Chapter 10 Pinch point analysis

Optimal assignment of multiple utilities in heat exchange networks

An extended energy saving method for modification of MTP process heat exchanger network

This paper presents the retrofit of the two-flow heat-exchange system with utility paths in order to optimize the heat recuperation capacity under the technical limitation conditions. Analytical dependences of heat load of the existing heat exchangers and utilities on the surface area of the new heat exchanger are obtained. The work shows that the determination of technological parameters for existing heat exchangers during the retrofit of the heat exchange system is an important task because they affect the cost of retrofit. For case study, two streams problem for heat transfer in heat network at the crude and gas separation units is considered in this paper. The existing system has three heat exchangers. The temperature measurements were fulfilled for all heat exchangers and the heat loads for heat exchangers and utility were calculated. The installation of one heat exchanger at the cool side of the system is proposed in retrofit. The dependences of the temperature changes for the hot and cold process stream from the value of the additional surface were obtained for each heat exchanger. Utility capacity and capacity recovery of thermal energy in the system is also analyzed.

Urban heating in northern China accounts for 40% of total building energy usage. In central heating systems, heat is often transferred from heat source to users by the heat network where several heat exchangers are installed at heat source, substations and terminals respectively. For given overall heating capacity and heat source temperature, increasing the terminal fluid temperature is an effective way to improve the thermal performance of such cascade heat exchange network for energy saving. In this paper, the mathematical optimization model of the cascade heat exchange network with three-stage heat exchangers in series is established. Aim at maximizing the cold fluid temperature for given hot fluid temperature and overall heating capacity, the optimal heat exchange area distribution and the medium fluids’ flow rates are determined through inverse problem and variation method. The preliminary results show that the heat exchange areas should be distributed equally for each heat exchanger. It also indicates that in order to improve the thermal performance of the whole system, more heat exchange areas should be allocated to the heat exchanger where flow rate difference between two fluids is relatively small. This work is important for guiding the optimization design of practical cascade heating systems.

Globally optimal power cycle synthesis via the Infinite-DimEnsionAl State-space (IDEAS) approach featuring minimum area with fixed utility

5516448 Process for making a high density detergent composition which includes selected recycle streams for improved agglomerate: Capeci Scott W; Lange John; Smith David J; Roberts Nigel S, North Bend, OH, United States assigned to The Procter & Gamble Company

The current research uses Aspen Software to find the best way to run the petrochemical methanol complex. This was done by using pinch technology and arranging the heat exchanger network. First, a process flow diagram of the Kaveh industrial plant was used to simulate different plant parts. Then retrofit the plant’s heat exchanger network to minimize capital costs and improve energy efficiency. Plotting the composite curve of the streams, the type, and the quantity of hot and cold utilities came next., and the most economical minimum temperature difference, etc. The best capital cost decreased by around 70%, while the utilities increased by about 50%, and the payback money lasted for 6 months. The methanol cycle was redesigned using coil-wound heat exchangers to improve operational flexibility because of high-temperature streams.The capital costs decreased by around 10%, and utility costs were saved with the liquefied natural gas heat exchangers.

A low-pressure gas supply system for dual fuel engines was designed to transport liquid natural gas from a storage tank to a dual fuel engine and gasify it during transportation. The heat exchange area and pressure drop in the spiral- wound heat exchanger, the volume of the buffer tank and the pressure drop in the pipeline of the gas supply system were calculated by programming using Python. Experiments were carried out during the process of starting and running the dual fuel engine using this gas supply system. Experimental data show that the gas supply system can supply gas stably during the process and ensure the stable operation of the dual fuel engine. The effects of the parameters of natural gas and ethylene glycol solution on the heat exchange area of the spiral-wound heat exchanger and the volume of the buffer tank in the gas supply system were studied. The results show that the heat exchange area calculated according to pure methane can adapt to the case of non-pure methane. The temperature difference between natural gas and ethylene glycol solution should be increased in order to reduce the heat exchange area. The heat exchange area selected according to the high pressure of natural gas can adapt to the low pressure of natural gas. The volume of the buffer tank should be selected according to the situation of the minimum methane content to adapt to the situation of high methane content. The main influencing factor in selecting the volume of the buffer tank is the natural gas flow. The results can provide guidance for the design of the gas supply system for dual fuel engines.

In the situation of high prices and depletion of the world energy, one way for energy management is process heat integration. In Specific, pinch technology has demonstrated that good process integration pays off through simplicity of plant design and good use of energy and capital. The principle is to predict what should be achieved (targeting), and then to set out how to achieve it (design). For modification of existing plants, retrofitting is used with the same thermodynamic principles that area of an aromatics plant, retrofitting the heat exchanger network to obtain the best design which results in high degree of energy recovery. In this area of plant, nine heat exchangers can be found. The streams that involve in this pinch analysis can be grouped into two types; hot and cold streams, which are thirty and twenty on for hot and cold streams respectively. First of all, the target of energy savings will be conducted for the specified payback period. In this step the problem table analysis and composite curves have been done in order to find the area and energy target. The result of these targets shows the very low payback period. The retrofit procedure then can be done by constructing the grid diagram and finding the heat exchangers crossing pinch point. Eliminating these exchangers plus adding some area of heat exchangers result in energy saving about 10-20%.

A new indicator for minimizing size of an ORC power plant based on heat exchanger and turbine design parameters

The objective of this paper is to evaluate and analyze energy savings and process optimization opportunities in the gas-oil separation plants (GOSPs) in upstream surface facilities. This approach resulted in the development of a new design for a compact gas-oil separation plant (C-GOSP) to meet the crude oil export specifications with less process equipment and operating costs, and higher oil product yield compared to conventional GOSPs. The new design was materialized as patents granted by the U.S. Patent and Trademark Office (USPTO). The innovative C-GOSP is based on the integration of the gas compression system with production traps to conserve energy consumption and minimize capital cost and increase crude production. Atmospheric and hot discharge gas from low pressure compressors will be rerouted and directly mixed with the incoming wild crude before entering the production traps. This process will result in simultaneously cooling the compressors' discharge gas and heating the incoming crude while increasing crude production. Hysys simulation was used to model and verify the feasibility of the C-GOSP. A 300 MBD production facility was used to benchmark the Hysys simulation model and to verify the feasibility of these promising energy saving opportunities. The extensive process simulation modelling using Aspen Hysys and benchmarked with the actual plant energy consumption revealed the feasibility of this innovative C-GOSP, which will result in the following benefits: Lowering the capital cost by eliminating the compressors discharge after coolers, liquid pumps, discharge KO drums and minimize the surface area of the crude heat exchangers. Lowering operating cost by eliminating the after coolers and heating medium required to heat the crude. Increase crude production yield by condensing the heavy hydrocarbon from the gas stream. Minimize the spacing requirements, which make ideal for offshore applications. The innovative approach of direct heating and cooling by mixing of hot and cold streams is superior to any other optimization approach. Consequently, a patent was granted from the USPTO on July 17, 2018, for the innovative C-GOSP. The patent number is 10023811.

On the benefit of integrating vortex tubes in PEMFC system for preheating hydrogen in FCEV technologies

Application of a two-phase turbine system to waste heat recovery was examined. Bottoming cycle efficiencies ranging from 15 to 30% were calculated for a 720/sup 0/F diesel exhaust temperature. A single stage demonstration unit, designed for non-toxic fluids (water and DowTherm A) and for atmospheric seals and bearings, had a cycle efficiency of 23%. The net output power was 276 hp at 8,100 rpm, increasing the total shaft power from 1,800 hp for the diesel alone, to 2,076 hp for the combined system. A four stage organic turbine, for the same application, had a rotational speed of 14,700 rpm while a four stage steam turbine had 26,000 rpm. Fabrication drawings were prepared for the turbine and nozzle. The major improvement leading to higher cycle efficiency and lower turbine rpm was found to be the use of a liquid component with lower sensible heat. A reduction in capital cost was found to result from the use of a contact heat exchanger instead of tube-fin construction. The cost for a contact heat exchanger was only $35-52/kWe compared to $98/kWe for a tube-fin heat exchanger. Design drawings and materials list were prepared. A program resulting in the demonstration of a two-phase bottoming system was planned and the required cost estimated. The program would result in a feasibility test of the nozzle and turbine at the end of the first year, a laboratory performance test of the bottoming system by the end of the second year and a field demonstration test and laboratory endurance test of the bottoming system during the third year. The blowdown test rig for the first year's program and test turbine were designed.

Convection heat transfer in a shell-and-tube heat exchanger using sheet fins for effective utilization of energy

Sizing, selection, and comparison of heat exchangers considering the lowest saving-investment ratio corresponding to the area at the tag end of the heat exchanger