DE102006002848A1 - Preparing fatty acid methyl ester, useful as biodiesel, comprises transferring unavoidable small batch of remains from fryers to polyethylene container through a filter and reducing the acid number of the batch by its alkality - Google Patents

Abstract

The production of fatty acid methyl esters from waste oils and oils by means of Biodiesel Kleininst plant for use as fuel has compared to the biodiesel process on some special features.
To use used fats and oils, one must interrupt the autocatalytic lipolysis due to thermal preloading when collecting and storing the raw materials, in order to minimize soap rod losses as well as to achieve good separation performances between glycerine and biodiesel phase.
This patent discusses variants of grease pretreatment as well as separation and washing technologies.

Description

It is known that vegetable fat methyl ester can be both acid-catalyzed by reaction of vegetable oils with methanol and catalyzed basic (B. Gutsche: technology of methyl ester production fat / lipid 1997, 418-427). Specifically, a pressureless, continuous process is used for combined acid and base transesterification by Connemann et. al. described ( DE 102 437 00 A1 ).

Known is also that in the alkaline catalyzed reaction, the content of free fatty acids an acid number SZ ≤ 2 do not exceed should, once to keep the soap losses low, to another to the separation behavior between biodiesel and glycerol phase not to worsen. Precisely this latter criterion is for the apparative Construction of Biodiesel Kleininstanlagen an essential procedural or economic factor.

Conversely, it is also known that deoxygenated oils can be prepared without adequate washing step alone by a good separation between biodiesel and glycerol phase by appropriate separators methyl ester of sufficient quality ( DE 103 10 203.5 ).

In Considering the shortage of markets for olive, Rapeseed, soybean, sunflower or cottonseed oil raises the question other sources of raw material, e.g. chemical and energetic use solid fats, frying oils or frying fat from the food sector. They are first as To regard high-quality raw materials, their storage after thermal alone Pretreatment leads in a relatively short time to increase the acid number and thus to quality losses and an elevated one Processing costs.

If these losses are to be minimized, it is necessary to stabilize the partial batches to be collected or a corresponding collection logistics (Table 1). Table 1: Strategy for collecting and processing secondary fats and oils

• a: bei 152 ml CH₃OH/kg Rohöl b: bei 200 ml CH₃OH/kg Rohöl

According to the invention, solid fats, such as white fat, bone fat, etc., can be stabilized from the fat melt by cooling the fat or oil to ≦ 60 ° C. in 1 m ³ containers and then adding catalyst-methanol mixture corresponding to the acid number of the oil. An immediate partial transesterification takes place by about 80% and a stopping of the acid catalytic fatty acid formation (Table 2). Table 2: Transesterification degrees in the pre-esterification in the cold state (20 ≤ T _U ≤ 30 ° C)

• a: at 152 ml CH ₃ OH / kg crude b: at 200 ml CH ₃ OH / kg crude oil

Leave with liquid frying oils Stabilize by 2 different processes.

If no ex-free zone can be defined for pre-esterification, a stabilizer consisting of a mixture of Ca (OH) ₂ and CaO is installed in a 1 m ³ PE sump. When pouring over the stabilizer both H ₂ O and H ₃ O ⁺ ions are eliminated. A 250 μm sieve prevents the ingress of solid residues.

Let yourself on the other hand an ex - protected room for collection and storage, may be the above catalyst-methanol mixture also in portions to frying oil be added.

The actual and complete Transesterification takes place in a biodiesel plant.

The embodiment of the invention is illustrated in 3 drawings ( 1 - three ) and will be described in more detail below.

The biodiesel plant ( 1 + 2 ) consists of a known static mixer (microreactor MR) with pumps (D1, D2), a post reactor (NR) for generating turbulent flows and a separator, as in three shown.

in the Show individual

1 Scheme of biodiesel production variant A,

2 Scheme of biodiesel production variant B,

three Separator principle for the separation of biodiesel and glycerol phase

The oil is supplied via the Connection (E 1), the methanol feed at the connection (E 2) and the water supply at the connection (W). The Product removal takes place at the connections (A) and (A1) for glycerol, for biodiesel / wash water (W1) or (W2) and for Biodiesel (BD) or for Washing water (A2).

mit t ≥ ta (2)

Volumenstrom,
d Durchmesser des Rohres,

Strömungsgeschwindigkeit,
t,t_A Verweilzeit und kinetisch notwendige Reaktionszeit für C_Öl → 0 The secondary reactor (NR) can be regarded as a tube of almost any length and diameter to be dimensioned, which has to realize a desired volume flow rate dV / dt (throughput). It results once from the preselected flow velocity v 0 the metering pump and is subject to the second kinetic restriction (reaction 2nd order), the t ≥ t _{a of} the necessary residence time for complete conversion of the oil must be met:

with t ≥ t a (2)

Volume flow,
d diameter of the pipe,

Flow velocity,
t, t _A retention time and kinetically necessary reaction time for C _oil → 0

mit
C_Bio, C_Gl, C_öl, C_MeOH Konzentrationen von Biodiesel, Glycerin, Öl und Methanol
K_c Gleichgewichtskonstante.To increase the volume flow so the diameter d or the tube length s can be increased. A third possibility consists in the reduction of t _A by increasing the methanol excess according to Eq. 3:

With
C _Bio , C _Gl , C _Oil , C _MeOH concentrations of Biodiesel, Glycerin, Oil and Methanol
K _c equilibrium constant.

It should be noted, however, that excessively high methanol excesses can not be achieved in practical operation since the excess methanol then collects in the glycerol phase and, ideally, the density difference required for separation ρ _Gl = 1.26 g / cm ³ and ρ _Biod. ≦ 0.9 g / cm ³ deteriorates to the disadvantage of separation. Ultimately, only methanol surpluses are favorable in practical operation with continuous driving, the glycerol phases with a density of ρ _Gl ≥ 1.1 g / cm ³ or density differences of both phases of about 1.2 result.

Of the Separator consists of a continuously flowing calming zone Gravity induced separation of glycerine and biodiesel phase. The separation efficiency (separation quality) must in continuous operation the preselected in the secondary reactor volume flow correspond.

Of the Sedimentation pot is with different flow baffles as Koagulationshilfsmittel stocked. They consist of known metal gazes. They will both arranged vertically as well as horizontally.

Surprisingly, it now achieves a particularly good separation effect, if the in three selected geometric arrangement of the release aids selects.

First, the mixture flows (RGM) through the gauze of the vertically installed in the separator tube and one achieves a pre-coagulation of the glycerol phase. Under light Pressure but the glycerol phase still passes through the pores. This Phase mixture then meets the almost horizontally placed Metallgittergazen. This Part works without pressure. The glycerol agglomerates wet easily inclined surfaces, but no longer pass through the pores. A glycerol film is formed, which in turn facilitates easier separation of other glycerol molecules. Due to the slight inclination of the metal gauze, the glycerine film rolls to the side and collects at the bottom of the vessel (GLY). The biodiesel phase is taken from the output (BD).

The separation quality was based on biodiesel material with an acid number content of 0.2 ≤ SZ ≤ 2 without pre-esterification stage tested. One recognizes from the received values that already at unwashed biodiesel phases reached potassium contents of about 10 ppm become.

• • Verzicht auf Reinigung,
• • Wäsche nach Verfahren A und
• • Wäsche nach Verfahren B.

Tabelle 3: Aufarbeitungsstrategien für Transmethylierungsprodukte

• 1) mit ICP – OES Fa. Varian bestimmt

The following strategies can be selected for the processing of the crude methylates:

• • refrain from cleaning,
• • Wash according to procedures A and
• • Laundry according to method B.

Table 3: Reaction strategies for transmethylation products

• 1) with ICP - OES Fa. Varian

The separation quality at the separator between glycerol and methyl ester phase is so high that, for example, residual methanol contents of around 0.5% in biodiesel and potassium contents of around 10 ppm are achieved. For a subsequent chemical utilization of methyl esters can therefore be dispensed with a washing stage. For energy use in vehicles, E-DIN 51606 prescribes an alkali content of Σ K, Na ≤ 5 ppm. However, they can not be reached by washing with drinking water, since the Na contents of the drinking water are significantly higher (Table 3 last and penultimate line). Washing with distilled water seems the only alternative, but uneconomic for micro-systems. The washes discussed below are based on the addition of 20 ml of H ₂ O (dist.) To 1 l of methyl ester. In the washing according to method A ( 1 ) works in quasi batch mode (10 'stirring, 1 h settling). In method B ( 2 ) a device unit of the same type as for separating glycerine and biodiesel phase is also used for washing or for separating washing water phase and biodiesel. Advantage of the latter method is that the overall unit consists of identical segments, the entire system also runs fully continuously. The quality of washing is about the same in both units (Table 3).

Experimental Procedure

Preparation of fatty acid methyl esters from old fats and oils using a biodiesel system

• A pre-esterification with an acid number of SZ = 2 and a temperature of approx. 20 ° C. 850 kg of cooking fat (duck fat) are poured over with a potassium methoxide solution consisting of 7.9 kg of KOH 220 l of methanol and stirred with a compressed air driven stirrer 5 '. The degree of transesterification is about 60% after 10 '. An acid number is undetectable.
• B Stabilization of frying fat with an acid number of SZ = 1.6 is achieved by passing through a 250 μm sieve into an initially introduced mixture of Ca (OH) ₂ and CaO as sediment in a 1 m ³ PE vessel. The acid number stabilizes at SZ = 0.3
• C transesterification
• Untreated deep frying oil with the acid number SZ = 1.6 is transesterified with methanolate solution. 154 g of CH ₃ OH are used per kg of crude oil. The content of KOH is 10 g KOH / kg frying oil. The degree of transesterification is 98%. The flow rate is 7-30 m / s.
• D laundry according to method A
• The product according to method C is mixed with 20 ml of H ₂ O (dist.) Per liter of methylate, stirred for 5 'and then allowed to settle. The washing results are shown in Table 3.
• E laundry according to method B
• Products According to Process C are mixed with 20 ml H ₂ O (dest.) Washed per I methylate. The flow rate is 6.14 kg / h. The washing results are shown in Table 3.

Claims (7)

Production of fatty acid methyl esters from waste fats, characterized in that kleinchargiger forced attack of fryers in 1 m ³ - PE - can be passed through a special filter which retains coarse particles and H ₂ O and reduced by its alkalinity, the acid number of the batch and keeps constant; Production of fatty acid methyl ester from waste fats characterized in that or in solid native fats, such as e.g. Brown fat, white fat or bone fat cooled these fat batches to 60 ° C and with a methanolic solution be pre-esterified in situ by potassium methoxide; Production of fatty acid methyl ester from waste fats characterized in that after each frit change the oil batches Be added portionwise with the methanolic potassium methoxide, that is, a portionwise pre-esterification is made; Production of fatty acid methyl esters from waste fats, characterized in that according to claim 2 to 3 partially esterified oil and grease batches in a continuous transesterification plant accordingly 1 subjected to a second complete transesterification; Production of fatty acid methyl esters from waste fats characterized in that the separation quality between biodiesel and glycerol phase of the continuous plant by a special geometric arrangement of metal gazes in the separator accordingly 2 is reached, wherein the density difference in the phases to be separated: glycerol phase / biodiesel phase should not be less than 1.2. Production of fatty acid methyl ester from waste fats characterized in that the reaction and washing stages of identical Apparatus units exist, Production of fatty acid methyl ester from waste fats characterized in that the arrangement according to claim 4 for transesterification any oils and fats is suitable, at acid number to SZ ≤ 2 without pre-esterification stage