Large-Scale Methamphetamine Manufacture

3.4 Primary reaction vessel construction

The design of one's primary reduction vessel should be tailored to the batch sizes and the quality of agitation one desires.
This writer constructed an adequate reaction vessel using a section of 8" stainless-steel pipe found at the scrapyard along with some stainless plate and threaded fittings (see pix).

In addition, a rocker was constructed using common steel plate, a gearmotor, and some pulleys purchased at the hardware store. A cyclic rate of 100 RPM was chosen arbitrarily (I guessed) and provision made in the design to allow one to swap pulleys and change the cyclic rate. A throw(rock) of 3" was determined to be the most one could expect given the motor torque (32 in-lb) and the weight of the vessel when fully charged (about 10lb). The motor used is a gearmotor from a scrapped copier which one can readily find at electronics surplus houses along with the required capacitor for less than $100. A new gearmotor of the proper size will cost 4-5 times that much. These are very useful, reliable motors that this writer uses for many purposes. Try to find ones with a machined face so they can be quickly mounted to brackets, etc. The resulting rocker provides a rocking rate of 110 rpm and completes a reaction in six hours.
Our stainless reaction vessel has an internal capacity of 7000ml, of which only 3500ml is used when fully charged with a 6.5-mole batch. This batch size was selected because of equipment and time restrictions-one can squeeze a 3500ml reaction into a 5000ml round-bottom flask for solvent stripping and the resulting 900g of methamphetamine base divides conveniently into two 450g portions for crystallization, which will take about 4 hours to perform. This is a full day's work for one person, resulting in 2lb of product.
An improved reaction vessel can be constructed using a paint shaker for optimum surface-area creation. These units hold one-gallon paint cans, which, when full of paint, weigh much more than our reaction solution, eliminating concerns about exceeding any weight limitations on the machine. One may have a reaction vessel made which will fit into the machine clamps and have the following properties; 1) it will be constructed of thin-wall 316 stainless steel and stand up to 100psi when sealed and will not collapse when a 29"Hg vacuum is pulled (this means a round body and thick ends), 2) it will have a threaded opening about 1.5-2" at one end to pour stuff into, and, 3) it will have an internal volume of at least 4000ml. The best way to do this is to have a machine shop roll a sheet of 0.065in 316 stainless sheet into a cylinder and then weld the seam. End pieces are cut from 0.375in 316 stainless and tig-welded to our thin-wall pipe. Prior to welding to the cylinder body, one end-piece is drilled out and a 1.5" stainless coupling with NPT thread is welded on. The unit is then pressure tested to 100psi and vacuum tested to 29"Hg. The threaded coupling is fitted with a bushing that allows a gas fitting to be attached. Use Teflon tape to seal all threads, including the gas fittings. Leaks must be avoided. This one gallon (4liters) vessel can hold 3500ml of reactants with ease, resulting in the same product volumes as one obtains using the rocker. The improvement comes in the vigorous agitation provided by the paint shaker; by making sure that the hydrogen inlet hose rises straight up from the vessel to avoid losing reactants into the hose, the reaction will reach completion in 3 hours instead of 6 using the same catalyst density of 1g/mole. Using very little ingenuity, one can obtain a paint shaker that holds 5-gallon pails and construct a reaction vessel which will do 30-mole batches in a few hours, resulting in about 10lb of finished product after processing. The batch can be processed in 22- liter glassware by reducing the ethanol volume slightly, but will require a high-volume vacuum source to do the distillation. The main drawback to doing huge batches is that if one makes a mistake, he has just blown a whole lot of very valuable precursor material. The prudent chemist does not bite off more than he can chew up in one day.