Heat Recovery from Gases

The gas streams come out from the converter passes of the sulphuric acid plant at sufficiently high temperatures (590-610 °C from the first pass) and need to be cooled further. Additional WHRB and economisers are installed in the plants which generate more steam and hot water. 

The hot gases come out at 415-450 °C from the last pass and can be used along with an economiser for boiling 28-30 % oleum to produce pure SO3 vapours. 

The WHRB is sometimes bypassed to maintain temperatures in the downstream units. The steam generation gets reduced at this time, and the turbine cannot get fiill supply. However, the electric motor is always kept on, and hence, the air blower continues to run at a normal speed. The power drawn by the motor is reduced automatically to the extent of load shared by the steam turbine. Thus, the electrical consumption gets reduced even when steam generation is not steady. 

The system works better when grid supply is available the capacity (power rating) of the motor is chosen properly for the load (the air blower in this case), and the turbine shall not generate surplus power. In certain process industries, the turbine is a backpressure type, and the exhaust steam from the turbine can be used for process heating also. 

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Heat recovery from gas turbine generators and gas turbine compressor drivers to generate steam or use heat directly in low temperature heater application. The steam generated via Heat Recovery Steam Generators (HRSGs) can be used for ... 

The policy for waste heat recovery from the flue gas varies between incinerator operators. Incinerators located on the waste producer s site tend to be fitted with waste heat recovery systems, usually steam generation, which is fed into the site steam mains. Merchant incinerator operators, who incinerate other people s waste and... 

Equipment. Partial-oxidation gasification section equipment in many plants consists essentially of (/) the gasification reactor (2) the waste-heat exchanger for heat recovery from the hot reactor gas or direct quench system (J) the economizer heat exchanger for further heat recovery (4) the carbon removal system for separating carbon from the reactor product gas and (5) the carbon recovery system for recycle of carbon. 

Owing to the cycHc nature of the TBRC operation, waste heat recovery from the off-gases is not practical and the SO2 content of the gas varies with the converter cycle. In order to supply a relatively uniform flow and strength SO2 gas to a sulfuric acid plant, a system has been installed at RonnskAr whereby the SO2 from fluctuating smelter gases is partially absorbed in water. During smelter gas intermption, SO2 is stripped with air and the concentrated gas deflvered to the acid plant. 

Heat recovery from furnace off-gas (LCV gas) normally used to preheat coke and blast air LCV gas has also been burned to heat melting baths and generate steam and power. 

Figure 9-18 T-Q Plot of Heat Recovery from Hot Exhaust Gas... 

Maximum heat recovery from both flue gas and process gas streams for steam production... 

In order to avoid the unfavorable process conditions, different flue-gas treatment processes for combustion plants based on catalytic filters were developed, which combine fly-ash removal with SCR of ISKh with NH3 [4—8], The advantages of these processes are space and treatment-cost savings, reduced internal and external mass transfer resistances compared to honeycomb SCR catalysts, heat recovery from offgases with good efficiency, and low corrosion problems due to the removal of both dust and NOx at high temperatures. 

Methanol Distillation. To maximize heat recovery from the reformed gas, a four column distillation system is used to produce high purity product (Federal Grade AA). ... 

Heat Recovery from Both Hot Calcine and Hot Flue Gas... 

One way to improve carbon emissions and overall efficiency is to ensure that all furnace operations employ efficient heat recovery from the flue gas. Ideally the flue gas should be cooled in order to recover the heat of condensation of the water produced in the combustion process. 

Figure 8 Potential application of catalytic filters in the IGCC cycle. Legend 1. gasifier 2. catalytic filter unit 3. combustion chamber 4. gas turbine-compressor setup 5. boiler for heat recovery from exhaust gases 6. condenser 7. steam turbine.

Increase heat recovery from the product gas to the feed streams to preheat the reactor feed and reduce the amount of oxygen that is needed. 

Experimental steam production Run 208 was shown to be approximately 1.91 g/g dry, ash-free MSW as compared to an original estimate of 5.5 g/g. When adjusted for calculated heat recovery from flue gas (there is no economizer in the experimental system), excessive heat losses from an uninsulated lower portion of the disengager, and the difference between experimental steam temperature and the original assumption of 121 C steam, the adjusted experimental steam rate was 5.61 g/g which is close to the original estimated rate(4). 

Air is introduced through both side walls, so that the penetration depth of 0.17 m expected for the air jet will be sufficient for tar-free operation. On the basis of the model the required reduction zone and the mass and energy balances are calculated. Two cases are presented, the first without any heat recovery from the fuel gas, the second with air preheated to 700 K. 

As illustrated by the Onahama smelter, it is essential to minimize the volume of the off-gases from a source. The capital and operating costs of a control system are determined primarily by the volume of gas that must be treated (9, 10). The growing application of emission controls has led recently to much more active development of methods and equipment for capture and cooling of waste gases as well as heat recovery from them (34,35). 

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