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  • Glycerol / glycerine / byproduct pre wash

    I read somewhere recently on this forum about someone doing a glycerine pre wash on their oil before doing the full reaction. I tried to find the thread again but couldn't easily locate it.

    In typical fashion, I just thought I'd give it a go at the spur of the moment and see what happened.

    I heated up the oil to about 40C, turned on my mixer and added about 15% of the oil volume (180L) of room temp glyc and mixed for about 30 min.

    I drained it off about 24 hrs later as I ran out of time to do the proper reaction that I had intended to do on the same day while the oil was still hot. It was noticeably thicker and darker than when it went in.

    That was several days ago now and I just titrated the oil tonight and it came in at 0.5. Normally this oil titrates at about 2 - 3, which seems amazing on face-value. But then I thought about it and it will only seemingly save about 300g of KOH in this instance.

    So is that the reason most people don't bother with it? Extra time and messing around and that it will only save (in this case) 300g of KOH? And in my case, wasted more electricity as now I need to heat the oil up for a second time which can use up to 4 kWh of electricity to go from 15C - 50C.
    3DB
    1995 Holden (Isuzu) Rodeo 2.8TD 4X4 - B100 since April 2013
    1976 Mercedes 300D Turbo 'The Coal Grenade' - B100 since May 2016 - SOLD
    1994 Peugeot 405 SRDT 1.9L intercooled turbo diesel (Shitbox Rally car.) - B100 since August 2019 - SOLD
    @thirddegreeburns on Instagram
    @thirddegreeburns2019 on Facebook


  • #2
    Re: Glycerol / glycerine / byproduct pre wash

    Hi 3DB,

    Originally posted by 3DB View Post
    So is that the reason most people don't bother with it? Extra time and messing around and that it will only save (in this case) 300g of KOH? And in my case, wasted more electricity as now I need to heat the oil up for a second time which can use up to 4 kWh of electricity to go from 15C - 50C.
    There is also some methanol in the glycerine used in the pre-wash that will be used along with the KOH.
    Because the pre-wash is effectively the first stage of a multi stage reaction, besides using some of the methanol and KOH remaining in the glycerine you can get by adding less total methanol.
    However, as you have noted, many people may find the the small savings in methanol and KOH cost is offset by the increased time and heating required to perform the multistage procedure
    That is certainly the reason I do not bother doing a glycerine pre-wash.
    tillyfromparadise
    Senior Member
    Last edited by tillyfromparadise; 22 May 2017, 11:33 PM.

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    • #3
      Re: Glycerol / glycerine / byproduct pre wash

      Most people here in the UK do bother doing it. During warmer months I actually now do the glyc wash outside at ambient temperature in the IBC where the oil is stored. I just connect up a pump to circulate and away we go. The glycerol is slower to drop doing it at a lower temperature, but it still does drop. If I need to remix the contents without drawing off any glycerol then using an airline connected to the bottom tap to mix is just as good as using the pump.

      This way the oil is ready to use when you want it, also the oil may have been washed more than once. I did a 10/90 warnqvist test on my oil the other day which showed 7.5mls of dropout.

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      • #4
        Re: Glycerol / glycerine / byproduct pre wash

        Hi smithey,

        Originally posted by smithy View Post
        Most people here in the UK do bother doing it.
        I am curious how you have determined that most of the people in the UK who make biodiesel use the glycerine pre-wash procedure

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        • #5
          Re: Glycerol / glycerine / byproduct pre wash

          Simply because of the proportional numbers that mention it on the UK Forums.

          Comment


          • #6
            Re: Glycerol / glycerine / byproduct pre wash

            Thanks, Tilly & Smithy.

            I can definitely see the benefits, but there is just that tradeoff on time and electricity.

            I'm also more inclined to do it at ambient temperature too, although that would put a lot of strain on my 1.5 kW paddle mixer motor here in winter.

            Just to confirm: now that I have reduced my titration number from, say, 3 to 0.5, my total addition of KOH will now be (7 + 0.5) = 7.5 g/L rather than (7 + 3) = 10 g/L?
            3DB
            1995 Holden (Isuzu) Rodeo 2.8TD 4X4 - B100 since April 2013
            1976 Mercedes 300D Turbo 'The Coal Grenade' - B100 since May 2016 - SOLD
            1994 Peugeot 405 SRDT 1.9L intercooled turbo diesel (Shitbox Rally car.) - B100 since August 2019 - SOLD
            @thirddegreeburns on Instagram
            @thirddegreeburns2019 on Facebook

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            • #7
              Re: Glycerol / glycerine / byproduct pre wash

              Hi 3DB

              Originally posted by 3DB View Post
              Just to confirm: now that I have reduced my titration number from, say, 3 to 0.5, my total addition of KOH will now be (7 + 0.5) = 7.5 g/L rather than (7 + 3) = 10 g/L?
              That is correct

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              • #8
                Re: Glycerol / glycerine / byproduct pre wash

                Hi Smithy,

                Originally posted by smithy View Post
                Simply because of the proportional numbers that mention it on the UK Forums.
                The problem with using that as a yardstick of what most people in the UK do is that it does not take into account the thousands of people in the UK who make biodiesel who do not participate on biodiesel discussion forums and have never heard of the glycerine pre-wash procedure.

                I recall one fellow on the UK forum who is a major proponent of the pre-wash procedure saying that he collected glycerine for his pre-wash from other biodiesel producers who do not use the pre-wash procedure.

                A more accurate statement might be that on the UK discussion forum were you participate there are several dozen active members and most of them use the glycerine pre-wash procedure.
                tillyfromparadise
                Senior Member
                Last edited by tillyfromparadise; 23 May 2017, 11:46 AM.

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                • #9
                  Re: Glycerol / glycerine / byproduct pre wash

                  I also forgot to ask how much I can reduce my methanol input by, if at all. Normally I would use 20% methanol x 180 L of oil = 36L
                  3DB
                  1995 Holden (Isuzu) Rodeo 2.8TD 4X4 - B100 since April 2013
                  1976 Mercedes 300D Turbo 'The Coal Grenade' - B100 since May 2016 - SOLD
                  1994 Peugeot 405 SRDT 1.9L intercooled turbo diesel (Shitbox Rally car.) - B100 since August 2019 - SOLD
                  @thirddegreeburns on Instagram
                  @thirddegreeburns2019 on Facebook

                  Comment


                  • #10
                    Re: Glycerol / glycerine / byproduct pre wash

                    Hi 3DB,

                    Originally posted by 3DB View Post
                    I also forgot to ask how much I can reduce my methanol input by, if at all. Normally I would use 20% methanol x 180 L of oil = 36L
                    Multi stage procedures use less total methanol to achieve the same results as a single stage procedure.
                    Some of the unknown amount of methanol in the Glycerol pre-wash will count towards the total amount of methanol used in the reaction.
                    There is a procedure that uses the 3/27 test to help determine the amount of methanol to use in the second stage reaction however I can not put my finger on the procedure at the moment

                    I am sure Smithy will be able to help you

                    Comment


                    • #11
                      Re: Glycerol / glycerine / byproduct pre wash

                      I always do a prewash, I also think that it removes any moisture in the oil.

                      Comment


                      • #12
                        Re: Glycerol / glycerine / byproduct pre wash

                        Originally posted by smithw View Post
                        I always do a prewash, I also think that it removes any moisture in the oil.
                        From tests I have done over the years on my well settled oil the glycerol pre treatment reduces the water content from around 850ppm to 350ppm.

                        3DB, I would initially try to reduce your methanol from 20% to 16%.

                        I keep my oil in a 600 litre IBC. if I need to add more oil and have no fresh glycerol to mix it with I re-mix the contents of the tank with the fresh oil and glycerol that was already in there (usually 100 litres) If I have fresh glycerol or oil I then re-mix, having run some or all of the oid glycerol out first.

                        As long as the contents are left a few days to settle, the oil is always 'ready to go' and not only shows alkaline properties (so it cannot be titrated) but also a considerable degree of conversion. At the moment I am fully converting a batch using around 11 to 12% methanol. So the savings can be considerable with a minimum cost of electricity if doing the mixing at ambient temps with a compressor.

                        Comment


                        • #13
                          Re: Glycerol / glycerine / byproduct pre wash

                          I always pre wash mine with the Glycerine - i add 40L from the previous batch to 200L of oil.

                          I do the heat up phase from 5AM on our lowest tarriff for two hours so the oil gets to about 40C, add the glycerine and let is settle for 12 hours - drain it off that evening and then do the full processing the next day - it adds a day to the process and about 50cents to the cost of a 200L batch.

                          I use KOH and estimate it saves me about 500g for a batch and using a two stage process i get away with about 15% methanol (first stage 10%) 2nd stage 5%

                          Craig
                          Holden Suburban K2500 1998 6.5L Turbo GM engine
                          210,000KMs (90,000 on new crate motor)

                          Currently 2 tanks in and working - 90 litre BIO tank and main tank of 160L WVO

                          30 plate FPHE in Engine bay and Helton Dual coil in rear
                          Walbro FRB-5 pusher pumps x 2

                          50,000KM on Veg and 10,000Km on B100

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                          • #14
                            Re: Glycerol / glycerine / byproduct pre wash

                            To put this into a bit more perspective,
                            The 2 stage procedure that Neutral developed uses 16.3% methanol- 163ml methanol per litre of oil reacted to pass Warnqvest.
                            This is without a glycerine pre-wash as the first stage and assuming the titration is not terribly high.
                            http://www.biofuelsforum.com/threads...hlight=neutral

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                            • #15
                              Re: Glycerol / glycerine / byproduct pre wash

                              Hi smithy,

                              Originally posted by smithy View Post
                              if I need to add more oil and have no fresh glycerol to mix it with
                              I am not sure what you mean by "fresh glycerol" Where does the fresh glycerol come from.




                              At the moment I am fully converting a batch using around 11 to 12% methanol.
                              Do you mean that after doing the pre-wash and remove the glycerol used in the pre-wash you only need to add a further 11%- 12% methanol to the reaction to pass the 3-27 test.

                              I see that craigcurtain does a total of three stages, the pre- wash and two further stages and uses a total of about 15% methanol additional to the methanol contined in the glycerol pre-wash
                              I am curious about the procedure you use after draining the glycerol pre-wash that uses a total of 11%- 12% methanol additional to the methanol contained in the glycerine pre-wash




                              So the savings can be considerable with a minimum cost of electricity if doing the mixing at ambient temps with a compressor.
                              Compressors are not cheap to run- it is the compressor that makes refrigerators so expensive to operate.
                              tillyfromparadise
                              Senior Member
                              Last edited by tillyfromparadise; 24 May 2017, 09:45 AM.

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