Product recycle loops in process for converting municipal solid waste into ethanol

1. A method for converting organic materials into ethanol comprising:

separating non-organic materials from a solid feedstock which may optionally contain entrained liquids, thereby creating a solid processed feedstock;

generating a primary syngas from the processed feedstock in a gasification unit;

generating superheated steam by cooling a stream comprising the primary syngas in a heat exchanger, thus outputting a cooled primary syngas stream;

generating electricity from the superheated steam;

removing or neutralizing one or more unwanted contaminants from the cooled primary syngas stream, thereby creating a scrubbed syngas;

compressing a compressor inlet stream comprising a first portion of the scrubbed syngas, thereby raising the pressure of the compressor inlet stream to a predefined level, and outputting a compressed syngas;

providing conditions within an alcohol synthesis reactor, including the presence of a catalyst, to cause components of at least a portion of the compressed syngas to react and produce an effluent comprising unconverted syngas and a mixture of reaction products including alcohols and water;

separating the effluent into a mixed-alcohol stream rich in water and alcohols, and one or more gas recycle streams rich in unconverted syngas; and

separating the mixed-alcohol stream into a number of streams comprising:

an ethanol stream comprising primarily ethanol;

a water stream comprising primarily water;

a methanol stream comprising primarily methanol; and

a heavy alcohol stream comprising primarily propanol and heavier alcohols;

conveying a methanol recycle stream comprising at least a portion of the methanol stream to a mixing point upstream of or within the alcohol synthesis reactor, thereby recycling the methanol recycle stream.

2. The method of claim 1 , wherein the alcohol synthesis reactor comprises a first reaction zone, a second reaction zone in fluid communication with the first reaction zone, and

a space between the first reaction zone and the second reaction zone; and wherein said space comprises the mixing point.

3. The method of claim 2 , wherein the first reaction zone and the second reaction zone are contained within separate reactor units.

4. The method of claim 1 , wherein the methanol recycle stream is in the gas phase.

5. A method for converting organic materials into ethanol comprising:

separating non-organic materials from a solid feedstock which may optionally contain entrained liquids, thereby creating a solid processed feedstock;

generating a primary syngas from the processed feedstock in a gasification unit;

generating superheated steam by cooling a stream comprising the primary syngas in a heat exchanger, thus outputting a cooled primary syngas stream;

generating electricity from the superheated steam;

removing or neutralizing one or more unwanted contaminants from the cooled primary syngas stream, thereby creating a scrubbed syngas;

compressing a compressor inlet stream comprising a first portion of the scrubbed syngas, thereby raising the pressure of the compressor inlet stream to a predefined level, and outputting a compressed syngas;

providing conditions within an alcohol synthesis reactor, including the presence of a catalyst, to cause components of at least a portion of the compressed syngas to react and produce an effluent comprising unconverted syngas and a mixture of reaction products including alcohols and water;

separating the effluent into a mixed-alcohol stream rich in water and alcohols, and one or more gas recycle streams rich in unconverted syngas; and

separating at least a portion of the mixed-alcohol stream into a number of streams comprising:

an ethanol stream comprising primarily ethanol;

a water stream comprising primarily water;

a methanol stream comprising primarily methanol; and

a heavy alcohol stream comprising primarily propanol and heavier alcohols;

conveying a fusel oil recycle stream comprising at least a portion of the heavy alcohol stream to the gasification unit;

within the gasification unit, partially oxidizing one or more components of the fusel oil recycle stream to convert at least some of said components to a mixture comprising carbon monoxide and hydrogen.

6. The method of claim 5 , further comprising mixing a methyl acetate stream with the heavy alcohol stream, to create the fusel oil recycle stream.

7. The method of claim 6 , further comprising:

separating said portion of the mixed alcohol stream into (A) a methanol-ethanol stream comprising methanol and ethanol, and (B) a heavies stream comprising propanol, other heavy alcohols, and water;

separating the heavies stream into (A) the heavy alcohol stream, and (B) the water stream;

separating the methanol-ethanol stream into (A) a methanol-methyl acetate stream comprising methanol and methyl acetate, and (B) the ethanol stream; and

separating the methanol-methanol acetate stream into (A) the methyl acetate stream comprising methyl acetate, and (B) the methanol stream.