THERMOCHEMICAL CONVERSION OF BIOMASS

Description

[0001] The invention relates to a process for processing biomass and biogenic residues into crude oils.

[0002] The term biomass refers to the total mass of organic materials, including those contained in biogenic residues and sewage sludge.

[0003] Plant biomass consists primarily of three biopolymers: cellulose, hemicelluloses (also known as polyoses), and lignin. In temperate woods, these biopolymers typically comprise 97–99% of the wood substance. Of this, cellulose accounts for 30–35%, hemicelluloses for 15–35%, and lignin for 20–35%. Extractives (1–3%) and inorganic components (ash) (0.1–0.5%) make up significantly smaller proportions. Generally, the lignin content is higher in coniferous woods than in deciduous woods, while the hemicellulose content is somewhat higher in deciduous woods.

[0004] The simplest way to convert biomass into oxygenated crude oils as liquid intermediates is through direct liquefaction. Direct liquefaction is a single-stage, low-temperature conversion process in the range of 250 to 550 °C. This process generally yields the following products: a liquid condensate phase containing the crude oil as the target product as well as the reaction water, a combustible gas phase as a by-product and a solid residue as a by-product.

[0005] In favorable conditions, hydrophobic crude oil forms, meaning that the crude oil is immiscible with water; that is, in contact with water, at least two immiscible liquid phases form: an oil phase and a water phase. The quality of the crude oil is determined by its calorific value. The calorific value is the maximum amount of usable heat during combustion at which the water vapor contained in the exhaust gas does not condense, relative to the amount of fuel used. A high oxygen content in the fuel negatively affects the calorific value (Hj), as can be seen from the following formula: Hi = 34 , 0 · m C + 101 , 6 · m H + 6 , 3 · m N + 19 , 1 · m S − 9 , 8 · m O − 2 , 5 · m H 2 O MJ / kg

[0006] Here, m(C), m(H), m(N), m(S), m(O) and m(H2O) are the percentage mass fractions of carbon, hydrogen, nitrogen, sulfur, oxygen and water divided by 100.

[0007] A very comprehensive description of all existing processes for direct liquefaction can be found in the study "Direct liquefaction of biomass - reaction mechanisms and product distributions - 114-50-10-0337 / 05-B" by Prof. Dr. Frank Behrendt.

[0008] The historic Pittsburgh Energy Research Center (PERC) process operates at very high pressure of around 200 bar using an aqueous medium, dissolved catalyst, recirculating oil, and a carbon monoxide-hydrogen gas mixture. The equally historic Lawrence Berkeley Laboratory (LBL) process is carried out without recirculating oil, but otherwise under the same complex conditions as the PERC process. Both processes were discontinued for technical and economic reasons due to their enormous complexity.

[0009] Shell's hydrolytic HTU (Hydrothermal Upgrading) process can liquefy many different biomass materials (even those with high moisture content) under very high pressure of approximately 180 bar. This produces a tar-like, oxygen-containing product that requires further processing to become a liquid oil. Direct Catalytic Pressure Liquefaction (DCL) according to the BFH process operates under high hydrogen pressure and uses expensive precious metal catalysts.

[0010] The pressure hydrogenation process / DoS (direct liquefaction of organic substances) according to Willner is also carried out under hydrogen pressure, but without catalysts.

[0011] All previously mentioned direct liquefaction processes, including historical ones, operate under pressure and are therefore very complex. In particular, the introduction of solid biomass into the pressure reactor always presents a problem with regard to the consistency of the biomass entering the reactor, as well as with regard to the feasibility, reliability, and economic viability of the process. Furthermore, pressure reactors are generally more expensive and more prone to operational problems than atmospheric pressure reactors.

[0012] In addition, the following direct liquefaction processes operate under atmospheric pressure: The KDV process (catalytic pressureless liquefaction) from Alphakat and the Willner variant are carried out in an oxygen-free, petroleum-derived heavy oil phase as the reaction medium under atmospheric pressure and require powdered solid catalysts. The latter poses an economic problem, as the catalysts are expensive and lose their activity very quickly in the reactor due to coking. Furthermore, the KDV process requires a constant supply of fresh heavy oil, as the reactor sump oil phase does not regenerate automatically when biomass is used. The KDV process also utilizes an internal heavy oil recirculation system maintained by a circulation pump.A fundamental problem is that the circulating oil has a reaction temperature, exposing the pumps to high thermal and corrosive stresses and leading to frequent failures. In the KDV process, the solids load, particularly due to the catalyst content but also the biogenic mineral content in the circulating oil, further exacerbates the problem. This subjects the pumps to additional high abrasion stresses, resulting in excessive wear and requiring the use of particularly expensive materials. Furthermore, in the KDV process, a stable and self-regenerating sump phase does not form when using biomass, whether with or without a catalyst, necessitating a continuous supply of fresh, external heavy oil.

[0013] Furthermore, the KDV process yields a large amount of solid residue and comparatively little crude oil as the target product. In addition, up to four immiscible liquid phases can be observed in the condensate during the KDV process, which makes technically viable use very difficult.

[0014] Flash pyrolysis is essentially a very rapid heating process to reaction temperature under atmospheric pressure. This yields a high volume of crude oil, which, however, is hydrophilic. This means it is miscible with water up to a water content of approximately 35%. Therefore, the crude oil is of inferior quality due to its extremely low calorific value, on the order of only 15 to 17 MJ / kg, and due to its high corrosiveness, particularly because of its high acidity, making it difficult to use or process technically.

[0015] The NTK process (low-temperature conversion) developed by Prof. Bayer (University of Tübingen) is a simple pyrolysis process under atmospheric pressure without rapid heating. However, this process is not suitable for liquefying plant biomass, but is primarily used for sewage sludge liquefaction. A fundamental problem with the NTK process is that it produces only comparatively low crude oil yields, but high yields of solid residue.

[0016] JP 2006 / 063310 A describes a thermochemical process using an organic petroleum solvent. This process generates a number of different phases or fractions. A portion of the condensate is recycled as a solvent for the biomass. Overpressure or underpressure is applied, and catalysts are used.

[0017] The object of the invention is to provide a process that can convert any type of biomass, plant and animal, as well as biogenic residues including sewage sludge, into crude oils with only low levels of solid organic residues under atmospheric pressure, without the addition of catalysts or heavy oils. In particular, it should be possible to produce hydrophobic crude oils without the need for an internal heavy oil cycle. A specific objective is to obtain hydrophobic crude oils with a calorific value of more than 25 MJ / kg.

[0018] The problem is solved by the method with the features specified in claim 1. The dependent claims describe advantageous embodiments of the invention. The direct liquefaction process according to the invention is a single-stage process; the conversion reactions are carried out at atmospheric pressure in a liquid heavy oil sump phase.

[0019] Another feature of the process according to the invention is that a stable and self-regenerating sump phase forms, so that no new external heavy oil needs to be supplied.

[0020] A key feature of the process according to the invention is that the heavy oil sump phase in the reactor must contain at least 5 wt.% organically bound oxygen.

[0021] The heavy oil used to form the sludge phase in combination with the supplied biomass can include, for example, wood tars or wood tars containing tall oil. Such wood tars can be either coniferous or deciduous.

[0022] In the process according to the invention, the shredded dried solid biomass is conveyed directly into the sludge phase.

[0023] The term biomass refers to the total mass of organic materials, including those contained in biogenic residues and sewage sludge.

[0024] Surprisingly, under these boundary conditions, the goal of producing hydrophobic crude oil while minimizing solid residue is achieved without the addition of catalysts and heavy oil, without special conditioning of the dried biomass (for example, preheating or mixing with heavy oil), and without an internal heavy oil cycle.

[0025] In the process according to the invention, a stable and self-regenerating sump phase forms, surprisingly unlike processes not based on the invention, which have an oxygen-free heavy oil phase (for example, the KDV process), so that no new external heavy oil needs to be added. The condensate also presents a completely different picture than in processes not based on the invention, which have an oxygen-free heavy oil phase (for example, the KDV process). As a rule, the condensate consists only of two immiscible liquid phases: the crude oil phase as the target product and an aqueous phase. In rare cases, three liquid phases are obtained if the crude oil phase contains components that are partly lighter and partly heavier than water. In this case, the crude oil phase divides into an upper and a lower liquid phase, while the aqueous phase is found in the middle.An economically decisive difference compared to non-inventive processes that have an oxygen-free heavy oil phase (for example, KDV processes) is that the inventive process yields significantly more crude oil product and less solid residue.

[0026] The calorific values ​​of the crude oil produced according to the inventive process are, at greater than or equal to 25 MJ / kg, sometimes higher than those achieved with non-inventive processes that have an oxygen-free heavy oil phase (for example, the KDV process). This is a surprising result, since the oxygen content of the sump phase should have a negative effect on the calorific value of the product oil.

[0027] Fig. 1Figure 1 shows a typical flow diagram of the continuously operated process according to the invention. The core component is the heated reactor, which maintains the heavy oil sump phase at reaction temperature. The shredded, dried biomass is conveyed directly into the sump phase via a conveying device (e.g., a screw conveyor), where it heats up rapidly upon contact with the heavy oil. The volatile reaction products exit the reactor at the top via the gas / vapor phase and are cooled and partially condensed. The condensate is collected, and the non-condensing reaction gas is used for further processing (e.g., combustion to power the process). At least two immiscible liquid phases separate in the condensate: at least one hydrophobic crude oil phase as the target product and an aqueous phase. The solid residue is removed from the bottom of the reactor, for example, after sedimentation.Other process steps such as filtration, press filtration, centrifugal separation, vacuum evaporation and / or solvent extraction can also be used to separate the solid residue.

[0028] The following are an example according to the invention (see Example 3) and two process examples not according to the invention. Under the non-inventive KDV conditions, in which an oxygen-free heavy oil phase is present, the product compositions differ significantly from those of Example 3 according to the invention.

[0029] The crucial boundary condition here is that the heavy oil sump phase in the reactor must contain at least 5 wt% organically bound oxygen. Comparing this with the closest prior art, the KDV process, which uses oxygen-free petroleum-derived heavy oils as the reaction phase, unexpectedly different results are obtained despite the comparatively minor change in the composition of the sump phase. As an example, the experimental conversion of shredded and dried cereal straw in an 8-liter laboratory reactor is described. The laboratory reactor is electrically heated externally and contains an internal agitator that keeps the heavy oil sump phase moving near the walls to ensure good heat transfer. The solid biomass is fed directly into the sump phase, which is maintained at reaction temperature, via a screw conveyor.The volatile reaction products exit the reactor at the top and are fed to the cooling condenser. The condensate is collected, and the remaining gas phase is fed to the exhaust gas cleaning system. After several hours of operation with a continuous biomass feed, the experiment is terminated, and all products, including the sludge phase, are analyzed. The solid residue content in the sludge phase is determined analytically. The reaction gas product is determined as the balance difference. All experiments described here are conducted with a continuous straw feed of 1 kg / h at 350°C. <0> Testing was carried out under atmospheric pressure. The calorific value of the straw is 15.9 MJ / kg. Example 1: KDV conditions with catalyst Catalyst: 30% Tricat Zeolite A4 suspended in the sump phase. Sump phase heavy oil: BP Energol CS 220 (heating value 43.0 MJ / kg, oxygen content 0%)

[0030] Result: 4 condensate phases (from top: Phase 1 = non-biogenic hydrocarbon phase, Phase 2 = light biogenic crude oil phase, Phase 3 = aqueous phase, Phase 4 = heavy biogenic crude oil phase) Mass balance in wt.%, based on the organic dry matter of the straw used: 4% crude oil, 36% aqueous phase, 33% solid residue, 27% gas (difference). Calorific value of the crude oil: 26.4 MJ / kg Example 2: KDV conditions without a catalyst Swamp phase heavy oil: BP Energol CS 220 (calorific value 43.0 MJ / kg, oxygen content 0%)

[0031] Result: 4 condensate phases (from top: Phase 1 = non-biogenic hydrocarbon phase, Phase 2 = light biogenic crude oil phase, Phase 3 = aqueous phase, Phase 4 = heavy biogenic crude oil phase) Mass balance in wt.%, based on the organic dry matter of the straw used: 12% crude oil, 33% aqueous phase, 34% solid residue, 21% gas (difference). Calorific value of the crude oil: 25.9 MJ / kg Example 3 : Inventive conditions (i.e., without a catalyst) Swamp phase heavy oil: Commentz coniferous wood tar with tall oil content (calorific value 38.1 MJ / kg, oxygen content 9%)

[0032] Result: 2 condensate phases (from top: Phase 1 = biogenic crude oil phase, Phase 2 = aqueous phase) Mass balance in wt.%, based on the organic dry matter of the straw used: 38% crude oil, 29% aqueous phase, 12% solid residue, 21% gas (difference). Calorific value of the crude oil: 28.1 MJ / kg Fig. 2 This is shown by a GC-MS analysis of the crude oil.

Claims

1. Method for producing crude oil from biomass by direct liquefaction under atmospheric pressure, involving the following steps: a) introducing dried crushed biomass into a reactor containing heavy oil to form a sump oil phase consisting of biomass and heavy oil; b) maintaining the temperature of the sump oil phase at a predetermined reaction temperature; c) condensing and collecting the volatile reaction products; and d) isolating and collecting the hydrophobic crude oil from the condensed volatile reaction products, characterized in that a stable and self-regenerating heavy oil sump phase is formed so that no new external heavy oil needs to be supplied, the method is carried out under atmospheric pressure and without catalysts, and the heavy oil sump phase has at least 5 wt.-% organically bound oxygen.

2. Method according to claim 1, characterized in that the biomass is continuously introduced into the reactor.

3. Method according to any one of the preceding claims, characterized in that the reaction temperature is in the range from 250 to 550°C.

4. Method according to any one of the preceding claims, characterized in that before introducing the biomass, the reactor is preheated to the reaction temperature.

5. Method according to any one of the preceding claims, characterized in that the heavy oil is wood tar.

6. Method according to any one of claims 1 to 4, characterized in that the heavy oil is wood tar with portions of tall oil.

7. Method according to any one of the preceding claims 1 to 4, characterized in that the heavy oil is softwood tar.

8. Method according to any one of the preceding claims 1 to 4, characterized in that the heavy oil is softwood tar with portions of tall oil.

9. Method according to any one of the preceding claims 1 to 4, characterized in that the heavy oil is hardwood tar.

10. Method according to any one of the preceding claims 1 to 4, wherein the heavy oil is hardwood tar with portions of tall oil.