Heat pumps in distillation (original) (raw)
Related papers
2010
Vapor recompression has become the standard heat pump technology in distillation and substantial energy savings in the order of 50% have been achieved. Economic applications of VRC are limited to column temperature differences of about 30 0 C, which is only one fifth of the across the pinch columns in operation. 2 nd generation heat pump systems based on further heat integration and novel heat pump equipment do not only increase the potential energy savings but also extend the application range to columns with a larger temperature difference.
COMPARISON OF VARIOUS HEAT PUMP ASSISTED DISTILLATION CONFIGURATIONS
V arious heat pump assisted process con® gurations are analysed for two industrial case studies using a design strategy based on preliminary screening, rigorous steady state simulation and economic evaluation. The in¯uence of heat pump type, heat load, column temperature difference, utility cost, exchanger minimum approach temperature (EMAT) on the energetic aspects and economic range of application are examined.
Economic application of heat pumps in integrated distillation systems
Heat Recovery Systems and CHP, 1994
ABSTRACT The influence of relevant parameters on the economics of distillation plants involving distinct heat pump cycles is scrutinised and the results are compared to conventional and integrated schemes. On the basis of the COP, energy costs and efficiencies, simple expressions are proposed for preliminary economic analysis and design of heat pump assisted distillation. The influence of heat pump type, purity requirement, column pressure drop, feed rate, energy cost, relative volatility etc. on the energetic aspects and economic range of application is presented. Heat pumps can be economical substitutes for conventional distillation process design whenever direct refrigeration or chilled water are required for condensation and for separating close boiling mixtures in columns of small pressure drop. A design strategy for selecting the most economical distillation system, considering different types of heat pump structures (vapour recompression, bottom flash, closed cycle, absorption cycle), is proposed, based on pinch technology, primary energy rate, energy cost factor and estimated payback time of excess capital. The strategy is demonstrated by industrial case studies.
Operation and experimental results on a vapor recompression pilot plant distillation column
Industrial & Engineering Chemistry Research, 1992
The open-loop steady-state and dynamic operation of a vapor recompression pilot-plant distillation column is studied under direct digital control of the loads to the process. Data acquisition, process control, and operator interface are programmed in a distributed control system. An ethanol-water mixture is separated. The manipulated inputs are cooling water flow rate and heat transferred a t the reboiler-condenser. Energy savings were of the order of 50% as compared to conventional distillation. The process presents quasi-linear stationary and dynamic behavior when subjected to small departures in heat input at the reboiler condenser. Time lags and delays are higher than in conventional distillation due to process interactions at the reboiler-condenser.
AIAA SPACE 2013 Conference and Exposition, 2013
Humans on a spacecraft require significant amounts of water for drinking, food, hydration, and hygiene. Maximizing the reuse of wastewater while minimizing the use of consumables is critical for long duration space exploration. One of the more promising consumable-free methods of reclaiming wastewater is the distillation/condensation process used in the Cascade Distillation Subsystem (CDS). The CDS heats wastewater to the point of vaporization then condenses and cools the resulting water vapor. The CDS wastewater flow requires heating for evaporation and the product water flow requires cooling for condensation. Performing the heating and cooling processes separately would require two separate units, each of which would demand large amounts of electrical power. Mass, volume, and power efficiencies can be obtained by heating the wastewater and cooling the condensate in a single heat pump unit.
Economic feasibility of heat pumps in distillation to reduce energy use
Applied Thermal Engineering, 2009
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Thermal integration of heat pumping systems in distillation columns
Applied Thermal Engineering, 1999
A methodology for the thermal integration of electrically driven heat pumping systems between intermediate stages in distillation columns using the concept of column grand composite curve is proposed. An optimization procedure based on a four way trade o between energy, capital, temperature lift and electricity to fuel cost ratio is discussed.
AIChE Journal, 2013
Costs of chemical processes are often dominated by separation costs. Between different separation techniques, distillation is the most important and commonly used in all chemical and petrochemical industries. Distillation handles more than 90% of separations and this trend seems unlikely to change in the near future. A renew interest in Thermally Coupled Distillation (TCD) appeared, in the last 15-20 years, due to the important potential savings in energy: typical values around 10 to 50% has been reported compared with conventional distillation sequences. Although, it has been proved that fully thermally coupled system are arrangement that requires the minimum energy in a sequence of columns, it is possible to identify situations in which some column sections are operating far away from the optimal conditions. Typically, there are a significant excess of vapor/liquid flow which is transferred from one to another section inside a distillation column increasing utilities and capital cost of TCD. This suboptimal situation can be solved introducing an intermediate reboiler/condenser to provide extra vapor/liquid needed in some section of TCD. Alternatively, it is possible to extract some liquid/vapor and consider it as an utility stream that can be used elsewhere in the plant. This paper presents an interesting alternative to solve these situations consisting on implement a vapor compression cycle using this extra vapor/liquid stream. This new arrangement gets an extra saving in energy around 20-30% compared with conventional TCD columns. Different examples, including heat and cold recovery cases, are presented. Furthermore in each example, all possibilities of distillation (direct, indirect and Petlyuk distillation) with and without vapor recompression cycle (VRC) are compared to ensure that this approach provides the best results
As demonstrated in the present simulation study, taking propylene/propane splitter as base case, an internally heat integrated distillation column (HIDiC), with rectification section operating at higher pressure and temperature than the stripping section, offers significant potential for energy saving compared to energy requirements associated with operation of conventional and heat-pump assisted distillation columns. The rectification section of a propylene/propane splitter contains usually two times more stages than the stripping section, implying a number of heat coupling possibilities, which appears to be strongly influencing the thermal efficiency of the HIDiC. The configuration with the stripping section stages thermally interconnected with the same number of stages in the upper part of the rectification section emerged as the most efficient configuration, allowing a reduction in energy use in the range 30 to 40 % compared with a state of the art heat-pump assisted column, depending on the trade off between the operating compression ratio and the heat transfer area requirement, the latter one being the key limiting factor.
Heat integrated distillation system design
2010
Distillation is the largest single energy consumer in the chemical process industries. However, distillation does not consume energy but degrades the heat input to the reboiler that is subsequently rejected in the condenser. The most effective way to reduce the energy consumption of distillation is by effective heat integration. However, the distillation design and operation must be considered simultaneously with its heat integration. For single distillation columns it is straightforward to identify appropriate heat integration opportunities. For complex distillation systems, the most appropriate combination of distillation system design and operation and heat integration are far from straightforward. The whole separation system together with its heat integration and utility system must be considered simultaneously. This presentation will explain new approaches to be design of heat integrated distillation systems. Examples will be developed from crude oil distillation and from low-temperature separation in chemicals production.