Waste heat power generation from ammonia synthesis

1. Although ammonia plants generate a large amount of waste heat, its quality is generally low; very few ammonia plants use this waste heat solely for power generation. 2. If the waste heat recovery boiler used for blowing air generates a large amount of steam with a high quality, it is possible to consider installing a turbine to generate electricity; however, the amount of electricity produced is limited – 3000 kVA would be considered a good output. 3. The following are the parameters for Hangqi engines: For the Hangqi C12-3.43/0.49 turbine, the consumption rates are as follows: when the steam inlet pressure is 3.43 Mpa, the exhaust steam pressure is 0.49 Mpa; the fuel consumption is 7.7 kg/Kwh, while the condensate consumption is 4.58 kg/Kwh. The power generation amount can be calculated. 4. Recently, a combined heat, work, and electricity generation technology has been proposed, in which a steam turbine is connected in series between an electric motor and machinery to drive the machinery. The most important aspect to consider in this regard is the utilization of the residual pressure when steam is generated and depressurized. 5. Ammonia synthesis plants that consume a large amount of steam throughout the plant and still need boilers to supply steam have an advantage in terms of power generation.

Ammonia synthesis plants have a large number of operating equipment; if high-pressure steam is available, it is advisable to use it to drive media such as feed gas, process air, and syngas, rather than converting it to electricity first in order to power these devices. In this way, by reducing the conversion process, energy loss is also reduced.

I agree with the opinion above: if high-pressure steam is used for power generation while the waste steam has no proper use other than being used for cooling before returning to the boiler, the energy utilization rate is extremely low, generally not exceeding 40%; the remaining energy is carried away by cooling water or air. It would be better to use that steam directly to drive equipment.

If a blow-air waste heat recovery boiler can produce a large amount of steam of high quality, it can be used for back-pressure power generation; the compressed steam can also be sent to the gas production section for the production of semi-water gas, which is an option worth considering.

Using low-quality waste heat recovery for cooling

Under technical upgrades, overheating drives the compressor or chiller

Low-grade waste heat can also be used to generate electricity