SE527646C2 - Production of engine fuel or hydrogen for fuel cells from lignocellulosic material, comprises disolving lignin, hydrolysis, fermentation and pyrolysis or gasification steps - Google Patents

Abstract

Production of engine fuel or hydrogen for fuel cells from lignocellulosic material comprises dissolving lignin and the resulting solid cellulosic material phase is hydrolyzed, fermented, pyrolyzed and/or gasified and synthesized to produce methanol, dimethyl ether, methane and/or Fischer-Tropsch products or to produce hydrogen. A method for producing fuel for internal combustion engines or fuel cells from lignocellulosic material comprising: (a) dissolving the lignin in the lignocellulosic material to form a liquid lignin-containing phase and a solid cellulosic material phase containing (hemi)cellulose; (b) hydrolyzing the cellulosic material; (c) fermenting the hydrolyzate to form ethanol; (d) pyrolyzing and/or gasifying the liquid phase to produce an energy-rich gas; and (e) synthesizing the gas to produce methanol, dimethyl ether (DME), methane and/or Fischer-Tropsch products. An independent claim is also included for a second method for producing the same fuel, comprising the above steps (1)-(4), followed by (5) producing hydrogen from the energy-rich gas.

Description

527 646 2 With hydrolysis of cellulose and hemicellulose, after fermentation to ethanol, the order of 30-35% of the energy contained in the raw material is obtained as ethanol and a further approximately 40% as a dried fuel. Drying requires a certain amount of energy and it is uncertain whether the process is self-sufficient in these circumstances. If it is not, some additional raw material is required for steam generation or the fuel product is partially utilized. Simply put, the amount of fuel product is controlled by the steam demand of the process. The greater the steam demand, the less fuel product.

The most technically difficult step for ethanol production from lignocellulose is the hydrolysis (dissolution) of cellulose, which is strongly inhibited as the cellulose is embedded in the lignin and requires strong (concentrated) acids or dilute acid and high temperature / high pressure or enzymes for a long residence time. .

The mentioned process paths are all fraught with weaknesses or difficulties from both a technical and business point of view. Technically, the gasification route means that almost half of the raw material is consumed for internal energy needs or obtained as a by-product (s). Bream gas or steam / hot water are in themselves salable products, but only if the location allows it. With black liquor as the raw material, the raw material supply is completely dependent on the pulp factory's production.

The ethanol production from lignocellulose produces an almost larger amount of fuel product (than ethanol) and generally has a steam requirement. Commercially, this means that the cost of ethanol becomes dependent on the yield of fuel product, on the current demand for the fuel product - and its value.

The present invention eliminates these fundamental problems and exploits the potential synergy between gasification and hydrolysis / fermentation of the same feedstock. One of the advantages of gasification is that the technology uses the entire carbon content of the raw material (actually energy content) while hydrolysis / fermentation on the one hand uses “only” the cellulose and hemicellulose parts, on the other hand it makes this more energy efficient. (The gasification breaks down all the constituents to CO and H2 for further synthesis while hydrolysis / fermentation uses already synthesized molecules (sugar) for biochemical transfer to ethanol) In the invention a third step in the overall process is used which enables gasification of the part which cannot be hydrolyzed / fermented at the same time as the energy-superior hydrolysis / fermentation pathway is used on the carbohydrates. The technology is made possible by the introduction of a similarly known technology - pulp cooking. In the first place, the invention relates to a pulp cooking technique which is not completely common, but the invention also covers the use of conventional sulphate pulp cooking and salt pulp cooking.

Through the combination of hydrolysis / fermentation and gasification / synthesis, the invention provides significantly greater freedom in the choice of raw material for the production of fuel. With a lower content of hydrolysable and fermentable components, the gasification will still automatically convert materials to DME, methanol, hydrogen, crude F-T oil, etc. Thus, no additional by-products arise as a result of “inferior” raw material for ethanol production.

In the development of ethanol production from lignocellulose, virtually all development lines undergo a hydrolysis (“release”) of the hemicellulose and cellulose in the raw material while the lignin is left as a solid residue (the previously mentioned fuel product). Both the hydrolysis and the subsequent fermentation are complicated by the lignin, which makes the cellulose more difficult to access for the hydrolysis chemicals and can form fermentation inhibitors.

In the present invention, the principle has been reversed so that the lignin is released from the cellulose which in pure form is led to hydrolysis / fermentation. Hydrolysis of pure cellulose has long been carried out using both strong and weak acids and enzymes. The rate of hydrolysis is for weak acid and enzymes considerably higher when “pure” cellulose is a raw material than when the cellulose is embedded in lignin. Furthermore, the final conversions are higher and the required catalyst inputs are less.

For the gasification, a release of the lignin according to the invention also means that the well-known feed-in problems in pressurized gasification are eliminated. The gasification processes in question usually operate at at least 10-20 bar pressure and in some cases up to 50-100 bar. The overall efficiency of gasification-synthesis gas production-synthesis generally increases with pressure as methanol, DME and, for example, crude F-T oil constitute intended products.

Dissolving lignin from lignocellulose (wood raw material) is an established technology in the pulp industry, and in addition to sulphate pulp cooking and salt pulp boiling, there was so-called “soda boiling” in the 19th century, in which sulfur was not used but “only” alkali. All three techniques are applicable within the invention, which also includes more or less established gasification technology and hydrolysis / fermentation technology. The later steps include various detailed solutions for carburetors and, for example, hydrolysis methodology.

In the description above, it may be obvious to combine a gasification process with a hydrolysis / fermentation process so that the excess energy in the former is utilized to enable a maximum extraction of fuel product in the latter. This process design is used below for comparison, but it does not utilize the advantages of gasification and hydrolysis / fermentation in relation to the content of the raw material.

The invention is illustrated by means of the drawing, in which the clock shows a block diagram of the present invention.

The principle of the invention is stated in the block diagram below. The main steps in the process are indicated by A, B and C.

The process begins with a dissolution of the lignin in the lignocellulose in a process step analogous to sulphate pulp boiling, salt pulp boiling or so-called soda boiling using “only” lye. Using a continuous boiler, no intermediate storage is required for process elements B and C.

The solid residue, primarily cellulose with a certain amount of hemicellulose (depending on the cooking chemical), is separated by sieving and filtration and washed with water to avoid cooking chemicals accompanying the cellulose. The cellulose is hydrolyzed using weak acid (sulfuric acid, SO 2 or similar), enzymes or strong acid (B1).

The conditions are the usual ones in the context; about 170 ° C in weak acid hydrolysis and on the order of room temperature for enzymatic hydrolysis and strong acid hydrolysis.

The solution is filtered and the solid residue (cellulose residues, undissolved lignites, etc.) is led to evaporation / gasification. The solution is pH-adjusted and provided with nutrients prior to a conventional fermentation to ethanol (B2). As pento-fermentation has developed, pento-fermenting organisms can also be used because pentoses can be released during both the cooking process and hydrolysis.

The by-products from the ethanol fermentation are present as beverages and in Lutter water (B3) and in both cases are led to evaporation / gasification (C 1).

The cooking liquid from the solution of lignin (the primary boiling) is led together with other residual product streams from B 1 -B3 to a power evaporator (Cl) to reduce the water loading in the gasification step. The gasification (C2) is carried out in principle in the same way as in black liquor gasification, in a conventional Texaco carburettor, or the corresponding carburettor that takes a fl surface / semi fl surface raw material. If the lignin solution is carried out with “soda boiling”, the sulfur load in the carburettor is small, which reduces its material problems considerably.

After gasification, gas purification, shift and carbon dioxide washing follow in an accepted manner to produce the synthesis gas in question (C3). In the case of hydrogen, a complete shifling of the gas to H2 is carried out. In the synthesis reactor, catalyst selection and other conditions determine which fuel is to be produced. 10 15 20 25 30 527 646 5 For process engineering reasons, in the synthesis (C4) a certain bleeding of combustion gas must take place, which contains certain components which, if the structure is too high, risk disturbing the synthesis reaction. This shielding gas, as well as steam from cooling the gas and from the exothermic shift stage, is used to supply the carbon dioxide separation with energy, as well as to ensure the required energy for evaporation (Cl) and hydrolysis stage (B 1).

Through the process according to the invention, over 90% of the cellulose and hemicellulose content of the raw material will be converted into sugars which are fermented in an accepted manner to ethanol. The remaining part of the raw material content, in the case of wood raw material 40-50%, consists of lignin, lignin products and other components in wood (organic acids, etc.). To these substances are added components generated by cellulose hydrolysis and fermentation (eg furfural and acetic acid). After evaporation and gasification, all of these are converted to synthesis gas and fuel product. As by-products from gasification and synthesis, a fuel gas and steam / hot water are obtained which correspond to at least 10-15% of the energy content of the raw material and are used as process energy.

In total, the invention allows 60-70% of the input energy to be obtained as a fuel; ethanol corresponding to about 30% and DME, methanol, hydrogen or crude F-T oil corresponding to the order of 30-40%.

The energy exchanges are of course affected by the composition of the raw material and, for example, whether pento-fermentation of the xylan content of the hemicellulose can be carried out efficiently.

Technical alternatives within the invention The invention is based on an initial separation of cellulose and hemicellulose content from lignin and other constituents in the raw material as well as two parallel lines for hydrolysis and fermentation to ethanol and gasification and synthesis to DME, methanol, hydrogen, etc. The invention presupposes further that these three elements are located together and that both the material streams and the media streams are continuously connected. For efficient utilization of the process, it is required that both side streams (residual and by-products from each line) as well as steam, etc. can be transferred from one line to the other.

On the other hand, the invention does not contain any significant limitations with regard to the detailed design of the three main steps (separation of cellulose / hemicellulose from lignin, etc., hydrolysis and fermentation to ethanol and gasification and synthesis to DME, methanol, etc.).

Separation of cellulose / hemicellulose and lignin, etc. in cooking process The separation of cellulose and hemicellulose from lignin, etc. can be carried out in at least three "conventional" ways; via sulphate and salt boiling and the older “soda boiling”. The three methods have different effects on both the hydrolysis line and the gasification line, but do not change in principle in the invention.

In sulphate boiling yesterday, sulfur in the cooking liquid, which places special demands on the gasification and gas handling. However, these effects are managed within the so-called “black liquor gasification” which takes place in the establishment phase when it comes to pulp production. In connection with black liquor gasification for electricity generation and methanol production, the far-reaching gas purification for synthesis gas is also included and these elements also largely utilize established technology. (Sulfur purification, etc. in synthesis gas production takes place regularly in many units) The energy efficiency of eg DME is calculated in black liquor gasification (from sulphate boiling) to 65-75%.

Sulphite boiling also includes sulfur, which in principle entails the same requirements for the carburettor and synthesis gas som production as the sulphate boiling. However, the lignin solution of lignin also gives a certain resolution of the hemicellulose. This fundamentally leads to a certain deterioration of the ethanol yield, which is, however, compensated by increased yield of DME, methanol or other propellant that is synthesized.

Soda cooking was apparently practiced for a short period in the 19th century but was abandoned in the pulp industry in favor of salt and sulphate cooking. The reasons were possibly a lower productivity and a lower quality of the pulp. Within the framework of the recovery, soda boiling means the advantage that no sulfur is included, which significantly simplifies the gasification step and reduces the requirements for gas purification in synthesis gas production.

Whether sulphate or sulphate boiling is carried out for the separation of cellulose / hemicellulose from lignin, etc., a chemical recovery cycle will be required.

In the pulp industry, this is established technology. With soda boiling, it may be possible to simplify chemical recovery, which, in that case, constitutes an additional advantage for this design of the separation step.

The separation of cellulose / hemicellulose å- from lignin, etc. via a cooking process naturally involves a vapor combustion in the process.

Hydrolysis and fermentation of cellulose / hemicellulose According to previously established technology and technology under development, cellulose (and hemicellulose) can be hydrolyzed with weak acid at temperatures 2 about 170 ° C and with concentrated acid and enzymes at about 30 ° C. For the principle of the invention, all three alternatives are relevant and in practice there are o kombinationa combinations of weak acid hydrolysis and enzymatic one in addition to only strong acid hydrolysis and only weak acid hydrolysis.

Strong acid hydrolysis involves a required work-up (concentration) of acid after the hydrolysis, which has often proved to be a difficult (and energy-intensive) part.

Weak acid hydrolysis also causes steam demand and handling of a residual product, neutralized acid. Enzymatic hydrolysis has so far been hampered by high enzyme costs, but an ongoing development is said to have hopes of drastically reduced costs.

Within the framework of the invention, the alternative methods for hydrolysis are an optimization issue for the overall process. reading of hexoses to ethanol is an established technology which has also been verified for wood raw material and other lignocellulosic materials. The invention here contains a potential in the form of pento-fermentation to ethanol, which means an increase in yield in that the xylan content of the hemicellulose can also be utilized in the hydrolysis / fermentation line. Due to the invention, however, this potential is significant only in the commercial situation that ethanol is in demand more than DME, methanol or other gasification / synthesis product. In this respect, the invention ensures that all materials that are not used for ethanol production can generate the other fuels.

Gasification and synthesis to DME, methanol, hydrogen, crude F -T oil, etc. The gasification line in the invention can have an alternative design both in terms of the carburettor and the gas treatment and synthesis. Most of these steps are established commercially in a variety of equipment for the sub-steps. The exceptions are the carburettor and the synthesis reactor, where the gasification technology has only been partially demonstrated for final gasification and an alternative technology for the synthesis has been proposed for a couple of decades (liquid phase sluice reactor).

Gas cooling, gas purification, shi 'reactor and gas washing are commercially available in your alternatives.

None of the choices of specific equipment affects the principle of acquisition, but rather constitutes optimization questions for the overall process.

Results of the invention relative to existing technology With a further development of the use of fuel from lignocellulose, large-scale plants will be required. In Europe, about 150 million m3 of petrol and slightly more diesel are currently used. In view of these volumes, it seems reasonable to compare possible units for wood-based fuel production with the plant sizes used by the pulp industry. 20 527 646 8 With a raw material intake of 1 million tonnes of TS wood / year, the increase gives room for an ethanol production of the order of 250-300 thousand / year and a DME production of about 200 thousand tonnes (corresponding to 160 thousand m3 of diesel).

The same raw material intake in a single ethanol axil addition gives approximately the same amount of ethanol (probably slightly less) with almost 300 thousand tonnes of solid fuel as a by-product. In an individual gasification plant, 350-400 thousand tons of DME are obtained. The by-product or by-product is then steam / hot water of 350-400 GWh.

The costs for these productions can be calculated to the order of SEK 1 / kWh ethanol and about SEK 0.4 / kWh DME, provided that the by-products can be sold at 10-14 öre / kWh for the ethanol's fuel product and 15-20 öre / kWh for DME's steam / hot water.

It can be questioned whether this can be achieved in large-scale operations.

In a process according to the invention, a weighted product cost of SEK 0.55-0.60 / kWh ethanol and DME is calculated without any by-product generation.

The energy efficiency rates for fuels are about 30% for a pure ethanol production, 55-60% for a pure DME production and for a process according to the invention slightly higher than for the gasification and synthesis of DME.

Overall, a process according to the invention provides a significant advantage over pure ethanol production and a poorer result than a pure gasification process for the production of DME. The effects of solid material feed in the latter as well as the potential difficulties in depositing steam / hot water are then not taken into account. The invention's ability to eliminate these problems is assumed to compensate well for the nominal increase in cost.

By co-locating a pure ethanol production and a gasification + synthesis to DME so that the required energy is transferred from the latter to the former, one of the problems in individual processes can be avoided. A calculation of the cost outcome for two units with 500,000 tonnes of TS raw material each, however, shows a cost of about 65 öre / kWh of fuel and still requires that the ethanol's fuel product be set aside at 10-14 öre / kWh.

Claims (9)

20 25 30 527 646 Patent claims A process for producing lignocellulosic material from combustion engine fuels and fuel cells for fuel cells, characterized by the release of lignin from the lignocellulosic material, wherein a surface-containing lignin-containing phase and a solid phase of cellulosic material, cellulose and hemicellulose, , hydrolysis of the cellulosic material, filtration of the hydrolyzate from the cellulosic material to ethanol, pyrolysis and / or gasification of the fl liquid phase For the production of energy-rich gas, and synthesis of the energy-rich gas into methanol, dimethyl ether, methane and / or Fischer-Tropsch products. 2. A method according to claim 1, characterized in that the release of the lignin from the lignocellulosic material, the hydrolysis and fermentation of the cellulosic material, the pyrolysis and / or the gasification of the fl surface phase and the synthesis are physically connected to each other by continuous materials and exchange of energy and inputs, such as steam and water. 3. A method according to claim 1 or 2, characterized in that lignin is released by sulfate boiling, salt boiling, soda boiling or modifications thereof using oxygen-containing gas and anthraquinone. 4. A method according to any one of claims 1-3, characterized in that gasification takes place at atmospheric pressure or overpressure with water vapor and oxygen-containing gas. 5. A method according to one or more of claims 1-3, characterized in that the pyrolysis takes place in an oxygen-poor environment. 6. A method of producing lignocellulosic material from combustion engine fuels and fuel cells for fuel cells, characterized by the release of lignin from the lignocellulosic material, wherein a surface-containing lignin-containing phase and a solid phase of cellulosic material, cellulose and hemicellulose, , hydrolysis of the cellulosic material, fermentation of the hydrolyzate from the cellulosic material to ethanol, pyrolysis and / or gas degassing of the fl liquid phase for the production of energy-rich gas, and 527 646 production of hydrogen gas from the energy-rich gas. 7. A method according to claim 6, characterized in that the release of the lignin from the lignocellulosic material, the hydrolysis and fermentation of the cellulosic material, the pyrolysis and / or the gasification of the surface phase and the synthesis are physically connected to each other by continuous materials and exchange of energy and inputs, such as steam and water. Process according to Claim 6 or 7, characterized in that lignin is released by sulphate boiling, salt-boiling or soda-boiling modifications thereof using oxygen-containing gas and anthraquinone. 9. A method according to any one of claims 6-8, characterized in that gasification takes place at atmospheric pressure or overpressure with water vapor and oxygen-containing gas. 10, A method according to any one of claims 6-8, characterized in that the pyrolysis takes place in an oxygen-poor environment.