EP3116830A1 - Salt separator and method for producing a methane-containing gas mixture from biomass by using a salt separator - Google Patents

Abstract

According to the invention, a salt separator (2) for separating salts and/or solid materials from a pumpable aqueous fluid mixture under process conditions, which preferably lie substantially in the range of the critical point for the fluid mixture, is disclosed, wherein the salt separator comprises the following components: a) a reaction zone in the form of a cavity (6) for transforming the pumpable aqueous fluid mixture into a raw mixture for further processing, e.g. a methanation reaction; b) a feed opening (8) for the pumpable aqueous fluid mixture to the cavity (6), wherein the feed opening (8) is realized in a rising pipe (10) that protrudes into the cavity (6); c) a first extraction opening (12) for the raw mixture freed of salts and/or solid materials, wherein the first extraction opening (12) is arranged in the upper region of the cavity (6); and d) a second extraction opening (16) for a brine comprising the salt and/or the solid materials, wherein the second extraction opening (16) is arranged in the lower region of the cavity (6) and is located lower down than the feed opening (8).

Description

The present invention relates to a salt separator and to a method for producing a methane-containing gas mixture from biomass using a salt separator.

By the term "biomass" is meant vegetable or animal material, by way of example wood, manure, manure, straw, grass, algae, sewage sludge and slaughterhouse waste, but the present process is also suitable for other substances with organic contents such as e.g.

Plastic waste, sewage, rubbish, used tires, waste paper, waste oils, organic solvents, fossil biomass (peat,

Coal, petroleum). The salt separator is generally suitable for the separation of salts from aqueous solutions with and without organics. In a study commissioned by the Swiss Federal Office of Energy (SFOE, Switzerland), Wädenswil University, "Scheurer, K .; Baier, U. Biogenic goods in Switzerland. Mass and

Energy flows. University of Wädenswil, commissioned by the SFOE, Program Biomass, Final Report, February 2001 ", points to the large, largely untapped energetic potential of manure The total manure yield (manure + manure) amounted to 2,283 million t DM (dry matter) in 1998/99. which corresponds to an energy content of 37 PJ The fermentation of 4,700 t DM of farmyard fertilizer yielded around 48 TJ of energy in the form of biogas in 1998, which represents only about 0.1% of the total energy potential in the

Represents farmyard manure. The fermentation also produces larger quantities of non-fermentable solid matter. Woody biomass can practically not be fermented. In the following, the term "hydrothermal" refers to an aqueous system under increased pressure and elevated Temperature, typically near or above

critical point of water (374 ° C, 221 bar). Near-critical and supercritical water make an interesting

Reaction medium to perform chemical reactions.

In particular, this medium is suitable for the hydrolysis and the conversion of biomass to liquid and gaseous

Products. Since the transition of a liquid system under pressure to supercritical does not involve a true phase transition

represents no enthalpy of enthalpy for the water contained in the biomass, what in

Unlike gas phase processes (e.g., atmospheric

Gasification of wet biomass). Therefore, hydrothermal processes have the potential for high thermal efficiencies. The most preferred reaction for the conversion of biomass to methane can be exemplified for wood with the following

Stoichiometry can be described:

CHi.520o.64 (s) + 0.3 H ₂ O (g) -> 0.53 CH ₄ (g) + 0.47 C0 ₂ (g) (1)

Under normal conditions (low water partial pressure), the reaction of biomass with water does not or does not proceed completely to Eq. (1), but it arises

By-products such as e.g. Tars or solid carbon (coke). Is it possible to choose the reaction conditions such that

Reaction (1) is complete, a high thermal efficiency can be expected because reaction (1) is slightly exothermic. The theoretical maximum possible efficiency is 95% (based on the lower calorific value H _{u of} the wood). An Applicant's system analysis for a commercial process showed recoverable efficiency in the range of 70-80% for wood. This was detailed in the literature "Vogel, F., and F. Hildebrand, Catalytic Hydrothermal Gasification of Woody Biomass at High Feed

Concentrations. Chem. Eng. Trans. 2, 2002, 771-777 "

described. This is significantly higher than the efficiency of other processes for converting wood to methane. However, the currently known processes for biomass methane production remain summarized with regard to the

achievable efficiencies behind the theoretical

Expectations, so that they can not be used economically at present.

To improve the efficiency of a hydrothermal process for methane production is in the European

Patent Application EP 1 772 202 A1 discloses a process for the production of methane from biomass, which comprises the following process steps:

 a) a biomass pulp is produced from the biomass while setting an optimal dry matter fraction,

 b) the biomass pulp is pressurized,

 c) for liquefying the solid organic constituents of the biomass pulp, the biomass pulp is heated under pressure,

 d) the thus pressurized and heated biomass pulp is further heated to at least the mixture's own critical temperature,

 e) under pressure and elevated temperature will be there

 precipitated solids separated from the fluid phase, and

 f) by means of a catalytic reactor at least a portion of the fluid phase is gasified under pressure and elevated temperature to a methane-rich gas.

In this way, a method has been created which has a very high efficiency, because a large part of the catalytic gasification disturbing substances, in particular salts, can be separated by precipitation under supercritical conditions of the mixture. In this way, for the catalytic gasification, a high yield of methane and a high reaction rate can be achieved with a high service life of the catalyst. Extensive articles in the literature show that the salt deposition in this hydrothermal process a

important for the achievable efficiencies of the overall process and for achievable service life of the

Methanierungskatalysators occurs. Nevertheless, all salt separators known hitherto have the disadvantage that the salt separation is either still not satisfactory or is satisfactory, but increased

thermodynamic or mechanical-constructive expenses are required. Next also make blockages and deposits in such Salzabscheidern a big

In particular, it has been found that the known salt separators do not work well, especially in the supercritical oxidation of water (Super Critical Water Oxidation).

Based on this prior art, the invention is therefore an object of the invention to provide a salt separator and a method for the hydrothermal generation of a methane-containing gas from biomass using a Salzabscheiders, the salt separator should be simple and operate and the process has a particularly high To have efficiency. This task is related to the salt separator

according to the invention by a salt separator for separating salts and / or solids from a pumpable

aqueous fluid mixture under process conditions, preferably substantially in the range of critical

Point for water are dissolved, the salt separator comprising the following components:

 a) a reaction zone in the form of a cavity for

 Transfer of the pumpable aqueous fluid mixture into a crude mixture for subsequent further processing, e.g. a methanation reaction;

 b) a feed opening for the pumpable aqueous

Fluid mixture to the cavity, wherein the Feed opening is realized in a riser, which projects into the cavity;

 c) a first extraction opening for that of salts and / or

 Solids freed crude mixture, the first

 Discharge opening is arranged in the upper region of the cavity; and

 d) a second vent for a salt comprising the salts and / or the solids, wherein the second

 Discharge opening in the lower area of the cavity

 is arranged and lower than the

 Feed opening.

Surprisingly, it is possible with this salt separator, the salts and / or solids contained therein upon entering the pumpable aqueous fluid mixture to deposit with a hitherto unknown efficiency and to remove from the further process stream. suitable

Fluid mixtures are, for example, a pumpable

Biomass porridge, geothermal wastewater, wastewater

Oil wells and generally all types of saline

Process water. For example, it is possible with this design for the salt separator without clogging a mixture of 100 millimolar sodium sulfate and 50 millimolar potassium sulfate, which regularly led to a solid precipitate and thus to a salt accumulation in the previously known salt separators, which can clog the salt separator.

In an advantageous embodiment of the present invention

Invention may be provided that the cavity

Cylindrically shaped and is substantially vertically aligned, the orientation in vertical

Direction is greater than the diameter of the cavity. Thus, the cavity has the shape of a rising column in which the increasingly freed from salt crude mixture rise and can be deducted for subsequent processing. Typically, it is also appropriate if the first Discharge opening is arranged in the region of the highest point of the cavity.

Accordingly, it is equally appropriate if the second

Discharge opening in the region of the lowest point of the cavity is arranged. A deduction of the salt and / or solid brine can then take place laterally, so that the

Supply of the pumpable aqueous fluid mixture can be carried out directly from below vertically into the cavity. In a further expedient embodiment of the present invention can then also be provided that the

Feed opening is located at the cavity-side end of a riser, which projects perpendicularly into the cavity. In this way also results in a sufficiently large spatial

Separation of feed opening and second exhaust opening, which results in a lying above the second exhaust port sump.

In order to be able to comply particularly well with the process conditions, which should be substantially in the range and preferably above the pseudo-critical point for the respective fluid mixture, it may be provided that the

Cavity is designed to be heated. For example, arranged on the walls of the cavity electrical

Resistance heating elements and / or induction heating can be provided. It is also possible to heat the

Outer wall by hot gases, such as Exhaust gases from a furnace or process exhaust gases. Furthermore, it is possible to increase the heating required by adding oxidizing agents in the incoming fluid, e.g. Nitrates, oxygen or

Hydrogen peroxide, reach.

With regard to the method, the above-mentioned object is achieved according to the invention by a method for generating a methane-containing gas mixture from biomass, in which from a pumpable aqueous biomass pulp before

Methanation reaction in a salt separator according to one of claims 1 to 5 configured, salts and / or solids are withdrawn.

Advantageous embodiments of the present invention will be described below with reference to the drawing for

 Salzabscheider and exemplified by him method for the gasification of biomass (such as wood or manure solid) explained in more detail. 1 shows a schematic view of a longitudinal section through a salt separator; and

Figure 2 shows a time course of the specific

 Conductivity of an educt of 10 wt% iso-propanol in water with a salt loading of 0.1 mol / l

 Sodium sulfate and 0.05 mol / 1 potassium sulfate in a salt separator according to Figure 1 at a temperature of 450 ° C and a pressure of 300 bar. Figure 1 shows a schematic view of a longitudinal section through a salt separator 2, as it is for the separation of

Salts and / or solids from an aqueous fluid mixture is used. The crude product freed of salts and / or solids is then subjected to further processing, e.g. a methanation reaction, fed, due to the

eliminated salt and / or solids a high

Selectivity and durability of any used

Catalysts and low corrosion of the process exposed surface can be achieved.

The salt separator 2 is typically one

Stainless steel housing 4 (or other suitable material such as titanium or a nickel alloy) constructed, which encloses a cylindrical cavity 6. The cavity 6 is in this sense a reaction space in which in the aqueous fluid mixture dissolved salts below those in the cavity. 6

prevailing thermodynamic conditions in the Substantially correspond to the critical point for the fluid mixture, can be precipitated. In the lower region of the cavity 6, a feed 8 is provided, through which the aqueous fluid mixture is introduced under high pressure of 200 to 400 bar at a temperature of about 350 to 500 ° C in the cavity 6. In this case, the aqueous fluid mixture exits at elevated position from a riser 10 into the cavity 6. Essentially at the highest position in the cavity 6 is a first discharge opening 12 for a salt and / or solids largely freed crude fluid, which then the actual further processing, such as a

Methanation reaction, to obtain the o.g. Benefits can be supplied. Essentially at its deepest

Position in the cavity 6, a second vent 16 is provided for a salt and / or solids-laden brine, which is thus discharged from the further processing process. To maintain the high temperatures in the cavity 6 arranged on the walls of the cavity heating elements 14 in the form of resistance and / or induction heaters are provided. However, alternatively or additionally, heating of the outer wall by means of hot gases, such as, for example, is also possible. Exhaust gases from a furnace or process exhaust gases. Furthermore, it is possible, the required heating by adding

Oxidizing agents in the incoming fluid, e.g. nitrates,

Oxygen or hydrogen peroxide.

In a completely surprising way, the introduction of the aqueous fluid mixture from below into the salt separator 2, the pleasing result of a substantial deposition of salts and / or solid from the then for

 Further processing provided raw fluid.

FIG. 2 also shows, by way of example, a time profile of the specific conductivity of a reactant of 10% by weight of isopropanol in water with a salt charge of 0.1 mol / l of sodium sulfate and 0.05 mol / l of potassium sulfate in one

Salt separator 2 according to FIG. 1 at a temperature of 450 ° C and a pressure of 300 bar. At this point, deliberately chosen isopropanol, as this well imitates the organics of a liquefied biomass pulp, which plays a role in the deposition of salts. As shown in the figure, the conductivity of the brine increases very rapidly to about 30 mS / cm. At the same time, the conductivity of the

"Clean" crude fluid near zero, indicating complete precipitation of the conductivity-causing sulfates from the crude fluid.

With reference to the already mentioned European patent application EP 1 772 202 A1, the process for producing methane should also be briefly described again:

The biomass is in a 1st process step

 conditioned, i. comminuted and brought to the desired dry matter content (TM), preferably by wet grinding. This creates a pumpable slurry. To improve pumpability, other additives (e.g., starch, waste oils) may be added to the biomass. The desired dry matter content is 5 to 80

 Mass percent, preferably about 15 to 40 mass percent. The method works particularly economically when the dry organic content is about 20 mass% or more.

The conditioned biomass pulp is in a 2.

 Process step brought to high pressure (200-400 bar) and conveyed continuously or intermittently. When

 Delivery units are particularly suitable extruder,

 High-pressure eccentric screw pumps, piston diaphragm pumps, and solids pumps.

In a third process step, the biomass pulp is heated under pressure to 200-350 ° C. The solid organic biomass components largely liquefy. For better heating and liquefaction this can Process stage static mixing elements and / or a

Catalyst (e.g., zinc oxide).

In a 4th process step, the pressurized, heated and liquefied biomass pulp in the

Salt separator 2 quickly to an even higher

Temperature level brought, preferably in the range or above the critical temperature of the respective mixture. As a guide here serves the critical temperature of water at 374 ° C and 221 bar. This can be achieved by external heat input (e.g., by a burner / catalytic

Burner fed with recycle product gas) or by adding suitable oxidants (e.g., oxygen, air, hydrogen peroxide, ammonium and other nitrates) directly to the 4th process stage (or any of the preceding process stages 1-3). As a result, most salts and residual solids precipitate and can be collected. The collected precipitates are continuously or periodically discharged through the second vent 16 from the process. The

Separating and recovering solids as salts prior to the catalytic gasification reactor under hydrothermal conditions, as well as the possible addition of salt-like oxidants (nitrates, e.g., ammonium nitrate) for partial oxidation of the biomass under hydrothermal conditions, improve performance and substantially increase the efficiency of the process. The deducted

Solids are due to the nature of

Starting materials very rich in nitrogen, phosphorus and potassium salts and are therefore ideal for

Further use as fertilizer, for example for the

Agriculture or for the cultivation of algae.

In a 5th process step the hot one arrives

Biomass stream (the hot raw fluid), now freed from most solids, in a fed with a suitable catalyst reactor where the gasification to Methane, carbon dioxide, hydrogen and traces of

 Carbon monoxide and higher hydrocarbons (ethane, propane) takes place. The catalyst preferably comprises ruthenium and may also have nickel (for example Raney® nickel) as well as furthermore also fractions of chromium and / or copper. Other catalysts based on Ni, Re, or Rh as the active metal are

 also usable. The reactor is preferably used as a fluidized bed reactor, as a monolith reactor or as

 Wall reactor (with catalyst coated tube or tube bundle) designed. But it could also be used pipes in which catalytically coated sheets are used.

In a sixth process step, the methane-rich

Product stream then fed to its further use. This process step can also be used to separate methane from CO ₂ and the remaining gas components. Thus, the product stream can also be cooled to about 50 ° C and the gas phase can be separated under pressure from the liquid phase. In a suitable apparatus (eg

 Washing column, membrane separation, adsorber), the methane can be separated from the other components from the gas phase and is then available under high pressure (about 200 to 400 bar). This is no longer necessary

 Compression step to the methane in gas cylinders

 as fuel at an LPG filling station

 to offer or to feed into the natural gas network. It is also conceivable, the compressed gas directly as

 To use fuel in a gas turbine process.

According to this, the provision of methane from biomass provides, inter alia, for natural gas filling stations and / or for the

Injection into the natural gas network, for bottling, or use as fuel in gas turbines suitable pressure a strong economic exploitation. Although the description of a method for the production of methane from biomass is in the foreground here, the salt separator according to the invention can also be used in

Process for the purification of other aqueous

Fluid mixtures are used. Suitable fluid mixtures here are, for example, a pumpable biomass pulp, geothermal wastewater, wastewater from oil wells and generally all types of saline process waters, with and without organic matter.

Claims

claims A salt separator (2) for separating salts and / or solids from a pumpable aqueous fluid mixture under process conditions which are preferably substantially in the range of the critical point for the fluid mixture, comprising:  a) a reaction zone in the form of a cavity (6) for transferring the pumpable aqueous fluid mixture into a raw mixture for further processing, e.g. a methanation reaction;  b) a feed opening (8) for the pumpable  aqueous fluid mixture to the cavity (6), wherein the feed opening (8) in a riser (10) is realized, which projects into the cavity (6); c) a first extraction opening (12) for that of salts  and / or solids freed raw mixture, wherein the first exhaust port (12) in the upper region of the cavity (6) is arranged; and  d) a second vent (16) for one of the salts  and / or sols comprising the solids, wherein the second extraction opening (16) is arranged in the lower region of the cavity (6) and lies lower than the feed opening (8). 2. salt separator (2) according to claim 1, characterized in that the cavity (6) is cylindrical and is substantially vertically orientable, the orientation in vertical direction greater than the diameter of the Cavity (6) is. 3. salt separator (2) according to claim 1 or 2, characterized in that the first exhaust opening (12) is arranged in the region of the highest point of the cavity (6). 4. salt separator (2) according to one of claims 1 to 3, characterized in that the second outlet opening (16) is arranged in the region of the lowest point of the cavity (6). 5. salt separator (2) according to one of the preceding Claims, characterized in that the feed opening (8) is located at the cavity-side end of a riser pipe (10) which projects perpendicularly into the cavity (6). 6. salt separator (2) according to one of the preceding claims, characterized in that the cavity is heated by means of heating elements. 7. Method for generating a methane-containing Gas mixture from biomass, in which salts and / or solids are taken off from a pumpable aqueous biomass pulp before the methanation reaction in a salt separator (2) according to one of claims 1 to 6.