Seeking help with gas distribution and boiling pot issues in a converter furnace
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In the water-coal slurry gasifier, there is a shift gas distribution system; manual control valves are available for the untreated and treated streams, and each stream is equipped with a boiling pot and a separator. At the output stage, the gases are mixed before entering the low-pressure washing unit. Moreover, there is a flow control valve at the outlet of the converter, which is used to regulate the amount of gas fed into the converter in order to adjust the hydrogen-to-carbon ratio. With the current significant reduction in system capacity, is it necessary to operate the manual control valves for the paths that are not involved in the conversion process, or is it sufficient to adjust only the valves for the path that is part of the conversion process? I thought that since the required ratio of untransformed gas volume remains constant, the valve used to adjust the hydrogen-to-carbon ratio in a single action would suffice. There is another issue: the boiling pot generates gas which is then sent through the pipeline network. Currently, the pressure in this network is low. To maintain this pressure, should the valve connecting the boiling pot to the network be closed or opened? If it is closed, less steam will be produced and the gas pressure will rise; if it is opened, more steam will be produced and the gas pressure will drop. I thought it should be turned up.
This post was last edited by wang06120325 on 2015-7-1 at 13:45. From the description above, it seems that your company produces methanol using partial shift technology. Since your process is not very clear and it’s difficult to determine with certainty, the manual control valve you mentioned is likely used when the self-regulating valve loses its ability to regulate. In addition to paying attention to the hydrogen-to-carbon ratio, it is also necessary to pay attention to the temperature of the converter bed layers. The second issue is the low pressure in the pipeline network; this should be reported to the thermal power team, as it is usually they who control the pipeline pressure using pressure regulators. Unless there are too many system users, which results in low pressure in the pipeline network, the waste heat boiler only generates steam as a by-product, and it cannot be used to control the pipeline pressure. Furthermore, when designing the waste heat exchanger, specific pressure values are set, as well as values for heat load and heat exchange area – all of these are calculated in advance and operations are carried out according to those design values. If the pressure setting of the waste heat exchanger is changed, it will affect its service life; and if leakage occurs within the exchanger, it will be counterproductive.
1. First of all, it should be noted that the gas flow ratio between the transformed and untransformed streams is not a fixed value; it is merely a reference value provided based on design parameters such as the hydrogen-to-carbon ratio of the process gas, the water-to-gas ratio, and the conversion rate； The ultimate goal for both the transformed and untransformed streams is to ensure that the hydrogen-to-carbon ratio after gas mixing meets the requirements of the subsequent processing stages. During operation, the hydrogen-to-carbon ratio at the outlet of the shift reactor varies depending on factors such as the ratio of process gas to water vapor, catalyst activity, and the temperature at the inlet of the shift reactor. By properly controlling the bed temperature and adjusting the hydrogen-to-carbon ratio after gas mixing, it is possible to adjust the opening degree of one or more valves accordingly, in line with your process requirements. 2. The pressure throughout the steam network is not affected by the steam generated as a by-product of the conversion process. As long as the steam from the waste boiler is connected to the network, the connection valve must be fully open. Then, the pressure control valve for the waste boiler can be set to a specific value based on the pressure in the steam network; if the pressure of the by-product steam is higher than that of the network, it will naturally flow into the network, while if it is lower, it will not flow in (due to the check valve). Thus, the pressure of the by-product steam is controlled by the network, and no further adjustments are necessary.