Disclosed is an integrated process for the production of urea and melamine, as well as a system for carrying out the process. The invention thereby pertains to an integrated process of the type wherein off-gas obtained from the production of melamine is entered into the process for the production of melamine, by condensation in the presence of water. A typical embodiment thereof is the condensation in the presence of an aqueous carbamate solution obtained from urea recovery. In accordance with the invention, said condensation takes place at a substantially lower pressure than the pressure at which the melamine off-gas is obtained. To this end, the pressure of the off-gas is reduced typically by 2-10 bar. In connection herewith, the system of the invention comprises a pressure reducing unit downstream of an outlet for the melamine off-gas, and upstream of a section for the condensation of the off-gas. The invention also includes a method for the modernization of an integrated system for the production of melamine and urea. This is accomplished by adding the aforementioned pressure reducing unit to a pre-existing system.

A method for revamping existing plants as well as a plant for the production of melamine with zero environmental impact and the relative process.

The disclosure pertains to a coupled plant process for the production of urea and melamine, with a urea synthesis section with HP CO.sub.2 stripping, and with a part of the CO.sub.2 feed supplied to a recovery section.

An integrated process, suitable for use in a new or retrofitted plant, produces an olefin or di-olefin via the dehydrogenation of an appropriate C3-C4 hydrocarbon feed includes (1) contacting the feed and a dehydrogenation catalyst having a Geldart A or Geldart B classification in a fluidized bed at a temperature from 550 C. to 760 C. and a pressure from about 41.4 to about 308.2 kPa (about 6.0 to about 44.7 psia) and a catalyst to feed ratio, w/w, from 5 to 100 to form a dehydrogenate product; separating the dehydrogenate product and unreacted starting feed mixture from a portion of the catalyst by means of a cyclonic separation system; reactivating the catalyst in a fluidized regenerator by combustion at 660 C. to 850 C., followed by contact with an oxygen-containing fluid at 660 C. or greater, and returning the catalyst to the dehydrogenation reactor; (2) compressing the product mixture to form a compressed product mixture; and (3) fractionating the compressed product mixture to form a product stream including at least the target olefin or di-olefin. The integrated process offers increased plant capacity, improved economics, and reduced environmental impact in comparison with other known and conventional processes.

Disclosed is a method for the integrated production of two different urea products. One is an aqueous urea solution suitable for use in NOx abatement (generally indicated as Diesel Exhaust FluidDEF). The other is a solution used as a fertilizer, viz. Urea Ammonium Nitrate (UAN). The production of DEF and UAN are integrated as follows: ammonia recovered from the production of urea is used as a feed to the production of ammonium nitrate. At least part of an aqueous urea stream from urea prodution, is mixed with ammonium nitrate so as to obtain UAN.

Disclosed is a method of increasing the capacity of an existing urea plant. With reference to the regular components of a urea plant, including a synthesis section comprising a high pressure carbamate condenser and a reactor, and a recovery section, the method comprises installing an additional reactor between the recovery section and the high pressure carbamate condenser. The additional reactor is preferably installed in connection with an ejector, so as to allow ground placement of the additional reactor.

Disclosed is a method and plant for the catalytic dehydrogenation of alkanes, such as propane. The plant is a plant of hybrid architecture wherein one or more membrane-assisted reactor configurations according to open architecture are combined with one or more membrane-containing reactors of closed architecture. Hydrogen remaining in the reaction mixture after separation in the membrane separation unit of a first open architecture configuration, is fed to a first membrane-reactor of the closed architecture type. Also disclosed are methods of modifying plants so as to create the hybrid architecture plant.

Process for the preparation of urea granules comprising the steps of obtaining an aqueous urea solution from one or more synthesis and recovery steps wherein ammonia and carbon dioxide are reacted together, subjecting the aqueous urea solution to an evaporation step wherein water is removed to obtain a urea melt (1), processing and treating said urea melt in a granulation step (7) and optionally in a cooling section (10) to obtain solid urea granules (14); the process further comprises a scrubbing step (3) of granulation offgas and an atmospheric evaporation step (32) to recover a urea solution (2) and a water-saturated air stream (18): the water-saturated air stream is fed back to the scrubbing section (3) without condensation, and the recovered urea solution is conveyed to the granulation step (7).

Disclosed is a method for the integrated production of two different urea products. One is an aqueous urea solution suitable for use in NOx abatement (generally indicated as Diesel Exhaust Fluid DEF). The other is a solution used as a fertilizer, viz. Urea Ammonium Nitrate (UAN). The production of DEF and UAN are integrated as follows: ammonia recovered from the production of urea is used as a feed to the production of ammonium nitrate. At least part of an aqueous urea stream from urea production, is mixed with ammonium nitrate so as to obtain UAN.

A process for producing a polyester solids mixture by adding together a proportion of recycled polyester material and a proportion of polyester material from a polyester manufacturing process. The proportion of recycled polyester material in the polyester solids mixture comprises 10-90% and has a b* value (BR), and the proportion of polyester material from a polyester manufacturing process in the polyester solids mixture comprises 90-10% and has a b* value (BN) and the resulting polyester solids mixture has a b* value (BM), wherein the BM<0, BN<0 and BR>BN.