The invention relates to an improved process and plant for the preparation of hydrocarbons useful as gasoline com- pounds from a feed comprising methanol.

Gasoline can be produced by conversion of raw methanol, pure methanol and/or dimethyl ether. In the process water is formed as a by-product. The water is separated (as pro- cess condensate) from the produced raw gasoline and recycle gas in a separator and send for water treatment as it com ^¬ prises a number of impurities.

In a first aspect of the present invention is provided a process which provides an optimized output from the gaso ^¬ line conversion.

In a second aspect of the present invention is provided a process which reduces the need for water treatment.

These and other advantages are achieved by a hydrocarbon production process comprising the steps of

In a conversion step converting at least a feed stream thereby obtaining a conversion effluent comprising water, hydrocarbons, unreacted, partially reacted feed and/or in- erts ,

In a separator separating the conversion effluent into at least a recycle stream, raw gasoline and a process con ^¬ densate stream comprising water,

- At one or more points mixing the feed stream and at least part of the recycle upstream the conversion step, and adding at least part of the process condensate stream to the feed stream, recycle stream and/or mixed feed- recycle stream. Various embodiments of the invention are disclosed and dis ^¬ cussed in the following. These embodiments can either be employed each alone or in combination.

The conversion effluent may comprise various hydrocarbons such as raw gasoline, higher alcohols, aldehydes, ketones, ethers, olefins and/or aromatics.

By the present process and plant any convertible substances in the process condensate can be re-entered into the con- version loop whereby the output of the process may be in ^¬ creased compared to setups where the process condensate is simply sent to water treatment.

Also the present plant and process reduce the need for wa- ter treatment as the convertible substances in the water is reintroduced into the conversion step instead of being re ^¬ moved in downstream treatment of the condensate.

The feed to the process is preferably a methanol rich stream which also may comprise any of the following Dime ^¬ thyl Ether (DME) , higher alcohols, ketones, aldehydes, raw methanol, other alcohols, ethers and/or H2/CO mixtures.

The process condensate from the conversion process may com- prise oxygenates of different types including alcohols, ke ^¬ tones, esters and/or aldehydes. The oxygenates can be separated from the remaining process condensate which mainly consists of water. The separation of the oxygenates can for example be performed by distilla ^¬ tion or stripping. The stream comprising the separated oxy- genates is referred to as the recovered oxygenate stream.

Preferably at least part of the process condensate added to the feed stream and/or the recycle stream and/or the mixed feed-recycle stream is a recovered oxygenate stream. I.e. the at least part of the process condensate stream to the feed stream, recycle stream and/or mixed feed-recycle stream may be the recovered oxygenate stream.

The composition of the process condensate and the recovered oxygenate stream may depend on the conversion process, feed etc .

Some exemplary compositions and ranges for pressures and temperatures are given below. The values are based on a feed of raw methanol and a conversion process based on a ZSM-5 catalyst at T = 250 - 475°C and P = 1 - 50 bar.

Process condensate :

Temperature = 75 - 105 °C, preferably 90°C

Pressure = 2 - 8 barg, preferably 5.4 barg

Composition :

Compound wtppm

Ethanol 50 wtppm

Methanol 10000 wtppm

Acetone 1100 wtppm

1-Propanol 200 wtppm Acetaldehyde 150 wtppm

Methyl Ethyl Ketone 250 wtppm

Water balance

Recovered oxygenate stream:

Temperature = 75 - 105 °C, preferably 90°C

Pressure = 15 - 40 barg, preferably 28 barg

Composition

Compound wtppm

Ethanol 2800 wtppm

Methanol 555000 wtppm

Acetone 61100 wtppm

1-Propanol 11100 wtppm

Acetaldehyde 8330 wtppm

Methyl Ethyl Ketone 13880 wtppm

Water balance

In most setups the conversion step is a methanol to gaso ^¬ line (MTG) process in which the produced hydrocarbons com ^¬ prises a mixture of various hydrocarbons boiling in the gasoline range, such as from C2 and higher e.g. up to C13, preferably C5+ . Generally speaking in the conversion pro- cess the conversion of oxygenates in the feed stream is carried out in a converter in the presence of a catalyst being active known in the art in the reaction of oxygenates to higher hydrocarbons, preferably C5+ hydrocarbons. In various setups more than one conversion reactor is used. In these setups the multiple converters may be arranged in parallel allowing recovery of one or more converter while one or more reactors are still in use. The recovered oxygenate stream may be added to the feed stream and/or recycle and/or the stream of mixed

feed/recycle in order to enter the conversion step thereby improving the output of the system compared to the case where the oxygenates are removed from the system together with the water etc. in the process condensate. I.e. the process provides an increased gasoline production because the unconverted oxygenates are recovered and recirculated back to the synthesis process instead of lost in the pro- cess condensate sent to water treatment. Furthermore the conversion of the recovered oxygenates reduce the need for treatment of the waste water as the oxygenates are utilized instead of being disposed of as part of the process conden ^¬ sate as known from existing processes.

Fig. 1 illustrates a process and plant 1 where feed 2 is mixed with recycle gas 3 and recovered oxygenate stream 4 is mixed into the feed/recycle gas stream at a mixing point 5.

Alternatively the recovered oxygenate stream is mixed into the recycle stream upstream the feed mix point 5 at a sec ^¬ ond mixing point 7. The mixing is preferable carried out by quenching the recovered oxygenate stream into the gas stream by means of a spray nozzle. Alternatively a static mixer can be used or the liquid and the gas can be mixed upstream of a heat exchanger.

Another alternative is to add the recovered oxygenate stream to the feed stream before the stream is evaporated or after the feed stream is evaporated as indicated by dot ^¬ ted lines 8 and 9. Another alternative is to spray/mix the liquid off-stream into the gas going to the reactor as indicated by dotted line 10.

The ketone, aldehydes and/or alcohols in the recovered oxy- genate stream is together with the feed methanol converted to gasoline in the reactor 11. The effluent 12 is

cooled/condensed in a series of heat exchangers 13 and the three phases are separated in the separator 14. The gas is recycled 15/purged 16 and the condensate 17 is sent to a distillation 18 for separation. The recovered oxygenate stream 4 from the separation comprises ketones, aldehydes and/or alcohols.