Robert’s valves added much finer control to gas flow and became a standard
component in high pressure chemistry
26
—at the time being widely known
throughout Germany as simply ‘Le Rossignol’ valves. Even as late as 1963 for
example, a British textbook of preparative inorganic chemistry confidently
declared that ‘the usual Le Rossignol’ valves can be used for fine control …’.
27
Today needle valves are ubiquitous, and many different designs are available
tolerating pressures of many thousands of atmospheres. As for Kirchenbauer,
‘his’
15 joints addressed the very serious engineering problem of working
continuously with gas at high pressure without leakage. This was achieved by
carefully turned screw joints with a male conical portion of 16° angle screwing
into a female portion of 20° angle, and together with a conical copper gasket,
perfectly gas tight connections were made.
28
‘Kirchenbauer’s’ joints were
widely used and frequently adapted, but subsequent literature often referred
to them as ‘Haber-Le Rossignol’ joints.
In addition to the problems of pressure and circulation, two other technical
aspects of the circulation apparatus exercised the ingenuity of the men, viz.,
the efficient utilisation of the exothermic nature of the reaction, and the
removal of ammonia. The (standard heat of) formation of ammonia from its
elements releases 46.2 kJ mol
−1 , a ‘gift’ which simply had to be adopted into
the process to minimise the thermal work done. Some sort of heat-exchanger
—later called the ‘heat regenerator’—had to be devised by means of which
fresh incoming gases were pre-heated by the exhaust gases before being raised
to operational temperature by the internal heating element. Cooling of the
exhaust in this way also displaced the equilibrium in favour of ammonia and
so with an efficient heat exchanger a ‘win win’ situation arose. This meant
that in the circulation machine, the ‘furnace’ holding the ‘contact substance’
had to be modified to accommodate the heat exchanger; a bundle of 127 steel
capillaries wound with iron wire and supported at either end by perforated
hexagonal plates, the capillaries passing through the perforations. Such a
device provided a huge surface area, the incoming gases passing around the
tubes carrying the exhaust gas and through the interstices achieving
remarkable heat transfer. No photographs of this original device exist but
precisely the same Le Rossignol model was used by the BASF for the
industrialisation of the synthesis, and the photograph in Fig. 8.3 shows one
such heat exchanger—damaged by ‘hydrogen attack’
29
—but displaying the
essential features of the design.
The final development in the evolution of the circulation apparatus was
stimulated by the discovery of a ‘spectacularly’ effective catalyst—probably
uranium—dispersed on an asbestos medium, (Sect. 8.5) capable of increasing
yields by as much as a factor of 20.
7 Prior to this, at low levels of conversion,
166
D. Sheppard
component in high pressure chemistry
26
—at the time being widely known
throughout Germany as simply ‘Le Rossignol’ valves. Even as late as 1963 for
example, a British textbook of preparative inorganic chemistry confidently
declared that ‘the usual Le Rossignol’ valves can be used for fine control …’.
27
Today needle valves are ubiquitous, and many different designs are available
tolerating pressures of many thousands of atmospheres. As for Kirchenbauer,
‘his’
15 joints addressed the very serious engineering problem of working
continuously with gas at high pressure without leakage. This was achieved by
carefully turned screw joints with a male conical portion of 16° angle screwing
into a female portion of 20° angle, and together with a conical copper gasket,
perfectly gas tight connections were made.
28
‘Kirchenbauer’s’ joints were
widely used and frequently adapted, but subsequent literature often referred
to them as ‘Haber-Le Rossignol’ joints.
In addition to the problems of pressure and circulation, two other technical
aspects of the circulation apparatus exercised the ingenuity of the men, viz.,
the efficient utilisation of the exothermic nature of the reaction, and the
removal of ammonia. The (standard heat of) formation of ammonia from its
elements releases 46.2 kJ mol
−1 , a ‘gift’ which simply had to be adopted into
the process to minimise the thermal work done. Some sort of heat-exchanger
—later called the ‘heat regenerator’—had to be devised by means of which
fresh incoming gases were pre-heated by the exhaust gases before being raised
to operational temperature by the internal heating element. Cooling of the
exhaust in this way also displaced the equilibrium in favour of ammonia and
so with an efficient heat exchanger a ‘win win’ situation arose. This meant
that in the circulation machine, the ‘furnace’ holding the ‘contact substance’
had to be modified to accommodate the heat exchanger; a bundle of 127 steel
capillaries wound with iron wire and supported at either end by perforated
hexagonal plates, the capillaries passing through the perforations. Such a
device provided a huge surface area, the incoming gases passing around the
tubes carrying the exhaust gas and through the interstices achieving
remarkable heat transfer. No photographs of this original device exist but
precisely the same Le Rossignol model was used by the BASF for the
industrialisation of the synthesis, and the photograph in Fig. 8.3 shows one
such heat exchanger—damaged by ‘hydrogen attack’
29
—but displaying the
essential features of the design.
The final development in the evolution of the circulation apparatus was
stimulated by the discovery of a ‘spectacularly’ effective catalyst—probably
uranium—dispersed on an asbestos medium, (Sect. 8.5) capable of increasing
yields by as much as a factor of 20.
7 Prior to this, at low levels of conversion,
166
D. Sheppard