A method for revamping a system comprising at least two ammonia production units, each unit comprising an ammonia converter each having an inlet for receiving a process gas and an outlet for releasing a purge gas, the method for revamping comprising the step of fluidly connecting the inlet of the converter of a first ammonia production unit to the outlet of the converter of a second ammonia production unit, for transporting the purge gas being produced by the converter of the second ammonia production unit, to the converter of the first ammonia production unit. Finally, the present disclosure describes a method for the reduction of a catalyst in an ammonia converter, in an ammonia production system comprising at least two ammonia production units and a system in which the method for the reduction of the catalyst can performed.

The invention is directed to a urea plant with a high pressure synthesis section and a recovery section. The high pressure synthesis section comprises a reactor, a stripper and a condenser, wherein the reactor operates at a higher pressure than the stripper and the condenser. The plant further includes a compression unit between the condenser and the reactor. The compression unit utilizes mechanical energy recovered from a decompression unit positioned downstream of the stripper and upstream of the recovery section.

The inventions is directed to a new design for catalyst tubes, which makes it possible to apply the concept of regenerative reforming into steam reformers having catalyst tube inlets and outlets at opposite sides of the furnace chamber. The catalyst tube comprises an inlet for process gas to enter the catalyst tube and an outlet for process gas to exit the catalyst tube, which inlet and outlet are located at opposite ends of the catalyst tube. The catalyst tube further comprises a first annular channel comprising the catalyst, a second annular channel for process gas to flow countercurrently or co-currently to the process gas flowing through the first annular channel.

An integrated process for producing C3-C4 olefins or di-olefins including: contacting a hydrocarbon feed and a catalyst feed in a fluidized dehydrogenation reactor under conditions such that a product mixture is formed and the catalyst is at least partially deactivated; transferring the product mixture and the catalyst from the reactor to a cyclonic separation system under conditions such that the product mixture is converted to form a new product mixture and is separated from the catalyst; transferring at least a portion of the catalyst to a regenerator vessel and heating it in order to combust the coke deposited thereon; subjecting the catalyst to a conditioning step to form an oxygen-containing, at least partially reactivated catalyst; and transferring the partially reactivated catalyst back to the fluidized dehydrogenation reactor.

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.

Method for revamping a multi-bed ammonia converter, wherein said converter comprises a plurality of adiabatic catalytic beds including a first catalytic bed and one or more further catalytic bed(s), said catalytic beds being arranged in series so that the effluent of a bed is further reacted in the subsequent bed; at least a first inter-bed heat exchanger arranged between said first catalytic bed and a second catalytic bed to cool the effluent of said first bed before admission into said second bed, and optionally further inter-bed heat exchanger(s) arranged between consecutive beds; said method involves the conversion of said first catalytic bed into an isothermal catalytic bed.

The invention provides a method and a plant for producing urea ammonium nitrate (UAN). The method involves the use of a condensation section, optionally in combination with a medium pressure decomposition section, between the dissociation and neutralization sections. The invention further provides a method of modifying an existing UAN plant. The advantages of the process of the invention are that the emission of CO.sub.2 can be reduced, the plant capacity can be increased and the high capital expenditure needed for CO.sub.2 compression equipment is reduced.

Combustion gas of an internal combustion engine passes through an exhaust system to an outlet opening. A detection device generates a state signal that describes an engine noise of the internal combustion engine. A control apparatus actuates at least one loudspeaker to produce a sound at the outlet opening based on the state signal to compensate for the engine noise or produce another engine noise, independently of the state signal based on predetermined audio data and thereby to use the at least one loudspeaker to audibly output an advisory signal described by the audio data.

A dual-pressure plant for the synthesis of nitric acid comprising: a reactor (4) providing a gaseous effluent (15) containing nitrogen oxides; an absorption tower (6) nitrogen oxides react with water providing raw nitric acid and, said absorption tower operating at a pressure greater than the pressure of the reactor; a compressor (5) elevating the pressure of the reactor effluent (15) to the absorption pressure; said plant also comprising a first bleacher (37) and a second bleacher (7), said first bleacher (37) stripping with air (39) nitrogen oxides from the output stream (27) of the absorption tower (6) providing a partially stripped nitric acid stream (40) and a nitrogen oxides-loaded air stream (41), the former being fed to the second bleacher (7) and the latter being recycled to the delivery-side of said compressor (5).

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).