The present invention relates to the use of a plate heat exchanger as feed/effluent heat exchanger in multiple reactor systems.

Plate heat exchangers are generally formed by an elongate impervious chamber and a bundle of plates arranged in the chamber and providing therewith a free space. The plate bundle consists of a stack of mutually parallel plates that provide between them a double circuit for the flow of two independent and generally counter-current fluids. A plate heat exchanger is a compact, cost efficient heat exchanger solution which is used whenever the process conditions can allow it. High pressure, above 10-20 bar, and a heavy fouling feed stream represent typical

limitations for the use of plate heat exchangers in the industry.

Many exothermal reaction systems include use of one or more feed/effluent exchangers E as shown in the appended figure. The principle is that cold feed gas (1) is heated by the outlet gas (2) from the reactor (s) R. The absolute pressure in such a feed/effluent exchanger can be high, i.e. up to several hundred bars, but the pressure difference is limited to the pressure drop in the reactor system, which can be kept below 20 bar, preferably below 10 bar. This allows for use of a plate heat exchanger as feed/effluent exchanger, provided that it is installed in a pressure shell that can withstand the high absolute pressure.

Regarding prior art, US 9.120.068 describes a chemical isothermal reactor with an internal plate heat exchanger having heat exchange radial plates and radial ducts parallel to sides of the plates for distributing and collecting a heat exchange fluid. A part of the radial ducts has a smaller cross section near the inner converging ends .

WO 2007/096699 describes a multiple reactor chemical production system, where multiple reactors in a common pressure shell one by one are connected to multiple plate type feed/effluent exchangers in a common pressure shell.

In EP 3 401 299 A1 , a reactor for conducting exothermic equilibrium reactions, especially for methanol synthesis by heterogeneously catalyzed conversion of synthesis gas, is described. The reactor enables re-adjustment and hence optimization of the reaction conditions along the

longitudinal coordinate of the reactor. It is divided into a multitude of series-connected reaction cells, each of which comprising a pre-heating zone, a cooled reaction zone, one or more cooling zones and a deposition zone for condensable reaction products. This way, the reaction conditions are adjustable to the respective local

composition of the reaction mixture and variable over the reactor length. A comparison of one standard shell-and-tube type heat exchanger with a plate heat exchanger in a pressure shell results in an advantage for the shell-and-tube type. For large capacity reactor systems, where two or more reactors operating in parallel are connected to two or more

feed/effluent exchangers of shell-and-tube type, it has however been found that these exchangers can be replaced by a single plate heat exchanger in a pressure shell, which results in a considerable cost saving.

Thus, the present invention relates to a process for performing one or more exothermal reactions, wherein a plate heat exchanger is used as feed/effluent exchanger in connection with two or more reactors, which are operating in parallel performing exothermal reaction (s) at a pressure above 30 bar abs .

The reactors are preferably boiling water reactors, quench type reactors, adiabatic reactors or any combination of these reactors working in series.

In the process according to the invention, the primary reaction in the reactors is preferably a conversion of synthesis gas to methanol or ammonia or dimethyl ether (DME) or any other exothermal reaction.

In one aspect, this invention provides a process of

(a) using a plate heat exchanger as feed/effluent

exchanger in connection with two or more reactors operating in parallel and performing one or more exothermal reaction (s) at a pressure above 30 bar abs, (b) wherein the reactors in (a) are boiling water reactors or quench type reactors or adiabatic reactors or any combination of these working in series, (c) and wherein the primary reaction in the reactors

(a) and (b) is a conversion of synthesis gas to methanol or ammonia or dimethyl ether (DME) or any other exothermal reaction. The invention is described in more detail in the example which follows.

Example

For a large scale methanol plant producing 5000 MT methanol per day, requiring 3 boiling water reactors in parallel, the standard use of 3 shell-and-tube feed/effluent heat exchangers has been compared with the use of only one plate heat exchanger installed in a pressure shell. The cost reduction by doing so was more than 25%.