the WHR steam plant is fundamental for proper feasibility analysis, and from this point of view, numerical simulation techniques can be a very powerful tool. In this work, the WHR steam plant modeling is presented paying attention to the simulation approach developed for the steam turbine and its governor dynamics. Starting from a nonlinear system representing the whole dynamic behavior, the turbogenerator model is linearized to carry out a proper synthesis analysis of the controller, in order to comply with specific performance requirements of the power grid. For the considered case study, simulation results confirm the validity of the developed approach, aimed to test the correct design of the whole system in proper working dynamic conditions.


Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 985
Author(s):  
Marco Altosole ◽  
Giovanni Benvenuto ◽  
Raphael Zaccone ◽  
Ugo Campora

From the working data of a dual-fuel marine engine, in this paper, we optimized and compared two waste-heat-recovery single-pressure steam plants—the first characterized by a saturated-steam Rankine cycle, the other by a superheated-steam cycle–using suitably developed simulation models. The objective was to improve the recovered heat from the considered engine, running with both heavy fuel oil and natural gas. The comparison was carried out on the basis of energetic and exergetic considerations, concerning various aspects such as the thermodynamic performance of the heat-recovery steam generator and the efficiency of the Rankine cycle and of the combined dual-fuel-engine–waste-heat-recovery plant. Other important issues were also considered in the comparison, particularly the dimensions and weights of the steam generator as a whole and of its components (economizer, evaporator, superheater) in relation to the exchanged thermal powers. We present the comparison results for different engine working conditions and fuel typology (heavy fuel oil or natural gas).


Author(s):  
Jennifer Strehler ◽  
Scott Vandenburgh ◽  
Dave Parry ◽  
Tim Rynders

The Town of Avon Colorado and the Eagle River Water and Sanitation District have partnered to design, construct, and operate a mechanical “Community Heat Recovery System” which extracts low-grade waste heat from treated wastewater and delivers this heat for beneficial use. Immediate uses include heating of the community swimming pool, melting snow and ice on high pedestrian areas in an urban redevelopment zone in order to improve pedestrian safety, and space heating for project buildings and an adjacent water plant pump station building. Points of use are located within one mile of the treatment plant. The initial system is sized to extract heat from 170 m3/hr (1.08 mgd) of wastewater plant effluent with a 298 kW (400 hp) heat pump. The heat pump will deliver 1,026 kW (3,500,000 BTU/hr) energy to the heat recovery system. A supplemental natural gas boiler provided to meet peak demands will provide an additional 1,026 kW (3,500,000 BTU/hr) energy. The system is expandable allowing the installation of a second heat pump in the future and roof-mounted solar thermal panels. Power for the waste heat recovery system is provided by wind-generated electricity purchased from the local electric utility. The use of wind power with an electric-powered heat pump enables the agencies to fulfill energy needs while also reducing the carbon footprint. The system will achieve a reduction in the temperature of the treated wastewater, which is currently discharged to the Eagle River during low river flow, fish-sensitive periods. The agencies expect to save tax payers and rate payers money as a result of this project as compared to other alternatives or the status quo because it results in a more sustainable long-term operation. At 2008 utility commodities pricing, delivery of heat generated from this system was estimated to cost about one-third less than that from a conventional natural gas boiler system. This facility is the first of its kind in the U.S. and received a “New Energy Community” grant from the State of Colorado. This project shows how local agencies can work cooperatively for mutual benefit to provide infrastructure which accommodates growth and urban renewal and simultaneously demonstrate strong environmental leadership. The potential application of this technology is broad and global. The installed system is expected to cost about $5,000,000; construction will be completed in 2010.


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