Waste heat recovery in a chemical process and plant, particularly for the synthesis of ammonia
AssigneeCasale SA
InventorsErmanno Filippi, Raffaele Ostuni
Life of this patent
Estimating the term…
Abstract
A method for recovering waste heat in a process for the synthesis of a chemical product, particularly ammonia, where the product is used as the working fluid of a thermodynamic cycle; the waste heat is used to increase the enthalpy content of a high-pressure liquid stream of said product (11), delivered by a synthesis section (10), thus obtaining a vapor or supercritical product stream (20), and energy is recovered by expanding said vapor or supercritical stream across at least one suitable ex-pander (13); the method is particularly suited to recover the heat content of the syngas effluent after low-temperature shift.
Claims13
A process for the synthesis of a chemical product, comprising the steps of:
- obtaining at least one make-up reactant in a front-end section;
- reacting said least one make-up reactant in a synthesis section, obtaining said product in a high-pressure liquid state;
- heating at least a portion of the liquid product delivered by the synthesis section by heat exchange with a waste heat source made available by said process, obtaining an expandable stream of said product in a vapour state or supercritical state;
- expanding said expandable product stream to recover energy, obtaining an expanded product stream, and
- condensing said expanded product stream by heat exchange with a suitable cooling medium, obtaining a product condensate stream;
- and
- wherein a portion of the product condensate is pumped substantially at the same pressure of said synthesis section;
- said portion of the product condensate is then re-heated by heat exchange with said waste heat source or a further waste heat source;
- after said heating, said portion of product stream is then expanded to recover energy and condensed back to liquid, thus forming a closed loop.
A plant for the synthesis of a chemical product, the plant comprising a front-end section adapted to provide at least one make-up reactant, and a high-pressure synthesis section for reacting said least one make-up reactant and obtaining said chemical product in a liquid state, the plant being characterized by comprising an energy recovery section, said energy recovery section comprising at least:
- a heat exchanger disposed to exchange heat between at least a portion of the liquid product delivered by the synthesis section, and a waste-heat source stream, obtaining an expandable stream of said product in a vapour state or supercritical state;
- an expander receiving said expandable stream in vapour state or supercritical state, and delivering mechanical energy produced by expansion of said stream, and
- a condenser downstream said expander, and disposed to condense the effluent of said expander;
- wherein a portion of the product condensate is pumped substantially at the same pressure of said synthesis section;
- said portion of the product condensate is then re-heated by heat exchange with said waste heat source or a further waste heat source;
- after said heating, said portion of product stream is then expanded to recover energy and condensed back to liquid, thus forming a closed loop.
A method for revamping a plant for producing ammonia, the plant comprising a front-end reforming section adapted to provide a make-up ammonia syngas, and a high-pressure synthesis loop, the method comprising the steps of:
- arranging a heat exchange for heating at least a portion of the liquid ammonia product, by means of heat exchange with at least one source of waste heat, so obtaining a stream of heated, high-pressure ammonia stream in a vapour or supercritical state;
- providing the provision of at least an expander, for the expansion of said ammonia stream and the production of energy from said waste heat;
- and
- providing a condenser adapted to condense the ammonia effluent at the outlet of said expander;
- wherein a portion of the product condensate is pumped substantially at the same pressure of said synthesis section;
- said portion of the product condensate is then re-heated by heat exchange with said waste heat source or a further waste heat source;
- after said heating, said portion of product stream is then expanded to recover energy and condensed back to liquid, thus forming a closed loop.
A method for recovering waste heat in a process for the synthesis of a chemical product, where at least one make-up reactant is obtained in a front-end section, and reacted in a synthesis section operating at a pressure higher than said front-end section, obtaining said product in a liquid state and at a high pressure, the method comprising the steps of:
- using said waste heat to increase the enthalpy content of at least a portion of the liquid product delivered by the synthesis section, by indirect heat exchange, thus obtaining an expandable product stream in a vapour or supercritical state, and
- recovering energy by expanding said vapour or supercritical stream across at least one suitable expander;
- wherein a portion of the product condensate is pumped substantially at the same pressure of said synthesis section;
- said portion of the product condensate is then re-heated by heat exchange with said waste heat source or a further waste heat source;
- after said heating, said portion of product stream is then expanded to recover energy and condensed back to liquid, thus forming a closed loop.
A method for revamping a plant for producing ammonia, the plant comprising a front-end reforming section adapted to provide a make-up ammonia syngas, and a high-pressure synthesis loop, the method comprising the steps of:
- arranging a heat exchange for heating at least a portion of the liquid ammonia product, by means of heat exchange with at least one source of waste heat, so obtaining a stream of heated, high-pressure ammonia stream in a vapour or supercritical state;
- providing the provision of at least an expander and a generator connected to said expander, for the expansion of said ammonia stream and the production of energy from said waste heat;
- and
- providing a condenser adapted to condense the ammonia effluent at the outlet of said expander;
- wherein a portion of the product condensate is pumped substantially at the same pressure of said synthesis section;
- said portion of the product condensate is then re-heated by heat exchange with said waste heat source or a further waste heat source;
- after said heating, said portion of product stream is then expanded to recover energy and condensed back to liquid, thus forming a closed loop.
Dependencies are inferred from the claim text.